Ten Feet Coal (Ingleton)
10FT
Twelfth Limestone
12LS
Helm Member
1HELM
Pridoli, Late Silurian.
Base of the lowest reddened laminated siltstone unit where it overlies thickly bedded, unreddened, coarse- to medium-grained sandstone forming the lower part of the Kirkby Moor Formation.
Restricted to The Helm and its immediate vicinity.
Laminated siltstone and mudstone with thinly interbedded, fine-grained sandstone that is pervasively reddened.
About 250m
Base of the lowest thick and unreddened sandstone bed from the upper part of the Kirkby Moor Formation.
First St John's Coal (South Yorkshire And Derby)
1SJC
Twenty Inch Coal (Forest Of Dean)
20CO
27 Yard Coal (West Yorkshire)
27YD
Second Ell Sill
2ES
Two Feet Six Coal (South Wales)
2F6C
Two-Feet Nine Coal, Four-Feet Coal And Six-Feet Coal (Undifferentiated) (South Wales)
Two-Feet Nine Coal And Four-Feet Coals (Undifferentiated) (South Wales)
2F94F
Two-Feet-Nine Coal (South Wales)
2F9C
Two-Feet-Nine Rider Coal (South Wales)
2F9RC
Two Foot Coal (Coalbrookdale)
2FCC
Two Feet Coal (South Wales)
2FCO
Two Foot Coal (South Lancashire)
2FSL
Two Foot Coal (South Staffordshire)
2FT
Two Foot Coal (Cheadle)
2FTC
Two-Foot Vein Coal (Pembrokeshire)
2FTV
Two-Foot Ironstone Seam
2IRS
Second St John's Coal (South Yorkshire And Derby)
2SJC
Second Waterloo Sill
2WS
Two Yard Coal (Cheadle)
2YD
Three Coals (South Wales)
Three Quarter Coal (Coalbrookdale)
3QCC
Threequarters Coal (South Lancashire)
3QCO
Three Quarters Coal (Warwickshire)
3QCW
Three Quarters Mine Coal (South Lancashire) [Duplicate Code: Use 3qco]
3QRS
Three Quarter Coal (Northumberland)
3QTRC
Three Quarters Coals (Milford, South Wales)
3QUC
Taw River Terrace Deposits, 3 Member And Taw River Terrace Deposits, 4 Member, Undifferentiated
3TAW4
River Terrace Deposits, 3 To 4 (Tamar)
3TMR4
Third Waterloo Sill
3WS
Four-Feet Coal (South Wales)
4FCO
Four Foot Coal (Derbyshire)
4FT
Four Foot Coal (Cheadle)
4FTC
Gala Unit 4 And Gala Unit 5 (Undifferentiated)
4GAL5
Fourth Waterloo And First Ell Coal (Vale Of Belvoir)
4W1E
Fourth Waterloo Sill
4WS
Five Feet Coal (South Wales)
5FC
Five Foot Coal (Milford, South Wales)
5FTC
Five-Feet-Gellideg Coal (South Wales)
5FTG
Taw River Terrace Deposits, 5 Member And Taw River Terrace Deposits, 6 Member, Undifferentiated
5TAW6
Six-Feet Coal (South Wales)
6FCO
Seven-Feet Coal (South Wales)
7FCO
Seven-Feet-Yard Coal (South Wales)
7FYC
Nine-Feet Coal (South Wales)
9FCO
Nine Feet Coal (Ingleton)
9FT
Ardmillan Group, Albany Group And Barr Group (Undifferentiated)
AAB
Altnacealgach Alkali Feldspar-Syenite
AAFS
Achnaha Quartz-Monzonite Facies
AAQM
Ardnamona Sandstone Formation
AASA
Recognised in the Republic of Ireland.
Achnaha Tonalite Facies
AATO
Achnaha Tonalite - Quartz-Monzonite Intrusion
AATQM
Abbrook Clay And Sand Member
Airdrie Blackband Coal (Central Coalfield)
ABBC
Airdrie Blackband Ironstone (Central Coalfield)
ABBI
Alberbury Breccia
ABBR
Ardwell Bridge Basic Volcanic Member
ABBV
Top of highest persistent sheet of fine-grained ultramafic rock in the Blackwater Formation.
500 to 750 m-wide outcrop extending from Dead Wife's Hillock [NJ 340 267] to Ardwell Bridge and along valley of River Deveron to Gaul Burn, Succoth [NJ 430 357], Cabrach area, Moray District. 1:50 000 sheets 75E and 85E.
Amphibolite/metabasalt, mostly aphyric, locally with pillow structures. Interbanded with greywacke grits and slaty to phyllitic pelites.
c. 550-650 m (based on outcrop width with no allowance for probable folding).
Top of highest persistent metabasalt sheet. Background lithology changes from greywacke grits with pelites to persistent pelites of the Corinacy Pelite Member.
Ayrshire Bauxitic Clay Member
ABC
Taken at lithological change from olivine basalt of the underlying Troon Volcanic Formation. The base is gradational from basalt through clayrock rich in sphaerosiderite to bauxitic clay. The base is considered to be stratiform, although it might be obscured by later lateritic weathering or diagenesis and some in situ alteration of basalt to bauxitic clay might have occurred.
Limited to north Ayrshire and parts of central Ayrshire
A pale grey to buff clayrock, of massive habit with conchoidal fracture, hard and compact. Texture ranges from fine-grained to ooidal, pisolitic and coarsely clastic. Mineralogically, "bauxitic in the chemical sense of containing more Al2O3 than can be accommodated with SiO2 to give kaolinite". The bauxitic clay may be considered a flint clay. The member may also contain sphaerosiderite, plant fragments, tree trunks and include beds of seatrock, coal and mudstone.
To about 20m
Taken at the base of the Lower Coal Measures; in Ayrshire this is marked by the Raise Coal seam that lies immediately above the Ayrshire Bauxitic Clay.
Aberchirder Pluton
ABCH
Abergorki Coal (South Wales)
ABCO
Aberdeen Formation
ABDN
Not seen: there is probably a major antiform running through the centre of the area of outcrop.
Occupies most of Sheet 77 and much of the eastern part of sheet 76E, together with small parts of sheets 86E and 87W. Probable extension into Sheet 67.
Interlayered psammite and semipelite, with subsidiary pelite and sporadic minor calcareous horizons.
Several kilometres, but not measureable due to intense folding and migmatisation over most of the outcrop.
Incoming of coarse, gritty psammite in area to north of Oldmeldrum. Elsewhere upper contact is obscured by lateral transition to Ellon Formation.
Aberedw Formation
ABDW
Abdy Coal (South Yorkshire And North Nottinghamshire)
ABDY
A-Bed Evaporite
ABE
Abbotsford Flags
ABF
Ayrshire Basanitic And Foiditic Plugs And Vents
ABFPV
Abercwmeiddaw Group
ABG
Drawn at the base of the Abercwmeiddaw Group where pale greyish blue, thickly bedded mudstones conformably rest upon black shales of the Nod Glas Formation.
The district around Corris and Aberllefenni (Merionethshire).
Thickly-bedded, mottled, grey-blue mudstones, passing locally into well cleaved slates.
450 metres approx.
Drawn at the conformable upward passage of the Abercwmeiddaw Group where mottled mudstones pass into blue mudstones with orange weathering of the Red Vein Formation.
Abergeldie Pluton
ABGD
Abbotsford Flags And Grieston Shales
ABGS
Abergwilli Formation
ABGW
Base not seen during the current phase of survey but was previously taken at the first occurrence of "tuning fork" graptolites. (Strahan et al. 1909).
The Abergwilli Formation is restricted in occurrence to an elogate belt along the southwestern margin of the Lower Palaeozoic Welsh Basin extending from aound Llandeilo in the east to Crosshands in the west. Possible correlatives, ascribed to the Didymograptus bifidus beds crop out farther south in the ground between St Clears and Whitland.
The Abergwilli Formation comprises interbedded, dark grey, micaceous burrow-mottled mudstone and laminated graptolitic mudstone with scattered thin sandstone beds and tuffs.
Approximately 680m
Upper boundary not seen during the current phase of survey but was previously taken at the base of the Didymograptus murchisoni bearing mudstones (now Felin Wen Formation) observed in a road bank opposite the corn mill in the village of Felin Wen (Strahan et al. 1909).
Abbey Head Bed
ABH
Faulted.
Coastal section at Abbey Head.
Coarse conglomerates interbedded with conglomeratic sandstones and a few thin marls.
40 metres minimum.
Unknown: probably faulted.
Abbotsbury Ironstone Formation
ABI
Allt Nam Biorag Psammite Member
ABIP
Top of the Creag na Sanais Semipelite Formation, where the predominant semipelite is overlain by predominantly feldspathic and quartzose psammites of the Allt nam Biorag Member
South of Newtonmore, between the Ericht - Laidon and Creag Liath faults
Feldspathic and quartzose psammites with some interbanded calc-silicates and semipelite units up to 0.5m thick; some cross-bedding seen.
c.400m
Incoming of the grey psammites of the typical Fara Psammite Formation, above the feldspathic and quartzose psammites, with or without calc-silicates, and semipelites of the Allt nam Biorag Member.
Aberkenfig Formation
ABKF
The base is a gradational boundary with white-weathering, black, fine-grained limestones and interbedded black mudstones of the underlying Oystermouth Formation passing upwards into the thin-bedded radiolarian cherts and mudstones of the Aberkenfig Formation. In the type section of the Kenfig Borehole, the base is at 48.46m depth.
Parts of the northern and southern peripheries of the South Wales Coldfield:- on the north crop in the Ammanford district, from Gam [c.SN 540 139] east, to east of Llandybie [c.SN 645 173]; on the south crop, from west Gower [c.SS 430 945] (not exposed) east to Swansea Bay, and east of Swansea Bay to the Sarn Park area [c.SS 920 830].
Dark grey fissile mudstones with thin bedded radiolarian cherts and siliceous mudstones.
To c.35m
The top is taken at the top of highest chert or siliceous mudstone of the Formation, where it is overlain by the lowest quartzite of the Twrch Sandstone Formation. In the partial type section of the Kenfig Borehole, the top is not seen, the Formation being unconformably overlain by marl and red clay of the Mercia Mudstone Group at 12.8m depth.
Aber Mawr Shale Formation
ABM
Not defined.
1:50,000 Sheet 209 (St. Davids) and adjacent Sheet 210.
Dark grey mudstones locally with interbedded tuffs.
c.400M
Aber Mawr Formation
ABMR
Not seen.
Ramsey Island, Pembrokeshire.
Dark, laminated graptolitic mudstones, with interbedded rhyolitic turbiditic tuffs and debrites.
More than 215m
Conformably overlain by the Porth Lauog Formation, the boundary being taken at the first debrite incutsion into the black mudstones.
Am Binnein Sandstone Formation
ABN
The top of the Auchencar Sandstone Formation.
Isle of Arran.
Purplish grey sandstones with subordinate beds of red-brown siltstone.
About 950 m to 670 m in the west of Arran.
The base of the Sannox Siltstone Formation in the Sannox area, and the unconformity with overlying Upper Devonian strata elsewhere on Arran.
Abercriban Oolite Subgroup
ABO
The base is placed at the sharp junction between a thin dolostone underlying the lowermost ooidal grainstone of the Abercriban Oolite Subgroup and the top of the grey mudstones forming the uppermost part of the Cwmynyscoy Mudstone Formation.
Northeast crop of the South Wales Coalfield, from Carn-yr-onen [SN 887 166] to Mynnyd Llangattock [SO 200 157].
Massive, pale grey, ooidal grainstone with some fine-grained micritic and dolomitic interbeds.
Up to 30m in the Chwar Pant-y-rhiw area [c.SO 200 157].
The top is placed at a palaeokarstic surface, below which the ooidal grainstone at the top of the Abercriban Oolite Subgroup becomes increasingly disordered upwards and irregular ooidal limestone masses become separated by grey-green mudstone films. The palaeokarstic surface marks a regionally developed unconformity, overlain by micritic to grainstone limestones of the Llanelly Formation.
Abdy Rock
ABR
Sharp upward change in a conformable succession from predominantly grey mudstone to sandstone - base of first sandstone above the Abdy or Winter Coal.
From southwest of Wath upon Dearne around the hamlet of Abdy [SK4430 9880], South Yorkshire, to Staincross Common, [SE3300 1100] Barnsley, South Yorkshire.
A thinly bedded, fine-grained, ripple cross-laminated, yellowish brown sandstone.
0 to 53m
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of last sandstone bed below the Two-Foot Coal and overlying Maltby (Two-Foot) Marine Band.
Auchencar Burn Sandstones Member
ABS
The top of the basal Quartz Sandstone Formation.
Red-brown and purple grey cross-bedded sandstones, with beds of quartzite conglomerate and red-brown siltstone.
About 120 m thick.
The base of the Creag Mhor Conglomerate Member, or locally, the Auchencar Lava Member.
Abbey Sand And Gravel
ABSG
Rests unconformably on bedrock or older Quaternary deposits. Passes laterally into First Terrace Deposits (eg. of Nene and Welland rivers).
Mapped near the western and southwestern margins of Fenland in Lincolnshire and Cambridgeshire. Probably extensive beneath younger deposits throughout Fenland except, perhaps, in the east. Passes laterally into alluvial deposits (First Terrace Deposits).
Sands and gravels, some with marine shells, including clayey, sandy gravels and pebbly sands.
0 - c.5m
Contact with pebbly, silty, sandy clays and clayey sands of the Crowland Bed (Booth, 1982). In the absence of the Crowland Bed, may not be separable from the lowest part of the Barroway Drove Beds.
Armboth Dyke
ABTH
Aberlady Formation
ABY
?Asbian to Brigantian.
The base is drawn at the base of the lowest of the Macgregor Marine Bands (Wilson, 1974), which in the type section is the Saltoun Marine Band (McAdam and Tulloch, 1985, p22).
Midlothian (part); East Lothian; Berwickshire (part).
Mainly pale coloured sandstones interbedded with grey siltstones and grey to dark grey mudstones; subordinate coal, seatrock, carbonates and ironstone.
Spilmersford Borehole 134m. Skateraw Borehole 139m.
The top is taken at the base of the Upper Longcraig Limestone, the local equivalent of the Hurlet Limestone (Wilson, 1989).
Atherfield Clay Formation
Unconformable to disconformable contact on Weald Clay (orangish brown/yellow or steely grey mudstone).
Kent to Dorset, and Isle of Wight.
Clays, silty clays and clayey silts (especially in upper part); locally sandy in upper part; locally glauconitic. Unweathered: dark grey or black. Weathered: chocolate brown, bluish grey and brown, mottled pinkish brown to orange.
5-18m in southwest Weald; c.55m in Isle of Wight.
Incoming of fine- to medium-grained sand of the Hythe Formation with negligible clay above silty or sandy clays of Atherfield Clay Formation.
Brithidir Breccia
ACBB
Brithidir Porphyry
ACBP
Allt-Y-Clych Conglomerate Formation
ACC
Sharp and erosional. Taken at base of first bed of pebbly mudstone or conglomerate above the Tycwtta Mudstones or Yr Allt Formation.
Central Wales, east of Tywi Anticline.
Conglomerates, pebbly mudstones and sandstones. A few thin mudstone beds.
12 - 80 metres.
Gradational but taken at base of first thick mudstone unit of overlying Pistyll Gwyn Mudstones.
Acutistriatum-Comptoni Bed
ACCO
Passage up from relatively unfossiliferous brownish grey mudstone of undifferentiated Peterborough Member into shelly mudstone with fauna of Comptoni Bed as described under Lithology; base of Bed 37 in type section (Hudson and Martill, 1984, p.118).
England; Dorset to Humberside.
Grey calcareous mudstone, becoming more shelly and shell-detrital upwards, grading into pyritic shell bed (Comptoni Bed), overlain by brownish grey shaly mudstone (at type section) or grey calcareous mudstone with pale grey ovoid argillaceous limestone nodules and burrowed top (from Bedfordshire south) ( Acutistriatum Bed). Comptoni Bed has rich fauna of oysters, nuculacean bivalves, belemnites, and ammonites (including Binatisphinctes comptoni). Acutistriatum Bed fauna is rich in forams, and includes ammonites, notably species of Kosmoceras, including K. acutistriatum
0.3 to 0.6m; 0.45m at type section.
Change up from brownish grey mudstone with fauna of Acutistriatum Bed, as described under Lithology, into greenish grey mudstone of undifferentiated Peterborough Member, top is burrowed; top of Bed 38 in type section (Hudson and Martill, 1994, p. 118).
Achscrabster Flagstone Member
ACFM
Alum Crag Grit
ACG
Ashcombe Gravel Member
ACGR
Achneim Striped Formation
ACHM
Achnaconeran Striped Formation
ACHN
Accerhill Sandstone
ACHS
Underlain by grey mudstones of the Crossdale Mudstone, including the Isohomoceras sp. nov. Marine Band.
Lancaster Fells.
Fine- to coarse-grained sandstone, with sandstone seatearths and thin coals.
10 to 28m; thickest in the type area.
Overlain by marine siltstones and mudstones with the Homoceras undulatum Marine Band.
Hematitic Tuffs
ACHT
Ach'Uaine Cluster
ACHU
Acklington Dyke
ACKN
Ackworth Member
ACKW
Top of Cambriense Marine Band (or where absent through washout: base of Ackworth Rock).
Yorkshire Coalfield.
Grey mudstones, siltstones and sandstones with thin coals.
c.100m
Base of Brierley Coal.
Ashy Cleugh Limestone
ACLS
Note that this unit was formerly incorrectly described in the Lexicon as the Ashy Cleugh Sandstone.
Accrington Mudstone
ACM
Achnacarry Striped Formation
ACNS
Auchmithie Conglomerate Member
ACO
The top of the Red Head Sandstone Member.
The south-east limb of the Sidlaw Anticline, on Sheets 49 and 57E,
Up to 245 m thick at Auchmithie.
The base of the Arbroath Sandstone Member, where this overlies the highest conglomerate bed of the Auchmithie Conglomerate.
Ackton Rock
ACR
West and south Yorkshire [Ackton, near Wakefield].
To c.10m
Acre Coal (Northumberland)
ACRE
Northern Northumberland.
Formerly considered part of the (English) Middle Limestone Formation.
c.0.6m
Aughnacloy Sandstone Formation
ACSF
Not seen, but it is assumed to be conformable with the calcareous mudstones and thin interbedded limestones of the underlying Benbulben Shale Formation.
Counties Armargh and Tyrone, Northern Ireland.
A pale grey, medium-grained, parallel laminated, calcareous sandstone, which is ooidal in parts, and locally fossiliferous silty mudstone containing brachiopods and corals.
From 160 m - 300 m thick.
Not seen, but seems to be conformable with the overlying Maydown Limestone Formation.
Achateny Breccia Member
ACTN
Acton Group
ACTO
Acuminata Beds
ACU
Transition from calcareous mudstone of the Bowden Way Beds to shell-detrital mudstone.
Central Dorset to Gloucestershire.
Shell-detrital mudstones with abundant Pracexogyra acuminata. NOTE: Map code 'Bdn' combines Acuminata Beds with Bowden Way Beds.
5.58 metres (Purse Caundle Borehole).
Transition from shell-detrital mudstone to argillaceous limestone (Fullers' Earth Rock).
Clogwyn Volcanic Group
ACV
Drawn at the base of the Clogwyn Group where the base of quartz-rhyolites possibly with tuffs and some hornblende-andesite; base not seen.
Clogwyn Melyn, near Nantlle, Caernarvonshire.
Mainly quartz-rhyolites, possibly with tuffs, and some hornblende-andesite.
305 metres approx.
Drawn at the conformable upward passage of the Clogwyn Group where rhyolites with some tuffs are conformably overlain by grits and feldspathic tuffs of the Tryfan Group.
Viriditic Tuffs
ACVT
Atherfield Clay Formation And Weald Clay Formation (Undifferentiated)
ACWC
See the Lithology descriptions for the component formations.
Ampthill Clay Formation And West Walton Formation (Undifferentiated) [Obsolete Code: Use Wwac]
ACWW
Addlethorpe Grit
A sharp upward change in a conformable succession from predominantly grey mudstone to sandstone. The base of the first sandstone above the Reticuloceras todmordense (R1a4) Marine Band (if recognised) or the Cayton Gill Shell Bed.
The Pennine foothills, between Leeds, Bradford and Harrogate.
A brown, medium-to-coarse-grained, thinly to thickly bedded, quartzo-feldspathic, flaggy, micaceous sandstone.
Up to 50 m thick.
A sharp upward change in a conformable succession from sandstone to predominantly mudstone. The top of the last sandstone below the Reticulatum-Vallites striolatus (R1c) Marine Band (where identified) or below the coarse-grained and pebbly Addingham Edge Grit.
River Terrace Deposits, 1 (Adur)
AD1
River Terrace Deposits, 1-2 (Adur)
AD1T2
River Terrace Deposits, 2 (Adur)
AD2
Sand and gravel, locally with lenses of silt, clay or peat. [Generic description: London ALGI].
River Terrace Deposits, 2 To 3 (Adur)
AD2T3
Sand and gravel, locally with lenses of silt, clay or peat. [Generic description].
River Terrace Deposits, 3 (Adur)
AD3
Adamson Band
ADB
Adwalton Black Bed Coal (West Yorkshire)
ADBB
Ashfield Coking Coal (Central Coalfield)
ADC
Ardclach Pluton
ADCL
Aid Crag Sandstone
ADCS
The area around Sweethope, Northumberland.
Highly variable lenticular cross-bedded garnet-rich sandstone.
15m to c.40m
Aberdeen Pluton
ADEEN
Ayr Diamond Coal
ADI
Arched Mine Coal
ADMC
Addlethorpe Marine Band
ADMS
Adail Mudstones Formation
ADMU
Allt Darrarie Intrusion
ADQD
Ashfield Rider Coal
ADRC
Thin coal "cyclothem" overlies Ashfield Coking Coal, within Limestone Coal Formation.
Glasgow area of the Midland Valley, Scotland.
Thin, impersistent coal in the Glasgow-Stirling region. Locally replaces Possil Fourteen Inch Coal or is replaced by sandstone.
Overlain by fissile mudstone below the Possil Fourteen Inch Coal, Limestone Shale Formation.
Ardnish Formation
ADS
Lithology change, grain size decreases. Sporadic ironstones define boundary.
Sea of the Hebrides Basin.
Sandstone, siltstone, fissile micaceous mudstone, with thin ironstones in the lower section. Gryphaea common.
55 to 78m
Overlain by fissile mudstones of the Pabay Shale Formation.
Ardnish Formation And Breakish Formation (Undifferentiated)
ADSB
Ashford Sand And Gravel
ADSG
Aldress Shale Formation
ADSH
Addingham Edge Grit
West Yorkshire.
The Addingham Edge Grit is a fine- to very coarse-grained, sporadically pebbly, feldspathic, thickly cross-bedded sandstone.
Ayr Ell Coal
AEC
Aeolian Deposits
AEOLD
Ayr Extra Coal
AEX
Altagoan Formation
Unknown but probably conformable with Iniscarn Formation.
Desertmartin area, Co.Londonderry, Northern Ireland.
Variable thin-bedded sediments: pebbly sandstones, laminated micaceous sandstones, siltstones, shaly mudstones, shales, thin micritic algal stromatolites.
Unknown
Unknown but probably conformable with Desertmartin Limestone Formation.
Achanarras Fish Bed Member
AFB
Ayr Forty Fathom Coal
AFF
Auchingree Four Inch Coal
AFIC
Ashfell Limestone Formation
AFL
Aran Fawddwy Formation
AFM
Allt-Tair-Ffynnon Formation And Nod Glas Formation (Undifferentiated)
AFNG
Allt Fawr Rhyolitic Tuff Formation
AFR
Lies unconformably on sandstones, tuffs and siltstones of Cwm Eigiau Formation and mudstones of the Nant Ffrancon Subgroup.
Pwllheli area, northwest Wales.
Rhyolitic ash-flow tuff.
Underlies siltstones, sandstones and calcareous mudstones of the Dwyfach Formation.
Ashfell Sandstone Formation
AFS
Late Arundian
Alston Formation
Generally Brigantian to Pendleian, but locally includes late Asbian strata at the base.
At top of Orton Formation: on Alston Block at base of a thin mudstone below Melmerby Scar Limestone; in Cumbria at conformable base of Sixth Limestone.
British Geological Survey sheets 23, 24, 31.
Bioclastic limestones, sandstones, mudstones, siltstones and rare coals typically in regular cyclothemic sequence.
c.340m
Overlain conformably by rocks of the Stainmore Formation, the boundary been taken at the top of the Great Limestone Member.
Allt Goibhre Semipelite Formation
AGBSP
Ashgate Coal (South Yorkshire, Nottingham And Derby)
AGC
Ashgate Lower Leaf Coal (Derby)
AGCL
Ashton Great Coal (South Lancashire)
AGCO
Ashgate Upper Leaf Coal (Derby)
AGCU
Aberystwyth Grits Group
AGF
Auglish Sandstone Member
AGH
Apparently conformable on un-named red mudstone and sandstone in Derryloran Formation (boundary not seen).
Aughlish and Lower Kildress Townlands, south east Tyrone, Northern Ireland.
Silica rich sandstone
Apparently conformably overlain by unnamed shale and "muddy" sandstone in Derryloran Formation (boundary not seen).
Alla Glen Limestone Member
AGLS
Aegiranum Marine Band
AGMB
Aymestry Group
AGP
Drawn at the base of the Aymestry Group where nodular limestone conformably rests upon flaggy calcareous siltstones with fine-grained limestone nodules of the Lower Ludlow Shales.
The south Shropshire area including Aymestry, Herefordshire.
Grey nodular limestones with siltstone bands in the lower part passing upwards into massive blue hearted crystalline limestones passing into grey nodular limestones. The middle is very fossiliferous.
Max thickness 70 metres approx.
Drawn at the conformable upward passage of the Aymestry Group where nodular limestones pass into olive green and buff flaggy siltstones of the Upper Ludlow Shales.
Aller Gravel Formation
AGR
Rests unconformably on Upper Greensand, where the contact is marked by an unconformable transition from pale green to pale brown sand with some glauconitic bands, iron staining with local chert from the Upper Greensand, to the overlying deposits of Aller Gravels. At Wolborough [SX 8535 7034], Aller Gravel has a faulted or unconformable contact with Upper Devonian Slates; here the contact is recognised by an abrupt change from the lithology of the Aller Gravel to coarse, locally dolomitised, limestones with red mudstone layers of the East Ogwell Limestone.
Sands Copse, Kingsteignton, Milber, Wolborough and Kingskerswell, south Devon.
Seen as 10-20cm-thick beds of lenticular-bedded abraded flint and chert gravels, with subordinate red-mottled silts and clays, coarse, angular, flinty gravelly clayey sand, with some cross-bedded coarse sand, lenticles of white clayey sand and reddish brown coarse sand. Locally finer-grained, more distinctly bedded flint gravels overlie the coarse gravels. The unit is interpreted to have been deposited by braided streams; the source is postulated to have been the Dartmoor highlands (Selwood and others, 1984; Cope et al., 1992), The constituents of the gravel vary locally, and may contain some or all of the following: flint, quartz and tourmaline rock, Greensand chert, Lower Carboniferous chert, Upper Carboniferous sandstone, white rounded clay clasts, vein quartz, dark grey hornfels and tuff.
To 25m
The Aller Gravels are locally overlain by the Palaeogene clays and sands of the Bovey Formation, indeed the Sandygate Borehole [SX 8672 7507] passes through this contact. In this location, the overlying Lappathorn Member of the Bovey Formation is comprised of siliceous clays, sands and silts with pink, red and brown iron staining; these are all underlain by flint gravels that are thought to represent the Aller Gravel.
Agill Sandstone
AGS
Agill Shale
AGSH
Abbotsgrange Silt Member
AGSI
Windermere Interstadial.
The relationship of the Abbotsgrange Silt Member (Forth Clay Formation) to the underlying Errol Clay Formation is probably unconformable. Never known to be in contact with the slightly older Kinneil Kerse Silt Member.
On the southern side of the Forth estuary, from east of Kincardine Bridge to Bo'ness.
Marine, well-bedded, very micaceous, black, grey and browish grey, loose silts, with many laminae and thin beds of fine-grained sand and dark grey silty clay. The unit has clasts up to 8cm of coal, basalt, mudstone and quartzite near its sandy base suggestive of local erosion of underlying strata. The deposit is considered to be prodeltaic in origin.
Veneer to 37m
Overlain unconformably by younger deposits such as the Letham Silt or Claret Clay members (Carse Clay Formation) or by the Bothkennar Gravel Member (Forth Clay Formation).
Arngrove Spiculite Member
AGSP
An upward transition from the silty mudstones of the West Walton Formation or locally, fine-grained silty sands and clayey silts of the Temple Cowley Member of the Kingston Formation to coarser-grained, spiculitic sandstone.
The area between Beckley, Wheatley and Brill north-east of Oxford as seen on the 1:50 000 sheet 237 (inset map), and passes south-westwards into the Temple Cowley Member. Restricted to sheet 237, although similar spiculites are present in the Purton area (sheet 252).
Pale grey, siliceous or calcareous sandstone or siltstone with abundant siliceous spicules of Rhaxella perforata (tetractinellid sponge).
Up to 4.2 m thick.
An upward transition from spiculitic sand or sandstone, to non-spiculitic sand and calcareous sandstone of the Beckley Sand Member of the Kingston Formation, or marls and limestones of the Oakley Member of the Stanford Formation.
Ayr Hard Coal (Ayrshire)
Assynt Hornblende Microdiorite Swarm
AHBL
Ashgill Formation
AHL
Lower boundary taken at the junction of the shales with underlying calcareous mudstones with limestone nodules; the boundary is unconformable in places. Locally base taken at junction with rhyolitic tuff of the underlying High Haume Volcanic Formation.
Northern England throughout the outcrop of the Windermere Supergroup.
Dark blue-grey shales, distinguished from underlying formations of the Coniston Limestone Group by its lower calcareous content and the near absence of limestone nodules. Dark silty mudstones are commonly pervasively bioturbated.
Summary about the Ashgill Formation.
c.20m at type section, thins eastwards to less than 2m in Longsleddale. 125 to 215m in Ulverston District, generally <25m elsewhere.
Base of overlying Skelgill Formation - black graptolitic mudstone.
Auchenhew Mudstone Formation
AHM
Iron stained-sandstones at the top of the Lag a Bheith Formation, are overlain abruptly by the Auchenhew Mudstone Formation.
Arran.
Intertidal and tidal-flat facies with halite pseudomorphs within sandstones, siltstones and mudstones comprise the majority of the succession. Bimodal palaeocurrents, symmetrical ripples, flaser and wavy bedforms are common. Trace fossils are also commonly found.
300m, although 45m is the maximum thickness recorded in a single exposure.
Overlain by dark grey to black marine muds of the Levencorroch Mudstone Formation.
Arbroath Sandstone Member
AHS
The top of the Auchmithie Conglomerate Member
The south east limb of the Sidlaw Anticline, in the Dundee-Montrose area, on sheets 49 and 57.
Green or purplish grey to bright purple-red, cross-bedded fine- to medium-grained sandstones with local intraformational conglomerates containing concretionary limestone clasts and rare mudstone beds.
Up to 365m thick.
Not seen, although unconformably overlain by the Stratheden Group (Upper Devonian).
Acer Hill Sandstone [Obsolete Entry: Incorrect Spelling: See Achs]
AHSA
Armsheugh Sand And Gravel Formation
AHSG
Sharp, irregular, erosional contact with underlying clay-rich gravel or clayey sand of the Lawthorn Diamicton Member, with relief amplitude of about 3.5m.
Probably local to west Ayrshire.
Sand and gravel, horizontal and cross stratified, interpreted to represent longtitudinal bars of proximal to medial reaches of a glaciofluvial outwash fan.
To 5.5m
Sharp, conformable contact with laminated sand and organic-rich clay and silt of the Sourlie Organic Silt Formation.
Abbeyhill Shales
AHSH
Dark blue shaly mudstones, locally crowded with ostracods.
These beds form the lowest part of the Gullane Formation, overlying rocks of the Arthur's Seat Volcanic Formation.Though listed here as of "unclassified" rank, these beds might be considered an informal member of the Gullane Formation.
Ashness Tuff Member
AHT
Taken at base of lapilli-tuff resting on Grange Crags Andesite (lava); contact sharp but conformable or, at its eastern extent resting unconformably on Skiddaw Group rocks.
North Lake District near Borrowdale (Ashness Wood to Dale Head).
Lithic-rich lapilli-tuff, very poorly sorted and massive to weakly eutaxitic.
Overlain by bedded to massive volcaniclastic sandstones contact is abruptly gradational, or by andesite of the undivided Birker Fell Andesite Formation.
Agnew's Hill Tuff Member
AHTM
Airy's Bridge Tuff Formation
AIB
Base of rhyolitic pyroclastic rocks. Unconformable on slumped surface of Whorneyside Tuff Formation and locally conformable and interbedded with the Whorneyside Tuff Formation. In places directly on the Birker Fell Andesite Formation.
Scafell - Crinkel Crags area to Borrowdale and Thirlmere, Wasdale, Coniston Fells, Duddon Valley to Stainton Fell, Cumbria.
Massive, white to pink weathered eutaxitic and parataxitic rhyolitic tuffs and lapilli-tuffs, with some intercalated units of pyroclastic breccia and widespread beds of laminated tuff. Some component units are markedly garnetiferous.
Defined by the base of the overlying formations that comprise a mixed succession of bedded pyroclastic rocks and volcaniclastic sandstones including: Lingmell Formation in the Central Fells, and the Duddon Hall Formation in the Coniston and Ulpha areas.
Aikbank Farm Glacigenic Formation
AIK
Sharp, undulating, unconformable contact with pale red stony clay diamicton and cobble gravel of the HolmrookTill Member of the Blengdale Glacigenic Formation.
Lower Wasdale, West Cumbria, inland of the limit of ice of the Irish Sea Ice Stream during the "Gosforth Oscillation"
Rhythmically laminated silt and clay [Whinneyhill Coppice Clay Member], overlain by pebbly silty clay diamicton and sand [Green Croft Till Member], overlain by laminated clay and silt [Holmeside Clay Member], overlain by coarsening-upwards sequences of sand and gravel [Mainsgate Wood Sand and Gravel Member].
To 60m
Either not overlain, or partially overlain by Flandrian peat or alluvial deposits.
Aisholt Limestone
AIL
Ailsa Craig Microgranite
AILC
Intrusive contact.
Limited to the island of Ailsa Craig.
Circular microgranite intrusion also intruded by dolerite dykes.
c.1 square km in total area (circular).
Ailleag Diamicton Formation
AILL
This unit was formerly considered Anglian to pre-Late Devensian.
Unconformable on bedrock.
Central Grampian Mountains of Scotland.
Compact, very poorly sorted, clast-supported, matrix-rich diamicton formed of angular fragments of weathered psammite (locally granite or porphyry) to boulder size in a yellow-brown or orange, commonly ferruginous, matrix of silty sand.
Sharp, unconformable, or gradational glacitectonic contact with Ardverikie Till Formation.
Ailstone Member (Warwickshire Avon)
AILT
River Terrace Deposits.
Sand and gravel, with possible lenses of silt, clay or peat. [Generic description].
Avicula Ironstone Seam
AIRS
Ayr Jewel Coal (Ayrshire)
Archerbeck Beds
AKB
Conformable contact with a thick seatearth lying c.90m above the Kinmont Limestone.
Confined to the Langholm district.
Alternating limestones, calcareous mudstones and mudstones with some calcareous sandstones. The strata contain a marine fauna of polyzoa, corals, brachiopods and bivalves.
The proposed term Archerbeck Limestone Formation [ARLS] was abandoned, efectively unused, but the term Archerbeck Beds is retained as an informal, unclassified subdivision at the top of the Tyne Limestone Formation, below the Cornet Limestone. The Archerbeck Beds were orginally defined under his name (within the Lower Liddesdale Group) in the Langholm Memoir (Lumsden et al., 1967).
c.100m. Limestones form up to 33% of the thickness.
Conformable contact with unfossiliferous sandstones and mudstones c.15m below the base of the Cornet Limestone.
Aymestry Limestone Formation
Transitional with Lower Ludlow Shale.
Welsh Borderland, West Midlands, Coalbrookdale and Malverns.
Blue-grey, nodular argillaceous limestone with greenish shaly calcareous mudstone (at Ludlow).
18 metres - 25 metres in Malvern area; up to 45 metres in type area.
Transitional with Upper Ludlow Shale locally; local unconformity in type area; locally at base of yellow ochreous shale in type area (Alexander, 1936).
First Abden Limestone
AL1
Second Abden Limestone
AL2
Alpha Coal (North Wales)
ALAC
Alluvium And Alluvial Fan Deposits (Undifferentiated)
ALAF
Alves Beds
ALB
Albion Glacigenic Group
ALBI
Sharp, planar unconformable contact with units of the Dunwich and/or Crag groups, or bedrock.
The whole of Great Britain lying to the north of the Anglian glacial limit crossing southern England, but mainly occuring between the Anglian and Devension glacial limits.
A suite of glacial, glaciofluvial, glaciolacustrine and glaciomarine deposits that contain clasts derived from rocks cropping out throughout northern, central and eastern England, Scotland and Wales, and offshore, including diamictons [till], sand, gravel, silt and clay.
To 120m
Ground surface or unconformable contact with units of the Caledonia Glacigenic Group, the Britannia Catchments Group or the British Coastal Deposits Group.
Albrighton Coal (Cumbria)
ALBN
Alphington Breccia Formation
ALBR
Rests on Whipton Formation or on basalt. Junction with the Whipton Formation is gradational over a vertical interval of about 10m, the boundary being drawn where breccia becomes the dominant lithology. Where the formation overlies basalt, a large hiatus is present between c.290 Ma basalts and c.260 Ma or younger Alphington Breccia.
Extends from Exeter City southwestwards through Alphington to Shillingford St George and Clapham (SX 895 870) areas.
Breccia, reddish brown, clayey, silty, fine-grained. Clasts predominantly culm shale and sandstone, together with hornfels, chert, quartz-porphyry, and lava. Most clasts less than 4cm; some range up to 0.1m and large boulders of porphyry are locally present.
Overlain by Heavitree Breccia, which forms a scarp above the Alphington Breccia owing to the difference in cementation between the two formations.
Albert Coal (Northumberland)
ALBT
Albany Group
ALBY
Faulted lower boundary.
Greywackes, mudstones, conglomerates.
At least approximately 1000m
Faulted upper boundary.
Alluvial Cone
ALC
Gravel-rich sand and silt, with a cone-like form. [Generic description].
Alloa Cherry Coal
ALCH
Allt Crom Complex
ALCR
Southern Monadhliath Mountains in northern part of the Dalwhinnie district (Scotland sheet 63E) and southern part of the Foyers district (Scotland sheet 73E).
Composed of a grey, aphyric, biotite granodiorite, with a marginal zone of pink leucogranite up to 200m wide. The granodiorite is composed of oligoclase, quartz and microcline, partly chloritised biotite and minor hornblende. Abundant disorientated rafts of host rocks of psammite and semipelite up to 500m long occur in the southern part of the complex, preserving a disrupted ghost stratigraphy, mainly seen on Sheet 63E, Dalwhinnie. Elsewhere, the granodiorite includes an area where the rafts are predominantly composed of appinitic diorite. These rafts are penetrated by veins of granodiorite but otherwise generally intact, albeit thermally metamorphosed. Contact metamorphism is intense within the rafts, most noticeably affecting semipelites and any calc-silicate rocks, and recognised up to 1.4 km away from the external contacts of the intrusion. In the northern part of the complex, mainly Sheet 73E - Foyers, the metasedimentary rocks become progressively more coherent so that some areas may be regarded as intact metasedimentary formations permeated by granodiorite veins of a variety of scales and to varying degrees of intensity. Subdivisions of the complex are recognised on the basis of the character of the metasedimentary rocks enclosed.
Allt Crom Granodiorite With Rafts Dominantly Of Appinitic Diorite
ALCRA
Allt Crom Granodiorite With Rafts Of The Coire Nan Laogh Semipelite Formation
ALCRC
Allt Crom Granodiorite With Rafts Of The Garva Bridge Psammite Formation
ALCRG
Allt Crom Granodiorite With Rafts Of The Loch Laggan Psammite Formation
ALCRL
Allt Crom Granodiorite With Rafts Of The Monadhliath Semipelite Formation
ALCRM
Allt Na Cuile Sandstone Member
ALCU
Alluvial Delta
ALD
Gravel-rich sand and silt, developed at the mouths of tributary valleys. [Generic description].
Allt Dregnie Phyllite Member
ALDP
At the top of flaggy psammites of the Corryhabbie Quartzite Formation.
Braes of Glenlivet, Glen Suie.
Micaceous psammites and semipelites with some pods and bands of calc-silicate rock. Contains a prominent white limestone in places. Phyllitic in places.
c. 140m in Glen Suie, including any thickening due to folding.
At the incoming of prominent thin beds of limestone in strongly banded rocks of the Glen Suie Limestone Member.
Aldie Till Member
ALDTI
Sharp, interdigitating glacitectonic boundary with compressed peat and organic sand of the Berryley Peat Bed or with a local unit of Head named informally as the Hardslacks Gelifluctate Bed; or an apparently gradational contact with dark grey diamicton of the Camp Fauld Till Formation; or on bedrock.
Moss of Cruden, Buchan.
Gravelly clayey sand and diamicton (till), greenish grey (5GY 6/1), stiff, massive to crudely-horizontally bedded, with broken rounded pebbles and cobbles of flint and quartzite reworked from the Buchan Ridge Gravels Formation, together with sparse mica schist, granite, mafic igneous and red sandstone clasts. The matrix is kaolinitic quartz sand. The lithology of the till varies laterally with the underlying bedrock. It thickens to the south and east of the Moss of Cruden, where it includes red granite and has a weak NW-SE clast fabric. The till locally incorporates large masses of weathered brown sand with sparse quartzite clasts of unknown derivation and origin.
<10m
Unconformable contact with red clayey diamicton of the Logie-Buchan Glacigenic Subgroup, or head deposits.
Alecks Coal (Lothian)
ALEX
Alluvial Fan Deposits
ALF
Alluvium (q.v.) with a low-angle cone form, developed at the mouths of tributary valleys [generic description: 'TMOS' procedures]; very localised source. [Description from East Anglian data].
Alluvial Fan Deposits 1
ALF1
Alluvium with a low-angle cone form developed at the mouths of tributary valleys [generic description: 'TMOS' procedures]; very localised source. [Descriptions from East Anglian data]. Older than 'Alluvial Fan Deposits'.
Alluvial And Glacial Deposits (Undifferentiated)
ALGD
Gravel, sand, silt and clay, with rare peat; interbedded. [Generic description].
Allt Goch Sandstone Formation
ALGO
Alturlie Gravels Formation
ALGR
Gradational, from the Ardersier Silts Formation below, or unconformable, with lodgement till or bedrock below.
The area surrounding the southern shore of the inner Moray Firth, between Inverness and Elgin.
Sand and gravel, typically a deltaic coarsening-upwards sequence. Origin thought to be glaciomarine.
At least 20m
Unconformable with Late Devensian raised marine deposits above, or the present ground surface.
Allargue Graphitic Schist Member
ALGS
At lower limit of graphitic pelite. Overlying calcareous semipelites and psammites of the Cock Burn Calcarous Schist Formation.
Poorly exposed on the valley sides in Upper Donside (around Corgarff and Allargue). Extends southeast approximately along A939 to Upper Fenzie.
Schistose graphitic pelite and subsidiary semipelite. Banded, slaty in parts.
At upper limit of graphitic pelite where it passes into semipelites of the Tornahaish Dark Schist and Limestone Formation.
Aller Halite Formation
ALHA
Alkaid Member
ALK
Allt Lwyd Formation
ALL
Unconformable on rocks of the Mawddach Group and the Rhobell Volcanic Group.
Northern, central and eastern Snowdonia.
Interbedded siltstone and coarse- to medium-grained, bioturbated and locally slumped sandstone, locally quartzose or volcaniclastic, subordinate conglomerate and rare mudstones; good sedimentary structures.
Excluded from the Aran Volcanic Group by Rushton and Howells, 1998, because its identity with a particular formation remains unproved, and it is isolated from the constituent formations of that group by the ground between the Trawsfynnydd-Cwm Bowydd and Fynnon Eidda faults. Forms the base of the Ogwen Group in Snowdonia; lies between the Mawddach and Aran Volcanic groups to the east and south. Includes the Garth Grit Member at the base and, locally, the Aran Boulder Bed Member at the top.
130 to 330m
Succeeded chiefly by the Offrwm Volcanic Formation in southern Snowdonia and by mudstones of the Nant Ffrancon Subgroup in the north. Locally unconformable contact in the Snowdonia district.
Allens Coal (East Midlands)
ALLC
Allt Breac Beds
ALLT
Ardvarney Limestone Member
ALM
Allermuir Volcanic Member
ALMR
Conformable: in north east, where pyroxene andesites and olivine basalts overlie biotite rhyolite/dacite of Capelaw Volcanic Member. In south west where, olivine basalts and pyroxene andesites overlie rhyolites and thin lenses of conglomerate of the Bell's Hill Volcanic Member.
Pentland Hills.
Lowest flows are fine-grained microporphyritic pyroxene-andesites and olivine basalts, followed by feldspar phyric basalt and pyroxene andesites. Intercalations between flows include rhyolite and basic tuff, agglomerate and pebbly volcanic grit and tuff.
At least 366m on Allermuir Hill.
Conformable: where pyroxene andesites, olivine basalts and locally basic tuff and breccia are overlain by rhyolitic tuff and flow-banded rhyolite of the Caerketton Volcanic Member.
Alne Glaciolacustrine Formation
ALNE
Unconformable on the Vale of York Formation and locally on bedrock.
Vale of York north of York Moraine as far north as Thirsk, west to Littlethorpe and Hunsingore, east to Stockton on the Forest. Lake deposits generally below +30m AOD, down to +14m AOD in the lowest area near York.
Laminated clay with silt (varved) and subordinate fine-grained sand beds, plus a little marginal sand and gravel.
To 22m
The present land surface or the base of the Sutton Sand Formation, or other "cover" sand deposits.
Alness Spiculite Member
ALNS
Altnaharra Psammite Formation
ALPS
Antrim Lava Group
ALR
Alpha Rider Coal (North Wales)
ALRC
Alluvium And River Terrace Deposits (Undifferentiated)
ALRT
Palaeoproterozoic To Palaeozoic Rocks (Undifferentiated)
ALRZ
Alderney Sandstone
ALS
Alport Sandstone
ALSA
Allenton Sand And Gravel
ALSG
The bedrock surface - commonly cryogenically involuted; other deposits may intervene.
Derwent Valley.
Sand and gravel with minor clay and silt lenses, commonly including deposits of head, both capping the terrace deposits and involuted with them.
Typically to 4m
Top of sand and gravel, commonly corresponding to terrace surface; commonly overlain by head that is involuted with sand and gravel to varying degrees.
Alum Shale (Of The Glasgow Area)
ALSH
These beds lie below the base of the Hurlet Limestone (also the base of the Lower Limestone Formation) and above the Hurlet Coal.
c.0.9m
Alloa Splint Coal
ALSP
Auchleuchries Sand And Gravel Formation
ALSSG
A sharp, undulating, erosional, unconformable contact with dark grey, pebbly clay diamicton of the Pitlurg Till Formation.
Eastern Aberdeenshire.
A mostly pale yellowish brown pebbly sand, containing a relatively large proportion of pink granite and seams of chocolate brown or dark grey clay, which is interpreted as having been derived from the underlying Pitlurg Till Formation.
To 12m
Sharp, planar or gradational glacitectonic, unconformable contact with a reddish brown, gravelly sandy clay diamicton of the Hatton Till Formation, and elsewhere overlain by yellowish brown, gravelly clayey sand diamictons of the East Grampian Glacigenic Subgroup, which contain psammite, metagreywacke and granite clasts.
Alternata Limestone Formation
ALT
C.30M IN THE NORTH Caradoc area increasing to c.120m southwards.
Allenton Terrace Deposits
ALTD
Allt Dhub Member
ALTDU
Fossiliferous sandstones overlying conglomerates (usually red) of the Sgaorishal Member.
Isle of Rum/Sea of the Hebrides Basin.
Fossiliferous, grey, well-bedded sandstones. Fragments of plant, wood, fish, shells and ostracods are common. The lithology changes to siltstone and the fossils found signify an enviromnent change from alluvial to estaurine and shallow-marine conditions that prevailed at the Jurassic, but the unit cannot be accurately dated as such. Not shown on 50k maps.
18m
No overlying unit on Rum.
Alton Coal (Leicester, Nottingham, Derby)
ALTN
Alluvium
ALV
Normally soft to firm consolidated, compressible silty clay, but can contain layers of silt, sand, peat and basal gravel. A stronger, desiccated surface zone may be present. [Generic description].
Alluvium 1
ALV1
Normally soft to firm consolidated, compressible silty clay, but can contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated surface zone may be present. [Generic description]. Older than "Alluvium".
Alluvial Deposits, Buried, Postglacial Estuarine-Marine [See Descriptions For Limitations Of Use]
ALVM
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area, as a subset of "Alluvial deposits overlying possible postglacial sequence". To avoid potential confusion it should be used only for similar purposes in future. Note that on the related Quaternary Domains map, this category was described as: "Possible buried postglacial estuarine-marine sequence".
Alluvial Deposits, Postglacial, Terrestrial [See Descriptions For Limitations Of Use]
ALVT
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area, as a subset of "Alluvial deposits overlying possible postglacial sequence". To avoid potential confusion it should be used only for similar purposes in future. Note that on the related Quaternary Domains map, this category was described as: "Postglacial terrestrial sequence".
Alecs Coal (Cheadle)
ALXC
Alveley Member
ALY
Conformable, transitional-gradational boundary, arbitrarily taken at the base of the first major red-bed stratum, overlying the grey mudstone-dominated Dark Slade Member of the Halesowen Formation.
West Midlands and Salop.
Red mudstone and sandstone, fine- to medium-grained with thin 'Spirobis' limestone beds and pedogenic limestone (caliche). Sandstone mostly sublitharenite.
152 to 274m in Alveley area; 50 to 140m in south Staffordshire.
Poorly defined, but arbitrarily taken at the base of a sandstone-dominated succession (Enville Member), characterised by conglomerates and pebbly sandstones with extrabasinal clasts, commonly of Carboniferous limestone and chert.
Ayr Major Coal
AMA
Abercorn Main Coal (Glasgow)
AMAC
Ampthill Clay Formation
AMC
Late Jurassic, Late Oxfordian to (locally) earlt Kimmeridgian (Tenuiserratum to Baylei zones).
Base of mudstones (as described under Lithology), resting on darker more silty mudstone of the West Walton Formation or on limestone/sandstone of that formation's members (Upware Limestone, Elsworth Rock) or of the Corallian Group; generally a marked colour change and break of slope at outcrop; change commonly well-marked on borehole geophysical (particularly gamma-ray) logs. Base of unit AmC1 in Fenland (Cox and Gallois, 1979).
Oxon/Wilts, where it passes progressively southwestwards into the Corallian Group (Horton et al., 1995; Gallois and Cox, 1994), to the Market Weighton area, where it is overstepped by Cretaceous rocks (Gaunt et al., 1980); also present in the Cleveland Basin (Powell et al., 1992).
Mudstone, mainly smooth or slightly silty, pale to medium grey with argillaceous limestone (cementstone) nodules; some rhythmic alternations of dark grey mudstone in the lower part; topmost beds are typically pale grey marls with cementstone.
Powell, J H, Cooper, A H and Benfield, A C. 1992, give details of a typical onshore Yorkshire sequence in the Kirklington Borehole.
0 to c.90m; typically c.25m in Oxon-Bucks., c.10m in the Bedfordshire type section; c.50m in Fenland, c.90m in north Lincolnshire.
Upward change to darker mudstone of the Kimmeridge Clay Formation; commonly an erosive non-sequence marked by phosphatic pebbles; generally a marked colour change and break of slope at outcrop; change comonly well-marked on borehole geophysical (particularly gamma-ray) logs. Top of unit AmC42 in Fenland (Cox and Gallois, 1979), but incomplete and succeeded unconformably by Cretaceous rocks in the vicinity of the type section.
Ancholme Group
AMG
Base of Kellaways Formation; commonly a shelly mudstone resting on limestone of the Cornbrash Formation.
Waddesdon, Buckinghamshire, between Oxford and Aylesbury (Thame district, Sheet 237), where Corallian Group wedges out (Horton, A, et al, 1995) to Market Weighton area, Yorkshire (Sheet 72). N.B. Mutually exclusive with the Corallian Formation/Group, thus not used south of Oxford, nor in the Cleveland Basin.
Predominantly grey, marine mudstone and silty mudstone; beds of argillaceous limestone nodules (or more or less persistent beds) at some levels; units of siltstone and sandstone at some levels, widespread near base (in Kellaways Formation), in middle part (West Walton Formation) and more locally at other levels (notably Kimmeridge Clay Formation of Oxon/Buckinghamshire); shelly marl, limestone and sandy limestone developed locally (notably in the West Walton Formation).
Probably zero (over Market Weighton High) to c.350m in central/eastern Lincolnshire (Louth district, Sheet 103), about 150-180m in Oxon/Buckinghamshire.
Unconformable junction of mudstones with uppermost Jurassic/Lower Cretaceous limestones and sandstones; in the southwest (Oxon/Buckinghamshire) Kimmeridge Clay Formation overlain by Portland Formation; farther north, Ancholme Group progressively overstepped towards the Market Weighton High.
Abhainn Mhor Gabbro Intrusion
AMGB
A'Mharagach Member
AMHAR
Abrupt transition to 'red beds' above the conglomerates of the Shellesder Member.
Sea of the Hebrides Basin/Isle of Rum.
Alluvial, pedogenesis and floodplain deposits (interpreted as cyclothems, Emeleus, 1997) are recorded in distinct red beds of fining upwards, arenaceous sediments, interbedded with cornstones. Not shown on 50K maps.
40m
Top underlies cross-stratified conglomerates of the Sgoarishal Member.
Ampthill Clay Formation And Kimmeridge Clay Formation (Undifferentiated)
AMKC
Alderwood Mudstone
AMM
Amaliae Marine Band
AMMB
Allt A' Mhuilinn Mudstone Formation
AMMU
An unconformity with the Dalradian Supergroup below.
The Ben Nevis area of Scotland.
Mainly mudstone and laminated siltstone, with quartzite-dominated conglomerate intercalations
About 15m thickness exposed.
The base of the predominantly volcanic rocks belonging to the Ben Nevis Volcanic Formation.
Ardmillan Group
AMN
Drawn at the base of the Ballatchie Formation where blue grey nodular mudstone,siltstone,fine-grained sandstone and conglomerate rest conformably upon boulder conglomerate with matrix supported clasts of basalt, dolerite and gabbro of the Benan Conglomerate Formation.
The Girvan area from Girvan south to Glen App.
Turbiditic sandstone, siltstone and mudstone with conglomerate at its base. Lateral impersistence and occurrence of similar lithologies at different horizons cause difficulties with stratigraphy.
Overlain unconformably by the Silurian Mulloch Hill Conglomerate Formation.
Amundsen Formation
AMND
Auchmeddon Gravel Member
AMNGR
Devensian (?MIS 2).
The lower boundary of the formation is a scoured, undulatory erosion surface (amplitude about 1.0m) on reddish brown diamicton of the Byth Till Formation.
Buchan, northeast Scotland. The member is only known from the vicinity of the Howe of Byth Quarry on Sheet 97 (Fraserburgh).
Gravel. Interpreted as glaciofluvial outwash. Grey, pebble to boulder grade. Clast-supported with a medium to coarse quartzose sand matrix. Clasts are subrounded to rounded and composed mainly of quartzite (probably reworked from underlying gravel deposits and Devonian conglomerates) - other lithologies are rare. The gravels are crudely horizontally bedded with local sand interbeds displaying horizontal stratification. Clast imbrication measurements indicates palaeocurrents flowing towards the south.
To 3m
The formation either occurs at the present ground surface or is overlain by Holocene peat or alluvial sediments.
Amphibolite And Calcsilicate-Rock Of Uncertain Origin
AMPCS
Amphibolite Of Uncertain Origin
AMPH
A'Mhoine Psammite Formation
AMPS
Alum Shale Member
AMSH
Ambaston Terrace Deposits
AMTD
Amethyst Member
AMTH
Ashdown Beds (A) [Obsolete Code: Use Asd]
The bracketed letter (A) after the name is a late-stage expedient, added to avoid potential problems related to holding identical entries in the database system.
Annagher Coal (Dungannon)
ANC
Ashton Mudstone Member And Crackington Formation (Undifferentiated)
ANCK
Andrews Coal (Lothian)
ANDC
Aberdeen Ground Formation
ANG
Eroded by pre-Ling Bank and pre-Coal Pit and Forth Formation erosive phases. Base not seen in most seismic sections except near the type borehole. Further to the west, the formation lies on Tertiary and occurs at outcrop.
Hard, heavily overconsolidated, commonly fissured, grey clay. Sporadic shell fragments and plant remains. Lenses and laminae of silt and fine-grained sand increasing in content towards the west. [Generic description: 1:50k map margins].
72.5 metres : maximum of around 130 metres in central part of Devil's Hole area.
See lower boundary.
Arran Northern Granite (Inner Granite)
ANGI
Arran Northern Granite (Outer Granite)
ANGO
Argyll And Northern Highlands Granitic Suite
ANHGR
Appinite Suite
ANITE
Anabacia Limestones
ANL
Andsell Mudstone Member
ANMU
Annaclare Group
ANNA
Annandale Sandstone Beds
ANSA
Conformable on Birrenswark Volcanic Formation.
Restricted to the Dalton area of Dumfriesshire (1:50000 Sheets 10 W, Lochmaben and 10 E, Ecclefechan [Scotland]).
Dark red, fine-grained to coarse-grained sandstone and locally derived conglomerate.
Gradational, passing up into sequence characterised by thin dolomitic limestones (cementstones), sandstones and mudstones.
Anker Sand And Gravel
ANSG
Ashton Mudstone Member
ANSH
?Visean to Kinderscoutian.
The lower boundary is taken at the incoming of bluish grey micaceous mudstones with scattered thin sandstones and siltstones of the Ashton Mudstone Member above the fossiliferous interbedded cherts, limestones and mudstones (Posidonia Beds) of the Teign Chert Formation.
Teign Valley (SX 84 84), and Exeter (SX 90 92) areas, south Devon. May extend westwards into the Okehampton area (SX 59 94), where it has previously been included in the Crackington Formation, but further investigation is needed.
Greyish blue, rusty-weathering mudstones with scattered thin sooty goniatite-bearing mudstones. Scattered siltstones and sandstones (up to 7cm thick) form less than 10% of the Member. The sandstones are commonly medium-grained, quartzitic and feldspathic and thought to be derived from the south. Plant fragments are locally abundant.
The upper boundary is taken at the gradational incoming of more abundant and relatively thicker sandstones of the overlying Crackington Formation above the mudstones with less than 10% sandstone of the Ashton Mudstone Member.
An Stac Semipelite And Psammite Formation
ANST
Base marked by interbanded garnetiferous quartzite and semipelite above psammites of Creag an Loin Psammite.
Central Highlands of Scotland. Newtonmore - Glen Banchor - Kincraig areas.
Striped association of semipelite, psammite and siliceous psammite with subordinate quartzite and calc-silicate rock, variably gneissose.
Invariably marked by a narrow zone of ductile shear overlain by gneissose arkosic psammites of the Creag Liath Psammite.
An Tamhanachd Member
ANTA
Acklinton Till Formation
ANTI
Anthracoceratites Marine Band
ANTMB
Younger than the Bilinguites superbilinguis Marine Band and older than the Cancelloceras cancellatum Marine Band.
Confirmed as present in several areas along the Namurian outcrop of southern Wales, between Druidston in the west and the Twrch Valley in the east (see Ramsbottom et al., 1978, Fig.4).
An Torran Pelite
ANTOR
Archerbeck Ochre Bed
AOB
Aonach Beag Semipelite Formation
AOBG
Boundary between platy feldspathic psammites of the Inverlair Psammite Formation and schistose micaceous psammites and semipelites. Base where micaceous psammite and semipelite become dominant.
Ardverikie Forest, southern Central Highlands of Scotland, largely on sheet 63E [Dalwhinnie].
Schistose semipelite and micaceous psammite with white quartzite beds locally abundant in the type area.
Generally to 200m but c.500m in the Aonach Beag area.
Transitional boundary into overlying Kinlochlaggan Quartzite Formation marked by either increasing psammite in locally increasing proportion of interbanded quartzite. Top at point where quartzite becomes dominant.
Athelstan Oolite Formation
AOL
South of Horsley [ST 840 975]; rapid passage up from fine-grained slightly argillaceous limestone with ooidal limestone lenses (Tresham Rock Formation), into massive ooid-limestones. Locally a thin grey mudstone bed may intervene. North of Horsley; sharp change up from grey mainly calcareous mudstone (Fuller's Earth Formation), or where absent, from shell-detrital limestone of the Dodington Ash Rock Member (Fuller's Earth Formation), into massive ooid-limestones.
Outcrop: Old Sodbury to Cirencester area, Gloucestershire, where the Athelstan Oolite passes into the White Limestone Formation (boundary is taken arbitrarily at the western and southern edges of the 1:50 000 sheet 235 (Cirencester). Subcrop: Hullavington, Wiltshire to Sandpool Farm (Somerford Keynes), Gloucestershire (Wyatt, 1996).
Limestone, white to pale yellow, poorly fossiliferous ooid-grainstones and ooidal limestones, in the southwest they are generally well sorted medium-grained and massive, rarely cross-bedded; in the northeast they become more bioclastic, less well sorted fine- to coarse-grained, commonly cross-bedded. Generally capped by bored, encrusted hardground (mapped on sheets 234 (1972 edition) and 251 (1970 edition) as "chinastone" or "Coppice Limestone" (Cave, 1977)). Lateral passage northeast into peloidal packstones and wackestones of the Ardley Member (White Limestone Formation), and the lower part passes southwestwards by decrease in ooid content into the Tresham Rock Formation.
About 3 to 21m
Bored and oyster encrusted hardground on ooidal limestone, overlain by pale grey, bioclastic ooidal limestones of Chalfield Oolite Formation, or where absent, brown and grey variably ooidal, sandy or muddy bioclastic lime-grainstone/packstone (Forest Marble Formation). Near the formation's southern limit, grey mudstone of the Fuller's Earth Formation intervenes beneath the Chalfield Oolite.
Allt Odhar Peat Formation
AOPT
? Early Devensian [see Lithology description].
Sharp, draped, conformable contact with underlying cobble gravel of the Odhar Gravel Formation.
Sheet 84W (Fortrose), southeast of Inverness.
Peat highly compressed, black, with lenses of pebbly peaty sand and bleached white sand. Containing beetle remains and pollen indicative of (early Devensian) interstadial conditions
Unconformable, glacitectonic contact with stiff, stony sand/clay diamicton of the overlying Athais Till Formation.
Applethwaite Member
Rests with a marked lithological change either on the rhyolitic ignimbrite of the Yarlside Volcanic Formation, or on the concretionary limestone of the Kentmere Member (Kirkley Bank Formation).
Southeastern part of the English Lake District, Cumbria, between Coniston [SD 300 980] and the Birkbeck Fells [NY 560 070].
Mainly a calcareous siltstone, although it occurs in graded units that range from a fine-grained sandstone with shelly lag accumulations at the base, to a bioturbated and fine-grained top. Cross-bedding is widespread, and there are rare interbeds of concretionary limestone. The unit is interpreted as a series of storm surge deposits.
Note that the Applethwaite Member was previously assigned to the Coniston Limestone Formation, a unit that is now redundant and does not equate to the Kirkley Bank Formation.
To about 60m
Overlain by uniform, bioturbated calcareous siltstone of the Torver Member. The top of the Applethwaite Member is taken as the top of the highest graded unit, which is transitional into the overlying and more homogeneous siltstone.
Ailnack Phyllite And Limestone Formation
APAL
At upper limit of quartzite of the Corryhabbie Quartzite Formation and at lowest occurrence of white limestone or semipelite.
Extends from Muckle Allt Venney (Glen Markie) southwest to Glenfiddich, Upper Glenlivet and Glen Suie to the Kylnadrochit-Fodderletter area (Strathavon), Water of Ailnack section and Glen Avon (Burn of Little Fergie to Foal's Crag) and Glen Builg. Southern limit - Loch Builg.
Semipelites with subsidiary psammites, generally phyllitic, more calcareous in its upper part. Distinctive white limestone bands typically. Also grey finely crystalline limestones and calc-silicate bands. In Glenlivet-Glen Suie area divided into three members.
Rapid gradation from calcareous semipelite and limestone to graphitic pelite/semipelite of Clashnoir Semipelite Formation.
Appin Group And Argyll Group (Undifferentiated)
APAR
Ardnamurchan Point Gabbro Ring Intrusion
APGB
Appletree Limestone
APL
Was formerly considered "S2" (Holkerian).
Area around Brampton, Cumbria.
Coral-rich limestone.
c.3.7m
Appin Limestone Member
APLI
Anthracoceras Paucilobum Marine Band
APMB
Aber Pensidian Mudstone Member
APMU
Conformable with the sandstones of the Dinas Island Formation.
Dark grey interbedded turbiditic and laminated hemipelagic mudstones.
Assapol Group
APOL
Appin Group
APP
Generally rapid transition from monotonous psammite, generally flaggy, with thin quartzite and semipelite units of underlying Grampian Group, to better sorted psammite or quartzite and semipelite or pelite.
Connemara; North Mayo; Donegal west of Main Donegal Granite; Lismore to Glen Spean; Kinlochlaggan; Kinloch Rannoch via Glen Shee to Braemar; Glen Livet; Dufftown to Banffshire coast (Findlater Castle to Portsoy). The Appin Group is also roughly equivalent to the Scatsta Division of Shetland.
Alternating units of psammite to quartzite and semipelite to pelite in Lochaber Subgroup. In the Ballachulish and Blair Atholl Subgroups, pelitic and calcareous lithologies dominate, although one clean-washed, locally pebbly quartzite in the Ballachulish Subgroup is persistent from Donegal to Banffshire. Many of the pelitic and calcareous rocks are graphitic.
Typically 4km where untectonised, but thinned sequence (1km or less) occurs over structural highs.
Transition from graphitic semipelite and limestone to psammite and quartzite with rare semipelite, or locally to diamictite.
Applecross Subswarm
APPC
Appleton Ell Coal
APPE
Proterozoic To Palaeozoic Rocks (Undifferentiated)
APRZ
Appleby Group, Stewartry Group And Permian Sedimentary Rocks (Undifferentiated)
APS
Assynt Porphyritic Trachyte Swarm
APT
Appin Transition Formation
APTR
Appleby Group
APY
Strongly unconformable mainly on a range of Carboniferous strata, locally on older formations.
Extends from northern part of Solway Basin in the north to northeast part of Cheshire Basin in the south and at least as far west as the Isle of Man and the eastern Irish Sea (Jackson and others, 1987).
Red, aeolian cross-bedded millet-seed sandstone, fluviatile sandstone and breccias ('Brockram') interbedded in varying proportions. In the Collyhurst Sandstone and correlatives grey, white and pale brown colours are also common and breccias are rare. Some interbedded red mudstones are present locally. NOTE: Group includes Penrith Sandstone, Brockram, Rougholme Point Conglomerate, Collyhurst Sandstone, Lockarbriggs Sandstone Formation and Dowell Breccia Formation.
Typically shows large variations over short distances.
Taken at point in sequence where sandstone becomes subordinate to mudstones, siltstones, carbonates and evaporites of the overlying Cumbrian Coast Group (St Bees Evaporites or Manchester Marls formations).
Aqueduct Coal (North Wales)
AQC
Ackworth Rock
Arun Terrace Deposits, 1 Member
AR1
Devensian: OIS 2-4.
Unconformably overlies Lower Cretaceous bedrock.
Valley of the River Arun, Haslemere, Horsham, Chichester district, Sussex.
Sand, sandy gravel, and gravel, locally clayey. Gravel component is predominantly subangular flint with subordinate debris of chert, polished quartz grains, and larger fragments of pebbly ferruginous sandstone derived from Lower Cretaceous sequences to the north.
Generally to 4m, but locally up to 10m
Ground surface.
Arun Terrace Deposits, 2 Member
AR2
Generally up to 4m, but locally up to 10m.
Arun Terrace Deposits, Facet 2a
AR2A
Valley of the Arun River, Haslemere, Horsham, Chichester district, Sussex.
Normally up to 4m, but locally up to 10m.
Arun Terrace Deposits, Facet 2b
AR2B
River Terrace Deposits, 2 To 3 (Arun)
AR2T3
Arun Terrace Deposits, 3 Member
AR3
Wolstonian: IOS 6-8.
Valley of the River Arun, Sussex.
Sand, sandy gravel, and gravel, locally clayey. Gravel component is prediminantly subangular flint with subordinate debris of chert, polished quartz grain, and larger fragments of pebbly ferruginous sandstone derived from Lower Cretaceous sequences to the north.
River Terrace Deposits, 3 To 4 (Arun)
AR3T4
Arun Terrace Deposits, 4 Member
AR4
Anglian: OIS 12.
River Terrace Deposits, 4 To 5 (Arun)
AR4T5
Arun Terrace Deposits, 5 Member
AR5
Anglian or older Pleistocene: OIS 12-14?
Sand, sandy gravel, and gravel, locally clayey. Gravel component is predominantly subangular flint with subordinate debris of chert, polished quartz grains, and larger fragments of pebbly ferruginous sandstone derived from Lower Cretaceous sequences in the north.
Arun Terrace Deposits, 6 Member
AR6
Valley of River Arun, Haslemere, Horsham, Chichester district, Sussex.
Arun Terrace Deposits, 7 Member
AR7
Sand, sand gravel, and gravel, locally clayey. Gravel component is predominantly subangular flint with subordinate debris of chert, polished quartz grains, and larger fragments of pebbly ferruginous sandstone derived from Lower Cretaceous sequences to the north.
Amman Rider Coal, Seven-Feet Coal And Yard Coal (Undifferentiated) (South Wales)
AR7FY
Armadale Ball Coal (Central Coalfield)
ARB
Aran Boulder Bed Member
ARBB
Taken at the conformable, diachronous upward passage from volcaniclastic sandstones of the Allt Lwyd Formation into conglomerate. East of the Harlech district it oversteps the lower part of the Allt Lwyd Formation to rest on strata of the Mawddach Group. The boulder bed passes distally into altered feldspathic sandstones.
Harlech and Bala districts.
Coarse, massive to graded volcaniclastic conglomerates and breccias comprising pebbles, cobbles and boulders predominantly of intermediate feldspar-phyric lava.
0 to 300m
Taken at the top of the Allt Lwyd Formation, where it is overlain by extrusive volcanic rocks and volcaniclastic sediments of the Benglog or Offrwm Volcanic formations. The boundary may be conformable or disconformable, represented by a condensed sequence within the Allt Lwyd Formation.
Armadale Ball Fireclay
ARBF
Arbikie Diamicton Member
ARBI
Probably Devensian.
Overlies sand, reddish-brown, pebbly and compact or unconformably overlies bedrock.
Valley of the Gighty Burn, lying north of Arbikie NO 6610 5085 and south of Mountboy NO 6650 5300.
Diamict of red-brown silty, clayey, stoney sand with distictive colour-mottled patches of sand that are intensely weathered lithic clasts that appear dark green, yellow, white, orange in colour. Also partly weathered lithic clasts and unweathered clasts that are matrix-supported in the sand matrix. Unweathered clasts are angular to rounded and lithologies include schist, quartz, white coarse-grained sandstone, red medium-grained sandstone, mafic rock, red-brown sandstone and purple sandstone.
0.32m to 1.3m
Overlain by diamict of the Mill of Forest Till without the distinctive colour-mottled weathered clasts, or unconformably overlain by recent deposits of alluvium or soil.
Middle Ardwell Beds [Obsolete Name And Code: Use Ard]
ARBM
Arbriachan Intrusion
ARBR
Anstruther Formation
ARBS
Not known at outcrop; would be taken at the lithological change from the sandstone dominated sequences of the underlying Fife Ness Formation into relatively mudstone/siltstone-rich cyclical deposits.
East Fife.
Mudstone, siltstone and sandstone in thin cycles with thin beds of limestone, dolomite and coal. Predominantly non-marine origin.
Maximum thickness exceeds 810m in east Fife
The conformable top of the Formation lies in a transitional sequence to the Pittenweem Formation and is taken at the base of the Cuniger Rock Marine Band.
Archerbeck Coal (Canonbie)
ARC
Argyll Carbonate Member
ARCA
Archiestown Pluton
ARCH
Amman Rider Coal (South Wales)
ARCO
Armadale Coxrod Coal
ARCX
Ardwell Farm Formation
ARD
Rests conformably on Balclatchie Formation.
Girvan district, southwest Scotland.
Flaggy wacke.
Underlies the Whitehouse Subgroup (not seen, faulted out).
Ardnamurchan Centre 1
ARD1
Ardnamurchan Centre 2
ARD2
Ardnamurchan Centre 3
ARD3
Ardtun Beds
ARDB
Ardmore Conglomerate Member
ARDC
Ardmore Grit Member
ARDG
Ardmore Formation
ARDM
Ardnamurchan Dyke-Swarm
ARDN
Ardnamurchan Central Complex
ARDNA
Ardara Pluton
ARDP
K - Ar 392-414 Ma (Pitcher and Berger, 1972).
Ardara Pluton Phase 1
ARDP1
Ardara Pluton Phase 2
ARDP2
Ardara Pluton Phase 3
ARDP3
Rb-Sr whole rock 405 +/- 5 Ma (Halliday et al, 1980).
Ardair Semipelite Formation
ARDR
Transitional with underlying micaceous psammites of the Loch Laggan Psammite Formation.Marked by increase in semipelite and thin-banded micaceous psammite content.
South-western Monadhliath Highlands, Glen Roy - Glen Banchor, and Adverikie and Ben Alder Forest areas.
Interbedded schistose semipelite and micaceous psammite in roughly equal proportions
770m in type area.
Sharp to transitional with thinly bedded feldspathic and micaceous psammites of the Creag Meagaidh Psammite Formation
Ardersier Silts Formation
ARDS
Unseen; on lodgement till or bedrock.
Southern shores of the inner Moray Firth, between Inverness and Elgin.
Rhythmically-bedded sequence of silty clays, silts and silty sands, typically graded. Subordinate diamicton and gravel. Origin thought to be glaciomarine.
Gradational contact with Alturlie Gravels Formation above, or unconformable boundary with younger deposits.
Ardverikie Till Formation
ARDT
Unconformable on (1) Linn of Pattack Silt Formation, or (2) Pattack Till Formation, or (3) bedrock.
Whole of Sheet 63E and beyond.
Stony sandy clay diamicton with angular to subrounded clasts up to boulder size; a typical lodgement till. Locally overlying a unit of deformation till derived from the destruction of underlying Linn of Pattack Silt Formation.
<12m
Conformable with units of outwash sand and gravel, morainic deposits or peat, etc.
Ardvreck Group
ARDV
The lower boundary is placed where white or pale grey, granule- or pebble-grade quartz arenites/subarkoses of the Basal Quartzite Member (Eriboll Formation) rest unconformably on rocks of the Lewisian Complex or the Torridon Group.
The Ardvreck Group forms a narrow belt, extending along the northwestern side of Scotland from the Durness-Eriboll area, through Assynt, Dundonnell, Kinlochewe and Kishorn, to Skye.
The lowest unit of the group is the Basal Quartzite Member (Eriboll Formation), which is cross-bedded, fine- to medium-grained, quartz arenite, although locally the base reaches pebble grade. Compositionally, the basal part is also feldspar rich, up to subarkose in places, but the proportion and grain size decreases rapidly upwards. The unit is overlain by cross-bedded quartz arenites of the Pipe Rock Member (Eriboll Formation), which is a fine- to coarse-grained, quartz arenite with abundant Skolithos burrows at most levels. Localised staining by ferric iron oxide is present in the upper part of the Member, commonly differentially distributed between burrows and matrix. The Eriboll Formation is conformably overlain by dolomitic siltstones, with minor dolomitic grainstones and dolomitic sandstones, of the Fucoid Beds Member (An t-Sron Formation). The Fucoid Beds Member is in turn overlain by the Salterella Grit Member (An t-Sron Formation) which marks a return to cross-bedded quartz arenites containing Skolithos, but also containing abundant agglutinated shells of Salterella.
The upper boundary is placed where dolostones of the Ghrudaidh Formation (Durness Group), which may be locally sandy or muddy, lie conformably on the Salterella Grit Member (An t-Sron Formation) of the Ardvreck Group.
Ardley Member
ARDY
Generally sharp, erosive boundary, with sandy mudstone or sandy limestone ('Roach Bed') overlying Excavata Bed (peloidal packstone) at the top of the Shipton Member.
Stroud to Cirencester area of Gloucestershire where it passes south-westwards into the Athelstan Oolite Formation, northeastward through Oxon ando Buckinghamshire to the Brackley area, where it arbitarily passes north-east into the Blisworth Limestone Formation. Restricted to Sheets 217, 218, 219, [234]. 235, 236, 237.
A pale grey to off-white or yellowish limestone, peloidal wackestones and packstones with common ooidal and shell fragmental grainstones, particularly to the southwest of the type area, also recrystallised limestone with beds of argillaceous limestone, sandy limestone, marl and mudstone or clay at some levels.
From 6 m to 10 m thickness - generally increasing thickening to the southwest, and about 7m thick in the type section.
Sharp, eroded and commonly with a hardground top surface of pale grey to white wackestone of the Bladonensis Bed at the top of the Ardley Member, overlain by clay/mudstone marl/limestone of the Bladon Member or the Signet Member, else where these are absent, with a sharp, erosive boundary with cross-bedded shell-fragmental ooidal limestone, or mudstone of the Forest Marble Formation. In the northeast, it is believed to be overlain directly by the Blisworth Clay Formation.
Ardnandave Sandstone Formation
ARES
Rapid transition from interbedded semipelite and arenite (Ben Lui Schist Formation) upwards into quartzose arenites. Locally metalimestone (Loch Tay Limestone Formation) is present. Metadolerite sills also intruded along contact zone in type area.
Within sheet 38E as currently defined, fringing the Ben Ledi - Ben Vane - Ardnandave Hill massif above Loch Lubnaig and limited to the west side of the Loch Tay Fault.
Metasandstone; arenite, locally quartzose and microconglomerate, with minor semipelite abundant locally.
c.1000m maximum (estimated)
Incoming of chloritic, more matrix-rich greenish to green and commonly rusty weathering arenites and wackes (at the base of the Loch Katrine Volcaniclastic Formation).
Arcow Formation
ARF
Taken at the sharp base of thickly bedded calcareous siltstones overlying laminated siltstones of the Austwick Formation.
Restricted to the Craven inliers, North Yorkshire
Medium to pale grey mottled, dominantly calcareous, extensively bioturbated, thickly bedded, "unstriped" siltstone with thin siltstone laminations.
Generally about 10m; but locally up to 35m
Defined by the base of the overlying Horton Formation.
Arch Farm Sandstone Formation
ARFS
A sharp, conformable base of green to grey, fine- to medium-grained sandstone with Lingula, of the Arch Farm Sandstone Formation, above the brown to green-grey medium to coarse-grained sandstone and conglomerate of the Calke Abbey Sandstone Formation; seen as a prominent step on gamma-ray logs.
Present in the subsurface in the area of Hathern Shelf, Loughborough District [SK32].
Green to grey, fine- to medium-grained, laminated or cross laminated sandstone in beds up to 1.7m thick, with pebble-rich lenses and shelly lags with Lingula fragments and seams up to several centimetres thick, consisting of green mudstone and siltstone with Lingula. All lithologies are seen as rip-up clasts in the basal parts of the sandstone beds.The upper part of the formation comprises coarse-grained, calcareous sandstone, with pedogenic fabrics, and conglomerate.
Measured as 9 m thick in the Ticknall Borehole, as detailed in the reference stratotype information.
The top of a medium- to coarse-grained pebbly sandstone, overlain by green, slickensided, smectite-rich mudstone with about 4 mm ferruginous concretions of the Arch Farm Sandstone Formation, sharply overlain by pale grey to white calcareous sandstone of the Cloud Hill Dolostone Formation.
Argill Marine Band [Local Name: Use Lsmb]
ARGMB
Argyll Group
ARGY
Generally transitional over a few metres at base of tillite of Port Askaig (Schiehallion) Boulder Bed.
Scottish Highlands and Islands, and Northern Ireland: see entries for component subgroups.
See descriptions for; Islay Subgroup, Easdale Subgroup, Crinan Subgroup and Tayvallich Subgroup.
Up to 9km
Top of highest limestone bed in Loch Tay Limestone Formation where present; in Glen Clova and Glen Esk below unit with beds of strongly magnetic semipelite.
Abercorn Rough Coal (Glasgow)
ARHC
Argoed Limestone Member
ARL
Taken at the base of a bed of grey calcareous mudstone, overlain by thin- to medium-bedded, fine- to coarse-grained crinoidal skeletal packstones, that overlies the clay palaeosol capping the underlying Cefnyrhendy Oolite Member, or the top of the underlying palaeokarstic surface if the clay palaeosol is absent.
Northern Vale of Glamorgan [ST 00 74]. Passes southwards into the High Tor Limestone Formation.
Thin- to medium-bedded, fine- to coarse-grained crinoidal skeletal packstones with a bed of grey calcareous mudstone at the base. Dolmitized along the southeast crop of the South Wales Coalfield. Deposited in an offshore platform setting and representing the basal Holkerian transgression.
10m
Gradational boundary in which the top is taken at the first bed of ooidal grainstone of the Cornelly Oolite Formation above the crinoidal skeletal packstones of the Member.
Ardross Lingula Band
ARLB
Conformable.
Mudstone with Lingula.
1.22m in type section.
Arbigland Limestone Member
ARLM
Interbedded marine limestone, siltstone and mudstone with thick cross-bedded, bioturbated medium-grained sandstone.
> 300m
The Arbigland Limestone Member is stratigraphically the highest unit in the district.
Armadale Main Coal (Central Coalfield)
ARM
Armagh Group
ARMA
Arley Coal (South Lancashire)
ARMC
Arfon Group
ARN
Drawn at the base of welded ash-flow tuffs of the Padarn Tuff Formation (base not exposed). (Correlative of Padarn Tuff Formation = Bwlch Gwyn Felsite, Anglesey).
Anglesey and Gwynedd, Wales.
Welded, felsic ash-flow tuff, volcanogenic conglomeratic sandstone, fine-grained interlaminated tuffite and tuffaceous sediment.
The upper part is considered to be of Cambrian age, the lower part is Precambrian or Cambrian.
Almost 4000m - derived from geophysical evidence as base in not exposed.
Drawn at conformable upward passage from siltstone and sandstone of the Fachwen Formation (east of Aber-Dinlle Fault) or tuff and tuffite of the Bangor Formation (west of Aber-Dinlle Fault) to purple-red siltstone of the Llanberis Slates Formation.
Arnage Pluton
ARNA
Arenig Rocks (Undifferentiated)
ARNG
Abercorris Group
ARO
Drawn at the base of the Red Vein Formation where blue mudstones with orange weathering rest conformably upon mottled mudstones of the Abercwmeiddaw Group.
Exposed in the area around Corris and Aberllefenni,(Merionethshire).
Weathered dark blue blocky mudstone, well cleaved homogeneous blue mudstone (slate), dark blue micaceous mudstones often sandy or gritty, weathered to a dull bronze.
633 metres approx.
Drawn at the conformable upward passage of the Narrow Vein Formation where well cleaved slate passes into a dark blue micaceous sandy and gritty mudstone of the Garwedd-Wen Formation.
Arniston Parrot Coal (Lothian)
ARP
Ardnave Phyllite And Greywacke Formation
ARPG
Archaean And Proterozoic Rocks (Undifferentiated)
ARPR
Arnbath Psammite Formation
ARPS
Base faulted out in coast section; elsewhere rapid transition is inferred from graphitic semipelites and limestones of Fordyce Limestone Formation.
Coast section from Red Haven to 150m southeast of Foul Hole [NJ 563 663-579 666]; extends southwards as far as Newpark [NJ 530 606].
Medium- to thickly-bedded psammite and semipelite; coastal section contains a basal quartzite member; elsewhere locally contains units of 'boulder bed', a metadiamicton with sparse cobble clasts of granitic and metasedimentary rocks.
Increases from c.75m at Newton [542 619] to c.200m at coast, where it is partly repeated by a ductile thrust of the Keith Shear Zone.
Change from interbedded psammite and semipelite to thick-bedded quartzite.
Archaean Rocks (Undifferentiated)
ARRU
Ardingly Sandstone
ARS
Arley And Exhall Sandstones
ARSA
Armadale Slatyband Ironstone
ARSI
Armadale Splint Coal
ARSP
Aulrothie Sandstone Member
ARSS
Unconformable contact on metamorphic basement.
Pathside area (NJ3785 5500) north-eastwards to Braes of Enzie (NJ4000 5995).
Red coarse-grained sandstone with thin pebbly beds.
Approximately 70 metres - lensing.
At base of main conglomerate sequence in Spey Conglomerate Formation.
Armadale Stinking Coal
ARST
Armathwaite Dyke
ARTH
Arnhash Till Member
ARTI
Overlies the Blackhills Sand and Gravel Formation unconformably.
From Elgin to Fraserburgh. Not yet used on any 50k maps.
Reddish brown to brownish grey till or diamicton, deposited by local readvances of the Moray Ice Stream.
The present land surface.
Offshore Artificial Deposits Not Mapped [For Digital Map Use Only]
ARTOF
Aruisg Psammite Formation
ARU
Armadale Upper Ball Coal
ARUB
Armadale Upper Cannel Coal (Central Coalfield)
ARUC
Arun Formation
ARUN
Incises bedrock or older superficial deposits.
Valley of the Arun River, Haslesmere, Horsham, Chichester district, Sussex.
River terrace gravels, sands and associated organic sediments.
Average 4m, although may reach 8 to 10m in places.
At surface or overlain by younger deposits including alluvium and head.
Aryleive Limestone Bed
ARYL
Rests unconformably directly on Caledonian igneous or Precambrian Moine [basement] rocks as the basal unit of the Bighouse Formation on the Middle Old Red Sandstone unconformity. Locally interbedded with conglomerates of the Portskerra Conglomerate Member.
Onshore in the Dounreay area of Caithness, northern Scotland.
A thickly-bedded, pale grey, nodular limestone.
From 3.5m to 4.0m
Overlain by interbedded, sandstone-dominated rhythmic sequence of sandstones, siltstones and laminated carbonate mudstones (fish beds) of the Baligill Limestone Member of the Bighouse Formation. At the type section site, however, the unit is instead overlain directly by a thin bed of angular pebbly conglomerate.
Arden Sandstone Formation
Placed at a rapid upward transition from the red mudstones or siltstones of the Sidmouth Mudstone Formation to the dominantly grey or green, partly or largely arenaceous beds of the Arden Sandstone Formation. Conformable in all areas. At outcrop, the boundary is typically marked by a change from the reddish-brown clayey soils of the Sidmouth Mudstone Formation to the grey, slightly sandy clay soils of the overlying Arden Sandstone Formation. Where the latter forms a marked cuesta feature, the boundary typically lies at a slight concave break in the scarp slope.
The outcrop of the Formation is traceable nearly continuously from Gloucestershire northward through Worcestershire and eastwards through Warwickshire into Leicestershire and Nottinghamshire. Less continuous outcrop is mapped in Somerset and east Devon. At subcrop, the Formation is proved in several cored and geophysically logged boreholes in the subsurface in the Central Midlands (Worcester and Knowle basins), East Midlands , and in southern England (Wessex Basin). It is not recognised in the Cheshire Basin and other basins farther northwest, though thin sandstones in the upper part of the Wilkesley Halite (Poole and Whiteman, 1966), might represent the Formation in the Cheshire Basin. At depth in Dorset and Somerset the Formation passes laterally into halite (Gallois, 2001).
Heterolithic, consisting of grey, green and purple mudstones interbedded with paler grey-green to buff coloured siltstones and fine- to medium-grained, varicoloured green, brown, buff, mauve sandstones; beds of conglomerate occur locally. Laminated and thinly interbedded sediments are commonly extensively bioturbated and show structures indicative of thixotropic deformation. The siltstones and finer sandstones show small-scale ripple drift cross bedding; thicker sandstone beds show trough and planar cross bedding. The proportion of fine to coarse clastics varies laterally within the Formation. The thicker sandstone units, composed of several individual beds, have a lenticular geometry and occupy the inferred former courses of fluvial distributary channels in a deltaic or estuarine environment. Less arenaceous, mudstone and siltstone-dominated successions occupy intervening interdistributary areas. The Arden Sandstone Formation is differentiated from the reddish-brown, blocky weathering mudstones of adjacent formations by its predominantly greenish grey colour, the presence of a significant, though often subordinate, proportion of sandstone, and the predominance of finely laminated lithologies throughout.
Typically 7m to 8m in the Warwickshire area near the type section, with a maximum of 20m in the Stowell Park Borehole [SP01SE/1, SP 0835 1176, Green and Melville, 1956] and a minimum, regionally, of 2 to 3m.
Placed at the base of the predominantly red mudstones and siltstones of the Branscombe Mudstone Formation where they rest on the interbedded dark grey-green siltstones and pale grey sandstones of the underlying Arden Sandstone Formation; the boundary is abrupt or a rapid, interbedded transition. At outcrop, the boundary is typically marked by a change from the grey, slightly sandy clay soils of the Arden Sandstone Formation to the reddish-brown clayey soils of the Branscombe Mudstone Formation. Where the Arden Sandstone forms a marked cuesta feature, the boundary lies at the down-dip limit of the dip slope.
Asaphus Ash Formation
ASA
Data unavailable.
Silicified andesitic tuffs and agglomerates with interbedded mudstones and siltstones containing a rich shelly fauna, particularly trilobites
Aldeby Sand And Gravel Member
ASAG
Unconformable, most commonly overlies silt- and clay-rich chalky till (diamicton) of the Lowestoft Formation, but also locally overlies well-sorted sands and gravels of the Crag Group and Happisburgh Formation.
Restricted to the valley sides of the River Waveney and Hundred River to the west and south of Lowestoft.
The Aldeby Sand and Gravel Member is lithogically very variable; it is composed predominantly of sand and gravel that also contains lenses of reworked chalky till, discrete beds of clay and silt, reconstituted chalk and masses of sand transported and apparently derived from the Happisburgh Formation. The gravel fraction is composed predominantly of clasts of angular flint with some quartz and quartzite. In places beds of well-rounded flint and quartz gravel are present. The Member is thought to have formed during wastage of the Lowestoft ice from the adjacent higher ground.
Thicknesses are imprecisely known but 18m was exposed at Oaklands Pit, Aldeby and 4m at Aldeby Quarry, (see Stratotypes).
The Aldeby Sand and Gravel is overlain unconformably by variable Head deposits, and peat and silt of the Breydon Formation, and locally by river terrace sand and gravel of the Britannia Catchments Group. The overlying sand and gravel is typically better sorted and more well bedded.
Airth Shellband
ASB
Assel Conglomerate Member
ASC
Base of conglomerate, resting on flaggy sandstone.
Girvan area, southwest Scotland.
A localized thick conglomerate within the generally flaggy Ardwell Farm Formation.
To 70m
Taken at top of conglomerate, overlain by flaggy sandstone.
Ardscalpie Formation
ASCP
Early Cambrian to Early Ordovician.
Ashdown Formation
ASD
Ashover Grit
ASG
The base of the first main sandstone or sandstones above the Bilinguites Marine Band. If no Marine Bands are proved it is the base of the third (not all of the sandstones may be present) main sandstone or group of sandstones below the top of the Millstone Grit Group.
Derbyshire, Leicestershire, Nottinghamshire.
Massive or cross-bedded, medium to coarse grained, often pebbly and feldspathic sandstone.
Up to 213 m thick.
The top of the first main sandstone or sandstones below the Bilinguites Marine Band. If no Marine Bands are proved it is the top of the third (not all of the sandstones may be present) main sandstone or group of sandstones below the top of the Millstone Grit Group.
Ashover Grit (Main Bed)
ASGM
Acton Scott Formation
ASGP
Drawn at the base of the Acton Scott Formation where mudstone facies rest conformably on blocky and rubbly mudstones and siltstones of the Cheney Longville Flags.
Caradoc - Wrekin District, Shropshire.
Grey rubbly micaceous silty mudstones with siltstone bands, in places orange-stained and weathering shaly.
c.60m near Church Stretton to c.150m in the Caradoc (south) area.
Drawn at the conformable upward passage of the Acton Scott Formation where the division from the overlying Onny Shales has been based on palaeontological grounds because of difficulty differentiating.
Ashbourne Gravel
ASGR
Pronounced irregular unconformity on underlying, mainly Triassic bedrock.
Sporadic outcrops extend from a location 750m due west of Spitalhill, northwards to 800m SW of Sandybrook Hall (SK 173 456 to SK 175 476).
Coarse gravel, hard and with a calcite cement,with abundant pebbles and cobbles of more than 55% Carboniferous limestone, 8 - 29% Carboniferous sandstone and minor proportions of quartzite and quartz. Interbedded with cemented quartzose sand.
Variable, locally up to 2.8m
Locally overlain by till (Quaternary).
Ashton Great Coal (Bristol Area)
ASGT
Abbey Shale Formation
ASH
Not penetrated in the borehole. Base gradational with Purley Shale Formation in partial type section.
North-west suburbs of Nuneaton, extending north-westwards to the southern suburbs of Atherstone (SP3530 9180 - SP3063 9712).
Dark grey, greenish or blueish black mudstones with thin beds of limestone and glauconitic sandstone. Locally with phosphate, pyrite and siderite nodules.
10-40 m. 109 feet (33.2m) minimum in reference section.
A stratigraphical discontinuity. Upper dark phosphatic mudstone bed is sharply overlain by basal pebble conglomerate of Mancetter Formation.
Ashdown Beds (B) [Obsolete Code: Use Asd]
ASHB
The bracketed letter (B) after the name is a late-stage expedient, added to avoid potential problems related to holding identical entries in the database system.
Ashclough Coal (South Lancashire)
ASHC
Ashover Coal
ASHCO
Ashington High Main Coal (Northumberland)
ASHI
Ashgill Rocks (Undifferentiated)
ASHL
Ashington Coal (Northumberland)
ASHN
Ardtrea Sill
ASI
An Sithean Granite
ASIG
Askham Limestone Member
ASKL
Sharp base of limestone bed on the underlying Wintertarn Sandstone Member.
North Cumbria and Edenside, west of the Pennine-Dent Fault Zone.
Limestone, dark grey, well-bedded, wackestone and packstone, porcellanous in parts. Prominent layers with algal oncoliths and coral colonies. The member is split into 2 leaves by a thin layer of red-brown mudstone.
Taken at the base of overlying shelly marine mudstone within the Alston Formation Yoredale depositional cycle.
Acton Scott Limestone
ASL
c.25m
Aston Limestone Formation
ASLS
Discites Zone to Sauzei Zone.
Disconformity: upward change from ooidal and peloidal limestone (Scottsquar Member) or sand, mudstone and sandy limestone (Harford Member) into limestone as in lithological description. Generally marked by a hardground.
North and mid-Cotswolds: west of Northleach, Cold Aston and Blockley, and northeast of Stroud, Gloucestershire. Present locally outside this area to the south of Cold Aston, and absent between Birdlip and Cirencester ('Birdlip Anticline'). (Barron, A J M, et al, 1997, fig.4).
Grey and brown variously shelly, ooidal, sandy, shell-detrital and bioturbated limestones; rubbly in parts, with sandy and shell-detrital marl beds. Component members: Lower Trigonia Grit, Gryphite Grit, Notgrove, Rolling Bank.
Type section up to about 6.45m. Maximum c.22m (Cleeve Hill area).
Disconformity: hardground: limestone as in lithological description, overlain by Salperton Limestone Formation.
Ashton Little Coal (Bristol Area)
ASLT
Alteen Shale Member
ASM
Abercorn Steam Coal (Glasgow)
ASMC
Ascog Member
ASO
Seen where grey-white fine-grained calcareous sandstone of the Ascog Member is interbedded with grey mudstone and dolomitic limestone (cementstone) of the Ballagan Formation. The boundary is picked where beds of dolomitic limestone (cementstone) are absent and sandstone becomes the dominant lithology.
Isle of Bute in Strathclyde, Scotland.
Red brown siltstone and sandstone with pedogenic limestone.
86m
Seen as a sharp change at the probably erosional base of the overlying Birgidale Formation, which comprises mudstone, sandstone, seatrock and coal.
An Socach Quartzite Formation
ASQ
An T-Sron Formation
ASR
Conformably overlies the Pipe Rock Member of the Eriboll Formation.
The An t-Sron Formation forms a narrow, discontinous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt, Dundonnell, Kinlochewe and Kishorn, to Skye.
Consists of two distinctive members: dolomitic brown-coloured siltstone, mudstone and sandstone (of the Fucoid Beds Member, and white quartzite and quartz arenite of the Salterella Grit Member.
From 20 to 50 m thick.
Conformably overlain by dark grey dolostones of the Ghrudaidh Formation of the Durness Group.
Avill Slates And Sandstones Member
ASS
Ashbank Sandstone Member
ASSM
The base of the lowest bed of sandstone in the Hatton Conglomerate Member in the vicinity of Ashbank House.
Blairgowrie area.
Predominantly a reddish-brown sandstone with thin beds of pebbly sandstone and conglomerate.
150 m thick.
The base of the lowest bed of conglomerate, overlying bedded sandstones in the vicinity of Ashbank House.
Asta Spilitic Formation
ASSP
Aston Mudstone Formation
AST
Upwards change in lithology for grey well-bedded (shaly) mudstone to grey thickly bedded (blocky) mudstone.
Grey thickly bedded (blocky) mudstone, commonly bioturbated.
c.100m (lateral variations from about 100 - 275m).
See Bishopsmoat Beds, Lower.
Astarte Bed
ASTA
Abercorn Splint Coal (Glasgow)
ASTC
Assynt Till Formation
ASTI
Patchy, discontinuous extent across Wester Ross and western Sutherland, west of the main Highland watershed.The Assynt Till Formation is composed of the following geographically distinct, mappable, members: Unapool Till Member, predominantly overlying Lewisian gneiss; Loch Lurgain Till Member, predominantly overlying Torridon Group sandstone; Allt Sgiathaig Till Member, predominantly overlying Eriboll Formation sandstone (quartzite); Traligill Till Member, predominantly overlying Durness Group limestone; and Allt an t-Strathain Till Member, predominantly overlying Moine Supergroup psammite.
Heterogeneous orange-brown to dark grey diamicton with wide ranging sedimentological properties, containing a diverse suite of clast lithologies including Lewisian gneiss, Torridon Group sandstone, Eriboll Formation sandstone (quartzite), Moine Supergroup psammite, Durness Group limestone, Canisp porphy, Borralan syenite and other minor igneous rocks. Orange-brown to dark grey poorly sorted diamicton ranging in texture from poorly consolidated, immature, stony till to over-consolidated, silt-rich, lodgement till. The till is typically autochthonous, being largely derived from the underlying bedrock, however it may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older.
Variable, ranges from 0.5-78m (maximum observed thickness).
Overlain locally by Holocene (Flandrian) deposits, typically peat or (glacio)fluvial gravel.
Astell Coal (South Wales)
ASTL
Aston Coal (Oxfordshire)
ASTN
Ashton Top Coal (Bristol Area)
ASTP
Ardalanish Striped Formation
ASTR
Arthur's Seat Volcanic Formation
ASV
Base of volcanic rocks on sedimentary rocks of Inverclyde Group (Ballagan Formation).
Mainly conjectural; thins in all directions.
The predominant rock types are basaltic lavas and tuffs and mugearite lavas; subordinate interbedded sedimentary rocks also occur.
c.300m
Top of volcanic rocks below sedimentary rocks of Gullane Formation.
Asfordby Volcanic Formation
ASVO
Allesley Member
ASY
Taken at the junction between the highest sandstone package in the Keresley Member (Corley Sandstone) and the overlying mudstone unit.
Warwickshire Coalfield (Sheet 169). Also likely to extend in the subcrop across the southern part of the Coalfield (Sheet 184).
Redbed sequence; mudstone-dominated at base but becoming more arenaceous towards top. Impersistent conglomerates at some levels.
c.140m
Defined at the incoming of mudstones of the essentially argillaceous Tile Hill Mudstone Formation.
Abercorn Stony Coal (Glasgow)
ASYC
Acton Turville Beds
Locally developed north of Bath, from Biddestone to Didmarton.
An Tamhanachd Member And Beannan Buidhe Member (Undifferentiated)
ATBB
Allt-Tair-Ffynnon Formation
ATF
Ayr Twenty Fathom Coal
ATFC
Arbuthnott-Garvock Group
ATGK
Diachronous, rising to higher levels towards the southwest. In the type area it lies at the top of the highest lava of the Crawton Volcanic Formation, where this is overlain by clast-supported conglomerate. Elsewhere its base is taken to lie at the eroded top of the Lintrathen Tuff Member or its presumed correlatives (cf. Paterson and Harris, 1969). Where these horizons are absent, on Sheets 66E and 67, the base has been taken at the base of the lowest of the series of andesitic lavas that characterise the lower part of the Group in this area.
Northern Midland Valley of Scotland, Arran to Stonehaven.
Sandstone predominates, interbedded with clast-supported conglomerate with well-rounded boulders, cobbles and pebbles predominantly of lava, psammite and quartzite in the northeast and adjacent to the Highland Boundary Fault. Siltstone and mudstone are interbedded with the sandstone, e.g. in the Dundee area and Strathallan. Piles of andesitic, basaltic and rhyolitic lavas, locally very thick, are interbedded with conglomerate and sandstone in many areas. Lenses and thicker formations of volcaniclastic sandstone are interbedded with conglomerate in the Stonehaven area and are associated with lavas elsewhere. Calcrete near top in many areas.
Variable; 2400 to 3150m in the Stonehaven area. The sedimentary rocks thin to the southwest, but in the Stirling area the Ochil Volcanic Formation alone reaches 2400m.
At the base of bright red, massive poorly sorted siltstone and sandy siltstone of the Cromlix Mudstone Formation, overlying coarser-grained sandstone or conglomerate of the Arbuthnott-Garvock Group. Locally diachronous in areas adjacent to the Highland Boundary Fault where conglomerate interfingers with the Cromlix Mudstone Formation.
Arbuthnott-Garvock Group And Strathmore Group (Undifferentiated)
ATGKS
Athelstaneford Sill
ATHFD
Atlantean Supersuite
ATLAN
Ayr Thirty Six Fathom Coal
ATS
Ayr Twenty Three Fathom Coal
ATTF
Athais Till Formation
ATTI
Sharp, undulating or planar, glacitectonic, unconformable contact with white, sandy, organic deposits of the Dalcharn Palaeosol Formation, compressed peat of the Allt Odhar Peat Formation, or bedrock.
Sheet 84W (Fortrose), SE of Inverness.
Stoney clayey sand diamicton, matrix-supported, moderate brown to yellowish brown, extremely compact, containing clasts of Devonian sandstone and siltstone, with some psammite, granite and schist. Many clasts are weathered, with orange weathering rinds. Mainly massive lodgement till, but contains lenses of stratified gravelly sandy diamicton and bedded sandy gravel. Locally includes a bed of glacitectonite at the base (Allt Odhar site).
Either a gradational contact with dark yellowish brown to olive grey stony sandy clay diamicton of the overlying Beinn an Uain Till Formation or a sharp, glacitectonic, boundary with some wedge structures filled by that till.
Ancestral Thames River Terrace Deposits (Undifferentiated)
ATTU
Abercorn Turf Coal (Glasgow)
ATUC
Appletree-Worth Sandstone
ATW
Austwick Formation And Arcow Formation (Undifferentiated)
AUAR
Auchensoul Bridge Mudstone Formation
AUB
Conformably overlies Kirkland Conglomerate.
Reddish-grey and greenish-grey silty calcareous mudstones.
30 metres.
Conformably overlain by Stinchar Limestone, lateral equivalent of Auchensoul Limestone and perhaps Confinis Flags.
Auchtitench Sandstone Formation
AUC
The base of the substantial thickness in excess of 30m of volcanogenic sandstones and conglomerates above the andesitic volcanic pile of the Duneaton Volcanic Formation seen in Duneaton Water in the New Cumnock area, and above the Biggar Formation in the Biggar area.
Ayrshire and Lanarkshire, and between the Ayrshire Coalfield and the Pentland Hills.
Yellow to red-brown, medium- and coarse-grained, poorly-sorted volcaniclastic sandstones with pebble beds and substantial interbeds of andesitic lava pebble conglomerates, and thin fine-grained sandstone, siltstone, mudstone and andesitic and basaltic lava beds.
Estimated to be up to at least 1800 m thick along the Duneaton Water, where the youngest beds lie in the core of a syncline.
The unconformity with the overlying Upper Devonian-Carboniferous strata, exposed in the burn north of Clocklowie Hill at NS 696 179, below a cornstone bed.
Auchinlea Sandstone
AUCH
Auchnahillin Monzonite
AUCHN
Auchencrow Burn Sandstone Formation
AUCR
The top of the Eyemouth Volcanic Formation.
The Eyemouth area, along the Eye valley between Ayton and Reston.
Reddish brown coarse-grained to pebbly sandstones with intercalated tuffs, siltstones and mudstones, local conglomerates and one thin cornstone.
At least 430 m and probably up to 1400 m thick.
The unconformity with the overlying Devono-Carboniferous conglomerates.
Auchenheath Dross Coal
AUDR
Austwick Formation
AUF
Taken at the base of carbonaceous siltstones that are overlain by turbiditic sandstones. Oversteps Crummack Formation and Ashgill strata to overlie the Ingleton Group.
Parallel bedded turbiditic sandstones separated by laminated siltstone. Laminated argillaceous siltstone up to 80m thick at base contain an abundant graptolite fauna indicative of the Sheinwoodian Stage of the Wenlock.
Up to 600m
Defined by the base of the overlying Arcow Formation.
Auch Gleann Psammite Formation
AUGL
Neoproterozoic (Cryogenian).
Includes all of the Grampian Group psammite rocks which extend across the northern parts of 1:50k sheets 46W (Crianlarich) and 46E (Killin).
Interbedded pink quartzofeldspathic psammite and grey micaceous grey psammite. Parallel bedded psammite layers 10-20cm thick develop plane parallel internal lamination defined by alternations of more micaceous and quartzofeldspathic layers at a mm scale. Similar scale but undulose bedded forms also present with rare preservation of hummocky cross stratification. Subsidiary 50-100cm-thick massive beds may have a lenticular form and may be indicative of channel or sand-wave macroforms. Semipelite to pelite comprises a very minor part of the Formation but forms in layers up to 15m thick.
>1000m.
Abrupt change to white weathering pinkish-brown quartzose psammite and quartzite of the succeeding Beinn a' Chaisteil Formation.
Auk Formation
AUK
Auchensoul Limestone Formation
AUL
Rests conformably on Kirkland Conglomerate.
Stinchar Valley area, Girvan. Laterally equivalent to Auchensoul Bridge Mudstone.
Impure sandy algal limestone.
Conformably overlain and laterally transitional into Auchensoul Bridge Mudstone Formation (Ince, 1984).
Auchencar Lava Member
AULA
The top of the Auchencar Burn Sandstone Member.
The base of the Creag Mhor Conglomerate Member, or sandstone within the Auchencar Sandstone Formation.
Auldearn (Park) Pluton
AULD
Auchlyne Formation
AULY
Neoproterozoic (Ediacaran).
Upper limit of the calcareous semipelite (typically pale green, phengite, chlorite schist) of the Ben Lawers Schist Formation.
Occurs at the stratigraphical boundary between the Ben Lawers Schist Formation and Ben Lui Schist Formation. Formation outcrops in the area west and northwest of Killin, in and around upper Glen Lyon and Glen Lochay.
Psammite, micaceous psammite and garnetiferous semipelite, with minor calcsilicate, calcareous garnetiferous semipelite and garnet-hornblende schist, the latter of possible volcaniclastic origin. Psammite dominates in the upper part of the formation, semipelite dominates in the lower part. Locally, muscovite-chlorite-talc schist with included fragments of carbonate, psammite and siliceous semipelite comprises a distinctive unit with a melange-like appearance within the Formation (Pubil Melange Member).
Transitional change upwards to schistose muscovite-biotite-garnet semipelite of the Ben Lui Schist Formation.
Auldshields Musselband (Central Coalfield)
AUM
Might be split into the Auldshields Upper Blackband (Musselband) Ironstone and the Auldshields Lower Blackband Ironstone.
Auchnahyle Formation
AUNH
Aurora Formation
AUR
Auchencar Sandstone Formation
AUSA
Machrie to Glen Rosa, Arran.
Red lithic sandstones, quartzite conglomerates and lava pebble conglomerates common towards the top of the succession, withnd one grey pyroxene andesite lava intercalation.
About 450 - 500 m thick.
The sandstone of the Auchencar Sandstone Formation, and the top of the Creag Mhor Conglomerate Member are overlain by the base of the Machrie Burn and Allt an Brighide Siltstones of the Am Binnein Sandstone Formation.
Auchenheath Smithy Coal
AUSM
Arundel Sponge Beds
AUSP
Auldthorns Formation
AUT
Conformably overlies the Shalloch Formation.
Coarse-grained greenish sandstones.
36m
Conformably overlain by the Quarrel Hill Formation.
Auchenheath Wee Gas Coal
AUWG
Airdrie Virtuewell Coal (Central Coalfield)
Avonmouth No.1 Coal
AV1
Avonmouth No.2 Coal
AV2
Appletreeworth Volcanic Formation
AVF
Base of rhyolitic tuff, overlying limestone of the Broughton Moor Formation or, where absent, the Kirkley Bank Formation.
Windermere to Broughton Mills, Cumbria.
Rhyolitic tuff within a succession of calcareous siltstones and impure limestones.
0 to 5m
Defined by base of overlying calcareous siltstones/impure limestones.
Aran Volcanic Group
AVG
Overlies the Mawddach and Rhobell Volcanic groups, with unconformity in places. The base is drawn at the base of the quartzose sandstones of the Garth Grit Member (Allt Llwyd Formation), where it rests unconformably upon bedded felsic rocks of the Rhobell Volcanic Group.
The surrounding area of Harlech known as the Harlech Dome, which includes most of the Snowdonia National Park.
A mixed suite of basalts, rhyolites volcaniclastic and sedimentary rocks.
Up to 2.5km in the Cadair Idris district.
Drawn at the conformable upward passage of the Craig Cau Formation (Cadair Idris District) into turbiditic mudstones and siltstones o the Ceiswyn Formation. The top of the group is not seen in the Harlech district, where the highest formation represented is the Aran Fawddwy Formation, comprising felsic ash-flow tuffs.
Aveline's Hole Limestone
AVHL
Anvil Limestone
AVL
Around East Kilbride, "Lanarkshire". Correlated with Second Hosie and First Kingshaw limestones elsewhere.
Avoniel Limestone
AVLI
Avoch Sandstone Member
AVM
Conformable lower contact on Kilmuir Conglomerate Formation.
100m, lensing.
Conformable upper contact with Drumderfit Conglomerate Member.
Avon Group
AVO
Conformable in southern settings, where it is taken at the sharp to gradational incoming of grey calcite mudstones, mudstones and limestones of the Group, above the red sandstones, siltstones and mudstones of the Upper Old Red Sandstone [Quartz Conglomerate Group, Tintern Sandstone Formation and Portishead Formation]. Boundary sharp in the Vale of Glamorgan and southeast crop of the South Wales Coalfield, where it is taken at the base of the Tongwynlais Formation. Elsewhere, boundary reported to be gradational at base of Shirehampton Formation or Avon Group undivided. Such boundaries are in urgent need of revision, especially that in South Pembrokeshire, where the uppermost part of the Skrinkle Sandstones is of similar facies to the Shirehampton Formation. In the Newport area of South Wales and the Bristol district the lower part of the Avon Group this has mistakenly been included in the Upper Old Red Sandstone formations on BGS maps. Disconformable along the north crop of the South Wales Coalfield, and Monmouth and Chepstow area where it is taken at the sharp erosive base of the transgressive skeletal and ooidal grainstones [Castell Coch Limestone Formation] of the group above the sandstones of the underlying Quartz Conglomerate Group, Tintern Sandstone Formation, Plateau Beds Formation, Grey Grits Formation and Brownstones Formation.
South Wales [SS 90 95], Monmouth and Chepstow [ST 53 94], Bristol [ST 60 74], the Mendip Hills [ST 50 53] and Clee Hill [Shropshire] [SO 60 74] areas. Passes southwards into the Pilton Shales Formation of North Somerset [ST 00 20].
Interbedded grey mudstones and thin- to medium-bedded skeletal packstones with one to several thick units of ooidal and skeletal grainstones. Thin units of calcite mudstone and mudstone locally present. Sparse thin ironstones. Represents mid to inner shelf/ramp deposits with coeval barrier, back barrier and coastal plain sediments.
156m in the south Mendip Hills, thinning northwards to 96m in the Bristol area, 54m in the Monmouth area. 140m in the southern Vale of Glamorgan, thinning northwards to 10m on the northwest crop [Ammanford area] of the South Wales Coalfield.
Gradational in southern settings, and taken at the incoming of stacked dark grey fine to coarse skeletal packstones with scattered mudstone partings [Barry Harbour Limestone Formation] of the Black Rock Limestone Subgroup above the interbedded mudstones and skeletal packstones [Cwmyniscoy Mudstone Formation] of the Avon Group. Boundary taken at the top of the last significant bed of grey mudstone. Along the eastern part of the north crop of the South Wales Coalfield, taken at the gradational incoming of the stacked dolomitised skeletal packstones [Sychnant Dolomite Formation] of the Clydach Valley Subgroup above the interbedded mudstones and skeletal packstones of the Avon Group. Along the remainder of the crop, the Group is overlain unconformably by the Dowlais Limestone Formation.
Assynt Vogesite Swarm
AVOG
Warwickshire Avon Valley Formation
AVON
Mid Pleistocene to Holocene (MI Stages ?11 or 9 to 1).
Unconformable, commonly channelled base on pre-Quaternary (mostly Triassic and Jurassic with some Carboniferous) bedrock, or on glacial deposits (till, sands and gravels) of the Wolston Formation, or pre-glacial fluvial sands and gravels of the Baginton Formation.
Avon Catchment (Warwickshire, Rugby to Tewkesbury area).
Fluvial terrace and alluvial deposits of the Warwickshire River Avon and all its tributaries; mainly sand, gravel, and mud; divided into six [or seven] "terrace" members (Frog Hall, Pershore, [Strensham], Cropthorne, New Inn, Wasperton and Bretford members), Holocene alluvium (Elmore Member of Bowen, 1999) and with local named organic deposits. Includes contemporaneous head, colluvium and soil deposits. Gravels are principally composed of "Bunter" quartz/quartzite, flint and Jurassic (mostly Lias) lithologies, derived from the Baginton Formation, Wolston Formation and the local bedrock of the catchment.
(A) Renamed the Warwickshire Avon Valley Formation to avoid confusion with the Bristol Avon Valley Formation. Other possibilities might have been Warwick or Stratford or even Midland Avon, the last having been used in the titles of some papers. (B) It is impractical to give a fully comprehensive definition of the base in lithological terms.
0 to c. 9m
Auchivarie Psammite Formation
AVPS
Ashprington Volcanic Formation
AVS
Ashow Formation
Taken at the incoming of a thick succession of red mudstone (50 to 65m thick) above the Kenilworth Sandstone Formation.
Southern part of the Warwickshire Coalfield.
Red-brown mudstone with subordinate, but locally thick, beds of red-brown and grey-green, fine- to medium-grained sandstone.
Up to 250m in Sandy Lane and Barford boreholes.
Taken at the base of the unconformable Bromsgrove Sandstone Formation (Triassic) in the type area.
Loch Awe Group
AWE
Drawn at base of quartzite conglomerate of the Loch Awe Group where it rests unconformably on the Ardrishaig Phyllites.
Strathclyde, Scotland.
Dark grey, black or blue limestones, highly pebbly quartzites, pebbly or non-pebbly, black-grey slates, conglomerate and pillow lavas associated with slate and limestone.
At least 90 metres.
Drawn at unconformable upward change from schistose volcanic rocks of the Loch Awe Group to recent deposits.
Ardwell Subgroup
AWL
Coincides with lower boundary of the Balclatchie Formation (on coastal outcrops) and lower boundary of the Craighead Limestone Formation (in the Craighead Inlier).
Sandstone, siltstone, mudstone, limestone and conglomerate; highly fossiliferous in places (shelly faunas).
To c.1600m
Coincides with upper boundary of the Ardwell Farm Formation.
Andrew Sandstone Unit
AWSA
Auchenwinsey Till Member
AWTI
Sharp, convex-up, undulose unconformity with underlying pinkish brown, very stiff, pebbly sandy silty shelly clay diamicton of the Eglinton Shell Till Member, or with dark grey stony diamicton of the Littlestone Till Formation, or bedrock.
West central Scotland.
Silty sandy stony clay diamicton ("lodgement till"), very stiff, dark grey, containing clasts of mainly local Westphalian lithogies (sandstone, mudstone, limestone and coal), with dolerite and local mafic igneous rocks. Forming drumlins.
Land surface or overlain by various younger Superficial units such as alluvium.
Mesoproterozoic Rocks (Undifferentiated)
AXRU
Aylesbeare Mudstone Group
AYB
Where undivided the Aylesbeare Mudstone rests on red-brown sandstone of the Dawlish Sandstone, possibly unconformably. See Clyst St Lawrence Formation and Exmouth Mudstone and Sandstone Formation for definition of base where those formations are present.
Extends from south Devon coast between Exmouth and Budleigh Salterton in a north-south trending belt to area west of the Quantocks (Sheet 295).
The undivided Aylesbeare Mudstone Group consists of reddish-brown silty mudstone and clayey siltstone; clayey fine-grained sandstone occurs locally, and less commonly, clean, fine- to medium-grained sandstone.
530m on south coast (Selwood, et al, 1984); about 400m in Exeter district.
Overlain sharply by the Budleigh Salterton Pebble Beds.
Allesley Sandstones And Conglomerates
AYC
Astbury Limestone Member
AYLM
Astbury Formation
AYLS
The base of the formation is taken at the conformable base of the mudstone-rich succession with subordinate limestone above the limestone-dominated succession of the Bowsey Wood Formation.
The formation occurs above the northern part of the Market Drayton Horst. The formation is limited in outcrop to a small inlier, about 1km long and 300m wide, at Limekiln Farm, Astbury [SJ 86 59].
Comprises mudstones, interbedded with limestones, sandstones and tuffs and subordinate coals and seatearths. At the type locality the basal 43 m of the formation is dominated by grey or brown calcareous mudstone with several thin beds of impure grey or dark grey limestone and in the upper part thin beds of yellow-brown tuff and tuffaceous limestone and mudstone. Above this, a 52 m thick succession comprises brown mudstone and calcareous mudstone and includes at least three coals and a 21 m thick succession of white or pale yellow coarse-grained and feldspathic sandstones with thin interbeds of siltstone or mudstone, informally referred to as the Astbury Sandstone.
Up to 100 m thick.
The top of the formation is taken at the top of the mudstone-dominated succession with subordinate limestones and sandstones, overlain conformably by the dark grey mudstone of the Bowland Shale Formation.
Ayre Formation
AYRE
Possibly temperate OIS 5, 7 or 9 (between Saalian and Early Devensian).
Overlies sand, gravel and diamicton of the Ayre Lighthouse Formation.
Northern part of the Isle of Man (50k sheets 36 and possibly 46).
Shelly silts and sands with a marine fauna (known only from boreholes).
8m at its type section.
Base of sand and gravel of the overlying Kiondroughad Formation.
Ayre Lighthouse Formation
AYRL
Possibly cold OIS 8, 10 or 12 (between Anglian and Wolstonian).
Unconformably overlies Permo-Triassic bedrock.
Sand, gravel and diamicton of northern origin that rests on Permo-Triassic bedrock (known only from boreholes).
c.70m at its type section.
Base of the shelly silts and sands of the overlying Ayre Formation.
Aylesbury Sand
AYS
Astbury Sandstone Member
AYSA
Aydon Shell Bed
AYSH
Neoproterozoic Rocks (Undifferentiated)
AZRU
Bottom First Waterloo Coal (Derby)
B1WC
Bottom Second Waterloo Coal (Derby)
B2WC
Bradford Threequarters Coal (South Lancashire)
B3QC
Bettws Four Feet Coal (South Wales)
B4FC
Burnley Four Foot Coal (Lancashire)
B4FT
Barton Group
Drawn at base of clay and flint pebbles of the Barton Clay where it rests conformably on grey-brown sand of the Selsey Sand.
Hampshire, England.
Yellow weathering, green-grey clay, with discrete fine-grained sand bands, yellow-pale grey weathering fine-grained sand, green-grey, sandy clay and clayey, silty fine-grained sand.
Approximately 175 metres.
Drawn at conformable upward passage from black clays of the Belton Sand to pale green clays of the Headon Formation.
Barracks Ash
BAA
The area around Barracks, Linlithgowshire.
Soft, fine-grained green feldspathic tuff, increasingly contaminated with epiclastic material northwards.
Beinn Airein-An Stac Member
BAAS
Badbea Breccio-Conglomerate Member
BAB
Barnstone Member And Barnby Member (Undifferentiated)
BABA
See the Lithology descriptions for the component members.
Barton Group, Bracklesham Group And Bagshot Formation (Undifferentiated)
BABB
See the Lithology descriptions for the component units.
Basal Beds Formation (Cumbria)
BABE
Unconformable base on Skiddaw Group or Eycott Volcanic Group rocks.
British Geological Sheets 22, 23.
Conglomerates with minor sandstones and mudstones.
Up to c.30m.
Overlain conformably by Dinantian sediments (Orton Group or Chief Limestone Group); locally by Cockermouth Lavas.
Basement Breccia (Shetland)
BABR
Basement Beds (Group)
BABS
Barton Clay Formation
BAC
Barncroft Beck Beds
BACB
Sharp between fossiliferous fissile clayey blue-grey mudstones with limestone nodules and thin sideritic lenses of Caton Shale below and siltstones with sandstones of the Barncroft Beck Beds above. Coincident with the base of the Claughton Member.
Variably interbedded sandy micaceous planty siltstones and fine-grained sandstones.
Approximately 85m
Base of coarse-grained Nottage Crag Grit above siltstones and fine-grained sandstones of the Barncroft Beck Beds.
Badenloch Pelite Member
BACH
Ponfeith Back Coal
BACK
Basal Clastics Member
BACL
Barras Conglomerate Member
BACO
A conformable and diachronous passage down and laterally south into the St. John's Knap Sandstone Member, delineated at the point where conglomerate becomes predominant upwards from the underlying formation.
Between Law of Lumgair (NO 8525 8180) and Chapel of Barras (NO 8355 7812).
A bimodal, clast-supported conglomerate with clasts mainly of lava, with psammite, quartzite, vein-quartz and feldspar porphyry in a coarse-grained lithic sandstone matrix.
From 100 m to 255 m thick.
Apparently conformable, probably diachronous, at the base of the lavas of the Montrose Volcanic Formation.
Bacton Group
BACT
Slightly unconformable, at an abrupt upward transition from the evaporites or dolomitic limestones of the upper part of the underlying Zechstein Group to the red or red-brown mudstones of the lower part of the Bacton Group.
Offshore UK, southern North Sea. Equivalent to the combined Roxby Formation and Sherwood Sandstone Group of onshore nomenclature, northeast England (Johnson et al., 1994).
Comprises a lower unit of red, red-brown and grey mudstones (Bunter Shale Formation), and an upper unit of red, orange and white dolomitic sandstones interbedded with red and grey mudstone (Bunter Sandstone Formation).
Up to 600m (Johnson et al., 1994).
Slightly unconformable, at abrupt upward change from sandstone of the Bacton Group to red-brown dolomitic mudstone with evaporites of the overlying Haisborough Group.
Basement Beds (Of Dudley)
BAD
Badanloch Granite Sheets
BADG
The sheets are subconcordant within the Moine metasedimentary rocks.
Caithness and Sutherland, Scotland.
A locally highly foliated sodic, plagioclase granite with biotite schlieren.
Variable.
The sheets are subconcordant within the Moine sedimentary rocks.
Bassenthwaite Diorite Intrusions
BADIN
In the outcrop area of the Skiddaw Group, mainly between Cockermouth and Keswick, Cumbria, and also in Black Combe, Cumbria.
A porphyritic, horneblende-diorite and microdiorite, dolerite and olivine-augite hornblendite. Radiometric age: 458 +/- 9 Ma (K-AR whole rock) (Rundle, 1979)
Plugs and sheet-like masses emplaced into the Skiddaw Group.
Baddoch Burn Limestone Member
BADL
Baddoch Quartzite Member
BADQ
Badsworth Rock
BADR
Badsworth Member
BADS
Base of First Cherry Tree Marker (mudstones with bivalves).
Mudstones, siltstones and sandstones. Grey beds with thin coals in lower part. Red beds above.
c.90m+
Not defined. (Highest preserved bed of Coal Measures beneath the sub-Permian Unconformity).
Ballyloughan Formation
BAF
Barmouth Formation
BAG
St David?s?
Conformable on siltstones and mudstones of the Hafotty Formation.
Harlech Dome.
Coarse grained turbiditic sandstone and subordinate mudstone.
Sharply and conformable overlain by silty mudstone of the Gamlan Formation.
Ballagh Limestone Member
BAGH
Sharp contact with dark grey limestones and shales of the Dartry Limestone Formation.
Exposed over 4km strike length in south County Fermanagh.
Massive bedded, pale grey to fawn, coarse crinoidal grainstone.
0 to 6m
Barony Glen Formation
BAGL
Courceyan (CM Biozone).
Concealed, but succeeds the Spincha Burn Conglomerate Formation from which it is distinguished by the absence of conglomerates and coarse-grained sandstones and the presence of palaeosols and calcrete horizons.
East side of the Dalradian Supergroup outcrop in the Sperrin Mountains and fringing the south side of Loch Foyle. Located west of the western edge of the basalt lavas of the Antrim Plateau.
Interbedded sandstone, siltstone, mudstone, calcrete, palaeosols, purplish brown, purplish red, grey, fawn, brown, green.
On 1:50 000 Sheet 18 the Barony Glen Formation is overlain unconformably by a succession of rocks including the Triassic Sherwood Sandstone and Mercia Mudstone groups, the Late Cretaceous Hibernian Greensand and Ulster White Limestone formations and the Palaeogene Lower Basalt Formation of the Antrim Lava Group.
Bayston-Oakswood Formation
BAGP
Late Neoproterozoic.
At the base of the Bayston - Oakswood Formation massive coarse purplish sandstone with small scattered pebbles rests unconformably upon purple and green shales and sandstones of the Portway Formation. The basal sanstone may reprent the dying out of the Haughmond Conglomerate, which forms the basal member of the Formation, overlying beds that might be equivalent to the Synalds Formation, in the Shrewsbury area.
Within the Church Stretton district: Long Mynd towards Shrewsbury.
Coarse-grained purple sandstones and grits with subordinate purple mudstones, siltstones and at least three beds of conglomerate.
Averages c.1800m.
Drawn at the conformable upward passage of massive sandstones of the Bayston - Oakswood Formation to more flaggy siltstones and laminated sandstones of the Bridges Formation.
Balnagown Group
BAGR
Drawn at base of yellow and red sandstones of the Balnagown Group where it rests unconformably on sandstone of the Strath Rory Group.
Highlands, Scotland.
Yellow and red, medium-grained, cross bedded sandstone of fluvial origin with scattered pebbles.
Not known.
Drawn at unconformable upward change from yellow and red sandstone of the Balnagown Group to probable Jurassic Strata.
Baron Hill Formation
BAH
Early Cambrian.
Unknown, however Greenly (1919) supposed that it overlay the Gwna Melange (now Gwna Group) of Anglesey, but there is some doubt about this, given the current uncertainties on the age of these divisions.
1:50,000 Geological Sheet 106 (Bangor). The formation represents part of the Arfon Group of the mainland that extends onto Sheet 105 Caernarfon.
Tuffaceous mudstones interbedded with massive, coarse-grained tuffaceous sandstones and conglomerates, containing clasts of felsic welded tuff, basalt and basaltic hyaloclastite.
At least 300 m thick.
Unknown; probably unconformably overlain by Ordovician strata along its southeastern crop.
Bail Hill Volcanic Group [Obsolete Code: Use Bail]
BAHL
Bailey Hill Formation
BAI
Presteigne - Knighton area, mid Wales.
Bail Hill Volcanic Group
BAIL
Rests on black mudstone, possiblythe the Glenkiln Shale Formation of the Moffat Shale Group.
Bail Hill area, Sanquhar, south Scotland. Includes Peat Rig Formation and Cat Cleugh Formation.
Lavas, pyroclastic rocks, etc, thought to be remains of a seamount volcano.
Bain Valley Formation
BAINV
Middle Pleistocene (Anglian) to Holocene (MI Stages 12 or 10 to 1).
Unconformable, commonly channelled base on Anglian glacial deposits or on pre-Quaternary bedrock.
Bain catchment, from headwaters near Doninton on Bain [TF 23 83] to confluence with River Witham near Tattershall [TF 21 59].
Fluvial terrace deposits of the River Bain. Mainly sand, gravel and mud; divided (in type area) into two principal "terrace" members (Thorpe and Castle) plus alluvium (Bain Member of Bowen, 1999), and an older (late Anglian) terrace (Martin/Tattershall Airfield of Bowen, 1999), plus local named organic deposits. Includes contemporaneous head, colluvium and soil deposits. Gravel dominated by flint and chalk pebbles, and other Jurassic/Cretaceous material derived mainly from glacial deposits of the Anglian Lowestoft Formation, plus an additional component of Upper Jurassic and Cretaceous material from the bedrock of the catchment.
0 to c. 8m
Bathgate Jewel Coal
BAJ
Banknock Shale Coal
BAKN
Banks Group
BAKS
Ballyshannon Limestone Formation
BAL
Lowest member of the formation, the Gortnaree Sandstone Member, conformably succeeds the Termon River Limestone Formation.
Northwest Carboniferous basin of Ireland.
Limestone, dark blue-grey, bioclastic, argillaceous packstones, interbedded with dark grey, silty shale; rarely with chert nodules in upper part; named members include sandstones.
120 - 450 metres.
Highest member of the formation, the Ederny Limestone Member, is overlain disconformably by the normal Bundoran Shale Formation or the sandstone basal member in the Kesh-Omagh area and southwest County Fermanagh.
Balbardie Blackband Ironstone
BALB
Ballyalicock Conglomerate Formation
BALC
Balchraggan Formation
BALCH
Balls Coal (South Wales)
BALCO
Balder Formation
BALD
Balfreish Microgranite
BALFH
Ballater Pluton
BALG
Ballaugh Formation
BALGH
Late Devensian (Lateglacial) to Holocene.
Generally alluvial fan gravels of the Ballaugh Formation unconformably overlie mixed sequence of the Orrisdale Formation [qv] (though some fan gravels interdigitate with deposits of the Orrisdale Formation). In other exposures the fan gravels overlie Lateglacial organic sediments of the Glen Balleira Formation.
Alluvial fan deposits.
Gravel-dominated sequences forming mountain front alluvial fans, commonly cryoturbated.
Unrecorded but diagrams suggest >20m thick locally.
Usually the ground surface.
Balleich Lava Member
BALH
A conformable contact with medium-grained sublithic sandstone of the Bofrishlie Burn Sandstone Member.
The north-west limb of Strathmore Syncline between Maol Ruadh and Balleich in Queen Elizabeth Forest Park.
A fine- to medium-grained, commonly vesicular and amygdaloidal olivine basalt.
Approximately 30 m thick.
Not seen, but quartz and quartzite conglomerate of the parent Craig of Monievreckie Conglomerate Formation, in close proximity above.
Balintober Intrusion
BALI
Ball Coal (Midlothian)
BALL
Ballysteen Formation
BALN
Balmakeith Till Member
BALT
Unconformable (commonly tectonised) contact on underlying pebbly sands of the Ardersier Silts Formation or unconformable on bedrock.
Outcrops in main late glacial cliff between Nairn and Kingsteps Quarry; farther eastwards on 1:50000 Sheet 84 E (Nairn).
Diamicton, firm, sandy and silty, moderate reddish-brown to "reddish-yellow" with abundant rounded clasts of red-brown Upper Devonian (Nairn Sandstone Formation) sandstone.
To 3.2m
Unconformable contact with overlying sands and silts of the Ardersier Silts Formation.
Ballencleuch Law Granite
BALW
Intrusive.
Thornhill area.
Granite sheet intruded into wackes of the Gala Group (Silurian).
Elongate sheet c.4.5km x 0.2km, orientated NE - SW.
Ballynahone Micrite Formation
BALY
Ballymartin Member
BAM
Bankhead Marine Band
BAMB
Bassey Mine Coal (Lancashire)
BAMC
Barrowmouth Mudstone Formation
BAMU
Blue Anchor Formation
BAN
?Norian to Rhaetian. The precise level of the Norian-Rhaetian boundary in the UK sequence is currently unknown. It could be in the upper Branscombe Formation or in the lower Blue Anchor Formation. The Arden Sandstone Formation is late Carnian, and the upper part of the Blue Anchor Formation is Rhaetian, but there are no dates at all for the whole of the Branscombe Formation or the lower part of the Blue Anchor Formation. The lowest beds of the Blue Anchor Formation in SW England are certainly older than those in the Midlands, where the base of the Blue Anchor Formation is unconformable.
Placed at an abrupt or rapid upward change from the red-brown, silty mudstones of the Branscombe Mudstone Formation to the green or grey-green, dolomitic mudstones of the Blue Anchor Formation. In parts of southern England and Wales the transition occurs over a greater thickness of beds or above a unit of interbedded red and green strata (e.g. on the west Somerset and south Devon coasts). The boundary may be locally unconformable, as suggested in the Warwickshire area by Old et al. (1987). At outcrop, the boundary is marked by a change in soil colour from the reddish brown clayey soils of the underlying Branscombe Mudstone Formation to the grey clayey soils of the Blue Anchor Formation. Typically, this boundary lies near the base of a scarp slope, which is formed by the Blue Anchor Formation and capped by limestones of the Penarth Group and lowermost Lias Group.
The formation is the highest unit of the Mercia Mudstone Group in the British Isles. The outcrop extends northwards from the south Devon coast, through Somerset, Avon, Gloucestershire, Worcestershire, Warwickshire, Leicestershire, Nottinghamshire, Lincolnshire, Humberside and Yorkshire and into Cleveland. Other outcrops occur in Gwent and Glamorgan, South Wales, and in the Cheshire and Carlisle basins. Outcrops in south Devon and Cleveland are in spatial continuity with occurrences of equivalent units offshore in the English Channel and Southern North Sea basins respectively.
The formation typically comprises pale green-grey, dolomitic silty mudstones and siltstones with thin arenaceous lenses and a few thin, commonly discontinuous beds of hard, dolomitic, pale yellowish-grey, porcellanous mudstone and silltstone ("Tea Green Marl" of Etheridge, 1865). In southern England and Wales only, the "Tea Green Marl" is overlain by the "Grey Marls" (Richardson, 1906). This unit (equivalent to the upper part of the Rydon Member and the whole of the Williton Member of Mayall, 1981) comprises grey, black, green and, rarely, red-brown dolomitic mudstones with, in the higher beds, yellowish-grey dolostones; also present are laminated siltstone beds with mudcracks, scarce pseudomorphs after halite, and locally abundant gypsum; miospores occur throughout and bivalve fossils and bioturbation become increasingly common upwards.
Type section: 36.54m (Warrington and Whittaker, 1984); primary reference section: 31.18m (Warrington and Ivimey-Cook, 1995). Maximum recorded thickness: 67.20m, Winterborne Kingston Borehole (BGS Borehole reference number SY89NW/1), Dorset (Rhys et al., 1982), inferred from geophysical logs. Elsewhere the Formation typically ranges from 5 to 20m; it is generally thinner (7 to 10m) in the more northerly basins.
Slightly unconformable or disconformable, marked by an abrupt upward transition from green or grey-green, dolomitic mudstones of the Blue Anchor Formation to black, fossiliferous shales of the Westbury Formation (Penarth Group). The unconformity surface is commonly slightly irregular and small clasts of Blue Anchor Formation lithologies may occur at the base of the Westbury Formation. The Blue Anchor Formation is both burrowed and bored to a depth of several centimetres below the boundary. In parts of southern England and Wales (e.g. on the west Somerset coast) the upper part of the formation (Williton Member of Mayall, 1981) includes lithologies similar to that of the overlying Westbury Formation, giving rise to an apparently gradational and interdigitating upper boundary. At outcrop, the boundary is marked by a change in soil type from the generally paler grey clay of the Blue Anchor Formation, to the darker grey clay of the overlying Westbury Formation of the Penarth Group. Typically, this boundary lies about half way up a scarp slope capped by limestones of the Penarth Group and lowermost Lias Group.
Banton [Main] Coal (Glasgow-Airdrie)
BANC
Banjaard Formation
BANJ
Bank Deposits
BANK
Typically sand and gravel; bank or bank-like form. [Generic description].
Banham Member
BANM
Resting unconformably on Upper Chalk
Mapped out in the Banham - Kenninghall - Quidenham area; for exact distribution see Diss Memoir, figure 9.
Suite of diamictons, sands and gravels, silts and clays characterized by abundant quartz-quartzite pebbles.
Max. 9m
Overlain abruptly by deposits of glacigenic Lowestoft Formation.
Bannagher Sandstone Formation
BANN
Banwy Member
BANW
Blue Anchor Formation And Penarth Group (Undifferentiated)
BAPN
Barron's Pike Sandstone
BAPS
Parts of the Bewcastle sheet area, Cumbria.
Ben Algan Quartzite Member
BAQU
Base of quartzites (not seen, cut-out by fault system along valley of River Spey).
Between Rothes Fault and River Spey NE of Craigellachie and Old Red Sandstone unconformity at Cairnty, Mulben (Sheet 85E).
Quartzite and quartzose psammite, buff to grey, well-bedded with abundant micaceous interbeds. Locally recrystallised, hard and massive.
c. 1250m seen.
Top of quartzites, overlain by flaggy and schistose semipelites of the Findlater Flag Formation.
Bardsley Rock
BAR
Barra Formation
BARA
Base lies on major erosion surface or associated Hebrides Formation overlain by Jura Formation or crops out.
Dark grey clay, very soft-very firm, silty and gritty with scattered pebbles.
66 metres in Borehole 78/2. Reaches maximum of 130 metres in western part of the sea of the Hebrides.
Barrington Member
BARB
Upward change from ferruginously weathering calcarenite with dominant mudstone clasts, pebbles and belemnite fragments.
Barrington (at least) to Pennard Hill in the north [ST 615 375]
Poorly ooidal micrites and calcarenites with common ammonites.
Upward change from limestone to clays (Down Cliff Clay) or, where absent, sands of the Bridport Sands.
Barnsley Coal (West And South Yorkshire)
BARC
Bare Coal (Warwickshire)
BARE
Locally becomes part of the Thick Coal.
Bargan Coal (South Lancashire)
BARG
Bardahessiagh Formation
BARH
Barnsley Rider Coal (West And South Yorkshire)
BARI
Barkley Breccia Formation
BARK
Barrasford Limestone
BARL
Barncraig Coal (Fife)
BARN
Barn Rock Member
BARO
Incoming of glauconitic and concretionary sandstone at the top of the silty clay coarsening upward sequence attributed to Division B (of London Clay) by King (1981).
Eastern Hampshire Basin in the vicinity of Portsmouth and Bognor Regis.
Very fine-grained glauconitic sandstone.
Erosive contact at the base of the silty clays of Division C (of London Clay), King (1981).
Barnesmore Pluton
BARP
Rb-Sr whole rock 397 +/- 7 Ma (O'Connor et al., 1987).
Barnesmore Pluton (Phase 2)
BARP2
Barnesmore Pluton (Phase 3)
BARP3
Barr Group
BARR
Drawn at the base of the Kirkland Conglomerate Formation where conglomerate with interbedded limestone rests unconformably upon igneous and metamorphic lithologies of the Ballantrae Complex.
Conglomerate, limestone and mudstone, shallow marine and fan delta deposits.
Drawn at the conformable upward passage of the Benan Conglomerate Formation where boulder conglomerate with matrix supported clasts of basalt dolerite and gabbro pass into blue grey nodular mudstone siltstone and sandstone of the Balatchie Formation.
Barrow Tuff Member
BART
Base of pyroclastic flow deposit, usually overlies volcaniclastic sandstone and locally sits directly on the Wrayslack Tuff Member in the Waberthwaite Formation.
Between Beckstone (SD 183 903) and Duddon Bridge (SD 197 881), near Broughton in Furness, Cumbria.
Dacitic lapilli-tuff, pink-weathered, foliated, with autobreccia at top.
Top of pyroclastic flow deposit that characteristically has a rheomorphic autoclastic breccia; Duddon Bridge Tuff Member above.
Barrow Terrace Deposits
BARW
Barton Sand Formation
BAS
Balmoral Sandstone Unit
BASA
Basal Andesite Sill-Complex
BASC
Bassingfield Sand And Gravel Member
BASG
Ballyalton Sill
BASI
Bass Coal (South Staffordshire)
BASS
The Bastard Sandstone Formation
BAT
The top of the New Orleans Conglomerate Formation.
South of Campbeltown on the Kintyre Peninsula on Sheet 12, excluding Sanda and neighbouring islands.
A finely laminated, locally cross-bedded sandstone, more quartzose than the underlying formation.
At least 100 m thick.
Not seen as dips into the sea, elsewhere on Kintyre it is unconformably overlain by the Stratheden Group.
Batchie Coal (Central Coalfield)
BATC
Bathgate Group
BATH
The base of the Group is taken in most areas at an upward transition from sedimentary rocks in the Strathclyde or Clackmannan groups.
Central Fife, west Lothian, Bathgate and Salsburgh areas. Component Formations: Bathgate Hills Volcanic Formation, Salsburgh Volcanic Formation, Kinghorn Volcanic Formation.
Olivine-rich microporphyritic basalts of Dalmeny and Hillhouse types, some macroporphyritic olivine-basalts of Craiglockhart and Dunsapie types; bedded tuffites, tuffaceous sedimentary rocks also present.
Very variable: maximum is over 450m
The top of the Group is taken at the highest known lava in the Passage Formation (in the Central Coalfield).
Banchory Till Formation
BATI
Unconformable: on pre Late Devensian superficial deposits or bedrock.
The East Grampian Highlands.
Gravelly and sandy diamicton composed principally of decomposed Neoproterozoic metamorphic rocks and Caledonian igneous rocks.
Very variable, generally 2 to 5m, over 8m proved in some sections
Conformably overlain by Glen Dye Silts Formation or Lochton Sand and Gravel Formation; otherwise unconformably overlain by Flandrian deposits, or at the ground surface.
Batty Mine Coal (North Staffordshire)
BATM
Balmoral Tuffite Member
BATU
Batavier Formation
BATV
Bad Na H-Achlaise Ultramafic Rocks
BAUM
Bristol Avon Valley Formation
BAVON
Early Pleistocene to Holocene.
Rests conformably on Jurassic, Triassic and Carboniferous bedrock.
The entire catchment of the Bristol Avon river and its tributaries, from Malmesbury and Frome to the mouth of the river.
The formation encompasses the fluvial, lacustrine and organic deposits of the Bristol Avon river. It includes floodplain alluvium and deposits of three river terraces. The floodplain alluvium comprises soft clays, silts and fine sands, with bodies of peat, all overlying sands and gravels. The terrace deposits include gravels, sands, silts and clays; the gravel clasts are dominantly local Jurassic limestones, Triassic sandstones and Carboniferous limestone, but also include some glacially-derived erratics from northwest England and the Welsh Borders.
Surface.
Balclatchie Formation, Ardwell Formation And Whitehouse Formation (Undifferentiated)
BAW
Black And White Coal (South Lancashire)
BAWC
Bay Member
BAY
Late Ordovician [Late Caradoc] Streffordian Stage, clingani Zone, morrisi Subzone (see Fortey and others, 2000, column 77).
Distinguished from the rest of the Ardwell Farm Formation below, by the incoming of dark grey graptolite-bearing shale.
The Girvan area of southwest Scotland.
Sandstone and dark grey graptolitic shale.
The Bay Member of the Ardwell Farm Formation in the Girvan foreshore area is a direct correlative of the Cascade Member of the same formation in the Penwhapple Burn area.
At least 45m
Overlain by the South Shore Formation of the Whitehouse Subgroup.
Bay Coal
BAYC
Bays Leap Coal (Northumberland And Durham)
BAYL
Brown Bank Tuff Formation
BBA
At the change from coarse, eutaxitic, fiamme-rich lapilli tuff at the top of the Bleawath Formation to generally lithic-rich sequence above. Various members of the Formation overlap on to the top of the Bleawath Formation.
Seen in Sellafield boreholes 2 (NY00/28), 4 (NY00SE/29), 5 (NY00SE/30), 10A (NY00SW/38), RCF1 (NY00SE/35), RCF3 (NY00SE/37), RCM1 (NY00SE/41) and RCM2 (NY00SE/40).
Sheets of massive, unbedded, poorly sorted, generally lithic-rich welded lapilli-tuff of andesitic and rhyolitic composition; interbedded volcaniclastic sandstone, siltstone, pumice lapilli-tuff and accretionary lapilli-tuff. Contains the rhyolitic welded lapilli-tuff (Seascale Hall Member) and, in BH RCF1, a rhyolitic lava flow or lava-like tuff.
255.55m in Type Section (355.5m in core because of andesite sill); 188m in Sellafield BH No.2; 127m in Sellafield BH No. 4; 45m in Sellafield BH No.5.
At the upward change from the generally lithic-rich sequence to homogeneous andesitic welded tuff of the Fleming Hall Formation.
Blackband Coal (New Cumnock)
BBAC
Blaeberry Formation
BBB
Transition from grey mudstones and silty mudstones of Kip Burn Formation.
Muirkirk to Strathaven, Strathclyde region, Central Scotland.
Dark greenish grey mudstone and silty mudstone, rusty weathering.
Transition to greenish grey sandstones and mudstones of Dunside Formation.
Bagshot Formation, Bracklesham Group, Barton Group, Becton Sand Formation And Chama Sand Formation (Undifferentiated)
BBBBC
Better Bed Band Coal (West Yorkshire)
BBBC
West Yorkshire area.
The Better Bed Band Coal is a thin, poor quality, but widespread coal not normally of economic value
Burnfoot Bridge Coal (New Cumnock)
BBC
Brathay Formation, Birk Riggs Formation And Coldwell Formation (Undifferentiated)
BBCW
Black Band Coal (North Staffordshire)
BBDC
Brewin's Bridge Dyke
BBDY
B-Bed Evaporite
BBE
Black Bed Coal (North Wales)
BBEC
Bottom Bensham Coal (Northumberland)
BBEN
Bitter Beck Formation
BBF
Not seen, thrust faulted over Kirkstile Formation.
Siltstone and mudstone with subordinate sandstone beds.
c.250m at Bitter Beck, up to 600m (very poorly exposed) south of Cockermouth (northwest corner of Map NY12).
Rapid interbedded transition to Watch Hill Formation. (NY 149 316).
Better Bed Fireclay
BBFC
Breaky Bottom Flint
BBFL
Black Band Ironstone Member
BBG
Base of the Bassey Mine Coal.
North Staffordshire Coalfield, but not shown on map.
Grey mudstone, siltstone and sandstone with 6 named coals, thick seatearths and 4 blackband ironstones. Ironstones pass laterally into limestone or calcareous mudstone to the south. Reddened mudstones increase in number and thickness to the south and west.
Up to 135 m in the Wolstanton Colliery No. 3 Shaft, SJ84NE/29 (SJ 8606 SJ 4800).
Passage by alternation from grey strata of the Black Band Ironstone Member to red strata of the Etruria Formation. Top of member taken at top of uppermost grey measures in succession.
Boulby Halite
BBH
Batchie (Blackband) Ironstone
BBI
Brocka Bank Grit
BBK
West Yorkshire area [Brocka Bank, near Ilkley].
Thickly bedded, coarse-grained sandstone.
To c.25m
Blind Beck Sandstone Member
BBKS
Conformable upon the top of the Shap Wells Conglomerate Formation.
The valley of the Birk Beck and Upper Lunedale, Cumbria.
A brick-red, trough cross-bedded, medium- to coarse-grained sandstone, with siltstone interbeds containing large abundant well-rounded sand grains with haematite pellicles interpreted to be of aeolian provenance.
Up to 200 m thick.
Marked by the unconformity at the base of the Dinantian Marsett Formation.
Blackband Lingula Band
BBLB
Baddoch Burn Limestone Member [Redundant Code: Use Badl]
BBLM
Balblair Intrusion
BBLR
Blackbyre Limestone
BBLS
Usually seen as a change from an apparently marine mudstone, known as the Balgrochan Beds, in the Lawmuir Formation.
The Paisley and Glasgow area.
A pale to dark grey, crinoidal, bioclastic, argillaceous limestone interpreted to be of marine origin generally with a massive lower portion and a thinly bedded upper part, and is a name applied to limestone beds within the Balgrochan Beds., which are mostly mudstones.
Generally up to 0.35m thick, and possibly up to 7.0m in the Paisley and Glasgow districts. Elsewhere, the unit is represented by the Balgrochan Beds.
Mostly identified by a change to probable marine mudstone of the Balgrochan Beds in the Lawmuir Formation overlain by non-marine strata locally including the freshwater Baldernock Limestone.
Bothwell Bridge Marine Band
BBMB
Benburb Mudstone Member
BBMM
Bottom Beaumont Coal (Northumberland)
BBMN
Bebside Bank Seam (D/De1)
BBNK
Basement Beds (Northern Pennines)
BBNP
Basement Beds (North West)
BBNW
Brooksbottoms Coal (South Lancashire)
BBOC
Beinn Buidhe Older Quartz-Gabbro Intrusion
BBOQG
Burn Of Benholm Peat Bed
BBP
Tectonic contact with grey shelly clay of Benholm Clay Formation.
NO 7943 6914 to NO 7943 6915. Burn of Benholm site.
Silty peat and organic silt, as lenses and rafts preserved between red-brown till and grey shelly clay.
Tectonic contact with Mill of Forest Till Formation.
Baddoch Burn Pelite Formation
BBPE
Beinn Bhreac Psammite
BBPS
Poorly exposed conformable contact with Creag Bhuidhe Semipelite and way-up criteria.
Central Highlands, SE of Loch Ness, Strathnairn to Strathdean, Slochd area.
Gneissose interbanded psammite, micaceous psammite and siliceous psammite. Locally migmatitic.
Transitional, locally tectonised contact. Structurally up into Flichity Semipelite - no way-up criteria.
Blanket Bog Peat
BBPT
Bouley Rhyolite Formation [Redundant Code: Use Brh]
BBR
Banbury Coal (North Staffordshire)
BBRC
Bottom Brockwell Coal (Northumberland And Durham)
BBRO
Brooksbottoms Grit
BBS
Bofrishlie Burn Sandstone Member
BBSA
A faulted contact with Highland Border Complex rocks.
The north-west limb of the Strathmore Syncline, adjacent to the Highland Boundary Fault, between Balleich and Drum of Clashmore.
A reddish grey to reddish brown, fine- to coarse-grained, commonly poorly sorted, locally massive, locally micaceous, sub-lithic sandstone, with igneous clasts.
Inferred to be 200 m thick in the Aberfoyle area.
A sharp contact with the overlying Balleich Lava Member of Craig of Monievreckie Conglomerate Formation.
Beck Bottom Stone Coal (West Yorkshire)
BBSC
Benbulben Shale Formation
BBSF
Conformable with underlying siltstone/sandstone dominated sequence of the Drumchorick Siltstone Formation and Mullaghmore Sandstone Formation (only in type area).
Mudstone, medium to dark grey, micaceous, calcareous, bioclastic, with thin to thick blue-grey, argillaceous, very fossiliferous limestones, thin calciturbidites and sandstones.
c.60 - 120 metres.
Conformable, rapid transition with succeeding limestone dominated sequence of the Glencar Limestone Formation, in the type area.
Bark Butts Silts Member
BBSI
Late Devensian.
At its type site, the Bark Butts Silts Member rests with an erosional contact on matrix-rich poorly sorted gravel of Lake District provenance (probably a cobbly upper facies of the Scale Beck Till Member).
West Cumbria, typically within Blengdale.
Interbedded clayey silt, sandy silt and silty sand with thin horizontal lamination and upward-fining varved interlamination towards its base.
At its type site the Bark Butts Silts Member is overlain by the erosional base of the Whin Grit Gravel Member.
Babbacombe Slates
BBSL
Brook-Bottom Tuff
BBT
Bottom Brass Thill Coal (Northumberland And Durham)
BBTC
Bottom Busty Coal (Northumberland And Durham)
BBU
Basement Beds (North Wales)
BBW
Brathay Formation, Birk Riggs Formation And Wray Castle Formation (Undifferentiated)
BBWC
Bloody Bay Sandstone
BBY
The units age, stratigraphical position and status are currently uncertain.
Massive cross-bedded sandstone.
Beltiboy Coal (Dungannon)
BBYC
Basement Conglomerate (North West)
Banffshire Coast And Caithness (Albion) Glacigenic Subgroup
BCAG
The hinterland of the Moray Firth, including the northeastern end of the Great Glen, the southern shores of the Moray Firth as far east as Buckie, the Black Isle, the land surrounding the Cromarty and Dornoch firths, Caithness and Orkney.
Suite of glacial, glaciofluvial, glaciolacustrine and glaciomarine deposits that include reddish to dark blue-grey clayey diamictons containing clasts and rafts of Mesozoic rocks derived from the bed of the Moray Firth; also pre-Late Devensian glaciomarine shelly muds.
To 10m
Ground surface or unconformable contact with units of the Banffshire Coast and Caithness Glacigenic Subgroup.
Barr Church Andesite Member
BCAM
Britannia Catchments Group
BCAT
Unconformable contact with units of the Albion Glacigenic Group, the Caledonia Glacigenic Group, the Dunwich Group, the Crag Group or bedrock.
The British Isles excluding Ireland.
A suite of fluvial, lacustrine, mass movement, periglacial and aeolian deposits that contain clasts derived from rocks cropping out throughout Great Britain and the Isle of Man, including alluvium, river terrace deposits, peat, head, cover sand and blown sand. Subdivided into subgroups defined geographically by drainage systems.
To 100m
Generally the ground surface, but locally units of this group interfinger with units of the British Coastal Deposits Group.
Black Cock Formation
BCB
Bottom Coal (Birmingham)
BCBM
Bryn-Crin Basaltic Trachyandesite
BCBT
Not applicable.
Amygdaloidal basaltic trachyandesite, characterised by abundant andesine phenocrysts, glomeroporphritic clots, augite and apatite in microcrystalline groundmass.
Bein Nan Coireag Conglomerate
BCC
Blackstone Coal (Coalbrookdale)
BCCC
Ballycastle Chalk Formation
BCCK
Maastrichtian. Belemnella occidentalis Zone.
Conformable on the Port Calliagh Chalk Formation at a prominent weathered-out bedding plane at the top of `Bed? F of that lower formation and characterised by tabulate flints.
Limited to the Ballymagarry and Ballycastle areas by pre-Palaeogene erosion
Limestone (chalk) with nodular flint bands which have a carious habit in the upper part of the formation. Divided into seven `Beds? (A to G).
13.72m at type-site.
Erosional contact with Palaeogene Basalts or Quaternary deposit.
Black Cliff Coal (Milford, South Wales)
BCCO
Banffshire Coast And Caithness Glacigenic Subgroup
BCD
Unconformable on bedrock or units of the Banffshire Coast and Caithness (Albion) Glacigenic Subgroup.
Southern coast of Moray Firth from Elgin to Peterhead, Caithness and Orkney.
Suite of reddish to dark blue-grey clayey diamictons containing clasts and rafts of Mesozoic rocks derived from the bed of the Moray Firth, also pre-Late Devensian glaciomarine shelly muds.
30m or more.
Extends to the surface or buried by Late Glacial to Postglacial deposits.
Barracados Cherts
BCDC
Brims Castle Dolomite Member
BCDL
Faulted at Red Geo against the older Scarden Sandstone Member, of the Mey Flagstone Formation.
Onshore and immediate offshore of the Dounreay area, Caithness, Northern Scotland.
Ferruginous, dolomitic cycles of laminite-limestone, siltstone and thin, fine-grained sandstone.
70m
Conformable at the top of the highest dolomitic laminite-limestone against the base of the overlying Tang Sandstone Member.
Ballycultra Formation
BCF
Brooch Fireclay
BCFC
Brandy Craig Lava Formation
BCG
Lower Arenig.
Overlies Slockenray Formation.
Girvan - Ballantrae area, southwest Scotland.
Pillowed and massive, porphyritic and aphyric lavas with local red horizons suggestive of subaerial weathering.
c.285m
Faulted against Kennedy's Pass Formation and younger rocks of the Barr and Ardmillan groups.
Bottom Crag Limestone
BCGL
Balclatchie Formation
BCH
Rests conformably on Benan Conglomerate (Barr Group).
Girvan District, southwest Scotland.
Blue-grey nodular mudstone, siltstone and impersistent conglomerate units.
Overlain conformably by the Ardwell Formation.
Beinn Chaisgidle (Centre 2) Suite
BCHA
Benches Coal (South Staffordshire)
BCHC
Beach Deposits
BCHD
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks. [Generic description].
Buchanan Clay Member
BCHN
The Buchanan Clay Member of the Clydebank Clay Formation rests with angular conformity on older Quaternary sediments. It is known to rest on the Gartocharn Till Formation (GATI) of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
The Buchanan Clay Member of the Clydebank Clay Formation is recognized in the lower Endrick valley near its confluence with Loch Lomond.
The typical lithology is a thinly bedded silt clay with many laminae and thin bands of silt and locally of sand. The deposits are brown, brownish grey and reddish brown, and are conspicuously colour banded, the banding being emphasised by the grey clay units. The consistency varies from soft to stiff and the deposits is of medium to high plasticity.
Veneer to more than 7m.
The Buchanan Clay Member of the Clydebank Clay Formation is overlain conformably by younger Quaternary sediments of the Kilmaronock Silt Formation of the Britannia Catchments Group (Clyde Catchments Subgroup).
Beach Rock
BCHR
Burnham Chalk Formation
BCK
Marked change from massive, rubbly-weathering chalks below, to harder, thinly bedded or nodular chalk above. This horizon lies just below the Ravendale Flint, a tabular or semi-tabular flint up to 0.25m thick, which is the lowest such flint in the Chalk Group and base of the chalk unit in which such flint bands are common. The lowest few metres of the formation comprises hard chalks and thick, closely spaced, tabular flints, which produce a topographic feature by which the base of the formation can be mapped, and a characteristic geophysical log signature enabling its identification in boreholes.
Yorkshire and Lincolnshire Wolds and the superficialdeposit-covered area to the east, from Flamborough Head south to the Mablethorpe-Chapel St Leonards area on the Lincolnshire coast (see Sumbler, M G, 1999, Fig.1).
White, thinly-bedded chalk with common tabular and discontinuous flint bands; sporadic marl seams. Formal subdivision: None herein but there are many named marl and flint bands throughout the succession that are used to divide the formation. They are all of bed status.
Generally about 140m; possibly significantly thinner (85-100m) over the Market Weighton High; 105m reported on the Yorkshire coast, but possibly much thicker (up to c.160m).
Top of highest flint band in the thick, flint-rich unit of chalk (ie. the Burnham Formation), succeeded by flint-free chalks (ie. the Flamborough Formation). At Flamborough Head, this is the High Stacks Flint, but elsewhere may be at a somewhat different horizon. The change is particularly marked on borehole sonic velocity logs.
Birky Cleugh Limestone
BCL
Boulder Clay And Laminated Clay (Alternate Beds)
BCLC
Composite of 'Boulder Clay': interbedded clay and silty clay, pebbly, reddish brown, stiff, sandy, possibly interbedded with sand and gravel-rich lenses and 'Laminated Clay': clay brown and yellow, laminated; ('Laminated Clay'). [Generic description].
Balnacraig Metabasite Member
BCMB
Branscombe Mudstone Formation
BCMU
Norian to ?Rhaetian. The precise level of the Norian-Rhaetian boundary in the UK sequence is currently unknown. It could be in the upper Branscombe Formation or in the lower Blue Anchor Formation. The Arden Sandstone Formation is late Carnian, and the upper part of the Blue Anchor Formation is Rhaetian, but there are no dates at all for the whole of the Branscombe Formation or the lower part of the Blue Anchor Formation. The lowest beds of the Blue Anchor Formation in SW England are certainly older than those in the Midlands, where the base of the Blue Anchor Formation is unconformable.
Conformable in all areas. Placed at the base of predominantly red, structureless mudstones where they rest on the interbedded dark green-grey siltstones and pale grey fine-grained sandstones of the underlying Arden Sandstone Formation; the boundary is abrupt, or a rapid, interbedded transition. Where the Arden Sandstone Formation is absent (Cheshire Basin and parts of the Wessex Basin), the boundary is placed immediately above the highest halite beds of the Sidmouth Mudstone Formation (Wilkesley Halite Member, Somerset Halite Member). At the type section, the base of the formation is drawn at a lower stratigraphical level than originally defined by Gallois (2001), to encompass approximately 15m of predominantly reddish-brown mudstone that was included by Gallois in the Dunscombe Mudstone Formation. At outcrop, the boundary is typically marked by a change from the grey, slightly sandy clay soils of the Arden Sandstone Formation to the reddish-brown clayey soils of the Branscombe Mudstone Formation. Where the Arden Sandstone forms a marked cuesta feature, the boundary lies at the down-dip limit of the dip slope. In the Cheshire Basin, where the Arden Sandstone Formation is absent, the boundary is mapped at the approximate down-dip limit of subsidence hollows and collapse breccias, which are associated with near-surface dissolution of halites (Wilkesley Halite Member) at the top of the Sidmouth Mudstone (Taylor et al., 1963).
The surface outcrop extends from the South Devon coast northwards into Somerset, Avon and Worcestershire. The formation crops out below parts of the English Central Midlands and Cheshire, and in a strip extending northwards from Nottingham into north Yorkshire. The formation occurs in the subsurface below much of the south Midlands and eastern England. It has equivalents in the Southern North Sea and East Irish Sea basins.
Mudstone and siltstone, red-brown with common grey-green reduction patches and spots. The mudstones are mostly structurless, with a blocky weathering habit. Gypsum/anhydrite, locally of economic importance, is common throughout in beds, nodules and veins. Many of these sulphate beds have been named (e.g. Tutbury Gypsum and Newark Gypsum of the East Midlands) and form distinct markers on geophysical logs. Sporadic thin beds of argillaceous sandstone and silty dolomite occur in the lower part of the formation. Beds of thinly interlaminated, dark grey-green mudstone and dolomitic siltstone occur locally towards the top of the formation (formerly separated in the East Midlands as the Glen Parva Formation, Warrington et al., 1980). Halite is recorded towards the base of the formation in Nettlecombe Borehole, Dorset, SY59NW/1, [SY50520 95440], but is absent elsewhere; halite pseudomorphs are rare.
Up to 240m in the Wessex Basin, 170m in the Worcester Basin; 25 to 60m in the East Midlands, up to 160m in the Cheshire Basin
Placed at an abrupt or rapid upward change from the red-brown, silty mudstones of the Branscombe Mudstone Formation to the green or grey-green, dolomitic mudstones of the Blue Anchor Formation. In parts of southern England and Wales the transition occurs above a unit of interbedded red and green strata (e.g. on the west Somerset and south Devon coasts). The boundary may be locally unconformable, as suggested in the Warwickshire area by Old et al. (1987). At outcrop, the boundary is marked by a change in soil colour from the reddish brown clayey soils of the Branscombe Mudstone Formation to grey clayey soils of the overlying Blue Anchor Formation. Typically, this boundary lies near the base of a scarp slope formed by the Blue Anchor Formation and capped by the Penarth Group.
Balcreuchan Group
BCN
Not seen. The probable oldest component, the Mains Hill Agglomerate Formation, has its base faulted out by the Stinchar Valley Fault.
Between Girvan and Ballantrae, Ayrshire, southwest Scotland.
An interbedded succession of basaltic pillow lava (some are boninitic) and breccia, agglomerate, volcaniclastic sandstone, tuff, siltstone, conglomerate and mudstone-supported melange, and hyaloclastite. Locally sheared and metamorphosed to amphibolitic schist and chlorite-epidote schist. The dominant lavas are contained in faulted, tectonic blocks and are not, for the most part, formally defined as formations. There is good stratigraphical correlation between some of the blocks, but connections are generally tenuous. A number of the more distinctive lithological units have been defined formally as formations.
1.5 to 2km
The major unconformity at the base of the overlying Barr Group.
Blisco Sandstone Member
BCO
Overlies Little Stand Tuff; base taken at change from massive rhyolitic tuff to bedded andesitic volcanclastic sandstone.
Pike of Blisco to Little Stand between Duddon Valley and Longdale, Cumbria.
Andesitic volcaniclastic sandstone with tuff and lapilli-tuff interbeds; bedded succession.
Overlain by unnamed dacite within the Birker Fell Andesite Formation.
Quetivel Mill Conglomerate
BCQC
Bell Crags Breccia Member
BCR
Erosional contact on bedded sandstone within the Seathwaite Fell Sandstone Formation.
North Lake District, between Borrowdale and Thirlmere.
Matrix-supported, poorly supported pebble to cobble breccia, fining upwards into pebbly sandstone.
Erosional contact with disturbed siltstone and sandstone, within the Seathwaite Fell Sandstone Formation.
Briscloonagh Sandstone Formation
BCS
Birch Sandstone Member
BCSA
Ballagan Formation, Clyde Sandstone Formation, Strathclyde Group And Clackmannan Group (Undifferentiated)
BCSC
Blaen-Y-Cwm Shale Formation
BCSH
Base disconformable on Pen-y-Garnedd calcareous tuffs and tuffites in West Berwyns or The Bryn Siltstone Formation in the North Berwyns.
Black and dark-grey graptolitic shales. Pyritous.
Thickness of type section - c.30 metres. Thickness of lateral variation - 0-30 metres.
Unconformably overlain by the siltstones of the Dolhir Formation.
Ballagan Formation, Clyde Sandstone Formation, Strathclyde Group And Lower Limestone Formation (Undifferentiated)
BCSL
Ballycastle Sandstone Group
BCSS
Unconformity with Dalradian.
Data not yet available.
Sandstone, conglomerate, siltstone, basalt lava, mudstone (including fissile mudstone), tuff, coals, seatearths, limestone.
Present erosion levels.
Ballagan Formation, Clyde Sandstone Formation And Strathclyde Group (Undifferentiated)
BCST
Beacon Tuff Member
BCT
Not exposed; thought to be sharp to gradational on grey lapilli tuff and volcanic breccia of the Benscliffe Breccia Member.
From Nanpantan Hills it extends southwards to Beacon Hill, Broombriggs Hill and Ling Hill. Poorly exposed west of Benscliffe Wood.
Medium- to thickly-bedded blue-grey, fine- to coarse-grained tuffs and tuffaceous siltstones, and beds of massive, grey, dacitic lithic-crystal tuff and lapilli tuff.
c.880m
Not exposed, but probably sharply overlain by volcaniclastic sandstones and breccia of the Sandhills Lodge Member.
Boyne Craig Till Formation
BCTI
Unconformable on bedrock, commonly decomposed.
Scotland sheet 96 (Portsoy).
Diamicton, clayey, sandy, gravelly, dark yellowish brown to orangey brown. Containing much decomposed calc-silicate rock and clasts of quartzite, psammite, gabbro and probable Triassic sandstone.
>5m
Unconformable contact with Old Hythe Till Formation or glacitectonic contact with Whitehills Glacigenic Formation.
Beechwood Conglomerate Bed
BCWC
Brick Clay
BCY
Varies from silt to clay, usually yellow-brown and massive. [Generic description].
Bottom Coatyards Coal
BCYD
Brithdir Member
The base is placed at the base of the Brithdir Coal, above "Pennant" sandstones and thin mudstones/siltstones of the Rhondda Member or above red/green mudstones of the Deri Formation on the east crop of the coalfield.
Extensive throughout the South Wales Coalfield, from Pembrey [SN 42 02] east to Blaenavon [SO 230 085] and, on the south crop, from Gower, [SS 545 960] to Pontypool [ST 268 990].
Green-grey, lithic arenites ("Pennant sandstones") with conglomerate lenses at bases of units; thin mudstone/siltstone and seatearth interbeds and mainly thin coals.
45m in the Pontypool area [ST 268 990] to 200m in the Swansea area [SS 660 945].
The top is placed at the base of the Hughes (Cefn Glas) Coal, where the coal rests on either "Pennant" sandstones or thin mudstones/siltstones at the top of the Brithdir Member. The coal is overlain by "Pennant" sandstones or thin mudstones/siltstones of the Hughes Member.
Bowden Way Beds And Acuminata Beds (Undifferentiated)
BDAC
Bracadale Formation
BDALE
Overlies the Beinn Totaig Formation.
Northern Skye.
Mugearites, benmoreites and trachytes, both porphyritic and non-porphyritic, are typical of these evolved flows.
Overlain by the Osdale Formation.
Bradford Dale Lava
BDB
Bardon Breccia
BDBR
Displays a sharp contact with the volcaniclastic sandstone of the Bardon Hill Volcanic Complex.
Mainly restricted to the western side of Charnwood Forest at Bardon Hill Quarry. May also extend eastwards to Birch Hill.
Massive to brecciated, green-grey, locally porphyritic andesite. Grades into hyaloclastic breccia with localised blocks of black-rimmed spherulitic andesite.
At least 200m thick.
Not seen, only found in fault contact with the volcaniclastic siltstones and sandstones of the Bradgate Formation.
Big Drum Coal (Lanarkshire)
BDC
Ben Dorrery Conglomerate Member
BDCM
Bradley Coal
BDCO
Baddinsgill Mudstone Member
BDD
Conformable on Lamb Rig Siltstone Member: First appearance of olive-grey silty mudstone.
Pentland Hills, Midland Valley.
Laminated grey and brown mudstones and silty shales. No sediment coarser than siltstone.
Conformable: Highest red, poorly lithified shales below coarse-grained sandstone of the Henshaw Formation.
Berriedale Flagstone Formation
BDF
Bedlam Gill Coal (Cumbria)
BDGC
Beaconsfield Gravel
BDGR
Erosional base on Tertiary-Cretaceous bedrock.
Thames Valley.
Gravel, variably clayey and sandy. [Generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
Erosional remnants of terrace surface.
Birdshill Limestone
BDH
Ben Dubhain Breccia And Conglomerate
BDHB
Bardon Hill Volcanic Complex
BDHV
Western Charnwood Forest, between Bardon Hill Quarry, Bardon Hill and Birch Hill.
An assemblage with no obvious stratigraphy, consisting of andesite breccia (Bardon Breccia) and porphyritic dacite (Peldar Porphyritic Dacite).
At least 250 m thick.
Possible fault contact with Precambrian volcaniclastic siltstones and sandstones of the Bradgate Formation.
Beinn An Dubhaich Limestone
BDL
Bradley Flags
BDLF
Base of lowermost thick fine-grained and micaceous sandstone above the Bradley Coal. Note that this definition is more restricted than the definition of Stephens et al. (1953), who included all sandstones above the Bradley Coal.
Restricted to the northwest part of the Bradford district (Sheet 69).
Fine-grained sandstone interbedded with micaceous mudstone. The sandstone is highly micaceous, flaggy, with planar bedding and lamination displaying primary current lineations, cross bedding with burrow traces in places and both wave and current ripple cross lamination.
Maximum of 25m at Bradley.
Passage from the fine-grained sandstone of the Bradley Flags into the overlying dark grey mudstones containing the Cravenoceras cowlingense Marine Band.
Brockley Down Limestone
BDLM
Bottom Durham Low Main Coal (Northumberland And Durham)
BDLO
Bedhampton Marls (One)
BDMA1
Bedhampton Marls (Two)
BDMA2
Bedhampton Marls (Three)
BDMA3
Blairdaff Moraine Formation
BDMO
Generally a sharp, undulating, unconformable contact with a yellowish brown, gravelly clayey sand diamicton of the Banchory Till Formation and other sandy tills of the East Grampian Glacigenic Subgroup.
East Aberdeenshire: sheets S76E, S77, S66E, S67.
Forms hummocky ground and cross-valley moraine ridges.
Typically yellowish brown, crudely bedded, angular to well-rounded clasts, with extremely variable sorting, of both matrix- and clast-supported clayey gravel, with boulders and sandy diamicton, composed of psammite, metagreywacke, granite and quartzite, with some gneiss, slate and dolerite, elsewhere locally formed of mainly granite or gabbroic rocks, forming hummocky ground and cross-valley moraine ridges.
Generally the present ground surface.
Breadstone Shale Formation And Micklewood Beds (Undifferentiated)
BDMW
Tortworth Inlier.
Bowden Way Beds
BDN
Transition from dark olive grey fissile mudstone to calcareous mudstone.
Sherborne Park, Sherborne, Dorset, to Milborne Wick, Somerset.
Calcareous mudstones with intervals of argillaceous limestone. NOTE: Map code 'Bdn' combines Bowden Way Beds with Acuminata Beds.
11.6m (Type Section), 21.2m (Purse Caundle Borehole).
Transition from calcareous mudstone to shell-detrital mudstones of the Acuminata Beds.
Beadnell Coal (Northumberland)
BDNL
Bindon Sandstone Member
BDNS
Bryn Dowsi Mudstone
BDO
Mudstones - dark grey. Underlying unit grey silty mudstones with sandstones, overlying unit pale mudstones.
50 - 120 metres.
Bad Step Tuff
BDP
Base of rhyolitic, lava-like tuff. Unconformable on various units within the underlying Long Top Tuffs of Airy's Bridge Tuff Formation.
Borrowdale, Eskdale to Langdale. Hard Knott (NY 233 025) to White Gill Crag (NY 298 070), Cumbria.
White to pink weathered rhyolitic, high-grade lava-like tuff; garnetiferous.
By overlying Crinkle Member of Airy's Bridge Tuff Formation.
Broadford Beds Formation And Pabay Shale Formation (Undifferentiated)
BDPY
Beinn Donn Quartzite Formation
BDQU
Border Group
BDR
The thickest development is at Bewcastle where base of the unit is not seen. Here it comprises the Lyne Formation (formerly Lower Border Group) and the Fell Sandstone Formation (formerly Middle Border Group). In Annerdale, the Lyne Formation is conformable on interbedded siltstones, sandstones and ferroan dolostones ("cementstones") of the the Kirkbean Member of the Ballagan Formation (Inverclyde Group), as seen in the Hoddon No.2 Borehole (NY17SE/3, NY1641 7285). At Kirkbean, the Lyne Formation is presumed to rest unconformably on the Ballagan Formation, and comprises siltstone and dolomitic limestone with fine-grained sandstone, contrasting with the predominantly thin dolomitic limestone and fine-grained sandstone Ballagan Formation sequence. At Brampton, the base of the unit is taken at the base of interbedded thick sandstones with thin limestones and mudstones of the Fell Sandstone Formation, which rests conformably on the Ballagan Formation. Southwest of Berwick-upon-Tweed, the Fell Sandstone Formation is characterized by the presence of seven thick sandstones separated by laterally persistent mudstones. The base is taken at the base of the lowest sandstone (Thornton Sandstone of Turner et al., 1993), which rests conformably on the "cementsones facoies" (siltstones,sandstones and ferroan dolostones) of the Ballagan Formation.
Northumberland and Solway basins, including the Solway Firth, Annandale, Langholm, Kelso district and Berwickshire from the Solway Coast (280000 548000) to the Berwickshire Coast at Berwick-upon-Tweed (400000 650000).
The Border Group comprises interbedded sandstones, siltstones and limestones, with conglomerate and ferroan dolostone ("cementstone"). Component formations include the Lyne Formation , which comprises siltstone and dolostone with fine-grained sandstone, and the Fell Sandstone Formation, which comprises medium- to coarse-grained sandstone with siltstone and subsidiary fine-grained conglomerate and dolostone. Some members of the Lyne Formation are notable for their algal beds (eg the Main Algal Member). The Kershopefoot Basalt Beds are thin olivine-basalt flows within the Fell Sandstone Formation.
More than 1350m
In Annandale, thick medium- to coarse-grained sandstones, siltstones and seatrocks of the Fell Sandstone Formation of the Border Group are overlain conformably by interbedded sandstone, siltstone and limestone the Tyne Limestone Formation (Yoredale Group). Locally in the Annandale and Langholm districts the base of the Tyne Limestone Formation is represented by interbedded tuffaceous sandstones and siltstones of the Glencartholm Volcanic Beds. In Bewcastle the base of the Tyne Limestone Formationis represented by marine fossiliferous limestone and mudstone of the Clattering Band. In the Clattering Band colonial corals, including Lithostrtion martini and L. portlocki and gigantoproductids (Semiplanus sp.) become common. The upper boundary of the Border Group is diachronous across the Northumberland and Solway basins.
Brithdir Coal (South Wales)
BDRC
Borders Glacigenic Subgroup
BDRGL
Sharp, unconformable contact with bedrock. Pre-Ipswichian Quaternary deposits are not proved within the Scottish Borders.
Distributed across the Merse of Berwickshire from the Lammermuir Hills in the north to the margins of the Cheviot Hills in the south. Units of the subgroup might occur locally beyond these geographical boundaries and beyond the approximate surface boundaries with adjacent glacigenic subgroups (e.g. the North Sea Coast Glacigenic Subgroup). Units might also extend offshore,
Suite of glacial, glaciofluvial and glaciolacustrine deposits including sandy diamictons (till), sand, gravel, silt and clay. The sediments were deposited by or are the deglaciation products of ice which emanated from the Southern Uplands and streamed eastwards aound the northern margins of the Cheviot Hills across the Merse of Berwickshire. The deposits contain clasts derived from Devonian and Carboniferous sedimentary rocks (sandstone, siltstone, mudstone) and volcanic and intrusive rocks (basalt, andesite) of the Cheviot Hills and the Kelso district. Varying proportions of Lower Palaeozoic wacke sandstone and siltstone are also present. Tills are generally matrix-supported diamictons with characteristically brownish grey or yellowish grey matrices. However, locally they can be reddish brown, either where the diamictons are weathered or are derived from red strata (e.g. Devonian outcrops).
To 30m
Unconformable contact with units of the Britannia Catchments Group (Tweed Catchments Subgroup) and the British Coastal Deposits Group.
Brithdir Coal (Lower Leaf) (South Wales)
BDRLL
Brithdir Rider Coal (South Wales)
BDRR
Brithdir Coal (Upper Leaf) (South Wales)
BDRUL
Bridport Sand Formation
BDS
Base of sand/silt or mudstone, as described in the Lithological Description, resting non-sequentially on limestone of the Beacon Limestone Formation or, north of c.Chipping Sodbury area in the Worcester Basin, a gradational boundary with mudstone of the Whitby Mudstone Formation (q.v.)
Wessex Basin to Worcester Basin (Dorset Coast to central Cotswolds, Cheltenham area).
Grey, weathering yellow or brown, micaceous silt, very fine-grained sand and fine-grained sand, locally with calcite-cemented sandstone beds and lenses, variably sandy clay/mudstone at base, including Downcliff Clay [Member] of type area (Knox, R W O'B, Morton, A C and Lott, G K, 1982; Hesselbo, S P and Jenkyns, H C, 1995, and references therein).
To c.120m
Non sequential; base of lowest limestone (commonly sandy) of the Inferior Oolite Group resting on sand/silt or mudstone (as in the Lithological Description), or on "[Cotswold] Cephalopod Bed" (sandy and argillaceous, ironshot commonly fossiliferous limestone) in the Worcester Basin area.
Berriedale Sandstone Formation
BDSA
Breadstone Shale Formation
BDSH
Not seen. Strata beneath the Breadstone Shale Formation are not exposed in the Tortworth Inlier.
The northern end of the Lower Palaeozoic Tortworth Inlier, between Purton (SO 691 042) and Newport (ST 699 977).
Fissile, micaceous, grey to bluish grey or greenish grey mudstone, with bands of fine-grained sandstone and rare thin calcareous beds with cone-in-cone concretions.
Estimated to be about 1500 thick.
Overlain by the Micklewood Beds (Tremadoc). Contact not seen but probably conformable and gradational. The Micklewood Beds are distinguished from the Breadstone Shale Formation by the more common occurrence of flaggy sandstone and siltstone beds.
Braich Tu Du Volcanic Formation
BDT
Overlies mudstones of the Nant Ffrancon Subgroup and locally the Foel Grach Basalt Formation, with which it interdigitates.
South of Foel Fras, south-west to Nant Peris.
Rhyolite lava flows with acidic tuffs.
Up to 195m, thinning to the north and south.
Overlain by Foel Fras Volcanic Complex, and locally by part of the Nant Ffrancon Subgroup.
Brewood Till Formation
BDTI
Sharp, unconformable contact with fluviatile gravel (Four Ashes Sand and Gravel Formation) containing mainly well rounded clasts derived from the Kidderminster Formation (Bunter Pebble Beds) conglomerates and numerous organic-rich lenses of Ipswichian to Middle Devensian age. The diamicton is heavily cryoturbated at the type section at Four Ashes where it has been loaded down into the underlying gravel.
The ground lying within the generally accepted Late Devensian glacial limit in Staffordshire, but outside the Wrexham-Ellesmere-Whitchurch-Barr Hill Moraine in Cheshire.
Reddish brown, gravelly sandy silty clayey diamicton dominated by locally-derived clasts such as of the Kidderminster Formation (Bunter Pebble Beds) conglomerates, but with a significant proportion of erratics including grey granite from the Southern Uplands, striated volcanic rocks, Eskdale Granite, Ennerdale Granophyre and slates from the Lake District, limestone, flint and marine shells. The tills are typically thinner, more eroded, more weathered and considerably more cryoturbated than those of the Stockport Glacigenic Formation lying to the north of the Wrexham-Ellesmere-Whitchurch-Barr Hill Moraine in Cheshire.
3 m at type section. Up to 17 m at Madeley in Telford district
The ground surface or unconformable contacts with glaciofluvial sand and gravel or younger Quaternary deposits.
Balderton Sand And Gravel Member
BDTN
Middle Pleistocene (MI Stage 7 to 6).
Unconformable, commonly channelled base, resting on pre-Quaternary bedrock and possibly, very locally, on the Skellingthorpe Clay Member of the Wolston Formation.
Newark upon Trent to Lincoln Gap (see Brandon and Sumbler, 1991, Figure 1) with possible outliers (Whatton Sand and Gravel) present to the southwest of Newark. British Geological Survey sheets 113, 114, 126, 127.
Predominantly cold-phase sands and gravels that underlie the Balderton Terrace. Orange-brown sandy gravel dominated by rounded pebbles of "Bunter" quartz/quartzite (c.75%) with subordinate subangular flint (c.15%), and rarer Triassic sandstone, etc. Infills a broad sinuous channel extending northeast from Newark towards the Lincoln Gap; terrace surface falls from c.20m above OD (c.10m above the Trent floodplain) to c.11m OD. Sections show intraformational and epigenetic ice wedge casts. Upper part locally includes a thin fluvio-aeolian coversand (Whisby Sand Bed, pre-Ipswichian) and a rubified paleosol (Hykeham Soil: Ipswichian). Basal part locally includes channel-filling organic silts (Thorpe on the Hill Bed), which yield a temporate flora and fauna assigned to MIS 7. Correlated with the Southrey Sand and Gravel Member (Trent Valley Formation, pre-diversionary River Trent east of Lincoln Gap) and Egginton Common Sand and Gravel Member (Trent Valley Formation).
The definition compiler notes: At Newark itself this terrace seems to be at c.18m, which (depending upon how the profile is drawn) could read as only 7m above the Trent - hence previous confusion with the Beeston Terrace. However, the terrace here could be degraded in some way, because it is slightly higher than this "downstream". If the profile is projected back towards Newark it "ought" to be 10 or 11m above the modern floodplain.
0 to c.9m; typically c.6 to 8m
Bodieve Tuff
BDV
Bodwr Coal (South Wales)
BDWR
Bembridge Beds
Isle of Wight.
Bealsmill Formation
BEAL
The depositional lower boundary is not seen as the base is always faulted. The lower boundary is thought to post-date the D1 deformation phase, with the formation resting unconformably on Dinantian sequences.
Mapped from Altarnun (SX 22 81), east Cornwall to northwest Dartmoor (SX 49 85), but thought to extend into the southwestern part of the Okehampton area (SX 53 87), mid Devon, where is has been mapped as Crackington Formation. Formational diagnosis needs further work, as does the area where it has not been mapped.
Thin- to thick-bedded commonly coarse and feldspathic sandstones interbedded with siltstones and dark grey mudstones. Scattered beds of ill-sorted pebble to cobble conglomerate up to 2m thick contain clasts including chert, lava and limestone as well as derived Dinantian and ?Namurian fossils. Some channels are present.
Unknown. Minimum thickness 120m
The depositional upper boundary is not seen but probably tectonic.
Bearreraig Sandstone Formation
BEAS
Upper? Toarcian to Upper? Bajocian.
Erosive unconformity on the Lias Group (PEE, RASL and SCS).
The Bearreraig Sandstone Formation consists of the Druim An Fhurain Sandstone Member (DAFS) and the Garantiana Mudstone Member (GaSh). See also the descriptions for these units. There are three cycles of deposition within the formation; the first is cross-bedded sandstone and sandy limestones, deposited as tidal sand waves. The cross-bedded facies passes laterally to massive sandstones with doggers, then to upward-coarsening cycles of mudstone, siltstone and sandstone. The third facies consists of mudstones, silty and sandy limestones.
To 488m
Change from marine sandstones to estuarine mudstones of the Cullaidh Shale Formation.
Beauly Member
BEAU
Bealbury Formation
BEAY
East Cornwall.
Green and blue green shale and siltstone, with purple slate.
Benthall Member
BEB
Transitional. Base of limestone-siltstone sequence of above type, resting conformably on calcareous siltstones of the underlying Tickwood Beds; lateral passage to reef facies.
North Shropshire.
Coarse-grained shelly limestone, interbedded with impersistent siltstone beds in lower and upper parts.
Base of thinly bedded crinoidal limestones of the overlying (undivided) uppermost part of the Much Wenlock Limestone Formation.
Beinn Bhreac Member
BEBH
Batchie Blackband Ironstone
BEBI
Belton Brae Vent
BEBR
Beannan Buidhe Member
BEBU
Beccles Formation
BEC
Becton Bunny Member
BECB
Best Coal (Coalbrookdale)
BECC
Becton Sand Formation And Chama Sand Formation (Undifferentiated)
BECH
Benholm Clay Formation
BECL
Unconformable on bedrock and conformable or tectonic contact on Birnie Gravel Formation.
Burn of Benholm area and coastal exposures on Kincardine coast between Inverbervie and St.Cyrus.
Dark grey shelly silty clay with broken marine bivalve shells and sparse clasts of sandstone, andesite, siltstone and limestone.
Tectonic contacts with Burn of Benholm Peat Bed or Mill of Forest Till Formation.
Berriedale Conglomerate
BECO
Becton Sand Formation
BECS
Belsay Dene Coal (Northumberland)
BEDC
Bedruthan Formation
BEDN
Bedrock Theme Not Mapped [For Digital Map Use Only]
BEDNM
This code is specifically intended for use in labelling digital geological maps and should not be used for any other purpose.
Belah Dolomite
BEDO
Offshore Bedrock Theme Not Mapped [For Digital Map Use Only]
BEDOF
Beinn Edra Formation
BEDRA
Overlies the Portree Hyaloclastite Formation.
Consists mainly of alkali basalt flows. Evolved composition lavas are present, but rare.
To 300m
Partially overlain by the Ramasaig Formation and the later Beinn Totaig Formation in central north Skye.
Bedchester Sands Member
BEDS
Upward change from usually clay-free glauconitic sand (Child Okeford Sands) to very clayey, fine-grained sand.
Patchy distribution across the south-western part of the Shaftesbury sheet (313); more continuous outcrop between Child Okeford (ST830 130) to (ST860 180).
Very clayey, fine-grained, glauconitic sand.
0-5 metres.
Usually capped by a thin pebble bed that marks the basal bed of the Gault. Where the pebble bed is absent, the boundary is drawn at the change from very clayey glauconitic sand, to glauconitic sandy clay.
Beefie Coal (Lothian)
BEE
Bee Coal
BEEC
Beeston Chalk Member
BEECK
Together with the Catton Sponge Bed below, the beds cover most of the Belemnitella minor I Zone of Christensen (1995, 1999).
The lower boundary placed at the surface above the Catton Sponge Bed.
The member comprises soft white chalk with irregular seams of large flints.
75 feet [22.8m] estimated by Peake and Hancock,
the upper boundary is poorly defined at a hardground on the coast at West Runton.
Beetle Bed
BEET
Broadearth Fireclay
BEFC
Beeding Flints
BEFL
Beldin Gill Ganister
BEG
Beggar Coal (Midlothian)
BEGG
Birnie Gravel Formation
BEGR
Burn of Benholm (Type Area) and local developments. Kincardine coast between Inverbervie and Gourdon.
Matrix-rich red-brown clayey gravel containing cobbles of schistose semipelite, quartzite, psammite, sandstone and some chalk flints locally.
Tectonic or unconformable contact with Mill of Forest Till Formation or Benholm Clay Formation.
Bedminster Great Coal (Bristol Area)
BEGT
Belton Grain Vein
BEGV
Leadhills-Wanlockhead mining district.
Lead-zinc vein cutting Ordovician greywacke.
Beeding Hardgrounds
BEHG
Bembridge Limestone Formation
BEL
Isle of Wight and Creechbarrow (Dorset).
Bellochantuy Bay Formation
BELB
Unconformably overlies Dalradian metasedimentary rocks.
Coastal exposures on the west coast of the Kintyre peninsula, Argyll, Scotland.
Bright red friable sandstone, with thin layers composed of well-rounded and polished grains of quartz, interbedded with beds of breccia. Clasts within the breccia are of vein quartz, quartzite and mica-schist. The sandstone may contain facetted pebbles [of dreikanter type]. Cross-bedding [false-bedding] is a conspicuous feature of the sandstone, which is interpreted as an aeolian sand-dune deposit. Greyish-white sandstone with a calcareous cement is noted at Muasdale [NR675 395].
The proven minimum thickness of the formation exposed in the roadside cliff at Bellochantuy is 6m [18ft] [Pringle, 1952]. However, this is considered only to be the edge of strata that extend under the sea and are continuous with other exposures of the Formation along the Kintyre coast [Pringle, 1952].
Overlying rocks no longer preserved.
Bellside Coal (Glasgow; Central Coalfield)
BELC
Beinn Leamhain Psammite Formation
BELE
Belfast Group
BELF
Bellside Ironstone (Central Coalfield)
BELI
Bellingham Coal (Northumberland)
BELL
Barness East Limestone
BELS
Bedminster Little Coal (Bristol Area)
BELT
Beoch Musselband
BEM
Beeding Marl
BEMA
Bettws Mill Tuff Member
BEMI
Bensham Coal (Northumberland)
BEN
Bencroy Shale Formation
BENC
Slieve Anierin
Bees Nest Member
BENE
Confined to scattered pockets on the Carboniferous Limestone outcrop of the Peak District, from north of Ramshorn [SK 088 463] to south of Monyash [SK 134 635].
Red, green and yellow silt and clay.
Ben Nevis Complex
BENEV
Benigarth Mica-Schist [?Formation]
BENI
Beinn Na Leac Member
BENL
First limestone bed above Dun Caan Shale Member.
Soft silty sandstones, harder calcareous sandstones becoming coarser upwards over the first 10m or so. The topmost part of the unit is thickly-bedded to massive sandstone with silty partings. Poorly fossiliferous, with rare bivalves, belemnites and ammonites.
21m
Overlain by cross-bedded sandstone of the Rasasay Sandstone Member.
Ben More Lava Formation
BENM
Bennachie Pluton
BENN
Ben Nevis Dyke Swarm
BENND
Benscliffe Breccia Member [Superfluous Entry: Use Cmba]
BENS
Not exposed; rests on fine-grained beds of Blackbrook Reservoir Formation, latter greenish-grey and commonly well-laminated.
Discontinuously exposed from Nanpantan (Rhododendron Hill) south to Benscliffe Wood, then north to Flat Hill. Possibly merges with Kite Hill Tuff north of latter.
Massive to thickly bedded sequence of dacitic volcanic breccia, lapilli tuffs and tuffaceous mudstones/siltstones.
c.21m in east, possibly over 100m in west.
Overlain by Beacon Tuff Member in east, and by Charnwood Lodge Volcanic Formation (undivided beds) in west.
Bentinck Coal (Northumberland)
BENT
Ben Vuirich Pluton
BENVU
Beoil Quartzite Formation
BEOQ
Gradational boundary with Dunalastair Semipelite Formation; boundary taken at base of first quartzite rib.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically in attenuated form as far west as Allt Druidhe [NN 6423 5693] and as far east as the Allt Kynachan [NN 7775 5723]. Not present east of the Loch Tay Fault, where it may have been tectonically excised;however some of the rocks of the 'Banvie Burn Series' may be equivalent.
Pelitic, semipelitic and psammitic rocks containing numerous characteristic ribs of pure white quartzite. Locally contains carbonate or graphite.
0 - 30m; probably much tectonic thinning.
Transitional boundary with Beoil Schist Formation; boundary taken at top of last quartzite rib.
Beoil Schist Formation
BEOS
Transitional boundary with Beoil Quartzite Formation; boundary taken at top of last quartzite rib.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically as far west as Allt Druidhe [NN 642 5712] and as far east as the Tomintianda Burn [NN 809 606]. Not present east of the Loch Tay Fault, where it is tectonically excised; however some of the rocks of the 'Banvie Burn Series' may be equivalent.
Schistose muscovite-rich pelite with a scattered garnet porphyroblasts and pods of vein quartz. Unusually mica-rich. Locally contains sporadic carbonate or graphite.
5 - 90m ; probably much tectonic thinning.
Apparently transitional boundary with Meall Dubh Striped Pelite; highly tectonised.
Beldorney Pelite Formation
BEPE
Sheared-out at western limit of Portsoy Shear-zone.
Cachnamuin Stripe, Bridgend (85E) to Bogforth, Cairnborrow (86W).
Pelite and semipelite, phyllitic and schistose, rarely slaty, commonly biotite-rich. Minor beds of psammite and quartzite. Thicker beds of gritty psammite.
Approximately 1250m maximum (based on maximum outcrop width and average dip).
Faulted-out, sheared-out or cut by mafic and ultramafic major intrusions and pods at eastern limit of the Portsoy Shear-zone.
Bellyhack Quartzite Member
BEQU
Base of massive quartzite, not exposed.
Core of Ardonald Anticline on Jock's Hill, Dufftown and from Clunymore to Hill of Bellyhack.
Quartzite, pinkish white, massive.
Over 200m.
Top of massive quartzite where overlain by flaggy micaceous psammites and semipelites of the Findlater Flag Formation.
Berllan Beds
BER
Benhar Coal
BERC
Beeston Regis Formation
BERE
Rests upon the Lowestoft Formation.
North-east Norfolk, possibly extending into north-east Suffolk.
Diamicton, comprising massive silty clayey sand with scattered pebbles of flint, sandstone, etc. containing rafts of chalk and bodies of "marly drift" (reconstituted chalk), interbedded with sands and laminated clays. (Age OIS 10 or 12).
About 50m thick.
Overlain by the Overstrand Formation.
Beragh Granite
BERG
Ben Rinnes Pluton
BERI
Ben Rinnes Pluton (Phase 1)
BERI1
Ben Rinnes Pluton (Phase 2)
BERI2
Ben Rinnes Pluton (Phase 3)
BERI3
Ben Rinnes Pluton (Phase 4)
BERI4
Blackstone Edge Sandstone
BES
The lower boundary is taken at the base of the first protoquartzitic sandstone-dominated unit above black fissile mudstone that includes a Hodsonites magistrorum Marine Band.
West Derbyshire - north-east Staffordshire. Revidge [SK075 598] - Blackbank [SK032 666].
Sandstone, protoquartzitic, in sharp-based medium-bedded units with some preserved sole marks on the bases of units, and mudstone with ironstone beds and nodules. Soft sediment deformation structures common in places.
30m
The upper boundary is taken at the base of mudstone-dominated succession overlying the Blackstone Edge Sandstone, below black fissile mudstone that includes a Reticuloceras reticulatum Marine Band.
Brodie Sandstone Unit
BESA
Ben Eagach Schist Formation
BESC
Base of dominantly graphitic succession above the dominantly semipelitic Killiecrankie Schist in Perthshire and the quartzitic Creag Leacach Quartzite Formation in the Glen Shee district.
North of Tyndrum eastwards to north of Loch Lyon and then from north of Schiehallion to east of Spittal of Glen Shee.
Black graphitic schist with fine-grained disseminated sulphides.
Not known
Top of dominantly graphitic succession below dominantly calcareous succession of the overlying Ben Lawers Schist Formation.
Belton Sand And Gravel
BESG
Betton Shale Formation
BET
Overlies Weston Flags Formation.
Grey shales and siltstones.
Underlies Meadowtown Formation.
Bedminster Toad Coal (Bristol Area)
BETD
Bettshanger L Coal (Kent)
BETL
Bedminster Top Coal (Bristol Area)
BETP
Beatrice Formation
BETR
Beverkae Limestone
BEV
Bewerley Shales
BEW
Bude Formation
On the north Cornwall and north Devon coast, the base is taken at the top of the Hartland Quay Shale, the uppermost of the named goniatite-bearing mudstones in the underlying Crackington Formation. Inland, where the Hartland Quay Shale cannot be mapped in pervasively folded terrain, as it is too thin, the base is taken at the incoming of softer, siltier thick-bedded sandstones of the Bude Formation above the dominantly thin- to medium-bedded sandstones and mudstones of the underlying Crackington Formation. In north Devon, south of Bideford, the base is taken at the sharp incoming of over 100m of grey mudstones and siltstones with two thin anthracitic coals (culm) above the cross-bedded thick-bedded Cornborough Sandstone that caps the top of the underlying Bideford Formation. Thick-bedded sandstone with internally massive beds typical of the Bude Formation, appear above these mudstones and siltstones.
Occupies large area in mid-Devon between the coast at Bude (SS 21 06) and the area west of Tiverton (SS 96 13).
Grey thick-bedded, somewhat argillaceous and silty sandstones, in laterally discontinuous internally massive beds 1-5m thick and commonly amalgamated into units up to 10m thick. When weathered the sandstones become buff and friable. Very thick beds of slumped and destratified strata are also present. Grey mudstones occur as interbeds up to 1m thick but locally packets of darker mudstone up to 20m thick with thin ironstone beds and bundles of thin sandstones are present, especially in the upper part of the Formation. Five named beds of black sulphurous "shales" with goniatite-bearing calcareous nodules occur within the Formation. Thin units of thin- to medium-bedded siltstones with Xithosurid trails are also present.
1290m+ calculated on the north Cornwall and north Devon coast.
The upper boundary is taken at an angular unconformity, where breccias of the Exeter Group rest upon sandstone and subordinate mudstone of the Bude Formation.
Birker Fell Andesite Formation
BFA
Taken at base of andesite succession unconformably overlying Skiddaw Group over most of the outcrop, except where andesites overlie bedded sandstones of the Letterbarrow Sandstone Formation in the west of the outcrop.
Stoneside Hill, west of Black Combe; Wasdale, Eskdale, Hard Knott, Harter Fell, and Devoke Water; Eskdale area, Borrowdale, Thirlmere, Matterdale Common, Gawbarrow, southeast of Ullswater, Haweswater and Swindale, Cumbria.
Predominantly a tabular sheeted succession of feldspar-phyric andesite lava flows, usually with blocky autobreccia at the top and base, and subordinate sills; includes some basalts, dacites and subordinate volcaniclastic deposits. Distinctive units are given Member status.
To c. 2.7km.
Overlain by Whorneyside Formation; change to andesitic lapilli tuff.
Broadford Beds Formation
BFB
Hettangian To Lower? Simemurian
Transitional, transgressive mudstones and sandstones from underlying Triassic.
Sea of Hebrides Basin.
The Broadford Beds Formation is fully described by Morton and Hudson, 1995, though Hesselbo et al, (1998) contradict this and rename the units described. BGS maps are based on the former reference. The description includes BHLS, BRKH and ADS, which are also documented in the Lexicon. The lower Broadford Beds are dominated by carbonate rocks, calcareous mudstones and mature sandstones. Coral-rich beds are abundant in the lowermost parts and are overlain by restricted marine-fauna-rich lagoonal sediments. A shallowing of marine conditions from neritic deposition during Blue Lias times to nearshore/lagoonal is inferred. The upper Broadford Beds comprise sandstones and sandy siltstones. Typically these are highly micaceous and ferriginous. An ironstone bed with chamosite is found on the Ardnish Peninsula. A diverse marine faunal assemblage is common.
50 to 100m
Abrupt facies change to Pabay Shale Formation.
Bude Formation And Bideford Formation (Undifferentiated)
BFBF
Big Flint Coal (Coalbrookdale)
BFCC
Bracklinn Falls Conglomerate Member
BFCO
A diachronous, transitional contact with the typical sandstone facies of the undivided Teith Sandstone Formation.
North-west limb of Strathmore Syncline between Lake of Menteith and Glen Artney.
Conglomerate with quartz clasts, interbedded with pebbly sandstones.
Variable, 150 m at Bracklinn Falls, 350 m at Craig of Port [NN 581 022], but not found south-west of Lake of Menteith, although it may correlate with a 2 m thick quartz conglomerate in Green Burn [NS 5115 9519].
Sharp, diachronous contact with sandstone and mudstone facies of the undivided Teith Sandstone Formation.
Bifidus Slate Formation
BFDS
Marked by rapid transition from massively bedded tuffs or tuffaceous sediments of the Beacon Hill Volcanic Formation.
Continuous outcrop from the coast to beyond Cadair Idris.
Mudstones with localised conglomerates, siltstones, tuffaceous debris flow deposits (Tal-y-Gareg Member).
95m (Sheet SH50NE) to 200m (Cadair Idris - Cox, 1925, Quarterly Journal of the Geological Society of London, Vol.81.
Marked by transition from bluish or olive green mudstones into nodular black mudstones (Fron Neurydd Formation).
Bankfield East Beds
BFEB
Bideford Formation
BFF
The lower boundary is taken at the incoming of channels overlain by syndepositionally disturbed units and thick, locally cross-bedded sandstones of the Westward Ho! Member above the regularly interbedded mudstones and turbidite sandstones of the Crackington Formation. The boundary is not exposed at the type section and has never been mapped, as the Westward Ho! Member was previously included in the Crackington Formation. Further work is needed on this boundary.
Bideford area (SS 45 27) eastwards to 6km west of South Molton (SS 71 26), mid Devon.
Mudstones with abundant thin to medium-bedded sandstones and siltstones with several thick units of thick-bedded sandstone. The upper two thirds of the sequence consists of nine coarsening upwards cycles (individually up to 180m thick) comprising in upwards order, black mudstone, silty mudstone, silt and sand-streaked mudstones, interbedded thin sandstones and mudstones, thick-bedded channelised cross-bedded sandstones capped by burrowed horizons and locally rootlets. The lower parts of some cycles contain units of thin-bedded 'Bourma-type' sandstone turbidites. Three of the thick cross-bedded sandstones capping the cycles are named, the topmost one being the Cornborough Sandstone. The lower third of the sequence (Westward Ho! Member) is not cyclic but comprises thin-bedded mudstones, siltstones and sandstones, some of which are turbiditic and others cross laminated and wave rippled. The Westward Ho! Member includes several channels filled by slumped and disturbed strata or, more rarely, cross-bedded or cross laminated sandstones.
1220m+ seen at the type section.
The upper boundary is taken at the sharp incoming of over 100m of grey mudstones and siltstones with two thin anthracitic coals (culm) of the overlying Bude Formation above the thick cross-bedded Cornborough Sandstone that caps the topmost cycle of the Bideford Formation.
Bencliff Grit Member
BFG
Base is a conformable passage with the underlying Nothe Clay Member, and marked by the upward gradational change from mudstone, becoming increasingly sandy upwards of the upper Nothe Clay, to fine-grained sandstone of the basal Bencliff Grit (Coe, 1995).
South Dorset.
Sandstone, fine-grained, and sandy siltstone, argillaceous, yellow and pale grey, medium- to very thick-bedded, with well developed swaley cross-stratification, planar and ripple lamination, and conspicuous erosional bases. In places these beds are intercalated with thin, discontinuous beds of sandy mudstone. The sandstones and siltstones locally contain large calcareous concretions (up to 1-2m in diameter), and the sandy mudstones are bioturbated with Diplocraterion. The sandstones are notably oil-impregnated.
Up to 7.5m
A sharp, planar, bored erosion surface at the top of the Bencliff Grit marks the upward change from fine-grained sandstone to thin allaceous limestones and mudstones of the basal Osmington Oolite Formation.
Broadford Gabbro (Skye Eastern Red Hills Centre)
BFGA
Bottom Fourth Waterloo Coal (Derby)
BFHWC
Blue Flats Ironstone (South Staffordshire)
BFI
Bowfell Links Sandstone Member
BFL
Taken at the base of well bedded volcaniclastic rocks generally overlying the Pavey Ark Breccia Member, but in places overlapping the Scafell Dacite and volcaniclastic breccia of the Cam Crags Member
From Thirlmere to Scafell and the Langdale Pikes, Lake District, Cumbria
Planar thin-bedded to ripple-cross laminated volcaniclastic siltstone and fine-grained volcaniclastic sandstone; some intercalated coarse-grained volcaniclastic sandstone containing elongate pumice fragments.
Up to 120m
Defined by the base of overlying volcaniclastic rocks of the Cockley Pike Member
Bishop's Frome Limestone Member
BFLS
Placed at base of thick mature calcrete, overlying red mudstones.
Hereford-Worcester-Tewkesbury districts, but may equate with 'Psammosteus' Limestone(s) present throughout Wales and the Welsh Borderland.
Rubbly, massive to nodular limestone-calcrete palaeosol horizons.
2 - 5m, locally up to 8m.
Placed at top of thick mature calcrete, above which sandstones of the overlying St.Maughans Formation appear.
Brushford Member
BFM
Didymograptus Bifidus Beds And Didymograptus Murchisoni Beds (Undifferentiated)
BFMB
Brofiscin Oolite Formation
BFO
The base of the Formation is taken at the sharp contact between the thin- to medium-bedded packstones of the underlying Barry Harbour Limestone Formation and the thick-bedded ooidal grainstones of the Brofiscin Oolite Formation. Along the southeast and east crop of the South Wales Coalfield the base is taken at the sharp junction between the dolomitized packstones of the Barry Harbour Limestone Formation and the overlying dolomitized oolite of the Brofiscin Oolite Formation.
Vale of Glamorgan [ST 00 74] and the south and east crops [ST 25 90] of the South Wales Coalfield, east of Swansea. Present in Gower [SS 50 90] but not mapped. Passes into the Clydach Valley Subgroup to the north.
Pale to purplish grey, thick-bedded to massive, cross-bedded, ooidal grainstone. On the southeast and east crop of the South Wales Coalfield the formation is dolomitized. Deposited as an ooid shoal.
17m in the north of the Vale of Glamorgan, thinning southwards to a feather edge in the south of the Vale of Glamorgan.
The top of the Formation is taken at the sharp junction of the ooidal grainstones of the Formation and the overlying thin- to medium-bedded skeletal packstones of the Friars Point Limestone Formation. Along the south and east crop of the South Wales Coalfield the top is taken at the sharp junction between the dolomitized oolite of the Formation and the very fine- to fine-grained dolomitized packstones of the Friars Point Limestone Formation.
Bottom Five Quarter Coal (Northumberland And Durham)
BFQ
Big Flint Rock
BFR
Beechcliff Sandstone
BFS
Bank Farm Sand And Gravel
BFSG
Brielle Ground Formation
Lower boundary is base pliocene.
Shelly marine glauconitic sands and clays.
Upper boundary is top pliocene.
Balgaverie Member
BGA
Late Ordovician, late(st) Caradoc (Streffordian), and linearis Zone (see Fortey and others, 2000, Column 78).
Base of sandstone lithology overlying dominantly silty mudstones of the enclosing undifferentiated Myoch Formation.
A suite of fossiliferous channel-fill sandstones in the upper part of the (silty-)mudstone-dominated Myoch Formation, containing distinctive late Caradoc shelly fossils.
About 8m
Taken at the top of the sandstone lithology beneath the overlying dominantly silty mudstones of the enclosing undifferentiated Myoch Formation.
Ballyagen Formation
BGAN
Balbardie Gas Coal
BGAS
Bowhousebog Coal
BGC
The precise Age is uncertain, but the bed lies within the limits of Arnsbergian to Langsettian.
Big Coal (South Wales)
BGCO
See Generalized Vertical Section, SS59SE
Ben Griam Conglomerate Member
BGCON
Unconformable on Moine metasedimentary rocks, which are mainly composed of migmatitic pelite and semipelite of the Loch Coire Formation, together with granitic sheets known as the Badenloch granite sheets, of the Caledonian Igneous Supersuite.
Mountain tops in the Ben Griam Mor and Ben Griam Beg area, Sutherland, about 28km northwest of Helmsdale.
Comprises a red conglomerate that contains clasts mainly of Moine Supergroup metasedimentary rocks and granite, and thin interbeds of sandstone.
Conformably overlain by sandstone of the undifferentiated Ousdale Arkose Formation.
Blengdale Tuff Formation
BGD
Not exposed, but taken at the base of the parataxitic silicic tuff resting on dominantly lithic-rich lithic-tuff of the Lowcray Formation.
Main exposures in Blengdale Forest to Ponsonby Fell, near Gosforth, Cumbria.
Rheomorphic, parataxitic tuff, rhyolitic in composition and locally autobrecciated. At top coarse breccia largely composed of clasts of tuff.
Estimated minimum preserved thickness c.250m
Not exposed, removed by recent erosion (overlain unconformably by Permian strata).
Bryn-Glas Formation
BGF
Overlies the Pencerrigtewion Member of the Drosgol Formation (Cave and Hains, 1986), with apparent conformity, although the boundary is likely to represent one or more syndepositional slide planes. Where the Pencerrigtewion Member disappears, the Formation cannot be distinguished from the underlying Drosgol Formation, and both have been grouped as the Garnedd-wen Formation.
Not specified.
Mid to dark grey massive mudstones, commonly slumped and destratified, with rafts and balled inclusions of sandstone; local thin-bedded siltstones.
30 to 195m
Conformably overlain by the anoxic hemipelagic mudstones of the Cwmere Formation.
Bron Y Graig Formation
BGG
Base unconformable on Ashgill sediments e.g. Maerdy Mudstone Formation.
Dark grey mudstones and yellow to light grey laminated siltstones, fine-grained grey to yellow sandstones, which are massive, graded or parallel and/or ripple laminated. Sporadic graptolites.
To 500m
Top succeeded by pale grey siltstones of the Bettws Mudstone Formation.
Beinn A'Ghlo Transition Formation And Glen Clunie Graphitic Schist Formation (Undifferentiated)
BGGC
Beenham Grange Gravel Member
BGGR
Sharp erosional base on Cretaceous-Tertiary bedrock.
Kennet Valley.
Gravel, variably sandy and clayey.
Commonly 1-6m, locally 10m
Terrace surface modified by erosion: underlies Beenham Grange Terrace 1 - 3m above Kennet Floodplain.
Lower Beenham Grange Gravel
BGGRL
Subdivision of Beenham Grange Gravel based on morphology, by break-of-slope only.
Upper Beenham Grange Gravel
BGGRU
Benglog Volcanic Formation
BGL
Llanvirn to Early Caradoc.
Overlies mudstones and siltstones of the Ty'r Gawen Mudstone Formation, though with possible unconformity or non-sequence in places. Northwards from the Cadair Idris district it oversteps the Melau Formation to rest on the Allt Lwyd Formation in the Harlech district.
Not yet specified.
Thick- to thin-bedded intermediate to mafic crystal tuffs and rare felsic tuffs, interbedded with pillowed lavas, hyaloclastites, and tuffaceous siltstones and mudstones.
To 250m
Conformably overlain by mudstones of the Ty'r Gawen Mudstone Formation in the Cadair Idris district, where it also passes laterally into the Pen y Gadair Volcanic Formation. In the northeastern part of this district it is overlain by the felsic tuffs of the Craig Cau Formation, with possible disconformity.
Baligill Limestone Member
BGLM
The lowest of the sequence of 3 thick [>1m] carbonate laminate [limestones] developed in the Bighouse Formation.
Onshore and immediately offshore of the Dounreay area, Caithness, Northern Scotland.
Laminated and bituminous microsparitic limestone interbedded with medium-grained sandstone and bituminous siltstone and mudstone.
The uppermost of the sequence of 3 thick [>1m] carbonate laminates [limestones] developed in the Bighouse Formation.
Bonds Glen Limestone Member
BGLS
Ballagan Formation
BGN
Not seen in type section; elsewhere transitional on cornstone-bearing sandstones of Kinnesswood Formation (as at a depth of 224.8m in British Geological Survey East Dron Borehole (NO11NW/24; NO1360 1572)).
Grey mudstones and siltstones, with nodules and beds of ferroan dolomite (cementstones), the beds generally less than 0.3m thick. Gypsum and, to a much lesser extent, anhydrite and pseudomorphs after halite occur. Desiccation cracks are common and the rocks commonly show evidence of brecciation during diagenesis. Both these features are associated with reddening of the strata. Where present, the restricted fauna is characterised by the bivalve Modiolus latus, but ostracods are more abundant. Thin sandstones are present in many areas, and thick localised sandstones are also now included in the formation.
About 900m (maximum) in the West Lothian area, and up to 250m in the Northern England Province.
The top is drawn at the top of the highest unit of mudstone and cementstone in any particular area. The Clyde Sandstone Formation usually overlies the Formation.
Bangor Formation
BGOR
Taken at the angular unconformity that separates the formation from the underlying volcaniclastic rocks of the Minfordd Formation.
In the immediate vicinity of Bangor, North Wales.
Volcanogenic sandstone and conglomerate, overlain by laminated fine-grained acid tuffites, including tuffaceous sandstone, siltstone and mudstone.
Up to 240 m thick.
Taken at the conformable transition into the purplish red siltstones of the Llanberis Slates Formation.
Bagshot Pebble Bed
BGP
Bwlch Groes Porphyritic Microgranite
BGPM
Porphyritic microgranite.
Unknown.
Bronllwyd Grit Formation
BGR
Uncertain, within range Comley?Merioneth.
Sharply defined but generally conformable base of coarse conglomeratic sandstone overlying the mudstones of the Llanberis Slates Formation.
Northern Snowdonia, North Wales.
Comprises thick bits of coarse-grained green-grey massive sandstone, and interbedded mudstone, which is locally manganiferous, and local conglomerates.
Formation not assigned to a group.
Gradational into basal mudstones of the Marchlyn Formation.
Big Rock Coal (South Wales)
BGRK
Bearing Grit
BGRT
The term is retained informally within the local lower part of the Pendleton Formation, pending revision of the mapping in the Pateley Bridge area, where the unit was formerly recognized as the lower leaf of their Grassington Grit Formation by Brandon et al. (1995).
Biggar Volcanic Formation
BGRV
The base of the volcanic pile above the Swanshaw Sandstone Formation in the Biggar area.
Biggar area, South Lanarkshire, Scotland.
A volcanic succession of basalts, andesites, trachytes and rhyolites, including rhyolitic tuff and breccia with minor intercalations of sandstone and conglomerate.
At least 100 m thickness locally.
The base of the overlying Auchtitench Sandstone Formation in the Biggar area.
Bagshot Formation
BGS
Drawn at base of thick, pale, fine-grained sands of the Bagshot Formation where it rests on silt and fine-grained sand of the Claygate Member (London Clay Formation).
London Basin.
Fine, white, buff and sometimes crimson sands, grey when unweathered, with sporadic seams of pale pipe-clay and local beds of flint-pebble gravel.
To c.120m south west of London; generally less than 30m
Generally eroded off. The formation includes the "Bracklesham Beds" and "Barton Beds" to the southwest of London.
Blackshale/Ashgate Group (Of Coals) (Nottingham)
BGSC
Baginton Sand And Gravel Formation
BGSG
Early Pleistocene to Mid Pleistocene.
Unconformable on pre-Quaternary bedrock.
The valley of the Proto-Soar River around Coventry, extending as far west as Snitterfield near Stratford-on-Avon. Eastwards it extends to Croft and Huncote (1:50 000 Sheets 155, 169) but does not extend onto Sheet 156.
The formation encompasses fluvial, lacustrine and organic deposits of the Proto-Soar River. The deposits are sands and gravels, with lenses of silt and clay. In the type area around Coventry, the formation includes gravels (the Baginton-Lillington Gravel of Shotton, 1953) overlain by sand (the Baginton Sand of Shotton, 1953). The gravels are up to 98% composed of grey and purple quartzite and vein quartz, largely of Triassic derivation, with a little Jurassic limestone, ironstone and robust fossils. The sands are fine- to medium-grained, clean and well-sorted. They are interpreted as the deposits of low-sinuosity braided rivers dominated by longtitudinal bars. They differ from the Bytham Sand and Gravel Formation by having a low proportion of Jurassic material.
Commonly overlain by Middle Pleistocene glacigenic deposits. Upper boundary may be difficult to determine where overlain by glaciofluvial sand and gravel, but the presence of more angular clasts, chalk, and poorer sorting in the latter is usually helpful.
Ballygomartin Sill
BGSI
Bogside Limestone
BGSL
Locally developed in the Bewcastle district, Cumbria.
The lowermost limestone in the Bewcastle Member in this area.
Bushley Green Member
BGT
Where river deposits overlie bedrock or glacial deposits.
River Severn Basin Chepstow.
Gravel, mainly flints and Triassic-derived quartzites. Local basal fossiliferous silts and sands. Sand and gravel, with clay, silt and mammalian bones; Fifth Terrace of the Severn; part of the Severn Valley Formation - [Generic description: academic papers and BGS Memoirs].
Up to 9m
The present day terrace surface.
Benarth Grits And Flags
BGTF
Bacton Green Till Member
BGTI
Mid Pleistocene.
The Bacton Green Till Member exhibits a gradational lower boundary with either the Mundesley Sand Member (outwash sands) or the Runton Till Member (subglacial till) of the Sheringham Cliffs Formation.
The Bacton Green Till Member crops out on the northeast Norfolk coast between Bacton Green and Sheringham.
The Bacton Green Till Member forms an extensive diamicton complex that consists of a stratified assemblage of stony diamicton with beds/laminae of sorted material including sand, silt and clay. It has been interpreted as being a subaqueous till deposited by melt-out and gravity flows (Lunkka, 1994; Lee et al., 2004). The calcium carbonate content of the matrix of the diamicton beds is typically within the region of 10-12% and is some 20% lower than tills from the underlying Lowestoft Formation.
The diamicton within the unit is stratified.
Variable but generally in the range of 10-15m.
Commonly the upper boundary of the Bacton Green Till Member is erosional - for example where it is overlain by the Weybourne Town Till and Runton Cliffs Sand and Gravel members of the Sheringham Cliffs Formation, and the Stow Hill Sand and Gravel of the Briton's Lane Formation. More rarely, in the Trimingham area, the till grades upwards into the Trimingham Sand and Trimingham Clay members.
Boat Of Garten Pluton
BGTN
BIOTITE-GRANITE, PORPHYRITIC PLUS TONALITE, PORPHYRITIC TO GRANODIORITE, PORPHYRITIC
Beinn A'Ghlo Transition Formation
BGTR
Black Rock Subgroup And Gully Oolite Formation (Undifferentiated)
BGUO
Barnt Green Volcanic Formation
BGV
Small area (fault boundries) immediately northwest of Barnt Green, Hereford and Worcester.
Crystal and crystal lithic tuffs, tuffaceous siltstones, sandstones and mudstones.
Uncertain - probable upward passage into Lickey Quartzite Formation.
Big Vein Coal (South Wales)
BGVC
Burgy Coal (South Lancashire)
BGYC
Bligh Bank Formation
Passage from brackish-marine to fully marine deposits (there is evidence of a basal stratigraphic hiatus in the Dutch sector).
Marine, medium- or fine- to medium-grained, clean, yellow-brown sands with characteristic Angulus pygmaeus bivalve assemblage.
Mostly <5 metres, but locally exceeds 25 metres in tidal sand ridges.
Sea bed.
Barrack Hill Andesite Member
BHAM
Brendon Hill Beds
BHB
Ballachulish Subgroup And Blair Atholl Subgroup (Undifferentiated)
BHBA
See the Lithology descriptions for the component subgroups.
Boyne Hollow Chert Member
BHC
Generally, loose shelly and phosphatic sands resting on the 'ragstone' at the top of the Shaftesbury sandstone. Chert beds appear a short distance above the Shaftesbury Sandstone.
From Compton Abbas (ST 870 185) northwards across the Shaftesbury sheet (313), and then across the Wincanton sheet (297).
Interbedded chert beds and nodules, up to 0.4 metres thick, with glauconitic sand and sandstone.
0-15m (6.3m+ at the type locality).
Above the highest bed of chert.
Boheeshane Chalk Formation
BHCK
Campanian. Gonioteuthis quadrata and basal Belemnitella mucronata zones. From Applinocrinus [Saccocoma] cretaceus Subzone (quadrata Zone).
Base defined by reference to the terminal pebble bed of the Creggan Chalk Formation and the stromatolitic `mulatto? surface in marginal areas.
North Antrim and East Antrim basins part of the Southern Uplands area and over parts of the Highland Border and Londonderry Shelf areas.
Limestone (chalk), with common massive flint bands and tabular flints. Some green-coated chalk pebble beds near the base and as a prominent bed associated with sponges in the middle of the sequence. Hard pellet chalk in softer matrix is common at some levels Divided into three main `Beds? (A, B and C) each further divided into numbered `units?. Each `Bed? separated by marked bedding planes that are locally emphasised by weathering. A number of notable fossil acmes throughout. Considered to be much finer-grained than older gritty members and termed `White Chalk? by Wolfe (1968). A distinctive massive flint band, which marks the upper limit of Gonioteuthis, is termed the Whitehead Flint Band (of bed status) whose type reference section is the old quarry at Whitehead [J 474 913].
Combined thickness at the type-site of 24.19m. Bed A 8.33m, Bed B 8.69m and Bed C 7.17m.
Taken at the well-developed erosional surface at the base of the Larry Bane Chalk Formation.
Bowland High Group And Craven Group (Undifferentiated)
BHCR
Berry Head Member
BHD
Blackhall Estheria Band
BHE
Bottom Hebburn Fell Coal (Northumberland)
BHEB
Blanket Head
BHED
Sheets of in-situ or partially moved weathering products of mostly <64 mm. grain size. May be frost-susceptible (clay-mica rich), cohesive deposits or non-frost-susceptible (granular) non-cohesive deposits. [Generic description: 'TMOS' procedures].
Beacon Hill Flags
BHF
West Yorkshire [Beacon Hill, south of Ripponden, Yorkshire].
Thinly laminated flaggy sandstones.
c.10m
Baily's Hill Flint
BHFL
Boghead Gas Coal
BHG
Brainshaugh Limestone
BHGL
Buller's Hill Gravel Member
BHGR
Described as Sparnacian to Bartonian. Thanetian is substituted for the obsolete term Sparnacian in current BGS usage.
The Buller's Hill Gravel, flint-rich gravels (as described in the lithology description) succeed the Tower Wood Gravel - a deposit of unbedded closely-packed unabraded flints in a matrix of clay and some sand. The boundary is marked by an unconformity and a variation in colour, with the overlying Buller's Hill Gravel being pale brown or pale grey, but typically darker than the underlying Tower Wood Gravel.
Occurs on both Great Haldon and Little Haldon in south Devon.
Unbedded, abraded flint gravels with subordinate clay bodies and sand beds. Flint fragments are up to 0.3m diameter, fragments of vein quartz, schorl (rock composed of tourmaline and quartz), quartzite and thermally-altered Carboniferous shale and chert are also present. This unit is interpreted to have been deposited in a fluvial environment; analysis of the clay matrix by Hamblin (1973) indicated incorporation of material reworked from the Tower Wood Gravel, and from Upper Palaeozoic rocks.
To 21m
The top of the Buller's Hill Gravel is in part removed by erosion, forming the modern land surface; elsewhere the flint-rich gravel of the Buller's Hill Gravel is succeeded by recent Head deposits of mixed lithology.
Barrhead Grit
BHGT
Bell's Hill Volcanic Member
BHHB
Unconformable: first appearance of pink flow-banded rhyolite unconformably overlying basalt and andesite flows of Bonaly Volcanic Member and thin conglomerates of the Greywacke Conglomerate Formation.
Pink, aphanitic, flow-banded rhyolite of flinty appearance with platy weathering. In thin section: cryptocrystalline, non-porphyritic, with no sign of fluxion or perlitic structures typical of higher rhyolites. The rhyolite is underlain locally by a thin conglomerate with subangular clasts of sandstone, chert and sporadic basic lava. Conglomerates are also intercalated with the rhyolite. At the top of the rhyolites sedimentary lenses are developed, consisting of bedded grey-green or purple micaceous sandstone with grains of quartz and microgranite, interbedded with conglomerates containing well-rounded greywacke, siltstone, microgranite and quartzite pebbles and angular rhyolite, microgranite, basalt and andesite pebbles derived from older lavas.
315m maximum.
Conformable: pink flow-banded rhyolite overlain by fine-grained basalt of the Capelaw Volcanic Member in the north. Overlain in the south by micaceous sandstones and conglomerates of the Greywacke Conglomerate Formation, and by andesites and basalts of the Allermuir Volcanic Member.
Ben Hiant Intrusion
BHI
Beacon Hill Sand And Gravel Member
BHIL
The lower boundary of Beacon Hill Sand and Gravel is erosional throughout much of the deposit's distribution area and it generally rests upon the Beacon Green Till Member of the Sheringham Cliffs Formation. In places, especially in the vicinity of Trimingham and Gimingham, the lower boundary is tectonic and wedges of Bacton Green Till have been thrust upwards into the deposit.
Coastal sections between Marl Point Mundesley [TG 2922383] and Trimingham [TG 283388], north Norfolk, and adjacent elevated ground inland between the coast and Gimingham.
The Beacon Hill Sand and Gravel Member consists of shelly, cross-bedded and rippled sands with flint-rich gravel seams and sporadic intraformational ice wedge casts and drop-soil structures (periglacial involutions). The lower horizons of the deposits are intensely glaciotectonized.
To approximately 12m
Where the Beacon Hill Sand and Gravel has been observed, it forms the highest stratigraphical unit within the succession intersecting the ground surface.
Barry Harbour Limestone Formation
BHL
The contact of the Cwmyniscoy Mudstone Formation with the overlying Barry Harbour Formation is gradational. In the uppermost part of the Cwmyniscoy Mudstone Formation, the proportion of packstone beds increases to exceed that of mudstone. The base of the Barry Harbour Limestone Formation is taken at the top of the last significant mudstone bed in the Cwmyniscoy Mudstone Formation, above which the succession becomes dominated by stacked fine- to coarse-grained skeletal packstones with scattered thin beds and partings of calcareous mudstone.
Vale of Glamorgan [ST 00 74]. Present in Gower [SS 50 90], Pembrokshire [SM 99 01], east crop of South Wales Coalfield [ST 25 90], Monmouth/Chepstow [ST 53 93] and Bristol/Mendip [ST50 65] areas but not mapped. Passes northwards in Wales into the Clydach Valley Subgroup.
Thin- to medium-bedded, dark grey, coarse- to fine-grained, commonly graded, skeletal [predominantly crinoidal, with subordinate brachiopods] packstones, either stacked or separated by thin beds and partings of calcareous mudstone. Planar, low angle and hummocky cross stratification, and cross lamination are common. Scattered bioturbation. Silicification of fossils and replacive elongate chert nodules common. In the Barry area, a unit [3 to 5m] of cross-bedded crinoidal grainstone, the Yorke Rock Bed, occurs at the top of the Formation. In the northwest of the Vale of Glamorgan, thin beds of ooid grainstone are present in the uppermost part of the Formation. Along the southeast and east crop of the South Wales Coalfield, the Formation is predominantly dolomitized; the upper part comprising very fine- to fine-grained, pale to dark grey, partly laminated and cross laminated dolomitised packstones with sparse fossiliferous lenses that are locally silicified.
80m in the south of the Vale of Glamorgan, thinning northwards to 32m on the south crop of the South Wales Coalfield.
In the Barry area, the top of the Formation is taken at the sharp contact between the crinoidal grainstones of the Yorke Rock Bed, and the thin- to medium-bedded, fine- to coarse-grained, skeletal packstones with scattered thin beds and partings of mudstone of the overlying Friars Point Limestone Formation. To the north of Barry, the top of the Formation is taken at the sharp contact between the thin- to medium-bedded packstones of the Barry Harbour Limestone Formation and the thick-bedded ooidal grainstones of the Brofiscin Oolite Formation. Along the southeast and east crop of the South Wales Coalfield the top is taken at the sharp junction between the dolomitized packstones of the Formation and the overlying dolomitized ooidal limestone of the Brofiscin Oolite Formation.
Berryhills Coal (Glasgow Area; Central Coalfield)
BHLC
Berryhills Limestone
BHLS
Glasgow and adjacent areas, Central Coalfield.
Belhelvie Basic Intrusion
BHLV
Beachy Head Marls
BHMA
Boat Harbour Marine Band
BHMB
Shale with ribs of clayband ironstone and marine shells.
5.48m at type section.
Low Haigh Moor Coal (West And South Yorkshire)
BHMC
West Yorkshire and South Yorkshire area.
Barrhead Main Coal
BHMCO
Bottom High Main Coal (Northumberland And Durham)
BHMN
Bottom High Main Coal (Derby)
BHMNC
Middle Bailey Hill Beds And Upper Bailey Hill Beds (Undifferentiated)
BHMU
Bath Oolite
BHO
Bottom Holers Coal (South Staffordshire)
BHOC
Ben Hope Sill Suite
BHOS
Ballygalley Head Plug
BHP
Ben Hiant Porphyritic Dolerite Intrusion
BHPD
Ben Hiant Pitchstone Sheet-Swarm
BHPI
Blelham Peat Formation
BHPT
Varies from sharply unconformable on bedrock and all Late Devensian or older Quarternary deposits (particularly tills), to disconformable on Lateglacial marine deposits of the Fern Beck Silt Member of the Hall Carleton Formation.
1.50k Sheets 28 Whitehaven, 37 Gosforth, western Cumbria, 38 (Ambleside) and 39 (Windermere) but can be applied to all Holocene to Lateglacial peat deposits within the Cumbria-Lancashire Catchments Subgroup area.
Peal, organic mud and silt, and fine silty sand infilling lake basins, lowland bogs and mires, kettle holes and alluvial tracts, also blanketing upland areas. It may contain fossilised remains of trees, herbs, grasses, etc, pollen, leaves and insect remains. Two members are recognised: Pow Beck Peat Member, which comprises compressed peat with wood fragments, twigs and seeds, interbedded with grey silt and tufa and some friable peat. It is of Holocene age and underlies alluvial deposits of the flood plain of the Pow Beck at St Bees, Cumbria; it locally underlies beach sand at St Bees beach. It overlies the Lowca Till Member of the Seascale Glacigenic Formation on St Bees beach, and overlies the Fern Bank Silt Member of the Hall Carleton Formation in the Pow Beck valley. The Seacore Peat Member comprises felted peat, thinly interbedded with humic sands in places. It contains insects and pollen of Lateglacial age (typically c.14000-10000 14C years BP) and forms part of the infill of kettle holes (noteably within the St Bees Moraine); it also occurs beneath the Pow Beck Member in the Pow Beck valley. In the kettle holes within the St Bees Moraine it is overlain by solifluction deposits of pebbly silty sand (of Loch Lomond Stadial age) and it overlies the glacitectonised sequence of deposits forming the moraine.
To 5 m thick in the Blelham Bog type area.
The ground surface, or overlain by Holocene blown sand of the Drigg Point Sand Formation or alluvium of the Ehen Alluvium Formation.
Bottom Harvey Coal (Durham)
BHRV
Brockholes Sandstones
BHS
Barnes High Sandstone Member
BHSA
Broomhouse Sand And Gravel Formation
BHSE
Dimlington Stadial to Windermere Interstadial.
Unconformably on bedrock or most commonly on older Quaternary strata particularly the Wilderness Till Formation of the Midland Valley Glacigenic Subgroup.
Central Scotland; Glasgow area, Stirling, Clackmannan, Tayside, north and south Lanarkshire, Lothians and Edinburgh, Fife and probably also Ayrshire.
Surface morphologies are of ice-contact; esker ridges, mounds and closed hollows.
Lithological associations are of rare matrix-supported bouldery gravel with sand, common framework-supported bouldery gravel with sand and pebbly coarse- to fine-grained sand, silt and clay. The most abundant is sand. The unit varies from loose to very dense and is up to 25m thick. Much of the gravel is massive to crudely bedded but planar beds and trough cross-bedded units are present. Sands are planar and trough cross-bedded, and ripple and horizontally laminated. Deformed bedding (including reverse faults and folds) probably marks the former contacts with dead-ice. The coarsest gravels were deposited by meltwaters flowing through tunnels in the wasting ice, massive deposits may have been laid down in the full-pipe sliding bed phase of water transport but most show cross-bedding features consistent with fluviodeltaic processes. Sandy clay diamictons might have been formed as debris flows in a fluvial context. Two members have been identified, the Ross Sand and Bellshill Clay.
The Broomhouse Sand and Gravel is named from Broomhouse, eastern Glasgow. Stratigraphical relationships and geographical distribution are in Browne and McMillan (1989a, Figures 2b, 3c and 4a).
Veneer about 25m.
Unconformably below younger Quaternary strata such as the Clyde Clay Formation but also exposed at surface.
Bulkeley Hill Sandstone Formation
BHSF
Conformable, within a gradational, interdigitating transition from the red, fine- to medium-grained sandstones of the Wilmslow Sandstone Formation to the interbedded red and green mudstone, brown flaggy sandstone and red-brown cross-stratified sandstone of the Bulkeley Hill Sandstone Formation.
Crops out at surface in the Bulkeley area, south Cheshire. Westwards, the formation is cut out beneath the erosional base of the overlying Helsby Sandstone Formation (Poole and Whiteman, 1966). In the subsurface to the east (Prees area), the formation is most fully developed in the hanging wall of the fault zone marking the eastern boundary of the Cheshire Basin, where seismic evidence (Evans et al., 1993) indicates a thickness of over 200m.
Sandstone, red, medium-grained with well-rounded "millet seed" grains, cross-stratified, interbedded with mudstone, red-brown and grey-green, and sandstone, brown, fine-grained, flaggy, micaceous.
Up to 22m at outcrop in the Bulkeley area, Cheshire (Poole and Whiteman, 1966), may reach up to 200m in the subsurface to the east, based on seismic evidence (Evans et al., 1993).
Unconformable, at the abrupt upward transition from the interbedded red and green mudstone, brown flaggy sandstone and red-brown cross-stratified sandstone of the Bulkeley Hill Sandstone Formation to deep red and grey mottled, coarse-grained pebbly sandstone at the base of the Helsby Sandstone Formation.
Barham Sands And Gravels
BHSG
Beachy Head Sponge Beds
BHSP
Boyn Hill Gravel Member
BHT
Rests unconformably on bedrock geology or older superficial deposits.
Thames Valley and associated tributaries.
Sand and gravel, with possible lenses of silt, clay or peat. [Generic description]. Poorly sorted, stratified gravel and locally tabular cross-bedded sand beds. Gravel assemblage is characterised by abundant angular flint (77-81%), sparse rounded flint (5-10%), sparse vein quartz (4-7%), sparse quartzite (1.5-5%), sparse Greensand chert (2.5-4%) and less than 1% of other types.
1-9m, average 5m
At surface.
Blackhall Till Formation
BHTI
Either rests directly on bedrock or as a sharp, subhorizontal, planar to gently undulating contact with limestone-rich gravel of the Limekiln Gill Gravel Formation.
Coast of County Durham and southern Northumberland.
Dark grey to greyish brown, locally reddish brown, very stiff, stony sandy silty clay diamicton with sparse fragments of shell. It contains clasts mostly of Carboniferous lthologies in southern Northumberland, with far-travelled rocks from the Southern Uplands and, south of Blyth, from the Lake District too; local Permian lithologies predominate south of the Tyne. Generally becomes more clayey and plastic upwards. Includes local lenses of sand and gravel.
Up to 15m
Generally a sharp, uneven, erosional contact with overlying red fine-grained sand of the Peterlee Sand Formation along the Durham coast.
Bottom Hutton Coal (Durham)
BHUC
Bathgate Hills Volcanic Formation
BHV
First occurrence of volcanic rocks above the Two Foot Coal in the West Lothian Oil-Shale Formation.
Bathgate Hills, west of a line from NT0066 to NT0980, extending westwards underground to a point west of the Rashiehill Borehole (NS839730).
Pyroclastic rocks and related basaltic lavas, mostly alkali olivine-basalts (basanite to hawaiite) and volcaniclastic rocks.
To 1000m
Highest occurrence of volcanic rocks, below the Roman Cement Limestone, Passage Formation.
Beacon Hill Volcanic Formation
BHVF
Marked by the rapid transition from bioturbated fine-grained sandstones (Basement Beds of Jones, 1933 op.cit) to massive tuffs.
Extends from coast north of Tywyn as far as Llanegryn Fault in the east. Equivalent to the Lower Acid Group (Cox, 1925. Quarterly Journal of the Geological Society of London, Vol.81) to the east of the Llanegryn Fault.
Massively-bedded and unbedded acid tuffs rich in embayed quartz xenocrysts. Locally, welding fabrics are preserved. Also includes agglomeratic tuffs, sandstones and mudstones.
Very variable - complicated by intrusion of dolerite sills. 40m - 420m.
Marked by the rapid transition from massive tuffs to mudstones, conglomerates and siltstones of the Bifidus Slate Formation.
Belhaven Point Vent
BHVN
Bromsgrove Sandstone Formation, Helsby Sandstone Formation, Wildmoor Sandstone Formation And Wilmslow Sandstone Formation (Undifferentiated)
BHWW
Beinn Iadain Mudstone Formation
BIAD
Birdsall Calcareous Grit Member
BICG
Bickerton Moraines Formation
BICKM
Bilton Coal Beds
BICO
Sharp on mudstone.
Bilton area, just north of Harrogate to Bishop Thornton, north of Harrogate.
Two coal seams separated by mudstone.
Sharp overlain by mudstone.
Binny Craig Sill
BICS
Birgidale Formation
BID
Visean (?early Asbian).
Base sharp, probably erosional, on the Clyde Sandstone Formation (top of Inverclyde Group), which is characterised by presence of pedogenic limestone and lack of coal seams.
Area around Birgidale Knock, south Bute, Scotland.
Grey mudstones, sandstones and seatearths with coal seams; non-marine.
c.16m (24m in Ascog Borehole).
Top is marked by the overlying Clyde Plateau Volcanic Formation. May be transitional, with interbedding of sedimentary rocks with lava flows.
Biddenham Member
BIDM
Unconformable, commonly chanelled base, resting on bedrock surface.
River Great Ouse Valley, Central England.
Fluviatile gravel with sand: contains thin fossiliferous clay layers with a temperate molluscan fauna. Numerous artifacts of Acheulian type have also been recorded.
0 to 4m
Barra Isles Dyke Swarm
BIDY
Bielby Peat Bed
BIEP
Bielby Sand Member
BIES
The Bielby Sand Member rests mainly on the Pocklington Gravel Formation or the Hemingbrough Glaciolacustrine Formation. In places there is a thin peat bed at the base. The contact is commonly sharp but locally gradational, with an increase in clay, gravel and/or peat content. North of Bielby, an increase in gravel and peat content marks the lower boundary.
The Bielby Sand Member is known to extend along the eastern side of the Vale of York from the Escrick Moraine in the north to the Humber in the south. The deposit is part of a Late Devensian drainage system and forms some levee-like features, particularly around Melbourne. In some areas it is covered by younger deposits but has probably commonly been removed by later erosion.
Dominantly yellow to pale brown and reddish yellow slightly clayey to slightly silty sand with local fine-grained gravels. The material is usually reddish brown and grey colour mottled as a result of near surface water processes. It is typically composed of moderately well sorted medium-grained quartz grains with minor bands of finer, coarser or pooly sorted material, including flint and chert. Thin beds (<5cm) of clayey sandy peat can occur within the unit.
General thickness is between 1 and 2m, but it can exceed 6m in parts and may form elevated topographic features.
The upper surface of the Bielby Sand Member is usually eroded and overlain by younger alluvial and aeolian deposits.
Brindister Flagstones
BIF
Big Coal (Somerset)
BIGC
Bighouse Formation
BIGH
Unconformable contact on Lower Devonian sandstone [Luachair Sandstone Member] and conglomerate [Tobaireach Conglomerate Member] of the Ousdale Arkose Formation. Also unconformable on Caledonian intrusive igneous rocks and Moinian metamorphic basement rocks.
Onshore and immediately offshore of Dounreay area, Caithness, Northern Scotland.
Sequence dominated by thickly bedded aeolian and fluviatile cross-bedded sandstone units with minor interbeds of conglomerate in the lower parts of the sequence, siltstones and microsparitic limestone interbeds also present. Thick mappable sandstone [Fresgoe Sandstone Member] present [topmost unit] also recognisable in borehole core and seismic records. Prominent laminated limestones [Baligill Limestone Member] present in the middle part of the Formation. Breccio conglomerate [Portskerra Conglomerate Member] present locally as basal unit of the formation; bed or beds of limestone [Arylevie Limestone Bed] present within or at the base of the Portskerra Conglomererate Member at some localities.
200 to 250m
Top of Fresgoe Sandstone Member, overlain by Sandside Bay Formation.
Bigholms Burn Peat Bed
BIGP
Big Rider Coal (South Wales)
BIGR
Bodmin Intrusion
BIIN
Bilton Coal
BILC
Bellshill Clay Formation
BILL
Dimlington Stadial.
Unconformity on bedrock or most commonly on older Quaternary strata, particularly the Wilderness Till Formation of the Midland Valley Glacigenic Subgroup. Conformably by passage on the Ross Sand Member.
Central Scotland; Glasgow area in the lower Clyde valley below Lanark and in tributary valleys including Strath Kelvin.
The typical lithological association is of silty clay with wisps, laminae and bands of silt and locally sand. The deposit is dark brownish grey to brownish grey. It may be varved with multiple silt units with graded bedding. Isolated clasts up to 1-2cm are interpreted as dropstones. The clays are of a firm to stiff consistency. Diamicton bands are present and there are dark tops to centimetre-scale varve units. The sedimentological features point to the Member being a proglacial lake bed deposit ("Lake Clydesdale") close to an ice margin. Its distribution in the Clyde valley southeast of Glasgow suggests that the ice margin retreated northwestwards through the area.
The Crossford Borehole (Browne and McMillan 1989a, Figure 24) is the standard section for the Bellshill Clay Member, between 0.5 and 6.91m in depth, where it rests on the Ross Sand Member. The name is from the Bellshill area where the unit is widely distributed at surface. Its stratigraphical relationships and geographical distribution in ibid are illustrated in ibid (Figures 2B, 3D and 4A).
Veneer to about 10m.
Unconformity below younger Quaternary strata such as the Clyde Clay Formation, but also exposed at the surface. Conformably by passage laterally and upwards into the Ross Sand Member.
Bilston Rock (South Staffordshire)
BILR
Birkfield Limestone
BILS
Brighton Marl
BIMA
Bilinguites Bilinguis Marine Band [See Also: R2b1 R2b2 R2b3]
BIMB
Lower Bishopsmoat Beds
BIML
Upward change in lithology from grey thickly bedded (blotchy) mudstone to grey interbedded siltstones and mudstones; thicker siltstones are calcareous and commonly show intense convolute lamination.
Grey interbedded mudstones and siltstones; thin siltstones show parallel lamination, thicker beds are calcareous and commonly show intense convolute lamination.
c. 125m. Lateral variations 0-400m.
Not seen in area of survey.
Upper Bishopsmoat Beds
BIMU
Upward change from grey interbedded siltstones and mudstones, the thicker siltstones with intense convolute lamination, to grey parallel laminated siltstones with subordinate mudstones.
Grey parallel laminated siltstones with subordinate mudstones; some thin fine-grained sandstone beds; convolute lamination uncommon.
Not surveyed. Total thickness c. 300m.
Bin Down Formation
BIN
Faulted off against purple and green mudstone of the Whitsand Bay Formation.
Geological sheet 348 (not mapped elsewhere).
Grey slaty mudstone and quartzitic sandstone with interbedded, apparently extensively silicified basic lava and volcaniclastic rocks.
Grey slaty mudstone passing up into purple and green slaty mudstone of the Whitsand Bay Formation.
Balmoral Index Coal
BINC
Binnend Limestone
BINL
Binnend Sandstone
BINS
The Burntisland area of Fife,
Sandstone.
33.32m. (Top 14.22m. Bottom 47.54m).
Bog Iron Ore
BIO
Impure, limonitic deposit, usually porous and probably formed as a result of bacterial action in swampy conditions; a low grade iron ore. [Generic description: Earth science dictionaries in the BGS library].
Beinn Iaruinn Quartzite Formation
BIQU
Birchlaw Limestone
BIR
Birchenwood Coal
BIRC
Birtley Limestone
BIRT
Birrenswark Volcanic Formation
BIRV
Irregular base on Upper Old Red Sandstone strata.
Lavas are best developed between Dinely and Langholm. They thin westwards towards Birrenswark Hill; the westernmost extension is west of Dumfries at Kirkbean Glen, Southerness, Kirkcudbrightshire.
Olivine-basalt lavas with impersistent sedimentary intercalations.
Faulted or irregular contact with Kirkbean Cementstone Member.
Bilsdean Sandstone
BIS
Type locality is at Bilsdean, near Cockburnspath, Berwickshire.
Yellow fine-grained even bedded sandstone.
c,12m
Bisat Group
BISA
Bogside Ironstone And Coal
BISC
Birstall Member
BISG
Soar Valley and tributary valley of Kingstone Brook.
Sand and gravel with minor clay and silt lenses.
To c.4m
Bishopston Mudstone Formation
BISHM
In the type area the lower boundary is placed at the base of thick, dark grey fossiliferous mudstones, where they overlie cherts and dark grey fissile mudstones of the Aberkenfig Formation conformably. The contact is not exposed there. Elsewhere, the lower boundary is placed at the base of thick grey, sporadically fossiliferous mudstones, which overlie the quartzitic sandstones of the Twrch Sandstone Formation disconformably.
The Formation crops out in a narrow belt around the periphery of the South Wales Coalfield and its extension in Pembrokeshire. The outcrop around the main coalfield extends from near Kidwelly [SN 360 050] on the north crop eastnortheast to near Brynmawr [SO 20 11] and south to near Caerphilly [ST 20 86] and west to Swansea Bay [SS 79 84]; in Gower from Bishopston to Mumbles; and in the Pembroke Peninsula from Druidston [SM 860 169] to Marros [SN 198 076]; and on the southern limb of the syncline from Tenby [SN 135 010] northwest to near the Cleddau River [c.SN 012 085].
Mid to dark grey mudstones, commonly fossiliferous, with some beds of mid grey siltstone and beds of interbedded siltstone and mudstone. Sporadic, minor pale grey quartzitic sandstones and rare thin coals.
To c.750m in the type area of Barland Common, Bishopston.
The top is placed at the top of the highest dark grey mudstone, where it is overlain disconformably by pale grey quartzitic sandstones of the Telpyn Sandstone Formation.
Binds Stone (South Staffordshire)
BIST
Bittadon Tuff Bed
BITB
Birchwood Semipelite Formation
BIWS
Burton Joyce Marine Band
BJMB
Originally defined in Nottingham and present in the Derbyshire-Nottinghamshire area and, as the equivalent Ditton Marine Band, in the Lancashire Coalfield.
St John's Rhyolite Formation
BJR
Within the outcrop of the Jersey Volcanic Group in northern Jersey.
Ignimbritic rhyolite flows.
Brockram
Sharp and irregular unconformable contact with older rocks, usually Dinantian, Westphalian or Ordovician (Borrowdale Volcanic Group). Geophysically the base is usually sharp, marked by a decrease in gamma-ray values and sonic interval transit times. This is most marked in West Cumbria where Brockram overlies the Carboniferous Limestone (Dinantian).
Vale of Eden, West Cumbria, Furness
Matrix and clast-supported breccias; clasts range from small pebble to cobble; the matrix is variously clay, silt and/or sand. The clasts reflect the local source rocks.
Very variable, up to 160m
May be sharp or transitional in West Cumbria. Sharp contact with overlying dolomite or dolomitic mudstones of the St Bees Evaporite Formation is marked by a rapid decrease in gamma-ray values and a less marked decrease in sonic interval transit times.
Birkby Fell Andesite Member
BKB
Base of lowest basaltic andesite/basalt flow. Rests on Devoke Water Member in type area; farther east on undivided feldspar-phyric andesites of the Birker Fell Andesite Formation.
Birkby Fell, Eskdale, Cumbria (SD 14 95) also Whincop, Eskdale (SD 180 993), Cumbria.
Dark grey to greenish grey basaltic and basaltic andesite lava flows; generally thin, porphyritic, simple aa-flows and intercalated bedded tuffs and volcaniclastic sandstones.
430 - >500m (upper boundary faulted in part). Absent to east of Devoke Water.
Overlain by blocky, porphyritic andesite flows of Birker Fell Andesite Formation (undivided).
Black Bed Coal (West Yorkshire)
BKBC
The Black Bed Coal is generally a good coal of former high economic importance despite common splits and local washouts. It has been mined extensively throughout the district, down to depths of more than 300m.
Black Band Member
BKBD
Cenomanian (Neocardioceras juddi Zone) to Turonian (Mytiloides spp. Zone).
Conformable at the basal surface of the Main Black Band as defined in Wood and Mortimore (1995) and Wood et al. (1997) with the underlying Plenus Marls Member defined herein.
A well-known marker throughout the Northern Province and in the offshore areas.
Interbedded black or very dark carbonaceous calcareous mudstone (the Black Band) and variegated calcareous mudstone (marl) succession terminating in the "sticky green clay" (Wood and Mortimore, 1995).
Generally about 0.5 to 0.6m but up to 1.4m in the Cleveland Basin.
Conformable at the junction between a sticky green clay (Bed 6 i.e. the top of the "Variegated beds", in Figure 4, Wood and Mortimore, 1995) and an extremely condensed succession of shell-detrital limestones with some thin very dark "marl" seams.
Black Band Coal (South Yorkshire)
BKBDC
Bowsebank Coal (Fife)
BKC
Blackclose Coal (Northumberland)
BKCC
Brock Crags Andesite Formation
BKCG
Taken at the base of the autobrecciated andesite overlying a few metres of sandstone of the Esk Pike Sandstone Formation. In some poorly exposed areas it may overlie silicic lapilli-tuff of the Lincomb Tarns Tuff Formation.
Brock Crags to Angle Tarn, south of Ullswater, Cumbria.
Locally brecciated andesite lavas, with thin intercalations of lapilli-tuff and volcaniclastic sandstone.
To at least 290m
Black Coal (Bristol Area)
BKCO
Birkenhead Sandstone Formation
BKD
Transitional from greyish red sandstones and siltstones of the Leaze Formation.
Muirkirk to Strathaven area, Strathclyde region, Central Scotland.
Sandstones, greyish orange, medium-grained, cross-bedded with a few thin pebbly beds.
Sharp boundary with dark greenish grey mudstones at base of Dippal Burn Formation.
Buckator Formation
BKF
Lower boundaries with the Boscastle Formation are taken at the gradational appearance of green grey mudstones with thin calcareous siltstones and limestones of the Buckator Formation above the dark grey sandstones and mudstones of the underlying Boscastle Formation.
Between Boscastle (SX 11 93) and Launceston (SX 33 85), north Cornwall.
Greenish grey mudstones with scattered thin calcareous siltstones. Several lenticular units of locally shelly limestone up to 0.6m thick are present. The formation intertongues with the Boscastle Formation, two tongues being present on the north Cornish coast.
35m+. Full thickness of formation not exposed.
Upper boundaries with the Boscastle Formation are taken at the gradational appearance of dark grey sandstones and mudstones of the overlying Boscastle Formation above the green-grey mudstones, with thin calcareous siltstones and limestones of the Buckator Formation.
Beckford Terrace Deposits
BKFD
Barkisland Flags
BKFL
Bank Farm Coal (Wyre Forest)
BKFM
Blackcraig Formation And Galdenoch Formation (Undifferentiated)
BKGA
Bothkennar Gravel Member
BKGR
Loch Lomond Stadial.
Markedly erosive base cut into the various members of the Forth Clay Formation, Wilderness Till Formation and bedrock.
Lower Forth valley, Forth estuary and Firth of Forth, concealed below younger estuarine and marine deposits.
Fine- to coarse-grained gravel, cobbles and boulders (one recorded to be at least 1.8m across in an old excavation at Bo'ness), subangular to rounded with some striated, locally in a matrix that varies from loose sand to firm clayey sandy silt. Clasts of mainly locally-derived Carboniferous and Devonian lithogies. The deposit is poorly sorted. It is considered to have been deposited by ice-rafting of materials during the Loch Lomond Stadial.
Veneer to at least 3.5m
Overlain unconformably by the early Holocene transgressive estuarine sand, silt and clay of the Letham Silt Member and also younger units including the Carse of Stirling Clay Member and later Claret Clay Member (Carse Clay Formation).
Baulking Sand Member
BKGS
Brock Hall Coal (Wyre Forest)
BKHA
Blackhill Coal (Northumberland)
BKHC
Black Hill Laccolith
BKHI
Beckingham Member
BKHM
Top of highest limestone in Granby Member.
East Midlands Shelf; thickens southwards towards London Platform; northwards, limestone beds develop within mudstone sequence.
Bluish-grey shaly mudstones, with rare thin limestones comprising a few per cent of the sequence.
21m to 24m; 22.10m in borehole F/B5.
Base of (ferruginous) Stubton Limestones in Foston Member, (see Brandon and others, 1990, for details of Stubton Limestones and other beds within Members).
Black Isle Sandstone Group
BKI
Unconformable base of Old Red Sandstone sequence.
Easter Ross-shire , Scotland.
Red sandstone sequence incorporating the Den Siltstone, Kilmuir Conglomerate and Raddery Sandstone Formations.
Unconformable base of the Balnagown Sandstone Group.
Birkdale Limestone
BKL
Black Law Plug (Greenock)
BKLAW
Brickiln Coal (North Staffordshire)
BKLC
Baldernock Limestone
BKLS
Black Law Vent And Plug (Jedburgh)
BKLW
Brinkmarsh Beds
BKM
Blackmine Coal (North Staffordshire)
BKMC
Black Metals Member
BKME
In the Central Coalfield, mudstone of this unit alternates (is interbedded) with sandstone of the overlying Limestone Coal Formation. The boundary is picked at the base of the lowermost bed of coarse siltstone or sandstone (Read, 1965). Locally, the erosive base of the sandstone has cut down into the member or is abruptly overlain by lavas in the Bo'ness area of the Livingston district (Read, 1965). In the Glasgow district the upper boundary of the unit is just below (within about 5m) of the Knott Coal horizon (Hall et al., 1998, fig.11).
Central Scotland.
A distinctive thick, laterally persistent dark grey mudstone (Read, 1965), distinguished by one or morebeds, termed "Black Metals Marine Bands" [not to be confused with the Black Metals Marine Band of Cumberland, of Duckmantian age], containing a varied shelly fauna indicative of a marine depositional environment (Wilson, 1967). The member also includes beds with Lingula and beds with a shelly fauna, including Naiadites, indicative of non-marine depositional conditions. Read (1965) describes a commonly recorded sequence within the member of mudstone with Lingula at the base, overlain by mudstone with non-marine bivalves or unfossiliferous mudstone, overlain by mudstone with a varied marine fauna comprising the middle part of the member and overlain by mudstone containing non-marine bivalves. The characteristic lithologies of the member vary laterally within the Midland Valley of Scotland. On the western side of the Central Coalfield in the Glasgow district, strata that comprise the member are described and illustrated by Hall et al. (1997, fig.11) as black and dark grey, carbonaceous mudstones and silty mudstones with characteristic development of brownish grey clayband ironstone nodules (California Clayband Ironstone). Sandstones are restricted to thin beds and comprise two or three metres thickness in a total interval thickness of about 32m. Eastwards from the Central Coalfield the member includes siltstone and sandstone beds that increase progressively in number and thickness to become the predominant lithology; seatearth and coal also appear (Read, 1965). In the western coastal Irvine district, the Logans Bands, thin beds of ironstone in a laterally persistent mudstone sequence containing Lingula and Naiadites or non-marine bivalves (Monro, 1999), have been correlated with the unit in southern and central Ayrshire by Simpson and MacGregor (1932) or Eyles et al. (1949).
The thickness of the unit is described by Read (1965) as exceeding that of the fining-upward cycles, otherwise typical of the Limestone Coal Formation, that are approximately 3m to 10m (10 feet to 30 feet) thick. In the Cardowan No.2 borehole, north of Glasgow on the western side of the Central Coalfield, the full development of the unit is 32.3m thick, from 470m to 502.3m depth (Hall et al., 1997, fig.11). The thickness of the member is similar in the Kincardine basin and the Fife-Midlothian basin. However, in the Kincardine basin in west Fife, the thickness of the member increases eastwards from 33m to a maximum of 66m, associated with the lateral change to an increasingly sandstone-bearing succession (Francis et al., 1970, p.190 and plate VIII).
In the Central Coalfield, the lower boundary of the unit is picked at the top of the Black Metals Basal Coal (Forsyth and Read, 1962). Eastwards the base is picked at the top of a laterally equivalent seatearth and correlated to a thin coal above the Torrance Four-inch Coal farther east in Fife (Read, 1965), fig. 2). Westwards, in the Glasgow district, marine fossils are recorded just above the lower boundary of the Black Metals Member, which is picked at the roof of the Upper Garscadden Coal (Hall et al., 1997, fig.11), where instead blackband ironstone (Upper Garscadden Ironstone) may be developed (Forsyth and Read, 1962).
Blackmires Limestone
BKML
Change up from grey calcareous mudstone of undifferentiated Granby Member; 62.40m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands; north Leicestershire to Lincolnshire. Not recognised in north Lincolnshire, or south Leicestershire, where it may pass south into part of the Rugby Limestone Member of the Blue Lias Formation (Ambrose, 2001).
Limestone, bioclastic, shelly, grey, weathering brown, laterally persistent. Fauna includes echinoderms, serpulids, bivalves and corals. In type section Borehole F/B5, a single limestone bed was proved; elsewhere in the vicinity up to three similar, closely-spaced beds were proved, of which the highest is most persistent.
0.3m in type section; up to 2m in Leicestershire
Change up into grey calcareous mudstone of undifferentiated Granby Member; 62.10m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Brackenslack Limestone
BKNL
Brockley Plug
BKP
Birk Riggs Formation
BKR
Conformably overlies the Brathay Formation.
Southern Lake District and north-west Pennines.
Sandstone, siltstone and mudstone turbidite with interbedded laminated hemipelagite.
Variable; c.75-380m.
Conformably overlain by the Coldwell Formation.
Black Rake Coal (Nottingham)
BKRC
Black Rocks Sill
BKRKS
Brook End Sandstone Member
BKS
Imprecise owing to harder mudstone lithologies; sandstone probably no more than c. 0.6m (proved in a borehole), but the magnitude of the feature suggests the horizon forming it is at least 2m thick.
Red fine-grained, well cemented sandstone and siltstone, either massive or with well developed bedding (cross bedding and parallel lamination). Overlying and underlying units are both red-brown silty mudstone. Unit includes harder silty mudstone lithologies indistinguishable in field.
2 - 3 metres (not exposed).
Birkhill Shale Formation
BKSH
Conformable on Upper Hartfell Shale Formation.
Southern Uplands of Scotland and Longford Down Inlier, Northern Ireland.
Black hemipelagic mudstone; grey mudstone with minor wacke sandstone.
Conformably overlain by wacke sandstones of the Gala Group
Lower Birkhill Shales
BKSL
Upper Birkhill Shales
BKSU
Branksome Sand Formation And Selsey Sand Formation (Undifferentiated)
BKSY
River Terrace Deposits, 2 To 3 (Blackwater)
BL2T3
River Terrace Deposits, 3 (Blackwater)
BL3
River Terrace Deposits, 4 (Blackwater)
BL4
Billingham Anhydrite Formation
BLA
Bowling Alley Coal (North Staffordshire)
BLAC
Ballachulish Pluton
BLACH
Bladon Member
BLAD
The base of the clay/mudstone marl of the Fimbriata-Waltoni Bed, or more rarely the limestone of the Upper Epithyris Bed where channelled through the Fimbriata-Waltoni Bed,as described in lthe lithological details, in most cases resting sharply on the eroded hardground top surface of pale grey to white wackestone of the Ardley Member of the White Limestone Formation.
Around Burford, Oxon, the unit passes westward into the Signet Member of the White Limestone Formation, north eastwood to the Brackley area where it passes into the lower part of the Blisworth Clay. Restricted to 1:50 000 Sheets 218, 219, 236 and 237.
A green and grey clay/mudstone, commonly lignitic and associated with fossiliferous marl of the Fimbriata-Waltoni Bed, succeeded by limestones of the Upper Epithyris Bed, including pale grey to white, more or less fossiliferous micrites, peloidal and shell fragmental marly wackestones or packstones, and minor ooidal grainstones.
Up to about 4m thickness.
A generally sharp, erosive boundary with cross-bedded shell-fragmental ooidal limestone or mudstone of the Forest Marble Formation.
Black Coal (South Wales)
BLAK
Blairfindy Limestone Member
BLAL
Bland Coal (South Lancashire)
BLAND
Ben Lawers Schist Formation
BLAS
Base of calcareous succession overlying the dominantly graphitic Ben Eagach Schist Formation.
Tyndrum to the Glen Shee area.
Calcareous schist with thin layers of psammite and hornblende schist with white metacarbonate rock, quartzite and graphitic pelite.
c.700m
Base of dominantly fine-grained amphibolitic succession of the Farragon Volcanic Formation west of Glen Shee. Base of dominantly psammite and semipelitic succession of Ben Lui Schist Formation east of Glen Shee.
Blane Water Silt Formation
BLAW
The Blane Water Silt Formation rests with angular unconformity on older Quaternary sediments including on the Gartocharn Till Formation (GATI) inside the Lock Lomond Stadial ice limit and outside on the Wilderness Till Formation of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup). In Strathblane the formation rests on members of the Clyde Clay Formation.
The Blane Water Silt Formation is recognised in the lower Endrick valley near its confluence with Loch Lomond and in the Blane Water valley above Strathblane.
The Killearn Borehole (Browne and McMillan, 1989, Plate 1, Figure 8) is the standard section for the Blane Water Silt Formation (0.5-15.61m depth). The typical lithology is of regular interbedded clay and silt forming varves with dark coloured tops. The clays are silty, reddish brown and brownish grey, with grey silt, some sand layers and wisps, and thin beds of diamicton up to 7cm thick. The clay is firm to stiff and of medium to high plasticity. Isolated stones up to 2cm are interpreted as dropstones. Lithological associations of the formation are consistent with deposition of muds on a lake bottom in contact and near to glacier ice.
Veneer to over 15m
The Blane Water Silt Formation is overlain conformably and by glaciotectonically emplaced younger sediments of the Drumbeg Sand and Gravel Formation and Gartocharn Till Formation in the Endrick valley outside and at the Loch Lomond Stadial ice limit. In Strathblane it is exposed at the surface.
Blackheath Beds [See Also Hwh]
BLB
Pebble beds, locally cemented to form conglomerates, and sands. The pebbles are almost exclusively well-rounded flints, and the sand comprises quartz with flint chips.
Use of term superseded by Harwich Formation, at least locally. See HWH.
0 to 12m
Blackband Coal (South Wales)
BLBA
Blackstones Band Igneous Complex
BLBAI
Blocking Coal (West Yorkshire)
BLBC
The Blocking [Bed] Coal (which corresponds to the Silkstone Coal of South Yorkshire) is a seam of fair quality for domestic purposes, but is usually divided by three dirt partings. It has been worked extensively throughout the district.
Black Bed Ironstone (West Yorkshire)
BLBI
The Black Bed Ironstone has been worked extensively around Bowling, Bierley and Low Moor. It consists of about 3m of mudstone with numerous bands of ironstone nodules, cumulatively about 0.6m. It commonly contains fish and plant remains.
Lower Blaisdon Beds
BLBL
Blake Brow Breccia Member
BLBR
Base of lowest thick unit (c.75m) of breccia and/or pebbly sandstone, resting with probable conformity on sandstone of the Deepdale Sandstone Formation.
Hart Crag and Hartsop above How, northeastern Lake District. (Between Grasmere and Patterdale).
Volcaniclastic breccia and pebbly volcaniclastic sandstone with some intercalated volcaniclastic sandstone.
200m (maximum)
Top of highest thick (c.20 - 30m) unit of breccia and/or pebbly sandstone, overlain by sandstone of the Deepdale Sandstone Formation.
Blue Lias Formation (Hebrides) And Breakish Formation, Interdigitated
BLBRK
This is composite unit is necessitated because there is a N-S facies change from shallow-water Breakish Formation [BRKH] (the former Broadford Beds BFB) on Raasay and Skye (though there is also some interdigitation there) to deeper water, alternating limestone and mudstone of the Blue Lias Formation [BLIH] in Morvern and Mull. In Ardnamurchan the 2 facies interdigitate in about 50-50 proportions (Oates 1976, 1978; Hesselbo et al 1998).
Upper Blaisdon Beds
BLBU
Blaeberry Coal
BLBY
Blackcleugh Limestone
BLC
Blackchapel Coal (Lothian)
BLCC
Blue Lias Formation, Charmouth Mudstone Formation And Dyrham Formation (Undifferentiated)
BLCD
Blandford Chalk Member
BLCH
Change from hard nodular chalk, to firm smooth chalk.
Probably continuous across the whole of southern England. Is equivalent to the combined Seaford and Newhaven Chalk of Mortimore, 1986, which may or may not be mappable units.
Firm, smooth, white flinty chalk; some thin marl seams present.
75 - 90 metres.
Taken just below a marked feature break that is thought to be formed either by a hardground or thick bed of flints. This appears to be the same feature that forms the 'secondary escarpment' of Gaster, 1944, in West Sussex.
Blackford Hill Member
BLCK
At base of tuff (where present) overlying trachytes and biotite andesites of Brad Hills Member, otherwise at base of thick pyroxene andesite flow.
Blackford Hill, Craigmillar Park Golf Course and King's Buildings campus, Edinburgh.
A thin local bed of tuff (3m), overlain by a thick flow of pyroxene andesite (100m), overlain by thin flows of feldspar-macro porphyritic olivine basalt (30m seen).
At least 130m
Not seen - unconformably overlain by Kinnesswood Formation rocks.
Bath Lodge Coal (Ballycastle, Northern Ireland)
BLCL
Rests on coaly shale.
Coal.
Overlain by dark shales.
Bull Cliff Bed
BLCLF
Balcomie Beds
BLCM
Block Coal (South Derbyshire)
BLCO
Blue Lias Formation And Charmouth Mudstone Formation (Undifferentiated)
BLCR
Balachuirn Sandstone Member
BLCS
Blind Cove Sandstone Member
BLCV
Base (probably conformable) of lowest of a series of thick units (2-25m) of pebbly sandstone, resting on bedded sandstone (undivided) of the Deepdale Sandstone Formation.
St Sunday Crag, Thornhow End, Deepdale, northeast Lake District (between Grasmere and Patterdale).
Pebbly volcaniclastic sandstone with intercalations of bedded fine- to coarse-grained volcaniclastic sandstone.
Overlain either by ignimbrite (St Sunday Crag Member) or breccia (Blake Brow Member).
Beinn An Leathaid Granodiorite Intrusion
BLDG
Ballylagan Member
BLE
Bleawath Tuff Formation
BLEA
Placed at upward change from sandstone of the Broom Farm Formation to eutaxitic lapilli tuff.
Seen in Sellafield boreholes 2 (NY00SE/28), 4 (NY00SE/29), 5 (NY00SE/30), 10A (NY00SW/38).
Massive eutaxitic lapilli-tuffs containing abundant pumice and nonvesiculated juvenile clasts; zoned andesitic to rhyodacitic composition; thin rhyodacite at base; laminated/bedded sandstones separate some igneous units.
c.416m (uncorrected for structural dip or borehole deviation from vertical). 201m, 322m, 200m proved but unbottomed in boreholes 4, 5 and 10A respectively.
At the reworked top of thick, massive welded tuffs at this change to thinner sheets of generally lithic rich lapilli tuffs of the Brown Bank Tuff Formation.
Blackbyre Coal (Glasgow; Central Coalfield)
BLEC
Ben Ledi Grit Formation
BLEG
Outgoing of chloritic and epidotic, pale to dark green and grey rocks or outgoing of clean, coarse arenites and incoming of more matrix-rich arenites and wackes.
Southern Highland Group outcrop across southern Highlands of Scotland, from Glen Clova and Glen Esk to the Kintyre peninsula, Argyllshire.
Metasandstone, arenite to wacke, pale to dark grey, fine- to very coarse-grained, locally gritty and pebbly, interbedded with semipelite and pelite; contains brown-weathering calcareous nodules in upper part. Generally becomes coarser-grained upwards.
In excess of 2000m (estimated)
Outgoing of chloritic and feldspathic coarse arenites and wackes and incoming of clean arenites (base of Keltie Water Grit and Loch Ard Grit formations).
Blenfire Coal (South Lancashire)
BLEN
Bailey's Beds
BLEY
Ballyleighery Formation
BLF
Belfast Marls Formation
BLFM
Cenomanian. Mantelliceras mantelli to basal Acanthocerus rhotomagense Zone.
Unconformable, oversteps various older units.
East Antrim Basin and Southern Uplands area of Northern Ireland.
Pale grey strongly bioturbated silty marls with a scattering of dark green glauconite grains (not exceeding 40%). Transitional `zone? at the top contains relatively little glauconite. Fossiliferous with concentrations into discreet laterally continuous shell-beds.
Maximum thickness of a little less than 3.0m known from a borehole near Magheramorne [J 433 975] in the Larne (sheet 21) area. Minimum thickness of 1.6m over the Knockagh Axis north of Belfast.
Conformable, junction arbitrarily drawn at the base of the lowest persistent hard calcareous siltstone of the overlying Island Magee Siltstones Formation. This junction appears at the top of a transitional zone showing an upward decrease in glauconite content
Blengdale Glacigenic Formation
BLGL
Sharp, irregular, unconformable contact of diamicton on bedrock, or undulating to planar, unconformable contact of diamicton on laminated silt and clay of the Stubble Green Silt or Carleton Hall Clay members of the Glannoventia Formation.
Western side of the Lake District and at depth beneath Lower Wasdale.
Interbedded units of gravelly sandy clay diamicton, sand, gravel, silt and clay, typically reddish brown, with clasts mainly of Borrowdale Volcanic Group rocks (rhyolite, welded tuff, slate), granite and granophyre from the Lake District.
To 20m
Ground surface, or sharp, undulating, unconformable contact of diamicton with overlying dark brown laminated clay of the Whinneyhill Coppice Clay Member of the Aikbank Farm Glacigenic Formation.
Balgrochan Beds
BLGR
Ballyboley Halite
BLH
Bullhead Bed
BLHB
Burton Lazars Head
BLHD
Blair Hill Tuff Member
BLHT
Blue Lias Formation
BLI
At the base of grey limestone or mudstone sharply overlying irregular surface of pale grey or bluish and greenish-grey or reddish brown mudstone of the Cotham Member (Lilstock Formation) or eroded, commonly bored, locally conglomeratic surface of pale porcellanous limestone of Langport Member (Lilstock Formation). Coincides with the base of the Lias Group, which is commonly markedly non-sequential.
Wessex Basin, Central Somerset Basin, Worcester Basin and adjoining marginal areas (Radstock-Bristol Shelf and South Wales), southern part of the East Midlands Shelf ie. Dorset coast to approximately Leicester.
Thinly interbedded limestone (laminated, nodular, or massive and persistent) and calcareous mudstone or siltstone (locally laminated). Individual limestones are typically 0.10-0.30m thick. In some areas, intervening mudstone units with relatively few limestone beds. Also includes littoral limestone facies of the Radstock Shelf - Mendip area and South Wales.
To c.140m
At the base of the Charmouth Mudstone Formation. In any one section, this coincides with marked upward decrease in abundence of limestone beds, locally associated with marked decrease in their individual thickness and lateral persistence. In many cases, the horizon to be taken is obvious. Where there is doubt; the thickness and vertical frequency of limestone beds should be considered, and the following guidelines used: at top of a more or less persistent, thick (>0.10m) limestone above which the overlying mudstone (beneath any subsequent similar limestone) is at least twice the thickness typical of the underlying limestone-mudstone interbedded unit and above which is no return, within the Lias Group, to limestone-mudstone spacing on that previous scale. In type section, top formerly taken at top of Scipionianum Bed but characteristic interbedded limestone/mudstone sequence continues above that Bed, and that upper boundary in type area should be drawn at a higher stratigraphical level. In Dorset coastal sections, top is at top of Grey Ledge (Bed 49 of Lang, W D, 1924); in Somerset coastal sections, top is at the top of Bed 238 of Whittaker, A and Green, G W, 1983.
Blue Lias Formation (Hebrides)
BLIH
Black Limestone (Isle Of Man)
BLIM
Southern Isle of Man
Blackbrook Reservoir Formation
BLK
Sharp contact with South Quarry Breccia Member of the Ives Head Formation.
The unit extends from Longcliffe Golf Course south to Benscliffe Wood and then north-east to Grace Dieu Warren.
Green to grey, graded volcaniclastic mudstones, siltstones and sandstones with massive beds of volcaniclastic sandstone and breccia.
c.625m
Sharply overlain by Benscliffe Breccia Member, of the Beacon Hill Tuff Formation.
Black Bass Coal (North Staffordshire)
BLKB
Blackcraig Formation
BLKC
Interfingers with the Kirkcolm Formation.
Southern Uplands of south Scotland.
Massive wacke and conglomerate.
Blakeney Formation
BLKN
Blackstone (Shropshire)
BLKS
Bee Low Limestone Formation
BLL
Taken where the top of the highest dark micritic or calcilutitic bed of the Woo Dale Limestone Formation is overlain by pale grey limestone of the Bee Low Limestone Formation.
Peak District, Derbyshire, UK.
Pale grey, pale brownish grey to grey, fine- to medium-grained calcarenites, thick-bedded with scattered crinoid debris; mainly biosparites, but biopelsparites and pelsparites also occur. Peloidal calcarenites are present in the lower part and the back reef facies. Pedogenic crusts and palaeokarstic features are common on many of the major bedding planes. Towards the apron reef, the limestones become increasingly micritic and poorly bedded, with more peloids and ooids and the local development of conglomeratic limestones.Two volcanic members are present, namely the Ravensdale Tuff and the Lower Miller's Dale Lava.
From 68 to 213m in the Buxton district, with 161.94m measured in the BGS Eyam Borehole.
Taken where the base of the lowest dark limestone bed of the Monsal Dale Limestone Formation overlies the pale grey limestone of the Bee Low Limestone Formation. Volcanic horizons (including the Upper Miller's Dale Lava Member and the Winstermoor Lava Member or equivalent beds of altered clay) intervene locally.
Bee Low Limestones Formation (Apron-Reef)
BLLA
Bull Coal (Somerset)
BLLC
Blackstokes Limestone Formation
BLLF
Bee Low Limestones Formation (Knoll-Reef)
BLLK
Blackhall Limestone
BLLS
Generally seen as a conformable change from marine mudstone underlying the Blackhall Limestone above a thin coal or seatearth within the Lower Limestone Formation, that forms the top of the Inchinnan Limestone cycle.
Throughout the outcrop and subcrop of the Lower Limestone Formation in the Midland Valley of Scotland, but locally absent in Ayrshire and Strathclyde, on highs largely created by the Clyde Plateau Volcanic Formation.
A pale to dark grey, crinoidal, bioclastic, earthy to hard limestone, interpreted to be of marine origin, with thicker occurrences comprising calcareous mudstone and lime mudstone beds, thinly bedded above and massive below. In the Glasgow area, the lower leaf of the limestone is a brownish grey ostracodal limestone.
From 0.45m to 3.70m in the Airdrie, Falkirk and Glasgow districts, whereas in interpreted on-shelf settings such as around Midlothian, it can be 15m to 18m.
Generally seen as a conformable change to thick marine mudstone containing the Neilson Shell Bed fauna that passes up into deltaic arenaceous deposits of the Lower Limestone Formation.
Ballymastocker Formation
BLLY
Ballinamallard Mudstone Formation
BLM
Not exposed, presumed to be gradation from underlying Ballyreagh Conglomerate Formation.
The south-western part of the Fintona Block, Northern Ireland.
Mudstone; grey-red and purple-red mottled, with micaceous siltstone and thin, fine-grained sandstones.
c.1000 metres.
Not exposed, everywhere faulted out.
Blackrock Marl
BLMA
Blackband Marine Band
BLMB
This code/name combination probably refers to the Lingula Band close to the top of the Scottish Middle Coal Measures Formation in Central Ayrshire.
Blairhall Main Coal (Cowdenbeath)
BLMC
Balmae Grits
BLMG
Blairhall Main Coal (Fife)
BLMO
Blackpool Mudstone Member
BLMU
Black Neuk Member
BLN
Late Ordovician, early Ashgill, Pusgillian, complanatus Zone (see Fortey and others, 200, column 77).
Rests on the mudclast conglomerate of the Forge Member of the Mill Formation.
Green and grey silty shales.
c.15m
Overlain by flaggy sandstones and siltstones of the Shalloch Formation.
Black Nore Sandstone Formation
BLNS
Blaen Onnen Oolite Formation
BLO
In the Clydach Valley, the base is a sharp, palaeokarstic surface cut in dolostones of the Pantydarren Formation, overlain by basal ooidal grainstones of the Blaen Onnen Oolite Formation. At the type locality, the base is placed at the base of massive ooidal grainstones that overlie a prominent 0.3 to 0.5m-thick rubbly bed of radiating fibrous calcite nodules.
Northeast crop of the South Wales Coalfield; its correlation with parts of the Abercriban Oolite Group in the Merthyr Tydfil district is unclear, and thus its known limits extend from Cwar yr Hendre [SO 090 146] east to Craig-y-Gaer [SO 2290 1263]. To the south of the Clydach Valley it becomes dolomitized, but it is present at Craig Quarry [SO 2723 0738] and may be crinoidal dolostone at Gallowsgreen Quarry, Varteg Hill [SO 2662 0677].
Massive medium-grained, ooidal grainstone and crinoidal dolostone.
To 14m
In the Clydach Valley the top is a sharp junction, where fine-grained dolostones of the Coed Ffyddlwn Formation overlie the topmost ooidal grainstones of the Blaen Onnen Oolite Formation. At the type locality, the top is an irregular palaeokarstic surface unconformably overlain by green clay forming the base of the Llanelly Formation.
Blockfield
BLOC
Variable lithology. In-situ or nearly in-situ rock debris of mountainous areas. Openwork, clast-supported accumilation of blocks (>64 mm.) without a cliff or steep slope above as an apparent source. May be active or inactive. [Generic description: 'TMOS' procedures].
Bath Lodge Lava Formation
BLOF
Blaen Onnen Oolite [Obsolete Code: Use Blo]
BLOO
Birdlip Limestone Formation
BLPL
Opalinum Zone to Bradfordensis Zone (and probably Concavum Zone).
Disconformity: change upward from mudstone, sandstone or ironshot limestone of Lias Group into predominantly ooidal limestone sequence as in lithological description.
Cotswolds Hills from north Oxfordshire (near Chipping Norton) to northeast South Gloucestershire District. Absent due to overstep by Salperton Limestone Formation in south Cotswolds and in Vale of Moreton area. (See Barron, A J M, et al, 1997, fig.4).
Predominantly pale coloured ooidal limestones of varying types; ferruginous and sandy (Leckhampton Member), pisoidal and shelly (Crickley Member) at the base, unfossiliferous and cross bedded in the middle (Cleeve Cloud Member), shelly and marly in the upper part (Scottsquar Member), uppermost beds include sand and clay (Harford Member).
Typically 40 to 46m; type section c.45m, maximum c.74m (Cleeve Hill area).
Disconformity, generally a hardground: overlain by Aston Limestone Formation where present, or Salperton Limestone Formation.
Blargie Quartzite Member
BLQA
Marked by 5m thick zone of interbanded quartzite and semipelite. Overlies semipelites of the An Stac semipelite and psammite.
Central Highlands of Scotland, Laggan, Glen Banchor and Kincraig areas.
Cream to pinkish white quartzite and siliceous psammite with subordinate semipelite.
Incoming of K-feldspar-bearing psammites of the Creag Liath Psammite.
Bad An Loin Quartzite Member
BLQU
Base of cream quartzites stratigraphically above the top of clean white quartzites of the Carn Dubh Quartzite Member.
Northern part of Glen Shee district, (Sheet 56W).
Cream quartzite and micaceous psammite.
Top of dominantly quartzite succession. Gradational boundary with increasing proportion of graphitic schist into the overlying dominantly graphitic Ben Eagach Schist Formation.
Blenfire Rock
BLR
Bellringer Coal (North Staffordshire)
BLRC
Blackrock Grit Formation
BLRO
Blair Shale Formation
BLRS
Conformable on the Drumyork Flags Formation.
The Girvan area of south-west Scotland.
Yellowish-brown, thinly bedded shales and sandstones containing three graptolite-bearing horizons.
84 m thick.
Conformably overlain by the Knockgardner Sandstone.
Blue Lias [Obsolete Code: Use Bli]
BLS
Ballasalla Beds
BLSA
Black Shales And Conglomerates
BLSC
Bullerthorpe Lane Sandstone
BLSD
Blackhills Sand And Gravel Formation
BLSG
Lies (in part) on the Essie Till Formation, the Whitehills Glacigenic Formation, and on bedrock.
From Elgin to Fraserburgh, southwards to New Pitsligo [NJ 880 560].
Glaciofluvial outwash and ice-contact sand and gravel, locally with shell fragments. Silt and clay in local glaciolacustrine pockets.
Present land surface. Locally overlain by the Arnhash Till Member of the Essie Till Formation.
Black Limestones And Shales
BLSH
Bofrishlie Slate Formation
BLSL
Incoming of dominant black slate and chert and the outgoing of pale arenites at top of Loch Ard Grit Formation. Probable faulted contact with Dalradian.
Southwest of Aberfoyle and northwest of the Highland Boundary Fault; not known beyond western margin of Sheet 35E.
Slate, black, graphitic, with pyrite and locally abundant chert laminae, and subordinate grey and pale green arenite near top. Lenses of spilite and amphibolite occur locally. Locally fossiliferous with a brachiopod faunal assemblage.
600m maximum
Appearance of carbonated serpentinite and jasper-rich rock of the Lime Hill Serpentinite; contact probably faulted.
Braemore Lodge Sandstone Member
BLSS
Unconformable contact onto crystalline basement rocks or conformable contact onto the Langwell Conglomerate Member of the Ousdale Arkose Formation.
Scotland Sheet 109E (Western part of Berridale outlier only known at present) may extend onto Sheets 103W Golspie, 103E Helmsdale and 110 Latheron.
Sandstone, flaggy, red, purple or green.
To 150m
Conformable with the base of the Braemore Mudstone Formation.
Blackstone (Jurassic)
BLST
Ben Loyal Intrusion
BLSY
Blue Tour Coal (Ayrshire)
BLT
Bellscamphie Till Formation
BLTI
Probably widespread over central Buchan and as pockets to the south and east (beneath Logie-Buchan Glacigenic Subgroup).
Diamicton, stony, sandy, strong brown or yellowish brown. Mostly rock types derived short distance to the northwest. Locally containing flint and quartzite from the Buchan Ridge Gravels.
2m or more
Unconformable with Pitlurg Till Formation or other, younger glacial or glaciofluvial deposits.
Bottom Little Limestone
BLTL
Bulthy Formation
BLTY
Ben Lundie Formation
BLU
Blue Limestone
BLUL
Ben Lui Schist Formation
BLUS
Top of hornblendic rocks of the underlying Farragon Volcanic Formation or calcareous rocks of Ben Lawers Schist Formation.
Ben Lui to Glen Isla.
Dominantly schistose to gneissose semipelite. Psammite locally developed in lower parts and pebbly psammite and psammite locally developed at top.
Base of calcareous lithologies of the Loch Tay Limestone Formation.
Broad Law Vein
BLV
Black Vein Coal (South Wales)
BLVC
Blackwater Pluton
BLWA
Blackwater Limestone Formation
BLWF
Blackwater Formation
BLWR
Faults and shear-zones of the Portsoy Lineament truncate base of formation along the whole of its strike length.
Between the Black Water and the headwaters of the River Deveron and on both sides of the Deveron Valley between Bridgend and Lynebain in an outcrop up to 3km wide. Cabrach area, Moray District. 1:50 000 Sheets 75E, 85E and 86W.
Greywacke grits, phyllitic pelites and andalusite bearing semipelites; quartzites; basic and ultramafic meta volcanic rocks.
2500 m (based on outcrop width only - no allowance for probable folding).
Base of highly magnetic biotite-andalusite-schist easily mapped and/or traced by magnetometer between NJ 405 312 and NJ 441 351 (the Garnel Burn Member of the Clashindarroch Formation).
Balleys Beds
BLYB
Blaguegate Yard Coal
BLYC
Blyth Coal (Nottingham)
BLYCO
Braslyd Coal (South Wales)
BLYD
Ballytrea Formation
BLYT
Blakeney Valleys Formation
BLYV
Mid Pleistocene to Holocene.
Unconformable on glacial and solifluction deposits and on Crag Group and Chalk Group bedrock.
North Norfolk, north of the watershed defining the catchment of the River Bure.
The formation encompasses the fluvial, lacustrine and organic deposits of the rivers that flow into the North Sea along the coast of north Norfolk. It includes floodplain alluvium and a restricted development of river terrace deposits. The floodplain alluvium comprises soft clays, silt and fine-grained sands, with bodies of peat, overlying fine- to coarse-grained sands and gravels. River terrace deposits are largely gravel and sand. The gravels are dominated by subangular to rounded flint, including large cobbles, but also include rounded pebbles pf quartz and quartzite, northern British erratics of glacial derivation, and a little chalk.
c.5m
Barr Limestone Formation
BLZ
Gradational increase in thickness and number of limestone beds from underlying Buildwas Formation.
South Staffordshire.
Grey, micritic limestone interbedded with grey mudstone containing large calcareous nodules.
9-10m at Walsall
Gradational decrease in thickness and number of limestone beds to overlying Coalbrookdale Formation.
Belemnite Marl Member
Base of hummocky limestone (base of bed 103 of Lang, W D, et al, 1922). Pale grey colour of Belemnite Marl Member contrasts strongly in cliffs with darker underlying Black Ven Marl Member. Non sequence at base between Sinemurian and Pliensbachian stages.
Southwest Dorset; mapped on sheet 327 (Bridport). Northern Limit not yet proved.
Pale grey and dark grey interbedded calcareous mudstones with abundant belemnites at many levels.
20 to 27m in coastal sections.
Top of Belemnite Stone (top of bed 121 of Lang, W D, et al, 1923). Conformable junction with Green Ammonite Member.
Broxburn Marls
BMA
Within the range Asbian to Brigantian.
Broughton Moor Formation And Appletreeworth Volcanic Formation (Undifferentiated)
BMAV
Bembridge Marls Formation
BMBG
Lower Bembridge Marls
BMBL
Upper Bembridge Marls
BMBU
Ballymagarry Chalk Formation
BMC
Campanian. Belemnitella mucronata Zone sensu lato.
Conformably overlies the Portrush Chalk Formation at a level of a well-marked bedding plane immediately below the inception of large flat lying and near continuous flint nodules.
Absent from the Highland Border High and East Antrim Basin presumably by pre-Palaeogene erosion.
Limestone (chalk) with extremely large flat lying and near-continuous flint bands. Divided into three `Beds? (A to C) separated by well-marked bedding planes.
10.95m at its type-site.
Marked by the base of the prominent continuous flint band termed the Long Gilbert Flint Band within the Tanderagee Chalk Formation.
Barytes Mine Conglomerate Member
BMCG
Contact above and below with the Sannox Siltstone Formation.
Conglomerate comprised of predominatly quartzite boulders.
8 m thick.
Badcall Meta-Clinopyroxene-Norite Subswarm
BMCN
N/a
The dykes of the Badcall Meta-clinopyroxene-norite Subswarm are found in a few localities in Assynt and at Badcall.
The Badcall meta-clinopyroxene-norites form a small number of dykes in Assynt and near Scourie. They are coarse-grained and have distinct chilled margins. They have a primary mineralogy of plagioclase-hypersthene-clinopyroxene-biotite plus minor olivine or quartz, with the clinopyroxenes having been replaced by amphiboles at the margins of some dykes. They have lower Ti, but higher Mg and Cr contents than the dolerite dykes of the Scourie Dyke Swarm.
Bassy Coal (South Lancashire)
BMCO
Builth Mudstones Formation
BMD
In-coming of pervasively laminated silty mudstones gradationally overlying the Dolfawr Mudstones, or sharply overlying the Alpine Bridge Member of the Cerig Formation.
Central Wales and Welsh Borders.
Laminated silty mudstones.
Not yet assessed.
Not yet diagnosed.
Black Metals Marine Band [Local Term: See Htmb]
BMET
Local name applied to the Haughton Marine Band (National Standard Name) in the Cumberland Coalfield area.
Borth Mudstones Formation
BMF
Brimham Grit
BMG
Lower Bentham Grit
BMGL
Upper Bentham Grit
BMGU
Black Coal (South Lancashire)
BMIC
Bank Moor Limestone
BML
Blaen Myherin Mudstones Formation
BMM
Balmore Marine Band
BMMB
Bottom Main Coal (Northumberland And Durham)
BMNC
Bellman Limestone Member
BMNL
Taken at the base of the lowest Waulsortian limesotne above the packstones and grainstones of the Peach Quarry Limestone Member. Where the latter is absent, the base of the member rests conformably upon dark grey fissile mudstones and packstones of the "Upper Coplow Shales".
Craven Basin, limited to the Clitheroe Anticline [SD 74] and northern limb of the Whitewell Antivline [SD 64].
Waulsortian biohermal limestones with subordinate packstones,wackestones and grainstones.
Up to 800 m thick.
The Waulsortian limestones are overlain unconformably by mudstones of the Hodder Mudstone Formation.
Beaumont Coal (Northumberland)
BMNT
Ballymoney Formation
BMNY
Bellmoor Member
BMO
Late Ordovician (Mid Caradoc).
Taken at base of sandstone lithology, resting on Benan Conglomerate Formation (of Barr Group).
Greywacke sandstones.
90 to 140m
Taken at top of sandstone lithology, beneath Kilranny Conglomerate Member (of Balclatchie Formation).
Bottom Moorland Coal (Northumberland)
BMOR
Bembridge Oyster Beds
BMOY
Beannach Metapicrite Subswarm
BMP
The dykes of the Beannach Picrite Subswarm are part of the Lewisian Gneiss Complex and only occur within it. They have only been mapped as a separate subswarm in the Assynt area where they occur between Glen Canisp and Scourie.
The Beannach Picrite Subswarm comprises the Mg-rich members of the Scourie Dyke Swarm. The dykes of the subswarm are most abundant within the Lewisian Gneiss Complex in the Assynt region, where they are found to the north of the Canisp Shear Ztne. They typically have a broadly east-west trend.The dykes of the subswarm are mostly coarse-grained, texturally hererogeneous and lacking in chilled margins.In composition they are picritic and have the primary mineralogy olivine - orthopyroxene - clinopyroxene - plagioclase - phlogopite - chromite. The dyles of eht Beannach Metapicrite Subswarm clearly post-date the majority of the metadolerites of the Scourie Dyke Swarm, although they are cross-cut by some late dolerites. One dyke of the subswarm has been dated at 2418 +7/-4 Ma (Heaman & Tarney, 1989).
Beinn Mheadhoin Pebbly Psammite Formation
BMPP
Not exposed; unknown.
Central Highlands of Scotland E of Great Glen fault - Strathnairn area. Sheet 73E (Foyers).
Feldspathic psammite (arkosic) with thin semipelite beds and gritty beds with abundant quartz and feldspar clasts.
Conformably overlain by Ruthven Semipelite Formation, sharp disconformity and marked lithological change from psammitic sequence to gneissose semipelite.
Broughton Moor Formation
BMR
Unconformable, but local evidence of continuous deposition from the underlying Torver Member with an horizon of chamositic ooliths at the junction passing up in places into a thin, laminated black shale in the lower part of the Broughton Moor Formation.
The outcrop extends from Limestone Hill in the east (NY 3405 0044) to Hobkin Ground Wood (SD 2297 9125) near Broughton Mills in the west. It is about 4 m thick across its whole outcrop so is too narrow to show on 50k map sheets, but is shown combined with the Appletreeworth Volcanic Formation on the 25k special Sheet of Coniston Fells.
Interbedded nodular and bioturbated micritic limestones.
From 4 m to 6 m thick.
Sharp and conformable with the overlying Appletreeworth Formation.
Bromsgrove Sandstone Formation
BMS
Disconformable on Wildmoor Formation or older formations; taken at base of lowest pebbly bed with chips of unweathered feldspar (Wills, 1976 p.37,99) at outcrop in type area.
Stafford and Worcester basins.
Sandstones, red, brown and grey, commonly pebbly or conglomeratic at the bases of beds, interbedded with red and brown siltstones and mudstones.
0->300m (Redditch area), 15-40m (Stoke-on-Trent area), c.500m (Worcester area).
Transitional at base of Mercia Mudstone Group.
Burn Of Mar Sandstone Formation
BMSA
Not seen, as either faulted against younger or older rocks, or juxtaposed against sheared and silicified serpentinite.
Isolated slivers within the Highland Boundary Fault system between Loch Lomond (Balmaha) and Gualann. 1:50k sheets 38W (Ben Lomond) and 38E (Aberfoyle).
A medium to coarse-grained and weakly cleaved, lithic sandstone arenite, which contains chloritised grains, possibly after serpentine, and chromite grains.
At least 200 m thick.
Not seen, as either faulted or unconformably overlain by Upper Devonian, Upper Old Red Sandstone Facies strata.
Barnham Silt And Clay Member
BMSC
Bromfield Sand And Gravel
BMSG
Sand and gravel, with possible lenses of silt, clay or peat. [Generic desciption].
Brimham Shale
BMSH
Black Mountain Shale Member
BMSM
Black Metal Coal (Cumbria)
BMT
Cumberland Coalfield area.
Bearsmouth Or Thorneyburn Coal
BMTBC
Brown Bank Formation
BNB
Overlies Eemian Marine Sands in type area, also overlies early and middle Pleistocene sediments (unconformably) in British sector.
Brackish-marine, grey-brown silty clays. Pass upwards into lacustrine clays in the east, include interbeds gravelly sand towards base in west. Extensively bioturbated, locally cryoturbated.
0 - 10m. (maximum 25m. in British Sector of Flemish Bight).
Overlain by Holocene Marine Sands or (locally) Weichselian Periglacial Sands (Twente Formation).
Bidean Nam Bian Andesite Member
BNBA
Banton Blackband Coal
BNBC
Brownber Formation
BNBF
Chadian or Arundian.
Interbedded sandstones (fine-grained, pale brown, laminated in part), limestones (calcarenites grainstones, ooidal in part) and dolomites (yellow, flaggy) containing abundant quartz pebbles near top (between underlying and overlying dark grey bioclastic limestones of the Coupland Sike and Breakyneck Scar limestones respectively).
15 metres, which is approx. thickness to neighbourhood of Raisbeck, beyond which it thickens to c.80 metres at west edge of NY60NW where it is a largely hard, laminated sandstone formation.
Banton Blackband Ironstone
BNBI
Benburb Lignite
BNBL
Lignite with rare gravel; interglacial in origin. [Generic description: academic papers and BGS Memoirs].
Barnby Member
BNBM
Top of highest limestone bed in Barnstone Member.
East Midlands Shelf area: South Yorkshire to north flank of London Platform.
Grey calcareous mudstones with rare thin argillaceous limestones comprising c.1% of the sequence.
22.05 metres in borehole F/B5 (SK95SW/17).
Base of lowest (unnamed) limestone bed in Granby Member (see references for details of beds within members).
Banbury Rock
BNBR
Benan Conglomerate Formation
BNC
Locally erosive contact with Stinchar Limestone Formation, basal beds are laterally equivalent to the Superstes Mudstone Formation.
North side of the Stinchar Valley, Girvan district. Lower part is lateral equivalent of Superstes Mudstone Formation.
Boulder conglomerate.
Overlain by Balclatchie Formation.
Banton Clayband Ironstone
BNCB
Bench Coal (Warwickshire)
BNCC
Beinn Na Cro Gabbro (Skye Eastern Red Hills Centre)
BNCG
Bench Coal
BNCH
Bryn Nicol Formation, Coed Ifan Facies
BNCIF
Beinn Churalain Quartzite
BNCN
Bin Coal (South Lancashire)
BNCO
Bannisdale Formation
BND
Conformably overlies the Coniston Group (Yewbank Formation).
Southern Lake District and Northwest Pennines.
Silty mudstone with subordinate siltstone and sandstone.
Conformably overlain by the Underbarrow Formation.
Bone Coal (South Lancashire)
BNEC
Bottom Neddy Coal
BNED
Ben Nevis Complex (Inner Granite)
BNEV1
Ben Nevis Complex (Outer Granite)
BNEV2
Ben Nevis Complex (Marginal Intrusion) (Pyroxene Diorite To Granodiorite)
BNEV3
Ben Nevis Complex (Marginal Intrusion) (Quartz Diorite)
BNEV4
Barras Nose Formation
BNF
The depositional lower boundary is not seen as the lower boundary is everywhere tectonic.
Occurs between the Boscastle/Tintagel area (SX 07 89), north Cornwall and the Launceston area (SX 30 78), east Cornwall. The outcrop in east Cornwall (BGS, 1993) needs further investigation.
Dark grey and black mudstones with variably abundant very thin beds and laminae of cross laminated and graded silstone and sandstone. The mudstones contain scattered sideritic, carbonaceous silty sandstone and argillaceous limestone nodules, containing goniatites. A thin fossiliferous limestone is present at or very near the top of the Formation. Volcanic material locally occurs as lenses of sheared vesicular lava and tuff.
21m+ on the coast in the Boscastle/Tintagel area; poorly constrained as a result of deformation.
The upper boundary is taken at the sharp contact of tuffs, lavas and agglomerates of the overlying Tintagel Volcanic Formation with the mudstones and thin siltstones of the Barras Nose Formation.
Burnfoot Shales
BNFS
Bu Ness Sandstone Formation
BNG
Drawn at the base of the Bu Ness Sandstone Formation where sandstone alternating with siltstone conformably rests upon thin co-sets of sandstone and thick co-sets of fine-grained sediments of the Observatory Sandstone Formation.
Fair Isle, Shetland Islands.
Grey to buff red-stained arkosic sandstone, pebbly grit and conglomerate, siltstone and mudstone.
c.200m
Drawn at the conformable upward passage of Upper Pebbly Grit of the Bu Ness Sandstone Formation, which is not overlain.
Bangley Dyke
BNGLY
Burning Mount Plug
BNGMT
Beeson Grits Formation
BNGR
Beinn Gaire Psammite Formation
BNGS
Brown Howe Tuff Member
BNH
Taken at the abrupt change from masive rhyodacitic tuff and lapilli-tuff of the Whelter Knotts Formtion, to well bedded pyroclastic rocks of intermediate compostion.
East of Haweswater Reservoir, northeastern Lake District, Cumbria.
Parallel-bedded, well sorted, acid andesitic or dacitic coarse-grained tuff and fine-grained lapilli-tuff with locally intercalated thin units of pyroclastic breccia containing large ragged bombs of scoriaceous andesite and intruded by many contemporaneous andesite sills.
To 135m, but greatly inflated by sills
Everywhere overlain by contemporaneous andesite intrusions.
Bonnyhill Craw Coal
BNHC
Burnhousemoor Member
BNHS
Burnwood Ironstone
BNI
Balnakiel Formation
BNK
Conformably overlies the Sangomore Formation.
The Durness Group forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye. The Balnakiel Formation does not occur in Assynt or Skye and appears to be limited to the more northern parts of the outcrop of the Durness Group.
Alternations of dark grey dolostones and dolomitic limestones and lighter grey bioclastic limestones.
About 140 m thick, although estimated at over 300 m thick by some authors.
Conformably overlain by the Croisaphuill Formation.
Bankhouses Limestone
BNKL
Bankhouses area, Westmorland.
Limestone, with local "reefs" of crinoid debris forming banks and mounds at the top of the "Lower Bankhouses".
Formerly considered to lie towards the base of the (English) Middle Limestone Formation. Comonly developed as a multiple group of limestones with intervening shale and sandstone beds, with the more prominent "members" being called Lower, Middle and Upper Bankhouses limestones.
From c.6m to c.27m where developed as a multiple unit.
Buckbanks Sandstone Member
BNKS
The base taken at the base of the first sandstone bed above laminated calcisiltites and mudstones of the Hodder Mudstone Formation (undifferentiated).
The member is present in the western part of the Craven Basin, in the western closure of the Whitewell Anticline (SD 64 47) and the northern limb of the Clitheroe (SD 75 45), Thornley (SD 62 40) and Throstle Nest (SD 63 44) anticlines.
A dark grey, brown weathered, massive, thick-to thin-bedded, fine-to medium-grained, calcareous, quartzitic, bioclastic (crinoid and brachiopod debris), finely micaceous sandstone, interbeddedwith thin, dark grey, calcareous, laminated mudstones and siltstones.
Maximum thickness of 11.5 m in the Thornley Anticline.
Taken at the passage of sandstone into the overlying laminated mudstones and thin-bedded calcisiltites of the Hodder Mudstone Formation (undifferentiated).
Bennane Lea Breccia Member
BNL
Highest exposed part of the Corseclays Sandstone Formation.
Known only at Bennane Lea, Ayrshire, southwest Scotland.
Lithology. Pebbly sandstone of the Bennane Lea Member is present at the northern limit of the outcrop of the parent Corseclays Formation. At Bennane Lea the sandstone contains matrix-supported sub-angular clasts predominantly of altered basalt. The member is a lateral facies variant developed at the base of the formation where it unconformably overlies Lower Ordovician igneous rocks (Stone, 1988). It was previously informally referred to as the 'Bennane Lea Member' by Peach and Horne as part of the 1894 resurvey and it is noted by Stone (1988) that the Bennane Lea Member has erroneously been referred to an 'upper breccia division' (Jackson et al., 1995).
c.20m
Bannockburn Lower Main Coal
BNLMA
Beacon Limestone Formation
BNLS
Non-sequential; downward change from ferruginous, conglomeratic limestone to argillaceous, silty or sandy beds of the Dyrham Formation.
Wessex Basin (including Central Somerset Basin) and Mendips-Radstock Shelf area, ie. Dorset coast to approximately Chipping Sodbury.
Limestone, ferruginous-ooidal in lower part, nodular in upper part; conglomeratic in parts; variably grey, pink, reddish-brown and brown in colour. Includes Eype Mouth Limestone Member (above) and Marlstone Member (below).
Up to 5m; typically less than 1.5m
Base of sands of the Bridport Sand Formation.
Brown Metal Coal
BNM
First Brown Metal Coal (West Yorkshire)
BNM1
The Brown Metal Coals are seams of variable quality and thickness and are not widely worked. They are commonly split and washed out by the Birstall Rock. The First and Second Brown Metals coalesce in the west.
Second Brown Metal Coal (West Yorkshire)
BNM2
The Second Brown Metal Coal (or Old Hards) is a seam of variable quality and thickness. The lower part is a high quality bituminous coal while the upper part is poor quality. The First and Second Brown Metals coalesce in the west.
Third Brown Metal Coal (West Yorkshire)
BNM3
The Third Brown Metal Coal is thin, of inferior quality and not extensively worked.
Bannockburn Main Coal
BNMA
Bottom Brown Metal Coal
BNMB
Bin Mountain Sandstone Formation
BNMS
Abrupt change from peritidal micrites and shales of Termon River Limestone Formation to thick beds of crinoidal calcareous sandstone/sandy packstone of Bin Mountain Sandstone Formation. Conformable.
Kesh-Omagh area of the northwest Carboniferous basin of Ireland.
Sandstone, pale to mid grey, very calcareous, fine- to medium-grained, small bioclast fragments, bioturbated, and limestones, blue-grey, oolitic, crinoidal, very sandy, scattered quartz pebbles.
Conformable, apparently gradual change from calcareous sandstones and sandy grainstones of Bin Mountain Sandstone Formation to dark blue-grey fossiliferous sandy packstones and packstones of Ballyshannon Limestone Formation.
Top Brown Metal Coal
BNMT
Brecknockshire Glacigenic Formation
BNOCK
Beinn Nan Ord Gabbro Ring-Dyke
BNOGB
Bannock Coal (Cumbria)
BNOK
Bryn Nicol Formation, Pen Derlwyn Facies
BNPDF
Basin Peat
BNPT
Barnsley Rock
BNR
West and south Yorkshire, especially the area around Rawmarsh and Wentworth and near Barnsley. Becomes thicker southwards from the Calder valley.
Flaggy sandstone of variable thickness and composition.
0 to c.36m
Black Nore Beds
BNRB
Banton Rider Coal
BNRC
Black Nore Sandstone (Jurassic)
BNRS
Bunter Sandstone Formation
BNS
Burns Sandstone Member
BNSA
Broxburn Shale
BNSH
Barnstone Member
BNT
Base of Lias Group: basal mudstone with sharp contact on Cotham Member of Penarth Group.
East Midlands Shelf area: between Market Weighton area to north, and north flank of London Platform to south.
Alternating grey mudstones and limestones; limestones generally 0.1 metres to 0.3 metres thick, argillaceous calcilutites forming c.30% of sequence; shell debris in limestones in basal 2 - 3 metres.
8.1m to 8.7m in stratotypes, 9.6m at Barnstone; ranging from c.5m - 10m over area of occurence.
At top of highest limestone bed in Member.
Bench Thin Coal (Warwickshire)
BNTC
Baillieston Till Formation
BNTI
Pre MIS 2.
Unconformity or glacial deformation boundary on bedrock or on assumed older (usually unclassified) Quaternary strata.
Central Scotland, related to ice streams sourced in the Highlands (in contrast to the Southern Uplands) during the Devensian some time prior to the Dimlington Stadial; Glasgow area including the Kelvin and Carron-Bonny Water valley system, north and south Lanarkshire, possibly Ayrshire.
The typical lithology is a glacially organized diamicton (till), composed of isolated boulders, gravel and pebbles in a matrix of sandy silty clay. The more elongated clasts are preferentially oriented and the deposit commonly has systematic sets of joints. The deposit is of a stiff to hard consistency and low plasticity. In general the colour of till reflects that of the local bedrock so may be totally different from one area to the next and can be reddish brown (Devonian and Upper Coal Measures) or brownish grey or black (Carboniferous).
Veneer to more than 20m.
Unconformity or glacial deformation boundary below younger Quaternary strata. Where data are available the Baillieston Till Formation is overlain by the Broomhill Clay Member and/or the Cadder Sand Member of the Wilderness Till Formation or this till itself.
Ben Nevis Volcanic Formation
BNVO
The base of the predominantly volcanic rocks above the Allt a' Mhuilinn Mudstone Formation.
Massive unsorted volcanic breccias and agglomerates, some andesitic, with hornblende-bearing andesitic lavas and sheets.
About 630 m presently exposed.
The top of the volcanic succession on Ben Nevis, partly removed by erosion.
Bottom Nether Witton Coal (Northumberland)
BNWC
Bonaly Volcanic Member
BNY
Not exposed. Faulted against Ballagan Formation to the north and overlain by Kinnesswood Formation to west.
Lowest flows are feldspar phyric andesites and upper flows are fine-grained andesites. Feldspar phyric olivine basalts and pyroxene-andesites, trachybasalts, rhyolites and trachytes are also present.
350m maximum
Unconformable: upper flows of andesites and basalts overlain by conglomerates and grits of Greywacke Conglomerate Formation and rhyolite of Bell's Hill Volcanic Member.
Burrington Oolite Subgroup
Taken at gradational junction of sparsely crinoidal dolomite of underlying Black Rock Limestone Subgroup and the ooidal limestone [locally dolomitised] of the Burrington Oolite Subgroup. In the eastern Mendip Hills, taken at the incoming of the ooidal limestones above the coarse crinoidal limestones of the Vallis Limestone Formation. Both contacts need further investigation.
Mendip Hills [ST 50 55] and Western-super-Mare [ST 30 60] area. Passes north into the Gully Oolite, Clifton Down Mudstone and Goblin Combe Oolite formations. Passes west into Gully Oolite, Caswell Bay Mudstone, High Tor Limestone and Goblin Combe Oolite formations. Passes east into Vallis Limestone Formation and supposedly the Black Rock Limestone Subgroup, but this needs further investigation.
Massive pale grey ooidal limestones and ooidal/crinoidal limestones. Beds of coarse crinoidal limestone in lower part and calcite mudstones in uppermost part. Locally dolomitised in lowermost part.
210m at Burrington Combe to 230m at Wells, thinning to a feather edge in the eastern Mendip Hills.
Taken at the incoming of calcite mudstones and dark splintery limestones of the Clifton Down Limestone Formation above the ooidal and ooidal/crinoidal limestones of the Subgroup.
Bow Breccia Formation
BOB
Rests directly on Upper Carboniferous Bude Formation, from Lower Creedy (SS 843 027) westwards to western edge of Exeter district, although thin Cadbury Breccia may locally intervene. East of Bradley Farm (SS 855 023) apparently overlies Cadbury Breccia.
Occupy the whole width of the Crediton Trough to the west of Bow (in the Okehampton district). In the Exeter district, present along the northern side of the trough from near Elston (SS 785 026) in the west, through Sandford to Bradley Farm (SS 855 023).
Breccia, reddish-brown, silty and sandy, with pebbles of sandstone, slate, shale, hornfels, acid lava, vein-quartz and quartz porphyry. Middle Devonian limestone clasts present at Solland (SS 615 021) and Westacott (SS 685 022). (Hutchins, 1958). Lamprophyres and basalts present near north Tawton, on southern side of trough.
Up to 140 (Crediton area). 430m (Bow). 380m (north Tawton). 180m+ (Sampford Chapple). 150m+ (Hatherleigh-Exbourne).
Passes gradationally up into the Knowle Sandstone Formation by gradual increase in the proportion of breccia.
Bosies Bank Formation
BOBA
Brig O' Balgownie Formation
BOBC
Unconformity with the Dalradian Supergroup below.
Aberdeen area of Scotland.
Mainly a well-rounded conglomerate with clasts of granite and psammite of local provenance, and some sandstone and mudstone interbeds.
Variable, up to 160 m proved.
Not seen, as the top is cut out by faulting.
Bone Bed Limestone
BOBL
Boulder Clay
BOC
Clay and silty clay, commonly pebbly and sandy, reddish brown, stiff, possibly interbedded with sand and gravel-rich lenses and rare peat. [Generic description].
Balloch Clay Member
BOCH
The Ballock Clay Member of the Clyde Clay Formation rests with angular unconformity on older Quaternary sediments or bedrock. It normally rests on the Inverleven Gravel Member of the Clyde Clay Formation or possibly on the Wilderness Till Formation (WITI) of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
The Balloch Clay Member of the Clyde Clay Formation is recognized in the Leven valley south of Loch Lomond.
Clayey silt, clay and sand, mid to dark grey, bedded and thinly laminated in places, with dark sulphide patches and fine mica; very soft to soft consistency and medium to low plasticity, isolated clasts up to 3cm (presumed dropstones), some graded units, sulphide patches, rare marine shells and plant remains.
Veneer to more than 40m.
The Balloch Clay Member of the Clyde Clay Formation is overlain unconformably by younger Quaternary sediments, normally the Clydebank Clay Formation of the British Coastal Deposits Group but will include buried deposits belonging to the deglacial phase at the end of the Loch Lomond Stadial.
Bochruben Formation
BOCHR
Boyne Castle Limestone Member
BOCL
Base of massive metalimestone bed above the semipelites of the Old Hythe Limestone Member.
From Moray Firth coast (Old Hythe to Boyne Bay) [NJ 6155 6625 - NJ 6165 6608] to 300m northwest of Hill of Chattie [587 630].
Thin-bedded metalimestone, 200m thick, with minor calc-silicate rock; shows abundant minor tight folding.
c.200m on coastal section; progressivley overstepped southwards by Whitehills Grit Formation.
Transition to laminated and striped calc-silicate rock at the base of the Whyntie Brae Limestone Member.
Brora Coal Formation
BOCO
Botney Cut Formation
BOCT
Bodgadle Member
BOD
Sudden influx of coarse crystal-lithic tuffs, above strongly welded Nant-y-Gledryd Member, or volcaniclastic sediments of the Yoke House Formation.
Rhyolitic crystal-lithic tuffs, rather variable characteristics, strongly welded locally.
Overlain by volcaniclastic sandstones, breccias of the Yoke House Formation, and locally by Nod Glas Formation.
Bodafon Beds
BODA
?Pridoli to Lochkovian (based on Figure 7, p.43 in House et al., 1977).
Anglesey.
3 to 45m
Bovey Formation
BOF
Late Eocene to Mid Oligocene (Curry et al., 1978).
Underlain along its eastern outcrop and south of Newton Abbot by the Aller Gravel and the Upper Greensand. Elsewhere unconformable upon, or faulted against, Devonian, Carboniferous or Permian Rocks.
Restricted to the Bovey Basin in Devon.
To 1200m (Curry et al., 1978).
the original top of the Formation is not preserved, and its eroded top now forms the land surface, underlying the modern soil.
Bopeep Flints
BOFL
Boggierow Intrusion
BOGGI
Insch Pluton (Boganclogh Sector)
BOGH
Boglochty Beds
BOGL
Bothyhill Gravels Member
BOGR
Unseen, probably gradational with Ardersier Silts Formation below.
Alturlie Peninsula, 6km eastnortheast of Inverness.
Sand and gravel, coarsening-upwards deltaic sequence, containing sparse cobbles of Inchbae granite-gneiss.
Unconformable, with (Late Devensian) raised beach gravels above.
Hodderense Limestone Formation
BOH
In the Craven Basin the lower boundary is drawn at the base of the first cream-coloured wackestone with dark blue micritic nodules of the Hodderense Limestone Formation, where it rests conformably on grey or dark grey mudstone and calcisiltite of the Hodder Mudstone Formation. In the south Isle of Man, the base of the formation is poorly defined. Where it occurs in the field close [SC 2580 6620] to the Visitor Centre at Scarlett, south of the old lime kilns, the wackestones and packstones of the underlying Knockrushen Formation are overlain by the massive lime mudstones of the Hodderense Limestone Formation. The base of the latter "is taken at the lowest mottled horizon" (Dickson et al., 1987), and this mottling is a result of the presence of blue or grey micrite nodules up to 3cm in size.
Craven Basin, northwest England, although removed beneath the unconformity in the Skipton area; also present in the south of the Isle of Man.
Pale olive and blue-grey, to cream-coloured porcellanous wackestones with characteristic dark blue, micritic nodules, sporadic interbedded packstones and common mudstones. Chert is common in the Isle of Man sections and some beds are multi-storey, displaying lag horizons composed of reworked micrite nodules, inadunate crinoids, bellerophontid gastropods, cephalopods, trilobites and sponges. Also present is the trace fossil Helminthoides.
Up to 15m thick in the Craven Basin and 14m in the south of the Isle of Man.
In the Craven Basin the upper boundary is drawn at the conformable upward passage from the highest nodule-bearing cream-coloured wackestone bed of the Hodderense Limestone Formation, to the first grey mudstone of the Pendleside Limestone Formation. In the south of the Isle of Man, at Scarlett Point [SC 2583 6633] the upper boundary of the Hodderense Limestone Formation occurs below the lowest black claystone of the wackestones, lime-mudstones and interbedded claystones of the Scarlett Point Member, Bowland Shale Formation.
Bowland High Group
BOHI
Not exposed or proved
The Craven Basin between Clitheroe and Skipton.
Pale to dark grey, packstone and wackestone with subordinate grainstones, partings and thin beds of calcareous mudstone and calcareous siltstone. Mudmound reef (Waulsortian) limestones are present in the upper part of the group.
Up to 2340 m thickness known (base not proved).
The uppermost limestone of the Bowland High Group, overlain by mudstones of the Hodder Mudstone Formation, marked by regional unconformity.
Bole Hill Sandstone
BOHIL
The base of the Bole Hill Sandstone overlies a regionally widespread mudstone containing the non-marine 'Daubhill fauna'. Locally the base is erosive, cutting through this mudstone into the underlying sandstones of the Wingfield Flags (Chisholm 1990, fig.9).
Sandstone is mappable at outcrop from [SK 368 663] to [SK 382 563]. Main part of sandstone is an east-west oriented palaeochannel with outcrop extending from [SK 368 663] at the northern margin of the channel to [SK 379 590] at the southern margin of the channel.
Sandstone, greenish grey, buff-weathered, argillaceous, fine- and very fine-grained; part poorly bedded, part current ripple-laminated and cross-bedded; mean cross-bed palaeocurrent flow direction toward the east (Chisholm 1990, fig.8).
To 40m (Chisholm 1990, fig.9)
The top of the Bole Hill Sandstone is overlain by the Kilburn Coal (Chisholm 1990, fig.9).
Botany Limestone
BOL
Bottom Little Coal (Somerset)
BOLC
Bold Formation
BOLD
Bolsa Member
BOLS
Insch Pluton (Boganclogh Sector Lower Zone)
BOLZ
Bollin Mudstone Member
BOM
Top of Tarporley Siltstone Formation.
Cheshire Basin.
The upper part is a dominantly laminated reddish-brown and greenish-grey mudstone with siltstones. The lower part is a structureless and laminated, dominantly reddish-brown mudstone. Within the lower part of the member, a unit termed the 'Lower Keuper Sandstone' has been recognised in the Stockport area. This unit closely resembles the Tarporley Siltstone Formation of adjacent areas.
1188ft 6ins in the Wilkesley Borehole (British Geological Survey; SJ64SW/7).(362.25m).
Base of Northwich Halite Member.
Bogside Main Coal
BOMA
Blacko Marine Band
BOMB
Boganglogh Margin Type Ultramafic Intrusion
BOMU
Insch Pluton (Boganclogh Sector Middle Zone)
BOMZ
Bonanza Coal
BON
Bone Coal (Dungannon)
BONC
Bonchester Hill Plug
BONH
Bonnington Intrusion (?Sill)
BONTN
Boon's Member
BOO
Sharp unconformable contact of granulestone on spheroidally-weathered Precambrian tuffs of the Caldecote Volcanic Formation.
North and south-east sectors of Boons Quarry south of Grange Farm.
Red massive granulestone and boulder-breccia beds at base, passing up to red lithic sandstone with thin breccia layers and capped by grey massive sandstone with minor siltstone. Sandstone and granulestone are massive, with sporadic parallel stratification and normal or inverse grading. Boulder breccias contain large (to 2m) rounded clasts detached from underlying weathered Precambrian rocks.
Possibly between 20 and 40m in general range. In partial type sections: a)3.0mb) 7.2m minimum c) 6.7m.
Conformable contact with Park Hill Member. The top is taken at the surface of the bed immediately beneath the first sandstone to show significant current bedding.
Bookham Conglomerate Bed
BOOC
Lower and Upper Cenomanian. Up to Acanthoceras rhotomagense Zone,
Unconformable, locally strongly erosive boundary with underlying Shaftesbury Sandstone Member.
Known for Dorset and Wiltshire over the Mid Dorset Swell
Clasts of very glauconitic shelly sandstone, up to cobble size, commonly with a phosphatic rind, together with phosphatised shells (bivalves & ammonites) in a matrix of sandy glauconitic chalk. The derived fauna is Latest Albian; the indigenous fauna is Early Cenomanian.
At the disconformable contact with phosphatic pebble bed at the base of the Zig Zag Chalk Formation or the West Melbury Marly Chalk Formation (at the base of the Chalk Basement Bed of Kennedy, 1970)
Balladoole Formation
BOOL
c.90m
Bog Quartzite Formation
BOQ
Unconformably overlies Llanvirn Hyssington Volcanic Formation.
Variable arenaceous beds with abundant joints.
Borestone Coal
BOR
Boreland Coal (Fife)
BORE
Allt A'Mhuilinn Pseudoleucite-Syenite And Associated Rocks
BORO
Borthwick Sill
BORT
Bognor Sand Member
BOSA
Incoming of sand and glauconite at the top of King's (1981) Division A of London Clay, (a coarsening upwards sequence of clays and silts).
Easternmost Hampshire Basin. Not mapped on or West of Southampton Sheet by BGS.
Glauconitic bioturbated or cross-bedded fine- and medium-grained sands, partially cemented.
At Whitecliff Bay passes up into sandy clayey silts of Division A (King, 1981) aspect but elsewhere is cut out by erosion surface at the base of the silty clays of Division B1 of London Clay (King, 1981).
Boscastle Formation
BOSC
The lower boundary is not seen as it is tectonic. However, the Formation inter-tongues with the Buckator and Teign Chert formations. Lower boundaries with the Buckator Formation are taken at the gradational appearance of dark grey sandstones and mudstones of the Boscastle Formation above the green grey mudstones with thin calcareous siltstones and limestones of the underlying Buckator Formation. Only an upper boundary is seen with the Teign Chert Formation.
Between Boscastle (SX 95 91) and Lewanwick (SX 27 81), north Cornwall.
Dark grey to black pyritous mudstones with thin laminated siltstones. Packets of thin- to thick-bedded grey fine- to coarse-grained quartzose sandstones punctuate the Formation. Adjacent to intertonguing contacts with the Buckator Formation, the sandstones are calcareous, locally shelly and locally accompanied by thick beds of bioclastic limestone and nodules of silicified limestone. The mudstones are locally burrowed. Rare thin beds of tuffaceous mudstone, and tuffs and lavas also occur.
Several hundred metres, but may be more or less due to the faulting, thrusting and folding.
The upper boundary is not seen as it is tectonic. However, the formation intertongues with the Buckator and Teign Chert formations. Upper boundaries with the Buckator Formation are taken at the gradational appearance of green grey mudstones with thin calcareous siltstones and limestones of the underlying Buckator Formation above the dark grey sandstones and mudstones of the Boscastle Formation. Upper boundaries with the Teign Chert Formation are taken at the incoming of silicified siltstones, mudstones and scattered chert beds of the Teign Chert Formation above the interbedded sandstones and mudstones of the Boscastle Formation.
Borrowash Sand And Gravel
BOSG
To 4.5m
Boscombe Sand Formation
BOSS
Bovisand Formation And Staddon Formation (Undifferentiated)
BOST
Bodlondeb Tuff Member
BOT
Bottom Coal (South Staffordshire)
BOTC
Bottom Furnace Coal (South Lancashire)
BOTF
Bogside Thick Coal
BOTH
Boueti Bed
BOU
Bouldnor Formation
BOUL
Insch Pluton (Boganclogh Sector Upper Zone)
BOUZ
Bovisand Formation
BOV
Faulted out; overthrust by the Whitsand Bay Formation. Transitional boundary with Whitsand Bay Formation in the Rame Peninsula; grey slaty mudstone passing down into purple slaty mudstone.
Geological sheets 348 and 349 (not mapped elsewhere).
Slaty mudstone, medium to dark grey, with thin sandstone beds and sporadic thin limestone beds. Packets of quartzitic sandstone beds are present in the form of the Upper and Lower Longsands Sandstone members.
At least 1300m.
Faulted out; Bovisand Formation thrust over the Staddon Formation for much of the area.
Bowhouse Coal (Fife)
BOW
Bowhousebog Ironstone
BOWI
Bowmore Sandstone Group
BOWM
Bowsey Wood Formation
BOWO
The base of the formation is not proved and the underlying succession is unknown
The formation occurs in the northern part of the Market Drayton Horst. The formation is limited in outcrop to a small inlier [about 1km long and 300m wide] at Limekiln Farm, Astbury [SJ 86 59]. The formation is also present in the subsurface within the Stoke-on-Trent, District, proved in the Bowsey Wood and Bittern's Wood boreholes.
Pale grey, massive and thickly bedded limestone. At the type locality the formation comprises very fine-to-very coarse-grained, slightly dolomitised packstones containing shell fragments with micritic [cyanobacterial] coatings, and calcareous mudstones
Minimum thickness of 13.5m measured at the type locality.
At Astbury [SJ 86 59], the top of the formation is taken at the conformable base of the mudstone-rich succession, with surbordinate limestone, of the Astbury Formation above the limestone- dominated succession of the Bowsey Wood Formation. In the Bowsey Wood and Bittern's Wood boreholes the top of the formation is an unconformity, overlain by mudstone of the Bowland Shale Formation.
Bottom Yard Coal (South Lancashire)
BOYD
Botany Grit
BOYGR
Boyne Limestone Formation
BOYL
First white limestone at the west side of Old Hythe Bay.
From Moray Firth coast (Old Hythe to Whyntie Head) [NJ 609 664 to NJ 630 658] to Hill of Chattie [NJ590 625].
Thin-bedded metalimestone, semipelite calc-silicate rock. Old Hythe Limestone Member: finely interbedded semipelite and psammite with lenses of quartzite and white cream metalimestone. Boyne Castle Limestone Member: thin-bedded metalimestone, 200m thick, with minor calc-silicate rock; shows abundant minor folding. Whyntie Brae Limestone Member: calc-silicate rock, laminated and striped, passing upward into semipelite with minor thin metalimestone and lenses of reworked carbonate material.
c.900m on coastal sections; progressively overstepped southwards by Whitehills Grit Formation.
Local unconformity at incoming of first major psammite bed (locally gritty) at base of Whitehills Grit Formation.
Bozeat Till
BOZE
Basal Permian Breccia (South West)
BPBR
Blae Pot Coal
BPCO
Brasspoint Flint
BPFL
Belper Grit
BPG
Black Park Gravel Member
BPGR
Late-Anglian.
Rests unconformably on bedrock geology (London Clay on Sheet 256).
Sand and gravel, with possible lenses of silt, clay or peat. [Generic description]. Horizontally stratified, matrix-supported gravel with thin tabular cross-bedded sand channels. Gravel assemblage is characterised by abundant angular flint (75-89%), sparse rounded flint (3-9%), sparse vein quartz (4-10%) and sparse quartzite (1-6%).
1-6m, average 3m
Bottom Pigeon House Coal (South Lancashire)
BPHC
Bampton Limestone Formation
BPLM
Between Brushford and Ashbrittle the lower boundary is taken at the incoming of thin- to medium-bedded soft siliceous mudstones with impure limestones and cherts of the Bampton Limestone Formation above the hard black finely laminated unfossiliferous cherty mudstones of the underlying Doddiscombe Formation.
Between Brushford (SS 92 26) and Ashbrittle (ST 04 21), Somerset.
Thin- to medium-bedded limestones, cherts, siliceous radiolarian mudstones (termed cherts in some literature) and mudstones. The limestones are locally partly silicified. The proportion of limestone, chert and mudstone varies vertically allowing a threefold division in the Bampton area; elsewhere these divisions have not been proved and there is evidence that north of Bampton the Formation is dominated by mudstones and cherts. At the base, the informal Hayne Beech Beds comprise soft, pale-weathering, siliceous radiolarian laminated shaly mudstones (cherts of literature) with some impure argillaceous limestones. Above, the Kersdown Chert Member comprises laminated cherts with interbedded shaly mudstones and a few limestones. The upper unit, the informal Bailey's Beds, consists of black shaly mudstones with limestones and minor cherts, the top 4m yields abundant spirally striated goniatites and pectinoid bivalves (Posidonia Beds).
c.80m
Between Brushford and Ashbrittle the upper boundary is taken at the incoming of dark grey predominantly unfossiliferous finely laminated silty mudstones with scattered siltstones of the overlying Dowhills Mudstone Formation above the highest limestone bed of the Bampton Limestone Formation.
Blae Pot Limestone
BPLS
Bottom Plessey Coal (Northumberland)
BPLY
Bampton Limestone Formation [Obsolete Code: Use Bplm]
BPM
Belper Lawn Coal (Leicester, Nottingham, Derby)
BPN
Basal Permian Sands Formation
BPS
Basal Permian Sandstone
BPST
Pleinmont Metasediments
BPT
Bedded Pyroclastic Formation
BPY
Overlies the Lower Rhyolitic Tuff Formation.
Central Snowdonia.
Bedded basaltic tuff, tuffite, breccia deposits, intrusive and extrusive basalts.
Overlain by acid tuffs of Upper Rhyolitic Tuff Formation.
Basal Quartz Sandstone Formation
BQS
Unconformable on rocks of the Dalradian Supergroup.
Quartz and schist breccia, with beds of sandstone, red and grey shale, and subsidiary quartz conglomerate.
240 m thick.
The base of the Auchencar Sandstone Formation.
Brunton Quarry Sandstone
BQSA
Bradford Four Foot Coal (South Lancashire)
BR4FT
Branxton Coal (Fife)
BRA
Bradford Coal Formation
BRAC
Brae Formation
BRAE
Brae Pluton
BRAEP
Braid Hills Volcanic Member
BRAI
At base of impersistent bed of basaltic tuff, which is possibly unconformable on olivine basalt of the Fairmilehead Member.
From Comiston Road [NT 242 695] in the west to Alnwickhill Camp [NT 264 690] in the east, and from Mortonhall Golf Club House [NT 245 693] in the south to the Hermitage of Braid [NT 260 703] in the north.
Thin basal bed of basaltic tuff overlain by flows of highly altered biotite-trachyte and ?biotite-andesite.
At top of highest flow of trachyte or biotite andesite where overlain by pyroxene andesite of the Blackford Hill Member.
Bracklesham Group [Obsolete Code: Use Brb]
BRAK
Brora Arenaceous Formation
BRARE
Brora Argillaceous Formation
BRARG
Boreray Basic Magmatic Breccia Intrusion
BRAY
Bracklesham Group
BRB
Marked lithological change from interbedded wavy-, flaser- and lenticular-bedded glauconitic fine-grained sand and silty clay above to dark grey bioturbated silty clay with thin ironstones of the uppermost London Clay Formation below.
Eastern Part of Hampshire Basin.
Interbedded laminated silts and silty clays; and sands and silty sands, locally shelly.
c.120m
Topmost bed of Group is the `Tellina Bed' (White, 1921) in the Selsey Sand Formation, composed of trough cross-laminated fine- to very fine-grained sandstone. It is overlain by olive grey glauconitic sandy clays of the Barton Clay Formation.
Bracklesham Group And Barton Group (Undifferentiated)
BRBA
Better Bed Coal (West And South Yorkshire)
BRBC
West to South Yorkshire area, probably extending into North Derbyshire as the Grenoside Sandstone Coal.
The Better Bed Coal is a thick, widespread, high quality bituminous coal that has been worked extensively in the district. It is low in ash and sulphur. Mudstone that forms its roof is rich in fish and plant remains.
Barbae Grits
BRBG
Broubster Till Member
BRBU
Caithness and Sutherland, mainly east of a line between Reay and Berridale (1:50 000 sheets 115 E and W, and sheet 110).
Diamicton, clayey and sandy, typically reddish brown to moderate brown, with clasts of Orcadian Devonian sandstones, conglomerates, siltstones and mudstones, some Caledonian igneous and Moine metamorphic rocks.
Up to 10 m thick.
Holocene strata.
Brandsby Roadstone Member
BRBY
Ballyreagh Conglomerate Formation
BRC
First appearance of conglomerates and pebbly sandstones above underlying Topped Mountain Sandstone Formation, gradational.
Southwestern part of the Fintona Block, Northern Ireland.
Sandstones and conglomerates; coarse, grey-green, purple-stained, matrix supported, cobbles of mainly greywacke and rhyolite.
At least 350 metres.
Conglomerates and coarse-grained sandstones become thinner towards the top, replaced by an increasing proportion of fine-grained sandstones and mudstones; gradational to Ballinamallard Mudstone Formation.
Brooch Coal (South Staffordshire) [Superfluous Code: Use Broo]
BRCH
Burton Cliff Formation
BRCL
Braemore Conglomerate Formation
BRCO
Bryncroes Formation
BRCS
Arenig (Fennian in upper part).
Unconformable on the metamorphosed and igneous rocks of the Sarn Complex.
A conglomeratic basal division grading upwards into thinly interbedded and interlaminated sandstones and mudstones.
Overlain by siltstones, mudstones and oolitic ironstones of the Trygarn Formation. The boundary, which is possibly a disconformity or non-sequence, is defined by the first oolitic ironstone bed within the Trygarn Formation.
Brodick Breccia
BRDB
Bridlington Crag
BRDC
Silty sand, green-grey, rarely shelly. [Generic description: academic papers and BGS Memoirs].
Bridgend Flags
BRDF
Bridge Limestone
BRDL
Blind Rock Dyke
BRDY
Breakyneck Scar Limestone Formation
BRE
Early Arundian.
(Contact between this formation and the Brownber Formation is exposed at NY 6103 0923 and NY 6125 0925, but the former is only c.25m thick there).
Dark grey, bioclastic, unevenly bedded limestones with interbedded dark grey shaly mudstones. (Between underlying dolomites, oolites, conglomerates and sandstones of the Brownber Formation and overlying orthoquartzites of the Ashfell Sandstone.
Approx. 150 metres. Thinning rapidly westwards to c.75 metres north of Newbiggin on Lune and c.25 metres near Howe Nook, Orton.
Cannot be defined precisely.
Brecks Coal
BRECK
The Dalton Rock lies some distance stratigraphically just below the base of this unit.
The Barnsley and Sheffield districts of Yorkshire.
Coal
From 0.3 m to 0.9 m thick.
The Wickersley Rock lies some distance stratigraphically just below the base of this unit.
Breedon Breccia
BREE
The lower boundary is where breccia unconformably overlies dolostone of the Carboniferous Limestone; it may also conformably overlie red mudstone/siltstones/sandstones of the Gunthorpe Member, but this relationship has not been observed.
Breedon-on-the-Hill to Barrow Hill, South Derbyshire.
Breccia, angular clasts of Carboniferous limestone (dolostone) set in a red-brown, very fine-grained, clayey sandstone matrix.
The upper boundary is where typically red-green mudstones, siltstones or sandstones of the Gunthorpe Member overlie breccia.
Breighton Sand Formation
BREI
Sharp to gradational (over several tens of cms) transition to underlying clay, silt or sand of the Hemingbrough Glaciolacustrine Formation, gravels of the Pocklington Gravel Formation, or directly to bedrock. A moderate to well developed basal dark brown peat (Skipwith or Bielby Peat Bed) is present in some localities. The presence of sparsley disseminated fine flint gravel is noted close to the lower boundary, particularly towards the Formation's eastern limits (Bielby Sand Member).
The Breighton Sand Formation is known to extend across the Vale of York, from the River Ouse in the west, to beyond Holme-on-Spalding-Moor in the east, The sands are known to extend south and north beyond the Selby district.
Dominantly yellow to pale brown and reddish yellow slightly clayey sand to silty sand with a variably developed very dusky red to black compressible peat to clayey sandy peat base. Typically composed of moderately well-sorted medium quartz grains with minor bands of finer, coarser or poorly sorted material, including finely comminuted flint and lithic clasts. Thin beds of clayey sandy peat and poorly developed fine- to medium-grained slightly gravelly clayey sand are noted towards the base of the formation.
Laterally the unit's boundaries vary from gradual thinning over several hundred metres to abrupt thinning of the sands to give rise to a strong topographic feature. The unit comprises three geographically discreet members: The Bielby Sand Member in th east of the district, the Naburn Sand Member to the north of the Escrick Moraine, and the Skipwith Sand Member to the south of the Escrick Moraine. Geomorphological evidence suggests that a separate fluvial system was associated with the deposition of each sand member. The Biielby Sand Member is assumed to have been deposited by a system flowing south between the Escrick Moraine and the Wolds; the Naburn Sandstone Member was deposited by a system flowing south behind the Escrick Moraine; the Skipwith Sand Member was deposited by a system that broke through the Escrick Moraine, flowing south to meet the east-flowing fluvial system responsible for the extensive spread of Breighton Sand Formation in the south of the district.
Average 1 to 2m but can exceed 6m in some cases.
Typically exposed at surface beneath a thin (0.2 to 0.5m thick) sandy soil or locally overlain by alluvial and aeolian deposits.
Brendon Formation
BREN
The lower boundary is not seen; all observed contacts are tectonic.
Launceston/St Mellion areas (SX 33 73), between Bodmin Moor and Dartmoor, east Cornwall.
Dark grey, locally siliceous, mudstone with laminae and thin beds of siltstone. Scattered packets of blue-grey to grey-green coarse grained greywacke sandstone with interbedded dark grey mudstone. There are locally distributed units of tuff and basaltic lava. As mapped and defined, this formation may include parts of previously contiguous and coeval formations. Further work is needed as this formation may represent a collection of mud-prone Dinantian lithologies brought together tectonically.
450m+, but more or less due to thrusting.
The upper boundary is not seen; all observed contacts are tectonic.
Bretford Sand And Gravel Member
BRET
Late Pleistocene (MI Stage ?3 to 2).
Unconformable, commonly channelled base, resting on Wolston Formation or Baginton Formation in upper Avon, or farther downstream (beyond Coventry), Lower Jurassic or Triassic bedrock.
Avon Valley and tributaries (BGS Sheets 183, 184, 199, 200, 201, 216).
River Terrace.
Predominantly cold phase sands and gravels that underlie the Avon First Terrace of Tomlinson (1925) and of BGS Maps. Dominated by clasts of "Bunter" quartz/quartzite lithologies with subordinate flint, generally somewhat finer in grade than older members. (See also Compiler's notes under Supplementary Information).
(A) the unit is referred to here as Bretford Sand and Gravel Member, though in Bowen 1999, and in previous BGS use it was simply Bretford Member. (B) Terrace surface is typically some 2m above the modern Avon alluvial floodplain; locally with a lower facet c.1m above the floodplain, with deposits extending beneath the latter. Best developed in the upper Avon. Correlation with members of the Severn Valley Formation is problematical. (C) The upper boundary is given as "ground surface" though head, colluvium or soil deposits may intervene. (D) All Avon (and Severn) terraces need review; classification of some outcrops on existing maps is dubious. Thus some Previous Names are necessarily approximate. In particular the depiction of this Terrace 1 on maps, particularly in the lower Avon, is suspect. It is divided into 1a and 1b "facets", which might be expected to converge with the Power House (Terrace 1) and Worcester (2) of the Severn, respectively. However the Power House, at least, is [supposedly] below the floodplain at the confluence, whereas patches of Avon Terrace 1, as far down as the confluence, lie 1 to 2m above. Actually depiction of the Severn Terraces might be wrong; some supposed Terrace 2 "islands" in the floodplain are almost certainly Terrace 1. Knock-on implications are that some of Terrace 3 should be 2, and so on.
Bretford Sand And Gravel Member, Lower Facet
BRETL
Bretford Sand And Gravel Member, Upper Facet
BRETU
Brathay Formation
BRF
Conformably overlies the Browgill Formation of the Stockdale Group.
Laminated mudstone and siltstone.
Conformably overlain by the Birk Riggs Formation.
Broom Farm Sandstone Formation
BRFA
At sharp upward change from eutaxitic lapilli tuff (Moorside Farm Formation) to bedded sandstone.
Seen only in Sellafield BH No.2 (NY00SE/28)
Bedded, generally coarse-grained, pebbly volcaniclastic sandstone with interbeds of laminated fine-grained sandstone and siltstone.
13.5m (uncorrected for structural dip or borehole deviation from vertical).
Overlain by Bleawath Formation; boundary at change to massive lapilli-tuff.
Burford Coal Member
BRFC
In the type section, dark grey, carbonaceous mudstone with basal coal of the Burford Coal Member, overlies conformably grey to red mudstone-dominated succession of the Crawley Member.
Oxfordshire Coalfield; proved in the subsurface only.
Grey mudstone, sandstone, seatearth and coal. In the upper part of the member there are several thin Spirorbis limestone beds and the secondary reddening of the succession.
138 m thick in the type section.
In the type section, reddish brown, blue mottled mudstone with calcareous nodules of the Windrush Member, overlies conformably grey mudstone of the Burford Coal Member. In the Steeple Aston Borehole, the upper boundary is an unconformity, overlain by fine-to-medium-grained sandstones of the Mercia Mudstone Group.
Bottom Ryhope Five Quarter Coal (Northumberland)
BRFQ
Breccia Gravel
BRGL
Gravel derived from the Clent and Kidderminster formations (UK Midlands); angular clasts in a sandy matrix;origin unknown, possibly Head. [Generic description: 1:50 k map margins].
Bridges Formation
BRGP
Late Proterozoic.
At the base of the Bridges Formation flaggy siltstones rest conformably upon massive sandstones of the Bayston-Oakswood Formation.
Church Stretton and Linley areas, Shropshire.
Mainly purple siltstones and sandstones, commonly laminated and moderately flaggy. Well-marked bedding and higher proportion of silt than in the underlying Bayston - Oakwood Formation.
Averages c.900m
Drawn where flaggy siltstone of the Bridges Formation is unconformably overlain by brown sandstones and conglomerates of the Hoar Edge Grit (Caradoc).
Brandon Grit
BRGR
Brown And Grey Sandstone Member
BRGS
The base lies at the top of the highest metre-thick red siltstone bed in the Castle of Cowie Member.
Stonehaven area.
Soft brown, grey and green, locally pebbly medium-grained quartzo-feldspathic sandstone. Volcaniclastic detritus makes its first appearance in this member.
233m minimum
At the base of the lowest exposed bed of pebbly volcaniclastic sandstone in the overlying Cowie Harbour Conglomerate Member.
Bouley Rhyolite Formation
BRH
Beer Head Limestone Formation
BRHD
Cenomanian. Mantelliceras mantelli to Calycoceras geurangeri Zones.
Disconformable on the burrowed Small Cove Hardground of the Upper Greensand Formation.
Confined to the area south of the mid-Dorset Swell in Dorset.
Complex thin sequence of bedded coarse calcareous sandstone, bioclastic limestone, calcarenite and shell-detrital limestone, with a distinct nodularity and well-developed hardgrounds. Glauconitic and phosphatic. Includes the Wilmington Sand Member in calcarenite facies. Subdivision: None herein but defined as comprising the Pounds Pool Sandy Limestone, Hooken Nodular Limestone and Little Beach Bioclastic Limestone members of the Beer Head Limestone Formation of Jarvis and Woodroof (1984).
Up to 10.4m at Hooken Cliffs.
Disconformable at the surface of the Humble Point Hardground with the Pinnacles Member (of Jarvis and Woodroof, 1984), which is the sub-Plenus Marls Member erosion surface.
Brand Hills Formation
BRHI
Lies unconformably on the late Neoproterozoic Hanging Rocks Formation (formerly the Hanging Rocks Conglomerate Member), latter comprising small-pebble conglomerates fining up to grey/purple volcaniclastic siltstone.
Crops out from New Plantation (SK 5010 0902) eastwards to Bradgate Park (SK 5340 0999) and northwards to The Brand (SK 5345 1328).
The formation's basal unit is the Swithland Camp Member, composed of purple siltstones and conglomerates. The upper part of the formation is composed of the Stable Pit Member of quartz-arenites and wackes, locally burrowed and cross-bedded.
c.35m
Conformable gradational passage upwards to grey slaty mudstones of the Swithland Formation, believed to be Lower Cambrian in age (e.g. McIlroy, et al, 1998).
Barrhill Group
BRHL
Rests on Moffat Shale Group.
Southern Uplands of Scotland between Leadhills and Glenn App/Carcow Faults.
Sandstone/siltstone turbidite sequence.
Faulted (Glenn App/Carcow Fault).
Bridgnorth Sandstone Formation
BRI
Unconformable on Coal Measures and interpreted early Permian breccias.
Worcestershire, Staffordshire, Shropshire. (Worcester Basin, Stafford Basin).
Cross bedded aeolian sandstones, mainly brick red, soft, medium-grained. Buff mottling common.
183m in type area. Up to 250m elsewhere.
Unconformably overlain by Kidderminster Formation.
Blocking Rider Coal (West Yorkshire)
BRIC
The Blocking Rider Coal is a thin and impersistent seam that is of no economic significance.
Bridge Limestone [Obsolete Code: Use Brdl]
BRID
Brierley Member
BRIE
c.50m
Base of Fourth Cherry Tree Marker (mudstones with bivalves and euestheriids).
Brig Formation
BRIG
Brooch Ironstone
BRIR
Brights Coal (Somerset)
BRIS
Brickearth
BRK
Brackaville Coal (Dungannon)
BRKC
Breakish Formation
BRKH
Unconformity - diachronous transgression at start of Jurassic.
The Breakish Formation comprises blue-grey micritic limestone and dark calcareous mudstones within the lower half of the unit. The upper half of the unit consists of bioclastic limestones, ooidal limestone and nodular limestones. Ammonites are rare within the succession, but bivalve and gastropod fragments are common. Bioturbation of the sediments is locally intense. Coral beds exist near Broadford.
0 to 65m
Abrupt lithology change to sandstone and siltstone.
Branksome Sand Formation
BRKS
Black Rock Limestone Subgroup
BRL
Conformable and taken at the gradational incoming of dark grey fine- to coarse-grained skeletal packstones with scattered mudstone partings of the Subgroup above the interbedded mudstones and skeletal packstones [Cwymyniscoy Mudstone Formation] of the Avon Group.
South Pembrokshire [SM 19 90], Gower [SS 50 90], southeast crop of the South Wales Coalfield [ST 17 85], Vale of Glamorgan [ST 00 74], Monmouth and Chepstow [ST 53 93], and Bristol [ST 60 74], areas and the Mendip Hills [ST 50 53]. In Wales, passes northwards into the Clydach Valley Subgroup.
Thin- to thick-bedded, dark grey to black, foetid, fine- to coarse-grained skeletal [mainly crinoid] packstones with subordinate thin beds of shaly argillaceous skeletal packstone and mudstone. Widespread burrowing. Tractional structures and silicified limestones characterise the lowermost part of the Subgroup. Unit of ooidal limestone [Brofiscin Oolite Formation] developed in lower part in Gower, Vale of Glamorgan and east crop of the South Wales Coalfield. The upper part of the Formation is dolomitized in the south, while along the southern and eastern crop of the South Wales Coalfield and in the Monmouth and Chepstow area, the entire Formation is dolomitized. Tuffs developed in the lower part of the Subgroup in the Weston super Mare areas [Middle Hope Volcanic Member]. Subgroup represents deposition in an inner to mid ramp setting with local ooid shoal development.
500m in the southern Vale of Glamorgan, thinning northwards to 70m in the Monmouth area. 365m in the eastern Mendip Hills, thinning northwards to 158m at Bristol and 104m to the north of Bristol at Cromhall.
The top of the Subgroup is taken at the sharp contact between the dolomitised packstones of the Subgroup and the overlying oolitic grainstones or dolomitised oolite of the Gully Oolite Formation. In the south the junction appears conformable but in the north a thin red clay overlying a palaeokarstic surface is locally present; in such cases the top is taken at the top of the red clay. In the eastern Mendip Hills it is taken at the incoming of pale grey coarse crinoidal limestones of the Vallis Limestone Formation, above the dolomitised packstones of the underlying Black Rock Limestone Subgroup. Little is known about this contact, which needs further investigation. In the Bristol area the top is taken at the junction of the sparsely crinoidal dolomites of the Black Rock Subgroup and the crinoidal limestones of the overlying Sub-Oolite Bed of the Gully Oolite Formation. Little is known about this contact, which needs further investigation.
Briton's Lane Formation
BRLA
The lower boundary of the formation is erosional, and sands and gravels truncate earlier deposits of the Sheringham Cliffs Formation.
The Briton's Lane Formation crops-out across much of northern Norfolk, from Trimingham in the east to Edgefield and Holt in central north Norfolk.
The Briton's Lane Formation consists of several coarse-grained sand and gravel outwash lithofacies that truncate and drape pre-existing sediments in the Cromer and Mundesley districts. No in-situ till deposits have been identified to date, but thrust slabs of till have been recognised at several localities.
Maximum thickness of the formation is estimated to be in the region of 50m.
The Briton's Lane Formation forms the uppermost stratigraphical units in northern Norfolk. However, sporadic palaeosols can be observed within the upper part of the deposit such as at Briton's Lane.
Brodick And Lamlash Beds
BRLB
Unconformable on Carboniferous to Upper Devonian.
Mainly red-brown and yellow sandstones with beds of breccia.
c.500 metres.
Overlain by Auchenhew Beds.
Broadlee Glen Sandstone Member
BRLG
The base is not seen, but is mapped in Broadlee Glen [NS 2258 7134] and distinguished from underlying strata of the undivided Clyde Sandstone Formation by plant debris and beds of grey mudstone in the Broadlee Glen Sandstone Member (BGS, 1990).
South of the River Clyde and also west of the Largs Fault Zone in Strathclyde, Scotland.
Grey and white cross-bedded sandstones with thin lenticular beds of grey mudstone and carbonised plant debris (Paterson and Hall, 1986; BGS, 1990). In the northern part of the Leapmoor Plantation [NS 221 715], it consists of white and cream, trough cross-stratified sandstone with thin lenticular beds of grey siltstone and abundant coalified wood fragments (Paterson et al., 1990).
Greater than 100m
Top - not seen, presumed overlain by Clyde Plateau Volcanic Formation (Paterson and Hall, 1986).
Broomhill Clay Formation
BRLL
Early Dimlington Stadial.
Unconformity on older Quaternary strata, such as the Baillieston Till Formation, or bedrock, or a glacial deformation boundary.
Central Scotland, related to ice streams sourced in the Highlands (in contrast to the Southern Uplands) during the early part of the Dimlington Stadial; more specifically the Glasgow area between Erskine Bridge and Baillieston and also the western Kelvin valley.
The typical lithology is thinly bedded silty clay with wisps, laminae and bands of silt and, locally, sand. The deposit is generally reddish brown with grey or buff silt and sand. Isolated clasts up to 14cm are present and are considered to be dropstones. The deposit is of a hard to stiff consistency and medium to high plasticity. Thin diamicton bands and patches occur locally, with some graded bedding (turbidity flows) and microfaulting. Laminations are probably varves, and might represent 600 to 1000 years of sedimentation.
Veneer to more than 15m.
Unconformity below younger Quaternary strata or, most commonly, a glacial deformation boundary with the overlying glacial diamicton of the Wilderness Till Formation.
Briton's Lane Sand And Gravel Member
BRLSG
The lower boundary is generally well defined with sands and gravels resting upon an erosion surface that cuts down into and draped over tills of the Sheringham Cliffs Formation.
The Briton's Lane Sand and Gravel Member is the most extensive part of the Brition's Lane Formation and forms the elevated sections of the Cromer Ridge between the Glavern Valley, Beeston Regis and Overstrand, north Norfolk. The member also forms some of the large sand and gravel outliers between West Runton and Weybourne and has been traced southwards inland for approximately 10km.
The Briton's Land Sand and Gravel Member consists of horizontal, massive and low angle planar cross-bedded gravels and cobble gravels with thin seams of horizontal and rippled sand. The lithology has a distinctive high flint content (c.85-89%) of which the majority is of non-chatter marked variety (c.78-85%). The gravels also contain a wide range of far-travelled crystalline erratics including rocks of British and Scandinavian provenance.
The maximum observed is 40m.
The Brition's Lane Sand and Gravel Member is commonly exposed at the surface although in places it has a thick palaeosol developed within the upper 2-3m.
Breckells Mudstone Member
BRM
Gradational and conformable transition from the interbedded reddish brown and greenish grey mudstones of the Coat Walls Mudstone Member to the dominantly reddish-brown, structureless mudstones of the Breckells Mudstone Member.
preserved in the Preesall syncline area, north Fylde peninsula, Lancashire.
Mudstone, reddish-brown, structureless, commonly brecciated, with common halite and gypsum.
209m seen in Blackpool district, Lancashire (Wilson and Evans, 1990).
Not present at outcrop or in the subsurface, onshore UK.
Bridgewick Marls (One)
BRMA1
Bridgewick Marls (Two)
BRMA2
Bridgewick Marls (Three)
BRMA3
Burntisland Marine Band
BRMB
Broomhill Main Coal (Northumberland)
BRMN
Braemore Mudstone Formation And Braemore Sandstone Formation (Undifferentiated)
BRMS
Braemore Mudstone Formation
BRMU
Burnside Sandstone Formation
BRN
Unconformable on the Ochil Volcanic Formation.
Sheets 40, 48, 49, Fife-Kinross-Leuchars.
Dull red or purple, fine- to very coarse-grained sandstones characterised by the presence of siliceous pebbles, which also form conglomeratic bands.
Up to 160 m thick, in the Lomond Hills area.
Drawn at the conformable upward passage from red or purple, pebbly sandstones of the Burnside Formation, to the brown, yellow, red, purple or cream sandstones of the Glenvale Formation.
Brynloi Coal (South Wales)
BRNC
Brennand Grit
BRNG
Sharp and erosional on massive bedded sandstone and siltstone of the Pendle Grit Member.
South-eastern Lancaster Fells; also western Settle area.
Very coarse, pebbly to medium-grained cross-bedded feldspathic sandstone with minor siltstone beds.
0 to 330m
Typically sharp at top of rootlet bed beneath base of grey micaceous siltstone and sandstone of the Roeburndale Member.
Bryn Nicol Formation
BRNI
Barneil Member
BRNL
Late Llanvirn to early Caradoc?
The exact base of the Member is not clearly defined, as the cherts may be interbedded or overlie the lavas. An analogous situation is seen in the Marchburn Formation in the Northern Belt of the Southern Uplands, where lavas and cherts are interbedded with each other, and the cherts are similarly identified as late Llandeilo to early Caradoc, based on conodont evidence.
Craighead Inlier, Girvan.
Red bedded chert, associated with pillow lava.
At least 50m
The lavas can be seen to be unconformably overlain by the Craighead Limestone Formation at Craighead Quarry.
Brandon Sandstone Bed
BRNS
Change from silty mudstone and siltstone of the undifferentiated Charmouth Mudstone Formation into sandstone as above, may be a conglomerate at base; at 171.88m depth in type section Copper Hill Borehole (SK94SE/56).
East Midlands; north Leicestershire to Lincolnshire. Not recognised in the Charmouth Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into mudstone-dominated Charmouth Mudstone Formation.
Pale grey, grey-brown weathering, silty, calcareous, fine sandstone, with shelly lenses, scattered mica grains and abundant burrows. Subordinate siltstone and mudstone beds. Fauna includes bivalves (including Pholadomya and Modiolus), forams, ammonites, belemnites and crinoids. Soil developed on outcrop is sandy, but may contain no brash.
1 to 4.5m; 4.43m in type section
Change from sandstone-dominated beds into mudstone and siltstone of undifferentiated Charmouth Mudstone Formation; at 167.45m depth in type section Copper Hill Borehole (SK94SE/56).
Brent Group
BRNT
Brown's Vein
BRNV
Bronydd Formation
BRNY
Broadlie Coal
BRO
Brora Brick Clay Member
BROBC
Brockwell Coal (Northumberland And Durham)
BROC
Broad Law Intrusion
BROD
Intrusive into Portpatrick Formation, possibly along a fault.
Southeast Scotland.
Lenticular granodiorite body c. 1km x 100m, elongated NE - SW.
c. 1km x 100m vertical intrusion.
Intrusive into Portpatrick Formation.
Broom Formation
BROM
Bridgeton Sand Member
BRON
Latest Main Late Devensian Stade to Earliest Windermere Interstadial.
The Bridgeton Sand Member rests with angular unconformity on bedrock or older Quaternary sediments. It commonly rests on the Wilderness Till Formation of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
The Bridgeton Sand Member of the Clyde Clay Formation is recognised in the lower Clyde valley west of Hallside/Greenoakhill (NS 670 600) downriver at least to near Erskine Bridge (NS 460 720).
The two typical lithofacies are beds of very fine- to medium-grained sand, and fine to coarse gravel and boulders with a sandy matrix. The deposit is loose to dense. At Shieldhall (Browne and McMillan, 1989a, Figure 19), west Glasgow, the Member showed a gross upward-fining succession of about 20m thickness. The sands and silts showed flat bedding, ripple-lamination and climbing ripple-lamination, and planar and trough cross-bedding (westward transport). There were indistinct channels filled with massive sand, and two discrete ones up to 2m thick (width not known) containing framework-supported fine to very coarse gravel. Microfaulting was rarely seen and consisted of small reversed faults. There was evidence of soft sediment deformation, in that these deposits and the overlying laminated clays, originally flat-lying, dipped centroclinally into basins at angles up to as much as 80 degrees. This member forms the basal part of the Clyde Clay Formation.
The Bridgeton Borehole (Browne and McMillan, 1989a, Figure 18) is the standard but incomplete section of the Bridgeton Sand Member) between 29.31 and 40.38m in depth (base of bore). Its stratigraphical relationships and geographical distribution are summarised in ibid (Figures 2B, 3C, D and 4A).
Veneer to over 20 metres.
The Bridgeton Sand Member is overlain unconformably or disconformably by younger Quaternary sediments, normally the Paisley Clay Member of the British Coastal Deposits Group or the Clyde Valley Formation of the Britannia Catchments Group (Clyde Catchment Subgroup). It is almost always concealed below younger sediments throughout its area of occurrence.
Brooch Coal (South Staffordshire)
BROO
Brora Shale Member
BROR
Brora Roof Bed
BRORO
Proplanulites koenigi Subzone of the Sigaloceras calloviense Zone.
Broadstone Sand Member And Oakdale Sand Member (Undifferentiated)
BROS
Broughton Coal
BROU
Bruar Psammite Formation
BRPS
Base not exposed in core of Meall Reamhar Synform; north of Allt a'Chireachan may pass downwards into Drumochter Succession.
In core of Meall Reamhar Synform from near Dalriach [NN 745 595] via Calvine [NN 805 658] and the Water of Bruar to at least the northern margin of Sheet 55W. Also extends westwards at least as far as the Allt a'Chireachain [NN 756 710 - 787 730]. Individual formations are not recognised in the north-western part of Sheet 55W.
Psammite, both thickly-bedded quartz-rich types with quartzite layers, and thinly bedded laminated feldspathic types. Contains a few mappable semipelite and pelite units.
>600m
Gradational boundary with overlying Tummel Quartzite Formation.
Barren Red Member (Somerset)
BRR
The base of the red and grey mottled mudstone of the Barren Red Member rests conformably on the uppermost coal seam of the grey, Farrington Member, dominated by the grey mudstone and subordinate sandstone. The coal seam may not be the same between coalfields.
Bristol, Somerset and Severn coalfields.
Red and grey mottled mudstone, seatearth, 'Pennant' type lithic sandstones, but no coal seams.
Up to 230 m thick in the Radstock Syncline and 275 m thick in the Coalpit Heath Syncline.
The top of the grey mottled mudstone of the Barren Red Member is overlain by the base of the Nine-Inch Vein Coal of the grey mudstone-dominated Radstock Member in the Somerset Coalfield.
Brown Rake Coal (Nottingham And Derby)
BRRC
Brockwell Rider Coal (Northumberland And Durham)
BRRI
Brownstones Formation
BRS
(1) Where sandstones become dominant over mudstone in the underlying St Maughans Formation. (2) At colour change from predominantly green sandstone of the Senni Beds below, to red of the Brownstones.
South Wales and Welsh Borderlands, as far north as the Clee Hills.
Red, brown and purple fluvial sandstones with red mudstone interbeds.
To 1200m
Where Upper Devonian or Lower Carboniferous beds overlie the Brownstones unconformably.
Braicklaich Sand Member
BRSA
Not observed but probably conformable on the Finglack Till Formation.
Alturlie Peninsula and the southern shore of the Inner Moray Firth east of Inverness. Sheet 84W.
Sand, silty sand and silt, rhythmically bedded, pale yellowish brown, capped by sand and gravel. Individual beds are generally graded sand/silt couplets, 0.2 to 0.4m thick, with planar or ripple-drift cross lamination. The beds are stacked into packages and are probably glaciomarine cyclopsams.
Ground surface or sharp, gently undulating, unconformable contact with raised beach deposits.
Brights Coal (North Staffordshire)
BRSC
Burghead Sandstone Formation
BRSF
Around Lossiemouth the base of the formation is the base of the predominantly waterlain pebbly sandstones unconformably overlying the Upper Old Red Sandstone strata. Farther to the west the formation overlies the Triassic Hopeman Sandstone Formation.
Moray Firth area.
Water-lain poorly sorted, brownish to grey arkosic pebbly sandstone; fine- to coarse-grained. Commonly cross-bedded or laminated, some massive. Some conglomerate beds and beds with common mudstone interclasts. Few siltstone beds.
Up to 73 m.
The top of the formation is the base of the aeolian beds belonging to the Lossiemouth Sandstone Formation or, where that is absent, the base of the Stotfield Cherty Rock Formation.
Brooksby Sand And Gravel
BRSG
Bronsil Shale Formation
BRSH
Probably conformable with White-leaved Oak Shale.
Around Bronsil (SO 750 374), south end of Malvern Hills.
Fissile silver-grey mudstone.
Probably 250m - 350m.
Faulted or unconformity.
Brays Silts Formation
BRSI
Base of palaeochannel cut in bedrock.
The Brays sand and gravel pit, near Mathon, Hereford and Worcester.
Greenish grey organic silts rich in an interglacial flora and fauna.
Up to c.1 metre.
Erosion surface overlain by Mathon Sand and Gravel.
Birstall Rock
BRSR
West Yorkshire area [Birstall, Yorkshire].
The Birstall Rock is a fine-grained, thickly bedded, cross bedded sandstone with common pebbles of ironstone, coal sandstone and mudstone, and common streaks of shaly coal.
To c.30m
Brassy Coal (Cumbria)
BRSY
Brithion Formation
BRT
Sharp but conformable contact with underlying mudstones of the Aran Volcanic Group.
Harlech district.
Volcanic breccias and felsic, welded ash-flow tuffs.
To 75m, but the formation wedges out southwestwards and northwards.
Conformably overlain by undivided siltstones of the Aran Volcanic Group.
Broadstone Clay Member
BRTC
Barton Limestone Member
BRTL
Broadstone Sand Member
BRTS
Brunel Beds
BRU
Barrule Formation
BRUL
Faulted at the base against the Maughold Formation, which is distinguished by the loss of any sandstone/siltstone interbeds.
Isle of Man.
Dark grey to black mudstone.
Up to 900 m thick.
In stratigraphical contact at the top with the Injebreck Formation, which is marked by a change from a mudstone/sandstone facies to a mudstone-dominated facies.
Brunachan Psammite Formation
BRUN
Brunton Quarry Coal (Northumberland)
BRUQ
Broad Vein Mudstone Formation
BRV
No lower boundary is exposed but the pale-medium blue mudstones of the Formation rest with sharp contrast upon the black mudstones of the Nod Glas Formation.
Passes west into Cardigan Bay. The outcrop of the Broad Vein Formation crosses sheet 149 diagonally from southwest - northeast (Tywyn - Aberllefenni).
Pale-medium blue, silty-mudstone, intensely bioturbated in parts.
400 to 560m
The upper boundary can be examined at Aberllefenni Quarry, where the contact is transitional, over 0.5m, from the pale-blue of the Broad Vein Mudstone Formation to a medium-blue, laminated silty mudstone of the Narrow Vein Mudstone Formation, accompanied by the development of lamination.
Brass Vein Coal (South Wales)
BRVC
Bricklieve Limestone Formation
BRVE
Browgill Formation
BRW
Conformably overlies the Skelgill Formation.
Laminated mudstone, siltstone and calcareous shale.
About 30m
Conformably overlain by the Brathay Formation.
Brow Vein
BRWV
Brixham Limestone Formation
BRXL
Bryans Coal (Lothian)
BRY
Lower Peat Member [Breydon Formation]
BRY1
Peat; two lithologies, 'brushwood' (freshwater) peat and 'phragmites' (brackish water) peat. Locally,as organic-rich clay. [Generic description: from East Anglian data].
Lower Clay Member [Breydon Formation]
BRY2
Silt and clay; of Flandrian age. [Generic description: 1:50 k map margins].
Middle Peat Member [Breydon Formation]
BRY3
Peat; two lithologies, 'brushwood' (freshwater) peat and 'phragmites' (brackish water) peat. Locally as organic-rich clay. [Generic description: from East Anglian data].
Upper Clay Member [Breydon Formation]
BRY4
Clay and subordinate silt. [Generic description].
Upper Peat Member [Breydon Formation]
BRY5
Peat; two lithologies, 'brushwood' (freshwater) peat and 'phragmites' (brackish water) peat. Locally, as organic-rich clay. [Generic description: from East Anglian data].
Brierley Coal (West And South Yorkshire)
BRYC
Breydon Formation
BRYD
Unconformable. Commonly overlies tills and outwash sands and gravels of the Happisburgh and Lowestoft formations and also sands, gravels and silts of the Crag Group. Also overlies gravels of the Yare Valley Formation (as in the type section). In the west of the outcrop the base of the formation locally overlies rocks of the Chalk Group and London Clay Formation (Thames Group).
Confined to the valleys of the River Bure and River Yare near Great Yarmouth.
This formation, which underlies much of the marshland in the Great Yarmouth district, is dominated by unconsolidated silt and clay with a shelly marine fauna. Sand is generally a minor component, though locally substantial sand bodies interrupt the argillaceous succession. Peat, of freshwater and brackish origins, is a major component adjacent to much of the marshland margin and particularly in the valleys of the River Yare and tributary streams. If also occurs as three widespread though locally inpersistent layers, at the base of the formation, within it, and at the top, mainly in the marshalnd fringe.
Up to 22m, but thins towards the margins of the outcrop.
At surface. Not overlain by other deposits.
Bottom Ryhope Little Coal (Northumberland And Durham)
BRYL
Bryncoch Coal (South Wales)
BRYN
Bryn Coal (South Wales)
BRYNC
Berry Slade Formation
BRYS
Taken at gradational boundary between medium- to thick-bedded crinoidal argillaceous packstones with chert nodules and shaly partings of the underlying Black Rock Limestone Subgroup, and the dolomitized reef limestones of the Formation.
Castlemartin area [SR 95 98], southwest Pembrokshire. Passes northwards into the Black Rock Limestone Subgroup.
Massive, grey Waulsortian reefs, comprising dolomitised carbonate mudstone with locally abundant spar-filled fenestrae [stromatactoid structure] and sparse crinoid debris. Reefs are locally overlain by and pass into a flank facies comprising thin-bedded dark limestones and dolomites with cherts and thin mudstones. Stratigraphic position of flank facies uncertain and requires further investigation.
80m at type section in south Pembrokshire.
Taken at junction of massive dolomitised reef limestones of the Formation and the overlying dark limestones with thin mudstones and cherts of the Linney Head Formation. Where the top of the Formation is in flank facies, the boundary is imprecise but taken at the increase in chert content at the base of the Linney Head Formation.
Brassey Coal (South Lancashire)
BRYSL
Brazilly Coal (Forest Of Dean)
BRZY
Bridgnorth Sandstone Formation [Obsolete Code: Use Bri]
Blown Sand
BSA
Sand, pale brown, fine-grained, uncemented. [Generic description: 'TMOS' procedures].
Blown Sand, 1
BSA1
Sand, pale brown, fine-grained, uncemented; older than 'Blown Sand'. [Generic description: 'TMOS' procedures].
Blackshale And Ashgate Coal (Vale Of Belvoir)
BSAC
Birnam Slate And Grit Formation
BSAG
Birnam area.
Slaty pelite and gritty psammite.
Boundary with unassigned part of Southern Highland Group.
Badenyon Schist And Limestone Formation
BSAL
Top of graphitic pelites of the underlying Glenbuchat Graphitic Schist Formation.
100m to 1.5km-wide outcrop extending N-S from Leadensider Burn, Glenbuchat [NJ338 201] to Cairnagour Hill [NJ330 057]. Also in the Lecht-Delnadamph area, Gordon District. Sheets 75W and 75E.
Schistose psammites and semipelites with minor schistose calc-silicate rock, impure carbonate rock, limestone and quartzite.
Up to 900m (based on outcrop width only, with no allowance for folding etc.).
Truncated by faults and shear-zones of the Portsoy Lineament.
Basket Shell Bed
BSB
Bolders Bank Formation
BSBK
Bishopbriggs Sandstone
BSBS
Blackshale Coal (South Yorkshire, Nottingham And Derby)
BSC
Barney's Cut Coal (Northumberland)
BSCC
The area around Barney's Cut (Lewis Burn), Northumberland.
Blackshale Lower Leaf Coal (Derby)
BSCL
Bastions Coal (South Lancashire)
BSCO
Blackshale Upper Leaf Coal (Derby)
BSCU
Belsay Dean Limestone
BSDL
Bromleysmill Shale Formation
BSF
Not seen in type area but presumed to rest conformably on Llandovery Purple Shales.
Southern and western surround of the Shelve Ordovician outcrops, ie the Camlad Valley.
Mudstone, bedding-fissile, medium-dark grey, variously bioturbated, graptolitic. Sparse thin argillaceous limestone layers with shelly faunas.
May be 500m
Overlain conformably (by rapid passage) by Aston Mudstone Formation. Unnamed dingle (SO 3038 9094).
Bowland Shale Formation
BSG
The conformable base upon the Pendleside Limestone Formation in the Craven Basin, on the Widmerpool Formation in the East Midlands, and the Pentre Chert and Cefn-y-Fedw Sandstone Formation in North Wales, on the Hodderense Limestone Formation in the south of the Isle of Man, is taken at the first appearance of black mudstone above variegated mudstones or fine-grained limestones. In south Cumbria the lower boundary of the formation is taken at the base of the Cravenoceras leion Marine Band, where the dark grey to black marine mudstone rests upon thinly interbedded limestones, mudstones and subordinate sandstones of the Alston Formation. The Bowland Shale Formation onlaps onto and eventually, by Pendleian times, extends over the carbonates of the Central Lancashire High (Trawden Limestone Group). In the Craven Reef Belt, in the Malham Cove/Gordale Scar area, the fissile mudstones with nodules and thin beds of ironstone and limestone of the Bowland Shale Formation, rest unconformably and diachronously on the Malham Formation (Great Scar Limestone Group), or Yoredale Group.
Widespread in the Craven Basin, including the Lancaster, Garstang, Settle, Clitheroe and Harrogate districts, south Cumbria and the Isle of Man; also in North Wales, Staffordshire and the East Midlands.
Mainly dark grey fissile and blocky mudstone, weakly calcareous, with subordinate sequences of interbedded limestone and sandstone, fossiliferous in more-or-less discrete bands.Furness and Settle areas: thick-bedded, blocky to sub-fissile, dark grey and black, organic-rich mudstone, with subordinate beds of dark grey siltstone, sandstone and pale brown dolomitic limestone. Marine bands are also present. Shows an upwards decrease in carbonate turbidites and a concomitant increase in siliciclastic sandstone turbidites.South Isle of Man: Black claystone with localized deposition of carbonate turbidites, debris flows, olistoliths, volcaniclastic deposits and lavas. At the base of the formation, the Scarlett Point Member comprises cherty and pyritous tabular beds of pale wackestone and lime-mudstone (dolomitized in places), which display gradational boundaries with interbedded black, fissile, blocky claystone. The limestone is burrowed and has inadunate crinoidal lags and scattered ammonoids. At the top of the formation, the Scarlett Volcanic Member is dominated by a series of volcaniclastic debris flows and gravity slides. Claystone rafts and megaclasts are entrained within the volcaniclastic rocks, and carbonate olistoliths and pillow lavas also occur. Between the members, where the formation oversteps the Balladoole Formation (Great Scar Limestone Group), coarse-grained detrital carbonates and debris beds are common. These include erosively based, graded packstone beds, conglomerate, megaclasts and large olistoliths (with reef limestone and ammonoid faunas) derived from the Balladoole Formation. The middle part of the exposed formation comprises black, calcareous, platy claystone with subordinate beds (up to 2 m thick) of dark wackestone, and dark detrital packstone debris. North Isle of Man: Siltstone, claystone and ironstone dominate, but includes two marine bands and five palaeosols.
Generally between 120m and 620m. The formation thickens northeastwards along the axis of the Central Lancashire High, from about 22m in the Roddlesworth Borehole (SD62SE/6), 68m thick in the Holme Chapel Borehole (SD82NE/68), and 102m in the Boulsworth Borehole (SD93SW/14). The underlying Trawden Limestone Group shows a thinning in the same direction (Evans and Kirby, 1999), suggesting the thickening of the Bowland Shale Formation reflects available accommodation space. In the Craven Reef Belt the Bowland Shale Formation is perhaps 30m to 200m thick (see Arthurton et al., 1988, figure 22). In south Cumbria, the Roosecote Borehole (see above) proved the formation to be 130m thick (see Johnson et al., 2001; Rose and Dunham, 1977). On the Isle of Man, the Bowland Shale Formation might be at least 186m thick. In the north Isle of Man, the Shellag Point Borehole [NX 4565 9965] proved only a part of the formation, reaching 27.55m in thickness.
The top of the formation is taken at the base of the Millstone Grit Group over most of the Pennine Basin and at the base of the Morridge Formation in Staffordshire and the East Midlands. The formation shows complex intertongueing with the Morridge and Cefn-y-Fedw Sandstone formations. It is seen as a conformable boundary defined by the base of the lowermost thick feldspathic sandstone of the Millstone Grit Group, or quartzitic sandstone of the Morridge and Cefn-y-Fedw formations, above thick dark grey mudstone of the Bowland Shale Formation.
Bessygill Limestone
BSGL
Beenham Stocks Gravel Member
BSGR
Erosional base on London Clay.
Kennet Basin and adjacent interfluves.
Gravel, variably clayey and sandy.
To 4m
Terrace surface at 100 - 105m OD around Beenham.
Big Smut Coal (Goyt Trough)
BSGT
Barshaw Sill
BSHAW
Bottom Shuttles Coal (South Lancashire)
BSHC
Ballymaglin Shale Member
BSHM
Blackshale Sill
BSHS
Buttershaw Limestone
BSHWL
Found only in the area of the Broughton Anticline. Probablt equivalent to the Embsay Limestone of the Skipton and Lothersdale anticlines, and to the Rain Gill Limestone of the Slaidburn-Ashnott-Middop-Whitewell anticlines farther west.
Basalanhydrit Formation
BSHY
Bryn Siltstone Formation
BSI
Base of siltstones lie with sharp contact on the Pandy Tuff Formation acid ash-flow tuffs.
Grey silty mudstones, siltstones and fine-grained sandstones (less well bedded than underlying Teirw Formation), tuffaceous sandstones and sporadic coarse-grained feldspathic tuffs and breccias. Includes, at its top, the Pen y Graig Tuff Member. The Formation is very fossiliferous.
Top of Pen y Graig Tuff Member succeeded by black mudstones of Blaen y Cwm Shale Formation.
Burnside Intrusion (Plug)
BSIDE
Blues Limestones
BSL
Ballanayre Slump Breccia
BSLB
Brinsley Coal (Nottingham And Derby)
BSLC
Bo'ness Lower Ironstone
BSLI
Ben Suardal Member
BSLL
Barracks Limestone
BSLS
Brinsley Thin Coal (Derby)
BSLTC
Blue Lias Formation, Scunthorpe Mudstone Formation And Charmouth Mudstone Formation (Undifferentiated)
BSMC
Beoil Schist Formation And Meall Dubh Striped Pelite Formation (Undifferentiated)
BSMD
Lower Banton Smithy Coal
BSML
Upper Banton Smithy Coal
BSMU
Beeston Coal (West Yorkshire)
BSN
Bottom Beeston Coal (West Yorkshire)
BSNB
The Beeston Bottom Coal is a thick and locally important seam of high quality. It merges to the west with the lower leaf of the Top Beeston to form the Churwell Thick Coal.
Beeston Rider Coal (West Yorkshire)
BSNR
Top Beeston Coal (West Yorkshire)
BSNT
The Top Beeston Coal is a bituminous coal of high economic importance that was mined principally in the area southeast of Leeds. It splits westwards, the upper part forming the Churwell Thin Coal, the lower portion forming the top of the Churwell Thick.
Older Blown Sand [Continued Use Not Recommended: See Bsa1]
BSO
Sand, pale brown, fine, uncemented; may contain rare flint pebbles in East Anglia; older than 'Blown Sand' in the same map area. [Generic description: 'TMOS' Procedures].
Budleigh Salterton Pebble Beds Formation
BSP
Rests sharply with marked lithological contrast on Aylesbeare Mudstone Group. Probable disconformity at the contact.
Extends from Budleigh Salterton on south Devon coast to near Minehead on north Somerset coast.
In Exeter and Newton Abbot districts: predominantly brown horizontally-bedded gravel with subordinate lenticular beds of trough cross-bedded pebbly sand and sand. The gravel is composed of well-rounded pebbles, cobbles and boulders in a coarse to fine gravel and silty sand matrix. The clasts are mainly (84 to 90%) metaquartzite together with porphyry, vein quartz, tourmalinite, and feldspathic conglomerate. From just south of Hillhead (ST 067 136), locally derived Devonian and Carboniferous clasts begin to appear. Near Milverton, the Formation is massive calcareous conglomerate with limestone clasts.
Budleigh Salterton: 30m. Exeter district: 15-20m. Hillhead: 24m. Taunton district: 30-35m.
Ventifact bed at top of the formation is present from Budleigh Salterton to Hillhead: it is overlain by sands or pebbly sands of the Otter Sandstone.
Brockelschiefer Member
BSR
Bass Rock Plug
BSRK
Bo'ness Six Foot Coal
BSSF
Beeston Sand And Gravel Member
BSSG
Upper Pleistocene (MI Stage 5e to 4). Formerly recorded as "Devensian" in original Informal Lexicon entry by A Brandon, 26/01/1998.The chronology is based upon analogy with an Ipswichian hippo fauna in the correlative Allenton Sand and Gravel of the lower Dove.
Unconformable, commonly channelled base, resting on pe-Quaternary bedrock.
Developed principally on the north bank of the Trent near the confluence with the Derwent in which the correlative Allenton Sand and Gravel is well developed. Present to a lesser extent elsewhere on Sheet 141 and 126; also thought to be present upstream on the Trent, Dove and Tame but extent uncertain pending resurvey (Sheet 140, 154, ?124).
Predominantly cold-phase sands and gravels that underlie the Beeston Terrace. Orange-brown sandy gravel, cryoturbated and decalcified in upper part at least, and dominated by rounded pebbles of "Bunter" quartz/quartzite (typically c.80%) with subordinate subangular flint (c.10%), plus minor Triassic and Upper Carboniferous sandstone, Lower Carboniferous chert and silicified limestone; probably contains a moderate proportion of Lower Carboniferous limestone where fresh at depth. Forms a fairly well preserved terrace in the type area, standing c.7m above the Trent alluvium in the type area. Merges into the correlative Allenton Sand and Gravel Member (Derwent Valley Formation), which includes the organic Crown Inn Beds (Ipswichian). Also correlated with the Wanlip Sand and Gravel Member (Soar Valley Formation) and the Fulbeck and ?Scarle Sand and Gravel members (Trent Valley Formation).
Clayton, Posnansky, etc, wrongly correlated the type Beeston Sand and Gravel with the older Balderton Sand and Gravel downstream, and also (it appears) with the younger Holme Pierrepont Sand and Gravel upstream. The Bassingfield Sand and Gravel of Sheet 126 is, given the fact that it is cleary somewhat degraded, at the right elevation to be Beeston (and too low to be Egginton Common/Balderton) and was correlated with the type Beeston by Clayton, etc. In my opinion it is Beeston Sand and Gravel. However, Lowe (1989) and Charsley et al. have it as a separate entity, presumably because they say it passes down into, and intercalates with sandy pebbly clay which they interpret as a glacial melt-out. But I suspect it more likely that these are contemporaneous head gravels etc. Currently this unit is only distinguished as such on Sheet 141 (Loughborough). It is undoubtedly present upstream, but the distribution shown by Clayton (1953) would seem to be mostly Holme Pierrepont Sand and Gravel. On Sheet 126 (Nottingham) it is named the Bassingfield Sand and Gravel (see above). I would not expect it to be present significantly downstream of Newark because [in my opinion] the river followed the Proto-Trent route at the time, where it is [probably] represented by the Scarle Sand and Gravel.
Belemnite Sands Member (Skye And Adjacent Areas)
BSSK
Lower Callovian.
Marine siltstones and sandstones replace the marine-brackish mudstones of the Upper Ostrea Member.
Siltstones and sandstones with a diverse bivalve fauna, belemnites and rare ammonites. A plesiosaur has also been found. The sandstones are commonly bioturbated, with local, small-scale cross-bedding and flaser bedding. One interpretation of the Member is that it was a migrating offshore sand bar, transgressing over the coastal lagoons described by 'Upper Ostrea Member'.
Sharp boundary, overlain by bituminous fissile mudstones of the Dunans Shale Member.
Bo'ness Splint Coal (Glasgow Area; Central Coalfield)
BSSP
Barn Scar Sand And Silt Member
BSSS
Sharp, undulating, draped, unconformable contact with reddish brown stony clay diamicton of the Holmrook Till Member of the Blengdale Glacigenic Formation.
Identified only in the vicinity of the Drigg Landfill Site, Holmrook, Cumbria, but probably extends off-shore filling a buried channel.
Thin interbedded and laminated reddish brown and yellowish brown fine- to medium-grained sand, silt and clay with sparse gravel. Disseminated coal fragments present throughout.
To 27m
Sharp, planar, unconformable contact with reddish brown gravelly sandy clay diamicton of the Ravenglass Till Member of the Seascale Glacigenic Formation.
Barney's Cut Sandstone
BSST
Ben Stumanadh Intrusion
BSSY
Binny Sandstone
BST
Blackstone Coal (Stoke)
BSTC
Black Stockarton Moor Subvolcanic Complex
BSTM
Bo'ness Upper Ironstone
BSUI
St Saviour's Andesite Formation [Redundant Code: Use San]
BSV
Bottom Saltwick Coal (Northumberland)
BSWC
Bryn Syllty Disturbed Bed
BSY
Berw Shear Zone
BSZ
Bargate Sandstone Member
The lower boundary is placed at a burrowed erosion surface where pebbly sand rests on pale grey, well-sorted, fine- to medium-grained, weakly cemented sandstone [Hythe Formation] [Ellison et al. 2002]. Locally, in the Alresford district, it interdigitates with pebbly, glauconite- andlimonite-rich clayey sand [Rogate Member, Sandgate Formation] [Farrant, 2002].
Restricted to the Alresford and Guildford districts. It forms a broad plateau south and west of Godalming [SU 95 43]. There are small outliers near Shere [TQ 0780 4730] and Abinger [TQ 1020 4680]. It is discontinuous around Albury Heath [TQ 058 466], Blackheath [TQ 038 464] and Farley Heath [TQ 046 430] and it is restricted to the northeastern part of the Alresford district.
In the Guildford district the Member comprises buff to brown, gritty to ferruginous, cemented, cross-bedded, coarse-grained sandstone with beds of pale grey calcareous sandstone. Locally a pebble bed occurs at the base, with clasts of Hythe Formation, glauconite pebbles, quartz granules, brown phosphatic pebbles and pebbles of Jurassic limestone. Locally, e.g. Milford Bypass [SU 9435 4413] the member is weakly calcareous and chert beds occur, including one at the base. Hard, calcareous sandstone doggers [Bargate Stone] have also been recorded near the top of the unit around Dorking. In the northeast part of the Alresford district it consists of friable, calcareous, glauconitic, fine- to medium-grained sandstones and cemented flagstones.
To 35m in the Alresford district and to 20m in the Guildford district.
In the Alresford district the upper boundary is characterised by a downsection change from grey, friable, well-sorted, fine-grained, glauconitic, weakly cross-bedded sandstone [Pulborough Sandrock Member] to brown, friable, calcareous, glauconitic sandstone, pebbly in part [Farrant, 2002]. In the Guildford district the argillaceous silts and fine- to medium-grained sandstones [Sandgate Formation] rest on brown, gritty, ferruginous, cemented, cross-bedded sandstone with beds of pale grey, calcareous sandstone [Ellison et al., 2002].
Beta Coal (North Wales)
BTAC
Beinn Totaig Formation
BTAIG
Overlies the Rasmasaig and Beinn Edra formations in northern Skye.
Alternating flows of alkali basalt with hawaiite and mugearite, showing eruptive alternation between unevolved and evolved lavas respectively. The evolved lava flows are commonly composite with the upper flow margins being strongly plagioclase-phyric.
To 600m
Overlain by the Bracadale Formation.
Betton Shale Formation [Duplicate Code: Use Bet]
BTB
Ballintoy Chalk Formation
BTC
Conformably overlies `Bed? B of the Larry Bane Chalk Formation. Oldest of the post-Larry Bane Chalk `Subgroup?.
Principal outcrop is within the North Antrim and East Antrim (Midland Valley) basins. Oversteps the Larry Bane Formation onto the Southern Uplands, Highland Border and the northernmost part of the Londonderry Shelf.
Limestone (chalk) with small flints scattered in the lower part and small discontinuous tabular flints in the upper part. The formation can be divided two `Beds? (A and B) separated by conspicuous separation planes. The formation is terminated by the `wavy-bedded? Altachuile Breccia (of member? status).
12.65m at its type site with Bed A 9.65m and Bed B 3.00m.
Conformably succeeded by the Glenarm Chalk Formation above the Altachuile Breccia (Member?).
Brass Thill Coal (Northumberland And Durham)
BTCO
Brantingham Member
BTF
Base of sediments as described above resting erosively on mudstone of Oxford Clay or (locally) mudstone, siltstone or sandstone of Kellaways Formation; small phosphatic pebbles at base in some sections.
Humberside, Worlaby to Market Weighton (Gaunt et al., 1992)
Pale to medium grey calcareous siltstone with thin lenticular or concretionary sandy and silty limestones and a few thin medium to dark grey mudstone beds; pale to medium grey, fine-grained, silty massive and bioturbated calcareous sandstones developed in lower part.
0 to c.18m
Base of silty mudstones and mudstones of overlying beds of West Walton Formation undifferentiated.
Bents Fireclay
BTFC
Beach And Tidal Flat Deposits (Undifferentiated)
BTFU
Composite of 'Beach deposits': Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks, and 'Tidal Flat Deposits': commonly silt and clay with sand and gravel layers; possible peat layers; from the tidal zone. [Generic description].
Buttergask Flagstone Member
BTG
The top of the Sheriffmuir Sandstone Member, where medium- to coarse-grained sandstones are overlain by fine-grained sandstones and siltstones of the Buttergask Flagstone Member.
The Stirling to Alloa area on the south-east limb of the Strathmore Syncline.
Grey and brown, fine-grained interbedded sandstones, siltstones and mudstones.
Up to 270 m thick.
The base of the Dunblane Formation, where the medium- to coarse-grained sandstones overlie a fine-grained sandstone and siltstone sequence.
Brotherton Formation
BTH
Upward transition from mudstones of underlying Edlington Formation.
Crops out from north Nottinghamshire to north Yorkshire. Pinches out south-west of a line from Worksop to Newark. Equivalent to Seaham Formation of Co. Durham.
Limestone, dolomitic, grey with abundant Calcinema.
Upward passage into Billingham Anhydrite, or, where that is absent, the Roxby Formation.
Bottom Holers Coal (Birmingham)
BTHL
Baddock Till Member
BTI
Unconformable contact with glacitectonised sands and silts of the Ardersier Silts Formation.
Ardersier Peninsula, southern shore of the Inner Moray Firth.
Stony, sandy clay diamicton, stratified, yellowish brown, containing clasts mainly of sandstone.
Ground surface or unconformable contact with overlying Late Devensian Raised Beach Deposits.
Buitenbanken Formation
BTK
Base Holocene.
Medium-grained, locally fine- or coarse-grained and locally gravelly sands; sediments represent marine reworking of late Pleistocene fluviatile gravels and shelly marine sands.
Maximum 5 metres, mostly < 2 metres.
Passage from nearshore sediments with Spisula Subtruncata bivalve assemblage to fully marine sediments with Angulus Pygmaeus bivalve assemblage.
Barrock Top Limestone
BTL
Blue Tour Limestone
BTLS
Bottom Tilley Coal (Northumberland And Durham)
BTLY
Bryn Tirion Member
BTM
Rests on skeletal and peloidal limestones of the lower parts of the Tandinas Limestone.
Porcellanous limestones (calcite mudstones) with spar filled fenestrae; intercalated thin dark grey shales.
4 metres; up to 11 metres at Tandinas Quarry and 8.5 metres at Flagstaff Quarry.
Overlain by the Penmon Limestone (massive and rubbly skeletal limestones).
Belle Tout Marls (One)
BTMA1
Belle Tout Marls (Two)
BTMA2
Belle Tout Marls (Three)
BTMA3
Butterly Marine Band
BTMB
Bottom Coal (Northumberland)
BTMC
Bottom Rock
BTMR
Betton Shale Formation And Meadowtown Formation (Undifferentiated)
BTMT
Bottom Vein Mine Ground (South Wales)
BTMV
Mine ground is a term used in South Wales to describe an ironstone-rich package of beds (rather than a single, specific bed). Generally such units are not mapped, but a few are delineated on 1:10K scale maps.
Burraton Formation
BTN
Transitional with Tavy Formation.
Mapped on Sheets 348, 337.
Dark grey to black lustrous slaty mudstone with grey siltstone laminae, and subordinate thin to thick medium- to coarse-grained grey-green sandstone beds.
Bourton Limestone Member
BTNL
Brassington Formation
BTON
The lower boundary is a sharp, unconformable contact on karstified limestones which form hollows, or 'pockets' for the formation.
Confined to scattered pockets on the Carboniferous limestone outcrop, recognised from north of Ramshorn (SK 088 463) to south of Monyash (SK 134 635).
White, pink and yellow siliceous sands with brightly coloured silts and clays, lying in pockets caused by karstic dissolution of Carboniferous limestones. Divided into: Kirkham Member, Bees' Nest Member and Kenslow Member.
Highly variable. 1 - 45m recorded.
Generally not preserved, but where present it is an unconformity upon which rests Quaternary till (boulder clay).
Black Top Coal
BTOP
Bottom Three-Quarter Coal (Northumberland And Durham)
BTQ
Bullhurst Rock (North Staffordshire)
BTR
Beta Rider Coal (North Wales)
BTRC
Bentleyford Shales Formation
BTS
Conformable on grey, micaceous shales of the underlying Shoot Rough Road Shales.
Shropshire.
Sooty black shales with black bituminous limestone concretions.
Non-sequence beneath grey to blue shales of the overlying Shineton Shales.
Britannia Sandstone Formation
BTSA
Biscathorpe Sand And Gravel
BTSG
Bunter Shale Formation
BTSH
Buttington Mudstone Formation
BTT
Long Mountain area.
c.107m
Beinn An Tuim Striped Formation
BTU
Bettws Mudstone Formation
BTWM
Pale greenish grey mottled mudstones.
130 to 170m
Bettyhill Formation
BTYH
Bettyhill Suite
BTYL
Upper Brioverian Group
Bualintur Formation
BUAL
Burtle Formation
BUB
Mid to Late Pleistocene.
The formation rests upon Jurassic and Triassic bedrock. It commonly overlies or fringes "reefs" or "islands" of Lower Lias or Late Triassic rocks.
Restricted to the "Somerset Levels" of northeast Somerset.
Sands and gravels. The sands are fine-grained and quartzose, with beds of comminuted shell. The gravels, which are composed of Chalk flint, quartz, sandstone, cherts, rounded lumps of red, green and grey Triassic mudstones and Liassic fossils, are marine in origin with a few interbedded palaeosols and freshwater sands. They contain fossilised marine, fresh water and terrestrial shells and remains of elephant, rhinoceras, horse, auroch, red, fallow and roe deer, hyaena and wolf. The marine shells indicate both cold and warm water climates and sandy, muddy and rocky habitat, and the freshwater shell Corbicula fluminalis indicates a climate warmer than now. The deposits form low mounds protruding through the surface of the Holocene silts and clays of the Somerset Levels Formation.
At surface, or else overlain by Holocene silts, clays and peats of the Somerset Levels Formation.
Burns Beds
BUBE
Buckie Limestone Formation
BUC
The unconformity with the Cullen Quartzite Formation.
Elgin and Buckie area, Scotland.
Mainly limestone, both bedded and massive; locally pink and concretionary. Towards the base the limestones contain fragments of quartzite and crystals of barytes. Towards the top of the formation it includes thin beds of red mudstone and sandstone, some of which are calcareous.
To 9m
The top of the formation is the unconformity with the Middle Devonian conglomerate (Spey Conglomerate Formation).
Buildwas Formation And Coalbrookdale Formation (Undifferentiated)
BUCD
Bull Crag Coal (Northumberland)
BUCG
Buchan Formation [Obsolete Code: Use Buhn]
BUCH
Bulldog Coal (South Lancashire)
BUCO
Bught Craig Member
BUCR
Buchlyvie Sandstone Member
BUCS
A gradational contact with the Dalmary Sandstone Member of the Teith Sandstone Formation, which is generally greenish grey and commonly contains plant remains.
The axial region of the Strathmore Syncline between Thornhill and Gartocharn.
A reddish grey, fine- to medium-grained, commonly cross-bedded sandstone, interbedded with siltstone and chocolate brown to brick red, silty mudstone.
At least 400 m thick.
The top is not seen, as it is faulted against and unconformably overlain by the basal conglomerate and sandstones of the Stockiemuir Sandstone Formation, of the Upper Devonian, Stratheden Group.
Beinn Udlaidh Quartzite Formation
BUDQ
First occurance of white to grey quartzite feldspathic quartzite above banded to laminated psammite.
Crianlarich Sheet 46W (Scotland)
A white to grey quartzite, locally feldspathic. Pebbly beds with clasts up to several centimetres across, are rare. Cross-lamination is only preserved in areas of low strain.
Variable, ranges from c.100 to 20m, depending on the structural setting.
Change from grey to white quartzite upwards to pelite and semipelite of the Leven Schist Formation.
Buttermere Formation
BUF
Tremadoc to Late Arenig.
Not exposed.
It is bounded to the north and northwest by the Causey Pike Fault. To the south and southeast the formation extends to the overlying Borrowdale Volcanic Group unconformity. To the west the extent of the formation is unclear, exposures in the River Calder may be Buttermere Formation or a lower part of the succession.
An olistrostrome deposit comprising disrupted, sheared and folded mudstone, siltstone and sandstone turbidite olistoliths. There are two members near the middle of the Formation, the Goats Gill Member, a sedimentary breccia and the sandstone-dominated Robinson Member.
The upper boundary is tectonic and overthrust by rocks of the Crummock Water Aureole.
Buff Coal (Bristol Area)
BUFC
Burra Firth Formation
BUFF
Buttermere Formation (Hornfelsed)
BUFH
Metamorphism probably Early Devonian.
Buchan Gravels Formation
BUG
Unconformable on Neoproterozoic rocks, or on the Moreseat Sandstone Formation.
Northeast Scotland.
Well rounded gravel and cobble gravel comprising white quartzite, vein quartz and flint, in white micaceous silty sand matrix or in a white sandy kaolinitic clay matrix.
10 to 25m+
Unconformable, below till or "head", or at the surface.
Bungilow Coal (North Staffordshire)
BUGC
Burway Formation
BUGP
Drawn at the base of silicified dust tuff of the Buxton Rock of the Burway Formation where it rests conformably upon green-grey shales of the Stretton Shale Formation..
Near Church Stretton, Shropshire.
Flaggy, green-grey mudstones, siltstones and sandstones. More massive sandstones at some horizons and with some bands of purple-grey siltstone or mudstone.
About 180m
Drawn at the conformable upward passage from coarse green-grey sandstone of the Cardingmill Grit Member of the Burway Formation to purple shaly mudstones and siltstones of the Synalds Formation.
Burnhead Intrusion
BUHD
Southern Uplands, Scotland.
Minor granitic pluton.
Elongate intrusion c. 1.7km x 0.5km with long axis orientated roughly E - W.
Buchan Formation
BUHN
Buildwas Formation
BUI
Base of the first grey-green, rubbly mudstones containing comminuted shell debris above mottled green, grey and purple mudstones of Rubery Formation. 1m thick transition in colour and upward decrease in number of hard siltstone beds.
West Midlands, Welsh Borders.
Olive-green and grey calcareous mudstone and nodular to lenticular calcareous mudstone and argillaceous limestone; shell fragments present throughout.
22-40m. Walsall 22m; Wenlock Edge 25.5-40m
Gradational increase in thickness and number of limestone beds into overlying Barr Limestone Formation.
Buccleuch Limestone [Obsolete Code: Use Bucc]
BUL
Bullhurst Coal (North Staffordshire)
BULC
Bulman Main Coal (Northumberland) [Also Known As Cancer Coal]
BULMA
Burdiehouse Limestone
BULS
Bulmer Vein
BULV
Buckle Marls (One)
BUMA1
Buckle Marls (Two)
BUMA2
Buckle Marls (Three)
BUMA3
Buckle Marls (Four)
BUMA4
Buckle Marls (Five)
BUMA5
Buckle Marls (Six)
BUMA6
Burn Side Conglomerate Member
BUN
Base of conglomerate lithology. This is the youngest conglomerate member in the otherwise mudstone-dominated Balclatchie Formation.
Conglomerate and sandstone.
Overlain by flaggy sandstones and siltstones of the Ardwell Farm Formation of the Ardwell Subgroup.
Bundoran Shale Formation
BUNS
Skea Sandstone Member (basal beds of the formation) rest disconformably on top of Ballyshannon Limestone Formation.
Mudstone, dark grey, calcareous, fossiliferous with thin to thick bioclastic limestones.
Increasing silt, mica and sand content in top part of formation, beneath coarse sandstones of basal Dromore Member of the Mullaghmore Sandstone Formation.
Buckhaven Planolites Bed
BUPL
Buxton Rock Member
BUR
The Buxton Rock is regarded as the basal member of the Burway Formation.The base is generally sharply defined, usually overlying dark grey mudstones of the Stretton Shale Formation. However, it is not uncommon for turbiditic sandstone facies, characteristic of the Burway Formation, to appear below the Buxton Rock. Lithologies comparable to the Stretton Shale Formation also occur locally up to 15m above the Buxton Rock (Greig et al, 1968; Wilson, 2000).
Welsh Borderlands, Shropshire, Church Stretton and the Long Mynd.
Massive, fine-grained silicified tuff.
7 m thick.
the unit has a sharply defined planar top, usually overlain by thinly interbedded turbiditic sandstones and mudstones of the Burway Formation (but see above).
Buchan Ridge Gravel Member
BURG
Unconformable, on Moreseat Sandstone Formation, Smallburn Sandstone Formation or deeply weathered crystalline basement.
Well rounded cobble gravel composed of flint and white quartzite in a white sandy kaolinitic clay matrix.
At least 25m
Unconformable, below till or 'head', or at the surface.
Burlington Member
BURL
Incoming of turbidite sandstones.
Sandstone in laminated silty mudstone.
30 metres. 15 - 30 metres.
Overlying laminated silty mudstones.
Burradon Coal (Northumberland)
BURN
Burton Formation
BURT
Bure Valley Formation
BURV
Unconformable on glacial and solifluction deposits and upon Crag Group and Chalk Group bedrock.
Valley of River Bure and its tributaries, in North Norfolk, down to its junction with the River Yare near Great Yarmouth.
Formation encompasses the fluvial, lacustrine and organic deposits of the River Bure and its tributaries. It includes alluvium and a restricted development of river terrace deposits. The floodplain alluvium comprises soft clays, silts and fine-grained sands, with bodies of peat, overlying fine- to coarse-grained sands and gravels. River terrace deposits are largely gravel and sand. The gravels are dominated by subangular to rounded flint, including large cobbles, but also include rounded pebbles of quartz and quartzite, northern British erratics of glacial derivation, and a little chalk.
Bruce Sandstone Member
BUSA
Bottom Usworth Coal (Northumberland And Durham)
BUSC
Bush Coal (Fife)
BUSH
Bussell's Member
BUSS
Base taken at upward change from coarse-grained pebbly sandstone to clayey sandstone and mudstone at type locality.
Outcrop forms low-lying ground, much mantled by superficial deposits, between Stoke Canon [SX 940 980], Columbjohn [SX 960 999], and Francis Court Farm [SX 980 995].
Reddish brown mudstone, sandy mudstone and clayey fine-grained sandstone, weathering to clay, sandy clay, and clayey sandstone. Contains a mappable bed of fine-grained sandstone near Columbjohn (eg SX 963 995).
24.4m in a borehole [SX 9458 9788] at Huxham Barton; 50m at Bussel's Farm [SX 9529 9873], 1km north-east of Huxham; more than 69m in the Columbjohn Borehole [SX 9584 9964], a further 1km north-east.
Overlain by sandstone of main part of Dawlish Sandstone.
Busty Coal (Northumberland And Durham)
BUST
Butterton - Swynnerton Dykes
BUSW
Bute Conglomerate Formation
BUT
Not seen, presumed to be unconformable on Lower Devonian.
Island of Bute, on sheets 21, 29.
Mainly conglomerate with subordinate red sandstone.
About 1500 m thick.
Sharp junction with the Kinnesswood Formation.
Bute Coal (South Wales)
BUTE
Beinn An Uain Till Formation
BUTI
Generally a gradational contact over 10-20cm, or locally a sharp, planar one, with stony, sandy diamictons of the underlying Athais Till Formation, or on bedrock.
Stoney sandy clay diamicton, matrix-supported, dark yellowish brown to olive-grey, fissile, massive, extremely compact, containing angular to subrounded clasts of gneissose psammite and semipelite, granite and some Devonian sandstone and siltstone. Typical lodgement till with well developed north-easterly fabric and containing concavo-convex discontinuities that are commonly sand-filled.
Erosional contact with gravel of the Carn Monadh Gravel Formation at the Allt Odhar Interstadial site, various younger deposits or the ground surface.
Butterton Sandstone Bed
BUTS
North Staffordshire.
Butterby Till Member
BUTTI
Commonly intercalated with dark grey, laminated silts and clays, or sand and gravel of the Tyne and Wear Glaciolacustrine Formation. Some contacts possibly glaciotectonic.
Durham lowlands and southern Northumberland.
Stiff, brown, gravelly sandy clay diamicton, commonly with well dispersed clasts of andesite, tuff and granite from the Lake District; greywacke and grandiorite from southern Scotland, and red sandstones probably of both Triassic and Devonian age, in addition to Carboniferous lithologies (sandstone, gritty sandstone, limestone, mudstone, coal). Commonly thinly intercalated with dark grey, laminated silts and clays, and lenses if sand and gravel.
To 15m
Generally the ground surface.
Builth Volcanic Group
BUVO
Burnwood Coal (North Staffordshire)
BUWC
Bushy Coal (South Wales)
BUYC
Batch Volcanic Member
Lies within the purple sandstones and mudstones of the Synalds Formation. Base is taken at the sharp base of the "Andesitic Ash", a distinctive purple and green coarse-grained tuff bed about 130m below the top of the Synalds Formation.
Lies within eastern part of the Long Mynd, Shropshire.
Purplish red mudstones and thin sandstones, interbedded with four beds of distinctive purple and pale greenish grey, coarse crystal lithic ash, and lithic lapilli tuff.
Taken at the top of a 2m-thick unnamed purple and pale grey tuff bed, about 21m below the top of Synalds Formation. Overlain by purple mudstones and siltstones of the Synalds Formation (undivided).
Bold Venture Beds
BVB
Ballyvoy Coals
BVC
Bellavally Formation
BVF
Borrowdale Volcanic Group
BVG
Unconformably overlies the Skiddaw Group; the base is taken at this unconformity where there is a profound change from a marine mudrock sequence to a volcanic one.
Central Lake District, also in Cross Fell Inlier and possibly Teesdale Inlier.
Medium to high-k, continental margin calc-alkaline basalt-andesite-rhyolite volcanic association of lavas, sills, pyroclastic and reworked pyroclastic deposits. NOTE: See definitions of component formations and members.
Variable, but probably up to 6000m.
Unconformably overlain by Windermere Supergroup.
Borrowdale Sill Suite
BVGS
Sills within, and contemporaneous with the Borrowdale Volcanic Group, the lower boundary of which is defined at the contact of each sill. Most occur within the Borrodale Volcanic Group, though some are present in the Skiddaw Group and were previously interpreted as lava.
Within the outcrop areas of the Borrowdale Volcanic Group and Skiddaw Group, Cumbria.
Aphyric and porphyritic basalt, basaltic andesite, andesite, dacite and rhyolite, many with peperitic breccia margins.
Individual sills up to 400m thick, typically much less.
Defined by the contact of each sill.
Bottom Victoria Coal (Northumberland And Durham)
BVIC
Black Ven Marl Member
BVM
Base of Birchi Tabular Limestone (bed 76 of Lang, W D, et al, 1923). Conformable on Shales-with-Beef Member.
Southwest Dorset and southeast Devon, United Kingdom. Mapped on Sheets 326 (Sidmouth) and 327 (Bridport). Northern limit not yet proved.
Dark grey thinly interbedded mudstones and organic-rich mudstone, with a few thin beds and doggers of muddy limestone.
43m
Base of Belemnite Marl Member, at base of hummocky limestone, (Lang, W D, et al, 1922, bed 103).
Belvoir Limestone Formation
BVR
?Late Chadian.
The base is inferred to be an unconformity (Riley, 1992), with the grey, buff or brown, dolomitic limestones of the Milldale Limestone Formation overlain by brown to white dolmitic, locally ooidal limestones of the Belvoir Limestone Formation.
Only proved in the subsurface at the type locality. May be present elsewhere in the subsurface on the Nottingham Shelf of the East Midlands Platform.
Brown to white, dolmitic, locally ooidal limestone with rare thin volcanic rock beds of 'green ash'.
120m thick in the type locality.
The top is inferred to be an unconformity (Riley, 1992), with the dolomitic, locally ooidal limestones of the Belvoir Limestone Formation overlain by a grey, pebbly sandstone present at the base of the overlying Plunger Limestone Formation.
Bovisand Formation [Obsolete Code: Use Bov]
BVSB
Ballyvoy Sandstone Formation
BVYS
Lowest coal seam (H) of Murlough Shale Formation overlying tuffaceous mudstone of Glenshesk Tuff Formation.
Sandstones with thin shales/siltstones, coal seams, seatearths, limestones and marine mudstones.
c 390m
Present day erosion level.
Blea Wyke Sandstone Formation
Gradational; rapid downward transition from pale silt and sand to darker grey mudstone of the Whitby Mudstone Formation.
Very local; Ravenscar coastal area, North Yorkshire (Cleveland Basin).
Micaceous, fine-grained sandstones and siltstones, grey-weathering and argillaceous in lower part, yellow-weathering and silty in upper part.
To c.18m
Unconformable base of ferruginous, pebbly sandstone of the Dogger Formation (Middle Jurassic).
River Terrace Deposits, 1 (Bramley Wey)
BW1
River Terrace Deposits, 2 (Bramley Wey)
BW2
Brynwhilach Two-Feet Coal (South Wales)
BW2F
Bretford Sand And Gravel Member And Wasperton Sand And Gravel Member (Undifferentiated) (Warwickshire Avon)
BWAT
Sand and gravel, with possible lenses of silt clay or peat. [Generic description].
Boghole And Whitemire Beds
BWB
Blisworth Clay Formation
BWC
Middle Jurassic, Upper Bathonian (Retrocostatum to Discus Zone).
Sharp but generally more or less conformable contact: limestone of the Blisworth Limestone Formation (or locally, near its northern limit, bluish and greenish grey variably shelly mudstones of the Rutland Formation) overlain by grey or variegated mudstone.
East Midlands Shelf, from just north of Milton Keynes, northwards to the Humber area where it is (probably) overstepped by the Cornbrash Formation.
Silicate-mudstone, grey, commonly variegated purplish red, yellow and green, poorly bedded to blocky. Commonly contains fossil rootlets and sideritic ironstone nodules, and locally with impersistant beds and lenses of argillaceous limestone including (mainly in the south) shell fragmental wackestones, packstones and grainstones, and (mainly in the north) sandstone. Mudstone weathers to highly plastic clay.
0 to c.10m; typically 2 to 4m throughout most of its range.
Sharp, generally disconformable contact: grey or variegated mudstone overlain by bioclastic limestone of the Cornbrash Formation or (very locally near its northern limit) by mudstone and sandstone of the Kellaways Formation.
Bewcastle Member
BWCB
Defined at the base of the Bogside Limestone. Conformable on Lynebank Member (Bewcastle).
Northumberland - Solway Basin. Bewcastle district (England Sheet 12).
Cyclical sequences of sandstone, siltstone, mudstone and thin limestones, locally dolomitic (cementstones); locally thin seatearths and nodular algal beds.
c.180m (Bewcastle)
Conformable upper boundary with the base of Main Algal One of the Main Algal Member (Lyne Formation) at Bewcastle.
Blidworth Coal (Nottingham)
BWCL
Baslow Coal (Derbyshire)
BWCO
Bodwrog Member
BWG
Caradoc (Longvillian)
Overlies, probably unconformably, the Allt Fawr Rhyolitic Tuff Formation, the base not being seen due to faulting.
Pwllheli and Nefyn districts, North Wales.
Medium- to coarse-grained sandstones and subordinate mudstones.
Gradational, conformable transition into calcareous mudstones and subordinate sandstones of the Plastirion Member, (the latter is perhaps better considered as the undivided part of the Dwyfach Formation).
Barrow Hill Complex
BWHL
Berwick Limestone
BWKL
Blisworth Limestone Formation
BWL
The base of the limestones overlying mudstones of the Rutland Formation.
Towcester district, Northants to Brigg, north Lincolnshire, passes south-west into the Shipton and Ardley members of the White Limestone Formation and to the north by intercalation into the marls and mudstones of the Rutland Formation.
Pale grey to off-white or yellowish limestones with thin marls and mudstones, fossiliferous, bioturbated peloidal, ooidal and shell-fragmental more-or-less argillaceous packstones and wackestones, subordinate cross-bedded ooidal shell-fragmental grainstones: fauna may include rhynchonellids particularly in the lower part in the south (see the Roade Member), and may be dominated by oysters, notably in the upper part in the north (see the Longthorpe Member).
Typically from 6 m to 7m thick in the type area, up to about 12m to the south-west, and 4m thick at Ketton.
Generally a sharp boundary of the limestones with mudstone, or locally an erosive contact with cross-bedded shell-fragmental ooidal limestone, both of the Blisworth Clay Formation.
Birdwell Rock
BWR
Bowland Shale Formation (Offshore) [Redundant Code: Use Bsg]
BWSF
Baronwood Sand And Gravel Formation
BWSG
Unconformable boundary with red diamicton of the Greystoke Till Formation below, or on bedrock.
The Vale of Eden and the southern Solway Lowlands north of the 'Scottish Readvance' limit.
Deposits occur as fans, flat-topped plateaux, mounds, ridge systems and terraces.
Sand and gravel with clasts mainly derived from the Vale of Eden (including brown "Penrith" and red "St Bees" sandstones, Carboniferous limestone and yellow sandstones), the Lake District (including andesitic lavas and welded tuffs) and the Alston Block (sandstones and grit), but also with some granodiorite, granite and other rocks from the Galloway Hills. Deposits occur as fans, flat-topped plateaux, mounds, ridge systems and terraces. Fans and plateaux commonly include deltaic sequences that coarsen upwards from laminated silt and clay, through fine- and coarse-grained sand to cobble gravel. Ridge systems commonly includes core of cobble gravel partially overlain and surrounded by sand and gravel that fine upwards. Terraces are commonly underlain by dense gravel. All deposits include lenses of, and are locally capped by, red gravelly diamicton (flow till).
At surface or overlain unconformably by Flandrian sediments.
Beck Wood Tuff Member
BWT
Base of rhyolitic tuff that rests on an erosion surface cut in dacitic lapilli-tuff (Waberthwaite Tuff Formation).
Outcrop in Beck Wood, 500m west of Beck Farm, near Millom, Cumbria.
Rhyolitic tuff - densely welded.
Top of rhyolitic tuff - probably an erosion surface - at contact with overlying dacitic lapilli-tuff of the Waberthwaite Tuff Formation.
Blidworth And Top Hard Coal (Vale Of Belvoir)
BWTH
Burrier Wick Till Formation
BWTI
Bottom Wheatworth Coal (West Yorkshire)
BWWC
Ben Wyvis Pelite Formation
BWYP
The eastern margin of the Garve Psammite Formation, where predominantly siliceous psammitic lithologies pass into predominantly pelitic lithologies to the east.
Forms a continuous belt, extending north-east from Loch Luichart and Loch Garve, thinning towards the north-east. At the Dornoch Firth, the western extent outcrops at (NH682874), and the eastern extent is defined by the Old Red Sandstone unconformity at Struie Hill (NH678866). The north-eastern extent terminates at a faulted contact just north of the Dornoch Firth near Newrton Point (NH718890). South of Loch Luichart it has an extensive outcrop, delineated south across Strathconnon, the Orrin Reservoir and Strath Farrar as far as Struy Forest, and west to Sgurr na Fearstaig (NH228437) close to the eastern end of Loch Monar. The outcrop continues south to Glen Affric, and probably also on the southern side of Glen Affric to the south and west of Loch Beinn a' Mheadhoin, where it thins and becomes discontinuous. The outcrop probably continues further to the south and west, to Loch Cluanie and beyond.
Migmatic, garnetifierous, tourmaline-bearing, gneissose pelite and semipellite, containing lenticles of quartzofeldspathic segregations, and quartzofeldspathic pegmatite veins and pods.
At least 2 to 3 km thick (Wilson 1975).
The western margin of the Tarvie Psammite Formation, where predominantly pelitic lithologies pass eastwards into predominantly psammitic lithologies.
Ballantrae Ophiolite Complex
Not seen; speculatively a thrust contact on crystalline basement.
About 75 square kilometres between Girvan and Ballantrae, Ayrshire, southwest Scotland.
Tectonically assembled complex consisting largely of sepentinised ultramafic rock and basaltic pillow lavas. The latter are associated with basaltic breccias and a range of volcaniclastic rocks, conglomerate, mudstone-supported melange and chert. Some of the sedimentary rocks contain a graptolite fauna. There are several generations of dolerite and gabbro intrusions, and tectonism has locally produced amphibolite and greenschist.
Highly speculative; at least several kilometres and possibly as much as 10km.
Major unconformity beneath the overlying sedimentary cover. Above different parts of the Complex this cover is assigned to the Barr and/or Ardmillan groups and/or the Old Red Sandstone.
Box Law Plug
BXLAW
Blackberry Bank Formation
BYBA
Ballyness Formation
BYC
Unconformable on a variety of rock units.
Bright red sandstones, quartz-pebble conglomerates and pebbly sandstones.
Rapid transition, conformable to succeeding peritidal carbonates and shales (Clogher Valley Formation)
Bytham Catchments Subgroup
BYCA
Unconformable on bedrock of Carboniferous to Pleistocene age.
Deposits of the subgroup follow the course of the pre-Glacial Proto-Soar and Bytham rivers, from Snitterfield near Stratford-upon-Avon in the west, to Croft and Huncote, Leicester, Castle Bytham and Witham-on-the-Hill, towards the Fen edge south of Bourne, through Shouldham Thorpe, south along the eastern margin of Fens to High Lodge, Middenhall, along the valleys of the Lark, Little Ouse, and Waveney, to the North Sea coast at Pakefield and Kessingland.
The subgroup encompasses all the fluvial, lacustrine and organic deposits of the Proto-Soar and Bytham rivers. Deposits of four separate river terrace levels are recognised as members of the Ingham Formation. Commonly a basal sandy gravel is overlain by pebbly sands, with few clay and silt beds. The gravels of all contain a high proportion of rounded pebbles of grey and purple "Bunter" quartzite of Triassic derivation, and of vein quartz, Jurassic and Cretaceous rocks are local important constituents. Sedimentary structures indicate deposition by braided rivers.
c.18m
Commonly overlain by Middle Pleistocene glacigenic deposits. Upper boundary may be difficult to determine where overlain by glaciofluvial sand and gravel, but the presence of more angular clasts, chalk, and poorer sorting in the latter is generally helpful.
Bychton Two Yard Coal (North Wales)
BYCH
Bottom Yard Coal (Northumberland)
BYCO
Bransty Cliff Sandstone Member
BYCS
Unconformable on Middle Coal Measures, base of lowest major reddened channel sandstone unit.
West Cumbria Coalfield.
Red, cross-bedded sandstone with mudstone interbeds and thin palaeosol horizons.
>100m
Top of highest major channel sandstone unit.
Barroway Drove Beds
BYD
Mainly silt and clay (Older Salt Marsh and Tidal Creek Deposits). [Generic description: 1: 50 k map margins].
Braslyd Fach Coal (South Wales)
BYDF
Ballydurnian Breccia Formation
BYDN
Braslyd Rider Coal (South Wales)
BYDR
Bressay Flagstone Formation
BYF
Blaen-Y-Glyn Formation
BYG
Ballygawly Gneiss
BYGN
Recignised in the Republic of Ireland.
Bucklebury Common Gravel Member
BYGR
Kennet Basin and interfluves.
1-5m commonly
Terrace surface around Bucklebury.
Boyle Sandstone Formation
BYLE
Byley Mudstone Member
BYM
Top of Northwich Halite.
Chesire Basin.
Alternations of structureless reddish brown mudstone and laminated greenish grey and reddish brown mudstones. NOTE: The contact between the Byley Mudstones and overlying Wych Mudstones is not currently shown on British Geological Survey maps, and they have been mapped as one division.
180.90 metres in Byley borehole (SJ 76 NW/7).
Top of highest substantial laminated greenish grey and reddish brown bed in this formation; base of Wych Mudstones.
Bassey Mine Coal (North Staffordshire)
BYMC
Bryn Brith Member
BYN
Conformable on the felsic ash-flow tuffs of the Offrwm Volcanic Formation or within the lowermost mudstones of the Cregennen Formation.
Cadair Idris district.
Massive lenticular beds of disturbed mafic tuff, tuffite and tuffaceous sandstone, with subordinate thin mudstones.
To 65m, and might be locally up to 150m.
Conformable within the mudstones of the Cregennen Formation.
Byne Hill Intrusion
BYNE
Leucotonalite ('trondhjemite').
Two similarly trending elongate bodies, each c. 1km x 0.25km
Brierley Rock
BYR
Baggy Sandstones Formation
BYS
The unit is conformable with the underlying Upcott Slates. The Baggy Sandstones sequence of grey and buff, fine- to medium-grained, thickly-bedded and massive sandstones, marked by local ferruginous staining is in sharp contact of cream, buff, green, grey and purple slates and silty slates of the underlying Upcott Slates.
Around Barnstaple in North Devon, the outcrop runs east to west between the coast and inland, near to Dulverton.
Interbedded brown and grey fine-grained sandstones, siltstones and greenish-grey shaly mudstones with thicker buff, fine- and medium-grained feldspathic and micaceous sugary sandstones.
To 450m
Conformable with the overlying Pilton Shales, though no sharp formation boundary lines can be traced. The top of the Baggy Sanstones, characterised by thickly-bedded and medium-grained sugary sandstones with partings of thinly-bedded micaceous sandstone, passes transitionally into the Pilton Shales, seen typically as shales and siltstones with placed at the top of the highest of the fine- to medium-grained sugary sandstones of the Baggy Sandstone.
Beckley Sand Member
BYSA
The lower boundary is gradational. East of Cumnor, there is an upward transition from the muddy and more finely sandy Temple Cowley Member or the spiculitic sandstone of the Arngrove Spiculite Member, into non-spiculitic sands and calcareous sandstone. West of Cumnor, there is a gradational change up from poorly fossiliferous fine-grained and sandy mudstone of the Hazelbury Bryan Formation, into medium- to coarse-grained sand and sandstone, with possibly some lateral passage.
From Beckley south-westwards through Oxford and Abingdon at least as far as Faringdon. At the north-eastern limit it is overstepped by the Stanford Formation as seen in the inset map on 1:50 000 Sheet 237.
A grey, weathering brown to yellow, quartzose, fine- to medium-grained Sand in the east, becoming coarser in the west, with calcareous sandstone beds and doggers, and thin, sandy, shelly bioclastic limestone beds. It is moderately fossiliferous, containing bivalves and ammonites.
Up to 20 m thick, measured as 11.15 m thick in the Cumnor borehole.
East of Garford, Oxon, there is a sharp non-sequential boundary with fine- to medium-grained sand and sandstone, overlain by bioclastic limestones or grey calcareous mudstones of the Stanford Formation, commonly marked by a pebble bed. West of Garford, there is a change up from medium- to coarse-grained sand and sandstone into shelly ooidal limestone commonly with a basal pebble bed of the Highworth Limestone Member.
Bunny Sand And Gravel
BYSG
Ballyrainey Sill
BYSI
Byestead's Sandstone
BYSS
Bytham Sand And Gravel Formation
BYTH
Unconformably overlies Jurassic bedrock.
The deposits occupy the valley of the pre-Glacial Bytham River from Castle Bytham east through Witham-on-the-Hill towards the Fen edge south of Bourne.
The formation encompasses fluvial, lacustrine and organic deposits of the Bytham River. Commonly a basal coarse-grained gravel is overlain by red fine- to medium-grained sand. The gravels are composed of Triassic grey and purple quartzite, vein quartz, Jurassic limestone and ironstone, and Carboniferous sandstone and chert. Sedimentary structures imply deposition in a braided river environment. The gravels are distringuished from the Baginton Sand and Gravel Formation to the west by their including a significant proportion of Jurassic as well as Triassic material.
Individual aggradations are usually 3 to 5m thick; may total 18m locally.
Byth Till Formation
BYTIL
The lower boundary of the unit is sharp, planar, subhorizontal unconformity on gravels of the Howe of Byth Gravel Formation. To the west of the Howe of Byth quarry the Byth Till has been observed sharply unconformable on Devonian red sandstones.
Buchan, northeast Scotland. The formation is known from the vicinity of the Howe of Byth quarry on Sheet 97 (Fraserburgh), but may be regionally significant and present locally across northeast Scotland.
Gravelly, slightly clayey, silty sand diamicton. Interpreted as a subglacial till. Dark reddish brown, weakly calcareous, matrix supported. Clast lithologies are dominated by quartzite, psammitic metasedimentary rocks and red Devonian sandstones and shale. Clasts are typically subangular to subrounded and Devonian shale lithologies are striated. Clast fabrics indicate glacial transport from the west. Interpreted as a subglacial till.
The upper boundary of the formation is a sharp, undulatory (relief up to 1m) erosional unconformity overlain by the Auchmeddon Gravel Formation.
Ballytober Sandstone Formation
BYTR
Bangley Trachytic Member
BYTRC
Early Visean.
The base is apparently conformable on the Hailes Lava Member that consists of basaltic lavas and volcaniclastic rocks.
East Lothian, outcrop of the Garleton Hills Volcanic Formation around North Berwick, East Linton, Garleton Hills, Stenton and in the subcrop farther west in the BGS Spilmersford Borehole near Pencaitland, but absent adjacent to the Lammermuir Fault.
The Bangley Trachytic Member consists of purple and blue-grey trachytic lavas with both feldspar-phyric (sodic plagioclase to sanidine) porphyritic and non-porphyritic types. Individual flows are known to be over 20m thick. Quartz-trachytes are also present. Red, brown and purple trachytic tuff and lapilli tuff with agglomerate and some sedimentary volcaniclastic rocks also are interbedded in units known to be at least 8m thick.
0 to 160m
The Member is overlain by the siliciclastic sedimentary rocks of the Gullane Formation (Strathclyde Group). The contact is considered unconformable with volcaniclastic conglomerate recorded locally at the base of the overlying formation.
Bay Vein
BYV
Byley Mudstone Formation And Wych Mudstone Formation (Undifferentiated)
BYWY
Boundary Zone Complex
Bryozoa Band (Ravenstonedale)
BZB
Boundary Zone And Yell Sound Division (Undifferentiated)
BZYS
Centre 1 Cone-Sheet-Swarm
Cumnock Twenty Three Fathom Coal (South Ayrshire)
C23F
Centre 2 Inner Basic Cone-Sheet-Swarm
C2IB
Centre 2 Outer Basic Cone-Sheet-Swarm
C2OB
Achnaha Quartz Gabbro Zone
C3AQG
Centre 3 Basic Cone-Sheet-Swarm
C3B
Faskadale Laminated Gabbro Zone
C3FLG
Glendian Laminated Gabbro Zone
C3GLG
Inner Layered Gabbro Zone
C3ILG
Centre 3 Layered Gabbro Lopolith
C3LGB
Olivine-Glomercrystic Gabbro Raft Zone
C3OGR
Outer Layered Gabbro Zone
C3OLG
Outer Quartz-Gabbro Zone
C3OQG
Sithean Mor Laminated Gabbro Zone
C3SML
Outer Unlayered Gabbro Zone
C3UGB
Castleford Four Foot Coal
C4FC
Carstone Formation
The Carstone Formation, which was deposited during a phase of unconformable transgression, oversteps many different lithostratigraphical units. Its base is erosional and locally burrowed into the underlying strata. The base can be recognized by a downward change from greenish-brown, massive, cross-bedded, commonly bioturbated, oolitic, ferruginous, medium- to coarse-grained and pebbly sandstone [from south to north]: palaeozoic sequences on the London Platform [e.g. Four Ashes Borehole]; quartz sands and thin mudstone [Dersington Formation]; buff and grey, clayey ferruginous sands and quartz sands [Sandringham Sands Formation] in central Norfolk, between Leziate and West Dereham; pale and medium clays [Kimmeridge Clay Formation] in central Norfolk [Mudford-Great Ellingham]; pale-medium grey, very fine- to fine-grained, bioturbated, shelly sandstones with phosphatic nodules [Roach Formation] in Northern Norfolk; Shelly, calcareous mudstone [Sutterby Marl] in southern Lincolnshire; Ironstone [Fulletby Formation] in central Lincolnshire; Dark, glauconitic mudstones and limestones [Tealby Formation] in northern Lincolnshire; brown, shelly oolitic ironstone [Claxby Ironstone Formation]; late Jurassic mudstones [Kimmeridge Clay and Ampthill Clay formations] and coarse-grained sandstone [Elsham Sandstone Member] at the Humber Estuary; pale to medium, fine- to medium-grained sandstones and dark mudstones [Kellaways Formation] in southern Yorkshire; Upper Lias mudstones on the south side of the Market Weighton High.
The southern limit of the formation is between Duxford and Soham, Cambridgeshire , and south east of the Four Ashes Borehole, on the London High, although it is not seen in outcrop in these areas. The Carstone extends northwards through Norfolk and its best exposure is in the cliffs and foreshore at Hunstanton. North of The Wash, the Carstone Formation is present in Lincolnshire, beneath the Wolds and forming a narrow outcrop along their western margin. In northern Lincolnshire it is thin and locally absent. North of the Humber the Carstone Formation is again thin and patchy, but it has been recorded near South Cave, Goodmanham, Millington and Kirby Underdale, finally disappering on the Market Weighton High.
The typical lithology of the Carstone Formation is a greenish-brown [rusty when weathered], massive cross-bedded, oolitic ferruginous sandstone. The formation is medium- to coarse-grained and pebbly in part, especially at the base where it becomes a conglomerate. Pebbles comprising quartz, quartzite, pyritised sandstone, ironstone, grey siltstone and rolled ammonites. Some beds are silty and/ or contain clay wisps. Glauconite may be present in variable amounts. The Carstone Formation is burrowed in places with common Arenicolites and Skolithus.
Usually up to about 5m, but it reaches its maximum thickness of 18.9m, in the Hunstanton Borehole.
In southern and central Norfolk the upper boundary is defined by a down-section transition from pale to medium grey mudstones and siltstones [Gault Formation] to greenish-brown, massive, cross-bedded, bioturbated, oolitic ferruginous sandstone. In northern Norfolk and Lincolnshire the boundary is marked by a sharp, perhaps gradational, down-section change from red, pink or cream limestones and marls [Hunstanton Chalk Formation] to greenish-brown, massive cross-bedded, bioturbated, oolitic, ferruginous sandstone.
Cardiff Group
CAA
Drawn at the base of the Hills Gardens Formation where beds of interbedded siltstones and sandstone conformably rest upon sandstone and siltstone of the Caecastell Formation.
The immediate area around Cardiff, South Wales.
Interbedded mudstones and thin siltstones with subordinate thin sandstones and bioclastic limestones.
155 m approx.
Drawn at the conformable upward passage of limestone of the Llanderyn Formation with mudstone, calcrete and sandstone of the Raglan Mudstone Formation.
Calke Abbey Sandstone Formation
CAAS
Unconformity with weathered, green mudstones of the Stockingford Shale Group, overlain by 13 m of thick basal conglomerate, commonly containing volcanic pebbles.
Not present at outcrop, but seen in the subsurface in the area of Hathern Shelf, Loughborough District [SK 32].
Brown to green-grey, medium to thick-bedded, medium- to coarse-grained sandstones, pebbly sandstones and conglomerates with low angle cross-bedding, with laminated to thinly bedded sequences of green or red mudstone and siltstone and thin, sharp-based and graded sandstone beds. Numerous reddened beds of poorly sorted structureless mudstone, siltstone and argillaceous sandstone with red to grey mottles along roots.
Measured as 70.6 m thick in the Ticknall Borehole.
Marine flooding surface, overlain by green to grey, fine- to medium-grained sandstone with pebble-rich lenses, and shelly lags of Lingula of the Arch Farm Sandstone Formation.
Cabrach Sandstone Formation
CAB
Basal conglomerate rests on gabbros of the Boganclogh Intrusion and on the Craigievor Formation of the Argyll Group, Dalradian Supergroup.
NW-SE-elongated outlier centred on Cabrach village, 6km x 1 to 2.5km.
Basal conglomerate overlain by grey, micaceous sandstones and beds of coarse conglomerate.
Faulted NW margin to outlier.
Craid A' Bhlair Formation
CABC
Caer Beris Member
CABE
Caerau Formation And Blaen Myherin Mudstones Formation (Undifferentiated)
CABM
Central Anglesey Shear Zone And Berw Shear Zone (Undifferentiated)
CABSZ
Calmstone Coal (Sanquhar)
CAC
Carn A' Chlamain Member
CACH
Cat Cleuch Formation
CACL
Conformably overlying black graptolitic mudstone containing N. gracilis fauna.
Bail Hill area, 4km north west of Sanquhar, Dumfries, Scotland.
Autobrecciated basaltic lavas containing large euhedral pyroxenes.
c.150m
Presumed conformably overlain by Peat Rig Formation and locally Kirkcolm Formation.
Camas Chil Mhalieu Formation
CACM
Castle Coal (Douglas)
CACO
Cadham Craw Coal
CADC
Cadham Little Coal
CADL
Cadham Main Coal
CADM
Cadder Sand And Gravel Formation
CADR
Unconformity on bedrock or on older unnamed Quaternary strata or the Baillieston Till Formation.
Central Scotland, related to ice streams sourced in the Highlands (in contrast to the Southern Uplands) during the Dimlington Stadial; currently identified in the Glasgow area.
The typical lithological assemblages consist of mainly framework-supported bouldery gravel and sand, and coarse- to fine-grained, locally pebbly, sand with silt. In a geotechnical sense, the deposits are usually dense to very dense. Much of the gravel is thickly bedded and trough cross-bedded in sets up to 3m thick. These interfinger with sands. The sands are trough cross-bedded, ripple-laminated and horizontally laminated.
From a veneer to more than 45m.
Unconformity or glacial deformation boundary below younger Quaternary till.
Carn An Daimh Transitional Member
CADT
Gradational boundary with the underlying Glen Taitneach Schist Member of the Gleann Beag Schist Formation located where psammite/quartzite becomes abundant.
Carn an Daimh area. [NO 136 718]
Interbedded quartzite and graphitic pelite with local graded bedding.
Top of the interbedded quartzite/psammite and graphitic pelite succession. Base of the quartzite succession of the Creag Leacach Quartzite Formation.
Cadham Under Coal
CADU
Carraun Shale Formation And Dergvone Shale Formation (Undifferentiated)
CADV
Armathwaite-Cleveland Dyke
CADY
The dyke is mapped from the coastal area of north-eastern England, across northern England, the Southern Uplands and Midland Valley of Scotland. It can be traced as part of a dyke swarm to the Isle of Mull.
Porphyritic basaltic andesite with plagioclase and pyroxene phenocrysts in a devitrified glassy groundmass. Locally it is amygdaloidal.
The dyke is generally 22 - 28 m. wide and 430 km. in mapped extent. [Macdonald, et al. 1988].
Caerketton Volcanic Member
CAE
Conformable: where pyroxene andesites, olivine basalts and locally basic tuff and breccia of the Allermuir Volcanic Member are overlain by rhyolitic tuff and flow banded rhyolite.
Rhyolitic tuff intercalated with flow-banded rhyolite and some thin flows of pale pink, porphyritic dacite or rhyolite.
Up to 300m on Castlelaw Hill
Conformable: where rhyolitic tuff and flow-banded rhyolite are overlain by Woodhouselee Volcanic Member: pale lilac or pink trachytes and andesites with phenocrysts of biotite and alkali feldspar. Boundary not always distinct; some interbedding of the two members takes place.
Cae Castell Formation
CAEC
Taken at the conformable base of the fine- to coarse-grained sandstones and pebbly sandstones of the Rhymney Grit Member, which sharply overlies the Pen-y-lan Mudstone.
Sandstones, siltstones and subordinate mudstones.
70 to 80m
Sharply and conformably overlain by the mudstones with thin sandstones and siltstones of the Cardiff Group.
Caenlochan Schist Formation
CAES
Caered Flags
CAF
Carn Fadryn Suite
CAFA
Carway Fawr Coal (South Wales)
CAFC
Carway Fach Coal (South Wales)
CAFCC
Carlingford Complex
CAFD
Caburn Flints
CAFL
Cnoc An Fhithich Banded Semipelite Formation
CAFS
Transitional, with interbanding of calcareous semipelite with thin grey limestone beds marks junction with upper limestone of Blair Atholl Dark Limestone and Dark Schist Formation.
From east side of Errochty Synform at Errochty Water [NN 7245 6480] discontinuously to near Braes of Foss [NN 7465 5590]. East of the Loch Tay Fault and north of the Killiecrankie Slide, it occurs from Allt Bhaic [NN 840 640] and on the eastern slopes of Glen Tilt [NN 886 680 - 898 713 and NN 912 714 - 942 745].
Banded alternation of rusty-weathering semipelite with 5 - 10cm beds of psammite in equal proportions; however 25% of upper part of formation consists of white, quartz-rich psammite alternating with dark, biotitic, graded pelite.
0 - 150m in Sheet 55W; probably tectonically attenuated.
Sharp boundary with buff limestone of Drumchastle Pale Limestone Formation at type locality; elsewhere taken at base of calc-muscovite-biotite pelite lithology transitional to Drumchastle Pale Limestone Formation.
Captain's Fireclay
CAFY
Carrickarnan Complex Granophyres
CAG
Cairngarroch Intrusion
CAGA
Rhins of Galloway, southwest Scotland.
Diorite.
c. 0.3 square km in total area (elongate)
Curragh Formation
CAGH
Generally unconformably overlying glacigenic or Lateglacial sediments or bedrock.
Isle of Man (50k Sheets 36, 45, 46, 56, 57).
Peat dominated accumulations in lowland basins and on upland plateaux. Some mud and pebbly sand may occur in the lower parts of basinal sequences.
Up to 6m recorded.
Cold Ash Gravel
CAGR
Carnethy Volcanic Member
CAHI
Conformable: where pale lilac or pink trachytes and andesites of the Woodhouselee Volcanic Member are overlain by feldspar-phyric and fine-grained microporphyritic basalts and andesites.
Feldspar-phyric and fine-grained microporphyritic basalts and andesites. Flows have amygdaloidal tops and bases.
Approximately 200m seen
Not seen: faulted against Carboniferous strata to the east.
Castle Hill Plug
CAHIL
Carnmenellis Intrusion
CAIN
Comprises:(GA) coarse-grained granite with abundant feldspar megacrysts >15mm; (GB) coarse-grained granite with sparse feldspar megacrysts >15mm; (GC) coarse-grained granite with abundant feldspar megacrysts <15mm; (GD) variable medium- to coarse-grained granite with abundant feldspar megacrysts >15mm; (GE) medium- to coarse-grained biotite-muscovite-granite; (GH) fine- to medium-grained, variably megacrystic granite, feldspar megacrysts <10mm.
Coire An Iubhair Formation
CAIUB
Calmy Limestone
CAL
Generally seen as a change from a marine mudstone which has the Edmondia punctatella Band at its base with the Upper Hirst Coal beneath in the Clackmannan basin within the Upper Limestone Formation.
Throughout the outcrop and subcrop of the Upper Limestone Formation in the Midland Valley of Scotland.
A pale to dark grey, fine-grained, crinoidal, bioclastic, limestone, interpreted to be of marine origin, generally with two or more leaves separated by about 30cm partitions of mudstone, one leaf of "calmy" type being off-white, fine-grained and massive with a conchoidal fracture. The name is not geographical in origin, but instead indicates a "hard, pale grey or fawn, fine-grained, muddy limestone with a conchoidal fracture".
From 0.5m to 4.5m in the Airdrie, Falkirk and Glasgow districts, and 15m in shelf settings in Ayrshire.
Commonly seen as a change to a thick marine mudstone, that passes up into deltaic arenaceous deposits within the Upper Limestone Formation.
Callan Group
CALA
Pre-Caledonian And/Or Caledonian Sheets
CALES
Calp Limestone Group
CALG
Caledonia Glacigenic Group
CALI
Sharp, unconformable contact with bedrock or units of the Albion Glacigenic Group.
The whole of Great Britain lying to the north and west of the Davensian glacial limit.
A suite of glacial, glaciofluvial, glaciolacustrine and glaciomarine deposits that contain clasts derived from rocks cropping out throughout northern England, Scotland and Wales, and offshore, including diamictons [till], sand, gravel, silt and clay.
At the ground surface or at unconformable contact with various units of the Britannia Catchments Group or the British Coastal Deposits Group.
Pre-Caledonian And/Or Caledonian Minor Intrusion Suite
CALIM
Calhame Limestone
CALM
Carlane Sandstone Formation
CALN
Sharpe change from underlying pink sandstones [with mainly angular grains] of the Ballina Bridge Formation.
Sub-surface on northwest shore of Lough Neagh.
Sandstone, pale orange-pink, medium-to coarse-grained, sub-to well rounded, weakly cemented.
Sharp contact with white carbonate at the base of the succeeding Magnesian Limestone Formation [Belfast Harbour Evaporite Formation].
Cairn Liath Quartzite Member
CALQ
Callant Limestone
CALS
Langham sheet area, with correlatives across Northern England and Southern Scotland.
Muddy limestone with bands of calcareous mudstone; less muddy in its upper part.
c.8m
Carluke Tower Coal (Central Coalfield)
CALT
Carluke Coals
CALU
The Carluke Coals include the First (Upper) Carluke Coal and the Second (Lower) Carluke Coal, overlying the Carluke Tower Coal.
Caerau Mudstones Formation
CAM
Gradational, but taken at the base of the incoming of abundant packets of turbidite mudstone interbedded with laminated hemipelagites above the Rhayader Pale Shales, a sequence dominated by interbedded turbidite mudstones and burrowed hemipelagites.
Central Wales.
Turbidite mudstones interbedded within packets dominated by either laminated or burrowed hemipelagites. Scattered thin turbidite sandstones.
Up to 410 metres.
Either sharp junction taken at the base of the lowest thick argillaceous sandstone of the Rhuddnant Grits or gradational junction taken at the entrance of abundant thin turbidite sandstones of the Glanyrafon Formation.
Caburn Marl
CAMA
Cambriense Marine Band
CAMB
Castell March Formation
CAMH
Caerau Mudstones Formation (Lower Tongue)
CAML
Camderry Member
CAMM
Cambrian Rocks (Undifferentiated)
CAMN
Campsie Dyke
CAMPS
Caerau Mudstones Formation (Upper Tongue)
CAMU
Cam Valley Formation
CAMV
Unconformable on Middle Pleistocene glacial deposits and on bedrock.
Entire catchment of the River Cam and its tributaries, from near Saffron Waldon, Essex to near Ely, Cambridgeshire.
The formation encompasses the fluvial, lacustrine and organic deposits of the River Cam and its tributaries. Four terraces are known. The terrace deposits comprise well bedded to rather poorly bedded sands and sandy gravels, deposited by a braided river in a periglacial environment. The pebbles are dominantly rounded chalk and rounded to angular flint, with a few glacial erratics. The three higher terraces are cryoturbated. Alluvial fan deposits comprise poorly sorted flinty chalky sand and gravel, with boulders of basalt and quartzite. The floodplain alluvium comprises silts, clays and fine sands, with bodies of peat, overlying sands and gravels.
To c.13m
Land surface.
Cae'r-mynach Formation
CAMY
Canaston Beds
CAN
Canna Formation
CANA
Generally overlies rockhead.
Sandy, dark greyish brown clay with gravel and cobbles.
28 metres in Borehole 81/14, generally thinner but reaches maximum of 50 metres to southwest of Canna.
Upper boundary is base of Stanton Formation.
Cannel Coal (North Wales)
CANC
Cannel Seam
CANL
Cannel Coal (Leicestershire)
CANN
Cann Sand Member
CANS
Sharp incoming of glauconitic sand above the dark grey sandy clay of the Gault. Base commonly marked by a spring line.
Across most of the Shaftesbury Sheet (313) and south-east part of the Wincanton Sheet (297).
Sand, fine-grained, glauconitic, micaceous.
A well-marked feature break, presumably coinciding with incoming of cemented sandstone in the overlying Shaftesbury Sandstone.
Cambrian And Ordovician Rocks (Undifferentiated)
CAOR
Croisaphuill Formation
CAP
Conformably overlies the Balnakiel Formation.
The Durness Group forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye. The Croisaphuill Formation does not occur in Assynt or Skye and appears to be limited to the more northern parts of the Durness Group's outcrop.
Fossiliferous mid grey and dark grey dolomitic limestones and limestones with burrow mottling and chert nodules. Fossils include brachiopods, gastropods, cephalopods and trilobites.
Conformably overlain by the Durine Formation.
Carsphairn Conglomerate Member
CAPH
Lens within Kirkcolm Formation.
Carsphairn area, southern Scotland.
Conglomerate: channel fill unit within turbidite succession.
Campbell Park Marine Band
CAPK
Castle Point Member
CAPO
Castle Point Pelite Formation
CAPT
Rapid transition from psammite and quartzite, through thin semipelite to graphitic pelite (John Legg's Well Graphitic Schist Member).
Coast section from John Legg's Well to Sandy Pots [NJ 580 665 to 584 665]; extends southwards as far as Clovenstone [NJ 548 517], together with isolated inliers and xenoliths in Portsoy basic intrusion.
Pelite, locally graphitic at base (John Legg's Well Graphitic Schist Member) and in central-upper part at coast, but less graphitic with rare metalimestone bands inland, passing upward into semipelite, flaggy. Prominent staurolite at Castle Point, and locally kyanite-bearing.
c.300 to 400m at coast, though there is duplication by folding and thrusting. Inland as far as the south end of Fordyce Hill, only about 100m is present between a major ductile shear zone and the Portsoy basic intrusion. East of Knock Hill [near NJ 550 550] the poorly exposed pelitic rocks cannot be differentiated from those of the Portsoy Limestone Formation.
Transition to thin banded metalimestones and calcareous semipelites (Sandy Pots Limestone Member) at base of Portsoy Limestone Formation.
Calettwr Quartzite Member
CAQ
Caochandye Quartzite Member
CAQU
Lower limit of quartzite above striped phyllitic semipelites of the Coralea Phyllite Member.
NNE trending outcrop, up to 250m wide extending from Allt na Craoibhe - Caorainn [NJ 318 252], over Caochandye Hill [NJ 323 209] to Water of Nochty [NJ 308 159], Moray District, 1:50 000 Sheet 75E.
Quartzite, pebbly in parts, usually massive.
To 200m (based on outcrop width).
Upper limit of quartzite, below striped and banded semipelites and psammites of the Coulins Burn Striped Member.
Cannel Rock (South Lancashire)
CAR
Caradoc Rocks (Undifferentiated)
CARA
Carboniferous Rocks (Undifferentiated)
CARB
Carhurlie Coal
CARC
Carse Clay Formation
CARCL
Late Devensian (Loch Lomond Stadial) to Holocene.
Unconformable on the sub-Carse Peat (Flanders Moss Peat Formation); unconformable on the Forth Clay and Errol Clay formations and older deposits including the Wilderness Till Formation and bedrock.
Lower Tay valley from northwest of Perth, Tay estuary and Firth of Tay; lower Earn valley east of Forteviot, and estuary (Carse of Gowrie); lower Eden valley east of Cupar and estuary; Montrose Basin area. Forth valley from Aberfoyle eastwards (Carse of Stirling), Forth estuary.
Clayey silt and clay, commonly rooty and structureless; also highly laminated with silt and very fine- to medium-, locally coarse-grained sand with pebbles up to 5mm and fragments of vivianite; grey and brownish grey, finely micaceous, dark sulphidic patches. In sand dominated successions in outer estuary situations, coarse gravel also occurs at the base of the local member. Fuller descriptions of lithology in the entries for members: the Gowrie Silt, Carse of Gowrie Clay, Carey Silt and Kingston Sand members in the Tay-Earn area and the Letham Silt, Carse of Stirling Clay, Claret Clay and Grangemouth Silt members in the Forth area.
Veneer to more than 27m
Upper boundary unconformable with modern alluvium, and commonly at the surface.
Carbost Conglomerate Member
CARCO
Carewoodrig Vent
CARE
Hawick area, southern Scotland.
Pyroclastic breccia or agglomerate in vent, with intrusions of trachyte, phonolite and dolerite.
Vent, elongate, c.1km x 2km.
Carlinden Shale Formation
CARL
Lowest shale band above conglomerates of Corbies's Tongue Formation.
Red and purple sandy shales and siltstones with calcareous nodules in places.
50 metres approximately, contacts not exposed.
Change from siltstone to sandstone.
Carmichael Group
CARM
Faulted out by the Carmichael Fault
Carmichael Inlier, Lanarkshire, Scotland
Within the Carmichael Inlier, comprises interbedded fine- and medium-grained red-brown to grey green sandstones, subordinate siltstones, mudstones and conglomerates containing mainly quartzite, quartz, chert and igneous pebbles; greyish olive mudstones common towards the base with thin interbeds of fossiliferous siltstone and sandstone. The base is cut out by the Carmichael Fault, but part of the Group is repeated to the south of the fault in the Eastfield Inlier
The incoming of the predominantly greywacke pebble bearing conglomerate belonging to the Greywacke Conglomerate Formation overlying fine- and medium- grained sandstones, siltstones and mudstones forming the Carmichael Group
Carnamuck Formation
CARN
Carn Odhar Granite Cupolas
CARNO
Carrickabrackan Plug
CARP
Carr Member
CARR
Carland Sandstone Member
CARS
Cadh-An-Righ Shale Member
CARSH
Carse's Vein
CARV
Castlecary Limestone
CAS
Generally marked by a change from marine mudstone, or resting on a thin coal or seatrock belonging to the Upper Limestone Formation.
Restricted by penecontemporaneous erosion to Fife (marine roof), the Lothians (in part and with marine roof), and to the east of Glasgow in the Stirling-Clackmannan-Falkirk areas, within the outcrop and subcrop of the Upper Limestone Formation in the Midland Valley of Scotland.
A white or pale to dark grey, medium- to fine-grained, crinoidal, bioclastic, locally dolomitic limestone, interpreted to be of marine origin, and containing algal nodules.
Generally up to 5m, but may be absent due to erosion in areas such as in Strathclyde, Ayrshire and parts of the Stirling district.
Commonly seen as an abrupt change to bituminous non-marine mudstone containing Curvirimula belonging to the Passage Formation. Marine mudstone roof in Fife, except where absent due to penecontemporaneous erosion, especially in the western Midland Valley of Scotland and in the centre of the Kincardine basin, where erosive-based sandstones form the base of the overlying Passage Formation.
Camasunary Sandstone Member
CASA
Cast Bed
CASB
Carrickmore Sandstone Group
CASG
Carraun Shale Formation
CASH
Camasunary Siltstone Member
CASI
Castle Formation
CASL
Base of lowest thick silt grade greywacke bed on sandstone grade greywacke/siltstone sequence of Patrick Burn Formation.
Thick beds of very fine-grained greywacke, interbedded with grey siltstone.
25m
Base of overlying dark grey mudstone of Kip Burn Formation.
Caburn Sponge Bed
CASO
Castle Espie Group
CASP
Castle Rocks Vent
CASR
Dunbar area.
Elongate vent filled with tuff.
Not specifically recorded: about 100 m long by 70 m wide, NNE-SSW orientated elongate intrusion,
Cassie Till Formation
CASS
Sheet NH74SE
Brown clay with stones: presumably a lodgement till.
Sharp contact with overlying Drummore Gravel Formation.
Castle Sand And Gravel Member
CASSG
Middle to Upper Pleistocene (MI Stage 5e to 2).
Unconformable, commonly channelled base, resting on Anglian Wragby Till or (locally) gravels of the Thorpe Sand and Gravel Member in the type area, and possibly locally on Upper Jurassic mudstone bedrock, if present, elsewhere.
Bain Valley; currently only separated reliably below Kirkby on Bain. Upstream extent uncertain but probably present at least as far upstream as Horncastle. (BGS sheets 103 and 115).
Predominantly cold-phase sand and gravels that underlie the Castle or First Terrace of the River Bain. Dominated by clasts of flint and chalk (though decalcified near ground surface) and a smaller proportion of Upper Jurassic and Lower Cretaceous lithologies plus minor exotics, notably ?Carboniferous sandstone and 'Bunter' pebbles (mostly derived from Anglian tills). Forms well-developed terrace surface typically about 1m above modern alluvial floodplain; the deposits extend beneath the latter and are incised into the adjacent Thorpe Terrace. Sections show syndepositional ice wedge casts but no epigenetic casts or cryogenic involutions. Locally includes cold-phase organic silts and peats, but channel-filling organic silts at the base (Tattershall Bed) yield a temperate flora and fauna assigned to MIS 5e. Correlates and merges with the following members of the Trent Valley Formation, Kirkstead Sand and Gravel Member (of the Proto-Trent) and broadly correlates with the combined Beeston and Holme Pierrepont Sand and Gravel Member, and Fulbeck and Scarle Sand and Gravel members (of the Proto-Trent).
Ground surface or against alluvium.
Cast Castle Formation
CAST
Between Kip Burn Formation and Patrick Burn Formation.
Siltstone and shale.
60 metres.
Central Anglesey Shear Zone
CASZ
Calcareous Tufa
CAT
Inorganic or organic calcium carbonate; deposited at or near springs. [Generic description: 'TMOS' Procedures].
Catterline Conglomerate Formation
CATC
Conformable upon the eroded top of the highest lava flow of the Crawton Volcanic Formation.
From Gourdon to Stonehaven.
A bimodal, clast-supported conglomerate with clasts mainly of lava, but also containing psammite, quartzite, vein-quartz and feldspar porphyry in a medium-grained lithic sandstone matrix, with single flows of andesite and three sandstone members.
From 870 m to 1080 m thick, Carroll 1995a.
Conformable and diachronous, north and south of the Bervie Bay Fault. The formation passes laterally westwards and northwards into the lavas of the Montrose Volcanic Formation.
Carsluith Intrusion
CATH
Creetown area of southwest Scotland.
Elongate microgranodiorite intrusion with porphyritic microdiorite dyke on northern margin.
c.0.5 square km in total area (c.3km long x 0.2km wide).
California Till Member
CATI
The California Till Member overlies the Corton Sand Member within the Scratby and California area. The contact between the two units is gradational.
The California Till Member has been logged in cliff sections between California Gap and Scratby to the north of Great Yarmouth, and occurs as separate mappable leaves of till inland in the Great Yarmouth and North Walsham districts.
The California Till Member consists of a stratified matrix-supported diamicton that comprises beds of massive brown sandy diamicton, separated by beds of massive and horizontal-bedded chalky sand with sporadic augen-shaped lenses of fine silty sand. It is similar in lithology to the Corton Till Member.
Maximum observed thickness of 13m at California Gap.
The upper boundary of the California Till Member is typically scoured and erosional, and is overlain by chalky outwash and till deposits of the Lowestoft Formation.
Catcraig Limestone
CATL
Eat Lothian (Catcraig, near Dunbar).
Cartlett Beds
CATT
Cattedown Member
CATTE
The age range quoted is deduced to cover the upper part of the recorded age range of the Plymouth Limestone Formation, and the lower limit might be slightly too low [awaiting literature check].
Caldecote Volcanic Formation
CAV
Extends from Nuneaton north-westwards to just south of Atherton Road (SP 3510 9266-3282 9509).
Grey, massive, feldspar and quartz crystal-lapilli tuff with subordinate angular to subrounded lithic blocks. Intercalations of grey to green, fine, well-laminated to massive tuffaceous mudstone, siltstone and sandstone.
130m minimum thickness in general area. 20m minimum in type section.
Unconformity surface. Overlain by Lower Cambrian beds of the Hartshill Sandstone Formation or by Triassic sandstone and breccia.
The Car Vent
CAVE
Carneddau Volcanic Formation
CAVO
Carstone (Isle Of Wight)
CAW
Cawdale Tuff Member
CAWD
Taken at the abrupt change to bedded pyroclastic rocks from either silicic lapilli-tuff of the Whelter Knotts Formation or from bedded volcaniclastic sandstone within the Mardale Formation.
Between Ullswater and the Haweswater Reservoir, eastern Lake District, Cumbria.
A massive, coarse tuff and tuff-breccia, with localised pyroclastic breccia and pebbly volcaniclastic sandstone.
To 80m
Taken at the abrupt change to bedded volcaniclastic sandstone of the main part of the Mardale Formation,
Carsey Coal
CAY
Cayton Clay Formation
CAYC
Cornbrash Formation
Middle Jurassic, Upper Bathonian (Discus Zone) to Lower Callovian (Herveyi Zone).
Generally sharp, disconformable non-sequence: bioclastic limestone resting upon mudstone (and bioclastic ooidal limestones, locally) of the Forest Marble Formation (Wessex Basin and south Midlands), or mudstone of the Blisworth Clay Formation (East Midland Shelf east and north) or mudstone with minor sandstone beds of the Scalby Formation (Cleveland Basin).
Dorset coast (Weymouth area) to Yorkshire coast (Scarborough area); absent over the Market Weighton High. Extensive in onshore subcrop, though absent over the interior of the London Platform.
Limestone, medium- to fine-grained, predominantly bioclastic wackestone and packstone with sporadic peloids; generally and characteristically intensely bioturbated and consequently poorly bedded, although better bedded, commonly somewhat arenaceous units occur in places, particularly in the upper part. Generally bluish grey when fresh, but weathers to olive or yellowish brown. Thin argillaceous partings or interbeds of calcareous mudstone may occur.
0 to c. 10.5m (Page, 1989); thickest in Wessex Basin but more generally 2 to 4m.
Base of succeeding Kellaways Formation or Cayton Clay Formation (in the Cleveland Basin); comprising mudstone, commonly shelly at base, resting generally sharply and conformably or non-sequentially on bioclastic limestone of the Cornbrash.
Brand Group
CBA
The base of the Group is unexposed, but is inferred to be unconformable upon units of Neoproterozoic III age that include intrusive rocks of the South Charnwood Diorites and tuffaceous mudstones, siltstones and sandstones of the Bradgate Formation.
Extends from Groby Lodge area, north-eastwards to outskirts of Nanpantan, along the eastern edge of Charnwood Forest.
The Group consists of quartz-arenites and turbiditic sandstones of the Lower Cambrian Brand Hills Formation, which in turn pass up to grey, cleaved mudrocks of the Swithland Formation.
Cardigan Bay Formation
CBAY
Early to Late Devensian.
An erosion surface with a gentle topographic variation of about 15m on the underlying St George's Channel Formation. Locally on pre-Quaternary erosion surface.
Irish Sea.
Upper and lower tabular unstratified (till) members, laterally grading to sands and gravels, separated by an intervening lenticular and tabular infill member. The Lower Till Member comprises stiff clay, abundant pebbles, slightly pebbly sand with shell clasts, together suggestive of a sub-glacial lodgement till, and elsewhere interpreted ice-proximal glaciomarine sands. The lenticular component comprises sands with subordinate muds, whereas the associated overlying tabular beds consist of fine-grained silty sands and sandy clays. The Upper Till Member shows a stiff to hard diamicton of clay with varying sand, gravel, shell, cobbles and boulders.
28 to 158m
Unconformity at base of overlying Upper Western Irish Sea Formation. Locally crops out at sea bed.
Conksbury Bridge Lava Member
CBB
In the Haddon Fields Borehole basalt of the Conksbury Bridge Lava Member is underlain by pale grey and cherty limestones with some calcilutites, included within the Fallgate Volcanic Formation
Present at outcrop in the lower part of Lathkill Dale, north of Alport. Also proved in Boreholes at Alport [SK2365]. Occurs about 27m (Shirley, 1950) or 19m (Aitkenhead et al., 1985) above the Lathkill Dale Lava Member. The member is not seen west of Over Haddon [SK203 663]
In the Haddon Fields Borehole the member comprises three flows of compact and amygdaloidal basalt. At Conksbury Bridge the member includes two flows: the upper flow includes a vesicular basalt at the top and base and a central non-vesicular dolerite; the lower flow has a highly vesicular and slightly haematised upper margin, which grades down into a non-vesicular dolerite (Walters, et al., 1981).
The thickest development is 51.71m, proved in the Haddon Fields Borehole.
At Conksbury Bridge, limestone of the Monsal Dale Limestone Formation rests upon a vesicular upper margin of a 5m thick lava flow of the Conksbury Bridge Lava Member (Walters and Ineson., 1981).
Creech Brick Clay Member
CBBC
Carrickmore Blackband Ironstone
CBBI
Chalky Till
CBC
Pebbly clay, rich in chalk clasts, locally with lenses of sand and gravel. [Generic description].
Cornbrash Formation And Cayton Clay Formation (Undifferentiated)
CBCA
Clydebank Clay Formation
CBCL
The Clydebank Clay Formation rests with angular unconformity on older Quaternary sediments or bedrock. It most commonly rests on the Wilderness Till Formation (WITI) of the Caledonia Glecigenic Group (Midland Valley Glacigenic Subgroup).
The Clydebank Clay Formation is recognised in the lower Clyde Valley north of Lanark, in the estuary of the Clyde, and in Loch Lomond.
The Clydebank Clay Formation comprises mainly clay and silt, with subsidiart sand and gravel deposits, forming four members (q.v.): from oldest to youngest these are the Buchanan Clay, Longhaugh Sand and Gravel, Erskine Clay and Gourock Sand members. More detail of the lithologies of the individual members is included in the related Lexicon entries.
Ranges from a veneer to more than 15m.
The Clydebank Clay Formation is overlain unconformably by younger Quaternary sediments, normally either the Clippens Peat Formation or Clyde Valley Formation of the Clyde Catchment Subgroup (Britannia Catchments Group). It is also extensively exposed at surface in the lower Clyde valley.
Cobble Coal (Cheadle)
CBCO
Cock Burn Calcareous Schist Formation
CBCS
At upper limit of quartzite of Corryhabbie Quartzite Formation.
Confined to inverted 'tea-cup' shaped outcrop south of Allargue and Corgarff on Upper Donside, cut by Cock Burn and River Don. To south, cut out by Glen Gairn Granite.
Calcareous semipelites and micaceous psammites, grey-green, phyllitic to schistose. Abundant laminated and striped calc-silicate and limestone bands.
At passage from calcareous semipelite and psammite into graphitic pelite of the Allarghe Graphitic Schist Member.
Cobden Sandstone
CBD
Coalburn Dross Coal
CBDC
Cressbrook Dale Lava Member
CBDL
At the type locality, the basalt at the base of the member is underlain by dark grey cherty limestones of the Monsal Dale Limestone Formation.
The member has a limited poorly exposed outcrop at Cressbrook Dale (SK17 74), with a thicker and extensive development in the subsurface to the north and east of this locality.
Typically comprises hyaloclastite, basalt and tuff, the latter locally with some limestone grains. At Cressbrook Dale the member is dominated by amygdaloidal basalt. At the type locality the lower part comprises brecciated lavas, with oxidised angular fragments of vesicular or non- vesicular basalt and a matrix of silica and chlorite, interdigitated with non-brecciated basalt lavas. At this locality, the top of the member is a 0.75m thick pale green, pyritic tuff
Maximum thickness of 80.88m proved in the Longstone Edge Borehole, SK27SW/5 [SK 2088 7335).
At the type locality, the pale green tuff at the top of the member is overlain by dark grey biomicrosparite limestones of the Monsal Dale Limestone Formation
C-Bed Evaporite
CBE
Coalburn Ell Coal
CBEC
Col-Bhein Formation
CBF
Cotes Bottom Flint
CBFL
Crossbrae Farm Peat Bed
CBFMP
Devensian (?MIS 5a or 5c).
Overlies Devonian red brown sandstone bedrock in sharp unconformity, and is inferred to overlie the Crossbrae Till Formation.
Buchan, northeast Scotland. The bed is known only from the vicinity of Crossbrae Farm, Turrif on Sheet 86E (Turrif).
Peat, black and dark brown, variably sandy, with laminae and thin beds of variably organic silty grey medium sands and quartzose medium to coarse sand. The most recent C14 dates indicate age of the bed is >61,900 years BP (SRR-5707). Interpreted as have formed under cold interstadial climate conditions in dwarf shrub tundra (combined evidence from pollen, plant macrofossils and coleoptera).
To 0.55m
A sharp unconformity with unnamed sand and gravel unit, which is in turn overlain by bedded diamicton of the Crossbrae Gelifluctate Bed. Elsewhere it is inferred that the peat bed was directly overlain by the Crossbrae Gelifluctate Bed.
Cambridge Greensand Member
CBG
Most of the unit is Cenomanian in age- Mantelliceras mantelli Zone, Neostlingoceras carcitanense Subzone. However, where a more complete succession is preserved, the base may be uppermost Albian (C. bemerodensis ostracod zone, equating to the M. perinflatum Subzone of the S dispar Zone) (Wilkinson, 1988).
Disconformity. Sharp contact; commonly burrowed on underlying grey Gault clay; glauconitic burrow infillings to 0.3 below junction.
Known from the north Hertfordshire and Cambridgeshire area within the Transitional Province.
Glauconitic marl: Thin but distinctive condensed basement bed of pale greenish grey marl rich in phosphatic nodules (so called "coprolites") at base. Much dark green glauconite as sand-sized grains, disseminated or concentrated in pods and layers giving a sandy texture and hence name "greensand". Rare erratic pebbles at base. (Hawkes, 1943).
Typically 0.1 - 1.0m thick. Locally thicker developments infilling hollows on top of Gault. 0.5 - 0.7m at Arlesey Brickpit (TL 188 347). (Hopson, 1992).
Rapid upward transition to "Chalk Marl" or Lower Chalk lacking distinctive glauconite grains and nodule concentrations.
Crossbrae Gelifluctate Bed
CBGEL
The lower boundary of the bed abruptly overlies dark brown diamicton of the Crossbrae Till Formation with a sharp, planar unconformity. Locally the basal boundary of the unit has also been observed to overlie abruptly an unnamed sand and gravel unit, which itself directly overlies the Crossbrae Farm Peat Bed.
Buchan, northeast Scotland. The bed is only known from the vicinity of Crossbrae Farm, Turriff on Sheet 86E (Turriff).
Gravelly, slightly clayey, silty sand diamicton. Variably coloured, dark brown to dark grey. Crudely medium-bedded, matrix supported, weakly to non-calcareous. Clasts are typically subangular to subrounded (with pelitic metasedimentary rocks commonly striated). Clast lithologies are dominated by quartzose and psammitic, and pelitic/semipelitic metasedimentary rocks, with less common red brown sandstone, felsite, grey granite, and mafic igneous rocks. Clast fabric orientations are typically normal to the present day ground topographic contours. The crude bedding of the diamicton is picked out by laminae of silty medium sand. Interpreted as periglacial gelifluctate deposits.
Up to 2.5m observed
The upper boundary of the bed is the present ground surface.
Conisbrough Group
CBGP
Cloberhill Blackband Ironstone
CBHB
Corbyn's Head Member
CBHD
Hanging Rocks Formation
CBHR
No longer seen, formerly stated to sharply overlie "coarse green hornstones" that are now referred to the Bradgate Formation.
Restricted to Charnwood Forest, the most definite occurrences are between Bradgate Park and Charnwood Forest Golf Course.
Grades from a basal facies of poorly sorted, grey, small-pebble conglomerates interbedded with coarse-grained sandstones, to graded sandstones and thin conglomerates, with grey tuffaceous mudstones and siltstones above.
Variable, 0 to 47m
Not seen. The unit fines upwards, towards the base of the overlying Swithland Formation, but an unconformity is suspected since the latter is now regarded as of Early Cambrian age.
Corrie Burn Horneblende Schist
CBHS
Not seen; faulted contact with Bolfrishlie Slate Formation.
Amphibolite, fine-grained, strongly schistose with a dark to pale green banded appearance on the centimetre scale, with striped chlorite albite schists at structural top.
Maximum 150m (estimated), possibly tectonic.
Tectonic contact (faulted) with Lime Hill Serpentinite.
Craigmark Blackband Ironstone
CBI
Clayband Ironstone Member
CBIF
Top of the dark grey fissile mudstone with marine fossils of the Cambriense Marine Band.
North Staffordshire Coalfield, although not actually shown on the map.
Grey mudstones and siltstones with thick seatearths, numerous ironstones and coals and brittle dark grey mudstones rich in fish debris. Channel sandstones are locally important.
Up to 161 m in Parkhouse Colliery.
Base of the Cannel Row Coal.
Carn Brea Intrusion
CBIN
Coarse-grained granite with abundant feldspar megacrysts >15mm.
Cambir Dolerite Sheet-Swarm
CBIRD
Blackbrook Group
CBK
Not seen or proved in Charnwood region.
Extends from the small inlier east of Grace Dieu Brook (SK 4397 1880) south-east to Ives Head and Benscliffe Wood.
Well-bedded to laminated, grey to green volcaniclastic mudstones, siltstones, sandstones with volcaniclastic breccias and dacite lavas, the latter confined to the concealed Morley Lane Volcanic Formation.
Overlain by grey, coarse-grained tuffs, lapilli tuffs and breccias of Benscliffe Breccia Member, Beacon Hill Formation, or by similarly coarse-grained lithologies of Charnwood Lodge Volcanic Formation, to the west.
Chercombe Bridge Limestone Formation
CBL
Late Eifelian to Givetian.
Claygate Member And London Clay Formation (Undifferentiated)
CBLC
Cairnbulg Diorite
CBLG
Cawledge Bend Limestone
CBLM
In the Alnwick district of Northumberland.
c.3m
Captain's Bridge Limestone
CBLS
South Ayrshire; the area around Captain's Bridge.
Crinoid-rich limestone.
c.9m
Caswell Bay Mudstone Formation
CBM
?Arundian.
The base of the formation is taken at the sharp erosional contact between the mudstone/clay palaeosol at the top of the Gully Oolite Formation and the overlying thinly bedded calcite mudstones and mudstones of the formation. A conglomeratic lag is locally present at the base of the Caswell Bay Mudstone Formation.
The Gower [SS 50 90], Vale of Glamorgan [ST 00 74], southeast crop of the South Wales Coalfield [ST 17 85] and Weston-super-Mare [ST 32 60] areas. Present in Pembroke [SM 97 03] and Tenby [SN 13 01] areas but not currently mapped. Passes northwards into the Llanelly Formation in Wales and Clifton Down Mudstone in the Bristol area [ST 60 73].
Thinly interbedded grey and green grey peloidal and bioclastic micrites, wackestones and packstones, and cryptalgal laminites. Dolomitisation is locally common; on the southeast and east crop of the South Wales Coalfield and in the Chepstow area, the formation is predominantly dolomitised.
15m on the south crop of the South Wales Coalfield, thinning southwards to a feather edge in the central Vale of Glamorgan, southwest Gower and southwest Pembrokeshire.
The top of the formation is taken at the sharp erosional contact between the thinly bedded calcite mudstones and mudstones of the formation and the overlying coarse peloidal and skeletal packstones/grainstones forming the lower part of the overlying High Tor Limestone Formation.
Carreg Bica Mudstone Member
CBMD
Caban Conglomerate Formation
CBN
Massive to thick-bedded conglomerates with subordinate beds of pebbly coarse sandstone.
Coalburn Nine Foot Coal
CBNC
Caban Conglomerate Formation: Caban Conglomerate Facies
CBNCF
Caban Conglomerate Formation (Lower Conglomerate Of Lapworth)
CBNL
Caban Conglomerate Formation: First Sequence Of Caban Conglomerate Facies
CBNS1
Caban Conglomerate Formation: Second Sequence Of Caban Conglomerate Facies
CBNS2
Caban Conglomerate Formation: Third Sequence Of Caban Conglomerate Facies
CBNS3
Caban Conglomerate Formation: Fourth Sequence Of Caban Conglomerate Facies
CBNS4
Caban Conglomerate Formation: Fifth Sequence Of Caban Conglomerate Facies
CBNS5
Caban Conglomerate Formation (Upper Conglomerate Of Lapworth)
CBNU
Caswell Bay Oolite Formation And Caswell Bay Mudstone Formation (Undifferentiated)
CBOM
Cockermouth Breccia-Conglomerate
CBR
Coalbrookdale Formation
CBRD
Transitional through 3m to 9m with the underlying Buildwas Formation in type area; similar transition with the underlying Woolhope Limestone in the Woolhope-Malverns area; base placed immediately above the highest nodular horizon of the Buildwas Formation or Woolhope Limestone.
Welsh Borderland and South Wales.
Compact, well-bedded, olive grey to dark blue-grey silty mudstones with some calcareous siltstones, nodular calcareous beds and bentonites.
192 - 265m in type area (excluding 10m of Farley Member).
Transitional, but in practice placed at base of lowest, regularly bedded limestone of the Much Wenlock Limestone.
Crowberry Ridge Tuff
CBRT
Canty Bay Sandstone
CBS
The type locality is at Canty Bay, near North Berwick, East Lothian. The sandstone appears to be a local development around this area.
White false-bedded sandstone containing pellets of red micaceous sandstone.
Swithland Camp Member
CBSC
Sharp, erosive base on underlying grey tuffaceous siltstones of the Broadgate Formation.
Confined to the type section; not observed or not exposed elsewhere.
Siltstones, purple-grey, with subangular to well rounded igneous pebbles and siltstone intraclasts.
Not seen, probable conformable passage into overlying beds of the Stable Pit Member.
Coalburn Smithy And Dross Coals
CBSD
Stable Pit Member
CBSP
Unexposed, but possibly a rapid transition from conglomeratic beds of the underlying Swithland Camp Member into fine-grained sandstones and siltstones at the base of the Stable Pit Member.
Outcrops discontinuously between Stable Pit and the Brand Hills.
Locally variable, ranging from pale grey, medium-grained, cross-bedded quartz arenite to dark maroon-grey, parallel-bedded, massive to graded graywacke sandstone.
Unexposed, but probably an upwards fining transition to grey, slaty mudrocks of the overlying Swithland Formation.
Coulins Burn Striped Member
CBST
Upper limit of quartzites of underlying Caochandye Quartzite Member.
N-S-trending outcrop, 500-1500m wide, extending from Allt na Craoibhe-Caorainn [NJ 320 256] to Tolduquhill area [NJ 30 15], Glen Nochty, Moray District. 1:50 000 Sheet 75E.
Semipelite and psammite, notably striped and banded.
Probably c. 400m (based on outcrop width and making no allowance for probable tight folding).
Lower limit of graphitic pelites of overlying Glenbuchat Graphitic Schist Formation.
Coalburn Six Foot Coal
CBSX
Coalburn Smithy Coal
CBSY
Corbie's Tongue Conglomerate Formation
CBT
Unconformity on Dalradian metasediments and Caledonian plutonic rocks.
Conglomerate, with rounded quartzite cobbles, reddened on the outside, set in a silty, or in places calcareous, matrix.
Approx. 10 metres in type section, probably increasing southwards to 15 - 20 metres on Glaschul Hill (NJ 458 149).
Transition from conglomerate to shale.
Crossbrae Till Formation
CBTIL
Wolstonian (?MIS 6).
A sharp, planar, unconformity on Devonian red-brown pebbly sandstones.
Buchan, northeast Scotland. The formation is curently only known from the vicinity of Crossbrae Farm, Turriff on Sheet 86E (Turriff). The unit may be regionally significant and present locally across northeast Scotland.
Dominantly brown/dark brown, very stiff, weakly calcareous, matrix supported, gravelly slightly clayey silty sand diamicton. Clast lithologies are dominated by quartzite/psammite and red brown Devonian sandstones, with less common pelitic/semipelitic metasediments, felsite, grey granite and mafic igneous rocks. Clasts are typically subangular - subrounded (with the pelitic metasedimentary rocks commonly striated). Clast fabrics indicate glacial transport from the northwest. Interpreted as a subglacial till.
Up to 0.7m observed
A sharp, planar, subhorizontal surface overlain by periglacial diamictons of the Crossbrae Gelifluctate Bed. The Crossbrae Till Formation is believed to be locally overlain by the Crossbrae Farm Peat Bed.
Chapelton Burn Member
CBUR
Not seen due to lack of exposure. The lower boundary occurs south of Chapelton Farm at approximately NS 2240 0434, between small stream exposures of the Chapelton Burn Member to the east, and small stream exposures characteristic of the Swanshaw Sandstone Formation to the west. The lower boundary is probably conformable, as red sandstones typical of the Swanshaw Sandstone Formation are exposed a few tens of metres to the east of the Chapelton Burn Member, and also because there is not much variation in dip between the two rock types.
The main outcrop is in Chapelton Burn, between Littleton and Glenhead farms, where the strata dip westwards. Extensions to the north and south cannot be defined, therefore it has been mapped as a discontinous lens of floodplain facies, surrounded by the more typical channel facies of the Swanshaw Sandstone Formation. The main Chapeltown Burn exposure is tentatively extended eastwards to the south of Chapelton Farm [NS 2240 0434], where similar rock types were observed during preliminary reconnaissance mapping (see BGS 2001, NS20NW, NS20SW and NS20NE 1: 10 000 maps). Another outcrop in the upper part of Chapelton Burn [NS2537 0557-2556 0564] was clearly identified by Jones (2001). This outcrop has been mapped as a small lens, because very small exposures between this and the main exposure show red sandstones and conglomerates typical of the Swanshaw Sandstone Formation. This exposure may be joined with the main Chapelton Burn exposure.
A coarse-grained sandstone with a pinstripe lamination, a sheet-like erosively-based fine- and medium-grained sandstone with red, white and green siltstones and mudstones.
At least 145m thick, as estimated from the partial type section.
The upper contact is faulted in Chapelton Burn at NS 2189 0467. To the east of the fault, within the Chapeltown Burn Member, the rock types are reddish-green mudstones and fine- to medium-grained sandstones. The fault plane is marked by a 1m-wide brecciated zone. To the west of the fault are flaggy red sandstones with cross-bedding, typical of the Swanshaw Sandstone Formation in this area.
Chirbury Group
CBY
Base of Spy Wood Sandstone Formation.
Shales, volcaniclastic members and sandstones.
>1500m, but poorly exposed.
Top not seen - unconformity.
Cwmbyr Coal (South Wales)
CBYR
Castell Formation
CCA
Central Cumbria (Albion) Glacigenic Subgroup
CCAG
The central Lake District, Shap Fell and the Howgill Fells.
Including mappable units of diamicton, gravel, sand, silt and clay, typically yellowish or greyish brown and containing clasts derived from the Lake District, Shap Fell and the Howgill Fells, including welded tuff (Borrowdale Volcanics), slate, granite, granophyre, limestone and sandstone.
Locally the ground surface, but generally overlain unconformably by deposits of gravel, sand, silt, clay and peat of the Central Cumbria Glacigenic Subgroup.
Cathcart Sill
CCART
Cornubian Catchments Subgroup
CCAT
Unconformable on bedrock of Devonian to Cretaceous age.
The catchments of the rivers of Devon and Cornwall from the River Axe westwards.
The Cornubian Catchments Subgroup encompasses all the fluvial, lacustrine and organic deposits of the rivers of Devon and Cornwall from the River Axe westwards. Floodplain alluvium comprises soft silts and clays, commonly with beds of peat and a basal bed of sand and gravel. River terrace deposits are largely sand and gravel. The gravels include a wide range of Palaeozoic and Mesozoic rocks, reflecting the rock types cropping out in the various catchments. Peat is a minor component, and minor marine deposits are included where they are intercalated in dominantly fluvial formations.
Up tp 22.5m recorded in the buried sub-drift valley of the 7th terrace of the Taw Valley Formation.
Corrycroar Beds
CCB
Cot Castle Blackband Ironstone
CCBB
Lower Cwm Clyd Beds
CCBL
Upper Cwm Clyd Beds
CCBU
Cushendun Formation
CCC
Cot Castle Clayband
CCCB
Callander Craig Conglomerate Member
CCCO
A sharp contact with fine- to medium-grained lithic sandstones of the (undivided) Ruchill Flagstone Formation, but near Gartmore, the Conglomerate is underlain by a red silty mudstone.
The north-west limb of the Strathmore Syncline, from Kelty Water near Corrie, to Meall Leathan Dhail, and possibly to Auchnashelloch Hill (although disputed by Francis, E H et al, 1970).
A poorly sorted, matrix supported, typically well bedded (planar) conglomerate with coarse clasts which are commonly sub-angular to angular.
Up to 150 m thick at Callander, 50m at Beinn Liath [NN 578 040], and 2 m near Gartmore.
A gradational contact with an overlying reddish grey, coarse- to fine-grained, locally pebbly, and commonly massive sandstone, of the undivided Ruchill Flagstone Formation.
Carrickarnan Complex Dolerites
CCD
Cannock Chase Formation
CCF
Cairnfield Calcareous Flag Formation
CCFL
At incoming of calcareous (greenish, tremolite-bearing) psammites and semipelites above the non-calcareous Findlater Flag Formation.
1) R. Fiddich NW of Dufftown to Forgie, Clochan and Cairnfield House (Sheets 85E and 95). 2) Craibstone and Deskford to Crathie Point and Garron Point (Sheet 96). (Below Keith Shear-Zone; probably equivalent stratigraphically to Pitlurg Calcareous Flag Formation above the Keith Shear-Zone.)
Calcareous, banded psammite and semipelite, grey and pale green, normally flaggy but schistose in places. Tremolitic amphibole commonly conspicuous in hand specimen. Thin beds of impure metalimestone locally.
c. 1200m in coastal section.
Below graphitic pelites with beds of pure metalimestone comprising the Mortlach Graphitic Schist Formation.
Coralline Crag Formation
CCG
"Lower" [Early] Pliocene.
Rests unconformably on the undulose, possibly tidally-scoured, surface of the Thames Group throughout its known distribution.
Restricted to southeast Suffolk, around Orford and Aldeburgh, as far north as Thorpeness and just into the adjacent offshore area. There are isoltated outliers at Ramsholt and Tattingstone.
Carbonate-rich skeletal sands. The acid-insoluble sand fraction is moderately- to poorly-sorted medium-grained sand, the mud content is low. Basal lag gravel rich in pebbles of phosphatic mudstone largely derived from the Thames Group.
c.25m maximum onshore.
Overlain unconformably by rocks of the Norwich Crag Formation across most of its extent, but Red Crag Formation material is banked against a buried ridge of the Coralline Crag in some areas and thin Red Crag deposits overlie the Coralline Crag locally.
Cloalcleugh Coal
CCGH
Central Cumbria Glacigenic Subgroup
CCGL
Generally unconformable on bedrock, but locally unconformable on older deposits of diamicton, gravel, sand, silt and clay assigned to the Central Cumbria (Albion) Glacigenic Subgroup.
Including mappable units of diamicton, gravel, sand, silt and clay, typically yellowish or greyish brown and containing clasts derived from the Lake District, Shap Fell amd Howgill Fells, including welded tuff (Borrowdale Volcanics), slate, granite, granophyre, limestone and sandstone.
Generally the ground surface, but commonly overlain unconformably by deposits of gravel, sand, silt, clay and peat of the Solway or Cumbria-Lancashire Catchments subgroups.
Craigcluggan Plug
CCGN
Caesar's Camp Gravel Formation
CCGR
Early Pleistocene.
Sharp, highly irregular contact with Palaeogene sands, obscured by a veneer of solifluction deposits.
Restricted to plateau remnants between Aldershot and Farnham, Surrey.
Unbedded and thickly bedded cobble gravel with interbedded coarse sands. Gravels are dominantly nodular flint to 0.2m diameter, with subordinate quartz and Greensand chert. The sand is subangular, dominantly quartz with some flint, and occurs as horizontal planar-bedded units, cross-bedded lenses, and channel-fill sands and silts. Fluvial and periglacial in origin, deposited by rivers draining to the northwest. Well-defined palaeosol in upper part of gravelly deposits, overlain by silty fine sand of aeolian origin.
To 6m
Land surface; no overlying deposits.
Cowleaze Chine Member
CCH
Cruachan Formation
CCHAN
Conachair Granite Pluton
CCHG
Colchester Formation
CCHR
Unconformable on bedrock: Cretaceous, Palaeogene and Crag Group. Differentiation from the Crag Group can be difficult where the latter is reworked, and the distinction must be made on the basis of sedimentological structures: the Crag Group is marine, the Kesgrave Catchment Subgroup is fluvial.
The formation is restricted to the Thames Valley, Essex and Suffolk. It does not extend into Norfolk. (Hamblin and Moorlock, 1995).
The formation encompasses fluvial, lacustrine and organic deposits of the pre-diversionary River Thames. Most of the surviving deposits are fluvial gravels, with sedimentary structures indicating deposition by a braided river. Lacustrine silts and clays and organic peats are uncommon. The gravels of the formation are characterised by quartz and quartzite from the Triassic, Carboniferous and Devonian rocks of the West Midlands, Welsh borderland and possibly southwestern Pennines, and felsic volcanic rocks from northern Wales. These lithologies form a lower percentage than in the Sudbury Formation, and are believed to be derived from that formation, but mega-erratics and felsic volcanic rocks from Wales and the Welsh borderland occur with a generally greater frequency than in the Sudbury Formation. The fluvial gravels occupy terrace levels and the members are defined on the basis of altitude and pebble clast content. The members comprise bodies of cross-bedded and massive, moderately sorted sand and gravel. The aggredations are generally entrenched into bedrock with a difference in surface elevation in the order of 5m. Intraformational ice wedge casts and pollen indicate periglacial, cool temperate and warm temperate climates.
individual terrace aggradations are typically 5-12m thick, total thickness may locally reach c.21.3m.
Commonly overlain by Middle Pleistocene glacigenic deposits. Upper boundary may be difficult to determine where overlain by glaciofluvial sand and gravel, but the presence of more angular clasts, chalk, and poorer sorting in the latter is usually helpful. The uppermost 1.0-1.5m of the formation is commonly affected by the Valley Farm Soil, a rubified and clay-enriched horizon, and/or by the Barham Arctic Structure Soil, a complex pedogenic horizon (Rose et al., 1985).
Carn Chuinneag And Inchbae Augen Gneiss
CCIA
Neoproterozoic (550 +/- 10Ma).
Corncockle Sandstone Formation
CCK
Rests unconformably on Lower Palaeozoic strata or on basal Permian breccias.
Lochmaben Basin, Dumfriesshire, south-western Scotand (Southern Uplands)
Fine- to medium-grained, well sorted, red quartz sandstone with large scale aeolian cross-bedding.
900m+ on geophysical evidence.
The Corncockle Sandstone Formation is stratigraphically the highest unit in the district.
Castell Coch Limestone Formation
CCL
Interbedded thin- to medium-bedded grey skeletal packstones and mudstones forming the upper part of the Tongwynlais Formation thicken upwards and pass up quickly, but gradationally, into the medium- to thick-bedded oolitic and skeletal grainstones of the Castell Coch Limestone Formation. The base of the Castell Coch Limestone Formation is taken at the incoming of a mudstone-free sequence. North of Risca, the Castell Coch Limestone Formation oversteps the Tongwynlais Formation to overlie the component formations of the Quartz Conglomerate Group. The base is taken at the sharp erosive contact between the green grey sandstones, quartz conglomerates and red and green mudstones of the Quartz Conglomerate Group and the overlying calcareous sandstones, sandy limestones, and skeletal and oolitic grainstones of the Castell Coch Limestone Formation. A persistent phosphatic, conglomeratic lag up to 0.7m thick is present at the base.
Vale of Glamorgan [ST 00 74] and South Wales Coalfield [SO 09 02], east of Swansea. Present but currently unmapped in the east crop of the South Wales Coalfield [ST 25 90], Gower [SS 50 90] and Monmouth and Chepstow areas [ST 53 93].
Grey, locally reddened, medium- to thick-bedded, cross-bedded, oolitic and skeletal grainstones deposited as part of a barrier complex. Thin units of grey mudstone, calcite mudstone and calcisiltite are locally present in the uppermost part of the Formation and represent back barrier peritidal deposits. North of Risca, conglomerates, calcareous sandstones and sandy limestones are present in the lowermost part.
30m on the north crop of the South Wales Coalfield [Abergavenny], thinning southwards to 9m in the south of the Vale of Glamorgan.
Where barrier mudstones, calcite mudstones and calcisiltites occupy the uppermost part of the formation, the top is taken at the sharp base of the overlying marine interbedded grey mudstones and packstones of the Cwmyniscoy Mudstone. The contact is commonly erosional and overlain by a packstone or grainstone bed rich in interclasts of the underlying back barrier mudstones. Where the uppermost part of the formation comprises barrier grainstones, the top is taken at the sharp incoming of the overlying interbedded grey mudstones and packstones of the Cwmyniscoy Mudstone Formation.
Cairn Of Claise Transition Formation
CCLT
Cwmyniscoy Mudstone Formation
CCM
Where back barrier mudstones, calcite mudstones and calcisiltites occupy the uppermost part of the underlying Castell Coch Limestone Formation, the base of the Cwmyniscoy Mudstone Formation is taken at the sharp incoming of marine, interbedded grey mudstones and packstones. The contact is commonly erosional and overlain by a packstone or grainstone bed rich in intraclasts of the underlying back barrier mudstones. Where the uppermost part of the Castell Coch Limestone Formation comprises barrier grainstones, the base of the Cwmyniscoy Mudstone Formation is taken at the sharp incoming of interbedded grey mudstones and packstones.
Vale of Glamorgan [ST 00 74] and South Wales Coalfield [ST 06 81], east of Swansea. Present but unmapped in the east crop of the South Wales Coalfield [ST 25 90], Pembrokeshire [SM 99 01] and Monmouth and Chepstow [ST 53 93] areas.
Interbedded grey mudstones and thin- to medium-bedded skeletal packstones deposited in a mid-shelf environment.
60m in the south of the Vale of Glamorgan, thinning northwards to 10m on the north crop of the South Wales Coalfield [Abergavenny].
The contact of the Cwmyniscoy Mudstone Formation with the overlying Barry Harbour Limestone Formation is gradational. In the uppermost part of the Cwmyniscoy Mudstone Formation, the proportion of packstone beds increases to exceed that of mudstone. The top of the Cwmyniscoy Mudstone Formation is taken at the top of the last significant mudstone bed above which the succession becomes dominated by stacked fine and coarse skeletal packstones with scattered thin beds and partings of calcareous mudstone. In the north crop of the South Wakes Coalfield, the Cwmyniscoy Mudstone Formation is overlain by the Sychnant Dolomite Formation or the Pwll-y-cwm Oolite Formation. The junction with the Sychnant Dolomite Formation is gradational. Thin beds of calcite mudstone and dolomitic limestone appear in the uppermost part of the Cwmyniscoy Mudstone Formation mudstone/packstone sequence. The top of the formation is taken at the incoming of abundant, thin-bedded, fine-grained, dolomitised skeletal packstones of the Sychnant Dolomite Formation. The contact with the Pwll-y-cwm Oolite Formation is sharp and taken at the incoming of thick-bedded pale grey oolitic grainstone above the interbedded mudstones and packstones of the Cwmyniscoy Mudstone Formation.
Caldon Low Conglomerate Member
CCN
Cumbrian Coast Group
CCO
Point in sequence where there is a sharp upwards change from either Brockram or red sandstone, to grey siltstones or dolomites.
North and east Irish Sea and bordering land areas west of the Pennines including west Cumbria, Vale of Eden, south Cumbria, Lancashire and north-east Cheshire, ie the 'Bakevellia Sea Basin' of Smith and others (1974); see also Jackson and others, 1987.
Comprises a basal sequence of grey siltstones and dolomites overlain by evaporites (St Bees Evaporite Formation), overlain by red siltstones, silty mudstones and calcareous sandstones (St Bees Shale Formation), which locally pass laterally into halite.
Ranges from 36m in type section to 300m+ in Irish Sea grabens.
Tends to be gradational therefore taken arbitrarily where sandstone (St Bees Sandstone Formation) becomes predominent over siltstone (St Bees Shale Formation).
Cracoe Limestone Formation
CCOE
?Holkerian to Brigantian.
The lower boundary has not been proved, but it is likely to comprise reef limestones of the Cracoe Limestone Formation resting upon the bedded, medium to medium-dark grey limestone of the Scaleber Quarry Limestone Member.
South of the Middle Craven Fault, occurring in a roughly west-east tract extending 20km east from Settle [SD83 63] to Burnsall [SE 01 61]. The apron reef has become dislocated into fault slices along the Craven Fault System. The formation passes northwards into the Cove Limestone and Gordale Limestone members and probably also the Lower Hawes Limestone (Alston Formation).
Medium and medium-pale grey limestones ranging from organic boundstones to packstones and wackestones with a variable grainsize depending on the bioclastic components.
Total thickness not proved, but in excess of 100m at the type locality.
The upper boundary is a marked unconformity, with the reef limestones of the Cracoe Limestone Formation overlain by dark grey mudstones of the Bowland Shale Formation.
Castell Crug Porphyritic Microgranite
CCPM
Pale-weathering, flow-foliated, locally porphyritic microgranite.
Overlain unconformably by a local Caradoc conglomerate.
Cam Crags Sandstone Member
CCR
Gradational (conformable) contact with bedded sandstone, within the Saethwaite fell Sandstone Formation.
Lake District, Central Fells.
Coarse-grained volcaniclastic sandstone and breccia, pebble breccia, pebbly sandstone, dark brown weathered..
Overlain (conformably) by siltstone, sandstone and breccia, within the Seathwaite Fell Sandstone Formation.
Calcrete
CCRET
Cumcrook Limestone
CCRK
Crying Crag Sandstone
CCS
Coalcleugh Shell Band
CCSB
Clay Cross Soft Coal (Derbyshire)
CCSC
Cot Castle Shell Bed
CCSH
Area of Cot Castle, near Strathaven, Lanarkshire.
Cannel Coal (South Lancashire)
CCSL
Base of first coal above mudstones of the Pennine Lower Coal Measures Formation overlying the Upper Mountain Coal..
Burnley [SD 83 32] (South Lancashire).
0.9m maximum.
Base of mudstone-dominated unit of the Pennine Lower Coal Measures Formation resting on the Cannel Coal.
Capel Curig Volcanic Formation
CCV
Conformable on sandstones and/or mudstones of undivided Nant Ffrancon Group.
Northern and central Snowdonia.
Acid ash-flow tuff.
Up to 340m
At base of sandstones of Cwm Eigiau Formation.
Castle Of Cowie Member
CCW
At the base of the lowest metre-thick red siltstone above the Purple Sandstone 'Member'.
Medium-grained, quartzo-feldspathic sandstone interbedded with red siltstone and silty sandstone.
74 m thick.
At the top of the highest metre-thick red siltstone bed beneath the Brown and Grey Sandstone 'Member'.
Covehithe Clay Member
CCY
Crosswood Ash
CDA
Cushendall Formation
CDAL
Caddroun Burn Beds
CDB
Church Door Buttress Breccias
CDBB
Coed Caedyrys Coal (South Wales)
CDCA
Clod Coal (Coalbrookdale)
CDCC
Clod Coal (North Staffordshire)
CDCO
Caedavid Coal (South Wales)
CDDC
Cardingmill Grit Member
CDDG
The base is transitional over a few metres, but is generally taken at the base of the first thick bed of coarse grained sandstone that succeeds relatively thinly interbedded fine grained, cross-bedded sandstones and mudstones of the Burway Formation.
Welsh Borderlands, Shropshire, Church Stretton and the Longmynd area.
Massive to thick-bedded and cross-bedded coarse-grained sandstones, commonly micaceous and locally pebbly, with a few thin siltstone beds.
Usually 25-30 m, but may achieve 58 m locally.
Drawn at the relatively sharp conformable upward passage from coarse sandstones of the Cardingmill Grit to purple mudstones and siltstones of the Synalds Formation.
Cribyn Ddu Member
CDDU
Calders Member
CDE
The Redhall (Humbie) Marine Band defines the base of the member, the lowest of the Macgregor Marine Bands. This bed is up to 0.3m thick and in Edinburgh is contained within at least 13.8 m of generally tough, black and dark grey mudstones, the lowest 9m of which form the top of the underlying Gullane Formation (Chisholm and Brand, 1994, p.100) and assigned to the currently undefined Wardie Shales Member.
West Lothian; Midlothian (part).
The Calders Member comprises a succession of black to grey mudstones, grey siltstones and white, grey and pink sandstones with thin beds of grey argillaceous limestones and dolostone (cementstone), and algal-rich black to grey oil-shales with some lapilli-tuff beds. The strata are not disposed in readily recognisable sedimentary cycles, and almost all are of lacustrine and fluvial origins. The member includes the Dalmahoy Oil-Shale, Hailes Sandstone (with a maximum thickness of about 57m that was much worked in the past for dimension stone, and the Pumpherston Oil-Shale. A regionally persistent but thin (<1 m thick) algal dolostone has been recognised at Hopetoun and Queensferry.
The average thickness is 290m (Cameron and McAdam, 1978, fig.2), but it is estimated to reach 350m west of Edinburgh.
Defined as the base of the Burdiehouse Limestone (Mitchell and Mykura, 1962, p.67). This distinctive limestone, at the base of the overlying Hopetoun Member, is a lacustrine deposit, 6 - 9m thick, containing abundant fossilised ostracod, plant and fish remains and rare algal oncoliths.
Cadeby Formation
CDF
At base of dolostone or dolomitic siltstone, overlying organic-rich mudstone (Marl Slate) or where that is absent, Permian basal sands and breccias.
Crops out in Nottinghamshire, south Yorkshire, west Yorkshire and part of north Yorkshire. Thickens in subsurface to east. Dies out south of line from Nottingham to Grantham. Equivalent to Raisby Formation of Co. Durham.
Dolostone, grey to buff grey, commonly oolitic or granular, with subordinate mudstone, dolomitic siltstone and sandstone.
At upward transition (usually sharp) into Edlington Formation or, farther east in the subsurface, the Hayton Anhydrite.
Craig An Daimh Gravel Formation
CDGR
Sharp, undulating, erosional, unconformable contact with stony sandy clayey diamicton of the Suidheig Till Formation.
Cobble gravel with a sandy, silty,clayey matrix, clast-supported, very dense, containing clasts mainly of Devonian sandstones and siltstones, with some granite and psammite. Strong weathering profile developed with pelitic schist clasts decomposed.
Gradational contact with white clayey gravel of the Rehiran Cryoturbate Member of the Dalcharn Palaeosol Formation.
Clifton Down Group And Hotwells Group (Undifferentiated)
CDHO
Boundary is marked by the incoming of more massive oolitic and crinoidal rocks above the relatively unfossiliferous calcite-mudstones of the Clifton Down Group, or where present, the Middle Cromhall Sandstone.
Bristol and north Somerset area. Lateral facies change to west south Wales and Forest of Dean.
Hard dark grey crinoidal oolitic bioclastic limestone with interbedded dark grey shales and mudstones.
175 feet (54m).
Change to predominantly arenaceous sandstone facies of the Upper Cromhall Sandstone or the sub-Namurian unconformity.
Creag Dhubh Psammite Formation
CDHP
Top of the Torr na Truim Semipelite Formation, where predominantly schistose semipelite is overlain by the flaggy bedded, predominantly psammitic succession belonging to the Creag Dhubh Psammite Formation.
Southwest of Newtonmore, from Glen Banchor southwards to the Ericht-Laidon Fault
Grey flaggy quartzo-feldspathic psammite with micaceous psammite interlayers grading into micaceous pelitic tops, including muscovite and biotite. Psammites 10 to 40cm thick are common, thinner near the base; amalgamated psammites up to 6m thick are known. Semipelites/pelites are usually about 1cm thick but locally up to 20cm thick.
Base of the Creag na Sanais Semipelite Formation, where predominantly gneissose semipelite overlies the psammitic succession belonging to the Creag Dhubh Psammite Formation.
Cleveland Ironstone Formation
CDI
Downward transition from shaly mudstone with scattered sideritic nodules to siltstone or sandstone of the Staithes Sandstone Formation.
Cleveland Basin, North Yorkshire.
Mudstone, silty, argillaceous siltstone and silty sandstone with seams of sideritic and berthierine-ooidal ironstone, which occur typically at the tops of small scale sedimentary cycles.
At top of highest ooidal ironstone OR at top of row of hard sideritic nodules, succeeded by grey mudstone of the Whitby Mudstone Formation.
Clifton Down Limestone Formation
CDL
In the Bristol area taken at the sharp contact between the interbedded dolomite and calcite mudstones of the underlying Clifton Down Mudstone Formation and the basal sandy limestone of the Clifton Down Limestone Formation. The boundary needs further investigation. In Broadfield Down and the Mendip Hills it is taken at the incoming of calcite mudstones of the Clifton Down Limestone Formation above the oolitic and oolitic/bioclastic limestones of the Goblin Combe Oolite Formation and undivided Burrington Oolite Subgroup respectively.
Bristol [ST 60 74] area and Mendip [ST 50 53]. Passes laterally into the Hunts Bay Oolite Subgroup in the Monmouth and Chepstow area [ST 53 94].
Splintery dark grey calcite and dolomite mudstones, pale grey oolitic, dark grey bioclastic and oncolitic limestones and some mudstones. Scattered cherts and silicified fossils in lower half. Sandy limestone at base in Bristol area. Deposited in a barrier/back barrier/shelf lagoon setting.
266m in the Avon Gorge at Bristol, thinning northwards to 137m north of Bristol and thinning southwards to 150-200m in the Mendip Hills.
Taken at the top of the last calcite mudstones of the formation, above which occur the dark grey crinoidal and bioclastic limestones and paler oolitic limestones of the Oxwich Head Limestone Formation.
Carlingford Limestone Group
CDLM
Cadell's Parrot Coal
CDLP
Cadgers Loan Sandstone
CDLS
Glasgow-Airdrie area, Central Coalfield.
Sandstone with pebbly bands and garnets.
c.90 feet. (c.100 feet near Fallin, Cowie, and Carbrook; 155 feet in Doll Mill Bore).
Clifton Down Mudstone Formation
CDM
Taken at irregular erosive contact of dolomite and calcite mudstones and mudstones of the formation above the clay palaesol of the underlying Gully Oolite Formation.
Bristol [ST 60 74] area and Broadfield Down [ST 50 65]. Passes northwestwards into the Llanelly Formation of South Wales and southwards into the Burrington Oolite Subgroup of the Mendip Hills.
Thin- to medium-bedded poorly fossiliferous, calcite mudstones, dolomite mudstones and mudstones. A unit of crinoidal and oolitic limestones occurs in the middle of the Formation, and a 15m-thick unit of oolitic and crinoidal limestone occurs in the upper part of Formation [said to correlate with the Goblin Combe Oolite Formation of Broadfield Down, but this is not proven]. Basalt, tuff and ashy limestone are present in the middle of the Formation on Broadfield Down. Carbonates of the Formation were deposited mainly in a back barrier setting.
60m at Bristol and northern Broadfield Down thinning to a feather edge on the southern side of Broadfield Down.
In the Bristol area the upper boundary is taken at the sharp contact between the interbedded dolomite and calcite mudstones and mudstones of the formation and the basal sandy limestone of the overlying Clifton Down Limestone Formation. The boundary needs further investigation. In Broadfield Down the upper boundary is taken at the incoming of ooidal limestones of the Goblin Combe Oolite Formation above the interbedded dolomite and calcite mudstones and mudstones of the Clifton Down Mudstone Formation.
Chemiss Den Marine Bed
CDMB
Cwm Degwel Mudstone Member
CDMD
Caradoc (?Onnian).
Conformable with the sandstones of the main part of the Dinas Island Formation.
Interbedded dark grey to black turbiditic and laminated hemipagic mudstones.
Overlain by burrow-mottled mudstones of the Nantmel Formation, the boundary possibly represents a non-sequence.
Calder Mudstone Member
CDMM
Charmouth Mudstone Formation, Dyrham Formation And Marlstone Rock Formation (Undifferentiated)
CDMR
Charmouth Mudstone Formation, Dyrham Formation, Marlstone Rock Formation And Whitby Mudstone Formation (Undifferentiated)
CDMW
Cairndinnis Plug
CDNIS
Criffel-Dalbeattie Pluton
CDPL
Intrusive margin of the pluton against surrounding contact metamorphosed rock.
The pluton is exposed in south-west Scotland. It extends from Auchencairn Bay [NX 83 52] in the south-west to Mabie Forest [NX 94 71] in the north-east.
An asymmetrically zoned intrusive body with an inner zone of medium- to coarse-grained porphyritic granite and an outer zone of foliated granodiorite. Both zones are intruded by thin aplite veins. A series of microdiorite dykes are linked genetically to the intrusion of the pluton.
Modelling of gravity data indicates that it extends to a depth of 9km. (Lintern, B C and Floyd, J D. 2000; Bott and Masson Smith, 1960).
Carn Dubh Quartzite Member
CDQU
Position where dominantly quartzite succession replaces the dominantly graphitic succession of the Blair Atholl Subgroup.
Northern part of Glen Shee district (Sheet 56W).
Clean white pebbly quartzite with cross-bedding.
To 200m
Top of clean white thickly bedded quartzites below the more thinly bedded, cream and less clean quartzites of the Bad an Loin Member.
Cheddar Limestone Member
CDRL
Taken at the appearance of dark limestones of the Cheddar Limestone Member above the ooidal and ooidal/crinoidal limestones of the Burrington Oolite Subgroup. Boundary equates with local base of the Clifton Down Limestone Formation.
Chedder [ST 48 54] area, central Mendip. Passes laterally into rocks of the Clifton Down Limestone Formation in all directions.
Dark grey crinoidal and splintery limestones, with chert in the upper part.
30-37m in the Cheddar area.
Taken at the incoming of pale grey ooidal limestones of the Cheddar Oolite Member above the dark limestones of the Cheddar Limestone Member.
Cheddar Oolite Member
CDRO
Taken at the incoming of pale grey ooidal limestones of the Cheddar Oolite Member above the dark limetones of the Cheddar Limestone Member.
Chedder [ST 48 54] area, south-central Mendip. Passes laterally into the Clifton Down Limestone Formation in all directions.
Pale grey ooidal limestone.
36 to 60m in the Cheddar area, south-central Mendip.
Taken at the incoming of dark grey fine-grained limestone, rich in corals, of the undivided Clifton Down Limestone Formation, above the pale ooidal limestone of the Cheddar Oolite Member.
Cheddleton Sandstones
CDS
Staithes Sandstone Formation And Cleveland Ironstone Formation (Undifferentiated)
CDST
Coire Dubh Breccias
CDUBH
Coed Duon Volcanic Formation
CDVO
In the type area, the Formation rests conformably upon pale grey, thin- to thick-bedded arkosic sandstone of the Ffairfach Grit Formation. The lower boundary is not exposed but is taken at the incoming of green, tuffaceous beds, constrained near the summit of Coed Duon.
The Coed Duon Volcanic Formation is restricted to the summit and southeastern slopes of Coed Duon, located around 8km eastnortheast of the town of Llandeilo in Carmarthenshire.
The Coed Duon Volcanic Formation comprises around 60m of green, fine-grained felsic tuff with abundant mafic crystal and rhyolitic lithic clasts, locally overlain by around 15m of white-weathering, fine-grained, pink rhyolite.
Around 75m
The Formation is conformably overlain by buff-weathering, thinly interbedded sandstone, siltstone and limestone of the Llandeilo Flags Formation. The upper boundary is not exposed but is taken at the top of the last outcrop of pale rhyolite or tuff.
Silts And Clays Of 25-Foot Drift Of Vale Of York
CDVY
Silt and clay. [Generic description].
Coldwell Formation
CDW
Conformably overlies the Birk Riggs Formation.
Occurs towards the base of the Windermere Supergroup and crops out as a narrow strip across the southeastern part of the Lake District from Millom to east of Windermere. It also occurs south of the Kirkby Fault in Furness, and in the Howgill Fells.
Comprises a lower unit of heavily bioturbated, calcareous siltstone with subordinate laminated muddy siltstones, which is the Randy Pike Member, overlain by laminated hemipelagite and then another unit of calcareous siltstone with laminated muddy siltstone in the upper part , which is the High Cross Member.
From 55m to 80m
Conformably overlain by the Wray Castle Formation.
Cille No.1 Coal (South Wales)
CE1C
Cille No.2 Coal (South Wales)
CE2C
Cille No.3 Coal (South Wales)
CE3C
Cille No.5 Coal (South Wales)
CE5C
Cumbrian Esk Alluvium Member
CEAL
Sharply erosional, unconformable on all older Quaternary deposits (particularly till at the Type Section) and on bedrock.
1:50k Sheet 37 Gosforth, south of Muncaster Fell.
Silts, clays, sands and gravels, underlying the floodplains of the Cumbrian Esk catchment. At the Type Section the top part of the alluvial sequence coarsens downwards from brown clay into sand.
11.58m at the Type Section, but probably typically 5 to 10m thick in the type area.
The ground surface, or overlain by peat of the Blelhem Peat Formation, or overlain by blown sand of the Drigg Point Sand Formation.
Ceardaich Sand And Gravel Formation
CEAR
Early Devensian to Late Devensian
Unconformable on bedrock; erosional on Pattack Till Formation; gradational on Linn of Pattack Silt Formation.
Sand and gravel; clasts mainly psammite, with granodiorite, granite and porphyry; large scale deltaic cross-bedding common.
Unconformable or glacitectonic contact with Ardverikie Till Formation.
Cennen Formation
CEB
Carlyle Beds
CEBS
Cooper Eye Coal (Northumberland)
CEC
Srath Na Creitheach Volcaniclastic Rocks (Skye Central Complex)
CECH
Chale Clay Member
CECL
Cille Coals (Undifferentiated) (South Wales)
CECU
Castle Eden Fissure-Fill Formation
CEDN
Unconformable contact with underlying fractured limestones and dolostones of the Zechstein Group (formerly Magnesian Limestone). The fissures are generally linear, vary from 1 to 7m wide and extend up to 25m vertically through the limestone cliffs to rockhead, locally along faults. Other fissure fills are cylindrical in shape. Fissure walls commonly bear subvertical slickensides resulting from compaction and many of the fragments are striated and polished.
Coast of County Durham.
Breccia formed of limestone and dolostone together with sparse clasts of red mudstone filling subvertical karstic fissures in the limestone and dolostones of the Zechstein Group (formerly Magnesian Limestone). Two distinct units occur. The lower "unfossiliferous fissure fills" are likely to be either Mesozoic or early Palaeogene in age as they are similar to evaporite dissolution breccias that occur elsewhere within the Permian limestones. The upper "fossiliferous fissure fills" contain clay in addition to limestone debris that has yielded assemblages of partially pyritized organic material including peat, seeds, tree trunks, ostrocods, mammalian bones and freshwater molluscs. The remains of over 100 species of plant have been identified from lower parts. Of this "Castle Eden Flora" 64% of the species no longer grow in Britain, or are extinct. This flora suggests an Early Pleistocene age, which is supported by the identification of Mammuthus meridionalis, an elephant that was common in Europe in the Early Pleistocene up to the Cromerian. Sparse glacial erratics of supposed Scandinavian origin have been found in fissure fill deposits south of Limekiln Gill [NZ 4776 3813].
Channelled erosional, unconformable contact with overlying limestone-rich gravel of the Limekiln Gill Gravel Formation or planar subhorizontal, unconformable contact with dark grey stony sandy silty clay diamicton of the Blackhall Till Formation.
Cromerian Complex Interglacial 2 To Elsterian Deposits, Undifferentiated (Offshore)
CEDU
Cromerian Complex Interglacial 2 to Elsterian.
Cefn Einion Formation
CEF
Cement Fireclay
CEFY
Central Coalfield area, Midland Valley of Scotland.
Cefn Coch Grit Member
CEG
Conformable within the silty mudstones that form the main part of the Gamlan Formation.
Harlech area, North Wales.
Coarse-grained, quartzose, thick-bedded turbiditic sandstones.
Conformable within the upper part of the Gamlan Formation, but may locally form the top of the latter at its junction with the overlying flaggy sandstones and mudstones of the Mawddach Group.
Central Highland Migmatite Complex
CEHI
Cwm Eigiau Formation
CEI
Late Soudleyan to Longvillian
Conformably overlies the rhyolitic ash-flow tuffs of the Capel Curig Volcanic Formation (Llewelyn Volcanic Group) or, where the latter are not present, it overlies mudstones of the Nant Ffrancon Subgroup.
Not yet provided.
Sandstones with siltstones and silty mudstones, tuffs and tuffites.
Overlain by ash-flow tuffs of the Lower Rhyolitic Tuff Formation (Snowdon Volcanic Group) and (on the Lleyn Peninsular) the Allt Fawr Rhyolitic Tuff Formation.
Cwm Eigiau Formation And Lower, Middle And Upper Crafnant Formations (Undifferentiated)
CEICV
Cowdenbeath Ell Coal
CELL
Cromerian Complex Interglacial 2 To Elsterian Mud And Sand, Interbedded (Offshore)
CEMAS
Carnbroe Marine Band (Central Coalfield)
CEMB
Cemetery Coal (Burnley)
CEMC
Cefnyrhendy Oolite Member
CEO
Gradational junction with the underlying skeletal, peloidal and oolitic packstone/grainstones of the underlying High Tor Limestone Formation. Base taken at incoming of a predominantly oolitic grainstone sequence.
Northern part of the Vale of Glamorgan [ST 00 74]. Passes southwards into upper part of High Tor Limestone Formation. Relationship to coeval Goblin Oolite Formation in the Bristol Mendip [ST 50 65] area, unknown.
Massive to thick-bedded, locally cross-bedded ooid grainstones. Palaeokarstic surface at the top. Locally overlain by a thin clay palaeosol. Dolomitized along the southeast crop of the South Wales Coalfield. Interpreted to have been deposited in a barrier environment.
13m in the northern Vale of Glamorgan, thickening southwards to 40m in the central part of the Vale of Glamorgan.
Taken at top of the clay palaeosol capping the Formation, or the top of the underlying palaeokarstic surface if the clay is absent. The palaeosol/palaeokarst is sharply overlain by a bed of grey calcareous mudstone, overlain by thin- to medium-bedded, fine- to coarse-grained crinoidal skeletal packstones of the Argoed Limestone Member of the Cornelly Oolite Formation.
Capledrae Parrot Coal
CEPA
Cwm Eigiau Formation And Pen-Ychain Rhyolitic Complex (Undifferentiated)
CEPC
Cephalopod Bed
CEPH
Cephalopod Limestone
CEPL
Cerig Formation
CER
Either disconformable on earlier Llandovery or Ashgill or conformable with Henfryn Formation. In latter case junction is gradational but taken at the base of the first thick mudstone bed above the pebbly mudstones, conglomerates and sandstones of the Henfryn Formation.
Grey to green mudstones with dark burrow mottles. Units of dark laminated hemipelagite common in lower half of formation in slope settings, rare to absent on shelf. Sparse thin sandstones. NOTE: At Llandovey (type area) it is underlain by either the Derwyddon Formation or the Wormwood Formation and overlain by the Gwernfelen Formation. In the Rhayader district it overlies the Henfryn Formation or rests disconformably on earlier Formations. It is overlain by either the Dolfawr Mudstones or the Builth Mudstones.
Either at the base of the incoming of thinly interbedded laminated and burrowed mudstones of the Dolfawr Mudstones, or at the base of the incoming of pervasively laminated mudstones of the Builth Mudstones.
Cerdic Formation
CERD
Ceres Thick Coal
CERES
Coetmor Sandstone Member
CES
Cefngarreg Sandstone Formation
CESA
Cromerian Complex Interglacial 2 To Elsterian Sand (Offshore)
CESND
Coire Eilde Tuffs
CET
Cethings Sandstone Member
CETS
Ceunant Slates
CEU
Cumbrian Esk Valley Formation
CEVY
Mainly Holocene (but terraces may extend from Lateglacial).
Sharply erosional, unconformable on all older Quaternary deposits (particularly till) and bedrock.
Sands, gravels, silts and clays forming river terraces and underlying floodplains of the Cumbrian Esk catchment.
11.58m thick at Partial Type Section, but probably typically 5-10m thick in the type area.
Cefn Rock
A sharp contact with underlying measures of the Pennine Middle Coal Measures Formation, which overlies an unnamed coal in its type area.
Denbighshire Coalfield (SJ 30 50).
Massive, quartzose sandstone with subordinate and impersistent beds of mudstone and coal.
Up to 37 m thick.
Contact with overlying measures of Pennine Middle Coal Measures Formation.
Chillesford Sand Member
CFB
Sand, fine- to medium-grained, with clay drapes; ripple-laminated. [Generic description: academic papers and BGS Memoirs].
Caerfai Bay Shales Formation
CFBS
Conformably overlies the St Non's Sandstone Formation.
1:50,000 Sheet 209 (St Davids) and adjacent Sheet 210, Pembrokeshire.
Purplish red mudstones with some siltstone beds and laminae, cross-bedded in lower part and with units of crystal tuff in the upper part.
15m
Passes upwards conformably by increase in grain size into the Caerbwdy Sandstone Formation.
Chillesford Clay Member
CFC
Clay, pale- to medium-grey, with scattered laminae of silt or fine-grained sand. [Generic description: academic papers and BGS memoirs].
Chapelhall Lower Fireclay
CFCL
Coal - 1"; Fireclay - 6' 3"; Fireclay fakey - 6"; Fireclay dark, - 4". Total 7' 2".
7'1" Lateral variations 2.1 metres.
Carrock Fell Complex
CFCO
Carrock Fell, Cumbria.
Layered cumulate gabbros and quartz-gabbros, forming the Mosedale Intrusions which have a calc-alkaline/transitional to tholeiitic composition, microgabbro, microgranite with apatite-bearing iron-rich microdiorite, micromonzodiorite and microgranite zones forming the tholeiitic Carrock Intrusions, quartz-phyric rhyolite of the Harestones Rhyolite, and a microgranite named the Iron Crag Microgranite. Several component intrusions have Ordocician radiometric ages (Mosedale Gabbros, Carrock intrusions).
A near-vertical, sheet-like mass of about 8.5 sq. km emplaced at the junction between the Skiddaw Group and the Eycott Volcanic Group.
Carrock Gabbro-Microgranite Intrusions
CFCOC
A microgabbro, cutting the main mass of micrographic microgranite, a narrow marginal zone of apatite-bearing, iron-rich gabbro, microdiorite, micromonzodiorite and microgranite. Radiometric age: microgranite 452.4 +/- 4.1 Ma (U-Pb, zircon) (Millward, D and Evans, J A, 2003.)
A near-vertical sheet like mass emplaced with the Carrock Fell Complex.
Harestones Rhyolite
CFCOH
A quartz-phyric rhyolite. Radiometric age: 419 +/- 4 Ma (Rb-Sr, whole rock) (Rundle, 1979); considered by many authors including Millward (2002) to have been re-set.
A near-vertical mass emplaced within the Drygill Shale Formation at the northern margin of the Carrock Fell Complex.
Iron Crag Microgranite
CFCOI
Feldspar-phyric, micrographic microgranite.
A near-vertical sheet, emplaced along the Roughton Gill Fault, at the western margin of the Carrock Fell Complex.
Mosedale Gabbros
CFCOM
Layered cumulate gabbros, with zones rich in xenoliths a zone of poikilitic leucogabbro, gabbro and hypersthene gabbro, cut by biotite quartz-gabbro. Radiometric age 468 +/- 9 Ma (K-Ar whole rock) (Rundle, 1979). Geochemically similar to the Eycott Volcanic Group, with which it is considered to be associated (Hunter, 1980).
A near-vertical sheet-like mass, emplaced at the junction between the Skiddaw Group and the Eycott Volcanic Group.
Chapelhall Upper Fireclay
CFCU
Channel-Fill Deposits
CFD
Sand and gravel, with silt and clay; infill of pre-existing channel. [Generic description: 1:50 k map margins].
Chalfield Oolite Formation
CFDO
South of Badminton [ST 78 83] the base is a sharp upward change from grey calcareous silicate mudstone with subordinate argillaceous limestone beds of the Fuller's Earth Formation into ooid-limestone or coarse-grained shelly ooidal limestone ("Grickstone Beds"), locally with limestone pebbles. North of Badminton, the base rests sharply on fine-grained ooid-limestone of the Athelstan Oolite Formation, which is commonly capped by a hardground (separated on sheet 251 (1970 edition) and known as "chinastone" or "Coppice Limestone" (Cave, 1977)), or locally where that formation is absent, on the underlying fine-grained slightly argillaceous limestone of the Tresham Rock Formation.
Outcrop: Wellow, 7km southwest of Bath, where the Chalfield Oolite passes laterally into the Frome Clay, northeast to Kemble, Gloucestershire, where it passes into the Signet Member (White Limestone Formation). The formation thins progressively and substantially northeast of Badminton, mainly due to erosion of the upper beds beneath the Forest Marble Formation, but also possibly through lateral passage into the Athelstan Oolite Formation. Subcrop: might be present at depth in the Weald (Wyatt and Cave, 2002).
Ooidal grainstone, predominantly pale grey and pale yellow to white fine- to coarse-grained, with variable bioclastic content, in medium to thick beds; cross-bedded in parts; bioturbated in parts. A median unit of pisoidal, bioclastic limestone (Twinhoe Member) is developed south of Corsham. The generally moderately bioclastic ooid-limestones below (Combe Down Oolite Member) are fine- to coarse-grained, and those above (Bath Oolite Member) are medium- to coarse-grained ooid-limestones. Where the Twinhoe Member is not recognisable, the Combe Down and Bath Oolite members might not be distinguishable. The uppermost beds of the formation include lenticular masses of coralliferous limestone (?Corsham Member). The basal beds from Tormarton north to Hawkesbury Upton comprise a unit of coarse-grained shelly ooidal limestone ("Grickstone Beds"). These resemble the basal limestone of the Forest Marble Formation and north of Little Badminton where the overlying Combe Down Oolite beds are absent they cannot be reliably distinguished. From Westonbirt northeast to Kemble the formation comprises pale bioclastic ooid-limestone, and the strata cannot be assigned to members, apart from, locally, the Corsham Member.
25 to perhaps 36m in the type area, thins northwards to less than 2m at Kemble. 35.2m in the Biddestone Borehole.
A non-sequence, taken above the highest pale coloured generally moderately bioclastic ooid-grainstone, either erosive or marked by a bored and/or oyster-encrusted hardground, overlain by grey or brown variably sandy bioclastic limestone, variously ooidal or shelly, or locally by calcareous silicate-mudstone (all of the Forest Marble Formation).
Cnoc An Fhithich Banded Semipelite Formation And Drumchastle Pale Limestone Formation (Undifferentiated)
CFDR
Craig-Y-Ffynnon Formation
CFF
Canonbie Five Foot Coal
CFFC
Chilfall Zoophycus Flint
CFFL
Clintsfield Grit
CFG
Feldspathic sandstone, locally flaggy, with several thin coal seams.
c.14m
Cefn Hir Member
CFH
Mafic and felsic tuffs and tuffites with interbedded mudstones and rare pillowed basalts.
To 90m
Conformable within the mudstones of the Cregennen Formation and locally overlain conformably by the mafic lavas and tuffs of the Llyn y Gafr Volcanic Formation.
Cribbwr Fach Coal (South Wales)
CFHC
California Clayband Ironstones
CFI
Common Flat Limestone
CFL
Uppermost limestone in the Lynebank Member of this area.
Clintsfield Coal
CFLD
Cefn Mawr Limestone Formation
CFML
Upper palaeokarstic surface/palaeosol of the Loggerheads Limestone Formation; base of lowest sequence of thinly interbedded, dark grey limestone and mudstones of the Cefn Mawr Limestone Formation.
Crops out on Anglesey [SH5080] and the Great Orme [SH7483] (Llandudno) in northwest Wales, in its type area to the east of the Clwydian Range [SJ2063], and at Llangollen [SJ2345] and near Oswestry [SJ2825] in northeast Wales. Also in the Corwen Outlier [SJ0543].
Thinly interbedded dark grey argillaceous limestones (wackestones and packstones) and mudstones with intercalated thick-bedded to massive, pale shelly limestones (packstones and grainstones) and lenticular, cross-bedded, coarsely crinoidal limestone (rudstone) bodies. Lithologies are arranged in cyclic sequences. Limestones at the top of each cycle commonly display calcrete and palaeokarstic features locally overlain by bentonitic clay palaeosols. Thin chert beds and nodules in upper part; rare sandstone beds. The Cefn Mawr Limestone Formation records principally Brigantian platform carbonate deposition on the North Wales Dinantian shelf. Each cyclic sequence records a shoaling upwards unit developed in response to transgressive and regressive movements in sea level. Many regressions culminated in emergence of the platform surface and formation of calcrete and karstic dissolution features. The sequences of thinly interbedded dark grey limestone and mudstone, diagnostic of the Formation, record deposition during marine transgressions, which repeatedly established deeper platformal conditions than ever prevailed during deposition of the preceding and similarly cyclic Loggerheads Limestone Formation.
40 to 275m
Where overlain by the Minera Formation, the top is taken at the base of the lowest sandstone within the latter; where overlain by the Pentre Chert Formation, the top is taken at the disconformable base of the latter.
Cefn Formation
CFN
Clee Sandstone Formation
CFO
Originally described as "Lower Devonian, Breconian". Emsian is given here as the closest approximation to the term "Breconian".
Colla Firth Permeation And Injection Belt
CFPI
Carn Fadryn Quartz Microdiorite
CFQM
Quartz microdiorite with quartz and plagioclase phenocrysts, apatite and zircon, in a fine-grained highly altered groundmass.
Cribbwr Fawr Coal (South Wales)
CFRC
Chwefri Formation
CFRI
Cefn-Y-Fedw Sandstone Formation
CFS
?Brigantian to Marsdenian
Drawn at base of sandstone and conglomerate of Cefn-y-Fedw Sandstone Formation where it rests conformably on sandy limestone of the Minera Formation or Cefn Mawr Limestone Formation. Intertongues on Halkyn Mountain with Pentre Chert Formation.
Northeast Wales between Halkyn Mountain [SJ2270] and Oswestry [SJ2826]. Three sandstone leaves, interpreted to belong to the Cefn-y-fedw Formation, are proved in the Blacon East No.1 Borehole (SJ36NE/23).
White and pale grey, fine- to medium-grained, planar- and cross-bedded, quartzose sandstones, pebbly sandstones and thin beds of quartz conglomerate; with units of calcareous sandstone, sandy limestone, chert and siliceous mudstones in lower part; locally thick beds of siltstone and mudstone, and thin, impersistent coal seams. Lithologies are commonly arranged in coarsening upwards cycles. The Formation records fluviodeltaic deposition across the former North Wales Dinantian platform. The cyclic arrangement of lithologies represent progradational sequences formed in response to contemporary movements in marine base level. The sandstones and conglomerates record the advance of delta distributary channels and mouth bars across finer pro-delta and interdistributary mud and silt facies.
To 585m
Highly diachronous, but taken at conformable contacts between sandstone of the Cefn-y-Fedw Sandstone Formation and mudstones of the Bowland Shale Formation. However, the two formations exhibit complex intertonguing.
Crayford Silt Member
CFSI
Overlies Interglacial gravel and sand
Crayford, and Cray and Darent valleys.
A typical "brickearth" type deposit.
Generically it varies from silt to clay, commonly yellow-brown. Origin uncertain. Commonly includes a high percentage of wind-blown, silt-sized quartz (possibly loess). Locally represented bt yellow to buff sand with shells at base passing up through brown, bedded sand with sandy silt to grey clay and shelly sand at the top.
2.4m (average)
At surface or overlain by floodplain gravel
Camp Fauld Till Formation
CFTI
?Wolstonian.
The unit rests on, and locally grades down into, and incorporates rafts of glauconitic Moreseat Sandstone Formation (Lower Cretaceous).
Sandy, silty diamicton (till), very stiff, grey (2.5Y N5) to very dark grey (7.5YR N3), massive to crudely horizontally bedded with sparse pebbles. Clast lithologies comprise mainly rounded quartzite and flint, with lesser amounts of subangular grey granite, mafic igneous, red sandstone and soft grey siltstone. The matrix is a micaceous sandy silt and clay; clay mineralogy is largely kaolinite, illite-smectite and minor glauconite.
At least 2m
Sharp, unconformable contact with compressed humified peat and organic sand of the Berry Peat Bed, where the upper part of the till is mottled (weathered).
Confusion Member
CFU
Rests on the Myoch Formation in Penwhapple Burn. The base of the Confusion Member (= base of Shalloch Formation) is there marked by the upward change from red and green mudstone to sandstone/siltstone flysch.
Grey flaggy greywacke sandstone and siltstone flysch.
c.42m
Succeeded by a 1.1m leaden-grey mudstone bed that marks the base of the Shalloch Formation at the coast, where this mudstone rests directly on the Mill Formation. The Confusion Member is therefore the lateral equivalent of the Mill Formation at the coast, but of different (Shalloch type) facies.
Cnoc Fyrish Conglomerate Formation
CFY
Clypeus Grit Member
Parkinsoni Zone to Zigzag Zone.
Upward change from shelly coarsely shell-fragmental limestone (Upper Trigonia Grit Member), to limestone as described under Lithology. Commonly a non-sequence, marked by a hardground, though locally appears to be transitional. Where Upper Trigonia Grit Member absent, boundary is hardground capping Aston Limestone or Birdlip Limestone formations, or unconformity on older beds.
Horton, northeast Avon (Green, G W, 1992; see also Barron, A J M, et al, 1997, p.281, figs. 4 and 5), through Gloucestershire Cotswolds to north Oxfordshire west of a line from Hook Norton to Tackley where overlapped by Great Oolite Group (Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D, 1987, fig.26).
Pale grey to pinkish brown fine- to coarse-grained ooidal, peloidal and shell-detrital packstone to grainstone, with large orange-skinned peloids/pisoids and aggregate grains; common whole shells especially in upper part. Characteristic fauna includes the large echinoid Clypeus ploti Salter, large myacean bivalves and terebratulid brachiopods (Stiphrothyris). From Stroud southwards, includes coral-rich limestone ('Upper Coral Bed') at base.
Typically 10 to 12m. Type section 10.5 to 12m. Maximum c.16m (Colesbourne area).
Upward change to mudstone (Fuller's Earth Formation) in southwest or into fine- to medium-grained ooidal grainstone (Chipping Norton Limestone Formation) in northeast. Generally transitional, but locally marked by a hardground (Sumbler, M G, Barron, A J M and Morigi, A N, 2000).
Creg Agheash Formation
CGA
Stratigraphical with the Lonan Formation.
Sandstone [quartz arenite], pale grey, thin to thick-bedded with interbedded laminated mudstone and siltstone.
Up to 750 m thick.
Stratigraphical with the Maughold Formation.
Central Grampian (Albion) Glacigenic Subgroup
CGAG
Unconformable contact with bedrock.
The Grampian Highlands bounded by the Great Glen and Moray Firth to the north, the Cairngorms and Gaick Plateau to the east, Strathmore to the south, and including the Inner Hebrides lying to the south of Mull.
Suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts predominantly of micaceous psammite, mica schist, granite and granodiorite, including sandy diamictons (till), sand, gravel, silt and clay. Mainly deposited from ice that radiated away from an ice-divide centred over Rannoch Moor.
Unconformable contact with units of the Central Grampian Glacigenic Subgroup.
Carraig Artair Member
CGAR
Carmill Gas Coal
CGAS
Craigs Breccias
CGB
Creag Buidhe Semipelite Formation
CGBH
Not exposed - interbanded with psammites of Dava Succession, undifferentiated.
Central Highlands of Scotland, SE of Loch Ness. Strathnairn to Slochd area.
Gneissose to migmatitic semipelite.
Conformable contact with structurally overlying Flitchity Psammite - no way-up criteria.
Craig Coals
CGC
Creggan Chalk Formation
CGCK
Campanian. Lower part of Offaster pilula Zone.
Point in the succession where there is a sudden increase in Inoceramus fragments. At Creggan this occurs 0.23m above the Oweynamuck Flint Band within the top of the Cloghastucan Chalk Formation.
North Antrim and East Antrim basins and the Southern Upland area. Oversteps onto the Highland border area and a limited northern part of the Londonderry Shelf.
Limestone (chalk), with common Inoceramus fragments (up to 20%) and many small burrow-fill flints scattered throughout. The upper part contains several green-coated pebble horizons that coalesce towards the basin margins to form a single conspicuous hardground with rolled and mineralised fossils most notably belemnites and echinoid steinkerns. Glauconitic in marginal overlap facies where the uppermost beds/surfaces are attenuated, gritty, glauconitic and algal-topped (stromatolitic).
3.45 m at the type locality.
Taken at the highest of several green-coated chalk pebble beds within the Inoceramus-rich limestone. This unit is termed the Bendoo Pebble Bed (of member? status) in the North Antrim Basin. Overlain by the Boheeshane Chalk Formation.
Congo Coal (Dungannon)
CGCL
Cefn Glas Coal (South Wales)
CGCO
Carghidown Formation
CGD
'Lower' (i.e. Northern boundary) - gradational from Kirkmaiden Formation.
Greywackes (beds dominantly less than 0.5 metres thick) with interbedded mudstones including some red mudstone beds. Includes few thicker massive arenite beds to east. Distinguished from 'underlying' Kirkmaiden Formation by presence of red mudstone beds. Distinguished from overlying Riccarton Group by presence of red mudstone beds and absence of dark grey finely laminated siltstone beds.
c 4000 metres section of vertical strata but some folding and locally intense faulting renders accurate assessment of stratigraphical thickness impossible.
Upper - faulted contact with Riccarton Group at Burrow Head (NX 4528 3414).
Cul Nan Gad Pluton
CGDI
Central Grampian Glacigenic Subgroup
CGDR
The Grampian Highlands as far as Strath Spey, the Cairngorm Mountains and Gaick Plateau to the east, including the Inner Hebrides to the south of Mull.
Diamictons, glaciofluvial sands and gravels and glaciolacustrine silts deposited by ice that (mainly) radiated out from a centre over Rannoch Moor. Clasts mainly derived from Central Highland Migmatite Complex and Caledonian igneous rocks.
Generally 5-10m, but locally 30m or more.
Craiganee Formation
CGE
Colwall Gelifluctate Formation
CGEL
Placed at junction of Beds 6 and 7 in augerholes at Colwall, where stony clay of the Colwall Gelifluctate overlies sandy silt/clay of the Cradley Silts (Barclay, et al, 1992).
Cradley - Glynch Brook Valleys in Mathon - Colwall area, Herefordshire.
Stiff, mainly yellow-brown gravelly silty clay or clayey silt with angular clasts of local lithologies.
Up to c.2 metres.
Not generally seen, but placed at junction with overlying younger solifluction or alluvial deposits.
Cwmcringlyn Formation
CGF
Creag Nan Gall Granodiorite
CGGD
Craigleith Sandstone
CGH
Status uncertain, but likely to be erosive on underlying argillaceous and arenaceous rocks of the Gullane formation.
Only known for certain in the Edinburgh area.
An off-white, typically fine-grained, siliceous sandstone, often thickly bedded with trough cross-bedding, and a little mica or carbonaceous material, famous as a building stone.
Up to 105m thick, in the City of Edinburgh.
Transitional by upward fining into non-marine siltstone and mudstone of the Gullane Formation, the Craigleith Marine Band lies a little further above.
Clogherny Member
CGHY
Conformable with normal Glenelly Formation schist.
Glenelly, Co.Londonderry, Northern Ireland.
Off-white quartz mica schists and flaggy medium grained to gritty quartzose psammites.
c.40m
Cayton Gill Shell Bed
CGI
Sharp contact between sandstone bed at the base of the unit and the underlying siltstone.
Present in the Harrogate, Leeds, Masham and Pateley Bridge areas.
Silty mudstone, calcareous and siliceous, shelly with beds of siltstone and sandstone.
3.54m in type section, 0 - 16m elsewhere
Sharp contact between fossiliferous sandstone and the overlying mudstone.
Collin Glen Formation
CGL
Creag Liath Psammite
CGLH
Typically a shear zone with structurally underlying striped semipelites of the An Stac Semipelite and Psammite.
Central Highlands of Scotland. Glen Banchor - Kincraig area.
Interbanded gneissose psammite, siliceous psammite with subordinate micaceous psammite and semipelite. Distinctive porphyroclasts of K-feldspar common.
Unconformity / stratigraphical break with overlying Grampian and Appin Group rocks.
Crag Limestone
CGLM
Parts of North Yorkshire and Northumberland (Limedale, Teesdale, Weardale, East Allendale and westwards to West Allendale and the Alston district.
Dark grey, fine-grained limestone; might pass westwards into dark ferruginous shelly sandstone (Lexique Stratigraphique).
To c.2m
Conglass Sandstone Formation
CGLS
Sedimentary junction with Raebeg Sandstone Formation, not exposed.
Immediately north-east of the Conglass Water in the north-east part of Tomintoul ORS outlier, upper Banffshire; a 50 km2 outlier, 15 x 5 km in extent, that is totally separated from; other ORS outcrops of the north-east Grampian area.
Sandstone, grey to greenish grey, massive to flaggy, few micaceous partings, cross-bedded, with beds of green siltstone. Siltstone also occurs as rip-up clasts in sandstone. Some channels with pebbly base.
ca 100m
Not known, upper part of formation removed by erosion.
Craigleith Sill
CGLTH
Cambuslang Marble
CGM
Creag Meagaidh Psammite Formation
CGMG
Sharply transitional - marked by incoming of flaggy psammites above semipelite-psammite interbeds of the Ardair Semipelite Formation.
Southern Monadhliath Mountains: Glen Roy - Laggan - Glen Banchor districts.
Flaggy to blocky feldspathic and micaceous psammites. Minor semipelite interbeds and calc-silicate rock lenses. Rare feldspathic quartzite.
500m - 765m maximum.
Sharply transitional into overlying fissile, schistose semipelites of the Clachaig Formation.
Cairngorm Granitic Suite
CGMGR
Creag Mhor Limestone Member
CGML
Creag Nam Ban Psammite Formation
CGNB
Cairngorm Pluton
CGOM
Cairngorm Pluton, Phase 1
CGOM1
Cairngorm Pluton, Phase 2
CGOM2
Cairngorm Pluton, Phase 3
CGOM3
Cairngorm Pluton, Phase 4
CGOM4
Cairngorm Pluton, Phase 5
CGOM5
Cairngorm Pluton, Phase 6
CGOM6
Carn Gorm Pegmatite Suite
CGPEG
Cairn Gibbs Psammite Formation
CGPS
Boundary placed arbitrarily at base of thick green bed unit that separates the dominantly psammitic Cairn Gibbs Formation from the underlying more varied Mount Blair Formation.
Eastern boundary of Sheet 56W (Glen Shee) west to Strath Ardle.
Schistose psammite and gritty psammite with minor units of phyllitic to schistose pelite.
Not seen in Glen Shee district.
Carnedd Y Filiast Grit Member
CGR
At base of sandstones forming top part of the Marchlyn Formation.
Northern Snowdonia.
Coarse-grained massive quartzose and pebbly sandstones.
Unconformity at top of Marchlyn Formation.
Coastguard Station Vent
CGRD
Colgate Sandstone
CGS
Cefn Gwyn Tuff
CGTU
Conformable with silty mudstones and siltstones of the Ceiswyn Formation.
Bala and Corwen districts, North Wales.
Non-welded felsic ash-flow tuff.
Conformable with the Ceiswyn Formation; immediately overlain by rocks of the Glyn Gower Siltstones Member.
Craig Cau Formation
CGU
Conformably overlies and laterally inter-tongues with the Ty'r Gawen Mudstone Formation in the south and west of the Cadair Idris district, and conformably overlies crystal tuffs of the Benglog Formation in the northeast, where its base is less clearly defined.
Cadair Idris area, North Wales.
Felsic ash-flow tuffs interbedded with subordinate tuffites and mudstones in the lower part of the formation, but becoming massive and welded in the upper part. Associated intrusive and extrusive rhyolites.
0 to 400m
Conformably overlain by mudstones of the Ceiswyn Formation.
Chalky Gravel
CGV
Gravel, chalk-rich. [Generic description].
Cwm Gwaun Formation
CGW
Arenig (Fennian).
Catgill Wood Sand And Gravel Member
CGWD
?Late Devensian.
Sharp erosional contact on diamictons of the Low Wath Till Member.
1:50k sheets 37 Gosforth and 38 Whiteheaven, Western Cumbria.
Clast-supported, poorly sorted gravel with lenses of sand. Clasts are mainly subangular to rounded, up to cobble size and composed of red (Permo-Triassic) and yellow (Carboniferous) sandstones, and coal.
1.2m thick at type section but up to 10m thick in boreholes around Egremont.
At the type section conformably overlain by silt and clay of the Ehen Valley Silt Member of the Seascale Glacigenic Formation.
Craig-Y-Glyn Formation
CGYG
Limited to fault bounded inliers in the central Berwyn Hills, Lwrch inlier (137), Llwyn-Onn inlier (136) (ca SJ 073 264), Garwallt inlier (136) (ca SJ 091 281).
Calcareous mudstones. (Well stratified rhyolitic and calcareous ash, and pale blue bedded limestone; with calcareous shale and calcareous, blue mudstone and shale).
Greater than 300m in the Lwrch inlier.
In faulted contact with mudstones of Llangynog Formation of Carodocian age.
Chalmerston Coal (Dalmellington, South Ayrshire)
Chirdon No.1 Coal
CH1C
Chirdon No.1 Limestone
CH1L
Chirdon No.2 Coal
CH2C
Chirdon No.2 Limestone
CH2L
Charnian Supergroup
CHA
Extends from Blackbrook (SK 452 185) south-eastwards to the Bradgate area of Charnwood Forest (SP 543 107), and thence beneath younger rocks south-westward to Nuneaton (SP 340 937). Present beneath younger strata westwards to Malvern 'line'.
Fine-, medium- and coarse-grained volcaniclastic sedimentary rocks with locally abundant tuffs and volcanic breccias. Intruded in Charnwood Forest by massive to brecciated andesites and dacites of the Whitwick Volcanic Complex and the Bardon Hill Volcanic Complex. The rocks are fractured, cleaved and show very low-grade metamorphism (Nuneaton) or upper greenschist metamorphism (Charnwood Forest).
3000m minimum.
Weathered and eroded, fractured or cleaved volcaniclastic rocks are overlain unconformably by strata ranging from earliest Palaeozoic to Mesozoic age.
Chalkey Coal (North Staffordshire)
CHAC
Charmouth Mudstone Formation And Dyrham Formation (Undifferentiated)
CHADY
Beinn A'Chaisteil Quartzite Formation
CHAI
Abrupt change to white-weathering pinkish-brown quartzose psammite and quartzite from the preceding psammite to quartzose psammite of the Auch Gleann Psammite Formation.
Can be traced as a prominent marker at base of Lochabar Subgroup from western edge of Crianlarich, east then northeastwards into southern parts of Blackwater, then eastwards across southern parts of Loch Rannoch to boundary with Schiehallion.
20 to 40cm-scale tabular to lenticular bedded grey to pinkish brown quartzite and quartzose psammite. Banded ribbed quartzite and semipelite unit comprising 5 to 10cm-scale interbeds of semipelite. The uppermost part of formation is more thinly bedded (3 to 5cm), and flaggy, comprising white-grey quartzite with minor biotitic quartzite and dark semipelite, and is probably about 5 to 10m thick.
Ranges from 10 - 20m up to c.250m thick, thicker typically in the southern part of the outcrops mapped to date. Approximately 90m thick at Beinn a'Chaisteil.
Abrupt change to the calcareous garnet-mica semipelite and muscovite-quartz semipelite marking the base of the Coire Daingean Semipelite Formation or to the massive garnet-mica semipelite and muscovite-quartz semipelite where the calcareous facies is not developed.
Chapelknowe Till Member
CHAK
Solway Lowlands.
Reddish brown, sandy, silty, clayey, stony diamicton with clasts of greywacke, red sandstone, siltstone and grey granodiorite. Generally very compact.
20m
Sharp, erosional contact with deposits of the overlying Plumpe Sand and Gravel Formation (or members thereof).
Ben Challum Quartzite Formation
CHAL
The change from calcareous "pitted" psammites and semipelites of underlying Ben Lawers Schist Formation appears sharp (in the Allt Challum section) with abrupt loss of any calcareous component and a decrease in the semipelite content, which is typically 50% or more in the Ben Lawers Schist Formation.
Occurs east of the Tyndrum Fault, across Beinn Chaorach, Ben Challum and into upper Glen Lochay, Sheet 46W. Always at the boundary between the Ben Lawers Schist Formation and Ben Lui Schist Formation.
5 to 10m-scale bedded/banded, pale brown quartzite to quartzose psammite with cm-scale schistose quartz, muscovite, +/- biotite semipelite interbeds. Approximately 70:30 psammite/quartzite to semipelite. Quartzite/quartzose psammite beds are thicker (20 to 40cm) in lower part (semipelite less than 3cm-thick layers and less than 20%) of the formation; hornblende schist layers (30 to 40cm thick) are conspicuous.
Transitional/gradational change upwards with increasing semipelite proportion into the Ben Lui Schist Formation. Upper limit taken where conspicuous quartzose psammite layers are <20%.
Charmouth Mudstone Formation
CHAM
Taken at the top of Blue Lias Formation or Scunthorpe Mudstone Formation. The top of the Blue Lias coincides with a marked upward decrease in frequency, thickness and lateral persistence of limestone beds. In many cases, the horizon to be taken is obvious. Where there is doubt, the thickness and vertical frequency of limestone beds should be considered, and the following guidelines used: at the top of a more or less persistent, thick (>0.10m) limestone above which the overlying mudstone (beneath any subsequent similar limestone) is at least twice the thickness typical of the underlying limestone-mudstone interbedded unit and above which there is no return, within the Lias Group, to limestone-mudstone spacing on that previous scale. In the type section, at the top of the Grey Ledge (bed 49 of Lang, W D, 1924). In the East Midlands Shelf (northwards), where the Blue Lias is absent but the Scunthorpe Mudstone occurs, the base of the Charmouth Mudstone is taken at the base of thin pebbly ferruginous oolite (Glebe Farm Bed) or, in north Lincolnshire, at the top of the Frodingham Ironstone.
Wessex Basin to East Midlands Shelf, i.e. Dorset Coast to c.Market Weighton area, Yorkshire.
Dark grey laminated shales, and dark, pale and bluish grey mudstones; locally concretionary and tabular limestone beds; abundant argillaceous limestone, phosphatic or ironstone (sideritic mudstone) nodules in some areas; organic-rich paper shales at some levels; finely sandy beds in lower part in some areas.
To c.335m
At marked or gradational upward change to coarser siliciclastic deposits of the Dyrham Formation. In the type section, this is at the base of the Three Tiers Sandstone. Where the Dyrham Formation is absent (East Midlands Shelf northwards) it is taken at the base of the Marlstone Rock Formation.
Charlbury Formation
CHAR
East of 'Moreton Axis' and to the north of Stow-on-the-Wold, west of the 'Moreton Axis': lower boundary well-defined by the incoming of limestone above the Sharp's Hill Formation, which is commonly a dark bluish gray clay. South of Stow, west of the 'Moreton Axis': well-defined by the incoming of limestone above the Lower Fuller's Earth mudstone succession.
East of 'Moreton Axis': limit based on cored boreholes and gamma-ray log characterisation. Extends in the subcrop 10km+ to north-east of Chipping Norton and about same distance east of Charlbury. Eastern limit at lateral passage into the Rutland Formation. Probably confined within 1:50 000 Geological sheets 218 (Chipping Norton) and 236 (Witney). West of 'Moreton Axis': confined to a c.10km-wide WNW-SSE - trending tract between Broadway, Gloucs. (at outcrop) and Fairford, Oxon (western limit at lateral passage into the Fuller's Earth Formation). Known distribution confined to 1:50 000 Geological Sheets 217 (Moreton in Marsh) and 235 (Cirencester).
East of 'Moreton Axis': mainly marly, shelly, shell-detrital limestones and some sparry oolites and oolitic limestones (limestone 60-80% of the formation); subordinate shelly, shell-detrital marls; minor mudstones; entire fossils abundant. West of 'Moreton Axis: shell-fragmental oolites (Farmington Member) and fine-grained sandy limestones, including tilestones (Eyford Member) dominate; the Sevenhampton Marl forms the uppermost unit; ironshot oolitic/pisolitic marls and marly limestones occur at base.
3m - 3.6m at the type section. 4.2m - 4.8m in boreholes near Stonesfield, Oxon, c. 3km south-east of type section. 4.83m in Stonesfield Borehole No 3 (reference section). About 8m in areas west of the 'Moreton Axis'.
Defined throughout by base of the Taynton Limestone Formation, which comprises mainly clean, sparry, commonly cross-bedded, shell-fragmental oolites and oolitic limestones in which entire fossils are rare; sporadic thin marl beds locally.
Creeslough Formation And Ards Black Schist (Undifferentiated)
CHAS
Castle Haven Conglomerate Member
CHAV
Overlies the Strathlethan Sandstone Member.
The Stonehaven area.
A massive, mainly clast-supported conglomerate, of 'Highland provenance, with lenses of horizontally-laminated, medium-grained sandstone.
1980 m thick (Carroll, 1995).
The base of the lowest lava flow in the Tremuda Bay Volcanic Formation.
Channelbush Coal
CHBC
Channelbush Limestone
CHBL
Chapelburn Coal
CHBN
Chamber Rock
CHBR
Chalbury Glauconitic Member
CHBY
Coalypath Coal
CHC
Clunch Coal (Coalbrookdale)
CHCC
Craighall Conglomerate Formation
CHCG
An unconformable contact on ignimbrites of the Crawton Volcanic Formation or on Dalradian Supergroup metamorphic rocks, varied along the Highland Border area.
The north-western limit of the Strathmore Syncline in the Highland Border area, north-east of Perth in the Midland Valley of Scotland. sheets 48W, 56W, in the Blairgowrie area.
A generally massive, well-rounded pebble and boulder (up to 0.6m diameter) conglomerate, of andesitic lava, locally quartzite and other lithologies of 'Highland' origin, interbedded with andesite, basaltic andesite and basalt lava members, together with minor sandstone, siltstone and mudstone beds.
Over 500 m thick.
The base of the Scone Sandstone Formation, which is locally overlain by the Hatton Conglomerate Member, with the Highland conglomerate overlying the volcanic conglomerate.
Chatwall Flags And Chatwall Sandstone (Undifferentiated)
CHCH
Carleton Hall Clay Member
CHCL
Gradational, conformable contact with underlying laminated silt and clay of the Carleton Silt Formation.
West Cumbria.
Silty clay, calcareous, laminated, very stiff, dark brown (Munsell Soil), with sparse dropstone pebbles and cold marine microflora. Laminae are stacked within graded, rhythmic units.
To 11.9m
Gradational, conformable contact with brownish grey sandy silt of the Stubble Green Silt Member of the Glannoventia Formation, or, sharp, planar, unconformable contact with stony diamicton of the Holmrook Till Member of the Blengdale Glacigenic Formation.
Crow Hill Conglomerate And Sandstone Member
CHCM
Chase Coals (South Staffordshire)
CHCO
Coleford High Delf Coal (Forest Of Dean)
CHDC
Castle Head Dolerite
CHDY
Chemiss Coal (Fife)
CHE
Cheshire Coal (South Lancashire)
CHEC
Chemical Deposits
CHEMD
Chenier Deposits
CHEN
Sand and gravel; inter-chenier deposits are typically more clay- and silt-rich. A chenier is a beach-ridge or linear mound on marshland. [Generic description: earth science dictionaries in the BGS library].
Cheviot Volcanic Formation
CHEV
The base of the volcanic rocks resting unconformably on Wenlock strata or, locally the White Hill Sandstone Formation.
The Cheviot Hills in Northumberland and the Scottish borders.
A thick pile of andesitic lava with associated pyroclastic and reworked volcanic rocks, subordinate biotite-phyric rhyolite and tuff.
At least 1000 m thick.
The top of the volcanic pile, uncomnformably overlain by the upper Devonian to lower Carboniferous rocks.
Cheviot Dyke Swarm
CHEVD
Cheviot Pluton
CHEVP
Chatwall Flags
CHF
Church Stretton to Caradoc (north) area.
Yellowish brown flags.
25 to 100m
Chiefswood Vent
CHFD
Melrose area, Scottish Borders.
Agglomerate-filled volcanic neck.
n/a
Intrusive contract
Chelford Sand Formation
CHFDS
Irregular contact with bedrock or deposits of the Oakwood Glacigenic Formation.
Cheshire.
White to "buff", well-sorted sand, with minor gravel, silt and peat lenses with sporadic in situ tree stumps and wood clasts.
To 20m.
Unconformable beneath till, sand and gravel of the Stockport Glacigenic Formation.
Cowdenbeath Five Foot Coal
CHFF
Chatsworth Grit
CHG
The first sandstone or sandstones above the Verneulites sigma or Bilinguites Marine Bands. If no marine bands have been proved, it is the base of the second main sandstone or sandstones below the top of the Millstone Grit Group.
South Yorkshire, Derbyshire, Nottinghamshire & Leicestershire.
Fine to coarse grained, massive and cross bedded, locally pebbly sandstones, with minor interbedded mudstone and siltstone.
Up to 90 m thick.
The top of the first main sandstone below the Cancelloceras Marine Band. If no Marine Bands are proved it is the top of the second or third main sandstone below the top of the Millstone Grit Group. Where the Redmire Flags are present it is the third sandstone; Where the Redmire Flags are absent it is the second sandstone. It is normally at least 30m below the top of the Group.
Chapelgreen Coal
CHGC
Chaigley Limestone Member
CHGL
Taken at the first coarse-grained packstone that lies above a succession of thin-bedded, laminated, calcisiltites and mudstones of the Hodder Mudstone Formation (undifferentiated).
Restricted to the western part of the Craven Basin, including the Dinckley (SD 70 35) and Thornley (SD 62 40) anticlines, southern limb of the Plantation Farm Anticline (SD 66 43) and the northern limb of the Clitheroe Anticline (SD 75 45).
Packstones and floatstones, bioclastic, mainly medium- to coarse-grained, dark grey, thin-to-medium-bedded, commonly graded and laminated. May show soft sediment deformation structures such as slump folds and convolute ripples. Many beds display erosive, tool-marked and fluted basal surfaces and some beds contain coarse-grained lags and mudstone lithoclasts. The interbedded mudstones are dark grey, fissile, pyritic and locally sideritic and mainly barren of macrofauna. Dark sandy ferruginous siltstones with plant debris also occur.
To 180m
Packstones and floatstones of the Chaigley Limestone Member are overlain by slumped, blocky, calcareous mudstones of the Hodder Mudstone Formation (undifferentiated).
Chelsfield Gravel Formation
CHGR
Unconformable on Upper Chalk or Thanet Sand or in uncertain, possibly overlying relationship above clay-with-flints head. Poorly exposed.
The deposit extends for 500m in the type area: other deposits occur on the Dartford (271) sheet from Knockmill [57 61] to Holly Hill [66 62]. May be present also south of Dartford sheet.
Well rounded flint pebble gravels, sandy gravels, pebbly sands and sands. Lithologies similar to those in Harwich Formation (formerly Blackheath Beds) from which it is thought to have been mainly derived.
Variable and uncertain, not exposed. Typically 2-5m. May be 10m where infilling hollows or pipes in Chalk.
Chapel House Coal (Northumberland)
CHHC
Chinastones
CHI
China Coal (Falkirk; Central Coalfield)
CHIC
Chick Coal (Bristol Area)
CHIK
Cligga Head Intrusion
CHIN
Cowdenbeath Jewel Coal
CHJ
Chilmark Member
CHK
Incoming of significant ooliths above sequence of micrites of the Wockley Member.
On north side of river Nadder between Fonthill Bishop and Chilmark; south of River Nadder between Wockley [ST 9555 2870] and Chicksgrove [ST 964 296] quarries.
Fine-grained oolitic limestone.
Base of "Dirt Bed" at base of Purbeck Formation.
Chatburn Limestone Formation
CHL
Not exposed or proved.
Widespread across the Craven Basin from the Whitewell area [SD64] in the west to the Skipton/Broughton area [SD95] in the east, where it includes the Haw Bank Limestone (q.v.).
Well-bedded, mostly grey to dark grey packstone limestones with chert lenses and subordinate partings or thin beds of shaly calcareous mudstone and siltstone.
At least 838m measured thickness (base not proved).
Taken where the dominant lithology described above, passes conformably upwards into either the dark shale-with-limestone lithology of the undifferentiated Craven Group in basinal areas, or into the paler, "more coarsely bioclastic and cleaner washed" limestone of the Clitheroe Limestone Formation on the Bowland High.
Cheney Longville Formation
CHLF
Yellowish brown siltstones and sandstones.
c.120m in the Church Stretton area; to c.250m in the Caradoc (north) area.
Camphill Gelifluctate Bed
CHLGE
The lower boundary of the unit is gradational (typically over 0.05m) with organic sand of the underlying Swineden Sand Bed in Kirkhill Quarry (infilled). In Leys Quarry (disused) it unconformably overlies white sand of the truncated Kirkhill Palaeosol Bed.
Buchan, northeast Scotland. The gelifluctate bed in only known within the immediate vicinity of Kirkhill quarry (infilled) (centred on NK 0120 5285) and Leys quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon).
Gravel and diamicton gravel. Crudely bedded over pale olive brown and pale pinkish brown, pebble-cobble gravel, clast supported with a matrix of coarse quartzose or felsitic sand typically overlying matrix supported pebble gravel with a silty sand matrix. Clasts are very angular and subangular. Clast lithologies are dominated by felsite with subsidiary psammites, quartzites, basic igneous rocks and red and grey granites. Thin beds of rippled fine-medium quartzose sand are present locally. In Kirkhill quarry (infilled) frost cracks penetrate downwards from within this bed, through the underlying Kirkhill Palaeosol Bed into the Pitscow Sand and Gravel Formation. In Leys quarry (disused) truncated ice wedge casts also descend from the top of the bed down through the Kirkhill Palaeosol Bed into the Pitscow Sand and Gravel Formation beneath. Interpreted as periglacial talus and gelifluction deposits.
To 2.5m
In Kirkhill Quarry (infilled) the upper boundary of the unit is a subhorizontal, planar erosion surface overlain unconformably by yellowish brown diamicton of the Rottenhill Till Formation. In Leys Quarry (disused) the upper boundary of the unit is an erosional unconformity, with channels (up to 1m in depth) filled with sandy gravels of the West Leys Sand and Gravel Formation.
Cheltenham Limestone Member
CHLM
The base is placed at the base of the lowest bedded limestone, where it sharply overlies the topmost rubbly limestone or clay with limestone nodules that forms the topmost bed of the underlying Clydach Halt Member.
Northeast crop of the South Wales Coalfield; the Cheltenham Limestone Member is the most widespread of the members of the Llanelly Formation, with the same geographic limits - from the Hepste Valley [SN 971 129] east to the Clydach gorge [SO 214 125] and southwards down the east crop on the west side of the Afon Lwyd valley to about 1km south of Blaenavon [SO 261 077].
Thin- to medium-bedded, mainly fine-grained limestones with pale green clay interbeds; the limestones are commonly arranged in fining-upwards cycles and comprise grainstone, wackestone and lime mudstone (including algal laminites).
1.7m at Cwar yr Hendre [SO 099 149] to 8m in the Clydach gorge [SO 224 125].
The top is placed at the sharp junction between the topmost fine-grained limestone of the Cheltenham Limestone Member and the base of the ooidal grainstone at the base of the overlying Penllwyn Oolite Member. A palaeosol horizon is commonly present at the top of the Member, its top marking the junction.
Chatburn Limestone Formation And Thornton Limestone Member (Undifferentiated)
CHLTL
Chalk Of Mull - Morvern
CHM
Cockhill Marine Band
CHMB
Cinderhill Main Coal (Nottingham And Derby)
CHMC
Carham Limestone Bed
CHML
Conformable boundary on sedimentary rocks, mainly mudstone and siltstone, of the Ballagan Formation.
Local development in the Ballagan Formation on the north and south banks of the River Tweed; best development around Carham, Northumberland.
White, nodular dolomitic limestone with MgCO3 content of 38.95% (Robertson et al., 1949), interbedded with chert.
To 7.5m
Conformable boundary with overlying interbedded mudstone, siltstone and sandstone of the Ballagan Formation.
China Rock
CHMR
Chama Sand Formation
CHMS
China Coal (Lancashire)
CHNC
Chonetes Shale
CHNS
These beds form the lowest part of the Fifth Shale [Member] and contain abundant Chonetes cf. hardrensis [according to the Lexique Stratigraphique International, 1971, p.95).
Chanter Member
CHNT
Carr House Coal (West Yorkshire)
CHOC
Child Okeford Sands Member
CHOS
Rests unconformably on various Jurassic formations.
Across the northern part of the Shaftesbury Sheet (313), south-eastern part of the Wincanton Sheet (297) and onto the Salisbury Sheet (298), beyond which it has not been mapped to date.
Glauconitic, fine- to medium-grained, locally clayey sand.
Upward change to extremely clayey glauconitic sand and sandy clay of the Bedchester Sands, or, in its absence, to the sandy clay of the Gault.
Chapel House Limestone Formation
CHPL
Drawn at base of conglomerate of the Chapel House Limestone Formation where it rests with significant non-sequence on the deeply fissured limestone top surface to the Stockdale Farm Formation, which comprises limestone, siltstone and mudstone. It lies directly on Lower Palaeozoic rocks elsewhere.
A series of inliers in the southernpart of the Askrigg Block, North Yorkshire, including Gordale Beck (SD 91 65), Stainforth Force on the River Ribble (SD 82 67) and Barrel Sykes, north of Settle (SD 82 64). Proved elsewhere in the subsurface of the Settle area in boreholes.
The lower part of succession is dominated by mid to mid-pale grey, medium- and coarse-grained calcarenite, oolitic grainstones interbedded with conglomerates, "mixed laminates" (ie. interbedded siltstone with sandstone and mudstone laminae), dolomicrites and fenestral or algal lime-mudstones. Argillaceous wackestones occur locally in the upper part of the formation.
Maximum of about 56m adjacent to the Middle Craven Fault, with 33.6m in the type section.
Drawn at sharp conformable upward passage from grainstone of the Chapel House Limestone Formation to darker limestones of the Scalebar Force Limestone Member (Kilnsey Formation).
Camphouse Quartz-Dolerite Intrusion
CHQ
Cross Hands Rock
CHR
Christchurch Member
CHRM
Chatelherault Sandstone
CHRS
Chatwall Sandstone
CHS
Church Stretton - Caradoc area.
Purple and brown sandstone.
to c.100m
Cromhall Sandstone Formation
CHSA
Lower boundary of the Cromhall Sandstone Formation is taken at the base of the lower tongue, which is taken at the base of the first sandstone overlying the calcite and dolomite mudstones and limestones of the underlying Clifton Down Mudstone Formation in the Bristol area and the Llanelly Formation in the Monmouth and Chepstow area. Base of middle tongue is taken at the base of the first sandstone in the upper part of the Clifton Down Limestone Formation. Base of the upper tongue is taken at the base of the first sandstone or mudstone above the skeletal and oolitic limestones of the Oxwich Head Limestone Formation.
Bristol, [ST 60 74] Monmouth and Chepstow area [ST 53 930]. Passes laterally southwards into formations of the Pembroke Limestone Group [Llanelly Formation, Clifton Down Mudstone, Clifton Down Limestone and Oxwich Head Limestone formations].
Includes up to three tongues. The lower tongue comprises brown and red fine- to coarse-grained quartzitic sandstone with subordinate mudstones and sparse thin limestones. Base is locally conglomeratic. The middle tongue is similar but contains units of dolomitised limestone. The upper tongue comprises grey and red coarse-grained quartzitic sandstones, sandy crinoidal and oolitic limestones, mudstones, siltstones and grey seatearths arranged in cyclic sequences. Units of crinoidal and oolitic limestone are locally developed. The formation was deposited mainly in a fluvial environment on a marine influenced coastal plain.
Lower tongue: 6m at Chipping Sodbury to 43m at Cromhall. Middle tongue: 27m at Chipping Sodbury to 30m at Tytherington. Upper tongue: 18m on Broadfield Down thickening north to 240m at Cromhall.
Lower tongue: Top taken at the incoming of calcite mudstones and oolitic and skeletal limestones of the Clifton Down Limestone in the Bristol area and the Hunts Bay Oolite Subgroup in the Monmouth and Chepstow area above the sandstones and mudstones of the lower tongue. Middle tongue: Top taken at the base of the entrance of the skeletal limestones of the Oxwich Head Limestone Formation above the sandstones and mudstones of the middle tongue. Upper boundary of the Cromhall Sandstone Formation taken at top of upper tongue: Top taken at entrance of limestones of the overlying uppermost Oxwich Head Limestone Formation or cherts and cherty marine mudstones of the overlying undivided Tenby Group above the sandstones and mudstones of the upper tongue.
Cheese Bay Sill
CHSBY
Charles Coal (South Staffordshire)
CHSC
Cowdenbeath Seven Foot Coal
CHSF
Cheltenham Sand And Gravel
CHSG
Bedrock surface beneath deposit or underlying superficial deposit. Base channelled, notably under Cheltenham.
Gloucestershire, Severn Vale, east of the river, from Tewkesbury [SO 90 32] through Cheltenham and Gloucester, possibly as far as Little Sodbury [ST 75 83].
Sand, quartzose, fine- to medium-grained, generally unbedded, with seams of poorly sorted predominantly limestone gravel, especially in the lower part. Sand probably derived by aeolian processes from nearby river terrace deposits. Gravel largely Middle Jurassic ooidal limestone derived probably by solifluction from the nearby Cotswold escarpment, plus ironstone and derived fossils. Rare clay lenticles.
Up to about 15m, very variable.
Upper surface of deposit, other deposits may overlie. Generally planar surface.
Champfleurie Shale
CHSH
Cowie Harbour Siltstone Member
CHSI
Grey, cross-laminated sandy siltstones of the Cowie Harbour Siltstone Member overlying red, trough cross-bedded medium-grained sandstone of the Red Sandstone Member
A fine- to medium-grained lithic sandstone interbedded with minor amounts of conglomerate and siltstone.
From 36 m to 90 m thick.
Grey, laminated sandy siltstones overlain by red, trough, cross-bedded and horizontally-laminated, medium-grained sandstone of the Carron Sandstone Formation.
Corkhill Sandstone Member
CHSM
Counter Head Siltstone Formation
CHST
Base of siltstone sequence conformably resting on the red conglomerate sandstones of the Dundarg Formation.
Counter Head to Gardenstown Seatown on southern Moray Firth coast.
Siltstone with pedogenetic carbonate.
Incoming of the first ripple cross laminate fine-grained micaceous sandstones of the Gamrie Bay Formation.
Craghouse Tuff Member
CHT
Junction of lapilli tuff with underlying unnamed volcaniclastic sandstone, or andesite sheet/lava flow, or Seatallan Dacite.
Wasdale area, Cumbria.
Lapilli-tuff; andesitic-dacitic, commonly eutaxitic, crystal-rich, ignimbrite.
Highly variable - 30-800m
Junction of lapilli-tuff with overlying volcaniclastic sandstone or andesite (Wrighthow Member).
Charlotte Coal (South Lancashire)
CHTC
Cowdenbeath Two Foot Coal
CHTF
Chudleigh Group
CHUD
In the Chudleigh area the lower boundary is taken at the incoming of black sooty and siliceous mudstones of the Chudleigh Group (Winstow Chert Formation) above the purple, green and grey mudstones of the underlying Tamar Group (Whiteway Mudstone Formation). The contact is generally sharp. In the Plymouth area it is taken at the incoming of dark grey cherts and siliceous mudstones of the Chudleigh Group (Winstow Chert Formation) above the mid grey silty mudstones of the Tamar Group (Saltash Formation).
In the Chudleigh (SX 870 784) and East Ogwell (SX 845 695) areas, south Devon and in the middle Tamar valley (SX 43 61) in the Plymouth area, on the Devon/Cornwall border.
Thin bedded cherts and siliceous mudstones, black mudstones and limestones passing up into thick-bedded to massive sandstones with subordinate conglomerate and mudstone.
Not known but probanly about 550m+
The upper boundary is taken at an angular unconformity where fine-grained glauconitic sandstone of the Upper Greensand Formation rests upon thick-bedded to massive, locally pebbly to conglomeratic sandstone of the Ugbrooke Sandstone Formation.
Allt A'Chuirn Quartzite Member
CHUI
The base is gradational with the underlying part of the Beinn an Dothaidh Formation, with an upwards change to quartzite as the dominant lithology.
The Member has a restricted occurance on the southern slopes of Beinn a' Chuirn, upper Auch Gleann. Sheet 46W (Crianlarich).
10 to 30cm-thick layers of quartzite, commonly ribbed in appearance; muscovitic semipelite typically accounts for less than 10% of the lithology, The base is gradational with the underlying part of the Beinn an Dothaidh Formation.
c 200m thickness is observed in the Allt a'Chuirn section but is greatly thickened by the effects of folding, estimated stratigraphical thickness is in the order of 30 to 50m.
Abrupt change to the more uniform garnetiferous semipelite rocks of the Beinn Dorain Semipelite Formation.
Chudleigh Limestone
CHUL
Churston Member
CHUR
Cheeveley Coal (Northumberland And Durham)
CHVC
Charles Hill Volcanic Member
CHVO
Defined at the base of the lowest lava flow or bed of volcaniclastic rock resting on non-cyclic fluvial and lacustrine sedimentary rocks of the underlying Fife Ness Formation, which consists of sandstones and mudstones with beds of carbonate (limestone and dolostone). The contact is nowhere seen and therefore might be tranistional, sharp or unconformable.
Known at Aberdour, Fife Coast and possibly in South Fod Borehole near Dunfermline. Volcanic rocks, now no longer exposed at Silverknowes [NT 205 776] on the shore of the Firth of Forth at Granton-Carmond, Edinburgh, have also been assigned to this member here interbedded into the Gullane Formation. This outcrop of basaltic lavas and tuffs, once quarried on the coastline, extends the supposed occurrence of the volcanic member across the Inchkeith Fault and intercalates it with the Abbeyhill Shales.
Consists of pale greenish-grey to grey, amygdaloidal, earthy weathered to hard microporhyritic olivine basalt (Dalmeny type) lava flows and beds of grey and "pink" volcaniclastic airfall and/or waterlain lapilli tuff. Beds of limestone and mudstone are known very locally (as on Meadulse).
Tens of metres, but very uncertain, assessed as more than 30m thick at Charles Hill.
Defined by the highest tuff bed that is overlain by the non-cyclic sedimentary rocks of the overlying Anstruther Formation, consisting of dark grey to black lacustrine mudstones with thin beds of argillaceous ostracod-bearing limestone and dolostone and pale grey sandstone.
Cowdenbeath Wee Coal
CHW
Chwarelau Coal (North Wales)
CHWA
Chert Beds (Of West Cumberland)
CHWC
Cherwerfri Formation
CHWE
Chatburn Limestone Group And Worston Shale Group (Undifferentiated)
CHWS
See the Lithology descriptions for the component groups.
Caerhys Shale Formation
CHY
1:50,000 Sheet 209 (St.David's).
Mudstones, tuffaceous near base and silty in upper part.
c 80 - 100 metres.
Claxby Ironstone Formation
Between Benniworth and Donnington-on Bain [Lincolnshire] the base is defined by a downsection change from grey and brown, ferruginous, oolitic mudstones [Hundleby Clay Member, Claxby Ironstone Formation] [Casey, 1973]. Farther north, where the Hundleby Clay Member is missing, argillaceous, oolitic ironstone is separated from the underlying pale-yellow sandstones [upper part of Spilsby Sandstone Formation] by an erosion surface. At Nettleton a basal conglomerate contains derived fossils from the Spilsby Formation [Casey, 1973; Kelly and Rawson, 1983]. Borehole evidence suggests that below The Wash, bioturbated, shelly silt and glauconitic sand [which appears to be the Hundleby Member] overlies brown ironstone and fine-grained, silty sand [Mintlyn Member of the Sandringham Sands Formation] [Wingfield et al., 1978].
The southerly extent of the Claxby Formation is below The Wash. It is present in Wash borehole 72/77A, but does not reach the Norfolk coast, where the coeval upper part of the Sandringham Sands Formation is found. The formation extends through southern Lincolnshire as far north as the Brigg district and finally disappears north of Audleby where the Tealby Formation oversteps it.
Pale grey to dark brown, ferruginous oolitic, silty clay with varying concentrations of oolitic ironstone and pink or cream, calcareous, siltstone bands at some levels. Chert and quartz grit are found at some horizons. Phosphatic nodules, which occur at some horizons, contain moulds of shelly fossils, including ammonites, belemnites and bivalves. In southern Lincolnshire, the lower part of the formation comprises pale, purple-grey, mottled brown, silty clay [Hundleby Clay Member]. The top of the formation is more calcareous and has been termed "calcareous beds" by some authors.
Up to 8m [an estimated 9m was recorded at Dalby by Owen and Thurrell, 1968]
The Claxby Ironstone Formation grades into the overlying Tealby Formation, although a minor erosion surface has been used to separate the calcareous mudstones at the top of the Claxby Ironstone Formation [Upper Claxby Ironstone Member of Gaunt et al., 1992], from the overlying oolitic clays of the Tealby Clay Formation.
Cistern Coal
CIC
Crewi Formation
CIF
Taken to be at the base of a laterally traceable anoxic mudstone (graptolitic) horizon (7878 0050).
Confined to southeast corner of Sheet 149, only present on Sheet SH70SE. Best exposed in base of River Crew.
Comprises banded mudstones and siltstones. Very minor sandstones. Banding is characteristically wide - 10-30cm +, is common. May reach 60cm. Turbiditic mudstones overlain by oxic or anoxic hemipelagite intervals. Graptolitic units may be present.
At least about 800m thick, top of formation not yet located.
Not seen on Sheet 149.
Cinderford Member
CIFD
Taken at the base of the Brazilly Coal, which rests conformably upon thick-bedded, coarse-grained sandstone of the Coleford Member of the Pennant Sandstone Formation.
Restricted to the central part of the Forest of Dean outlier (SO 60).
Mainly grey mudstone and siltstone, with some reddening, coal and sandstone. The lower part of the succession is dominantly argillaceous and included relatively thick coals, including the Brazilly and Crow coals. The middle part of the member includes the Serridge Sandstone, which passes from exclusively sandstone in the north to interbedded sandstone and shale to the south. The upper argillaceous part of the member includes further coal seams (Woodgreen Coals).
From 180 m thick in the north, to 300 m in the south of the Forest of Dean Coalfield.
The member is the youngest unit within the Forest of Dean outlier. The top of the member is not proved.
Cilan Formation
CIG
Conformably overlies manganiferous siltstones belonging to the Trwyn-y-Fulfran Formation. Boundary taken at the first coarse-grained sandstone of the Cilan Formation.
St Tudwal's Peninsula, northwest Wales.
Coarse-grained, thickly-bedded turbiditic sandstones.
Overlain conformably by red, brown and green siltstones and subordinate sandstones of the Ceiriad Formation.
Caledonian Supersuite
CIGSS
Claxby Ironstone Formation And Hundleby Clay Formation (Undifferentiated)
CIHC
Craig Hill Breccia Formation
CIL
Base of the lowest breccia bed, overlying pillow lavas of the Balcreuchan Group (undivided).
Northeast of Colmonell, Ayrshire, southwest Scotland.
Polymict breccia of basalt, amphibolite and various granite clasts, interbedded with some basaltic pillow lavas and rare chert beds.
About 100m
Top of the highest breccia bed where it is overlain by pillow lavas of the Balcreuchan Group (undivided).
Ciliau Formation
CILI
Cinder Bed
CIN
Cinder Bench Coal (South Staffordshire)
CINBC
Cinder Coal (South Staffordshire)
CINC
Caerfai Group
CIS
Drawn at base of basal conglomerate of the Caerfai Group where it rests unconformably on slates and tuffs of the Ogofgolchfa Group.
South-west Wales.
Reddish, basal conglomerate, green, fine-grained micaceous sandstone, purple-red mudstone and purple-red micaceous sandstone.
400m approx.
Drawn at conformable upward passage from purple-red sandstone of the Caerbwdy Sandstone to coarse, pebbly sandstone of the Solva Group.
Creag Innich Sandstone Formation
CISA
Outgoing of dominantly semipelite or pelitic slaty lithologies or the outgoing of variable green to rusty weathering arenites, wackes and semipelites; incoming of cleaner, coarse-grained quartzose arenites.
Currently only defined within Sheet 38e (aberfoyle), where it occurs locally on either side of the Aberfoyle Slate and the Loch Katrine Volcaniclastic Formation in synformal folds; similar lithology known from Ben Lomond.
Metasandstone, arenite to quartz-arenite, grey to buff-grey, locally gritty.
1300m maximum (estimated, but considered to lens out laterally)
Incoming of variable arenite, wacke and semipelitic lithologies, and more matrix-rich rocks in general.
City Sandstone Member
CIT
Claxby Ironstone Formation And Tealby Formation (Undifferentiated)
CITB
Claxby Ironstone Formation, Tealby Formation And Roach Formation (Undifferentiated)
CITR
Chalk Group
Generally unconformable (at a burrowed surface) on the underlying Lower Cretaceous strata (Upper Greensand and Gault Formations in the Southern Province and on the Hunstanton Formation in the Northern Province). Oversteps onto older strata in limited basin marginal situations.
The group is known throughout the onshore outcrops in England (Yorkshire to Kent, Sussex and Dorset), and offshore in the Southern Central and Northern North Sea areas.
Mainly chalk, some nodular or forming cemented layers, with marl seams in parts, beds of flint nodules or flint layers in the upper parts, and beds of limestone, chalky marl amd marly chalk in the lower part with glauconitic marl or sand at base.
The thickness of the whole group is variable depending on the degree of post-Cretaceous erosion and the relative development of its constituent formations. Onshore the thickest development is within the Hampshire/Sussex area of the Southern Province, where up to about 560m of strata are preserved; the most chronostratigraphically complete succession is in Norfolk but is thought there to be only some 400m thick; within the Northern Province up to 530m are preserved but the thickest succession is within the North Sea area where about 1000 to 1300m are preserved.
Unconformable beneath the Palaeogene or Quaternary basal unconformity onshore in the UK. Conformable beneath Danian age Maureen Formation in parts of the North Sea. Elsewhere unconformable.
Crosskirk Bay Formation
CKBA
Base of lowest medium-grained sandstone unit overlying siltstone-dominated cyclic sequence of the Dounreay Shore Formation.
Sandstone-dominated rhythmic cycles of interbedded sandstone, siltstone and calcareous laminite limestone.
More than 290m
Highest unit in local stratigraphy. Top not seen.
Crackington Formation And Bude Formation (Undifferentiated)
CKBU
Coking Coal (Somerset)
CKCO
Chudleigh Knighton Clay And Sand Member
CKCS
Cocker Combe Tuff
CKCT
Crackington Formation
CKF
Due to thrusting along the south crop of the Formation, the base is seen only between Okehampton (SX 59 94) and the Teign Valley (SX 84 84), east Dartmoor, Devon. The base is gradational and taken at the incoming of more abundant and relatively thicker sandstones of the Crackington Formation above the mudstones with less than 10% sandstone in the underlying Dowhills Mudstones Formation. Between the Bideford area (SX 45 27) north Devon and the Westleigh area (ST 06 17), west Somerset, the base is taken at a similar level. However, in the Bideford area, the base needs further investigation, as the Dowhills Mudstone Formation (Limekiln Beds of Prentice 1960a) was included in the Crackington Formation by Edmonds et al. (1979).
North Cornwall (SX 15 97), Devon (SS 7010) and west Somerset (ST 06 17).
Rhythmically bedded, dark blue-grey mudstones and subordinate predominantly grey sandstones and siltstones. Sandstone percentage varies from 20-75%, both vertically and geographically. The sandstones are parallel-sided "Bouma-type" turbidites with abundant well-developed sole structures. Individual beds are from a few centimetres to 0.4m thick and rarely up to 1m thick. Thicker sandstones are locally present, mainly in the uppermost part, but tend to be massive and lack sole structures. Packets with abundant sandstones are commonly developed and mappable. On the north Cornwall and Devon coast, six named units of dark grey to black pyritic shale with goniatite- and fish-bearing calcareous nodules are present in the upper part of the Formation. The thickest of these units is up to 7m thick. A few thick units of slumped or destratified beds are also present in the uppermost part of the Formation, as are scattered ironstone nodules.
>c.1000m in the Exeter district; 250m in the Bideford area.
On the north Cornwall and north Devon coast, the top is taken at the top of the Hartland Quay Shale, the uppermost of the named goniatite bearing mudstones in the Crackington Formation. Inland, where the Hartland Quay Shale cannot be mapped in pervasively folded terrain as it is too thin, the top is taken at the incoming of softer, more silty and argillaceous thick-bedded sandstones of the overlying Bude Formation above the dominantly thin- to medium-bedded sandstones and mudstones of the Crackington Formation. In the Bideford area the top is taken at the incoming of channels overlain by syndepositionally disturbed units and thick, locally cross-bedded, sandstones of the Westward Ho! Member of the overlying Bideford Formation above the regularly interbedded mudstones and turbidite sandstones of the Crackington Formation.
Cockhill Limestone
CKHL
Carganamuck Limestone Formation
CKLF
Carrickmore Marine Band
CKMB
Creekmoor Clay Member
CKMC
Cockermouth Volcanic Formation
CKML
Taken at base of lowest basalt sheet that conformably overlies conglomerate of the Marsett Formation; the formation oversteps the eastwards, unconformably to overlie the Skiddaw and Eycott groups.
Northern margin of Lake District Lower Palaeozoic massif, from just west of Cockermouth to Bothel (wholly on sheets E22 and E23). Intrusions of microgabbro ("dolerite") and lapilli-tuff on Little Mell Fell (E30 Appleby) may be intrusive equivalents of the Cockermouth Volcanic Formation (Macdonald and Walker, 1985).
Olivine-phyric basalt and tholeiitic andesite. Up to four sheets of massive to intensely amygdaloidal and scoriaceous rock, dark blue-grey to grey. Interpreted to be lavas. No intercalated pyroclastic or sedimentary rocks are present.
105m in the Cockermouth area, thinning to 30m near Sunderland; 67m thick in the type section.
Conformably overlain by interbedded mudstone, sandstone and thin limestone of the Marsett Formation.
Creekmoor Sand Member
CKMS
Clackmannan Group
CKN
Mostly Namurian but ranges from Brigantian to early Langsettian.
Drawn at base of lowest limestone of the Lower Limestone Formation; normally conformable.
Midland Valley of Scotland.
Sequences of sandstones, siltstones, mudstones, limestones, ironstones, coals and seatrocks; commonly cyclic; marine faunas common in lower parts of cycles.
Up to about 1500m.
Drawn at conformable upward passage from Passage Formation to Lower Coal Measures.
Carrick O'Hara Formation
CKOH
Chalk Rock Member
CKR
Turonian. Sternotaxis plana (now Plesiocorys plana) Zone.
The diffuse lower limit of cementation of the lowest bed of chalkstone at this level.
Known throughout the Southern Province and in the Chiltern area of the Transitional Province, eastwards to south Norfolk.
Very hard chalk and chalkstone, some nodular, including mineralised hardground surfaces, and marl seams.
Although Bromley and Gale's (1982) definition of the Chalk Rock is accepted, it is BGS practice to include the unit in the Upper Chalk. As the Upper Chalk has 'formation' status, the Chalk Rock is reduced in rank from 'formation' (Bromley and Gale, 1982) to 'member'. This should be re-appraised if the 'Upper Chalk Formation' is redefined formally. NOTE 2. Gale, Wood and Bromley (1987) treat the Chalk Rock as a Member of the 'White Chalk Formation' (= Middle and Upper Chalk of BGS).
About 0.5m up to 4 to 5m where fully developed.
"Where the Hitch Wood Hardground is developed, ... at the flint nodule horizon that marks the base of the overlying nodular chalk unit". In other areas, at the Pewsey Hill Hardground or the Ogbourne Hardground.
Cock Rig Formation
CKRI
Conformable on Deerhope Formation: Lowest pinkish-grey medium- to coarse-grained sandstone.
Medium- and coarse-grained, locally flaggy, cross-stratified sandstones, interbedded with clast-supported and poorly graded conglomerates.
Conformable: highest olive medium-grained sandstone below grey-green mudstones of the Wether Law Linn Formation.
Chalky Siltstone Member
CKSI
Chalk Silt
CKSL
Cuckfield Stone Member
CKST
Down-section change from fine-grained, silty, cross-bedded, buff sandstone with local thin mudstones and limestones [Cuckfield Member] to mudstone [Grinstead Clay Formation]. Locally, e.g. near Skaynes Hill, the Lower Grinstead Clay Member is cut out and fine-grained, silty, cross-bedded [festoon bedded], buff, calcareous sandstone [Cuckfield Stone Member] rests directly on fine-grained, pale grey to white, cross-bedded, soft, quartz sandstone [Ardingley Member of the Lower Tunbridge Wells Sand Formation].
The Cuckfield Member occurs in much of Horsham, including around Cuckfield, Drewitts and Ardingley. It disappears northwest of an arc from Handcross to Turners Hill and to the south of East Grinstead [Gallois and Worssam, 1993]. It can also be traced into the Royal Tunbridge Wells district from Turner's Green to the area east of Greenhurst [east of Maresfield] and between East Grinstead to Royal Tunbridge Wells. The member has also been identified in a small area in the northeastern corner of sheet 318, north of Burgess Hill.
Fine-grained, silty, cross-bedded, buff, calcareous sandstone with thin mudstones and limestones locally. In some areas, for example, in the Scayne's Hill-Chailey area, the Lower Grinstead Clay Member thins and disappears and the Cuckfield Stone Member expands with "sandrock" comprising the upper part of the member and festoon-bedded sandstone in the lower part of the member.
To 8.3m
Down-section change from shales and clay-ironstone beds [Grinstead Clay Formation] with a basal pebble bed [Cuckfield Pebble Bed] to fine-grained, silty, cross-bedded, buff sandstone with local thin mudstones and limestones [Cuckfield Stone Member].
Cockley Beck Tuff Member
CKT
Base of garnetiferous, dacitic lapilli-tuff. Unconformable, in type area overlies volcaniclastic breccia and sandstone (Dale Head Member); elsewhere overlies a variety of basaltic, andesitic and dacitic lava.
Duddon Valley - Eskdale; Cockley Beck to Dale Head and Foxbield Moss, Cumbria.
Garnetiferous eutaxitic dacitic lapilli-tuff with thin interbedded laminated garnetiferous tuff locally.
0 to 60m
Overlain by a variety of lavas that range in composition from basaltic andesite to dacite, and locally overlain by valcaniclastic sandstone.
Cockley How Tuff Member
CKY
Most distinct where basal parataxitic lapilli-tuff rests on bedded sandstone (Deepdale Sandstone Formation).
Confined to areas south and east of Deepdale Park, Deepdale, northeastern Lake District (between Grasmere and Patterdale).
Dacitic ignimbrite in the form of massive lapilli-tuff but with a lithologically distinct basal layer of parataxitic lapilli-tuff.
45m (maximum)
Indistinct, but overlain by bedded sandstone (Deepdale Sandstone Formation).
Carboniferous Limestone Supergroup
Typically rests with an angular unconformity above Lower Palaeozoic or older strata. Where the base of the limestone or dolostone succession rests directly upon the unconformity, the unconformity marks the base at the supergroup. Locally, red sandstones or conglomerates with common calcrete palaeosols or bedded and nodular anhydrite with subordinate dolostone and mudstone occur immediately above the uncomformity. In other circumstances the comformable base of the Supergroup is taken at the base of the lowermost bed of limestone or dolostone above a predominant succession of sandstone, conglomerate or anhydrite.
Extensive across England and Wales, including south and west Cumbria, the Yorkshire Dales, North and South Wales, the Peak District and the Bristol area.
Dominated by typically bioclastic to micritic, bioturbated with common shelly, crinoidal and algal beds of limestone and coral biostromes which are darker grey, and commonly dolomitised in the lower part. The upper part is dominated by paler grey, thinner-bedded limestones with common palaeokarst surfaces, overlain by clay wayboards, which are possible weathered bentonites. Sandstone is locally common, particularly in the upper part of the Supergroup.
The Supergroup comprises a single group in each tectonic province, and hence thickness is the same as for each component group; e.g. Peak Limestone Group about 800m in the Peak District, the Great Scar Limestone Group attains about 800m in northern England, and the thickest development is in the Stainmore Trough [NY]. The Clwyd Limestone Group of North Wales [SH and SJ] measures up to 900m.
Typically a sharp conformable boundary with the top of the uppermost limestone bed succeeding a predominantly limestone-dominated succession, overlain by dark grey mudstone of the Craven Group, quartzitic sandstone of the Tenby Group, sandstone, or dark grey mudstone and dark grey, thinly bedded limestone of the Yoredale Group.
Clayknowes Coal (Lothian)
CLA
Clachghlas Granite
CLACH
Claerwen Group
CLAE
Clachaig Semipelite And Psammite Formation
CLAG
Change from graded beds of feldspathic and micaceous psammite of the Creag Meagaidh Formation up into semipelite-dominated succession.
Southern Monadhliath Mountains. On sheet 63W and 63E in an arc extending from west of Creag Meagaidh around [NN 385 875] through Meall Cos Charnan [NN 432 774] to Creag Pitridh [NN 485 810] with another occurrence in Coire Sgoir [NN 493 740], NNEfor 6km.
Schistose to locally gneissose semipelite with interbeds of micaceous psammite and feldspathic psammite. Locally interbanded psammite and semipelite in places on a few centimetres scale.
0 to 580m generally. Locally up to 820m although this may be tectonically thickened.
Transitional contact into psammites and quartzites of the overlying Inverlair Psammite Formation.
Clair Group
CLAI
Clach Alasdair Conglomerate Member
CLAL
Clashindarroch Formation
CLAS
Above Blackwater Formation at base of highly magnetic biotite-andalusite-schist easily mapped and/or traced by magnetometer between NJ 405 312 and NJ 441 351 (the Garnel Burn Pelite Member).
South eastern corner of Sheet 85E and southern margins of Sheets 86N and 86E north of the Boganclogh and Insch Basic Intrusions.
Phyllitic semipelite and pelite, represented by andalusite-cordierite schist in part with rare quartzite and psammite.
Boundary with overlying Macduff Formation, where the more semipelitic and pelitic lithologies give way to more psammitic lithologies with grits and conglomerates. Imprecise boundary, probably transgressive.
Claughton Member
CLAU
Sharp junction between fossiliferous fissile clayey blue-grey mudstones with limestone nodules and thin sideritic lenses of Caton Shale Member below and siltstones with sandstones of the Claughton Member.
Lancaster Fells. Moseley (1956) used Keasden Flags for the same unit in the Keasden area. Used in the Settle Memoir but not defined. Keasden Flags is a synonym for Claughton Member.
Typical delta slope facies. Predominantly sandy grey micaceous shaly siltstones with irregular interbeds of fine- to medium-grained micaceous plant-rich sandstone, very variable thickness and bedding commonly syndepositionally slumped. NOTE: Moseley named the delta slope sequence between the entirely marine Caton Shales and the delta top Crossdale Grit (now Silver Hills Sandstone), the Claughton Flags. Thus it is proposed to rename the unit Claughton Member since it is predominantly siltstone and is analogous to the Roeburndale Member below the Caton Shale Member.
c.200-300m in the Claughton area, but upper part not represented.
Not seen; believed to be sharp, at erosional base of delta-top coarse-grained sandstone of the Silver Hills Sandstone.
Clavellata Formation
CLAV
Usually a coarse shelly oolite, resting (locally with angular discordance) on fine, evenly graded oolite of the Todber Freestone (where present), or on clay and sandy clay of the Newton Clay.
From the middle of the Wincanton Sheet (297), southwards across the whole of the Shaftesbury Sheet (313). Almost certainly it is the same as the Trigonia Clavellata Beds of the Dorset coast.
Variable from bioclastic oolite, fine- to medium-grained oolite, biomicrite, with thin beds of marl, sandy marl and fine-grained sand.
Fairly abrupt change to sandy clays and clayey sands of the Sandsfoot Formation.
Clay Coal (South Wales)
CLAY
Clarborough Member
CLB
Conformable, at gradational upward passage from reddish-brown mudstone of the underlying Sidmouth Mudstone Formation (undivided) to the more strongly indurated, silty gypsiferous mudstone of the Clarborough Member.
Surface outcrop limited to north Nottinghamshire, East Retford area.
Mudstone, silty, reddish brown with common veins of satin spar gypsum and indurated beds of reddish brown or greenish grey siltstone and very fine-grained sandstone, dolomitic.
3 to 12m
Conformable, at gradational upward passage from the more strongly indurated, silty gypsiferous mudstone of the Clarborough Member to the reddish-brown mudstone of the overlying Sidmouth Mudstone Formation (undivided)
Clackmannan Blackband
CLBB
Cleaver Bank Formation
CLBK
Cloghastucan Chalk Formation
CLC
Santonian. Marsupites testudinarius Zone.
At the type site boundary is at a prominent bedding plane immediately above a wavy bedded unit at the top of the underlying Galboly Chalk Formation. Outside the type area the basal contact is disconformable and the junction is marked by an erosion surface with glauconitised chalk pebbles, which includes rolled sponge psuedomorphs.
Present in the North Antrim and East Antrim basins and parts of the Highland Border and Southern Uplands areas. Absent over the Londonderry shelf.
Limestone (chalk), with an overall "gritty" texture and with some flint bands (mainly small and "spindle-shaped") most notably the coalescing nodular flint course termed the Oweynamuck Flint Band (of bed status defined at the eastern bluff in White Park Bay [D 029 448]). Beds of green-coated chalk pebbles at some levels. Common brachials and calyx plates of Marsupites.
Thin succession of 2.33m thickness at its type-site. Absent over structural highs and overlapped by succeeding member.
The upper limit is taken at the top of a thin (0.15m) wavy bedded unit underlying Creggan Chalk Formation chalks rich in Inoceramus debris. The wavy bedded unit contains a marked increase in Inoceramus compared to the rest of the Cloghastucan Chalk Formation.
Cumbria-Lancashire Catchments Subgroup
CLCA
Probably unconformable and in places strongly incised into highly variable sediments of the Caledonia or Albion Glacigenic groups and bedrock.
West and south Cumbria and Lancashire: the westerly and southerly catchments of the Lake District and Lancashire west of the Pennines between Whitehaven and Liverpool, including the catchments of the river valleys and their tributaries of the Rivers Lune, Wyre, Ribble, Ehan and Esk.
Alluvial silt, sand, clay and gravel with some peat. Associated River Terraces are dominated by sand and gravel, gravelly sand or sandy gravel with rare clay and silt.
Highly variable depending on the relative stratigraphical positions of each of the component units. In the major river valleys the thickness may vary between 2 and 5m, but probably does not exceed 10m. For deposits flanking the major river valleys, the thickness probably varies between 1 and 3m.
Ground surface or unconformable below artificial deposits.
Clock's Cleuch Coal
CLCC
Caley Crags Grit
CLCG
West Yorkshire [Caley Crags, 1.5 miles southeast of Otley].
Cleeve Cloud Member
CLCL
Murchisonae Zone
Upward change from pisoidal limestones (Crickley Member) or ferruginous, sandy, muddy limestone (Leckhampton Member) into limestone as described in lithology.
Mid and north Cotswolds: north of Horton, south Gloucestershire, and west of Fairford, Stow-on-the-Wold and Moreton-in-Marsh, Gloucestershire (Barron, A J M, et al, 1997, fig.4).
Off-white to pale brown well-sorted medium-, coarse- and very coarse-grained oolite grainstone, well bedded and cross-bedded; burrowed and sparsely shell-detrital in parts, locally (in east and north) yellowish and sandy.Locally highly shell detrital in lower part.
Type section (Leckhampton Hill); c.25m. Maximum; 51m (British Geological Survey Cleeve Common Borehole) (Barron, A J M, 1999).
Limestone as described in lithology with sharp top, commonly a hardground, overlain by Scottsquar Member or hardground overlain by Salperton Limestone Formation.
Cockleshell Coal (Derby)
CLCO
Clydach Valley Subgroup
CLD
The base is placed at the base of the lowest bed of fine-grained dolostone (of the Sychnant Dolomite Formation), where there is a conformable, interdigitating gradation from the mudstones of the underlying Cwmynyscoy Mudstone Formation.
In a narrow outcrop around the northeast and east crops of theSouth Wales Coalfield, extending from about 2km north of the Clydach valley [SO 219 142] south to the Pontypool area. [c.ST 280 985].
Massive ooidal grainstones with interbedded fine-grained, thinly bedded dolostones.
20m in the type area of the Clydach valley [SO 225 125] to 60m near Pontypool [SO 289 015].
The top is a major, regionally developed palaeokarstic surface that truncates the massive, pale grey ooidal grainstone of the Gilwern Oolite Formation. It is unconformably overlain by grey, micritic limestones and green clays (Clydach Halt Member) at the base of the Llanelly Formation, which comprises mainly well-bedded, cyclical micrite to grainstone limestones with green clay interbeds.
Clackmannan Diamond Coal
CLDC
Clydach Halt Member
CLDH
The base is placed at the base of green claystone and rubbly limestones (calcretes), where they overlie and infill an irregular palaeokarstic surface at the top of the underlying Gilwern Oolite Formation.
Northeast crop of the South Wales Coalfield, with sporadic development or preservation from Pontsticill, as seen in Baltic Quarry [SO 0659 1184] and Odynau Tyler Bont Quarry [SO 0635 1125], east to the Gilwern Hill area [c.SO 250 117].
A heterolithic, lenticular unit of conglomerates, limestone layers and nodules, green clays and sandstones with some dolostones.
Generally up to 1 to 2m, 6m locally; 4m at the type locality [SO 235 127].
The top is placed at the incoming of well-bedded, thinly bedded, cyclic limestones (the Chelternham Limestone Member), where the basal bed of limestone sharply overlies the topmost green clay or rubbly limestone of the Clydach Halt Member.
Claddens Dyke
CLDY
Clent Formation And Enville Formation (Undifferentiated)
CLEB
Clement Coal (South Wales)
CLEM
Clun Forest Formation
CLF
Clune Fish Bed
CLFB
Cliff Coal (Milford, South Wales)
CLFC
Clackmannan Four Foot Coal
CLFF
Clackmannan Forty Inch Coal
CLFI
Cliffe Flints
CLFL
Claisfearn Semipelite
CLFN
Corsewall Formation
CLG
Not seen (Faulted: Glen App fault west of Loch Ryan).
Southern Uplands, south Scotland.
Boulder conglomerate and wacke turbidite unit.
Not seen (faulted).
Claygate Member
CLGB
Drawn at base of lowest fine-grained sand bed, conformable on silty clay.
Interbedded fine-grained sand, silt and clay.
Average thickness of 16m in London area; 17m to 25m in Essex.
Drawn at conformable upward passage from silt and fine-grained sand of the Claygate Member to the Bagshot Formation.
Cloghan Hill Limestone Member
CLGH
Lower boundary with Knockmore Member, marked by incoming of shales and shaly limestone.
At base comprises small mud mounds and enveloping shales, silts and bioclastic shaly limestone, overlain by interbedded shales, silts and thin limestones, overlain to the top by thin-bedded, non-shaly limestones with coral bioherms and unfossiliferous small mud mounds.
c 30 metres in type section; up to 50 metres to west of type section.
Upper contact is with bedded argillaceous cherty limestone of Dartry Limestone Formation.
Cloghany Limestone Member
CLGL
Lower boundary is abrupt contact with poorly fossiliferous and cherty argillaceous limestones of Dartrey Formation.
Highly bioclastic, crinoidal microspar grainstone.
0.97 metres in type section. Range 0.56 - 1.25 metres.
Upper contact is base of lowest shale of succeeding Carn Limestone Member.
Cloughton Formation
CLH
The lower boundary is conformable, or disconformable, at the abrupt upward transition from the fossiliferous mudstone and ripple laminated sandstones of the upper part of the Eller Beck Formation to the cross-stratified, plant debris-rich sandstones, siltstones and mudstones of the Cloughton Formation.
North Yorkshire Moors, Cleveland Hills and Howardian Hills; well exposed in several coastal cliff sections between Hawsker Bottoms (northwest of Robin Hood's Bay) and Gristhorpe Bay, southeast of Scarborough. South of the Howardian Hills the unit is truncated by the unconformity at the base of the Chalk. Equivalent strata in Humberside and Lincolnshire are dominated by limestones (Cave Oolite and Lincolnshire Limestone, Cope et al., 1980). Offshore, the formation is equivalent, in part, to the Strangways Formation of the West Sole Group (Lott and Knox, 1994).
Forms steep cliffs on the North Yorkshire Coast, and generally steep slopes on the escarpments of the North Yorks Moors, and a positive topographical feature in the Hambleton and Howardian Hills, especially where sandstone dominated. Mudstone units generally form topographical slacks.
The lower and upper parts of the formation (Sycarham and Gristhorpe members respectively) are dominated by planar laminated grey mudstones and siltstones with yellowish grey, fine- to medium-grained, cross-stratified sandstones. Plant remains and rootlets are common in both members, with rare thin coals, and grey mudstone seatearths. Mudstones, ferruginous sandstones and ooidal limestones with a marine macrofossil and trace fossil assemblage occur in the middle part of the formation, differentiated as the Lebberston Member (Hemingway and Knox, 1973) and also known formerly as the Whitwell Oolite and/or the Millepore Bed.
Hemingway and Knox (1973) erected a second marine unit termed the Blowgill Member, comprising mudstone and limestone, at the base of the Cloughton Formation. This was subsequently shown to be part of the underlying Eller Beck Formation, and not a member of the Cloughton Formation (Powell and Rathbone, 1983).
50 to 70m on the North Yorkshire Coast between Whitby and Scarborough and inland in the North Yorkshire Moors and Cleveland Hills; 36 to 50m (thinning southwards) on the western escarpment of the North Yorkshire Moors (Frost, 1998; Powell et al., 1992).
The upper boundary is conformable, at the abrupt transition from the sandstones, siltstones and mudstones with rootlets and plant remains of the upper part of the Cloughton Formation, to the bioturbated and fossiliferous, variably calcareous mudstones, siltstones and fine-grained sandstones, and limestone of the lower part of the Scarborough Formation.
Clent Formation And Haffield Breccia Formation (Undifferentiated)
CLHB
Cloud Hill Dolostone Formation
CLHD
The lower boundary is an unconformity, possibly in part a shear surface, with biosparites and micrites of the Milldale Limestone Formation of early Asbian age below, locally marked by the incoming of mudstone-dominated sediments, such as the Cloud Wood Member, and may be crowded with Thallasinoides trace fossils.
The outcrop is restricted to inliers at Barrow Hill, Cloud Hill and Breedon Hill across south Derbyshire and north-west Leicestershire; the subcrop extends at least to the Ticknall area [SK 35 24].
Grey, pale buff and reddish grey, fine- to coarse-crystalline, thin to very thickly bedded dolostones, with shaly mudstone or clay partings and beds. Bioclastic grainstones interbedded with mudstones and dolostones are defined as the Cloud Wood Member, calcareous mudstones seen where undolomitised. The mudmound reef dolostones are typically buff to grey, massive, fine-grained and fossiliferous with common brachiopods, crinoids, corals, gastropods, nautiloids and ammonoids.
At least 125 m thickness proved at type section.
The top is taken at the incoming of the first palaeosol of friable siltstone and sandstone, displaying carbonate nodules of the overlying Ticknall Limestone Formation.
Cliffe Hardground
CLHG
Clift Hills Phyllitic Formation
CLHI
Clitheroe Limestone Formation And Hodder Mudstone Formation (Undifferentiated)
CLHOM
Close Hill Siltstone
CLHS
Gradational to grey planty siltstones with common planty micaceous fine- to medium-grained sandstones over 10cm. (Delta slope deposits).
Not known; probably extensive. Known from large area of Lancaster Fells, and probably extends throughout Lancaster Sheet.
Siltstone, grey, sandy, micaceous, calcareous with rhythmic layers of fine-grained red-brown weathering, sandstone to 1cm; sporadic to common layers of sandy calcisiltite; rare to common Sanguinolites and bellerophontids. NOTE: This is a distinct/unique lithology within the Roeburndale Formation. The formation consists of delta slope siltstones with sandstones. There were previously three known marine bands with goniatite/bivalve faunas. The Close Hill Siltstone is a fourth new marine band.
c. 60m
As lower boundary.
Castell Limestone Formation
CLI
Llandeilian to Aurelucian
Conformably overlies the Caerhys Shale Formation with gradational boundary.
Bluish grey limestones with interbedded mudstones.
Passes conformably upwards into Caradoc shales.
Cambois Little Coal (Northumbria)
CLIC
Cliff Member
CLIF
Succeeds the grey-green well-bedded mudstones and siltstones and thinly bedded sandstones of the Farden Member, with the very fossiliferous Starfish Beds at its summit.
Grey unbedded silty mudstone with sparse brachiopod fauna (slump sheet).
Succeeded by grey-green bedded mudstones and siltstones of the Waterfall Member.
Carn Llidi Gabbro
CLIN
Quartz gabbro and microgabbro
Clinterty Pluton
CLINT
Clackmannan Jewel Coal
CLJC
Coldbeck Limestone Formation
CLK
Early Chadian.
At base of 'Spongiostroma Band' of Turner, 1950. (Stone Gill, Ravenstonedale).
Dark grey, fine-grained limestones with interbedded mudstones and flaggy dolomites characterised by abundance of algal macrostructures including stromatolites and oncolites. Overlying Park Hill Limestone is more bioclastic, contains productoid brachiopods, is more dolomitic and lacks abundance of algal macrostructures. The upper part of underlying Stone Gill Limestone has thick-bedded porcellanous limestones and thin-bedded dolomites with 'Camarotoechia proava'.
52 metres strata visible in continuous section in Stone Gill but Turner (1950,p.30) estimated that a further 31 metres are cut out by faulting. Maintains a thickness of about 50 metres across NY60NE and NY60NW as far as Gaisgill, then thins westward to 20 metres at west edge of NY60NW.
At top of Algal Nodular Beds under Coldbeck Bridge. (Stone Gill, Ravenstonedale).
Clerkhill Appinite Suite
CLKH
Clitheroe Limestone Formation
CLL
Seen at Ings End (SD 8145 4455), thin-bedded, dark grey silty packstones and interbedded mudstones of the Chatburn Limestone Formation pass upwards conformably into paler, more coarsely bioclastic cleaner-washed limestones of the Clitheroe Limestone Formation.
Craven Basin, Lancaster [SD46] to Skipton [SD95] - extent southward not defined.
Predominantly pale grey and commonly coarsely crinoidal, packstones, wackestones and subordinate grainstones and mudstones with Waulsortian mudmound reef limestones present at two levels (for detailed lithogical description, see Miller, et al., 1972 and Lees, et al., 1985).
To 1500m
Seen as a sharp, unconformable boundary between the dominantly limestone succession of the Clitheroe Limestone Formation and the overlying grey to dark grey, thin-bedded calcisiltites and calcareous mudstones with thin limestone interbeds of the Hodder Mudstone Formation. At the type section this upper boundary is equivalent to the base of the Limekiln Wood Limestone Member identified as the "Salthill Cap Beds" of Miller, et al., 1972, and corresponds to a widespread unconformity.
Cloberhill Coal
CLLC
Clackmannan Lower Five-Foot Coal (Clackmannan)
CLLF
Normally fireclay underlying the lower boundary, with presumably a conformable contacts.
Main Clackmannan Coalfield, Stirling, Alloa, Midland Valley of Scotland.
Thickness=up to 1.5m in two leavesUsed on maps: equivalent coal the Alloa Cherry shown on Sheet 39E solid, Alloa, 1974 edition based on resurvey 1950-61 by M. Armstrong, A.C. Bishop, E.H. Francis and W.A. Read
Up to 1.5 m thick, in two leaves.
Mudstone above, also probably conformable. In the western part of the area the overlying unit can be an erosionally based sandstone.
Clitheroe Limestone Formation (Knoll-Reef)
CLLK
Clady Limestone Member
CLLM
Craigenhill Limestone
CLLS
Collinwell Sands Formation
CLLW
Uppermost Cenomanian and Turonian. Rhynchostreon suborbiculatum Zone.
Disconformable at an erosional surface upon the Island Magee Siltstones Formation.
Fully developed in the area southwest of Belfast within the East Antrim Basin and Southern Uplands area. Elsewhere in Northern Ireland the formation may be represented in the condensed successions of the undivided Hibernian Greensands Group.
Pale green to grey coarse-grained unconsolidated sands with some glauconite. Becomes whitish and poorly glauconitic in the Carrickfergus district.
Maximum of 2.4m at Rungill Burn in the Carrickfergus district.
Unconformable at an erosion surface with younger Kilcoan Sands Formation beneath the so-called Turonian non-sequence within the Hibernian Greensands Group; and beneath the erosion surface at the base of the Ulster White Limestone Group.
Cliffe Marls (One)
CLMA1
Cliffe Marls (Two)
CLMA2
Cove Lower Marine Band
CLMB
Type locality is at Cove Harbour, near Cockburnspath, Berwickshire.
Calcareous sandstone with many fossils.
Also known as Cove Lower Limestone. Formerly included within the "Calciferous Sandstone Group/Measures/Series". Correlated with the Dun Limestone and the Redesdale Ironstone of Northumbria.
c.4.5m
Clackmannan Musselband Coal
CLMC
Claughton Moor Siltstones
CLMS
Boundary not exposed but believed to be sharp where predominantly siltstone strata overlie predominantly sandstone beds at the top of the Nottage Crag Grit (where this is present) within c.1m of strata.
Laminated grey, micaceous sandy siltstones with sparse marine fauna.
c.24m
Conformable base of Moorcock Sandstones: interbedded fine-grained sandstone and siltstone resting upon the laminated siltstones of the Claughton Moor siltstones.
Clisiophyllum Multiseptatum Band
CLMT
Cleveleys Mudstone Member
CLMU
Clifford's Mesne Sandstone
CLN
The May Hill and Gorsley areas, Welsh Borders.
3 to 24m
Clowne Coal (Nottingham, Derby And South Yorkshire)
CLNC
Calne Sands Formation
CLNE
Clackmannan Nine Foot Coal (Clackmannan)
CLNF
Closeburn Limestone Formation
CLO
Late Asbian to Brigantian; B2 to P2 goniatite zones.
Unconformable on Lower Palaeozoic turbidites.
Southern part of the Thornhill Basin at Closeburn, Barjarg, Dollard Hill.
Fossiliferous marine shale, red dolomitic limestone, sandstone and seatearth.
Unconformably overlain by Upper Carboniferous strata.
Clava Lodge Clay Member
CLOCL
Sharp, unconformable contact with Drummore Gravel Formation below.
Sheet NH74SE.
Silty clay with sparse well rounded, high sphericity pebbles of psammite and quartzite, containing in situ high-boreal shells/microfauna.
4.9m at type section
Gradational contact, generally marked by colour change (olive-grey to pale yellowish-brown), with the Dalroy Sand Member above.
Clod Coal (South Derbyshire)
CLOD
Cockloft Coal (South Lancashire)
CLOFT
Clogherny Member [Duplicate Code: Use Cghy]
CLOG
Carlops Shale
CLOP
Probably late Visean. Detailed age data are not currently available. The quoted age of "Visean" is intended to reflect the associated uncertainty, and is based upon the age of the parent Hopetoun Member, which is currently recorded as Asbian to Brigantian.
Claypole Limestones Bed
CLPL
Change up from grey, calcareous mudstone with rare thin limestones of the undifferentiated Granby Member; at 71.78m depth in type section Fulbeck Airfield Borehole f/B5 (SK95SW/17).
East Midlands; north Leicestershire to Lincolnshire. Not recognised in north Lincolnshire, or south Leicestershire, where it may pass south into part of the more argillaceous and less bioclastic Rugby Limestone Member of the Blue Lias Formation (Ambrose, 2001).
Two c 0.25m limestone units, separated by c 1m of mudstone beds with nodular limestone beds in the upper part. The limestone beds are shelly, medium grey, argillaceous packstone/grainstone. Fauna includes forams, bivalves, ammonites, ostracods and echinoderms. The lower part forms a positive feature.
1.48 to 3m; 1.48m in type section.
Change up into grey, calcareous mudstone of the undifferentiated Granby Member; at 70.30m depth in type section Fulbeck Airfield Borehole f/B5 (SK95SW/17).
Clippens Peat Formation
CLPT
Late Devensian to Holocene. The basal 3cm of each peat bed from the Linwood Borehole (see Lithology) have been radiocarbon dated to 7110_50 years BP for the base of the upper peat and 9540_50years BP for the base of the lower. A single specimen of the marine gastropod Onoba semicostata was found in the clay bed, tentatively indicating a marine origin, the transgression ending earlier than 7100 years ago.
The Clippens Peat Formation of the Clyde Catchments Subgroup rests possibly by transitional passage on underlying members and formations or with angular unconformity on older Quaternary sediments or bedrock.
The Clippens Peat Formation of the Clyde Catchment Subgroup is recognised discontinuously throughout the Clyde valley catchment.
The Linwood Borehole (Browne and McMillan, 1989a, Figure 17) contains the typical section of the Clippens Peat Formation. Below 45cm of very peaty stony soil there was 1.3m of peat, resting on 5cm of grey rooty clay, followed by a further 84cm pf peat to the base of the formation at 2.64m depth. The base of the upper bed of peat was at 8.43m OD and the base of the lower at 7.54m OD.
Reliable indicators of saltmarsh vegetation are not found in the peat record but ericaeous pollen taxa may indicate the development of a coastal heath. The formation was originally defined as found only in the Linwood area (Browne and McMillan, 1989a, Figure 5) but now includes all late Devensian and Holocene peats in the Clyde Catchment.
Veneer to over 5m.
The Clippens Peat Formation of the Clyde Catchments Subgroup is exposed at surface in the Clyde valley catchment and also overlain by younger sediments.
Creag Leacach Quartzite Formation
CLQU
Base of dominantly quartzite succession overlying dominantly graphitic succession of the Blair Atholl Subgroup. Base of boulder bed, where developed.
Braemar, Ballater and Glen Shee districts.
White quartzite lenses succeeded upwards by cream quartzite and micaceous psammite.
Top of dominantly quartzitic succession below dominantly graphitic succession of the overlying Ben Eagach Schist Formation.
Coral Rag Formation (Southern England)
CLR
Upward change from sandy mudstones of Hazelbury Bryan Formation to a dominantly marly and ooidal sequence.
Wiltshire-Dorset, in this formalised sense. In its original use across much of England, but now slowly being restricted as the outcrop is revised and the sequence split up.
Ooidal and pisoidal, marl, marly limestone and limestone.
6 to 15m
Upward change from dominantly limestone succession to a dominantly arenceous succession of the Sandsfoot Formation.
Coral Rag Member (Cleveland Basin)
CLRG
Clifton Rock
CLRK
West Yorkshire area {Clifton, northwest of Huddersfield, Yorkshire].
The Clifton Rock consists of up to three leaves of fine-grained cross-bedded or ripple cross-laminated sandstone and includes a thin coal. The Shertcliffe Coal rests on the top leaf, sometimes termed the Shertcliffe Seatstone.
Collering Sandstone
CLS
Cephalaspis Sandstone-Cornstone
CLSC
Claragh Sandstone Formation
CLSG
Variable; either resting unconformably on Dalradian Supergroup metamorphic rocks or unconformably overstepping older Carboniferous strata, everywhere with a basal conglomerate.
Sandstone, fawn to pale brown, coarse- to very coarse-grained, lithic arkose to subarkose with pebbly horizons, thin to very thick beds; slumped cross-bedded channels, basal conglomerate with calcrete nodules.
0 to at least 350m
Fining upwards into heterolithic alternating shales, siltstones and thin sandstones; succeeded abruptly and conformably by either peritidal carbonates of Termon River Limestone Formation or sandstones of Bin Mountain Sandstone Formation.
Clava Shelly Formation
CLSH
Unconformable, glacitectonic boundary of the Clava Lodge Clay Member of the Clava Shelly Formation with the Drummore Gravel Formation below.
Diamicton, olive-grey, very stiff, fissile, with sparse shell material and silty sand. See also details of the Dalroy Sand (DROY), Clava Lodge Clay (CLOCL) and Culdoich Till (CUTI) members.
11m at type section
Unconformable, glacitectonic boundary with Finglack Till Formation above.
Clyst St Lawrence Formation
CLSL
Rests unconformably on Crackington Formation between Westwood (SY 020 990) and Clyst Hydon; elsewhere contacts faulted. Near Cullompton (in Sheet 310) apparently rests unconformably on Bude Formation and Cadbury Breccia.
Outcrop extends from Westwood (SY 020 990), northwards through Clyst St Lawrence (ST 030 001) to Langford Green (ST 030 030) and Mutterton (ST 030 050).
Reddish brown silt and sand, ranging from sand, through silty sand, silty clayey sand, sandy silt, clayey silt, and sandy clayey silt; the sand content is mainly fine- to very fine-grained. Probably sandstone and siltstone where unweathered.
Passes gradationally upwards into reddish brown silty mudstones of the undivided Aylesbeare Mudstone.
Clent Formation
CLT
Unconformable/disconformable boundary between underlying mudstone/sandstone of Salop Formation (Enville Member) and coarse breccia above (in type area); gradational boundary in Wolverhampton area.
West Midlands; South Staffordshire and Birmingham areas.
Breccia, sub-angular, with red-brown mudstone matrix, clasts predominantly 'Precambrian-Uriconian' volcanic rocks and subordinate Lower Palaeozoic rocks. Red pebbly mudstone and sandstone in Wolverhampton area.
c.138m in Clent Hills, c.240m in Wolverhampton/Baggeridge area to north.
Generally, modern erosion surface in type area, locally overlain unconformably by Kidderminster Formation (Triassic).
Clackmannan Two Foot Coal
CLTF
Clogau Formation
CLU
Conformably overlies sandstone of the Gamlan Formation (Harlech Grits Group). Boundary is transitional over 5m.
Northern, eastern and southern flanks of the Harlech Dome, North Wales.
Black pyritous and carbonaceous mudstones and silty mudstones with rare silt laminae and sparse fine-grained sandstone beds.
Basal unit of the Mawddach Group.
90 to 105m
Sharply but unconformably overlain by silty mudstone and sandstone turbidites of the Maentwrog Formation.
Cluanie Suite
CLUA
Cluanie Granodiorite
CLUAG
Clackmannan Upper Five Foot Coal (Clackmannan)
CLUF
Clunes Complex
CLUNS
Clyde Valley Formation
CLVY
Unconformably overlies older Quaternary deposits and bedrock.
Recognized in the Clyde catchment area as the alluvial deposits of the Clyde and all its tributaries, from highest to lowest order.
In the Clyde valley catchment, especially the Clyde and its major tributaries, the formation consists of a wide range of lithologies encompassing pebbles, fine to coarse gravel, cobbles and boulders in a sandy matrix and coarse- to fine-grained sand, silt and clay. Beds rich in organic remains occur as well as peat (in the floodplain deposits). A partial type section is recorded in the BGS Law Borehole (Law Formation of Browne and McMillan, 1989a, 39-40 and Figure 22). The lithology here is of massive, flat laminated and also cross-bedded, grey, fine to coarse-grained sand with silt and traces of fine gravel. In the BGS Lochwinnoch Borehole (ibid, Figure 25) loose to dense, dark brownish grey, framework supported, sub-angular to rounded fine to medium gravel with sand is recorded. Bedded silt with thin peat units and organic layers are intercalated. The stratigraphical relationships of the Clyde Valley Formation (formerly Law Formation) are illustrated in ibid (Figure 3) and its geographical distribution in ibid (Figure 2e). Although the above associations for the formation are different in grain size, they are both the products of fluvial processes operating on different scales. At Law the deposits are of a minor meandering stream and at Lochwinnoch of an intermediate sized alluvial fan laterally infilling the basin in the Lochwinnoch Gap.
See additional information woven into the Lithology description.
Veneer to several metres.
Normally the land surface.
Colwick Member
CLW
Originally defined as a Formation (Elliott, 1961; Warrington et al., 1980) the term was not used during the remapping of the Nottingham sheet and adjacent areas (e.g. Charsley et al., 1990), being subsumed into the Sneinton Formation. Following referral of the former Sneinton Formation to the nationally applicable Tarporley Siltstone Formation, the beds originally referred to the Colwick Formation are now treated as a local, upper member of the Tarporley Siltstone Formation in the southern apart of the East Midlands Shelf (c.f. Retford Member).
Cloud Wood Member
CLWD
Base is marked by an unconformity/shear surface with sheared mudstone resting on dolomite of the Milldale Limestone Formation.
Known only in Cloud Hill Quarry.
Dark grey mudstones with thin dolostone and dolomitic siltstones, passing up into dolostones with common, thin grey and red mudstone beds and partings.
To 36m
The top is marked by an abrupt change from thinly bedded dolostone with common mudstone partings to massive, finely crystalline dolostone.
Clwyd Limestone Group
CLWYD
In places conformably succeeds reddened siliciclastic facies of the "Basement Beds"; elsewhere rests with marked unconformity on Lower Palaeozoic rocks.
Crops out on Anglesey (SH 50 80) and on the North Wales mainland between Bangor (SH 54 70) and Oswestry (SJ 27 23); and on the Corwen Outlier (SJ 05 43).
Diverse range of limestone facies with subordinate sandstone and mudstone units, and exhibiting local dolomitisation. Records the initiation and growth of a carbonate platform along the northern flank of the Wales-Brabant Massif.
To 900m
Conformable base of Pentre Chert Formation or Cefn-y-fedw Sandstone Formation in northeast Wales; elsewhere marked by an unconformity with younger Carboniferous or Permo-Triassic rocks.
Clwyd Group (Knoll Reef)
CLWYK
Corseclays Sandstone Formation
CLY
Stratigraphical boundary with the underlying Park End Breccia Formation is concealed but inferred to be conformable. At Bennane Lea the base of the Formation is unconformable and oversteps onto Early Ordovician igneous rocks.
In the immediate vicinity of Ballantrae, Ayrshire, southwest Scotland.
Red cross-laminated, micaecous fine-grained sandstone. Grains mostly of subrounded quartz, a significant minority of grains with a high degree of sphericity are probably of aeolian origin. Locally, at Bennane Lea [NX 091 858], the sandstone is pebbly and referred to the Bennane Lea Member.
The minimum preserved thickness of the Formation exceeds 500m, as exposed along the coast between Ballantrae and Bennane Lea.
The extent of the Corseclays Formation is delimited by erosion and the upper boundary of the Formation is not seen. It is not known if younger Permian or Triassic strata overlie the Formation.
Clackmannan Yard Coal
CLYC
Clyde Catchments Subgroup
CLYCA
Unconformable contacts with units of the Midland Valley, Mearns, Central Grampian and Southern Uplands Glacigenic subgroups, and bedrock.
The present physical catchments of the rivers Clyde, Kelvin, Endrick and the rivers of Ayrshire. The catchments extend across Strathclyde, (Ayrshire, Lanarkshire and Dunbartonshire).
A suite of fluvial, lacustrine, mass movement and periglacial deposits that contain clasts derived from Palaeozoic rocks and glacigenic deposits cropping out in the catchment of the River Clyde and other rivers flowing directly to the Firth of Clyde, including the River Leven, and Waters of Girvan, Ayr and Irvine. The deposits include alluvium and river terrace deposits of the Clyde Valley Formation, fluvial deposits of the Strathendrick Formation and Strathkelvin Formation, lacustrine deposits of the Kilmarnock Silt Formation, peat of the Clippens Peat Formation and other units defined simply as lithogenetic categories. The deposits of the subgroup comprise gravel, sand, silt, peat and head. Rock types are principally of Carboniferous and Devonian strata (sandstone, siltstone) with volcanic (basalt) and intrusive igneous rocks (microdiorite) of Midland Valley provenance. Variable but generally minor components of Dalradian metasedimentary and Caledonian igneous rocks derived from the Grampian Highlands are present. Southern Uplands sourced greywacke sandstone and siltstone and Caledonian igneous rocks form a component of clastic fluvial deposits in parts of catchments close to the Southern Uplands.
Generally the ground surface, but units of this Subgroup interfinger locally with units of the Great Britain Coastal Deposits Group.
Clyde Clay Formation
CLYD
Windermere Interstadial to Loch Lomand Stadial.
The Clyde Clay Formations rests with angular unconformity on older Quaternary sediments or bedrock. It normally rests on the Wilderness Till Formation (WITI) of the Caledonian Glacigenic Group (Midland Valley Glacigenic Subgroup).
The Clyde Clay Formation is recognised in the lower Clyde valley north of Lanark, in and around the estuary of the Clyde and Firth of Clyde and linked sea lochs, and in Loch Lomand. It is also present under the coastal plain of Ayrshire.
The Clyde Clay Formation has six members, from oldest to youngest - the Bridgeton Sand consists of beds of fine- to medium-grained sand, and sandy fine to coarse gravel in an upward-fining succession. The Paisley Clay consists of clays and silts, finely colour banded in shades of greyish brown, grey and reddish brown. The Linwood Clay consists of thickly bedded to massive silts, clayey silts and silty clays, medium to dark grey becoming brownish grey downwards, with sand layers, black sulphide bands and many marine shells. The Killearn Sand and Gravel is commonly reddish brown and yellow, fine- to medium-grained sand with clay layers and beds of gravel. The Inverleven Gravel typically is angular to subrounded boulders, cobbles and gravel in a clayey sand matrix with barnacles. The Balloch Clay consists of clayey silt, silt, clay and sand, mid to dark grey, brownish grey and locally reddish brown, bedded and thinly laminated, normal and reverse graded units, with dark sulphide patches and rare marine shells. Their stratigraphical relationships and geographical distribution are summarized in Browne and McMillan, 1989a, Figures 2b, c and d, 3A, B, C and D and 4A, B and C.)
Veneer to more than 50m.
The Clyde Clay Formation is overlain unconformably by younger Quaternary sediments, normally either the Clydebank Clay Formation of the British Coastal Deposits Group or the Clippens Peat Formation or Clyde Valley Formation of the Britannia Catchments Group (Clyde Catchment Subgroup). It is also extensively exposed at surface in the lower Clyde valley.
Clyth Formation
CLYTH
Coal Measures Group [Obsolete Except In Northern Ireland: Use Pcm, Swcm, Cmsc]
Base of Gastrioceras subcrenatum Marine Band (=Subcrenatum Marine Band) or at base of coal-bearing sequence if this marker band cannot be identified.
Britain, except Devon and Cornwall, and parts of Ireland for the Group; England and Wales for divisions LCM, MCM and UCM.
Alternation of sandstone, grey siltstone and grey mudstone, with frequent coal seams and seatearth horizons. NOTE: Definitions for the base of the Coal Measures, and the bases of the Middle and Upper divisions, are those of Stubblefield and Trotter (1957), but the top of the Coal Measures in the Pennine Basin is newly defined on a purely lithostratigraphical basis, (Powell et al., 1999). In areas such as South Wales, where no significant Carboniferous red-beds overlie the coal-bearing measures, the top of the Coal Measures may be defined differently.
Up to 1600m in the Potteries Syncline; to c.1900m in Lancashire.
Base of lowest conformably overlying red-bed formation - Etruria Marl or lateral equivalent.
Comber Andesite Member
CMAM
Cromar Pluton
CMAR
Cautley Mudstone Formation And Ashgill Formation (Undifferentiated)
CMAS
Colsterdale Marine Beds
CMB
Benscliffe Breccia Member
CMBA
Not seen, but inferred to be a sharp contact on grey, laminated volcaniclastic siltstones of the Blackbrook Reservoir Formation.
The unit extends from Hanging Stone (above), southwards to Benscliffe Wood and, northwards, and is last seen at Rhododendron Hill (SK 4980 1693), Nanpantan.
Grey, very thickly bedded, massive andesitic and dacitic volcanic breccia, grading to lapilli tuff, with subordinate beds of fine-, medium- and coarse-grained andesitic to dacitic tuff.
Grades up into medium- and coarse-grained tuff, with subordinate lapilli tuff beds, and pale grey, laminated to bedded tuffaceous mudstones, siltstones and sandstones of the Beacon Hill Formation. In the west it thickens and merges laterally with the Charnwood Lodge Formation (lower part).
Cambeck Member
CMBB
Conformable on Main Algal Fourteen of the Main Algal Member (Lyne Formation) of Bewcastle.
Rhythmic cycles of sandstones, thin limestones and mudstones, the beds abundantly shelly; some algal beds.
204m (Bewcastle).
Conformable upper boundary with the base of the locally developed Whitberry Bed of the Fell Sandstone Formation.
Coombe Coal (Nottingham And Derby)
CMBC
Combe Member
CMBE
Chalk gravel in a fine-grained chalk clay matrix, with flint pebbles; commonly overlain by a metre of pale brown silty chalky loam; waterlain. [Generic description: 1:50 k map margins].
Buck Hills Member
CMBG
Sharp to locally gradational base on Sandhills Lodge Member, latter comprising volcaniclastic sandstone and sediment-clast breccia.
Buck Hills.
Blue-grey, laminated, graded volcaniclastic mudstones and siltstones with beds of massive to graded medium-grained volcaniclastic sandstone.
About 790m
Sharp contact with interbedded volcaniclastic sandstones and breccias of Outwoods Breccia Member.
Beacon Hill Formation
CMBH
Probable sharp contact, at base of Benscliffe Breccia Member, on grey-green, laminated, fine- to medium-grained volcaniclastic beds of the Blackbrook Reservoir Formation.
Extends from Nanpantan Hills, south to Bradgate Park, then north-west to Ulverscroft Mill.
Varied sequence of grey to blue-grey epiclastic and tuffaceous mudstones, siltstones and sandstones with subordinate volcanic block-breccias and lithic-crystal tuffs.
About 1840m
Sharply overlain by Bradgate Formation beds, of blue-grey, laminated volcaniclastic mudstones, siltstones and sandstones.
Combe Martin Beach Limestone
CMBL
Carmichael Burn Formation
CMBN
Faulted out by the Carmichael Fault.
Pale greyish olive, greenish grey and greyish red mudstones and thin beds of olive-grey and purplish siltstones, locally containing marine fossils. One interbedded unit of greyish orange to greyish red quartose sandstone.
c.168m
Top of the predominantly mudstone succession of the Carmichael Burn Formation below the fairly sharp incoming of the Fence Conglomerate Member of the Westgate Formation
Camberley Sand Formation
CMBS
Creag Mhor Conglomerate Member
CMC
The base of the lowest conglomeratic unit within the Auchencar Sandstone Formation or locally the Auchencar Lava Member.
A coarse conglomerate with boulders of mainly andesite lava, with predominantly quartzite boulders in the lower part.
270 m thick.
The base of the Am Binnein Sandstone Formation.
Comin Coch Formation
CMCC
Charnwood Lodge Volcanic Formation
CMCL
Not exposed, taken at base of the Benscliffe Breccia Member, consisting of grey, crystal-rich volcanic breccia. This member overlies grey-green fine- to medium-grained volcaniclastic rocks of the Blackbrook Reservoir Formation.
North-west Charnwood Forest, from Grace Dieu to Bardon Hill.
Andesitic to dacitic volcanic block-breccias and lithic lapilli tuffs, massive to poorly stratified, divided into members in part. The unit is the lateral equivalent of the Beacon Hill Formation.
About 1300m
Sharp or gradational over 1m with Bradgate Formation, latter consisting of dark to medium grey laminated volcaniclastic siltstones and sandstones with disturbed bedding.
Comb Coal (South Yorkshire And Derby)
CMCO
Carmel Formation
CMF
Charmandean Flint
CMFL
Carrickmore Granite
CMGR
Caw Mill Sandstone
CMI
Sharp upward change in a conformable sucession from predominantly grey siltstone to sandstone - base of first sandstone bed above the Brennand Grit.
Abbeystead Forest [SD 5500 5400] southeast of Lancaster.
A medium-bedded, brownish grey, fine- to medium-grained, turbiditic sandstone.
0 to 10m
Sharp upward change in a conformable sucession from sandstone to predominatly siltstone - top of last sandstone below the Long Bridge Sandstone.
Carn Marth Intrusion
CMIN
Coarse-grained granite with abundant feldspar phenocrysts >15mm.
Crummack Formation
CMK
Taken at the base of calcareous mudstone and black graptolitic mudstone that contains a Rhuddanian and Aeronian fauna, overlying mudstone and siltstone of the Sowerthwaite Formation.
Mudstone and siltstone, black, graptolitic. Mudstones at the base of the formation are calcareous and contain a shelly fauna. Towards the top of the formation calcareous siltstones contain nodules and thin beds of limestone.
Up to 35m
Defined by the base of the overlying Austwick Formation.
Cleatham Limestone
CML
Lower Bajocian, Discites Zone.
Quasi-conformable contact with predominantly calcareous mudstone and siltstone of the underlying part of the Raventhorpe Member where present, or more or less disconformable contact with sandstones and mudstones of the underlying Grantham Formation, overlain by limestone.
BGS 1: 50 000 sheets 80, 89, North Lincolnshire (south of the Humber).
Limestone, predominantly calci-silty and calci-muddy with more or less abundant shell debris and peloids (wackestone and packstone) and fine quartz sand, ferruginous in some beds. Locally containing calcareous mudstone or siltstone interbeds, locally with ooidal packstone and grainstone at the top.
Use of the term Cleatham Limestone (mapped on sheets 80 and 89) should not be perpetuated in any review of the Lincolnshire Limestone. Even if the term is deemed valid the Member status should be dropped and the term returned to informal "Cleatham Limestone" status. Member status is inappropriate as it lies within the "Reventhorpe Beds Member" of Gaunt et al., 1992. Recommended stratigraphical revision of the Lincolnshire Limestone Formation places the latter as part of the Lower Lincolnshire Limestone Member. Due to the confusion over the status of the Cleatham Limestone and the Raventhorpe Beds, the Parent Unit is indicated as Lower Lincolnshire Limestone Member. The Cleatham Limestone is a mixed bag of limestones that were mapped south of the Humber. If a local thin leaf of underlying mudstones is ignored the unit is the same as the Hydraulic Limestones (south of the Humber) of previous authors, which were excluded from the Raventhorpe Beds. Ashton (1975, 1980) complicated the issue by placing some of the Cleatham/Hydraulic Limestone in his Santon Oolite Member (lower leaf). The unit is a useful entry as regards mapping though, given its modest thickness and undistinguished lithology it might better be considered as "Limestone in Raventhorpe Beds". [Condensed from notes by M G Sumbler, 29/09/2005.]
0 to c.2m
Conformable contact between limestone below and predominantly calcareous mudstone and siltstone of the overlying part of the Raventhorpe Member (Lincolnshire Limestone Formation).
Cilmaenllwyd Coal (South Wales)
CMLC
Crammel Linn Sandstone
CMLS
Clenchers Mill Member
CMM
Combe Mudstone Formation
CMMU
The lower boundary is taken at the incoming of bluish black and black mudstones of the Combe Mudstone Formation above the olive green and pale grey mudstones of the underlying Trusham Mudstone Formation.
Teign Valley (SX 84 84) and Ilsington area (SX 78 76), east Dartmoor, south Devon.
Very fissile bluish black "shales", locally characterized by white, silty laminations and closely spaced vertical joints, particularly in higher horizons. Siliceous nodules become common in the upper part. The formation is unfossiliferous apart from ?wood fragments.
45m in the Ilsington area, thickening northwards to 90-200m in the Teign valley area.
The upper boundary is taken at the incoming of interbedded cherts and siliceous mudstones of the overlying Teign Chert Formation above the bluish black and black mudstones of the Combe Mudstone Formation. The boundary is taken at the base of the first bedded chert.
Causemountain Formation
CMN
Cementstone Formation
CMNT
Coal Mosie (Clackmannan)
CMO
Carn Monadh Gravel Formation
CMOGR
Sharp, undulating, erosional, unconformable contact with stony, sandy, clayey diamictons of the underlying Beinn an Uain Till Formation.
Moy Estate on Sheet 84W (Fortrose), southeast of Inverness.
Forming ice-marginal fans.
Silty sandy gravel, horizontally stratified, thin-bedded, pale olive grey, with subsidiary beds of sand, clast-supported gravel and silty sandy gravel diamicton. Pebbles consist of red and grey granites, semipelitic gneiss, psammite and brown flaggy sandstone.
Not overlain.
Carnmoney Plug
CMP
Park Breccia
CMPB
The unit probably extends laterally for several kilometres, around the nose of the south-plunging Charnwood anticline, but is only seen at Bradgate Park in the east, and by the road bridge carrying the B587 across the A50 at Raunscliffe [SK4863 1090], to the west.
Grey, sediment-raft volcaniclastic breccia consisting of angular, commonly elongate or raft-shaped fragments of fine-grained, laminated tuff in a coarse-grained matrix of plagioclase and quartz crystal fragments.
Gradational upward passage into grey, bedded tuffs of the Beacon Hill Formation.
Campsie Limestone Member
CMPL
The base of the clastic, generally conglomeratic beds, with limestone concretions, above the cross-bedded sandstones within the Scone Sandstone Formation.
The Strathmore Syncline, in the northern part of the Midland Valley of Scotland.
Predominantly sandstones with concretionary limestone beds and lenses, subsidiary conglomerate and mudstone with minor pebbly sandstone.
Up to 57 m thick in the type section.
The base of the purple-brown mudstones belonging to the Cromlix Mudstone Formation
Crom Psammite Formation
CMPS
Overlies the Vach Pelite Formation, where predominantly pelitic lithologies pass into predominaintly psammitic lithologies.
Comprises a large outcrop north of Loch Luichart, around the Carn Chuinneag intrusion, beneath large areas of Strathgarve Forest, Gabat Forest, Wyvis Forest, and the area around Loch Vaich and Gleann Mor. The north-eastern margin is defined by the faulted Old Red Sandstone unconformity, trending north-east from Loch Fleet in the north-east, to Strathglass in the south-west. It may continue to the north, on the eastern side of the Rogart Pluton at the western end of Strath Bora. The extent to the north and west of the Rogart Pluton is unclear. The eastern limit is largely defined by the Sgurr Beag Thrust running north-east to south-west from Loch Luichart (NH360620) to Dornoch Firth (NH645875). South of Loch Luichart the south-eastern extent is constrained by the Strathconnon Fault. The southern boundary is constrained by the Sgurr Beag Thrust occurring in the area from Sgurr a'
Well-bedded, flaggy to massive, white to pale grey and buff psammite, with abundant sedimentary structures. Garnetiferous semipelite bands are common in the lower portion, and it is locally pebbly in the upper part.
Not recorded.
Overlain by the Diebidale Pelite Formation, where predominainlty psammitic lithologies pass into predominantly pelitic lithologies. The upper boundary is locally obscured by the Sgurr Beag Thrust, the Carn Chunneag-Inchbae Granite Gneiss, or the Old Red Sandstone unconformity.
Cwmere Formation
CMR
Cwm Mawr Coal (South Wales)
CMRC
Note that this seam is within the Brithdir Member of the Pennant Sandstone Formation and should not be confused with the Cwmmawr Coal within the South Wales Middle Coal Measures Formation farther east.
Carn Mor Sandstone Member
CMSA
Abrupt disconformity, marine, transgressive sandstones on the mudstones of the Great Estaurine Group.
Coarse-grained (pebbles to 3cm), bioturbated sandstone. Numerous brachiopods and belemnites, many remaining only as moulds. [Thalassinoides] burrows extend into the mudstone below the Formation.
9m+
Unconformity to mudstones of the Staffin Shale Formation.
Scottish Coal Measures Group
CMSC
Different in different areas. (See notes in lithology).
Midland Valley of Scotland, and adjacent areas.
Cyclic alternation of mudstone, siltstone and sandstone with common coal seams at some levels. NOTE: FORMERLY - (1) Upper (Barren) Coal Measures. (2) Productive Coal Measures (comprising Middle Coal Measures and Lower Coal Measures). The Coal Measures of England and Wales were defined by Stubblefield and Trotter, 1957, and divided into Upper, Middle and Lower with their respective bases at the Cambriense, Vanderbeckei and Subcrenatum marine bands. MacGregor, 1960, divided the Scottish Coal Measures into Upper (Barren), with base at the Aegiranum marine band, Middle, with base at the Vanderbeckei marine band and Lower which, in the apparent absence of the Subcrenatum marine band in Scotland, he proposed should have its base at a suitable arbitrary line. The position taken for this line in different coal basins is shown in Ramsbottom, et al. 1978. It is proposed that these local bases of the Lower Coal Measures, and the boundaries defined by MacGregor for the Middle and Upper Coal Measures be retained. The long standing terms should be retained but since only the Middle Coal Measures is fully defined, they are regarded as informal. As the terms are applied differently in England and Wales, it is proposed that Scotland should be added to Coal Measures in parenthesis. The terms "Barren" and "Productive" are misleading in a Scottish context and should be dropped.
Variable
Unconformity at base of Permian or younger rocks.
Combe Martin Slates Member
CMSL
?Givetian to Frasnian.
Sliding Stone Slump Breccia Member
CMSS
Sharp contact on grey, laminated tuffaceous mudstones and siltstones of the Beacon Hill Formation.
The unit forms a thin 'marker horizon' in the western, southern and eastern parts of the Bradgate Formation, between The Hollies (SK 478 118) and Bradgate Park (SK 5308 1149).
Grey, coarse-grained volcaniclastic sandstone with abundant angular clasts and large folded and contorted rafts of grey, laminated mudstone and siltstone. Beds of volcaniclastic sandstone and siltstone become increasingly intercalated towards the top of the unit.
Variable, possibly up to 18m.
Grades upwards, by decrease in proportion of beds with mudstone rafts, into volcaniclastic sandstones and siltstones of the Hallgate Member.
Cromer Till (Lowest Member)
CMTL
Cautley Mudstone Formation
CMU
Not exposed, but taken at the base of the lowest bed of mudstone overlying a small exposure of purple andesite, putatively belonging to the Borrowdale Volcanic Group.
Restricted to the Cautley and Dent districts of Cumbria.
Calcareous mudstone with impersistent limestone beds; includes units of sandstone at the base and higher in the succession [Wilsey Beck Sandstone Member]; also of rhyolitic tuff [Cautley Volcanic Member].
Up to 570m
Taken at the unconformity with the overlying Ashgill Formation.
Maplewell Group
CMV
Coarse-grained tuffs and breccias of the Benscliffe Breccia Member sharply overlie green-grey thinly bedded to laminated fine- to medium-grained volcaniclastic beds of the Blackbrook Reservoir Formation.
The unit is distributed within the centre and flanks of the Charnwood anticline, generally between Nanpantan, Benscliffe Wood and High Sharpley.
Varied sequence of meta volcaniclastic and meta tuffaceous sandstones, siltstones and mudstones with vitric tuffs and volcanic block-breccias (mainly dacitic).
Approximately 2000m
Sharply, possible unconformably overlain by the Brand Group. Latter consists locally of small-pebble conglomerate or coarse-grained volcaniclastic sandstone of the Hanging Rocks Conglomerate Formation.
Craig Of Monievreckie Conglomerate Formation
CMVC
A faulted contact to the north-east of Aberfoyle.
The north-west limb of the Strathmore Syncline, from Maol Ruadh to north of Callander.
A clast supported conglomerate, with some bimodal sorting seen as generally massive volcanic clasts near the base of the unit, giving way to quartzite and psammite upwards and south-westwards along strike. Subsidiary sandstones include the Bofrishlie Burn Sandstone member, located below the basaltic Balleich Lava Member.
Up to 1200 m thick.
A pronounced diachronous transitional contact with the conglomeratic or sandstone facies of the Ruchill Flagstone Formation.
Coal Measures Group And Warwickshire Group (Undifferentiated)
CMWK
Colinburn Coal (Central Coalfield)
Canna Lava Formation
CNAL
Basal Member (Canna Lava Formation)
CNAL1
Tighard Member
CNAL2
Cnoc Bhrostan Member
CNAL3
Carn A' Ghaill Member
CNAL4
Beul Lama Sgorr Member
CNAL5
Eilean A' Bhaird Member
CNAL6
Carron Basalt Formation
CNB
Rests with irregular contact on Carboniferous Coal Measures strata.
Between Glenvalentine (NS 880 077) and Thornhill area (NX 880 950) in the Thornhill Basin; also at Locherben (NX 953 970).
Olivine basalt lava flows interbedded with thin breccias and sandstones.
Overlain by sandy breccias and sandstone of the Durisdeer Formation.
Coronation Coal (Fife)
CNC
Concretionary Limestone Member
CNCL
Gradational, by interdigitation with the underlying Hartlepool Anhydrite Formation.
Durham Province, onshore and offshore outcrops, of the English Zechstein Group: County Durham, Tyne and Wear, Cleveland and northernmost North Yorkshire.
Lithologically varied dolostone with calcite concretions formed by a variety of primary and secondary sedimentary processes. Interpreted as the basin slope deposit of the Roker Formation (see Smith, 1994, fig.46 on page 94).
Up to a maximum of about 95 - 100m.
Base of the overlying Forden Evaporite Formation, marked by the incoming of anhydrite and halite.
Cnoc Nan Cuilean Intrusion
CNCS
Namurian To Stephanian Rocks (Undifferentiated)
CNCSU
Clanyard Formation
CND
Conformable on Moffat Shale Group at Clanyard Bay.
Thick-bedded greywacke with interbedded thin black shale bands and thick ( up to 40 metres) silty mudstone units.
Craig Hen-Gae Member
CNE
Conformably overlies the main part of the Ceiswyn Formation, the boundary being taken where laminated hemipelagic mudstones become equal or dominant in the sequence.
Cadair Idris district, North Wales.
Black hemipelagic mudstones, thinly interbedded with grey turbiditic mudstones and siltstones.
200 to 300m
Conformably overlain by the Nod Glas Formation, the boundary being taken where the turbidite mudstone disappears and the sequence consists wholly of black, graptolitic, pelagic mudstone.
Coronea Formation
CNEA
Cannel Coal (Midgeholm)
CNEL
Coire Nan Easan Tuffs
CNET
Confinis Formation
CNF
Overlies and is partly lateral equivalent of Auchensoul Bridge Mudstone.
Stinchar Valley area, Girvan.
Blue-grey calcareous flaggy sandstone.
50m
Overlain conformably by the Stinchar Limestone Formation.
Canonbie Nine Foot Coal
CNFC
Caithness Flagstone Group
CNFL
Top of red bed sandstones of Yesnaby Sandstone Group in Orkney and of Sarclet Group in Caithness.
Orcadian Basin - Shetland to Moray Firth, Northern Scotland.
Flagstone, rhythmic mudstone-limestone, siltstone, sandstone units. NOTE: See component formations for Type Sections.
Base of yellowish brown sandstones of the Orkney Sandstone Group .
Charlestown Green Limestone
CNGR
Carnduff Halite
CNH
Craignook Coals (Midgeholm)
CNKC
Craignook Sandstone
CNKS
Chipping Norton Limestone Formation
CNL
Middle Jurassic, Bathonian (Zigzag Zone) (Possibly extending into adjoining zones).
Conformable/non-sequential on fine- to coarse-grained ooidal and peloidal limestone, locally ironshot, of Clypeus Grit Member. Oversteps northeastwards to rest non-conformably on Grantham Formation, Northampton Sand Formation and Whitby Mudstone Formation.
North Gloucestershire to north Oxfordshire, where it passes northeastwards(on BGS 1:50 000 sheet 218) into the Horsehay Sand Formation (shown on 1968 edition of sheet 218 as the 'Lower Estuarine Series', now known as the Grantham Formation, but now thought to be generally absent south of Kettering).
Limestone, off-white to pale brown fine- to medium-grained ooidal and coated peloidal grainstone, with common fine burrows, medium- to coarse-grained shell debris and flakes of greenish grey mudstone and dark lignite and minor amounts of fine-grained sand. Thick-bedded and cross-bedded or massive, weathering to flaggy or platy. Thin shell-detrital and ooidal marl and mudstone intercalations in places. Becoming very sandy eastward ("Swerford Beds" facies). Locally a mudstone bed ("Roundhill Clay" of Richardson, L, 1929) up to c.1m thick occurs at the base.
Rapid passage upwards into mudstone-dominated Fuller's Earth Formation or Sharp's Hill Formation.
Cannel Coal (Machrihanish)
CNLC
Coire Nan Laogh Semipelite Formation
CNLH
Sharp contact with underlying grey feldspathic psammites of the Gairbeinn pebbly psammite member - well exposed in Garbh Choire [NN 4628 9895] and south of Uinneag Mhin Choire [NN 4651 9955].
Central Highlands of Scotland, sheets 63W, 63E and 74W.
Schistose to gneissose semipelite, garnetiferous, with interbanded micaceous psammite. Minor feldspathic and siliceous psammite beds; calc-silicate lenses common.
Transitional through upper psammite and semipelite unit defined by incoming of thick turbiditic psammites of the Loch Laggan Psammite Formation.
Cornelly Oolite Formation
CNLL
The base of the formation is gradational and taken at the incoming of a predominantly oolitic grainstone sequence above the skeletal packstones or skeletal/oolitic packstone/grainstones of the underlying High Tor Limestone Formation.
Central and western Vale of Glamorgan [ST 00 74]. Passes eastwards into undivided Hunts Bay Oolite Subgroup. Present in Gower [SS 50 90] and Pembrokeshire [SM 99 01], but not mapped.
Thick bedded, cross bedded, pale grey ooid grainstones with scattered beds of medium grey fine-grained skeletal packstone. Compound ooids of pisolitic proportions common. Thin mudstone associated with the palaeokarstic surface at the top of the Cefnyrhendy Oolite Member, present in the northeast of the Vale of Glamorgan.
135m in the west of the Vale of Glamorgan, thickening to 180m in the eastern part of the Vale of Glamorgan.
The top of the formation is taken at the base of the first bed of calcite mudstone of the overlying Stormy Limestone Formation occuring above the ooid grainstones and subordinate skeletal packstones of the Cornelly Oolite Formation.
Carn Limestone Member
CNLM
Carnallitic Marl
CNM
Cannapark Limestone
CNPL
Cannel Row Coal (North Staffordshire)
CNRC
Coire Na Rainich Hybrid Ring-Dyke
CNRH
Chipping Norton Limestone Formation And Rutland Formation (Undifferentiated)
CNRL
Coire Na Rainich Peridotite Raft
CNRP
Caran Sandstone Unit
CNSA
Crendon Sand
CNSD
Carleton Silt Formation
CNSI
Sharp, gently undulating, unconformable, draped contact with underlying stony sandy clay diamicton of the Maudsyke Till Member of the Blengdale Glacigenic Formation.
Silt and clay, laminated, very stiff, pinkish grey, dusky red and light reddish brown (Munsell Soil). Laminae up to 10 mm thick, fining upwards.
To 11.6m
Gradational, conformable contact with overlying dark brown calcareous clay of the Carleton Hall Clay Member of the Glannoventia Formation.
Canisp Porphyry Sills
CNSP
Cnoc Na Sroine Quartz-Syenite
CNSQ
Creag Na Sanais Semipelite Formation
CNSS
Top of the predominantly psammite beds belonging to the Creag Dhubh Psammite Formation, below the predominantly semipelitic beds of the Creag na Sanais Semipelitic Formation.
South of Newtonmore, west of Crubenmore on Sheet 64W
Dark grey gneissose semipelite composed mainly of muscovite, biotite, quartz, some plagioclase and garnet, with local thin fine-grained biotite-rich and quartoze psammite interbeds.
Base of the predominantly psammitic Allt nam Biorag Member, Fara Psammite Formation, above the predominantly semipelitic beds of the Creag na Sanais Semipelite Formation.
Cefnnantmel Member
CNT
Taken at sharp incoming of sandstone dominated sequence above burrow mottled mudstones with sparse thin sandstones.
Cross-laminated thin sandstones with subordinate mudstones. Rich shelly fauna.
Gradational but taken at incoming of mudstone dominated sequence of burrow mottled mudstones with sparse thin sandstones.
Con Tom Member
CNTM
Carnhill Mugearite
CNU
Cairnharrow Formation
CNW
Thin- to medium-bedded greywacke with variable proportion of interbedded silty mudstone including some thick (to 40m) units. Includes pockets of distinctive thick-bedded parallel laminated greywacke with abundant concretions.
Cheshire - North Wales Catchments Subgroup
CNWCA
Catchments of Cheshire and North Wales including the valleys and tributaries of the rivers Mersey, Weaver, Dee, Clwyd and Conway.
Alluvial silt, sand, clay and gravel with some peat. Associated River Terraces are dominated by sand and gravel, gravelly sand or sandy gravel with rare clay and silt. The Subgroup also includes coastal and inland basin peat and a variety of mass movement deposits.
Highly variable depending on the relative stratigraphical positions of each of the component units. In the major river valleys the thickness may vary between 2 and 5m, but probably does not exceed 10m. For deposits flanking the major river valleys, the thickness probably ranges between 1 and 3m.
Clanyard Bay Formation
CNY
Conybeare Group
CNYB
No.1 Comrie Blackband Ironstone
CO1
No.2 Comrie Blackband Ironstone
CO2
No.3 Comrie Blackband Ironstone
CO3
Coalsnaughton Main Coal (Clackmannan)
COAM
British Coastal Deposits Group
COAS
Unconformable contact with units of the Britannia Catchments Group, the Caledonia Glacigenic Group, the Albion Glacigenic Group, the Dunwich and/or Crag groups, and bedrock.
A suite of near-shore marine, coastal and estuarine deposits of sand, gravel, silt, clay and peat that contain clasts derived from rocks cropping out throughout Great Britain and the Isle of Man. Includes glacio-isostatically uplifted [raised] deposits lying to the north of a hinge-line crossing northern England between the Ribble and Tyne, and isostatically uplifted Interglacial shoreline deposits around the coast of southern Britain.
Generally the ground surface, but units of this Group commonly interfinger with units of the Britannia Catchments Group. Raised beaches of Late Devensian age commonly interdigitate with units of the Caledonia Glacigenic Group.
Cosheston Group
COB
The base of the group is coincident with the base of the Llanstadwell Formation. This is placed at the base of the lowest primary-coloured green bed at the western end of the railway cutting in the naval depot at Newton Noyes, Pembrokeshire [SM 9150 0530]. This is a 0.32m thick greenish grey, coarse grained, parallel-laminated siltstone 21.7m above the base of the section logged by Thomas et al (2006), which lies conformably on red mudstones of the underlying Gelliswick Bay Formation (formerly Red Marl Group).
The Group comprises an area of 27 square km in the Milford Haven area, south Pembrokshire. It mainly crops out in the Burton Anticline, between the Benton Fault in the north [c.SM 97 08] to near Cosheston [SN 003 034] in the south, and from Llanstadwell [SM 95 05] in the west to New Shipping [SN 04 04] in the east. A smaller outlier to the west of the main outcrop extends from Newton Noyes [SM 92 05] in the west to Wear Point [SM 940 043] in the east.
Predominantly grey-green very fine- to coarse-grained, plant-bearing sandstones, red-brown and purple-brown siltstones; some intraformational conglomerates in the lower part (Llanstadwell and Mill Bay formations); extraformational conglomerates in the upper part (Lawrenny Cliff and New Shipping formations), becoming dominant at the top of the Group (New Shipping Formation). The rocks are arranged predominantly in fining-upward rhythms.
To 1800m
The upper boundary is not seen, the highest (New Shipping) Formation being unconformably overlain by strata of the Avon Group (formerly the Lower Limestone Shales) of early Carboniferous age. This junction is seen on the shore on the east side of the Carew River [SN 03852 04105] southsoutheast of New Shipping Point. It is a scour surface with up to 2cm relief cut in medium- to coarse-grained purple sandstone overlain by a bed of quartz grit up to 4cm thick with shell fragments.
Coatbridge Balmoral Coal (Central Coalfield)
COBC
Coastal Barrier Deposits
COBD
Sand or gravel; form a major longshore bar, the surface of which is below the mean still water level. [Generic description: earth science dictionaries in the BGS library].
Cockburn Formation
COBN
Corrieyairack Subgroup And Glen Banchor Succession (Undifferentiated)
COBS
Cockburns Law Intrusion
COBU
Conwy Castle Grit Member
COC
Corbie Coal (Lothian)
COCG
Coire Cheap Formation
COCH
Sharp base at the marked quartzite-pelite / semipelite boundary at the top of the Kinlochlaggan Quartzite Formation. Alternatively lies above the Kinlochlaggan 'Boulder Bed'.
Ardverikie Forest between Aonach Beag [NN 455 740] and the River Spey at [NN 933 571], sheet 63E [Dalwhinnie].
Semipelite and pelite, schistose to gneissose and locally kyanite-rich, containing calc-silicate rock and metalimestone units. Cut by abundant amphibolite sheets.
Not known, but at least 200m
Not seen ie. this is the youngest unit exposed in the major Kinlochlaggan syncline.
Cairnsmore Of Carsphairn Pluton
COCI
Coire Na Circe Formation
COCIR
Cock Coal (Bristol Area)
COCK
Coal seam
Coagh Conglomerate Member
COCL
Coolcran Conglomerate Member
COCM
Corston Coal (Bristol Area)
COCO
Corbie Craig Coal
COCR
Combe Down Oolite
CODO
Combe Downs Member
CODS
The base is taken where the base of the lowermost bed of sandstone or siltstone of the Combe Downs Member rests conformably upon pale to mid grey or purplish grey mudstone of the Pilton Mudstone Formation.
Mapped from east of Shillingford [SS 993 244] to west of Bathealton [ST 068 249] on the Tiverton Sheet (310). Expected to occur more extensively on the southern part of the Dulverton Sheet (294), where a type locality might be found, leading to a more suitable name for the Member.
Pale to mid grey to pale brown, ochreous-weathered or purple mottled, very fine- to fine-grained, locally micaceous sandstone interbedded with purplish grey, pale brown, pink or red-brown, finely micaceous siltstone, mid grey, purple-grey and red-brown mudstone and thin limestone beds. The limestone beds, to 0.1m thick, are typically soft and comprise mid grey, sparry calcarenite with abundant shelly material. Limestone and sandstone interbeds on the centimetre-scale are locally seen. Sandstone beds are typically 30cm thick, but in places coalesce to form thicker sandstone packages to 60cm thick. Sandstone and siltstone beds are commonly thinly planar laminated or cross laminated, locally massive. Mudstone beds range from thinly laminated or thinly bedded to massive. Crinoid ossicles and intact stems and brachiopod valves are locally common in all lithologies.
c.200m, but difficult to determine due to folding and faulting.
The top is taken where the top of the uppermost bed of sandstone and siltstone is conformably overlain by silvery pale greenish grey fissile mudstone of the Pilton Mudstone Formation.
Coddington Till Formation
CODT
Placed generally where the till overlies the clays and silts of the underlying White House Silts. Locally, the base rests on Mathon Sand and Gravel.
Cradley - Glynch Brook Valleys, Herefordshire.
Consolidated, red silty clay or clayey silt with pebbles to boulders of local and exotic lithologies.
Maximum proved thickness of c.10 metres.
Placed at junction of red till and overlying grey to yellow-brown stony clay solifluction/gelifluction deposits of Colwall Gelifluctate.
Coedana Complex
COED
Anglesey Special 1:50 000 Geological Sheet, but unit probably extends offshore. Comprises a belt of rocks that extends NE-SW across central Anglesey, but is also found in thrust slices in NW Anglesey, and in inliers surrounded by younger strata. Lateral boundaries unknown; certainly faulted in part, but with igneous contacts and metamorphic gradients also.
Migmatitic pelites and semi-pelites, calc-silicate gneisses, amphibolites and granite, with hornfelsed aureole.
Coedana Granite
COEDG
Anglesey, North Wales.
Porphyritic alkali-feldspar granite, commonly mylonitised.
Coleford Member
COFD
Taken at the base of the lowermost sandstone of 'Pennant'-type (lithic arenite) of the Coleford Member. Occurs conformably above coarse-grained sandstone of the Trenchard Formation in the north of the Forest of Dean Coalfield and unconformably upon limestone and sandstone of the Pembroke Limestone Group in the south.
Restricted to the Forest of Dean Coalfield (SO 60).
Predominantly a thick-bedded, coarse-grained sandstone of "Pennant"-type (lithic arenite), with subordinate interbeds of grey and green mudstone with ironstone concretions and coal. The sandstone is trough cross-bedded to planar bedded and beds commonly show erosive scours. Sandstone beds from beneath the Coleford High Delf seam are typically fine- to medium-grained. Coal seams up to 1.5 m thick are present within the succession.
180m in the north to 300m in the south of the Forest of Dean Coalfield.
Taken at the base of the Brazilly Coal, present at the base of a grey mudstone- dominated succession of the Cinderford Member of the Grovesend Formation. The coal rests conformably upon thick-bedded, coarse-grained sandstone of the Coleford Member.
Cairnsmore Of Fleet Pluton
COFG
The pluton is exposed in south-west Scotland. It extends from Cairnsmore [NX 49 65] in the south-west to New Galloway [NX 62 76] in the north-east.
The pluton is compositionally zoned comprising a marginal coarse-grained feldspar-phyric granite enclosing a central fine- to medium-grained aphyric granite. The outer zone has been divided into a marginal biotite-granite and an inner biotite-muscovite-granite.
Geophysical studies indicate that it extends to a depth of 10 - 12km. (Parslow, 1968; Parslow and Randall, 1973).
Fleet Pluton (Phase 1)
COFG1
Fleet Pluton (Phase 2)
COFG2
Cosham Flint
COFL
Coed Ffyddlwn Formation
COFYD
The base is a sharp junction between the topmost ooidal grainstone of the underlying Blaen Onnen Oolite Formation and the basal dolostones of the Coed Ffyddlwn Formation.
Northeast crop of the South Wales Coalfield, from Chwar Pant-y-rhiw [SO 2020 1560] southeast to about the area of Gallowsgreen Quarry, Varteg Hill [SO 2662 0677].
The lower part comprises fine-grained dolostones, the upper part (the Darren Ddu Limestone Member) comprises thinly bedded micritic limestones, fine grainstones and mudstones.
To 18m
The top is a sharp erosion surface overlain by the basal, coarse grainstone (Craig-y-Gaer Coral Bed) of the overlying Gilwern Oolite Formation.
Corbar Grit
COG
The base of the unit is poorly defined. In the field and on stratigraphic logs, the lower boundary is taken at the base of the first sandstone within a sandstone-dominated unit overlying a mudstone-dominated part of the Millstone Grit Group, overlying an unnamed sandstone within the latter; where this is absent the unit is the first sandstone-dominated unit above the mudstone-dominated part of the Millstone Grit Group overlying limestones of the Monsal Dale Limestone Formation.
Longclough (Cheshire) [SJ 987 737], Whitehills [SJ 973 728] (Cheshire); Edgemoor (Derbyshire) [SK 0343 7345].
Sandstone, fine-grained, flaggy, feldspathic, with subordinate mudstone, in up to 4 turbiditic cycles.
The upper boundary is taken at the base of a mudstone-dominated succession of the Millstone Grit Group above sandstones of the Corbar Grit.
Carse Of Gowrie Clay Member
COGCL
Unconformable, on the sub-Carse Peat (Flanders Moss Peat Formation) and older Holocene and late Devensian units including the Carey Silt Member.
Lower Tay valley from northwest of Perth, the Tay estuary and Firth of Tay, the lower Earn valley, east of Forteviot, and estuary, the lower Eden valley, east of Cupar, and estuary, the Montrose basin area.
Clayey silt and clay, commonly rooty and structureless; highly laminated with silt and very fine- to medium-, locally coarse-grained sand with pebbles up to 5mm and fragments of vivianite; grey and brownish grey, finely micaceous with sporadic dark sulphidic patches.
Veneer to 10m
Upper boundary (unconformable?) with transgressing Gowrie Silt Member (Carse Clay Formation) and commonly at the surface.
Crousa Gravels
COGR
Pliocene (probable).
An unconformable contact with the underlying gabbro of the Lizard Series, which here is weathered and covered with rounded boulders of less weathered gabbro. Gravel of white and dark grey quartz pebbles, with tourmalinite and granite in the lowest part of the Crousa Gravels are stratified, and contain discontinuous layers of sand and clay.
The Lizard Peninsula, Cornwall.
Comprises rounded pebbles of white quartz, 2.5 to 15cm in diameter, uncommon dark grey or blue quartz-tourmaline rock and rare granite, which is very weathered. Near the base of the deposit, the gravel is stratified and contains thin interrupted intercalations of yellow sand and white clay. Towards the top of the deposit, the gravels are disturbed and bedding planes are commonly curved, probably as a result of freeze-thaw action.
To 6.1m
The present day erosion surface landscape is locally covered by thin Head deposits. Vegetation growing on the Crousa Gravels is typically a scanty growth of heather and thorn.
Coull Grit Formation
COGT
Codden Hill Chert Formation
COH
Note: the Age Range shown (Arundian to Brigantian) derives from an earlier Partial Lexicon entry. A generalized age of "Dinantian" may be more appropriate and realistic, pending acquisition of more specific evidence.
The lower boundary is taken at the incoming of thin-bedded dark grey siliceous mudstones and shaly mudstones of the Codden Hill Chert Formation above the dark grey slightly siliceous mudstones of the Doddiscombe Formation (Unit D of the Pilton Beds of Prentice 1960). The Doddiscombe Formation has not been mapped on Sheet 293 (Barnstaple by Edmonds et al (1985), being included in the Pilton Mudstone Formation and/or Codden Hill Chert Formation. Further investigation is needed.
Between Fremington and South Molton, north Devon (SS 70 28).
Lower half (Tawstock Formation of Jackson, 1991) comprises thin- to medium-bedded pale and dark grey siliceous mudstones, shaly mudstones and cherts. Upper half (Hearson and Rubble Hills formations of Jackson, 1991) comprises thin- to medium-bedded limestones, turbidites and mudstones with streaky laminated cherts in the uppermost part. Two thin tuffs are present and Pectinoid bivalves are common in the upper half. Facies variations mapped on Sheet 293 (Barnstaple) by Edmonds et al (1985) have been shown by Jackson (1991) to be illusory and due to faulting resulting in stratigraphic omissions. Similarly a facies recognised by Prentice (1960) in the Fremington area and dominated by limestones and mudstones has been shown by Jackson (1991) to be the upper half of the Formation with the lower half thrust out.
West of South Molton, the upper boundary is taken at the incoming of dark grey to black pyritic mudstones within thin siltstones of the overlying Dowhills Mudstone Formation above the streaky laminated cherts and mudstones of the Codden Hill Chert Formation. The boundary is taken at the top of the highest chert bed. The Dowhills Mudstone Formation (Limekiln Beds of Prentice, 1960), was included in the Crackington Formation by Edmonds et al. (1985) on Sheet 293 (Barnstaple). Further investigation is needed.
Collingham Head
COHD
Found dominantly on the south (north-facing) side of the lower Wharfe valley (Yorkshire), but also occurs more patchily along the northern valley side and in tributary valleys. The deposit forms a recognisable solifluction "terrace" between essentially superfical deposit-free ground above and flat-topped erosional benches in the valley below.
Mainly comprises soliflucted glacial material, dominantly till (diamicton), locally incorporating blocks and smaller fragments of near-source bedrock material.
Coilacreich Intrusion
COIL
Cokeyard Coal (Ayrshire)
COK
Cockshead Coal (North Staffordshire)
COKC
Coke Coal (Bristol Area)
COKE
Colla Firth Formation
COLA
Coldingham Formation
COLB
Llandovery to Wenlock?
Coldingham area, Berwickshire, southeast Scotland.
Thinly-bedded greywacke sandstone, shale and calcareous siltstone.
Colinswell Marine Band
COLM
Mudstone.
5.79 metres. (Top 230.35 metres, bottom 236.14 metres).
Collieston Formation
COLN
Colpatie Coal
COLP
Cornet Limestone
COLS
Coll-Tiree Swarm
COLTI
Colluvium
COLV
Corry Member
COM
Coatbridge Musselband
COMB
Coatbridge Musselband Coal (Central Coalfield)
COMC
Coal Measures Supergroup
COME
Coatbridge Musselband Ironstone
COMI
Commodore Formation
COMM
Conwy Mudstones Formation
COMU
Grey mudstones and siltstones with thin, flaggy, cross-bedded and ripple marked sandstones.
Early Cambrian Rocks (Undifferentiated)
COMY
Connswater Marl Formation
CONN
Conwy Valley Formation
CONWY
Sharp, unconformable and locally channelised, predominantly on bedrock and Late Devensian head and Welsh glacigenic deposits (e.g. Eryri Till Formation). Interdigitates in a complex manner with Tidal Flat Deposits (Gwynllwg Formation of Bowen, 1999) in the estuary.
The valley of the River Conwy and its tributaries (Gwynedd and Clwyd), northern Wales.
Unconsolidated, stratified gravels, sands, silts and clays forming the alluvial deposits of the Afon Conwy (River Conway) and its tributaries. Includes contemporaneous head, colluvium and pedogenic deposits within the catchment area. Clasts principally consist of local Lower Palaeozoic turbidites admixed with Ordovician volcanic rock clasts derived from Snowdonia and the Harlech Dome (either primarily, or secondarily from the reworking of glacigenic deposits). Aggradational riverr terraces and major alluvial fans are dominated by pebble cobble gravels and medium- to coarse-grained sand, and locally by silty clay with pebble and cobble beds (Warren et al, 1984), the modern floodplain is dominated by silt and clay, and locally includes lenses of peat.
Generally to around 10m, with up to 2m exposed locally (Warren et al. 1984).
Generally the present ground surface or, locally, overlain by peat.
Coralline Oolite Formation
COO
Cooldaragh Formation
COOH
Cook Formation
COOK
Coolbeg Breccia Formation
COOL
Cairns Of Ord Intrusion
COORD
Coal Pit Formation
COP
Basal erosion surface dissects Fisher, Ling Bank and Aberdeen Ground Formations.
Sandy silty clay and interlaminated clay and fine-grained silty sand; clay generally stiff and overconsolidated with some pebbles. Shell fragments and complete valves abundant in places.
76 metres in erosive feature; lateral variations between 0-180 metres.
Eroded at top by pre-Forth Formation erosive phases.
Corinacy Pelite Member
COPE
Top of thick persistent unit of greywacke grit at the top of interbedded grits and metavolcanic rocks characteristic of the lower part of the Blackwater Formation.
SE flank of River Deveron Valley between Hill of Bank [NJ 3829] and Succoth [NJ 43 35] Cabrach area, Moray District, 1:50 000 sheets 75E (just), 85E and 86W.
Pelites, dark-grey, graphitic in parts, commonly andalusite-bearing, phyllitic to slaty. Bands of metabasalt and ultramafic rock, particularly in lower part.
900m (based on outcrop width of 1km, with no allowance for probable folding).
Base of overlying thick quartzite (the Grumack Hill Quartzite Member).
Coralea Phyllite Member
COPH
Limit of quartzites at top of Kymah Quartzite Formation.
250 - 500m wide outcrop extending N-S from around Allt na Craoibhe - Caorainn [NJ 31 25] to Water of Nochty [NJ 305 162]. Also in synclinal core around Steplar Road [NJ 30 26], Moray District 1:50 000 Sheet 75E.
Phyllitic semipelites, grey-green, laminated to striped with minor limestone beds.
c. 300m (based on outcrop width with no allowance for probable folding).
Base of pebbly quartzites of the Caochandye Quartzite Member.
Coplow Limestone Member
COPL
Taken at the base of the lowest Waulsortian limestone, which rests conformably upon fissile mudstones of the "Lower Coplow Shales".
The Craven Basin, generally to the south and west of the Bowland High, within the Ashnott and Clitheroe anticlines [SD 74], Slaidburn and Newton [SD 75], Thornley [SD 64] and Whitwell [SD 64] anticlines.
Pure, massive and biohermal Waulsortian limestones with surbordinate packstones, grainstones and thin fissile mudstones.
Up to 300 m thick.
Generally, Waulsortian limestones of the Coplow Limestone Member are overlaain unconformably by mudstones of the Hodder Mudstone Formation. In the Clitheroe Anticline the upper part of the Coplow Limestone Member is present, with Waulsortian limestones overlain conformably by poorly exposed dark grey fissile mudstones and packstones of the 'Upper Coplow Shales'.
Corrydon Psammite Member
COPS
Between Meall Odhar [NO 11 65] and the western margin of the Glen Shee Pluton: Top of attenuated Farragon Volcanic Formation. Between north-east contact of Glen Shee Pluton and head of Glen Isla [NO 17 71]: Top of Ben Lawers Schist Formation.
Meall Odhar area [NO 11 65] to the head of Glen Isla [NO 17 71].
Schistose psammite and semipelite, fine-grained and quartzite.
In the west: Gradational passage into dominantly gneissose semipelite of the Duchray Hill Gneiss Member. In the east: top of white fine-grained quartzite below gneissose semipelites of the Duchray Hill Gneiss Member.
Corryhabbie Quartzite Formation
COQU
At lower limit of persistent pasmmite or quartzite above the Mortlach Graphitic Schist Formation.
Loch Builg, Inchrory and Carn Mor, upper Strath Don northwards via Glen Avon, Glen Livet. Glen Fiddich to the Balloch Hills near Keith. Small outcrops farther north around Windyhills. 1:50 000 Sheets 75W, 75E, 85E, 86W, 96 (just).
Orthoquartzite, fawn to white; cross-bedded with pinkish haematite streaks. Thin micaceous interbeds common. Gritty in parts. Flaggy, micaceous psammites locally at top and base.
Generally 80-300m. Wider outcrops may be due to folding.
At upper limit of persistent psammite or quartzite below phyllites and calcareous schists of the Ailnack Phyllite and Limestone Formation or the Cock Burn Calcareous Schist Formation.
Conwy Rhyolite Formation
COR
Overlies mudstones of the Nant Ffrancon Subgroup. Interdigitates with the Foel Fras Volcanic Complex.
Conwy Mountain (2km west-north-west of Conwy) to around Foel Fras (8km west-north-west of Dolgarrog).
Rhyolite lavas and inter-flow breccias, tuffs and intercalated sedimentary rocks.
To c.1000m, thins southwards.
Underlies mudstones of the Nant Ffrancon Subgroup. Interdigitates with the Foel Fras Volcanic Complex.
Coral Bed
CORA
Corbiehall Coals
CORB
Corbie Craig Coal (Lothian)
CORC
Specifically the Peebles/Biggar area.
Carnmore Sandstone Member
CORE
Not seen, everywhere concealed. Occurs within Meenymore Formation and thus reverts to mixed argillaceous-arenaceous sequence typical of the formation.
Slieve Beagh (Lisneshea) area of south Co. Fermanagh, Northern Ireland.
Sandstone, pale grey to fawn, medium- to very coarse-grained, pebble bands, litharenite, dolomite-cemented locally.
About 75m
Not seen, everywhere concealed.
Corgarff Limestone Member
CORG
Lower limit of crystalline limestone within pelites and semipelites of Tornahaish Dark Schist and Limestone Formation.
On Upper Donside, mainly near Corgarff and Corgarff Castle. Intermittent outcrops extend southeast from Tornahaish to Mammie Hill: also north of Delnadamph.
Limestone, bluish-grey, crystalline, commonly thinly banded, with chert lenses. Blocky to flaggy, rarely massive. Tight to isoclinal internal folding common in parts.
12 - 20m. Typically 15m, may be thinner and impure by Allargue House.
Upper limit of crystalline limestone within Tornahaish Dark Schist and Limestone Formation. Schistose calcareous semipelite above. Thence non-calcareous semipelite.
Corby Hall Intrusion
CORH
Corkerhill Clayband Ironstone
CORK
Blaes; CBI 5"; Blaes 3' 0"; CBI 9"; Blaes.
13".
Corbridge Limestone
CORL
Cormorant Formation
CORM
Corrennie Intrusion
CORN
Cork Rock
CORO
Corral Coal (Dailly)
CORR
Corton Sand Member
CORS
Dominated by sand; with interbedded clay (till) and some gravel in the lower part. [Generic description: from East Anglian data].
Corse Diamicton Member
CORSE
Devensian (??MIS 3 - 2).
The lower boundary of the diamicton is complex due to its, in part, glaciotectonic emplacement. In some situations it rests with an unconformable, undulatory, sharp to gradational basal contact on brown diamicton of the Rottenhill Till Formation. (It might also include a leaf of the overlying Hythie Till Formation, e.g. northeast face, Leys Quarry (disused). In other situations (e.g. north face, Kirkhill Quarry) its basal boundary is seen as a sharp, planar, subhorizontal, erosion surface on red felsitic gravel of the Corsend Gelifluctate Bed.
Buchan, northeast Scotland. The member is only known within the immediate vicinity of Kirkhill quarry (infilled) (centred on NK 0120 5285) and Leys quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon). Buchan, northeast Scotland.
Pebbly, clayey, sandy silt diamicton. Typically black and dark grey, weakly calcareous, matrix-supported. The matrix contains a rich Mesozoic (principally Jurassic and Lower Cretaceous) palynoflora. Clasts are of pebble grade and typically subangular to rounded and composed of quartzitic and psammitic metasedimentary rocks, with sparse felsite, chalk and shell fragments. Deformed and attenuated beds and rafts of pinkish yellow fine-grained, slightly pebbly, sand are locally common. Interpreted as having been initially deposited as subglacial till but subsequently, at least in part, glaciotectonically deformed and rafted into position during a subsequent glacial event.
To 4.7m
The upper boundary of the diamicton is also complex. In some situations (e.g. northeast face, Leys Quarry (disused) it displays a sharp to gradational, interdigitating (glaciotectonic) upper and lateral contact with brown diamicton of the Hythie Till Formation within which it occurs as attenuated masses and rafts. Where overlying diamicton of the Hythie Till Formation is locally absent the Corse Diamicton Formation occurs at the present ground surface. In other situations (e.g. north face, Kirkhill Quarry (infilled) the diamicton's upper boundary is a sharp, erosional, channelised surface and it is overlain by the Kirkhill Church Sand Member. (Blackhills Sand and Gravel Formation).
Corvanaghan Formation
CORV
Not seen due to faulting.
Central County Tyrone, Northern Ireland. Corvanaghan, Fir Mountain, Beleevenamore, Evishanoran.
Predominantly quartz feldspar biotite granular gneiss with subordinate mica schist and pelite. Metamorphosed up to sillimanite grade.
Cornbrook Sandstone Formation
COS
The pebbly sandstones of the Cornbrook Sandstone Formation are considered to rest unconformably upon limestones of the Oreton Limestone Formation at the type locality of Cornbrook Dingle, although the exposed contact is faulted, and upon the Devonian St Maughans Formation (Lower Old Red Sandstone Group at the reference section in Benson's Brook.
The Clee Hills area of Shropshire [SO 60 75].
Comprises conglomerate and pebbly quartzitic sandstones, coarse- to fine-grained. The sandstones are orange or brown, locally stained red, and thick-bedded. Thin mudstone beds, bluish grey or green. locally red, with seatearths and thin coals. The base of the formation comprises of a massive conglomerate with clasts up to 25 cms in diameter of quartz and quartzite, and subordinate slate, with sandstone from the Old Red Sandstone Group, and Dinantian limestone.
From 55m to 215m
At Benson's Brook, the boundary has been considered to occur where thick seatearths and sandstones of the Pennine Coal Measures Group rest unconformably upon thick sandstones and conglomerates of the Cornbrook Sandstone Formation (Dixon, 1917). In contrast, the boundary has been argued to be faulted at this locality (Jones and Owen, 1961).
Coracle Sandstone Member
COSA
Carse Of Stirling Clay Member
COSCL
Mid Holocene.
Unconformable, on the sub-Carse Peat (Flanders Moss Peat Formation) and older Holocene and late Devensian units including the Letham Silt Member.
Upper Forth valley from Aberfoyle eastwards to near the Forth estuary in the Falkirk area; area of the estuarine deposits of the Main Post-Glacial Shoreline and associated raised beach surfaces.
Clayey silt and clay, commonly rooty and structureless; highly laminated with silt and very fine- to medium-, locally coarse-grained sand; grey, black and brownish grey, finely micaceous, dark sulphidic patches, shells and shell fragments, vivianite grains. These are deposits of an estuarine tidal flat complex formed just before and during highest Holocene sea-level (Main Post-Glacial Shoreline).
Veneer to perhaps as much as 15m
Upper boundary partly unconformable with transgressing Claret Clay Member (Carse Clay Formation) and unconformably overlain by surface peats; commonly at surface partly because of peat clearances from the 18th century onwards. It also passes laterally into the peat bodies of East and West Flanders Mosses.
Coupland Sike Limestone Member
COSL
At the base of limestone, overlying a 5m unit of interbedded sandstone and mudstone, which forms a topographic depression at the top of the underlying Park Hill Limestone Member. The junction is nowhere exposed now, but the interbedded unit was formerly seen in a road cutting at [NY 7248 0448] during the construction of the Ravenstonedale By-pass, and the junction was recorded in M6 Site Investigation Boreholes at [NY 5885 0998]
Ravenstonedale, Cumbria between the M6 and the Dent Fault zone, south of Kirkby Stephen.
Packstone, dark grey, well bedded, blocky, partly dolomitized and bituminous, with the common occurrence of the coral Dorlodotia. Cyclically interbedded with thin mudstone and siltstone beds. The limestone beds are a fairly constant 0.75m thick.
The above data replaces existing Partial entry.
40 to 50m
Taken at the base of the overlying Brownber Formation, where there is a change from dark grey cyclically bedded limestone to pale grey ooidal limestone and calcarenite.
Coa Sandstone Member
COSM
Cocklett Scar Sandstone
COSS
Rapidly gradational at incoming of persistent sandstones interbedded with siltstones above shaly mudstones with siderite mudstones above the Eumorphoceras ferrimontanum Marine Band.
Lancaster Fells (Lancaster 1:50 000 sheet).
Interbedded fine- to medium-grained, thin to thick-bedded sandstones and grey micaceous shaly siltstones.
Rapidly gradational at top of persistent sandstones interbedded with siltstones below calcareous siltstones with very few sandstone beds of the Close Hill Siltstone.
Colonsay Group
COSY
Cotgrave Sandstone Member
COT
Conformable, at the abrupt base of the lowest pale grey sandstone bed of the Cotgrave Sandstone Member where it overlies the red-brown mudstone of the underlying Gunthorpe Member.
Mappable at surface in south Nottinghamshire and Leicestershire; not traced north of Newark.
Sandstone, fine- to medium-grained dolomitic, pale greenish grey, interbedded with mudstone and siltstone, dark greenish-grey. Common gypsum nodules.
Formerly considered a Member of the Edwalton Formation, which is now itself downgraded to Member status, the Cotgrave Sandstone Member is retained as a locally recognizable (and readily mappable) unit within the Sidmouth Mudstone Formation.
1 to 5m (4.5m in Cropwell Bridge Borehole, SK63NE/28).
Conformable, at the abrupt or rapid upward transition from interbedded green mudstone and pale grey fine-grained sandstone of the Cotgrave Sandstone Member to reddish brown structureless mudstone at the base of the Edwalton Member.
Comrie Three Foot Coal
COTH
Corton Till Member
COTI
Comrie Two Foot Coal
COTN
Cove Vein
COV
Cottonshope Volcanic Formation
COVO
Taken at the broadly conformable base of the lowest basalt sheet that sharply overlies a sequence of red and grey flaggy sandstones with ochreous brown spots, interbedded with purple, red lilac and green mudstone containing ochreous concretions, and thin concretionary carbonate (cornstone) beds (Lower Freestone Beds of Taylor et al, 1971), possibly part of the Kinnesswood Formation.
Southwest flanks of the Cheviot massif: exposed in Cottonshope Burn, Spithope Burn, Hungry Law, and between the Bareinghope Burn and the Chattlehope Burn, Northumberland.
Basalt, olivine-phyric, tholeiitic; several sheets of intensely fractured dark blue-grey rock, each passing up into highly amygdaloidal, scoriaceous and pillow-like tops, which contain infills of overlying sedimentary rock. Upper part of formation is intercalated with dark grey and greenish grey sandstone and argillaceous dolostone ("cementstone") of the overlying Ballagan Formation. Interpreted as lavas.
To 24m
Taken at the base of overlying interbedded sandstone, mudstone and argillaceous dolostone sequence of the Ballagan Formation (formerly Cementstone Group); the upper contact is intercalated.
Cow Rock Conglomerate Member
COW
The basal member of the Scart Grits Formation, conformable on locally eroded shales of the underlying Woodland Formation.
Quartzitic micro-conglomerate, grit and sandstone.
From 14 to 24 m thick.
Conformably overlain by the undivided part of the Scart Grits Formation.
Coylumbridge Formation
COYB
Conformable and transitional with Kincraig Formation but poorly exposed. Marked by change to dominantly psammite.
Northern Cairngorm Mountains and Mid-Speyside, Central Highlands of Scotland, sheets 74E and 64E.
Flaggy, laminated feldspathic psammite and micaceous psammite with minor bands of schistose semipelite; quartzite locally important.
500m to 1km.
Conformable transition up into more siliceous and feldspathic psammites of the Glen Spean Subgroup south of the Cairngorm Mountains.
Coyles Of Muick Intrusion
COYM
Colsay Sandstone Member
COYS
Cowleigh Park Formation
CPA
Unconformable on Proterozoic rocks or faulted boundary with Proterozoic or Cambrian rocks.
Cowleigh Park-Malvern district, Hereford and Worcester; also Eastnor area, southern Malverns (Ziegler and others, 1968).
Interbedded purple, brown, green and grey sandstones, grits and conglomerates and shales.
Non sequence, overlain by Wyche Formation.
Chester Pebble Beds Formation
CPB
Drawn at base of sequence dominated by sandstones containing pebbles and conglomerates; pebbles do not have a local derivation. Conformable on the Kinnerton Formation or unconformable on Palaeozoic rocks.
Sandstone, fine- to coarse-grained, commonly pebbly, with conglomerates and sporadic siltstones; cross-stratified.
<90m - >220m
Transition at base of Wilmslow Sandstone Formation.
Coalpit Bay Mudstone Formation
CPBM
Corsewall Point Conglomerate Member
CPC
Conformable/interfingers with wackes of Corsewall Formation.
Rhins of Galloway, south west Scotland.
Boulder, cobble and pebble conglomerate.
Campsie Claybands
CPCB
Culver Chalk Formation And Portsdown Chalk Formation (Undifferentiated)
CPCK
Carboniferous-Permian Extensional Supersuite
CPEX
Copster Green Sandstone
CPGS
The base of a prominent, feature-forming sandstone unit approximately 180 m above the base of the sandstones of the Pendle Grit Member.
The Copster Green area [SD63], and the extreme south-eastern part of Garstang 50k sheet.
A coarse-grained, and pebbly, feldspathic sandstone, thickly-bedded, wavy-bedded, planar cross-bedded or massive, reddened, with subordinate beds of siltstone. Pebbles of quartz and mudstone are noted.
135 m thick at Dinckley [SD 6884 3564], and 100 m thick at Clayton-le-Dale [SD 6726 3322].
The base of a sandstone-dominated unit of the Pendle Grit Member above the highest prominent pebbly sandstone unit within a pebbly-sandstone dominated sequence of the Copster Green Sandstone.
Camphill Limestones
CPHL
Northumberland; type area around Gunnerton.
Three limestones separated by clastic beds.
Total grouping is about 25m thick.
Cockley Pike Sandstone Member
CPK
Taken at the mostly very abrupt change from siltstone and very fine-grained sandstone of the Bowfell Links Member to massive very coarse-grained sandstone. Locally there is some interdigitation between the two members.
From Thirlmere to Scafell and Langdale, Lake District, Cumbria
Massive to weakly stratified, coarse- to very coarse-grained volcaniclastic sandstone and breccia
Up to 250m
Defined by the base of the overlying volcaniclastic rocks of the Sprinkling Tarn Member
Chonetes Polita Limestone
CPL
The Wick (Carboniferous) inlier, Gloucestershire.
Reddish, "gritty", shelly, crinoidal limestone.
Copney Pillow-Lava Formation
CPLF
Boundary not exposed.
Copney and Creggan rocks - mid County Tyrone, Northern Ireland.
Fine-grained dark-grey to black vesicular lavas (basalt - basaltic andesite) with locally well developed pillow structure.
Estimated 500m
Celtic Palaeogene Minor Intrusion Suite
CPMI
Carn Powell Member
CPOW
Clap Round Facies Formation
CPR
No definition.
Interbedded thin turbidite sandstones and turbidite mudstones with burrowed hemipelagites.
Crossopodia Shales
CPS
Captain Sandstone Member
CPSA
Carperstane Sill
CPSTN
Cam Spout Tuff
CPT
Taken at the base of bedded silicic tuff overlying eutaxitic lapilli-tuff of the Long Top Tuff Member, and lying between 25 and 75m above the base of the member or 5 to 15m above the top of the Oxendale Tuff where that is present
Cumbria,Thirlmere to Scafell and Langdale in the central Lake District
Cream and brown-weathered, bedded, fine-grained tuff with accretionary lappili that forms a widespread distinctive marker unit.
Up to 6m, but is typically less than 1m
Defined by the overlying eutaxitic lapilli-tuff of the main part of the Long Top Tuff Member
Curran Point Halite Member
CPTH
Carboniferous And Permian Rocks (Undifferentiated)
CPU
Clyde Plateau Volcanic Formation
CPV
Base is taken at the lithological change from lavas, tuffs or volcaniclastic sediments into underlying clastic sedimentary rocks
Strathclyde and Central Scotland.
Lavas, tuffs and volcaniclastic sediments with a wide range of compositions.
To c.1000m
Taken at the base of the Kirkwood Formation; defined as lithological change from volcaniclastic sedimentary rocks into underlying basaltic lavas
Capelaw Volcanic Member
CPW
Conformable: where fine-grained basalt overlies pink flow-banded rhyolites of the Bell's Hill Volcanic Member.
Lower three or four flows are fine-grained basalt, with pyroxene andesite occuring in north east. Upper flow is biotite dacite or biotite rhyolite, pale pink or lilac, silicified and kaolinitised, with large feldspar and biotite phenocrysts.
Attains 175-200m at Green Craig on Allermuir Hill. Thins southwards to less than 80m at Capelaw Hill.
Conformable: where biotite dacite or biotite rhyolite is overlain by basic andesites and olivine basalts of the Allermuir Volcanic Member.
Capelaw Acid Volcanic Formation
CPWA
Capelaw Basic Volcanic Formation
CPWB
Climpy Gas Coal (Forth Area)
CPYG
In the Forth area of Scotland, mainly on Sheet NS95.
Within the Upper Limestone Formation at a point midway between the basal Index Limestone and the overlying Lyoncross Limestone. Its lateral extent is limited, but it has been worked, and it is a useful stratigraphical horizon.
Coppy Hill Limestone
CPYL
Hartshill Sandstone Formation
Sharp unconformable contact of coarse beds on weathered tuffaceous Precambrian rocks of the Caldecote Volcanic Formation. Basal beds are red breccias or grey conglomerates.
Known extent: from Nuneaton town centre, extending north-west for 5.2km to Worthington Farm (SP 3529 9197 - 3192 9572).
Grey to maroon medium-grained sandstone, glauconitic in upper part. Mudstone present only as rare beds 0.10m thick, or as drapes to sandstone beds.
Thickness in the type area is 275m.
Sharp sedimentary break. Dark grey glauconitic sandstones of the formation are overlain by red mudstone of Purley Shale Formation.
Calattwr Quartzite Member And Hirnant Limestone Member (Undifferentiated)
CQHL
Coquet Valley Formation
CQU
Sharp, undulating, erosional contact, mainly on grey tills (diamicton) of the North Pennine or North Sea Coast Glacigenic subgroups, or on bedrock.
The valleys of the River Coquet, Aln and Wansbeck and their tributaries, northern England
Mainly sand and gravel forming river terraces and silty, clayey sand forming floodplains and concealing sand and gravel. Including units of silty sand, silt, clay and peat. Clasts mainly sandstone, gritstone, mudstone, limestone and coal.
Ground surface, locally covered by peat.
Corallian Group
First appearance of medium- or coarse-grained sand above the Oxford Clay Formation. In some areas, this also defines the top of that Formation but elsewhere, there is an intervening silty unit (West Walton Formation).
Dorset to Oxfordshire, and North Yorkshire.
Complex succession of interdigitating limestones, marls, sandstones, sands, siltstones, silts, spiculites, mudstones.
To c.100m
In the Dorset reference area, at the base of the Inconstans Bed (Kimmeridge Clay Formation), which also marks the Oxfordian-Kimmeridgian stage boundary, but elsewhere at the base of the thick mudstone succession that spans that stage boundary (ie Ampthill Clay and equivalents, and Kimmeridge Clay).
Crawfordston Coal (Ayrshire)
CRA
Crank Coal (North Wales)
CRAC
Ceiriad Formation
CRAD
Conformably overlies coarse-grained, thickly-bedded turbidites of the Cilan Formation (Harlech Grits Group).
Red, brown and green siltstones with subordinate, similarly coloured fine-grained sandstones.
At least 40m
Conformably overlain by interbedded grey, blue-grey siltstones and mudstones, with thin beds of pale sandstone, of the Nant-y-big Formation.
Crag Group
CRAG
A sharp, planar unconformity upon strata extending from the Chalk Group in the west to the London Clay Formation of the Thames Group in the east. Usually there is a glauconitic conglomerate of rounded flints at the base of the Crag Group.
East Anglia, and extending southwestwards into Hertfordshire.
A suite of shallow-water marine and estuarine sands, gravels, silts and clays deposited on the southwest flank of the North Sea Basin. The sands are characteristically dark green from glauconite but weather bright orange with haematite 'iron pans'. The gravels in the lower part of the group are almost entirely composed of flint. Those higher in the group include up to 10% of quartzite from the Midlands, igneous rocks from Wales, and chert from the Upper Greensand of southeastern England.
To 70m onshore
Overlain by deposits of the Dunwich Group, Albion Glacigenic Group, Britannia Catchments Group or British Coastal Deposits Group. Also interdigitates with the Dunwich Group, from which it can be distinguished by the marine origin of the sediments (all Dunwich Group fromations are fluvial). May be distinguished from the Albion Glacigenic Group by the absence of Northern British erratics in the Crag Group.
Craigie Coal (Dailly)
CRAI
Creag An Loin Psammite Formation
CRAN
Central Highlands of Scotland. Glen Banchor and Kincraig areas.
Interbanded psammite and micaceous psammite, siliceous psammite, quartzite and semipelite.
Up to 200 m exposed.
Defined by the incoming of coarse granular quartzite beds - transition into overlying An Stac Semipelite and Psammite.
Crane Formation
CRANE
Caradoc And Ashgill Rocks (Undifferentiated)
CRAS
Crathes Pluton
CRAT
Caerau Coal (South Wales)
CRAU
Craven Group
CRAV
Not exposed or proved over most of its extent, although locally an unconformity above the limestone-dominated Bowland High Group in the Craven Basin or a disconformity above the limestone dominated Clwyd Limestone Group, marks a sharp boundary with the overlying mudstone dominated succession of the Craven Group.
Craven Basin, between Clitheroe and Skipton; northeast Wales; Derbyshire and the East Midlands.
Grey to dark grey, siliciclastic to calcareous mudstone, limestone packstone and wackestone in sharp-based beds, with localised sandstone, siltstone and chert and mudmound reef limestones. Formations are typically defined by variations in abundance of mudstone and limestone.
In the Craven Basin at least 1450m; across the Widmerpool half-graben 3000m known and 5000m from seismic; North Wales 400m thick.
Taken at the base of the lowermost thick feldspathic sandstone of the interbedded sandstone, siltstone, mudstone succession of the Millstone Grit Group. In Staffordshire, it is taken at the base of the lowermost quartzitic sandstone of the interbedded sandstone, siltstone, mudstone succession of the Morridge Formation.
Main Craw Coal
CRAW
Crayford Silt Formation [Duplicate Code: Use Cfsi]
CRAY
Carey River Basalt Formation
CRBA
Lowest basalt lava resting on sandstone of Eglish Sandstone Formation.
Basalt lavas.
Highest basalt lava overlain by tuff beds representing base of Glenshesk Tuff Formation.
Crabtree Coal (North Staffordshire And Cheadle)
CRBC
Cleland Roughband Ironstone
CRBI
Creech Barrow Limestone Member
CRBL
Crediton Breccia Formation
CRBR
Overlies unconformably early Permian formations - Knowle Sandstone, Bow Breccia, Cadbury Breccia, Thorverton Sandstone, except in Crediton area, where the Creedy Park Sandstone intervenes.
Extends from Nymet Tracey [SS 728 006] in Okehampton District (as part of the 'Crediton Conglomerates' of Edmonds, E A, et al, 1968), into the Exeter district at Knowle [SS 783 015], and thence to Crediton, eastwards through Shobrooke [SS 863 011] to south of Raddon [SS 910 010], east of there, passed into Yellowford Formation.
Reddish brown, poorly to moderately cemented breccia with a silt, sand and clay matrix. Clasts mostly less than 4cm. Clasts of sandstone, siltstone, slate, shale, hornfells, chert, acid lava and tuff, quartz-porphyry, vein quartz, and a variety of tournalinised rocks. Poorly developed bedding in units mostly over 1m thick. Thin interbedded or lenses of red mudstone throughout.
Up to 240m
Overlain by Newton St Cyres Breccia fairly sharply, with feature locally developed at the junction. East of Shute [SS 890 001] overlain by the Shute Sandstone.
Caerbwdy Sandstone Formation
CRBS
Comley to St David's
Conformably overlies the mudstones of the Caerfai Bay Shales Formation.
Pembrokeshire.
Fine-grained purple micaceous and feldspathic sandstones, pebbly near the top, with thin mudstone interbeds.
Overlain by greenish grey sandstones of the Solva Group. The boundary was considered to be sharp and unconformable by Jones (1940) but Stead and Williams (1971) considered it to be conformable and transitional.
Crag Group And Bytham Sand And Gravel Formation (Undifferentiated)
CRBY
Crow Cherts
CRC
Typically in the Arkendale area of Yorkshire; locally in the Richmond and Kirby Stephen districts.
Comprises the Crow Chert and the Second Crow Chert, overlying the Crow Limestone (qv).
Arran Central Complex
CRCA
Crediton Breccias [Obsolete Code: Use Crbr]
CRCG
Crutherland Coals And House Coal
CRCH
Crackers Coal (Lancashire)
CRCK
Crow Coal (West Yorkshire)
CRCL
The Crow Coal is widespread but not normally of economic significance because it usually consists of numerous thin seams interbedded with mudstone and seatearth. It has been worked in a few districts for gas production, as the seams are of good quality.
Crutherland Coals
CRCO
East Kilbride-Strathaven area, Hamilton Sheet (23W).
Coal: coalescence of House, Jaunt and Smithy Coals.
Carscallon Sandstone
CRCS
Carrickateane Formation
CRCT
Corkey Rocks Plug
CRD
Crow Delf Coal (Forest Of Dean)
CRDC
Craighead Limestone Formation
CRDL
Irregular unconformity on pillow lavas. The latter are possibly Balcreuchan Group (Arenig) but could be of much younger (Carodoc) age.
Area around the south and east side of Craighead Hill. Girvan, Ayrshire, Scotland.
Massive limestone, with conglomeratic base resting on irregular surface of pillow lava.
Not seen (faulted), but thought to be overlain by the Plantinhead Member of the Ardwell Farm Formation.
Crane Dyke Member
CRDY
The top of the conglomerates belonging to the Isle Port Conglomerate Member.
Ayrshire, Scotland.
Grey to brown, fine-grained to pebbly sandstones fining up into siltstones and mudstones with locally developed calcrete nodules, with localised thin beds of mudstone breccia and pebbly mudstone.
About 70 m thick.
The base of the volcanics forming of the Carrick Volcanic Formation.
Creepie Coal (Sanquhar)
CRE
Crathie Sheets
CREI
Cregennen Formation
CREN
Conformably overlies the felsic tuffs and tuffites of the Offrwm Volcanic Formation.
Cadair Idris, southern Snowdonia, North Wales.
Dark grey or black graptolitic mudstones interbedded with felsic acid and mafic tuffs and tuffites in places; sandstones and conglomerates occur locally.
To 350m
Conformably overlain by the felsic tuffs and conglomerate of the Brithion Formation in the north of the Cadair Idris district, and by pillowed basaltic lavas and mafic tuffs of the Llyn y Gafr Volcanic Formation elsewhere within the district.
Cretaceous Rocks (Undifferentiated)
CRET
Cromer Forest Bed Formation
CRF
Rests disconformably on Chalk or on Wroxham Crag Formation, and interdigitates with Wroxham Crag Formation. The interdigitated succession is as follows, from top down: Bacton Member (Cromer Forest-bed Formation); Mundesley Member (Wroxham Crag Formation); Runton Member (upper part, Woman Hithe Gravel of Reid, 1882; Wroxham Crag Formation); Runton Member (lower part, Woman Hithe Clay of Reid, 1882; Cromer Forest-bed Formation); Paston Member (Wroxham Crag Formation); Sheringham Member (Cromer Forest-bed Formation); Sidestrand Member (Wroxham Crag Formation).
The formation is restricted to North Norfolk. If further deposits of the Ancaster River were discovered farther west, ie west of the Wash, they would constitute a new formation.
The formation encompasses the fluvial, lacustrine and organic deposits of the postulated "Ancaster River", which is believed to have flowed from the Pennines to the North Sea along a line corresponding approximately to the present north coast of Norfolk. Four members are recognised in north Norfolk coastal sections. The Sheringham Member (lowest member) comprises freshwater organic mud, clay and sand. The Runton Member includes laminated freshwater silty clay. The West Runton Member comprises layers of alluvial clay and organic freshwater mud. The Bacton Member (highest Member) comprises clay and organic mud.
c.6m
Overlain by Middle Pleistocene glacial deposits (Happisburgh, Lowestoft, Sheringham Cliffs and Briton's Lane formations).
Cromarty Fish Bed
CRFB
Crawford Group
CRFD
The Southern Uplands of Scotland, and Longford Down in Northern Ireland.
Lava, chert, tuff and mudstone succession.
To about 190m
Thought to be overlain by Glenkiln Shale Formation of the Moffat Shale Group.
Crawfordjohn Dyke
CRFJ
Crawfordjohn area.
Dyke of porphyritic nepheline gabbro intruded into Ordovician wackes of the Southern Uplands Terrane.
Dyke, about 33m wide and 200+m long orientated NW - SE.
Corfe Member
CRFM
Croft Member
CRFT
Base of mudstone of above type, resting unconformably on shelly glauconitic limestone of the Lower Comley Limestones.
Lilleshall Inlier, Shropshire.
Black, fissile, mudstone interlaminated with micaceous siltstone and very fine-grained sandstone.
Not proved.
Crows-Foot Coal (South Wales)
CRFTC
Crinoid Grit Member
CRG
Craigbardahessiagh Granodiorite
CRGD
Craigenglen Beds
CRGL
Craigmalloch Formation
CRGM
Conglomerates, greywackes and flaggy siltstones.
c. 500m
Corallian Formation [Offshore Areas]
CRGR
Crags Vent
CRGV
Crag Hill Beds
CRH
Cenrhos Coal (South Wales)
CRHC
Crockey Hill Esker Member
CRHE
Not observed but interpreted to rest discontinuously over older till and/or may interdigitate laterally with interbedded glaciofluvial and glaciolacustrine sand and clay.
The Crockey Hill Esker Member is restricted to a narrow north-south to northwest-southeast trending belt to the south of York from Escrick to Fulford.
Pale brown, reddish brown and browish yellow, slightly silty, slightly to very gravelly fine to coarse sand. Gravel is subangular to subrounded and comprises a mixed lithology of sandstone, limestone and quartz with rare igneous clasts. Generally thinly bedded (<20mm). Bedding weakens, becoming disturbed, towards the upper surface, with evidence of cryoturbation. Rare laterally impersistant clay lenses.
Known to be a minimum of 7m in a temporary excavation at Crockey Hill.
Exposed at surface. In places overlain by thin aeolian sands.
Crag Hill Limestone Member
CRHL
Not seen in any of the outcrops.
Nodular-bedded argillaceous limestone with siltstone partings.
At least 30m
Defined by the base of the overlying Sowerthwaite or Crummack Formations.
Cross Hill Andesite
CRHM
Cromdale Hills Quartzite Member
CRHQ
Cribarth Formation
CRIB
Cramond Island Sill
CRIS
Crinkle Tuff Member
CRK
Base of high-grade rhyolitic pyroclastic rocks. Locally unconformable on older parts of Airy's Bridge Tuff Formation.
Crinkle Crags to Scafell, Great Gable, Base Broan and Bell Crag. Yewbarrow, Illgill Head, Cumbria.
Rhyolitic tuffs, lapilli-tuffs and pyroclastic breccias that are mostly very densely welded; rocks are conspicuously garnetiferous. Widespread intercalations of laminated rhyolitic tuff.
Contact with overlying formations comprising a mixed succession of bedded pyroclastic rocks and volcaniclastic sandstones, containing lavas and sills of andesite and basaltic andesite.
Carrickmore Shale Member
CRKM
Carrickmore Blackband Ironstone (0.6 m) overlain by marine shales.
Shale, dark grey with marine fauna; limestone, shaly, crinoidal, ironstone.
Top of grey shales succeeded by massive pink-red sandstones typical of Ballyvoy Sandstone Formation.
Cromer Knoll Group
CRKN
Corsankell Limestone
CRKS
Carrick Volcanic Formation
CRKV
Marked by basalts and basaltic andesites conformably above the predominantly sandstone succession of the Swanshaw Sandstone Formation.
South and Central Ayrshire, Scotland. Farther east, the volcanic pile near Cumnock is attributed to the Duneaton Volcanic Formation.
A volcanic succession of basalt and basaltic andesite sheets and flows with subordinate volcaniclastic and epiclastic sandstones and conglomerates.
About 600m
The unconformable junction with the Upper Devonian Stratheden Group.
Crickley Member
CRKY
Murchisonae Zone.
Upward transition from ferruginous, bioturbated, sandy, muddy shell-detrital limestone (Leckhampton Member) into limestones as described in lithology.
Mid-Cotswolds. Absent east of Northleach, and in north Cotswolds due to overstep by (or passage into) lower part of Cleeve Cloud Member. Southern limit somewhat uncertain, (see Barron, A J M, et al, 1997, fig.4).
Pale grey to yellowish brown limestones; lower part dominated by medium- to coarse-grained ooidal shell-fragmental grainstone ('Lower Limestone'), passing up into rubbly, poorly sorted, shelly, shell-detrital, moderately to highly pisoidal grainstones and packstones ('Pea Grit') with thin marl beds. South of Painswick, the succession is apparently replaced by ooidal grainstones comprising the Frocester Hill Oolite and Selsey Hill Oolite of Mudge, D C, 1978a, but the relationship between these strata and the type Crickley Member is uncertain.
Typically about 7m. Type section (Crickley Hill); c.15.7m, probably the maximum (Ager, D V, 1969).
Upward gradation from pisoidal limestones as described in lithology, into ooidal grainstones (Cleeve Cloud Member) in mid and north Cotswolds; a non-sequence marked by a hardground in southern Cotswolds (Mudge, D C, 1978a).
Craigies Lava Member
CRLA
Corrie Limestone
CRLM
Creagan Loisgte Member
CRLO
Creag Liath Pelite Member
CRLP
Carrickmacsparrow Limestone Member
CRM
Conformable but abrupt upward change from dark grey, cherty biomicrosparite
Fawn, coarse-grained crinoidal biosparite (packstone); abrupt contacts above and below with bedded, dark grey, cherty biomicrosparite.
4m in type section, maximum of 11m elsewhere.
Conformable but abrupt upward change to dark grey, cherty biomicrosparite
Cuniger Rock Marine Band
CRMB
Crawford Group And Moffat Shale Group (Undifferentiated)
CRMF
Cromhall Coal (Bristol Area)
CRML
The Langsettian age is based on Kellaway and Welch (1993, p.88), but there is a possibility that the seam is of late Namurian age.
According to Kellaway and Welch (1993, p.88) the Cromhall "Vein" of the Coalpit Heath Basin are thought to lie within the Lower Coal Measures Formation, but elsewhere in the same publication (p.65) the Cromhall "Vein" is described as being part of the "Quartzitic Sandstone Group", which was considered locally to be the uppermost part of the "Millstone Grit".
Creggan Mooar Formation
CRMR
In stratigraphical contact at the base with the Glen Rushen Fornmation, which is marked by a change from a mudstone-dominated facies to a mudstone/sandstone facies with manganiferous ironstone beds;.
A dark grey mudstone, with pale siltstone laminae and sandstone [quartz arenite] as thin to medium beds, distinctive manganiferous ironstone laminae.
About 500 m thick.
The top is faulted against the Dalby Group of the Niarbyl Fm, which is marked by a change from a mudstone/sandstone facies with manganiferous ironstone beds to a sandstone-dominated facies.
Craigmaddie Muir Sandstone Member
CRMS
Crugan Mudstone Formation
CRMU
Disconformally overlies the dark grey graptolitic mudstones of the Nod Glas Formation.
Area around Pwllheli, northwest Wales.
Brown-grey and green siliceous mudstones.
Not present in the area.
Carron Sandstone Formation
CRN
Grey, laminated sandy siltstone of the Cowie Harbour Siltstone Member conformably overlain by a thick sequence of red, fine- to medium-grained, trough cross-bedded and horizontally-laminated sandstone
North-eastern Midland Valley, Stonehaven area.
A fine- to coarse-grained locally pebbly lithic sandstone with lenses of conglomerate.
Measured as between 1200 m to 1800 m thick in the type area, and broadly consistent across unit extent, it is presumed to lap onto basement of the Highland Border Complex and probable Dalradian rocks, and also to be overlapped by younger groups.
At the base of a thickly-bedded or massive conglomerate of the Downie Point Conglomerate Member of the Dunnothar Castle Conglomerate Formation overlies planar bedded or cross-bedded pebbly sandstone
Crinoid Bed
CRNB
Carne Formation
CRNE
Late Eifelian to ? Givetian.
Conformable above Pendower Formation.
Roseland and Meneage areas, south Cornwall.
Sandstone with interbedded, laminated slaty mudstone and siltstone. The sandstones are predominantly fine- to medium-grained and form thinning- and fining-upwards sequences. Channel fills and slumps are evident in the lower to middle parts of the Formation, while the upper part is characterised by thinly to thickly bedded turbidites.
Structural thickness of c.240; c.250m in Type Section.
Conformable below Roseland Breccia Formation.
Cornstone Beds (Of Inverness, Nairn, Banff)
CRNI
Crovie Sandstone Group
CRO
Drawn at the base of the Dundarg Sandstone Formation (Crovie Sandstone Group) where it rests unconformably upon rocks of the Macduff Formation: conglomerate resting upon schist.
Crovie, near Banff, in the Grampian region.
Conglomerates, sandstones, flags and marls with ribs of limestone and pale red sandstone.
c.275m
Unconformably overlain by the Middle Devonian Gardenstown Congomerate Formation (GDC) of the Inverness Sandstone Group.
Crow Coal (Dungannon: Duckmantian)
CROC
Crow Limestone
CROL
c.3.6m
Crossdale Mudstone
CROM
Sharp basal boundary placed at the change from the sandstone-dominated Silver Hills Sandstone to the overlying mudstone-dominated Crossdale Mudstone.
Craven Basin area, northwest England.
Mainly blocky grey to dark grey laminated and fossiliferous mudstone, which becomes fissile on weathering. The mudstone contains siderite mudstone lenses and nodules at some levels. There are several thin marine bands composed of dark grey, platy mudstone with scattered oblate carbonate septarian nodules. Thin beds of sandstone are present and notably common in the uppermost few metres.
Note that the beds comprising the "informal" Crossdale Mudstone form parts of the two adjacent Silsden and Samlesbury formations, within the Millstone Grit Group.
14 to 23m in Crossdale; estimated 165m in Dolphinholme area.
Sharp upper boundary placed at the change from the mudstone-dominated Crossdale Mudstone overlain by the Accerhill Sandstone, a thickly bedded sandstone-dominated succession.
Cromarty Sandstone Member
CROS
Cowglen Rough Coal (Glasgow)
CROU
Crow Coal (Cumbria)
CROW
Coire Riabhach Phosphatic Formation
CRPH
Coniacian to Santonian in Mortimore et al., (2001).
Conformable (or a non-sequence at an erosion surface) with the underlying Lochaline White Sandstone Formation.
Limited to the Beinn Iadain area. Because of its relative thinness it is questionable as to whether this bed is a `mappable? unit and as such worthy of formational status, however it is prominent in sections logged in Morvern and may prove the correlative of the basal unit of the Gribun Chalk Formation as mapped on Mull where glauconite is seen in the sequences associated with erosional surfaces. It may also be a key link with the Northern Ireland succession where Mortimore et al. correlate it with the Cloghfin Sponge Formation at the base of the Ulster White Limestone Group.
Up to five beds of glauconitic sand with phosphate nodules and fossil casts.
Usually less than one metre.
Unconformable (or a non-sequence at an erosion surface) with the overlying Gribun Chalk Formation.
Creedy Park Sandstone Formation
CRPS
Rests unconformably on Knowle Sandstone.
First mapped in Creedy Bridge area [SS 847 012]; extends westwards through and north of Crediton to the Knowle area. Not recognised in the Okehampton district (Edmonds and others, 1968).
Reddish brown sandstone, mostly fine-grained and with some clay and silt; locally with breccia beds. Weathers to sand near surface.
Up to 80m in Crediton area.
Overlain by Crediton Breccia; may pass laterally in places into Crediton Breccia.
Crathie Point Calc-Silicate Member
CRPT
Base of lowest limestone bed in sequence of flaggy semipelites and psammites of Cairnfield Calcareous Flag Formation.
From coast at Crathie Point [NJ 5475 6725 - 5495 6715], as far inland as Broom [NJ 543 662], south of which it cannot be distinguished from the rest of the Cairnfield Calcareous Flag Formation.
Thin-bedded flaggy calc-silicate, calcareous semipelite and impure metacarbonate rock, with beds of metalimestone; bands of distinctive schistose garnet-muscovite-biotite semipelite in upper part. Calcareous psammite beds sparse but more abundant near top.
c.200 to 250m on coast section, but locally tightly folded; not measurable inland.
Transitional decrease in frequency of limestone beds and increase in proportion of calc-psammites relative to calc-semipelites.
Craigievar Formation
CRR
Not seen: a major antiform, now largely obscured by the Tomnaverie, Coull and Lumphanan intrusions, causes the formation to be flanked by younger rocks both to the north and to the south.
Occupies most of the central part of Sheet 76W (Alford) extending into the eastern part of Sheet 75E (Glenbuchat) and the western part of Sheet 76E (Inverurie).
Interlayered psammite, semipelite and pelite, with semipelite dominant. Contains beds of calc-silicate rock, especially in the vicinity of Towie (NJ 440 127).
Several kilometres, but not measurable due to the intense folding and migmatisation over most of the outcrop.
Change to the more uniform semipelitic lithology, but with mappable units of gritty psammite, which characterises the Suie Hill Formation. Upper contact to the west of the Rhynie Devonian inlier occurs at the base of a magnetic pelite unit (NJ 394 246 to NJ 459 215). To the east of the Rhynie Devonian it runs through poorly exposed ground (NJ 471 165 to NJ 622 184), where it abuts the Bennachie Granite. The fault-displaced contact reappears at NJ 630 134 to NJ 650 134.
Carrack Formation
CRRC
Crigglestone Rock
CRRO
Craig Rofft Sandstone Member
CRRS
Brigantian (based on unpublished foraminiferal determinations by BGS)
Base not exposed, but should be taken at entry of sandy limestones and calcareous sandstones above underlying sand-free limestones of the Cefn Mawr Limestone Formation.
Great Orme at Llandudno (SH 76 83), North Wales.
Red and purple, fine- to medium-grained, sandy limestone (grainstone) and calcareous sandstone with scattered quartz pebbles and lenses of coarse shell material. Lower part is bioturbated and mottled; upper 2m are cross-stratified. The sandstone forms the upper part of a Brigantian shoaling-upwards cycle and formed in a shallow water, upper shoreface setting. The Craig Rofft Sandstone is currently shown on Sheet 94 within the Great Orme Limestone, a redundant Asbian formation now superceded by the Loggerheads Limestone Formation. However, unpublished foraminiferal dating by BGS has shown that limestones underlying the limestone member are Brigantian in age. These limestones therefore equate with the Cefn Mawr Limestone Formation and their lithology (dark grey packstones) confirms that they should be included in that formation, as must the Craig Rofft Sandstone.
4 to 5m
Undulating upper surface of calcareous sandstone beneath a thin, impersistent, calcretised porellanous limestone bed exposed in Craig Rofft Quarry.
Crawshaw Sandstone
CRS
The base of the first sandstone or sandstones above the Subcrenatum Marine Band (the base of the Pennine Lower Coal Measures Formation).
Medium to coarse-grained, locally pebbly sandstone, massive or cross-bedded.
Up to 55 thick.
The top of the last main sandstone above the Subcrenatum Marine Band (the base of the Pennine Lower Coal Measures Formation) and below the Listeri Marine Band.
Corley Sandstone
CRSA
Carrickaness Sandstone Formation
CRSF
Crossdale Grit
CRSG
Caradoc Shales
CRSH
Cradley Silts Formation
CRSI
Placed at base of Bed A3 in an augerhole section proved at Colwall, Hereford and Worcester, where it overlies red-brown clays (Bed A2) of the White House Silts. (Barclay, et al, 1992).
Colwall, in headwaters of Cradley Brook, Hereford and Worcester.
Grey fossiliferous, clayey silt with sand grains and local rock fragments and a peat layer up to 0.1 near top.
1 metre.
Placed at base of Beds A7a and B7a, in Colwall augerholes, where they are overlain by stony clay of the Colwall Gelifluctate.
Corallian Beds (Skye)
CRSK
Crathie Schist And Limestone Formation
CRSL
Carronrigg Smithy Coal (Drumbowie)
CRSM
Caerbwdy Sandstone Formation And Solva Group (Undifferentiated)
CRSO
Clashnoir Semipelite Formation
CRSP
The top of the Kylnadrochit Semipelite Member, Ailnack Phyllite and Limestone Formation, where strongly layered lithologies with calcareous character pass up into more pelitic lithologies.
Braes of Glenlivet.
Semipelite and pelite, grey, weakly banded, graphitic in part.
c. 330m in type section in Braes of Glenlivet.
The incoming of the first grey limestone at the base of the Inchrory Limestone Formation.
Corstorphine Sill
CRST
Corton Formation [Obsolete/Duplicate Code: See Corf]
CRTB
Very silty, sandy clay or clayey sand, commonly laminated; with few pebbles. Sand lenses occur. [Generic description: from East Anglian data].
Carriteth Coal (Northumberland)
CRTC
c.0.5m
Cropthorne Sand And Gravel Member
CRTD
Mid Pleistocene (MI Stage 7 to 6).
Unconformable, commonly channelled base, resting on Wolston Formation or Baginton Formation in upper Avon, or farther downstream (beyond Coventry), on Lower Jurassic or Triassic bedrock.
Avon Valley, Rugby to Tewkesbury (BGS Sheets 183, 184, 199, 200, 201, 216).
Predominantly cold phase sands and gravels that underlie the Avon Fourth Terrace of Tomlinson (1925) and of BGS maps. Dominated by clasts of "Bunter" quartz/quartzite lithologies with subordinate flint. Locally includes the organic Ailstone Bed, assigned to MIS 7, at its base. Probably equates with the Kidderminster Station Member of the Severn Valley Formation. (See also Compiler's notes under Supplementary Information.)
(A) The unit is referred to here as Cropthorne Sand and Gravel Member, though in Bowen 1999, and in previous BGS use it was simply Cropthorne Member. (B) Terrace surface typically some 11 to 15m above modern Avon alluvial floodplain in the Rugby area, increasing downstream to c.25m near the confluence with the Severn at Tewkesbury. (C) The upper boundary is given as "ground surface" though head, colluvium or soil deposits may intervene. (D) All Avon (and Severn) terraces need review; classification of some outcrops on existing maps is dubious. Thus some Previous Names are necessarily approximate.However, despite problems with lower terraces, it appears that the Cropthorne (Avon 4) meets the Kidderminster Station (Severn 4) fairly convincingly. (E) Accounts prior to Bowen (1999) include deposits now separated as the Strensham Member.
Crovie Till Formation
CRTI
Unconformable on bedrock or on older Quaternary deposits, including (locally) the Whitehills Glacigenic Formation.
Elgin to Fraserburgh, inland to New Pitsligo [NJ 880 560].
Till with strong input from local psammitic rocks together with erratics from the west or northwest. Colour variable, commonly reddish-brown.
To 5m
Land surface, or buried by late glacial or post glacial deposits.
Craigballyharkey Tonalite
CRTO
Carneddol Rhyolitic Tuff Formation
CRTU
Overlies Foel Ddu Rhyodacite.
Rhyolitic ash-flow tuffs.
Underlies and is partly interleaved with the Yoke House Formation and (locally) Nod Glas Formation.
Crumpy Coal
CRU
Cruachan Intrusion
CRUA
Crug Limestone
CRUG
Cruiser Formation
CRUI
Crumbouke Coal (South Lancashire)
CRUM
Craighead Volcanic Formation
CRV
Lower boundary not seen.
Basaltic pillow lava, with associated bedded chert.
At least 500 m thick.
Unconformably overlain by the Craighead Limestone Formation.
Crockanaver Limestone Member
CRVL
Abrupt contact on dark blue-grey, crinoidal, argillaceous packstones of normal Ballyshannon Limestone Formation.
Limestone, medium grey-fawn biosparites, oolitic, crinoidal, thick beds, stylolitic, shale-free, quartz-clastic.
Variable, either with shales/nodular limestone bed that marks base of succeeding Ederny Limestone Member or, rarely, with argillaceous packstones typical of normal Ballyshannon Limestone Formation.
Crawley Member
CRW
In the type section, greyish blue, brown, yellow and red mudstone of the Crawley Member overlies conformably dark grey, carbonaceous mudstone of the Witney Coal Member.
Oxfordshire Coalfield; in the subsurface only.
Thick beds of red mudstone with common desiccation cracks, interbedded with conglomerate, grey seatearth, sandstone and mudstone and scarce thin coals
Maximum thickness of 205 m in the type section.
Crummock Water Intrusion
CRWA
Crowland Bed
CRWB
Crow Coal (Dungannon: Pendleian)
CRWC
Crease Limestone And Whitehead Limestone (Undifferentiated)
CRWT
Coralliferous Group
CRX
Drawn at the base of the Coralliferous Group where shale rests conformably upon conglomerate of the Conglomerate Group.
Marloes Bay, Pembrokeshire.(now Dyfed).
Grey shales and mudstones, thin calcareous grits, and argillaceous limestones with abundant corals.
170m max./approx.
Drawn at the conformable upward passage of the Limestone Beds of the Coralliferous Group with the sandstone of the Sandstone Group.
Cryne Coal (Lothian)
CRY
Craig-Y-Cwm Formation
CRYC
Topmost surface of a persistent calcrete, overlain by quartz pebble conglomerate, the latter appearing in the succession for the first time at this level (Lovell, 1978).
From Blaen Onneu area near Crickhowell, Gwent eastwards and southwards to Pontypool, Gwent, South Wales.
Mainly quartz pebble conglomerates, with fine-grained quartzitic grey-green sandstones, pebbly sandstones and red-brown mudstones.
5 m. to a maximum of about 12 m.
Surface cut in quartz pebble conglomerates, overlain by pale yellow to white micaceous sandstone of the Garn-gofen Formation (Lovell, 1978).
Crychan Formation
CRYH
Collyhurst Sandstone Formation
Lower boundary is a major plane of unconformity, generally on reddened Carboniferous Coal Measures strata.
Lancashire and Cheshire.
A soft red sandstone with abundant beds of "millet seed" sand grains alternating with beds of fine-grained sharp sand (Tonks, and others, 1931); some interbedded grey sandstones locally.
Ranges from 0 - 262m in type area and 0 - 715m around Formby (Falcon and Kent, 1960).
Taken at the point where red mudstone and siltstone, characteristic of the overlying Manchester Marls, become predominant over sandstone.
Calder Sandstone Formation
CSA
The lower boundary on the underlying St Bees Sandstone Formation is sharp and is taken at the upward change to typical aeolian sandstones from typical fluvial sandstones, which are finer grained and better cemented. Geophysically the boundary is sharp, marked by an increase in sonic interval transit time and an increase in gamma-ray values.
West Cumbrian Coast, between Sellafield and Drigg/Ravenglass
Red brown, medium to coarse, generally poorly sorted well rounded sandstone, cross bedded. Onshore aeolian sandstones are dominant: offshore fluvial sandstones are dominant.
469-529m in Sellafield boreholes
Taken at the top of a thick (40-50m) fluvial sandstone unit that is well cemented and overlain by coarser, less well cemented aeolian sandstones (Ormskirk Sandstone Formation). The top is marked by a rapid decrease in gamma-ray values and an increase in sonic interval transit times.
Craigburn Shell Bed
CSB
Corrie Sandstone And Brodick And Lamlash Beds (Undifferentiated)
CSBL
Cascade Conglomerate Member
CSC
Girvan area, Southwest Scotland.
A localised thick conglomerate unit at or near the top of the generally flaggy Ardwell Farm Formation. Thickly bedded. Grey-green and buff- to yellow-weathering grits with scattered pebbles and boulders up to 60cm across of dolerite, spilite, gabbro, granophyre, granite and olive green mudstone rafts in a slightly calcareous matrix.
Taken at the top of the conglomerate and return to flaggy sandstone.
Cromerian Complex Interglacial 2 To Saalian Channel Fill Deposits, Undifferentiated (Offshore)
CSCFU
Cromerian Complex Interglacial 2 to Saalian.
Cowglen Sclutty Coal (Glasgow)
CSCO
Cover Sand
CSD
Sand and silt, commonly wind-blown (aeolian). [Generic description].
Cromerian Complex Interglacial 2 To Saalian Diamicton, Firm To Hard (Offshore)
CSDFH
Colsterdale Limestone
CSDL
Castledikes Sandstone
CSDS
Corsend Gelifluctate Bed
CSEND
Devensian (??MIS 4 - 3).
The lower boundary of the bed is a planar, subhorizontal erosion surface truncating weathered diamicton of the Fernieslack Palaeosol Bed/Rottenhill Till Formation.
Buchan, northeast Scotland. The bed is only known within the immediate vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) on Sheet 87W (Ellon).
Gravelly sandy silt diamicton. Crudely bedded, brown, matrix supported, non-calcareous. Clasts are typically angular to subangular. Clast lithologies are dominated by felsite with lesser amounts of quartzitic and psammitic metasediments, basic igneous rocks, red stained quartzites, red-brown sandstone, grey granite and pelitic metasediments. In thin section silt droplet fabrics have been recorded indicating incipient pedogenesis under cold climate conditions. A truncated ice-wedge cast has also been recorded descending from the upper surface of this deposit into the Rottenhill Till Formation beneath. Interpreted as a periglacial gelifluctate.
To 0.80m
The upper boundary of the bed is a planar, subhorizontal erosion surface overlain either by black clayey diamicton of the Corse Diamicton Formation or brown diamicton of the Hythie Till Formation.
Canonbie Seven Foot Coal
CSFC
Castle Hill Flints
CSFL
Crossgates Sandstone
CSGS
Caton Shale
CSH
Sharp boundary, with grey to blue-grey mudstone of the Caton Shale Member above fine-grained sandstone of the Ward's Stone Sandstone.
Lancaster Fells area.
Mudstone (claystone) grey to blue-grey, shaly, fossiliferous (bivalves and goniatites) with common calcite mudstone nodules and siderite-mudstone lenses in upper part.
Sharp boundary at base of lowest sandstone in Claughton Member. Highest 1 or 2m of the Caton Shale typically silty, with Lingula.
Castlehead Coals
CSHC
Castlehead Lower Coal
CSHL
Cushnie Pluton
CSHN
Castlehead Upper Coal
CSHU
Crofthead Slatyband Ironstone
CSI
Canonbie Six Foot Coal
CSIX
Cockleshell Limestone
CSL
Cross Lane Limestones Bed
CSLL
Change up from grey, calcareous mudstone of the undifferentiated Granby Member; at 76.26m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Group of several (seven at type section) thin (typically 0.1m) limestone units separated by mudstone beds. The limestone beds are shelly, pale grey, weathering pale brown, with abundant coarse sand-grade shell debris. Fauna includes forams, serpulids, gastropods, bivalves and echinoderms. The lower part forms a positive feature.
1.5 to 2m; 1.92m in type section.
Change up into grey, calcareous mudstone of the undifferentiated Granby Member; at 76.34 m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Castle Hill Marls (One)
CSMA1
Castle Hill Marls (Two)
CSMA2
Castle Hill Marls (Three)
CSMA3
Cromerian Complex Interglacial 2 To Saalian Mud And Sand, Interbedded (Offshore)
CSMAS
Camas Malag Formation
CSMG
Early Jurassic? uncertain to Hettangian?
Unconformable on a palaeokarstic surface eroded into Ordovician dolostones of the Durness Group.
Sea of the Hebrides Basin
The limestone unit infills a pre-existing palaeokarstic surface and comprises clasts of Ordovician limestone (Durness Group), within an early Jurassic, yellowish, crinoid-rich, micrite matrix.
<1m
Separated by a dolerite sill from overlying fissile mudstones and limestones of the Breakish Formation; Farris et al (1999) suggested that, apart from the sill, the sequence is conformable.
Cowglen Smithy Coal (Glasgow)
CSMI
Cape Shore Formation
CSO
Apparently conformable boundary with Ferder Formation within map area.
Soft to firm, highly to moderately silty clay with sporadic shell fragments and pebbles. Geotechnical strength lower than underlying Ferder Formation, also less sandy. Less pebbles/shells and more streaky and laminated in appearance than the overlying Sperus Formation.
10 metres in Borehole 78/9 but thickens to 45 metres to the plateau edge and thicker in the northern part of the Norwegian Trench area.
Top boundary unconformable with thin sand Holocene sedimentation at the sea bed, or apparently conformable with the overlying Sperus Formation.
Cloghfin Sponge Formation
CSP
Santonian. Uintacrinus socialis Zone in part.
Everywhere the base rests unconformably upon eroded Hibernian Greensand Group successions. In the most complete Hibernian Greensands Formation sequences (Kilcoan [J461 985]) the base of the Clochfin Sponge Formation is 4.27m above the conspicuous `Inoceramus Bands?.
Limited to the East Antrim Basin Northern Ireland.
Chalk and chalk conglomerate/breccia, glauconitic, with conspicuous hexactinellid sponge psuedomorphs. Three separate beds recognised (A, B, C) each with characteristic shape-variants of the irregular echinoid Echinocorys.
As defined in the type-site the beds are 1.47m thick.
The exact relationship with the overlying Galboly Chalk Formation is not certain (Fletcher, 1978 p. 8 para. 2). It is taken a well-developed separation plane below which the beds contain arenaceous `contamination?.
Corrie Sandstone
CSS
Camps Shale
CSSH
Cross Slieve Group
CSSL
Central Monzogranite Facies, Starav Intrusion
CSTAR
Central Scotland Late Carboniferous Tholeiitic Dyke Swarm
CSTD
Cowglen Stinking Coal (Glasgow)
CSTI
Cronk Sumark Slate
CSU
Clennery Scar Vein
CSV
Ceiswyn Formation
CSW
Formation is underlain by volcanic rocks of the Craig-y-Llam Formation. Boundary placed at top of air fall tuffs or bedded tuffaceous mudstones. Abrupt transition from volcanic rocks to mudstones but contact appears conformable.
Occupies the central part of Sheet 149. Passes west into Cardigan Bay and east into a group of distinguishable rock units collectively termed the "Lower Bala Group" (Bassett, and others, 1966. Quarterly Journal of the Geological Society, Vol.122).
Interbedded silty-mudstones and siltstones with subordinate sandstones and tuffs. Anoxic mudstones common in upper part. Disturbables occur throughout formation, but are more common in lower part.
Approximately 1400m in type locality area. Exceeds 1550m at western end of outcrop.
Formation is overlain by anoxic, black, graptolitic mudstone of the Nod Glas Formation with little or no siltstone or sandstone content. The boundary is conformable/transitional over 1.5m and is marked by the disappearance of mudstone turbidites of the Ceiswyn Formation.
Chee Tor Limestone Member
Taken at the conformable transition from the top of the highest dark micritic or calcilutitic bed of the Woo Dale Limestone Formation to the pale grey to grey calcarenite with rare calcilutites or very fine calcarenites of the Chee Tor Limestone Member.
Positive identification of rocks assigned to the Member is restricted to the area around Buxton and the valley of the River Wye.
A homogeneous, massive to thickly bedded, pale grey to grey calcarenite. Bed boundaries are typically defined by stylolitic or clay partings, with beds generally ranging from 0.5 to 5.0m, up to a maximum of 10.2m thick. Rare calcilutites or very fine calcarenites occur in the basal 13m, where beds tend to be thinner.
Average thickness is 120m
Calcarenites of the Chee Tor Limestone Member are overlain by basaltic lavas of the Lower Miller's Dale Lava Member.
Clattering Band
CTB
Castell Coch Limestone [Duplicate Code: Use Ccl]
CTC
Claret Clay Member
CTCL
Mid to late Holocene.
Unconformable, on older Holocene and late Devensian units including the Bothkennar Gravel Member and the Wilderness Till Formation. Locally the Carse of Stirling Clay Member passes transitionally upwards into the Claret Clay Member in the Alloa-Grangemouth area of the Forth estuary.
Lower Forth valley from Stirling eastwards to near the Forth estuary in the Falkirk area; area of the estuarine deposits of the Lower Post Glacial Shorelines and associated raised beach surfaces.
Clayey silt and silty clay, finely laminated and crudely stratified with silt and very fine- to medium-, sometimes coarse-grained sand; grey, black and brownish grey, finely micaceous, sulphur-rich, contains shells and shell fragments, and vivianite grains. Massive where bioturbated. These are deposits of an estuarine tidal flat complex formed after the time of highest Holocene sea level (Main Post-Glacial Shoreline).
Veneer to perhaps as much as 18m
Upper boundary mainly at surface or overlain unconformably by modern alluvial deposits, eg, Grangemouth Silt Member.
Caister Coal Formation
CTCO
Tournaisian And Visean Rocks (Undifferentiated)
CTCVU
Camnant Mudstone Formation
CTE
North limit: Careg Wiber Bank, but inliers on Cwm-Brith and Castle Banks.
Mudstone with upwards increasing frequency of sandstone and conglomeratic sandstone interbeds in upper part of formation.
Gradational.
Chert Formation
CTF
Canonbie Three Foot Coal
CTFC
Coniston Group
CTG
Conformably overlies the Wray Castle Formation.
Sandstone, siltstone and laminated hemipelagite. NOTE: All component parts have individually defined type sections or areas. These cover the entire group: see Yewbank, Moorhowe, Poolscar, Latrigg and Gawthaite formations.
Conformably overlain by the Bannisdale Formation.
Cat Gill Limestone
CTGL
Clitheroe area, Lancashire.
Well-bedded pale grey, fine-grained cherty limestone.
c.3m to c.18m
Cairn Trench Intrusion
CTGR
Causeway Tholeiite Member
CTH
Churwell Thin Coal (West Yorkshire)
CTHN
The Churwell Thin Coal is a widespread bituminous seam, usually thin but of economic importance in the area of Farnley and Churwell. It coalesces with the Churwell Thick to form the Beeston Seam (Green et al, 1878).
Cumnock Thirty Inch Coal (South Ayrshire)
CTIC
Carn Teikever Granite
CTK
Churwell Thick Coal (West Yorkshire)
CTKC
The Churwell Thick Coal occurs as an independent seam only in the area of Churwell. Farther west the seam splits into the Shertcliffe Coal and the Little Coal
Cookstown Limestone
CTL
Cotham Member
CTM
Placed at sharp, commonly channelled base, resting on underlying Westbury Formation.
Present throughout England.
Grey and grey-green calcareous mudstones and shales and laminated and lenticular calcareous siltstones with beds of coarse-grained oolitic sandstone.
Placed at base of porcellanous limestones of overlying Langport Member.
Catton Coal
CTNC
Castletown Limestone
CTNL
Southern part of the Isle of Man, around Castletown.
Boiclastic limestones and shaly mudstones with some ooidal limestones.
Clicker Tor Picrite Intrusion
CTPI
Augite-picrite with 60% serpentinized olivine, 30% poikilitic and interstitial augite and subordinate hornblende.
Chester's Quarry Sill
CTRQY
Church Bay Tuffs And Skerries Grits (Undifferentiated)
CTSG
Cautley Volcanic Member
CTV
Taken at the base of the lowest bed of volcaniclastic rock overlying grey flaggy mudstone of the main part of the Cautley Mudstone Formation.
Silicic tuffs, buff to pink in colour; thickly bedded at base becoming finer grained and thinly bedded at top
Up to 24m
Passes up into grey splintery mudstone of the Cautley Mudstone Formation.
Culm Supergroup
In north Devon and west Somerset, the lower boundary is taken at the incoming of black, locally siliceous mudstones of the Culm Supergroup (Teign Valley Group) above the soft mid to dark grey mudstones with scattered very thin fossiliferous limestones, siltstones and sandstones of the underlying Exmoor Group (Pilton Mudstone Formation), In south Devon, it is taken at the incoming of black, locally siliceous mudstones of the Culm Supergroup (Teign Valley Group) above the olive green and pale grey mudstones of the Trusham Mudstone Formation. Elsewhere in the south the base is thrust out.
Devon, north and east Cornwall and west Somerset, southwest England.
The lower part predominantly comprises euxinic black mudstones, bedded cherts, siliceous mudstones, thin limestones and local basaltic tuffs and lavas. Local shallow water quartzites, greenish mudstones and limestones and dark grey mudstones with thin sandstones are developed in the south. There are local small-scale turbidite systems comprising interbedded sandstones, conglomerates and mudstones or interbedded limestones and mudstones. The upper part comprises large scale turbidite and delta systems of thin- to thick-bedded sandstone, siltstones and mudstones. The delta systems contain rare thin coals.
Cumnock Claud Coal (South Ayrshire)
CUC
Culver Chalk Formation
CUCK
Campanian. Gonioteuthis quadrata Zone.
Conformable. As defined in Mortimore (1986), the base of the Culver Chalk lies low in the quadrata Zone, at the Castle Hill Marl. Strong marls commonly occur for several metres above the Castle Hill Marls, up to and including the Pepper Box Marls which are now taken as the base.
Limited to Sussex, Hampshire Wiltshire and Dorset and as widely spaced outliers to the north in the Southern Province. It occurrence and distribution beneath the Quaternary deposits of East Anglia in the Transitional Province is not well known.
Soft white chalk, relatively marl free with flint seams. Flints are generally large and in the upper part tabular.
65 to 75m and exceptionally 90m but can be significantly less where synsedimentary channelling occurs.
Conformable at the Portsdown Marl (Mortimore, 1986).
Cuckoo Coal (Bristol Area)
CUCO
Cullaidh Shale Formation
CUD
Upper Bajocian to Late Bathonian.
Marine to brackish water transition reflected in minor lithology changes from siltstone/sandstone to mudstone.
Brackish-lagoonal fissile mudstones, commonly with oil-shale at the base and fissile mudstones, commonly bioturbated.
4 to 6m
Lithology change to mudstones and sandstones of the Elgol Formation.
Garantiana Mudstone Member And Cullaidh Shale Formation (Undifferentiated)
CUDGM
Cudworth Coal (Yorkshire)
CUDW
Cumnock Ell Coal (South Ayrshire)
CUE
Currarie Formation
CUF
Lowest occurrence of slumped heterogenous association of the same or all the above lithologies.
Heterogeneous association of red silicious mudstone locally with cherty bands, containing in places, slumped blocks of pillow lava. Also lava breccia, greenish grey mudstone, grey-green cherts.
The upper limit is the apparent occurrence of the same.
Cumnock Fifty Fathom Coal (South Ayrshire)
CUFI
Cuckmere Flint
CUFL
Cumnock Forty Fathom Coal (South Ayrshire)
CUFO
Outer Gabbros, A1 (Cuillin Centre)
CUIA1
Outer Gabbros, A2 (Cuillin Centre)
CUIA2
Outer Gabbros, A3 (Cuillin Centre)
CUIA3
Outer Bytownite Troctolites, B1 (Cuillin Centre)
CUIB1
Outer Bytownite Troctolites, B2 (Cuillin Centre)
CUIB2
Outer Bytownite Troctolites, B3 (Cuillin Centre)
CUIB3
Cuillin Centre (Skye Central Complex)
CUIL
Outer Bytownite Gabbros, Phase 1 (Cuillin Centre: Unit C)
CUIL1
Outer Bytownite Gabbros, Phase 2 (Cuillin Centre: Unit C)
CUIL2
Outer Bytownite Gabbros, Phase 3 (Cuillin Centre: Unit C)
CUIL3
Outer Gabbros (Cuillin Centre)
CUILA
Outer Bytownite Troctolites (Cuillin Centre)
CUILB
Outer Bytownite Gabbros (Cuillin Centre: Unit C)
CUILC
Inner Cross-Cutting Bytownite Gabbro (Cuillin Centre: Unit D)
CUILD
Inner Bytownite Troctolites (Cuillin Centre: Unit E)
CUILE
Inner Gabbros (Cuillin Centre: Unit F)
CUILF
Layered Peridotites (Cuillin Centre)
CUILP
Coire Uaigneich Granite (Cuillin Centre)
CUILU
Layered Peridotites, P1
CUIP1
Layered Peridotites, P2 (Cuillin Centre)
CUIP2
Layered Peridotites, P3 (Cuillin Centre)
CUIP3
Layered Peridotites, P4 (Cuillin Centre)
CUIP4
Layered Peridotites, P5 (Cuillin Centre)
CUIP5
Layered Peridotites, P6 (Cuillin Centre)
CUIP6
Cushat Limestone
CUL
Upper bed is dark, crinoidal limestone overlying dark shaly grit in turn overlying crinoidal grit.
Two beds each about 0.3m thick separated by c.0.7m of dark shaly mudstone.
Cumnock Low Ell Coal
CULE
Cullardoch Diorite
CULL
Culnagrew Sandstone Formation
CULS
Culvennan Intrusion
CULV
Kirkcowan area, southwest Scotland.
Minor pluton of pyroxene diorite, with two small subsidiary outcrops (each c. 200m diameter) to the south of the main body. An associated breccia-filled vent lies about 0.5km to the west of the main body.
Elongated body c. 2km x 0.7km, with long axis orientated c. 075 degrees
Cumnock Major Coal (South Ayrshire)
CUM
Cove Upper Marine Band
CUMB
Impure sandy limestones, locally crinoidal, and calcareous shales.
Also known as Cove Upper Limestone. Formerly included within the "Calciferous Sandstone Group/Measures/Series". Correlated with the Linkhead Limestone and the Woodend Limestone.
c.0.45 to 1.8m
Main Coal (Cumbria)
CUMN
Cumnock Musselband Coal (South Ayrshire)
CUMU
Cucklington Oolite Member
CUO
Fairly abrupt change from oolitic, grey clay, to shelly limestones.
Most of the way across the Shaftesbury Sheet (313) and across the southern part of the Wincanton Sheet (297).
Shelly, locally sandy, oosparite; lower beds commonly micritic, with interbeds of oolitic marl.
2 - 5m (2.73m in the type quarry; 3.86m in the East Stour Borehole - ST82SW/9).
Fairly abrupt change from limestone to mudstone, locally oolitic, of the Hinton St. Mary Clay. Where the Hinton St. Mary Clay is absent, the limestones pass up fairly abruptly into the Sturminster Pisolite.
Cushendall Porphyry
CUPY
Cullen Quartzite Formation
CUQU
Base of thick-bedded quartzites (not seen in any of the exposures).
1) Coast between Buckie and Cullen, inland to Hill of Maud (Sheets 95 and 96). 2) Ben Aigan, Craigellachie to Cairnty (Sheet 85E). 3) Core of Ardonald Anticline, from Jock's Hill to Hill of Shenwall (Sheet 85E).
Pale quartzites, mostly pure; thickly bedded with trough cross-bedding and large channel fills, to flaggy and more planar bedded.
c. 2,400m on coast, c. 1,250m seen inland
At top of flaggy quartzites where overlain by flaggy micaceous psammites and semipelites of the Findlater Flag Formation.
Curdly Ironstone
CUR
Curving Coal (South Wales)
CURV
Cullivait Silts Formation
CUS
Either overlies Bedrock or red-brown diamicton of the Gretna Till Formation. Base of unit is not exposed at the Partial Type Section.
Northern margin of the Solway Firth, principally between Dumfries and Gretna, but extending inland to Dalswinton and Canonbie. These deposits also occur concealed beneath the alluvial sediments of the River Esk between Gretna and Carlisle.
Glaciolacustrine deposits infilling basins and hollows associated with glaciofluvial outwash deposited during Late Devensian deglaciation.
Glaciofluvial Deposits; in some instances dropstones indicate deposition in ice-dammed lakes.
Interbedded silty clay, sandy silt, and silty sand, forming upward coarsening flat-lying units; generally moderate reddish brown to brown or greyish brown. Sandy silts and silty clays are typically thinly bedded in finely-laminated to massive beds; silty sands display planar lamination, ripple lamination and small-scale tabular cross-bedding. Rounded greywacke dropstone cobbles disrupt the lamination in silt and clay units at the Partial Type Section.
Typically 3-5m, but >10m proved in boreholes south of Canonbie.
Taken at the base of the Kilblane Sand and Gravel Formation at the Partial Type Section; overlain by red-brown diamicton of the Gretna Till Formation in the Reference Section.
Culfargie Sand Member
CUSA
Diachronous transitional base with, and passing laterally into, the Powgavie Clay (Forth Clay Formation), and also the Errol Clay Formation.
River Tay just northwest of Perth, River Earn from Dunning eastwards and adjacent to the Tay/Earn estuary.
Typically deltaic and estuarine, commonly very fine- to medium-grained, finely micaceous, mainly flat laminated grey sand with silt and some clay laminae. Scattered pebbles occur up to 2cm size along with rare pebble beds, and there are black sulphidic patches. Coarser deposits including much higher proportions of coarse sand and gravel beds are known in the western areas of occurrence.
35m known at Culfargie.
The Culfargie Sand Member has a complex upper boundary with multiple unconformities with younger strata including the Carey Silt Member, Kingston Sand Member and Carse of Gowrie Clay Member (Carse Clay Formation). Also is known at surface as the top deposit of later Devensian raised beach landforms.
Culham Sands With Cherts Member
CUSC
Seventeen Fathom Coal (Cumnock; South Ayrshire)
CUSF
Cushendun Granodiorite
CUSH
Cutcombe Slates Member
CUSL
Culchavie Striped Formation
CUST
Rapid transition from quartzite of the underlying Kymah Quartzite Formation to striped semipelite - psammite unit.
c. 1km south of Cook's Cairn in the Blackwater Forest, and from the Allt na Craoibhe - Caorainn south to the Head of Glen Buchat, the Peat Hill, and SSE to Glen Conrie and Upper Glenfenzie (Sheet 75E). Also around summit of Carn Oighreag, on Hill of Allargue. On Sheet 75W stretches SSE from Reidh Dorch, across the Muckle Fergie Burn to Cairn Culchavie (Upper Donside) and Cairn Sawvie, where it is cut by the Glen Gairn Granite.
Notably striped, semipelites and psammites, laminated and thinly banded, slaty to schistose. Psammites more quartzose and abundant near the base of the formation. Semipelites dominate towards the top.
Upper limit of semipelite at base of graphitic pelite of the Glenbuchat Graphitic Schist Formation.
Cumnock Three Dirt Coal (South Ayrshire)
CUTD
Twenty Fathom Coal (Cumnock; South Ayrshiore)
CUTF
Culdoich Till Member
CUTI
Sharp, unconformable or glacitectonic boundary with either bedrock or the Cassie Till Formation.
Pebbly silty clay diamicton containing shell fragments of high-boreal to low-arctic aspect, clasts typically well rounded, high sphericity.
2.5m at type section.
Sharp, unconformable, glacitectonic boundary with the Dalroy Sand Member.
Cuthill Limestone Member
CUTL
Base of massive, banded crystalline limestone in semipelites of the Keith Limestone Formation.
Keith area, Braehead (85E) to Drum (86W), and Muldearie (85E).
Metalimestone, mid-grey, colour-banded, generally massive but with many open joints and cavities.
28m proved in boreholes.
Top of massive, banded, crystalline limestone overlain by semipelites with thin beds of quartzite and calc-silicate rock (Keith Limestone Formation).
Cumberworth Thin Coal (South Yorkshire)
CUTN
Thirty Six Fathom Coal (Cumnock; South Ayrshire)
CUTS
Cademan Volcanic Breccia Member
CVB
Not seen, but mapping shows unit to be spatially associated with the Grimley Andesite, with which it may in part be gradational.
North-western Charnwood Forest, between High Cademan and Grace Dieu Wood.
Massive volcanic block-breccia comprising angular to sub-rounded andesitic to dacitic blocks in a crystal-lapilli matrix.
Clovelly Court Shales
CVC
Carvichen Pluton
CVCH
Catshole Vein Coal (Pembrokeshire)
CVCO
Colne Valley Deposits
CVD
Gravel, sand, silt and clay, with organic-rich interbeds. [Generic description: academic papers and BGS Memoirs].
Crawton Volcanic Formation
CVF
The base of the lowest lava or tuff overlying the Whitehouse Conglomerate Formation or the Gourdon Sandstone Formation.
Stonehaven to Gourdon, and in the north-west limb of the Strathmore Syncline between Stonehaven and Dunkeld.
Macroporphyritic shoshonite lavas, aphyric and microporphyritic olivine basalt and basaltic andesite lavas, tuffs and volcaniclastic sedimentary rocks.
The top of the lava or tuff underlying the Catterline Conglomerate Formation.
Clogher Valley Formation
CVG
Cove Harbour Sandstone
CVHS
Yellow and reddish massive coarse-grained false-bedded sandstone with abundant lenticles of red and buff sandy shale.
Formerly included within the "Calciferous Sandstone Group/Measures/Series".
c.26m
Cove Limestone Member
CVLS
Drawn at the base of pale grey limestone of Cove Limestone Member where it rests conformably (but gradationally and slightly diachronously) on the mid dark-grey limestone of the Scalebar Quarry Limestone Member, Kilnsey Formation, or locally, unconformably on Lower Palaeozoic strata (eg, in Crummack Dale) [SD 781 707 to 767 710].
Southern part of the Askrigg Block, north of Settle.
Pale grey to very pale grey limestone, mainly medium- and coarse-grained calcarenite, bioclastic and peloidal packstones and grainstones, massive to weakly bedded. Subordinate micrites ("Porcellaneous Bed"), variably fenestral, and clay beds occur locally, the latter occurring in places above palaeokarstic surfaces. The member generally produces a topography characterised by steep grassy slopes, although the uppermost 6m forms a continuous scar (sub-vertical face), commonly with an overhang.
72m thick in its type section at Malham Cove; 114m in the Cominco Borehole S2, south of the Middle Craven Fault.
Is taken at a conspicuous bedding plane at the base the scar forming, pale grey limestones of the Gordale Limestone Member.
Clava Mudstone Member
CVM
Conformable boundaries within the lower part of the Nairnside Sandstone Formation.
Dark grey and olive mudstones with dark limestone concretions and lenses. Also rare sandstones.
c 10 metres.
Craven Grit
CVN
Clousta Volcanic Member
CVR
Craigavad Sandstone Formation
CVS
Carrickarade Vent
CVT
Cwrt-Yr-Ala Formation
CWA
Churchway Coal (Forest Of Dean)
CWAY
Coed Wenallt Beds
CWB
Crapwell Coppice Limestone
CWCL
This is an informal unit, not used by the BGS, within the Athelstan Oolite Formation. For more information refer to Cave, 1977.
Crow Coal (Northumberland And Durham)
CWCO
Cowie Sandstone Formation
CWE
An angular unconformity on meta-igneous and metasedimentary rocks of the Highland Border Complex.
The Stonehaven area and west to Elfhill [NO 797 849].
A fine- to medium-grained, locally pebbly, lithic sandstone interbedded with minor conglomerate, siltstone, mudstone and acid lavas.
From 490-640 m thick according to Carroll (1995), and 730 m thick estimated by Armstrong and Paterson (1970).
The top of the highest bed of laminated, grey siltstone of the Cowie Harbour Siltstone Member, that is conformably overlain by red, cross-bedded, fine- to medium-grained sandstone of the Carron Sandstone Formation.
Colwell Limestone
CWELL
Clay-With-Flints Formation
CWF
?Pliocene to ?Early Quaternary.
The Clay-with-Flint Formation rests upon Palaeogene formations, Chalk Group or Upper Greensand. Where it rests upon a Palaeogene formation or Upper Greensand, the base is taken at the base of intense cryoturbation. The base may be flat or may be highly uneven where it rests in dissolution hollows, particularly where it rests upon the Chalk. If the material is soliflucted and comes to rest on an inclined surface on a hillside, then it is classed as Head and not as a part of the Clay-with-Flints Formation.
Co-incidental with the outcrop of the Chalk Group, along the Chiltern Hills as far as Letchworth (Hertfordshire), the North Downs as far as Dover, the South Downs as far as Eastbourne, westwards to Sidmouth (Devon), with extension across the Upper Greensand outcrop of Devon and Somerset as far as the Blackdown Hills above Wellington, Somerset.
The Clay-with-Flints Formation is a residual deposit formed from the dissolution, decalcification and cryoturbation of bedrock strata of the Chalk Group and Palaeogene formations and, in the extreme west of the outcrop, the Upper Greensand Formation. It is unbedded and heterogenous. The dominant lithology is orange-brown and red-brown sandy clay with abundant nodules and rounded pebbles of flint. Angular flints are derived from the Chalk, and rounded flints, sand and clay from Palaeogene formations. There is commonly a discontinuous basal layer up to 100m thick, with dark brown to black matrix, stiff, waxy and fissured, with relatively fresh flint nodules stained black or dark green with manganese or glauconite. The deposit locally includes bodies of yellow fine- to medium- grained sand, reddish brown clayey silt, and sandy clay with beds of well-rounded flint pebbles, derived from Palaeogene formations. In the extreme west of the outcrop, in Devonshire, the deposit locally comprises sand and clayey sand containing angular, shattered blocks of chert. This is derived wholly from the Upper Greensand Formation, in areas where the Chalk Group has been removed by erosion.
Up to c 10m, but very variable where let down into dissolution pipes in the Chalk Pipes and hollows may be 1 to 50m in diameter.
Commonly occurs at surface. Mainly overlain by Middle Quaternary glacial deposits, particularly in Hertfordshire. Locally overlain by Late Quaternary head or fluvial deposits.
Cowpits Five Foot Coal (Lothian)
CWFF
Corwen Grit Member
CWG
Base overlies calcareous sandstones of the Dolhir Formation.
Coarse grained sandstones, thin siltstones and a locally developed limestone member at the base. Richly fossiliferous.
70 metres. Lateral variations, 21 metres - 70 metres.
Top is succeeded by pale grey siltstones with some interbedded thin sandstones of the Fron Frys Formation.
Cwar Glas Member
CWGL
Taken at the base of the first packet of thick bedded fine-grained sandstone with hummocky cross statification and parallel lamination of the Cwar Glas Member above the mudstones and siltstones with abundant thin to medium bedded fine-grained sheet sandstones of the Hafod Fawr Formation.
Northeast Carmarthenshire (SN 73 24), South Wales.
Greenish grey mudstones and siltstones with abundant thin to medium bedded fine-grained sheet sandstones. Scattered burrows. Packets of thicker bedded green grey and purple fine-grained sandstone with hummocky cross statification and parallel lamination occur throughout the member. In the west of the outcrop the member becomes predominantly sandstone.
0 to 66m
Taken at the incoming of low angle cross bedded lilac coloured conglomerates, conglomeratic quartzites and coarse-grained quartzites of the Mynydd Myddfai Formation above the thick bedded greenish grey and purple fine-grained sandstones of the Cwar Glas Member of the Hafod Fawr Formation.
Clogwyn Gottal Tuff
CWGOT
Conformably overlies silty mudstones of the Nant Ffrancon Subgroup.
Poorly sorted, heterolithic, felsic tuff with clasts of rhyolite, tuff and sedimentary rocks, interbedded with volcaniclastic sandstones and siltstones.
Conformably overlain by sandstones of the Cwm Eigiau Formation.
Chorleywood Gravel Formation
CWGR
Cowie Harbour Conglomerate Member
CWHC
The base of the lowest bed of poorly-sorted, volcaniclastic conglomerate or pebbly sandstone above a succession of grey-green volcaniclastic sandstones of the 'Brown and Grey Sandstone 'Member' of Carroll, 1994.
Sandstone, pebbly sandstone and largely volcaniclastic conglomerate.
From 20 m to 30 m thick. The type section is cut by strike-parallel faults of unknown displacement.
The base of the lowest bed of cross-bedded medium-grained sandstones of the Red Sandstone 'Member' overlying green and red, massive, coarse-grained pebbly volcaniclastic sandstones of the Cowie Harbour Conglomerate Member.
Claywood Ironstone
CWIR
Cawk Cove Sandstone Member
CWK
Unconformable contact with ignimbrite of the Helvellyn Tuff Formation.
Deepdale and Rydal Head, northeast Lake District (between Grasmere and Patterdale).
Stratified pebbly volcaniclastic sandstone with a few intercalations of bedded coarse-grained volcaniclastic sandstone.
90m (maximum)
Indistinct contact with bedded volcaniclastic sandstone (undivided) of the Deepdale Sandstone Formation.
Castlewood Limestone
CWL
Caaf Water Limestone Formation
CWLS
Passes down into the Dalry Sandstone Formation.
Limestones as part of a cyclical sequence of limestone, mudstone, siltstone and sandstone.
105 metres but thinning to around 10 metres southwards.
Passes up into the Monkcastle Sandstone Formation.
Clown Marine Band
CWMB
Cwm Clyd Sandstone
CWMC
Cwm Graig Ddu Formation
CWMG
Cwmmawr Coal (South Wales)
CWMMC
Note that this seam is within the South Wales Middle Coal Measures Formation and should not be confused with another Cwm Mawr (or Cwmmawr) Coal within the Brithdir Member of the Pennant Sandstone Formation farther to the west.
Cwm Barn Formation
CWN
Taken at base of first pebbly mudstone or conglomerate above the mudstone dominated sequence of the Rhayader Pale Shales.
Central Wales, northwest flank of Tywi Anticline.
Interbedded conglomerates, sandstones and turbidite mudstones with some thick units of pebbly mudstone. Subordinate thin laminated or burrowed hemipelagites.
Up to 150m.
Gradational but taken at base of mudstone dominated sequence with sparse thin turbidite sandstones of the Caeran Mudstones.
Crown Coal (North Wales)
CWNC
Ceiswyn Formation And Nod Glas Formation (Undifferentiated)
CWNG
Cowleigh Park Formation [Obsolete Code: Use Cpa]
CWP
Cowhythe Psammite Formation
CWPS
Not seen at type section due to Portsoy Shear Zone.
From Moray Firth coast [NJ 592 661 - NJ 609 664] southwards to 4km east of Huntly [NJ 570 406].
Psammite and semipelite, interbedded, thinly-banded, gneissose in part. Calcareous near base (dominantly calc-silicate beds). Also contains limestone unit in lower part (Rosehall Croft Limestone) and beds of calcareous semipelite near top. Locally migmatitic with quartz and leucotonalite veining.
Probably 800m in coast section; may reach 1.5km around Cornhill.
Lowest (white) limestone on western side of Old Hythe Bay.
Cairnwell Quartzite Formation
CWQU
Cowie Rock
CWRK
Of the Stirling area, etc.
Westphalian Rocks (Undifferentiated)
CWRU
Cowlairs Sandstone
CWS
Massive, false-bedded sandstone.
Corton Woods Sand And Gravel Member
CWSG
Pleistocene (post Anglian).
The Corton Woods Sand and Gravel Member rests unconformably on the pebbly silt and clay of the Pleasure Gardens Till Member (of the Lowestoft Formation), but also locally in cliff sections at [TM 5464 9660] a layer of black clayey silt up to 0.4m thick intervenes. The Member may also overlie the sands of the Corton Formation; where this occurs, the base is marked by the incoming of gravel.
Restricted to the area of northern Lowestoft, East Anglia.
The Corton Woods Sand and Gravel Member is composed of medium gravels and fine- to coarse-grained sands. The gravels comprise mainly flint, with subordinate quartz and quartzite. The gravels tend to be strongly imbricated in coastal sections. Inland there are few exposures and they comprise pebbly, well-rounded, medium-grained sands.
Probably up to about 7m, but only 4.3m at type section.
The upper surface of the Corton Woods Sand and Gravel Member is typically exposed at surface, but very locally is overlain by Head in several small valleys.
Collyweston Slate
CWSL
Crow Sandstone
CWST
Caw Sandstone Formation
CWT
Base of volcaniclastic sandstone or breccia that overlies, with local unconformity, the Lickle Tuff Formation (Stickle Pike Tuff Member) rhyolitic tuff.
Confined within the Ulpha Basin. Main outcrop is on Caw (SD 230 944) extends south to Appletree Worth (SD 247 930), north to Grassguards Fault (SD 230 960) and west to Stickle Pike (SD 212 917), Cumbria.
Volcaniclastic sandstone and breccia, bedded, coarsening upwards.
0 to 700m
Overlain by dacitic lapilli-tuff of the Lag Bank Tuff Formation.
Careg-Wiber Volcanic Formation
CWV
North limit: Castle Bank (hill) (SO 0900 6154). West, east and south limits outside of limits of Sheet 178.
Volcaniclastic sandstone and conglomerate with few intercalations of mudstone, some interbedded basaltic lava and/or volcanic breccia, sediments overly tuffite and/or ash flow tuff.
Approx. 1200 metres.
Cwmystwyth Grits Group
CWY
Clwyd Valley Formation
CWYDV
Sharp, unconformable and locally channelised, predominately on bedrock and Late Devensian head and glacigenic deposits (e.g Ruabon Member and Wheeler Member of Bowen, 1999, p.89, and Lleyn Formation). Interdigitates in a complex manner with Tidal Flat Deposits (Gwynllwg Formation of Bowen, 1999) in the estuary (Warren et al, 1984).
The valley of the River Clwyd and its tributaries (Clwyd), northern Wales.
Unconsolidated, stratified gravels, sands, silts and clays forming the alluvial deposits of the River (Afon) Clwyd and its tributaries. Includes contemporaneous head, colluvium and pedogenic deposits within the catchment area. Clasts comprise variable proportions of Lower Palaeozoic turbidites, Ordovician volcanic rocks, Permian/Trias sandstone and Carboniferous Limestone and Coal Measures reflecting the underlying bedrock geology and complex glacigenic sequence. North of approximately Denbigh, the deposits in the Clwyd and the Wheeler valleys, as well as those in the lower reaches of the Elwy valley, may contain exotic (Irish Sea Ice-derived) materials reworked from the Lleyn Formation. Aggradational river terraces and major alluvial fans are dominated by pebble cobble gravels and medium- to coarse-grained sand; the modern floodplain is dominated by silt and clay, and locally includes lenses of peat (Warren et al, 1984).
Rowlands (1955) proposed that some of the terraces might relate to a moraine-dammed lake (Lake Clwyd) formed after the complete withdrawal of ice from the Vale; Warren et al. (1984) found no evidence of any of the deposits relating to any of Rowlands' proposed ice-dammed lakes.
Generally to around 10m; 8m were recorded by Warren et al (1984) in the Vale of Clwyd and 6m are exposed near Plasnewydd [SH 9460 6640].
Cromlix Mudstone Formation
CXF
Conformable, locally diachronous or interfingered base of red, massive or laminated and poorly-sorted, siltstone or mudstone, overlying fine- to medium-grained cross-bedded sandstone or conglomerate of the Arbuthnott-Garvock Group.
Northern Midland Valley, between Stirling and Drumlithie.
Characteristically soft, bright red to dull brownish-red, maroon or purplish-brown, with green reduction spots in the north-eastern Midland Valley, generally massive but often thinly laminated, poorly-sorted, fine-grained silty sandstones, sandy siltstones, siltstones and mudstones, which lithologies may be locally interbedded with thin lenses of medium to coarse-grained pebbly sandstone.
From 240 m to 1200 m, passing laterally into the Teith Sandstone Formation (or former Edzell Sandstone Formation) towards the northwest.
Conformable and gradational, generally diachronous, interfingering with and passing up into the Teith Sandstone Formation (or former Edzell Sandstone Formation) with increasing abundance of sandstone lithologies.
Croxton Sand And Gravel Member
CXSG
Cymerig Limestone Member
Caradoc (Woolstonian).
Conformable boundary with the calcareous tuffaceous mudstones of the Gelli-grin Calcareous Ash Formation.
Massive or concretionary, dark blue-grey, coarsely crystalline limestone with interbedded calcareous, locally tuffaceous, mudstones.
Gradational, passing conformably upwards into the calcareous tuffaceous mudstones of the Gelli-grin Calcareous Ash Formation.
Cwm Yr Aethnen Mudstones Formation
CYA
Dark blue mudstones and laminated siltstones.
0 to 150m
Corrieyairack Pluton
CYACK
Southwestern Monadhliath Mountains in north-eastern part of the Glen Roy district and north-western part of the Dalwhinnie district (Scotland sheets 63W and 63E).
Granodiorite, aphyric, pinkish-white, massive equigranular, medium- to coarse-grained, hornblende-/biotite-bearing rock. Separate mafic (more hornblende-rich) granodiorite body at southern end of main pluton. Detached white to pink, medium- to coarse-grained, xenolithic leucogranite body to south of main pluton. Minor granite veins throughout pluton.
Comley Breccia Bed
CYBB
Unconformable on Lower Comley Sandstone Formation.
Comley area, Shropshire.
Sedimentary breccia of glauconitic sandstone and pink limestone clasts, set in a matrix of glauconitic sandstone.
3 to 4m
Appears to be conformably overlain by the main part of the Hill House Grits.
Cadbury Breccia Formation
CYBR
Rests unconformably on Bude Formation or Crackington Formation.
Extends along northern side of Crediton Trough from near Lower Creedy, Crediton (SS 845 030), eastwards to near Clyst Hydon.
Brown to reddish-brown unbedded to very roughly bedded breccia, consisting of angular to subrounded pebbles and cobbles of Culm Sandstone in very poorly sorted gritty, clayey, sandy, silt. The clasts are mainly locally derived Culm Sandstone generally not exceeding 0.3m diameter; other clasts include vein quartz, chert and fossiliferous sandstone of Pilton Beds type. Unnamed unit of sand and clay mapped with Cadbury Breccia between Greenslinch (SS 969 035) and Hele (SS 999 030).
Up to 270m
Overlain in eastern part of Crediton Trough by Thorverton Sandstone (q.v.), Crediton Breccia (q.v.) or Bow Breccia (q.v.).
Craigskelly Conglomerate
CYC
Unconformable on Ordovician.
Flaggy sandstones with prominent calcareous lenses full of shells.
Conformably overlain by Woodland Formation.
Chavery Coal (Derbyshire And South Yorkshire)
CYCO
Chavery Coal (Lower Leaf)
CYCOL
Chavery Coal (Upper Leaf)
CYCOU
Clyde Sandstone Formation
CYD
Conformable base taken in a transition from the underlying mudstone/cementstone association of the Ballagan Formation to a sandstone dominated succession.
Scottish Midland Valley.
Predominantly sandstone, commonly pebbly with beds of red-brown or grey mudstone. Pedogenic carbonate as nodules and beds especially in lower part, also present as rip-up clasts.
0 to 300m+
The top is marked by the overlying Clyde Plateau Volcanic Formation.
Coatyards Coal (Northumberland)
CYDC
Coatyards Limestone [Duplicate Code: Use Cylm]
CYDS
Cwm-Yr-Eglwys Formation
CYEM
Cerrig Gwynion Grits Facies (Caban Conglomerate Formation)
CYG
Medium- to coarse-grained, thick-bedded sandstones, pebbly in places.
Craig-Y-Gaer Coral Bed
CYGC
?Chadian.
The base is placed at a sharp, irregular, partly stylolitized erosion surface where the coarse grainstone at the base of the Craig-y-Gaer Coral Bed rests, locally with angular discordance, on micritic lime mudstones at the top of the underlying Darren Ddu Member of the Coed Ffyddlwn Formation.
Clydach Valley [SO 215 126], on the northeast crop of the South Wales Coalfield.
Pale grey, shelly, fossiliferous, crinoid-rich coarse grainstone.
2 to 3m
The upper boundary is locally gradational, but mainly a sharp, stylolitized irregular surface above which are the ooidal grainstones that form most of the Gilwern Oolite Formation.
Coed-Y-Glyn Sill
CYGS
Alkali-feldspar trachyte
Cwm-Yr-Hob Member
CYH
Disappearance of thick mudstone turbidite units of underlying undifferentiated Bailey Hill Formation.
Dies out southwards; southern limit at c. (SO 158 795); northwards extends at least as far as (SO 120 850).
Interlaminated and very thinly interbedded grey silty mudstone, siltstone/fine-grained sandstone and carbonaceous (anoxic) hemipelagite; disruptive bioturbation negligible.
Up to 220m thick.
First appearance of significant disruptive bioturbation, indicating onset of oxic bottom conditions.
Carreg Yr Imbill Dolerite
CYID
Coarse-grained microgabbro with gabbroic pegmatite and olivine metadolerite patches.
Clynekirkton Sandstone Formation
CYK
Craig Y Llam Formation
CYLF
A well exposed transition from disturbed or bedded mustones of the Tyr Gawen Formation to massive, locally nodular ash-flow tuffs. Contact disrupted in places by loading and fluidisation of underlying mudstone.
Extends westwards from Cadair Idris as far as Ffridd Cocyn (6250 0450) where it dies out.
Massive, ash-flow tuffs, locally lapilli-rich, with subordinate rhyolites, mudstone debris flows and tuffaceous sediments.
Well exposed. Transition from massive tuff, rhyolite or tuffaceous siltstones into mudstone. Contact placed where mudstone becomes dominant.
Coatyards Limestone
CYLM
Conybeare Group [Duplicate Entry: Use Cnyb]
CYNB
Cystoid Limestone Member
CYO
Base of limestone above grey mudstones.
Howgill Fells - may correlate with the Troutbeck Member of the Lake District.
Pale grey argillaceous limestone.
1.5 to 3m
Top of limestone, transitional to grey mudstone.
Craig Yr Odyn Mudstone Member
CYOM
Conformable within the sandstones of the Dinas Island Formation.
Dark grey turbiditic and interbedded black laminated hemipelagic mudstones.
20 to 50m
Claymore Sandstone Member
CYSA
Carey Silt Member
CYSI
Loch Lomond Stadial to Holocene.
Unconformable and transgressive base on older units including the Tay-Earn Gravels and Culfargie Sand members of the Forth Clay Formation and the Errol Clay Formation.
River Earn from Bridge of Earn and the Tay east of Perth eastwards to the Tay bridges at Dundee adjacent to the Tay/Earn estuary.
Very fine- to coarse-grained sand, silt and clay, grey and brownish grey, well laminated to thin bedded, some pebbles up to 4cm, finely micaceous, rooty near top below sub-Carse Peat (Flanders Moss Peat Formation); depending on location within the palaeo-estuary, the dominant material varies from sand to clay. The deposit forms a series of raised beaches/terraces related to transgressive and regressive cycles of sea-level change.
Up to 8m
Overlain unconformably by the sub-Carse Peat (Flanders Moss Peat Formation) and trangressive estuarine clay, silt and sand of the Carse of Gowrie Clay Member.
Cantray Till Member
CYTI
Either a planar, gradational contact over 10 to 20cm with underlying stony, clayey, sandy diamictions of the Athais Till Formation, or a sharp, planar, glacitectonic boundary with that Formation. Locally filling wedge structures in the top surface of the Athais Till Formation.
Stony sandy clay diamicton, matrix supported, "strong brown" (Munsell Soil) to dark yellowish brown, fissile, massive, extremely compact, containing angular to subrounded clasts of gneissose psammite and semipelite, granite and Devonian sandstone and siltstone. Typical lodgement till with well developed north-easterly fabric and containing concavo-convex discontinuities that are commonly sand-filled. Commonly includes rip-up masses of the underlying till unit (Athais Till Formation).
Generally a gradational contact, but a sharp change in colour, with dark yellowish brown stony sandy clay diamicton of the overlying Ruallan Till Member.
Christy's Walls Coal
CYWA
Coastal Zone Deposits (Undifferentiated)
CZD
Shingle, gravel, sand, silt and clay, locally with peat layers; may be bedded or chaotic; from the coastal zone. [Generic description].
Dalmellington Two Foot Coal
D2FT
Appin Phyllite And Limestone Formation
DAAP
Appin Quartzite Formation
DAAQ
Ards Quartzite
DAAR
Ards Black Schist
DAAS
Damery Beds
DAB
Blair Atholl Subgroup
DABA
At top of Ballachulish Subgroup; generally at the transition from banded semipelite and limestone to more graphitic pelite with limestone beds.
Islay; Lismore; Appin; also a strip from near Blair Atholl to the Moray Firth coast at Sandend Bay (between Cullen and Portsoy). Also occurs in Ireland around Glencolumbkille and Falcarragh (Donegal) and in Connemara (Co. Galway).
Semipelite and pelite, much of it graphitic; interbedded with limestone units, the lower limestones typically graphitic, the uppermost typically dolomitic
c.300 to 600m (but locally tectonically thinned to 50m)
At base of Islay Subgroup; generally transitional over a few metres where pale dolomitic limestone passes into psammite or quartzite with beds or larger units of diamictite.
Banded Group
DABD
Ballygrant Formation
DABG
Ballachulish Subgroup
DABH
At top of the Lochaber Subgroup: in most areas there is a prominent limestone at the base of the Ballachulish Subgroup: also pelites become markedly graphitic at boundary.
Islay; Appin to Lochaber; also a thin strip from near Loch Errochty to the Moray Firth coast at Sandend Bay (between Cullen and Portsoy). Also occurs in Ireland extensively in Co. Donegal.
Basal limestone, succeeded upward by graphitic pelite; this in turn overlain by persistent quartzite, which is overlain by striped semipelite with thin limestone units.
c.500-1100m (but locally tectonically thinned to 100m)
At base of Blair Atholl Subgroup: generally at the transition from banded semipelite and limestone to more graphitic pelite with limestone beds.
Ballachulish Limestone Formation
DABL
Dab Limestone Unit
DABLS
West Shetland Basin
Bharradail Phyllite Member
DABP
Binnein Quartzite Member
DABQ
Binnein Schist Member
DABS
Darroch Coal (North Ayrshire)
DAC
Cuil Bay Slate Formation
DACB
Colla Firth 'Group' [Obsolete Code: Use Cola]
DACF
Drawn at base of psammite of Colla Firth Group where it rests conformably on the Weisdale Limestone.
Shetlands, Scotland.
Composed of micaceous psammite with subordinate semi-pelite, calc-silicate rock and crystalline limestone. Migmatitic gneiss also occurs.
About 3500 m thick.
Drawn at conformable upward passage from psammite of the Colla Firth Group to the Girlsta Limestone.
Creeslough Formation
DACH
Craithie Point Group
DACP
Corvanaghan Formation [Obsolete Code: Use Corv]
DACV
Dark Group
DADG
Dark Limestone
DADL
Cnoc Donn Quartzite Formation
DADQ
Dark Schists
DADS
Ell Coal (Dailly )
DAE
East Burra Group
DAEB
Eilde Quartzite Member
DAEQ
Eilde Schist Member
DAES
Lower Falcarragh Pelite
DAFC
Fintown Pelite
DAFI
Falcarragh Limestone
DAFL
Druim An Fhurain Sandstone Member
DAFS
Basal limestones resting on the Raasay Ironstone Formation or Portree Shale Formation.
Cross-bedded sandstones and sandy limestones comprise most of the Member. These are commonly either massive or thinly bedded and contain crinoid ossicles, bivalves, bryzoan, belemnites and brachiopod fragments, especially in the lower part of the succession. Limited to Straithaird peninsula, intense lateral variation.
Abrupt change from sandstone to mudstone of the Garantiana Shale Member.
Dailly Ground Coal
DAG
Glen Banvie Formation
DAGB
Girlsta Limestone [Obsolete Code: Use Girl]
DAGL
Glen Coe Quartzite Member
DAGQ
Dailly Subgroup
DAI
Disconformity at the base of the Camregan Grits Formation, resting on the Newlands Subgroup.
Flaggy sandstones, gritty sandstones, siltstones and mudstones.
About 1226 m thick.
Conformably overlain by the Knockgardner Formation, the basal unit of the Straiton Subgroup.
Dalness Ignimbrite Member
DAIG
Lossit Limestone Formation
DAIL
Coire Daingean Semipelite Formation
DAIN
Change from white-weathering pinkish-brown quartzose psammite and quartzite of the preceding Beinn a'Chaisteil Quartzite Formation.
Recognized across northeastern parts of Sheet 46W (Crianlarich) west and north of Loch Lyon, also recognised northwest of Bridge Balgie Fault in upper Glen Lyon to Loch an Daimh in western part of Sheet 46E (Killin) and southwestern part of Sheet 54E (Loch Rannoch).
Formation comprises a lower calcareous semipelite unit succeeded by a massive schistose garnet-mica semipelite that constitutes the dominant lithology in the formation. The lower calcareous unit comprises 0 to 30m of calcareous garnet-mica schist and muscovite-quartz schist; extremely pitted weathering is conspicuous. The calcareous unit is succeeded by massive, poorly bedded garnet-mica schist and muscovite-quartz schist, poor in biotite but with abundant quartz sweats. Garnets are typically 1-2mm across, commonly chloritised and wrapped by muscovite. The unit is typically resistant to weathering and commonly forms brown-weathering cliffs 5 to 10m high.
Sections through the formation on Beinn a'Chaisteil and in Allt Coire an Lochain suggest of the order of 70m where not intensely folded. Contrast this with a thickness of at least 350m exposed in the back wall of Coire an Lochain on Beinn 'a Chreachain. In Coire Daingean the unit is 120 to 140m, again probably thickened by folding.
Change to the alternating muscovite-rich semipelite, psammite and quartzite of the Beinn an Dothaidh Heterolithic Formation. A calcareous semipelite or calcsilicate-rock (c.5m thick) may be present at the base of the succeeding unit.
Kinlochlaggan Limestone
DAKI
Kintra Dolostone Formation
DAKL
Glen Egedale Slate Formation
DAKP
Kinlochlaggan Quartzite [Obsolete Code]
DAKQ
Dalharco Limestone
DAL
South-central Ayrshire; type locality No.1 Borehole, Dalharco Colliery, northeast of Patna.
Dalness Breccias
DALB
Dalby Group
DALBY
Visible contacts are all faulted against the Manx Group and Peel Formation. It is likely that both lower and upper stratigraphical contacts are unconformable - the lower on the Manx Group where distinguished by being sandstone-dominated facies as opposed to a mudstone, the upper probably with overlying Permian or Triassic red-bed facies.
Sandstone (wacke), thin- to medium-bedded with interbedded siltstone and mudstone, locally including laminated carbonaceous siltstone and thin beds of meta-bentonite.
About 1200 m thick.
Not seen, -see lower boundary details.
Loughros Group And Falcarragh Pelites (Undifferentiated)
DALF
Lismore Limestone Formation
DALL
Dargan Limestone Formation
DALM
Dalradian Supergroup
DALN
Lochaber Subgroup
DALO
Generally sharp transition from underlying Grampian Group, from monotonous psammites, generally flaggy, with thin quartzite and semipelite units to better sorted psammite or quartzite and semipelite or pelite.
Core of Islay antiform: Appin to Ballachulish; Loch Leven to Glen Spean; Kinlochlaggan; Strath Fionan to Baddoch Burn (very attenuated); Dufftown to Banffshire coast west of Sandend; Glenlivet, Derback, Inchrory area (Valley of River Avon).
Alternating units of psammite to quartzite and semipelite to pelite; in places becoming calcareous near the top of the Subgroup. Many of the finer-grained lithologies are flaggy, but in some places this may be a tectonic effect. Succession from Grampian Group into Lochaber Subgroup continuous in some areas, e.g. Schiehallion, Banffshire, but in Glen Spean there may be a tectonically modified unconformity at the base of the Leven Schist.
Variable locally 1500m where untectonised (Lochaber, Banffshire); in Schiehallion district thickness reduced to about 80m, but full succession can still be recognised.
Incoming of more calcareous sediment, and more graphite in the pelitic and semipelitic rocks, indicating a decrease in the amount of input clastic material.
Leven Schist Formation
DALS
Dalvrecht Slate Formation
DALV
Main Coal (Dailly)
DAM
Dalserf Mussel Band (Central Coalfield)
DAMB
Mullach Dubh Phyllite Formation
DAMD
Maol An Fhithich Quartzite Formation
DAMF
Monadhliath Schist
DAMS
Dorset Anhydrite
DANH
Owengarve Calcareous Formation
DAOF
Parrot Coal (Dailly)
DAP
Pale Limestone
DAPL
Dallas Psammite Formation
DAPS
Passes downwards into more mixed psammites and semipelites, locally gneissose. Possibly locally shear zone boundary. Onlap of Upper Devonian sediments obscures lower contacts in parts.
Stretches west from the Spey Valley around Rothes in an east-west swathe some 18 km wide at least as far as the Dorback Burn. Turns southwards and passes into the partly equivalent Nethybridge Psammite Formation. Overlain unconformably by Middle and Upper Devonian conglomerates and sandstones to the north. To the east truncated by the Rothes Fault, though possibly equivalent to some of the Grampian Group (undefined) psammites and quartzites farther east.
Pale grey, pink and white, flaggy to blocky, thin- to thick-bedded, siliceous and feldspathic psammite, locally with thin muscovite-rich beds and laminae. Subordinate quartzite beds common. Micaceous psammite and thin semipelite beds also present. Locally distinctive beds of interbanded psammitic and semipelitic gneiss, with quartz-feldspar augen and veins.
Up to 3000m, and possibly thicker.
Passes up with gradational contact up into the Knockando Quartzite Formation over much of its outcrop. Truncated to the north-east by the Rothes Fault, and North-east of this structure possibly equivalent to undefined psammite and quartzite units within the Grampian Group.
Glencolumbkille Limestone
DAQC
Dark Slade Member
DAR
At base of mudstone-dominated succession resting on litharenites of lower Halesowen Formation; or at change of gamma log character.
Staffordshire, Shropshire, Warwickshire.
Mudstone with subordinate sublitharenite sandstones and thin beds of Spirorbis limestone. Colour grey with mottled grey/brown palaeosols (but may be reddened). Distinctive geophysical log character, with gamma peaks.
40 to 90m; 60.5m in type section.
At base of overlying Salop Formation. In places where Member is grey there is a change to orange-red colours. Boundary also marked by a change of gamma log character.
Darnley Coal
DARC
Dartry Limestone Formation
DARL
Conformable and abrupt, planar or interdigitating with Glencar Limestone Formation.
Limestone, dark grey, argillaceous, sparsely fossiliferous with disseminated chert in tabular or nodular form; interbedded with thin, dark grey to black silty, micaceous shale.
Up to 350m
Disconformable with succeeding Meenymore Formation, locally erosional.
Dart Formation
DART
Conformably overlying rocks of the Dungiven Formation (q.v.)
Dart Mountain and South Sperrins, Co. Londonderry, Northern Ireland.
Medium-grained gritty psammites and intercalated slightly graphitic mica schist.
c.2.5km
Overlain conformably by rocks of the Glenelly Formation (q.v.).
Darwin Formation
DARW
Dawlish Sandstone Formation
DAS
South of Exminster, interdigitational with Heavitree Breccia. From Exminster to Monkerton (SX 970 940), sharp base on Heavitree Breccia or Monkerton Formation. North of Monkerton to near Broadclyst, rests unconformably on Crackington Formation. In Crediton Trough, rests on Shute Sandstone.
Extends from Dawlish in south through Topsham to Broad Clyst as c.3km-wide outcrop. In Crediton Trough, present between Brampford Speke in west to near Budlake in the east.
Reddish brown sands and sandstones, cross-bedded, with intercalated thin lenses and beds of breccia and mudstone. North of Broadclyst, two mappable units predominantly of mudstone have been named: Poltimore Mudstone and Bussell's Member.
Overlain sharply and probably unconformably by mudstones of the Aylesbeare Mudstone Group in the Exeter district; in the Newton Abbot district is overlain interdigitationally by the Exe Breccia.
Dalmary Sandstone Member
DASA
A transitional contact, showing interbedding with the Cromlix Mudstone Formation, eg. in the Brocklin Falls Conglomerate Member in the Burn of Mar [NS 442 909], and locally a sharp contact, such as in Kelty Water [NS 5016 9503].
The north-west limb of the Strathmore Syncline, from Auchensail, Cardross [NS 342 798] to the southern slopes of Bheag near Callander, and as far as the Arrevore Burn [NN 775 126].
A greenish grey, fine- to coarse-grained, lithic sandstone, commonly with rip-up mudstone clasts, characterised by beds locally rich in plant remains.
Up to 1500 m thick.
A transitional contact with the Buchlyvie Sandstone Member of the Teith Sandstone Formation, which is reddish grey, unfossiliferous and contains red siltstone and mudstone interbeds.
Clonmass Formation
DASC
Dartford Silt Member
DASI
Mainly overlies or incises Boyn Hill Gravel Member or bedrock.
Dartford District.
Varies from silt to clay, commonly yellow-brown. Origin uncertain. Commonly includes a high percentage of wind-blown, silt-sized quartz (possibly loess). May also be "overbank" deposits or solifluction deposits. [Generic description].
0.3 to 4.6m, commonly about 3m.
At Surface or overlain by head deposits.
Ballachulish Slate Formation
DASL
Scatsta Pelitic Formation
DASP
Drawn at base of pelite of Scatsta Pelitic Formation where it rests conformably on psammite of the Yell Sound Division of the Moine.
Composed of mainly pelitic schists, some of which contain staurolite. Migmatisation is also present.
1250m approx.
Drawn at conformable upward passage from pelite of the Scatsta Pelitic Formation to quartzite of the Scatsta Quartzitic Formation.
Scatsta Quartzitic Formation [Obsolete Code: Use Scat]
DASQ
Drawn at base of quartzite of the Scatsta Quartzitic Formation where it rests conformably on pelite of the Scatsta Pelitic Formation.
Shetland, Scotland.
Pure and impure quartzites interbanded with medium to fine-grained mica-schists.
2750m approx.
Drawn at conformable upward passage from pelite and quartzite of the Scatsta Quartzitic Formation to the Weisdale Limestone.
Dasses Sill
DASS
Daugh Coal (Sanquhar)
DAU
Dava Succession
DAVA
Central Highlands of Scotland, Glen Bachor, and between Strathnairn and Grantown-on Spey.
Heterogenous succession of predominantly gneissose psammite, semipelite and subordinate quartzite.
Sheared, tectonised or interpreted unconformable contact with overlying Grampian Group strata.
Davy Coal
DAVC
Dales Voe Grit Member
DAVO
Dailly Wee Coal
DAW
Weisdale Limestone [Obsolete Code: Use Weil]
DAWL
Whiteness Limestone [Obsolete Code: Use Wnsl]
DAWN
Daylesford Member
DAY
Aghyaran Formation
DBAF
Ardrishaig Phyllite Formation
DBAP
Asta Spilitic Formation [Obsolete Code: Use Assp]
DBAS
Drawn at base of metaspilite of the Asta Spilitic Formation where it rests conformably on the Laxfirth Limestone.
Metasedimentary phyllite along with hornblendic phyllites and coarse-grained hornblendic rocks.
250m approx.
Drawn at conformable upward passage from meta-spilite of the Asta Spilitic Formation to semi-pelite of the Clift Hills Phyllitic (Formation).
Didymograptus Bifidus Beds
DBB
Awaits modern stratigraphical study.
Grey silty graptolitic mudstones with thin tuffaceous horizons.
Unspecified
Bonahaven (Bunnahabhain) Dolomite Formation
DBBD
Boultypatrick Grit
DBBG
Bonawe Succession
DBBS
Double Coal Rock
DBC
Upper Crana Quartzite Formation
DBCA
Creran Bridge Quartzite Formation
DBCB
Creagan Formation
DBCG
Cranford Limestone
DBCL
Carn Mairg Quartzite Formation
DBCM
First appearance of massive pebbly quartzite within 80m transition zone from impure quartzites and semipelites of Killiecrankie Schist Formation.
From Creag Sparadain [NN 968 653], where it is cut off by the Killiecrankie Slide, southwards via the north side of Beinn Eagagach [NN 855 575] and Carn Mairg [NN 683 515], to Loch Awe [NN 11 26], where it is cut off by the Etive Complex.
Massive white pebbly quartzite and rusty gritty psammite, with local pink feldspathic quartzite and calcareous semipelite.
0 - 900m in Sheet 55W
Point within transitional sequence where micaceous, graphitic pelite typical of Ben Eagach Schist Formation dominates over quartzite.
Crinan Subgroup
DBCN
Incoming of coarse pebbly quartzite or psammite at base of Crinan Grit or Upper Erins Quartzite (Argyll); change from calcareous pelite or volcaniclastic rocks to non-calcareous turbiditic semipelite, pelite and psammite (Perthshire to Banffshire).
Connemara; North Mayo; Donegal; Newtown Stewart to east of Strabane; Armoy to Torr Head; Kintyre, Knapdale; Crinan to Loch Awe; from Loch Fyne, via Tyndrum, Loch Tay, Loch Tummel, Glen Shee, Deeside, Donside and Ladder Hills to the coast from Aberdeen to Ellon, Peterhead to Fraserburgh, and Portsay to Boyne Bay.
Coarse-grained quartzite present in Argyll at base of subgroup; upper part of subgroup in Argyll and whole of subgroup elsewhere formed of interbedded semipelite and pelite with minor psammite - this facies denotes the commencement of deep-water turbiditic sedimentation. Gritty psammite and semipelite near top in Glen Dochart - Kikin.
Bottom of lowest limestone bed in Loch Tay Limestone Formation where present; from Glen Clova to Deeside change from dominant semipelite to psammite or quartzite with calcareous beds.
Craignish Phyllite Formation
DBCP
Lower Crana Quartzite Formation
DBCQ
Crinan Grit Formation
DBCR
Croaghubrid Pelite Formation
DBCS
Crinan Subgroup And Tayvallich Subgroup (Undifferentiated)
DBCT
Culdaff Limestone
DBCU
Creran Flags Formation
DBDF
Dungiven Formation (A) [Obsolete Code: Use Dunn]
DBDI
Degnish Limestone Formation
DBDL
Dunrossness Phyllitic Formation [Obsolete Code: Use Duph]
DBDP
Drawn at base of pelitic wacke interpreted to belong to the Dunrossness Phyllitic (Formation) where it rests conformably on pelite and semi-pelite interpreted to belong to the Clift Hills Phyllitic (Formation).
Chlorite-chloritoid phyllite containing a few thin bands of quartzite. Kyanite occurs in quartz segregations and staurolite in metamorphic aureoles.
750m approx.
Drawn at conformable upward passage from pelitic wacke interpreteted to belong to the Dunrossness Phyllitic (Formation), to meta-spilite of the Dunrossness Spilitic Formation.
Durn Hill Quartzite Formation
DBDQ
Change from interbedded psammite and semipelite of Arnbath Formation, where present, or pelite and limestone of Fordyce Limestone Formation, to thicker-bedded quartzite.
Coast section from 150m southeast of Foul Hole to John Legg's Well [NJ 579 666 to 580 665]; extends southwards as far as Braco [NJ 498 512]. Equivalent to the Kymah Quartzite farther south.
Quartzite, massive to blocky, locally feldspathic. Micaceous quartzite at base in southern part of outcrop.
c.400m on Durn Hill, thinning to c.150m at coast. Probably repeated by folding and thrusting on Knock Hill and farther south.
Rapid transition to pelite (graphitic near coast) at base of Castle Point Pelite Formation.
Deeside Limestone [Obsolete Code: Use Dli]
DBDS
Dungiven Formation (B) [Obsolete Code: Use Dunn]
DBDU
Dales Voe Grit [Obsolete Code: Use Davo]
DBDV
D-Bed Evaporite
DBE
Easdale Subgroup
DBED
Abrupt transition from quartzite to graphitic pelite (Jura, Easdale) or mixed semipelite, pelite and psammite (Perthshire).
Connemara; North Mayo; Donegal; Jura, Knapdale and Mid-Argyll; from Loch Fyne, via Tyndrum, Loch Tay, Loch Tummel, Glen Shee, Deeside, Donside and Ladder Hills to the Moray firth coast from Portsoy to Boyne Bay.
Semipelite and pelite, the pelitic lithologies graphitic in lower part and calcareous in upper part, with pebbly quartzite developed in part of succession over wide areas; volcaniclastic formation locally present at top of subgroup.
Up to 3km
Top of Farragon Volcanic Formation in Perthshire; base of Crinan Grit or Upper Erins Quartzite in Argyll.
Erins Quartzite Formation
DBEQ
Easdale Slate Formation
DBES
Devil's Bridge Formation
DBF
Aberystwyth area, west Wales.
Dinas Bran Formation
DBG
Overlie Vivod Group (or M. Leintwardinensis Beds) of Wills and Smith, 1922. Junction not seen. Vivod Group consists of thinly bedded flaggy mudstones.
Between Llangollen and Pontcysyllte, Dee Valley (Vale of Llangollen) Clwyd.
Mudstones, sandy, slightly calcareous, micaceous, thinly bedded, uncleaved.
Up to about 225 m thick.
None - occurs in the core of the Llangollen Syncline.
Durbog Coal (North Wales)
DBGC
Glendaruel Limestone [= Loch Tay Limestone]
DBGL
Gaughin Quartzite Formation
DBGQ
Donegal.
Derbyhaven Formation
DBH
The formation is more than 90m thick (Chadwick et al., 2001).
Dibhole Coal (West Yorkshire)
DBHC
The Dib Hole Coal is a thin impersistent seam that is of no economic importance. Its significance lies in its association with the Dib Hole Marine Band and the top of the Grenoside Sandstone Cycle (Chisholm, 1990).
Clift Hills Phyllite Group [Obsolete Code: Use Clhi]
DBHP
Drawn at base of pelite and semi-pelite of the Clift Hills Phyllitic Group where it rests conformably on meta-spilite of the Asta Spilitic Group.
Colour banded semi-pelitic phyllite with intercalations of quartzite. Laminated phyllites contain muscovite and some are graphitic. Thick units of coarse, feldspathic grit occur.
2300m approx.
Drawn at conformable upward passage from semi-pelite and pelite of the Clift Hills Phyllitic Group to pelitic wacke of the Dunrossness Phyllitic Group.
Dalmellington Blackband Ironstone
DBI
Islay Quartzite
DBIQ
Islay Subgroup
DBIS
Connemara; North Mayo; Donegal; Islay, Jura, from Loch Rannoch to Glen Tilt, from near Spittal of Glen Shee via Upper Deeside, Donside and Ladder Hills to the coast between Sandend and Portsoy.
Diamictite ('Boulder Bed') with limestone clasts in its lower part and quartzite and granite clasts in upper part attains maximum thickness in Port Askaig area and on Garvellachs; overlying quartzite reaches 5km in thickness on Jura but is more usually 0.5 - 1km thick; dolomitic beds are locally developed near base of quartzite. In Ladder Hills area graded psammites and semipelites intervene between diamictite and quartzite.
Up to 5km
Abrupt transition from quartzite to graphitic pelite (Easdale) or mixed psammite, semipelite and pelite (Perthshire).
Jura Quartzite [Obsolete Code: Use Juqu]
DBJQ
Jura Slate [Obsolete Code: Use Jusl]
DBJS
Limestone Of Jura-Tayvallich Succession
DBJT
Kilchrenan Conglomerate Formation
DBKC
Kinnairds Head Formation
DBKH
Drawn at base of quartzite of the Kinnairds Head Formation where it rests conformably on quartzite of the Mormond Hill Quartzite.
Grampian, Scotland.
Grit, greywacke, semi-pelite with some calc-silicate rock and rare marble.
Drawn at conformable upward passage from limestone and semi-pelitic wacke of the Kinnairds Head Formation to semi-pelitic wacke of the Rosehearty Group.
Dalla Bank Limestone
DBKL
Killeter Quartzite Formation
DBKQ
0 to 1100m
Killiecrankie Schist Formation
DBKR
Change from fine-grained quartzite of Schiehallion Quartzite Formation to dark, layered semipelite and thin-bedded psammite containing 0.08m layers of fine-grained garnet-amphibolite.
From Carn Liath [NN 994 666], where it is cut off by the Killiecrankie Slide, southwards to Kinloch Rannoch [NN 659 576]. to the west of this, it is cut off by the Schiehallion Slide.
Pelite, semipelite and psammite, well-bedded, usually garnetiferous, locally slightly graphitic and kyanite-bearing. Cross-bedding developed at lower boundary; includes quartzite beds in A9 section near Killiecrankie.
First appearance of massive pebbly quartzite of Carn Mairg Quartzite Formation within 80m transition zone from impure quartzites and semipelites of Killiecrankie Schist Formation.
Killeter Quartzite Formation [Obsolete Code: Use Dbkq]
DBKT
Danny Bridge Limestone Formation
DBL
Late Asbian.
Disturbed Blackheath Beds
DBLB
Loch Na Cille Boulder Bed
DBLC
Lower Erins Quartzite Formation
DBLE
Laxfirth Limestone [Obsolete Code: Use Laxf]
DBLL
Douglas Bridge Limestone Member
DBLM
Base of limestones and calcareous mudstones overlying fluvial sandstones, siltstones and mudstones of the Barony Glen Formation.
Newtownstewart Basin, Sperrin Mountains, County Tyrone, Northern Ireland.
Micritic limestone, pale grey, laminated and nodular. Algal mat stromatalites and sparse, marine, shelly fauna. Limestones interbedded with calcareous mudstone, siltstone and sandstone.
Uppermost limestone overlain by fluvial sandstones, siltstones and mudstones of the Barony Glen Formation.
Laphroaig Quartzite Formation
DBLQ
Lough Esk Psammites
DBLS
Lower Whitehills Group
DBLW
drawn at base of phyllites of whitehills group where it rests conformably on the boyne limestone.
grampian,scotland.
dark,flaggy quartzites,purple quartzose phyllites.white limestones.calcareous flags and pebbly grits.(correlative of whitchells group-pelitic group and upper psammitic group).
not defined.
drawn at conformable upward passage from pebbly grit of the whitehills group to andalusite schists of the boynaie bay group.
Murlough Bay Formation
DBMF
Mormond Hill Quartzite Member
DBMH
Termon Formation
DBMI
Dippal Burn Formation
DBN
Sharp boundary on sandstones of Birkenhead Sandstone.
Dark greenish grey shaly mudstones in lower part, overlain by greenish grey sandstones, siltstones and silty mudstones.
Transition to reddish-grey sandstones and siltstones of Monument Formation.
Newtownstewart Formation
DBNF
Dogger Bank Formation
DBNK
Owencam Formation
DBOF
Port Ellen Phyllite [Obsolete Code: Use Peph]
DBPE
Port Askaig Tillite Formation
DBPT
Doweel Breccia Formation
DBR
Interdigitates with and overlies the Locharbriggs Sandstone Formation.
Mainly on the western side of the Dumfries Basin.
Interbedded breccias, fluviatile and aeolian sandstones; rare siltstones present at lower horizons.
>200m
Forms the top of the Permian sequence in the Dumfries Basin.
Dee Bridge Sandstone
DBS
Yellow sandstone with plant remains.
Scarba Conglomerate [Obsolete Code: Use Scco]
DBSC
St Catherines Graphitic Schist
DBSG
Shira Limestone And Slate Formation
DBSL
Slieve Tooey Quartzite Formation
DBSO
Schiehallion Quartzite Formation
DBSQ
Sharp change from diamictite of Boulder Bed to fine-grained well-bedded quartzite. However, a 10-20m bed of reworked granite diamictite occurs near the base of the Schiehallion Quartzite Formation on Cnocnan Aighean [NN 7292 5551].
From 1km north-east of Forest Lodge, where it pinches out in a tight fold core, southwards to the north shore of Loch Tummel and Loch Kinardochy via Schiehallion to the north-west side of Beinn a Chuallaich. West of this it is cut off by Schiehallion Slide.
Quartzite, white to grey, fine-grained. The upper half of the formation is especially pure and glassy, with little feldspar or mica. Includes Tempar Dolomitic Member and some beds of conglomerate.
0 - 800m in Sheet 55W (most thinning is tectonic).
Sharp (<10m) change from fine-grained quartzite of Shiehallion Quartzite Formation to dark, layered semipelite and thin-bedded psammite containing 8cm layers of fine-grained garnet-amphibolite.
Stonefield Schist Formation
DBSS
Schiehallion Boulder Bed Formation
DBST
Gradation from biotite calc-pelite to calcareous diamictite over 10m.
From east end of Loch Errochty [NN 7190 6609] to Loch Kinardochy [NN 775 550] west of Loch Tay Fault; around Loch Tummel [NN 833 596] and at Kirkton of Lude [NN 900 690], east of Loch Tay Fault.
Lower part: Calcareous diamictite with dominantly calcareous clasts. Central part: Schistose and feldspathic psammite and quartzite (discontinuous). Upper part: Quartz-rich diamictite with dominantly granite and quartzite clasts.
0 - 250m in Sheet 55W
Sharp contact between quartzose diamictite and thinly-bedded quartzite. However, 10 - 20m bed of reworked granite diamictite occurs near base of Schiehallion Quartzite Formation on Cnoc nan Aighean.
Duddon Bridge Tuff Member
DBT
Base of andesitic lapilli-tuff succession. Usually rests on brecciated top of Barrow Tuff Member.
Between Ulpha Park (SD 187 910) and Duddon Bridge (SD 196 882), near Broughton in Furness, Cumbria.
Andesitic lapilli-tuff, massive.
c.250m excluding basaltic andesite sill (130m)
Defined by base of overlying Duddon Hall Formation - parallel bedded andesitic tuff.
Drigg Beach Till Member
DBTI
Generally planar subhorizontal unconformity generally on the Kirkland Wood Sand and Gravel Member of the Gosforth Glacigenic Formation.
1:50k Sheet 37 Gosforth, Drigg area, Western Cumbria.
Dusky red stiff plastic silty and clayey diamicton with well dispersed sand grains and angular clasts (up to 30mm) of Borrowdale Volcanic Group rocks, Skiddaw Group siltstones and sandstones; some granite, red and white sandstone; sparse shell fragments. Rip-up clasts of underlying units common.
1.07m thick at its type section.
Overlain by the erosional base of the Drigg Holm Sand Member of the Gosforth Glacigenic Formation and by Holocene peat in a hollow on the foreshore at Barn Scar.
Tayvallich Limestone Formation
DBTL
Torr Head Limestone Formation
DBTR
Tayvallich Slate And Limestone Formation
DBTS
Tayvallich Subgroup
DBTV
Connemara; North Mayo; Donegal; Newtown Stewart to east of Strabane; Armoy to Torr Head; Kintyre, Tayvallich Peninsula; Loch Awe; from Loch Fyne, via Tyndrum, Loch Tay, Loch Tummel, Glen Shee, Deeside, Donside and Moray Firth coast at Boyne Bay - Whitehills.
Dominated by calcitic limestone, in part slumped, resedimented; however, east of mid-Deeside the limestone is replaced by psammite and quartzite with thin beds of calcsilicate rock; lavas, hyaloclastites and graphitic pelites present in Tayvallich area; Banffshire Coast - thick semipelite and calc sequence in upper part.
Generally 100-250m, but in Aberdeenshire and Banffshire where semipelitic and psammitic lithologies come in, it may reach 2.5km
Top of highest limestone bed in Loch Tay Limestone Formation where present; in Glen Clova and Glen Esk below unit with beds of strongly magnetic semipelite, Banffshire Coast - incoming of dominantly turbiditic psammite and semipelite.
Upper Erins Quartzite Formation
DBUE
Altmore Formation
DCAF
Loch Avich Grit Formation
DCAG
Loch Avich Lavas Formation
DCAL
Aberfoyle Slate Formation
DCAS
Undefined; base not observed.
Southwest of Loch Tay Fault from Loch Venachar to Loch Lomond (= to Luss Slates) and farther southwest, where known as 'Dunoon Phyllites'.
Pelite and semipelite, grey to black in general, but purple or green locally, with thin units of coarse gritty sandstone developed locally.
c.500m (estimated)
Outgoing of grey and black to purple slates and incoming coarse gritty and microconglomeratic arenites of the Creag Innich Sandstone Formation.
Beinn Bheula Schist Formation
DCBB
Ballykelly Formation
DCBF
Bullrock Greywacke Member
DCBG
Baranailt Limestone Member
DCBL
Down Cliff Clay Member
DCC
Base probably a non-sequence: sandy mudstone resting sharply on fossiliferous fine limestones of the Beacon Limestone Formation.
Dorset from Bridport to Shaftsbury; Shepton Mallet area of east Somerset.
Grey, calcareous, bioturbated silicate mudstones, locally very finely sandy and micaceous, which generally increases upwards. In upper part, beds up to 0.5m thick of pale grey calcareous very fine-grained silicate-sandstone or finely sandy limestone occur. Fauna includes ammonites.
Dorset coast: 10 to 21m. Inland Dorset: 0 to 121m (Bristow et al., 1995). East Somerset up to 12m.
Top is marked by the change up from sandy mudstone to sands or sandstones of the undivided Bridport Sand Formation.
Carnaneigh Green Beds
DCCA
Double Coal (Coalbrookdale)
DCCC
Claudy Formation
DCCF
Doddiscombe Formation And Codden Hill Chert Formation (Undifferentiated)
DCCH
Cloghan Green Beds
DCCL
Croaghgarrow Formation
DCCR
Dart Formation [Obsolete Code: Use Dart]
DCDF
Dunkeld Grit
DCDG
Dunoon Phyllite Formation
DCDP
Dart Formation [Redundant Entry: Use Dart]
DCDS
Clift Hills 'Division'
DCF
Fahan Grits
DCFG
Fahan Slates
DCFS
Green Beds Formation
DCGB
Greencastle Green Beds
DCGC
Glengawna Formation [Obsolete Code: Use Gaa]
DCGF
Glenelly Formation (A) [Obsolete Code: Use Glly]
DCGG
Glendun Formation
DCGN
Glenelly Formation (B) [Obsolete Code: Use Glly]
DCGO
Glen Sluan Schist Formation
DCGS
Black Schist + Chert
DCHB
Chert And Black Shale With Sandstone Bands [Within Hbs]
DCHC
Pelite Of Glenesk
DCHP
Dunaskin Clayband Ironstone
DCI
Parts of Ayrshire.
Innellan Group
DCIG
Drawn at base of semi-pelitic wacke of the Innellan Group where it rests conformably on psammitic wacke of the Bullrock Greywacke.
Pebbly schistose grits, schistose grits, greywackes, black and green slates. Black slates occur with sporadic seams of dark lime and grit. Conglomerate also occurs. (Innellan Group = stratigraphic equivalent of the Dunoon Phyllites).
1000m approx.
Drawn at unconformable upward change from conglomerate and semi-pelitic wacke of the Innellan Group to probable Upper Old Red Sandstone.
Innellan Formation
DCIN
Inishowen Head Grits
DCIS
Kells Grit
DCKG
Denbury Crinoidal Limestone Formation
DCL
Leny Grits
DCLE
Lower boundary with Aberfoyle Slates.
Cleaved greywackes commonly with grit and pebbly greywacke bands. Slate interbeds. NOTE: Leny Grits replaces Upper and Lower Leny Grits where the two units cannot be adequately defined.
Leckpatrick Green Beds
DCLP
Loch Ranza Slate Formation
DCLS
Londonderry Formation
DCLY
Dolyfan Conglomerate Member
DCM
Mullaghcarn Formation (A) [Obsolete Code: Use Mca]
DCMF
Mullaghcarn Formation (B) [Obsolete Code: Use Mca]
DCMG
Margie Limestone Member
DCML
A conformable contact with psammite and/or pelite of the Margie formation.
The river Esk and adjacent area within the Highland Boundary Fault system north-west from Edzell, Angus, Scotland.
A coarse-grained, calcitic meta-limestone, generally sandy and locally containing slate pebbles to which the limestone forms a carbonate matrix, which varies in colour from blue-grey to dark grey.
2 m thick.
Mullyfa Formation
DCMY
North Sannox Grits Formation
DCNS
Isle of Arran
Deep Coal (South Staffordshire)
DCO
Pitlochry Schist Formation
DCPS
Change from silty limestone at top of Loch Tay Limestone to dominantly semipelitic and pelitic rocks.
From Glen Brerachan [NO 01 63], 9km north-east of Pitlochry, south-westwards through Pitlochry [NN 94 58] to Kenmore [NN 77 45] and at least as far as Loch Tay Fault in Sheets 46 and 47. Also small outlier west of Glen Doll Fault [NO 23 78].
Semipelite dominant with interbedded pelite, micaceous psammite and volcaniclastic rocks (Green Beds), and containing minor pebbly psammite. Metamorphosed to garnet-mica schist in type area.
300 - 500m (estimated 300+m in Sheet 55W); not mapped separately in Sheet 55E, but transition to Ben Ledi Grit or equivalent probably occurs 300 - 500m above base of Southern Highland Group, close to main 'Green Beds' unit.
Change from dominantly semipelitic rocks to dominantly psammitic rocks (not seen in Sheet 55W). In parts of the outcrop outwith Sheet 55W, the change coincides with the main volcaniclastic unit.
Rosehearty Formation
DCRG
Drawn at base of semi-pelitic wacke of the Rosehearty Formation where it rests conformably on limestone and semi-pelitic wacke of the Kinnairds Head Formation.
Pebbly grits, greywacke and andalusite schists.
Drawn at conformable upward passage from semi-pelitic wacke of the Rosehearty Formation to semi-pelitic wacke of the Macduff Slates.
Runabay Formation
DCRH
Downton Castle Sandstone Formation
DCS
Base of Ludlow Bone Bed Member (if present); sharp junction with underlying Upper Ludlow Shale (Upper Whitcliffe Formation).
Welsh Borderland.
Ludlow Bone Bed Member locally at base; Platyschisma Shale Member (to 2m) above; mainly yellow, fine-grained, micaceous, well-sorted cross-bedded sandstone (Sandstone Member), with siltstone and olive green mudstone.
About 15m in type area; 17m at Ludlow, 15-20m in South Staffordshire
Top of highest sandstone below red mudstones of the Ledbury (Raglan Mudstone) Formation or below the conformable base of the olive green mudstones and siltstones of the Temeside Shales Formation.
Down Cliff Sand Member
DCSA
Base of Starfish Bed.
Southwest Dorset. Mapped on Sheet 327 (Bridport). Northern limit not yet proved.
Grey-brown, muddy, very fine-grained sands and sandy mudstones, closely interbedded.
Top of Margaritatus Stone.
Shanaghy Green Beds
DCSG
Dun Caan Shale Member
DCSH
Unseen?
Dark grey sandy, fissile mudstones with concretions of sandy limestone.
12m
Overlain by thinly bedded calcareous sandstones of the Beinn na Leac Sandstone Member.
Sheskin Limestone Member
DCSL
Saxa Vord Group
DCSV
Dog Crag Tuff Member
DCT
Base of lapilli-tuff rests on a non-sequence that occurs at the top of the Whinny Bank Formation - an interbedded succession of siltstone and andesitic lapilli-tuff.
Wicham Valley:- between Bankside (SD 158 831) and Lacra Bank (SD 145 815)
Eutaxitic lapilli-tuff, composition probably dacitic (or andesitic), interpreted as pyroclastic flow deposit.
Parallel bedded tuff and lapilli-tuff of the Po House Tuff Formation.
Downton Castle Sandstone Formation And Temeside Mudstone Formation (Undifferentiated)
DCTE
Down Cliff Sand Member And Thorncombe Sand Member (Undifferentiated)
DCTS
Tayvallich Volcanic Formation
DCTV
Upper Whitehills Group
DCUW
Grampian,Scotland.
Dark,flaggy quartzites,purple,quartzose phyllites,white limestones,calcareous flags and pebbly grits.(correlative of Whitehills Group-pelitic group and upper psammitic group).
Drawn at conformable upward passage from pebbly grit of the Whitehills Group to andalusite schists of the Boyndie Bay Group.
Doldowlod Conglomerate Member
Taken at base of first thick bed of conglomerate, sandstone or pebbly mudstone. Sharp.
Interbedded conglomerates, sandstones, pebbly mudstones and mudstones.
Up to 450m.
Taken at top of last thick bed of conglomerate, sandstone or pebbly mudstone. Upper boundary gradational where overlain by further Nantmel Formation strata or sharp where overlain by Yr Allt Formation.
Ddolhir Beds [Originally Dolhir]
DDB
Doddiscombe Formation
DDC
The original Lexicon entry for Doddiscombe Formation carried an "age" of Courceyan. This precision was not repeated by the author of the current entry, who suggests "Dinantian".
Between Brushford and Wellington the lower boundary is taken at the incoming of hard black finely laminated unfossiliferous, slightly siliceous mudstones of the Doddiscombe Formation above the soft medium to dark grey mudstones with scattered very thin limestones, siltstones and sandstones of the underlying Pilton Mudstone Formation. West of South Molton, the lower boundary is taken at the incoming of dark grey to black, rarely fossiliferous slightly siliceous, finely laminated mudstones (Unit D of the Pilton Beds of Prentice 1960), known to equate with the Doddiscombe Formation, above the fossiliferous mudstones with thin sandstones and siltstones of the underlying Pilton Mudstone Formation. The Doddiscombe Formation has not been mapped by BGS west of South Molton; instead it has been included in the Pilton Mudstone Formation and/or the Codden Hill Chert Formation. Further work is therefore needed.
Between Brushford (SS 92 26) and Wellington (ST 13 20), Somerset. Known to extend west of South Molton to the Barnstaple area (SS 50 33) as the dark unfossilferous silty mudstones, Unit D of the Pilton Beds of Prentice (1960). This unit has not been mapped by BGS west of South Molton and further work is needed.
Hard, black, slightly siliceous, finely laminated mudstones with sparse very thin siltstone beds. There are scattered thin lenticular ?chert and phosphate nodules and sparse impure limestones and local pale calcareous mudstones. The formation is rarely fossiliferous.
8 to 80m; lower thickness likely to be tectonic.
Between Brushford and Wellington the upper boundary is taken at the incoming of thin to medium bedded soft siliceous mudstones with impure limestones and cherts of the Bampton Limestone Formation above the hard black, finely laminated unfossiliferous cherty mudstones of the underlying Doddiscombe Formation. West of South Molton, the upper boundary is taken at the incoming of dark grey interbedded siliceous mudstones and shaly mudstones of the overlying Coddon Hill Chert Formation above the dark unfossiliferous slightly siliceous mudstones (Unit D of the Pilton Beds of Prentice 1960), known to equate with the Doddiscombe Formation. Neither this boundary nor the Doddiscombe Formation has been mapped by BGS west of South Molton and further work is needed.
Daren-Ddu Coal (South Wales)
DDCO
Dalmellington Diamond Coal
DDDC
Dry Doddington Nodule Bed
DDDN
Change up from bluish grey, shaly mudstone of undifferentiated Beckingham Member; at 40.56m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands; north Leicestershire to Lincolnshire. Not recognised in north Lincolnshire, or south Leicestershire, where it passes south into either part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or part of the mudstone dominated Charmouth Mudstone Formation.
Sequence of grey mudstone beds with numerous ovoid, grey, ochreous-weathering, argillaceous limestone nodules 0.05 to 0.2m in diameter, which are conspicuous in the soil. Some nodules are rich in small bivalves (Modiolus), and with gastropods. May include thin, silty, shelly, ferruginous limestone beds at base. Forms a strong feature with a dip slope in places.
About 2m; 1.94m in type section
Change up into grey, shelly, bioclastic limestone of the undifferentiated Beckingham Member; at 38.62 in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Dura Den Member
DDF
The top of the coarser-grained sandstone within the Glenvale Sandstone Formation.
The Stratheden area of the Midland Valley of Scotland, on sheets 40E (uncertain), 48E and 49. Additionally a thin lens-shaped unit is restricted to the Cupar area.
Red, cream and green siltstones, alternating with fine-grained cream sandstones, coarser pebbly sandstones and thin partings of red or green mudstone.
Approximately 40 m thick.
Drawn at the conformable upward passage from siltstone and sandstones of the Dura Den Member to the white or cream sandstones of the Knox Pulpit Sandstone Formation.
Dundarg Sandstone Formation
DDG
Disturbed Ground (Undivided)
DDGR
Variable composition; Man-made superficial deposit. Areas of ill-defined surface workings and excavations; complex association between areas of subsidence and Made Ground. [Generic description].
Duddo Limestone
DDL
Darren Ddu Limestone Member
DDLM
The base is placed at the sharp, planar junction between pale grey lime mudstone at the base of the Member and the underlying fine-grained dolostone of the lower part of the Coed Ffyddlwn Formation.
Clydach valley, on the northeast crop of the South Wales Coalfield [SO 215 125].
Thinly bedded, pale grey micritic limestones (lime mudstones), locally peloidal, with grey-green mudstones and cream laminated dolomitic mudstones; algal laminite locally at the top.
The upper boundary is placed at an irregular, stylolitized surface cut in the topmost pale grey lime mudstones of the Member, which is overlain by a coarse bioclastic grainstone (the Craig-y-Gaer Coral Bed) at the base of the Gilwern Oolite Formation.
Diddup Limestone
DDLS
Drumderfit Conglomerate Member
DDM
Conformable lower contact on Avoch Sandstone Member.
Red cobble-boulder conglomerate.
+ 100 metres lensing.
Conformable upper contact with Goose Sandstone Member.
Daren-Ddu Rider Coal (South Wales)
DDRC
Ddugaled Coal (South Wales)
DDUC
Dalmellington Ell Coal
Dean Coal (Northumberland And Durham)
DEAN
Dersingham Formation
DEB
A downward change from ferruginous, fine-grained sandstone to unconsolidated, fine- to medium-grained, cross-bedded, generally clean, pale quartz sands [Leziate Member of the Sandringham Sands Formation].
Crops out at Heacham to Babingley River and Roydon to Ashwicken, and outliers occur at Rising Lodge and East Winch. It is cut out by the overstepping Carstone in the vicinity of East Winch. Boreholes at Gayton and Hunstanton penetrated the Formation.
The Formation comprises a rythmic succession of thinly interbedded, fine-grained sands, ferruginous sandstones, silts and clays. The Formation varies laterally from ferruginous fine-grained sands and sandstones around Dersingham and Roydon Common, to silts in the Hunstanton Borehole. Clay [Snettisham Clay Member] is present at the top of the Formation, such as in the Hunstanton Borehole, at Dersingham and at Snettisham. It passes laterally into the Tealby Formation under The Wash.
To c.16m
Ferruginous, medium-grained, generally oolitic and pebbly sand, locally clayed at the base [Carstone Formation], overlies mudstone [Snettisham Clay Member] around Dersingham and Snettisham. At Hunstanton, silty, oolitic, pebbly clays at the base of the Roach Formation overlie a rhythmic succession of brown and red clay and clayey silt, oolitic in part; and separated by an interburrowed erosion surface.
Delta Bench Coal (North Wales)
DEBC
Deception Coal (Lothian)
DEC
Desertcreat Group
DECG
Deep Conglomerate Formation
DECO
The base of the formation is placed at the top of a thick succession of andesitic lavas of the Montrose Volcanic Formation where this is conformably and somewhat diachronously overlain by a massive clast-supported conglomerate, above which it passes laterally into, and interfingers with, sandstone of the Tannadice Sandstone Member of the Scone Sandstone Formation.
North-eastern Midland Valley, between Drumlithie and the River South Esk.
A pebbly and cobbly, well-rounded, clast-supported conglomerate of lava, psammite, quartzite and feldspar-porphyry in a matrix of poorly-sorted, fine- to medium-grained lithic sandstone, commonly with lenses of trough cross-bedded pebbly sandstone.
Up to 880 m thick in the type area, passing laterally into sandstone of Tannadice Sandstone Member towards the south-west.
A clast-supported conglomerate conformably, somewhat diachronously and locally interfingered with the base of a red, massive or laminated, poorly-sorted siltstone of the Cromlix Mudstone Formation.
Dee Valley Formation
DEEVA
Probably unconformable, irregular and in places strongly incised into lithologically variable sediments of the Caledonia or Albion Glacigenic groups or into bedrock.
Cheshire, within the river valley and tributaries of the River Dee.
Alluvium of silt, sand and clay with some peat, grading to gravel towards the base. River Terraces are composed of silty sand or sandy gravel with rare clay.
Dundee Flagstone Formation
DEF
The top of the andesitic lava flows at Tealing House and Newton, near Dundee, the base of which is not generally exposed because it lies at the core of the Sidlaw Anticline.
Dundee-Inverkeilor area on Sheets 48E, 49, 57E (uncertain) and 57W.
Medium- to coarse-grained, cross-bedded sandstones and substantial, distinctive, flaggy sandstones interbedded with minor siltstones and mudstones, interdigitated with the Ochil Volcanic Formation.
Up to 1800 m thick.
The top of the highest bed of flaggy sandstone and siltstone which is characteristic of the Dundee Flagstone Formation, and below the Scone Sandstone Formation.
Derfel Limestone Member
DEL
Caradoc (Costonian or Harnagian).
Not seen, but interpreted as a fault against falsic ash flow tuffs of the Aran Fawddwy Formation (formerly the Llyn Conwy Formation) at its stratotype by BGS mapping in 1993. (Corwen provisional 1:50 000 Sheet 120). Elsewhere considered to be conformable on the Aran Fawddwy Formation.
Corwen and Bala areas.
Dark, blue-black pyritous, slightly calcareous, shelly mudstone, sporadically but richly fossiliferous.
1m to 2m.
Not seen, but appears to be conformable with the mudstones of the Ceiswyn Formation.
Delamere Sandstone Member
DELA
Lowermost occurrence of dominantly pebbly sandstone overlying pebble-free weakly cemented sandstone of the Wilmslow Sandstone Formation.
Cheshire Basin; possibly southern part of the East Irish Sea Basin.
Sandstone and pebbly sandstone with subordinate mudstone beds. Reddish-orange and pale yellow. Planar and trough cross-bedded or massive. Common intraformational pebbles of sandstone and mudstone and extraformational quartz, up to 2.5cm. The Member is more strongly cemented than those immediately above and below, and is therefore commonly more resistant and consequentially commonly feature-forming.
40m (Helsby area); c.90m (north Wirral).
Uppermost occurrence of pebbly sandstone under weakly cemented pebble-free sandstone of the Frodsham Soft Sandstone Member (Helsby Sandstone Formation), or under interbedded siltstone and sandstone of the Tarporley Siltstone Formation (Mercia Mudstone Group).
Denny Lower Blackband Ironstone
DELB
Parrot coal : 6.5 cm - blackband ironstone : 17.5 cm - coal 5 cm.
29 cm.
Delta Coal (North Wales)
DELC
Delnadamph Volcanic Member
DELV
Lower limit of metavolcanic units within graphitic pelites and semipelite sequence of the Glenbuchat Graphitic Schist Formation.
Stretches from the Tomintoul Old Red Sandstone outlier via Muckle Fergie Burn and Inchmore (Delnadamph) to Clach Choutsaich and Brown Cow Hill (Glen Gairn Granite).
Actinolite-rich finely to coarsely crystalline amphibolite, locally vesicular, pillowed in parts. Amphibolitic schists, hornblende-bearing psammite, quartzite and pelite interbeds.
Upper boundary of amphibolitic material in partly graphitic semipelite and pelite sequence of the Glenbuchat Graphitic Schist Formation.
Den Coal (Fife)
DEN
Dearcaige Quartzite Member
DEQU
Deri Formation
DER
The base of the Formation is diachronous and gradational, and placed at the base of the first development of red, green or purple mudstone, where it overlies grey mudstones of the South Wales Coal Measures Group.
The Formation is confined to the eastern part of South Wales Coalfield, extending from the Cynon Valley near Penrhiwceiber [ST 05 97] eastwards (see Downing and Squirrell, 1965, Figure 1).
The Formation comprises mottled red, purple, green and orange mudstones and mudstone palaeosols, pale green siltstones and pale grey quartz arenites and conglomerates. Thin coals fail progressively eastwards towards the Usk Anticline.
The top of the Formation is diachronous and gradational, and placed where the topmost development of red, green or purple mudstone, or white quartz arenite, is overlain by either grey mudstones of the South Wales Coal Measures Group or, on the east crop of the South Wales Coalfield, where it is overlain by the Brithdir Coal, marking the local base of the Pennant Sandstone Formation.
Derry Coal (Dungannon)
DERC
Deep Rider Coal
DERI
Derlwyn Formation
DERL
Derrycreevy Sandstone Formation
DERR
Derwyddon Sandstone Formation
DESA
Dersingham Beds/Snettisham Clay [Obsolete Code: See Deb And Snc]
DESC
Dunfermline Splint Coal (Fife)
DESP
Dunfermline Under Coal (Fife)
DEU
Denny Upper Blackband Ironstone
DEUB
Ironstone rib - 4cm; Slaty blaes - 5 cm; Hard ironstone rib - 2.5 cm; Slaty blaes - 15 cm; Foul coal - 15cm.
Devonian Rocks (Undifferentiated)
DEV
Devonian And Carboniferous Rocks (Undifferentiated)
DEVC
Dalmellington Extra Coal
DEX
Darwen Flags
Dipple Fish Bed
DFB
Dunaskin Fireclay
DFC
Debris Flow Deposits
DFD
Typically boulders, cobbles, gravel, sand and mud; deposited by mountainside debris flows with levees resulting from heavy rainfall and/or snow avalanches. [Generic description].
Douglas Four Foot Coal
DFF
Dyffryn Flags Facies (Caban Conglomerate Formation)
DFN
Not defined
Interbedded turbidite mudstones, laminated hemipelagites and abundant thin turbidite sandstones.
Dundry Freestone
DFR
Dumfries Sandstone
DFS
Dipton Foot Shell Bed
DFSB
Dunsil And First Waterloo Coal (Vale Of Belvoir)
DFWC
Denbigh Grits Formation
Dingle Conglomerate Member
DGC
Dixon Ground Member
DGD
A transition over a few hundred millimetres from massive, hard, poorly fissile grey siltstone of the Browgill Formation, into pale blueish or greenish grey muddy siltstone with a slightly better cleavage.
A narrow unit, extending across the south eastern Lake District, mapped as a distinct unit to about 4km southwest of Coniston village. It is present farther to the southwest, but has not been mapped due to poor exposure. It is shown on the Coniston 25k map but not the 50k Ambleside or Kendal sheets. It is also recognised in the Howgill Fells, and crops out on Sheets E38 and E39, but is only shown on the former.
Alternating pale grey, bioturbated siltstone and laminated hemipelagite.
From 10m to 30m thick.
Taken at the top of the highest, pale grey, massive or bioturbated mudstone bed that is succeeded by more than 200mm of laminated hemipelagite.
Douglas Ell Coal
DGE
Dun Gallain Grit Formation
DGGR
Dungavel Hill Conglomerate Member
DGHC
Drigg Holm Sand Member
DGHS
Generally undulating erosional contact on to Drigg Beach Till Member of the Gosforth Glacigenic Formation.
1:50k Sheet 37 Gosforth. Seascale, Ravenglass and Lower Wasdale areas, Western Cumbria.
Fine-to medium-grained sand with stringers of granule gravel and channels containing clast-supported gravel. The gravel comprises subangular to subrounded clasts of Skiddaw Group sandstones and siltstones, red and yellow sandstone, Borrowdale Volcanic Group rocks, granite, granophyre, coal and ironstone.
Sub horizontal planar unconformable (?locally glacitectonic) contact with the the base of the Fishgarth Wood Till Member of the Gosforth Glacigenic Formation.
Dunaghy Formation
DGHY
Dungavel Group
DGL
Drawn at base of conglomerate of the Middlefield Conglomerate where it rests conformably on sandstones of the Logan Formation of the Waterhead Group.
Sandstone and conglomerate.
775m approx.
Drawn at conformable upward passage from sandstone of the Plewlands Formation to Greywacke Conglomerate of the Old Red Sandstone.
Drummangarvagh Member
DGM
Drigg Moorside Silt Member
DGMS
Generally conformable on the Fishgarth Wood Till Member of the Gosforth Glacigenic Formation.
1:50k Sheet 47 Gosforth, Drigg area, western Cumbria.
Thinly interbedded sequence of brown silty clay, clayey silt, very fine-grained sand and yellow brown fine- to medium-grained sands. Some beds of clay contain granules and fine pebbles.
8.6m thick at its type section.
Unconformably overlain by Holocene deposits such as blown sand and peats.
Douglas Nine Foot Coal
DGN
Dungoil Linear Vent-System
DGOIL
Drigg Point Sand Formation
DGPS
Unconformable (blanket) on all older Quarternary deposits.
1:50k Sheets 37 Gosforth and 38 Whitehaven, Western Cumbria, (and could be applied to coastal Blown Sand along the Cumbria-Lancashire coasts).
Fine- to medium-grained quartz sand forming coastal dunes, typically up to 15m high in the type area.
Typically 5-10m thick but up to 15m thick in type area.
The ground surface.
Dogger Formation
DGR
The lower boundary is generally sharp, disconformable or unconformable on the gently folded Lower Jurassic Lias Group. Marked by an abrupt change where grey fissile mudstone of the Lower Jurassic Whitby Mudstone Formation is overlain by sandstone, ironstone or limestone of the Dogger Formation. The boundary is less distinctive in the Peak Trough (Knox, 1984) (e.g. exposed at Blea Wyke; Ravenscar) [NZ 991 015] where the bioturbated sandstone of the Blea Wyke Sandstone Formation (late Toarcian in age ) is overlain by the yellow brown sandstone of the Dogger Formation (Aalenian in age).
Cleveland Basin, North Yorkshire, including the North Yorks Moors, North Yorkshire coast (between Boulby and Gristhorpe Bay) and the Howardian Hills. Offshore, the Dogger Formation is equivalent, in part, to the Wroot Formation (Lott and Knox,1994) in the southern North Sea and in part to the Drake Formation in the Brent Province (Butler et al., 2005). The formation is locally absent in the Cleveland Basin, especially on parts of the Egton Sheet (Ingleby Greenhow) and Thirsk Sheet (Hambleton Hills), where the Dogger Formation has been removed by penecontemporaneous erosion prior to deposition of the overlying Saltwick Formation (Ravenscar Group).
Forms a small bench or positive topographical feature above the Whitby Mudstone Formation; less distinctive where it overlies the Blea Wyke Sandstone Formation at Ravenscar.
Highly variable and heterolithic with substantial lateral interdigitation and lithofacies changes. In the Whitby area and coastal sections to the southeast, the formation consists mainly of grey, weathering yellow-brown, ferruginous sideritic sandstone, medium- to coarse-grained, with sporadic phosphatic pebbles; berthierine (chamosite) ooids may be present. In central, north and west Cleveland there is a complex interdigitation between grey, weathering yellow-brown, berthierine (chamosite) ooidal ironstone (with siderite mudstone matrix) and pale grey limestone, medium-grained, bioclastic wackestone and packstone with peloids and ooids, generally bioturbated and locally cross-bedded. In Rosedale [SE 729 946] the Dogger Formation consists of magnetite and/or ferric cronstedite spinel and berthierine oolitic ironstone (Hemingway, 1974). In addition, partings, lenses and beds of grey, fossiliferous fissile mudstone may occur. Sandstones and ironstones are characteristically highly bioturbated and yield marine fossils including bivalves and scattered ammonites; corals, bryozoans, crinoids and brachiopods are locally present in the limestones.
Variable, both locally and regionally; generally about 0.75 to 2m thick on the Yorkshire Coast and in ferruginous sandstone/ironstone lithofacies; limestone and mudstone lithofacies, up to 12.2m locally preserved. Maximum thickness of 29m in the Rosedale area [SE 729 946] (where present as the Rosedale Ironstone). May be absent, locally, due to erosion prior to deposition of the overlying Saltwick Formation (Ravenscar Group).
The upper boundary is unconformable or disconformable, generally sharp. Marked by an abrupt upward transition from ferruginous sandstone, ironstone or limestone at the top of the Dogger Formation to cross-stratified, non-bioturbated sandstone, siltstone and mudstone (commonly with plant fragments) of the overlying Saltwick Formation (Ravenscar Group).
Douglas Stoney Coal
DGS
Douglas Seven Foot Coal (Douglas)
DGSF
Dudgeon Formation
DGSL
Douglas Smithy Coal
DGSM
Drigg Till Formation
DGTI
Sharp, irregular, uncomformable contact with bedrock (mostly sandstone of the Sherwood Sandstone Group).
Drigg area and Lower Wasdale, West Cumbria.
Stony, sandy silty clay diamicton, reddish brown, extremely compact, with clasts mainly of welded tuff, greywacke and slate and granite derived from the western Lake District, together with red (Permian) and yellow (Carboniferous) sandstone and coal from West Cumbria, and sparse granodiorite from Scotland.
Sharp, gently undulating, unconformable contact with laminated silt and clay of the Stubble Green Silt Member of the Glannoventia Formation, or sharp, planar, unconformable contact with sandy clay diamicton of the Holmrook Till Member of the Blengdale Glacigenic Formation.
Dolgau Mudstones Formation
DGU
Grey, green and locally purple mudstones; local burrow mottling.
Dolgau Mudstones Formation (Lower Tongue)
DGUL
Dolgau Mudstones Formation (Upper Tongue)
DGUU
Douglas Water Arenite Formation
DGW
Top of the underlying Parishholm Conglomerate. (Boundary not exposed).
Lower Palaeozoic inlier of the Hagshaw Hills, Scotland. (50k Sheets 23E, 23W and 15W).
Pale red and yellow or brownish sandstones with greenish-grey intraclasts of shale, variably cemented.
About 78m
Transitional boundary taken where the proportion of mudstone similar to that of the overlying Dovestone Redbeds exceeds that of the sandstone.
Dungeon Ghyll Sandstone Member
DGY
Taken at the base of dominantly disrupted units overlying volcaniclastic rocks of the Three Tarns, Cam Crags and Harrison Stickle members
Scafell Pike to the Langdale Pikes, and from Seathwaite Fell (Borrowdale) to Thirlmere, Cumbria
Volcaniclastic siltstone, sandstone and breccia characterised by widespread syndepositional deformation and slumping such that bedding, particularly in the finer lithologies, is rarely preserved
Up to 60m
Defined by the base of overlyig pyroclastic rocks of the Pavey Ark Breccia Member
Duddon Hall Tuff Formation
Base of bedded tuff and lapilli-tuff (air-fall), unconformably overlying Airys Bridge Tuff Formation, (rhyodacitic tuff) and Waberthwaite Tuff Formation (dacitic tuff).
Ulpha Basin and Coniston Fells from Duddon Bridge (SD 19 88) via Ulpha (SD 19 93) to Wallowbarrow Heald (SD 21 97), Buck Pike (SD 261 972) to east of Birk Fell (NY 295 015), Cumbria.
Bedded tuff and lapilli-tuff (air-fall) with some pyroclastic breccia, intercalated andesite and basaltic andesite lava.
200 to 450m
At base of overlying formations including Ulpha Formation (andesite), Holehouse Gill Formation (mudstone and sandstone) and Wallowbarrow Formation (andesitic lapilli-tuff).
Dam House Bridge Tuff Member
DHBT
Taken at the base of the lowest bed of volcaniclastic rock overlying calcareous siltstone and argillaceous limestones of the Norber Formation
Restricted to the Austwick area of N Yorkshire
Siltstone and mudstone with interbedded units of lithic crystal tuff, probably of silicic composition
Up to 40m
Taken at the top of the last bed of tuff where it is overlain by siltstone and mudstone within the main part of the Sowerthwaite Formation
Douglas Humph Coal
DHC
Doghole Coal (South Lancashire)
DHCO
Dale Head Breccia Member
DHD
Base of volcaniclastic breccia and sandstone. Overlies unnamed basaltic andesite lava and locally a thin (3m) tuff. Probably unconformable.
Dale Head - Cockley Beck area in the Duddon Valley, Cumbria.
Massive units of heterolithic volcaniclastic breccia and sandstone.
Succeeded by overlying parts of the Birker Fell Andesite Formation, including the Cockley Beck Tuff (garnetiferous, dacitic lapilli tuff) and a variety of basaltic andesite and andesite lava.
Duchray Hill Gneiss Member
DHGN
Base of dominantly semipelitic succession overlying the dominantly psammitic and quartzitic Corrydon Psammite Member in the Glen Shee area and the volcanic Farragon Volcanic Formation farther west.
Glen Shee to upper Glen Isla.
Schistose to gneissose semipelite, generally garnetiferous. Stromatic to granoblastic migmatites in the east passing westwards into predominantly schistose rocks.
Base of calcareous rocks of the overlying Loch Tay Limestone Formation.
Dollis Hill Gravel Member
DHGR
Rests unconformably on bedrock geology.
Tributary of ancestral River Thames in the Finchley - Hoddesdon area of North London.
Gravel, sandy and clayey in part, with some laminated silty beds.Sand and gravel, locally with lenses of silt, clay or peat and organic material - [Generic description].
Overlain by Anglian Till in many places; otherwise at surface.
Donald's Hill Ignimbrite Formation
DHI
Early Paleocene.
Welded tuff (as described under Lithology) disconformably overlies the karstified chalk surface of the Late Cretaceous Ulster White Limestone Formation. The upper few centimetres of the chalk are faintly stained yellow in some areas. Locally the base of the tuff oversteps onto Triassic, Carboniferous and Dalradian "basement" rocks.
On the western margin of the Antrim Plateau (Northern Ireland) for a distance of about 30km from the west flank of Donald's Hill to Sounding Hill quarry, southsoutheast of Magherafelt, County Londonderry.
Tuff, creamy white, grey to pinkish grey, formerly ignimbritic, silicic welded ash-flow, with streaky poorly banded matrix, quartz phenocrysts and vlvanogenic lithic and crystal fragments now completely replaced by cryptocrystalline silica; clasts, exclusively of flint nodules reworked by erosion from Cretaceous chalk.
0.6 to 1.1m
The welded tuff of the Donald's Hill Ignimbrite Formation is overlain by basalt lave flows of the Antrim Lave Group.
Daddyhole Member
DHL
Dumdruff Hill Lava Member
DHLA
The base is unconformable on the Eaglesham Lava Member that consists of basaltic lavas.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton around Ballageich (NS 520 520) and Braidley Moss (NS 610 410) south of Dumdruff Hill.
The Dumdruff Hill Lava Member consists of trachyandesites and trachytic lavas.
45 to 70m
The Member is overlain in part by the Gowk Stane Pyroclastic Member and the Harelaw Lava Member, with which it is partly interbedded. The upper Flow Moss Lava Member also locally rests on this Member.
Doon Hill Conglomerate Member
DHLC
Succeeds the dark grey mudstones of the Laggan Member of the Balclatchie Formation.
Thickly bedded conglomerate with partings of blue-grey green-weathering mudstones passing upwards into poorly-bedded dark green conglomerate with pebbles of spilite, gabbro, red granite, vein quartz and chert.
c.240m
Succeeded by the mudstones of the Pumphouse Member of the Balclatchie Formation.
Derryhill Lava Member
DHLM
Dowhills Mudstone Formation
DHLS
In the north crop of the Culm synclinorium, between Brushford and Ashbrittle, the lower boundary is taken at the incoming of dark grey predominantly unfossiliferous finely laminated silty mudstones with scattered siltstones of the Dowhills Mudstone Formation above the highest limestone bed of the underlying Bampton Limestone Formation. Between Ashbrittle and Wellington the lower boundary is taken above the highest limestone bed of the underlying Westleigh Limestone Formation. West of South Molton the lower boundary is taken at the incoming of dark grey to black pyritic mudstones above the streaky laminated cherts and mudstones of the underlying Coddon Hill Chert Formation. The boundary is taken at the top of the highest chert bed. These pyritic mudstones, the Limekiln Beds of Prentice (1960) were included by Edmonds et al. (1985) in the Crackington Formation. Further work is needed in this area. In the south crop of the Culm synclinorium between Exeter and the Teign valley, the lower boundary is taken at the incoming of bluish grey micaceous mudstones with scattered thin sandstones and siltstones of the Ashton Mudstone Member above the fossiliferous interbedded cherts, limestones and mudstones (Posidonia Beds) of the Teign Chert Formation.
On the north crop of the Teign Valley Group between Bideford (SS 45 27), north Devon and Wellington (ST 13 20), Somerset. Between the Bideford area (SS 45 27) and Brushford (SS 92 26) west Somerset, the formation has not been mapped by BGS. In this area it probably equates with the Limekiln Beds (Prentice 1960), included in the Crackington Formation by Edmonds et al. (1979). Further work is needed in this area to resolve this. Due to thrusting along the south crop of the Teign Valley Group, the formation is seen only between the Teign valley (SX 84 84) and Exeter (SX 90 92), Devon. It may be present in the Okehampton area (SX 59 94) but has not been mapped, probably being included in the Crackington Formation. Further work is needed.
Dark grey to black, rather soft, pyritous mudstones with scattered thin siltstone and sandstone beds (less than 10%). There are some thin chert beds on the north crop of the Culm synclinorium. The Ashton Mudstone Member is the lateral equivalent of the Formation on the south crop; it is thought to be characterised by more abundant and thicker sandstones. Further work is needed to confirm this.
210 to 430m on south crop, 30m on north crop.
The upper boundary is gradational and taken at the incoming of more abundant and relatively thicker sandstones of the overlying Crackington Formation above the mudstones with less than 10% sandstone in the underlying Dowhills Mudstone Formation.
Doghole Rock
DHMR
The lower boundary in the Mary Ann Opencast Borehole (SD83SW/78), is taken at the base of a silty sandstone of the Doghole Rock, that lies above the Doghole Coal.
Burnley [SD 83 32] to Ightenhill [SD 81 34] areas.
Sandstone, highly siliceous, with subordinate mudstone.
The upper boundary in the Mary Ann Opencast Borehole (SD83SW/78), is taken at the base of a silty sandstone of the Doghole Rider Coal, a thin coal at the base of a shale-dominated sequence overlying the Doghole Rock.
Dornoch Mudstone Unit
DHMU
Dhoon Pluton
DHN
Dalmahoy Sill
DHOY
Deerhope Formation
DHP
Conformable: at grey shales overlying highest Reservoir Formation, sandy siltstone.
Laminated fossiliferous siltstones, mudstones and shales, no sediment coarser than siltstone, bioturbation common in fine-grained sediment. Fossils include rugose corals, brachiopods, bivalves, trilobites and pelmatozoans.
390m in North Esk Inlier
Conformable: red shales immediately underlying lowest Cock Rig Formation, medium-grained sandstones.
Doughend Sandstone Member
DHS
Probably Frasnian, being the lowermost part of the Kinnesswood Formation, which spans from Frasnian to Courceyan,
Drumgesh Shale Formation
DHSH
Droitwich Halite Member
DHT
Conformable, and drawn at the abrupt or slightly gradational upward transition from reddish brown mudstone (Sidmouth Mudstone Formation, undivided) to halite at the base of the Droitwich Halite Member.
Droitwich area, Worcester Basin, west of Inkberrow Fault.
Halite, in thick beds up to 12m thick, interbedded with mudstone, reddish-brown, blocky ,with abundant halite nodules and veins.
159m in type section
Conformable, and drawn at the abrupt or slightly gradational upward transition from halite at the top of the Droitwich Halite Member to the reddish brown mudstone of the Sidmouth Mudstone Formation (undivided).
Dove Holes Tuff
DHTU
Diamonds Ironstone (South Staffordshire)
Diamicton
DIAM
Clay and silty clay, commonly pebbly and sandy, stiff, possibly interbedded with sand and gravel-rich lenses and rare peat. An unsorted, unstratified deposit of uncertain age; colour variable, generally reflecting nature of source rock material. [Generic description: 'TMOS' Procedures].
Diatomite
DIAT
Siliceous deposit of lacustrine origin, soft, consisting mainly of opaline diatom frustules. [Generic description: 'TMOS' Procedures].
Dinwoodie Beds
DIB
Dicky Gobbler Coal (South Derbyshire)
DICG
Dicky Hare Semipelite Member
DICH
Rapid transition from thin-bedded quartzite of Logie Head Quartzite Member.
From coast at West Sands [NJ 5310 6810 - 5340 6765] as far as the southeast side of Crannoch Hill [NJ 521 664].
Semipelite, thin-bedded, micaceous, locally garnetiferous, and thin psammitic beds.
c.150m on coast section, with some repetition by folding; appears to thin inland but this may be effect of faulting
Faulted boundary on coastal section.
Ditcheat Clay Member
DICL
Upward change from dominantly limestone succession of Spargrove Limestone or, where absent, from the dark grey mudstones of the Pylle Clay.
From Wraxhall [ST 600 365] in west (limit of current mapping) in an arc north-eastwards through Milton Clevedon to north of Stoney Stratton.
Silty clays and silts
Somewhat transitional, but marked by upward passage into fine-grained sandy clays of the Pennard Sand Member.
Dilhorne Coal (Cheadle)
DICO
Dinas Dolerite
DIDO
Highly altered olivine microgabbro
Diebidale Pelite Formation
DIEP
Overlies the Crom Psammitic Formation, defined as where predominantly psammitic lithologies pass into predominantly pelitic lithologies.
Surrounds the northern part of the Carn Chuinneag intrusion, forming a nearly continuous outcrop from Glen Diebidale (NH440830), to the western end of the Dornoch Firth (around NH560890), to Kildermorie Forest (NH470790), its southerly extent apparently thinning out near Beinn nan Eun (NH448760).
Massive, schistose, garnet-mica bearing pelite and semipelite, with calc-silsicate bands, increasingly pelitic towards the top.
The upper boundary cannot be seen, as it is obscured by the Carn Chuinneag-Inchbae Granite Gneiss Intrusion.
Digg Siltstone Member
DIGS
Middle Oxfordian.
Dirrington Great Law Sill
DIGT
Dinas Island Formation
DIIS
Dilhorne Coal (Derbyshire)
DILC
Dingle Mudstone Member
DIM
Passage down into fissile largely hemipelagic Gyfennie Wood Shales Member of the Nantglyn Flags Formation.
Around Newtown.
Mudstone, homogeneous, medium-grey with common thin (<05cm) fine-grained sandstone layers. Commonly parallel laminated.
At abrupt onset of thicker (>30cm) fine-grained sandstones, commonly defined also by a lenticular bed of intraformational conglomerate.
Diamond Coal (Northumberland)
DIMND
Dimlington Silts
DIMS
Sand and silt; laminated; thought to be water-lain (possibly lacustrine). [Generic description: academic papers and BGS Memoirs].
Dinantian Rocks (Undifferentiated)
DINA
Dinantian Volcanic Rocks (Undifferentiated)
DINV
Diseworth Sandstone
DIS
The base is defined by green siltstone or sandstone overlying red mudstone of the undivided Gunthorpe Formation.
South Derbyshire - north-west Leicestershire.
Pale greenish grey siltstone and fine-grained sandstone; parallel lamination, cross lamination, load structures and convolute bedding.
The top is defined by red mudstone of the undivided Gunthorpe Formation overlying green siltstone or sandstone.
Discovery Coal (Lancashire)
DISC
Drumlish Conglomerate Formation
DISH
Abrupt and probably disconformable on the Drumgivery Limestone Member, at top of Tullanaglare Mudstone Formation.
Milltown Segment of the Fintona Block, Northern Ireland.
Conglomerate, grey-purple, massive beds with cobbles and pebbles of volcanic and metamorphic origin; volcaniclastic, coarse sand matrix, channels cross-bedded; sandstone, purple-red, coarse-grained.
At least 1000m.
Not exposed; faulted out.
Distinkhorn Pluton
DISK
Distinkhorn Dyke Swarm
DISKD
Dittisham Member
DIT
Diver Coal
DIV
Dyneley Knoll Flags
Drumchorick Siltstone Formation, Benbulben Shale Formation And Tubbrid Sandstone Formation (Undifferentiated)
DKBT
Dumbreck Cloven Coal (Central Coalfield)
DKC
Drummuck Subgroup
DKG
Drawn at base of basal conglomerate of the Auldthorns Formation where this rests conformably on alternating shales and sandstone of the Shalloch Formation.
Confined to Craighead Inlier, Ayrshire, Scotland.
Consists mainly of mudstones, some olive-green in colour, with sandy beds and basal conglomerate or grit.
c.380m
Drawn at unconformity at base of Silurian Mulloch Hill Conglomerate.
Dirk Sandstone Member
DKSA
Drumchorick Siltstone Formation
DKSF
Conformable abrupt change from top sandstone stratum of Mullaghmore Sandstone Formation.
Siltstone, dark grey, calcareous, micaceous, sandy, bioturbated, fossiliferous, interbedded with mudstone and thin, commonly lenticular, calcareous sandstone and limestone, with thin beds of crinoidal calciturbidites.
90m
Gradational upwards, conformable, with predominantly calcareous mudstones of Benbulben Shale Formation.
Devoke Water Tuff Member
DKT
Overlies Skiddaw Group in type area where it is the lowest Member of the Birker Fell Andesite Formation (and of the BVG). On Latterbarrow overlies the Latterbarrow Sandstone, where the base of the Devoke Water Tuff Member is taken at the bed of lapilli-tuff overlying sandstone.
Devoke Water, Cumbria (SD 14 96); Whincop, Eskdale (SD 18 99) and Stony Tarn (NY 20 02); roof pendants above Eskdale Granite (around NY 185 016), Cumbria; also on Latterbarrow-Town Bank, north of Gosforth, Cumbria (NY07 10).
Weakly bedded and cross-bedded lapilli-tuff and tuff of basaltic/basaltic andesite composition; locally intruded by penecontemporaneous sills; pyroclasts include abundant Skiddaw Group mudstone and sandstone.
550 - 620m; complete thickness unknown because of faulting.
At change to basaltic/basaltic andesite flows of Birkby Fell Member, or to overlying andesite sheets of Birker Fell Andesite Formation (undivided).
Dalton Formation
DLB
At siltstone parting at top of Redhill Limestone Formation, exposed in road-cutting on north side of Elliscales roundabout on Dalton bypass, A590, Furness.
South Cumbria, north Lancashire.
At base, mid to dark grey even-bedded carbonate grainstones and packstones; middle part, dark grey thinly bedded packstones and wackestones with many shaly interbeds; upper part, even bedded packstones and grainstones.
Base of overlying Park Limestone.
Lower Dalton Beds
DLBL
Middle Dalton Beds
DLBM
Delnabo Conglomerate Formation
DLBO
Base rests unconformable upon Dalradian metasedimentary rocks.
The Tomintoul Old Red Sandstone outlier of upper Banffshire - a 50 sq km outlier about 15 by 5km in extent, which is totally separated from other Old Red Sandstone outcrops of the northeast Grampian area.
Coarse conglomerate and subsidiary arkosic sandstone, purple-red to red-brown. Coarse breccia and breccio-conglomerate at base locally.
Sedimentary transition into Raebeg Sandstone Formation.
Delabole Member
DLBS
U. Palmatolepsis marginifera to L. Velifer Biozone.
Gradational with the Tredorn Slate Formation.
Isolated exposures in the vicinity of Delabole village, north Cornwall.
Bluish grey slate within the Tredorn Slate Formation.
30 to 50m (estimated structural thickness).
Upper Dalton Beds
DLBU
Dalmellington Lower Diamond Coal
DLD
Blair Atholl Dark Limestone And Dark Schist Formation
DLDS
Sharp boundary with semipelite and graphitic pelite of Tullochroisk Semipelite Formation.
From north shore of Loch Errochty [NN 710 660] almost continuously to the Loch Tay Fault [NN 790 550 - 791 572]. East of the Loch Tay Fault and north of the Killiecrankie Slide, it occurs from Conbhar [NN 825 616] to 1km east of Forest Lodge in Glen Tilt [NN 943 743] and via Loch Moraig as far as the south end of Loch Loch [NN 988 735].
Lower part - grey to cream-weathering graphitic calcite limestone, with millimetre thick ribs of quartz; Central part - black, rusty-weathering, highly graphitic pelite; Upper part - grey graphitic limestone with quartz ribs, similar to lower part.
1 - 120m in Sheet 55W; probably tectonically attenuated; appears to be thicker in Sheet 55E.
Transitional, with interbanding of calcareous semipelite with thin grey limestone beds marks junction with the Cnoc an Fhithich Banded Semipelite Formation.
Dolgellau Formation And Dol-Cyn-Afon Formation (Undifferentiated)
DLDY
Derwenlas Formation
DLF
Deeside Limestone Formation
DLI
Incoming of dominantly calcareous lithologies at the top of the Queen's Hill Formation. This is usually sharp, with only rare calc-silicate layers in the Queen's Hill Formation rocks.
Main outcrop is a 100m to 1km strip in the Dee Valley from NO 408945 (Pollagach Burn) to NO 595955 (Mains of Midstrath) (Sheets 65E and 66W). There is also an outcrop area around and to the south east of Banchory (NO 690970 to NO 745928 - Sheet 66E).
Dominantly calc-silicate rock, ranging from calcareous psammite to hornblende-zoisite-schist, but containing layers up to 10m thick of fine-grained crystalline limestone with disseminated sulphides.
Varies from 30m to 100m; probably thickens eastwards from Pollagach Burn to Mains of Midstrath.
Change to dominant psammite, often slightly calcareous, with minor layers of calc-silicate rock and semipelite, at base of Tarfside Formation.
Darvel Lava Member
DLLA
The Darvel Lava Member is unconformable on older strata, the Swanshaw Sandstone Formation (Lower Devonian).
Dunlop-Eaglesham moors between Glasgow, Kilmarkock and Hamilton, limited area around Darvel (NS 6000 4000) and Newmilns (NS 5000 3700) just north of the Inchgottrick Fault.
The Darvel Lava Member consists of alkali basalts/ankaramites. Near the unit top trachybasalt also occurs.
The Member is mainly overlain by the Kirkwood Formation of the Strathclyde Group. The contact is considered unconformable with the volcaniclastic sedimentary rocks draping an eroded land surface formed from the Member. Locally (east) it is interbedded with or overlain by the Gowkstane Pyroclastic Member.
Derreens Limestone Member
DLM
Dalradian Supergroup And Moine Supergroup (Undifferentiated)
DLMO
Durham Low Main Post Sandstone
DLMP
Derryloran Formation
DLN
Unconformable on pre-Carboniferous basement.
South-east Tyrone, Northern Ireland.
Conglomerate, grit, sandstone and minor sandy dolomitic limestone.
None
Durham Low Main Coal (Northumberland And Durham)
DLO
Dolphinholme Mudstone
DLP
Top of Accerhill Sandstone; medium- to coarse-grained sandstones with abundant plant debris, overlain sharply by the mudstone-dominated Dolphinholme Mudstone.
Ellel, Forton, Lancashire.
Mudstone, dark grey, with poor bivalve fauna.
c 60m
Abrupt change to medium-grained, thinly bedded sandstone of the succeeding Ellel Crag Sandstone, with abundant plant debris, allochtonous coal lenses and thin siltstone interbeds.
Dalreoch Formation
DLR
Sandy and pebbly greywackes.
About 1000 m thick.
Drumgrange Limestone
DLS
Known in the subsurface in the area around Dalmellington, Ayrshire.
Dulais Coal (South Wales)
DLSCO
Duloch Sandstone
DLSS
The Dunfermline area of Fife, particularly near Duloch.
Dalton Rock
DLT
Thickly bedded soft brown sandstone.
Dirleton Plugs
DLTON
Dolgellau Formation
DLU
Conformably overlies sandstones of the Ffestiniog Flags Formation with a sharp to gradational contact.
Northern, eastern and southern flanks of the Harlech Dome, Snowdonia.
Black to dark grey laminated pyritous mudstones and laminated siltstones, carbonaceous.
Raised from member of the Cwmhesgen Formation to formation status (Howells and Smith, 1997; Pratt, Woodhall and Howells 1995).
35 to 150m
Conformably and transitionally overlain by sandstones and siltstones of the Dol-Cyn-Afon Formation. At Ogof-Ddu marked by phosphatic sandstones with graptolites.
Duloch Under Limestone
DLUL
Dalmellington Major Coal
DMA
Mine Adit
DMAD
Drumpark Marine Band
DMB
Drummournie Biogenic Member
DMBG
Gradational contact over 10cm or so with white, clayey, silty gravel of the Rehiran Cryoturbate Member below.
Pebbly, sandy, clayey silt (diamicton), very dense, crudely laminated, fissile, olive grey, with wisps of white silty pebbly sand, disseminated peaty material and charcoal. Pebbles are bleached white. Containing pollen of Interglacial vegetation.
Sharp, gently undulating, unconformable contact with stony sandy clay diamicton of the Athais Till Formation.
Douglas Main Coal (Douglas)
DMC
Druim Chuibhe Psammite Formation
DMCB
Diamond Coal (North Staffordshire)
DMDC
Dissolution Mining
DMDI
Dunsmore Gravel
DMG
Sharp, irregular and erosional upon various Anglian age Quaternary deposits that include the Oadby Till.
Patches of Dunsmore Gravel extend from just south of Leamington Hastings (SK 45 67), northwards to around Bagworth (SK 423 053).
Red, brown and yellow, commonly ochreous, matrix-supported flinty gravel with lenses of coarse sand. Most deposits are poorly sorted and clay-rich.Sand and gravel, clayey brown and yellow; Late Glacial to Postglacial. [Generic description: 1:50 k map margins].
Variable, generally from 1 - 3 m. but up to 7.8 m. proven where channelised.
Generally the present-day land surface. The deposit may locally be covered by recent deposits such as head or alluvium. The Dunsmore Gravel is thought to grade laterally into the 'Fifth Terrace' of the river Avon.
Desertmartin Limestone Formation
DML
Demesne Limestones
DMLM
Dodman Formation
DMN
?Lower Devonian
Dodman Thrust.
Headland between Mevagissey Bay and Veryan Bay, southeast of thrust between Hemnuck Beach and Gorran Haven, south Cornwall, Channel coast.
Meta-sandstone and meta-siltstone turbidite beds (to 2m) with thinner interbeds of grey meta-mudstone, which is phyllitic towards the base and schistose at the top of the exposed sequence.
Incomplete, c.1000m onshore.
Unseen, offshore, but believed to be the Normannian Thrust.
Deep Main Coal (Vale Of Belvoir)
DMNC
Diamond Coal (Patna)
DMND
The coal overlies the Top Hosie Limestone (Brigantian to Pendleian) and underlies the Black Metals Member (Pendleian).
Patna, east Ayrshire, Scotland.
Coal, in two or more leaves that are recorded as up to 47 and 33 inches thick, in that part of the Limestone Coal Group sequence in the Patna area underlying the Black Metals Marine Band and above a Lingula Band.
Douglas Muir Quartz-Conglomerate Member
DMQ
Drawn at the base of the conglomerate of the Douglas Muir Quartz Conglomerate where it rests apparently unconformably on volcaniclastic sediments of the Kirkwood Formation, as at a natural exposure at NS 5307 7752.
Strathclyde, Scotland, and north of the River Clyde eastwards from the type area at Douglas Muir [NS 525 746] to [NS 5712 7731], site of the Strathblane-Balmore Tunnel No.8 Borehole NS57NE/28, but not in the adjacent parts of the Airdrie Sheet (31W).
Consists mainly of hard, white conglomerates with subordinate pebbly sandstones with a few lenses of purplish-grey/grey mudstone up to 30cm thick. Trough cross-bedding is common in sets from 0.2m to 1.0m thick. Many of the units are upward fining in grain size. The clasts and pebbles are almost exclusively of vein quartz and well-rounded, averaging 2cm but up to 10cm in diameter, but some blocks of sandstone up to 15cm across are also present. Palaeocurrent directions indicate transport of the original sediments towards the southsouthwest.
20m at the type locality at Douglas Muir Quarry, and up to 70m maximum elsewhere.
The boundary is transistional, as seen at a natural exposure at NS 5730 7774, by upward passage by interbedding from conglomerate to white and pale grey sandstones of the Craigmaddie Muir Sandstones of the Lawmuir Formation.
Dartmoor Intrusion
DMR
Granite.
Shallow Mine Working
DMSH
Dyffryn Mymbyr Tuff Member
DMT
Mineral Extraction (Undivided)
DMU
Downend Member
Base of member is the base of the lowest mappable lithic sandstone of "Pennant" type above the grey and red mudstone-dominated succession of the Winterbourne Formation. The base is diachronous; In the Somerset Coalfield the base of the member occurs between the Aegiranum and Cambriense Marine Beds, wheras in the Bristol Coalfield it occurs above the Cambriense Marine Band
Bristol and Somerset Coalfields
Sandstone with some conglomerate and pebbly sandstone and sporadic fissile mudstone beds. Some workable coal seams are also present. Sandstone is typically a coarse-grained lithic arenite of "Pennant" type
660m in the Somerset Coalfield [ST75]
The top of the Downend Member is defined at the top of the Mangotsfield Coal and associated thin fissile mudstone, overlain by the sandstone-dominated succession of the Mangotsfield
Dionide Beds
DNB
Dun Coal (Scremerston)
DNCL
Doolie Ness Conglomerate Member
DNCO
Gourdon-Inverbervie area.
A clast-supported conglomerate of mainly 'Highland' provenance.
At least 60 m thick, full thickness not seen or proved.
The top of the uppermost conglomerate bed in the lower part of the Gourdon Sandstone Formation.
Denend Gravel Formation
DNDGR
Anglian (?MIS 12) to Wolstonian (?MIS 8).
The base of the unit has been observed in geological test pits within Leys Quarry (disused) to have a sharp, planar, erosional contact on olive-brown sandy diamicton of the Leys Till Formation.
Buchan, northeast Scotland. This formation is only known within the immediate vicinity of Leys Gravel Quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon). The unit might be regionally significant and present locally across northeast Scotland.
Gravel with subsidiary beds of sand. Dominantly pale olive brown and pale pinkish brown pebble-cobble-boulder gravels. Typically clast supported with medium to coarse quartzose and felsitic sand matrix. Clasts are typically subrounded and rounded and dominated by felsite with less common metasediments, red granites and mafic igneous lithologies. Sand interbeds are medium to coarse grained and both felsitic and quartzose. Locally the gravels and sands display Fe and Mn stains and cements. The deposit displays large-scale cross-beds and is locally deformed (faulted and folded by ice melt-out). Palaeocurrent analysis indicates transport to the northwest, west and southwest. Interpreted as glaciodeltaic and glaciofluvial outwash.
In the northwest and northeast faces of Leys Quarry (disused) the formation is observed to have an erosional upper boundary. The overlying Pitscow Sand and Gravel Formation was deposited into a -2m deep channel eroded into the Denend Gravel Formation. In other (southern) faces of the quarry the upper boundary is the ground surface. In this situation the gravels typically display more recent periglacial disturbance (head deposits, involutions and ice-wedge casts).
Dandy Rock
DNDY
Dunnerdale Sandstone Formation
DNF
Base of volcaniclastic sandstone that rests unconformably on the Wallowbarrow Tuff Formation (andesitic tuff), Ulpha Andesite Formation (andesite lava) and Holehouse Mudstone Gill Formation (mudstone and sandstone). Andesite intrusions intervene locally.
Duddon and Lickle valleys. Wallowbarrow Crag (SD 222 967) to Hotton (SD 204 902) and Lickle Valley (SD 230 920), Cumbria.
Volcaniclastic sandstone, locally with volcaniclastic breccia; sequence coarsens upwards. Units within this contain ichnofossils [Johnson et al, 1994].
0 - 400m (excluding penecontemporaneous sills).
Contact with overlying Lickle Formation (dacitic and rhyolitic tuff) and locally intervening intrusive basaltic andesite and andesite.
Darnley Fireclay
DNFC
Coal 10" - Fireclay 4' 6" - Blaes and Ironstone 8 " - Coal 7 " - Sclit 8" - Coal 5"- Fireclay 8' 0" - Sandstone. Fireclay seam.
13' 10" (4m).
Durness Group
DNG
Defined where dark grey dolostones of the Ghrudaidh Formation rest conformably upon the Salterella Grit Member of the An T'Sron Formation. The boundary is gradational over approximately a metre.
The Dunrness Group forms a narrow, discontinuous belt, extending along the North-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye.
Pale grey, buff and dark grey dolostones with intervals of dolomitic limestone, limestone and subordinate chert.
About 750m
The stratigraphical top of the Durness Group is not seen owing to tectonic truncation by the Moine Thrust Zone in its type area.
Dun Limestone Member
DNL
Generally a conformable change from a thin marine mudstone overlying a thin coal or seatearth.
Confined to Berwickshire and north Northumberland in the Tyne Limestone Formation (TYLS) of the Yoredale Group (YORE). The contained marine fauna is equivalent to that of the MacGregor Marine Bands of the Midland Valley of Scotland.
A dark grey, argillaceous, crinoidal, shelly limestone with algal nodules, interpreted as being of marine origin, weathering to a rusty ochreous colour.
From 1.2m to 1.6m in the Eyemouth and north Berwickshire districts.
Generally a conformable change to marine mudstone, which in turn passes up into deltaic arenaceous deposits of the Tyne Limestone Formation.
Doon Limestone
DNLS
Downend Member And Mangotsfield Member (Undifferentiated)
DNMG
Denton Mill Limestone
DNML
Dalcharn Palaeosol Formation
DNPS
Gradational contact over 20 to 50cm with weathered, clayey cobble gravel of the Craig an Daimh Gravel Formation below.
Sheet 84W (Fortrose), SE of Inverness
Sandy, pebbly, clayey silt (diamicton), very dense, crudely laminated, fissile, olive grey, with wisps of white silty pebbly sand, disseminated peaty material and charcoal. Pebbles are bleached white. Containing pollen of Interglacial aspect. Passing down into clayey, sandy, silty gravel (diamicton), matrix-supported, very dense, very pale grey to white, with disseminated black charcoal and peaty material. Gravel similar in composition to that occurring in Craig an Daimh Gravel Formation below, but bleached white or pale yellow.
Sharp, gently undulating, unconformable contact with stony sandy clay diamicton of the Athias Till Formation.
Dufton Shale Formation
DNSH
Taken at the base of sandstones and siltstones of the 'corona facies', overlying volcaniclastic rocks of the Harthwaite Formation [Borrowdale Volcanic Group]
Restricted to the Cross Fell Inlier, Cumbria
Dark grey, partly calcareous, siltstone and mudstone, with thin beds, lenticles or nodules of silty limestone. Poorly fossiliferous sandier beds occur near the top and base; at the base these include debris from the Borrowdale Volcanic Group with the commonly occuring brachiopod Trematis corona ['corona facies']
About 400m
Overlain by limestones of the Swindale or Keisley limestone formations, or where these are absent, the Ashgill Formation
Dounreay Siltstone Member
DNSM
Dent Group
DNT
Unconformably overlies the Borrowdale Volcanic Group.
Varied assemblage of shallow marine clastic lithologies and limestone, pyroclastic rocks and rhyolitic lava.
Unconformably overlain by the Skelgill Formation of the Stockdale Group.
Duneaton Volcanic Formation
DNV
The base of the volcanic rocks seen in the Duneaton Water above the sandstones of the Swanshaw Sandstone Formation.
Between the Ayrshire and Douglas Carboniferous basins, Ayrshire and Lanarkshire, Scotland,
Mainly andesitic and basaltic lavas, commonly amygdaloidal, including olivine basalts, pyroxene andesites and feldsparphyric lavas with subordinate volcanic breccias, tuffs and minor sandstone interbeds.
Estimated to be from 440m in the reference section in the Duneaton Water tributary to at least 1200 m thick.
The top of the pile of volcanic rocks seen in the Duneaton Water below the Auchtitench Sandstone Formation rudites and arenites.
Dolhir Formation
Unconformable on various Caradoc Formations.
Micaceous siltstones and mudstones with subsidiary sandstone and limestone bands. Variable basal limestone (Dolhir Limestone Member) to fissile mudstone (Tyn-y-Twmpath Member). Formation has rich shelly (brachiopod) fauna. Includes Corwen Grit Member at top of formation.
490 metres. Lateral variations, 320 - 490 metres.
Top of Corwen Grit Member succeeded by pale grey-green siltstones and mudstones of the Fron Frys Formation.
Doulting Beds
DOB
Dobbin Sandstone Formation
DOBB
Douglas Coal
DOC
Doctors Coal
DOCC
Dougaled Coal (South Wales)
DOCO
Dove Crag Tuff Member
DOCR
Slight unconformity on bedded volcaniclastic sandstone (Deepdale Sandstone Formation).
Hart Crag and Dove Crag, northeastern Lake District (between Grasmere and Patterdale).
Andesitic lapilli-tuff and tuff, in part welded, with eutaxitic texture.
Not preserved (Hart Crag) or intruded by an andesite sill (Dove Crag).
Doe Coal (South Lancashire)
DOEM
Doethie Formation
DOFA
Douglas Fireclay Member
DOFC
Generally underlain by fluvial sandstones of the Passage Formation.
Ayrshire.
Pale to dark grey seatclay and seatearth, some with high alumina properties.
Up to 6m
Generally overlain by the Troon Volcanic Member of the Passage Formation.
Dolwen Formation
DOG
Unexposed. Seen in the Bryn-teg Borehole, the base appears to lie unconformably on rocks of the Bryn-teg Volcanic Formation.
Core of the Dolwen Pericline (upper part); lower part proved in the Bryn-teg Borehole, SH63SE/1 [SH 6992 3214] .
Fine- to medium-grained sandstone with siltstone, pebbly sandstone and conglomerate.
Lowest part of the Harlech Grits Group.
Overlain by the Llanbedr Formation. The boundary is conformable and transitional.
Dog Falls Psammite Formation
DOGF
Doonbought Plug
DOHT
Dolfawr Mudstones Formation
DOL
Base of lowest laminated hemipelagite overlying the Cerig Formation.
Thinly interbedded shelly pale green mudstones and laminated hemipelagites.
Up to 55 metres.
Base of Builth Mudstones.
Dolyhir Limestone Formation
DOLI
Doagh Limestone Member
DOLM
Dowbridge Mudstone Formation
DOMU
East Irish Sea Basin.
Donegal Appinite Suite
DONA
40Ar - 39Ar on hornblendite from Kilrean appinite, 410 +/- 6 Ma (O'Connor et al., 1982).
Recognised in the Rupublic of Ireland.
Loch Doon Pluton
DOON
Major zoned granitic pluton. Isotopic age 408.6 +/- 2.8 (RB-SR); 408 +/- 4 (K-Ar).
'Hour-glass' shaped intrusion c. 19km x 11km with long axis orientated roughly N-S.
Doon Dyke Swarm
DOOND
Beinn Dorain Semipelite Formation
DORA
Abrupt change from the alternating muscovite-rich semipelite, psammite and quartzite of the Beinn an Dothaidh Formation to the more uniform garnetiferous semipelite rocks of the Beinn Dorain Semipelite Formation. The uppermost parts of the Beinn an Dothaidh Formation are dominantly quartzite in the area around Beinn a' Chuirn (Allt a'Chuirn Quartzite Member).
Formation occurs on Beinn Dorain, Beinn a'Chaisteil and Beinn an Dothaidh, southwest Grampians.
Massive, poorly-bedded garnet mica semipelite and muscovite-quartz semipelite, poor in biotite but with abundant quartz sweats. Typically weathers darker grey/brown to brown than the older Coire Daingean Formation; semipelites of the Beinn Dorain Formation are commonly steely grey on fresh surfaces and may take on a "knotted" appearance where conspicuous garnet is wrapped by phyllosilicates. Garnets are typically 3 to 4mm in diameter and always appear fresh (dark red) compared to the more commonly chloritised garnets in the Coire Daingean Formation. Magnetic susceptibility is twice that of the Coire Daingean semipelite (<0.5 cf. <0.2 mu).
Minimum c.130-150m.
Dorback Intrusive-Complex
DORB
Dougaled Rider Coal (South Wales)
DORC
Dornoch Formation
DORN
Downholland Silt
DOS
Silt and clay, pale blue, commonly shelly. [Generic description: academic papers and BGS Memoirs].
Doupster Oil Shale
DOSH
Dromore Sandstone Member
DOSM
Conformable; abrupt change from interbedded blocky mudstones, micaceous and blocky siltstones and blue-grey silty sandstones, at top of Bundoran Shale Formation, to orange weathering, thick beds of medium-grained sandstone.
Sandstone, white-fawn, medium to coarse-grained, micaceous; calcareous horizons, weathering orange-brown, are friable and sparsely fossiliferous, bioturbated, cross-bedded, sporadic beds of crinoidal, sandy packstone.
Abrupt change, probably disconformable, between sandstones and overlying part of Mullaghmore Sandstone Formation, predominantly grey calcareous mudstones and thin peritidal limestones.
Dorset Stour Formation
DOST
The fluvial deposits rest unconformably on Jurassic, Cretaceous and Palaeogene strata.
The catchment of the Dorset Stour and its tributaries.
Floodplain alluvium and river terrace deposits. The floodplain alluvium comprises overbank deposits of mottled dark grey and orange organic silt, silty clay and clayey sand, and peat, overlying sand and gravel. Thirteen river terraces are preserved. The river terrace deposits comprise very sandy gravels. The clasts are sub-angular to sub-rounded, poorly sorted, up to 10cm in diameter, dominantly flint, with a little Upper Greensand chert, "sarsen" stone, vein quartz, Jurassic limestone, Chalk, and well-rounded flints from the Palaeogene, in a matrix of clayey sand. Deposits of the higher terraces are cryturbated.
Up to 11m, including up to 4m of alluvial overbank deposits.
Beinn An Dothaidh Formation
DOTH
Neoproterzoic (Cryogenian).
Sharp change massive garnetiferous semipelite of the Coire Daingean Semipelite Formation to the alternating muscovite-rich semipelite, psammite and quartzite of the Beinn an Dothaidh Formation. A calcareous semipelite of calcsilicate-rock (c.5m thick) may be present locally at the base of the Beinn and Dothaidh Formation.
This formation is recognized across the northeastern parts of Sheet 46W west and north of Loch Lyon and also west of the Bridge Balgie Fault in upper Glen Lyon to Loch an Daimh in the western part of Sheet 46E, and southwestern part of Sheet 54E.
Lower part comprises a calcareous semipelite to calcsilicate rock about 5m thick, locally tremolite-bearing. The calcareous unit is succeeded by alternating layers (approximately 10 to 30cm thick) of muscovite-rich semipelite, psammite and thin quartzite. Grossular-bearing amphibolite schist and coarser plagioclase-amphibolite are locally developed within the formation. In the area around Beinn a'Chuirn, quartzite is more dominant in the uppermost parts of the Beinn an Dothaidh Formation; this unit is recogniZed as the Allt a'Chuirn Quartzite Member.
The formation is estimated to be about 180 to 200m thick on Beinn a'Chaisteil but is typically apparently thickened by the effects of fold duplication.
Change to the more uniform garnetiferous semipelite rocks of the Beinn Dorain Semipelite Formation. In the area around Beinn a'Chuirn, quartzite is more dominant in the uppermost parts of the Beinn an Dothaidh Formation; this unit is recognised as the Allt a'Chuirn Quartzite Member.
Douk Ghyll Beds
DOU
Double Coal (Warwickshire)
DOUB
Douglasbrae Limestone
DOUG
Base of lowest thin bed of limestone in pelite matrix, within semipelites of Drummuir Calcareous Member.
Keith area from Bridge of Maisley to former Braehead Limeworks (quarries almost completely filled with refuse).
Thin beds of metalimestone, commonly brecciated, in a pelite matrix.
Approximately 20m
Top of highest thin bed of limestone in pelite matrix, within semipelites of Drummuir Calcareous Member.
Doularg Formation
DOUL
Conformably overlies another part of the Albany Group.
Silty mudstones.
Faulted against the Albany Group.
Dounalt Limestone Formation
DOUN
Dobbie's Vein
DOV
Dove Rock Vent
DOVE
The Dunbar area.
A small, circular vent, consisting of an inner zone of tuff and an outer zone of partly brecciated sandstone. A small basanite intrusion in the centre is probably younger, perhaps late Carboniferous to Permian.
About 50 m in diameter.
Dovey Valley Formation
DOVEY
Sharp, unconformable and locally channelised on bedrock and Late Devensian head deposits and Welsh glacigenic deposits (including Eryri and Plynlimon till formations). Interdigitates in a complex manner with Tidal Flat Deposits (Gwynllwg Formation of Bowen, 1999) in the estuary.
The valley of the River Dovey and its tributaries (Gwynedd, Powys and Dyfed), west Wales.
Unconsolidated, stratified gravels, sands, silts and clays forming the alluvial deposits of the River Dovey (Afon Dyfi) and its tributaries. Includes contemporaneous head, colluvium and pedigenic deposits within the catchment area. Clasts principally consist of local, Lower Palaeozoic turbidites. Aggradational river terraces and major alluvial fans are dominated by pebble cobble gravels and medium- to coarse-grained sand; the modern floodplain is dominated by silt and clay, and locally includes lenses of peat.
Generally to around 10m.
Downton Group
DOW
Base of Ludlow Bone Bed Member (where present) of Downton Castle Sandstone Formation, at sharp, locally scoured junction with underlying Whitcliffe Formation (Upper) (formerly Upper Ludlow Shales) (White and Lawson, 1989).
Welsh Borderlands and West Midlands; south central and east central Wales.
Sandstone, mudstone, red, green, yellow and purple with thin phosphatic bone bed and tuffs.
342-504m in type area (Main Outcrop of White and Lawson, 1989).
Base of the main `Psammosteus' Limestone of the Ditton Group (Series) in Corve Dale (Ball and Dineley, 1961; White and Lawson, 1989).
Dowra Sandstone Member
DOWS
Doxall Coal (Bristol Area)
DOXC
Douglas Parrot Coal
DPC
Deep Coal (Coalbrookdale)
DPCC
Dunrobin Pier Conglomerate Member
DPCG
Unconformably overlies Triassic nodular carbonate rock of the "Stotfield Cherty Rock".
Northwest margin of the Inner Moray Firth Basin.
Fluvial and alluvial conglomerates with interbedded sandstones. Organic-rich horizons with palynomorphs are poorly exposed at Golspie. Most information has been gleaned from boreholes.
32m
Overlain by carbonaceous siltstone and claystone of the Dunrobin Castle Member.
Downie Point Conglomerate Member
DPCO
At the base of the lowest thick development of cobble conglomerate at Stonehaven Bay overlying brown and grey sandstones of the Carron Sandstone Formation.
A conglomerate with rounded clasts up to 0.6m across, mainly of 'Highland' provenance.
Up to 225 m thick.
The base of the Strathlethan Sandstone Member, which is base of the lowest volcaniclastic sandstone bed, resting on conglomerate.
Deepdale Sandstone Formation
DPD
Base of lowest sandstone, pebbly sandstone or tuff rests unconformably on the Helvellyn Tuff Formation, but locally there is overstep onto the Middle Dudd and Esk Pike Formations.
Grisedale, Deepdale and Dovedale, including Helvellyn and Fairfield, northeast Lake District, Cumbria.
Massive bedded units of volcaniclastic sandstone with intercalations of pebbly sandstone, breccia (both also volcaniclastic), tuff and lapilli-tuff. Includes the St Sunday Crag Member - lapilli-tuff.
Overlying strata not preserved.
Downan Point Lava Formation
DPF
The formation is truncated at the base by the Dove Cave Fault.
Basaltic pillow lavas interbedded with breccias, tuff and rare chert.
The formation is truncated at the top by the Stinchar Valley Fault.
Dirt Pot Grit
DPG
Deep Hard Coal (South Yorkshire, Nottingham And Derby)
DPHC
Dunkpool Limestone
DPL
Deer Park Andesite
DPM
Deepmine Coal
DPMC
Deer Park Shales
DPS
Deep Soft Coal (Nottingham And Derby)
DPSC
Deep Soft Rock
DPSR
Doup Crag Tuff Member
DPT
Taken at the abrupt change from massive tuff/lapilli-tuff of the main part of the Woundale Tuff Formation, to bedded and cross-bedded tuff or pyroclastic breccia; the boundary is an erosion surface
Cumbria, on the west side of Woundale (NY405 056), via Doup Crag (NY419 092) and Park Head Fell (NY428 097] at the head of the Troutbeck valley to Threshtwaite Mouth [NY428 102]
Andesitic lapilli-tuff, interbedded with some units of pyroclastic breccia and sparse beds of tuff; bedded and cross-bedded. Interpreted as a mixture of pyroclastic surge and fallout deposits
Up to 200m
An erosion surface that is either overlapped by fluviolacustrine sedimentary rocks of the Seathwaite Fell Sandstone Formation or overlain by dacite tuff and lapilli-tuff of the Glaramara Tuff
Quarff Succession And Melange
DQU
The Quarff Succession and Melange are tectonic units consisting of Dalradian Supergroup metasedimentary rocks that cannot be allocated to one of the main groups.
Dunaskin Rock
Ayrshire - around Dunaskin, near Dalmellington.
Coarse-grained sandstone.
Drap Coal (South Wales)
DRAP
Dounreay Shore Formation
DRAY
Top of uppermost medium-grained cross-bedded sandstone of the underlying, sandstone dominated cyclic sequence, of the Sandside Bay Formation.
On shore and immediately offshore of Dounreay area, Caithness, Northern Scotland.
Siltstone dominated rhythmic cycles of interbedded siltstone, fine-grained sandstone, bituminous mudstone and calcareous laminite limestone.
Base of lowest medium-grained sandstone of the overlying, sandstone dominated, cyclic sequence of the Crosskirk Bay Formation.
Dunrobin Bay Formation [See Also Dunr]
DRB
Dunrobin Castle Member
DRBC
Drumbeg Sand And Gravel Formation
DRBG
Unconformity on bedrock or most commonly on older Quaternary strata including the Clyde Clay Formation and the Wilderness and Gartocharn Till Formation of the Midland Valley Glacigenic Subgroup. It has complex lateral relationships with the Blane Water Silt Formation into which it both grades and also is thrust laterally by glaciotectonic effects at the terminus of the Loch Lomond Stadial Ice Sheet. It also has complex contacts with the Gartocharn Till Formation for the same reason (Phillips et al., 2002).
Central Scotland; Glasgow area, Stirlingshire near, at and within the limits of the Loch Lomond Stade Ice Sheet in the Endrick, Blane and Leven valleys.
The standard section is contained in the Gartness Borehole (Browne and McMillan, 1989, Figure 7), 0.5 to 10.17m depth. The two typical lithological associations of the formation are fine- to locally medium-grained sand with silt layers, and silt with sand and clay layers. The sediments are reddish brown or orange. Derived marine fossils are present in the sediments. Pebbly layers are present at the top as are rare bands of diamicton up to 4cm thick. When faulting is present any adjacent bands of clay are usually sheared and contain striaited polished surfaces. The lithofacies association of the formation are typical of a deltaic environment of deposition in contact with active and decaying glacier ice.
Veneer to about 25m
Unconformity below younger Quaternary strata such as the Clydebank Clay Formation but also exposed at the surface.
Druid Conglomerate Member
DRC
The base of the lowest, mainly quartzite, pebble conglomerate within the Am Binnein Sandstone Formation.
A coarse conglomerate with mainly quartzite boulders and some pebbly sandstones.
275 m thick.
The Top of the mainly quartzite pebble conglomerates within the Am Binnein Sandstone Formation.
Dunnottar Castle Conglomerate Formation
DRCC
At the base of the lowest bed of conglomerate of 'Highland' provenance overlying the Carron Sandstone Formation.
A conglomerate with boulders up to 1m across, o f mainly 'Highland' provenance, with interbedded sandstone lenses.
From 2385 m to 2482 m thick, according to Carroll, 1995.
The base of the lowest lava flow in the overlying Tremuda Bay Volcanic Formation.
Drumbrick Sandstone Member
DRCK
Daren Rhestyn Coal (South Wales)
DRCO
Dunnottar-Crawton Group
DRCR
Base of Downie Point Conglomerate Member (Dunnottar Castle Conglomerate Formation), where thickly-bedded or massive conglomerate overlies pebbly sandstone of Carron Sandstone Formation with apparent conformity. This marks the base of a thick, conglomerate-dominated succession.
Northeastern Midland Valley of Scotland, Lintrathen to Stonehaven.
Conglomerate, clast-supported, with angular to well-rounded boulders, cobbles and pebbles. In the lower part these consist predominantly of lava, psammite and quartzite, but in the upper part the conglomerates are of markedly different provenance and were deposited from streams flowing in opposing directions. Poorly-sorted volcaniclastic sandstone and conglomerate are interbedded with non-volcaniclastic conglomerate. Non-volcaniclastic deposits consist of poorly-sorted conglomerate, with angular clasts, and bimodally-sorted conglomerate with rounded clasts. Flows of trachybasalt, trachyandesite and andesitic lava occur in the lower and middle parts of the group. The top of the Dunnottar-Crawton Group is characterised by the intermittent occurrence of volcanic rocks including trachybasaltic lavas and welded dacitic tuff (Lintrathen Tuff Member).
Variable; 3300m in the Stonehaven area, thinning southwestward to less than 1500m. Presumed to be overlapped by younger groups to the southwest.
In the type area, this is taken as the top of the highest lava of the Crawton Volcanic Formation, where it is overlain by a clast-supported conglomerate at the base of the Arbuthnott-Garvock Group. Elsewhere it is taken as the top of the thick deposit of welded tuff (Lintrathen Tuff Member), or at the base of the lowest of the series of lavas belonging to the Arbuthnott-Garvock Group. Believed to be progressively overstepped towards the south-west by the Arbuthnott-Garvock Group.
Drefach Group
DRE
The lower boundary of the Group is taken at the base of the Felin Wen Formation. The boundary is not exposed, but the incoming of the Formation was previously described by Strahan et al. (1909), from outcrop in a road bank opposite the corn mill in the village of Felin Wen, which yielded Didymograptus murchisoni graptolites.
The Drefach Group crops out in a narrow belt extending from Fishguard Bay in the west to Llangadof in the east.
The Drefach Group comprises mudstones, limestones and tuffs of Llanvim to Caradoc age exposed on the southwestern margin of the Lower Palaeozoic Welsh Basin. In its type area, south of the village of Drefach, Carmarthenshire, the Drefach Group comprises a lower Felin Wen Formation (formally the Didymograptus murchisoni Beds) overlain by the Asaphus Ash Formation. This is succeeded in turn by the Hendre Shales Formation, Mydrim Limestone Formation and Mydrim Shales Formation (eg Strahan et al. 1909).
Greater than 600m in the type area.
The upper boundary is taken at the top of the Mydrim Shales Formation. The boundary is not exposed, but in the type area is defined by a faulted contact with pale grey burrow-mottled mudstones of the Nantmel Mudstones Formation of Ashgill age.
Drumcullen Formation
DREN
Gradational decrease in proportion of red mudstone from underlying White Brae Mudstone Formation [formerly Permian Upper Marls].
Sub-surface on northwest shore of Lough Neagh and in Ballymacilroy Borehole No.1 [J0574 9761].
Sandstone, orange-red, very fine-to medium-grained, poorly sorted, weakly calcareous dolomitic cement, mudstone up to 25%, deep orange-brown.
Gradational, with loss of red mudstones in succeeding Toomebridge Sandstone Formation.
Drosgol Formation
DRF
Conformably overlies the Nant-y-Moch Formation, the boundary being either gradational or sharp, and taken at the point where thinly interbedded mudstones and sandstones give way to massive mudstones.
Dark grey, brown to buff weathering, massive, homogenous mudstones with thick beds of sandstone locally, and evidence of penecontemporaneous slumping and dewatering.
290 to 405m
Taken at the top of the well bedded Pencerrigtewion Member, where it gives way to massive disturbed mudstones of the Bryn-glas-Formation, the boundary being gradational and apparently conformable, although likely to be a syndepositional slide plane.
Drum Fireclay
DRFC
Drummore Gravel Formation
DRGR
Sharp, with Cassie Till Formation.
Sheet NH 74SE.
Clayey, sandy, gravelly diamicton containing abundant clasts of sandstone. Distinctly weathered.
Unconformable, glacitectonic, with Clava Lodge Clay Member of the Clava Shelly Formation.
Deep Rider Coal (Warwickshire)
DRID
Drake Formation
DRKE
Draughton Limestone
DRL
Drumflugh Limestone Member
DRLM
Dryburn Foot Limestone
DRLS
Derenenach Mudstone Formation
DRM
Dykebar Marine Band
DRMB
Drimmie Lava Member
DRML
Drumochter Succession
DRMO
Southeast of Loch Ericht and Glen Truim extending southwest to Loch Rannoch and northeast to Glen Tromie. In southeast part of sheet 63E [Dalwhinnie].
Psammite and micaceous psammite, grey and flaggy, with thin micaceous partings. To the east of the A9 road typically grey to pink quartzose psammite and interbanded psammite and micaceous psammite with prominent calc-silicate rock concretions. Minor units of semipelite, locally with associated thin quartzite beds.
Drumowen Sandstone Member
DRMS
Below base of main sandstone are blue-grey bioclastic packstones with low sand content which increases in basal few centimetres, conformable on normal Ballyshannon Limestone Formation.
Restricted to northeast corner of the Kesh-Omagh area of the northwest Carboniferous basin of Ireland.
Sandstone, fawn to pale brown and pale grey, iron-stained, micaceous, calcareous, unfossiliferous, parallel laminations, ripple cross-bedding, bioturbated, fine- to medium-grained, quartz arenite to subarkose.
c.2.7m
Directly underlies micritised limestones of Ederny Limestone Member; conformable.
Draughton Shales
DRNS
Dross Coal
DRO
Drowsell Coal (North Wales)
DROC
Dalroy Sand Member
DROY
Gradational, at colour change, (pale yellowish brown to olive grey) with Clava Lodge Clay Member, or glacitectonic boundary with Culdoich Till Member.
Silty fine- to medium-grained, micaceous sand, containing graded beds and sparse drop-stones. Typically glacitectonised.
6.1m at type section, 4.2m at section NH74SE E9
Sharp, unconformable, glacitectonic boundary with Finglack Till Formation.
Dropping Craig Bed
DRP
Coastal section at Orroland Heugh.
Purplish red, commonly conglomeratic, sandstones passing up into thick red, silty and sandy marls, commonly packed with cornstone nodules.
Drumchastle Pale Limestone Formation
DRPL
Sharp boundary with semipelite and quartzose psammite of Cnoc an Fhithich Formation at type locality; elsewhere taken at base of transitional calc-muscovite-biotite pelite.
From east side of Errochty Synform [NN 7200 6604] discontinuously to core of the Allt Mor synform [NN7688 5453]. East of Loch Tay Fault and north of Killiecrankie Slide, it occurs west of Creag Chlacharnach [NN 980 675] and in Glen Tilt [NN 888 680 - 896 713 and NN 912 713 - 944 743 - 920 705].
Pale buff granular limestone at base, overlain by tremolite-biotite pelite, pale dolomitic limestone and green tremolite-biotite limestone.
0 - 30m in Sheet 55W; probably considerably tectonically attenuated.
Transitional boundary via 5m bed of biotite calc-pelite between green tremolite-biotite limestone and carious-weathering calcareous diamictite.
Dumblar Rigg Sandstone
DRS
Locally in the area of the Bewcastle sheet, Cumbria.
Drygill Formation
DRSH
Not seen: faulted.
Confined entirely to a small outlier on north side of Carrock Fell (Lake District), Cumbria, British Geological Survey, 1:50k sheet 23 (Cockermouth).
Mudstone and shale, grey to black, calcareous, fossiliferous. Locally extensively bleached.
Approximately 200m exposed; true total thickness not known.
Dorrery Sandstone Member
DRSM
Druim Na Saille Pelite Formation
DRSP
Devon Red Sandstone
DRST
Diachronous; boundary lithologically defined.
Dartington Limestone Member
DRTL
Dartmouth Group
DRTM
?Lockovian to Pragian.
This is a thrust-fault contact; this unit forms the hanging walls of two thrusts to the west of the Cawsand Fault. The thrusts are dextrally displaced by the Portnadler, Portwrinkle and Rame Faults, and place the Dartmouth Group on top of the Bovisand Formation of the Meadfoot Group. In the field, the lower boundary of the Dartmouth Group is distinguished by an abrupt transition from grey slaty mudstone with thin interbeds of grey-green siltstone and fine-grained sandstone of the Meadfoot Group at the fault plane, up into reddish purple mudstone and green silty mudstone to muddy siltstone of the Dartmouth Group.
Within the Variscan outcrop in southwest England, the Dartmouth Group forms an approximately east-west trending band, between Watergate Bay [SW 8335 6519] on the north Cornwall coast to Scabbacombe Head [SX 9224 5119] on the east coast of south Devon.
In the Plymouth region, the Dartmouth Group is divided into the Whitsand Bay Formation and the Bin Down Formation; this is an intercalation towards the top of the Whitsand Bay Formation. The Whitsand Bay Formation comprises reddish purple mudstone and silty mudstone (beds commonly up to 2m thick), green silty mudstone to muddy siltstone (with bedding units of between 5 to 10m thick), green to mauve siltstone (in massive beds up to 6m thick that are predominantly structureless but have local lenses and laminae), grey-green with some purple sandstone (beds up to 0.8m thick with local conglomerate above erosional bases) and off-white to pale green quartzite (isolated beds up to 0.5m thick, with some grading and low-angle cross lamination). The Bin Down Formation includes grey to dark grey cleaved mudstone, grey siltstone (laminated in place) and pale grey quartzitic sandstone. Interbedded with these sedimentary rocks are basaltic lavas and volcaniclastic beds including tuff and hyaloclastite.
To 3300m
This is a transitional boundary with the overlying Bovisand Formation of the Meadfoot Group. The contact is seen at Tregantle Cliffs [SX 388 526], where the uppermost strata of the Whitsand Bay Formation of the Dartmouth Group comprise interbedded red and green slaty mudstone with sporadic thin quartzose sandstone beds and grey slaty mudstone; this sequence is succeeded by rocks of the overlying Bovisand Formation, which comprise bioturbated grey mudstone with sandstone laminae, thin beds and load casts and black phosphatic nodules. Near Oldhouse Cove [SX 367 536] the contact is expressed as an upward passage into grey slaty mudstone with thin interbeds of grey-green siltstone and fine sandstone, with dark grey mudstone becoming predominant over an interval of 20m.
Drumard Member
DRU
Drumarg Conglomerate Formation
DRUA
Drummuir Calcareous Member
DRUC
Lowest bed of thin limestone (where present) in upper part of Pitlurg Calcareous Flag Formation. Background lithology changes from banded calcareous psammite and semipelite to less obviously calcareous semipelite with some psammite.
Keith area, Towie to Little Ardrone.
Semipelite and psammite, schistose to phyllitic with many thin beds of calc-silicate rock and metalimestone.
up to 250m.
Base of graphitic pelites with beds of limestone comprising the Mortlach Graphitic Schist Formation.
Drumhirk Formation
DRUM
Drumman More Sandstone Formation
DRUN
Drews Coal (South Wales)
DRWC
Drumwhirn Member
DRWN
The basal contact is faulted in the type area. The presence of grey silty mudstone and dolomitic limestone ("cementstone") interbedded with sandstone distinguishes this basal member of the Ballagan Formation from the underlying sandstone-dominated Kinnesswood Formation.
On sheets Ayr 14W and Carrick 8W, NS20SE, part of NS30SW near Dailly, South Ayrshire. The full lateral extent of the unit is not yet confirmed.
A white-buff and yellow medium- to fine-grained, thinly planar bedded sandstone intercalated with finely laminated grey calcareous siltstone, calcareous mudstone, grey silty mudstone and rare thin non-marine, dolomitic muddy limestone ("cementstone").
At least 275m at the type area, but the base is faulted. The unit is interpreted to be laterally variable in thickness.
Mapped as a conformable contact on NS20SE in the Lindsaystone Burn section at (NS 2824 0080), but not actually exposed. Defined as the lithological change from yellow sandstone with grey silty mudstone to red-purple sandstone with conglomerate and pedogenic carbonate typical of the Lindsayston Burn Member.
Dryden Flags Formation
DRY
Change from dominantly arenaceous to dominantly argillaceous lithologies.
Brownish green shales and siltstones with a few sandstone bands; contains interbedded chert and rhyolitic to andesitic lava and ash at NJ 494 277, near Windyfield.
Approx. 260 metres in type section, but not seen; probably approx. 800 metres present in Castlehill (NJ 515 283) area.
Removed by erosion.
Dryden Limestone
DRYL
Dores Sandstone
DSA
Dun Scalpsie Banded Amphibolite
DSBA
Early Cambrian to Early Ordovician. Temporarily the latter limit is coded pragmatically as "Arenig".
The unit is currently unclassified within the Highland Border Ophialite-Complex pending recognition and adoption of unit types for tectono-metamorphic units.
Douglas Splint Coal (Douglas)
DSC
Dunside Formation
DSD
Transition from silty mudstones of Blaeberry Formation: taken at lowest thick sandstone bed.
Greenish grey micaceous fine-grained sandstone with pale olive mudstones.
35m
Transition to greyish red sandstone and siltstone sequence of Leaze Formation.
Scatsta 'Division'
DSE
Den Siltstone Member
DSF
Contact not exposed, but mapped as an angular unconformity on gneissose feldspathic psammite of the Rosemarkie Metamorphic Complex (Moine). Lowest beds in the sedimentary sequence are not exposed, but the oldest exposed beds are downfaulted against Rosemarkie Metamorphic Complex (Moine) rocks.
Mainly green and greenish grey calcareous flaggy siltstones with subordinate silty sandstones and sporadic thin limestones. Some maroon and grey units. Beds of red breccio-conglomerate developed at the base.
To c.150m
Generally mapped as being unconformably overlain by beds of bouldery conglomerate containing well-rounded clasts of igneous and metamorphic rock including granite, gneissose psammite and porphyritic andesite. The conglomerate is assigned to the Kilmuir Conglomerate Formation (Fletcher et al, 1996). Only one exposure of the contact is known [NH7263 5359] where an apparently concordant boundary occurs between fine-grained sandstone and the overlying conglomerate.
Drumlithie Sand And Gravel Formation
DSG
Unconformable on bedrock or conformable on Mill of Forest Till Formation or Ury Silts Formation.
Howe of Mearns area and flanking the coastline between Stonehaven and the mouth of the River Dee.
Sand and gravel, red-brown, with clasts predominantly of Devonian sandstone, mudstone and andesite. Locally with lenses of silt and clay.
Very variable, generally 5 to 10m; more than 23m proved in boreholes.
Either at the ground surface or unconformably overlain by Flandrian deposits.
Douglas Six Foot Coal
DSIX
Desoglin Limestone
DSL
Dunsil Coal (West And South Yorkshire, Nottingham And Derby)
DSLC
Dounans Limestone Formation
DSLM
Limestone is unconformable on largely carbonated and silicafied Lime Hill Serpentinite.
Ground around Lime Craig Quarry, Aberfoyle, but possible correlations in the Highland Border Complex are known at several localities adjacent to the Highland Boundary in Scotland; eg Margie Limestone, North Esk.
Limestone, massive, grey, fractured and veined; dolomitised and silicified over much of outcrop. Locally fossiliferous with a trilobite - brachiopod - gastropod faunal assemblage.
c.20m (estimated).
Not seen; unit has faulted and/or unconformable relationship with overlying Old Red Sandstone conglomerates and sandstones.
Doobally Sandstone Member
DSM
Dalswinton Moraine Formation
DSMO
Formed during the Late Stage deglaciation of the Nith Valley towards the end of the Main Late Devensian glaciation
Not seen: probably unconformable on Lower Palaeozoic greywacke or Permian sandstone bedrock.
Northwestern flank of the valley of the River Nith in the vicinity of the village of Dalswinton c.8km northwest of Dumfries.
Large lateral moraine ridges rising 10-20m above the level of the floodplain of the River Nith
Moundy Glacial Deposits (Morainic Drift)
Glacial diamicton, bouldery, silty and sandy; very poorly exposed.
The Upper Boundary is the present ground surface.
Subsurface Structure (Undivided, Unrelated To Mining)
DSR
Doubler Stones Sandstone
DSS
Diamonds Ironstone And Silver Threads Ironstone (Undifferentiated) (South Staffordshire)
DSTI
Deerness Volcanic Member
DSV
(a) Conformable contact on Eday Flagstone, (b) Conformable contact on Eday Flagstone, (c) Conformable and cross cutting contacts within lavas.
Deerness, Tankerness, Copinsay and Shapinsay: Orkney Islands.
(a) Basic lava (b) Tuff and tuffaceous sandstone (c) Agglomerate extrusions associated with sills of olivine-dolerite and teschenite locally, which can be distinguished only at coastal exposure. NOTE: The recognised lithologies crop out extensively on the Deerness Peninsula, Orkney. Poor exposure makes subdivision impractical inland, though intrusive and extrusive rock types have been recognised at some sites. Where intrusive basic rocks are recognised they are excluded from the Member. The name is changed from Eday Lavas because some of the rocks are sills, the Eday Flagstone, Eday Sandstone, etc. already exist, and the volcanic rocks do not occur on Eday, which is the type site for the remainder of the Eday sequence.
(a) 2 flows: one >7m, second thin (0.5m) (b) 5m at Muckle Castle type section (c) unknown-thin.
(a) Conformably overlain by tuffaceous sandstone within Eday Flagstone, (b) Conformably overlain by Eday Flagstone, (c) Conformable with Eday Flags and conformable/cross-cutting within lavas.
Douglas Three Foot Coal (Douglas)
DTF
Ditton Group
DTG
Douglas Thirty Inch Coal
DTI
Deformation Till
DTILL
Duntulm Formation
DTM
Trangressive surface, drowned fluvial delta changes to marine-lagoonal facies.
Sea of the Hebrides and Inner Hebrides Basins.
Marine-brackish lagoonal facies dominate the formation, primarily consisting of mudstones, oyster limestones and algal limestones.
Return of fresh water conditions, minor lithology change.
Dalton Limestone (Northumberland)
DTNL
Dunnet Shell Bed
DTSB
Dunnet Shale
DTSH
Dirty Coal (South Wales)
DTYC
Durisdeer Formation
Passes down into the Carron Basalt Formation.
Confined to the northern part of the Thornhill Basin between Lower Dalveen and Gateslack.
Sandy breccias, breccia sandstones, sandstones and rare siltstones and mudstones.
Passes up by alternation into the Thornhill Sandstone Formation.
Dunbarella Bed
DUA
Craven Basin, northwest England.
Dark, fissile, calcareous mudstone with sporadic petroliferous, wackestone nodules - 'bullions'. Bed crowded with bivalves - 'Dunbarella' and 'Pteronites'.
It is a useful marker horizon since in the southern limb of the Plantation Farm Anticline the bed lies within the Chaigley Limestone, allowing correlations with areas such as the Ashnott Anticline, where the Chaigley Limestone is absent. The bed occurs also in the Whitewell Anticline.
Dumbreck Sandstone
DUBR
Dunglass Coal
DUC
Duddon Conglomerate Member
DUCO
At base of conglomerate sequence unconformable on the top of the Lower Palaeozoic basement.
Furness, Cumbria confined to the area of the Duddon Estuary.
Conglomerate, sandstone and mudstone, mainly red-brown with pale green and mottled layers. Large clasts (pebbles up to 15cm) are well rounded, commonly with thin ferruginous skins. Clast lithologies all occur locally and include Borrowdale Volcanic Group andesite, tuff and rhyolite, Silurian "grit" and "greywacke" and Eskdale Granite and Ennerdale granophyric microgranite.
0 to 191m
There is an upward change from conglomerate beds to grey, red and green marine mudstone and limestone with subordinate thin conglomerate beds. The junction may be sharply gradational or possibly an onlap surface.
Dure Clough Sandstone
DUCS
Transitional from grey, micaceous, sandy siltstones with few thin sandstones (commonly less than 0.1m) of the Roeburndale Member (undifferentiated to the sandstone-dominated Dure Clough Sandstones.
Mapped only in the Brennand Fell area of Lancashire [SD 65] but probably more widespread. Equivalents cannot be identified elsewhere because of the absence of biostratigraphical markers.
Sandstones with mostly thin interbedded siltstones - a delta slope facies. Sandstone, grey, weathering orange-brown, fine- to medium-grained, micaceous, thin- to thick-bedded in packets up to c.25m thick. Siltstone, grey micaceous bed c.15m thick in the middle of the unit.
c. 70-100m in the Lancaster area; about 250m in the Garstang district (former Park Wood Sandstone Member).
Sharp transition the sandstone-dominated Dure Clough Sandstones to grey micaceous siltstones with few thin sandstones (commonly less than 0.1m) of the Roeburndale Member (undifferentiated).
Dalmellington Upper Diamond Coal
DUD
Dalmellington Upper Ell Coal (South Ayrshire)
DUE
Dunblane Sandstone Member
DUF
Where medium- to coarse-grained sandstones overlie the top of the fine-grained sandstones and siltstones of the Buttergask Flagstone Member.
The south-east limb of the Strathmore Syncline, in the Stirling to Alloa area.
Purple and brown, medium- and coarse-grained sandstones, subsidiary purple mudstones and rare pebbly sandstone beds.
About 750 m thick.
The base of the lowest siltstone or mudstone of the Cromlix Mudstone Formation.
Dufftown Limestone Member
DUFF
At the top of the underlying calcareous phyllites and semipelites, with thin limestone laminae of the Pitlurg Formation, where they give way to uniform limestone.
Banffshire coast at Sandend southwest along strike of Dalradian Supergroup outcrop to Cairngorms.
Mid to dark grey, fine- to coarse-grained limestone with some dolostone; pelitic in places, but generally pure.
Very variable; laterally impersistent. Thickened by folding in part. In Glenrinnes c. 150m thick.
At the top of the limestone where it gives way to pelites and semipelites of the Mortlach Graphitic Schist.
Dunnet Head Sandstone Formation
DUH
Drawn where the yellow and brown sandstones of the Dunnet Head Sandstone rests unconformably on the flagstones of the Caithness Flagstone Group.
Caithness, northern Highlands. (Highland Region).
Unfossiliferous yellow and brown sandstones with grit beds.
c.733m
The Dunnet Head Sandstone is overlain unconformably by superficial deposits.
Dunconnel Hill Plug
DUHIL
Dunaskin Limestone
DUK
One of the thickest and most persistent limestones in the Dalmellington district of Ayrshire, best development being proven in boreholes near Dunaskin.
Limestone with a few thin partings of calcareous mudstone.
Maximum of about 13m.
Duke Coal (South Wales)
DUKC
Duke Coal (Northumberland)
DUKE
Dulas Coal (South Wales)
DULC
Dull Coal (West Yorkshire)
DULL
Dunnet Marls
DUMA
Grey calcareous mudstones with thin ribs of brown sandstone.
Overlies the Dunnet Shale(s) and overlain by the Binny Sandstone.
Dump Marine Band
DUMB
Drumgivery Limestone Member
DUML
Conformable, rapid gradation from Tullanaglare Mudstone Formation into this member.
Limestone, pink, unbedded, pedogenic, unfossiliferous, micrite, with fine detrital quartz.
Probably disconformable; overlain abruptly, but without apparent erosion, by coarse conglomerates of Drumlish Formation.
Dumbarton Rock Plug
DUMRK
Dalkeith Under Coal (Lothian)
DUNC
Dunans Clay Member
DUNCL
Dunfallandy Hill Pluton
DUNHI
Dunion Hill Plug
DUNI
Dunlin Group
DUNL
Dungiven Formation
DUNN
Sperrin Mountains, Co. Londonderry, Northern Ireland.
Intercalated metalimestone, basic metavolcanics, graphitic and micaceous schist, quartzites and psammites.
Base of major amphibolitic green beds (Glenga Amphibolite Member) at base of Dart Formation.
Dunalastair Quartzite Formation
DUNQ
Sharp contact with underlying Grampian Group psammites.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically in attenuated form from closure of Errochty Synform [NN 712 671] and as far east as tributary of Allt Kynachan [NN 7609 5670]. Also occurs at the culmination caused by the intersection of the Clunes and Bohespic antiforms [NN 745 633]. Not present east of the Loch Tay Fault, where it may have been tectonically excised; however some of the rocks of the 'Banvie Burn Series' may be equivalent.
Quartzite and quartzitic psammitic, beds 100 - 300m thick well developed; less feldspathic than Grampian Group psammites. Cross-bedding shown by feldspar-rich and heavy mineral-rich laminae.
0 - 90m; probably much tectonic thinning.
Sharp boundary with Dunalastair Semipelite Formation, marked by change from quartzite to mixed psammite and semipelite.
Dunrobin Bay Group [See Also Drb]
DUNR
Dunalastair Semipelite Formation
DUNS
Sharp boundary with Dunalastair Quartzite Formation, marked by change from quartzite to mixed psammite and semipelite.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically in attenuated form from closure of Errochty Synform [NN 712 671] and as far east as the Allt Kynachan [NN 7775 5723]. Also occurs at the culmination caused by the intersection of the Clunes and Bohespic antiforms [NN 745 633]. Not present east of the Loch Tay Fault, where it may have been tectonically excised; however some of the rocks of the 'Banvie Burn Series' may be equivalent.
Biotite-muscovite semipelite with psammitic laminae 5 - 30mm thick, giving the unit a ribbed appearance.
Gradational boundary with Beoil Quartzite Formation; boundary taken at base of first quartzite rib.
Dunans Shale Member
DUNSH
Dunwich Group
DUNW
Seen as a sharp planar unconformity, resting on strata from Triassic to Pleistocene (Crag Group) in age. The unit can be distinguished from the Crag Group on the basis of the fluvial origin of the deposits of the Dunwich Group, as the Crag Group is interpreted to be marine to estuarine.
The southern limit is taken as the course of the River Thames above its point of diversion, and below that, the southern limit of the Kesgrave Catchmrnt Subgroup, i.e. a line from SU 770 830 near Marlowe to TM 120 160 near Clacton-on-Sea. There is no northern limit but no deposits are currently identified north of East Anglia and the Midlands. Farther north all such deposits could have been destroyed by the advancing ice responsible for deposition of the Albion Glacigenic Group. Offshore the delta plain sediments of he Yarmouth Roads Formation, correlated with the Cromer Forest-bed Formation, extend over the Southern and Central North Sea basins northwardsto about 55 degrees 30N 56degrees N.
Fluvial gravels with subsidiary sands, clays and silts. The Group comprises the interpreted fluvial terrace sequences of those rivers that were either destroyed by or, in the case of the Proto-Thames, significantly modified by, the overriding ice sheets that deposited the Albion Glacigenic Group. The pebble contents of these various gravels can be used to demonstrate the denudation history of the source areas of the sediments.
To c.15m
Most commonly overlain by deposits of the Albion Glacigenic Group, from which it can be distinguished by the presence of northern-British derived errratics in the Albion Glacigenic Group. It is less commonly overlain by deposits of the Britannia Catchments Group or British Coastal Deposits Group. It also interdigitates with Crag Group deposits.
Drumskinny Sandstone Member
DUNY
Not recognised in field, occurs within Mullaghmore Sandstone Formation.
Sandstone, white to fawn, feldspathic, medium- to coarse-grained, micaceous, calcareous, bioturbated, with thin siltstones and mudstones.
Dalkeith Upper Coal (Lothian)
DUP
Dunrossness Phyllitic Formation
DUPH
Durine Formation
DUR
Conformably overlies the Croisaphuill Formation.
The Durness Group forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye. The Durine Formation does not occur in Assynt or Skye and appears to be limited to the more northern parts of the Durness Group's outcrop.
Light grey fine-grained dolomitic limestones.
80 m thick, although estimated at 200m by some authors.
The top of the formation is tectonically truncated by the Moine Thrust Zone.
Duricrust
DURIC
Durlston Formation
DURN
First occurrence of very shelly micrite (Cinder Bed) above more pure micrites at the top of the Lulworth Formation.
Mapped within the South Dorset area, covered by British Geological Survey 1:50 000 scale Sheets 341, 342 and 343. The unit can be defined elsewhere in southern England (e.g. elsewhere in Wessex Basin and south-east England), separated from the Lulworth Formation beneath by the Cinder Bed. Occurs in the subcrop throughout the Wessex Basin of southern Britain. Away from the type area of Dorset, the presence of the formation can be interpreted from described outcrops from the Weald, and to the west, in the Vale of Wardour in Wiltshire. It is presently identified on mapsheets E328 [Durl], (E341/342 [Durl] and E342/343) [Durl]. It is also likely to be present at depth but not depicted on E283, E284, E286, E301, and part of the Purbeck group shown on the following sheets E219 [Pb], E220 [Pb], E237 [Pb], E252 [g14], E270 [Pb], E271 [Pb], E285 [PB], E287 [g14], E288 [shown in GVS but not symbolised], E289 [shown in GVS but not symbolised], E297 [Purbeck Formation shown but only Oakley Marl Member symbolised], E298 [Pb, and Formations to be released late 2004], E299 [Pb], E300 [Pb], E302 [g14], E303 [g14], E304[g14], E305/6 [g14], E316 [pb], E317/332 [Pb], E318/333 [shown in GVS but not symbolised], E319 [g14], E320/321 [g14], E327 [g14].
Dominated by interbedded, shelly limestones and dark mudstones. The shell material often contains Unio and Viviparus. Detrital quartz is present through much of the formation in West Dorset (west of Stair Hole), but is confined to the Stair Hole Member in East Dorset (Worbarrow and Durlston). The Durlston Formation comprises two members in Dorset, which, in ascending order are: the Stair Hole Member and the Peveril Point Member. Elsewhere the formation is undivided, or is itself incorporated into an undivided Purbeck Limestone Group. The formation includes the informal Upper Purbeck Beds, and the upper part of the Middle Purbeck Beds, above the base of the Cinder Bed, of the traditional scheme. Within the Weald, an equivalent of the Cinder Bed has been identified, thus allowing the succession there to be considered within the formal terminology.
18 to 57m
Last occurrence of significant limestone before monotonous Wealden sandy mudstones.
Dunnet Sandstone
DUS
Overlain by the Binny Sandstone.
Variably developed in the Midland Valley of Scotland. Type area around Pumpherston, Linlithgowshire.
A thick group of alternating sandstones, shaly sandstones and conglomerates, with red and green marls.
To c.220m
Overlies the Burdiehouse Limestone.
Dud Sandstone
DUSA
Dunbar Sandstone Formation
DUSF
Dundonald Sill
DUSI
Dunrossness Spilitic Formation
DUSP
Drawn at base of meta-spilite of the Dunrossness Spilitic Formation where it rests conformably on pelitic wacke interpreted to belong to the Dunrossness Phyllitic (Formation).
Metamorphosed lavas and pyroclastic rocks. The spilites are intercalated with metasediments, mainly graphitic phyllites, quartzites and cherts.
Approximately 1000 metres.
Drawn at unconformable upward passage from meta-spilite of the Dunrossness Spilitic Formation to the Old Red Sandstone.
Dunbeath Till Formation
DUTI
Caithness and Sutherland northeast of a line between Reay and Berridale (1:50 000 sheets 115E and W, 116E and W, 110).
Sandy, silty and commonly gritty, diamicton, typically pale to dark brown; clasts include Devonian mudstones, sandstones and flagstones, with some Caledonian igneous and Moine metamorphic rocks.
Base of the Reisgill Burn Till Formation, typically the base of the Forse Till member.
Dolgarrog Volcanic Formation
Overlies Upper Crafnant Volcanic Formation. Characterized by ill-sorted pyroclastic deposits with much included argillaceous debris.
South and west of Dolgarrog.
Basalt, hyaloclastite, basaltic tuffs and pillow breccias.
Underlies the Nod Glas (= Cadnant Shales).
Denham Valley Terrace Deposits
DVA
Daviot Conglomerate Formation
DVC
Unconformable base on Pre-Cambrian rocks.
Red and purple cobble-boulder conglomerate with sporadic thin sandstone lenses and rare thin limestone lenses.
200 metres +.
Conformable upper contact with Nairnside Sandstone Formation.
Devoke Water Greisen
DVK
Dovestone Redbeds Formation
DVR
Transition from underlying Douglas Water Arenite, taken where the proportion of red mudstones exceeds that of sandstone.
Lower Palaeozoic inlier of the Hagshaw Hills, Scotland, (50k Sheets 23E, 23W and 15W).
Red and greyish-red mudstones, siltstones and shales, weakly bedded with minor small-scale cross-bedding.
72m
Top of uppermost bed of reddish mudstone beneath the predominantly grey arenaceous beds of the overlying formation (which may be stained red).
Devil's Hole Sandstone Member
DVSA
Dergvone Shale Formation
DVSH
Fermanagh and Leitrim
David's Stone Limestone
DVSL
Dry Valley Deposits
DVY
Normally soft to firm consolidated, compressible silty clay, but may contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated surface zone may be present. Formed within some at-present dry or intermittently wet valleys. [Generic description: 'TMOS' Procedures].
War Damage (Undivided)
DWA
Bomb Crater
DWBC
Collapsed Building
DWCB
Dowsing Formation
DWDL
Dwyfach Formation
DWF
Underlain by rhyolitic ash-flow tuff of the Allt Fawr Rhyolitic Tuff Formation. Probably also unconformable on Nant Ffrancon Subgroup mudstones and siltstones, and Upper Lodge Formation lavas and tuffs.
Medium- to coarse-grained sandstones and subordinate interbedded mudstones (Bodwrog Member), passing upwards into grey calcareous mudstones and siltstones with subordinate sandstones (Plastirion Member).
150 to 600m
Overlain by, and partly interbedded laterally with a sequence of lavas and tuffs with some volcaniclastic sediments of the Llanbedrog Volcanic Group.
Downwash Gravel
DWGR
Gravel and sand, from active slope processes. [Generic description].
Whiteness 'Division'
DWH
Dowlais Limestone Formation
DWL
The base is placed at a regional unconformity, the basal limestone of the Dowlais Formation overstepping the underlying formations westwards on the north crop of the South Wales Coalfield, from the Llanelly Formation (green and red-mottled clay) in the east to the Avon Group (thinly bedded fissile mudstones and limestones) in the west.
North crop of the South Wales Coalfield, from Kidwelly [SN 415 077] to Gilwern Hill [SO 2450 1280].
Tabular, thick-bedded, mid- to dark grey, fetid, bituminous, fossiliferous, peloidal grainstone, packstone and wackestone limestones with dark grey shale interbeds; minor dark grey, micritic limestones and pale grey ooidal limestones and some local basal sandstones.
To about 120m
The top is placed at the conformable junction of the dark grey limestones of the Dowlais Formation with the overlying pale grey ooidal limestones of the Penderyn Oolite Member of the Oxwich Head Limestone Formation. From the type area eastwards, the formation is truncated by a pre-Namurian unconformity.
Dalzell Works Lingula Band
DWLB
Dayia Beds
Dalry Blackband Ironstone
DYBI
Dyrham Formation And Beacon Limestone Formation (Undifferentiated)
DYBN
Dykebar Coal
DYC
Dalry Clayband Ironstone
DYCI
Dandy Coal (Lancashire)
DYCO
Dungy Drift Coal (Somerset)
DYDC
Dulcey Dock Member
DYDK
Drumyork Flags Formation
DYF
Rests conformably on Lauchlan Formation.
Girvan area, south-west Scotland.
Grey-green sandstone, flaggy towards top.
Conformably overlain by Blair Shale.
Dyehouse Coal (South Lanacashire)
DYHC
Dyserth Limestone Group (Knoll-Reef)
DYLK
Dykebar Limestone
DYLS
Generally seen as a change from marine mudstone (Dykebar and Balmore Marine bands) belonging to Lawmuir Formation overlying thin coal or seatrocks.
The Paisley and Glasgow area of the Midland Valley of Scotland.
A pale to dark grey, argillaceous, shelly, bioclastic limestone, interpreted to be of marine origin.
Up to 1.4 m thick in the Paisley and Glasgow districts, elsewhere represented by the Dykebar and Balmore Marine Bands.
Generally a changes to a marine mudstone, the Dykebar and Balmore Marine bands Dykebar and Balmore Marine bands, belonging to the Lawmuir Formation, and overlain by non-marine sandy strata
Dysart Main Coal (Fife)
DYMA
Dysart Musselband
DYMB
Dykebar Marls
DYMR
Dol-Cyn-Afon Formation
DYN
Conformable on black mudstones of the Dolgellau Formation.
Northern, eastern and southern flanks of the Harlech Dome, Cwm Pennant, Snowdonia.
Grey mudstone and silty mudstone and siltstone with bioturbated sandstones locally.
Uppermost division of the Mawddach Group. Includes informal sandstone members in southern Snowdonia. Upgraded from Dol-cyn-afon Member of Allen and Jackson, 1985 (Howells and Smith, 1997; Pratt, Woodhall and Howells, 1995). Preferred name for the formations of Tremadoc age, including the Afon Gam and Glanypwll formations and the "Tremadoc Slates".
340 to 400m, locally thickening to 900m
Unconformably overlain by sandstones or conglomerates of the Allt Lwyd Formation (Nant Ffrancon Subgroup), and locally to the southeast of the Harlech Dome by rocks of the Rhobell Volcanic Group.
Dirty Rider Coal (South Wales)
DYRC
Dyrham Formation
DYS
Marked or gradational downward change from silty mudstones to smoother argillaceous sediments of the Charmouth Mudstone Formation; commonly coincides with negative change of slope and/or line of seepage that may correspond with a sandy bed (e.g. Capricornus Sandstone in the Cotswolds; Sumbler, M G, Barron, A J M and Morigi, A N, 2000). On Dorset coast, at base of Three Tiers Sandstone (Hesselbo, S P and Jenkyns, H C, 1995) (base of Bed 6 of Howarth, M K, 1957).
Wessex Basin, Worcester Basin and East Midlands Shelf (Dorset coast to c.Grantham, Lincs).
Pale to dark grey and greenish grey, silty and sandy mudstone, with interbeds of silt or very fine-grained sand (locally muddy or silty), weathering yellow. Variably micaceous. Impersistent beds or doggers of ferruginous limestone (some ooidal) and sandstone, which tend to occur at the top of sedimentary cycles. Sporadic large cementstone nodules.
To c.125m
At base of ferruginous limestone or ironstone of the Marlstone Rock Formation or Marlstone Member of the Beacon Limestone Formation.
Durley Sand Member
DYSA
Appearance of sandy clay and sandy silt in coarsening-upwards sequence of Division D (1) of London Clay of King (1981).
Known only in the Durley area of Hampshire, north-east of Southampton. As mapped confined to 1: 10 000 Sheet SU51NW. Passes laterally into Whitecliff Member or wedged out.
Buff, clayey, fine-grained sand.
Up to 8m. Lenticular.
Erosional surface at base of Wittering Formation (laminated clays or sands).
Dalmahoy Shale
DYSH
Eastern part of the Midland Valley; Midlothian - particularly the area around Dalmahoy.
Soft bluish shaly mudstones, locally relatively oil-rich (sapropelite), with nodular and tabular ironstones.
Dyrham Formation And Marlstone Rock Formation (Undifferentiated)
DYSM
Cravenoceras Leion Marine Band
E1A1
Cravenoceras Brandoni Marine Band
E1B1
Tumulites Pseudobilinguis Marine Band
E1B2
Cravenoceras Malhamense Marine Band
E1C1
Cravenoceras Cowlingense Marine Band
E2A1
Eumorphoceras Ferrimontanum Marine Band
E2A2
Cravenoceras Gressinghamense Marine Band
E2A2A
Eumorphoceras Yatesae Marine Band
E2A3
Cravenoceratoides Edalensis Marine Band
E2B1
Cravenoceratoides Nitidus Marine Band
E2B2
Cravenoceratoides Nititoides Marine Band
E2B3
Nuculoceras Stellarum Marine Band
E2C1
Nuculoceras Nuculum Marine Band [1 Of 3]
E2C2
Nuculoceras Nuculum Marine Band [2 Of 3]
E2C3
Nuculoceras Nuculum Marine Band [3 Of 3]
E2C4
Earnley Sand Formation
Rests on Wittering Formation. Base of formation marked by the transgressive surface overlain by glauconitic silty sands and pebble bed.
Eastern Hampshire Basin.
Glauconitic silty sands and sandy silts.
Overlain by the Marsh Farm Formation. Boundary marked by the upward change from the glauconitic sands of the Earnley Sand Formation to the thin-bedded clays and silts with glauconitic sand laminae of the Marsh Farm Formation.
Eagle Crag Sandstone Member
EAGC
Taken at the base of the lowest bedded volcaniclastic rock within the sequence of volcaniclastic sedimentary rocks and associated andesite sills, resting on andesite or, locally, dacite within the Birker Fell Andesite Formation.
From Haycock, southwest of Buttermere to the area east of Derwent Water, Cumbria
Volcaniclastic siltstone, sandstone, conglomerate and breccia in a bedded succession; intercalated subordinate units of tuff, eutaxitic lapilli-tuff and accretionary lapilli-tuff. Intruded by many peperitic andesite sills.
Defined by the base of overlying andesite sheets of the Birker Fell Andesite Formation.
Earnley Sand Formation And Marsh Farm Formation (Undifferentiated)
EAMF
Eagle Sandstone
EASA
Easington Raised Beach Formation
EASN
The beach gravel rests on a bevelled, subhorizontal platform, bored by marine molluscs, cut into limestones and dolostones of the Zechstein Group (formerly Magnesian Limestone) at about 30m above sea level.
Partly cemented, well sorted gravel and sand containing marine shells. The gravel is composed predominantly of limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone) towards the base, with an increasing content upwards of Carboniferous rock types. Cheviot andesite, Borrowdale Volcanic Group rock types and dolerite. Also including sparse halleflinta, rhomb-porphyry and garnet-hornblende schist of supposed Scandinavian affinity. Twelve temperate genera of marine mollusc have been identified from the deposit, and borings by marine molluscs and annelid worms in the rock platform as well as in cobbles confirm that the deposit is in situ.
Thought to be a planar horizontal or undulating unconformable contact with dark grey diamicton of the Blackhall Till Formation, but contact is obscured and inaccessible.
Eastern Granite (Northmaven Pluton)
EAST
East Barra Meta-Igneous Complex
EBAR
Eller Beck Formation
EBB
The lower boundary is conformable, at the abrupt upward transition from the plant debris-rich, cross-stratified sandstones, siltstones and mudstones of the Saltwick Formation to the fossiliferous, ooidal ironstone or ferruginous sandstone at the base of the Eller Beck Formation.
The Cleveland Hills, North York Moors, Hambleton and Howardian Hills in north-east England (Fox-Strangways, 1892; Hemingway and Knox, 1973; Hemingway, 1974). It has not been identified offshore in the Southern North Sea, but probably forms part of the Wroot Formation (Lott and Knox, 1994).
The formation forms a bench on the sea cliffs of the Yorkshire coast between Peak Scar, Ravenscar [NZ 980 022] to just south of Hayburn Wyke [TA 017 964] and between Whitby, East Cliff [NZ 902 114] and Hawsker Bottoms [NZ 940 084]. Inland in the Cleveland, Hambleton and Howardian Hills, it generally forms a small, positive topographical feature where a distinctive sandstone bed is present (Barrow, 1877; Knox, 1973); the feature is less prominent in the Hambleton and Howardian Hills where the lithofacies change to mudstone, thin limestone and ironstone (Powell and Rathbone, 1992).
Shallow-marine transgressive unit representing the first major marine transgression across the Mid-Jurassic fluvio-deltaic hinterland.
In the Cleveland Hills and on the North Yorkshire Coast the formation typically comprises marine ironstone, sandstone and mudstone. Two main lithological units are present; the lower unit, generally less than 3m thick, consists of grey mudstone with subordinate sideritic ironstone, with a bed of ooidal ironstone at the base. The upper unit, typically 4-6m thick, consists predominantly of fine- to medium-grained sandstone, commonly ripple laminated. Southwards, the formation passes into a more calcareous and finer-grained unit dominated by mudstones, argillaceous limestones and ferruginous sandstones (the "Blowgill Member" of Hemingway and Knox, 1973). Fossil marine bivalves and bioturbation are common, especially in the mudstones and ironstones. Diplocraterion burrows are commonly present in the sandstones.
Typically 4.5 to 6m, up to a maximum of 8.2m in the type section at Walk Mill Foss, Eller Beck, Goathland [NZ 833 023] (Barrow, 1877; Hemingway and Knox, 1973). Thins south-eastwards in the Hambleton Hills to c.4m thick.
The upper boundary is conformable, or disconformable, at the abrupt upward transition from the fossiliferous mudstone and ripple laminated sandstones of the upper part of the Eller Beck Formation to the cross-stratified, plant debris-rich sandstones, siltstones and mudstones of the Cloughton Formation (Sycarham Member).
Easton Bavents Clay Member
EBC
Clay, pale to mid grey, with thin beds of silt or fine-grained sand. [Generic description: academic papers and BGS Memoirs].
Easebourne Member
EBO
Sharply defined contact on similar but less well cemented sands of Hythe Formation.
Between Chithurst (Gatehouse) SU8323 and Petworth SU9820, south-western Weald (Sussex).
Fine- to medium-grained glauconitic sands, some very well cemented (calcareous), with minor clay interbeds.
Incoming of conspicuous clay-rich sands and clays at base of Fittleworth Member.
Exe Breccia Formation
EBR
Overlies and interdigitates with the Dawlish Sandstone Formation, which is essentially a red sandstone in planar- or cross-bedded units with sparse pebble seams.
Newton Abbot District, Devon.
A red breccia containing clasts from 30 - 100mm in diameter, in a silty sandy matrix, with cross-bedded and planar-bedded sandstone sets up to 3m thick. Breccia clasts include sandstone, slate and quartz porphry.
85m
Disconformable with the overlying Exmouth Mudstone and Sandstone Formation, which comprises predominantly thick units of red-brown mudstone with sporadic sandstone beds.
Eyebroughty Sill
EBRTY
Ebchester Sand And Gravel Formation
EBSG
Erosional unconformable contact with stiff, dark greyish brown, stony, sandy silty clay diamicton of the Wear Till Formation.
Northern Pennines.
Sand and gravel containing clasts of Carboniferous lithologies (sandstone, gritty sandstone, limestone, mudstone, gannister, coal), including far-travelled clasts from Scotland and the Lake District (greywacke sandstone and siltstone, granite and granodiorite).
Generally the land surface, or erosional unconformable contact with sand and gravel forming more recent river terraces.
East Brow Member
EBW
Succeeds coarse green sandstone and conglomerate of the Escarpment Member of the Auldthorns Formation. Distinguished from the Escarpment Member by having almost no conglomerate and a large number of mudstone units.
A sequence of greyish-green fine- to medium-grained sandstones and mudstones on the east brow of Quarrel Hill.
c.30m (estimate).
Succeeded by green and purple mudstone of the Quarrel Hill Formation.
East Carlton Grit
West Yorkshire [East Carlton, northwest of Leeds].
Eccliffe Member
ECC
Upward change from bioclastic oolites and micrites to even-grained oolite.
From the A30 on the northern edge of the Shaftesbury Sheet (313), northwards across the southern half of the Wincanton Sheet (297).
Fine- to medium-grained, flaggy oolite.
Top marked by a change from fine-to medium- grained flaggy oolite to sandy and ooidal mudstone (Sandsfoot Clay Member, where present), or non-sequence overlain by fine-grained sand or sandy clay, locally with phosphatic nodules at the base (Sandsfoot Grit Member, Sandsfoot Formation).
Eggardon Grit
ECG
Eggardon Chert Beds
ECHB
Ecton Limestone Formation
ECL
The base of thicker-bedded, paler grey peloidal and crinoidal bioclastic limestone above dark grey, thinly-bedded, fine-grained limestones of the Milldale Limestone Formation.
The Dovedale-Manifold Valley, and the southwestern part of the Peak District inlier [SK 09 60] to [SK 13 48], Derbyshire and Staffordshire.
The lower part of the formation is dominated by thinly to thickly bedded, brownish-grey, finely bioclastic and peloidal to conglomeratic limestone, containing chert nodules and mudstone partings, in sharp based, poorly graded turbiditic beds. In the middle, thinly bedded and laminated dark grey micritic limestone passes up into thicker bedded limestone. The upper part of the formation, includes dark grey fine-grained limestone, and coarser-grained, sharp-based graded beds of turbiditic origin.
From 225m in the type area, increasing to a maximum of 258m proved around Grindon [SK 093 541].
A transitional conformable base taken at the lowest thick grey mudstone of the Widmerpool Formation, above grey limestones of the Ecton Limestone Formation.
Ecton Limestones Formation (Knoll-Reef)
ECLK
Eccup Marine Band
ECMB
Escarpment Member
ECP
Succeeds alternating flaggy sandstones and shales of the Shalloch Formation.
Coarse green sandstone and conglomerate (lower 2m conglomerate, upper 4m sandstone).
Succeeded by sandstones and mudstones of the East Brow Member of the Auldthorns Formation.
Ecton Member
ECTN
Nene Valley, Central England.
Gravel with sand, clay and, locally, peat.
0 to 4.5m
At ground surface or at base of overlying alluvium.
Edderton Fish Bed
Edmondia Coal (Nottingham)
EDC
Edinburgh Castle Plug
EDCP
Eday Flagstone Formation
EDF
Eldroth Grit
EDG
Base taken where the predominantly sandstone sequence of the Eldroth Grit overlies siltstones of the Kirkbeck Member.
Trough cross-bedded feldspathic, medium- to coarse-grained sandstone, typically thickly bedded. Ganister palaeosols are present in the upper part of the unit.
30m (Bentham area); 50-60m (Settle district).
Taken at the top of the highest sandstone of the Eldroth Grit, commonly containing rootlets, overlain by mudstone or siltstone of the Millstone Grit Group (undifferentiated).
Eday Marl Formation
EDMA
Edge Marine Band
EDMB
Ederny Limestone Member
EDNY
Either gradational, with normal limestones of the formation (ie downward decrease in micritisation) or abrupt, with base marked by 0.06 - 0.2m layer of grey shales and noduler limestones; also rests on Drumowen Sandstone and Crockanaver Limestone members.
Limestone, pale grey, micritised, sparsely bioclastic crinoidal packstone with wisps and disrupted layers of yellow silty shale.
Pitted top of the member overlain by up to 0.18 metres of multi coloured clays representing disconformable base of succeeding Bundoran Shale Formation.
Earl David's Parrot Coal (Fife)
EDP
Elidir Group
EDR
Eden Shales Formation
EDSH
Conformable base on Penrith Sandstone Formation.
Red shales and mudstones with local beds of gypsum and anhydrite, rare dolomitic limestones.
Up to c.100m
Conformable upward passage to St Bees Sandstone Formation.
Edlington Formation
EDT
Sharp, upward passage from dolostone of Cadeby Formation.
East Midlands and NE England. Dies out south of Nottingham. Passes eastwards into thick dolostones and evaporites.
Mudstone, red-brown, with subordinate siltstone and sandstone, greenish-grey sandstone more common in Nottinghamshire. Dolostone and gypsum/anhydrite locally common.
Upward passage into dolomitic limestone of Brotherton Formation.
Edenside Till Formation
EDTI
Edwalton Member
EDW
Mapped at the surface in south Nottinghamshire and Leicestershire; recognisable in borehole core and geophysical logs in the subsurface throughout East Midlands and northeast England.
Mudstone and siltstone, red-brown and greenish grey, with beds of indurated, variably dolomitic siltstone and very fine-grained sandstone common in the lower half; finely disseminated gypsum common in upper half.
Originally defined as a Formation, the unit is retained as a local member within the nationally recognized Sidmouth Mudstone Formation.
35 to 45m
Conformable, at the abrupt upward transition from structureless, reddish brown and greenish grey mottled, gypsiferous mudstone at the top of the Edwalton Member to the lowest fine to medium-grained sandstone bed of the Arden Sandstone Formation.
Eday Group
EDY
Drawn at the base of the Lower Eday Sandstone Formation where it rests conformably upon the Rousay Member of the Upper Stromness Flagstone Formation.
Orkney Islands
Comprises yellow sandstones with thin fossiliferous flags below and red and unfossiliferous above. Containing one volcanic horizon.
Not overlain: highest Group in the Orkney Islands.
Eem Formation
At type locality overlies Saalian glacial till. In Flemish Bight, overlies Lower and Middle Pleistocene formations (unconformably).
Fine- to medium-grained shelly marine sands/intertidal or shallow sub-tidal in north west Flemish Bight with interbeds of clay.
15.71 metres. Lateral variations 5 - 30 metres. Maximum 30 metres in Flemish Bight Sheet.
At type locality, overlain by Weichselian periglacial sands (Twente Formation). In Flemish Bight, is overlain by Twente Formation, Brown Bank Formation (early Weichselian brackish-marine clays) or Halocene sands.
Eemian Mud And Sand, Interbedded (Offshore)
EEMAS
Esk Evaporite Member
EEV
Conformable, at gradational upward transition from red-brown mudstone to mudstone with halite at the base of the Esk Evaporite Member.
Cleveland, northeast England. Proved only in the subsurface, not mapped at outcrop.
Mudstone, red-brown, with halite beds and veins, and common mudstone breccias formed from halite dissolution.
7m at the type section, ranges up to 50m.
Conformable, at gradational transition from mudstone with halite of the Esk Evaporite Member to red-brown mudstone of the undifferentiated Sidmouth Mudstone Formation.
Eskmouth Extra Coal
EEX
Within the range ?Yeadonian to Langsettian. Yeadonian might be appropriate rather than Namurian, but there is no real evidence. It is likely that the seam is no older than this. Note the Lethem Well Coal in Fife is described in similar loose fashion and is at about the same position in the Passage Formation. On balance it is likely that both coals are Langsettian, but the key 6 Group Marine bands are difficult to identify as such in Fife and the Lothians.
Elland Flags
The Elland Flags consist of fine- to medium-grained flaggy to thickly bedded micaceous sandstone. The unit occurs as a number of sandstone leaves that are interbedded with dark micaceous and carbonaceous mudstone, locally containing thin dirty coals.
Elland Flagstones Leaf 1
EF1
Elland Flagstones Leaf 2
EF2
Elland Flagstones Leaf 3
EF3
Elland Flagstones Leaf 4
EF4
Elland Flagstones Leaf 5
EF5
Elland Flagstones Leaf 6
EF6
Elland Flagstones Leaf 7
EF7
Elland Flagstones Leaf 8
EF8
Elland Flagstones Leaf 9
EF9
Eathie Fish Bed
EFB
East Fife Basanitic And Foiditic Plugs And Vents
EFBFP
Eight Feet Coal (South Staffordshire)
EFC
Easton Four Feet Coal (Bristol Area)
EFFC
Egmond Ground Formation
Overlies Early or Middle Pleistocene sediments.
Fine-grained, sparsely shelly marine sands with clay interbeds (markedly less shelly than younger sands of the Eem Formation).
0 - 10 metres
Overlain by Eemian marine sands (Eem Formation), early Weichselian brackish-marine clays (Brown Bank Formation) or Holocene marine sands.
East Grampian (Albion) Glacigenic Subgroup
EGAG
Sharp, unconformable contact with bedrock.
The East Grampian Highlands, Cairngorm Mountains and Gaick Plateau.
Suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts derived predominantly from weathered Neoproterozoic metamorphic rocks (psammite, metagreywacke, slate) and Caledonian igneous rocks (granite, granodiorite, gabbro), including sandy diamictons (till), sand, gravel, silt and clay. Deposited from ice that radiated from the Eastern Grampian mountains.
Unconformable contact with units of the East Grampian Glacigenic Subgroup.
Ellens Geo Conglomerate
EGC
East Grampian Glacigenic Subgroup
EGD
Unconformable: base of Banchory Till Formation.
Till, sand and gravel and laminated silt and clay, composed principally of decomposed Neoproterozoic metamorphic rocks and Caledonian igneous rocks; deposited by glacial ice that radiated from the East Grampian Highlands.
Very variable, generally 5 to 10m; more than 40m proved in some sections.
Unconformable: top of Lochton Sand and Gravel Formation.
Eastern Gneisses And Hillswick Group (Undifferentiated)
EGHI
Ellenthorpe Gill Limestone
EGL
Named after Ellenthorpe Gill, near Clitheroe, Lancashire.
Dark grey lenticular limestones.
East Greenland Province
EGLND
Eastern Gneisses
EGNS
Edergole Formation
EGS
Eglish Sandstone Formation
EGSA
Conglomerate, sandstone and thin sandy siltstone.
Base of basalt lavas of succeeding Carey River Basalt Formation.
Egginton Common Sand And Gravel Member
EGSG
Middle Pleistocene (MI Stage 6). Formerly stated to be Wolstonian in original Informal Lexicon entry by A Brandon, 26/01/1998.
Unconformable, commonly channelled base, resting on pre-Quaternary bedrock.
Occurs as outliers on north bank of Trent in type area (Sheet 141); thought to be present upstream, particularly on the north bank of the Dove downstream of Uttoxeter (Sheet 140) and probably elsewhere, (e.g. on the south bank of the Trent near Alrewas, Sheet 154) but extent uncertain pending resurvey.
Predominantly cold-phase sands and gravels that underlie the Egginton Common Terrace. Intensely cryoturbated, decalcified poorly sorted sand and gravel, dominated by rounded pebbles of "Bunter" quartz/quartzite (up to c.90%) with subordinate subangular flint (up to c.15%), Carboniferous chert, sandstone, etc., Fairly well developed and extensive terrace surface c.12-13m above the Trent/Dove floodplain in Type Area. Upper part locally includes a rubified paleosol (Hykeham Soil; Ipswichian). Correlated with the Borrowash Sand and Gravel Member (Derwent Valley Formation) and Burstall Sand and Gravel Member (Soar Valley Formation) and Balderton Sand and Gravel Member (Trent Valley Formation).
Eastern Gneiss And Sand Voe Group [Intimate Mixture]
EGSV
Eastgate Sandstone Member
EGT
Transitional incoming of a predominantly sandstone succession belonging to the Eastgate Sandstone Member above the Kirk Hill Conglomerate Member of the Westgate Formation
Carmichael Inlier near Carmichael, Lanarkshire, Scotland
Mainly greyish medium-grained sandstone, locally a coarse-grained subgreywacke varying from dark greenish grey to pale red in colour. Also local thin beds of pebbly sandstone, conglomerate and micaceous sandstone
To 400m
The fairly sharp base of the greywacke-pebble bearing Greywacke Conglomerate Formation above the predominantly sandstone succession of the Eastgate Sandstone Member of the Westgate Formation
Elsterian To Holsteinian Diamicton, Firm To Hard (Offshore)
EHDFH
Elsterian To Holsteinian Deposits, Undifferentiated (Offshore)
EHDU
Ehen Alluvium Formation
EHEN
Mainly Holocene (but terraces may extend into Lateglacial).
1:50k Sheets 37 Gosforth and 38 Whitehaven, western Cumbria and applied to all alluvial deposits within the west Cumbria area, between Whitehaven and Muncaster, of the Cumbria-Lancashire Catchments Subgroup area.
Sands, gravels silts and clays forming river terraces and underlying floodplains.
Typically up to 12m thick in the type area.
Elsterian To Holsteinian Mud And Sand, Interbedded (Offshore)
EHMAS
Elsterian To Holsteinian Mud, Firm To Hard (Offshore)
EHMFH
Elsterian To Holsteinian Sand (Offshore)
EHSND
Glac An Dorchadois Member, Brutach Dearg Member And Cnoc Creaghach Member (Undifferentiated)
EIG35
Eigg Lava Formation
EIGL
Laig Member
EIGL1
Gleann Charadail Member
EIGL2
Glac An Dorchadois Member
EIGL3
Brutach Dearg Member
EIGL4
Cnoc Creagach Member
EIGL5
Cora-Bheinn Member
EIGL6
Basal Member (Eigg Lava Formation)
EIGLB
Eil-Arkaig Dyke Swarm
EILAG
Eildon Hills Laccolith
EILD
Eildon Hills, Melrose, Scottish Borders.
Trachyte.
Eilde Flags Formation
EILDE
Eilean Shona Neck
EILSH
Eighteen Inch Coal (South Wales)
EITC
Ettrickbridge Formation
EKB
Within Upper Hartfell Shale Formation.
Southern Uplands of Scotland.
Sandstone turbidite unit.
c.55m
Edendork Coal
EKC
East Kilbride Common Coal
EKCC
East Kirkton Limestone
EKL
Eskdalemuir Formation
EKM
Silurian, uppermost Llandovery.
Faulted; stratigraphical contact not preserved.
Southern Scotland.
Sandstone, typically fine- to medium-grained but ranging from very fine- to coarse-grained. Generally medium- to thick-bedded over thicknesses of tens of metres interspersed with units up to few metres very thin to thin-bedded. Sparse very thick beds of massive sandstone. Interbedded siltstone or silty mudstone generally in thin beds. Sandstone and siltstone typically pale green when fresh with characteristic deep rusty brown weathering reflecting relatively high carbonate content. Distinguished from the Glendearg and Selcoth Formations by relatively high carbonate content and associated weathering character.
Uncertain, likely to be several thousand metres.
Faulted; no stratigraphical contact preserved.
Ekofisk Formation
EKOF
Edgton Limestone Member
East Lothian Basanite And Foiditic Plugs And Vents
ELBAF
Ellenora Coal (Douglas)
ELC
Elgin Calcrete Formation
ELCA
Requires fieldwork, or further research.
The Moray Firth coast around Elgin.
Pale grey and reddish brown, calcareous, marly sandstones, which have been significantly replaced by calcite and chert.
Ellel Crag Sandstone
ELCR
Abrupt change from mudstone of Dolphinholme Mudstone to sandstone of the Ellel Crag Sandstone.
Ellel and Forton, Lancashire.
Sandstone, fine-to-medium-grained, large scale cross-bedding; coaly layers.
Abrupt change from sandstone of the Ellel Crag Sandstone to mudstone/siltstone of overlying unnamed beds within the Millstone Grit Group.
Eilean Dubh Formation
ELD
Conformably overlies dark grey dolostones of the Ghrudaidh Formation. A zone of interbedded dark and pale grey dolostones occurs at the boundary. The base of the Eilean Dubh Formation is taken at the appearance of laminations and/or chert layers.
The Durness Group, which contains the Eilean Dubh Formation, forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye.
Pale grey to buff, flaggy, laminated dolostones with intraformational breccias and minor chert development towards base and top of unit. Stromatolites particularly abundant in Durness area.
About 150 m thick.
Conformably overlain by dark dolostones and white chert of the Sailmhor Formation.
Eglwyseg Limestone Formation
ELF
Ellergill Beds
ELG
Eilean Liath Grit Formation
ELGT
Eilean Dubh Formation And Ghrudaidh Formation (Undifferentiated)
ELGU
Ellerker Limestone
ELL
Quasi-conformable contact between predominantly calcareous mudstone and siltstone of underlying part of Raventhorpe Beds and porcellanous limestone of this informal Bed.
BGS 1:50 000 sheets 80, 89; northernmost Lincolnshire (the Humber area), northwards to the Market Weighton area.
Limestone, hard, porcellanous, silty, with fine-grained shell debris (silty, shell fragmental wackestone).
Though defined here, this term should not be perpetuated. Even if deemed valid as a stratigraphical unit, its Member status should be dropped and informal (Ellerker Limestone) usage adopted. Member status is inappropriate as the Bed is within the Raventhorpe Beds "Member" (Gaunt et al., 1992), which is now placed within the Lower Lincolnshire Limestone MEMBER. Due to the confused status of the Ellerker Limestone and the Raventhorpe Beds, the Parent is indicated as the Lower Lincolnshire Limestone Member. The unit was not considered a member even by its inventors (Gaunt et al., 1992). It is a thin unit within the Raventhorpe Beds/Member (sensu Gaunt et al) that could be mapped in areas mostly north of the Humber. It is part of the Hydraulic Limestones of previous authors, which also included the underlying strata down to the base of the Raventhorpe Beds. Gaunt et al showed that it lay at a higher horizon that the Cleatham Limestone (approximating to the Hydraulic Limestones south of the Humber). Hence the different names, though both are essentially limestones "floating" close to the base of the Raventhorpe Beds and may be the same horizon. If not for the exclusion of the thin (typically 1m or so) underlying part of the Raventhorpe Beds it could be said that the Elerker/Cleatham Limestone IS the Hydraulic Limestone of older (pre-Ashton and Gaunt et al) accounts. Whereas the unit is a useful mapping entity it would better be indicated as "Limestone in Raventhorpe Beds". See also Cleatham Limestone. [Condensed from notes by M G Sumbler, 29/09/2005.]
0 to c.1m.
Quasi-conformable contact between porcellanous limestone of this informal Bed and predominantly calcareous mudstone and siltstone of the overlying part of the Raventhorpe Beds.
East Linton Lava Member
ELLA
The base is conformable or locally unconformable on the North Berwick Pyroclastic Member. The change is from basaltic pyroclastic rocks to mafic lava flows.
East Lothian, outcrop of the Garleton Hills Volcanic Formation around North Berwick, East Lothian, Garleton Hills, Stenton and in the subcrop farther west in the BGS Spilmersford Borehole near Pencaitland, but absent adjacent to the Lammermuir Fault.
The East Linton Lava Member consists characteristically of macroporphyritic ankaramites (Craiglockhart type) and basaltic hawaiites (Dunsapie type), both with olivine and clinopyroxene (large augite) phenocrysts and the latter, also plagioclase. Non-porphytic trachybasalts of mugearite type and one of leucite-bearing kulaite are also present. Beds of tuff and lapilli tuff also occur in the succession. Flows are usually 5 to 15m thick, the upper half being slaggy and vesicular.
0 to 90m
The Member is overlain by the Hailes Lava Member. The contact is conformable and locally unconformable. The change is from either ankaramite and basaltic hawaiites to olivine-basalt and mugearite.
Ell Coal (Central Coalfield)
ELLC
Ell Index Coal (Central Coalfield)
ELLI
Might be a redundant (junior) synonym of GLASGOW ELL INDEX COAL (GEI).
Ellen Seam
ELLN
Ell Coal (Warwickshire)
ELLW
Elmsall Coal (West Yorkshire)
ELMC
Elswick Mudstone Formation
ELMU
Eileans Sandstone Member
ELN
Base not seen, presumed transitional on Millport Cornstones Member.
Cumbrae Islands in Strathclyde, Scotland.
Mainly white, cross-bedded sandstone.
About 150m
Top not seen, presumed overlain by extrusive igneous rocks of the Clyde Plateau lavas.
Ellon Formation
ELON
Elsworth Rock Formation
ELR
Drawn at base of limestone and ironshot clay of the Elsworth Rock Formation where it rests conformably on the Upper Oxford Clay.
Cambridge district.
Highly variable, marly limestone bands and nodules and ferruginous, oolitic clays.
2.5 - 10.5 metres.
Drawn at conformable upward passage from limestone of the Elsworth Rock Formation to the Ampthill Clay.
Elrick Psammite And Semipelite Formation
ELRK
Poorly constrained, possibly unconformable, on Dava Succession semipelites and psammites.
Central Highlands of Scotland, Upper Strath Dearn.
Psammite and micaceous psammite interlayered with garnetiferous semipelite.
1 to 2km.
Transitional up into turbiditic psammites of the Loch Laggan Psammite Formation.
Elsham Sandstone Member
ELS
Elton Formation
ELT
Elenid Till Member
ELTI
Lower Elton Formation, Middle Elton Formation And Upper Elton Formation (Undifferentiated)
ELTU
Elvington Glaciolacustrine Formation
ELV
Not observed. In most places the Elvington Glaciolacustrine Formation will overlie tills of the Vale of York Formation as proved in borehole SE64NE/10, where 4.6m of soft grey brown clay is recorded resting on "brown boulder clay" (glacial till).
The Elvington Glaciolacustrine Formation is constrained between the York Moraine Member to the north (between York in the west and Sand Hutton in the east) and the Escrick Moraine Member to the south (from Stillingfleet in the west to Sutton in the east. It extends as far west as Copmanthorpe and as far east as Sutton Upon Derwent.
Firm to stiff, rarely soft, mottled reddish brown (5YR 4/3) and grey (GLEY 2 3/1) thinly laminated clay. Sporadically interlaminated with silt and fine reddish brown sand. Commonly fissured. Gypsum, in the form of opaque, tabular selenite is found locally within the laminated clay below a depth of 2.5m. Crystal size is typically 15 to 35mm along the longest axis.
Minimum thickness of 4.2m proved in borehole (SE64NE/17)(SE6838 4634) but generally exceeds 5m in thickness. 4.6m proved in borehole SE64NE/10.
An outcrop overlain by aeolian or fluvial sand or clayey sand. The contact is sharp where proven in auger bores.
Elbow Formation
ELW
Base of basal peat bed (where present).
Brackish-marine fine-grained sands and clays with discontinuous basal peat bed.
Passage to fully marine sands.
Elwick Moraine Member
ELWK
Uneven, unconformable contact on bedrock or dark brown stony sandy silty clay diamicton of the Wear Till Formation. Lateral unconformable contact with reddish brown stony sandy silty clay diamicton of the Horden Till Formation.
Lowlands of County Durham.
Forms linear ridges and mounds with kettleholes.
Varied lithologies including ill-sorted gravel, red sand and red sandy diamicton with clasts of limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone), Carboniferous lithologies (sandstone, limestone) and Cheviot andesite. Forming linear ridges and mounds with kettleholes.
To about 12m
Elygrain Vent
ELYG
Pyroclastic breccia or agglomerate in vent, with intrusions of trachyte.
Vent, elongate, c.200m x 1500m
Easter Main Coal
EMA
Eastside Marine Band
EMB
Embleton Microdiorite Intrusions
EMBL
The area east of Cockermouth, Cumbria.
Microdiorite, aphyric basalt, andesite and microgranodiorite. Radiometric age: 444 +/- 24 Ma (Rb-Sr whole rock) (Rundle, 1979).
Embsay Limestone Member
EML
Drawn at base of boulder beds of the Embsay Limestone Member where it rests unconformably on mudstones. ('Halton Shales with Limestone' of Hudson and Mitchell, 1937).
Craven Basin, north-west England. (Lothersdale and Skipton Anticlines).
Pale packstones and grainstone, frequently pellety or oolitic and locally cherty, interbedded with dark, calcareous, silty mudstones, calcisiltites, conglomerates and breccias.
Up to 100 metres.
Drawn at conformable upward passage from limestone of the Embsay Limestone Member to shaly calcisiltites and mudstones. ('Skibeden Shales with Limestone' of Hudson and Mitchell, 1937).
Eaglesham Lava Member
EMLA
The base is apparently conformable on the Moyne Moor Lava Member that consists predominantly of trachybasalt, but might locally be unconformable.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton, in the eastern part of the area between Newton Mearns (NS 575 518) and Eaglesham (NS 536 557).
The Eaglesham Lava Member consists of mainly macro- to micro-porphyritic olivine, clinopyroxene and plagioclase or plagioclase alkali-basalt lavas but include ankaramites and feldspathic trachybasalts. One trachytic flow is known.
The Member is overlain by the Dumdruff Hill Lava Member. The contact is considered conformable.
Emerald Formation
EMLD
Eype Mouth Limestone Member
EMLS
Edmondia Marine Band
EMMB
Originally used as a local name in the coalfields of South Derbyshire, Derbyshire-Nottinghamshire and Yorkshire, but subsequently adopted as the standard name for the marine band at this level throughout the UK [Ramsbottom and others, 1978].
Exmouth Mudstone And Sandstone Formation
EMSA
In Exeter district, lower boundary taken at sharp change from the sandstone of the underlying Dawlish Sandstone, to mudstone. Between Lympstone and Exmouth the formation rests sharply and probably unconformably on the Exe Breccia (Selwood and others, 1984).
Extends from south Devon coast between Exmouth and Straight Point (SY 036 798) northwards through Exeter district to near Aylesbeare. Not recognised north of Aylesbeare (SY 030 923).
Reddish brown silty mudstones with intercalated reddish brown lenticular sandstone beds, exceptionally to 30m thick, but mostly 5 to 10m thick. The thickest, most persistent, sandstones occur at the top, and probably correlate with sandstones exposed at Straight Point on the coast.
About 200m in Exeter district; 255m on the coast (Selwood and others, 1984).
See definition of lower boundary of Littleham Mudstone.
Eagle Moor Sand And Gravel Member
EMSG
Middle Pleistocene (MI Stage 12 or 10). Formerly stated simply to be Anglian in original Informal Lexicon entry by A Brandon, 26/01/1998.
Unconformable, commonly channelled base, resting on pre-Quaternary bedrock or locally, east of Eagle Moor, on the Skellingthorpe Clay Member of the Wolston Formation.
Newark on Trent to Lincoln Gap (British Geological Survey sheets 113, 114, 126, 126; see Brandon and Sumbler, 1991, Figure 1) with probable outliers upstream in the Uttoxeter-Derby area (sheets 140, 141; included in Trent, Trent-Derwent and Soar Valley formations) and possibly elsewhere.
Predominantly cold-phase sands and gravels that underlie the Eagle Moor Terrace. Dominated by rounded pebbles of "Bunter" quartz/quartzite with subordinate subangular flint (typically 25% in the Type Area), etc. Clayey and poorly sorted. In Type Area occurs as hill-top outliers falling from c.36m OD near Newark (c.25m above Trent floodplain) towards the Lincoln Gap, being at c.+32m OD at Eagle Moor and possibly descending more rapidly to the east. Outliers upstream in the Loughborough district 30m+ above Trent floodplain. Correlated with the Martin Sand and Gravel Member (Trent Valley Formation), east of the Lincoln Gap.
0 to c. 6m; typically c. 2 to 3m
Embury Shale
EMY
Black sulphurous shaly mudstones with calcareous nodules yielding goniatites characteristic of the Subcrenatum Marine Band.
Enville Member
Poorly defined; taken arbitrarily at base of sandstone dominated succession that overlies the Alveley Member and is characterised by conglomerates and pebbly sandstones with extra-basinal clasts, commonly of Carboniferous limestone and chert.
Salop and West Midlands.
Red mudstone and red-brown, fine- to coarse-grained sandstone, locally pebbly, and lenticular beds of conglomerate. Sandstone mostly sublitharenite; conglomerate clasts mostly Carboniferous limestone and chert.
100-275m in West Midlands.
Unconformable/disconformable; sharp junctions with overlying Clent Formation (breccia) in the Clent Hills; gradational boundary with mudstone dominated Clent Formation; or taken at the base of red mudstone/sandstone with Uriconian volcanic clasts in Gospel End area (West Midlands)
Ennerdale Intrusion, Diorite [Obsolete Code: Use Enin + Rock Type]
ENDI
Endrick Sand Member
ENDR
Transitional base with the underlying Kilmaronock Silt Member (Strathendrick Formation).
The Endrick Sand Member of the Strathendrick Formation is only known to occur in its type area in the Loch Lomond basin including the lower part of the Endrick valley.
The Mains of Kilmaronock Borehole (Browne and McMillan, 1989, Figure 6) contains the standard section in the Endrick Sand Member (5.99m to 13.6m in depth). The typical lithology is loose, fine- to medium-grained sand with some silt layers. The deposit is reddish brown and contains abundant plant remains and some dark organic clay bands. The sand usually appears to be flat-bedded but traces of cross-bedding are also present. Overall the deposit becomes coarser-grained upwards. The sediment at Mains of Kilmaronock might have been deposited by a meandering river in similar environments to those of the present Endrick. They could also be partly deltaic in origin.
Veneer to over 7.5m
Sharp conformable contact with the overlying Erskine Clay Member (Clydebank Clay Formation).
Edge Hill Nine Foot Coal (New Cumnock Area)
ENF
Ennerdale Intrusion, Granite [Obsolete Code: Use Enin + Rock Type]
ENGR
Ennerdale Intrusion
ENIN
From Wasdale to Ennerdale, western Lake District.
A medium-grained granophyric granite and microgranite, with zones of diorite, dolerite and hybridised rocks.
A laccolith, about 1km thick, and with an area of about 53 sq. km intruded into the Skiddaw Group and the lower part of the Borrowdale Volcanic Group.
Earnock Blackband Ironstone
ENKB
Earnock Clayband Ironstone
ENKC
Enler Group
ENLE
Drawn at base of breccia of the Coolbeg Breccia Formation where it rests unconformably on turbidites of the Tullykevin Formation.
County Down, Northern Ireland.
Breccia containing greywacke, sandstone and mudstone set in a sandy matrix. Red-brown buff and white sandstone and red-brown silstone.
About 320 m thick.
Drawn at conformable upward passage from sandstone of the Kennel Sandstone Formation to breccia of the Newforte Breccia Formation.
Ennerdale Intrusion, Granophyre [Obsolete Code: Use Enin + Rock Type]
ENN
Ennerdale Intrusion, Microdiorite [Obsolete Code: Use Enin + Rock Type]
ENNR
Esha Ness Sedimentary Rocks
ENS
Enterkin Mudstone Formation
ENT
Brigantian to early Pendleian.
Northern part of the Thornhill Basin, Enterkin Burn, River Nith, Starn Burn.
Reddened fossiliferous marine mudstone, sandstone and seatearth.
Esha Ness Volcanic Formation
ENV
East Ogwell Limestone Formation
EOL
Eocene To Miocene Rocks (Undifferentiated)
EOMIO
Eocene To Pliocene Rocks (Undifferentiated)
EOPC
Edmondia Punctatella Bed
Emley Rock
West Yorkshire area [Emley, Yorkshire].
The Emley Rock is a fine-grained flaggy sandstone with mudstone partings.
Ercall Granophyre
ERCL
Shropshire, Welsh Borders.
Granophyric granite.
Not applicable: unconformably overlain by Lower Cambrian sandstones.
Erwan Fach Formation
ERFA
Ernan-Glass Metabasic Swarm
ERGL
Eglwys Rhobell Formation
ERL
Erlend Basalts
ERLBA
FAROE-SHETLAND BASIN
Erlend Acid-Intermediate Intrusives
ERLI
Glacial Erratic (Parent Rock Unspecified)
ERRA
Variable lithology. A glacially transported rock whose lithology shows it could not have been eroded from the local 'country' rocks. [Generic description].
Errol Clay Formation
ERRCL
Unconformable, draped contact with underlying glaciofluvial sand and gravel or till.
East coast and firths of Scotland from Berwick-upon-Tweed to Inverness.
Massive to thinly bedded and coarsely laminated calcareous, silty and sandy clay interbedded with sand, commonly forming a fining-upwards sequence. Generally reddish brown, but locally brownish and yellowish grey or pale to dark grey. Streaks and mottling of dark grey to black sulphide are common and calcareous concretions occur towards the base locally. Contains a sparse glaciomarine fauna.
To at least 12m
Overlain conformably at the type section by dark grey clay of the Powgavie Clay Formation.
Errington Member
ERRM
Eriboll Formation
ERSA
Defined where a thin conglomerate at the base of the Basal Quartzite Member lies above an angular unconformity and oversteps both the Complex and the Torridon Group
The Eriboll Formation forms a narrow belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt, Dundonnell, Kinlochewe and Kishorn, to Skye
Predominantly quartz arenite and quartzite with a thin basal conglomerate. Comprises a lower unit (Basal Quartzite Member) and an upper unit containing abundant Skolithos burrows (Pipe Rock Member).
From 150 m - 225 m thick.
Defined at the boundary with the overlying Fucoid Beds Member of the Ant-Sron Formation
Erskine Clay Member
ERSK
The Erskine Clay Member of the Clydebank Clay Formation rests with angular unconformity on older Quaternary sediments or on bedrock. It is known to rest unconformably on the Inverleven Gravel Member of the Clyde Clay Formation and possible disconformably on the Endrick Sand Member of the Strathendrick Formation (Clyde Catchments Subgroup).
The Erskine Clay Member of the Clydebank Clay Formation is recognised in the lower Clyde valley and in the estuary of the Clyde, and in Loch Lomond.
The typical lithology is of very silty clay with sand and silt laminae and bands. The deposit is generally brownish grey of greyish brown and contains sulphide. The sand and silt is ripple-laminated in places. Isolated cobbles and gravel are present, and organic debris is also to be found. The deposit is of firm to soft consistency and medium plasticity.
Veneer to more than 4m
The Erskine Clay Member of the Clydebank Clay Formation is overlain by younger Quaternary sediments, normally the Gourock Sand Member. It is also exposed at the surface in the lower Clyde valley.
Earthy Coal (Lancashire)
ERTY
Eryry Glacigenic Formation
ERYG
Elgol Sandstone Formation
ESA
Late Bajocian to Early Bathonian.
Easton Seven Feet Coal (Bristol Area)
ESFC
Eskdale Intrusion, Granodiorite [Obsolete Code: Use Esk + Rock Type]
ESGD
Eskdale Intrusion, Microgranite [Obsolete Code: Use Esk + Rock Type]
ESGM
Eskdale Intrusion, Granite [Obsolete Code: Use Esk + Rock Type]
ESGR
Eglinton Shelly Till Member
ESHTI
Sharp, unconformable, planar to gently undulating contact with dark brown, laminated organic silt and clay of the Sourlie Organic Silt Formation.
Pinkish brown, very stiff, pebbly sandy silty clay diamicton containing clasts of local sandstone, mudstone, coal and dolerite, far travelled sedimentary, igneous and metamorphic rocks and shell fragments, including sparse paired valves of marine molluscs yielding Late Devensian amino acid ratios. (Described as being similar to the shelly lodgement tills of Ayrshire, but probably a deformation till).
To 3.5m
Sharp, convex-up, undulose unconformity with overlying dark grey silty sandy stony clay diamicton of the Auchenwinsey Till Member.
Enfield Silt Member
ESI
Rests on river terrace deposits.
Lea Valley tributary of Thames. North London, Sheet 256.
Varies from silt to clay, commonly yellow-brown and massive. [Generic description].
1 to 5m, average 2m in thickness.
Eskdale Intrusions
ESK
Two sheet-like masses of granite and granodiorite cropping out over 53 and 23 sq. km respectively, and intruded into the Skiddaw Group and the Borrowale Volcanic Group.
Corney Fell to Wasdale, western Lake District.
A pink, medium-grained muscovite granite, aphyric and porphyritic microgranite, coarse-grained granite, medium-grained granodiorite, microgranodiorite, biotite-rich granodiorite, and quartz-mica greisen locally containing topaz and quartz-andalusite rock associated with granite. The age of the granite is 450 +/- 3 Ma (U-Pb, zircon) (Hughes et al, 1996)
Unspecified.
Eskdale Moor Injection Breccia
ESKM
Escrick Moraine Member
ESKRM
Not exposed. The Escrick moraine is generally resting in older glaciolacustrine deposits of the Heminbrough Glaciolacustrine Formation. The contact between these two deposits can be irregular and glaciotectonised.
The limites of this Member are defined by the morphological limits of the Escrick Moraine from Stillingfleet in the west past Elvington towards Stamford Bridge in the north.
Mainly greyish brown to yellowish brown, poorly sorted, gravelly sandy clay to slightly gravelly clay matrix with a little, ranging to much, gravel and cobbles (Morainic Till).
Up to 20 to 30m recorded in borehole SE44SE/364 and 18.4m in borehole SE44SE/356; in type section it is up to 13.4m thickand in all boreholes the deposit rests on thin laminated clay belonging to underlying Heminbrough Glaciolacustrine Formation.
Not exposed, or the present land surface. The unit is overlain locally by younger fluvial and aeolian deposits.
Eskett Limestone Formation
ESKT
The base of the Sixth Limestone Member, at the base of the lowest significant limestone bed above the mudstone, at the top of the underlying Seventh Limestone Formation.
West and North Cumbria between Whitehaven and Penrith. The western limit is the truncation below the Permo-Triassic basal unconformity. The Eastern limit is taken at the Kirk Rigg Fault along the line of the A66 highway, west of Penrith (McCormack, 2001).
Limestone with thin interbeds of sandstone, siltstone, mudstone, bentonitic mudstone and seatearth mudstone.
From 100m to 150m
The top of the First/Great Limestone Member, marked by a succession from thick-bedded limestone to mudstone and sandstone of the Hensingham Grit Member.
Ellery Syke Limestone
ESL
Esk Pike Sandstone Formation
ESP
Base of bedded volcaniclastic sedimentary rock sequence, unconformably overlying Lincomb Tarns Tuff Formation (dacitic lapilli-tuff).
Esk Pike - Great End - Alton Crags; Easdale, Helvellyn, Scandale, Grisedale and Hartsop Dodd, Cumbria.
In Type Area, laminated volcaniclastic mudstone and siltstone ("hornstone") with interbeds of volcaniclastic sandstone and eutaxitic lapilli tuff. Becoming massive bedded volcaniclastic sandstone with intercalations of volcaniclastic breccia, tuff and lapilli-tuff to the east.
170m in Central Fells, reaching 200m in the Helvellyn area
Not seen in Type Area, but around Hellvellyn it is defined by the base of various overlying formations, including the Middle Dodd Dacite, Deepdale and Helvellyn formations.
Essie Till Formation
ESTI
Sharp uncomformable, undulating contact with Hatton Till Formation or bedrock, or gradational, planar, glacitectonic contact with laminated silt and clay of the Ugie Clay Formation. At partial type section NK05SE 1 the unit unconformably overlies unnamed greenish grey sand and gravel, which in turn rests on olive brown diamicton of the Hythie Till Formation.
Buchan, northeast Scotland, between Peterhead and Fraserburgh, on sheets 97 and 87E.
Pebbly sandy silty clay diamicton, calcareous, dark bluish grey but mottled orangey brown near top, and dark greenish grey at depth, containing well-dispersed clasts of red granite, quartzite and schistose metasediments, and sparse fragments of shell, red marl, red sandstone and chalk. The unit locally includes rafts of red clayey diamicton and black fossiliferous mudstone. Commonly including a lower unit that is dark reddish brown.
To 10m.
Generally sharp, erosional with overlying glaciofluvial or alluvial sand and gravel or ground surface.
East Stayvoyage Vein
ESV
Eathie Beds
ETB
Edge Hill Eleven Foot And Three Foot Coals (New Cumnock Area)
ETC
Etruria Formation, Halesowen Formation And Salop Formation (Undifferentiated)
ETHS
Earlswood Till
ETIL
Eighteen Inch Coal (Cumbria)
ETIN
Etive Dyke Swarm
ETIVD
Etive Pluton
ETIVE
Etruria Formation
ETM
Passage by alternation from grey mudstones of the Pennine Coal Measures Group to red, purple mudstone of the Etruria Formation. Locally, in Shropshire, Warwickshire and Lincolnshire, the lower boundary is an unconformity (Symon Unconformity).
English Midlands, Lancashire, Yorkshire and North Wales.
Red, purple, brown, ochreous, green, grey and commonly mottled mudstone, with lenticular greenish-grey, referred to as 'espleys', common pedogenic horizons, but coal seams are rare.
Up to about 300 m thick in the type area.
Overlain conformably by predominantly grey sandstone and mudstone strata of the Halesowen Formation, although locally, in South Staffordshire the upper boundary is an unconformity.
Etive Rhyolite Member
ETRH
Ettrick Group
ETRK
Llandovery: guerichi Biozone to spiralis Biozone.
Conformable sedimentary contact with the Moffat Shale Group.
Southern uplands. Scotland.
Interbedded turbidite (wacke) sandstone and mudstone/siltstone. Sandstone typically fine- to medium-grained but ranging from very fine- to coarse-grained; generally medium- to very thick-bedded (commonly up to 2m) over thicknesses of tens of metres interspersed with units up to a few metres very thin to thin-bedded. Units of coarse-grained, massive sandstone tens of metres in thickness occur locally in parts of the group. Except in the latter, interbedded siltstone or silty mudstone is generally present in thin to medium beds. A basal massive siltstone unit a few metres thick at transition from underlying Moffat Shale Group. Sandstone and siltstone are typically greenish grey when fresh, pale brown weathering. Distinguished from the Gala Group to the north by the well-bedded character and relatively high proportion of interbedded mudstone. Other distinguishing factors include the younger age range, abundant garnet in coarse-grained sandstone and relatively low Sr and Ni content in whole rock sandstone composition. Distinguished from Hawick Group to the south by the common occurrence of thick to very thick beds of sandstone, abundant garnet in coarse-grained sandstone and paler, less pervasive weathering reflecting relatively low carbonate content of the sandstone.
Uncertain, likely to be several km.
Faulted, none preserved.
Eastertown Siltstone Member
ETS
Conformable lower contacts with sandstones in Nairnside Sandstone Formation.
Grey and green laminated siltstones and mudstones.
+ 50 metres.
Conformable upper contacts with sandstones in Nairnside Sandstone Formation.
Etwall Sand And Gravel Member
ETSG
Middle Pleistocene (MI Stage 8). Formerly stated to be Wolstonian in the original Informal Lexicon entry by A Brandon, 26/01/1998. The chronology is based in its position above the Eggington Common Member and below the assumed Eagle Moor Member.
Occurs as outliers on the north bank of the Trent in the Type Area (Sheet 141); thought to be present upstream, particularly on the north bank of the Dove downstream of Uttoxeter (Sheet 140) and probably elsewhere. (e.g. on the south bank of the Trent near Alrewas, Sheet 154) but the extent is uncertain pending resurvey.
Predominantly cold-phase sands and gravels that underlie the Etwall Terrace. Intensely cryoturbated, decalcified poorly sorted sand and gravel, dominated by rounded pebbles of "Bunter" quartz/quartzite (typically c.80%) with subordinate subangular flint (up to c.20%), Carboniferous chert, sandstone, etc. Fragmentary terrace surface appears to be c.20m above the Trent floodplain in the type area. The upper part locally includes a rubified palaeosol (Hykeham Soil; Ipswichian). The Member is correlated with the Ockbrook Sand and Gravel Member (Trent Valley Formation) and Knighton Sand and Gravel Member (Soar Valley Formation).
0 to c.3m
Etive Formation
ETVE
Edge Hill Twelve Foot Coal (New Cumnock Area)
ETWC
Eight-Yard Limestone
ETYL
Eureka Coal (South Derbyshire)
EUC
Eycott Volcanic Group
EVG
Taken at the base of volcanic rocks overlying mudstones of Skiddaw Group; in parts defined by base of Overwater Formation. Angular unconformity seen in some localities (Millward and Molyneux, 1992); elsewhere proved from biostratigraphical evidence from underlying Skiddaw Group.
Bothel-Binsey-Brae Fell-Caldbeck Fells; Eycott Hill; Greystoke Park (BGS 1:50k sheets 23, 24, 29); Melmerby Fell (Cross Fell Inlier) (BGS 1:50k sheet 24), Cumbria.
Medium-K continental-margin type basalt-andesite-rhyolite volcanic association, transtional between tholeiitic and calc-alkaline affinities. Comprises porphyritic basalt, basaltic andesite, andesite and dacite lava flows and sills with intercalated volcaniclastic deposits, comprising tuff, lapilli-tuff, breccia, conglomerate and volcaniclastic sedimentary rocks.
To 3200m
Unconformity with overlying Carboniferous strata.
Ehen Valley Sand And Gravel Member
EVSG
At its type site a gradational contact on to the Ehen Valley Silt Member of the Seascale Glacigenic Formation. Elsewhere it overlies either the Catgill Wood Sand and Gravel Member, which is typified by rounded cobbles of red (Permian) and yellow (Carboniferous) sandstone, or the Low Wath Till Member of the Seascale Glacigenic Formation.
On 50k Sheets 28 (Whitehaven) and 37 (Gosforth).
Pale yellowish brown fine- to medium-grained quartzose sand, which coarsens upwards into pebbly sand and then into gravel. Coal debris is a common component and microfaults, shears and cracks (lined with reddish brown silt and clay) are characteristic of its upper few metres. It forms part of the infill of the buried valleys of the Ehen, Calder and lower Uldale. Cross-lamination within the sand indicates that it was deposited by southward directed braided outwash streams on sandur, probably during the deglaciation of the main Late Devensian ice sheet.
Typically between 9.0 and 30m
Generally unconformably overlain by diamictons of the Roythersyke Till Member of the Gosforth Glacigenic Formation.
Ehen Valley Silt Member
EVSI
At its type site conformable on the Catgill Wood Sand and Gravel Member of the Seascale Glacigenic Formation, elsewhere conformable with diamictons of the Low Wath Till Member of the Seascale Glacigenic Formation.
Very fine-grained sand, silt and clay, greyish brown to dark grey, typically fines downwards and contains much finely disseminated coal debris; generally thickly laminated. Thin diamictons present in thick silt sequences recorded in boreholes. It forms part of the infill of the buried valleys of the Ehen Calder and Lower Uldale and was laid down principally in a glaciolacustrine environment, probably during the deglaciation of the main Late Devensian ice sheet.
8.7m exposed at its type section; 21.25m thick in reference section (Nirex borehole QBH 21; BGS registered borehole NY01SW 602).
At its type site a gradational contact into the Ehen Valley Sand and Gravel Member of the Seascale Glacigenic Formation. Elsewhere it is conformably overlain by diamictons of the Rothersyke Till Member of the Gosforth Glacigenic Formation.
Ellwand Slate
EWD
Eemian To Weichselian Diamicton, Firm To Hard (Offshore)
EWDFH
Eemian To Weichselian Gravel (Offshore)
EWGRV
Earthwork Sandstone
EWKS
8 to 12m
Eelwell Limestone Member
EWL
Taken at the generally conformable, sharp base of the first bed of limestone that overlies measures of the Alston Formation, typically sandstone.
Widespread limestone member within the Alston Formation, occurring throughout the Northumberland Trough in northern England and the Scottish Borders, lying stratigraphically below the Three Yard Limestone and above the Oxford Limestone. This definition incorporates its correlated unit in the Langholm and Bewcastle areas of the Scottish Border region, the Harelawhill Limestone.
Limestone, massive, grey, bioclastic, generally devoid of mudstone partings; typically rich in algal remains with a prominent fauna of brachiopods and corals; appreciably dolomitized in part, giving a brown-weathered and vuggy appearance.
5 to 10m
Taken at the top of the uppermost limestone bed that is overlain by a sequence of dark grey mudstones and siltstones, containing ironstone nodules locally.
Eemian To Weichselian Sand And Gravel, Interebedded (Offshore)
EWMAS
Eemian To Weichselian Mud, Firm To Hard (Offshore)
EWMFH
Eemian To Weichselian Sand (Offshore)
EWSND
Ewingston Sill
EWTON
Excelsior Coal (Leicestershire)
Exeter Group
EXE
Basal formations in Crediton Trough (Cadbury Breccia, Upton Formation, Bow Breccia, Knowle Sandstone) rest unconformably on Bude or Crackington formations. Around and south-west of Exeter, basal formations (Dawlish Sandstone, Whipton Formation, Knowle Sandstone) rest unconformably on Crackington Formation. See definitions of component formations.
From Torbay in the south, north through Newton Abbot to Exeter; all New Red Sandstone strata in the Crediton Trough and probably the Tiverton Trough.
Component formations are predominantly breccia, with subordinate sandstone. All formations are alluvial fan deposits.
At least 700m.
Unconformably overlain by Aylesbeare Mudstone Group.
Extensus Flags
EXF
Exceat Flint
EXFL
Exmoor Group
EXM
North Devon and west Somerset. (SS 80 40).
Grey mudstones with subordinate thin- to medium-bedded siltstones, sandstones and a few limestones. The Group is punctuated by three sandstone-dominated formations. The lower two are predominantly red, purple green and grey sandstones with minor conglomerates and trace mudstones. The upper one is interbedded grey to buff sandstones, siltstones and mudstones.
The upper boundary is taken at the incoming of hard black finely laminated unfossiliferous and silty mudstones of the Teign Valley Group (Doddiscombe Formation) above the soft mid to dark grey mudstones with scattered very thin fossiliferous limestones, siltstones and sandstones of the underlying Exmoor Group (Pilton Mudstone Formation).
Exhall Sandstone
EXSA
Elwy Formation
Base succeeds ribbon banded mudstones of the Nantglyn Flags Formation.
Disturbed beds, striped silty mudstones and subordinate sandstones with lateral facies changes.
>1750 metres.
Unconformably overlain by Carboniferous Limestone.
80 Yard Band Coal
EYBC
80 Yard Band Coal (West Yorkshire)
EYC
The Eighty Yard Band Coal is thin but widespread in its development. It is of no economic importance although it is associated with seatearth fireclay around Elland and Brighouse.
Eype Clay Member
EYCL
Base of Three Tiers Sandstone. Sharp boundary on mudstone of Green Ammonite Member.
Pale grey, micaceous, variably silty mudstone with many small siderite nodules. At base, Three Tiers Sandstone, c.7m thick, consisting of three units each 0.5 to 1m thick of very fine-grained sandstone, separated by sandy shale.
60m
Base of Starfish Bed (Downcliff Sand Member).
Eyebroughty Vent
EYEBY
Eyford Member
EYF
Base of limestone/sandstones as described in lithology, resting on fissile mudstone of underlying un-named unit of Fuller's Earth Formation.
Chedworth area, Gloucestershire (where it passes westwards into mudstone of the Fuller's Earth), eastwards to the Burford area, Oxon (where it passes into the Charlbury Formation).
Pale grey, fissile, finely ooidal grainstone interbedded with grey, laminated fissile calcareous sandstone, locally decalcified to loose orange-brown sand, with minor beds of shelly and shell-fragmental limestone, marl or fissile mudstone.
0 to 7m; 6 to7m in type section.
Sharp generally erosive base of coarse-grained ooidal grainstone of Taynton Limestone Formation.
Eyam Limestone Formation
EYL
Dark grey to grey brown basal limestone, resting upon clay or mudstone partings of the Eyam Limestone Formation, on a potholed surface above pale to medium grey limestone of the Monsal Dale Limestone Formation. Around Ashford-in-the-Water [SK 19 69], where both formations are dark grey, the boundary is taken at the top of the laminated beds of the Monsal Dale Limestone Formation.
The Peak District of the East Midlands.
A thinly bedded, dark grey, cherty, bioclastic limestone with fossiliferous beds of brachiopods, corals and crinoids and a few dark mudstone intercalations, which is overlain by massive pale reef limestone in the south. The reef facies occur at the base in the central and southern parts, and in the upper part in the north, and is typically a core of massive biomicrite with a distinctive brachiopod fauna, passing laterally and downward into well-bedded, coarsely crinoidal biomicrites and biosparites.
At Eyam Dale, 54 m thick including 30 m of reef facies; at Wardlow Mires No 2 borehole, it is 9.18 m, and contains no reef facies.
A gradational top, marked by a transition from dark grey, bioclastic limestone or pale grey massive reef limestone of the Eyam Limestone, to dark grey, calcareous mudstone of the Widmerpool Formation.
Eyam Limestones Formation (Flat-Reef)
EYLF
Eyam Limestones Formation (Knoll-Reef)
EYLK
Eyemouth Vent
EYMO
Eynort Mudstone Formation
EYNM
80 Yard Rock
EYR
The Eighty Yard Rock is a thin, fine-grained flaggy sandstone widespread throughout the West Yorkshire district.
Generally c.10m, locally to c.40m
Eyemouth Volcanic Formation
EYVO
At White Heugh, south of St Abb's Head, where the lavas overlie the 'Bell Hill sediments' of the Great Conglomerate Formation and north-west of Coldingham, unconformably overlying Silurian strata.
Between Eyemouth and St Abb's Head.
Olivine-phyric basaltic lavas, basaltic andesites and andesites with interbeds of tuff and tuffaceous rocks, and rare dacite or rhyodacite.
From 500 to 600 m thick.
The top of the basaltic to andesitic lavas, below the Auchencrow Burn Sandstone Formation.
Fachwen Formation
Comley?
Unconformity on ash-flow tuffs of the Padarn Tuff Formation (Arfon Group).
Conglomerates, sandstones and thin volcanic tuffs at base passing up into siltstones and sandstones.
40 - 50 m thick.
Overlain conformably by mudstones of the Llanberis Slates Formation.
Farrington Member And Barren Red Member (Undifferentiated)
FABR
Fallowhill Coal
FAC
Fluvio-Aeolian Deposits
FAEOL
Fan Gravel
FAG
Coarse sand and gravel; deposited in an alluvial fan; bedded limestone gravel in the Moreton-in-Marsh area. [Generic description: earth science dictionaries in the BGS library].
Fairmilehead Volcanic Member
FAI
Not seen: faulted against andesite lavas of the Carnethy Volcanic Member.
Bounded on the south by the fault running parallel to the Edinburgh City bypass (NT 242 676-260 671); on the north a fault and by the overlying Braid Hills Member (NT 250 692-264 690) and on the east and west by unconformably overlying Kinneswood Formation rocks (NT 242 676-242 694 and NT 260 671-264 690).
A varied succession of pryroxene and hornblende andesites and biotite trachytes, with olivine basalt flows at the top, and beds of andesitic and rhyolitic tuff.
At least 430m: succession disrupted by faulting.
At the possibly unconformable base of the Braid Hills Member, which is marked by an inpersistent bed of basaltic tuff between olivine basalt of the Fairmilehead Member and trachyte of the Braid Hills Member.
Fair Sandstone Unit
FAIR
Faroe-Shetland Basin
Farlough Coal
FALC
Farlington Marls (One)
FAMA1
Farlington Marls (Two)
FAMA2
Fachwen Formation And Minfford Formation (Undifferentiated)
FAMI
Fankerton Limestone
FANK
Local name in the Stirlingshire area, particularly at Fankerton, near Denny.
Single bed of crinoidal limestone or, locally, two limestone beds separated by bluish shaly mudstone.
c.0.6 to 1.5m
Fanad Pluton
FANP
Rb-Sr whole rock 402 +/- 10 Ma (O'Connor et al., 1987).
Ffernant Formation
FANT
Rests unconformably on cleaved and folded Silirian rocks (Elwy Formation).
West side of the Vale of Clwyd (SH 8976) and in the Dyserth area, (SJ 0678) North Wales.
Red,purple and variegated silty mudstones, siltstones and sandstones with lenticular bodies of conglomerate. Breccias dominantly composed of weathered Lower Palaezoic mudstone clasts occur at base. The silty mudstones locally display glaebular calcrete profiles including abundant calcareous nodules and thin units of nodular locally dolomitised limestone. The formation records the accumulation, within palaeovalleys and embayments, of screes and alluvial sediments during the initial phases of Dinantian transgression, prior to the establishment of carbonate platform conditions of the Clwyd Limestone Group.
To 330m
Sharp, erosive contact with limestones at the base of the Llanarmon Limestone Formation (Clwyd Limestone Group).
Faunal Organic Deposits
FAORG
Faraday Road Member
FAR
Faulted out.
Plymouth area, 50k geological sheets 348/349.
Thin, sharp and erosively based, dark grey, commonly foetid crinoidal packstone intercalated with calcareous mudstone or argillaceous, fine-grained wackestone. In type area, 50m of grey-green, basaltic tuffaceous mudstone is present at the top.
Not known, part of reef deposit.
Conformably succeeded by grey slaty calcareous mudstone of the Prince Rock Member.
Farigaig Formation
FARG
Far House Member
FARH
At the top of the last red mudstone of the Hebblethwaite Member or (where this Member is absent) where laminated mudstone gives way to massive mudstone.
Across the Howgill Fells and Lake District.
Pale grey mudstone, massive.
About 8m in the Howgill Fells, 2-10m regionally.
At the base of the lowest unit of thinly laminated silty mudstone of the Brathay Formation.
Farm Coal (South Wales)
FARM
Faroes Province
FAROE
Faroe Plateau Basalts
FAROP
Fairlie Sandstone Formation
FAS
A transitional boundary drawn at the base of the white or cream sandstones of the Fairlie Sandstone Formation where it rests conformably on the red-brown sandstones of the Kelly Burn Sandstone Formation.
East of the Largs Fault Zone, Strathclyde, Scotland, sheets 29, 21, 22W.
White or cream, fine-grained, cross-bedded and finely laminated sandstones with beds of cross-bedded sandstone containing quartz pebbles.
Approximately 300 m thick.
Drawn at the unconformity from the white or cream sandstones of the Fairlie Sandstone Formation to the lava of the Clyde Plateau Volcanic Formation, or locally the Kinnesswood Formation.
Four Ashes Sand And Gravel Formation
FASG
Sharp erosional and unconformable on bedrock (Sherwood Sandstone Group).
Four Ashes, Staffordshire and the immediate surrounding area.
Gravel with organic-rich horizons of peat and grey, peaty clay. Gravel is dominantly well-rounded sandstone derived from the Sherwood Sandstone Group.
0.45 to 4.6m
Either the ground surface or sharp contact with lower surface of red, sandy gravelly clay of the Stockport Glacigenic Formation.
Farragon Volcanic Formation
FAVO
Base of dominantly fine-grained amphibolitic succession overlying the Ben Lawers Schist Formation.
Farragon Hill area to Glen Shee.
Hornblende schist, fine-grained with layers and lenses of hornblende psammite. Interfingers with the Ben Lawers Schist Formation in the east of outcrop and locally with intercalated psammite in the upper parts of the Formation.
Generally 200 to 300m, although thicker in the Ben Vrackie area [NN 94 63].
Gradational boundary with Ben Lui Schist Formation located where psammite and semipelite become the dominant lithology.
Falfield Beds
Fulletby Beds
FBB
See Roach Formation.
Fore Burn Complex
FBC
Southwest Scotland.
A series of approximately concordant microdiorite and tonalite sheets, sills or small stocks intruded into an Early Devonian succession of lavas, tuffs and sandstones. Intrusion breccias form a series of pipes along a fault zone. The whole complex has experienced widespread tourmalinisation.
Fish Bed Formation
FBD
Base of lowest grey sandstone bed above the reddish mudstones of the underlying Dovestone Redbeds. The sandstone may be stained red or brown.
Lower Palaeozoic inlier of the Hagshaw Hills, Scotland, (50k Sheets 23W, 23E and 15W).
Greenish-grey silty mudstones and siltstones with interbedded fine-grained sandstone beds to 1m thick. The siltstones are laminated and have some small-scale cross-bedding.
58m
Upper surface of highest greyish-coloured sandstone or siltstone below the overlying reddish mudstones of the Gully Redbed Formation; transitional.
Fireclay Balls Ironstone (South Staffordshire)
FBI
Fireclay Balls Ironstone
FBIR
Fireach Beag Kyanite Gneiss Member
FBKY
Friars Bay Marls (One)
FBMA1
Friars Bay Marls (Two)
FBMA2
Friars Bay Marls (Three)
FBMA3
Farrington Member, Barren Red Member, Radstock Member And Publow Member (Undifferentiated)
FBRP
Findern Clay
Top of bedrock at base of Elvaston palaeochannel; Oadby Till intervenes locally.
Elvaston palaeochannel, Derbyshire.
Clay and silt, partly laminated, with dropstones; minor sand and gravel.
To 19m
Either base of overlying river terrace sand and gravel, base of overlying Oadby Till or present day land surface.
Fireclay Coal
FCC
Fireclay Coal (Birmingham)
FCCB
Fungous Coal (Coalbrookdale)
FCCC
Foughill Complex Dolerites
FCD
Frome Clay And Fullers Earth (Undifferentiated) [Obsolete Code: Use Fefr]
FCFE
Fireclay Group Of Coals (North Wales)
FCGC
Flitchity Psammite Formation
FCHY
Flamborough Chalk Formation
FCK
Top of highest flint band of underlying thick, flint-rich unit of chalk (ie. Burnham Formation); in type section this is the High Stacks Flint but elsewhere may be at a somewhat different horizon.
East Yorkshire and north-east Lincolnshire, Flamborough Head to Grimsby area (see Sumbler, M G, 1999, Fig.1).
White, well-bedded, flint-free chalk with common marl seams (typically about one per metre). Common stylolitic surfaces and pyrite nodules. Formal subdivision: None herein. Divided into three members by Whitham (1993) that are in ascending order the South Landing Member, Danes Dyke Member and the Sewerby Member. There are many named marls units of bed status.
Up to about 265m (onshore); basal c.160m exposed in type section.
Base of lowest flint of succeeding thick, flint-rich unit (ie. Rowe Formation).
Fireclay Coal (Cumbria)
FCLY
Fairy Cave Mudstone Member
FCM
Sharp limestone/mudstone junction, underlain by the Pant Limestone Member.
Black argillaceous limestone and mudstone.
1.7 metres.
Sharp limestone/mudstone junction, overlain by the White Orr Limestone Member.
Finavon Conglomerate Member
FCO
The Finavon Conglomerate was originally thought to conformably overlie the Melgund Formation (Armstrong and Paterson, 1970, p.14), however, it has since been determined to be a lens-shaped body within the Tannadice Sandstone Member, rendering the Melgund Sandstone Member superfluous.
The Forfar Brechin area. At Den of Dun, east-north-east of Brechin, the Finavon Conglomerate lies directly on the highest fine-grained member of the Dundee Flagstone Formation, on Sheets 57W, 57E.
The Finavon Conglomerate Member forms a conglomeratic lens within the Tannadice Sandstone Member, which (Armstrong and Paterson, 1970, p.14) considered to be the top of a conglomerate body locally marking the base of the Tannadice Sandstone Member.
Flint Coal Rock
FCR
Ferricrete
FCRET
Five Clouds Sandstones
FCS
The lower boundary is taken at the base of a thickly bedded sandstone overlying grey mudstone of undivided Millstone Grit Group in the Upper Hulme Stream Section (SK06SW/14); the precise nature of the boundary is not recorded.
Danesridge, Staffordshire [SJ 96 65] to Stanley Moor, Derbyshire [SK 04 71].
Sandstone, pale brown to pink, coarse-grained, thickly bedded and massive, feldspathic, with ferruginous concretions and scattered mudstone clasts, and subordinate mudstone beds.
At least 81.6m (the total thickness has not been proven; 81.6m is the maximum proving for the unit).
The upper boundary is taken at the base of the first mudstone-dominated succession of undivided Millstone Grit Group overlying the Five Clouds Sandstones; the precise nature of the boundary is not recorded.
Fireclay Coal (South Staffordshire)
FCYC
Fascally Siltstone Member
FCYSI
Brora area, eastern Scotland.
c.34m
Ferder Formation
Lower boundary is a marked unconformity with "channeling" up to 50 metres deep. In places erosion has removed all Quaternary material below this reflector.
Pebbly and shelly, sandy silty clay to clayey silty sand. Stiff to very stiff, possibly till. Shell fragments common at top, middle and base of unit, sand and clay partings are common. Less sandy than underlying Mariner Formation, geotechnically stronger than overlying Cape Shore Formation.
50 metres. Thins to south and west. Thickens to north and east on the North Sea Plateau and may be 200 metres or more in the northern part of the Norwegian Trench.
The upper boundary is unconformable with Holocene sand at the sea bed or apparently conformable/disconformable below the Cape Shore Formation.
Firedamp Coal (North Wales)
FDC
Flaggy Delf Coal (South Lancashire)
FDCO
Forest Of Deer Pluton
FDER
Findhorn Pluton
FDHN
Central and northern Monadhliath Highlands, Strath Dearn. In the Tomatin (sheet 74W) and Fortrose (sheet 84W) districts.
Pluton composed of 3 main facies of grey to pink-grey, medium to coarse-grained granodiorite and monzogranite, abundant enclaves of metasediment. Minor small bodies of green-grey diorite and monzodiorite. Aplitic microgranite veins.
Findhorn Pluton, Phase 1
FDHN1
Findhorn Pluton, Phase 2
FDHN2
Findhorn Pluton, Phase 3
FDHN3
Fordell Marine Band
FDMB
Farden Member
FDN
Succeeds the largely unbedded siltstones and mudstones of the Lady Burn Formation.
Greyish-green well-bedded silty mudstones with thinly bedded greenish-black fine- to medium-grained sandstones in the upper part. Includes the 3 very fossiliferous Lady Burn Starfish beds (STFB) (A_C) near the top of the member.
c.40m.
Succeeded by bluish grey soft nodular mudstones of the Cliff Member of the South Threave Formation.
Faringdon Sand Formation
FDNS
Foel Ddu Rhyodacite Formation
FDR
Overlies Penmaen Tuff Formation comprising lava flows and tuffs of intermediate composition, plus associated sediments.
Rhyodacitic lavas and tuffs.
<100m to >250m
Overlain by crystal-lithic tuffs with variable characteristics, of the Carneddol Rhyolitic Tuff Formation.
Fiddler Shell Bed
FDSB
Widely developed over the southeastern part of the Scottich Central Coalfield basin.
Interbedded calcareous shaly mudstones and impure limestones.
Fuller's Earth Formation
In the northeast Cotswolds, passage up from fine- to medium-grained ooid-grainstone of the Chipping Norton Limestone Formation (Great Oolite Group) into silicate-mudstone, or (Cotswolds to the English Channel) generally sharp, commonly non-sequential, junction between predominantly coarse-grained peloidal, ooidal and shell-fragmental limestones or (St George's Channel) calcareous sandstone of the Inferior Oolite Group overlain by silicate-mudstone.
Onshore: Dorset coast to the Burford area, Oxfordshire. Through the mid Cotswolds, the Upper Fuller's Earth passes north into various limestone formations (see e.g. Wyatt, 1996). In subcrop, widespread in the Wessex Basin. Offshore: English Channel - Celtic Sea - St George's Channel basins.
Silicate-mudstone, grey, bedded, variably calcareous, grading to lime-mudstone, fossiliferous, with units of thinly interbedded, more or less silici-muddy limestone (including the Fuller's Earth Rock Member, Dodington Ash Rock Member), and well-bedded sandy limestone and calcareous sandstone (including the Eyford Member and Througham Member). Where the Fuller's Earth Rock Member is present, the mudstone beds below and above are termed the Lower Fuller's Earth Member and Upper Fuller's Earth Member respectively, and parts of these may be given local names (see separate entries). The commercial fuller's earth bed occurs in the upper part of the formation in the Bath area. In the English Channel Basin the formation is predominantly mudstone with carbonaceous material at some levels and shell beds. In the St George's Channel Basin it is predominantly mudstone but includes calcareous sandstone beds.
Compilers' notes: As with most units, it is difficult to define this formation in simple 'Lexicon' terms. For example it is hard to include the Fuller's Earth Rock Member but exclude the Frome Clay Formation when defining boundaries in essentially lithological terms - it all depends on context. Having said that, there is a case that the Lower and Upper Fuller's Earth[s] should be separate formations, likewise the Fuller's Earth Rock. If attempted, logically, the UFE should retain the name, as that is where the commercial fuller's earth lies, but this would mean there is no Fuller's Earth in the north Cotswolds! Regrettably there are no good exposures of this unit, and so the cited sections are boreholes (M G Sumbler 25/9/05). The offshore succession and boundaries are relatively poorly known (G K Lott, 2008).
5 to over 260m (thickest in the Wessex Basin area). Offshore: generally over 100 to 300m in the English Channel (Hamblin et al., 1992) (Barton et al., 2008), up to 300m in the Celtic Sea-St George's Channel (Tappin et al., 1994).
Generally sharp, commonly non-sequential, junction between variably calcareous silicate-mudstone, and limestones of overlying parts of Great Oolite Group: including (from Bath south to Dorset and in the English Channel) fossiliferous limestones of the Wattonensis Beds of the Frome Clay Formation, and (northeast of Bath) ooidal and shell-fragmental limestones, including the Chalfield Oolite Formation, Athelstan Oolite Formation, Taynton Limestone Formation, or fine-grained limestone of the Tresham Rock Formation.
Feal Intrusion
FEAL
Fearnaght Formation
FEAR
Fearn Pluton
FEARN
Fishburn Estheria Band
FEB
First Ell Coal (Nottingham And Derby)
FEC
Four Foot Earth Fireclay
FEFC
Fullers Earth Formation And Frome Clay Formation (Undifferentiated)
FEFR
Fen Gravel
FEG
Rests unconformably on bedrock or on older (mostly glacial) Quaternary deposits.
Exposed intermittently at the margins of Fenland in Lincolnshire, Northamptonshire, Huntingdonshire, Cambridgeshire, Suffolk and Norfolk, especially at the western and southern margins. Presumed widespread at depth within Fenland. As used, includes the distal portions of river terrace systems entering Fenland, but by implication excludes parts of the same river systems outside Fenland. It is therefore not a valid lithostratigraphical division, but seems a useful term to retain in the broad sense of Skertchly (1877).
Sands and gravels (including pebbly sands and sandy gravels), some clayey or silty with some silts and clays. The distal (seaward) portions include marine shells.
0 to c.10m
Contact with pebbly, silty, sandy clays and clayey sands of the Crowland Bed (Booth, 1982), or unconformably overlain by Flandrian deposits. In the absence of the Crowland Bed, the distal portions of the Fen Gravel may not be separable from the lowest Flandrian deposits.
Fells Limestone
FEL
Eastern part of the Midland Valley.
Grey or locally cream limestone with spirorbids and ostracods.
c.0.6 to c.1.2m
False Ell Coal (Derby)
FELC
Fell Sandstone Formation
FELL
Locally unconformable, diachronous base on range of Lower Carboniferous strata, locally defined as base of Whitberry Marine Bed [onshore areas].
Onshore limits include the Tweed Basin and northern part of the Northumberland-Solway Basin from Burnmouth, Berwickshire in the northeast to Southerness, Kirkcudbrightshire in the southwest.
Medium- to thick-bedded, fine- to coarse-grained cross-bedded sandstone, locally conglomeratic, with siltstone, mudstone, seatearth and locally developed thin coals and limestones [onshore areas].
c.530m maximum [onshore areas]
Locally unconformable, diachronous, at base of Clattering Marine Bed, Kingsbridge Limestone or Glencartholm Volcanic Member of the Tyne Limestone Formation [onshore areas].
Felmersham Member
FELM
Fluviatile gravel with sand.
0 to 3m
Ground surface, or at base of overlying alluvium.
Fence Conglomerate Member
FEN
Sharp incoming of conglomerate belonging to the Fence Conglomerate Member above the predominantly mudstone member of the Carmichael Burn Formation
Greenish grey conglomerate with small, mainly igneous, but also chert and quartzite pebbles in a coarse-grained sandstone matrix.
Top of the conglomerate beds belonging to the Fence Conglomerate Member overlain by brownish grey sandstones of the Newside Arenite Member of the Westgate Formation.
Fenton Coal (West And South Yorkshire)
FENC
Fenland Formation
FEND
Unconformable of glacial deposits and upon Jurassic and Cretaceous bedrock.
The Fens of Cambridgeshire and Lincolnshire, and continuing along the coast of Lincolnshire as far as Humberston near Cleethorpes.
Formation encompasses the marine, estuarine and terrestial deposits that were formed in the Fens and adjacent areas during the Holocene and previous interglacial periods. The complex includes fresh and brackish water peats, salt marsh clays, fluvial silts and fine-grained sands, marine sands, and beach-face sands and gravels. In centre of the Fen Basin, five stratigraphical units are present. In ascending order these are basal sand and gravel, the Fen Lower Peat, Barroway Drove Beds, Nordelph Peat and Terrington Beds. Barroway Drove Beds comprise intertidal soft grey clays and silty clays cut by tidal channels and creeks infilled with silt and fine-grained sand. Terrington Beds comprise marine and brackish water silts and fine-grained sands. Marine sands and gravels marginal to the Fen Basin are the Woodstone Member (silty clays and fine sands), the March Gravel Member (sandy gravel to clayey pebbly sand) and the Abbey Sand and Gravel Member (clayey, sandy gravels).
Fenwick Limestone (Northumberland)
FENL
Fen Peat
FENPT
Feorlin Sandstone Formation
FEOR
Fuller's Earth Rock Member
FER
A rapid upward transition from calcareous mudstones of the Lower Fuller's Earth Member into shelly, muddy limestone by increase of shell-detritus.
Bath area and southern Cotswolds to central Dorset.
Bioturbated argillaceous limestones and calcareous mudstones with an abundant Ornithellid fauna.
Typically 5 to 7m in North Dorset, locally 11m, thin or absent in west and south Dorset, 3 to 5m in Bath-Frome area; 5.25m in type section.
Decrease of shell-detritus into calcareous mudstones of the Upper Fuller's Earth Member.
Fen Silt
FES
Freshney Sandstone Member
FESA
Fells Shale
FESH
West Lothian.
A formerly productive bed of oil-shale.
c.2m
Feshiebridge Psammite Formation
FESP
Not interpreted to date but taken as the top of the Ord Ban Subgroup (Sheet 74E), where the semipelite, metacarbonate, calc-silicate, quartzite and amphibolite succession is overlain by interbedded psammite, semipelite and pelite belonging to the Feshiebridge Psammite Formation.
Northeast of Kingussie - Moor of Feshie
Graded psammite, laminated psammite and micaceous psammite with bands of semipelite to pelite. Interpreted as an originally turbiditic succession.
possibly 0.5 to 2km
Incoming of the predominantly semipelite succession at the base of the Falls of Phones Semipelite Formation, above the interbedded psammite and pelite succession of the Feshiebridge Psammite Formation
Fethaland Metagabbro
FETHG
Frances Extra Coal
FEX
48 Yard Band Coal (West Yorkshire)
FEYC
The Forty-eight Yard Band Coal is a thin coal of low quality, but has been worked north of Halifax.
48 Yard Rock
FEYR
The Forty-Eight Yard Rock is a fine-grained, thinly bedded, impersistent sandstone.
Ffestiniog Flags Formation
Conformable and transitional, with the Maentwrog Formation. Marked by change in colour from pale to dark grey in mudstones, and an increase in sandstone.
Regular alternatives of quartzose siltstone and sandstone in beds up to 2m thick, interbedded with silty mudstone; abundant sedimentary structures.
475 to 1020m
Conformably overlain by mudstones of the Dolgellau Formation. Sharp contact locally.
Ferguslie Fireclay
FFC
Five-Foot Coal (Tranent)
FFCO
Four Feet Coal (Titterstone Clee)
FFCTC
Ffairfach Grit Formation
FFG
In the type area, the formation rests upon black, micaceous, graptolitic mudstones of the Abergwilli Formation (formerly known as Didymograptus bifidus Beds). The lower boundary is taken at the incoming of beds of indurated, medium-grained arkosic sandstone, which gradually pass up into massive sandstone (Williams, 1952). The contact is not exposed, but a near complete section is preserved in railway cuttings, small quarries, and in the banks of the River Cennen just south of the village of Ffairfach (Ordovician GCR).
The Ffairfach Grits Formation principally crops out on the southern flank of the Tywi valley, south of the town of Llandeilo in Carmarthenshire. It is preserved in the hinges and on the limbs of a northeast trending series of tectonically disrupted anticlines and synclines between Golden Grove in the southwest and Rhyd-y-saint in the northeast. The Ffaifach Grits also form a thin unit exposed to the north of the Tywi in Dynefor Park.
The Ffairfach Grits Formation comprises massive, pink-weathering, medium- to coarse-grained arkosic sandstone with scattered, impersistent pebbly horizons with felsic tuff and rhyolite locally developed toward the top of the Formation.
To 160m
The Formation is overlain by fossiliferous, buff weathering, thinly interbedded fine-grained sandstone, silty calcareous mudstone and limestone of the Llandeilo Flags Formation. The contact between the two formations is not exposed and has been argued as being disconformable (Bergstrom et al., 1987). The most intact section across the boundary is preserved in the railway cutting south of Ffairfach, which has also been taken as the type section for the Llandeilo Flags Formation itself (Rushton et al., 1999).
Four Fathom Limestone Member
FFL
Taken at the generally conformable, sharp base of the first bed of limestone that overlies measures of the Alston Formation. On the Alston Block, usually overlies less than 2m of dark grey seatearth mudstone and mudstone with abundant plants that overlies as a prominent sandstone referred to there as the Natrass Gill Hazle. In the Bellingham district a coal underlies the limestone.
Occurs throughout northern England and the Scottish borders, lying below the Great Limestone near the top of the Alston Formation.
Limestone, packstone, fine-grained, medium and dark grey, thick bedded and wavy-bedded, with few mudstone partings; somewhat argillaceous, particularly at the top. Typically contains layers of nodules and lenses of black chert. Crinoidal but not particularly fossiliferous on the Alston Block; contains conspicuous coral biostromes to the north and south of the Alston Block. Goniatites indicative of the P2c biozone have been found in mudstones above the Four Fathom Limestone in the Mount Pleasant Borehole [NZ034 152] near Barnard Castle (Johnson et al, 1962).
7-10m north of the Lake District and in Northumberland; 5 to 12m on the Alston Block; about 9m on the Askrigg Block, but locally up to 25m.
Taken at the top of the uppermost limestone bed that is overlain by a sequence of dark grey mudstones, the lowermost of which are calcareous and fossiliferous. On the Askrigg Block the limestone member is overlain by a dark grey or almost black chert referred to as the Underset Chert.
Flagstaff Limestone Formation
FFLF
Fen Farm Limestones Bed
FFML
Change up from grey, calcareous mudstone of the undifferentiated Granby Member; at 58.14m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands; north Leicestershire to Lincolnshire. Not recognised in north Lincolnshire, or south Leicestershire, where it passes south into part of the more argillaceous and less bioclastic Rugby Limestone Member of the Blue Lias Formation (Ambrose, 2001).
Group of about three thin (0.1 to 0.3m) limestone beds, separated by up to 0.5m of calcareous mudstone beds. Limestones are bioclastic packstone/grainstone, shelly, grey, weathering pale orange brown. Fauna includes bivalves, echinoderms, ammonites, corals and the trace fossil Kulindrichnus. Whole Gryphaea shells and crinoid (Pentacrinus) debis abundant on the outcrop. Forms a strong feature with a broad dip slope.
1.39m in type section; up to 2m in Leicestershire.
Change up into bluish grey, shaly mudstone of the undifferentiated Buckingham Member; at 56.75m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Fron Frys Formation
FFR
Overlies mudstones of the Laundry Mudstones Formation.
Central and northeast Wales.
Mudstones and siltstones.
Overlain by pale green-grey mudstones of the Dolgau Mudstones Formation.
Ffinnant Sandstone Formation
FFSA
Five Feet Coal (Leicestershire)
FFTC
Foel Fras Volcanic Complex
FFV
Overlies mudstones of the Nant Ffrancon Subgroup and locally on the Foel Grach Basalt and Braich Tu Du Formation. Interdigitates with the Conwy Rhyolite Formation.
Foel Fras (8km west-north-west of Dolgarrog), south-west to Nant Ffrancon.
Trachyandesite lavas, tuffs and intrusions. Tuffs may be reworked, massive and welded, or bedded and unwelded.
About 1000m. Outflow much thinner, of the order 100m.
Underlies siltstones of the Nant Ffrancon Subgroup.
Four Foot Coal (Wyre Forest)
FFWF
Foel Grach Basalt Formation
FGB
Rests on part of the Nant Ffrancon Subgroup and locally on the Braich Tu Du Volcanic Formation.
Carnedd Llewelyn to Carnedd Dafydd.
Basalt and basalt breccias.
400m in north; c.180m to the south.
Overlain by outflow of the Foel Fras Volcanic Complex and by part of the Nant Ffrancon Subgroup.
Foughill Complex Granophyres
FGCG
Fluvioglacial Deposits
FGD
Gravel, sand, silt, clay or peat, bedded or chaotic; of glaciofluvial origin. [Generic description].
Fluvioglacial Gravel
FGG
Sand and gravel, locally with silt and clay lenses, of glaciofluvial origin. [Generic description].
Foel Gron Granophyric Microgranite
FGGM
Fine-grained aplitic microgranite.
Fogger Reef Limestone
FGL
Local to the area around Fogger (Fogga) near Bell Busk, Yorkshire.
Poorly bedded porcellanous and "tuffaceous"-appearing limestones with associated contemoraneous breccias/conglomerates.
Forge Sandstone
FGS
The Coatbridge - Baillieston district, east of Glasgow.
c.17m
Fresgoe Sandstone Member
FGSA
Overlies a thinly interbedded, sandstone-dominated rhythmic sequence of sandstones, siltstones and laminated carbonate mudstones (fish beds) of the Bighouse Formation.
A thickly bedded, cross-stratified, pale grey to pale yellow, medium-grained sandstone. The unit represents the first thick sandstone in a generally more thinly-bedded sequence. It is consequently a mappable unit. It is a notable reflector in seismic sections and a marker horizon in borehole cores, marking the top of the Bighouse Formation in the Dounreay area.
The base of the overlying Sandside Bay Formation, which displays a cyclic depositional sequence dominated by sandstones, with thicker well-developed carbonate laminated mudstones (fish beds).
Ffridd Graig-Wen Formation
FGW
Forth Formation
In the Tay-Forth area (1:250,000 Sheet 56 deg. north, 4 deg. west) the Forth Formation generally rests unconformably on the St Abbs/Wee Bankie Formations or rockhead. Locally it may rest conformably on the St Abbs Formation. Further east in the Marr Bank/Devil's Hole areas (56 deg. north, 2 deg. west, + 56 deg.) the unit may form an infill to deep erosive channels hence resting unconformably on the pre-existing sediments.
Varies from muds and silty muds to sands and gravelly sands. The former muddy lithologies tend to occur mainly in the lower part of the sequence. NOTE: In this area (56 deg north, 3 deg west + 56 deg north, 4 deg west) it has been possible to subdivide the formation into two members (see attached sheets). Unfortunately, although this unit can be extended over a wide area of the west central North Sea, it has not beeen possible to subdivide the unit elsewhere without present knowledge.
Varies from < 5 metres - 60 metres.
Top of unit is unconformably overlain by seabed sediments.
St Andrews Bay Member
FHA
Base of unit unconformably overlies all pre-existing sediments.
Varies from pebbly muddy sands, and silty muds to interlaminated silts and muds.
c.23 metres.
Top of unit unconformably overlain by seabed sediments.
Fitzroy Member
FHF
Basal erosion surface dissects most quaternary formations in the area.
Soft clay and silty clay often with black sulphide laminae and dropstones: significantly less consolidated than underlying sediments.
49.5 metres - variable - as the infill of erosive features.
Upper surface is irregular, overlain by Whitehorn Member of the Forth Formation.
Flathill Flint
FHFL
Largo Bay Member
FHG
Generally rests unconformably on the St Abbs Formation although locally it may be conformable.
Interbedded, soft to firm, grey muds and silty muds, and dark grey-brown silts, with rare small pebbles.
c.16 metres.
Top of unit has been eroded and these sediments are unconformably overlain by the St Andrew's Bay Member.
Froghall Ironstone
FHI
Restricted to the Cheadle Coalfield.
Flat Holm Limestone Member
FHL
Taken at the sharp erosive contact of the massive to thick-bedded pale grey skeletal and ooidal limestones of the Flatholm Limestone Member and the thin- to medium-bedded dolomite and calcite mudstones and mudstones of the underlying Caswell Bay Mudstone Formation.
Flat Holm Island [ST 22 64], South Wales.
Dark grey, medium-bedded skeletal limestones with thick-bedded, locally cross-bedded, commonly ooidal limestones at base. Units of interbedded dolomite mudstone, dolomite siltstone and mudstone punctuate the succession. Deposited as a transgressive barrier and offshore shelf sequence.
31m
Taken at the top of the uppermost unit of the interbedded dolomite mudstone, dolomite siltstone and mudstone of the Member, which is overlain by massive to thick-bedded pale grey skeletal and ooidal limestones of the remaining part of the High Tor Limestone Formation.
Fourth Hosie Limestone
FHLS
Faraday House Shell Bed Marine Band
FHMB
Fernham Sand Member
FHMS
Falhouse Rock
FHR
West Yorkshire area [Falhouse, Lower Whitley, Yorkshire].
The Falhouse Rock is a fine-grained, thinly bedded sandstone that forms a number of leaves interbedded with mudstone.
To c.20m, commonly less.
Fair Head Sill
FHS
Whitethorn Member
FHW
Overlies Fitzroy Member of the Forth Formation on irregular erosive surface.
Very fine-grained lithic sand with shell fragments.
11m - reaches up to 30m in deeper features.
Occasionally overlies pre-Forth Formation sediments.
Fourth Waterloo Coal (Nottingham And Derby)
FHWC
Frodingham Ironstone Member
Fittleworth Member
FIB
Incoming of conspicuous clay-rich sands and clays at top of fine-grained to medium-grained 'Bargate Beds' (now Easebourne Member) where present.
From Stedham, West Sussex [SU 86 22] (where the combined Fittleworth Member and Selham Ironshot Sands Member are replaced by the Rogate Member) and probably eastwards to Heath Common (TQ 11 14).
Glauconitic sandy clays and clayey sands: orange-brown where weathered; bright green where not. From Stedham, West Sussex (SU 6 22) to east of Selham, West Sussex (SU 94 20), about 9km, the Fittleworth Member is divided by the Selham Ironshot Sands Member. Samuel (1994) proposed that the upper division (c.2m thick) be named the 'Upper Fittleworth Member', with a corresponding lower division (to c.8m thick), here named the 'Lower Fittleworth Member' (see separate Lexicon entries for these units).
From Stedham to Storrington, incoming of fine-grained well-sorted sands of Pulborough Sandrock; from Storrington eastwards, incoming of silty clay of Marehill Clay Member.
Fibua Formation
FIBU
Finnarts Conglomerate Member
FIC
Lowermost occurrence of pebbles or cobbles in greywackes.
Two lenticular bodies of mainly coarse greywackes with pebbles, cobbles and boulders.
Uppermost occurrence of pebbles, cobbles or boulders in mainly coarse greywacke sequence.
Fionn Choire Formation
FICH
Firth Coal Formation
FICO
Findlater Castle Quartzite Member
FICQ
Sharp change from thinly-banded psammite and semipelite to thick-bedded quartzite.
From coast at Findlater Castle [NJ 5425 6730], as far inland as the A98 road [NJ 531 667]; quartzite units within the Findlater Flag Formation to the southwest of the A98 cannot with confidence be correlated with the Findlater Castle Quartzite Member.
Quartzite, cross-bedded, granular, white; large-scale ripple marks prominent.
c.7m on coast section; possibly 10 to 20m inland.
Top of highest quartzite bed; overlain by flaggy thin-bedded psammite and semipelite.
Fidra Sill
FIDRA
Findlater Flag Formation
FIFL
Base of thinly bedded, flaggy psammites and semipelites above massive or thick-bedded quartzites of the Grampian Group (eg Cullen Quartzite Formation).
1) Newmill (Sheet 85E) and Drybridge (Sheet 95) to coast between Logie Head and Crathie Point (Sheet 96). 2) Core of Ardonald Anticline from SW of Jock's Hill (Sheet 85E) to Ardonald (Sheet 86W). 3) From Rothes Fault at Maggie Knockater to Burn of Mulben (Sheet 85E).
Mainly thinly banded, flaggy, micaceous psammite and semipelite with more dominant semipelite locally.
c. 1350m on coast section; over 400m inland.
Top of non-calcareous flaggy psammites and semipelites that pass upwards into banded calcareous flags of the Pitlurg, Cairnfield or Foddsletter Formations, depending upon locality.
Findon Group
FIG
Drawn at the base of the Findon Group where conglomerate rests conformably upon marl of the Crovie Group.
Gamrie parish, Grampian region.
Coarse conglomerate with a seam of red clay containing fossil fish.
24 metres.
Drawn at the conformable upward passage of the Findon Group from conglomerate and breccia overlain by superficial deposits.
Finsbury Gravel Member
FIGR
Rests unconformably on bedrock geology (London Clay).
Fair Isle Group
FIL
Fintona Group
FIN
Unconformable in the northeast and east on the early Caledonian Tyrone Igneous Complex and the Lower Silurian at Pomeroy. Elsewhere in Fintona Block the contact is faulted.
The Fintona Block, Northern Ireland.
Clastic sediment, red-bed conglomerates, sandstones, siltstones and mudstones; contemporaneous acid volcanic rocks in the lower levels.
Difficult to gauge owing to lack of a distinctive lithostratigraphy. Estimated unreliably as c.3000m in east outcrop (1:50,000 Sheet 34, Pomeroy).
Either not exposed and faulted out, or overlain unconformably by Lower Carboniferous basal clastics and Visean marine sediments on the south side of the Fintona Block.
Fourteen-Inch Coal (Glasgow Area; Central Coalfield)
FINC
Findhorn Formation
FIND
Findon Fish Bed
FINF
Findochty Quartzite Member
FINQ
Not seen; covered by unconformably overlying Devonian rocks.
Along coast section from Buckpool, Buckie [NJ 413 656] to Toshie's Long Craigs [NJ 4970 6835]; cannot be differentiated inland.
Quartzite, thickly- to very thickly-bedded, rarely pebbly, cross-bedding well-developed. Contains thin beds of muscovite-rich and garnetiferous biotitc semipelite.
c.1200m on coast section; cannot be distinguished separately inland.
Fairly sharp change to medium- to thin-bedded quartzite of Logie Head Quartzite Member.
Finglack Till Formation
FINT
Sharp, unconformable, glacitectonic contact with Clava Shelly Formation or with bedrock.
Sheet 84W (Fortrose)
Stiff stony sandy clay diamicton (Lodgement Till), predominantly sandstone clasts.
8m or more
Sharp contact with glaciofluvial sheet deposits, ice contact deposits or moundy glacial deposits.
Finery Coal (South Wales)
FINY
Five Quarters Coal ( Lancashire)
FIQC
Five Quarters Coal (South Wales)
FIQW
Fiery Delf (Lancashire)
FIRD
Fiery Coal (In South Wales Middle Coal Measures Formation)
FIRY
Fisher Formation
FIS
Basal surface is planar overlying Ling Bank Formation.
Very stiff overconsolidated clay, silt and shelly sand. Clay is generally sandy with pebbles of varying origin including chalk.
39.5 metres, varies between ca 50 metres and absent where totally eroded.
Upper surface is irregular, eroded by pre-Forth and Coal Pit Formation erosive phases.
Findhorn Siltstone Unit
FISI
Fiskavaig Formation
FISK
Fishguard Volcanic Group
FIV
Drawn at base of rhyolitic and dacitic lavas of the Porth Maen Melyn Volcanic Formation where it rests conformably on dark mudstones of the Aber Mawr Shale Formation.
Rhyolitic and dacitic lavas, basaltic pillow lavas. Spilitic breccias, acid tuffs and intercalated volcaniclastic sediments. (Correlative of Fishguard Volcanic Group-Llanrian Volcanic Group.
Approx. 1800 metres.
Drawn at conformable upward passage from rhyolitic lavas of the Goodwick Volcanic Formation to dark grey mudstones of the Caerhys Shale.
Fjerritslev Formation
FJEV
Fork Vein Coal (South Wales)
FKVC
Freeland Sand And Gravel Member
Mid Pleistocene (MI Stage 12).
Unconformable, commonly channelled base, resting on Jurassic bedrock or (locally near head of River Evenlode) on Quaternary Wolston Formation.
Upper Thames catchment, ie, River Thames and most tributaries (excluding River Thame, where named equivalents occur) upstream of the Goring Gap. Well-developed in lower Evenlode around the type locality, with sporadic outliers along the course of the Thames elsewhere, particularly in the Nuneham Courtney area [SU 54 97].
Predominantly cold phase sands and gravels that underlie the Freeland Terrace. Dominated by clasts of "Bunter" quartz/quartzite, typically with sporadic ironstone and rare flint, in a sandy loam matrix. Limestone clasts are generally rare probably because of pervasive decalcification. Near Oxford [SP515 014] [probable] equivalents [probably] overlie the organic Sugworth Beds, thought from palaeontology to be "Cromerian" (MIS 13+).
(A) The unit is referred to here as Freeland Sand and Gravel Member though in Bowen (1999), and in previous BGS use, it was simply Freeland Member. (B) Following the "traditional" view, this unit was placed in the Northern Drift Formation by Bowen, 1999 (i.e. (?)Kesgrave Formation of the current scheme). However, Sumbler (2001) showed that it is the oldest unit of the [Upper] Thames Valley Formation. In fact few would dispute this because, even before 2001, this was generally accepted (e.g. Hey, 1986; Whiteman, 1992; Bridgland, 1994; in fact most except Gibbard) as the correlative of the Black Park of the Middle Thames. As this is essentially an Anglian outwash terrace, even then it was accepted implicitly that the Freeland postdated the truncation of the extended proto-Thames ?Northern Drift or Kesgrave River?. (C) Terrace surface is some 40m above modern (Evenlode) alluvial floodplain at the type locality, diminishing somewhat upstream. (D) The upper boundary is given as ?ground surface? though head, colluvium or soil deposits may intervene. (E) Apart from at the type locality, recognition of this terrace is based on elevation, and in some areas (notably on Sheet 236, 253 and 254) the mapping is suspect. Prior to Sumbler 2001, the outcrops now recognized in the Upper Evenlode (Sheet 235, 218) were included in ?Moreton Drift? and there is indeed a component of glaciofluvial outwash there.
0 to c.4m, typically <2m
Flatt Coal
FLA
Fladdabister Limestone (?Formation)
FLAD
The subdivisions of the Quarff Succession and Melange are tectonic units consisting of Dalradian metasedimentary rocks that cannot be allocated to one of the main groups.
Fletcher Bank Grit
FLB
The lower boundary is taken in the Fletcher Bank Borehole at the base of a sandstone dominated sequence overlying a mudstone-dominated succession of the Millstone Grit Group.
Southern Pennines, Manchester [SJ 8398] to Clitheroe [SD 7441], west of the Pennine Anticline. Appears with several codesused on the same mapsheet as: E68, GG RV; E75, FB Rv; E76, Rv FB GG, E85, GG.
Sandstone and pebbly sandstone, coarse-grained with angular grains, with quartz and quartzite pebbles, massive and current-bedded, and subordinate beds of mudstone and coal.
110.97 m is the maximum measured thickness [SD81SW/3], allthough the bottom was not proved.
The upper boundary is taken at the base of a mudstone-dominated succession overlying sandstones of the Fletcher Bank Grit; often coincident with the base of an unnamed coal.
Flex Coal (Lothian)
FLC
Field Coal (South Wales)
FLDC
Fluvial Diatomite
FLDI
Soft siliceous deposit, consisting mainly of opaline diatom frustules; of fluvial origin. [Generic description: 'TMOS' Procedures].
Fladen Group
FLDN
Fleetwood Dyke Group
FLDY
Flett Formation
FLET
Flags Formation
FLG
Upper limit : seabed.
Very soft, soft to firm sandy/silty clays or muddy sands often laminated, usually olive to dark grey and containing sulphides. The laminae show coarsening upwards sequences. Pockmarks identified on seismic records in some areas.
3.4 metres +. Up to 15 metres on seismic sections.
Lower limit : Ferder, Mariner and Shackleton Formation beneath an unconformity which may be ice scoured.
Fleming Hall Tuff Formation
FLH
Taken at the base of the sequence of homogeneous, thick, generally lithic - poorly welded tuffs, above the Brown Bank Ignimbrite Formation, which is composed of thinner sheets of lithic-rich andesite and rhyolitic lapilli tuff. Locally a coarse lithic-rich lag-breccia occurs at the base of the lowest member.
Crops out east of Gosforth, Cumbria, as far as the Thistleton Fault (Lake District Boundary Fault). Also proved in Sellafield boreholes 2 (NY 00SE/28), 4 (NY00SE/29), 5 (NY00SE/30), 10A (NY00SW/38), 11A (NY00SE/34), 12A (NY00SW/39); RCF1 (NY00SE/35), RCF2 (NY00SE/36), RCF3 (NY00SE/37), RCM3 (NY00SE/39), PRZ1 (NY00SE/45), PRZ2 (NY00SE/44) and PRZ3 (NY00SE/42).
Andesitic tuff and lapilli-tuff (eutaxitic to parataxitic). At least three welded ignimbrite sheets, locally separated by thin beds of sandstone. Side Farm Member comprises poorly sorted beds of lapilli-tuff and pyroclastic breccia.
403m in type section; 506m in Sellafield BH No.4 (NY00SE/29). Thicknesses are incomplete and uncorrected for dip, as boreholes deviated from vertical.
Not seen, but mapped at the change from densely welded tuff to a mixed sequence of lithic-rich tuff and parataxitic tuff of the Loweray Formation.
Fourlaws Limestone
FLL
Northumberland; type area around Fourlaws.
Crinoidal limestone.
c.3.5m
Foel Formation, Llanarmon Formation And Loggerheads Limestone Formation (Undifferentiated) (Knoll-Reef)
FLLK
Foel Formation, Llanarmon Formation And Loggerheads Limestone Formation (Undifferentiated)
FLLL
Fletcher Bank Grit And Midgley Grit (Undifferentiated)
FLMI
Flanders Moss Peat Formation
FLMP
Unconformable base on various local members of the Forth Clay Formation, Wilderness Till Formation (Main Late Devensian) and bedrock; also transitional base on clay gyttja and laterally passing into laminated minerogenic sediments of the Carse Clay Formation.
Surface and buried peats in the Forth (from east of Aberfoyle). Earn (from Dalreoch Bridge eastwards) and Tay (eastwards from just north of Perth) valleys and Forth, Eden and Tay estuaries, Montrose basin areas. (Theoretically many members may be set up to reflect localised developments of peat).
Peat, fine- and coarse-textured, dark to pale brown and locally orange, with wood fragments and a wide variety of organic remains also including Sphagnum; wedges laterally in some areas into laminated minerogenic sediments of the Carse Clay Formation.
Veneer at least 7m
At surface or overlain partly unconformably by Holocene transgressive estuarine sand, silt and clay of the Carse Clay Formation including the Letham Silt Member and the Carse of Stirling Clay Member.
Fulmar Formation
FLMR
Flounder Formation
FLND
Floral Organic Deposits
FLORG
Flodigarry Shale Member
FLOS
Fen Lower Peat
FLPT
Peat. [Generic description].
Flying Reed Coal
FLRC
Filltirgerig Beds
FLT
Flatts Coal (North Staffordshire)
FLTC
Flichity Semipelite Formation
FLTY
Unknown contacts either unexposed or tectonised. No way-up criteria.
Central Highlands of Scotland. Strathnairn to Findhorn area.
Gneissose semipelite with minor quartzites, more common near contacts with adjacent units.
Transitional boundary with structurally overlying Flitchity Psammite. No way-up criteria.
Flugga Sandstone Member
FLUS
Fluvial Deposits
FLUV
Fleswick Anhydrite
FLWA
Fleswick Dolomite
FLWD
Lower Flaxley Beds
FLXL
Upper Flaxley Beds
FLXU
Folly Coal (Milford, South Wales)
FLYC
Fauldhead Musselband
Forest Marble Formation
FMB
South Midlands and Cotswold region: base of silicate-mudstone, greenish grey, or limestone, typically grey to brown variably sandy medium to coarsely bioclastic grainstone or packstone, resting with erosive, commonly channelled, disconformity on white to yellow, peloidal, ooidal or lime mud-rich, less silici-muddy limestone of the White Limestone Formation or the Chalfield Oolite Formation, or on a bored and oyster-encrusted hardground surface of the ooidal limestone of the Athelstan Oolite Formation. South of the Mendip Hills: marked by the Boueti Bed, a fossiliferous lime-mudstone, resting non-sequentially on olive-grey bioturbated mudstone of the Frome Clay Formation (formerly Upper Fuller's Earth).
Onshore: Buckingham area (where either overstepped by the Cornbrash Formation or passes into the Blisworth Clay Formation) to the Weymouth area, Dorset Coast. Present at depth in the Weald. Offshore: English Channel, Bristol Channel, St George's Channel.
Silicate-mudstone, greenish grey, variably calcareous and in the south notably sandy, with lenticular typically cross-bedded limestone units that form banks and channel-fills, especially in lower part. A variety of limestone types occur, of which grey, weathering brown and flaggy, variably sandy medium to coarsely bioclastic grainstone or less commonly packstone predominates, especially at the base, which is increasingly ooidal north from Bath (termed the Acton Turville Beds from Biddestone to Didmarton). Other types include fissile sandy limestone, grading to calcareous sandstone, and oyster-limestone. South of the Mendip Hills, a silici-muddy, fossiliferous lime-mudstone (Boueti Bed) lies at the base. Bivalves and brachiopods dominate the fauna, and lignite debris and fish scales and teeth are common, but infauna and signs of bioturbation are rare. The formation consists of interbedded mudstone and limestone in the Weald and English Channel basins, but in St George's Channel Basin it comprises rhythmically bedded mudstone, siltstone and fine sandstone.
Up to 5m thick in Buckinghamshire, 10 to 30m in Oxfordshire and Gloucestershire, 30 to about 50m in north Dorset, 30 to 75m in south Dorset and the English Channel (Hamblin et al., 1992)(Barton et al., 2008), St George's Channel 242m proved (Tappin et al., 1994)
Generally mudstone in the upper part of the Formation, overlain sharply and non-sequentially by ooidal shelly wackestone/packstone of the Cornbrash Formation.
Finnie's Main Coal
FMC
Forest Marble Formation And Cornbrash Formation (Undifferentiated)
FMCB
Fairbottom Coal (South Lancashire)
FMCO
Felsenmeer
FMEER
Forden Mudstone Formation
FMF
Ford Formation
FML
The incoming of oolitic and pisolitic or reef equivalent dolostone above the fine-grained dolostone of the Raisby Formation. Boundary is transgressive, overlapping older Permian formations to lie unconformably on Carboniferous rocks.
Durham province, County Durham, Tyne and Wear, Cleveland and northernmost North Yorkshire.
Dolomite that comprises three distinct facies: shelf-edge reef that separates a broad belt of back-reef and lagoonal beds to the west from a belt of fore-reef talus aprons and off-reef beds to the east.
1 - 150m, generally 100 - 120m
Either the sharp, conformable base of the overlying anhydrites of the Hartlepool Anhydrite Formation or the reddish-brown mudstone and siltstone of the Edlington Formation
Ford Formation (Patch-Reef)
FMLP
Ford Formation (Shelf-Edge Reef)
FMLS
Foulport Mudstone Member
FMN
Conformable on the underlying Doughend Sandstone Member and marked by a change from yellow sandstone with a few concretionary nodules to red-brown mudstone and siltstone of the Foulport Mudstone Member (Monro, 1999; BGS, In preparation).
Cumbrae Islands in Strathclyde, Scotland. Unit shown on S21W and part of 21E Irvine, in press [FMN], S29E and part 21E, Dunoon and Millport, in preparation [FMN].
A reddish-brown silty mudstone with a few sandstones and beds with nodules of pedogenic limestone.
About 200m
Conformable and overlain by variegated sandstones with concretions of the West Bay Cornstone Member.
Fontmell Magna Sand Member
FMS
Upward change from sandy clay into sand.
A limited area around Fontmell Magna, Dorset (ST 867 170).
Fine-grained, clayey, weakly calcareous sand and sandstone.
Upward change from sand into sandy clay.
Fife Ness Formation
FNB
The conformable base of the Formation lies in a lithological transition and is taken above the highest bed of carbonate conglomerate belonging to the underlying Clyde Sandstone Formation (formerly Balcomie Beds).
Predominantly of sandstones arranged in upward-fining cycles; argillaceous rocks are commonly poorly bedded: mainly fluvial in origin.
Maximum thickness exceeds 230m in east Fife.
Not known at outcrop: would be taken at the lithological change to the relatively mudstone/sitlstone-rich cyclical deposits of the overlying Anstruther Formation from the sandstone dominated sequences of the Fife Ness Formation.
Fence Member
FNC
Basal member of the Doularg Formation: succeeds the sandstone, pebbly grit and conglomerate of the Craigmalloch Formation.
Mudstone (unfossiliferous to date).
1.5m seen, possibly up to 4m total.
Succeeded by the Gorse Member of the Doularg Formation, consisting of poorly-bedded mudstone with decalcified limestone nodules containing a brachiopod and trilobite fauna.
Fenton Limestone Bed
FNTL
Change up from grey mudstone of undifferentiated Foston Member; at 27.10m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands; north Leicestershire to Lincolnshire. Not recognised in the Scunthorpe Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into either part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or part of the mudstone dominated Charmouth Mudstone Formation.
Hard, olive grey, brown weathering, finely sandy (especially in the north), silty, bioclastic, fine-grained limestone, in one or locally two beds, with small ammonites and pectiniids. Fauna also includes forams, serpulids, brachiopods, other bivalves, ostracods and echinoderms. Forms a weak feature.
0.3 to 1.0m; 0.34m in type section
Change up into grey mudstone of undifferentiated Foston Member; at 26.76m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Flockton Coal (Undifferentiated) (West Yorkshire)
FNUC
Folkestone Formation
Contact of sand or sandstone with underlying silty clay or clayey silt of Marehill Clay Member (Sandgate Formation) or with heterogeneous sequence of clays, silts and sands (Sandgate Formation, undifferentiated).
West Sussex and SE Hampshire; otherwise circum-Weald.
In Sussex: medium- and coarse-grained, well-sorted cross-bedded sands and weakly cemented sandstones; elsewhere includes calcareous sandstones.
In general; upward disappearance of sand at base of Gault Clay but typically at base of short condensed sequence at base of Gault. In Sussex, base of 'Iron Grit' (hard, pebbly, limonitic, coarse-grained sandstone) (see Casey, 1961).
Fochabers Sandstone Formation
FOC
At top of the Spey Conglomerate Formation, the essentially conglomeratic sequence at the base of the Old Red Sandstone succession in the Fochabers area.
Red-bed sandstones with sporadic silty calcareous mudstones with fossil fish-bearing limestones/concretions.
Approximately 100m
At diachronous base of the Findhorn Sandstone Group in the Fochabers area where it is marked by yellow to reddish brown fossiliferous sandstones, containing fish, of the Alves-Scaat Craig Beds.
Forth Clay Formation
FOCL
Early Windermere Interstadial to Early Holocene.
Generally transitional, locally unconformable on the Errol Clay Formation or on glaciofluvial deposits; locally overlies bedrock.
River Tay from just northwest of Perth and the Earn from Forgandenny eastwards, and adjacent to the Tay/Earn estuaries; some of the units might occur in the Eden and Montrose basins. Also the River Forth east of Aberfoyle, the Forth estuary and the Firth of Forth.
Clay, silt and sand with sporadic dropstones. For details of lithologies see entries for constituent members.
In the Tay-Earn and Eden-Montrose basins the formation comprises the Powgavie Clay, Culfargie Sand and Tay-Earn Gravels members. In the Forth area, the formation is represented by the Kinneil Kerse Silt, Abbotsgrange Silt and Bothkennar Gravel Members.
Veneer to >38m
Unconformable top related to marine transgression and regression and associated erosion, overlain by members of the Carse Clay Formation (the Carey Silt and Carse of Gowrie Clay members in the Tay area, the Letham Silt, Carse of Stirling Clay and Claret Clay members in the Forth area), or by the Flanders Moss Peat Formation (the sub-Carse Peat).
Foot Coal (Milford, South Wales)
FOCO
Fodderletter Calcareous Flag Formation
FODD
Fordon Evaporite [Obsolete Code: Use Foev]
FOE
Fordon Evaporite Formation
FOEV
In the Durham province: contact (gradational transition) with the underlying Roker Formation (including the Concretionary Limestone Member) dolostone, marked by the incoming of evaporite rocks. In the Yorkshire province:contact with the top of the Kirkham Abbey Formation dolostone, the incoming of evaporite rocks.
Zechstein Basin of Northeast England.
A thick and varied sequence of evaporites including anhydrite and halite, with some gypsum and dolostone. Passes laterally into Seaham Residue at outcrop in Durham, and into part of Edlington Formation in Yorkshire outcrop.
396m in type section; thins to small residue at outcrop.
Drawn at base of Brotherton Formation (Yorkshire province) or Seaham Formation (Durham province], marked by the incoming of limestone.(Stated as base of Upper Magnesian Limestone in Smith, et al., 1974).
Foel Formation
FOF
Late Chadian.
Locally conformably overlies reddened "Basement Beds" (Ffernant Formation or Penbedw Formation); but elsewhere rests unconformably on Silurian rocks of the Clwydian Range (Nantglyn Flags Formation and Elwy Formation.
Confined to the north and east of the Clwydian Range in northeast Wales, between Moel Hiraddug [SJ0778] and Gelli Gynan. [SJ1854].
Heterolith of dark-grey, peloidal limestones, shelly, oncolitic and locally oolitic limestones, porecllanous limestones, and fossil plant-bearing calcareous siltstones and calcareous sandstones. Limestones locally dolomitised. The oldest exposed parts of the Clwyd Limestone Group, the Foel Formation records peritidal deposition during the onset of the Dinantian transgression of North Wales.
To 88m
Conformable contact with thicker-bedded limestones of the Llanarmon Limestone Formation.
Foggs Coal (South Lancashire)
FOGC
Foul Hosie Limestone
FOHO
Fooden Limestone
FOL
The Clitheroe district, Lancashire.
Dark-blue limestones and shaly mudstones.
Folkeston Coal (Milford, South Wales)
FOLC
Foel Fadian Formation
FOLF
Forest Lodge Member
FOLO
Foyle Marl
FOMA
Fluvial And Older River Sands And Gravels
FORA
Sand and gravel; of fluvial origin; includes modern and historical deposits. [Generic description].
Fluvial And Older River Sands And Gravels With Associated Clay
FORC
Sand and gravel with silt and clay; of fluvial origin; includes modern and historical deposits. [Generic description].
Forth Catchments Subgroup
FORCA
Unconformable contact with units of the Midland Valley, Mearns and Central Grampian Glacigenic subgroups and bedrock.
The present physical catchments of the River Forth and the Firth of Forth. The catchments extend across Stirlingshire, Clackmannanshire, south Fife and the Lothians.
A suite of fluvial (river terrace sand and gravel and alluvium) and related lacustrine (clay, silt) and organic (peat) deposits. The fluvial sand and gravels are derived from bedrock and glacigenic sediments. Clasts are composed of mainly Palaeozoic rocks cropping out in the Midland Valley of Scotland and southern Grampian Highlands. Rock types are principally of Carboniferous and Devonian strata (sandstone, siltstone) with volcanic (basalt) and intrusive igneous rocks (microdiorite) of Midland Valley provenance. Variable but generally minor components of Dalradian metasedimentary and Caledonian intrusive igneous rocks derived from the Grampian Highlands are present.
Generally the ground surface, but units of the subgroup may be overlain locally by mass movement deposits or may locally interfinger with units of the British Coastal Deposits Group.
Fordyce Limestone Formation
FORD
Base of dark pelites and semipelites overlying paler calcareous, banded phyllitic semipelites and psammites of the Tarnash Phyllite and Limestone Formation. (Base not seen in type section.)
Sandend Bay to Mill of Wood Burn, Keith (Sheets 86W, 96W)
Mostly semipelite and pelite with beds of metalimestone, some thick and massive. Minor beds of calc-silicate rock and quartzite.
700m maximum (based on outcrop width and average dip), >160m on coast at Sandend Bay.
Top of dark pelites and semipelites beneath Durn Hill Quartzite Formation. (Top not seen in type or reference sections.)
Forties Sandstone Member
FORS
Foula Sandstone
FOS
Folkestone Formation And Sandgate Formation (Undifferentiated)
FOSA
Folly Sandstone
FOST
Presteigne - Knighton area of mid-Wales.
Forse Till Member
FOTI
Caithness and Sutherland, northeast of a line between Reay and Berridale (1:50 000 sheets 115E and W, 116 E and W and sheet 110)
Diamicton, sandy, silty and clayey, typically dark grey to olive grey and grey brown, often weathered and mottled in the upper parts to orange, brown and yellow, cobble and boulder sized-clasts include Devonian flagstones, Jurassic and Lower Cretaceaous mudstones, siltstones, sandstones and shell fragments together with Moine metamorphic and Caledonian igneous rocks.
The base of the Ellanmore Lower Gelifluctate Member (Hall and Whittington, 1989), which although distinctive, is considered too thin at less than 1m thick, to be formalised as a separate unit.
Foel Tyrch Formation
FOTY
? to Fennian (uppermost Arenig).
Foula Formation
FOUL
Foundered Strata
FOUN
Forth Valley Formation
FOVA
Late Devensian to Holocene.
Recognized in the Forth catchment area as the alluvial deposits of the Forth and all its tributaries, from highest to lowest order, includes valleys of the River Tyne (East Lothian), Water of Leith, Almond, Avon, Carron, Devon and Teith.
A wide range of lithologies encompassing pebbles, fine to coarse gravel, cobbles and boulders in a sandy matrix and coarse- to fine-grained sand, silt and clay. Some beds rich in organic remains and peat occur in the floodplain deposits.
Fownhope Formation
FOW
At unconformity at top of the Ordovician Tremadoc, pale grey siltstones and claystones where they are overlain by red beds of the Fownhope Formation. At 3628 feet depth in the Fownhope Borehole.
Proved only in Fownhope Borehole; seismic evidence indicates its presence at depth to the west.
Interbedded red-brown siltstones and sandstones.
1302 feet drilled in Fownhope Borehole; about 370m corrected for dip.
At colour change from red-beds to green-grey siltstones and sandstones of the Huntley Hill Formation. At 2326 feet depth in the Fownhope Borehole, and prominent seismic marker.
Foxholes Coal (South Lancashire)
FOXH
Foyers Igneous Complex
FOY
Foyers Formation
FOYS
Freemanstown Picrite
Fishpool Farm Grits
FPFG
Flood Plain Gravel
FPGR
Gravel and sand, locally with silt and clay interbeds; sheet-like form, restricted to the floodplain environment. [Generic description: 1:50 k map margins].
Falls Of Phones Semipelite Formation
FPHS
Top of the Feshiebridge Psammite Formation (Etteridge Lodge Psammite and Pelite Formation), where interbedded psammite and subordinate semipelite and pelite is overlain by predominantly gneissose biotite-rich semipelite of the Falls of Phones Semipelite Formation.
Southeast of the Ericht-Laidon Fault, south of Newtonmore, extending from Crubenmore to Phones Lodge on Sheet 64W.
Semipelite, mainly gneissose but locally schistose, dominantly biotite- (but subsidiary muscovite-garnet-) bearing, with local lenses of micaceous psammite.
Base of the Gaick Psammite Formation, where predominantly quartzose and feldspathic psammites overlie the predominantly gneissose biotite-rich semipelite of the Falls of Phones Semipelite Formation
First Piper Coal (South Yorkshire, Nottingham And Derby)
FPIC
Friars Point Limestone Formation
FPL
In the Barry area, the base of the Formation is taken at the sharp contact between the crinoidal grainstones of the Yorke Rock Bed that caps the Barry Harbour Limestone Formation, and the overlying thin- to medium-bedded, fine- to coarse-grained, skeletal packstones with scattered thin beds and partings of mudstone of the Friars Point Limestone Formation. North of Barry, the base of the Formation is taken at the sharp junction of the oolitic grainstones of the Brofiscin Oolite Formation and the overlying thin- to medium-bedded skeletal packstones of the Friars Point Limestone Formation. Along the southeast and east crop of the South Wales Coalfield the base is taken at the sharp junction between the dolomitized oolite of the Brofiscin Oolite Formation and the very fine- to fine-grained dolomitised packstones of the Friars Point Limestone Formation.
Vale of Glamorgan [ST 00 74]. Present in Gower [SS 50 90], Pembrokeshire [SM 99 01], east crop of the South Wales Coalfield [ST 25 90], Monmouth/Chepstow [ST 53 93] and Bristol/Mendip [ST 50 65] areas but not mapped. Passes northwards in Wales into the Clydach Valley Subgroup.
Thin- to thick-bedded, dark grey to black, foetid, fine- to coarse-grained skeletal [mainly crinoid] packstones with subordinate thin beds of shaly argillaceous skeletal packstones and mudstone. Widespread burrowing and a lack of tractional structures characterises all but the lowermost part of the formation. The upper part of the formation is dolomitised in the south, while along the southern and eastern crop of the South Wales Coalfield the entire Formation is dolomitised. Formation deposited in a mid ramp enviroment.
410m+ in the south of the Vale of Glamorgan, thinning northwards to 76m on the south crop of the South Wales Coalfield.
The top of the formation is taken at the sharp contact between the dolomitised packstones of the Formation and the overlying oolitic grainstones or dolomitised oolite of the Gully Oolite Formation. In the south the junction appears conformable but in the north a thin red clay overlying a palaeokarstic surface is locally present; in such cases the top is taken at the top of the red clay.
Foul Port Mudstone Member
FPM
Five-Quarter Coal (Northumberland And Durham)
Fisson's Quarry Conglomerate
FQC
River Terrace Deposits, 2 (Frome, Glos)
FR2
River Terrace Deposits, 3 (Frome, Glos)
FR3
River Terrace Deposits, 4 (Frome, Glos)
FR4
Frances Craig Sill
FRAN
Fraserburgh Formation
FRAS
Frome Clay Formation
FRC
The base of the Wattonesis Beds Member, a thin unit (3m) of argillaceous limestones and mudstones, base defined by a increase of shell-detritus in the calcareous mudstone.
Bath, Somerset, to Dorset coast.
Olive-grey mudstone with minor limestone units.
20 to 50m in Wiltshire and Somerset, 45 to 70m in Dorset, 68.1m in Spetisbury Borehole (see References).
The base of the Boueti Bed (Forest Marble Formation) a thin shell-fragmental muddy limestone with abundant Goniorhynchia boueti.
Frith Crag Breccia Member
FRCR
Taken at the base of the unit of tuff-breecia overlying andesite within the Birker Fell Andesite Formation
Restricted to the area between Haweswater and Ralfland Forest, northeastern Lake District, Cumbria
Massive tuff-breccia, matrix- to clast-supported
Up to 160m
Defined by the base of the overlying andesites of the Birker Fell Andesite Formation
Freehay Member
FRE
Where conglomerates become the dominant lithology over sandstone.
Cheadle area, Staffordshire.
Conglomerates with subordinate pebbly sandstones and sporadic mudstone bands.
To 56m
Where conglomerate ceases to predominate over sandstone.
Fremington Member
FREM
Frizington Limestone Formation And Eskett Limestone Formation (Undifferentiated)
FRESK
Farrington Member
FRF
Base of Member taken at the top of the Rudge Vein Coal in the Somerset Coalfield; top of the High Vein Coal in the Bristol Coalfield; top of the Avonmouth No. 2 Coal in the Severn Coalfield. Underlain by sandstones of the Mangotsfield Member and overlain by grey mudstone of the Farrington Member.
Grey mudstone with subordinate sandstone (lithic arenite) beds and numerous thin coal seams associated with comparatively thick seatearth clays.
Up to 425m in the Radstock part of the Somerset Coalfield.
Top of the uppermost coal seam of the Farrington Member, overlain conformably by red and grey measures of the "Barren Red Member".
Fron Fawr Formation
FRFA
?Arundian to Early Asbian.
Rests unconformably on Silurian rocks (Elwy Formation and Dinas Bran Beds).
West of Eglwyseg Rocks escarpment (SJ 22 45), north of Llangollen, North Wales.
Red, purple and variegated silty mudstones, siltstones and sandstones with lenticular conglomerates and basal breccias. The silty mudstones locally display glaebular calcrete profiles including abundant calcareous nodules and thin units of nodular limestone. Records the accumulation of terrestrial scree and alluvial deposits in a fault controlled embayment prior to the establishment of the Clwyd Limestone Group carbonate platform.
Conformable contact with limestones of the Leete Limestone Formation.
Four Feet Coal (Warwickshire)
FRFT
Frog Lane Coal (South Wales)
FRGL
Frogmore Gravel
FRGR
Forster's Hill Limestone
FRH
Frog Hall Member
FRHA
Mid Pleistocene (MI Stages 9 to 8).
Unconformable, channelled base on Wolston Formation or Triassic bedrock.
Confined to immediate vicinity of Stretton-on-Dunsmore, Warwickshire [SP 41 73], largely within a minor un-named tributary of the River Leam ("Alluvial fan gravels" of BGS Sheet 184).
Predominantly cold phase sands and gravels that infill a channel incised, to a level several metres below the Dunsmore Gravel "plateau", into the Wolston Formation and underlying Triassic bedrock and grade southwards into the valley of the River Leam (a principal Avon tributary). Lithologically similar to the Dunsmore Gravel Member (Wolston Formation), being dominated by clasts of Triassic ("Bunter") lithologies and flint, but compositionally more mature, and also containing clasts of ironpan (ferricrete) derived from Dunsmore Gravel. At the type locality it includes organic peaty deposits ("Frog Member") assigned to MIS 9 at base. Probably contemporaneous with the Pershore Member (Avon Valley Formation).
(A) The unit is referred to here as the Frog Hall Member as this is the name used in Bowen 1999. For consistency with other members in this part of the framework it should perhaps be Frog Hall Sand and Gravel Member. (B) The temperate ?Frog Member? (= Frog Hall Bed[s] of manuscripts) is included here in the Frog Hall [Sand and Gravel] Member, though Maddy had this as a member in its own right in Bowen (1999). (C) The upper boundary is given as ?ground surface? though head, colluvium or soil deposits may intervene.
0 to c 9m.
Frigg Sandstone Member
FRIS
Fochriw Coal (South Wales)
FRIWC
Farlow Sandstone Group
FRL
Fourlaws Coal (Northumberland)
FRLC
Northumberland.
Formerly considered to be within the lower part of the Lower Limestone Formation.
Frizington Limestone Formation
FRLI
The lower boundary is generally marked by a disconformity at the top of the underlying Courceyan age Marsett Formation (formerly Basal Beds (Cumbria) Formation), or locally, the Cockermouth Volcanic Formation. The disconformity surface may be identified in borehole records, but in outcrop in West Cumbria, the boundary is conveniently taken at the sharp change from conglomerate, sandstone, mudstone or basalt lava to cross-bedded calc-arenite and limestone. The disconformity represents a depositional hiatus spanning the Chadian and Arundian stages, except in a single instance in the Sellafield area where a few metres of late Chadian strata are preserved below the formation base (Sellafield Borehole No.3, Barclay et al., 1994). In places along the northern margin of the Lakeland fells (Eastwood et al., 1968) the formation oversteps the Marsett Formation and directly overlies Lower Palaeozoic Skiddaw Group or Borrowdale Volcanic Group rocks, and as such, the lower boundary is the base Carboniferous unconformity.
Between Whitehaven and Penrith, in west and north Cumbria, the western limit is truncated below the Permo-Triassic basal unconformity, and the eastern limit is taken at the Kirk Rigg Fault, along the line of the A66 highway, west of Penrith (McCormac, 2001).
A buff to dark grey, bioclastic, sandy grainstone to packstone and fenestral lime mudstone, displaying tabular or cross bedding, containing stromatolites and Lithostrotion, Syringopora and Siphonodendron coral colonies.
From 50m to 100m
The top of the limestone beds with a Holkerian fauna, or the base of the limestone beds containing a late Asbian fauna. In addition, the top of the beds of mudstone interbedded with calcrete and palaeokarstic limestone (Sixth Shale Member of the West Cumbria orefield) boundary picked in the Sellafield Borehole No.3 (Barclay et al., 1994), corresponds to a prominent palaeokarstic surface, and in the Uldale area [NY 2560 3700], the top of the Formation is a palaeosol containing a thin coal seam (Eastwood et al., 1968).
Frizington Limestone Formation And Sixth Limestone (Cumbria) (Undifferentiated)
FRLM6
Frodsham Sandstone Member
FRM
Lowermost occurrence of non-pebbly weakly-cemented sandstone, with characteristic 'dome-shaped dune' structures on the dominantly pebbly sandstone of the underlying Delamere Pebbly Sandstone Member.
Cheshire Basin; possibly also the southern part of the East Irish Sea Basin.
Sandstone, reddish-orange, predominantly fine-grained; well-sorted with spherical to subspherical-grains; large-scale dune bedding common; characrterised by presence of 'dome-shaped dune' structures. Weakly cemented in comparison to underlying Delamere Pebbly Sandstone Member.
55m in the Marston region, North Cheshire. 30.14m at Ford Pumping Station (SJ28NE/3), Wirral. 21.1m in the Heron Road Borehole (SJ28NW/22), Wirral.
Uppermost occurrence of weakly-cemented non-pebbly sandstone with characteristic dome-shaped dune structures, under interbedded siltstone and subordinate sandstone of the Tarporley Siltstone Formation (Mercia Mudstone Group).
Fron Newydd Member
FRN
Caradoc (gracilis to ?multidens biozones).
Conformably overlies the Llyn y Gafr Volcanic Formation in the east of the outcrop where the boundary is sharp but poorly exposed. Unconformable contact to west, greatest at Llwyngwril, where it overlies the Allt Llwyd Formation.
Continuous outcrop from the coast as far as Cross Foxes (at least). Changes facies however.
Black pyritic mudstones with abundant phosphate nodules. Ooliths common in nodules - less common in matrix. Localised developments of pure oolitic ironstone.
Mostly about 25m in thickness but locally ranges up to 180m thick at western end of outcrop. Some rapid lateral variations in thickness.
Conformable transition from black nodular mudstones to paler mudstones of the Ty'r Gawen Mudstone Formation lacking in nodules. Contact not seen but makes a distinct feature or hollow.
Fernagh Formation
FRNA
Where seen, intrusive contact with structurally underlying Tonalite intrusion.
Fernagh, Brackagh South and Cashel Rock, County Tyrone, Northern Ireland.
Pale buff, pinkish and green aphanitic sometimes flow banded and auto-brecciated lavas and partly intrusive felsite.
Max 300m
Not exposed but most likely to be conformable with overlying tuffs and lava of Tyrone Volcanic Group.
Farne Group [Offshore]
FRNE
Frome-Piddle Formation
FRPI
The fluvial deposits rest unconformably on Chalk Group and Palaeogene strata.
The catchment of the rivers Frome and Piddle and their tributaries, Dorset, up to OD +125m.
Floodplain alluvium and river terrace deposits. The floodplain alluvium comprises clay and silt overbank deposits, with local peat, overlying sand and gravel. The surviving river terrace deposits are largely gravel with interstitial sand. The major pebble lithologies are flint, quartz and Mesozoic chert. The gravel units were deposited by braided rivers under periglacial conditions.
Ferruginous Sands Formation
FRS
The lower boundary is marked by a down-section change from Ferruginous sands and sandstones with concretions, via a narrow transition to silty clays of the Upper Atherfield Clay Formation.
Isle of Wight and southern Dorset.
The formation comprises: A succession of three upward coarsening clay rich and glauconitic, shelly and bioturbated sands and sandstones with nodules at the base ["Lower Gryphaea Beds", "Lower Gryphaea Group", "Group IV" and including the "Terebratula Beds"]. Glauconitic, very fossiliferous sands with phosphatic nodules [near the base] and calcareous nodules ["Scaphites Group", "Group V"]. Grey-green, argillaceous sand with bands of concretions, and common ammonites and bivalves ["Lower Criceras Bed", "Group VI"]. Muddy sands and sandy clays with phosphatic nodules and shelly ["Walpen Clay and Sand", "Group VII"; "Whale Chine Member"]. Brown-weathering, fossiliferous clayey sand with horizons of large phosphatic nodules. Gradually upward coarsening. ["Upper Criceras Beds", "Group VIII"] Greenish and grey sands with a band of gritty olive-green, calcareous nodules at the base. Gradually upward coarsening, ["Walpen and Ladder Sands", "Group IX", "Ladder Chine Member"]. Ferruginous, clayey sands with bands of Exogyra and plant debris, ["Upper Gryphaea Beds", "Group X","Member X"]. Glauconitic, bioturbated, sands and clays with shell and plant debris ["Cliff-end Sands", "Group XI", "Member XI"]. Glauconitic sand with dark, grey, pyritic clay drapes and lenses of coarse, current-bedded, friable sandstone ["Foliated Clay and Sand", "Group XII", "Old Walpen Chine Member"]. Glauconitic, pale-green, yellow and brown sands with a marked erosion surface and pebble bed at the base and a fossiliferous nodule horizon in the middle of the unit which has been called "Urchin Bed" ["Sands of Walpen Undercliff", "Group XIII", "New Walpen Chine Member"]. Brown and yellow sands and cemented sandstones with three bands of iron and abundant moulds and impressions of shelly fossils. Bioturbated, particularly at the top ["The Ferruginous Bands of Blackgang Chine", "Group XIV", "Member XIV"].
To c.161m
The upper boundary has been defined in a number of ways. Fitton [1847] and Casey [1961] placed the boundary at the top of "Group XV", where upsection coarsening estuarine silty mudstones pass upwards into interlaminated black clays and white sands and finely overlain by the white, quartzose sands of the Sandrock Formation. Mapped lines were based on this definition. Wach and Ruffell [1990] placed the boundary within "Group XV" where the estuarine silty mudstone passes up into the interlaminated black clays and white sands. "Group XV" is a transitional bed of estuarine mudstone passing up into the estaurine sands of the Sandrock Formation. The underlying ferruginous, glauconitic sands and sandstones are essentially marine. The boundary between "Group XV" [Fitton, 1847; Casey, 1961] is a scoured erosion surface separating the estuarine mudstones from a marine sandstone with a highly burrowed and indurated top. It makes a sequence boundary. This is the current definition of the base of the unit [Insole et al., 1998; Ruffell and Watch, 1998].
Freshfield Sandstone Member
FRSA
Frondderw Tuff Member
FRT
Lithic tuff at base conformably overlies the siltstones of the Glyn Gower Siltstone Member, within the Ceiswyn Formation.
Corwen and Bala districts, North Wales.
Coarse- to fine-grained rhyodacitic lithic tuff and tuffaceous sandstones and siltstones with rare fossils.
2 metres. Lateral variations 0 - 17 metres.
Tuffaceous sandstones are conformably overlain by mudstones of the Ceiswyn Formation.
Fiery Coal (In Swansea Member, South Wales)
FRYC
Firestone Sill
Medium-grained siliceous sandstone, hard, locally either brown or white.
2m to 30m; average 10m
Forres Sandstone Group
FSA
Disconformity at base of Nairn Sandstone on Inverness Sandstone Group beds. Base is transgressive onto metamorphic basement.
Ardersier to Spey Bay (near Buckie)
Red-bed sandstones with rare siltstones, some pebbly beds and 'cornstones'.
At the change in facies from red beds to marine sedimentary rocks.
Fraser Shell Bed
FSB
Faringdon Sponge Gravel Formation
FSG
An erosion surface separates the sponge gravels from the underlying Jurassic Ampthill Clay and Coral Rag.
The Upper Aptian Faringdon Formation is preserved as an isolated deposit within the NW-SE orintated Faringdon Trough (Arkell, 1947), a fault controlled depression (Ruffell & Wignall, 1990) on the eroded Jurassic surface. The formation rests disconformably on the Late Jurassic between Faringdon, Fernham and Baulking (Arkell, 1947, Poole & Kelk, 1971; Poole et al., 1971).
The formation is composed of red and yellow sponge gravels, in the lower part of the unit, overlain by clayey sands and sandy clays and capped by ferruginous sands and sandstones. The sponge gravels are highly fossiliferous, with abundant sponges, and "the matrix is a coarse quartz sand with many small, smooth quartz and lydite bebbles" (Arkell, 1947). The "Red Gravel" shows ferruginous staining. Locally thers is a pebble bed at the base. Resting on an erosion surface, a pebble bed passes up into glauconitic sandy clays, clayey sands and silts. The clay minerals are dominantly calcium montmorillonite and illite with small amounts of Kaolinite and fuller's earth is well developed in two seams. Brown, ferruginous, cross-bedded, medium to coarse-grained sands and sandstones, resting on an erosion surface, occurs at the top of the formation. Scattered pebbles, bands of grit and cherty sandstones also occur in places. Fossil fragments are common. The top of the member is indurated to form a hard sandstone which caps a number of hills in the Abingdon district.
Up to an estimated 49m.
The upper boundary of the Faringdon Formation is rarely seen. In the Uffingham Borehole and some of the Baulking boreholes, mudstones of the Gault Formation is seen to rest disconformably on the sands of the Faringdon Formation.
Fen Sand And Gravel
FSGR
Gravelly sand overlying flint and limestone. [Generic description: 1:50 k map margins].
Fraser Shale
FSH
Fernieslack Palaeosol Bed
FSLCK
Ipswichian (?MIS 5e).
The lower boundary of the palaeosol bed is gradational (over c.0.10m) between the pedogenically modified diamicton and the relatively unaltered diamicton of the Rottenhill Till Formation.
Buchan, northeast Scotland. The palaeosol bed is only known within the immediate vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) and Leys Quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon).
Sandy, clayey, silty sand diamicton, brown. Interpreted as a truncated gleyed brown earth soil profile developed under temperate climate conditions. The truncated palaeosol bed represents the pedogenically modified upper c.0.80m of the Rottenhill Till Formation. Pedogenic development is indicated by the following properties: the upper 0.70m of the deposit has a strong brown colour in contrast to the lower part of the deposit which is yellowish brown. It also displays coarse mottles of yellowish red and greyish brown to brown due to Fe oxide segregation. Mafic igneous and granite clasts have been converted to gruss in situ and clay minerals show alteration from illite to mica-smectite up profile. Disrupted void argillans (evidence of clay translocation and subsequent disruption) and erect pebbles have been recorded in thin section, indicating that the palaeosol has superimposed cold climate soil features.
The upper boundary is a subhorizontal, planar, erosion surface overlain by gravelly sandy diamicton of the Corsend Gelifluctate Bed. The upper horizon of the palaeosol bed (not preserved) was eroded at some point prior to deposition of the gelifluctate.
First Smalley Coal (Leicester And Derby)
FSMC
Felton St Mary's Limestone
FSML
In and around the Coquet Valley, near Felton, Northumberland.
Ochreous-weathering, grey, bedded, crinoidal limestone.
c.1.8m
Foston Member
FSTL
Base of distinctively iron-rich limestone beds (Stubton Limestones), below which mudstones (Beckingham Member) contain only rare and thin limestone beds; at 34.65m depth in type section.
East Midlands Shelf; southwards the characteristic limestones pass into mudstones; northwards limestones develop in underlying Beckingham Member.
Grey mudstones containing laterally persistent beds of individually distinctive limestones, totalling c.10% of sequence thickness.
30.07m in type section.
In type area, at erosive base of a ferruginous bed of oolitic wackestone (Glebe Farm Bed) at the base of the Charmouth Mudstone Formation; (at 4.58m depth in type section).
Fivestanks Oil-Shale
FSTS
Froswick Tuff Formation
FSW
Marked by the abrupt change from bedded volcaniclastic rocks of the Mardale Formation to massive pyroclastic rocks.
Northeastern Lake District, from Kentmere to Place Fell, southeast Ullswater; Hart Fell, Haweswater; Bampton Common, Mardale Common and Wet Sleddale.
Eutaxitic to parataxitic, andesitic to dacitic lapilli-tuff, locally lithic rich with minor tuff-breccia and bedded tuff and lapilli-tuff.
To 640m
Defined by the base of the overlying Woundale or Seathwaite Fell Sandstone formations.
Foxley Tuff Formation
Foot Coal (Coalbrookdale)
FTCC
Fulledge Thin Coal (Lancashire)
FTCO
Flow Till
FTIL
Variable lithology; glacial sediments that flow after they have been deposited by ablation. [Generic description: earth science dictionaries in the BGS library].
Flockton Thick Coal (West And South Yorkshire)
FTKC
The Flockton Thick Coal, or Adwalton Stone Coal is comprised of three leaves separated by dirt that in some districts preclude economic extraction. The top leaf, a cannel coal, was worked as a gas coal and for oil. The lower leaves are bituminous.
Flockton Thin Coal (West And South Yorkshire)
FTNC
The Flockton Thin Coal or Adwalton Black Bed Coal is a good quality dull coal with common dirt partings. It is uniform in thicknes and has been worked extensively in the area around Dewsbury and Batley.
Foot Coal (South Lancashire)
FTSL
First Waterloo Coal (South Yorkshire, Nottingham And Derby)
FTWC
Name applied variably, and nomenclature needs revision.
Fort William Formation
FTWM
Forty Yard Coal (South Yorkshire, Nottingham And Derby)
FTYD
Fucoid Beds Member
FUB
The An t-Sron Formation, including the Fucoid Beds Member, forms a narrow, discontinuous belt, extending along the North-western side of Scotland from the Durness-Eriboll area, through Assynt, Dundonnell, Kinlochewe and Kishorn, to Skye
Ferruginous, potash-rich brown coloured dolomitic siltstone with argillaceous, quartzose intervals, and minor limestones.
From 12 m to 27 m thick.
Conformably overlain by the Salterella Grit Member.
Furnace Coal (Northumberland)
FUC
Furnace Coal (Lancashire)
FUCL
Furnace Coal (Yorkshire)
FUCY
Fulbeck Sand And Gravel Member
FULB
Upper Pleistocene (MI Stage 5e to 4 or ?2). It was originally thought (Brandon and Sumbler, 1988) that essentially the whole of the deposit was Ipswichian but subsequently it became clear that the temperate fossiliferous deposits were local basement remnants and that the bulk of the deposit was a cold-stage aggradation. This is probably largely MIS 4, but could extend into MIS 2 (and could therefore in part correlate with the Holme Pierepont Sand and Gravel of the Trent).
Woolsthorpe-by-Belvoir [SK 84 34] to Auborne [SK 93 63] BGS sheets:142, 143, 127, 114).
Predominantly cold-phase sands and gravels that underlie the Fulbeck Terrace. Typically a clean, well-sorted medium-grained sand with gravel that at depth is dominated by subangular and subrounded pebbles of Jurassic limestone (mainly Lias Group and Lincolnshire Limestone Formation), with a smaller proportion of other Jurassic lithologies, flint, "Bunter" quartz/quartzite, etc, derived from older drift deposits. Commonly appears dominated by "Bunter" and flint pebbles near the surface due to decalcification. Infills a shallow channel partly coinciding with the valley of the modern River Brant, extending northnortheastwards from Woolsthorpe to Auborne. Terrace surface falls to c.6m OD at the northern end where the deposits are covered by Brant alluvium and probably are truncated by the deeper channel of the River Witham. Sections show cryogenic involutions and epigenetic ice wedge casts infilled with coversand. Basal part locally includes channel-filling organic silts (Little Syke Bed), which yield a temperate fauna and flora assigned to MIS 5e. Correlated with Beeston Sand and Gravel Member (Trent Valley Formation), and Scarle Sand and Gravel Member (Trent Valley Formation).
Partly because of misunderstandings about the age relationships, Howard (in Bowen, 1999) ascribed the downstream end of the Fulbeck Sand and Gravel (which would lie on Sheet 114) as a separate Bassingham Fen Member. The latter name is superfluous and is now subsumed into the Fulbeck Sand and Gravel.
0 to c.5m; typically 1 to 2m
Ground surface or (chiefly at northern limit) overlain by alluvium.
Fungus Coal [Coalbrookdale]
FUN
Coalbrookdale.
Funzie Conglomerate Formation
FUNC
Faulted (tectonic lens).
The eastern part of Fetlar, bound to the west by faults.
A conglomerate with mainly quartzite pebbles, including some pebbles of ophiolitic affinity.
Several kilometres thick.
Fallgate Volcanic Formation
Not proven.
The eastern margin of the Derbyshire Dome, in the Peak District, around Ashover (SK 36).
Basaltic lavas, commonly amygdaloidal and locally brecciated, hyaloclastites and tuffs with thin beds of limestone.
Measured as 293m in the Fallgate Borehole, base not reached.
Overlain conformably, with the top marked by the sharp base of the lowest bed of dark limestone, commonly containing Girvanella or Saccamminopsis of the Monsal Dale Limestone Formation.
Fiddlers Vein Coal (Pembrokeshire)
FVCO
Five-Feet Coal (North Staffordshire)
FVFC
Felin-Wen Formation
Taken at the sharp incoming of silt-laminated mudstone of the Felin-wen Formation above the hemipelagic laminated and burrowed mudstone of the Aber Mawr Shales Formation. Base not observed in the Newcastle Emlyn district.
Newcastle Emlyn district, may be a synonym, in part or in full, of the Murchisoni Beds of the Carmarthen district, but further work is needed.
Silt-laminated mudstone with sparse, scatterd thin sandstone or calcareous sandstone beds.
c.70m
Taken at the sharp incoming of tuff or tuffaceous sandstone, or locally calcareous sandstone and shelly limestone of the overlying Asaphus Ash Formation.
Felin-Wen Formation And Hendre Shales Formation (Undifferentiated)
FWHS
Fawes Wood Limestone Formation
FWL
Frances Wood Coal
FWO
The Forks Wash Pool Sandstone
FWPS
Foot Of Whisky Sike Coal (Northumberland)
FWSC
Locally known in the area near Whisky Sike (Lewis Burn), Northumberland.
c.0.3m
Fawcett Coal (Northumberland)
FWTC
Fishgarth Wood Till Member
FWTI
Generally planar or undulating contact on the Drigg Holme Sand Member of the Gosforth Glacigenic Formation.
Typically a hard, moderate reddish brown, matrix-supported, massive, calcareous sandy silty clay diamicton, with dispersed subangular to rounded clasts up to 15cm in diameter. The clasts are mainly of red sandstone, Borrowdale Volcanic Group rocks, granite, granophyre, brown siltstone and sandstone; some coal, black shale and comminuted shell fragments.
Typically c.2.5m, but up to c.5m thick.
Overlain by silts, sands and clays of the Drigg Moorside Silt Member of the Gosforth Glacigenic Formation.
Freshwater West Formation
FWW
Flexible Limestone
FXBL
Foxfield Coal (Cheadle)
FXC
Foxdale Pluton
FXD
Foxmould Member
FXMD
Unconformity resting on strata ranging from Triassic (in west) to Lower Jurassic (in east).
Devon and West Dorset. Mapped on Sheets 326 (Sidmouth) and 327 (Bridport); continuation on Sheet 311 (Wellington).
Sandstone, glauconitic, calcareous in part, greenish grey weathering to foxy brown sand; concretionary (doggers) and tabular sandy limestones at several levels.
Mineralised hardground surface (Culverhole Hardground) above which concretionary calcareous sandstones are absent and cherts are common.
Ferriby Chalk Formation
FYCK
Erosion surface, locally developed as a hardground, overlain by nodular chalk (lowest Cenomanian) of the Paradoxica (or Sponge) bed or, in the Cleveland Basin (e.g. Speeton) the Crowe's Shoot Member (Gaunt, G D, et al, 1992; Mitchell, S F, 1995).
Scarp area of Yorkshire and Lincolnshire Wolds, and superficial deposit-covered area to southeast, from Speeton Cliffs south to the Skegness area on the Lincolnshire coast (see Sumbler, M G, 1999, Fig.1).
Grey, soft, marly, flint-free chalk, typically weathering buff in exposures; locally includes pinkish bands; some harder, gritty, shell-debris-rich beds, and thin discrete marl seams. Formal subdivision: None herein but the formation includes a number of named (see Wood and Smith, 1978) units that are considered of bed status. Jeans (1980) proposed a scheme of seven members but this has not gained widespread use in the literature.
Typically 20-25m, thinning over the Market Weighton High (c.10-15m) but expanding into the Cleveland Basin, being c.35m in cliffs at Speeton, and c.50m inland.
Uneven erosion surface that may be stained with iron minerals and glauconite, at the top of a succession of marly chalk (Ferriby Formation); succeeded by Plenus Marls Member (Welton Formation), a unit of marls and marly chalks that generally forms a topographical slack at outcrop, which facilitates the mapping of the Plenus Marls, and thus top of the Ferriby Formation; also readily recognized from geophysical log signature in boreholes.
Fiery Coal (South Lancashire)
FYCO
Foel Y Ddinas Mudstones Formation
FYD
Base succeeds grey siltstones, mudstones and thin sandstone laminae of the Moelfryn Mudstones.
Dark blue silty mudstones. Includes Calettwr Quartzite and Hirnant Limestone at the top of the formation.
125 metres.
Top - succeeded by striped dark-blue shales with subsidiary siltstones of the Cwm-yr-Aethnen Mudstones.
Fylde Halite Member
FYHA
Five Yard Limestone Member
FYL
Taken at the sharp base of limestone overlying measures within the Alston Formation; directly underlain by burrowed, current and ripple-bedded, medium-grained sandstone; a thin coal is present in places.
Member within the Alston Formation of the Alston and Lake District blocks in Cumbria, Northumberland and Durham, lying stratigraphically between the Scar (below) and the Three Yard (above) limestone members. Possibly correlated with the Eelwell Limestone of the Northumberland Trough. Also present in the northern part of the Askrigg Block and in the Stainmore Trough. Well exposed along the Pennine escarpment, in Teesdale and Weardale.
Limestone, dark grey, argillaceous, becoming grey compact towards base. In the south, fine-grained with thin evenly bedded mudstone parting with many fossils. In the north, becoming increasingly crinoidal and locally characterised by coarse crinoidal debris. Intercalated thin unit (to 2.1m) of black fossiliferous calcareous mudstone, which divides the member into two parts. Styolitic particularly near base (Johnson et al, 1996). On Dun Fell the limestone has yielded goniatites indicating the P2b biozone (Johnson and Dunham, 1963).
3 to 8.5m
Taken at base of the overlying mudstone within measures of the Alston Formation.
Fyal Lava Member
FYLM
Fynnon Limestones
FYNL
Flying Reed Coal (South Staffordshire)
FYRC
Five Yard Coal (North Wales)
FYRD
Fault Zone Rocks, Unassigned
FZRU
Gisburn No.1 Limestone
Cancelloceras Cancellatum Marine Band
G1A1
Unnamed Marine Band Of Cancelloceras Cumbriense Zone
G1B
Cancelloceras Cumbriense Marine Band
G1B1
Gisburn No.2 Limestone
Gisburn No.3 Limestone
Gisburn No.4 Limestone
Gisburn No.5 Limestone
Gafallt Shales Facies (Caban Conglomerate Formation)
N/A.
Thinly interbedded turbidite mudstones and burrowed hemipelagites with scattered thin turbidite sandstones.
Glengawna Formation
GAA
Gradational boundary with underlying Glenelly Formation.
0.5-1.5km wide belt in north County Tyrone, Killyclogher-Gortin Glen to Glenlark.
Interbedded psammite, semi-pelite and graphitic pelite.
c.1km
Gradational boundary with overlying Mullaghcarn Formation.
Green Ammonite Member
GAB
Top of Belemnite Stone (bed 121 of Lang, W D, et al, 1923). Conformable junction with Belemnite Marl Member.
Southwest Dorset, United Kingdom. Mapped on Sheet 327 (Bridport). Northern limit not yet proved.
Medium grey mudstones, with irregular limestones developed at three principal horizons (Lower Limestone; Red Band; and Upper Limestone). Phelps, 1985, beds 7 to 41.
To 31m
Base of lowest bed of the Three Tiers Sandstone (=base of Eype Clay Member of Dyrham Formation).
Gubbin And Balls Ironstone (South Staffordshire)
GABI
Garva Bridge Psammite Formation
GABR
Central Highlands of Scotland, sheet 73E, 63E, 63W, southern Monadhliath Mountains.
Feldspathic psammite, micaceous psammite and schistose semipelite.
min. 2 km.
Sharp but conformable boundary with overlying Core nan Laogh Semipelite. Contact locally sheared, probably a disconformity.
Glenarm Chalk Formation
GAC
Base delimited by a prominent weathered-out bedding plane immediately above the Altachuile Breccia (Bed) of the Ballintoy Chalk Formation.
Maximum development in the East Antrim (Midland Valley) Basin and found over the Highland Border high and well developed in the North Antrim Basin. Becomes attenuated including several non-sequences and overstepped by younger formations across the Londonderry Shelf and in the Southern Uplands Belfast district.
Limestone (chalk), with flints ranging from small nodular at the base through nodular to tabular flints in the middle part of the sequence to massive nodular at the top. The Formation can be divided into four `Beds? (A to D) by subdivision on bedding planes. In the North Antrim Basin the Formation includes two well-developed hardgrounds, the North Antrim Hardgrounds (of member? status) and the sequence is therefore incomplete. In the Midland Valley (East Antrim) Basin only limited wavy bedding and scattered green glauconitised pebbles indicate interrupted sedimentation. This area is regarded as the `standard?.
8.10m at the type area.
Weathered-out bedding plane below conspicuously shelly wavy-bedded chalk at the base of the conformable Garron Chalk Formation.
Garn Caws Sandstone Formation
GACA
The base is placed at the base of silica-cemented ("quartzitic") sandstone or conglomerate where it rests with sharp base on an erosion surface cut in the underlying Gilwern Clay Member of the Llanelly Formation.
Northeast crop of the South Wales Coalfield, from the area of Cwar yr Hendre [SO 099 149] eastwards to the type area of Garn Caws [SO 120 164], and farther eastwards to the Clydach Valley [c.SO 215 127].
White, silica-cemented ("quartzitic") sandstones and conglomerates with some thin intercalated plant-bearing green-grey mudstones and seatearth.
To 12m (maximum at Blaen Onneu Quarry [SO 155 169].
The top is placed at the top of the silica-cemented ("quartzitic") sandstone, where it is sharply and unconformably overlain by the basal limestone of the Dowlais Limestone Formation.
Glen Achall Psammite And Semipelite Member
GACH
The lower boundary of the Member is defined in Glen Achall as the lowest appearance of a thick (>2m) unit of garnet-bearing semipelite above the Moine Thrust.
The Member has so far only been identified in the hills around Glen Achall, east of Ullapool, between the Rappach Water in the north and Glen Douchary in the south. However, continued mapping in the area is likely to result in it being traced for greater distances.
The Glen Achall Psammite and Semipelite Member comprises psammites, with abundant subsidiary semipelite beds that vary in thickness from a few centimetres to tens of metres. The psammites are grey to pink weathering and vary from tabular to cross-bedded, with bedfordms from 10cm to 1m in thickness. Semipelite beds up to a metre thick are common, but the key characteristic of this member is the presence of several garnet-bearing semipeilite units that attain several tens of metres in thickness. The semipelites are typically fine- to medium-grained and strongly foliated, consisting of quartz plus feldspar plus biotite plus muscovite plus garnet. Some of these semipelite units can be traced for several kilometres across moderately exposed ground around Glen Achall, which represents the type area for the Member, however, some of the semipelite units pinch out laterally.
The upper boundary of the Member is defined in Glen Achall as the uppermost limit of thick (>2m) garnet-bearing semipelite units. A discontinuous quartzite bed forms the very top of the Member in some outcrops. In this area, the top of the Member also represents the top of the A'Mhoine Psammite Formation.
Gartartan Conglomerate Member
GACO
A sharp contact with the purple and reddish-grey, sublithic sandstone of the undivided Ruchill Flagstone Formation.
Gartmore to Lochan Balloch, north-east of which it virtually coalesces with Ben Dearg Conglomerate to form A'Chrannach Conglomerate (lower leaf) near Callander.
A poorly sorted, matrix supported, planar bedded, conglomerate with clasts of quartzite, quartz and igneous lithologies.
From 20 - 25 m between Gartmore House and Shannochill, increasing to 100 m thickness at Lochan Balloch [NN 592 043].
A sharp contact with the Cromlix Mudstone Formation, which comprises a poorly sorted silty sandstone around Gartartan, commonly with a thin conglomerate bed 30 - 40 m above the junction. North-eastwards, basal Cromlix beds exhibit a transition to a fine-grained, massive, well-sorted sandstone, eg; at Over Shannochil [NS 5428 9930].
Garburn Dacite Formation
GAD
Taken as the base of the dacite overlying volcaniclastic sandstone of the Esk Pike Formation. The two are mostly separated by later syn-BVG andesite intrusions.
On the north side of Garburn Pass, from near Limefitt Park [NY 420 033] via Garburn, Buck Crag [NY 440 048] and Piked Howes [NY 446 050] to Goat House Crag, Kentmere [NY 451 046], east of Kentmere from Stile End [NY 469 049] to South of Wray Crag [NY 476 052].
A flow-foliated and brecciated plagioclase-phyric dacite, interpreted as lava.
Defined by overlying sedimentary rocks of the Windermere Supergroup.
Garn Dolerite
GADO
Transgressive.
Coarse amygdaloidal microgabbro.
80m
Gaerfawr Formation
GAFA
Garth Grit Member
GAG
Unconformity on siltstones of Dol-cyn-Afon Formation or mudstones of Dolgellau Formation (both in Mawddach Group): forms the basal unit of the Allt Lwyd Formation.
South central Snowdonia.
Quartzose conglomeratic sandstone.
0 to 70m
At base of siltstones and sandstones of the undivided Allt Lwyd Formation.
Garn-Gofen Formation
GAGO
Erosion surface cut in conglomerates of the Craig-y-cwm Formation, overlain by pale yellow to white micaceous sandstone [Lovell, 1978].
From Blaen Onneu - Daren Cilau area near Crickhowell, Gwent eastwards and southwards to Pontypool, Gwent, South Wales.
Interbedded sandstones and red-brown mudstones. The sandstones in the basal part are pale grey-green quartzites; those in the upper part are grey-green, soft, friable, richly micaceous and feldspathic.
Up to a maximum of 20 m.
Sharp junction between overlying limestone of the Castell Coch Limestone of the Lower Limestone Shale Group and the topmost sandstones of the Garn-gofen Formation. A thin but persistent conglomerate marks the base of the Castell Coch Limestone.
Garth House Formation
GAHO
Gala Group And Hawick Group (Undifferentiated)
GAHW
Gairbeinn Pebbly Psammite Member
GAIR
Transitional, placed where feldspar clasts and pebble bands become abundant within the Garva Bridge Psammite Formation.
Western part of Monadhliath Mountains in Central Highlands. Mostly in NW part of sheet 63E [Dalwhinnie] and on sheet 73E [Foyers].
Pink, grey and fawn feldspathic psammite and micaceous psammite with pebbly layers, particularly towards the top of the member.
up to 700 m.
Abrupt and locally transitional over a few metres. Placed where highly strained pebbly psammite, psammite and some quartzite are overlain by schistose to gneissose semipelite.
Garsdale Limestone Formation
GAL
Late Holkerian to early Asbian.
Gala Unit 1
GAL1
Southern faulted boundary: Stair Haven Fault. Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age).
Mapped from the eastern side of Luce Bay (Sheet 4W) to New Galloway (Sheet 9W). Possible correlation with the northern part of the Donaghadee Block of the Ards Peninsula, Northern Ireland.
Graded beds that may include wacke sandstone, siltstone and mudstone in variable proportion, interpreted as turbidites. Rare interbedded mudstones have yielded fauna of the acuminatus Biozone.
c. 2000m of near vertical strata
Northern faulted boundary: Orlock Bridge Fault.
Gala Unit 2
GAL2
Southern faulted boundary: Sandhead Fault. Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age).
Mapped from the Sandhead on the Rhins of Galloway (Sheet 1/3) to Peebleshire (Sheet 24E). Correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
c. 1000m of near vertical strata
Northern faulted boundary Luce Bay to New Galloway: Stair Haven Fault. East of New Galloway: Orlock Bridge Fault.
Gala Unit 3
GAL3
Southern faulted boundary: Strandfoot Fault. Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age up to the acinaces Biozone).
Restricted to the western side around Money Head on the Rhins of Galloway (Sheet 1/3). Possible correlation with the Central Belt Turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
Graded beds that may include wacke sandstone, siltstone and mudstone in variable proportion, interpreted as turbidites.
c. 900m of near-vertical strata
Northern faulted boundary (Rhins of Galloway): Sandhead Fault.
Gala Unit 4
GAL4
Southern faulted boundary: Gillespie Burn Fault. Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age).
Mapped from Float Bay on the Rhins of Galloway (Sheet 1/3) to Peebleshire (Sheet 24 E). Correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
Graded beds that may include wacke sandstone, siltstone and mudstone in variable proportions, interpreted as turbidites. Conglomeratic beds are a feature of this unit. Siltstone interbeds yielded fauna of the cyphus to triangulatus Biozones.
c. 1500m of near vertical strata.
Northern faulted boundary: Sandhead Fault.
Gala Unit 5
GAL5
Southern faulted boundary: The Hooies Fault (Rhins of Galloway), Garheugh Fault (Wigtown). Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age up to magnus Biozone).
Mapped from Ardwell Bay on the Rhins of Galloway (Sheet 1/3) to Peebleshire (Sheet 24 E). Correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
c. 900m of near vertical strata.
Northern faulted boundary: Gillespie Burn Fault.
Gala Unit 6
GAL6
Southern faulted boundary: southernmost splay of Drumbreddan Bay Fault (Rhins of Galloway); Pibble Fault (Wigtown). Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age up to convolutus Biozone).
Mapped from Drumbreddan Bay on the Rhins of Galloway (Sheet 1/3) to Peebleshire (Sheet 24 E). Correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
c. 600m of near-vertical strata.
Northern faulted boundary: The Hooies Fault (Rhins of Galloway); Garheugh Fault (Kirkcowan and Wigtown).
Gala Unit 7
GAL7
Southern faulted boundary: Port Logan Fault (Rhins of Galloway); Cambret Fault (Wigtown Peninsula); Laurieston Fault east of Wigtown Bay. Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age up to sedwickii - halli Biozones).
Mapped from Port Logan Bay on the Rhins of Galloway (Sheet 1/3) to Peebleshire (Sheet24E). Correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
c. 1850m of near vertical strata
Northern faulted boundary southernmost splay of Drumbreddan Fault (Rhins of Galloway); Pibble Fault (Kirkcowan and Wigtown); Garheugh Fault (to the north-east).
Gala Unit 8
GAL8
Southern faulted boundary: Mochrum Fault (Rhins of Galloway and Wigtown Peninsula). Stratigraphical lower boundary with underlying Moffat Shale Group (of Ordovician to Silurian age up to sedwickii to possible turriculatus Biozones).
Mapped from Port Logan Bay on the Rhins of Galloway (Sheet 1/3) to Wigtown (Sheet 4E). Possible correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
c. 800m of near vertical strata (Rhins)
Northern faulted boundary: southernmost splay of Port Logan Fault (Rhins of Galloway); Cambret Fault (Kirkcowan and Wigtown).
Gala Group
GALA
Southern faulted boundary: Laurieston Fault. Stratigraphical lower boundary with underlying Moffat Shale Group [of Ordovician to Silurian (gracilis to sedwickii biozones) age.]
Mapped from the Rhins of Galloway (Sheet 1/3) to Eyemouth (Sheet 34). Correlation with Central Belt turbidites of Llandovery age in the Ards Peninsula, Northern Ireland.
Graded beds that may include wacke sandstone, siltstone and mudstone in variable proportions, interpreted as turbidites. Rare interbedded graptolite-bearing beds.
c. 6000m of near-vertical strata.
Gale Seam
GALE
Galloway Granitic Suite
GALGR
Gualdswell Lava Member
GALM
Glaslyn Formation
GALN
Gamma Coal (North Wales)
GAMC
Ganister Clay Coal (Northumberland And Durham)
GANC
Glen App Conglomerate Member
GAPC
Limits are defined by the presence of pebbles, cobbles or boulders.
Boulder, cobble and pebble conglomerates with pebbly coarse-grained greywackes.
~2200 metres - 0 metres.
Garve Psammite Formation
GAPS
Located at the Sgurr Beag Thrust Plane, which is commonly interdigitated with Lewisianoid tectonic slices. This formation is structurely the lowest Moine group unit in the Sgurr Beag Nappe.
Forms a thin, nearly continuous belt running south-west to north-east from Loch Luichart (NH383602) to Loch Coire (NH525762). South and west of Loch Luichart, it is repeated in a series of folds and thrusts; e.g.Sgurr Beag Thrust, extending to the west at Loch Bhad Ghaineamhaich (NH323590), where it terminates against the Strathconon Fault.
Buff to pale brown and pink, flaggy, siliceous and feldspathic psammite with micaceous partings, some heavy mineral bands and numerous streaky lenticles displaying quartzofeldspathic segregations.
Defined by the western edge of the Ben Wyvis Pelite Formation, with the appearance of predominantly pelitic rocks to the east. The boundary has probably been significantly tectonically modified.
Garheugh Formation
GAR
Very thickly bedded massive sandstone including units of medium to thick-bedded greywackes (up to 500 metres thick).
Garw Coal (South Wales)
GARC
Garwood Group
GARD
Glen Garry Vein Complex
GARRY
Garrison Sill
GARS
Garron Point Tremolitic Flag Member
GART
Transition from dominantly bluish and purplish grey calcareous flaggy semipelite to dominantly greenish grey tremolitic lithologies.
From coast at Garron Point [NJ 5525 6700-5550 6700], as far inland as fault at [NJ 532 633], south of which it is covered by Devonian sedimentary rocks.
Semipelite, flaggy, calcareous and minor micaceous psammite, green with tremolitic amphibole porphyroblasts prominent in most exposures. Upper part locally contains thin, lenticular bands of metalimestone.
c.250 to 300m on coast section; not measurable inland.
Sharp change from tremolitic flags to interbedded graphitic pelite, semipelite and metalimestone of Mortlach Graphitic Schist Member.
Garvald Sill
GARV
Great Arc Sandstone
GAS
The lower boundary is taken at the base of the first sandstone of a sandstone-dominated unit above the Lower Mountain Coal.
Wigan (SD 5805), Manchester (SJ 8398) and Rochdale (SD 8913) areas.
Sandstone, buff-grey, fine-to medium-grained, micaceous, thickly-to thinly-bedded, cross-bedded and ripple-laminated.
20 m maximum thickness.
The upper boundary is taken at the base of a mudstone-dominated succession overlying the sandstone of the Great Arc Sandstone; often coincident with the base of the seatearth underlying the Upper Foot Coal.
Garantiana Mudstone Member
GASH
Abrupt lithology change from Druim an Fhurian Sandstone Formation.
Dark mudstones and clays with rare calcareous nodules mark the commencement of the Member. North of Skye the mudstones and siltstones pass laterally into calcareous sandstones.
Basinwide unconformity, overlain by mudstones of the Great Estaurine Group.
Gask Intrusion
GASK
Glenade Sandstone Formation
GAST
Gartocharn Till Formation
GATI
Unconformity or glacial deformation boundary on older Quaternary strata such as the Linwood Clay Member and the Wilderness Till Formation; also on bedrock. Complex relationships laterally with fluvioglacial and deltaic/lacustrine sediments (Drumbeg Sand and Gravel Formation and Blane Water Clay Formation) forming part of the Loch Lomond Stadial Terminal Moraine Complex in the Leven and Endrick valleys in the Loch Lomond Basin.
West central Scotland, related to ice streams sourced in the Highlands during the Loch Lomond Stadial; Loch Lomond area including the Leven and Endrick valleys, sea lochs in the northern Firth of Clyde and the Stirling area to the northwest of Callander.
Consists of massive silty clay with isolated pebbles, gravel and boulders, and knots of sand. It is brown or dark brownish grey with many dark sulphide patches and marine shells. It is of stiff to hard consistenct and medium to high plasticity. It contains joints and low angle thrust surfaces, some of which are polished, striated and grooved. Locally rafts and more diffuse patches of bedded clay are present.
Veneer to over 6m
Unconformity below younger Quaternary strata or glacial deformation boundary. Where data are available the Gartocharn Till Formation is overlain by the Drumbeg Sand and Gravel Formation and by the Buchanan Clay Member of the Clydebank Clay Formation in the Loch Lomond area.
Gawber Coal (West Yorkshire)
GAWC
Glen Banvie Pluton
GBANV
Glacial Brick Clay
GBCY
Varies from silt to clay, commonly yellow-brown and massive; of glacial origin. [Generic description].
Garn Bach Dacite
GBDA
Porphyritic dacite with phenocrysts of andesine and glomeroporphyritic plagioclase clots, rare microdioritic xenoliths, minor amounts of zircon, apatite and altered mafics in a finely recrystallized felsitic groundmass.
Great Britain Superficial Deposits Supergroup
GBG
Generally sharp but locally gradational unconformable contact with bedrock of Neogene age and older.
The whole of Great Britain [England, Scotland and Wales], including the Isle of Man, the Scilly Isles and Scottish islands, together with adjacent offshore areas.
The Great Britain Superficial Deposits Supergroup embraces all natural superficial deposits cropping out in England, Scotland and Wales, and the Isle of Man. Deposits comprise diamicton [including till], sand, gravel, silt and clay.
To 200m in onshore Britain
Glen Bay Gabbro Intrusion
GBGB
Glen Bay Granite Intrusion
GBGN
Garibaldi Blackband Ironstone (Central Coalfield)
GBI
Gubbin Ironstone [Also Known As Grains Or Chance]
GBIR
Glenbuck Group
GBK
Base of Parishholm Conglomerate.
Hagshaw Hills Inlier, Lanarkshire. 50k sheets 23W, 23E and 15W.
Conglomerates, red mudstones, grey siltstones and fine-grained sandstones with fish bed. NOTE:For Reference Sections see component formations (Gully Red Beds, Fish Bed Formation, Dovestone Red Beds, Douglas Water Arenite and Parishholm Conglomerate).
c. 340m
Base of overlying Hareshaw Conglomerate.
Grainbeck Limestone
GBKL
Grayber Limestone
GBL
Gleann Beag Limestone Member
GBLS
Golan Burn Member
GBM
Conformable with normal Glenelly Formation schist below.
Owenkillen Valley, County Tyrone, Northern Ireland.
Impure limestone with silvery schistose semipelite and fine-grained slightly calcareous quartz-feldspar psammites.
Conformably overlain by normal Glenelly Formation schist.
Glenbuck Group And Monks Water Group (Undifferentiated)
GBMK
Glas Bheinn Porphyritic Dolerite Intrusion
GBPD
Garnel Burn Pelite Member
GBPE
Junction of magnetic biotite-andalusite schist with underlying quartzite of the Grumack Hill Quartzite Member (Blackwater Formation).
Watershed ridge on SE side of River Deveron valley between NJ 441 351 and Auchmair NJ 405 312.
Biotite-andalusite schist, grey, coarse-grained, highly magnetic; forms prominent "tombstone-like" outcrops.
Upper limit of coarse-grained biotite-andalusite schist outcrops and/or limit of magnetic anomaly at base of semi-pelites of Clashindarroch Formation.
Glenkiln Shale Formation
GBS
Conformable on Crawford Group.
Black cherty hemipelagic mudstone and grey mudstone and siltstone.
c.20m +
Conformably overlain by Lower Hartfell Shale Formation
Gleann Beag Schist Formation
GBSC
Base of dominantly calcareous and graphitic rocks. Stratigraphic boundary with the underlying dominantly semipelitic Tulaichean Schist Formation.
Southern part of Sheet 65W (Braemar) and northern part of sheet 56W (Glen Shee).
Mostly dark metacarbonate rock and psammite with some graphitic pelite and garnet calcareous schist passing up into graphitic pelite with thin beds of metacarbonate rock.
To 550m
Top of dominantly graphitic rocks below the overlying dominantly quartzite succession of the Creag Leacach Quartzite Formation.
Gair Burn Coal
GBUC
Glen Buck Pebbly Psammite Formation
GBUCK
Not seen - faulted against Moine and Old Red Sandstone rocks.
Central Highlands of Scotland - Sheets 73W and 63W.
Quartzofeldspathic psammites (local arkosic) with semipelite, pebbly and microconglomeratic beds.
Up to 800 m.
Not seen - faulted and sheared against Tarff Banded Formation. Contact defined in part by the Eilrig Shear Zone.
Glenburn Volcaniclastic Member
GBV
Mid Visean
Seen in the Glenburn Borehole at 22.85m depth (IGS, 1981). The base is sharp and marked by a lithological change from grey, aphyric, fine-grained mugearite lava of the underlying Clyde Plateau Volcanic Formation, to reddish purple muddy siltstone.
Glen Park, Paisley, Scotland.
Interbedded purplish red, medium-grained sandstone, reddish purple silty mudstone and reddish purple muddy siltstone. Some of the sandstone grains are volcaniclastic.
Variable thickness from 5.5m in the Glenburn Borehole, to more than 30m at outcrop in Glenburn Park.
Clearly seen at Craigie Linn Waterfall, in Glen Park, Paisley, Scotland. The top of the member is sharp and marked by a lithological change from well-bedded purple tuffs and volcaniclastic sedimentary rocks to grey plagioclase microphyric basalt lava (Jedburgh type) of the overlying Clyde Plateau Volcanic Formation, that comprises sub-angular clasts of yellowish sandstone and basalt in a fine-grained purplish grey matrix.
Greys Crags
Glas Choire Sandstone Member
GCAL
Glen Caladale Formation
GCALA
Gillcambon Till Formation
GCBTI
Early Devensian.
Uneven, unconformable on bedrock.
The Vale of Eden and the southern Solway Lowlands.
Extremely compact, reddish-brown, stony silty sandy clay diamicton containing clasts of red sandstone and Scottish rock types (granodiorite, granite, greywacke) in addition to Lake District volcanoclastic rocks and Carboniferous rocks.
Unconformable, planar or uneven. At the Type Section there are rip-up clasts of Gillcambon Till within the overlying grey diamicton of the Greystoke Till Formation.
Gravel Caverns Conglomerate Member
GCC
Mid Frasnian to Late Frasnian.
The relationship of the conglomerate to the enclosing mudrock is complex. Sheets and small channels occur commonly and there is considerable invasion of the enclosing mudrock by pebbles at both upper and lower contacts.
Polzeath area.
Greenish grey mudstone with thin black calcareous beds and beds of poorly sorted, matrix-supported conglomerate up to 1.6m thick.
90m (Gauss, G A and House, M R, 1972).
Ganey Coals Bed(S) (Coalbrookdale)
GCCC
Gwscwm Coal (South Wales)
GCCO
Glacial Channel Deposits
GCD
Variable lithology. Any infilling, by glacial deposits, of a channel formed by glacial processes. [Generic description].
Grange Crags Andesite Member
GCG
Flow banded andesite lava rests sharply on volcaniclastic rocks; in part rests unconformably on the Skiddaw Group (mudstones).
North Lake District near Borrowdale. (Ashness Wood to Dale Head).
Aphyric, fine-grained andesite lava, flow banded at base and autobrecciated at top.
Brecciated andesite lava overlain sharply by volcaniclastic rocks.
Great Conglomerate Formation
GCGL
Unconformable on the Silurian and Ordovician rocks of the Southern Uplands terrane.
The Southern Uplands Terrane, Scotland, bounded by the Southern Uplands Fault to the north-west in the Dunbar - Lauder - St Abb's area,
Red and purple conglomerates, fine- to coarse-grained, chiefly composed of rounded greywacke pebbles and boulders in a red-brown sandstone matrix with some interbedded pebbly sandstones, thin red-brown siltstones and mudstones.
120m to greater than 350m
Not generally seen as faulted against the Devono-Carboniferous in the Dunbar area. In the St Abb's area, it is overlain by Eyemouth Volcanic Formation.
Gerrards Cross Gravel Formation
GCGR
Ancestral Thames course (Vale of St. Albans).
Sand and gravel, locally with lenses of silt, clay or peat and organic material. [Generic description].
1-10m, average 4m thick.
Glen Clunie Graphitic Schist Formation
GCGS
Ganister Coal (Goyt Trough)
GCGT
Garibaldi Clayband Ironstone
GCI
Galboly Chalk Formation
GCK
Santonian. Uintacrinus socialis Zone (in part).
The exact relationship with the underlying Cloghfin Sponge Formation is not certain (Fletcher, 1978 p. 8 para 2). It is taken a well-developed separation plane above which the beds contain no appreciable arenaceous `contamination?.
Known throughout the North Antrim and East Antrim Basins and part of the Southern Upland, Highland Border and northern Londonderry Shelf. Absent elsewhere.
Chalk, with some flint bands and `incipient flints?. Marl partings common to base with some glauconite.
5.85m at its type section.
At a prominent bedding plane (an erosion surface in part) immediately above a zone of wavy and disturbed bedding. Overlain by the Cloghastucan Chalk Formation.
Gaick Psammite Formation
GCKP
Top of the Falls of Phones Semipelite Formation, where the predominant semipelite passes into predominantly feldspathic and quartzose psammites of the GaickPsammite Formation.
Strathspey to Glen Tilt and Glen Garry; widespread within the Strathtummel Basin.
Thick sequence of predominantly grey laminated fine-grained quartzose psammite with scattered biotite flakes and laminae. Some darker grey biotitic micaceous psammite interbeds with muscovite on partings. Calc-silicate lenses present and minor quartzite and semipelites near the base of the Formation. Most bedded units are 0.1 to 0.5m thick and some are cross-bedded
1 to 2km (but difficult to be precise)
Equivalent to the top of the Bruar Psammite Formation (Sheet 55W) i.e. the base of the Tummel Quartzite Formation, where white quartzite units predominate above the predominately psammite succession of the Gaick Psammite Formation.
Green Cleugh Siltstones
GCL
Glen Clunie Schist Formation [Obsolete Code: Use Gcgs]
GCLS
Glen Calcareous Member
GCM
Goblin Combe Oolite Formation
GCO
In the Bristol area and Broadfield Down it is taken at the incoming of ooidal limestones of the Formation above the dolomite and calcite mudstones and mudstones of the underlying Clifton Down Mudstone Formation. In the Weston-super-Mare area and Steepholm it is taken at the incoming of massive, coarse crinoidal and ooidal limestones of the Formation above the grey to dark grey, medium-bedded skeletal limestones of the High Tor Limestone Formation.
Bristol [ST 60 74], Broadfield Down [ST 50 65] and Weston-super-Mare [ST 30 60] areas. Passes northwards into the Clifton Down Mudstone Formation and southwards into the Burrington Oolite Subgroup.
Pale grey to grey, thick-bedded to massive, medium- to coarse-grained oolite and ooidal limestone with lenses of crinoidal limestone. Deposited in a barrier environment.
15m in the Bristol area [Avon Gorge] thickening to 70m at Weston-super-Mare.
In the Weston-super-Mare area it is taken at the incoming of the calcite mudstones of the Clifton Down Mudstone Formation above the ooidal limestones of the Formation. In the Bristol area it is taken at the incoming of calcite mudstones and skeletal limestones of the Clifton Down Limestone Formation above the ooidal limestones of the Formation.
Greenscoe Tuff Formation
GCOE
Unconformity. Erosion surface cut in Skiddaw Group.
East side of Duddon Estuary (Furness Inlier) between Green Haume (SD 221 751) and Soutergate (SD 227 813), Askam in Furness, Cumbria.
Interbedded sucession of silty mudstone, andesitic lapilli-tuff and tuff-breccia with andesite intrusions. The volcanic component increases up the succession.
Unconformity. Overlain by clastic/carbonate succession of the Dent Group.
Glen Coe Quartzite Member [Redundant Code: Use Dagq]
GCOEQ
Greenan Castle Pyroclastic Member
GCP
Where seen overlying sandstones, mudstones and cementstones of the underlying Ballagan Formation on the shore at Greenan Castle, possibly disconformable on (lithified) Ballagan Formation.
A local unit on the shore and around Greenan Castle (south of Ayr, Scotland), which dies out approximately 1km inland.
Bedded pyroclastic rocks and volcaniclastic sedimentary rocks comprising lithic lapilli tuffs and tuffs.
Thickness of 23 m at Greenan Castle in the Ayr district, yet dies out laterally.
Unconformably overlain by mudstones and sandstones of the Lawmuir Formation on the shore at Greenan Castle.
Gwscwm Rider Coal (South Wales)
GCRC
Glencoe Ring Intrusions
GCRI
Glencoe Ring Intrusions, Early Fault Intrusion
GCRIE
Glencoe Ring Intrusions, Main Fault Intrusion
GCRIM
Gisburn Cotes Beds
GCT
Green Croft Till Member
GCTI
Generally sharp, planar, glacitectonic, unconformable contact with dark brown clay of the Whinneyhill Coppice Clay Member of the Aikbank Farm Glacigenic Formation.
Mainly dark reddish brown (Munsell Soil) pebbly silt diamicton with interbeds of subglacially sheared pebbly sand, silt and clay. The diamicton contains clasts of igneous and metamorphic rock types from the Lake District together with some red sandstone and coal.
Sharp, unconformable contact with overlying reddish brown clay and silt of the Holmeside Clay Member of the Aikbank Farm Glacigenic Formation. Taken at the top of the uppermost bed of diamicton in the sequence.
Glencoe Caldera-Volcano Complex
GCVC
Grovesend Formation
GDB
The base is placed at the base of the Swansea Four-Feet Coal of the Swansea district (equivalent of the Llantwit No.3 Seam in the Pontypridd district and the Mynyddislwyn Seam east of the Taff valley), where it overlies mudstone seatearth at the top of the predominantly arenaceous Swansea Member in the Swansea district and the similar Hughes Member in the east of the coalfield. It is a conformable boundary in the west, but is assumed to be an unconformable one in the east (Woodland et al., 1957; Squirrell and Downing, 1969; Barclay, 1989). Also taken at the base of the laterally correlatable Rudge Coal in the Radstack part of the Somerset Coalfield, the High Coal of the Bristol Coalfield and the Avonmouth No.1 Coal of the Severn Coal Basin.
Small areas in the South Wales Coalfield, the Formation being preserved in the cores of synclines and fault troughs from Llanelli [SN 50 00] to Llanhilleth [SO 25 05]. Also in the Somerset, Bristol, Forest of Dean and Oxfordshire coalfields.
Predominantly argillaceous, comprising mudstones and siltstones, with well developed coals; minor lithic ("Pennant") sandstones; locally developed red mudstones in the type area.
To 426m in the South Wales Coalfield; 700m in the Oxfordshire-Berkshire coalfields.
The Grovesend Formation is the youngest unit found in the South Wales and Forest of Dean coalfields. It is overlain unconformably by sandstones of the Sherwood Sandstone Group in the Newent Coalfield, by mudstones of the of the Mercia Mudstone Group in the Oxfordshire Coalfield and either the Sherwood Sandstone or Mercia Mudstone groups in the Bristol/Somerset Coalfields.
Gardenstown Conglomerate Formation
GDC
Unconformity on various formations of the Early Devonian Crovie Group.
Afforck, Gamrie Bay, Quaynane, Turriff to east of Banff.
Conglomerate with thin lenticular sandstone and rare fish-bearing silty mudstone, e.g. Findon Fish Bed.
Top of Orcadian Old Red Sandstone sequence on the southern side of the Moray Firth east of Banff.
Gellideg Coal (South Wales)
GDCO
Glen Doll Pluton
GDDI
Glendearg Formation
GDE
Silurian, Llandovery, guerichi Biozone to spiralis Biozone.
Sandstone, typically fine- to medium-grained but ranging from very fine- to coarse-grained. Generally medium- to thick-bedded over thicknesses of tens of metres interspersed with units up to few metres very thin to thin-bedded. Scattered very thick beds in some cases parallel laminated throughout. Interbedded siltstone or silty mudstone generally in thin beds. Sandstone and siltstone typically greenish grey when fresh, pale brown weathering. Distinguished from the Selcoth Formation by the occurrence of very thick beds of parallel laminated sandstone. Other distinguishing factors include the wider age range (although overlapping in lowersmost part) and no evidence of a basal stratigraphical relationship with the Moffat Shale Group. Distinguished from Eskdalemuir Formation by the occurrence of very thick beds of parallel laminated sandstone and paler, less pervasive weathering reflecting lower carbonate content of the sandstone.
Uncertain, may be few hundred metres to 2000m
Glen Dessary Syenite S1
GDES1
Glen Dessary Syenite S2
GDES2
Glen Dessary Pluton
GDESY
Galdenoch Formation
GDF
Interfingers with Kirkcolm Formation.
Massive wacke and siltstone turbidite sequence.
c.500m
Danian To Ypresian Rocks (Undifferentiated)
GDGY
Glacial Deposits, Heterogeneous
GDH
Glacial Deposits, Heterogeneous (Irish Sea Ice)
GDHI
Gordale Limestone Member
GDLL
Taken at a conspicuous bedding plane at the base of the scar-forming pale grey, well-bedded limestone of the Gordale Limestone Member above the pale grey massive limestone of the Cove Limestone Member.
Southern part of the Askrigg Block, north of Settle, Yorkshire.
Scar-forming, mid to pale grey limestone, well bedded, varying from thick to very thick-bedded. Variations include fine- and medium-grained (more rarely coarse-grained) bioclastic calcarenite packstones, wackestones and subordinate grainstones, with thin conglomerates adjacent to the Middle Craven Fault. The wackestones and packstones commonly show pseudobrecciation and the grainstones are cross-bedded. Undulating palaeokarstic surfaces are present, commonly overlain by thin mudstone "clays" (bentonites). Topographically, the member forms conspicuous stepped scar features and prominent limestone pavements.
94m thick in its type section at Gordale Scar, elsewhere a thickness of 70-75m is typical.
The conformable upper boundary is drawn at the upward passage from pale grey limestones of the Gordale Limestone Member to darker grey limestone of the Lower Hawes Limestone at the base of the Alston Formation, Yoredale Group.
Gastropod Limestone
GDLS
Archerbeck Borehole and adjacent area. Correlared with Scar Limestone of Cumbria.
Grigadale Microgranite Intrusion
GDMGR
Glendouran Breccia Formation
GDN
Unconformity at the base of the formation overlying the Ordovician Kirkcolm Formation in Holmhead Burn [NS 8820 2082].
Small outlier, c.2-4km southsouthwest of Crawfordjohn, south Lanarkshire.
Mainly poorly sorted breccio-conglomerates containing clasts mainly of greywacke sandstone and siltstone. Some pebbly and gravelly sandstone interbeds.
Faulted off and not exposed, but lies towards the northeast in this local basin.
Glen Doe Psammite Formation
GDOE
Transitional with underlying Coire nan Laogh Semipelite Formation, contact taken at decrease of semipelite to <20% of the succession.
Northwestern part of Monadhliath Mountains, particularly in Glen Doe, Corrieyairack Pass and forest areas, and River Fechlin section and surrounding mountains.
Uniform turbiditic, feldspathic and micaceous psammite with thin semipelite interbeds and calc-silicate rock lenses.
Normal conformable contact with Tarff Banded or Monadhliath Semipelite formations, taken at incoming of semipelite to >20% of the succession.
Garbh-Dhail Quartz-Gabbro Ring-Intrusion
GDQGB
Goodrington Member
GDRN
Danian Rocks (Undifferentiated)
GDRU
Glen Derry Diorite
GDRY
Grindslow Siltstones
GDS
Glen Dubh Sandstone Formation
GDSA
Glen Dye Silts Formation
GDSI
Generally conformable on the Banchory Till Formation.
Laminated brown to olive grey silt and clay.
Generally 2 to 3m; 5m proved in boreholes
Generally overlain conformably by the Lochton Sand and Gravel Formation.
Glacial Deposits
GDU
Variable lithology. Heterogeneous glacial deposits lacking constructional form. [Generic description: 'TMOS' Procedures].
Glacial Deposits, 1
GDU1
Variable lithology. Heterogeneous glacial deposits lacking constructional form; older than 'Glacial Deposits' in the same map area. [Generic description: 'TMOS' Procedures].
Glacial Deposits (Irish Sea Ice)
GDUI
Goodwick Volcanic Formation
GDV
Drawn at base of rhyolitic lavas and tuffs of the Goodwick Volcanic Formation where it rests conformably on pillow lavas of the Strumble Head Volcanic Formation.
1:50,000 Sheet 209 (St.David's) and adjacent Sheet 210.
Rhyolite lavas and rhyolitic tuffs.
Up to 160 metres.
Drawn at conformable upward passage from rhyolitic lavas and tuffs of the Goodwick Volcanic Formation to calcareous flags.
Glasgow Ell Coal (Central Coalfield)
Glas Eilean Basaltic Vent
GEB
Great Easby Clay Formation
GECL
Unconformable boundary with red diamicton of the underlying Gillcambon Till Formation, or on bedrock.
The Solway Lowlands around Carlisle.
Dark reddish brown clay, silt and very fine-grained sand, generally thinly laminated and locally varved. Sparse dropstones.
10m or more.
Generally a sharp, planar, or gradational glacitectonic boundary with red diamicton correlated with the Plumpe Bridge Till Member of the Gretna Till Formation.
Geordie Coal
GECO
Gedden Coal
GED
Gelli Dolerite
GEDO
Amygdaloidal microgabbro.
To 235m
Gees Coal (South Lancashire)
GEES
Glenvale Sandstone Formation
GEF
The boundary is gradational, and is drawn at the base of the brown, yellow, red, purple or cream sandstones of the Glenvale Sandstone Formation, where it rests conformably on the red or purple pebbly sandstones of the Burnside Sandstone Formation.
The Fife and Kinross area of the Midland Valley of Scotland, sheets 40, 48 and 49.
Brown, red, purple, yellow and cream coloured feldspathic sandstone, commonly containing bands of red siltstone and pebbles of silty mudstone, but no siliceous pebbles.
Up to 350 m thick in the Lomond Hills area.
Drawn at the probable conformable upward passage from brown, yellow, red, purple or cream sandstones of the Glenvale Formation to the white or cream sandstones of the Knox Pulpit Sandstone Formation. In the Cupar area, the Dura Den Member intervenes.
Eocene And Oligocene Rocks (Undifferentiated)
GEGO
Glasgow Ell Index Coal (Central Coalfield)
GEI
Glas Eilean Lava Formation
GEIL
K/Ar dating of the lavas gives an age of 285+/- 5Ma, approximating to the Sakmarine-Asselian stage boundary within the Lower Permian [Jin et al., 1997].
Conglomeratic sandstone at the base of the Formation, approximately 7m thick [Pringle and Bailey, 1944], is inferred to overlie Dalradian rocks unconformably [Upton et al., 1987].
Onshore exposures on the islet of Glas Eilean and the Black Rock Skerries, and underlying the Sound of Islay between the islands of Islay and Jura, Argyll, Scotland.
Alkali olivine-basalt intercalated with sedimentary rocks. A basal reddish-brown conglomeratic sandstone, with clasts up to about cobble size, and red to reddish-brown fine-grained sandstone is overlain by a sequence of basalt lavas [Pringle and Bailey, 1944]. Each lave flow is less than 2m thick [Upton et al., 1987] and amygdaloidal; some flows have slaggy tops. Reddish sandstone is present as isolated lenses. Sandstone, calcareous sandstone and sandy limestone may overlie and infill fissures within the lavas [Pringle and Bailey, 1944]. The thicker lava flows occur towards the base of the succession, average flow thickness decreases upwards with increasing amount of sedimentary intercalations. The basalts are sparsely microphyric with phenocrysts mostly of olivine, plagioclase and augite [Upton et al., 1987].
>120m
Gelli-Grin Calcareous Ash Formation
GEL
Conformably overlies the upper part of the Ceiswyn Formation in the Bala district, but might pass into the latter formation in the Cadair Idris district, where its correlative is the Craig Hen-gae Member (of the Ceiswyn Formation).
Calcareous volcanaclastic sandstone, tuffs and tiffites.
Conformably overlain by the black mudstones of the Nod Glas Formation, but also passes laterally into its lower part (Lockley, 1980). Also overlain unconformably by the Rhiwlas Limestone Formation.
Gelli Coals (South Wales)
GELI
Goose Sandstone Member
GEM
Conformable lower contact on Drumderfit Conglomerate Member.
Red sandstone, largely of fluvial origin.
c. 200 metres.
Conformable upper contact with Kellen Burn Mudstone Member.
General's Rock Sandstone
GENR
Geordie's Coal
GEOC
Eocene Rocks (Undifferentiated)
GERU
Glen Effock Schist Formation
GES
First incoming of dark, greenish, biotitic and feldspathic semipelite with layers showing high magnetic susceptibility at top of Tarfside Psammite Formation.
Arcuate belt 4-5km wide in the southern parts of Sheets 65E and 66W from c. NO 3876 to NO 6280.
Dominant semipelite, but with considerable psammite and pelite. Psammites micaceous but fairly massive, rarely gritty. Greenish feldspathic semipelite with high magnetic susceptibility and associated micaceous psammites locally abundant near the base of the Formation. Beds of white quartzite with specks of green mica occur, particularly near the top of the Formation. Calc-silicate rocks are extremely rare.
Apparently 2500m thick in Greenburn - Colmeallie area (NO5578 to NO5977), but this figure is probably inflated by tectonic thickening.
Gradational transition with incoming of muscovite-staurolite-schist and increase in proportion of gritty psammite and decrease in proportion of greenish feldpathic semipelite at base of overlying Glen Lethnot Grit Formation.
Gortnaree Sandstone Member
GESM
Conformable and abrupt; calcareous sandstones and very sandy limestones at base of member rest on 0.16m of calcareous silty shale and argillaceous limestone at top of Termon River Limestone Formation.
Sandstone, medium grey, weathering to brown rottenstone, fine- to medium-grained, calcareous, interbedded with pale blue-grey, variably arenaceous, bioclastic, crinoidal packstone with pellets.
Conformable and gradational; decreasing arenaceous content upwards into normal Ballyshannon Limestone Formation. Boundary located at base of blue-grey bioclastic packstones.
Great Estuarine Group
GEST
Gelli Tuff Member
GETU
Glen Ea's Vein
GEV
Gilfach Coal (South Wales)
GFACH
Gutterford Burn Flagstones
GFB
Glaciofluvial Ice Contact Deposits, Devensian (Welsh Ice)
GFCDW
Gorllwyn-Fach Member
GFCH
Gosford Bay Sill
GFDBY
Glaciofluvial Deltaic (And/Or Subaqueous Fan) Deposits
GFDD
Variable lithology, typically sand and gravel; formed as glaciofluvial deltas and/or subaqueous fans. [Generic description].
Glaciofluvial Deltaic Deposits, Devensian (Irish Sea Ice)
GFDDI
Glaciofluvial Deposits, Devensian (Irish Sea Ice)
GFDIS
Glaciofluvial Deposits, Mid Pleistocene
GFDMP
Cromerian to Oxygen Isotope Stage 6.
Glaciofluvial Deposits
GFDU
Sand and gravel, locally with lenses of silt, clay or organic material; of glaciofluvial origin. [Generic description].
Glaciofluvial Deposits, 1
GFDU1
Sand and gravel, locally with lenses of silt, clay or organic material; of glaciofluvial origin; older than "Glaciofluvial Deposits [undifferentiated]" in the same map area. [Generic description].
Glaciofluvial Deposits, Anglian
GFDUA
Glaciofluvial Deposits, Devensian
GFDUD
Glaciofluvial Deposits (Irish Sea Ice)
GFDUI
Gruney And Fethaland Formation
GFF
Glaciofluvial Ice Contact Deposits
GFIC
Sand and gravel, locally with lenses of silt, clay and organic material. Moundy topography is characteristic, but flat-topped mounds are common. Glaciofluvial deposits laid down on, under or against a glacier or ice-sheet. [Generic description: 'TMOS' Procedures].
Glaciofluvial Ice Contact Deposits, Anglian
GFICA
Generally unconformable on older strata.
Great Britain north of the Anglian ice limit.
Sand and gravel.
Variable younger strata including Anglian Till and younger deposits, through to present day, or upper surface exposed.
Glaciofluvial Ice Contact Deposits, Devensian
GFICD
Glaciofluvial Ice Contact Deposits, Devensian (Irish Sea Ice)
GFICI
Glaciofluvial Ice Contact Deposits, Mid Pleistocene
GFIMP
Cromerian to Oxygen Isotope Stage 6
Gwern Feifod Lava Member
GFL
Conformably overlies volcaniclastic blue-grey mudstone of the Llangynog Formation.
Flow-foliated and brecciated, vesicular felsic lava.
Overlain by volcaniclastic mudstones and tuff [Gwern Feifod Tuff].
Graig Fawr Limestone Member
GFLS
Entry of massive "reef" limestones above well bedded Loggerheads Limestone; also passes laterally southwards into the Loggerheads Limestone, and passes laterally northwards into the Prestatyn Limestone Formation (Craven Group).
Dyserth area (SJ 06 80), North Wales.
Knoll reef limestones comprising highly fossiliferous, massive, pale, fine-grained, recrystallised and locally dolomitised limestones with abundant calcite-lined former cavities with internal geopetal sediment (stromatactis). Contains a rich brachiopod and goniatite fauna. During the time of late Asbian carbonate platform development in North Wales a series of knoll reefs formed along, and serve to define, the platform margin. The knoll reef facies interdigitate with platformal facies on one side, and resedimented basinal facies of the Craven Group on the other.
Massive "reef" limestones overlain by dark grey mudstones and thin argillaceous limestones of the Teilia Formation.
Glaciofluvial Fan Deposits
GFN
Glaciofluvial Fan Deposits 1, Devensian
GFND1
Glaciofluvial Fan Deposits 2, Devensian
GFND2
Glaciofluvial Fan Deposits, Devensian
GFNQD
Giffnock Sandstone
GFNS
Glasgow district south of the Clyde; impersistent elsewhere. Originally named after Giffnock, 4.5 miles southsouthwest of Glasgow.
Gyfenni Wood Shale Formation
GFS
Passage into undifferentiated Nantglyn Flags.
Western parts 1:50,000 map sheet 165 (Montgomery).
Mudstones, bedding-fissile, silty, grey-brown (when weathered); largely graptolitic hemipelagite.
<100m
(SO 2135 9014) Overlain by Bailey Hill Formation which in places includes the Dingle Mudstone Member at its base.
Glaciofluvial Sheet Deposits, 1, Devensian
GFS1D
Glaciofluvial Sheet Deposits, 2, Devensian
GFS2D
Glaciofluvial Sheet Deposits, 3, Devensian
GFS3D
Glaciofluvial Sheet Deposits, 4, Devensian
GFS4D
Gutterfoot Sand Member
GFSA
Gradational on underlying St Bees Till Member.
1:50k Sheets 37 Gosforth and 38 Whitehaven, western Cumbria.
A coarsening-upwards sequence of yellowish brown clayey silt ad silty clay, passing upwards into silty fine-grained sand and finally into fine- and medium-grained sand.
About 8 to 12m thick
Unconformabley overlain by younger deposits including the reddish-brown thinly nterbedded sand, sandy silt and diamicton of the Peckmill Sand Member, How Man Till Member, and the trough cross-bedded sand and gravel of the Peel Place Sands and Gravel Member (of the Gosforth Glacigrnic Formation).
Glaciofluvial Sheet And Channel Deposits
GFSCD
Glaciofluvial Sheet Deposits
GFSD
Sand and gravel, locally with lenses of silt, clay or organic material; characteristic 'sandur' (sheet) and valley train form; of glaciofluvial origin. [Generic description: 'TMOS' Procedures].
Glaciofluvial Sheet Deposits, 1
GFSD1
Glaciofluvial Sheet Deposits, 2
GFSD2
Glaciofluvial Sheet Deposits, 3
GFSD3
Glaciofluvial Sheet Deposits, Anglian
GFSDA
Glaciofluvial Sheet Deposits, Devensian
GFSDD
Glaciofluvial Sheet Deposits, Devensian (Irish Sea Ice)
GFSDI
Glaciofluvial Sheet Deposits, Devensian (Welsh Ice)
GFSDW
Great Farlow Sandstone Formation
GFSF
Glaciofluvial Sand And Gravel
GFSG
Sand and gravel, locally with lenses of silt, clay and organic material; of glaciofluvial origin. [Generic description: from East Anglian data].
Glaciofluvial Sheet Deposits, Mid Pleistocene
GFSMP
Glen Fintaig Semipelite Formation
GFSP
Glaciofluvial Sub-Glacial Deposits
GFSU
Sand and gravel, locally with lenses of silt, clay or organic material; deposited by subglacial streams. [Generic description].
Gwern Feifod Tuff Member
GFT
Conformably overlies the felsic Gwern Feifod Lava Member [Llangynog Formation].
Coarse- to fine-grained welded felsic crystal lapilli tuff.
About 10m
Conformably and gradationally overlain by volcaniclastic mudstones of the main part of the Llangynog Formation.
Glaciofluvial Terrace Deposits
GFTD
Sand and gravel, locally with lenses of silt, clay or organic material; of glaciofluvial origin; terrace-like landform. [Generic description].
Glaciofluvial Terrace Deposits, 1
GFTD1
Glaciofluvial Terrace Deposits, 2
GFTD2
Glaciofluvial Terrace Deposits, 3
GFTD3
Geomorphological terrace (3) fromed of glaciofluvial deposits. May occure in valley-floor or valley-side settings. Where flights of terraces are identified these are numbered informally (1, 2, 3, etc) in order of increasing age. Terrace 3 occurs at higher elevation, and is therefore probably older, than glaciofluvial terrace 2 (GFTD2).
Glaciofluvial Terrace Deposits, 4
GFTD4
Geomorphological terrace (4) fromed of glaciofluvial deposits. May occure in valley-floor or valley-side settings. Where flights of terraces are identified these are numbered informally (1, 2, 3, etc) in order of increasing age. Terrace 4 occurs at higher elevation, and is therefore probably older, than glaciofluvial terrace 3 (GFTD3).
Glaciofluvial Terrace Deposits, Devensian
GFTDD
Glaciofluvial Terrace Deposits, Mid Pleistocene
GFTMP
Glaciofluvial Deposits, Devensian (Welsh Ice)
GFUDW
Glasallt-Fawr Formation
GFWR
Gwastaden Group
Drawn at the base of the Gwastaden Group where mudstones rest conformably upon shales of the Blue Black Shales Formation.
Rhayader district, Radnorshire and Breconshire.
Mudstones, shales, flags and grits.
552 metres approximately.
Drawn at the conformable upward passage of grits of the Gwastaden Group where it is unconformably overlain by the Caban Group.
Glen Girnock Calcareous Formation
GGC
Gorge Sandstone
GGES
Grassington Grit
GGF
A sharp upward change in a conformable succession from the predominantly grey mudstone to sandstone-base of first pebbly sandstone bed above the Pendle Grit Member.
The Yorkshire Pennines to the east of the River Ribble.
A medium- to thickly-bedded, brownish grey, medium- to coarse-grained sandstone and pebbly sandstone, which is massive to coarse bedded; beds of siltstone can occur throughout and locally coals are developed. The unit is interpreted as a delta top sandstone.
From 75 to 100m
A sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of the last coarse-grained or pebbly sandstone below the synsedimentary slumped siltstones and sandstones of the Roeburndale Member.
Great Glen Fault Zone
GGFZ
Gallagh Bridge Formation
GGH
Sharp contact with white dolomitic limestone of the underlying Magnesian Limestone Formation.
Sandstone, red, fine-to-medium-grained, dolomite cement; thin layers of red siltstone and mudstone, brown mudstone up to 15%.
Gradational but rapid decrease in cemented sandstone and increase of red mudstone and siltstones in the overlying Drumderg House Formation [formerly known as Permian Upper Marls].
Greengate Well Limestone
GGL
Pale grey compact even-bedded limestone and subordinate shaly calcareous mudstone.
c.10m maximum, thinning eastwards to about 5m; locally split by c.1.5m of calcareous shaly mudstone.
Goat Gills Member
GGM
Base not seen.
Breccia, mainly of siltstone in a siltstone matrix.
Approx. 100 metres.
Top sharp with overlying (inverted sequence) Robinson Member.
Gun Gardens Marls (One)
GGMA1
Gun Gardens Marls (Two)
GGMA2
Gun Gardens Marls (Three)
GGMA3
Glyngwilym Coal (South Wales)
GGMC
Gun Gardens Main Marl
GGMM
Glen Gairn Pluton
GGN
From Rb-Sr whole rock isochron ages: 404 +/- 6Ma, equivalent to Pridoli to Lochkovian (Harland et al, 1990), or Praghian to Emsian (Gradstein and Ogg). Taken as Ludlow to Early Devonian for convenience.
Glen Gour Quartzite And Pelite Formation
GGQP
Glen Gloy Quartzite Formation
GGQU
Green Grove Sandstone
GGS
Gorpley Grit
GGT
Gwern Gof Tuff Formation
GGTU
Rests on sandstones and mudstones intercalated in the Llewelyn Volcanic Group above the Foel Fras Volcanic Complex.
East of Carnedd Dafydd to east of Tryfan.
Non- to weakly-welded acidic ash-flow tuffs with cross-laminated, well-bedded tuffaceous sandstone derived from the tuffs.
Underlies sandstone and siltstone in the Llewelyn Volcanic Group that underlies the Capel Curig Volcanic Formation..
Glass Houghton Rock
West/south Yorkshire, especially between Castleford and Sharlston [Glass Houghton, near Castleford, Yorkshire].
Brown and grey micaceous sandstone.
30m in Glass Houghton area; known to 42m in borehole cores.
Great House Agglomerate
GHAG
Unconfirmed, but deduced as "Early Carboniferous" (Welch and Trotter, 1960).
Garth Hill Beds
GHB
Gibbet Hill Conglomerate Bed
GHC
Grain Heads Siltstone Member
GHD
Conformable: green-grey bioturbated mudstones immediately overlying medium- to coarse-grained sandstones of the Cock Rig Formation.
Highly fossiliferous silty mudstones, siltstones and fine-grained sandstones.
Conformable: highest laminated sandy siltstones and fine-grained sandstones with abundant bioclasts on bedding planes, below Lamb Rig Siltstone Member.
Garabal Hill - Glen Fyne Pluton
GHGFP
Great House Intrusion
GHIN
Grumack Hill Quartzite Member
GHQU
Junction with underlying pelites (Corinacy Pelite Member).
NW flank of watershed ridge (including Grumack Hill) on the SE side of the River Deveron Valley, between NJ 448 355 and Hill of Bank (NJ 388 290) NB The outcrop does not include the actual summit of Grumack Hill.
Quartzite, buff, grey to off-white and gritty psammite.
c. 400m
Junction with overlying, highly magnetic biotite-andalusite-schist (Garnel Burn Pelite Member of the Clashindarroch Formation).
Gorse Hall Rock
GHR
Grinshill Sandstone
GHSA
Garleton Hills Volcanic Formation
GHV
Base of volcanic rocks resting on sedimentary rocks of Inverclyde Group (Ballagan Formation).
Little known; thins in all directions.
Basaltic and trachytic lavas and tuffs predominate; but subordinate volcanic-derived sedimentary rocks also occur.
380m in Garleton Hills (240m at North Berwick; 257m in Spilmersford Borehole).
Glur-Bheinn Member
GIBH
Garibaldi Coal (Central Coalfield)
GIC
Gillers Inn Coal (Bristol Area)
GICO
Gillis Field Microporphyroblast Gneiss Member
GIFG
Gilmerton Ironstone
GIIR
The Midlothian "basin" - specifically around Gilmerton.
A "blackband" ironstone, lov=cally containing fish remains.
The bed, which is in the sequence above the Gilmerton (Hurlet) and below the North Greens limestones, was formerly worked.
Gillespie Coal (Lothian)
GILC
Gill Coal (Douglas)
GILL
Gilnahirk Group
GILN
Gin Head Vent
GINH
Ginstane Ironstone
GINI
Gin Head (Older) Vent
GINO
Girlsta Limestone Formation
GIRL
Gras Isaf Coal (South Wales)
GISC
Gillfoot Sandstone Member
GISD
Gradational contact with strata of the Southerness Limestone Formation.
Gillfoot Bay, Southerness, Kirkudbrightshire, south-western Scotland (Southern Uplands).
Interbedded medium- to coarse-grained sandstone and conglomerate.
120 to 150m
Gradational with the Powillimount Sandstone Formation, taken as the top of the uppermost conglomerate associated with reddened strata.
Georges Island Till
GIT
Gilwern Volcanic Formation
GIVO
Giffnock Jewel Coal (Glasgow)
GJC
Gourock Sandstone Member
GKA
Although the boundary is not exposed it has been mapped in the vicinity of Gourock Golf Course [NS 2230 7630] on the basis of the presence of thick beds of white, cross-bedded pebbly sandstone belonging to the Gourock Sandstone Member overlying the more thinly bedded rocks of the Knocknairshill Member.
Greenock district south of the River Clyde, also west of the Largs Fault Zone, Strathclyde, Scotland.
White, cross-bedded sandstone with thin beds of red-brown silty mudstone; nodules and thin beds of pedogenic carbonate. This unit is distinguished from other units of the Clyde Sandstone Formation by the presence of thicker beds of sandstone, a lesser proportion of mudstone and less abundant calcareous nodules (Paterson and Hall, 1986; BGS, 1990). The sandstone is described as thick multi-storey bodies of white pebbly sandstone by Paterson et al. (1990).
Top not seen, but is presumed to be overlain by sandstone and mudstone strata of the Broadlee Glen Sandstone Member (Paterson and Hall, 1986) that include distinct plant debris and beds of grey mudstone (BGS, 1990).
Gortnaskea Coal (Dungannon)
GKC
Garnkirk Main Fireclay
GKFC
Glasgow area.
Garnkirk Lower Fireclay
GKLF
Gledstone Kennels Beds
GKN
Glenshesk Tuff Formation
GKTU
Lowest tuff layer resting on highest basalt lava flow of Carey River Basalt Formation.
Interbedded purplish brown, grey, tuffaceous mudstone; pale grey, tuffaceous sandstone; green, vitric and lithic, coarse tuffs.
Lowest coal seam (H) of the Murlough Bay Coals overlying mudstone.
Glen Kyllachy Intrusion
GKYL
Great Limestone Member
Taken at the generally conformable, sharp base of the first bed of limestone that overlies measures of the Alston Formation; in most localities the limestone directly overlies the Tuft Sandstone, a brown, micaceous fine-grained sandstone that has a rooty upper part and which locally may be overlain by a thin carbonaceous smear or a coal.
Occurs throughout northern England at the top of the Alston Formation
Limestone (bioclastic packstone), medium to dark blue-grey, thickly bedded with thin shaly mudstone partings along uneven or wavy bedding planes. There is much crinoid debris throughout and there are many other beds rich in brachiopods and/or corals. The internal stratigraphy of the member is, in parts, remarkably consistent throughout the region and four informal divisions are recognised (Fairbairn, 1980), and referred to from the base upwards as the Bench, Main and Transitional posts and the Tumbler Beds. Beds rich in fossils are widespread. Most noteable and widespread are: the Chaetetes Band (Johnson, 1958) which occurs near the base; this comprises a sponge biostrome along with locally abundant brachiopods, corals and ostracods; within the Main Posts are the Brunton Band comprising the rare alga Calcifolium (Johnson, 1958; Cossey, et al, 2004), and the Frosterly Marble (Johnson, 1958). At the top, the Tumbler Beds, typically 2-5m thich, comprise thick beds of limestone interbedded with persistent mudstone units.
14-18m north of the Lake District; c 12m in the Vale of Eden; 16-22m on the Alston Block; 22-24m with a maximum of 40m on the Askrigg Block and 8-15m in the Northumberland Trough; c 22m in the Langholm area and Archerbeck Borehole.
Taken at the top of the uppermost limestone beds that is overlain by a sequence of dark grey siltstones and mudstones at the base of the Stainmore Formation.
Glass Coal (Midlothian)
GLA
Glacigenic Deposits
GLACI
Glenga Amphibolite Member
GLAM
Conformable on Dungiven Limestone Formation.
Glenga and Oughtnager Townlands, County Londonderry, Northern Ireland.
Pale to dark green amphibole schist with local thin lenticles of impure limestone.
Maximum 700m
Chloritic greenbeds passing upwards into Dart Formation clastic lithologies.
Glassee Coal (Fife)
GLAS
Gunnscroft Limestone
GLB
Glen Banchor Succession
GLBA
Central Highlands of Scotland. Newtonmore - Kincraig areas and possibly with representatives in the Aviemore - Fortrose and Nairn districts.
Strongly gneissose heterolithic association - dominantly of psammite, striped psammite and semipelite quartzite. Locally migmatitic with minor pods and lenses of amphibolitic metabasic rock.
1 - 1.5 km estimated.
Unconformity interpreted with overlying Grampian and Appin Group metasediments.
Glaciolacustrine Beach Deposits
GLBD
Glebe Farm Bed
GLBF
Sharp change up (probably an erosive non-sequence) from mudstone with argillaceous limestone nodules of undifferentiated Foston Member into limestone with pebbles as above; at 182.60m depth in type section Copper Hill Borehole (SK94SE/56). Base of Glebe Farm Bed marks base of Charmouth Mudstone Formation in this area.
East Midlands: north Leicestershire to Linclonshire. Not recognised in the Charmouth Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into mudstone-dominated Charmouth Mudstone formation.
Grey, brown weathering, bioclastic limestone bed up to 0.1m thick, with abundant bivalve fragments and limestone pebbles, overlain by brownish grey, weathering to reddish, ferru-ooidal limestone/calcareous ooidal ironstone bed up to 0.3m thick. Fauna includes gastropods, bivalves, forams, ammonites, belemnites and crinoids.
0.2 to 0.5m; 0.20m in type section.
Change up from limestone/ironstone as above into grey mudstone of Charmouth Mudstone Formation; at 182.40m depth in type section Copper Hill Borehole (SK94SE/56).
Glass Coal (Musselburgh, Midlothian)
GLC
Globe Coal (Somerset)
GLCO
Glen Lochsie Calcareous Schist Member
GLCS
Stratigraphical boundary with the underlying Tulaichean Schist Formation. Boundary placed at a massive weathering, dark, garnet-biotite rock, where developed.
Northern part of Glen Shee district.
Dark metacarbonate rock and psammite with graphitic pelite and some garnet calcareous schist; crystalline metacarbonate rock locally developed at top of member.
Top of prominent blue-grey coarsely crystalline metacarbonate rock below the overlying dominantly graphitic Glen Taitneach Schist Member.
Glauconitic Sandstone Member
GLCSA
Glaciolacustrine Deposits [See Descriptions For Limitations Of Use]
GLD
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also GLDF, GLDG and GLDS. The full description on the original map was "GLACIOLACUSTRINE DEPOSITS (mainly beyond Scottish Readvance)".
Glaciolacustrine Deltaic Deposits
GLDD
Sand, gravel and clay; formed during the melting of glacier ice. [Generic description: 1:50 k map margins].
Glaciolacustrine Deltaic Deposits, Devensian
GLDDD
Glaciolacustrine Deposits, Mostly Fines [See Descriptions For Limitations Of Use]
GLDF
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also GLD, GLDG and GLDS. The full description on the original map was "GLACIOLACUSTRINE DEPOSITS (mainly beyond Scottish Readvance), Mostly fines.
Glaciolacustrine Deposits, Mostly Gravels [See Descriptions For Limitations Of Use]
GLDG
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also GLDF, GLDS and GLD. The full description on the original map was "GLACIOLACUSTRINE DEPOSITS (mainly beyond Scottish Readvance), Mostly gravels"..
Glen Dhoo Formation
GLDH
A pale grey mudstone, with a variable proportion of siltstone laminae and sandstone dispersed in thin; sandstone locally predominant in thin to thick-bedded packets; siltstone, massive, dominant locally; minor occurences of andesitic tuff and volcanic breccia
About 300 m thick.
Faulted contact only with the Ladyport Formation, which is distinguished by a change from a siltstone/sandstone-dominated facies to a mudstone-dominated facies in the Ladyport.
Glaciolacustrine Deposits, Mostly Sands [See Descriptions For Limitations Of Use]
GLDS
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also GLDF, GLDG and GLD. The full description on the original map was "GLACIOLACUSTRINE DEPOSITS (mainly beyond Scottish Readvance), Mostly sands".
Glen Member
GLE
Abrupt changes at top and bottom of member to interbedded shale and micrites of Meenymore Formation.
Grey-buff coloured gritty-coarse grained compact sandstone interbedded with thin horizons of mudflake breccia containing fragments of shale and laminate micrite from underlying Meenymor Formation.
c 20 metres (estimated).
Glenfinnan Group And Loch Eil Group (Undifferentiated)
GLEIL
Glenboig Limestone
GLEL
Glenfinnan Group
GLEN
Glencolumbkille Pelite Formation
GLEP
Gwent Levels Formation
GLEV
Rests unconformably of Triassic bedrock.
The Gwent Levels. From Caldicot, Monmouthshire, to Cardiff.
Formation encompasses marine, estuarine and terrestrial deposits that were formed in the Gwent Levels area during the Holocene transgression. The deposits are dark blue-grey silty clays and silts with subordinate sands and beds of peat, submerged forests and gravel. The deposits rest on a rockhead platform at -5 to -7.5m OD, intricately dissected by river valleys, and their upper surface is approximately level at c 4.5 to 7m OD. The river valleys are infilled with gravels and sands that become shelly upwards. Typically two beds of peat are included, up to 0.6m thick. The lower of these forms the lowest unit in the formation, except where it rests upon the valley-fill sands and gravels, and was formed c 8500-8000 years BP when a birch forest was inundated by the rising sea. The other formed c.5000-4500 years BP during a slowing down of the rising sea level, and is now found resting horizontally at OD.
10 to 15m, increasing to 35m in buried channels.
Glenboig Lower Fireclay (Central Coalfield)
GLFC
? Arnsbergian.
Glenfuir Coal [Central Coalfield]
GLFU
Lutetian And Bartonian Rocks (Undifferentiated)
GLGB
Lutetian To Priabonian Rocks (Undifferentiated)
GLGI
Glamorgan Glacigenic Formation
GLGL
Glacial Gravel
GLGR
Sand and gravel, locally with interbeds of silt and clay; of glacial origin. [Generic description].
Glenbuchat Graphitic Schist Formation
GLGS
Lower limit of graphitic pelites above striped phyllitic semipelites and psammites of the Culchavie Striped Formation.
Elongate, N-S trending outcrop, up to 750m wide, extending from area of Scors Burn [NJ 322 229] to Glen More [NJ 328 044]. Also in Lecht area, Gordon District. 1: 50 000 Sheet 75E.
Graphitic pelites and semipelites, slaty to schistose with minor psammite and rare banded limestone.
To 500m.
Upper limit of graphitic pelites at the base of schistose semipelites of the Badenyon Schist and Limestone Formation.
Glen Lethnot Grit Formation
GLGT
Gradational transition from Glen Effock Schist Formation marked by incoming of silvery muscovite-rich pelite, increase in proportion of gritty psammite and decrease in proportion of green feldspathic semipelite.
Occurs in the southeast corner of Sheet 65E and the southern border of Sheet 66W from White Hill (NO 402 731) to Bannock Hill (NO 610 760).
Mixed psammite, semipelite and pelite. Psammites typically gritty. Pelites include types rich in staurolite and muscovite, and some are also kyanite-bearing. Schists rich in iron-ore minerals form mappable units in places. Beds of quartzite with specks of green mica occur rarely near the base of the Formation.
At least 3000m indicated in Glen Esk; tectonic thickening probably less than in Glen Effock Schist Formation.
Not seen: faulted against Highland Border Complex.
Glynbourne Hardgrounds
GLHG
Glaciolacustrine Deposits
GLLD
Silt and clay, laminated, commonly rich in organic matter, locally with interbedded peat; of glaciolacustrine origin. [Generic description: academic papers and BGS Memoirs].
Glaciolacustrine Deposits, 1
GLLD1
Glaciolacustrine Deposits (Anglian)
GLLDA
Glaciolacustrine Deposits, Devensian
GLLDD
Glaciolacustrine Deposits (Irish Sea Ice)
GLLDI
Glaciolacustrine Deposits (Age Unknown)
GLLDU
Glaciolacustrine Deposits, Mid Pleistocene
GLLMP
Glenelly Formation
GLLY
Conformable with Dart Formation.
Sperrin Mountains, counties Tyrone and south Londonderry, Northern Ireland.
Mixed series of quartz feldspar psammites and semi pelitic biotite schists with tourmaline.
at least 2.7km
Conformable with Glengawna Formation.
Glenkeel Member
GLM
Glynde Marls (One)
GLMA1
Glynde Marls (Two)
GLMA2
Glenboig Marine Band
GLMB
Glion Cam Formation
GLMC
Glascoed Mudstone Formation
GLMD
The central part of the (Silurian) Usk Inlier, South Wales.
Calcareous silty mudstones and siltstones, with limestone nodules, localised thin bentonitic clays, and very fossiliferous containing a diverse shelly fauna, mainly of brachiopods.
At least 220 m thick.
At the base of sandstone-dominated beds of the Ton Siltstone Formation.
Glauconitic Marl Member
GLML
Upper Cretaceous, Cenomanian. Mantelliceras mantelli Zone, Neostlingoceras carcitanense Subzone. (Note: over synsedimentary highs such as the Mid Dorset Swell the age range may well included zones up to Acanthoceras rhotomagense).
Base of glauconite-rich sand or clay resting disconformably, at a strongly burrowed surface, on pale grey siltstones of the Upper Greensand (or grey mudstones of the Gault), which contain only a trace of glauconite at most. [Note: bioturbation may carry glauconitic sediment down into underlying formation].
Known throughout much of the Southern Province in Kent, Surrey, Sussex, Hampshire and Berkshire.
Calcareous glauconitic sand and glauconitic sandy silty chalk with phosphatic nodules.
2-4m throughout much of Southern Province, may be only a few tenths of a metre elsewhere over synsedimentary structural highs. Up to 5m in Kent and at Eastbourne, East Sussex.
Upwards cessation of sand and/or abundant glauconitic grains (and phosphatic pebbles)(can occur as a rapid transition over 10cm or less) into grey, sparsely glauconitic chalky marl or marly chalk, comprising the rest of the West Melbury Marly Chalk Formation and part of the Zig Zag Chalk Formation (broadly equivalent to the traditional scheme 'Chalk Marl').
Glen More (Centre 1) Suite
GLMO
Glen Balleira Formation
GLNBA
Late Devensian (Lateglacial 18.5 to 12.5 ka PB).
Unconformably overlies glacigenic deposits (diamictons, laminated muds, sands and gravels) of the Jurby and Orrisdale formations.
Northern part of the Isle of Man. (50k sheets 36 and possibly 46).
Peat, organic mud and calcareous marl that infills kettlehole basins.
2m of calcareous marl, capped by peaty clay, is recorded in a kettlehole infill at Glen Wyllin.
Usually the ground surface, but may be overlain by Holocene sediments (such as peat, with Holocene plant and insect remains, or brown sand).
Glacan Mor Basic Magmatic Breccia Intrusion
GLNM
Glendowran Formation
GLNN
Glacially Over-Ridden Terrain (By Readvance Ice) [See Descriptions For Limitations Of Use]
GLO
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also GLOD, GLOF, GLOG and GLOS. Note that on the related Quaternary Domains map, this category was described as: "GLACIALLY OVER-RIDDEN TERRAIN (by Readvance Ice) (recognised by scattered hill-hole pairs, extensional normal faulting dying out at depth, surficial Scottish Readvance diamicton and associated subglacial shearing)".
Glacially Over-Ridden Terrain (By Readvance Ice), Mostly Till [See Descriptions For Limitations Of Use]
GLOD
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also GLO, GLOF, GLOG and GLOS. Note that on the related Quaternary Domains map, this category was described as: "GLACIALLY OVER-RIDDEN TERRAIN (by Readvance Ice) (recognised by scattered hill-hole pairs, extensional normal faulting dying out at depth, surficial Scottish Readvance diamicton and associated subglacial shearing), Mostly till".
Glacially Over-Ridden Terrain (By Readvance Ice), Mostly Fines [See Descriptions For Limitations Of Use]
GLOF
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future.To avoid potential confusion it should be used only for similar purposes in future. See also GLO, GLOD, GLOG and GLOS. Note that on the related Quaternary Domains map, this category was described as: "GLACIALLY OVER-RIDDEN TERRAIN (by Readvance Ice) (recognised by scattered hill-hole pairs, extensional normal faulting dying out at depth, surficial Scottish Readvance diamicton and associated subglacial shearing), Mostly fines (glaciolacustrine)".
Glacially Over-Ridden Terrain (By Readvance Ice), Mostly Gravels [See Descriptions For Limitations Of Use]
GLOG
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also GLO, GLOD, GLOF and GLOS. Note that on the related Quaternary Domains map, this category was described as: "GLACIALLY OVER-RIDDEN TERRAIN (by Readvance Ice) (recognised by scattered hill-hole pairs, extensional normal faulting dying out at depth, surficial Scottish Readvance diamicton and associated subglacial shearing), Mostly gravels (sandar)".
Gleann Oraid Formation
GLORD
Glacially Over-Ridden Terrain (By Readvance Ice), Mostly Sand [See Descriptions For Limitations Of Use]
GLOS
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also GLO, GLOD, GLOF and GLOG. Note that on the related Quaternary Domains map, this category was described as: "GLACIALLY OVER-RIDDEN TERRAIN (by Readvance Ice) (recognised by scattered hill-hole pairs, extensional normal faulting dying out at depth, surficial Scottish Readvance diamicton and associated subglacial shearing), Mostly sand (deltaic)".
Glen Loy Complex
GLOY
Glenfiddich Pelite Formation
GLPE
Top of Inchrory Limestone, where limestone gives way sharply to pelite.
River Deveron, 6.5km west of Huntly, through the east side of Glenfiddich, the Braes of Glenlivet to the south, to the east of the River Avon to the Glen Gairn Granite.
Black pelite and semipelite with subordinate laminae of psammite.
>600m, ignoring any repetition/thickening due to folding.
Incoming of persistent psammite bands at base of Ladder Hills Formation.
Glaciolacustrine Proglacial Deposits
GLPG
Silt and clay, laminated, commonly rich in organic matter, locally with interbedded peat; of proglacial glaciolacustrine origin. [Generic description: academic papers and BGS Memoirs].
Glen Loch Phyllite And Limestone Formation
GLPL
Glascarnoch Psammite Formation
GLPS
Forms a continuous north-south trending belt approximately west of gridline 2300, crossing the western end of Loch Glascarnoch northwards to the western end of Gleann Beag, and continuing north into Strath Mulzie. Extent beyond Strath Mulzie is unclear. The western boundary is not well defined to the north, but appears to extend to Inverlael Forest in upper Loch Broom, trending southwards through Braemore Forest to Loch Fannich. To the south and west of Loch Fannich through Starth Bran, the western boundary runs approximately along Glen Carron, then trending southwards to the western end of Loch Monar, but this is unclear. The extent of the outcrop is also unclear south and west of Loch Monar, where it may terminate on the north-west side of the Strathconon Fault.
Massive, white to grey and buff, feldspathic and siliceous psammite with rare semipelitic and pelitic bands.
Lower (western) margin of Vaich Pelite Formation where predominantly psammitic lithologies pass into predominantly pelitic lithologies.
Glen Loin Quartzite Member
GLQU
Glanyrafon Formation
GLR
Gradational contact with Caeran Mudstones, at top of highest thick argillaceous sandstone bed of the Rhuddnant Grits.
Thinly interbedded turbidite sandstones and mudstones with both laminated and burrowed hemipelagites.
Up to 300m.
Gradational contact with Dolgan Mudstones.
Lower Limestone
GLRB
Glanyrafon Formation (Lower Tongue)
GLRL
Glen Rushen Formation
GLRN
In stratigraphical contact at the base with the Injebreck Fm, which is marked by a change from a mudstone/sandstone facies to a mudstone-dominated facies
Dark grey to black mudstone, with pale siltstone laminae.
From 250 m to 500 m thick.
In stratigraphical contact at the top with the Creggan Moar Fm, which is marked by a change from a mudstone-dominated facies to a mudstone/sandstone facies with manganiferous ironstone beds.
Gull Rock Shale
GLRS
Black to dark grey, commonly sulphurous shaly mdstones with bands of nodules yielding Gastrioceras listeri, G coronatum and G circumnodosum, as well as fish remains.
Glanyrafon Formation (Upper Tongue)
GLRU
Glyn Gower Siltstones [Obsolete Code: Use Gyg]
GLS
Lower Streaky Andesite Member
GLSA
Glaciolacustrine Subaqueous Fan Deposits
GLSAF
Glaciolacustrine Silt And Clay
GLSC
Silt and clay, interbedded, commonly laminated; of glaciolacustrine origin. [Generic description].
Gleaston Dolomite
GLSD
Glaciolacustrine Sub-Glacial Deposits
GLSG
Silt and clay, laminated, commonly rich in organic matter, locally with interbedded peat; of subglacial glaciolacustrine origin. [Generic description: academic papers and BGS Memoirs].
Glenshalloch Shales
GLSH
Conformably overlies the Newlands Farm Formation (NWF)
Soft, thinly-bedded, greyish green siltstones and mudstones with a graptolite fauna.
About 305 m thick.
Conformably overlain by the Saugh Hill Grits Formation (SHSG).
Glen Suie Limestone Member
GLSU
At top of Allt Dregnie Phyllite Member where micaceous psammites, phyllites and semipelites give way to banded limestones and semipelites.
Mixed limestone and semipelite with pelites and calc-silicate rocks; strongly banded in main part, with limestone dominating in uppermost part.
c. 225m in Glen Suie, including any thickening due to folding etc.
At base of Kylnadrochit Semipelite Member where limestone becomes very subordinate to semipelite.
Gault Formation
GLT
Unconformity. Rapid transition from sands of Lower Greensand, and overlapping on to Palaeozoic strata.
Extensive outcrop in eastern England from Norfolk, south-westwards across the Midlands to Devon, and in the Isle of Wight and the Weald.
Pale to dark grey or blue-grey clay or mudstone, glauconitic in part, with a sandy base. Discrete bands of phosphatic nodules (commonly preserving fossils), some pyrite and calcareous nodules. Thin variable junction beds at base have some limestones. In Norfolk, becomes a marl before passing northwards into 'Red Chalk'.
2m in Norfolk thickens southwards to 20m in Cambridgeshire, 60m in Bedfordshire, 90m in Weald, 104m in Glyndebourne Borehole.
Diachronous transition into Upper Greensand facies (glauconitic sand) in west giving way to unconformable junction with Cambridge Greensand in east at base of Lower Chalk.
Glynllifon Trachydacite
GLTD
Porphyritic trachydacite, with sodic andesine phenocrysts, glomeroporphyritic clots and mafic pseudomorphs, apetite and zircon in a weakly flow foliated microcrystalline groundmass.
About 350m
Glascoed Mudstone Formation And Ton Siltstone Formation (Undifferentiated)
GLTS
Glenluce Intrusion
GLUC
Glenluce area of southwest Scotland.
c. 1 square km in total area (3 small ovoid outcrops).
Glenlivet Granite
GLV
Glynch Valley Formation
GLVA
Generally where the fluvial deposits rest on bedrock or older superficial deposits.
The formation consists of fluviatile menbers related to a river draining the present valleys of the Leadon and its tributaries, including the Glynch, Ell and Moor End brooks in Gloucestershire and Worcestershire.
Sand and gravel, interpreted as terrace deposits, or silty clay interpreted as alluvium deposits.
Variable, up to 5m.
Present day river terrace or upper surface of alluvium.
Glencoe Volcanic Formation
GLVO
The Glen Coe area of Scotland.
Andesitic lavas and sheets comprising flow laminated rhyolites, tuffs, tuffaceous breccias, minor sandstones, mudstones and conglomerates.
Over 1000 m thickness presently exposed.
The top of the volcanic succession, which has been partly removed by erosion.
Gelliswick Bay Formation
GLW
Glen Coal (West Lothian)
GLWL
Gorsley Limestone
GLY
Glycymeris Sandstone
GLYC
Gleillydd Coal (South Wales)
GLYD
Greenmoor Rock
Between Barnsley and Sheffield, Yorkshire.
The Greenmoor Rock is a fine-grained thinly bedded, ripple cross-laminated sandstone. Within this district it usually occurs as groups of thin sandstone and siltstone beds interbedded with greenish grey mudstone.
Between 30 and c.45m
Glasgow Main Coal (Central Coalfield)
GMA
Glasgow Main Under Coal (Central Coalfield)
GMAU
Glaciomarine Beach Deposits
GMBD
Giffnock Main Coal
GMC
Gasworks Mudstone And Cartlett Beds (Undifferentiated)
GMCB
Gingham Coal (South Lancashire)
GMCO
Glenmard Mudstone Member
GMD
Base of lowest mudflow unit with olistoliths.
At least four discrete mudflows, with olistoliths of green mudstones, rottenstone and shelly debris, separated by bedded mudstone and thinly bedded sandstone.
Succeeded by normal bedded mudstones of the Quarrel Hill Formation.
Glaciomarine Deltaic Deposits
GMDD
Variable lithology, typically sand and gravel; any deposit from deltas within the glaciomarine environment. [Generic description].
Glaciomarine Deposits
GMDU
Variable lithology; any deposit from the glacio-marine environment. [Generic description].
Great Mine Limestone
GML
The lower boundary is taken at the base of the first limestone-dominated unit above the base of the mudstone and sandstone of the Halesowen Formation.
Between Ancoats [SJ 8560 9865] and Belle Vue [SJ 8740 9640], Greater Manchester.
Limestone [no further details currently available]
1.5 to 2.7m
The upper boundary is taken at the base of a mudstone and sandstone dominated succession of the Halesowen Formation above limestone of the Great Mine Limestone.
Gorestown Mudstone Member
GMM
Glen Moriston Vein Complex
GMOR
Gomersal Rock
GMR
See Lexicon entry for Lepton Edge Rock.
Gribin Mudstones
GMS
Gamrie Bay Sandstone Formation
GMSA
Incoming of first ripple cross-laminated fine-grained micaceous sandstone above the Counter Head Siltstone Formation.
Gardenstown - New Aberdour on southern Moray Firth coast.
Sandstone and siltstone (ripple cross laminated).
45m
Base of red pebbly sandstones of the Pennan Sandstone.
Glaciomarine Subaqueous Fan Deposits
GMSAF
Glaciomarine Sea Bed Deposits
GMSBD
Grangemouth Silt Member
GMSI
Late Holocene.
Unconformable on the Claret Clay Member (Carse Clay Formation), and on older Holocene and late Devensian units including the Wilderness Till Formation.
Lower Forth valley from Stirling eastwards to near the Forth estuary in the Falkirk area; area of the estuarine deposits of the modern estuary and also under reclaimed land.
Clayey silt and silty clay, finely laminated and crudely stratified with silt and very fine- to medium-, locally coarse-grained sand (gravelly at base of member); grey, black and brownish grey, finely micaceous, sulphur-rich, contains shells and shell fragments. Massive where bioturbated. Contains some thin peat beds (maximum 9cm). Cross bedded sands represent tidal channel deposits. The member is an estuarine tidal flat complex formed after the time of highest Holocene sea-level (Main Post-Glacial Shoreline).
Veneer to perhaps as much as 18m.
Upper boundary at the land surface or the sea bed.
Glaciomarine Subtidal Deposits
GMSTD
Glaramara Tuff
GMT
The base is taken at the sharp contact at the base of dacitic pyroclastic rocks overlying sandstones with an overall andesitic composition. In places the contact is an erosion surface of low relief.
Discontinous outcrop within the uppermost part of the Seathwaite Fell Sandstone Formation and beneath the Lincomb Tarns Formation, throughout the central Lake District, Cumbria.
A widespread package of dacitic pyroclastic rocks including coarse lithic-rich lapilli-tuff and pyroclastic breccia, bedded tuff with beds containing accretionary lopilli, and nodular eutaxitic lapilli-tuff. The uppermost part comprises massive to bedded pebbly sandstone with accumulations of broken accretionary lapilli in channels and scours.
About 20m in type area.
Defined by the overlying sandstones of the uppermost part of the Sprinkling Tarns Member or, where not distinguished, by the uppermost part of the Seathwaite Fell Sandstone Formation.
Gamlan Formation
Conformable, sharply overlain by turbiditic siltstones of the Barmouth Formation.
Northern, eastern and southern flanks of Harlech Dome.
Grey, green and purple colour-banded, locally pyritic mudstones and thin, coarse-grained turbiditic sandstones. Upper part of Formation manganiferous, with thin mudstone beds near the top.
Locally includes the Cefn Coch Grit as the terminal member.
150 to 240m
Conformable and transitional with overlying black mudstones of the Clogau Formation (Mawddach Group).
Gnapiog Coal (South Wales)
GNAP
German Bands Ironstone
GNBI
Garden Course Coal (Somerset)
GNCC
Glenlee Formation
GNE
Faulted (Orlock Bridge Fault); probably ultimately rests on the Moffat Shale Group.
Lenticular outcrop between the Thornhill Basin and Dalry, Kirkcudbrightshire: Southern Uplands of Scotland.
Faulted (Glen Fumart Fault).
Gourdon Sandstone Formation
GNF
Not exposed, but stratigraphically above the Tremuda Bay Volcanic Formation.
Gourdon to Inverbervie and Whistleberry (NO 860 753).
A dull red, coarse-grained, pebbly, angular, lithic sandstone with clasts predominantly of fragments of volcanic rocks, and conglomerate.
At the base of the lowest conglomerate bed within the Whitehouse Conglomerate Formation or at the base of the Crawton Volcanic Formation where the Whitehouse Conglomerate Formation is absent.
Gunnerton Fell Limestone
GNFL
Gleann Nan Gabhar Slate Member
GNGS
Glen Kyllachy Pluton
GNKY
N/A
Central Highlands, Glen Kyllachy Forest. Mainly in limited ovoid area some 4km x 2km centred on Glen Kyllachy.
Weakly foliated granite, granodiorite and tonalite, pale cream, medium- to coarse-grained.
Gurrington Slate Formation
GNL
Mid Frasnian to ?Early Tournaisian.
Glen Loth Formation
GNLF
Greenan Sandstone Formation
GNNS
Unconformable on Dalradian Supergroup metamorphic rocks
The Milltown Segment of the Fintona Block and south side of Greenan Mountain, County Tyrone.
Sandstone, purple-grey weathering distinctive orange-purple, medium- to coarse-grained, parallel and cross-laminations, thin layers of purple-red and green mudstone; basal breccia of metamorphic clasts.
At least 550m, probably to more than 1000m
Not exposed, faulted out.
Grindstone Post Member
GNP
Ganister Rock
GNR
Rossendale and adjacent areas, Lancashire.
Green Slates
GNS
Greenheugh Sandstone Formation
GNSA
The top of the predominantly argillaceous Redheugh Mudstone Formation.
Southern Uplands Terrane of Scotland.
A red-brown, mainly medium- to coarse-grained sandstone with some locally pale yellow and green coloured beds and subordinate intercalated thin red mudtones and silstones.
Estimated at about 170 m thick.
The first cornstones in the sandstones of the Kinnesswood Formation.
Glen Scaddle Intrusion
GNSC
?Neoproterozoic.
Granton Sandstones
GNST
Midlothian, specifically around Granton.
Massive, thick-bedded sandstones, alternating with more thinly bedded layers, commonly with carbonaceous and shaly partings.
Variable, but averaging c.18m
Garnant Coal (South Wales)
GNTC
Palaeogene And Neogene Rocks (Undifferentiated)
GNU
Garnedd-Wen Formation
GNWF
On Foel Crochan (7706 1050) the lower boundary is transitional over 2.65m. Sandy bands (1-2m) thick occur separated by 10-20cm silty-mudstones. The boundary is taken as the base of the first sandstone band.
Passes west into Cardigan Bay, and south to the Pennal Fault. Outcrop Garnedd-Wen Formation crosses Sheet 149 diagonally from south-west to north east.
A heterogenous mixture of silty-mudstones, siltstones, fine- to coarse-grained feldspathic and non-feldspathic sandstones, greywackes and conglomerates.
1000m-3000m south-west to north east.
Not seen, probably transitional.
Greenhow Limestone
GNWL
Govan Blackband Ironstone (Glasgow)
GOBI
Gortfinbar Conglomerate Formation
GOCF
Very confused relationship. May be unconformable on underlying Shammaghery Sandstone Formation, may be normal but abrupt, commonly faulted or not exposed.
Pebble to boulder conglomerates with sandstone beds; 2 horizons of contemporaneous 'andesitic' lavas.
From about 2440 m - 2720 m thick.
Supposedly interfingers laterally with and merges gradationally upwards into Raveagh Sandstone Formation
Goodig Coal (South Wales)
GOCO
Gossabrough Metadiamictite Formation
GOD
Goleugoed Formation
GOED
Goodockhill Fireclay (Central Coalfield)
GOFC
Coal 1'8" - Dark fireclay 1' 6" - Light fireclay 5' 9" - Sandstone 2'7".
7'3" (2.2 metres).
Great Oolite Group
GOG
Unconformity at top of Inferior Oolite Group.
Dorset, Somerset, through the south-west Midlands, Oxon, Northants, part of Lincolnshire and northwards as far as the Market Weighton High (covering areas formerly including the outcrop of the now obsolete "Redbourne Group"), Hebrides, East Scotland: Also proved in borings in Kent, the London area and Norfolk.
Calcareous (rarely oolitic) and argillaceous formations.
c.23m in Grantham area.
Junction with basal clays of Ancholme Group (base of Kellaways Clay, over much of area of occurrence).
Graigog Coal (South Wales)
GOGC
Gosforth Glacigenic Formation
GOGL
Generally undulating erosional contact on to older sequences including the Ravenglass Till Member of the Seascale Glacigenic Formation.
The formation includes a complex, commonly thinly interbedded sequence of sands, gravels, silt clays, pebbly clay diamictons and stony sandy clay diamictons (tills) containing clasts from Scotland and the northern Irish Sea basin and the west Cumbrian coalfield, as well as from the western Lake District.
Typically 10 to 20m
Generally the land surface, but locally the base of the Holocene Hall Carleton, Drigg Point Sand and Ehen Alluvial formations.
Graigog Rider Coal (South Wales)
GOGRC
Gordon House Member
GOH
Godolphin Intrusion
GOIN
?Stephanian.
Medium- and coarse-grained biotite-granite.
Gowlaun Shale Formation, Lackagh Sandstone Formation And Bencroy Shale Formation (Undifferentiated)
GOLB
Golden Coal (South Wales)
GOLC
Golden Coal (Lothian)
GOLL
Gormack Lavas Member
GOLM
Golspie Formation
GOLS
Glenmore Member
GOM
Gonachan Glen Linear Vent-System
GONGL
Goodall's Coal
GOO
Gortnagross Sandstone Member
GOR
Probably conformable on red dolomitic limestone (Kildress Limestone Member).
Gortnagross and Lower Kildress Townlands, south east Tyrone, Northern Ireland.
Silica rich sandstone.
Conformable with unnamed overlying interbedded sequence of red mudstone and sandstone in Derryloran Formation.
Glen Orrin Intrusion
GORIN
Gormire Limestone Member
GORM
Gorse Member [Offshore]
GORS
Gowlaun Shale Formation
GOS
Gourock Sand Member
GOSA
The Gourock Sand Member of the Clydebank Clay Formation rests, possibly by passage, on the underlying Erskine Formation where developed, and with angular unconformity on older Quaternary sediments or bedrock.
The Gourock Sand Member of the Clydebank Clay Formation is recognised in the lower Clyde valley, in the estuary of the Clyde, and in the Loch Lomond area (lower Strathendrick).
The parent Clydebank Clay Formation consists of four members (qv): from oldest to youngest, the Buchanan Clay, Longhaugh Sand and Gravel, Erskine Clay and Gourock Sand. The Gourock Sand Member is named from Gourock No.2 Borehole [NS 244 777] in the inner Firth of Clyde. Here, the main lithology is grey, fine- to coarse-grained sand. In the Bridgeton Borehole in east Glasgow (Browne and McMillan, 1989a, Figure 18), the uppermost metre consists of brown silt and clay with thin bands and wisps of peat. The basal part is of sandy fine gravel. At Shieldhall [NS 536 664] (ibid, Figure 19), temporary sections showed trough and parallel cross-bedded sands with gravel units. Dark coloured beds rich in organic detritus were about 50cm thick. The lithological association is compatible with an estuarine origin, the range varying from fluvial processes in the east to almost fully marine in the west. The sediments were deposited along very shallow channels probably linked in a anastomosing pattern isolating low lying islands and forming a complex with extensive intertidal flats in the estuary. The stratigraphical relationships and its geographical distribution are illustrated in ibid (Figure 2f, and 3A, B, and C).
Ranges from a thin veneer to more than 5m.
The Gourock Sand Member of the Clydebank Clay Formation is exposed at surface in the lower Clyde valley and in lower Strathendrick.
Gowrie Silt Member
GOSI
Unconformable terraced estuarine deposits, commonly on the Tay-Earn Gravels Member (Forth Clay Formation) and other late Devensian and Holocene units.
Lower Tay valley from east of Perth; Tay estuary and Firth of Tay; lower Earn valley (from Bridge of Earn eastwards) and estuary; Eden estuary; Montrose Basin area.
Estuarine clayey silt and clay, may be rooty and structureless or highly laminated with silt and very fine- to medium-grained sand; grey and brownish grey, finely micaceous, with dark sulphidic patches. Brown and grey, fine-grained shelly sand locally indicates a more open marine environment.
Upper boundary most commonly at the surface.
Godor Tuff Member
GOT
Gradational conformable contact with underlying volcaniclastic mudstones of the Llangynog Formation.
Fine- to coarse-grained welded crystal lithic lapilli tuff.
18 to 24m
Gradational conformable contact with overlying volcaniclastic mudstones of the Llangynog Formation.
Gorteagh Tonalite
GOTO
Govan Coal
GOVC
Gowk Stane Member
GOWK
The pyroclastic and volcaniclastic strata of the unit are inferred to overlie and be penecontemporaneous with the Eagelsham and Dumdruff Hill lavas within the Clyde Plateau Volcanic Formation (MacPherson and Phillips, 1997; MacPherson et al., 2000). Volcaniclastic and pyroclastic breccia of the Gowk Stane Member appears to overlie directly trachyandesite of the Dumdruff Hill lavas at East Revoch Farm [NS 569 508], although the contact is not exposed (MacPherson and Phillips, 1998).
Between Eaglesham [NS 570 520] and Darvel [NS 565 375] in Strathclyde, Scotland.
A mixed sequence of pyroclastic, epiclastic and volcaniclastic sedimentary rocks that are locally derived and mainly trachytic in composition (MacPherson and Phillips, 1997). There is a marked lateral variation in deposits within the unit. In the northern part of the crop, south of Eaglesham [NS 570 520] to the vicinity of Carrot Farm [NS 575 481], and north-east of Darvel the member consists of primary pyroclastic rocks with limited epiclastic reworking. These include rocks of trachytic and basaltic composition. The pyroclastic rocks are poorly sorted, grey to grey-green, fine- to coarse-grained lapilli tuff and/or agglomerate. Beds are generally less than 0.5 m thick and exhibit normal grading, either within the tuff mattrix or in the distribution of blocks in typically matrix-supported agglomerate. In the southern part of the crop, such as that exposed in Glen Water [NS 587 432] to [NS 579 413], the Gowk Stane Member is dominated by fluviatile volcaniclastic sedimentary rocks that were locally derived by penecontemporaneous weathering and erosion of the pyroclastic deposits and lavas (MacPherson and Phillips, 1997). This thickly bedded sedimentary sequence consists of interbedded mudstone, siltstone and tuffaceous sandstone with sporadic conglomerate units. The mudstones are pinkish-brown, the sandstones are greenish grey to buff and poorly to locally well sorted with fragments of volcanic rock. Cross-bedded channel and chaotic mass movement (lahar-type) deposits are recognized (MacPherson and Phillips, 1977).
At least 60m thick, from vertical section on British Geological Survey 1:10 000 Series Scotland sheet NS54SE (Whitelee Forest).
Not seen, but is inferred to be overlain by the Upper Flow Moss Lava Member, within the Clyde Plateau Volcanic Formation (MacPherson and Phillips, 1997; MacPherson et al., 2000).
Gowna Group
GOWN
Glassmullen Plug
Glen Parva Member
GPCL
Palaeocene And Eocene Rocks (Undifferentiated)
GPGE
Gaick Plateau Moraine Formation
GPM
Overlies bedrock or is in unconformable contact on the Ailleag Diamicton Member.
The deposits occur across the Gaick Plateau in the central Grampian Highlands.
Diamicton, mainly clast-supported, gravelly, sandy, silty, and matrix-rich gravel. Poorly consolidated, formed of angular to subangular fragments of weathered psammite and porphyry, mainly less than 64mm in diameter with some cobbles and boulders, yellowish brown overall.
To 8m
Generally the ground surface or overlain locally by peat.
Gloddaeth Purple Sandstone Formation
GPS
Note that the Gloddaeth Purple Sandstone was formerly considered to be part of the Dyserth Limestone Group (now within the Clwyd Limestone Group), of Asbian age (Warren et al, 1984). Its current designation as Westphalian is based on more recent determinations of spore samples.
An unconformable contact with red and purple sandstone resting on massive to pseudobrecciated and locally dolomitised limestones of the Loggerheads Limestone Formation (Clwyd Limestone Group).
Llandrillio-yn-Rhos area (SH 820 810), North Wales.
Purple and red sandstone, cross-bedded with pebbly horizons. Warren et al., cite the Gloddaeth Purple Sandstone to be of Dinantian age, however, unpublished palynomorph assemblages obtained from a road cutting in the late 1980's by the Robertson Group, and which include the taxa Dictyotriletes birecticulatus and Endosporites globiformis, indicate an age no older than upper Westphalian A. The well preserved natuer of the assemblage suggested to the Robertson's palynologists that it had not been re-worked. Further investiation may allow the rank and parentage of the Gloddaeth Purple Sandstone to be revised. The possibility that it represents an early local facies of the Warwickshire Group cannot be discounted.
Over 23 thick.
Not seen, presumed to be red and purple sandstone overlain by unconformable red Permo-Triassic sandstones of the Sherwood Sandstone Group.
Grenoside Sandstone
The area between Sheffield and Kirkburton, Yorkshire.
The Grenoside Sandstone is a fine-grained, thinly bedded, cross-laminated, micaceous and carbonaceous sandstone. Within this district it usually occurs a two units of intebedded sandstone and laminated grey micaceous mudstone.
Grain Burn Member
GRAB
Conformable base of lavas on pyroclastic rocks within Peat Rig Formation along Grain Burn.
Porphyritic lavas of hawaiite/mugearite composition.
Conformable top of lavas below pyroclastic rocks within Peat Rig Formation along Grain Burn.
Graigola Coal (South Wales)
GRAC
Grampound Formation
GRAD
Probably Givetian.
Faulted contact.
At least along the northern margin of the Mevagissey (353) Sheet area and in the northeastern corner of the Falmouth (352) Sheet area.
Thinly interlaminated grey slaty mudstone and mid-grey siltstone, weathering yellowish green, with sporadic thin beds of sandstone and sparse lenticular limestone.
Carrick Thrust (in Mevagissey map area).
Grainsgill Greisen
GRAI
Grampian Group
GRAM
Eastward from the Great Glen over much of the central Grampian Highlands as far as Cullen (Banffshire), Braemar (Aberdeenshire), Tummel Bridge (Perthshire) and almost to Dalmally (Argyll). In Ireland occurs at the southern extremity of the Dalradian outcrop in Donegal, and also on the north coast of County Mayo around Belmullet, and on Achill Island.
Locally arkosic quartzofeldspathic psammite in units 100-1000m thick, with subsidiary semipelite to pelite units. Quartzite units occur locally towards the top of the succession. Amphibolite and calcsilicate rock are rare. Succession from Grampian Group into Lochaber Subgroup continuous in some areas, e.g. Schiehallion, Banffshire, but in Glen Spean there may be a modified unconformity at the base of the Leven Schist.
Up to 5km in any one area; total thickness estimated at 9km.
Generally sharp transition from uniform psammite, generally flaggy, with thin quartzite and semipelite units of underlying Grampian Group, to better sorted psammite or quartzite and semipelite or pelite.
Grampian Group And Appin Group (Undifferentiated)
GRAPP
Graven Complex
GRAV
Greasborough Coal
GRBCO
No known description.
The Barnsley District.
0.5 m thick
Granby Member
GRBL
Base of lowest limestone in unit; at 87.35m in type section, borehole F/B5 (SK95SW/17); at top of Barnby Member.
East Midlands Shelf (south Yorkshire to London Platform area).
Grey calcareous mudstones with numerous thin, laterally persistent, shelly, bioclastic limestones occurring in groups and comprising more than 10% of the sequence.
30.60m in borehole F/B5.
Top of highest limestone in unit; at 56.75m in type section borehole F/B5 (SK95SW/17), at base of Beckingham Member.
Basal Green Beds (South Wales)
GRBW
Sandstones, conglomerates and mudstones.
Grinstead Clay Member
GRC
The base is an erosian surface that may be acompanied by a pebble bed ['Top Lower Tunbridge Wells Pebble Bed']. The boundary is placed below the pebble bed and defined by a down-section change from mudstones [Grinstead Clay Formation] to sandstones [Lower Tunbridge Wells Sand Formation, Ardingly Sandstone Member]. Locally, near Scaynes Hill, the Lower Grinstead Clay Member is cut out and fine-grained, silty, cross-bedded [festoon-bedded], buff, calcareous sandstone [Cuckfield Stone Member] rests directly on fine-grained, pale grey to white, cross-bedded, soft, quartz sandstone [Ardingley Member of the Lower Tunbridge Wells Sand Formation].
The formation outcrops from Leigh, west of Tunbridge [on the Seven Oaks sheet], to East Grinstead, Cuckfield and Uckfield on the Tunbridge Wells sheet [Bristow & Bazley, 1972]. On the Horsham sheet [Gallois & Worssam, 1993] it outcrops from East Grinstead to Handcross as far as the Pilstye Farm Fault [it is obscured below the upper Tunbridge Wells Sand Formation south of the fault] and is again seen from the Ardingley area to the south of Horsted Keynes. Inliers are seen between Drewitts and Haywards Heath. The formation is present in the very north-eastern corner of the Brighton & Worthing sheet [318], north of Burgess Hill and extends onto the Lewes Sheet [319] where it is present between Chailey to between Isfield and Little Horsted.
The formation comprises soft grey to greenish-grey mudstones and silty mudstones with subordinate thin beds of siltstone, nodular clay ironstone, and shelly limestone. The top of the formation weathers to a red colour. Locally, rootlet horizons and Equisetites-rich beds occur. In some areas the formation is divided into the Upper and Lower Grinstead Clay members by a bed of calcareous sandstone [Cuckfield Stone Member].
Up to 26.9m known
Silty sands [Upper Tunbridge Wells Sand Formation] rests on mudstones with thin limestones and clay-ironstone beds [Grinstead Clay Formation]. The top of the Grinstead Clay Formation is often weathered to a red colour that may extend as far down as the Cuckfield Stone Member, but rarely below.
Grampian Catchments Subgroup
GRCA
Unconformable contact with units of the Central Grampian, East Grampian, Inverness, Banffshire Coast and Caithness, and Logie-Buchan Glacigenic subgroups, and with bedrock.
The Eastern Grampian Highlands and Buchan.
A suite of fluvial, lacustrine, mass movement, periglacial and aeolian deposits that contain clasts derived from rocks cropping out in the eastern Grampian Mountains and Buchan, including alluvium, river terrace deposits, peat, head and blown sand.
Generally the ground surface, but units of this Subgroup locally interfinger with units of the British Coastal Deposits Group.
Gur Coal (Coalbrookdale)
GRCC
Gouther Crag Breccia Member
GRCG
The abrupt change from bedded volcaniclastic sandstone within the Mardale Sandstone Formation to volcaniclastic breccia.
Swindale, Cumbria, between Dry Grove Gill [NY 510 122] and Mullender [NY 522 132].
A massive, poorly sorted volcaniclastic breccia, comprising heterolithic volcanic clasts, including abundant pink-weathered rhyolite clasts.
Taken at the sharp base of the overlying thin unit of bedded volcaniclastic sandstone, which is succeeded by massive, weakly eutaxitic, dacitic lapilli-tuff.
Garron Chalk Member
GRCK
Conformable on the Glenarm Chalk Formation at a bedding plane, above which wavy-bedded conspicuously shelly chalk with corals and bryozoa occurs.
North Antrim Basin, East Antrim (Midland Valley) Basin and over structural highs with the exception of the southern and western Londonderry Shelf. Oversteps younger beds over structural highs.
Limestone (chalk) with characteristic giant flints (`massive flint rolls?) and significant Inoceramus fragments. Is divided into three `Beds? (A to C).
9.65m in type section.
Conformable with Portrush Chalk Formation at a bedding plane above wavy-bedded sediment with small nodular flints.
Corrieyairack Subgroup
GRCO
Central Highlands of Scotland, notably in the southwest part of the Monadhliath Mountains.
Feldspathic psammites, semipelites and micaceous psammites, subordinate quartzites, calc-silicate rocks.
up to 10km.
Overlain conformably by quartzose psammites, semipelites and quartzites of the Appin Group.
Gully Redbed Formation
GRD
Transitional boundary; upper surface of highest greyish-coloured sandstone or siltstone of the underlying Fish Bed Formation.
Lower Palaeozoic Inlier of the Hagshaw Hills, Scotland (50k sheets 23W, 23E and 15W).
Reddish-brown silty mudstone, siltstones and shales, some fine laminations. Some very small scale cross-bedding; slightly micaceous.
95m
Base of lowest bed of conglomerate in the overlying Hareshaw Conglomerate.
Grampian Group And Dava Succession (Undifferentiated)
GRDA
Greensand Group
GRDG
Green Member
GRE
Grendon Member And Ecton Member (Undifferentiated)
GREC
Grendon Member
GREN
Formerly considered "Wolstonian" (Saalian). Now changed to Pleistocene (DJLO 16/10/2006)
Unconformable, commonly channelled base, resting on bedrock surface.
0 to 7.6m
Gretna Till Formation
GRET
Reddish brown, sandy, silty, clayey diamicton with clasts of greywacke, red sandstone, siltstone and grey granodiorite. Uppermost 3m generally quite variable in lithology and compactness, with lenses of sand, gravel, silt and clay. Commonly becoming more compact and stony with depth.
At surface or overlain conformably by glaciofluvial / glaciolacustrine or Flandrian sediments.
Grey Shale Member
GREY
Grantham Formation
GRF
Generally a sharp erosional, or in some places apparently transitional boundary, with ferruginous sandstone or ironstone of the Northampton Sand Formation, the top of which may be rootletted, or where the latter is absent, grey mudstone of the Whitby Mudstone Formation, with a localised conglomeratic bed of reworked Northampton Sand pebbles at the base.
From approximately the line of the River Humber, where the unit may be overstepped by the Lincolnshire Limestone Formation, southwards to the Kettering-Peterborough area, just beyond the southern limit of the Lincolnshire Limestone, where it is assumed to be overstepped by the Rutland Formation (see Bradshaw, 1978). Beds between the Humber and Market Weighton, formerly classified as the "Lower Estuarine Series" of de Boer et al. (1958) are now included in the Lincolnshire Limestone (Gaunt et al., 1980, pp.8, 29; 1992, p.45). The supposed "Lower Estuarine Series" and "White Sands" in the area south of Kettering-Peterborough are now known to represent the much younger, late Bajocian-Bathonian, Stamford Member of the Rutland Formation or, in the Brackley district, the equivalent Horsehay Sand Formation.
Mudstones, sandy mudstones and argillaceous siltstone-sandstone, which is commonly ferruginous, and containing generally abundant plant debris, interpreted as both non-marine and marine facies, comprising several shallowing-upwards,delta-type rhythms with typically a tripartite succession comprising: a generally pale, locally carbonate-cemented and commonly ferruginous more or less argillaceous sand or sandstone at the base, which may have a rootleted seatearth at the top, overlain in the type area at least, by a median unit of marine shaly sandy mudstone designated the Stainby Member, which farther to the south is represented by a dark carbonaceous shaly clay, named the "Coaly Bed", which may be equivalent, overlain by an upper, possibly rhythmic succession of alternating sand or sandstone with mudstone or sandy mudstone that may be rootletted in parts.
From typically about 2m to 5m in the type area, and extremely variable, locally ranging up to 15m in channels, for example, 13.6m measured in the Copper Hill Borehole [SK 9787 4265] near Ancaster.
A sharp or apparently transitional and somewhat arbitrary interpreted boundary with limestones of the Lincolnshire Limestone Formation. which may be very sandy at the base, distinguished from the Grantham Formation by the presence of shell debris and peloids.
Grantham Formation And Northampton Sand Formation (Undifferentiated)
GRFN
Grey Grits Formation
GRG
Graig Coal (South Wales)
GRGC
Glenshirra Subgroup
GRGL
Central Highlands of Scotland. Glen Shirra, Strathnairn and Eastern side of the Great Glen.
Feldspathic, siliceous and micaceous psammite with subordinate quartzite and semipelite, distinctive pebbly bands in upper part.
2.5 km to 3 km.
Sharp, attenuated contact with overlying semipelite unit of the Corrieyairack Subgroup.
Glacial Raft (Great Limestone)
GRGLS
Gryphite Grit Member
GRGR
Ovalis Zone (locally lower part may be Discites Zone [Parsons, 1976]).
Upward transition from less sandy, more finely shell-detrital and more ironshot limestones with Aulacothyris meriani (Oppel) (Lower Trigonia Grit Member) into limestone as described in lithology with L. buckmani.
Cotswolds: north of North Cerney and west of Northleach, Cold Aston and Condicote. Absent between Birdlip and Cirencester (Barron, A J M, et al, 1997, fig.4).
Grey and brown hard, rubbly, shelly, coarsely shell-detrital, bioturbated, variably sandy peloid grainstones, packstones and wackestones with thin mudstone, sandstone and marl beds; bioturbated, some ferruginous peloids; characteristic fauna includes abundant Gryphaea spp and belemnites in upper part, and colonial worm Sarcinella and brachiopod Lobothyris buckmani (Davidson) in lower part.
Typically 3 to 5m, maximum 7m. Type section (Leckhampton Hill); 6.6m (Richardson, L, 1906).
Upward transition into sparsely shelly peloidal and ooidal grainstones (Notgrove Member), or hardground overlain by Salperton Limestone Formation.
Glen Spean Subgroup
GRGS
Transition up from graded micaceous psammites of the Corrieyairack Subgroup into clean feldspathic and siliceous psammites.
Glen Spean, Lochaber and the Central Grampian Highlands of Scotland.
Dominantly siliceous, feldspathic and micaceous psammite with some quartzite. Semipelite developed locally near the base.
To 2km
First appearance of regionally transgressive semipelites of the overlying Lochaber Subgroup (Appin Group).
Greta Grit
GRGT
Lower boundary is taken where the Greta Grit overlies gradationally the dark grey fissile mudstones and micaceous laminated siltstones with the Bilinguites gracilis Marine Band.
Pale brown, medium- to coarse-grained cross-bedded sandstone with ganisters and mudstone interbeds.
Varies from 26m (in River Greta section) to 88.7m (in Seat Hall Borehole) (SD66NE/2).
The upper boundary is taken where the Greta Grit is overlain sharply by mudstones with Bilinguites bilinguis (see Settle Memoir). In the type section, the overlying beds contain the Gastrioceras cancellatum Marine Band (Ford, 1954).
Garheugh Formation [Obsolete Code: Use Gar]
GRH
Getting Rock Ironstone (South Staffordshire)
GRI
Gribun Chalk Formation
GRIB
Upper Cretaceous, Cenomanian in Lowden et al, (1992); Santonian in Hancock, (2000); Santonian to Campanian in Mortimore et al., (2001).
Unconformable on the Coire Riabhach Phosphatic Formation or the Lochaline White Sandstone Formation.
Principally on the island of Mull and within the Morvern district.
Silicified chalk. Reworked chalk and conglomerate as (?) debris flow. Flinty in part.
c.5m at Gribun, about 1m elsewhere.
Unconformable with the Clach Alasdair Conglomerate Member of the Strathaird Limestone Formation or Beinn Iadain Mudstone Formation (basal Paleocene age).
Grid Sandstone Member
GRIS
Glenramskill Formation
GRK
Unconformity on Dalradian Supergroup metasediments, with localised thin basal breccia.
The Kintyre peninsula, south of Peninver [NR 762 253], but excluding Sanda and neighbouring islands, on Sheet 12.
Conglomerates, breccias and sandstones all composed of dominantly Dalradian Supergroup rocks.
Comprises the Basal Breccia member at approximately 110 m thick which is overlain by the Quartzite Conglomerate member which is about 330m thick, to giving a total unit thickness of 440 m at type section.
The base of the New Orleans Conglomerate Formation.
Greys Limestones Member
GRL
Greengairs Lime Coal (Airdrie; Central Coalfield)
GRLC
Glencar Limestone Formation
GRLF
Conformable but rapid from underlying Benbulben Shale Formation.
Limestone, grey, weathering pink-brown, argillaceous, bioclastic, interbedded with equal thickness of dark grey shale and mudstone.
Conformable; always abrupt, locally interdigitating with succeeding Dartry Limestone Formation.
Garlant Coal (South Wales)
GRLT
Grey Marl Member
GRML
Godir Rhyg Mudstone Member
GRMU
Conformably overlies turbidite sandstones within the main part of the Dinas Island Formation.
Interbedded grey turbiditic and laminated hemipelagic mudstones.
Passes conformably upwards into turbidite sandstone within the main part of the Dinas Island Formation.
Green Coal (South Wales)
GRNC
Greenhill Felsic Member
GRNH
Grange Sandstone
GRNS
South Central Fife, in the Burntisland area [NT 19 86 to NT 25 86].
A white to pale grey, generally fine-grained siliceous sandstone, described as evenly bedded and hard, but displaying cross-bedding as well. Intraclasts of ripped-up mudstone, siltstone and coaly plant remains are uncommon and localized in occurrence.
36.27m in Reference Section.
Granite
GRNT
Gramscatho Group
GRO
Grange-Over-Sands Formation
GROS
Probably overlies bedrock or sediments of the Irish Sea Coastal Glacigenic Subgroup.
Estuarine and alluvial deposits in the Cumbrian part of Morecambe Bay.
Probably silt, clay and sand, with gravel and peat.
At least 12m
Gristhorpe Member
GRPE
Great Row Coal (North Staffordshire)
GRRC
Grit Sill
GRS
Grauer Salzton Formation
GRSA
Greengairs Smithy Coal (Central Coalfield)
GRSC
Graptolite Shales
GRSH
Grindstone Limestone
GRST
Great Coal (Somerset)
GRTC
Grantown Pluton
GRTN
Greenshiels Intrusion
GRTO
Ghrudaidh Formation [Also Grudaidh Formation] [Obsolete Code: Use Gud]
GRU
Grugie Pluton
GRUE
Gruting Greenschist Formation
GRUT
George's Roust Vein
GRV
Grinllwm Slates
GRW
Greywacke Conglomerate Formation
GRWC
In the type section, defined as the lowest bed of conglomerate with predominant greywacke clasts overlying the Quarry Arenite Formation. Elsewhere generally unconformable on Lower Palaeozoic rocks.
Overlies the Lower Palaeozoic inliers in the southern part of the Midland Valley from Girvan to North Esk, on 50k sheets 14W, 14E, 15W, 23W, 23E, 24W, 32W.
Conglomerate of cobbles and boulders up to 250mm diameter but most clasts are less than 70mm, mostly subrounded, consisting of greywacke, minor chert and quartzite, with a few sandstone beds.
From 25 m to 560 m thick.
The upper surface of the highest bed of greywacke conglomerate below the overlying Swanshaw Sandstone Formation.
Grey Beds
GRY
Taken at the base of a sequence of grey mudstones overlying breccia, elsewhere resting on reddened Carboniferous rocks.
Barrow-in-Furness.
Grey mudstones and siltstone, containing fragmentary plant remains together with thin impersistent limestone beds, seen as a muddy sandstone in the south.
From 10 m to 20 m thick.
Defined by the base of the 'Magnesian Limestone' where present, or by the basal rocks of the St Bees Shale Formation.
Grenzanhydrit Formation
GRZH
Gwespyr Sandstone
Entry of feldspathic sandstones above the Cancelloceras cancellatum Marine Band in north Flintshire and the Cancelloceras cumbriense Marine Band in south Flintshire and the Wrexham area.
Between Point of Air [SJ1080] and the River Dee south of Wrexham [SJ2742].
Fine-grained, feldspathic and micaceous sandstones, cross-stratified on a variety of scales, with conglomerate-lined scours and intercalated siltstone and mudstone beds. Intertongues with Craven Group mudstones in its lower part and Pennine Lower Coal Measures Formation in its upper part. The Gwespyr Sandstone records the entry and southwards advance of a northerly derived "Millstone Grit" deltaic facies into the North Wales area.
To 260m
Base of thin sequence of mudstones and seatearths immediately underlying the Llwyneinion Half Yard Coal.
Gray Sandstone Group
GSA
Drawn at the base of the Gray Sandstone Group where it rests conformably upon the Coralliferous Group.
Pembrokeshire coast, Dyfed, southwest Wales.
Green-grey yellow weathering hard quartzitic sandstones and tough mudstones, fossiliferous within decalcified sandy rottenstone.
274m to 609m approximately.
Drawn at the conformable upward passage from the Gray Sandstone Group to the Red Marls Formation of the Lower Old Red Sandstone.
Glenade Sandstone Formation And Bellavalley Formation (Undifferentiated)
GSBV
Great Seam Coal (Lothian)
GSC
Glen Shira Subgroup And Corrieyairack Subgroup (Undifferentiated)
GSCK
Great Scar Limestone Group
GSCL
Pennines of Yorkshire/Lancashire/Westmorland.
To c.180m
Greenses Coal (Northumberland)
GSCO
Goat Scar Dacite Member
GSD
Irregular contact with lower ignimbrite sheet of the Lincomb Tarns Tuff Formation, which discordant relationship suggests that the lower parts of the dacite are intrusive. Elsewhere the dacite overlies the ignimbrite, but is obscured in places by later syn-BVG andesite intrusions.
From Hallow Bank Quarter, Kentmere [NY 463 060], via Goat Scar to the south of Buckbarrow Crag on the east side of Longsleddale [NY 484 072], Cumbria.
Dacite, interpreted to be a lava dome with associated coulee-type flow, partly intrusive and partly extrusive, interbedded with lapilli-tuff.
Overlain by upper ignimbrite sheet of the Lincomb Tarns Tuff Formation, but separated from it by later syn-BVG andesite intrusions.
Gorse Member [Onshore]
GSE
Succeeds the unfossiliferous mudstone of the Fence Member of the Doularg Formation.
Poorly-bedded mudstone with decalcified limestone nodules containing a brachiopod and trilobite fauna.
c.7m
Succeeded by calcareous silty mudstone of the Jubilation Member of the Doularg Formation.
Glacial Sand And Gravel
GSG
Sand and gravel with rare clay interbeds; often cross-bedded; of glacial origin. [Generic description: academic papers and BGS Memoirs].
Gypseous Shales
GSH
Glen Shee Pluton
GSHEE
Gubaveeny Shale Member
GSHM
Gobb Sill
GSI
Ballycastle Sheet, Northern Ireland.
Goodockhill Slatyband Ironstone (Central Coalfield)
GSLI
Grieston Formation
GSN
Glasgow Splint Coal (Central Coalfield)
GSP
Gaisby Rock
GSR
Name used only in the Bradford area, West Yorkshire.
Generally flaggy sandstone with thin shaly mudstone partings.
Reaches 40m around Gaisby, generally thinner.
Grindstone Sill
GSS
Note that regardless of its local name, this bed is a sandstone rather than an igneous intrusion.
Glacial Silt
GST
Silt; of glacial origin. [Generic description].
Glacial Silts And Clays
GSTC
Silt and clay; of glacial origin. [Generic description].
Great Strickland Limestone
GSTL
Gastropod Beds
GSTP
Glenstaghey Formation
GSY
Guiseley Grit
GSYG
West Yorkshire area [Guiseley between Leeds and Otley].
Coarse-grained, massively bedded sandstone, somewhat finer and flaggy in its lower part.
c.12 to 21m
Garth Tuff Member
Highly discordant on mudstones of the Nant Ffrancon Subgroup.
White weathering, primary felsic ash-flow tuff.
Conformably overlain by silty mudstones and fine grained sandstones of the Capel Curig Volcanic Formation.
Gleaston Formation And Bowland Shale Formation (Undifferentiated)
GTBS
Great Course Coal (Somerset)
GTCC
Gawthwaite Formation
GTE
Sandstone, with subordinat siltstone and mudstone.
Conformably overlain by the Latrigg Formation of the Coniston Group.
Gaythorn Limestone
GTL
Great Ladstones Breccia Member
GTLA
Taken at the change from generally well bedded volcaniclastic sandstone to significantly coarser and weaker bedded volcaniclastic rocks.
Northeastern Lake District, east of Swindale.
A massive to weakly bedded, volcaniclastic breccia and pebbly coarse-grained, clast- to matrix-supported and very poorly sorted sandstone with dominantly silicic or andesitic fragments.
The member is the uppermost unit of the Mardale Formation, and is overlain, along a sharp contact, by the Froswick Tuff Formation.
Glen Tilt Intrusive-Complex
GTLT
Greatmoor Hill Vent
GTMO
Pyroclastic breccia or agglomerate in vent, with intrusions of trachyte and dolerite.
Vent, roughly circular, c.900m in diameter.
Garnet Mica Schist 'Unit'
GTMS
The pelitic, tectonically upper, part of the Sand Voe Group.
Godir Tudur Mudstone Member
GTMU
Caradoc (?Onnian)
Interbedded dark grey turbiditic and hemipelagic mudstones
To 50m
Passes conformably upwards into the main part of the Dinas Island Formation
Garleton Hill Vent
GTNHI
Glen Turret Psammite And Semipelite Member
GTP
Change from more massive and quartzose psammite at top of Glen Tanar Quartzite Member; this change is typically gradational.
South of Mount Battock Granite and east of Loch Lee, forming one strip around Lower Glen Mark (NO 420 800 to NO 415 850) and another around Glen Turret (NO 530 780 to NO 543 834).
Psammite, mostly feldspathic and slightly micaceous, interbedded with and transitional to muscovite-biotite-semipelite with low magnetic susceptibility: contains beds of calc-silicate rock and rare limestone.
Apparently 1500m thick in Glen Turret and vicinity, but this is probably inflated by tectonic thickening. Thins rapidly south-westwards and is absent on Auld Craig (NO 455 782).
Incoming of beds of dark biotitic semipelite with high magnetic susceptibility at base of Glen Effock Schist Formation.
Glen Tanar Quartzite Member
GTQ
Change from dominant calc-silicate rock to dominant psammite at top of Deeside Limestone Formation (not seen south of Mount Battock Granite).
(i) Deeside: north of Mount Battock Granite and south of Deeside Limestone Formation from NO 413 943 to NO 565 955; (ii) Invermark - Tarfside: south of Mount Battock Granite and north of the Glen Effock Schist Formation from NO 415 845 to NO 545 825.
Psammite, quartzitic to slightly feldspathic, with thin (<5cm) micaceous partings, and containing beds up to 1-2 metres thick of calc-silicate rock and impure limestone.
(i) North of Mount Battock Granite: probably no more than 500m (top cut out by granite). (ii) South of Mount Battock Granite: probably c. 1250m exposed, with little tectonic thickening (base not seen).
Gradational change, by thickening of micaceous partings, to become interbedded psammite and semipelite (where Glen Turret Psammite and Semipelite Member is present). Elsewhere incoming of beds of semipelite with high magnetic susceptibility (Glen Effock Schist Formation).
Great Row Member
GTR
North Staffordshire Coalfield, although not shown on the map.
Grey mudstones and siltstones with seatearths, numerous ironstones and thick coals. Channel sandstones are locally important.
Up to 92 m in Parkhouse Colliery.
Glen Taitneach Schist Member
GTSC
Base of dominantly graphitic succession stratigraphically overlying blue-grey metacarbonate rock at the top of the Glen Lochsie Calcareous Schist Member.
Northern part of Sheet 56W and southern part of Sheet 65W.
Graphitic pelite, silver-grey, locally garnetiferous with thin beds of metacarbonate rock. Striped psammites and graphitic pelites locally developed.
Gradational contact with the overlying locally developed Carn an Daimh Transitional Member, marked by the increase in proportion of psammite and quartzite. Where the Transitional Member is absent, sharp boundary with Creag Leacach Quartzite Formation.
Great Coal (Titterstone Clee)
GTTC
Grantown Formation
GTWN
In part tectonic against underlying gneissose psammites and semipelites of Dava Succession - not seen.
Mid Spey Valley around Grantown-on-Spey, Central Highlands of Scotland, sheet 74E.
Weakly gneissose semipelite and subsidiary psammite beds, calc-silicate and metacarbonate rocks.
max. 500m
Transitional, with increasing sandy content, up into psammites of the Nethybridge Formation, but contact relations not well exposed.
Glasgow Upper Coal (Central Coalfield)
Gubeon Coal (Northumberland And Durham)
GUB
Gras Uchaf Coal (South Wales)
GUCO
Ghrudaidh Formation
GUD
Conformably overlies the Salterella Grit Member of the An T'Sron Formation. The boundary is gradational over about a metre.
The Durness Group , including the Ghrudaidh Formation, forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye.
Dark to mid-grey dolostones containing burrow mottling, oolitic and bioclastic grainstones and rare stromatolites.
From 50 m to 60 m thick.
Conformably overlain by pale grey and buff flaggy dolostones of the Eilean Dubh Formation. A zone of interbedded dark and pale grey dolostones occurs at the boundary. The actual contact with the Eilean Dubh Formation is taken at the appearance of laminations and/or chert layers.
Gourock Formation
GUF
Glenboig Upper Fireclay (Central Coalfield)
GUFC
Gault Formation And Upper Greensand Formation (Undifferentiated)
GUGS
Gubbin Ironstone (South Staffordshire)
GUI
Guirdil Member
GUIRD
Gullane Formation
GUL
Visean (Chadian to ?Holkerian).
The base is taken at the top of the Garleton Hills, Arthurs Seat or equivalent volcanic beds, where present; elsewhere at the lowest carbonaceous, coaly or rooty beds.
Lothians; south Fife; Berwickshire.
Mainly pale sandstones interbedded with grey to dark grey mudstones and siltstones. Subordinate coal, seatrock, ostracod-limestone/dolomite and sideritic ironstone. Thin marine bands also occur.
Spilmersford Borehole 132m, Skateraw Borehole 121m+, Birnieknowes Borehole 150m. Estimated thickness in Edinburgh area is c. 560m.
The top is drawn at the base of the lowest of the Macgregor Marine Bands (Wilson, 1974).
Gunthorpe Member
GUN
Conformable, gGradational upward passage from dominantly finely laminated mudstone and sandstone of Radcliffe Member into blocky, deformed mudstone of the Gunthorpe Member.
Mapped at surface in south Nottinghamshire and Leicestershire; traceable using geophysical logs in subsurface throughout East Midlands and Northeast England.
Mudstone, red-brown, with subordinate dolomitic siltstone and fine-grained sandstone, greenish grey, common gupsum veins and nodules.
70-90m (71m in Cropwell Bridge borehole, SK63NE/28)
Conformable, at abrupt base of lowest pale grey sandstone bed of the Cotgrave Sandstone Member, overlying red-brown blocky mudstone of the Gunthorpe Member.
Gully Oolite Formation
GUO
The base is taken at the gradational to sharp contact between the dolomitised sparsely crinoidal packstones of the Friars Point Limestone Formation or its parent the Black Rock Limestone Subgroup and the overlying oolitic grainstones or dolomitised oolite of the Formation. In the south the junction appears conformable but in the north a thin red clay overlying a palaeokarstic surface is locally present; in such cases the top is taken at the top of the red clay. The base of the formation in the Bristol area is locally taken at the junction of the sparsely crinoidal dolomites of the Black Rock Limestone Subgroup and the crinoidal limestones of the overlying Sub-Oolite Bed.
Gower [SS 50 90], Vale of Glamorgan [ST 00 74], southeast crop of the South Wales Coalfield [ST 17 85], Monmouth/Chepstow [ST 53 93], Bristol [ST 60 74], Weston-super-Mare [ST 30 60] and Broadfield Down [ST 50 65] areas. Present but not mapped in the Tenby [SN 13 01] and Pembroke [SM 97 03] areas. Passes east in the Mendip Hills [ST 50 53] into the Burrington Oolite Subgroup.
Medium- to thick-bedded, pale grey, oolitic grainstone with subordinate beds of fine-grained skeletal packstones. Cross-laminated and cross-bedded, some burrowing. Locally dolomitized, especially on the southeast and east crop of the South Wales Coalfield and in the Chepstow area. A palaeokarstic surface overlain by a green/red mudstone/clay palaeosol caps the Formation. Locally in the north Bristol to Tytherington area 6-21m of grey crinoidal limestones, the Sub-Oolite Bed, occurs at the base of the Formation.
83m in the southern Vale of Glamorgan, thinning to 19m on the southeast crop of the South Wales Coalfield.
The top of the Formation is taken at the sharp erosional contact between the mudstone/clay palaeosol at the top of the Formation and the overlying thin-bedded calcite mudstones and mudstones of the Caswell Bay Mudstone Formation [South Wales] or the Clifton Down Mudstone Formation [Bristol and Broadfield Down area]. A conglomeratic lag is locally present at the base of the Caswell Bay Mudstone Formation. In the southern part of the outcrop, the Formation is overlain by the High Tor Limestone Formation, the capping palaeosol being absent. Here the top is taken at the irregular erosional contact between the oolitic grainstones of the Formation and the overlying coarse skeletal packstone/grainstones of the High Tor Limestone Formation.
Gupton Formation
GUP
Glen Urquhart Complex
GURQ
Upper Streaky Andesite Member
GUSA
Gutter Coal (Titterstone Clee)
GUTC
Gully Member
GUY
Succeeds more typical Penwhapple Formation graptolitic siltstone and mudstone in Penwhapple Burn.
Slumped debris flow unit containing limestone clasts with shelly faunas within graptolitic shaly mudstones and siltstones of the Penwhapple Formation.
Succeeded by normal graptolitic siltstone and mudstone of the Penwhapple Formation.
Glencartholm Volcanic Member
A conformable boundary upon sedimentary rocks, mainly sandstone, of the Fell Sandstone Formation. Volcanic debris is absent in the underlying sandstones of the Fell Sandstone Formation.
Not recorded. Section on the left bank of the River Esk continued from stratotype: "Because there is no continuous sequence and because the strata are poorly bedded and faulted, the total thickness is difficult to assess. The strata dip owards the south or southeast at between 5 and 60 degrees. The lowest beds of blue grey tuffs and tuffaceous sandstones, which outcrop for about 165m downstream of the Mumbie Fault, are in excess of 21m thick. These beds are overlain by interbedded tuffs, tuffaceous sandstones, siltstones and cementstones with numerous beds of chert, cherty sandstone and limestone. Some of these beds are richly fossiliferous (Peach and Horne, 1903). The top of the Glencartholm Volcanic Beds, comprising a strike section of bluish and greenish grey bedded tuffs and tuffaceous mudstone is seen in Heck's Burn at NY 3821 7974." Scattered outcrops are present from Annandale (NY 317000 573000) to east of Langholm (NY 345000 583000).
Tuff and localised basalt lavas, with interbedded mudstone, sandstone and thin limestone. These volcanic beds are distinguished by the presence of tuffaceous sedimentary rocks, mainly sandstones with varying proportions of volcanic debris.
From 150m to 180m
Conformable boundary with the sandstone and mudstone of the Tyne Limestone Formation. The top of the unit is taken at the top of the highest tuffaceous sandstone.
Glannoventia Formation
GVA
Gradational, conformable contact with underlying pinkish grey, dusky red and pale reddish brown laminated silt and clay of the Carleton Silt Formation.
West Cumbria, Wasdale basin and coastal zone immediately to the west (around Drigg and Hall Carleton).
Yellow and grey, laminated, shelly, silty sand passing downwards into brownish grey shelly silt and dark brown laminated calcareous clay. Containing cold water marine microfauna of probable mid-Devensian age.
Sharp, planar, unconformable contact with stiff stony diamicton of the Holmrook Till Member of the Blengdale Glacigenic Formation.
Girvanella Nodular Band
GVB
Garvagh Bridge Member
GVBR
Conformable with underlying un-named part of Glenelly Formation schist, at top of thin chloritic green bed.
Pale grey impure metalimestone with greenish quartzo-feldspathic semipelites and calcareous schists.
Conformable within normal Glenelly Formation schist.
Garland Vein Coal (Pembrokeshire)
GVCO
Gavells Clough Sandstone
GVCS
Lower boundary is sharp and erosional, with sandstone resting either on grey, micaceous, sandy, siltstones overlying Eumorphoceras ferrimontanum Marine Band, or on mudstone of the marine band itself.
Brennand Fell and Abbeystead areas.
Sandstone, pale orange-brown, medium-grained, in part coarse-grained, micaceous, thick-bedded; mostly apparently massive, though with some cross bedding.
To 5m, but variable.
Upper boundary is seen only in right tributary to Sapling Clough [SD627 564] on Brennand Fell, where top 0.5m of the Member is micaceous and laminated with large lenticuler ferruginous concretions and grades rapidly upwards into grey micaceous sandy siltstones of the Roeburndale Member.
Glashvin Silt
GVIN
The Staffin area of northern Skye.
Girvan Group
GVN
Unconformable upon the Ardmillan Group.
Sandstone, conglomerate, siltstone and mudstone.
2837 m thick.
Unconformably overlain by the Lanark Group or the Inverclyde Group.
Givens Coal (Northumberland)
GVNC
River Terrace Deposits, 1 (Godalming Wey)
GW1
River Terrace Deposits, 1a (Godolming Wey)
GW1A
River Terrace Deposits, 1b (Godalming Wey)
GW1B
River Terrace Deposits, 2 (Godalming Wey)
GW2
River Terrace Deposits, 3 (Godalming Wey)
GW3
Gwaenysgor Limestone Formation
GWAE
Glenwells Conglomerate Formation
GWC
Conformably overlies the Glenwells Shale Formation.
A poorly-sorted conglomerate with pebbles at least 8 cm in diamete, interbedded with coarse-grained sandstones.
About 100 m thick.
Conformably overlain by the Newlands Farm Formation.
Gilwern Clay Member
GWCL
The base is placed at the karstified top of the underlying Penllwyn Oolite Member, where the basal green clay of the Gilwern Clay Member drapes the irregular surface of the Penllwyn Oolite Member.
Northeast crop of the South Wales Coalfield, from Cwar yr Ystrad [SO 081 142] to the Gilwern Hill area [SO 247 120].
Green and red-brown and purple mottled clay with limestone ("calcrete") nodules and, locally, a grey rootlet bed (seatearth) and a thin coal at the top.
5m (Cwar yr Hendre) to 7.4m (Llanelly Quarry).
The top is placed at the sharp, disconformable junction between the topmost clay (a seatearth at Llanelly Quarry) and the overlying sandy limestone forming the base of the Dowlais Limestone Formation. Where the Garn Caws Sandstone is present, the top is placed at the irregular scoured surface where the topmost clays of the member are erosively overlain by the Garn Caws Sandstone Formation [note that Wright (1981) included this sandstone in the Gilwern Clay, but it was subsequently given separate formation status by Barclay (1989)].
Gwendraeth Coal (South Wales)
GWCO
Great Wanney Crags Sandstone
GWCS
Specifically at Great Wanney Crags, near Penchford, Northumberland, and in adjacent areas.
Coarse-grained cross-bedded sandstone.
12 to 30m
Great Whinscale Dacite Member
GWD
Base of distinctive lava flow; underlain by thin un-named units of volcaniclastic sandstone or by the Little Stand Tuff.
Yoadcastle (SD 15 95) south of Devoke Water to Little Stand (NY 25 03), Harter Fell (SD 218 997) and around Seathwaite Tarn (SD 249 984), Cumbria.
Extensive white-weathered aphyric, dacitic lava flow, platy-foliated with marginal autobreccias.
Generally 75 - 85m; locally 20 - 65m.
Top of distinctive lava flow; overlain by volcaniclastic sandstone sequence of the Blisco Member, or by the Grey Friar Tuff, or by un-named andesite lava flows of the Birker Fell Andesite Formation.
Garscube Wee Coal
GWEC
Gwastadnant Grits
GWG
Glenwhargen Formation
GWH
Interfingers with the Portpatrick Formation.
Quartzose wacke and conglomerate turbidite unit.
0 to 500m
Interfingers with Portpatrick Formation.
Great Whin Sill
GWHIN
Taken at the sharp intrusive contact of the component sills, where they are in contact with sedimentary strata below.
Crops out throughout Northern England from Holy Island, south to Alnwick, to the Hadrian's Wall country, and to the Pennine escarpment to Teesdale; proved in mine workings and boreholes to underlie the area, enclosed at the east of the outcrop, and may extend for some considerable distance offshore.
A locally pegmatitic quartz-dolerite, with finer grained 'chilled' contact rock. Sills are typically columnar jointed, and comprise up to three leaves are present in places. The component sills and associated dykes cut strata up to and including those of Carboniferous, Duckmantian (Westphalian B) age, and derived pebbles are reworked into breccias of Early Permian age. Radiometric dates (K-Ar, Ar-Ar and U-Pb) are in the range of 301-294 Ma. The large volume of literature on this sill is listed, referred to and discussed in Stephenson et al., 2003.
Individual leaves average a thickness of about 30m; the thickest individual leaf is 73 m.
Taken at the sharp intrusive contact with the strata overlying the sill.
Gwrych Limestone
GWL
Gwersyllt Little Coal (North Wales)
GWLC
Gasworks Mudstones
GWMU
Gorllwyn Coal (South Wales)
GWNC
Gorllwyn Rider Coal (South Wales)
GWNR
Gilwern Oolite Formation
GWO
The base is placed at an erosion surface. In the type area, this is cut in micritic limestones of the underlying Coed Ffyddlwn Formation (Darren Ddu Member), which is overlain by coarse shelly, crinoidal grainstone (Craig-y-Gaer Coral Bed) at the base of the Gilwern Oolite Formation.
Northeast crop of the South Wales Coalfield, from between Blean Onnen Quarry and Chwar Pant-y-rhiw [c.SO 185 165] east to the Clydach Gorge and south down the east crop of the coalfield, where it is dolomitized, but perhaps correlatable with 14.4m of massive, cross-bedded dolomites at Gallowsgreen Quarry [SO 2662 0677], Varteg Hill.
Massive ooidal grainstone, shelly, crinoidal bed at base; becomes dolomitized on the east crop of the coalfield.
10m in the Clydach Gorge to 20m on the east crop.
The top is a major palaeokarstic surface, with extensive dissolution and palaeosol formation of the ooidal grainstone at the top of the Formation. This is overlain by micritic limestones and green clay (Clydach Halt Member) forming the basal part of the overlying Llanelly Formation.
Glenview Limestone Member
GWOM
Golan Well Pebbly Psammite Member
GWPP
Glen Isla area, Glen Shee district (Sheet 56W).
Pebbly psammite and psammite.
Base of metamafic rocks or calcareous rocks of the Loch Tay Limestone Formation.
Glasgow Shale Coal (Central Coalfield)
GWS
Graig-Wen Sandstone Formation
GWSA
Taken at the unconformable contact of the Graig-wen Sandstone with the underlying limestones and mudstones of the Dolhir Formation. The contact is locally an irregular palaeokarstic surface with the Graig-wen Sandstone penetrating through solution pits in the limestone into the underlying mudstones. It is likely the Graig-wen Sandstone Formation may be conformable with the Dolhir Formation near its feather edge but further work is needed.
Meifod area (SJ 09 09), northeast Wales. Passes north and northeastwards into the lowermost part of the Laundry Mudstone Formation.
Massive to medium-bedded grey calcareous sandstone. Locally shelly. Thin mudstones in uppermost part. Represents transgressive shoreface sand in response to the post glacial rise in sea level at the end of the Ordovician.
Taken at the gradational (over about a metre) incoming of the mudstone dominant sequence of the Laundry Mudstone Formation above the sandstones and subordinates thin mudstones at the top of the underlying Graig-wen Sandstone.
Glenwells Shale Formation
GWSH
Conformably overlies the Mulloch Hill Sandstone Formation (MLHS).
Hard, light and dark grey, laminated mudstones and siltstones with a graptolite fauna.
About 97 m thick.
Conformably overlain by the Glenwells Conglomerate Formation (GWC).
Gasworks Sandstone Formation
GWST
Haverfordwest area, Pembroke, South Wales.
c.85m
Garwallt Tuff Member
GWT
Conformably overlies mudstones of the Llangynog Formation.
No data.
Lapilli-crystal tuff with varying amounts of epiclastic material.
5 to 6m
Conformably overlain by volcaniclastic mudstones of the Llangynog Formation.
Gwynedd Supergroup
GWYN
Not (yet) in widespread use in BGS. Confirmation of its status currently awaits Stratigraphical Framework Committee acceptance, etc.
Grey Friar Tuff Member
Base of dacitic lapilli tuff. Unconformable, locally overlies Great Whinscale Dacite and elsewhere un-named basaltic andesite and andesite in the Birker Fell Andesite Formation.
Cockley Beck Fell - Grey Friar - Seathwaite Tarn - Troutal Fell, Cumbria.
Massive, dacitic lapilli-tuff; contains significant quantities of lithic clasts, mainly of siltstone and sandstone derived from the subvolcanic, Skiddaw Group, basement.
Overlying parts of Birker Fell Andesite Formation, usually volcaniclastic sandstone or andesite.
Grimley Andesite
GYA
All boundaries seen are faulted, except where one small sheet is chilled against the Peldar Dacite Breccia in Whitwick Quarry.
Extends from Whitwick Quarry northwards into Whitwick and Thringstone villages, and eastwards to Hob's Hole. To the south, it is last seen in Bardon Quarry.
Grey to green, massive to autobrecciated, sparsely porphyritic high-silica andesite or dacite. Locally grades to monomictic (andesite-clast) block-breccia in Bardon Quarry.
Grammysia Member
GYB
Greenyards Coal
GYC
Grey's Crag Coal (Northumberland)
GYCC
Grey Chalk Subgroup
GYCK
Unconformable, set at the burrowed erosion surface marking the base of the Cenomanian. In the Southern Province this marks the distinct change from chalk-free to chalk-rich sediment. In the Northern Province the boundary is at an erosion surface between the Ferriby and Hunstanton formations.
The Subgroup is known throughout the onshore outcrops in England and offshore in the Southern, Central and Northern North Sea areas. In the Northern Province the term Ferriby Chalk Formation is analogous.
Clayey ("marly") chalk without flint. The Lower part comprises limestone/marl "couplets" equivalent to the West Melbury Marly Chalk Formation in the Southern Province. Upper part distinctly less "marly" with notable calc-arenite beds and is equivalent to the Zig Zag Chalk Formation of the Southern Province. The Ferriby Formation of the Northern Province is the lateral equivalent of the Grey Chalk Subgroup and comprises grey, soft, "marly", flint-free chalk, typically weathering buff in exposures; locally includes pinkish bands; some harder, gritty, shell-debris-rich beds, and thin discrete "marl" seams.
Variable, generally between 45 and 90 m in Southern Province. Is equivalent to the 30m or so of the Ferriby Chalk Formation of the Northern Province.
Conformable at the highest bedding plane beneath the lowest bed of the Plenus Marls Member of the Holywell Nodular Chalk Formation in the Southern Province and the Welton Chalk Formation in the Northern Province. (Note that the Plenus Marls Member is now considered as part of the overlying subgroup, thus providing a consistent datum throughout the Chalk Group of England and the North Sea).
Gannochy Conglomerate Formation
GYF
The base of the lowest conglomerate above Loup's Bridge, resting on poorly sorted muddy sandstone of the Cromlix Mudstone Formation [NO 5947 7165].
The Edzell area, where it is laterally equivalent in part to the Teith Sandstone Formation and the Strathfinella Hill Conglomerate Member.
Red conglomerates, with sandstones and rare mudstones. The conglomerates are interpreted to be principally all of 'Highland' provenance.
250 m thick.
The top of the clast-supported orthoconglomerate beds immediately downstream of Loup's Bridge [NO 5948 7164], which are overlain by the Teith Sandstone Formation.
Glyn Gower Siltstones Member
GYG
Conformable and gradational with mudstones of the Ceiswyn Formation, generally taken at the top of the Cefn Gwyn Tuff where the latter is present.
Corwen and Bala districts.
Laminated siltstones and fine-grained sandstones with subordinate mudstones and rare thin tuffs.
130m to 150m.
Conformable and gradational with mudstones of the Ceiswyn Formation, but generally taken at the base of the overlying Frondderw Tuff, where the latter is present.
Gayle Limestone
GYL
Gregynog Mudstone Member
GYM
Diachronous, upon the greywacke sandstones of the Denbigh Grits/Penstrowed Grits.
So far 1:50 000 map, Sheet 165 (Montgomery), western edge.
Mainly mudstone, silty medium-dark grey homogeneous, slumped and in part thinly interbedded with thin fine-grained sandstones.
At least 130m.
Where the bedding becomes prominent in rhythmic ribbon banded mudstones and siltstones of the Nantglyn Flags type. In practice, at the base of the Mottled Mudstone Member.
Glyn Formation
GYN
Top of underlying micaceous siltstones and mudstones of the Dolhir or Cyrn-y-Brain Beds.
Glyn Ceiriog and Llanelidan-Eglwyseg area of east Wales.
Fine- to coarse-grained sandstones and thin siltstones; a locally developed limestone member (Glyn Limestone) at base on Mynydd Fron Frys.
Overlain by shales and slates of the Fron Frys Formation.
Ypresian Rocks (Undifferentiated)
GYRU
Grey Shale
GYSH
Greenway Tuff Member
GYT
Greystoke Till Formation
GYTI
Planar or uneven unconformable boundary with red diamicton of the Gillcambon Till Formation below, or unconformable on bedrock.
The Vale of Eden and southern Solway Lowlands north of the "Scottish Readvance" limit.
Grey stony sandy clay diamicton with clasts of Lake District volcanoclistic rocks and Carboniferous Limestone. Contains rip-up clasts of underlying Gillcambon Till at Type Section. Elsewhere in Edenside the unit contains relatively more Permo-Triassic red sandstone and Carboniferous sandstones.
At land surface or overlain unconformably by glaciofluvial/glaciolacustrine or Flandrian sediments.
Hughes Member
The base is placed at the base of the Hughes Coal or its equivalent (Cefn Glas, Wenallt, Bettws Four-Feet, Ty-du, etc) in a predominantly arenaceous sequence of the Pennant Sandstone Formation, where the coal rests on mudstone/siltstone seatearth at the top of the Brithdir Member.
Widespread outcrop throughout the South Wales Coalfield, from Llanelli [SN 49 02] to near Pontypool [ST 268 980].
Green-grey, lithic arenites ("Pennant sandstones"), with thin mudstone/siltstone and seatearth interbeds, and mainly thin coals.
From 45m near Pontypool [SO 250 150] thickening westwards to 270m near Swansea [SS 570 960].
The top is placed at the base of the Golden Seam or its equivalent (Swansea Three-Feet, Graigola) at the base of a predominantly arenaceous sequence of the Swansea Member, where the coal rests on mudstones/siltstone and seatearth at the top of the Hughes Member. In the east of the coalfield, the top is placed at the base of the Mynyddislwyn Coal.
Isohomoceras Subglobosum Marine Band [1 Of 3]
H1A1
Isohomoceras Subglobosum Marine Band [2 Of 3]
H1A2
Isohomoceras Subglobosum Marine Band [3 Of 3]
H1A3
Homoceras Beyrichianum Marine Band
H1B1
Isohomoceras Sp. Nov. Marine Band
H1B2
Hudsonoceras Proteum Marine Band
H2A1
Homoceras Undulatum Marine Band
H2B1
Vallites Eostriolatus Marine Band
H2C1
Homoceratoides Prereticulatus Marine Band
H2C2
Halesowen Formation
In the Halesowen type area a sharp unconformable junction between the red mudstone of the Etruria Formation and overlying grey-green, locally pebbly sandstone of the Halesowen Formation. May be conformable elsewhere. If the Halesowen Formation is red, the base is drawn at the base of the first litharenite above the Etruria mudstones.
Mostly the southern part of the Pennine Basin, central England from Oxfordshire to Lancashire and Nottinghamshire, and North Wales.
Grey-green, micaceous sandstone (litharenite), and grey-green mudstone, with thin coals and limestone beds known as the 'Spirobis' limestone, with local intraformational conglomerate, strata may be reddened, locally.
About 110 m thick in the type area; 76 - 152 m thick in South Staffordshire; 70 - 127 m thick in Warwickshire; about 200 m thick in Wyre Forest; 350 m thick in North Staffordshire; remaining thickness about 125 m in the East Midlands and about 200 m in Lancashire.
At the base of the the Salop Formation. At outcrop an upward change from grey to orange-red locates the boundary, except where the Halesowen Formation is itself red; in this case the boundary is drawn arbitrarily, above the top of the highest litharenite sandstone. Although in boreholes, the gamma ray log character is used.
Hathern Anhydrite Formation
HAA
Not proved in the Hathern No.1 Borehole, but probably an angular unconformity resting upon pre-Carboniferous rocks.
Lies at depth within the Hathern Shelf and possibly the Widmerpool Half-Graben, in the Long Eaton No.1 Borehole (SK43SE/161) [SK 4640 3166].
Bedded and nodular anhydrite, interbedded with grey dolostone, mid-to-dark grey mudstone or calcareous mudstone, and massive to nodular limestone.
At least 97m
The top is defined at the top of the highest anyhydrite or mudstone unit, and is overlain in the Hathern No.1 Borehole by thickly-bedded, grey, brown and black, fine-grained limestone with shaly beds, identified as the Milldale Limestone Formation. Anhydrites, possibly belonging to the Hathern Anhydrite Formation, are overlain by mudstone, siltstone and thin limestone beds of the Long Eaton Formation in the Long Eaton No. 1 Borehole (SK43SE/161) [SK 4640 3166].
Hampshire Avon Formation
HAAV
The fluvial deposits rest unconformably on Palaeogene and Cretaceous strata.
The catchment of the Hampshire Avon and its tributaries.
Floodplain alluvium and river terrace deposits. The floodplain alluvium comprises overbank deposits of mottled dark grey and orange organic silt, silty clay and clayey sand, tgether with peat, overlying sand and gravel. Fourteen river terraces are preserved. The river terrace deposits comprise very sandy gravels. The clasts are sub-angular to sub-rounded, poorly sorted up to 5cm in diameter, dominantly flint, with a little Upper Greensand chert, "sarsen" stone, vein quartz, Jurassic limestone, and well-rounded flints from the Palaeogene, in a matrix of clayey sand. Deposits of the higher terraces are cryoturbated.
To 8m, including up to 4m of alluvial overbank deposits.
Harptree Beds
HAB
Heavitree And Alphington Breccias
HABR
Hales Clay Member [See Also Hwh]
HAC
Halibut Carbonate Formation
HACA
Hawkesbury Clay
HACL
Hand Coal (Northumberland)
HACO
Hackness Rock
HACR
Haddenham Formation
HADD
Harra Ebb Sandstone Formation
HAE
Unconformably lies on Moinian basement.
Orkney Islands.
Interbedded sandstones and siltstones with tongues and lenses of breccia and conglomerate.
100m at Harra Ebb NY 215 148 Mainland, Orkney.
Not known - in fault contact with Qui Ayre Sandstone Formation.
Hafod Member
HAFD
Halfway Farm Formation
HAFM
Hafod Fawr Formation
HAFOD
Haggard Coal (Milford, South Wales)
HAGC
Hackney Gravel Member
HAGR
Rests with unconformity on bedrock geology (eg London Clay).
Average 6m, range to 10m.
Hazel Greave Grit And Guiseley Grit (Undifferentiated)
HAGU
Haigh Yard Coal (South Lancashire)
HAGY
Hauptanhydrit Formation
HAHY
Haisborough Group
HAI
Offshore UK, southern North Sea. Equivalent to, and in continuity with, the Mercia Mudstone Group of onshore north-east England (Johnson et al., 1994).
Mudstone, reddish brown and grey, dolomitic, with thick units of bedded halite and common anhydrite.
To 900m (Johnson et al., 1994).
Conformable, at an abrupt upward change from red-brown and grey-green mudstones of the Haisborough Group to the dark grey mudstones and grey fine-grained sandstone of the overlying Penarth Group.
Hall Carleton Formation
HALC
?Lateglacial (Late Devensian) to Holocene.
Unconformable on all older glacial diamictons and glaciofluvial sand and gravel deposits. In its type area it overlies diamictons of the Gosforth Glaciogenic Formation.
Coastal zone of 1:50k Sheet 37 Gosforth, around western Cumbria (but could be applied to all Holocene to Lateglacial raised marine and estuarine deposits and raised beaches of the Cumbria and Lancashire coastal area).
Generally a fining upward sequence of medium- to fine-grained pale brown sand with interlaminations of silt that passes upwards into mottled olive clay and silt with thin beds and partings of peat and peaty (humic) silt. These fine-grained sediments contain microfossil assemblages indicating deposition in marine, estuarine and brackish water since deglaciation. It also includes sand and gravel forming Holocene raised beaches.
Typically c.3-6m, but 14m thick in BGS/Nirex borehole QBX 2-A (BGS Registered borehole SD09NE 22).
The ground surface or overlain by blown sand of the Drigg Point Sand Formation.
Hallane Formation
HALL
?Early Devonian.
Faulted - thought to be part of the Parautochtonous succession.
BGS 1:50 000 scale Sheet 353 (Mevagissey), (England and Wales).
A dark grey slaty mudstone, with black mudstone nodules, sporadic thin siltstone lenses and dispersed limestone lenses, crinoidal and shelly in part and with subordinate laminated mudstone and siltstone.
Unknown: details obscure due to complex folding; possibly several hundred metres.
Hambleton Mudstone Member
HAM
Conformable, at the rapidly gradational upward transition from the pale brown or pinkish red sandstones of the Ormskirk Sandstone Formation (Sherwood Sandstone Group) to the grey, laminated mudstones and micaceous siltstones of the Hambleton Mudstone Member.
North Fylde peninsula, Lancashire.
Mudstone, grey, interlaminated with siltstone, pale grey, micaceous.
Originally referred to as the Hambleton Mudstones (Wilson and Evans, 1990) and raised to Formation status by Warrington et al. (1980) the unit is retained but with Member rank as part of the nationally recognized Sidmouth Mudstone Formation (Howard et al., 2008).
30m to 37m (Wilson and Evans, 1990)
Conformable, within a gradational upward transition from grey, laminated mudstones and micaceous siltstones of the Hambleton Mudstone Member to laminated reddish brown and greenish grey mudstones (Sidmouth Mudstone Formation, undifferentiated).
Hams Coal (North Staffordshire)
HAMC
Hake Mudstone Member
HAMU
Hanborough Gravel Member
HAN
Mid Pleistocene (MI Stage 11 to 10).
Unconformable, commonly channelled base, resting on Jurassic bedrock.
Upper Thames catchment, ie, River Thames and most tributaries (excluding the River Thame) upstream of the Goring Gap. Well developed in the lower Evenlode around the type locality, and less well developed along the lower Cherwell, and also along the main valley of the Upper Thames (ie, upstream of the Goring Gap).
Predominantly cold phase sands and gravels that underlie the Hanborough or Fourth Terrace of BGS Maps. Dominated by clasts of Middle Jurassic limestone, though at many localities pervasively decalcified, leaving a remaine deposit dominated by "Bunter" quartz/quartzite. Temperature indicators such as straight-tusked elephant occur in lower part, probably derived from earlier sediments of MIS 11 date.
Compiler?s Notes: (A) Unit named the Hanborough Gravel Member though in Bowen 1989 and in the former BGS list of computer codes it is Hanborough Member. Note that most other "terrace" units are described as "Sand and Gravel" members. (B) Parent was originally Upper Thames Valley Formation. Despite correlation problems at Goring, the change is acceptable as member names in the Upper Thames remain discrete. (C) Terrace surface some 30m above modern (Evenlode) alluvial floodplain at the type locality, and (apparently) an approximately similar height elsewhere. (D) The upper boundary is given as ?ground surface? though there may be head, colluvium or soil deposits intervening. (E) Apart from at the type locality the recognition of this terrace is based on elevation. Mapping in some areas may be suspect so not all Fourth Terrace is necessarily the Hanborough. In the Upper Evenlode (Sheets 235, 218) there are limestone gravels that probably include equivalents but this has a different name (Spelsbury Member) because it is probably a composite deposit including younger materials. There is a reasonable Hanborough Member on the Cherwell (128) Sheet, however. There is no truth in the claim (Tomlinson, 1929; Arkell, 1947) that it equates with the Paxford Gravel of the Moreton-in-Marsh area, which underlies the bulk of the Anglian Moreton Drift.
0 to c.6m
Hawks Nest Coal
HANC
Rests on dark shale and seatearth.
Coaly shale and coal.
Overlain by dark grey fossiliferous shale.
Hannaborough Intrusion
HANN
Olivine biotite bearing lamprophyre in vent agglomerate.
Hanchurch Sandstone Bed
HANS
Hambleton Oolite Member
HAO
Happendon Coal (Douglas)
HAP
Harwood Band
HAR
Belfast Harbour Evaporite Formation
HARB
Harnlo Coal (South Wales)
HARC
Hard Coal (South Lancashire)
HARD
Hardy Coal (Northumberland) [Also Known As Stony Coal]
HARDY
Harehill Pluton
HARL
Harris Member
HARR
Hartley Coal (Dailly)
HART
This coal is close to the base of the Limestone Coal Formation and is not the same as the Hartley Coal of Stirling, etc (which lies at a higher level within the Limestone Coal Formation).
Harvey Coal (Northumberland And Durham)
HARV
Hastings Beds (Subgroup)
HAS
Base of silts and sands of Ashdown Formation on soft mudstones of the Upper Purbeck.
The Weald.
Ferruginous sandstones, siltstones and shales.
Top of highest sandstone of the Tunbridge Wells Sand Formation beneath clayey silts and silty clays (without sandstones) of the Weald Clay Formation.
Hangman Sandstone Formation
HASA
Conformable on Lynton Formation. Boundary taken where sandstones become dominant in upward succession.
North Devon - west Somerset coasts (sheets 277 and 278).
Mainly sandstone, purple, grey and green, commonly thick-bedded and parallel laminated, locally convolute-bedded or cross-bedded, fine- to medium-grained. Interbeds of cleaved shale, siltstone and silty very fine-grained sandstone, and some thicker units of cleaved purple mudstone interlaminated with very fine-grained sandstone. Minor local developments of conglomerate and pebbly sandstone, stratigraphical position uncertain. Divided into five units by Tunbridge (1978).
Tunbridge (1978) proposed the term "Hangman Sandstone Group" divided into five formations, in ascending order: Hollowbrook Formation (70m), Trentisoe Formation (c.1250m), Rawns Formation (148m), Sherrycombe Formation (90m) and Little Hangman Formation (c.100m). However, it has not proved possible either on Sheet 277 or Sheet 278, to map these component units and it is therefore considered that Formational status is more appropriate, with Tunbridge's units having Member status.
1097m (Evans, 1922). 1350m (Lane, 1965). 1658m (Tuunbridge, 1978). 2000-2500m (Edmonds et al. 1985).
Commonly faulted but probably conformable with Ilfracombe Slates.
Harnage Shale Formation
HASH
Dominantly olive-brown silty mudstones, with some sandstone beds.
c.120 to 250m
Haist Pebbly Sandstone Member
HAT
Slightly unconformable on Lyre Geo Sandstone Member; base marked by grade-laminated sandstones.
Well-cemented fine-, medium- and evenly coarse-grained sandstone, with sporadic granule and clay intraclasts and pebbly horizons.
195m at Regal Burn ND 2804 9803 to ND 2937 9756, Hoy Island, Orkney.
Top marked by grade-laminated sandstones at top of pebble-bearing sandstone sequence.
Hanworth Till Member
HATI
Rests unconformably on earlier Middle Pleistocene strata. Rests upon Lowestoft Formation at Lower Street [TG 16 34] and Alby Hill [TG 19 34]. Rests upon Corton Sand at Suffield [TG 23 31] and Buxton [TG 21 23]. Rests upon Happisburgh Till at Erpingham [TG 18 30]. West of Erpingham may cut through the Happisburgh Till to rest upon Wroxham Crag Formation.
Known from mapping and trial pits between Lower Street, Gallows Hill, and Buxton. Southward extent unknown as not yet mapped. Eastward extent unclear as it passes below the Briton's Lane Formation, may be cut out unconformably by it. Northward extent also unclear as it passes below the Briton's Lane Formation, but not cut out unconformably, passes into "contorted drift" members of the Sheringham Cliffs Formation. Westward extent unclear as the relationships of the Hanworth Member and the Lowestoft Formation have not been resolved, but Hanworth Member eventually passes into "marly drift" members of the Sheringham Cliffs Formation.
Brown silty sandy clay diamicton incorporating masses up to at least 100m across of "marly drift". The brown diamicton is apparently massive and contains much flint, quartz and quartzite, sediments of Cretaceous, Jurassic, Permo-Triassic, Carboniferous and Devonian derivation, and igneous erratics "marly drift" is pale grey or buff massive highly consolidated diamicton consisting almost entirely of re-constituted chalk and black hearted fresh flints, with minor Jurassic input. The Hanworth Member contrasts with other sandy tills of the Sheringham Cliffs Formation in that it is not contorted.
Overlain unconformably by the Briton's Lane Sand and Gravel (Mid Pleistocene).
Hatton Till Formation
HATT
Unconformable on bedrock, Kippet Hills Sand and Gravel Formation or older tills, eg. Pitlurg Farm Till Formation.
Coastal lowland north of Aberdeen, east of Ellon and south of Peterhead.
Diamicton, clayey, pebbly, calcareous, red, crudely stratified. Besides local rock types it contains red (Devonian) sandstone, Mesozoic/Tertiary mudstone and limestone, shell fragments.
10m or more
Occurs to surface or beneath post glacial deposits.
Hauchielin Coal (Tranent - Haddington)
HAU
Haddington's Vein
HAV
Hawksmoor Formation
HAW
Usually unconformable on Palaeozoic rocks. Where conformably overlying the Huntley Formation, base taken where conglomerate or sandstone containing locally derived clasts gives way to sandstones and conglomerates with few such clasts.
Needwood Basin.
Red-brown, yellow, or yellow-mottled, very fine- to coarse-grained sandstones, commonly cross-bedded, locally micaceous, silty or argillaceous, pebbly or conglomeratic. Generally friable.
Base of overlying Hollington or Denstone formations (disconformable).
Haw Hill Borehole Formation
HAWH
Haweswater Intrusions
HAWS
Around the Haweswater Reservoir, from Willdale Beck [NY 483 166] to Harper Hills [NY 510 140]., Cumbria.
Dolerite with subordinate gabbro and microdiorite, and minor intrusive breccia. No radiometric age has been published but an Ordovician age is inferred because of geochemical similarities with the Borrowdale Volcanic Group and the presence of cleavage in parts of the gabbro.
At least eight plugs and dyke-like masses within a total area of 19km2, and having a combined outcrop of about 2.6km2.
Harthwaite Tuff Formation
HAWT
Taken at the base of the sequence of bedded volcaniclastic rocks resting on densely welded rhyolitic tuff of the Knock Pike Tuff Formation. The basal beds contain fragments of the underlying Knock Pike Tuff
Bedded volcaniclastic siltstones and sandstones with intercalated silicic crystal and vitric tuffs
About 300m
Defined by the base of the unconfomably overlying sedimentary rocks of the Dufton Shale Formation
Hayes Sandstone Formation
HAY
Haymoor Bottom Clay Member
HAYC
Half Yard Coal (Warwickshire)
HAYD
Haystacks Andesite Member
HAYS
At the base of the andesite lava sequence resting on volcaniclastic rocks within the Birker Fell Andesite Formation.
North Lake District, near Buttermere.
Andesite lavas with flow banding and columnar jointing, interdigitated with massive and bedded breccias in upper part of unit. Also some bedded volcaniclastic sedimentary rocks.
About 500m
Defined by the base of overlying bedded breccias, sandstones and tuffs of the Round How Member.
Halesowen Formation [Obsolete Code: Use Ha]
Helmsdale Boulder Beds Formation
HBB
Hard Bed Band Coal (South Derbyshire)
HBBC
Hard Bed Band Rock (West Yorkshire)
HBBR
Hundleby Clay Member
HBC
An erosion surface separates the mudstones of the Hundleby Clay Member from the sandstones of the Upper Spilsby Sandstone Formation in southern Lincolnshire and the Wash. In other parts of Lincolnshire (e.g. Langton, Mavis Enderby, Mardon Hill and Raithby to Hundleby), the base of the member is placed at a down-section change from mudstones (Hundleby Clay Member) to ironstone (Claxby Ironstone Formation). As a result of interdigitation, the local base of the member may be higher within the Claxby Ironstone Formation.
Confined to southern Lincolnshire. The northern feather edge is between Cawkwell and Stenigot according to Owen & Thurrell (1968) and the member extends to the south-east around Spilsby. It occurs in the Skegness Borehole and apparently extends below The Wash where a similar clay situated between two sandstones, occur above the Sandringham Sands Formation and below the Tealby Formation.
Purple-grey, brown-mottled silty clay which becomes progressively sandier towards the top. It interdigitates with the ironstone of the Claxby Ironstone Formation. Between Belchford and Hundleby it comprises 'unctuous, plastic clay' throughout (Owen & Thurrell, 1968).
Up to c. 5.5 m
Downsection change from ironstones (upper part of the Claxby Ironstone Formation) to clay (Hundleby Clay Member).
Holcombe Brook Coal (South Lancashire)
HBCO
Hebburn Dyke
HBDY
Hope Beck Formation
HBE
Occurs within the Skiddaw inlier in the vicinity of Hope Beck and on the east side of Dodd. It is not recognised in any other inlier.
Dark grey siltstone and mudstone in laminated and very thin beds, with up to 5% sandstone mainly in thin and medium beds; sporadic pebbly mudstone beds are also present.
600 to 800m
Taken at junction with the overlying Loweswater Formation.
Hetton Beck Limestone Member
HBEL
Park Laithe Borehole (SD 9629 5813) showed an unconformable relationship with the underlying Clitheroe Limestone Formation (Thornton Limestone Member).
Confined to Craven Basin.
Packstones, wackestones and floatstones, with a variety of thick, thin, wavy, and nodular bedding, interbedded with subordinate grainstones, limestone lithoclasts, possible 'in situ' Waulsortian limestones and thin mudstones. Silicification and dolomitisation common, with slumps and gravity slides present locally.
To 130m
In the Eshton-Hetton Anticline, the Hetton Beck Limestone is overlain by various lithologies including wackstones, laminated calcisiltites, mudstones and boulder beds.
Holm Burn Flagstone
HBF
Hawks Brow Flint
HBFL
Hibernian Greensands Group
HBG
Cenomanian to Santonian. Various basal Upper Cretaceous zones up to Micraster coranguinum Zone.
Unconformable on a variety of older formations at a major regional erosinal break at the base of the Belfast Marls Member.
Throughout Northern Ireland. As a thin basal Cretaceous unit over structural highs and in the North Antrim Basin, where the group is undivided. Fullest development in the Midland Valley (East Antrim Basin) and the Southern Uplands as defined in Fletcher (1977) where group is divided.
Glauconitic `marls?, argillaceous siltstones and calcareous sandstones, and quartzose sands. Sequence divided into four formations noted above.
About 21m to 22m in the Carrickfergus, Larne, Antrim and Belfast sheet areas.
Unconformable at a major regional erosional break. Overlain by various members of the Ulster White Limestone Group.
Black Shale And Chert
HBHB
Greenstone Conglomerate
HBHG
Greenstone And Spilite Volcanics
HBHS
Hobbyhorse Bay Limestone Formation
HBL
Taken at a sharp junction between the dark limestones, cherts and mudstones of the Linney Head Formation and the overlying thick-bedded coarsely crinoidal limestones of the Formation.
Castlemartin area [SR 95 98], south west Pembrokeshire. Relationship to coeval Gully Oolite Formation to the north unknown.
Grey, thick-bedded, coarsely crinoidal packstones. Locally dolomitized. Deposited in a distal ramp setting.
17m at type locality in southwest Pembrokeshire.
Taken at sharp junction between dolomitised crinoidal packstones at the top of the Formation and the crinoidal packstones with mudstone partings of the overlying Pen-y-holt Limestone Formation. This boundary is unsatisfactory but has not been changed as it defines the base of the Arundian Stage and needs further work.
Hamble Formation
HBLE
Unconformable on Palaeogene bedrock.
The catchment of the Hamble River and its tributaries, in the Southampton area.
Floodplain alluvium and river terrace deposits. The floodplain alluvium comprises overbank deposits of brown organic silty clay, together with peaty clay, and peat, overlying sand and gravel. The surviving river terrace deposits comprise sand and gravel, commonly cross-bedded, locally overlain by overbank deposits of clayey and sandy silts and silty clays. These fine-grained deposits may be partly aeolian in origin. The major gravel lithology is flint, dominantly sub-rounded to sub-angular, with a little well-rounded. The sand fraction is composed of well-rounded quartz grains and sub-angular flint. The older, higher terraces are commonly cryoturbated.
To c.12m
Henry's Bridge Member
HBM
Gradational and conformable with normal clastic Dart Formation lithologies.
Glenelly, Co. Londonderry, Northern Ireland.
Greenish brown compact chloritic schist with albite porphyroblasts, interbedded semi pelite.
c.47m
Gradational and conformable upwards gradation into normal Dart Formation Lithologies.
Hard Bed Marine Band [Local Name: See Mfmb]
HBMB
Hunts Bay Oolite Subgroup
HBO
The base of the Subgroup is gradational and taken at the incoming of a predominantly oolitic grainstone sequence, locally with units of calcite mudstone, above the skeletal packstones or skeletal/peloidal/oolitic packstone/grainstones of the underlying High Tor Limestone Formation.
Pembroke [SM 97 03], Tenby [SN 13 01], Gower [SS 50 90], Vale of Glamorgan [ST 00 74], east crop of the South Wales Coalfield [ST 17 85] and Monmouth and Chepstow [ST 53 93] areas. Passes eastwards into the Clifton Down Limestone Formation of south Pembrokeshire [SM 99 01] and northwards in South Wales into the Dowlais Limestone Formation.
Mainly ooidal limestones, with subordinate skeletal, peloidal and oncolitic limestones and calcite mudstones. Mainly dolomitised on the southeast and east crop of the South Wales Coalfield.
245m in central Vale of Glamorgan thinning northwards to a feather edge in the Forest of Dean.
In the Vale of Glamorgan the top is taken at the sharp contact, defined by a palaeokarstic surface, between the heterolithic lithologies of the Subgroup and the overlying partially dolomitised sandy skeletal packstones and the calcareous sandstones of the Pant Mawr Sandstone Member [Oxwich Head Limestone Formation]. In the Gower and Pembrokeshire it is taken at the palaeokarstic surface separating the heterolithic lithologies of the Subgroup from the mottled and pseudobrecciated skeletal packstones of the overlying Oxwich Head Limestone Formation.
Highland Border Ophiolite-Complex
HBOR
Latest Neoproterozoic to Ordovician.
Pending complete definition of this unit, please refer also to the Supplementary Information for Highland Border Complex (HBX).
Haffield Breccia Formation
HBR
Unconformable on Coal Measures and older rocks.
Malvern - Abberley Hills; equates with Clent Breccia of West Midlands. (Mitchell, and others, 1962).
Unsorted clast-supported breccio-conglomerate, weakly cemented; clasts of igneous volcanic and Lower Palaeozoic lithologies.
To 75m
Unconformably overlain by Bridgnorth Sandstone Formation.
Hebridean Province
HBRID
Hartfell Shales
HBS
Helsby Sandstone Formation [Obsolete Code: Use Hey]
HBSF
Higher Bent Coal (South Lancashire)
HBTC
Hebblethwaite Member
HBW
At the lowest appearance of red coloured mudstones above the green-grey mudstones and siltstones of the lower part of the Browgill Formation.
Unit extends intermittently across the Howgill Fells inliers, and is known in several Lake District sections, (Ingham, J K, et al, 1978).
Red-brown mudstones, typically massive, but with thin horizons of paler brown calcareous nodules.
At the top of the last red mudstone, in the transition to the pale grey mudstone of the overlying Far House Member.
Highley-Brooch Coal (Wyre Forest)
HBWF
Highland Border Complex
HBX
Not seen: tectonic contact with Highland Boundary Fault system.
Highland Border area, Scotland, at the boundary between the Midland Valley and Grampian terranes. Several fault-bounded, lenticular outcrops strung out between Garron Point, Stonehaven, in the northeast, and Glen Sannox, Arran, in the southwest. Includes all rocks younger than the Dalradian Supergroup and older than the Old Red Sandstone, and lying immediately to the northwest of the Highland Boundary Fault and southeast of the Dalradian outcrop.
Four distinct assemblages, all showing varying degrees of greenschist facies regional metamorphism, have so far been recognised: (4) gritty sandstone, limestone and mudstone (probably Caradoc); (3) metabasalt, chert and mudstone equivalents; (2) limestone and basal serpentinite conglomerate (mid-Arenig); (1) serpentinite, metagabbro and hornblende-schist. The status of associated limestone (Leny Limestone) and black shale is unclear (probably Early Cambrian).
[UNDER REVIEW; POSSIBLY OBSOLETE] All the mapped units formerly encompassed by the Highland Border Complex are now contained within the Highland Border Ophiolite-complex and the Trossachs Group. These latter units now "adopt" all the children of the Highland Border Complex. Technically, therefore, the Highland Border Complex should now be obsolete. However, the term is still quoted very widely, and it is uncertain whether a need for it remains, albeit in a radically re-defined form.
Not calculable; isolated fault-bounded blocks. The relatively thin sections preserved are the remnants of a complete crustal thickness.
Not seen: tectonic contact with the Highland Boundary Fault system. Unconformably overlain by Devonian Old Red Sandstone facies strata.
Habberley Shale Formation
HBY
Green-grey shaly mudstones, siltstones and fine-grained sandstones.
c.800m
Defined by facies change to Stiperstones Quartzite Formation. May be non-sequence at top.
High Camlarg Coal (Dalmellington, South Ayrshire)
Hoo Cannel Coal (North Staffordshire)
HCC
Hatton Conglomerate Member
HCF
The base of the lowest bed in which metamorphic rock types predominate in conglomerate clasts, overlying the Craighall Conglomerate Formation with its typically volcanic clasts.
The Blairgowrie to Alyth area, northern Midland Valley.
A well-rounded cobble and boulder conglomerate of mainly metamorphic rock types, with beds of pebbly sandstone.
About 950 m thick
The top of the highest conglomerate bed beneath a sequence of cross-bedded pebbly sandstones of the Tannadice Sandstone Member exposed in the River Ericht at [NO 1787 4577].
Huckster Conglomerate Member
HCG
Taken at the relatively sharp, but conformable contact with the underlying purple shaly mudstones and siltstones of the Lightspout Formation.
Welsh Borderlands, Church Stretton and the Long Mynd.
A massive conglomerate with subordinate pebbly sandstone. The conglomerate is generally composed of clasts of white quartzite in a red-brown sandstone matrix.
Up to 18 m thick.
Poorly exposed, but taken at the conformable transition from conglomerate and coarse pebbly sandstone into the purple siltstones and sandstones of the main part of the Portway Formation.
Higher Chamber Coal (South Lancashire)
HCHC
Holywell Nodular Chalk Formation
HCK
Upper Cretaceous, Cenomanian (uppermost) to Turonian. Metoicoceras geslinianum to Mytiloides spp. Zones. (the inferred top of the Mammites nodosiodes Zone).
Conformable. Base of the formation taken at the bedding plane immediately below the lower marl bed in the Plenus Marls Member. (Note that the Plenus Marls Member is now considered as part of this formation thus providing a consistent datum throughout the Chalk Group of England and the North Sea).
Known throughout the Southern Province, within the Chilterns and northward into East Anglia in the Transitional Province.
Generally hard nodular chalks with thin flaser marls and significant proportions of shell debris in part. Base marked by the interbedded coloured marl and chalk succession characteristic of the Plenus Marls Member (a term applicable in both the Southern and Northern Provinces). The Melbourn Rock Member above the base can be distinguished by its lack of shell material.
In thicker sequences this formation is generally 25 to 35m thick. It thins rapidly into the `Transitional? Province of the North Downs, Berkshire Downs and the Chilterns (10 to 15m) and is almost absent in the southwest of Dorset and in Devon.
Conformable. Taken at the Gun Gardens Main Marl in the expanded sequences of the Southern Province and at the highest shell detrital bed in mapping terms.
Huntershill Cement Limestone
HCLS
Throughout the Scottish Central Coalfield.
Holwill's Conglomerate
HCO
Scottish Highlands Late Carboniferous To Permian Alkali Dyke Suite
HCPAD
Houghton Common Rock
HCR
Hennel Cleugh Sandstone
HCS
Local development in the Hennel Cleugh area of the White Lyne valley, Cumbria.
Even -grained arkosic sandstone, locally with shaly partings.
Harbour Cove Slate Formation
HCSL
Mid Frasnian to Fammenian.
At lower Merope Island the Harbour Cove Slate Formation rests conformably on slate and lava of the Trevose Slate Formation.
Trevone - Wadebridge - St Mabyn - St Tudy - St Teath - St Isaac Bay, north Cornwall.
Homogeneous green and grey-green slaty mudstones with thin beds of black, commonly pyritous mudstone and yellowish brown sideritic mudstone. The higher parts of the formation contain beds of purple mudstone, commonly with small-scale colour banding. Coarse-grained tuffs up to 100m thick occur locally. Beds of ferruginous and calcareous nodules becoming increasingly common towards the top of the formation.
Estimated to be 260m near Padstow, and 600m east of the Allen Valley Fault..
Faulted in the area of the Camel Estuary but mapped as a conformable boundary with the Polzeath Slate Formation in the St Minver synclinorium.
Hard Bed Band Coal (West And South Yorkshire)
HDBB
The Hard Bed Band Coal is thin but widespread and has been extensively mined at shallow depth, mainly because of the value of the associated fireclay. It is closely associated with the 36 Yard Coal that overlies it.
Hard Bed Coal (West And South Yorkshire)
HDBC
The Hard Bed or Ganister Coal was formerly of high economic vale as an engine or domestic coal, worked principally in the western part of the coalfield. The roof of the seam is a distinctive layer of crushed goniatites (Listeri Marine Band).
Hen-Dy-Capel Ironstone Member
HDCI
Overlies dark grey mudstone, with minor sandstone and siltstone, of the Llanengan Formation. Boundary is probably a disconformity or non-sequence.
Oolitic ironstone.
Overlain by mudstones and siltstones, with sandstones, of the Trygarn Formation, or undivided Nant Ffrancon Subgroup siltstones and fine-grained sandstones.
Hard Coal (Bristol Area)
HDCO
Haddo House Pluton
HDHS
Hafod Ifan Limestone Member
HDL
Bluish-grey biosparite largely comprising cystoid fragments.
2.3 metres. Lateral variations 0 - 2.5 metres.
Succeeded by siltstones and sporadic thin sandstones of the Hwylfa Formation.
Hard Mine Coal [Obsolete Code: Probably Replaced By Hard]
HDMC
Headsmuir Sandstone
HDMS
Haverford Mudstone Formation
HDMU
Harford Sands
HDS
Hudleston Formation
HDST
Hereford Till Member
HDTI
Head And Talus (Undifferentiated)
HDTS
Haywood Under Coal
HDU
Huddersfield White Rock
HDW
The Huddersfield White Rock is a medium- to coarse-grained, massive to flaggy, cross-bedded, micaceous sandstone.
18 to 45m
Headley Heath Member
HDY
Rests unconformably on bedrock (Chalk), occupying cavities.
Riegate and Dorking District.
Silty, sandy, gravelly clay.
Headon Formation
Heathen Coal (South Staffordshire)
HEAC
Head
HEAD
Polymict deposit: comprises gravel, sand and clay depending on upslope source and distance from source. Poorly sorted and poorly stratified deposits formed mostly by solifluction and/or hillwash and soil creep. Essentially comprises sand and gravel, locally with lenses of silt, clay or peat and organic material. In the Bristol area: red or brown silt and stony clay with cobbles of hard rock, eg Carboniferous limestone or sandstone. Argillaceous frost-shattered rock debris either in-situ or soliflucted. Soliflucted deposits have variable sand/clay content. [Generic description].
Head, 1
HEAD1
Polymict deposit: comprises gravel, sand and clay depending on upslope source and distance from source. Poorly sorted and poorly stratified deposits formed mostly by solifluction and/or hillwash and soil creep. Essentially comprises sand and gravel, locally with lenses of silt, clay or peat and organic material. In the Bristol area: red or brown silt and stony clay with cobbles of hard rock, eg Carboniferous limestone or sandstone. Argillaceous frost-shattered rock debris either in-situ or soliflucted. Soliflucted deposits have variable sand/clay content. Older than "Head" in the same map area. [Generic description].
Head, 2
HEAD2
Polymict deposit: comprises gravel, sand and clay depending on upslope source and distance from source. Poorly sorted and poorly stratified deposits formed mostly by solifluction and/or hillwash and soil creep. Essentially comprises sand and gravel, locally with lenses of silt, clay or peat and organic material. In the Bristol area: red or brown silt and stony clay with cobbles of hard rock, eg Carboniferous limestone or sandstone. Argillaceous frost-shattered rock debris either in-situ or soliflucted. Soliflucted deposits have variable sand/clay content. Older than "Head" and "Head 1" in the same map area. [Generic description].
Heath Member
HEATH
Interpreted as generally where fluvial deposits rest on bedrock, or older superficial deposits.
The River Leadon and its tributary valleys, including Glynch and Ell Brooks, Gloucestershire and Worcestershire.
Variable, up to 3 m thick.
The upper surface of the present day river terrace.
Head Brickearth
HEB
Varies from silt to clay, usually yellow-brown and massive. Poorly sorted and poorly stratified, formed mostly by solifluction and/or hillwash and soil creep. [Generic description].
Helen's Bay Formation
HEBA
Hebden Formation
HEBD
The base of the dark grey, shaly mudstone Hodsonites magistrorum Marine Band with eponymous fauna, where the formation overlies the mudstone-dominated Samlesbury Formation. Elsewhere, where this marine band has not been found, the base of the formation equates with the base of the Cayton Gill Shale in the south of the Askrigg Block (Wilson, 1977) and the base of the Mousegill Marine Beds in the Stainmore Trough (Owens and Burgess, 1965). In the south of the Central Pennine Basin the base is taken at the base of the first thick quartz-feldspathic sandstone of Kinderscoutian age, present above the Bowland Shale Formation.
North Lancashire and north Yorkshire, between Lancaster [SD 47 61] and Harrogate [SE 30 55], extending southward to north Derbyshire [SK18] and on the Askrigg Block and Stainmore Trough.
Fine- to very coarse-grained and pebbly, feldspathic sandstone interbedded with grey siltstone and mudstone, with subordinate marine black shales, thin coals and seatearths. The lower part of the formation is dominated by a turbiditic facies of thinly interbedded siltstone and fine-grained sandstone with laterally impersistent and locally thick, massive, coarse to very coarse-grained sandstones. The upper part of the formation is dominated by sheet-like laterally persistent, cross-bedded sandstones, interbedded with siltstone and mudstone; Coal and seatearth are largely restricted to the upper part of the formation. A distinctive feature of the lower part of the formation within the Askrigg Block succession is the presence of brachiopod-bearing sandstones, the Cayton Gill Shell Bed and Ure Shell Bed (Wilson and Thompson, 1965; Wilson, 1977).
Preston 335m, Bradford 275m and Derbyshire 600m thick; southern part of the Askrigg Block about 100m; Stainmore Trough 40m.
The sharp conformable base of the dark grey, shaly mudstone of the Bilinguites gracilis Marine Band with eponymous fauna, typically overlain by mudstone of the Marsden Formation.The marine band is underlain by sandstone including the Upper Kinderscout Grit of the Hebden Formation. Elsewhere, where the marine band is absent, in the Askrigg Block the base of the formation is taken at the base of the Wandley Gill Shale, described by Wilson and Thompson (1965) as 3 m of shale with a Lingula Band at the base, overlying a seatearth at the top of the Upper Brimham Grit. In the Stainmore Trough the base of the formation is taken at the base of a 6 m thick shale with Productus carbonarius, which overlies a 0.15m-thick shaly coal (Owens and Burgess, 1965).
Hebburn Fell Coal (Northumberland And Durham)
HEBF
Head Brickearth, Older
HEBO
Varies from silt to clay, usually yellow-brown and massive. Poorly sorted and poorly stratified, formed mostly by solifluction and/or hillwash and soil creep; older than "Head Brickearth" in the same map area. [Generic description].
Hebrides Formation
HEBR
Lies on major erosion surface, thought to be related to the Devensian Glacial Maximum.
Not drilled, but seismic interpretation suggests it is a boulder clay or diamicton.
Generally very thin, less than 15 metres, but very locally up to 50 metres.
Overlain by Barra Formation.
Head Brickearth, Younger
HEBY
Varies from silt to clay, usually yellow-brown and massive. Poorly sorted and poorly stratified, formed mostly by solifluction and/or hillwash and soil creep. Younger than "Head Brickearth" in the same map area. [Generic description].
Head Gravel [Not Recommended: Use Head]
HEG
Polymict deposit derived locally from older gravel-rich deposits. Formed mostly by periglacial solifluction/gelifluction but may include hillwash or soil creep (usually termed "colluvium"). [Generic description]. Essentially comprises gravel with subordinate sand and clay depending on upslope source and distance from source. [Description from East Anglian data]. Specifically a bedded limestone gravel in the Moreton-in-Marsh area. [Description from academic papers and BGS Memoirs].
Hoar Edge Grit Formation
HEGR
Brown sandstones and conglomerates.
0 to c.45m
Heysham Harbour Sandstone
HEH
Change from un-named siltstone in Millstone Grit Group to sandstone.
Heysham Harbour area, Lancashire.
Sandstone, greenish grey, medium- to coarse-grained, thinly laminated to medium-bedded; rootlet bed at top.
Rootlet bed/change to marine mudstones including Bilinguites gracilis Marine Band.
Headon Hill Formation
HEHI
Heimdal Sandstone Member
HEIS
Helmsdale Granite
HELM
Helmsdale Granite, Phase 1
HELM1
Helmsdale Granite, Phase 2
HELM2
Hemingbrough Glaciolacustrine Formation
HEM
Unconformable, resting directly on bedrock or underlain by basal glaciofluvial deposits.
Present at or near the surface in the Vale of York, from the Escrick Moraine in the north to Doncaster in the south, extending as a concealed unit beneath till deposits to the north of the Escrick Moraine beyond York to approximately 2km east of Knaresbrough.
Unfossiliferous laminated clays, silts and sands with rare dropstones (typically fine-grained pale coloured sandstone, grey limestone and dark mudstone).
Either the present land surface or overlain by later superficial deposits, commonly represented by sand deposits of the Breighton Sand Formation or its constituent members.
Hemlaw Vent And Plug
HEML
Hemsworth Member
HEMS
Hendre Shales Formation And Mydrim Shales Formation (Undifferentiated)
HEMY
Henfryn Formation
HEN
Disconformably overlies Ashgill Formation.
Pebbly mudstones, conglomerates and sandstones. Rapid lateral facies changes common.
15-80 metres.
Gradational but taken at base of first thick mudstone unit above the sandstones and conglomerates of the formation.
Hen Coal (Bristol Area)
HENC
Herma Ness Gneiss Member
HENG
Herma Ness Marble Member
HENM
Hens Sike Coal
HENS
Headon Beds And Osborne Beds (Undifferentiated)
HEOS
Helpet Edge Rock
HER
Rossendale anticline area.
Coarse-grained, massive sandstone [grit].
Herring Formation
HERN
Heron Group [Offshore]
HERO
Herring Coal (South Staffordshire)
HERR
Hermod Sandstone Member
HERS
Hewett Sandstone
HES
Hendre Shales Formation
HESH
Hemington Member
HETD
Upper Pleistocene to Holocene (MI Stage 2 to 1).
Unconformable, commonly channelled base, resting (generally) on Holme Pierrepont Sand and Gravel or (more locally) pre-Quaternary bedrock.
Extensively developed along much of the Trent, Derwent and Soar within Sheet 141 and 142; distribution elsewhere uncertain pending resurvey or revision, but probably present at least on adjoining sheets (?125, 126, 140, ?154, 156), where currently mapped mainly as alluvium.
Gravels, sands and loams that underlie the Hemington Terrace. Forms a terrace typically c.0.5 to 1m above the modern floodplain in the type area, and often distinguishable from the latter by the presence of mediaeval ridge and furrow. Generally comprises a lower unit of planar cross-bedded (laterally accreted, meandering river) gravel (up to 5m) and an upper unit of overbank silt (up to 2m); may also include organic muds in channels at the base. Gravel much as Holme Pierrepont Sand and Gravel, i.e. dominated by rounded pebbles of "Bunter" quartz/quartzite (c.80%) with subordinate subangular flint, etc., but typically less sandy and orange-brown (not pinkish).
0 to c.7m; typically c.5m.
Ground surface, or base of alluvium.
Hevda Phyllite Formation
HEVP
Helsby Sandstone Formation
HEY
Disconformity. Normally recognised by pebbly sandstones/conglomerates at base of Helsby Formation, overlying pebble-free sandstones of the Wilmslow Formation.
Sandstone-dominated, with sporadic conglomerates, particularly towards the base, and siltstones.
Transitional into base of the Tarporley Siltstone Formation, or where absent, the Bollin Mudstone Formation (argillaceous-dominated formations).
Hafotty Formation
Late Comley to early St David?s.
Sharp conformable contact on coarse-grained, thick bedded turbiditic sandstones of the Rhinog Formation.
Harlech Dome, North Wales.
Grey, thinly-bedded turbiditic sandstones and mudstones interbedded with manganiferous mudstones.
170 to 300m
Conformably overlain by coarse-grained turbiditic sandstones of the Barmouth Formation.
Hoes Farm Member
HFA
At base of a 0.85m-thick fine-grained sandstone above mudstone of the Atherfield Clay Formation.
South-west Weald.
Clayey fine-grained sand, sandstone, siltstone and mudstone.
Top of the bored and eroded surface of a 0.6m-thick indurated mudstone, beneath the fine- to medium-grained sandstones of the rest of the Hythe Formation.
Hill Of Fare Intrusion
HFAR
Higher Florida Coal (South Lancashire)
HFCO
Harford Member
HFD
Bradfordensis Zone to Concavum Zone.
Upward change or passage from peloidal and ooidal packstones and grainstones (Scottsquar Member) to lithologies as described in Lithological Description. Locally a non-sequence marked by a hardground (Buckman, J, 1901; Cave, R and Penn, I E, 1972).
Cotswold Hills, Gloucestershire: north of Chedworth, west of Bourton-on-the-Water and Moreton-in-Marsh (Barron, A J M, et al, 1997, fig.4).
Interbedded yellow silty fine-grained sand, cemented in parts ('Harford Sands'), grey and brown mudstone, shelly and sandy in parts ('Snowshill Clay' and 'Naunton Clay') and variably sandy and ooidal limestone ('Tilestone'). The succession is characterised by rapid lateral facies transitions and a mix of fully marine and quasi-non-marine facies.
Up to 14m. Type section (Harford Cutting); 3.05m+ (Parsons, C F, 1976). Thickens northward.
Sharp contact, generally a hardground, overlain by Aston Limestone Formation, or hardground overlain by Salperton Limestone Formation.
Hafod Coal (South Wales)
HFDC
Harrington Four Foot Coal (Cumbria)
HFF
Highfield Farm Limestones Bed
HFFL
Change up from grey mudstone with small phosphatic nodules and ammonites, and large limestone nodules of the undifferentiated Foston Member; at 13.11m depth in type section Fulbeck Airfield Borehole (SK95SW/17).
East Midlands: north Leicestershire to Linclonshire. Not recognised in the Scunthorpe Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into either part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or part of the mudstone-dominated Charmouth Mudstone Formation.
One to two bluish grey, weathering yellowish brown, silty, slightly sandy, shelly limestone beds 0.02 to 0.8m thick, separated by mudstone (0.35m thick in type section). Both limestone and mudstone contain pyritic shells and debris and the limestones include much amorphous pyrite. Fauna includes bivlaves (including common pectiniids and numerous Gryphaea), ammonites, belemnites, ostracods and echinoderms. Forms a weak feature.
0.1 to 1.5m; 0.52m in type section.
Change up into grey mudstone of the undifferentiated Foston Member; at 12.59m depth in type section Fulbeck Airfield Borehole (SK95SW/17).
Haig Fras Granite
HFGR
Hogg Fence Ironstones
HFI
Holt Farm Group
HFM
Drawn at the base of the calcareous sandstone shale facies where it rests conformably upon the lagoonal red beds of the Hopcroft Hall Group.
Steeple Aston, Oxfordshire.
A limestone shale facies comprising a dark grey marine shale sequence. A grit and sandstone facies comprising pale whitish grey fine-grained sandstone and a calcareous sandstone shale facies comprising alternating thinly bedded dark grey fine-grained silty sand with fragmental limestone.
65m approx.
Drawn at the unconformity between the limestone shale facies of the Holt Farm Group with the overlying basalt igneous intrusion.
Home Farm Member
HFMB
At base of the grey quartzose conglomerate or, where absent, the lower maroon carbonate-cemented sandstone. Sharpness of contact suggests a disconformity.
From Nuneaton town centre, extending northwest for 5.2km to Worthington Farm, Mancetter (SP 3533 9199 - SP 3192 9572).
Basal quartzose conglomerate and calcareous sandstone overlain by maroon sandy limestones with siltstone layers, hardground surfaces and stromatolites. Shelly faunas locally abundant.
1.5-2m in general area; 1.8m in type section.
Sharp hardground surface, on which rests basal grey, glauconitic sandstone of Woodlands Member; a thin mudstone drape occurs locally.
Hill Of Foudland Pelite Member
HFPM
Marked by the incoming of more homogenous pelitic slaty rocks within the host Macduff Formation grits, psammites and pelites.
The member crops out in a c.1km wide linear belt from the northern margin of Boganclogh Basic Intrusion (NJ3045) to a point c.2km north east of Hull of Tillymorgan at c.(NJ675355).
Pelite and semipelite, generally very fine-grained, dark grey to black, often with a prominant slaty cleavage, with rare lenses of fine-grained psammite.
Unknown, because of complications due to folding.
Marked by the incoming of gritty, more heterogeneous rocks of the host Macduff Formation.
Hendy Farm Shales
HFS
Hopeful Vein
HFV
Half Yard Coal (Cumbria)
HFYD
Hensingham Grit
Hagley Volcanic Formation [Duplicate Code: Use Hgy]
HGA
Haggis Grit And Conglomerate
HGC
Hensingham Group And Coal Measures Group (Undifferentiated)
HGCM
Hummocky (Moundy) Glacial Deposits, Devensian (Welsh Ice)
HGDDW
Hargate End Limestone
HGEL
Greenhow area, Yorkshire.
Hanged Man Bed
HGF
Coastal section at Port Mary.
Conglomerates and conglomeratic sandstones.
Hope Gap Flints
HGFL
Harlech Grits Group
HGG
Not exposed in core of Harlech Dome but proved resting on Bryn Teg Volcanic rocks in Bryn Teg borehole.
Exposed in the central area of the Harlech Dome.
Sandstones, mudstones and turbiditic siltstones, conglomerates and manganese ore beds. See component formations (in descending order: Gamlan, Barmouth, Hafotty, Rhinog, Llanbedr, Dolwen) for detailed account of lithologies.
Base of Clogau Formation (Mawddach Group).
Hoghill Gravel Bed
HGGR
Generally an unconformable boundary on bedrock. Locally resting on reddish brown, stony clayey diamiction that possibly correlates with the Chapelknowe Till Member of the Gretna Till Formation.
Very dense, clast-supported diamicton comprising angular clasts of greywacke siltstone in a matrix of pale yellowish brown, silty sand.
Sharp erosional or gradational, glacitectonic boundary with the overlying undivided Langholm Till Formation.
Hope Gap Hardgrounds
HGHG
Hall Gill Sandstone
HGI
Sharp upward change in a conformable succession from predominantly grey siltstone to sandstone - base of first sandstone bed above the Long Bridge Sandstone.
Sharp upward change in a conformable succession from sandstone to predominantly siltstone - top of last sandstone below the Park Wood Sandstone Member.
Halligill Limestone
HGL
Hogg Limestone
HGLS
Hope Gap Marls (One)
HGMA1
Hope Gap Marls (Two)
HGMA2
Haldon Gravel Formation
HGR
High Grit Sill
HGRIT
High Grains Sandstone
HGS
White Lyne catcment, Cumbria.
Alternating bands of sandstone andsandy, shalety mudstone, locally massive and current-bedded.
c.6 to c.12m
Holdgate Sandstone Member
HGSA
Hagley Shale Formation
HGSH
Highgate Coal (South Yorkshire)
HGTC
Hibernian Greensands Formation And Ulster White Limestone Formation (Undifferentiated)
HGUW
Haddiscoe Sand And Gravel Member
HGV
The gravels overlie and cut down into silt and clay-rich chalky tills of the Lowestoft Formation. They also overlie sands of the Happisburgh Formation.
Restricted to the southwestern flanks of the Yare and Waveney valleys and isolated deposits on the northern flanks of the Waveney valley near Somerleyton, Norfolk-Suffolk border.
The Haddiscoe Sand and Gravel Member comprises black, well-rounded fine to coarse flint gravel. Within the gravel large rotated blocks of sand are preserved, which are thought to have been in a frozen condition at the time of deposition.
Up to about 15m
The Haddicoe Sand and Gravel Member is generally at the surface, but is locally overlain in valleys by Head, and on the lowermost ground by silt and peat of the Breydon Formation.
Hagshaw Group
HGW
Lower Palaeozoic Inlier of the Hagshaw Hills (50k Sheets 23E, 23W and 15W).
Grey mudstone, siltstone and turbiditic greywacke.
Top of Ree Burn Formation (qv). (Base of the Parishholm Conglomerate).
Hagley Volcanic Formation
HGY
Overlies Aldress Shale Formation.
Volcaniclastic sandstones, breccias and wackes; mottled sandstones and shales.
Underlies Hagley Shale Formation.
Heathery Heugh Sandstone
East Lothian.
Haverigg Haws Anhydrite Member
HHA
Huntley Hill Formation
HHB
High Hazles And Brinsley Coal (Vale Of Belvoir)
HHBS
High Hazles Coal (South Yorkshire, Nottingham And Derby)
HHC
Hob's House Coral Band
HHCB
Heath Hayes Coal (South Staffordshire)
HHCO
Holyhead Formation
HHD
Drawn at base of first thick (up to 25 m) massive orthoquartzite conformably overlying the bedded turbiditic sandstones and mudstones of the South Stack Formation.
North Wales, Anglesey.
Massive, coarse orthoquartzites, locally pebbly, with a few thin beds of schist. Following work by Phillips (1991), the Holyhead Quartzite Formation has been re-defined to include the South Stack Moor Beds of Greenly (1919). The latter are a sequence of orthoquartzites, lithologically similar to the Holyhead Quartzite, but included by Greenly in his South Stack Series. The term Holyhead Quartzite is now an informal name reserved for a 50m thick quartzite unit within the core of the Rhoscolyn Anticline, and the name 'Holyhead Quartzite Formation' is obsolete. The preferred designation for the division is Holyhead Formation (Phillips 1991), which accords with Shackleton's (1969) definition.
150 - 200 m thick.
Conformably overlain by the Rhoscolyn Formation. The top of formation is drawn at top of highest thick orthoquartzite, underlying the interbedded turbiditic sandstone and mudstones of the Rhoscolyn Formation.
Humphrey Head Limestone Member
HHDL
Contact of dark grey even-bedded packstone with underlying palaeokarstic surface cut in pale grey grainstones of undivided Urswick Limestone Formation.
South Cumbria.
Limestone: dark grey, even-bedded packstone at base, passing up into thickly bedded grainstone, paler grey.
Palaeokarstic surface at top of paler grey grainstones; rapid change to dark limestone and mudstone of Gleaston Formation above.
Hells Hole Dyke
HHDY
Hill House Flags Member
HHF
Appears to overlie the greenish grey Quarry Ridge Shales (Upper Comley Sandstone Formation) conformably, but little is seen of the junction.
Church Stretton area, Comley, Shropshire.
Dark, flaggy sandstones, phosphatic and calcareous in places. This division appears to be partly erected on biostratigraphical grounds, and so little of it is exposed that its status has to be regarded as doubtful. Propose that it be retained as an informal term, with Member status regarded as provisional, until a fuller study of the divisions of the Upper Comley Sandstone Formation is undertaken.
1m exposed.
Conformably overlain by the Hill House Grits, also of the Upper Comley Sandstone Formation.
Harrock Hill Grit
HHG
Hunt Hill Intrusion
HHGR
Hill House Grits Member
HHGT
In places conformable on the Hill House Flags of the Comley area, but locally unconformable on the Lower Comley Sandstone Formation.
Coarse-grained, brown-weathering glauconitic quartzose sandstones with conglomerate beds.
11 to 12m
Conformably overlain by the Hill House Shales, also of the Upper Comley Sandstone Formation.
Househill Clayband Ironstones
HHI
Hillhouse Limestone
HHL
Hollybush Limestone
HHLS
Generally changes from a thin coal or seatrocks overlain by a marine mudstone of the Craigenglen Marine Band belonging to the Lawmuir Formation.
A pale to dark grey, argillaceous, shelly, bioclastic, limestone, interpreted to be of marine origin, generally with a massive lower portion and a thinly bedded upper sequence.
Up to 5.0 m thick in the Paisley and Glasgow districts, elsewhere represented by the Craigenglen Beds.
Generally succeeded by a marine mudstone of the Craigenglen Marine Band, belonging to Lawmuir Formation, which is overlain by sandy non-marine strata.
Hearson Hill Mudstone
HHM
Hell Hole Coal (South Lancashire)
HHOC
High Haume Tuff Formation
HHR
Probable non-sequence: at base of rhyolitic tuff, above calcareous silty mudstone of the Broughton Moor Formation or, where this is absent, the Kirkley Bank Formation.
Low Furness, Ordovician inlier, south Cumbria. Correlatives occur elsewhere within the Windermere Supergroup outcrop of Northern England.
Welded rhyolitic tuff.
Probably conformable, at top of rhyolitic tuff and base of overlying silty mudstone or calcareous mudstone of the Ashgill Formation.
Ham Hill Limestone Member
HHS
The base displays a change upward from sands or sandstones of undivided Bridport Sand Formation into bioclastic limestone.
The Yeovil-Crewkerne area of south Somerset, where it wedges out laterally into undifferentiated Bridport Sand Formation.
A brown, shelly, bioclastic limestone, parallel- bedded and cross-bedded, interpreted to have been deposited in a shallow marine tidal channel.
Up to 27 m thick.
The top is generally a non-sequence displaying a sharp change upward from bioclastic limestone to cream or grey shelly or ooidal limestone or calcareous mudstone of the Inferior Oolite, elsewhere it may be conformable, displaying a change up into sandy mudstone of undivided Bridport Sand Formation.
Hill House Shales Member
HHSH
St Davids.
Conformably overlie the Hill House Grits (Upper Comley Sandstone Formation).
Greenish grey shaly mudstones with beds of fine-grained glauconitic and calcareous sandstone.
Up to 100m
Unknown, but succeeded in the Comley area by the Shoot Rough Road Sandstone.
Harlow Hill Sandstone
HHST
Harrath Tuff Member
HHT
Base of rhyolitic tuff that rests on an erosion surface cut in dacitic lapilli-tuff of the Waberthwaite Formation; basaltic andesite intrusions may intervene.
Between Harrath (hill) and Corner Croft, north of The Hill, near Millom, Cumbria.
Rhyolitic tuff - densely welded, foliated, white-weathered.
60 to c.250m
Top of rhyolitic tuff - probably an erosion surface at contact with overlying dacitic lapilli-tuff of the Waberthwaite Formation.
Holt Heath Member
HHTD
Glaciofluvial Sheet Deposit.
Gravel overlain by sand; a high proportion of the gravel includes exotic clasts from Scotland, Lake District and Malvern Hills; third terrace of the River Severn, also known as the 'Main Terrace'; part of the Severn Valley Formation. [Generic description: academic papers and BGS Memoirs].
Though previously considered a river terrace deposit of the Severn and its tributaries in the West Midlands, Maddy (1997) has defined this as a Late Wolstonian glaciofluvial outwash deposit.
Hagley Volcanic Formation, Hagley Shale Formation And Whittery Volcanic Formation (Undifferentiated)
HHWY
Ben Hiant Breccia Member
HIAN
Hill Of Blairs Pluton
HIBL
High Cross Member
HIC
Higher Comberoy Formation
HICO
Restricted to small fault-bounded outcrop (0.6km squared) between Brook Hill (ST 002 006)in the west, and Higher Comberoy Farm (ST 016 005) in the east, near Clyst St Lawrence, Devon.
Lower unit of reddish-brown silt and clayey, very fine-grained sand; middle unit of reddish-brown fine-grained breccia; upper unit of reddish-brown clayey, very fine-grained sand.
Lower unit at least 30m. Middle unit 7-16m. Upper unit at least 9m. (At least 55m in total.)
Hirundo Formation
HIDO
Hidra Formation
HIDR
Hill Farm Formation
HIFA
High Coal (Bristol Area)
HIGH
Hibaldstow Limestone
HIL
Lower Bajocian, Laeviuscula [? to Sauzei] Zone
More or less disconformable contact with dominantly micritic low-energy limestone, or mudstone of the Lower Lincolnshire Limestone Member (Kirton Cementstone Beds), overlain by ooidal and bioclastic grainstones.
BGS 1:50 000 sheets 80 and 89 or (for Hibaldstow Beds) North Lincolnshire, from Lincoln to the Humber.
Limestone, high-energy ooidal and shell bioclastic grainstones, with "non-oolitic limestone containing spar-filled shells" (probably secondarily recrystalized and micritized limestone) at base.
This entry is included only to define the unit thus called on BGS sheets 80 and 89. It should not be perpetuated in any formal lithostratigraphical review of the Lincolnshire Limestone. It is for information only, describing a superfluous term, and it is not recommended for future use other than in a local, informal sense. The unit is defined as per the usage of Gaunt et al. (1992), which corresponds to the current (MGS's) concept of the Upper Lincolnshire Limestone, though not necessarily those of previous authors, whose usage referred to everything above the Kirton Shale. As the term is to be superseded there seems little point in defining stratotypes, but the Hibaldstow Airfield No.1 Borehole is suggested as a primary reference section. A few metres are exposed at the southern end of Greetwell Quarry, but it is unclear where to draw the base of the Upper Lincolnshire Limestone. No better exposed quarry sections are currently known. See also comments on the Upper Lincolnshire Limestone. [Condensed from notes by M G Sumbler, 25/09/2005.]
c.6 to 13m
Disconformable, commonly markedly eroded and karstified contact between ooidal and bioclastic grainstones and non-calcareous, non-marine sandstone, siltstone and mudstone of the overlying Rutland Formation (Thorncroft Sand Member).
Hildesay Granite
HILDY
Highfield Limestone
HILS
High Main Coal (Warwickshire)
HIMA
Hirnant Limestone Member
HIR
Hirta Cone-Sheet-Swarm
HIRTA
Hind Sandstone
HIS
Plane above the Tumulites pseudobilinguis Marine Band in Bowland Shale Formation where sandstone of the Hind Sandstone rests sharply upon dark grey mudstone of the Bowland Shale Formation.
Not identified outside Bowland Fells area, except at Dinkley where exposed in River Ribble section.
Sandstone, medium- to coarse-grained in thick to massive sharp-based beds with shaly partings - turbidite facies.
7m at Hind Clough (probable maximum thickness), 1.7 at Blue Scar, 1.27m at the Trough of Bowland.
Plane below the Cravenoceras malhamense Marine Band where sequence changes gradationally from being predominantly sandstone to being predominantly mudstone of the Bowland Shale Formation.
Hillmorton Sand
HISA
Sand with subordinate gravel. [Generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
High Wood Marine Beds
HIWD
Hillswick Group
HIWK
These are Moine-like rocks west of the Walls Boundary Fault, separated from the Sand Voe Group by the Northmaven Complex. They were not named separately by Mykura (1976) or Phemister (1978), but were named by Robinson (1983).
Hildasay Sandstone Member
HIYS
Vallites Henkei Marine Band
HKMB
Hanging Knotts Tuff Member
HKT
Hackley Limestone
HKYL
Hillend Algal Band
HLAB
Highlands Plugs And Vents
HLAND
Hollybush Coal (Glasgow - Greenock)
HLBC
Holcombe Brook Grit
HLBG
Halberton Breccia Formation
HLBR
Hollybush Sandstone
HLBS
Local name in the Paisley district.
c.13 TO 15m
Holbrook Coal
HLC
Holywell Nodular Chalk Formation, New Pit Chalk Formation, Lewes Nodular Chalk Formation, Seaford Chalk Formation, Newhaven Chalk Formation And Culver Chalk Formation (Undifferentiated)
HLCCK
Helmeth Grit Member
HLG
Uncertain. Considered by Greig et al (1968) to rest unconformably on the Ragleth Tuff Formation, but Cobbold and Whittard (1935) and Pauley (1991) suggested a conformable contact based on lithological similarities with the underlying rocks. The base is marked by a sharp transition from lithic tuffs and interbedded purple mudstones of the Ragleth Tuff Formation, the boundary being taken at the base of the first massive sandstone bed.
The Welsh Borderlands in Shropshire, and the Church Stretton area.
Massive, coarse-grained, buff, brown or blue-grey tuffaceous sandstones in at least four beds, interbedded with greenish grey and purple mudstones.
Uncertain. Pauley (1991) considered the possibility of an unconformity with the overlying Stretton Shale Formation at this level on the basis of variations in dip between the two units. Accordingly he placed the Helmeth Grit as a Member in the upper part of the Ragleth Tuff Formation. The boundary is therefore taken at the top of the highest coarse-grained sandstone bed beneath the pale greenish grey mudstones of the Stretton Shale Formation.
Heales Lock Gravel
HLGR
Hallaig Sandstone Member
HLGS
Unseen.
Skye/Sea of the Hebrides Basin.
The Hallaig Sandstone Member is composed of moderately well-cemented medium to fine sand. Three cycles of grading were interpreted; from bioturbated sandstones with thin siltstones at the base to cross-stratified sandstones at the top of the unit. Hasselbo et al (1988, 1999) and Hesselbo and Coe (2000) include this Member within their redefined Pabay Shale Formation, which has not been accepted by the British Geological Survey. It was originally the highest sandstone within the Broadford Beds and hence is now the highest Member within the Ardnish Formation, as defined by Morton (1999).
Unconformably overlain (locally) by Pabay Shale Formation - see Morton, 1999, and reply by Hesselbo et al.
Holehouse Gill Mudstone Formation
HLH
Base of mudstones, unconformably overlying bedded tuffs of the Duddon Hall Formation.
Northwest side of Dudden Valley from Bigert Mire (SD 179 927) to The Crook (SD 207 949), Cumbria.
Mudstone, dark grey, with interbeds of sandstone and conglomerate.
0 to 450m.
Overlain by various formations, including Ulpha Formation (andesite), Wallowbarrow Formation (andesitic lapilli-tuff) and Dunnerdale Formation (volcaniclastic sandstone).
Lower Holywell Beds
HLHO
Holwell Limestone
HLL
Holly Lane Coal (North Staffordshire)
HLLC
Holey Limestone
HLM
Holbrook Marine Band
HLMB
Holywell Nodular Chalk Formation, New Pit Chalk Formation, Lewes Nodular Chalk Formation, Seaford Chalk Formation And Newhaven Chalk Formation (Undifferentiated)
HLNCK
Holywell Nodular Chalk, New Pit Chalk, Lewes Nodular Chalk , Seaford Chalk, Newhaven Chalk, Culver Chalk And Portsdown Chalk Formations (Undifferentiated)
HLPCK
Hill Peat
HLPT
Peat; of upland areas. [Generic description: 'TMOS' Procedures].
Hollin Rock
HLR
The type section displays a sharp base of grey sandstone overlying dark mudstones with ironstones, about 4.44m above top of Massy (Drowsell) Coal (J500 of British Coal). Elsewhere the base channels down in places to below the Hollin Coal (H800 of British Coal).
The Flintshire Coalfield (SJ 27 68), north-east Wales.
Fine to coarse or pebbly, commonly feldspathic, cross laminated and channel bedded sandstone. The base often channels into the beds below. The sandstone is locally interbedded with thin mudstones. The Hollin Rock Member represeents a widespread deltic sandstone body, or series of bodies, within the Flintshire Coalfield, and may record a period of distributary channel and mouth bar advances at a time of lowered sea level.
Up to 75 thick.
The type section shows a sharp contact between hard, white sandstone and overlying seat earth (fireclay), about 3 m below base of the Etruria Formation.
Hayle Sandstones
HLS
Holers Coal (South Staffordshire)
HLSC
Holywell Nodular Chalk Formation, New Pit Chalk Formation, Lewes Nodular Chalk Formation And Seaford Chalk Formation (Undifferentiated)
HLSCK
Helvellyn Tuff Formation
HLV
Base of lapilli-tuff, or locally that of a very thin basal tuff layer, rests with slight unconformity on sandstone of the Esk Pike Formation.
Helvellyn, Fairfield, Striding Edge eastwards to Glenridding, northeastern Lake District, Cumbria.
Dacitic lapilli-tuff, with eutaxitic foliation at the base and with intercalations of tuff.
400m maximum known.
Highest lapilli-tuff or (locally) tuff is overlain unconformably by volcaniclastic rocks of the Deepdale Sandstone Formation.
Hollybush Coal (Bristol Area)
HLYB
Hamstead Beds
Houston Marls
HMA
Hampen Formation
HMB
Limestone and marl (as in Lithological Description), resting sharply on cross-bedded coarse-grained ooidal grainstone of the Taynton Limestone Formation or on mudstone/sandy limestone of the Fuller's Earth Formation.
c.Frome Valley, west of Cirencester (where passes it into the upper part of "Througham Tilestones"/Dodington Ash Rock) eastwards to Oxford-Brackley area (where it passes into the Rutland Formation).
Limestones with subordinate interbedded marls; limestones characteristically grey to brown, thinly bedded, fine- to very fine-grained, well-sorted, ooidal grainstone to packstone, commonly slightly sandy or silty, with small-scale cross-bedding.
c.4-11m; 8.96m at type locality.
More or less sharp boundary with purer, off-white or yellowish peloidal packstone, wackestone or grainstone of the White Limestone Formation.
Humber Group
HMBG
Hurlford Main Coal (North Ayrshire)
HMC
High Main Coal (Leicestershire)
HMCL
Haigh Moor Coal (West Yorkshire)
HMCO
It is not clear whether there is one 'Haigh Moor Coal'. the Haigh Moor group is roughly equivalent to the Waterloo Coals of Nottinghamshire.
High Moor Sandstone And Doubler Stones Sandstone (Undifferentiated)
HMDS
Holm Farm Limestones Bed
HMFL
Change up from grey, calcareous mudstone with rare thin limestones of undifferentiated Barnby Member; at 87.35m depth in type section Fulbeck Airfield Borehole (SK95SW/17).
East Midlands: north Leicestershire to Linclonshire. Not recognised in north Lincolnshire, or south Leicestershire, where it passes south into part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation (Ambrose, 2001).
Group of three limestone units separated by mudstone beds. Each unit may comprise up to four limestone beds, the lowest (Bed X of Brandon et al, 1990) is shelly and rubbly and includes bivalves and ammonites, the uppermost is bioclastic and pyritic packstone/grainstone, shelly, pale grey, weathering pale brown, with abundant coarse sand-grade shell debris, and a fauna including serpulids, gastropods, bivalves and echinoid spines, and also the trace fossil Kulindrichnus. The uppermost limestone forms a strong positive feature.
4.5 to 5m; 4.59m in type section.
Change up into grey, calcareous mudstone of undifferentiated Granby Member; at 82.76m depth in type section Fulbeck Airfield Borehole (SK95SW/17).
Hell's Mouth Formation
HMG
Base not exposed; possibly rests unconformably on Neoproterozoic rocks.
Laterally-persistent coarse- to medium-grained green sandstones, interbedded with green and grey siltstones.
>190m
Conformably overlain by manganiferous siltstones of the Trwyn y Fulfran Formation.
Hummocky (Moundy) Glacial Deposits
HMGD
Lithologically diverse and complex glacial deposits that have characteristic moundy topographic form. Composed of rock debris, clayey till and poorly- to well-stratified sand and gravel. [Generic description: 'TMOS' Procedures].
Hummocky (Moundy) Glacial Deposits, Devensian
HMGDD
Hamstead Marshall Gravel
HMGR
Holmehead Limestone
HMH
Middle Holywell Beds
HMHO
Lower High Main Coal (Leicestershire)
HML
Hairmyres Limestone
HMLS
Ham Mudstone
HMM
Burrington Combe area, western Mendip Hills.
High Main Marine Band [Local Name: See Mtmb]
HMMB
Local name applied to the Maltby Marine Band (National Standard Name) in the coalfield areas of Northumberland and Durham.
High Main Marine Band Coal (Northumberland)
HMMC
High Main + Metal Coal (Northumberland)
HMME
High Main Coal (Northumberland And Durham)
HMN
High Main Coal (Nottingham And Derby)
HMNC
High Main Post Member
HMNP
Hampole Beds
HMP
Generally 0 to 2m, locally reaching 4m at Cadeby Quarry.
Haigh Moor Rock
HMR
West and south Yorkshire, especially Wakefield/Pontefract area and towards Barnsley.
Commonly fine-grained and false bedded sandstone, locally flaggy, with impersistent bands of sandy mudstone.
High Mains Formation
HMS
Conformably overlies the South Threave Formation of the DrummuckSubgroup.
Craighead Inlier, Girvan area, southwest Scotland.
Fine- to medium-grained grey sandstone.
30m, thinning to zero
Unconformably overlain by the Mulloch Hill Conglomerate (Silurian).
High Moor Sandstone
HMSA
Hopeman Sandstone Formation
HMSF
The unconformity with the Devonian Upper Old Red Sandstone.
Predominantly yellowish aeolian sandstones, some deposited by sheet floods; fine- to coarse-grained, with well rounded grains. Basal beds are pebbly. Large-scale, crossbedded or laminated; rarely contorted. Some beds friable, others hard and siliceous. Contains fossil reptiles.
61m (Clarkly Hill No. 1 Borehole [NJ 1270 6833]) to 70m +
The top of the formation is taken at the base of the waterlain sandstones of the Burghead Sandstone Formation.
How Man Till Member
HMTI
Generally planar or undulating contact on to older units including the top of the Gutterfoot Sand Member of the Gosforth Glacigenic Formation, the top of the Townhead Boulder Gravel Member, and the top of the Ravenglass Till Member of the Seascale Glacigenic Formation.
1:50k Sheets 28 Whitehaven and 37 Gosforth. St Bees to Seascale area, western Cumbria.
Stiff, reddish brown, matrix-supported sandy clay diamicton, with well dispersed angular to subrounded clasts up to boulder size. The clasts are mainly of red sandstone, Skiddaw Group slate, Borrowdale Volcanic Group rocks, Coal Measure sandstone, coal, limestone, ironstone, dolomite, grey ?Criffel granite, granophyre, granodiorite, quartzite, vein quartz, andesite and shell fragments.
To c.1.7m
Erosional base of the Peel Place Sand and Gravel Member of the Gosforth Glacigenic Formation or overlain by Holocene deposits such as blown sand or peat.
Hamilton Sandstone
HMTS
Henllan Ash Member
HNA
Base contrasts with flaggy laminated siltstones and sandstones below.
Light grey feldspathic sandstones. Rare large-scale cross-bedding. Locally muddy and strongly bioturbated. Rich shelly fauna.
190 metres. Lateral variations 20 - 190 metres.
Top marked by incoming of mudstone.
Harden Beds
HNB
Huncliffe Rock
HNC
Holywell Nodular Chalk Formation And New Pit Chalk Formation (Undifferentiated)
HNCK
Honeycombed Sandstone Member
HNCS
Taken at sharp junction of the calcareous sandstone of the Member and the underlying dark bituminous skeletal/peloidal grainstone/packstone/wackestone of the Dowlais Limestone Formation.
Northwest crop of the South Wales Coalfield [SN 94 14].
Calcareous, locally conglomeratic, sandstone, with distinctive honeycomb weathering, locally in two tongues, separated by pale grey oolitic grainstone. Deposited as a transgressive shoreface sand/ooidal limestone.
4 to 12m
Taken at the top of the upper tongue of calcareous sandstone of the Member, above which the pale grey ooid grainstones of the Penderyn Oolite Member enter.
Horton Neptunian Dyke
HND
Railway cutting, Horton in Ribblesdale, Yorkshire.
Late Ordovician (?Cautleyan) sediment infilling a fissure or fissures within early Ordovician (or ?older) rocks of the Ingleton Group.
Horton Formation
HNF
Taken at the sharp comformable base of a thick sequence of sandy siltstone overlying thickly bedded calcareous siltstone of the Arcow Formation.
Medium to dark grey laminated, micaceous and partly calcareous sandy siltstone containing carbonaceous debris. Near the base calcareous nodules occur in layers. Includes unit of turbiditic sandstone referred to as the Studfold Sandstone Member.
Up to 710m
Defined by the base of the overlying Neals Ing Formation.
Hanging Stone Tuff
HNG
Taken at the base of bedded silicic tuff overlying eutaxitic lapilli-tuff of the Long Top Tuff Member, and lying between 25 and 75m above the base of the member or 5-15m above the top of the Oxendale Tuff where this is present
Cumbria, Thirlmere to Scafell and Langdale in the central Lake District
Cream and brown-weathered, bedded, fine-grained tuff with accretionary lapilli that forms a widespread distinctive marker unit at the top of the Long Top Tuff Member.
Up to 3m, but is typically less than 1m
Defined by the overlying eutaxitic lapilli-tuff of the Crinkle Tuff Member
Hathern Gravel
HNGR
Coarse gravel and angular cobbles; clasts composed of Carboniferous Limestone chert and limestone. [Generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
Honley Marine Band
HNMB
Henshaw Siltstones
HNS
Horden Till Formation
HNTI
Generally planar, unconformable, subhorizontal boundary with underlying gravel of the Peterlee Sand and Gravel Formation, where the contacts may be sharp or gradational with glacitectonic intercalation. The till locally rests directly on bedrock.
Typically very stiff, dark brown or purplish brown, stony silty sandy diamicton containing clasts mainly of limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone; mostly Upper Division), Carboniferous lithologies, purple porphyry from the Cheviots and shell fragments. The till is invariably weathered reddish brown at the top, and locally throughout.
To 12.2m
Commonly a gradational contact with overlying brown pebbly clay with vertical prismatic jointing (Prismatic Clay Member). Lateral interdigitating boundary with the Tyne-Wear Glaciolacustrine Formation to the west.
Hermaness Ultramafic Zone
HNUZ
Hopton Agglomerate
HOAG
Asbian or Brigantian
Intrusive igneous body with transgressive contacts with limestones of the Bee Low Limestone Formation to the north and east.
Volcanic neck, at Hopton, near Wirksworth, Derbyshire.
Volcanic breccia composed of small lapilli and subangular blocks of dolerite and basalt to 0.6m across.
Overlain unconformably by mudstones of the Millstone Grit Group, whoch crop out to the south and west of the volcanic neck.
Hollowbrook Member
HOB
Conformable on rocks of the Lynton Formation (q.v.).
North Devon - west Somerset
Mainly sandstone, grey, quartzitic, clean, parallel-laminated, with inter-bedded cross-laminated units and some mudstone interbeds. Ladder ripples and reactivation surfaces are present. Local channels filled with flaser and lenticular beds. Trace fossil Arenicolites and Tentaculitids.
70m (Tunbridge, 1978)
Overlain ?conformably by rocks of the Trentishoe Member (q.v.).
Howe Of Byth Gravel Formation
HOBGR
Devensian (?MIS 3).
In the most recent exposures in Howe of Byth Quarry the lower boundary of te unit was a sharp, locally channelled, unconformity on weathered Devonian red sandstone.
Buchan, northeast Scotland. The formation is currently only known from the vicinity of the Howe of Byth Quarry on Sheet 97 (Fraserburgh). The unit might be of regional significance and present locally across northeast Scotland.
Gravel with subsidiary beds of diamicton and sand. Typically brown/dark brown and olive grey. Dominantly clast supported with a medium to coarse quartzose sand matrix. Clasts are subrounded and rounded and composed mainly of quartzite (probably reworked from Devonian conglomerates) with sparse metasedimentary rock, granites and grey/black ?Mesozoic mudstones. Red sandstone clasts are present in the lowest part of the formation where it directly overlies Devonian red sandstone bedrock. The gravels are crudely horizontally bedded and interbeds of sand show both horizontal stratification and local planar cross bedding. Both gravels and sands display locally strong staining and cementation by Fe and Mn. Palaeocurrent measurements from cross beds and imbricate clasts is towards the south. Common medium beds of yellowish brown gravelly silty sandy diamicton are present and are interpreted as debris flow deposits. The upper 1 to 2m of the deposit display crude involutions and erected clast fabric indicating disruption by periglacial soil processes. Interpreted as glaciofluvial outwash and debris flow deposits.
To 13m
The upper boundary of the formation is a sharp, planar, subhorizontal, unconformity overlain by reddish brown diamicton of the Byth Till Formation.
Hopes Coal
HOC
Hole Coal (Bristol Area)
HOCO
Hodge Coal (Northumberland And Durham)
HODG
Horrace Formation
HOF
Incoming of laminated silty mudstone above Harlock Formation (sandstone).
Laminated silty mudstone. Underlying and overlying units are greywacke sandstones.
Base of overlying formation/subgroup turbidite sandstones.
Hosie Fireclay
HOFC
Holt Heath Sand And Gravel
HOHE
Where sand/gravel overlies bedrock or glacial deposits.
River Severn valley from Bridgnorth to Woolaston.
Gravel, sand and pebbly sand, variably cross-bedded to parallel laminated; clasts mostly Triassic quartzites with flints; Lake District, Scottish and Malvernian rocks.
Up to 10m
The present dry terrace flat.
Holme High Limestone Group
HOHI
The base of grey and grey-brown dolostone of the Holme High Limestone Group, resting unconformably upon Lower Palaeozoic green slate strata in the type locality.
Not seen at outcrop, but proved in the subsurface over the Holme High, a W-E structure extending from Heywood [SD 80 10] to Holmfirth [SE 20 10], bounded to the north by the Holme and Heywood faults, and to the south by the Alport Basin.
A pale to dark grey, typically darker towards the base, micritic to crystalline limestone, with subordinate partings and thin beds of dark grey shale, and locally abundant chert , crinoid and brachiopod debris. A thin vesicular brecciated basalt is present near the base of the type locality, and dolostone or dolomitic limestone is predominant in the basal 120m above this.
Seen as 613 m in the type locality, with an estimated maximum of about 1250 m.
The sharply conformable base of overlying dark grey, carbonaceous, fissile mudstone of the Bowland Shale Formation, above the pale grey limestone of the Holme High Limestone Group.
Holcombe Brook Grit And Huddersfield White Rock (Undifferentiated)
HOHU
Hookes Coal (Milford, South Wales)
HOKC
Hollington Formation
HOL
Drawn where well-cemented pale coloured sandstones overlie red, softer, finer grained sandstones of the Hawksmoor Formation; erosion surface commonly present.
Needwood Basin; Staffs/Leics/Derbys.
Sandstone, fine- to coarse-grained, part pebbly, with subordinate siltstone/mudstone; commonly in upward-fining units.
Transitional to Denstone Formation, where sandstone-dominated sequence gives way to finer-grained lithologies.
Hollin Coal (North Wales)
HOLC
Holderness Formation
HOLD
Hosie Limestones
HOLS
HOLS is a composite or generalised description of one or more of the Hosie Limestones, used where the indvidual limestones cannot be recognised. It may be comprised of one or more of TOHO, SHLS, MAHO, MIHO, FHLS or FOHO.
Holywood Group
HOLY
Hodder Mudstone Formation
HOM
The contact with the underlying Clitheroe Limestone Formation is unconformable and shows considerable regional overstep. Many sections show a sharp lithological change from pale grey wackestone limestone of the Clitheroe Limestone Formation to grey mudstone or, locally, limestone conglomerate.
Craven Basin, Lancaster [SD 46] to Skipton [SD 95].
Predominantly grey to dark grey mudstone, with subordinate and variable detrital limestone, siltstone and sandstone. Mudmound reef (Waulsortian) limestones, limestone boulder conglomerates and breccias locally, near the base. Soft sediment deformation, slumps, debris flows and gravity slides are widespread.
Taken where grey mudstone with subordinate limestone, siltstone and sandstone, passes up into the pale olive and blue-grey to cream-coloured porcellanous mottled wackestone, of the Hodderense Limestone Formation.
Holywell Marls (One)
HOMA1
Holywell Marls (Two)
HOMA2
Holywell Marls (Three)
HOMA3
Holywell Marls (Four)
HOMA4
Holywell Marls (Five)
HOMA5
Holywell Marls (Six)
HOMA6
Scottish Highland Ordovician Minor Intrusion Suite
HOMI
Hopetoun Member
HON
Drawn at the base of the Burdiehouse Limestone (Mitchell and Mykura, 1962 p67), resting on strata of the Calders Member. This distinctive limestone is a lacustrine deposit, commonly 6-9m thick, containing abundant fossilised ostracod, plant and fish remains.
West Lothian and part of Midlothian.
A sequence of black to grey mudstones, grey siltstones, white, grey and pink sandstones and white to pale-greenish grey calcareous mudstones ("marl") with thin beds of black to grey oil-shales, coals (Hurlet, Two Foot and Houston seams), grey to white, pure to argillaceous limestones and dolostones that comprise the upper part of the West Lothian Oil-Shale Formation. Some lapilli-tuff beds and thin coal seams are present. The strata are not generally disposed in readily recognizable sedimentary cycles and almost all are of lacustrine and fluvial origins. The member includes the Camps, Under Dunnet, Dunnet, Broxburn, Fells, Grey, Mungle, Raeburn and Fraser shales (oil-shales), and the Dunnet and Binny sandstones that were worked in the past for dimension stone. The limited number of thin marine bands include the Dunnet, Raeburn and Fraser Shell Beds (fossiliferous mudstone beds with a marine fauna) and the Under or Gilmerton Bone Bed Limestone. Lacustrine limestones are present, such as the Barracks Limestone with the regionally important and thick Burdiehouse Limestone at the base of the member. The Bathgate Hills Volcanic Formation (Bathgate Group) basaltic lavas and tuffs are interbedded near the top in the West Lothian and Falkirk areas.
Average thickness is approximately 830m in the Lothians (Cameron and McAdam, 1978, Fig.2).
The top of this generally non-cyclic unit is defined at the base of the Hurlet Limestone, this marine limestone forming the base of the marine-dominated cyclic successions of the overlying Lower Limestone Formation (Clackmannan Group). The Hurlet Coal is the topmost named bed in the member in West Lothian.
Hope Group
HOP
At top of Mytton Flag Formation (Shelve Group).
Dominant grey shaly mudstones and siltstones with two distinctive volcanic formations.
<2000m - variable.
At base of Weston Flags Formation (Middleton Group).
Horn Coal
HOR
Horda Formation
HORD
Horseshoe Vent
HORSH
Hollybush Sandstone Formation
HOS
Conformable on Malvern Quartzite.
South Malvern Hills.
Dark green, flaggy, micaceous sandstone with abundant chlorite and glauconite (Groom, 1902; Worssam and others, 1989).
Conformable junction with White-Leaved Oak Shale.
Hope Shale Formation
HOSH
Holborn Sandstone Member
HOSM
Hosie Sandstone
HOSS
Locally developed, mainly in the East Kilbride district.
Dominantly yellow sandstone.
Highly variable, but locally reaches c.30m.
Holkham Till Member
HOTI
The Holkham Till Member is unconformably on older deposits. Locally it overlies gravel of an Ipswichian raised beach in the Hunstanton and Morston areas. Elsewhere it overlies a variety of Lower to Upper Cretaceous formations. There is an abrupt and very obvious lithological change across the boundary from the underlying arenaceous material or chalk, to the clay-silt dominated lithology of the till.
Along much of the northern coastal area of Norfolk from west of Hunstanton to Morston.
The Holkham Till Member is a dull reddish brown sandy clayey diamicton, which contains chalk and flint clasts together with Carboniferous and Triassic material and a variety of igneous and metamorphic rocks.
The Holkham Till Member is at surface or is locally overlain unconformably by sand and gravel of the Ringstead Sand and Gravel Member, by Head, and silt and clay of the British Coastal Deposits Group. The junction with the overlying deposits is unconformable and because of the change in lithology is easily discernable.
Houston Coal (West Lothian)
HOU
Housetter Granite
HOUG
Houston Oil Shale
HOUO
Hoy Volcanic Member
HOV
Holme Wood Coal
HOWCO
Holme Wood Marine Band
HOWMB
Hope Shale Formation And Weston Flags Formation (Undifferentiated)
HOWN
Holsworthy Group
HOWY
Due to thrusting along the south crop of the group, the base is seen only between Okehampton (SX 59 94) and the Teign Valley (SX 84 84), east Dartmoor, Devon. The base is gradational and taken at the incoming of dark grey mudstones with abundant thin- to medium-bedded turbidite sandstones of the Holsworthy Group (Crackington Formation) above the dark grey mudstones with sparse scattered thin turbidite sandstones of the underlying Teign Valley Group (Dowhills Mudstone Formation). Between the Bideford area (SS 45 27) north Devon and the Westleigh area (ST 06 17), west Somerset, the base is taken at a similar level. However, in the Bideford area, the base needs further investigation as the Limekiln Beds (Prentice 1960) included in the Crackington Formation by Edmonds et al. (1979) may be part of the Dowhills Mudstone Formation. South of the main crop, the Group occurs in tectonic slices between Bodmin and Dartmoor and no base is seen. The base here is thought to be unconformable on the underlying Teign Valley Group.
Culm Synclinorium, between the north Cornwall (SX 15 97) and north Devon (SS 45 27) coast and eastwards to Exeter (SS 93 92) and Tiverton (SS 95 13) in east Devon. To the south tectonic slices occur in the area south of Launceston (SX 32 77) between Bodmin Moor and Dartmoor.
Grey mudstones with abundant thin- to thick-bedded sandstones, subordinate siltstones and a few conglomerate beds. Mudstones and subordinate thin- to medium-bedded sandstones dominate the lower part and medium- to thick-bedded sandstones with subordinate mudstones and siltstones dominate the upper part. Scattered slumped units occur in the upper part.
The upper boundary is taken at an angular unconformity, where breccias of the Exeter Group rests upon sandstone and subordinate mudstone at the Bude Formation.
Hoy Sandstone Formation
HOY
Drawn at the conformable upward passage from the Hoy Volcanics Formation or at the base of sandstones with subordinate bands of marl, where they rest unconformably on the Lower Eday Sandstone Formation.
Hoy, Orkney.
Red, pink, and yellow sandstones with subordinate bands of marl. Many exhibit current bedding and trace fossils.
The formation is not overlain.
Hopedale Limestone Formation
Upward change from dark cherty micritic limestone of the underlying Milldale Limestone Formation, to grey, coarsely bioclastic or conglomeratic limestones present at the base of the Hopedale Limestone Formation.
Southern part of the Peak District, Derbyshire and Staffordshire.
A heterogeneous succession of typically mid grey, locally dark grey, fine- to coarse-grained calcarenites, with limestone clasts and coarse crinoid debris common at the base of the Formation, and in the vicinity of knoll-reefs.
60m in Hopedale [SK 129 549], to 300m around Gag Lane, to the northnortheast of Thorpe [SK 16 51].
In the upper part, seen as mostly calcarenites, with a sharp change to darker mudstones at the base of the Widmerpool Formation.
Hartlepool Anhydrite Formation
HPA
Sharp contact with underlying Ford Formation dolostone.
Western parts of the Zechstein Sea basin; in northeastern England on the basinward (east) side of the Ford Formation reef-edge.
Anhydrite rock; translucent blue-grey and grey with a faint to well-marked, coarsely marbled appearance that results from an anastomosing (penemosaic) net of pale brown dolostone.
To 150m.
Gradational upwards passage into the overlying Roker Formation dolostone.
Hilton Plant Beds
HPB
Hopwas Breccia Formation
HPBR
Unconformable on Carboniferous and older rocks and also on the Permian Clent and Nechells breccias, which contain a greater variety of extrabasinal clasts (Smith and others, 1974).
South Staffordshire, Warwickshire and Leicestershire coalfields area (Hains and Horton, 1969).
A coarse breccia composed of locally derived material and up to 10% Carboniferous limestone clasts, interbedded with sandstones and subordinate mudstone beds.
Variable, but thicknesses of 30m are recorded (Smith and others, 1974).
Overlain by red sandstones of the Polesworth Formation.
Hauptdolomit Formation
HPDO
Hartfell Pebbly Grit
HPG
Happisburgh Glacigenic Formation
HPGL
The lower boundary of the Happisburgh Formation is commonly erosional in northeast Norfolk and the Waveney Valley and truncates shallow marine deposits of the Wroxham Crag Formation. More rarely, such as at sites like Leet Hill in southern Norfolk, coarse-grained outwash deposits (the Leet Hill Sand and Gravel Member) exhibit a gradational lower contact with river terrace deposits of the Bytham Catchment Subgroup.
The southern limit of the Happisburgh Glacigenic Formation occurs within the Lowestoft district. From there it can be traced northwards across the Great Yarmouth, North Walsham and Mundesley districts, and westwards onto the Norwich and Diss sheets. In coastal sections, deposits of the formation can be observed discontinuously between Pakefield (near Lowestoft) to Overstrand in northeast Norfolk.
Consists of a range of diamictons, sands and gravels, sands and laminated silts and clays. The diamictons (Happisburgh Till, Corton Till and California Till members) are typically sandy matrix-supported diamictons that contain a high abundance of flint and quartzose lithologies relative to chalk, distinguishing them from the more chalky tills of the overlying Lowestoft Formation.
The upper boundary of the Happisburgh Formation is erosional and angular, and truncated by the more chalky tills of the Lowestoft Formation.
Hopcroft Hall Group
HPH
Drawn at the base of metamorphised mudstones of the Hopcroft Hall Group where it rests unconformably upon an igneous infrurian a dark purple hernfels making the contact.
Reddish purple,green and grey,calcareous silty mudstones with calcareous nodules and a few thin fine-grained sandstone bands.
24m approx.
Drawn at the conformable upward passage of mudstones with derncation craks of the Hopcroft Hall Group to the calcareous sandstone shale facies of the Holt Farm Group.
Higher Pigeon House Coal (South Lancashire)
HPHC
Hopedale Limestones Formation (Knoll-Reef)
HPK
Happisburgh Glacigenic Formation And Lowestoft Formation (Undifferentiated)
HPLO
Hope's Nose Beds
HPN
Happisburgh Sand Member
HPSA
The transition from the laminated silts and clays of the Ostend Clay Member (also part of the Happisburgh Formation) to the sandy facies of the Happisburgh Sand Member is erosional and marked by a thin gravel lag.
Cliffs sections between Happisburgh Coastguard Station and Happisburgh lighthouse, northeast Norfolk.
The Happisburgh Sand Member consists of yellowish brown and yellow-orange stratrified sands. The sands exhibit a range of bedding structures including planar and trough cross-bedding, ripples, horizontal bedding, channel structures and sporadic horizons of convolute bedding.
Varies between 6 and 8m
The transition from the sandy Happisburgh Sand Member to the diamicton facies of the Corton Till Member is erosional.
Hopkins Shell Bed
HPSB
Holme Pierrepont Sand And Gravel Member
HPSG
Upper Pleistocene (MI Stage 2). Formerly stated to be Devensian in the original Informal Lexicon entry provided by A Brandon, 26/01/1998.
Extensively developed along the upper and middle Trent and tributaries downstream from the Devensian ice limit (on Sheet 140) downstream, and [probably] on the lower Trent to the Humber but precise extent in some areas pending resurvey.
Predominantly cold-phase sands and gravels that underlie the Holme Pierrepont Terrace. Generally pinkish, poorly sorted and compositionally rather immature matrix-supported, sandy, trough-cross bedded (braided river) gravels with syndepositional ice-wedge casts. Gravel dominated by rounded pebbles of "Bunter" quartz/quartzite (typically c.80%), plus flint, Triassic and Upper Carboniferous sandstone, Lower Carboniferous cherts, etc, and other "exotic" lithogies. Forms a fairly well preserved terrace typically 1 to 2m above the floodplain in the upper and middle Trent, with the deposits extending beneath those of the younger Hemington Terrace and the floodplain alluvium.
Typically 0 to c.12m; typically up to c.8m in the middle Trent valley.
Ground surface, or base of alluvium or of the Hemington Member.
Happisburgh Till Member
HPTI
The basal contact between the Happisburgh Till Member and the underlying Wroxham Crag Formation is represented by an upward transition from tidally laminated sand and silt to till.
The Happisburgh Till Member can be observed in coastal sections between Happisburgh and Overstrand in northeast Norfolk.
The Happisburgh Till Member is a yellowish grey to grey matrix-supported diamicton that has a sandy clay matrix texture. The clast content of the diamicton is <1% and composed predominantly of flint, vein quartz and quartzite with a subsidiary assemblage of far-travelled British erratic lithologies including Carboniferous limestone, Carboniferous coal, Devonian Red Sandstone, Permian Red Sandstone, Permian "Magnesian" limestone, felsic and basaltic porphyry, Dalradian metasediments. The diamicton has been interpreted as a subglacial deformation till.
Typically between 2 to 7m
The upper boundary of the Happisburgh Till Member is variable but generally consists of a series of ridges and troughs that have been interpreted as a range of subglacial and ice-marginal landforms. The till is overlain by a series of laminated clays (Ostend Clay Member) and sands (Happisburgh Sand Member).
Hospital Coal (Derby)
HPTL
Huntley Quarry Beds
HQB
Hartland Quay Shale
HQS
Dark grey shaly mudstone with bands of calcareous nodules; contains flattened Anthracoceratids, fish remains and conodonts.
At or very close to the base of the Bude Formation.
Heyden Rock
Re-establish Heyden Rock as an informal term. During an approach to rationalise sandstone nomenclature in the Millstone Grit, the Heyden Rock was made obselete. The Midgley Grit was chosen as an extensive sheet which is coarse- to very-coarse grained, fining gradually towards the south of the Pennine Basin and withsouthward-directed palaaeocurrents. Subsequent research on the Glossop Sheet has sown that in the limited area in the southeast part of the Glossop Sheet, northeast part of Chapel-en-le-Frith and northwest of the Sheffield Sheet a further sandstone, very coarse-grained with palaeocurrents towards the west has been identified. It is requested that the original term Heyden Rock be reinstated, though the outcrop is less extensive than during previous surveys. For example Heyden Brook, from which the sandbody derives its name is now mapped as the southern extremity of the Midgley Grit.
Humph Rider Blackband Ironstone
HRBI
Hunder Beck Limestone
HRBK
Hard Coal (South Wales)
HRDC
Hard Vein Coal (South Wales)
HRDV
Horrocksford Beds
HRF
Harlock Formation
HRG
Incoming of greywacke, sandstones and siltstones above silty mudstones of Brathay Formation.
Interbedded greywacke, sandstones and siltstones. Underlying and overlying laminated silty mudstone.
c.250 metres. (Lateral variations ~200 = ~300 metres).
By base of overlying Horrace Formation - laminated silty mudstone.
Higher Ravenhead Coal (South Lancashire)
HRHC
Humph Rider Coal
HRIC
Harlaw Limestone
HRLL
Hurlet Seam
HRLS
Harley Coal (South Yorkshire)
HRLY
Hardmine Coal (North Staffordshire)
HRMC
Harrogate Roadstone
HRO
A sharp upward change in a conformable succession from predominantly grey mudstone to limestone. The base of the first limestone bed above the Harlow Hill Sandstone.
The Harrogate area,
A grey, medium- to coarse-grained, thinly to thickly bedded, crinoidal limestone, interpreted to have a turbiditic origin. Individual beds show slumping at the base, are massive bedded above and the tops may be ripple cross-laminated.
A sharp upward change in a conformable succession from limestone to predominantly mudstone. The top of the last limestone bed below the Cravenoceras malhamense (E1c1) Marine Band.
Horbury Rock
HRR
West Yorkshire area [Horbury, near Wakefield].
Relatively soft, fine-grained yellow and brown sandstone, wedge-bedded, with layers of sandy mudstone.
To c.50m
Horse Roads Sandstone
HRS
Near Cockburnspath, Berwickshire.
Green-grey massive fine-grained sandstonewith thin lenticular conglomerates fo cementstone pebbles.
Formerly included within the "Calciferous Sandstone Series" ("Group"; "Measures").
Hareshaw Conglomerate Formation
HRSC
Base of lowest bed of conglomerate above the Gully Redbeds.
Lower Palaeozoic Inlier of the Hagshaw Hills, Scotland.
Conglomerate, pebbly sandstone and coarse sandstone with a few scattered pebbles. Poorly sorted to unsorted with cobbles and boulders to 0.4m; more commonly with smaller clasts of well-rounded quartzite, vein quartz, fine-grained acid igneous rocks, chert and greywacke.
Probably transitional upwards into the Quarry Arenite. Top is upper surface of highest conglomerate bed below the Quarry Arenite.
Holmrook Till Member
HRTI
Variable, but mainly a sharp, irregular, unconformable contact with bedrock, or an undulating to planar, unconformable contact with laminated silt and clay of the Stubble Green Silt or Carleton Hall Clay members of the Glannoventia Formation.
Western side of Lake District inland of the limit of the "Gosforth Oscillation".
Very dense, pale reddish grey to red (Munsell Soil), very gravelly sandy clay diamicton with many cobbles and boulders, with clasts of Borrowdale Volcanic Group rocks (rhyolite, welded tuff, slate), granite and granophyre. Generally matrix supported and massive, but with some interbeds of cobble and boulder gravel, and of pebbly clay.
To 11m
Variable, mainly a sharp, undulating, draped unconformable contact with overlying dark brown laminated clay of the Whinneyhill Coppice Clay Member of the Aikbank Farm Glacigenic Formation or a sharp, planar, unconformable contact with reddish brown, gravelly sandy clay diamicton of the Ravenglass Till Member of the Seascale Glacigenic Formation.
Horner's Vein
HRV
Hairy Craig Sill
HRYCG
Haslingden Flags
Hillhead Sandstone Formation
HSA
Conformable on the Ishes Flagstone Formation. At its type site, the base is taken as a gradual facies change from grey calcareous, laminated fine-grained flaggy sandstone of the Ishes Flagstone, to ared coarser-grained sandstone.
Sheet S84W (Fortrose).
A red and grey, planar-bedded, quartzose, sabdstone with interbeds of micaceous siltstone and silty mudstone.
Up to 920 m thick.
Overlain unconformably by red flaggy sandstone of the Nairn Sandstone Formation.
House Coal
HSC
Hardrow Scar Limestone
HSCL
Holmeside Clay Member
HSCLY
Sharp, unconformable contact with underlying dark reddish brown pebbly silt diamicton of the Green Croft Till Member of the Aikbank Farm Glacigenic Formation. Taken at the top of the uppermost bed of diamicton in the sequence.
Interbedded moderate to reddish brown (Munsell Soil) clay and silt with subordinate beds of gravel and silty sand. The fine-grained lithologies are typically laminated and some laminae are graded (rhythmites). Sparse shell fragments.
To 17.7m
Sharp, undulating, erosional boundary with overlying pale brown fine-grained sand of the Mainsgate Wood Sand and Gravel Member of the Aikbank Farm Glacigenic Formation.
Highlands Felsic Minor Intrusion Cluster
HSFMI
Helmshore Grit
HSG
The central and southwestern part of the Rossendale anticline area.
Hughes Member, Swansea Member And Grovesend Formation (Undifferentiated)
HSGD
Ham-Scarfskerry Flagstone Formation
HSK
Hailes Lava Member
HSLA
The base is conformable or locally unconformable on the East Linton Lava Member (olivine, clinopyroxene and locally plagioclase-phyric basaltic lavas; ankaramites and basaltic hawaiites) or locally unconformable on the North Berwick Pyroclastic Member.
East Lothian, outcrop of the Garleton Hills Volcanic Formation around North Berwick, East Linton, Garleton Hills, Hailes and in the subcrop farther west in the BGS Spilmersford Borehole near Pencaitland, but absent south of Hailes adjacent to the Dunbar-Gifford Fault.
The Hailes Lava Member consists of dark grey, feldspar-phyric olivine-basalts ("Markle type") with sparse to abundant, large or small feldspar phenocrysts, non-porphyritic basalts and pale purple-grey, platy jointed mugearites. Thicknesses of flows are up to 17m. The feldspar-phyric basalts characterize this unit of about six flows.
The Member is overlain by the Bangley Trachytic Member. The contact is conformable and locally unconformable. The change is from olivine-basalt and mugearite lava flows to trachytic lava flows with trachytic tuff and lapilli tuffs.
Hinton St Mary Clay Member
HSM
Fairly abrupt change from the oolitic shelly limestones of the Cucklington Oolite.
Across the central part of the Shaftesbury Sheet (313) - from Fifehead Street, Quintin (ST 772 102) - Marnhull (ST 783 189).
Clay, grey, commonly oolitic.
Fairly abrupt change to the pisolitic limestones of the Sturminster Pisolite.
Highlands Mafic Minor Intrusion Cluster
HSMMI
Highlands Older Suite
HSO
Highlands Older Minor Intrusion Subsuite
HSOMI
Hard Splint Coal
HSP
Hailes Sandstone
HSS
Midlothian; named specifically after Hailes, Edinburgh.
White, grey-blue or pink massive sandstone (freestone) in two major units.
c.65m
Hebrides Subvolcanic Suite
HSSV
Horsham Stone Member
HST
Down-section change from thinly bedded, ripple marked, calcareous sandstone (Horsham Stone Member, Weald Clay Formation) to clays (Weald Clay Formation). A thin clay ironstone occurs in the clay sequence, immediately below the Horsham Member.
The member can be traced as a prominent feature between Horsham and Crawley, but it also extends to the south and east of Christ's Hospital, Horsham, and extends as far as Cowfold, Bolney and Staplesfield (1:50K sheet 302). It also extends along the northern margin of the Brighton & Worthing district (1:50K sheet 318/333) from Twineham Green east to Wivelsfield and North Common. The member has been penetrated by a number of boreholes in the West Weald (Gallois & Worssam, 1993).
South and east of Christ's Hospital, the Horsham Stone Member comprise two thinly bedded, ripple-marked, calcareous sandstone units with an intervening buff and grey clay (Weald Clay facies). However, the clay unit thins and disappears leaving a thickened, single sandstone unit between Horsham and Crawley. Locally Equisetites soil horizons occur, but elsewhere, brackish-marine faunas are present.
Up to c. 11 m
Down-section change from silty clays, locally sandy immediately above the Horsham Stone Member (Weald Clay Formation) to thinly bedded, ripple marked, calcareous sandstone, sometimes lignitic (Horsham Stone Member, Weald Clay Formation).
Henshaw Formation
HSW
Conformable: lowest pebble grit horizon immediately overlying red Wether Law Linn Formation shales.
Red medium- and coarse-grained sandstones and conglomerates with finer grained sediments.
At least 725m
Not seen - unconformably overlain by Greywacke Conglomerate Formation (lower 'Old Red Sandstone') and faulted against Kinnesswood Formation (Inverclyde Group).
Highlands Younger Suite
HSY
Highlands Younger Minor Intrusion Subsuite
HSYMI
Probably spans mid Silurian (Wenlock) to Early Devonian.
Hascosay Slide Zone Mylonites
HSZM
On the western boundary, the rocks of the slide zone belong to the Shetland Boundary Zone. There is no lithological discordance at the junction but it is marked by a continuous and rapid increase in the intensity of the schistosity.
It is about 15 km long and up to 1 km wide. It extends along the north-east coast of Yell and is offset 5 km dextrally by the Bluemull Sound Fault.
Closely-packed masses of coarse-grained, dominantly hornblendic rocks, cut by and contained within, fine-grained and dominantly hornblendic blastomylonites.
Up to 1 km in width.
On the eastern boundary, the rocks to the east of the slide zone belong to the Dalradian of the East Mainland succession (Unst and Fetlar Succession). There is no lithological discordance at the junction, but it is marked by a continuous and rapid increase in the intensity of the schistosity.
Hayton Anhydrite
HTA
Hirnant Beds
HTB
Hartwell Clay
HTC
High Tor Limestone Formation, Cefnyrehndy Oolite Member And Hunts Bay Oolite Subgroup (Undifferentiated)
HTCHB
Higher Two Coal (South Lancashire)
HTCO
Hartfield Formation
HTFD
The basal strata unconformably overlie, or are faulted against, rocks of Lower Palaeozoic age. The underlying sequences are commonly steeply inclined, well-indurated, fine-grained wacke sandstone and mudrock and have a marked angular discordance with the overlying, shallowly inclined strata of the Hartfield Formation.
Lochmaben Basin, Dumfriesshire, southwestern Scotland [Southern Uplands].
Red, laminated and cross-laminated silty sandstone interbedded with pebbly sandstone and lenses of breccio-conglomerate. The sandstone is medium- to thick-bedded, silty, medium- to fine-grained with small [<0.5mm] detrital mica flakes and including many frosted and rounded quartz grains. Intervals of pebbly sandstone and breccia occur within the sandstone, not necessarily at the top of the sandstone beds. The clasts are pebble sized, mostly tabular and platey and aligned parallel or near parallel to bedding, defining a crude lamination, and matrix supported in red sandy siltstone or silty sandstone. The clast composition is red or grey mudrock, grey micaceous wacke sandstone, cream-coloured quartzite and, locally, deeply weathered basalt and amygdaloidal basalt. The Formation may also include interbeds of brick red, dune cross-bedded, fine- or very fine-grained sandstone without detrital mica grains.
The thickness of the Hartfield Formation from the mapped extent in Kinnel Water [NY0679 9246] to [NY0671 9163] and Mollin Burn [NY 0575 9223] to [NY 0605 9141] is approximately 150m and 170m, respectively.
Strata of the Hartfield Formation are conformably overlain by brick-red sandstone of the Corncockle Sandstone Formation. The boundary is picked at the base of a continuous sequence of fine-grained, well sorted sandstone with large scale cross-bedding and single grain "pin stripe" lamination typical of the overlying Formation.
Heather Formation
HTHE
Heathen Coal
HTHN
Harrison Stickle Breccia Member
HTK
Taken at the base of dominantly pebble breccia units overlying bedded volcaniclastic sedimentary rocks of the Three Tarns Member.
Bow Fell and Langdale Pikes, Cumbria
Lithologically variable succession of pebble-grade breccia, pebbly sandstone and lapilli-tuff
Up to 30m
Defined by the base of overlying volcaniclastic rocks of the Dungeon Ghyll Sandstone Member
Huntly-Knock Pluton
HTKN
High Tor Limestone Formation
HTL
The base is taken at the sharp erosional contact between the thin-bedded calcite mudstones and the mudstones of the underlying Caswell Bay Mudstone Formation and the overlying coarse peloidal/skeletal/oolitic packstone/grainstones forming the lower part of the Formation in South Wales and the Weston-super-Mare areas. A basaltic lava is present in the lower part of the sequence in the Weston-super-Mare area. In the southern parts of the Welsh outcrop, the Formation overlies the Gully Oolite Formation. Here the base is taken at the sharp erosional contact between the oolitic grainstones of the Gully Oolite Formation and the overlying coarse skeletal packstone/grainstones of the Formation.
Gower [SS 50 90], Vale of Glamorgan [ST 00 74] and the Weston-super-Mare [ST 32 60] areas. Present but not mapped in the Tenby [SN 13 01] and Pembroke [SM 97 03] areas. Passes northwards into the Llanelly Formation in Wales and into the Clifton Down Mudstone in the Bristol/Broadfield Down [ST 50 650 area. Passes eastwards into the Burrington Oolite Subgroup in the Mendip Hills [ST 50 54].
Mid grey, predominantly thick-bedded, fine- to coarse-grained, burrowed, skeletal packstones, with thin beds and partings of shaly dolomite mudstone and siltstone. Some thin-bedded dark grey bituminous skeletal packstones interbedded with thin argallaceous wackestones and mudstones. Coarse, locally cross bedded, peloidal/skeletal/oolitic packstones/grainstones developed in lower and upper parts in northern sections. On the southeast crop of the South Wales Coalfield the Formation is predominantly dolomitized.
55m on the south crop of the South Wales Coalfield, thickening southwards to 133m in west/central Vale of Glamorgan.
The top of the formation is gradational and taken at the incoming of a predominantly oolitic grainstone sequence [Hunts Bay Oolite Subgroup] above the skeletal packstones or skeletal/pelioidal/oolitic packstone/grainstones of the Formation.
Haughton Marine Band
HTMB
Houghton Thin Coal (South And West Yorkshire)
HTNC
Haughton Limestone
HTONL
Holt Town Sandstone Bed
HTS
Lancashire.
Halton Shales
HTSH
Hurlet Limestone And Blackhall Limestone (Undifferentiated)
HUBL
Humph Coal (Central Coalfield)
HUC
Hunstanton Formation
HUCK
Sharp or [apparently] gradational boundary of marly chalk with ferruginous sandstones of Carstone Formation or (in Cleveland Basin) with mudstone of Speeton Clay Formation; commonly marked by a line of phosphatic nodules (burrow-fills).
Present in Yorkshire (including the Cleveland Basin where it attains its maximum development) and Lincolnshire and extends southwards to its type locality of Hunstanton on the north Norfolk coast.
Rubbly to massive chalks with marl bands; typically pink to brick-red in colour (due to disseminated hematite), but locally upper part may be grey, rather than red, due to secondary alteration of the iron minerals. Commonly somewhat sandy, particularly in lower part. Formal subdivision: None herein. The Hunstanton Formation as defined by Mitchell (1995a) describing the thick succession at Speeton in the Cleveland Basin is divided into five members. These are in ascending order the Queens Rocks Member, Speeton Beck Member, Dulcey Dock Member, Weather Castle Member and the Red Cliff Hole Member.
c.1m in type section, typically 3m in Lincolnshire and south Yorkshire, thinning over the Market Weighton High but expanding to c.30m into the Cleveland Basin, with c.24m in cliffs at Speeton.
Erosion surface, locally developed as a hardground, overlain by nodular chalk (lowest Cenomanian) of Paradoxica (or Sponge) Bed or (in Cleveland Basin) Crowe's Shoot Member (Mitchell, S F, 1995); this horizon (the base of the Lower Chalk in Norfolk, or elsewhere of the Ferriby Formation) may or may not correspond with the upper limit of red chalks.
Hutton Coal (Northumberland And Durham)
HUCO
Hughes Coal (South Wales)
HUGC
Hugin Formation
HUGI
Hutton Henry Peat
HUHY
Note that this bed is a raft of Ipswichian peat, now lying within the Late Devensian Wear Till Formation.
No lower boundary as such because field relationships confirm that the item is a glacial raft enclosed by dark grey stony diamicton of the Wear Till Formation. The peat is sheared, folded and streaked out towards the southwest in a similar direction to that indicated by the erratic content and fabric of the enclosing till.
Durham lowlands.
A transported glacial raft of very strongly compressed, sheared and folded peat containing well preserved fragments of moss and high percentages of Hornbeam palynomorphs. Such values are typical of the later temperate stages of the Ipswichian Interglacial.
No upper boundary as such because field relationships confirm that the item is a glacial raft enclosed by grey stony diamicton of the Wear Till Formation. The peat is sheared, folded and streaked out towards the southwest in a similar direction to that indicated by the erratic content and fabric of the enclosing till.
Hulme Member
HUL
Conformable at base of conglomerate at bottom of gravel-dominated part of the Hawksmoor Formation.
Western Needwood Basin.
Gravel dominated, comprising conglomerates, pebbly sandstones, and infrequent non-pebbly sandstones and argillaceous rocks.
0 - >115m
Conformable at top of conglomerate at top of gravel-dominated part of the Hawksmoor Formation.
Hummocky Moraine
HUMMO
Huntley Formation
HUN
Unconformable on Carboniferous rocks.
Needwood Basin (Staffordshire, Leicestershire, Derbyshire).
Poorly-sorted matrix-supported conglomerate and very coarse-grained pebbly sandstone; there is a large proportion of locally-derived subrounded to angular clasts.
Conformable, where sandstone or conglomerate with many locally-derived clasts give way to conglomerate or sandstone with few such clasts (Hawksmoor Formation).
Hurlet Limestone
HUR
Generally seen as a conformable change from marine mudstone overlying the Hurlet Coal at the top of the Lawmuir Formation or West Lothian Oil-Shale Formation in West Lothian, or a coal at the top of the Pathhead Formation in Fife, or Aberlady Formation in East Lothian.
Located throughout the outcrop and subcrop of the Lower Limestone Formation of the Midland Valley of Scotland, but locally absent in Ayrshire and Strathclyde on highs, largely created by the Clyde Plateau Volcanic Formation.
A pale to dark grey, crinoidal, and shelly bioclastic limestone, interpreted to be of marine origin, containing argillaceous partings where it is thickly developed.
From 0.75m to 1.5m, and locally 11m, in the Airdrie, Falkirk and Glasgow districts. In shelf settings, such as in Midlothian, it can be as much as 14m thick.
Generally seen as a conformable change to thick marine mudstone that passes up into deltaic arenaceous deposits of the Lower Limestone Formation.
Hurlet Coal
HURC
Generally identified by a grey, rooted seatearth or seatclay just above the non-marine Baldernock Limestone, almost at the top of the Lawmuir Formation in the Glasgow area, or almost at the top of the West Lothian Oil-shale Formation in West Lothian (no Baldernock Limestone). Considered as a conformable contact and defined as the lithological change from the underlying strata.
Present throughout the outcrop of the Lawmuir Formation in the Glasgow-Paisley area of the Carboniferous of the Midland Valley of Scotland, but absent on highs largely created by the Clyde Plateau Volcanic Formation; also developed in West Lothian in the West Lothian Oil-shale Formation of the Bathgate area.
A bright banded coal, containing vitrinite with some inertinite (including fusinite = mineral charcoal); commonly recorded as pyritous and dirty but with good coking properties.
Varies from a few centimetres, to 2.4m (south of Blackburn in West Lothian) to 1.32m in the Milngavie No.1 Borehole [BGS Registered No.NS57SE/39, NGR NS 5501 7335] in the Glasgow district. Known to be 1.6m thick in the Bathgate area of West Lothian, encountered at a depth of 152.3m in Murrayfield No.1 Borehole, BGS Registered No.NS96NE/276, NGR NS 9875 6554.
Usually seen as a change to mudstone, locally Lingula-bearing or marine, underlying the Hurlet Limestone, that forms the base of the Lower Limestone Formation. Noteworthy, is the presence in some areas (eg Lennoxtown northeast of Glasgow) of the marine Alum Shale bed (1-2m thick) in this interval. Considered as a conformable contact and defined as the lithological change to the overlying strata.
Hurdlow Sandstones
HUS
Humbie Shell Bed
HUSB
Humby Vein
HUV
Heavitree Breccia Formation
HVBR
Overlies Alphington Breccia; defined by marked increase in amount of Murchisonite feldspar. Basal beds form a prominent scarp over the less well cemented Alphington Breccia.
Outcrops in and south of Exeter between Heavitree, Exminster and Kennford.
Reddish brown, mainly fine-grained, breccia; clasts (mainly less than 8cm, some 30cm+) of Culm sandstone, vein quartz, hornfels lava, granite, and potassium feldspar (Murchisonite). Well cemented locally.
From Exminster southwards Heavitree Breccia is overlain by and interdigates with the Dawlish Sandstone. North of Exminster Heavitree Breccia is overlain fairly sharply by Dawlish Sandstone. In the Hill Barton area (SX 956 928) thin Heavitree Breccia is overlain fairly sharply by Monkerton Formation.
Hevdadale Intrusion
HVDD
Harwood Beds
HWB
Hwch Coal (South Wales)
HWCH
Highworth Clay Member
HWCL
Basal contact may be erosional. In Wiltshire, sharp change up from yellow to grey fine to medium sand, sandstone and muddy sandstone (Hazelbury Bryan Formation) or in Oxfordshire change up from bedded shelly ooidal limestone (Highworth Limestone Member) or sandy ooidal limestone (Pusey Flags Member) into mudstone or sandy mudstone of the Highworth Clay Member. In reference section Faringdon Borehole (SU39SW/1), the base is at 6.71m.
North Wiltshire to south-west Oxfordshire. Best developed in the area of Highworth and Hatford. May be represented at Spirt Hill, near Calne, Wilts (Arkell, 1951).
Variably sandy grey to brown mudstone.
2 to 3m in type area, 1.2m at Lamb and Flag Quarry, c.3.7m at Wootton Bassett.
Passage up from grey to brown mudstone or sandy mudstone into sand or sandstone with ooids (Highworth Grit Member) in Oxfordshire. Non-sequence overlain by shelly, shell detrital ooidal limestone of the Stanford Formation (Calne Freestone) in Wiltshire.
Haugh Wood Formation
HWD
Not seen at outcrop; placed at 982 feet in Fownhope Borehole, where green-grey siltstones of the Yartleton (Haugh Wood) Formation overlie interbedded siltstones and sandstones of the Huntley Hill Formation.
Woolhope Inlier
At outcrop, flaggy, blue-grey, calcereous sandstones with interbedded olive siltstones and overlain by purple and olive siltstones; in Fownhope Borehole, green-grey siltstones with minor claystones (107.7 m. proved) overlain by 135.3 m. of green-grey sandstones with interbedded siltstones.
93m at outcrop (base not seen); 243m drilled in Fownhope Borehole.
Base of limestone of the Woolhope Limestone Formation.
Highworth Grit Member
HWGR
Base is marked by an upward passage from grey to brown variably sandy mudstone (Highworth Clay Member) or from sandy ooidal limestone (Pusey Flags Member) into sand or sandstone with ooids of the Highworth Grit Member.
North Wiltshire to southwest Oxfordshire. Best developed in the area of Highworth and Hatford. Might be represented at Spirt Hill, near Calne, Wiltshire (Arkell, 1951).
Cross-bedded yellow, orange and white sand and sandstone, sparsely ooidal, with pebbles, very rare ammonites, passing down into clayey sand. Sandy ooidal limestone locally developed.
2 to 3m in the type area, 1.2m at Lamb and Flag Quarry, c.3.7m at Westbury and Wootton Bassett.
Top is a non-sequence, may be bored or eroded. Change up from sand and sandstone of the Highworth Grit Member into bedded bioclastic or ooidal limestones of the Stanford Formation.
Harwich Formation
HWH
Sharp contact on Lambeth Group - burrows extend into the bed beneath.
London Basin and parts of East Anglia.
Glauconitic sandy clays and very fine-grained glauconitic sands; marine fauna, locally brackish.
Up to 20m in East Anglia; less that 1m in Central London.
With the Walton Member of the London Clay Formation - a stratigraphical discontinuity.
Hawick Group
HWK
Faulted - base gradational through Cairnharrow Formation to Gala Group.
Thin- to medium-bedded greywacke and interbedded silty mudstone with thin red mudstone beds in Carghidown Formation and laminated fossiliferous carbonaceous siltstone beds in Ross Formation. Greywackes calcareous except in Cairnharrow Formation.
Unknown, possibly up to several km thick.
Faulted - top gradational through Ross Formation to Riccarton Group.
Hawkcraig Point Sill
HWKS
Hawes Limestone
HWL
Where limestone overlies sandstone of the Thorney Force Sandstone.
c.21m
Where limestone is overlain by mudstone of the Gayle Shale.
Harelaw Lava Member
HWLA
The base is unconformable on the Moyne Moor and Neilston Lava members, which consist of basaltic lavas.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton, discontinuous across an area around Halker (NS 410 500), Neilston (NS 520 580), Glenouther Rig (NS 480 480) and Blackwood Hill (NS 550 470).
The Harelaw Lava Member consists of trachytes, trachyandesites and trachybasalt lavas.
>70m
The Member is overlain by the upper Flow Moss Lava Member. The contact is considered unconformable and locally even intrusive. The trachytic lava flows are thought to have had significant dome-like topographical expression immediately after eruption.
Lower Hawes Limestone
HWLL
Harwich Formation And Lambeth Group (Undifferentiated)
HWLM
Highworth Limestone Member
HWLS
Base is either: (in east) sharp change up from medium- to coarse-grained sand/sandstone of Beckley Sand Member into shelly ooidal limestone with basal conglomerate, or a non-sequence with interbedded yellowish silty and clayey fine quartz sand with sandstone "doggers" and sandy mudstone (Hazelbury Bryan Formation) overlain by shelly ooidal limestone with local conglomerate (Highworth Limestone Member).
North Wiltshire to southwest Oxfordshire. Best developed in the area of Highworth; wedges out eastwards near Garford; thins out westwards to zero near Blunsdon. May be thinly represented at Spirt Hill, near Calne, Wiltshire.
Bedded shelly ooidal limestone, locally sandy or pisoidal, with thin interbedded calcareous mudstones. Commonly has a basal mudstone chert and sandstone pebble conglomerate, and coralliferous limestones are developed in the Highway area.
2 to 3m in type area, 2.6m at Lamb and Flag Quarry, thins laterally, 0.3m at Wooton Bassett.
Top is marked by upward change from shelly ooidal limestone of the Highworth Limestone Member into cross-bedded fissile sandy ooidal limestone or calcareous mudstone (Pusey Flags Member), where present, or variably sandy grey to brown mudstone (Highworth Clay Member). Contact might be erosional.
Upper Hawes Limestone
HWLU
Handsworth Rock
HWR
Local development in the area southeast of Sheffield, Yorkshire.
Pale (whitish) fine-grained, thickly bedded sandstone, locally "shaly".
Maximum of around 12m in the aea near Handsworth Hall, decreasing rapidly along the outcrop both to the northwest and the southeast.
Hawick Group And Riccarton Group (Undifferentiated)
HWRC
Hwylfa Formation
HWY
Base unconformable on various Caradoc formations.
Grey and dark grey siltstones, muddy siltstones and subordinate parallel laminated sandy siltstones and fine- to medium-grained feldspathic sandstones. Includes locally present basal Hafod Ifan Limestone.
450 metres.
top succeeded by pale grey siltstones of the Bron-Y-Graig Formation.
Hythe Formation
Incoming of fine- to medium-grained sands above the silty or sandy clays of Atherfield Clay. Generally sharply defined. See also Hoes Farm Member.
Weald
In western Weald, comprises mainly fine- to medium-grained, sparsely glauconitic sands, sandstones and silts, locally pebbly, in some areas with calcareous or siliceous cement of some beds or lenses. Some clay interbeds, including Fuller's Earth. In Kent and eastern Sussex, alternating sandy limestones and glauconitic sandy mudstones.
Unconformable to disconformable contact at base of heterogeneous sediments of Sandgate Formation; can be marked by a condensed lithofacies.
Hythe Formation And Atherfield Clay Formation (Undifferentiated)
HYAC
Hazelbury Bryan Formation
HYB
The base generally displays a change up from the grey mudstone of the Weymouth Member of the Oxford Clay Formation, into a sequence of sandy mudstone, muddy sandstone, sand and sandstone beds. In places, the basal bed is a fine-grained sand.
From north Dorset to southwest Oxfordshire, the unit passes east around Cumnor Hill (Oxford), into the more argillaceous West Walton Formation, and the Temple Cowley Member of the Kingston Formation. Between Farringdon and Cumnor the upper part may pass laterally east and vertically into the Beckley Sand Member of the Kingston Formation.
In north Dorset it is seen as coarsening upwards cycles typically from 8m to 10m thick, and up to 20m thick, of grey to brown sandy mudstone, muddy sandstone and yellow, brown and grey very fine- to medium-grained quartzose sand, with thin sandy siltstone beds in parts. Sand is locally cemented into lenticular beds and doggers of calcareous, 'blue-hearted' sandstone to sandy limestone. In Wiltshire, the sandy mudstone beds are subordinate. The beds are generally very shelly and bioclastic in Dorset to west Wiltshire, but poorly fossiliferous in north Wiltshire to Oxfordshire. Well-cemented fossiliferous sandstone beds occur in the upper part: the Seend Cleeve Sandstone Member in west Wiltshire (Wright and Cox, 2001), Lyon's Gate Bed in Dorset (Bristow et al. 1995), and a spiculitic sanstone bed, near Purton, Wiltshire (Ringsbury Spiculite Member; Arkell, 1941). Contains a fauna of bivalves and ammonites.
From 6m to 53m thick in north Dorset, and 6m to 18m thick in Wiltshire.
The upper boundary varies along the outcrop. In Dorset there is a sharp change from a sequence of sandy mudstone, sand and sandstone strata to a sand-free, or virtually sand-free, commonly ooidal, grey clay, of the Woodrow Clay Member and the Stour Formation. in East Somerset it is overlain unconformably by grey mudstone of the Gault Formation. In Wiltshire, the sandy strata are overlain non-sequentially by grey or brown mudstone of the Highworth Clay Member, or grey bioclastic ooidal and non-ooidal limestone of the Highworth Limestone Member, both part of the Kingston Formation, or else by a non-sequence, overlain by grey limestone of the Stanford Formation. In Oxfordshire, there is a passage up from poorly fossiliferous fine-grained sand, sandy siltstone and mudstone into moderately fossiliferous medium- to coarse-grained grey to brown sand of the Beckley Sand Member of the Kingston Formation.
Hayne Beech Member
HYBC
Holly Bush Member
HYBH
The incoming of common beds of sandy dolostone/dolomitic sandstone in the Milldale Limestone.
Only known in Cloud Hill Quarry.
Fine to coarsely crystalline sandy dolostone, dolomitic sandstones and dolomites with thin stylolitic shaly mudstone and clay partings.
In the type section the top is taken at the top of the highest sandy dolomite, here additionally containing derived pebbles. The member is suceeded by grey, medium to thickly-bedded dolostones of the undivided Milldale Limestone Formation.
Hazelbury Bryan Formation And Kingston Formation (Undifferentiated)
HYBK
Half Yard Coal (North Wales)
HYC
Hylton Castle Coal (Northumberland And Durham)
HYCC
Half Yard Coal (Cheadle)
HYCO
Harby Head
HYHD
Half Yard Coal (Hanwood)
HYHW
Hartley Coal (Stirling, Clackmannan)
HYLC
Occuring locally within the Limestone Coal Formation at the same level as the Cowdenbeath Seven Foot Coal elsewhere. This is not the same as the Hartley Coal of Dailly [HART], which lies close to the base of the Limestone Coal Formation.
Half Yard Limestone
HYLS
Hyner Mudstone Formation
HYMU
Middle Teign Valley (SX 84 85), eastern Dartmoor, south Devon.
Hard dark blue-grey or bluish green-grey, generally mottled, silty shales and mudstones. Calcareous bands and nodules, and calcareous shales and mudstones occur near the top, together with a calcareous siltstone (locally yielding trilobite and pelagic ostracod faunas). Within the metamorphic aureole of the Dartmoor Granite, calc-flints and hornfels are developed and siliceous nodules are characteristic of the lower parts of the Formation.
The upper boundary is taken at the gradational incoming of grey and green micaceous shales of the overlying Trusham Mudstone Formation above the dark blue or bluish green mottled shales and calcareous beds of the Hyner Mudstone Formation. Commonly this boundary cannot be detected in the metamorphic aureole of the Dartmoor Granite.
Hyssington Volcanic Member
HYS
Lower boundary is passage from Mytton Flags Formation into dark shales of the Hyssington Volcanic Formation shale.
Interbedded sequence of grey shales, vitroclastic acid tuffs and volcaniclastic sandstones and wackes.
c.1000 metres, much variation.
No upper boundary because of unconformity.
Horsehay Sand Formation
HYSA
Seen as the passage from lithologically similar sand and sandstone beds with marine shelly fauna, ooidal and shell-detrital limestones of the Northampton Sand Formation (Inferior Oolite Group) where present, or mudstone beds of the Whitby Mudstone Formation (Lias Group) into barren, sand-dominated beds. The non-sequential boundary with the Northampton Sand Formation, may appear conformable or gradational probably as a result of weathering effects, or locally channelled and disconformable [Horton et al. 1987, p.56].
Oxfordshire north-east of Sibford Gower, Hook Norton and Tackley [Horton, 1977, fig. 4], where it passes south-west (on BGS 1:50 000 sheet 218) into the Chipping Norton Limestone Formation; North-west Buckinghamshire; Northamptonshire, south-west of Eydon and Wappenham (on BGS 1:50 000 sheet 202), where the overlying Taynton Limestone Formation passes lithologically north-east into the Wellingborough Member of the Rutland Formation (unpublished BGS data), the Horsehay Formation which can no longer be differentiated passes lithologically into the Stamford Member.
Unbedded to weakly bedded and cross-bedded, pale grey and brown to off-white, medium- to fine-grained, quartzose sand, locally cemented into calcareous or weakly ferruginous sandstone with thin dark grey mudstone and siltstone beds in places, rootlets and lignitic debris common, shells and shell debris very rare.
To 7m
Marked by the presence of mudstones, marls and limestone beds of the Sharp's Hill Formation where present, or ooidal and shell detrital limestones of the Taynton Limestone Formation. The boundary is non-sequential, and may be marked by an eroded or leached and rootleted surface.
Hythie Till Formation
HYTIL
Typically the formation has a sharp, planar, subhorizontal, erosional basal boundary on sediments of the Corsend Gelifluctate Bed (e.h. east and south faces, Kirkhill Quarry (infilled). In other situations the basal boundary can be more complex - e.g. northeast face, Leys Quarry (disused). Here the formation displays either a sharp, undulating, unconformable, basal boundary on brown diamicton of the Rottenhill Till Formation; or a sharp to gradational basal/lateral, glaciotectonic, boundary with sheets and rafts of black clayey diamicton of the Corse Diamicton Member (Whitehills Glacigenic Formation).
Buchan, northeast Scotland. The formation is known in the vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) and Leys Quarry (disused) (centred on NK 0040 5250), and more widely as a surface, or subsurface deposit in the area of north and south Ugie Water valleys on Sheet 87W (Ellon). The unit might be regionally significant and present locally across northeastern Scotland.
Gravelly, clayey silty sand diamicton. Typically brown/dark brown (10YR 4/3), with greyish brown/grey ped faces, very stiff, non-calcareous, matrix-supported. Clast angularity ranges from angular to subrounded. Clast lithologies are varied and include psammitic, pelitic and quartzitic metasedimentary rock, felsite, mafic igneous rocks, slate, grey granite and sparse red sandstone, flint and a single Norwegian "Rhomb Porphyry". Clast fabrics indicate glacial transport from the west and westsouthwest. Interpreted as a subglacial till.
Typically the upper boundary is the present ground surface. Within the valleys of the north and south Ugie Waters the upper boundary can be sharp, erosional with overlying glaciofluvial or alluvial sands and gravels.
Hyner Mudstone Formation And Trusham Mudstone Formation (Undifferentiated)
HYTM
Half Yard Coal (Wyre Forest)
HYWF
Hazel Greave Grit
HZG
Hazon Coal (Northumberland)
HZNC
Ince Four Foot Coal (South Lancashire)
I4FT
Ince Six Foot Coal (South Lancashire)
I6FT
Ince Seven Foot Coal (South Lancashire)
I7FT
Inverness (Albion) Glacigenic Subgroup
IAG
Sharp, unconformable, uneven contact with bedrock.
The hinterland of the Moray Firth, including the northeastern end of the Great Glen, the southern shores of the Moray Firth as far east as Buckie, the Black Isle and the land surrounding the Cromarty and Dornoch firths.
Suite of glacial, glaciofluvial, glaciolacustrine and glaciomarine deposits that contain clasts derived predominantly from the comminution of Devonian (Old Red Sandstone) sandstone, siltstone and conglomerate. Including sandy diamictons (till), sand, gravel, silt and clay.
Ground surface or unconformable contact with various units of the Inverness Glacigenic Subgroup.
Interbasaltic Formation
Ibrox Coal (Glasgow)
IBBC
Ibrox Blackband Ironstone (Glasgow)
IBBI
Iubhair Beag Calcareous Formation
IBGC
Where tremolite schist becomes dominant overlying the magnetite-semipelite of the underlying Sron Garbh Formation. Rapid transition.
Ardverikie Forest between An Lairig [NN 50 77] and the Allt Mhainisteir [NN 53 86]. Sheet 63E [Dalwhinnie].
Tremolite-rich calc-silicate schist with layering produced by variations in mica content. Minor semipelite.
c. 60m at most. More typically 10m
At the top of the highest tremolite schist unit - overlain by semipelites of the Coire Cheap Formation.
Injebreck Formation
IBK
In stratigraphical contact with the Barrule Formation.at the base, which is marked by a change from a mudstone-dominated to a mudstone/sandstone facies
A dark grey mudstone, with pale siltstone laminae and quartz arenite sandstone as thin to medium beds locally forming packets up to several tens of metres; debrite (pebbly mudstone) locally in the south becoming extensive in the north.
In stratigraphical contact with the Glen Rushen Formation, which is marked by a change from amudstone/sandstone facies to a mudstone-dominated facies.
Igneous Conglomerate
Inferior Cannel Coal (Lancashire)
ICCO
Ice Contact Deposits
ICD
Variable lithology. Glacial deposits laid down on, under or against a glacier or ice sheet. Moundy topography is characteristic, but flat-topped mounds are common. [Generic description: 'TMOS' Procedures].
Inchard Gneisses
ICGN
Ages of the protolith igneous rocks lie in the range of 2840 to 2680 Ma.
Has a sheared contact with the Scourian Gneiss to the southwest. It is unconformably overlain by the Torridonian Group, and in the east, by the Eribol Formation. The unit is aso intruded by the Rubha Ruadh Granite.
Outcrops of the Inchard Gneiss stretch from approximately the Laxford River in the south to Cape Wrath in the north, from the Moine Thrust belt in the east to the coast in the west. Bodies of gneiss, belonging to he Lewisian Complex within the Moine Thrust belt to the north of Loch Stack are also likely to be part of the Inchard Gneiss.
Comprises grey to pink biotite- and locally hornblende-bearing, granodioritic to tonalitic felsic gneisses, with subordinate bodies of gneissose mafic and ultramafic rock. The general grade of metamorphism is amphobilite facies. The gneiss is comonly migmatitic.
On the BGS DigMap the unit has previously been shown as LLX, LS or L.
It is probably at least several kilometres thick, and it is thought that it potentially extends down to the Moho; i.e. greater than 5km.
Not applicable, but see details under "Lower Boundary".
Icconhurst Sandstone
ICS
Inverclyde Group And Strathclyde Group (Undifferentiated)
ICSC
Ida Formation
IDA
Irvinestown Dyke
IDY
Instow Fish Bed
IFB
Ince Furnace Coal (South Lancashire)
IFCO
Ivy Farm Laminated Silt Member
IFLS
Abrupt but conformable lower boundary with either the diamicton facies of the Walcott Till Member or the sandy facies of the Mundesley Sand Member.
The Ivy Farm Laminated Silt Member can be identified and traced within cliff sections between Trimingham and Overstrand, north norfolk.
The Ivy Farm Laminated Silt Member consists of two distinctive lithofacies: (1) rhythmically-bedded dark grey clays and pale grey silts that grade upwards into a pale yellow laminated marl; (2) horizontally bedded and rippled fine-grained pale grey sand rich in the heavy mineral zircon.
In excess of 22m. The true thickness is difficult to determine because the unit is truncated by several large-scale basal shear planes.
In the Trimingham area, the upper boundary of the silts and clays of the Ivy Farm Laminated Silt Member is truncated by the diamicton facies of the Bacton Green Till Member.
Iford Marls (One)
IFMA1
Iford Marls (Two)
IFMA2
Ilfracombe Slates Formation
IFS
Interglacial Beach Deposits
IGBD
Clay, silt, sand and shingle; sheet, dune or bank forms; of beach origin, from interglacial periods. [ Generic description].
Interglacial Deposits
IGD
Variable lithology, gravel through to clay; from interglacial periods. [Generic description].
Interglacial Fluvial Deposits
IGFD
Variable lithology; of fluvial origin, from interglacial periods. [Generic description].
Interglacial Lacustrine Deposits
IGLD
Usually organic-rich, interbedded sand, silt and clay; of glaciolacustrine origin, from interglacial periods. [Generic description].
Interglacial Marine Deposits (Undifferentiated)
IGMD
Deposits of variable lithology; of marine origin, from interglacial periods. [Generic description].
Unnamed Igneous Rocks Of Palaeogene Age
IGPA
Inner Hebrides Group
IHEB
Cenomanian to Early Campanian (Late Cretaceous).
Ijmuiden Ground Formation
Unconformably overlies Westkapelle Ground Formation; passes laterally westwards into Smith's Knoll Formation.
Presumed fine-grained sands, silts and clays (no samples in British sector). Characterised in seismic profiles by overlapping units bounded by Sigmoid reflectors, with evidence of prograding towards the west onto the Westkapelle Ground Formation. Probably prodelta deposits.
0 - 200 metres, occurs only east of 2 deg. 40' East.
Unconformably overlain by Winterton Shoal or Yarmouth Roads Formation or locally by Eem Formation in Dutch sector.
Index Limestone (England And Wales)
South Staffordshire and Warwickshire.
Limestone with Spirorbis.
Index Limestone (Scotland)
ILS
Generally a conformable change from a marine mudstone almost at the top of the Limestone Coal Formation. The Index Limestone as it is usually called, forms the base of the Upper Limestone Formation.
Throughout most of the outcrop of the Upper Limestone Formation of the Midland Valley of Scotland, but locally absent in Ayrshire and Strathclyde on highs partly created by the Clyde Plateau Volcanic Formation and poorly developed in central and east Fife because of an on-delta facies change.
A pale to dark grey bioclastic (crinoidal) marine limestone, with algal nodules. The name is not geographical in origin, but indicates a marker bed for the Limestone Coal Formation coal seams below.
From 0.6 m to 2.2m in the Airdrie, Falkirk and Glasgow districts, and 3m in the Irvine area of Ayrshire.
Generally a conformable change to a thick marine mudstone, which may also include the Huntershill Limestone, that passes up into deltaic arenaceous deposits of the Upper Limestone Formation.
Ilford Silt Member
ILSI
Rests on Taplow Gravel, Hackney Gravel and Boyn Hill Gravel river terrace deposits.
Thames Valley, north shore, from Ilford, possibly as far as Grays.
Sandy clay and silt.
Typically 1-3m but upto 6m, possibly more.
Inchmurrin Conglomerate Member
IMC
The Inchmurrin Conglomerate Member is commonly faulted against Dalradian or Highland Border Complex rocks. Mapping in the Gualann area suggests that the Inchmurrin Conglomerate Member lies within the Ruchill Flagstone Formation, overlying the Craig of Monievreckie Conglomerate Formation.
Cardross-Drymen area, the north-west limb of the Strathmore Syncline, Sheets 30W, 38W, 38E.
A conglomerate with clast sizes mostly from 10 to 15 cm, predominantly of quartzite in the lower part but with igneous and volcanic clasts also, at higher levels.
Originally, the top of the Inchmurrin Conglomerate Member was found to be unexposed or obscured by faulting (Paterson, Hall and Stephenson, 1992, p.7). Later mapping in the Balmaha-Gualann area (1995 season), suggests that the Inchmurrin Conglomerate Member is a conglomerate body within the Ruchill Flagstone Formation. Where not affected by faulting, it is overlain by a flaggy, locally pebbly sandstone of the Ruchill Flagstone Formation.
Isle Of Man Catchments Subgroup
IMCA
Generally unconformably overlying glacigenic sediments or bedrock.
The Isle of Man (50k sheets 36, 45, 46, 56, 57).
Alluvial gravel, sand, silt and clay forming floodplains, alluvial fans and river terrace deposits, peat, mud and pebbly sand infilling lowland basins and blanketing upland hillsides and peat, humic clayey silt and calcareous silt infilling kettleholes.
Highly variable but >20m locally, typically 2.5m thick.
Generally the ground surface, locally overlain by blown sand.
Inchmickery Sill
IMIS
Interglacial Marine Shoreface And Beach Deposits
IMSB
Clay, silt, sand and shingle; from beach and marine shoreface environments, and interglacial periods. Beach deposits may have sheet, dune or bank forms. [Generic description].
Invernaver Pelite Member
INAV
Innes Carbonate Member
INCA
Inchrory Limestone Formation
INCH
Above Clashnoir Semipelite Formation at lower limit of grey crystalline limestone lithology. In parts grades downwards into semipelites with limestone interbeds.
From 3km SSE of Inchrory (Glen Builg) north in Glen Avon to Bridge of Avon. In Braes of Glenlivet and Glen Suie. Scattered outcrops in Glen Markie. In Keith area and Braes of Edingight, Limehillock Quarry areas.
Limestone, blue-grey, medium to coarsely crystalline, thin- to medium-bedded, rarely thick-bedded. Chert nodules in parts. Thin interbeds of graphitic to calcareous pelite and semipelite. Amphibolite pods in some areas.
50 - 150m, possibly locally thicker (to 400m) due to folding/faulting.
Upper limit of grey crystalline limestone. Marked change or rarely rapid transition to overlying pelite and semipelite of the Glenfiddich Pelite Formation.
Inchcolm Sill
INCM
Inch Coal (South Lancashire)
INCO
Indefatigable Grounds Formation
INDG
Index Limestone [Duplicate Code: Use Ils]
INDX
Inshes Flagstone Formation
INF
Conformable lower contact with Leanach Sandstone Formation.
Red, green and grey flaggy sandstones with rare grey calcareous mudstones and limestones.
100 metres +.
Upper contact not seen, (established).
Ingleton Group
ING
Base not reached.
Restricted to the Craven Inliers, North Yorkshire. Also recovered from the Beckermonds Scar Borehole, in upper Wharfedale about 10km northeast of Horton-in-Ribblesdale [Wilson and Cornwell, 1982]
Interbedded succession of grey-green turbiditic sandstone,siltstone and conglomerate.
At least 600m
Unconformably overlain by Upper Ordovician and Silurian strata.
Ingleston Vent
INGL
The intrusive contacts with the country rock is poorly exposed, which together with diffuse internal structures, makes field relationships difficult to define.
Kirkcudbright Sheet 5W (Scotland).
Subvolcanic explosion-breccia vent, with mainly igneous rocks set in a matrix of decomposed lamprophyre.
Unit thickness is unknown, but the vent is about 50m in diameter.
Inishtrahull Gneiss
INGN
Inchinnan Limestone
INLS
Inferior Oolite Group
INO
Disconformity: change upwards from Lias Group (mudstone with or without sand, ironshot marl and limestone beds) into predominantly limestone succession as described in the lithology. Locally (in Mendips area and at depth on the London Platform) unconformably overlies older beds including lower Lias, Triassic, Carboniferous and Devonian strata.
Outcrop: Dorset, Somerset, Avon, Gloucestershire, Oxfordshire, Northamptonshire, Lincolnshire and Yorkshire (south of Market Weighton High). Subcrop: southern England, apart from interior of London Platform (Parsons, C F, 1980; Sumbler, M G, 1996).
Varied sucession of ooidal, peloidal, marly, sandy, ferruginous and shelly limestones, with subordinate sandstone, calcareous mudstone and mudstone beds.
0-106m at outcrop. Dorset-Somerset; up to 30m (but thickens rapidly in subcrop). South Cotswolds; 10-20m. North Cotswolds; 20-106m. Oxfordshire-Northamptonshire; up to 30m. Lincolnshire; up to 50m. Present at depth in Wessex-Weald Basin where up to 120m thick (Kingsclere No.1 Borehole).
In Dorset-Somerset, change from ooidal limestones upward into Fuller's Earth Formation mudstone with beds of finer-grained limestone. In Cotswolds, change from predominantly ooidal limestone (Salperton Limestone Formation) into mudstone (Fuller's Earth Formation) or into sandy fine-grained ooidal limestone (Chipping Norton Limestone Formation) where present, of Great Oolite Group. Generally transitional, but locally an erosive non-sequence marked by hard ground. In North Oxfordshire to Lincolnshire, sharp upward change (unconformity) from fine-grained sandstone (Grantham Formation) or ooidal limestone (Lincolnshire Limestone Formation; where present) into mudstone, siltstone, limestone and sandstone succession of Great Oolite Group (Rutland Formation).
Inverness Sandstone Group
INS
Inverness - Nairn.
Red sandstone sequence incorporating the Daviot Conglomerate, Nairnside Sandstone, Leanach Sandstone, Inshes Flagstone and Hillhead Sandstone formations.
Unconformable base of the Nairn Beds.
Insch Pluton
INSCH
Insch Pluton, Lower Zone
INSLZ
Insch Pluton, Middle Zone
INSMZ
Innse Quartzite Member
INSQ
Insch Pluton, Upper Zone
INSUZ
Inverclyde Group
INV
At base of Kinnesswood Formation - at incoming of common pedogenic carbonate above a red-bed sequence, the Stratheden Group. Normally conformable, locally unconformable in west.
Sandstones containing pedogenic limestone and dolomite nodules ('cornstones'), fine-grained carbonate as beds, nodules and pebbles, and grey and brown mudstones containing thin beds of limestone and dolomite ('cementstones'); subordinate siltstone and mudstone.
To c. 1500m
At top of Clyde Sandstone Formation (in west) or of Tyninghame Formation (Lothian) or of Balcomie Beds (Fife); at incoming of coal, blackshale, seatearth or volcanic rocks of the Strathclyde Group; conformable or unconformable.
Inverness Glacigenic Subgroup
INVG
The hinterland of the Moray Firth, including the northeastern end of the Great Glen, the southern shores of the Moray Firth as far east as Buckie, the Black Isle, and the land surrounding the Cromarty and Dornoch firths.
To 40m
Ground surface or unconformable contact with various Flandrian deposits.
Inverlair Psammite Formation
INVL
Transitional boundary, the lower boundary placed where thicker and laterally more extensive psammites become dominant and the semipelites of the underlying Clachaig Semipelite and Psammite Formation become scarce.
Southern part of the Central Highlands of Scotland bounded to the NW by Glen Roy and the uppermost Spey Valley, to the south by Glen Spean and extending east to Ardverikie Forest and the River Pattack [NN 54 86].
Feldspathic and siliceous psammite and feldspathic quartzite with interbedded layers of semipelite. Minor micaceous psammite locally.
0 to 900m
Transitional contact where psammites and quartzites are replaced by semipelite-dominated succession of the overlying Appin Group.
Inverleven Gravel Member
INVN
Windermere Interstadial to Loch Lomond Stadial.
The Inverleven Gravel Member of the Clyde Clay Formation rests with angular unconformity on older Quaternary sediments or on bedrock. Most comonly it rests on the Paisley Clay Member of the Clyde Clay Formation or on the Wilderness Till Formation (WITI) of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
The Interleven Gravel Member of the Clyde Clay Formation is recognised in the lower Clyde valley from east of Erskine Bridge westwards to the estuary of the Clyde, and in the Leven valley south of Loch Lomond.
The typical lithology is angular to subrounded boulders, cobbles, gravel and pebbles in a clayey sand matrix. The clasts appear to have had barnacles growing on them although no in-situ examples were retrieved. The formation also contains intact, faded, life-coloured shells of the scallop Chlamys islandica. The shells are not significantly abraded.
Veneer to more than 3m
The Interleven Gravel Member of the Clyde Clay Formation is overlain conformably or disconformably by younger Quaternary sediments, commonly either the Balloch Clay Member of the Clyde Clay Formation or the Clydebank Clay Formation of the British Coastal Deposits Group. It is not exposed at the surface.
Inge Volcanic Formation
INVO
Inverscaddle Formation
INVSC
Inver Volcanic Formation
INVV
Inzie Head Gneiss Formation
INZ
Inferior Oolite Group And Great Oolite Group (Undifferentiated)
IOGO
Iona Group
IONA
Inferior Oolite Group (Skye)
IOSK
Iron Post Limestone
IPL
Ipstones Edge Sandstones
IPS
Inch Rock
Iris Anhydrite Member
IRAN
Irchester Member
IRCH
Generally a sharp boundary with the underlying Roade Member comprising ofsimilar limestones generally containing K sharpi, or else a marl or mudstone bed at this level, which may prove a reliable marker, such as the mudstone at the base of the equivalent Ardley Member of the White Limestone Formation in Bucks-Oxon.
The Towcester district to Kettering district, Northants, passings outh-west into the equivalent Ardley Member of the White Limestone Formation, and passing north into the equivalent Longthorpe Member of the Blisworth Limestone Formation.
A pale grey to off- white or yellowish limestone with thin marls and mudstones, fossiliferous, bioturbated peloidal, ooidal and shell-fragmental more or less argillaceous packstones and wackestones, with subordinate cross-bedded, ooidal, shell-fragmental grainstones, containing a fauna mainly of bivalves, and locally brachiopods, such as Digonella digonoides, described as the Digonoides Beds of Torrens, 1967.
Typically from 5 m to 7 m thick, measured as 6.15 m in type section.
Generally a sharp boundary of the limestones with mudstones of the Blisworth Clay Formation.
Ireleth Member
IRE
In Millom Park, it is a member within the Kirkley Bank Formation where it overlies volcaniclastic sandstone of the Low Scales Member; the base of the Ireleth Member is taken at the base of the limestone. Elsewhere the member overlies locally the Skiddaw Group and Borrowdale Volcanic Group.
Restricted to the Millom Park and the Furness inliers, Cumbria.
Pale to dark grey, massive or thickly bedded limestone, commonly pervasively recrystallised with bedding planes which are either stylotitic or totally obscured; dolomitisation and haematite staining common in the south of the inlier with the limestone becoming cavernous and mottled brown in colour.
Up to 30 m thick.
Defined by the base of a sequence of calcareous siltstone within the main part of the Kirkley Bank Formation.
Irfon Formation
IRF
Irish Law Plug
IRLAW
Iona-Ross Of Mull Dyke Swarm
IRMD
Iniscarn Formation
Rests unconformably on Pre-Carboniferous basement (Dalradian - Ordovician).
Conglomerate and breccia with subordinate argillaceous beds.
Not known; probably conformable with Altagoan Formation.
Ingham Sand And Gravel Formation
ISAG
Unconformable on bedrock of the Chalk Group and Crag Group.
Recognised over a wide area of central East Anglia, from the Lark Valley in the west, to Knettishall in the valley of the Little Ouse, and along the valley of the Waveney to the North Sea coast at Pakefield and Kessingland.
Formation encompasses fluvial, lacustrine and organic deposits of the pre-Glacial Bytham River. Deposits of four separate terrace levels are recognized as members of the formation. Commonly a basal fine to coarse-grained sandy gravel is overlain by fine- to coarse-grained pebbly sands, with few clay and silt beds. The gravels contain a high proportion (up to 54%) of rounded pebbles of grey and purple "Bunter" quartzite of Triassic derivation, up to 47% vein quartz, and up to 56% flint derived from the local Chalk. There are traces of chalk and of igneous and metamorphic rocks. Sedimentary structures indicate deposition by braided rivers. The formation can be distinguished from formations of the Kesgrave Subgroup by the high ratio of quartzite to vein quartz in the gravels.
Commonly overlain by Mid Pleistocene glacigenic deposits. Upper boundary may be difficult to determine where overlain by glaciofluvial sand and gravel, but the presence of more angular clasts, chalk, and poorer sorting in the latter is usually helpful.
Irthing Shell Bed
ISB
Isabella Seam
ISBL
Interglacial Silt And Clay
ISC
Silt and clay, interbedded or chaotic; from interglacial periods. [Generic description].
Irish Sea Coast (Albion) Glacigenic Subgroup
ISCAG
Irish Sea Coast Glacigenic Subgroup
ISCG
Cheshire, Lancashire, North Wales, western Cumbria and the Solway Lowlands.
Diamicton, gravel, sand, silt and clay, typically reddish brown and containing clasts of red and yellow sandstone, greywacke sandstone and siltstone, granite and granodiorite. Welded tuff (Borrowdale Volcanic Group), mudstone, coal, shell fragments and reworked marine microfossils are common to the south of the Solway Firth.
Ground surface or unconformably overlain by Flandrian deposits.
Isles Of Scilly Intrusion
ISIN
Comprises an inner, fine-grained, granite (G1) and an outer, coarse-grained, granite (G).
Iron Scars Limestones
ISL
Islay Limestone
ISLL
Island Sandstone Member
ISM
Isohomoceras Subglobosum Marine Band [See Also: H1a1, H1a2, H1a3]
ISMB
Island Magee Siltstone Formation
ISMS
Cenomanian. Acanthoceras rhotomagense Zone
Conformable with Belfast Marls Formation with the boundary arbitrarily taken at the base of the first upwardly occurring hard calcareous siltstone above the transitional top of the preceding formation
East Antrim Basin and the Southern Uplands area of Northern Ireland.
Hard and soft grey siltstones and marls (calcareous siltstones) that weather to a pale yellow colour.
A maximum of 8.0m in the Magheramorne area and a minimum of 0.67m over the Knockagh Axis north of Belfast.
Disconformable with the Collinwell Sands Formation and unconformable with the Kilcoan Sands Formation beneath the so-called Turonian non-sequence of the Hibernian Greensands Group.
Isle Port Conglomerate Member
ISP
Pebble conglomerates of at least 1m thickness sharply overlying red-brown fine- and medium-grained sandstone, towards the top of the Swanshaw Sandstone Formation.
South Ayrshire, Scotland.
A greyish, clast-supported, pebble conglomerate with mainly fine-grained greywacke sandstone pebbles and cobbles but also clasts of chert, siltstone, granular sandstone, limestone and granite and with thin intercalations and lenses of greyish medium- and coarse-grained sandstone.
Pebble conglomerates are conformably succeeded by greyish medium- and fine-grained sandstones, towards the top of the Swanshaw Sandstone Formation.
Iron Tors Limestone Member
The base of the member is not proved in exposures but it is conjectered to rest conformably upon thin-bedded limestones of the undivided Woo Dale Limestone Formation.
The northern part of the Peak District inlier, limited to Iron Tors (SK 15) in Wolfscote Dale.
Massive, pale grey to grey-brown peloidal calcarenites.
Estimated to be 107 m thick.
The passage from the massive, pale grey to grey-brown peloidal calcarenites of the Iron Tors Limestone Member to grey to pale grey calcarenites, commonly laminated and including biopelsparites, and subordinate thinly interbedded calcilutites of the Woo Dale Limestone Formation (undivided).
Itchen Formation
ITCH
Unconformable on Palaeogene and Cretaceous bedrock.
The catchment of the River Itchen and its tributaries in the Southampton-Alresford area.
Floodplain alluvium and river terrace deposits. The floodplain alluvium comprises overbank deposits of brown organic silty clay, together with peaty clay and peat, overlying sand and gravel. Tufa occurs as 1 to 2m-high raised hummocky spreads. The surviving river terrace deposits comprise sand and gravel, planar bedded or cross-bedded, locally overlain by overbank deposits of clayey and sandy silts and silty clays. These fine-grained deposits may be partly aeolian in origin. The major gravel lithology is flint, dominantly sub-rounded to sub-angular and a little well-rounded, and subordinate quartz, ironstone and "sarson". The sand fraction is composed of fine- to coarse-grained well-rounded quartz grains, with subangular flint in the coarse fraction. The older, higher terraces are commonly cryoturbated.
Intertidal Deposits
ITD
Variable lithology. Gravel through to clay, may be rich in organic matter; from the intertidal coastal zone. [Generic description].
Intertidal Deposits (Undifferentiated)
ITDU
Intertidal Deposits (Undifferentiated), 1
ITDU1
Variable lithology. Gravel through to clay, may be rich in organic matter; from the intertidal coastal zone. Older than 'Intertidal Deposits [undifferentiated]' in the same map area. [Generic description].
Intertidal Sandbank Deposits
ITSBD
Intertidal Sandflat Deposits
ITSFD
Ives Head Formation
IVH
At base of lowest bed overlying lavas of Morley Lane Volcanic Formation, at 541m depth in Morley Quarry Borehole.
Grey, volcaniclastic mudstones, siltstones and sandstones with volcanic breccias; well-bedded and graded.
c.780m
Overlain, apparently conformably, by green-grey interbedded fine- to medium-grained volcaniclastic beds of the Blackbrook Reservoir Formation.
Ince Yard Coal (South Lancashire)
IYCO
Inziebar Blackband Ironstone
IZBB
Jet Amber Coal (South Lancashire)
JACO
Jampot Dolerite
JADO
Transgressive intrusion.
Microgabbro, locally porphyritic.
Jacket's Point Formation
JAPT
Believed to be conformable on the Harbour Cove Slate Formation, but faulted.
Port Isaac Bay to St Teath, north Cornwall.
Grey slaty mudstone with sandstone, conglomerate and associated volcanic rocks.
Not seen, faulted.
Jaunt Coal
JAU
Jack And Balls Ironstone (South Wales)
JBI
Jubilation Member
JBL
Succeeds the 15cm calcareous sandstone (the Separation Sandstone Bed) that separates the Jubilation Member from the underlying poorly-bedded mudstone with decalcified limestone nodules of the Gorse Member of the Doularg Formation.
Calcareous silty mudstone containing a brachiopod and trilobite fauna; carbonate content concentrated in bands.
At least 13m
Joan And Brown Rake Coal (Vale Of Belvoir)
JBRC
Joyce's Coal (South Derbyshire)
Johnstone Clayband Ironstone
JCI
Locally occurs as two leaves.
Callovian And Oxfordian Rocks (Undifferentiated)
JCJO
Jerrycalf Limestone
JCL
Jordanhill Blackband Ironstone
JDHB
Jordanhill New Blackband Ironstone
JDNB
Stone streaked with coal 4" (10cm). Blackband ironstone 6" (15cm).
10" (25.5 cm).
Jubilee Coal (Central Coalfield)
Jeffery's Vein
JEV
Jericho Gryphaea Bed
Change up from mudstone with large argillaceous limestone nodules and small phosphatic nodules at some levels, of undifferentiated Charmouth Mudstone Formation into mudstone with abundant Gryphaea (as described under Lithology). In reference section Copper Hill Borehole (SK94SE/56), base lies at 121.45m depth.
East Midlands: north Leicestershire to Linclonshire. Not recognised in the Charmouth Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into part of the mudstone-dominated Charmouth Mudstone Formation. Berridge et al, (1999) assert that the Jericho Gryphaea Bed, plus the overlying strata equivalent to the Pecton Ironstone Bed correlate with the '85 Marker' (Ibex Zone) (Horton and Poole, 1977) of the Charmouth Mudstone Formation of the south Midlands.
Grey mudstone beds with numerous Gryphaea, sporadic limestone nodules and thin shelly limestone beds. Fauna also includes serpulids, other bivalve species, ammonites and belemnites. Forms a slight feature, and Gryphaea conspicuous in clay soil.
1 to 3m; 2.85m in reference section.
Change up from mudstone with limestone nodules and numerous Gryphaea (as described under Lithology) into silty limestone, overlain by mudstone with ironstone nodules (equivalent to the Pecton Ironstone Bed of north Lincolnshire) of undifferentiated Charmouth Mudstone Formation; at 118.60m depth in reference section Copper Hill Borehole (SK94SE/56).
Jee's Member, Home Farm Member And Woodlands Member (Undifferentiated)
JHFW
Johnny Hall's Trees Limestone
JHTL
Juarjorge Pluton
JJDI
Gourock Granite
JJGG
Jurassic Rocks And Cretaceous Rocks (Undifferentiated)
Jukes Formation
JKES
Jee's Member
JMB
Gradational into Tuttle Hill Member. Base taken at lowest bed to show variegation and increased proportions of variegated silty and muddy partings.
From Nuneaton town centre, extending north-west for 5.2km to Worthington Farm, Mancetter (SP 3533 9199 - SP 3192 9572).
Sandstone, red to maroon fine-grained, feldspathic and glauconitic, in gently-tapering beds with bimodal tabular-planar and trough cross-bedding. Interbedded with red and green colour-variegated siltstone and mudstone.
Sharp, erosive contact with grey basal conglomerate or maroon calcareous sandstone of Home Farm Member.
Middle Jurassic And Upper Jurassic Rocks (Undifferentiated)
JMJU
Jefferson Mountain Vein Coal (Pembrokeshire)
JMVC
Jonah Coal (South Wales)
JNAH
Joan Coal (West And South Yorkshire, And Nottingham)
JNC
The Joan Coal is a thin and impersistent coal that commonly includes layers of mudstone or cannel. It has been worked in the Dewsbury district but is otherwise little economic value.
Junceum Limestone
JNCL
Bathonian And Callovian Rocks (Undifferentiated)
JNJC
Jenkin Coal (South Wales)
JNKN
Junction Limestone
JNL
Bathonian Rocks (Undifferentiated)
JNRU
Joan Sill
JOAS
John O'Groats Sandstone Formation
JOG
Drawn at the base of thin impure sandstone of the John O'Groats Sandstone Formation where it rests unconformably upon thin limestones of the Upper Caithness Flagstone Subgroup.
Caithness, Northern Highlands, Scotland, Grampian Region.
Red sandstones, with sporadic bands of flagstone, thin impure limestone and shale.
c.609m
The red sandstone of this Formation is not overlain.
John O' Gate Coal (North Wales)
JOGC
Johnston Intrusive Complex
JOIN
Not applicable; contacts mostly faulted.
Southwest Wales, Pembrokeshire.
Intrusions of quartz diorite, tonalite, granite,and pegmatite, with some hybrid rock types.
Jonathan Mudstone Member
JOMU
Jones Formation
JONES
Joanne Sandstone Member
JOSA
Jock's Pool Limestone
JPL
Jackie Parr Limestone Formation
JPLS
Proved in boreholes only. Thought to be possibly unconformable or transitional. The boundary is taken at the top of the lowermost limestone above a sandstone-dominated sequence of the Village Farm Formation.
Lilleshall (North Shropshire) [SJ73 15].
Interbedded limestone and sandstone sequence with subordinate dolomite, pebbly sandstone and claystone. Heavily pedogenic. Sandstone variable composition; limestone typically packstone or grainstone.
30.5m maximum proved (from Lilleshall L6 borehole).
Proved in boreholes only. Thought to be possibly unconformable. The boundary is taken at the top of the uppermost limestone below a sandstone-dominated sequence of the Lydbrook Sandstone Formation.
Jop Ridding Sandstone Member
JRSA
Taken at the base of the tuffaceous sandstone, unconformably overlying the siltstone and limestone sequence of the Norber Formation.
Unbedded greenish or purplish grey, medium-grained tuffaceous sandstone.
Taken at the base of the overlying siltstone and mudstone of the main part of the Sowerthwaite Formation.
Jorsalfare Formation
JRSF
Johnstone Shell Bed
JSB
Jenny Start Limestone
JSL
Joshua Mudstone Member
JSMU
Josephine Sandstone Member
JSSA
Jew Limestone And Tyne Bottom Limestone (Undifferentiated)
JTBL
Julius Mudstone Member
JUMU
Jura Quartzite Formation
JUQU
Jura Formation
JUR
Overlain only by modern sediment.
Very soft-firm silty clays with scattered gravel and pebbles.
32 metres. May be up to 300 metres in east, thins to west away from Scottish mainland.
Overlies either rockhead or Barra Formation.
Jurassic Rocks (Undifferentiated)
JURA
Jurby Formation
JURBY
Disconformably overlies diamictons, sands and gravels (that contain exotic clasts) of the Orrisdale Formation. The unit crops out along the northwest coast of the Isle of Man.
Northern part pf the Isle of Man. (50k sheets 36 and possibly 46).
Stratigraphically complex glacigenic sequence of local provenance, including laminated and massive muds with dropstones, interstratified gravel sand and mud, and muddy diamicton.
As now defined this Formation includes three members (Killane, St Patrick's and Ballateare members). It does NOT equate with the Jurby Formation of Thomas (1999), which is abandoned.
Unrecorded, but diagrams suggest >10m thick.
Unconformably overlain by peat, organic mud and calcareous marl of the Glen Balleira Formation that infills kettlehole basins.
Middle Jurassic Rocks (Undifferentiated)
JURM
Upper Jurassic Rocks (Undifferentiated)
JURU
Judy Sandstone Member
JUSA
Jura Slate Member
JUSL
Jew Limestone Member
JWL
Taken at the sharp base of limestone beds, overlying a generally conformable ganister sandstone of the Alston Formation, or north of the Lake District resting on a few metres of siltstone, mudstone and sandstone.
Exposed on the North Pennine escarpment, on the northern flanks of the Lake District massif and in the Vale of Eden, and in Teesdale, Cumbria; also in Weardale, Durham, in the Cowgreen-Maizebeck area and was formerly seen on the site of the Burnhope reservoir in Weardale.
Limestone, bioclastic, dark grey, thick wavy beds with fissile mudstone parting, and usually with abundant fossils. At many localities it contains a Saccaminopsis band about two thirds of the thickness above the base (Burgess and Holliday, 1979). A complete section is recorded from the Rookhope Borehole, but the lower 5m are intensely mineralized, whereas the upper part is black crinoidal limestone (Johnson and Nudds, 1996). In Cumbria, the member is composed of pale porcellaneous limestone with spots at the base, overlain by well bedded grey and grey-blue limestone that is crowded with Saccaminopsis fusulinaformis, and in some beds with abundant "Lithostrotion" (Eastwood et al., 1968).
Varies between 5 and 9.5m on the Alston Block; 9.1 to 12.2m north of the Lake District massif.
Overlain, generally conformably, by siltstone and mudstone of the Alston Formation.
Jersey Shale Group
JYSH
Jersey Volcanic Group
JYVO
Kilsyth No.1 Blackband Coal (Glasgow Area; Central Coalfield)
Kilsyth No.1 Blackband Ironstone
K1I
Kilsyth No.1 Blackband Under Coal
K1U
Kilsyth No 1 Blackband Under Coal overlies the Berryhills Limestone and a thin seat earth within the Limestone Coal Formation.
Glasgow -Stirling area of the Midland Valley, Scotland.
Rarely present but correlatable thin coal. Locally indistinct and commonly replaced by sandstone. Correlation value is defined as its underlying association with the 60cm Kilsyth No.1 Blackband Coal, which is widely worked.
Overlain by a "cyclothem" containing the 60cm thick Kilsyth No.1 Blackband Coal within the Limestone Coal Formation.
Kilsyth No.2 Blackband Ironstone
Ironstone.
11" (28cm).
Kilsyth No.3 Blackband Ironstone
Kame Terrace Deposits
KAMET
Kame And Kettle Deposits
KAMKE
Killearn Sand And Gravel Member
KARN
Latest Main Late Devensian to Loch Lomond Stadial.
The Killearn Sand and Gravel Member of the Clyde Clay Formation rests with angular unconformity on older Quaternary sediments or bedrock. It normally rests either unconformably or by interdigitation on the Paisley Clay and Linwood Clay members of the Clyde Clay Formation or on the Wilderness Till Formation (WITI) of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
Lower Clyde valley in the Glasgow conurbation, around the Clyde estuary and in the Loch Lomond basin in the Endrick valley.
The Killearn Borehole [NS 5100 8467] (Browne and McMillan, 1989a, Figure 8) contains the standard section of the Killearn Sand and Gravel Member (15.61 to 34.8m depth). The deposit forms an upward coarsening deltaic unit up to 17.95m and then fines up to the top of the member at a depth of 15.61m. The chief lithology is fine to medium grained sand. Silt and clay layers also occur, especially near the top and base, and there is also bands of fine gravel or sand with gravel (3cm maximum) in the upper part. They are dense to very dense and reddish brown or orange in colour. Other deposits are present locally in the Clyde valley in central and eastern Glasgow. They include deposits of beaches and river terraces as well as deltas. The stratigraphical relationships and geographical distribution of this member are illustrated in Browne and McMillan (1989a, Figures 2c, 3A, C, D and 4A, B) and also by sections described by Rose (1975) at Erskine Bridge [NS 4703 7286] and by Carruthers (1904) at Clydebank Cemetary [NS 4755 7285]. In both, the beach deposits are bedded sand and gravel.
Ranges from a thin veneer to more than 15m.
The Killearn Sand and Gravel Member of the Clyde Clay Formation is overlain unconformably by younger Quaternary sediments normally belonging to the British Coastal Deposits Group. It is also exposed at surface.
Albian Rocks (Undifferentiated)
KARU
Katrine Vein
KAV
Killey Bridge Formation
KBB
Kilburn Coal (Leicestershire, South Derbyshire, Nottingham And Derby)
KBC
Thin, but widespread, the best seam for nationwide correlation.
Kilbride Limestone Member
KBDL
Kintyre Shell-Beds
KBDS
Knockshinnoch Blackband Ironstone (New Cumnock)
KBI
Kingbridge Limestone
KBL
Kibblestone Formation
KBN
Interpreted to be disconformable at the base of the lowest sandstone with aeolian characteristics lying above pebbly, more poorly sorted (water-laid) sandstones/siltstones of Kidderminster Formation.
South of Swynnerton Fault in the Moddershall-Stone area, Staffordshire.
Sandstone, grey-ochreous mostly medium-grained, dune-bedded, cross-stratified with "pin-stripe" lamination. Well sorted, non-pebbly, mica very rare.
Conformable at base of lowest siltstone/mudstone of the overlying Maer Formation.
Kilburn Sill
KBNS
Kelly Burn Sandstone Formation
KBS
Passes downwards into the Skelmorlie Conglomerate Formation.
Great Cumbrae-Inverclyde area, west of the Largs Fault Zone, on sheets 21, 22 (uncertain), 29, 30(W).
Mainly red, cross-bedded, pebbly sandstone with subordinate conglomerate beds.
Apparent disconformity at the base of the Kinnesswood Formation.
Kilblane Sand And Gravel Formation
KBSG
Unconformable on older glacigenic sediments, such as till of the Gretna Till or Langholm Till formations, or sandy and silty glaciolacustrine deposits of the Cullivait Silt Formation; locally rests directly on bedrock.
Northern margin of the Solway Firth, principally between Dumfries and Gretna, but extending inland to beyond Dalswinton, Lochmaben, Lockerbie and Canonbie.
Three types of landform are recognised associated with these deposits: Sinuous discontinous Esker ridges (single strand), typically 10-20m in height and up to c 1km in length. Elongated Mounds and hummocky topography with intervening poorly drained hollows (fluted kame and kettle topography). Flat-topped kame terraces standing up to 20m above the adajacent river floodplains, sandar plains, glaciofluvial fans and lower glaciofluial terraces flanking valleys infilled with Holocene fluvial and marine sediments. (All generally mapped as Glaciofluvial Sheet Deposits).
Esker ridges ~ Glaciofluvial Subglacial Deposits and Glaciofluvial Ice-contact (Esker) Deposits. Fluted kame and kettle mounds and ridges ~ Glaciofluvial Ice-contact Deposits. Kame terraces, Sandar plains, Glaciofluvial fans and terraces ~ Glaciofluvial Sheet Deposits.
Sand and gravel, with cobbles and pebbles predominantly of Permo-Triassic sandstone and Lower Palaeozoic sedimentary and volcanic rocks in a matrix of medium- to coarse-grained sand; typically pale yellow to reddish brown. Greywacke and granitic clasts are common in subordinate amounts. Esker deposits are typically poorly sorted, cobbly and bouldery, well-bedded with high-angle cross-bedding. Some interbeds of coarse sand. Fluted kame and kettle deposits are typically moderately sorted, thickly bedded, cobbly, commonly in upward-fining steeply tabular cross-bedded or trough cross-bedded units. Glaciofluvial Sheet deposits are typically thickly bedded well-sorted gravels, with interbeds of coarse- to medium-grained sand. Commonly horizontally bedded, but tabular high-angle cross-bedded units common. The upper surface is commonly involuted and beds of laminated and rippled sandy silt and clay with dropstone cobbles are present locally, indicating the presence of temporary glacial lakes.
Variable, typically 3-10m, esker deposits may be > 15m thick, the worked spreads of ice-contact deposits may exceed 10m in thickness locally; kame terrace deposits and sandar are typically 2-8m thick.
Locally overlain by Holocene alluvial and raised marine deposits, and peat. Some exposures in sheet deposits are capped by gravelly friable pale brown to reddish brown diamicton (supraglacial flow till) typically 0.3-0.6m in thickness). Involutions and possible frost-wedge casts are present in the upper parts of terraced and kame-terrace deposits.
Kirk Burn Silt Formation
KBSI
Lies on bedrock (Middle Old Red Sandstone) or older Quaternary deposits (Crovie Till Formation or Whitehills Glacigenic Formation).
Portknockie to New Aberdour.
Interbedded silt, clay and fine-grained sand, yellowish brown to dark grey. Local ferruginous nodules. Glaciolacustrine. Very locally interbedded with, or overlain by, thin diamicton (Carnhash Till Member).
Surface, or overlain by younger deposits of Holocene/Flandrian age (peat, alluvium, etc).
Keighley Bluestone
KBST
Kimmeridge Clay Formation
In the type area, at the base of the Inconstans Bed, which also marks the Oxfordian-Kimmeridgian Stage boundary.
(Outcrop) - Dorset to North Yorkshire. Offshore the Formation is considered to extend from the Kimmeridgian to the Late Ryazanian, and forms part of the Humber Group.
Mudstones (calcareous or kerogen-rich or silty or sandy); thin siltstone and cementstone beds; locally sands and silts.
To c.500m
At the base of the 'Portland Sand'. In the type area, this has traditionally, but not unanimously, been taken at the base of the Massive Bed, which also marks the Kimmeridgian-Portlandian stage boundary. In other areas, taken where silty/sandy mudstones pass up into argillaceous sandstones/siltstones (possibly marked by a spring-line) or, where non-sequential, at the base of the Upper Lydite Bed.
Knucklas Castle Formation
KCA
Kimmeridge Clay Formation And Ampthill Clay Formation (Undifferentiated) [Obsolete Code: Use Amkc]
KCAM
Knucklas Castle Beds [Obsolete Code: Use Kca]
KCB
Kilmuir Conglomerate Formation
KCF
Conformable lower contact on Den Siltstone Formation.
Red-purple cobble and boulder conglomerate.
500 metres +.
Conformable upper contact with Raddery Sandstone Formation.
Kailblades Coal (Lothians)
KCG
Kilchattan Formation
KCH
Kirton Cementstone Beds
KCM
Lower Bajocian, Ovalis Zone.
Conformable contact between the underlying less argillaceous limestone (peloidal or ooidal wackestones and packstones - Santon Oolite) and calcareous siltstone (Raventhorpe Beds) succession, generally lacking mudstone interbeds, overlain by interbedded calcareous mudstone and argillaceous limestone of the Kirton Cementstone Beds.
BGS 1:50 000 sheets 72, 80, 89, 102 and possibly 114. Lincoln area to Market Weighton.
Silicate- and calcareous mudstone, interbedded with thin and more or less argillaceous limestones (calcilutite and shelly and peloidal wackestone). Locally includes coralliferous limestone bodies (knoll reef).
[Compiler's notes] This entry defines the Kirton Cementstone as mapped on sheets 72, 80 and 89. However it should not be perpetuated in any formal lithostratigraphical review of the Lincolnshire Limestone. Whilst it may remain a valid stratigraphical unit, the member status is inappropriate. Following stratigraphical revision of the Lincolnshire Limestone Formation, it forms part of the Lower Lincolnshire Limestone Member which (with Upper Lincolnshire Limestone) is one of the two constituent members of the Formation.I recommend that the Status of the unit be downgraded to Kirton Cementstone Beds or (possibly) Kirton Beds (formal or informal), although the latter term has been used in a wider sense, for some authors equating with the whole of the Lower Lincolnshire Limestone. Either way, the Member suffix should be dropped. As an informal unit the parent should be Lower Lincolnshire Limestone Member. [M G Sumbler 25/09/05]
0 to c.9.5m
Disconformable, commonly channelled contact between interbedded calcareous mudstone and argillaceous limestone of the Kirton Cementstone and high energy ooidal limestones of the overlying Upper Lincolnshire Limestone Member [Hibaldstow Limestone/Cave Oolite]. Near its northern limit only, disconformable contact with ferruginous sandy calcareous sediments of the Hunstanton Formation (Cretaceous).
Kirton Cementstone Beds (Knoll-Reef)
KCMK
Conformable contact between the underlying mudstones of the Kirton Cementstone or peloidal and ooidal wackestones and packstones of the Scawby Limestone and coralliferous limestone of the knoll-reef.
BGS 1:50 000 sheets 89, 102 and 114; North Lincolnshire, Lincoln to the Humber,
Limestone (calcilutite and wackestone), commonly accummulated around a framework of corals, bivalves and other organisms, forming localised lenticular bodies typically less than 100m in lateral extent ("knoll-reef").
[Compiler's notes] I am unclear why this unit has acquired a quasi-formal name and needs a Lexicon entry. It is not really a lithostratigraphical unit, just a lithological type within the Kirton Cementstones. As such, it is fairly sensibly indexed "K" (= Knoll) on sheet 80 and 89. I would have called it "knoll-reef limestone" or such-like on the map. [M G Sumbler, 25/09/05]
Conformable contact between coralliferous limestone of the knoll-reef and overlying mudstones of the Kirton Cementstone.
Kilcoo Sandstone Formation
KCOO
Campanian Rocks (Undifferentiated)
KCRU
Kip Carle Sandstone
KCS
Near Cove, East Lothian.
Coarse yellow false-bedded sandstone, with plant remains and thin coal.
Kimmeridge Clay (Skye)
KCSK
Kirkland Conglomerate Formation
KDC
Unconformable on Balcreuchan Group, Ballantrae Complex.
Stinchar Valley area, Girvan. Nature of lateral boundaries unknown.
Pebble, cobble and boulder conglomerate.
Conformably overlain by Confinis Flags Formation/Auchensoul Limestone Formation/Auchensoul Bridge Mudstone.
Kidderminster Formation And Chester Pebble Beds Formation (Undifferentiated)
KDCP
Kirkland Formation
KDF
Not seen
Restricted to the Cross Fell and Teesdale inliers, Cumbria
Grey mudstone and siltstone with subordinate beds of brown weathered, pyritic mudstone and dark blue grey calcareous mudstone, interbedded with thick units of volcaniclastic rock and locally intruded by altered basalt and andesite sills [previously lavas]
At least 1000m
Knightswood Gas Coal (Glasgow Area; Central Coalfield)
KDG
Kilmarnock Diamond Coal (North Ayrshire)
KDIC
Kidlaw Plug (And Associated Vent)
KDLAW
Kidderminster Formation
KDM
Unconformable on the Bridgnorth Sandstone, the Clent Breccia or older rocks.
Worcestershire, West Midlands, south Staffordshire and west Warwickshire. (Worcester Basin, Stafford Basin, Knowle Basin).
Pebble conglomerates and reddish brown sandstones. The sandstones are cross-bedded and pebbly. The conglomerates have a reddish brown sandy matrix and consist mainly of pebbles of brown or purple quartzite, with quartz conglomerate and vein quartz. (Mitchell and others, 1962).
0 to 200m
Passage upwards into the Wildmoor Sandstone Formation, the upper boundary being placed arbitrarily above the highest pebble bed in the sequence.
Kingsand Rhyolitic Formation
KDR
Unconformably overlies steeply dipping Lower Devonian strata.
Three isolated outcrops within the Rame Peninsula, south-west of Plymouth.
Brownish to purplish pink rhyolite lava, brecciated in part, with reddish brown conglomero-breccia of the Sandway Cellar Conglomerate Member.
Kindroughad Formation
KDRD
Possibly cold OIS 4, 6 or 8 (between Saalian and Weichselian).
Unconformably overlies a bedrock platform at between 41 and 53m below OD and partly overlies the Ayre Formation. At the type section of the Kindroughad Formation, it overlies coarse grained gravel and clay of the Ayre Formation.
Sand, gravel and diamicton of northern origin (known only from boreholes).
c.60m at its type section.
Base of the Shellag Formation. At the type section of the Kindroughad Formation, the base of the Shellag Formation comprises a clayey diamicton with cobbles.
Kildress Limestone Member
KDS
Interpreted to be conformable on the unnamed lower red sandstone/conglomerate succession in Derryloran Formation (boundary not seen).
Kildress, County Tyrone, Northern Ireland.
Limestone, dolomitic, silty and ferrugenous.
Interpreted to be conformably overlain by white, soft quartz sandstone (Gortnagross Sandstone Member); boundary not seen.
Kennedy's Pass Breccia Formation
KDY
Ordovician (Early Arenig).
Faulted against the Brandy Craig Formation.
Non-stratified, monomict, brown and green aphyric lava-breccia with spporadic isolated pillows and intact lava-masses.
c.115m
Faulted against younger rocks of the Barr and Ardmillan groups (Llanvirn - Caradoc).
Keadew Formation
KEAD
Kennox Blackband Coal (Douglas)
KEBC
Kessock Bridge Silt Formation
KEBR
Conformable contact with Ardersier Silt Formation.
Area around the Inner Moray Firth and Beauly Firth, Inverness. Geological Sheet 84W (Fortrose).
Clayey silt and fine-grained sand with well dispersed, angular lithic pebbles, chiefly of psammite and sandstone. Shell fragments particularly common towards the top of the unit. Contains a mid-boreal, shallow water fossil assemblage of Windermere Interstadial age.
Erosional contact with Longman Gravel Formation.
Kelly Coal
KEC
Kettlewell Crag Member
KECR
Keenaghan Shale Formation
KEEN
Rests unconformably on the Moine Lough Derg Group psammites.
Belleek-Kesh area of the northwest Carboniferous basin of Ireland.
Shale, dark grey, silty, very micaceous, non-calcareous; thin beds of grey-blue, muddy unfossiliferous micrite and grey, coarse-grained, calcareous sandstone.
Conformable and gradational with overlying Ballyshannon Limestone Formation.
Keirs Limestone
KEIR
The type locality was at Keirs Limeworks, about half a mile southwest of Waterside, Dalmellington, Ayrshire.
Keith Intrusions
KEITH
Kennox Jewel Coal (Douglas)
KEJ
Kennox Kiltongue Coal (Douglas)
KEK
Kent's Thick Coal (West And South Yorkshire)
KEKC
Cenomanian And Turonian Rocks (Undifferentiated)
KEKT
Kilmarnock Ell Coal (North Ayrshire)
KELC
Kennox Lower Drumgray Coal (Douglas)
KELD
Kelhope Dyke
KELH
Kesgrave Formation And Lowestoft Formation (Undifferentiated)
KELO
Composite deposit: pebbly sand, gravel and silt (Kesgrave Formation), with (Lowestoft Formation), primarily a stiff, bluish-grey clay when fresh; orange-brown to brown where weathered; with varying amounts of chalk, flint, silt and sand derived mostly from Jurassic and Cretaceous strata. [Generic description: from East Anglian data].
Keills Limestone Member
KELS
Kelso Subsuite
KELSO
Strathkelvin Clay And Silt Member
KELV
Unconformity on older Quaternary strata including the Broomhouse Sand and Gravel Formation and Wilderness Till Formation.
Known currently in Strath Kelvin and possibly in the Bonny Water valley around Banknock.
The typical lithological association of the Strathkelvin Clay and Silt Member of the Kelvin valley is of silty clay with many layers of silt and locally of sand. Interbedded peat is also found. Bands relatively rich in organic detritus also occur. In general the clays are dark brown. The deposits are either of floodplain or lacustrine origin.
Veneer to over 9m
Unconformity below younger Quaternary strata including the Law Sand and Gravel Member on which it can also rest conformably. The Clippens Peat Formation may underlie and overlie this member.
Kennox Musselband Coal (Douglas)
KEM
Kempton Marl
KEMA
Kennox Mid Coal (Douglas)
KEMI
Kemnay Pluton
KEMN
Kerr Moraine Formation
KEMO
Generally conformable with the Gretna Till Formation, or rests unconformably on bedrock.
Interbedded diamicton, boulder gravel, sand, silt and clay. Typically reddish brown with clasts of red sandstone dominant, but locally yellowish brown with clasts of yellow sandstone dominant.
Kennox Nine Foot Coal (Douglas)
KEN
Kent's Thin Coal (West And South Yorkshire)
KENC
Kennelburn Ironstone
KENI
Blackband 1'3" - Blaes with 3" clayband rib 1'3" - Coal 10" - Blaes with clayband lenticles up to 6" in thickness; base not seen.
1.2 metres.
Kennel Sandstone Formation
KENN
Keith-Portsoy Granite
KEPO
Keristal Member
KERI
Stratigraphical with undivided Lonan Formation, marked by change from a sandstone-dominated facies to a mudstone-dominated facies (in the Lonan).
A thick-bedded quartz-arenite sandstone.
From 5 m to 10 m thick.
Stratigraphical with undivided Lonan Formation or Santon Member.
Kerrera Sandstone Formation
KESA
Argyll, Scotland.
Mainly green and red sandstones with conglomerates and subordinate siltstones, mudstones and limestones.
Up to 128m thick on Kerrera.
The incoming of the Lorn Plateau Volcanic Formation, locally laterally interfingering with the sandstones.
Kesgrave Formation (A) [Obsolete Name And Code: See Kgca]
KESF
Pebbly sand, gravel and silt. [Generic description: from East Anglian data].
Kennox Upper Drumgray Coal (Douglas)
KEUD
Kennox Virtuewell Coal (Douglas)
KEV
Kennox Wee Coal
KEW
Kempsey Formation
KEY
Not known; only proved in Kempsey Borehole; western limit is East Malvern Fault.
Lithic sandstone and tuffaceous siltstone, purple-green, with poorly sorted angular to subrounded clasts of tuff, agglomerate and acid to intermediate lava (Whittaker, 1980).
Proved thickness of 705.6m (2318 feet).
Unconformity beneath Permian Bridgnorth Sandstone.
Knock Farril Conglomerate
KFC
Kilfillan Formation
KFL
Very thickly bedded, massive greywacke units (up to 100 metres thick) separated by relatively thinly bedded greywacke and silty mudstone.
Not defined due to faulting.
Kilmarnock Five-Quarter Coal (North Ayrshire)
KFQ
At change from coal to other strata at 86.14 metres in Warrix No.1 Borehole.
Ayrshire coalfield.
Coal between Major and Linn Bed Coals.
Variable, about 1.00 metre in type section.
At change from coal to other strata at 85.10 metres in Warrix No.1 Borehole.
Kinderscout Grit
Drawn at the base of the lowermost thick sandstone of the Kinderscout Grit, which rests with an unconformable base upon a mudstone/siltstone dominated succession of the Millstone Grit Group (undivided) or Grindslow Shales of Derbyshire.
Northern England:- Yorkshire, Lancashire, Derbyshire.
Medium- to very coarse-grained sandstone with shale pellets, feldspathic, massive or cross-bedded and frequently pebbly sandstone, shales and sandy shales, siltstone and sandstone with shale. Can be subdivided into the Lower and Upper Kinderscout grits throughout most of Yorkshire, where the Butterly Marine Band occurs between the sandstone leaves.
Approximately 170 m thick.
Drawn at conformable upward passage from sandstone of the Kinderscout Grit to a marine band containing Bilinguites gracilis of the Marsden Formation.
Kilmarnock Gas Coal (North Ayrshire)
KGC
Kesgrave Catchment Subgroup
KGCA
The unit is restricted to the Thames Valley, Essex and Suffolk. BGS 1:50 000 Sheets 206-208, 221-225, 239-242, 255-257. It does not extend into Norfolk.
Encompasses fluvial, lacustrine and organic deposits of the pre-diversionary River Thames, and the pre-glacial soils developed on such deposits. Most of the surviving deposits are fluvial gravels, with sedimentary structures indicating deposition by a braided river. Lacustrine silts and clays and organic peats are uncommon. The gravels are characterised by quartz and quartzite from the Triassic, Carboniferous and Devonian rocks of the West Midlands, Welsh Borderland and possibly southwestern Pennines, and by felsic volcanic rocks from northern Wales. The presence of mega-erratics and glacially-fractured sand grains indicate glacial erosion in the headwater regions of the river. The fluvial gravels occupy terrace levels and formations and members are defined on the basis of altitude and pebble clast content. The members comprise bodies of cross-bedded and massive, moderately sorted sand and gravel. The aggradations are generally entrenched into bedrock with a difference in surface elevation of at least 5m. The upper part of the gravels which dominate the subgroup are commonly affected by pedogenesis. The Valley Farm Soil is a rubified and clay-enriched horizon affecting the top 1.0-1.5m and indicating warm interglacial conditions. The Barham Arctic Structure Soil is a complex pedogenic horizon affecting the topmost 1.0-1.5m of the subgroup and of the Valley Farm Soil (Rose and Allen 1976, Rose et al 1985).
c.21.3m aggregate thickness with individual terrace aggradations typically 5-12m thick.
Commonly overlain by Mid Pleistocene glacigenic deposits. Upper boundary may be difficult to determine where overlain by glaciofluvial sand and gravel, but the presence of more angular clasts, chalk, and poorer sorting in the latter is usually helpful. The uppermost 1.0-1.5m of the subgroup is commonly marked by the Valley Farm Soil and/or the Barham Arctic Structure Soil.
King Coal (South Lancashire)
KGCO
Kenley Grit Member
KGR
Knockgerran Shales
KGS
Kilmarnock Tourha' Coal (North Ayrshire)
KHA
Kirkham Member
KHAM
Confined to scattered dissolution pockets on the Carboniferous Limestone outcrop of the Peak District, from north of Ramshorn [SK 088 463] to south of Monyash [SK 134 635].
White, pink and yellow siliceous sands and pebbly sands.
Kershopefoot Basalt Beds
KHB
Not seen but presumed to be conformable with sedimentary rocks of the Fell Sandstone Formation. Underlain by sedimentary strata, mainly sandstones of the Fell Sandstone Formation.
Scattered outcrops east of Langholm, Dumfries and Galloway between 340000 583000 and 350000 583000.
Porphyritic olivine-basalt lava. Neither top, nor base is exposed in the Langholm District. As described in the Langholm memoir it is unclear whether associated "sediments" are interbedded with or below the basalt at the type locality of Kershope Quarry, but they probably sit at the base of the basalt. The lithology of the KHB is therefore defined only as olivine-basalt.
Not seen but presumed to be conformable with sedimentary rocks of the Fell Sandstone Formation. Overlain by sedimentary strata, mainly sandstones of the Fell Sandstone Formation.
Knockhill Blackband Ironstone
KHBB
Kelhead Breccia Member
KHBR
Unconformable on strata of the Tyne Limestone Formation of Carboniferous age, or Early Palaeozoic rocks.
Localised distribution in Annandale, south-west Scotland, on Sheets 6W, 6E, 10W and 10E.
A coarse-grained, poorly sorted, limestone breccia, mostly derived from local Carboniferous Limestone, with minor sandstone. The Kelhead Breccia is considered to be a local representative of the BRockram within the Annan sub-basin of the Carlisle Basin. Although Holliday et al. (2001) included thin (<4m) basal breccias of the Annan sub-basin within the Eden Shales Formation, it is recommended that the significantly thicker and lithologically distinctive Kelhead Breccia be assigned as a member of the Brockram.
15 m thick.
Locally unconformably overlain by strata of the Eden Shales Formation.
Knockshinnoch High Coal (South Ayrshire)
KHC
Kilsyth Coking Coal (Glasgow-Airdrie)
KHCC
Kilsyth Cloven Coal
KHCL
Kilnholme Coal
KHCO
Kippet Hills Gravels Formation
KHG
Generally unconformable on bedrock or older tills (eg Pitlurg Farm Till Formation). Locally interbedded with Hatton Till Formation.
Gravels and sands. Besides local rock types (eg psammite) clasts include distinctive Mesozoic/Tertiary limestones and mudstone/shell fragments of Red Crag affinity from the Aberdeen Ground Formation.
15m or more locally
Occurs to surface or capped unconformably by the Hatton Till Formation or postglacial deposits.
Kelsey Hill Gravels (Beds)
KHGB
Muddy sand and gravel with subordinate smooth red-brown clay. [Generic description: 1:50 k map margins].
Khantore Pluton
KHGR
Kirk Hill Vent
KHIL
Kirkhill Church Sand Member
KHLCH
The basal boundary of the deposit is unconformable, sharp, channelled surface cut into underlying dark grey to black diamicton of the Corse Diamicton Member (Whitehills Glacigenic Formation).
Buchan, northeast Scotland. The member is only known within the immediate vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) on Sheet 87W (Ellon).
Sand, pale yellow brown, slightly gravelly, fine and medium, quartzose. Sparse, rounded, quartzite and psammite metasedimentary pebbles. The deposit displays a thin and medium horizontal bedding and some planar cross bedding indicating palaeoflow to the west and southwest. Brown silt laminae are sporadically present. Heavy mineral suite similar to that of the Corse Diamicton Member. Interpreted as glaciofluvial outwash.
To 1.5m
The upper boundary of the formation is generally the present ground surface.
Kirkhill Palaeosol Bed
KHLPS
Hoxnian (MIS 11) to Wolstonian (?MIS 7).
The lower boundary of the palaeosol bed is gradational over c.0.5m where pedogenically modified sand passes downwards into relatively unmodified sand of the Pitscow Sand and Gravel Formation.
Buchan, northeast Scotland. The palaeosol bed is only known in the immediate vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) and Leys Quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon).
Pale grey to white gravelly sand. The bed consists of an upper horizon (Ea) pale grey, up to 0.19m thick. This merges downwards into a second horizon (Bs), up to 0.07m thick and greyish brown with some mottling. Both horizons are developed in slightly gravelly, coarse, pale olive-brown sands of the Pitscow Sand and Gravel Formation. The single or multiple Fe pans are developed in sands below the Bs horizon. In the Ea horizon felsite clasts are typically bleached and softened. Organic carbon and Fe have been translocated down profile into the Bs horizon. Interpreted as a truncated podzolic soil profile formed under humid temperature climate conditions with some superimposed cold climate features.
Up to -1.0m of pedogenically modified gravelly sand has been recorded.
Typically the upper boundary of the palaeosol bed is an undulatory erosion surface with an amplitude of up to 0.20m and is unconformably overlain by organic sands of the Swineden Sand Bed. On the margins of channels/basins cut into bedrock seen in Kirkhill Quarry (infilled), units up to the Rottenhill Till Formation may rest unconformably on the truncated Kirkhill Palaeosol Bed.
Knockshinnoch House Coal (New Cumnock, South Ayrshire)
KHO
Kingshouse Breccias
KHOB
Kingshouse Tuffs
KHOT
Kenilworth Sandstone Formation
KHS
The base is marked by the incoming of thick sandstones above the argillaceous Tile Hill Mudstone Formation. These beds form a strong north-facing scarp from Hurst Farm [SP 28 74] through Gibbet Hill [SP 30 75] to Stoneleigh [SP 33 72].
Kenilworth area, southern part of the Warwickshire Coalfield.
Sandstone, red-brown with subordinate thin beds of red mudstone; towards the base, conglomerate is locally present (Gibbet Hill Conglomerate), and lenses of breccia occur toward the top of the formation. Pebbles in the conglomerate comprise mostly 'Valentian' sandstone/quartzite and red Carboniferous chert; other quartzites, vein quartz, Carboniferous limestones and Precambrian tuffs occur in minor amounts (Shotton, 1929). Breccia clasts comprise mudstone, siltstone and ironstone with sparse quartzite, limestone and red chert (Old et al., 1987).
c. 100m
The top is taken at the base of thick red mudstone of the overlying Ashow Formation.
Knott Hill Formation
KHSA
Gradational - transition from undivided Skiddaw Group silty mudstone over 10-20m through laminated sandy siltstone into sandstone.
Within 1km of summit of Knott Hill.
Sandstone, thin-bedded and laminated distal turbidites.
Unknown. Top not seen, younger part of formation eroded or faulted out.
Kilsyth Sump Coal (Glasgow)
KHSC
Kite Hill Tuff Member
KHT
Not exposed, but believed to be a sharp, apparently conformable contact with underlying grey-green, finely laminated volcaniclastic mudstones and siltstones of the Blackbrook Reservoir Formation.
Outcrops in northwest of Charnwood Forest between Charnwood Nature Reserve (SK 4670 1620) and Strawberry Hill Plantation (SK 4550 1718).
Massive to flaggy, thick to thinly bedded lapilli tuffs and volcanic breccias.
About 330m, Grades laterally south-eastwards into Benscliffe Breccia Member.
Upwards conformable, gradation into stratified volcanic breccias and tuffs of the undivided Charnwood Lodge Volcanic Formation; contact not exposed, but defined at first occurrence of very coarse or lapilli-grade tuffs.
Kelman Hill Ultramafic Volcanic Member
KHUV
Base of lowest recognisable ultramafic sheet in the Blackwater Formation.
500m-wide outcrop extending from Meikle Firbriggs [NJ 355 293], across the Black Water and along the Deveron Valley to Burn of Succoth [NJ 428 358], Cabrach area, Moray District. 1:50 000 sheets 75E and 85E.
Fine-grained pale green ultramafic rocks with abundant tremolitic amphibole, commonly fragmented/brecciated; and some metabasalts, aphyric but rarely pyroxene-phyric. Interbanded with greywacke grits and slaty to phyllitic pelites.
c. 400 to 500m (based on outcrop width with no allowance for probable folding).
Top of highest recognisable ultramafic sheet in the Blackwater Formation.
King Blackband Ironstone (Glasgow)
KIBI
Knockshinnoch Index Coal (New Cumnock)
KIC
Kirkton Clay Member
KICL
Not observed, but probably comformable on the Finglack Till Formation.
Ardersier Peninsula and the southern shore of the Inner Moray Firth.
Clay,silt and silty sand, thinly horizontally interbedded and interlaminated rhythmically, pale yellowish brown to orange, stiff. Individual beds are generally graded. Convolute bedding is common in silt beds. The beds are stacked into packages, probably glaciomarine cyclopels, 0.3 to 0.8m thick.
Kirkbean Cementstone Member
KICM
Rests on basalt lavas of the Birrenswark Volcanic Formation.
Kirkbean area, Southerness, Kirkcudbrightshire, south-western Scotland, (Southern Uplands).
Thinly interbedded greenish-grey carbonaceous siltstone and argillaceous limestone (cementstone).
Not exposed, probably gradational with the Southerness Limestone Formation.
Kilmorack Conglomerate
KICO
Kildonnan Member [Duplicate Code: Use Kildn]
KIDO
Kidston Group
KIDS
Kilwinning Ell Coal (North Ayrshire)
KIE
Kingston Columnar Flints
KIFL
Kirkaby Gneiss Formation
KIGN
Kingswood Great Coal (Bristol Area)
KIGT
Kilbarchan Sills
KILBN
292 -302 Ma, based on recent Ar/Ar dates of related bodies (Stephanian-Early Permian) (fide M A E Browne, 08/02/2007).
Kiltongue Coal (Lanarkshire, Central Coalfield)
KILC
Kildonan Psammite Formation
KILD
Kildonnan Member
KILDN
Kilchrist Hybrids (Skye Eastern Red Hills Centre)
KILH
Kingswood Little Coal (Bristol Area)
KILI
Kilmaronock Silt Member
KILK
The Kilmaronock Silt Member of the Strathendrick Formation rests by transitional passage on the underlying Buchanan Clay Member (Clydebank Clay Formation) or with angular unconformity on other, older, Quaternary sediments or bedrock.
The Kilmaronock Silt Member of the Strathendrick Formation is only known to occur in its type area in the Loch Lomond basin including the lower part of the Endrick valley.
The Mains of Kilmaronock Borehole (Browne and McMillan, 1989, Figure 6) contains the standard (and only) section in the Kilmaronock Silt Member (13.6-19.95m in depth). The typical lithology is a very thinly bedded lacustrine silt with many clayey silt and silty clay layers. Sand layers are also common. The deposits are brown, dark brown, browish grey and grey, with plant remains and locally with dark organic-rich bands. Grains and flecks of vivianite are present throughout. The deposit is of a firm and locally stiff consistency and medium to low plasticity.
Veneer to over 6 metres.
The Kilmaronoch Silt Member is only known to be overlain conformably by the Endrick Sand Member forming the lower part of an upwards coarsening unit.
Kilchrist Member
KILL
Kiltongue Musselband Coal
KILM
Kiln Member
KILN
Kilnhurst Coal (Yorkshire)
KILNC
Kilchrist Pyroclastic Rocks (Skye Eastern Red Hills Centre)
KILP
Kilmalieu Psammite
KILPS
Kilskeery Group
KILS
Faulted contact excising base of Topped Mountain Sandstone Formation, not seen.
The south-western sector of the Fintona Block, Northern Ireland.
Consists of three formations: Topped Mountain Sandstone Formation (lowest), Ballyreagh Conglomerate Formation and Ballinamallard Mudstone Formation.
About 2500m
Faulted contact excising top of Ballinamallard Mudstone Formation; not seen.
Killuney Conglomerate Formation
KILU
Kilwinning Main Coal (North Ayrshire)
KIM
Kincardine O'Neil Intrusion
KINC
Kinnegar Grits Formation
KING
King Coal (Glasgow Area; Central Coalfield)
KINGC
Kinlocheil Quartzite Formation
KINQU
Kilchiaran Phyllite Formation
KIPH
Kirkroad Coal
KIR
Kirnhole Coal (Ayrshire)
KIRN
Kirtomy Gneisses
KIRY
Kirklinton Sandstone Formation
KIS
Conformable base on St Bees Sandstone.
BGS sheets 11, 16, 18, 22 and 23
Fine- to medium-grained red, locally white, strongly cross-bedded sandstone with abundent millet-seed grains.
Up to about 90m
Conformably overlain by Stanwix Shales Formation.
Kingsteps Sandstone Formation
KISA
South-east of the Great Glen Fault, around Nairn.
Comprises of a basal breccio-conglomerate overlain by yellow and reddish grey, cross-bedded, coarse grained sandstones commonly containing mudstone rip-up clasts and associated pebbly beds. Thin beds of marly mudstone are sporadically distributed, together with thin conglomerates. The whole unit is calcareous throughout.
Kilwinning Stone Coal (North Ayrshire)
KIST
Kittlepurse Coal (Lothian)
KIT
Kilchiaran Phyllite Formation [Incorrect Code: Use Kiph]
KITH
Kilsby Tuff Member
KITU
Kilmarnock Jewel Coal (North Ayrshire)
Kirkley Bank Formation
KKB
Base of the calcareous siltstone succession or volcanogenic sedimentary succession (Low Scales Beck Member) that rests directly on the underlying Borrowdale Volcanic Group succession.
Low Furness and Lake District, Windermere Supergroup outcrop, Cumbria.
Predominantly calcareous siltstone and calcareous mudstone, with nodules, beds and members of mostly impure limestone.
120-150m (Rose and Dunham, 1977 - see bibliography)
Top of calcareous siltstone succession that is succeeded by either nodular bedded, micritic limestone of the Broughton Moor Formation or rhyolitic tuff that forms the High Haume Volcanic Formation.
Kirkburton Sandstone
KKBS
Sharp upward change in a conformable succession from predominantly grey mudstone/siltstone to sandstone - base of first sandstone above the Black Bed Coal.
Southeast of Huddersfield in Lepton [SE2030 1540] - Kirkburton [SE2450 0350] - Penistone [SE2450 0350] area West Yorkshire.
A medium-bedded, very fine- to medium-grained, ripple cross-laminated, micaceous, buff to pale brown sandstone, interbedded with greenish grey siltstone.
0 to 20m
Sharp upward change in a conformable succession from sandstone to predominantly grey mudstone - top of last sandstone bed below the Crow Coal.
Kirkcolm Formation
KKF
Southern Uplands of Scotland between Leadhills Fault and Glen App/Carcow Fault).
Faulted (Glenn App Fault/Carcow Fault)
Kirkhill Conglomerate Member
KKH
Incoming of the predominantly conglomerate succession belonging to the Kirk Hill Conglomerate Member above the Newside Arenite Member of the Westgate Formation
Mainly conglomerate, with quartzite pebbles most common, but also chert, vein quartz and igneous rocks set in an olive-grey and brownish grey sandstone matrix; some sandstone lenses.
The top of the predominantly conglomerate succession belonging to the Kirk Hill Conglomerate Member of the Westgate Formation below the Eastgate Sandstone Member
Kirkhope Formation
KKHP
Llandovery: turriculatus Biozone to griestoniensis Biozone.
Turbidite (wacke) sandstone with variable proportion of mudstone/siltstone. Sandstone typically fine- to medium-grained but ranging from very fine- to coarse-grained; generally medium- to very thick-bedded (commonly up to 2m) over thicknesses of tens of metres interspersed with units up to a few metres thick that are very thin- to thin-bedded; usually with interbedded mudstone in very thin to thin beds, but passes laterally into sections with little interbedded mudstone that include units, tens of metres in thickness, of coarse-grained, massive garnetiferous sandstone. Sandstone and siltstone are typically greenish grey when fresh, pale brown weathering. Distinguished from the Selcoth Formation (Ettrick Group) to the north by the variable proportion of mudstone and the occurrence of relatively thick-bedded to massive, locally coarse-grained garnetiferous sandstone. The Kirkhope Formation is younger than the Selcoth and Thornylee formations. Distinguished from the Glendearg Formation (Ettrick Group) to the south by the common occurrence of very thick massive units of coarse-grained garnetiferous sandstone, although partly overlapping in age range suggesting some lateral equivalence. The Kirkhope Formation is distinct from the Glenbearg Formation in Gbase Sr data, although this distinction is less evident in sandstone whole rock composition.
Uncertain, likely to be at least several hundred metres.
Conformable sedimentary contact with rocks of the Moffat Shale Group.
Kirklatch Marine Band
KKMB
Shale with ribs of clayband ironstone, Sanguinolites and other bivalves.
0.15m in type section
Knocknairshill Member
KKS
Interbedded with grey mudstone and dolomitic limestone (cementstone) of the underlying Ballagan Formation. The lower boundary is picked where dolomitic limestone and grey mudstone beds are absent and at the base of the first thick interval of sandstone containing medium, fining-upward beds of brownish grey fine-grained sandstone and reddish brown silty mudstone.
Greenock district south of the River Clyde to the east and west of Largs Fault Zone, Strathclyde, Scotland.
Mainly white or pale red cross-bedded sandstone with beds of red-brown silty mudstone, nodules and beds of pedogenic limestone (Paterson and Hall, 1986). The member comprises well-developed upward-fining fluvial cycles including pedogenic carbonate (cornstone) within the mudstone deposits in most cycles (Paterson and Hall, 1986; Paterson et al., 1990).
c.130m
Boundary of the unit with the white-cross-bedded sandstones of the overlying Gourock Sandstone Member is mapped in the vicinity of Gourock Golf Course [NS 2230 7630] but is not exposed. In the Knocknairshill Borehole type section, the member is unconformably overlain by volcaniclastic strata of the Clyde Plateau Volcanic Formation and so the stratigraphical top is not seen.
Kinneil Kerse Silt Member
KKSI
Early Windermere Interstadial.
The relationship of the Kenneil Kerse Silt Member (Forth Clay Formation) to the underlying Errol Clay Formation is transitional.
On the southern side of the Forth estuary east of Kincardine Bridge to Bo'ness.
Marine, grey, soft to firm, clayey silt and dusky yellowish-brown silty clay interlaminated, containing sub-angular ice-rafted clasts (dropstones) of coal, basalt, mudstone and sandstone; characterised by laminations and in some cases, many thin beds of pale coloured silt and sand that are ripple bedded in places. Sporadic mottling and banding in black sulphide. The deposit is considered to be prodeltaic in origin.
Veneer to 12m
Diachronous transitional top with the Abbotsgrange Silt Member is speculative; known only to be overlain unconformably by younger deposits such as the Claret Clay Member (Carse Clay Formation) and Bothkennar Gravel Member (Forth Clay Formation).
Kilmarnock Splint Coal (North Ayrshire)
KKSP
Kilkivan Coal (Machrihanish)
KKVN
Kilnpool Limestone
First Kingshaw Limestone
KL1
Second Kingshaw Limestone
KL2
Kellaways Formation
KLB
Middle Jurassic, Lower Callovian (Herveyi Zone to Calloviense Zone).
Generally sharp, conformable or non-sequential junction with bioclastic limestone of underlying Cornbrash Formation, overlain by grey mudstone, commonly a thin unit of shell-fragmental, more or less sandy mudstone occurs at base (where this is more strongly cemented it is included in the Cornbrash Formation).
Dorset coast (Weymouth area) to Malton area, Yorkshire (just north of the Market Weighton High). Extensive in onshore subcrop, though absent over the interior of the London Platform.
Mudstone, grey, commonly silici-silty or silici-sandy, with (predominantly in the upper part) beds of generally calcareous siltstone and sandstone.
0 to perhaps (in south Dorset) 50m; typically c.20m in the Wessex Basin, and c.5 to 8m on the East Midlands Shelf.
Generally sharp but conformable junction between sandstone/siltstone in upper part of formation with mudstone of overlying Oxford Clay Formation; in expanding successions, (Wessex Basin), arbitrary boundary drawn at the top of the highest substantial sandstone or sandy mudstone, above which the succession is predominantly mudstone; in the Market Weighton area, sharp disconformable contact with chalky argillaceous sediments of the Chalk Group/Hunstanton Formation.
Kilburn Rock
KLBR
Kellaways Formation And Brantingham Member (Undifferentiated)
KLBT
Kellaways Clay Member
KLC
Generally sharp, conformable or non-sequential junction with bioclastic limestone of the underlying Cornbrash Formation overlain by grey mudstone. Commonly a thin bioclastic unit of shell-fragmental, more or less sandy mudstone occurs at the base (where this is more strongly cemented it is included in the Cornbrash Formation).
Dorset coast (Weymouth area) to the Market Weighton High. Extensive in onshore outcrop, though absent over the interior of the London Platform.
Silicate mudstone, grey, commonly smooth in basal part (see Previous Names), but more generally silici-silty or silici-sandy, locally with thin beds of siltstone and sandstone, and nodules of argillaceous limestone.
0 to perhaps (in south Dorset) c.50m; typically c.20m in the Wessex Basin, and 2 to 3m on the East Midlands Shelf.
Transitional junction; boundary drawn at the base of the lowest substantial sandstone/siltstone unit of the overlying Kellaways Sand Member resting on the predominantly mudstone succession.
Kiloran Flags Formation
KLFL
Kellaways Formation And Langdale Beds Member (Undifferentiated)
KLLA
Kinlochlaggan Quartzite Formation
KLLQ
Rapid transitional boundary (quartzite, psammite, semipelite and micaceous psammite) with the underlying Aonach Beag Semipelite Formation. Where psammite is interbedded with semipelite below, boundary is placed where psammite becomes the dominant lithology. Elsewhere boundary is where quartzite replaces semipelite and psammite.
Largely confined to the Ardverikie Forest area, sheet 63E (Dalwhinnie), between Aonach Beag [NN 455 740] and the River Spey at [933 571].
Massive, white, orthoquartzite, feldspathic quartzite and siliceous psammite. Locally prominent white to pink feldspars. Pebbly beds developed locally. Sporadic development of a 'boulder bed' near the top of the formation.
Sharp upper contact placed where quartzite (or 'boulder bed' where present) is abruptly replaced by semipelite, pelite and / or metalimestone / calc-silicate rocks of the Coire Cheap Formation.
Kincairney Lava Member
KLM
Kays Lea Marine Band [Local Term: See Lsmb]
KLMB
Kilbirnie Mudstone Member
KLMD
Taken at the top of the Top Hosie Limestone, the highest group of thin limestones characterized by the presence of Posidonia corrugata.
Presently used within north Ayrshire.
Mostly dark grey mudstone with ironstone, sporadic shelly marine bands, and also siltstone, medium-grained rooty grey sandstone and coal. The strata occur in upward-coarsening cycles, some capped by thin coal beds. The member includes the Dalry Clayband Ironstone, a grey argillaceous ironstone, and the Johnstone Shell Bed mudstone, with a marine brachiopod and bivalve fauna.
Taken at the lithological change from mudstone of the Kilbirnie Mudstone Member to the overlying dominantly sandstone-bearing cyclical sequences of the parent Limestone Coal Formation. The upper boundary is diachronous.
Kiln Bank Tuff Member
KLN
Base of dacitic tuff that rests with unconformity on an erosion surface in the Dunnerdale Sandstone Formation (volcaniclastic sandstone) and locally on the Wallowbarrow Tuff Formation (andesitic lapilli-tuff).
Within the Ulpha Basin. Between Wallowbarrow Heald (SD 210 970), Turner Hall (SD 230 960) to Great Stickle (SD 211 915) and Lickle Valley (SD 240 920), Cumbria.
Massive, crystal-rich, eutaxitic dacitic lapilli-tuff.
70 to 180m
Contact with overlying volcaniclastic sandstone, or Paddy End Member of the Lickle Tuff Formation.
Kiln Coal (Scremerston)
KLNC
Kenslow Member
KLOW
Grey clays with plant remains.
Kellaways Formation And Oxford Clay Formation (Undifferentiated)
KLOX
Kellaways Formation, Oxford Clay Formation And Corallian Group (Undifferentiated)
KLOXC
Klibreck Psammite Formation
KLPS
Kellaways Sand Member
KLS
Middle Jurassic, Lower Callovian (Koenigi Zone to Calloviense Zone).
Transitional junction; boundary drawn at the base of the lowest substantial sandstone/siltstone unit resting on the predominantly mudstone succession of the underlying Kellaways Clay Member.
Dorset coast (Weymouth area) to the Malton area of Yorkshire (just north of the Market Weighton High). Extensive in onshore subcrop, though absent over the interior of the London Platform.
Silicate sandstone and silicate siltstone, pale grey, calcareous cemented, with interbeds of sandy and silty mudstone. Sandstone/siltstone generally weakly cemented, but locally strongly cemented, typically into "doggers".
0 to c.10m; typically c.3 to 5m on the East Midland Shelf; thin or absent over much of Dorset.
Generally sharp but conformable junction between sandstone/siltstone and mudstone of the overlying Oxford Clay Formation; in expanded successions (Wessex Basin), arbitary boundary drawn at the top of the highest substantial sandstone or sandy mudstone, above which the succession is predominantly mudstone; in the Market Weighton area, sharp disconformable contact with chalky argillaceous sediments of the Chalk Group/Hunstanton Formation.
Kilnsey Formation
KLSL
Drawn at the base of dark grey limestones with mudstone partings of the Scaleber Force Limestone Member (of the Kilnsey Formation) where it rests sharply and conformably on paler grainstone of the Chapel House Limestone Formation.
Series of inliers in the southern part of the Askrigg Block, North Yorkshire, including Kilnsey [SD 97 68], Langcliffe [SD 82 65] and Austwick [SD 77 68].
Dark to medium light grey, thick to thin-bedded, bioclastic limestone with mudstone beds and partings..
Up to 224m in boreholes south of the Middle Craven Fault. The Formation thins rapidly northwards to 53m in the Kilnsey area.
Drawn at the conformable upward passage from mid dark-grey limestone of the Scalebar Quarry Limestone Member (of the Kilnsey Formation) into pale grey limestone of the Cove Limestone Member, Malham Formation.
Kendal Till Formation
KLTI
Kelly Coal (Dungannon)
KLYC
Kilmarnock Major Coal (North Ayrshire)
KMA
Knockshinnoch Main Coal (New Cumnock)
KMAC
Kirkby's Marine Band [Local Name: See Htmb]
KMB
Local name applied to the Haughton Marine Band (National Standard Name) in the Durham and Northumberland coalfield areas.
Kirkmabreck Intrusion
KMBR
Knottyholm Coal
KMC
Kilmarnock Mcnaught Coal (North Ayrshire)
KMCC
Kennmoor Coal (Bristol Area)
KMCO
Kirkby Moor Formation
KMF
Taken at the change from banded mudstone-siltstone units of the Bannisdale Formation to sandstone, in part thin-bedded and cross-laminated, or thick bedded massive fine-grained sandstone.
Southern Lake District, Cumbria; Howgill Fells, Cumbria.
A sequence of thick beds of massive or convulate laminated, and thin-bedded ripple-cross laminated, fine-grained sandstone. The formation includes rocks previously included within the Underbarrow and Scout Hill Flag formations.
More than 430m
Unconformably overlain by various Devonian and Carboniferous rocks.
Kilmelford Intrusion
KMFD
Kirkham Glacigenic Formation
KMGL
Unconformable and locally deeply incised contact with bedrock.
North Lancashire, approximating to an area between the Lake District Massif and the Kirkham Moraine.
A glacigenic sequence of till (sandy, gravelly clay with cobbles and boulders) and laminated silt and clay separated by variably continuous lenses or beds of sand and gravel. Erratics are dominated by Carboniferous rocks and Lake District and Irish Sea derived bedrock. Correlated with the Stockport Glacigenic Formation of Cheshire (Worsley, 1991).
Highly variable, locally up to 100m
Either the ground surface or overlain by various units of the Britannia Catchments Group and British Coastal Deposits Group.
Kiltongue Musselband Ironstone
KMI
Knockshinnoch Mid Coal (New Cumnock, South Ayrshire)
KMID
Kilmaluag Formation
KML
Transitional limestone facies change from Duntulm Formation limestones.
Alternating shales, mudstones, argillaceous limestones and dolomitic limestones. Frequent desiccation cracks and mud-clast conglomerates. Vertebrate and breccia beds. Inferred ephemeral lagoonal setting.
Gradational boundary to alluvial facies of the Skudiburgh Formation.
Knottyholm Marine Band [Local Name: Use Somb]
KMMB
Local name applied to the Sutton Marine Band (National Standard Name) in the Canonbie Coalfield area.
Kirkmaiden Formation
KMN
'Lower' (Northern) boundary not seen.
Greywackes (beds dominantly less than 0.5 metres thick) with mudstone interbeds. Strata to north much more thickly bedded with substantial proportions of massive arenite. Strata to south (Carghidown Formation) distinguished by presence of red mudstone beds.
c.6000 metre section, strata steeply dipping but intensely folded and faulted. Stratigraphic thickness could be as little as 1 - 2 km.
"Upper" (Southern) boundary gradational into Carghidown Formation.
Kentmere Pike Tuff Formation
KMR
Taken at the abupt change from volcaniclastic sedimentary rocks of the Seathwaite Fell Sandstone Formation to dacitic lapilli-tuff indicating an erosion surface, which is usually obscured by later, syn-BVG andesite intrusions.
The east side of Kentmere Valley [NY 468 081], via Hallow Bank Quarter and Kentmere Pike [NY 465 078] to the west side of Longsleddale [NY 471 079].
A dacitic lapilli-tuff, with flow joints, localised breccia and some interbeds of tuff, lapilli-tuff and volcaniclastic sandstone. It is laterally impersistent, possibly filling hollows in an erosion surface, interpreted as a densely welded, rheomorphic high-grade ignimbrite.
Overlain by eutaxitic lapilli-tuff of the Lincomb Tarns Tuff Fomration, but the relationships are obscured by later syn-BVG andesite intrusions.
Maastrichtian Rocks (Undifferentiated)
KMRU
Kiltongue Mussel Band
KMUB
Kirkbean Sand And Gravel Formation
Unconformable on older glacigenic sediments, such as till of the Gretna Till Formation; locally rests directly on bedrock.
Northern margin of the Solway Firth, principally southwest of Dumfries; isolated spreads north of Canonbie and Langholm.
Three types of landform are recognised associated with these deposits : Sinuous discontinous esker ridges (single strand), typically 7-10m in height and up to c 300m in length. Mounds and hummocky topography (kame and kettle topography). Glaciofluvial fans and terraces flanking valleys infilled with Holocene fluvial and marine sediments (all generally mapped as Glaciofluvial Sheet Deposits).
Esker ridges ~ Glaciofluvial Subglacial Deposits. Kame and kettle mounds and ridges ~ Glaciofluvial Ice-contact Deposits. Glaciofluvial fans and terraces ~ Glaciofluvial Sheet Deposits.
Sand and gravel, with cobbles and pebbles of Ordovician, Silurian, Devonian and Carboniferous rocks in a matrix of medium- to coarse-grained sand; typically pale yellow to palebrown. Granitic clasts are commonly a major component. Esker deposits are typically poorly sorted, cobbly and bouldery,well-bedded with high-angle cross-bedding, involutions and slumps. Some interbeds of coarse sand. Kame and kettle deposits are poorly exposed, but appear to be typically moderately sorted, silty, sandy, clast-supported gravel with rounded to subrounded cobbles and pebbles. Glaciofluvial Sheet deposits are poorly exposed but appear to be typically well-sorted sandy gravel, with interbeds of coarse- to medium-grained sand.
Variable, typically 4-10m, esker deposits may be > 12m thick; moundy ice-contact deposits and sheet deposits are typically 2-8m thick.
Locally overlain by Holocene alluvium and peat, and by Holocene and Lateglacial raised marine deposits. Some exposures are capped by gravelly friable pale brown to reddish brown diamicton (supraglacial flow till) typically 0.3-0.7m in thickness).
Kent No.1 Coal
KN1
Kent No.10 Coal
KN10
Kent No.11 Coal
KN11
Kent No.12 Coal
KN12
Kent No.13 Coal
KN13
Kent No.14 Coal
KN14
Kent No.2 Coal
KN2
Kent No.3 Coal
KN3
Kent No.4 Coal
KN4
Kent No.5 Coal
KN5
Kent No.6 Coal
KN6
Kent No.7 Coal
KN7
Kent No.8 Coal
KN8
Kent No.9 Coal
KN9
Killen Burn Mudstone Member
KNB
Conformable lower contact on Goose Sandstone Member.
Red sandstones, largely of fluvial origin with calcareous mudstone intervals containing fish remains.
70 metres +.
Conformable upper contact with Millbuie Sandstone Member.
Knott Copy Grit
KNC
Sharp upward change in a conformable succession from predominantly grey mudstone to sandstone - base of first sandstone bed above the Reticuloceras dubium Marine Band.
Pennine foothills between Settle [SD8100 6400] and High Bentham [SD6700 6930].
A thickly bedded, trough cross-bedded, coarse-grained, feldspathic sandstone; medium-grained in upper 5m with ganister top.
0 to 40m
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of last sandstone bed below the Reticuloceras stubblefieldei Marine Band.
Kincraig Formation
KNCG
Contact typically sheared with arkosic-banded dominantly psammitic gneisses of the underlying glen banchor succession. Over large parts of the area contact zone is marked by sheet of amphibolite.
Middle and upper parts of Spey Valley, eastern and southern Monadhliath Mountains, Central Highlands of Scotland. Sheet 74W.
Schistose to gneissose semipelite, locally phyllitic and calcareous. Banded calc-silicate rocks, quartzite, amphibolite, metacarbonate rocks and striped psammite and semipelite.
90 - 100 m estimated.
Incoming of well-bedded, grey turbiditic, locally graded psammites of the Loch Laggan Psammite Formation.
Kensworth Nodular Chalk Member
KNCK
Turonian and Coniacian. Sternotaxis plana (now Plesiocorys plana), Micraster cortestudinarium Zones.
Conformable at the top of the Chalk Rock Member above the flint nodule horizon marking the top of the Hitchwood Hardground.
Known within the Leighton Buzzard and Hitchin areas of the Chilterns.
Very hard nodular chalk and chalkstone, including mineralised hardground surfaces.
c.2.5 to c.4m in Hitchin and Leighton Buzzard districts.
Conformable: at top of obviously indurated chalks near the base of the Upper Chalk but overlying the Chalk Rock Member. Note that this does not necessarily coincide with the top of the Top Rock.
Kendal Group
KNDL
As for the base of the Bannisdale Formation; gradational from the sandstone-dominated Coniston Group into siltstone and mudstone units.
Northwest England; southern Lake District, Cumbria; Howgill Fells, Cumbria.
Comprises a lower sequence of graded siltstone-mudstone couplets with locally extensive intercalations of turbiditic sandstone (Bannisdale Formation).
The Group is the youngest within the Windermere Supergroup and is defined to include all formations that lie stratigraphically above the Coniston Group.Child Unit names: Bannisdale Formation, Underbarrow Formation, Kirkby Moor Formation and Scout Hill Formation. These formations were previously ungrouped within the Windermere Supergroup. NOTE that this is NOT a redefinition of the Kendal Formation of Moseley (1984). It follows informal usage by Cocks et al. (1992), King (1992, 1994), Woodcock and Strachan (2000). Individual formations are defined in Kneller et al. (1994).
Possibly more than 4.2km
Kenfig Formation
KNFIG
Laterally variable at type locality; conformable Flandrian deposits in the vicinity of Kenfig Pool (Cheney et al, 2000) and elsewhere unconformable on bedrock or superficial deposits.
Coastal embayments on the north shore of the Bristol Channel, particularly in Swansea Bay, Carmarthen Bay and Freshwater Bay.
Stratified, unconsolidated, fine- to medium-grained quartz sand with shell debris.
Exceptionally reaches 10m, but generally in accordance with the topographic expression of dune forms.
Generally the ground surface; locally contact with overlying Flandrian deposits.
Knockgardner Sandstone Formation
KNG
Conformable on the Blair Shale Formation.
Girvan to Straiton area of south-west Scotland.
Grey-green, thinly-bedded, sandstones and siltstones, with some thick-bedded massive sandstones.
From 137 m to 180 m thick.
Conformably overlain by the Straiton Grit Formation.
King Coal (North Staffordshire)
KNGC
Knock Head Grit Member
KNHG
Change from calcareous semipelite and psammite to non-calcareous psammite-dominated lithologies at top of Whitehills Grit Formation; commonly marked by change to locally coarsely gritty psammite.
From Moray Firth coast [NJ 6514 6564-NJ 663 654], southwards to northern margin of Aberchrder Granite [NJ 630 530].
Interbedded psammite, locally pebbly, semipelite and pelite in graded units. Finer-grained beds metamorphosed to slates, phyllites and mica-schists. Minor calc-silicate pods. Contains andalusite, cordierite and locally staurolite porphyroblasts.
c.0.5km; relatively little repetition by folding.
Transition to graded units with greater proportion of semipelite. Psammites only rarely pebbly.
Knockencorsan Hill Intrusion
KNHIL
Knightswood Coal (Glasgow Area; Central Coalfield)
KNIC
Knightswood Under Coal (Glasgow Area; Central Coalfield)
KNIUC
Overlies "cyclothems" between Black Metals and Knott Rider Coal within the Limestone Coal Formation.
Thin, impersistent but highly correlateable coal in the Glasgow-Stirling region. This coal is the highest of three in between the Black Metals to Knightswood Gas Coal and is often associated with thick Lingula beds, often washed out.
Overlain by Knightswood Gas Coal within the Limestone Coal Formation. Up to 8m of Lingula-rich, fissile mudstone is often present between these beds.
Knockando Quartzite Formation
KNK
Knipe Scar Limestone Formation
KNL
Underlying Potts Beck Limestone comprises interbedded pale grey limestones (of those in Knipe Scar Limestone), dark grey limestones and sandstones (up to 3 metres thick).
Pale grey, scar-forming limestones, mostly thick-bedded biosparites and biopelsparites commonly pseudobrecciated, and probable thin siliciclastic bed, not exposed at type section.
61m seen, but top 16 metres of formation not present - but exposed in sections on Limestone Scars within 1 km to east and can be seen to comprise comparable thick-bedded pale grey limestones. Thickness fairly constant along outcrop on NY60NW and NY60NE with slight eastward increase up to c.90 metres on Little Asby Scar.
Overlying beds are a variable sandstone/siltstone/mudstone unit between Knipe Scar and Robinson Limestones.
Kilbryan Limestone Formation
KNLM
Kilslevan Limestone Member
KNLS
Knockmore Limestone Member
KNM
(1) Completely enclosed by bedded argillaceous limestones of the Dartry Formation. (2) Occurs at base of formation where it is underlain by limestones of the Glencar Formation. (3) Occurs at top of Dartry Formation where it may be overlain by either Meenymore Formation or sandstones of the Glenade Formation.
Not yet defined.
Unbedded grey micrites arranged as lenticular mounds with bedded cover and off-mound limestones. Limestones of Dartry Formation everywhere comprise dark grey, bedded argillaceous micrites, invariably with bedded blue-black chert (secondary).
100 to 130m in type section; 0 to 290m elsewhere.
See Lower Boundary details.
Kilconquhar Marine Band
KNMB
Silty mudstone with Lingula and Orbiculoidea.
0.63m in type section.
Kennethmont Intrusion
KNMT
Kenn Formation
KNN
Early Pleistoocene to Mid Pleistocene.
Rests upon Triassic bedrock.
Restricted to Avon and north Somerset; occurrences at Kenn, Court Hill, Nightingale Valley, Failland Ridge, Bathampton Down and Bleadon Hill.
The formation includes glacigenic deposits interpreted as till, outwash and glacio-marine. Coarse outwash sands and gravels, poorly to well sorted, are interbedded with reddish purple till. Both contain clasts of Carboniferous limestone, Upper Greensand chert, Jurassic limestone, and Cretaceous flint, up to cobble and boulder size, with small quantities of Devonian red quartzite, sandstones and conglomerates. Pennant sandstone and yellow Triassic sandrock.
To c.14m
Mostly at surface. At Kenn, overlain by Cromerian (MIS 15) deposits and by Holocene silts and clays.
Knott Coal (Glasgow)
KNO
Kilchoman Phyllite Formation
KNPH
Knock Pike Tuff Formation
KNPK
Taken at the base of densely welded rhyolitic tuff, resting on a bedded, mixed sequence of volcaniclastic sandstone and rhyolitic tuff of the Studgill Tuff Formation.
Pale grey, densely welded silicic tuff and lapilli-tuff with a very prominent parataxitic texture; there may be some lava.
Defined by the base of the overlying mixed succession of silicic tuff and volcaniclastic sandstone of the Harthwaite Tuff Formation.
Kent's Rock
KNR
Barnsley area of South Yorkshire.
Knockrushen Formation
KNRN
Knowle Sandstone Formation
KNS
On northern side of the Crediton Trough, Bow Breccia with passes up into Knowle Sandstone by gradual increase in the proportion of sandstone; thus the boundary is somewhat arbitrary. Around Posbury and in the Dunchideock area (southwest of Exeter), rests directly on Crackington Formation.
Present in Okehampton district from south of Bow to Knowle; and in Exeter district from Knowle to Sandford area. (All within Crediton Trough).
Reddish brown sandstone, mostly well cemented, with common breccia beds and lenses, commonly cross-bedded. Contains interbedded lamprophyre and basalt lavas.
120-150m at eastern edge of Okehampton district, to 100m in Crediton area, 18m at Bow.
Overlain unconformably by Creedy Park Sandstone along north side of Crediton Trough. At Posbury and Dunchideock, overlain by basalt, in turn overlain by Crediton or Alphington Breccia.
Kingston Sand Member
KNSA
Gravelly erosive base locally unconformable, assumed to be deeply channelised into the Errol Clay Formation.
Tay estuary and the Firth of Tay.
Sand, very fine- to medium-grained with silt and clay laminae, grey and brownish grey, finely micaceous, with some shells and comminuted shell debris and dark sulphidic patches. The sediments contain a marine microfauna of temporate estuarine type. Locally, the unit has a gravelly base and clasts to 20cm of schist and quartzite.
20m known at Kingston; up to 14.9m at Barry Buddon.
Upper boundary (unconformable?) with transgressing Carse of Gowrie Clay Member but may pass laterally into the Carey Silt Member (Carse Clay Formation).
Kinnerton Sandstone Formation
KNSF
Where fluviatile/marine mudstones and siltstones of the Manchester Marl Formation or laterally persistent fluviatile argillaceous sandstones of the Bold Formation (south Cheshire Basin) pass into cross-stratified aeolian sandstones of the Kinnerton Formation.
Sandstone, red-brown to yellow, generally pebble-free, fine- to medium-grained, cross-stratified. Dominantly aeolian.
Where aeolian sandstones of the Kinnerton Formation pass into fluviatile, commonly pebbly, sandstones of the Chester Pebble Beds Formation.
Knighton Member
KNSG
Knock Semipelite Member
KNSP
Knighton Terrace Deposits
KNTD
Sand and gravel. [Generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
Kincorth Pegmatitic Granite
KNTH
Kennet Valley Formation
KNTV
Kinghorn Volcanic Formation
KNV
Conformable; at base of lowest basaltic lava flow. Locally the base is complex as a result of interdigitation with the uppermost part of the Sandy Craig Formation.
Around Kinghom on 1:10k sheet NT28NE, north of Burntisland on sheet NT28NW; extending northwards onto the southernmost parts of NT29SW and SE and westwards onto the easternmost part of NT18NE.
Basaltic lava flows, mostly subaerial but some subaqueous with associated hyaloclastite and pillows, interbedded with tuffs, sandstones, mudstones and limestones.
Conformable; at top of highest basaltic lava on tuff in transition to sediments of Pathhead or Lower Limestone Formation.
Kinnesswood Formation
KNW
The transitional base is taken between strata with cornstones and the underlying aeolian sandstones without cornstones of the Knox Pulpit Formation (Stratheden Group).
Midland Valley, Scotland.
Characteristically sandstone with carbonate (limestone or dolomite) nodular pedogenic horizons (cornstone).
To c.400m
The top is generally a conformable boundary beneath the Ballagan Formation, but in the type area is erosional beneath strata of the Pathhead Formation of the Strathclyde Group.
Knorri Beds
KNY
Kilbucho Conglomerate
KOC
Coniacian To Campanian Rocks (Undifferentiated)
KOKC
Kilcoan Sands Formation
KOS
Coniacian to Santonian. Micraster cortestudinarium to Micraster coranguinum zones.
Disconformable at an erosion surface above the mid-Hibernian Greensands `unconformity?. Rests on each of the older formations in the group and overlaps onto pre-Cretaceous strata over the most positive structural highs.
Fully developed in the Island Magee area and within the East Antrim Basin and Southern Uplands area. Elsewhere in Northern Ireland the formation may be represented in the condensed successions of the undivided Hibernian Greensands Group.
Pale green glauconitic sands thought largely to be derived from the Collinwell Sands Formation. Three conspicuous Inoceramus bands divide the succession into three unequal parts.
Up to 7.3m at Kilcoan.
Disconformable at an erosion surface beneath various younger members of the Ulster White Limestone Group.
Keuper Anhydrite Member
KPAN
Kip Burn Formation
KPB
Sharp base on greywacke/siltstone sequence of the Castle Formation.
Grey and dark grey laminated mudstones and silty mudstones. A few calcareous nodules.
Transition to greenish grey silty mudstone of the Blaeberry Formation.
Knox Pulpit Sandstone Formation
KPF
Passes downwards into the Glenvale Sandstone Formation, or the Dura Den Member in the Cupar area. The formation is distinguished from those adjacent by characteristic sedimentary structures.
The Fife and Kinross area of the Midland Valley of Scotland, on sheets 40, 48, 49.
A soft, weakly-cemented, white, feldspathic sandstone, characterised by a marked variation in grain-size between adjacent laminae. The Knox Pulpit Sandstone Formation is probably continuous with the redundant Kemback Formation.
Up to 180m thick in the Lomond Hills area.
Drawn at the conformable upward passage from the white or cream sandstones of the Knox Pulpit Sandstone Formation to the white, yellow or brown sandstones of the Kinnesswood Formation.
Kempton Park Gravel Formation
KPGR
Rests on bedrock geology of London Clay, or Woolwich and Reading Beds.
Average thickness 6m, but much thicker where infilling deep hollows.
Keuper Halite Member
KPHA
Kilpothall Ironstones
KPI
Aptian And Albian Rocks (Undifferentiated)
KPKA
Kupferschiefer Formation
KPSC
Kilmarnock Parrot Coal (North Ayrshire)
KPT
At change from coal to other lithology at 106.29 metres in Oldhall No.1 Borehole.
Coal between Linn Bed Coal and the Kilmarnock Turf Coal.
Variable, about 1 metre in type section.
At change from coal to other lithology at 105.35 metres in Oldhall No.1 Borehole.
King And Queen Coal (South Lancashire)
KQCO
Kreftenheye Formation
In Netherlands rests on Pliocene marine sands in type section. Rests on Eem Formation (marine sands) or Ijmuiden Ground Formation (early Pleistocene prodelta sediments in Flemish Bight).
Fine- to medium-grained fluviatile sands, locally gravelly and commonly containing marine shells reworked from Eem Formation.
16 metres (maximum 8 metres in Flemish Bight Sheet).
Overlain in Flemish Bight by Holocene marine sands.
Kirkham Abbey Formation
KRA
Kirkby's Back Coal
KRBC
Knockorr-Bombie Glen Vent
KRBG
Subvolcanic explosion-breccia composite vent of mainly igneous rocks set in a matrix of probable decomposed lamprophyre/basalt.
Unit thickness is not known, but the body is about 250 x 100m, with the main vent extending 100 x 40m.
Kilranny Conglomerate Member
KRC
Taken at base of conglomerate lithology, resting on the Bellmoor Member (of the Balclatchie Formation).
Conglomerate.
Taken at the top of the conglomerate lithology, beneath the Ardwell Farm Formation.
Killiecrankie Schist Formation And Carn Mairg Quartzite Formation (Undifferentiated)
KRCM
Knott Rider Coal Or Cannel (Glasgow)
KRIC
Kirkton Formation
KRK
Overlies Raven Gill Formation.
Chert, red and grey siliceous mudstone with chert nodules.
Is overlain by Glenkiln Shale Formation, Moffat Shale Group.
Kirkham Mudstone Member
KRM
Originally defined as a Formation (Wilson and Evans, 1990) the unit is retained but with Member rank as part of the nationally recognized Sidmouth Mudstone Formation (Howard et al., 2008).
Keresley Member
KRS
Taken immediately above the sandstone unit named informally as the Arley and Exhall sandstones at the top of the Whitacre Member.
Warwickshire Coalfield (northern part) sheet 169. Also likely to extend in the subcrop across the southern part of the Warwickshire Coalfield. (sheet 184).
Redbed sequence; mudstone dominated in lower part but becoming increasingly arenaceous towards top. Thin Spirorbis limestone beds at some levels. Impersistent conglomerates in upper part.
Range 197m-306m. Mean 258m
Taken at the highest mappable sandstone (Corley Sandstone) beneath the basal argillaceous sequence of the overlying Allesley Member.
Kidderminster Station Member
KRT
Where river deposits rest on bedrock, or glacial deposits.
River Severn Basin from Chepstow to Bewdley.
Gravel composed of Triassic derived quartzites with flint, Welsh erratics and locally derived material.
Up to 5m
Present day terrace flat.
Kirkwood Formation
KRW
Taken at the junction of tuffaceous mudstones and tuffs with underlying basaltic lavas of the Clyde Plateau Volcanic Formation
Tuffaceous mudstones and tuffs.
Variable, to c.35m
Taken at the base of the overlying Lawmuir Formation or Lower Limestone Formation. The boundary is commonly irregular with interdigitation of lithologies.
Kilranny Hill Formation
KRY
Faulted against serpentinite.
Massive and faintly-bedded, fine to very coarse crystal-lithic arenites, laminated silty and cherty mudstones, well-bedded arenites, and sporadic polymict pebble- to boulder-conglomerate. Contains early Arenig graptolites.
Interdigitates with lavas of the Pinbain Formation.
Knuckton Shell-Beds Limestone
KSBL
The southwest part of the Barnard Castle sheet.
Grey thinly bedded fine-grained siliceous sandy shelly limestone.
Keasden Sandstones
KSD
Kersdown Chert Member
KSDC
The current Age Range (Asbian to Brigantian) derives from a previous, Partial, Lexicon entry. A more general Age of "Visean" may be more realistic pending acquisition of more definitive data.
The lower boundary is taken at the incoming of abundant blocky chert with few limestones of the Kersdown Chert Member above the siliceous radiolarian shaly mudstones with some silicified limestones forming the lower part (Hayne Beech Beds) of the Bampton Limestone Formation.
Dark grey to black laminated thin- to thick- bedded blocky cherts with interbedded shaly siliceous mudstones and a few partly silicified limestones. Scattered chert nodules occur within the limestones.
The upper boundary is taken at the incoming of black shaly mudstones with limestones and minor cherts (Bailey's Beds), forming the upper part of the Bampton Limestone Formation, above the blocky cherts with few limestones of the Kersdown Chert Member.
Kirkstead Sand And Gravel Member
KSDSG
Upper Pleistocene (MI Stage 2 west of the Lincoln Gap, or 5e to 2 east of the Lincoln Gap). The chronology is based on the assumption that west of the Lincoln Gap (where Scarle Sand and Gravel can be separated) it is broadly correlative with the Holme Pierrepont of the Trent, whereas east of the Gap it includes everything that is Ipswichian or later, thus including correlatives of the Scarle Sand and Gravel, as in the Castle Sand and Gravel Member of the Bain.
Unconformable, commonly channelled base, resting on pre-Quaternary bedrock or Wragby Till Member (Lowestoft Formation).
Comprises the younger, mainly Devensian fluvial deposits (i.e. excluding Flandrian alluvium) of the Witham catchment and of the Proto-Trent area (i.e. east of the Trent between Newark to Gainsborough). Note that adjoining the Trent the deposits could be classified mainly as Holme Pierrepont Sand and Gravel but the limits suggested above are an attempt to indicate a possible boundary line on the basis of this definition. The unit is not delineated as such on any published BGS map.
Predominantly cold-phase sands and gravels representing the youngest deposits of the Proto-Trent, and the pre-Flandian deposits of the Witham. The former are typically dominated by rounded pebbles of "Bunter" quartz/quartzite with subordinate subangular flint, etc. but the latter have a greater proportion of flint and local Jurassic limestone, etc. Surface c.1 to 2m above the Trent floodplain, at Spalford, and typically 3 to 6m below Witham floodplain level in the Type Area. West of the Lincoln Gap, correlated with the Holme Pierrepont Member (Trent Valley Formation); whilst east of Lincoln Gap also includes older materials correlated with the Scarle and Fulbeck Sand and Gravel members (Trent Valley Formation) and Castle Sand and Gravel Member (Bain Valley Formation).
As defined this is a rather unsatisfactory portmanteau term to cover all the younger sands and gravels of the Proto-Trent and Witham areas that are not otherwise named. Very little is known about these deposits so more specific names have not yet ben applied. Younger parts include Witham gravels of local derivation and, mainly on Sheet 102, there are deposits that might represent southwards outflow from Lake Humber.
0 to c.8.5m; typically 4 to 5m
Ground surface or base of alluvium or blown sand (Spalford Member).
Kleppe Senior Formation
KSE
Apparently conformable on Norwegian Trench Formation.
Soft, highly plastic, silty clay with sand lenses and partings. Sporadic shell fragments, carbonaceous spots and inclusions. Bedding rarely visible, bioturbation may be present. Unit underlying it is a much stiffer clay unit, possibly a till.
Ten metres maximum in Cormorant map sheet area, deduced from seismic section. Thickness to the south and east in the Norwegian Trench. Small pockets (<1m) on the plateau area of the Cormorant map.
Disturbed by interpreted iceberg ploughmarks, current erosion and bioturbation. Overlain by thin Holocene sand sedimentation.
Knocksoghey Formation
KSF
Kilmarnock Shale Coal (North Ayrshire)
KSHC
Kershaw Coal (Lancashire)
KSHW
Kincurdy Silts Formation
KSI
Sharp, gently undulating erosion surface on Red Craig Gravels Formation below.
Confined to Rosemarkie Glen, Rosemarkie, Black Isle.
Thinly interlaminated silt, sandy silt and plastic clay with dropstones and lenses of diamicton; becoming coarser-grained upwards.
Sharp, planar, associated with glacitectonic shearing at base of overlying (unnamed) till.
Kentisbury Slates Member
KSL
Knockshinnoch Laight Coal (New Cumnock, South Ayrshire)
KSLC
Kingshaw Limestone
KSLS
Killooman Shale Member
KSM
Kirksanton Beds
KSN
Kirkconnell Splint Coal (Sanquhar)
KSP
Kingsley Sandstone [Obsolete Code: Use Kys]
KSS
Kokoarrah Shelly Sand Member
KSSA
Sharp, conformable contact with brownish grey sandy silt of the Stubble Green Silt Member of the Glannoventia Formation.
Yellow, becoming grey downwards, thinly laminated silty sand with laminae of silt, containing fragmentary marine bivalves of probable mid-Devensian age.
Kirk Stile Formation
KST
Taken above the uppermost thin sandstone of the underlying Loweswater Formation on Whiteside End.
The Kirk Stile Formation crops out north of the Causey Pike Fault within the Skiddaw inlier. The fault forms the southern boundary of the Formation. Elsewhere it is unconformably overlain by rocks of the Eycott Volcanic Group or Carboniferous limestones.
Thinly laminated to very thinly bedded dark grey siltstones and mudstones, local lenticular units of ithic wacke; underlain by greywackes of the Loweswater Fromation; overlain by the volcaniclastic Eycott Volcanic Group.
Taken as the youngest beds beneath volcaniclastic rocks of the Eycott Volcanic Group.
Knightswood Stone Coal (Glasgow Area; Central Coalfield)
KSTC
Kirk Stile Formation (Chiastolite Hornfelsed)
KSTCH
Kirk Stile Formation (Hornfelsed)
KSTH
Katystaklinn Vein
KSV
Kelso Volcanic Formation
The olivine basalts of the Kelso Volcanic Formation conformably overlie sandstone of the Kinneswood Formation (Inverclyde Group).
The Kelso Volcanic Formation is restricted to Berwickshire and forms a roughly horseshoe-shaped outcrop between the Blackadder Water (380250 650540) near Duns and Carham-on-Tweed (379790 638340), northwest of the Cheviot Massif in the Tweed Basin. It is correlated with the Birrenswark Volcanic Formation of the Solway Basin.
The Kelso Volcanic Formation comprises effusive alkali olivine-basalts either associated with tuffs or with sedimentary strata (volcaniclastic-sandstone). Up to 12 basalt, basaltic hawaiite and hawaiite lavas are intercalated with thin tuffs and sedimentary rocks. The lower flows are mostly feldspar phyric in contrast to the upper ones which contain olivine and clinopyroxene phenocrysts. The rocks are pervasively altered. The lavas were extruded during the main initial phase of extensional faulting associated with development of the Northumberland Trough.
About 120m, thinning northwards.
The olivine basalts of the Kelso Volcanic Formation are conformably overlain by "cementstone"-bearing strata comprising interbedded sandstone, siltstone and ferroan dolomite of the Ballagan Formation (Inverclyde Group).
Kitty Beck Limestone
KTBL
Kitty Beck and adjacent areas, White Lyne catchment, Cumbria.
Grey ar red massive limestone with abundnat detrital quartz.
Kettleholm Breccia Formation
KTBR
Unconformable on Early Palaeozoic wacke sandstone of the Hawick and Riccarton groups.
Localised distribution in Annandale, south-west Scotland, on Sheet S10W.
A coarse- to medium- grained breccia, composed of subrounded, poorly sorted, red micaceous wacke and shale clasts.
20 m thick.
Knockshinnoch Turf Coal (New Cumnock)
KTC
Ketch Member
KTCH
Knockshinnoch 2 Foot 7 Inch Coal (New Cumnock, South Ayrshire)
KTFS
Knockshinnoch 2 Foot 3 Inch Coal (South Ayrshire)
KTFT
Kettlepot Ganister
KTG
Keith Limestone Formation
KTHL
Bounded by lowest thrust plane in the Keith Shear-zone, normally marked by a sheet of highly sheared, gneissose metagranite.
Entirely within the Keith Shear-zone between Blackhill Wood (NJ 403 490) and Clochmacreich (NJ 493 582), Keith, Banffshire. Also between Rosarie (NJ 380 501) and Hillockhead (NJ 400 497)
Mostly semipelite with thick beds of metalimestone and thinner impure metalimestone, calc-silicate rock and quartzite.
Maximum seen 300 m, but this is attenuated by shearing.
Highest thrust plane in the Keith Shear-zone, normally marked by a sheet of highly sheared metagranite.
Kettla Member
KTLA
Kinmont Limestone
KTLS
Kirkton Gelifractate Bed
KTNGF
The base of the unit was observed to sharply overlie, and be buttressed laterally against felsite bedrock at a channel/basin margin in the southeast face B of Kirkhill Quarry (infilled).
Buchan, northeast Scotland. This bed is only known within Kirkhill Quarry (infilled) (centred on NK 0120 5285) on Sheet 87W (Ellon).
Gravel. Typically clast supported with a matrix of coarse felsitic sand. Pale olive-brown and pale pinkish brown. Clasts are typically angular and subangular with rare subrounded shapes. Clast litholigies are dominated by felsite with rare quartzitic and psammitic metasedimentary rocks and red granite. It displays crude, medium scale, moderately high angle cross-bedding. Interpreted as periglacial gelifractate/talus.
To 2m
The upper boundary of the unit was observed in the southeast face B of Kirkhill Quarry (infilled) to be gradationally overlain by, and to interdigitate laterally with, felsitic sands and gravels of the Pitscow Sand and Gravel Formation.
Kingston Formation
KTON
East of Cumnor, sharp change up (minor non-sequence) from dominantly muddy strata (West Walton Formation) into dominantly sandy succession. West of Cumnor, gradational change up from poorly fossiliferous fine-grained sand and sandy mudstone (Hazelbury Bryan Formation) into moderately fossiliferous medium- to coarse-grained sand (Beckley Sand Member) or sharp change up into shelly, ooidal or coralliferous limestone, locally with basal conglomerate (Highworth Limestone Member) or mudstone (Highworth Clay Member).
From Calne in Wiltshire, it is overstepped by Lower Cretaceous strata to Boarstall, northeast of Oxford, where it wedges out into the Ancholme Group (Horton et al. 1995).. The greatest development of this unit is between Faringdon and Beckley in Oxfordshire.
Generally medium-grained quartzose sands, locally fine- and coarse-grained, with carbonate cemented beds and doggers which are sandy limestone or calcareous sandstone; some beds of spiculitic sandstone which are relatively sand-free, shelly and/or ooidal limestone, sandy or silty mudstone, and calcareous mudstone. Strata are generally grey when fresh, weathering to brown or yellow.
Up to about. 30 m around Oxford, and up to 15 m thick in the Calne-Highworth area.
The base of (predominantly non-sandy) limestones of the overlying Stanford Formation, or locally, of the Lower Cretaceous sandstone or mudstone; generally a sharp, non-sequential boundary, commonly marked by a pebble bed.
Knuckton Shell Beds
KTSB
Brough area and the northern part of the Barnard Castle sheet.
Calcareous mudstone and siltstone with shelly fossils.
Kinlet Sill
KTSI
Kilmarnock Turf Coal (North Ayrshire)
KTU
Kintradwell Boulder Beds Member
KTW
Upper Cretaceous Rocks (Undifferentiated)
Kupferschiefer Formation [Obsolete Code: Use Kpsc]
KUPF
Kilmarnock Upper Wee Coal (North Ayrshire)
KUWC
Kevin Limestone Formation
Disconformity above the well-bedded, grey to dark grey, medium- to fine-grained limestones of the Milldale Limestone Formation. The disconformity is locally overlain by a localised, poorly sorted conglomerate with pebbles of reef-limestone and sparse quartz grains. Elsewhere the base of the formation is taken at the base of the lowermost thickly-bedded, pale grey limestone above the disconformity.
Seen in outcrop in the Weaver Hills [SK09 46] , and probably present in the subsurface part of the Hathern shelf, of Staffordshire.
Pale grey, thickly bedded, internally massive, fine- to coarse-grained biosparite limestone, with prominent bedding planes, some with brown pedogenic crusts and bentonite clay partings. The formation includes two areas of knoll-reefs.
At least 150 m thickness in the type area, although poorly constrained, and thins northward of the type area to 80-150m in the Hopten's Cross area [SK 072 481], and to the east of the type locality, the formation is cut out by Namurian overstep.
Disconformity overlain sharply by dark grey, siliceous mudstones of the Craven Group, with local erosional scouring into the top of the formation
Kevin Limestones Formation (Apron-Reef)
KVA
Kniveton Lava
KVB
Kilgetty Vein Coal (Pembrokeshire)
KVCO
Kingsteignton Volcanic Group
KVG
Drawn at base of spilitic tuff of Kingsteignton Volcanic Group where it rests conformably on grey-green slates of the Nordon Slate.
Devon.
Spilitic lavas, interbedded dark green, spilitic tuffs and slates with lenses of limestone; some limestone is crinoidal.
195m approx.
Drawn at conformable upward passage from spilitic lava and tuff of the Kingsteignton Volcanic Group to grey limestone of the Chercombe Bridge Limestone.
Kniveden Sandstones
KVS
Kiln Wood Beds
KWB
Knockshinnoch Wee Coal (New Cumnock, South Ayrshire)
KWC
Kingswood Toad Coal (Bristol)
KWDT
Kilmarnock Wee Coal (North Ayrshire)
KWEE
Keltie Water Grit Formation
KWG
Outgoing of coarse, chloritic and feldspathic gritty arenites and wackes and incoming of quartzose arenite (at top of Ben Ledi Grit Formation).
Between the northern shore of Loch Venachar, Perthshire, Scotland, and the area around the Keltie Water, north-east of Callander, Perthshire, thence northeast to Comrie.
Arenite, cream to buff, pale grey when fresh, coarse-grained locally gritty; interbedded with siltstone, black graphitic slate, pale grey-green to buff shales, locally calcareous, and thin pale to dark grey limestones.
Top not seen
Knock Wood Lava Member
KWLM
Kirkland Wood Sand And Gravel Member
KWSG
At its type section it overlies till of the Seascale Glacigenic Formation; elsewhere its basal contact is not seen, but the unit occurs stratigraphically above possible Winney Hill Coppice Clay Member of the Aikbank Glacigenic Formation in the Kirkton Wood West Section [log NY00SE(S) ME 166; Nirex Science Report SA/97/045 (Issue 2.0) 1997].
1:50k Sheet 37 Gosforth. Drigg to Santon Bridge area, western Cumbria.
Clast-supported gravel with subrounded to rounded clasts up to cobble grade of Borrowdale Volcanic Group igneous rocks, siltstone, lithic sandstone; some red sandstone, white sandstone, coal and granite. Sparse (reworked) shell fragments and dinoflagellate cysts present in sandier parts of the unit.
6.8m thick at its type section.
Unconformably overlain by the Drigg Beach Till Member of the the Gosforth Glacigenic Formation, with the uppermost c.0.3m (below the contact) pervasively sheared.
Killingworth Coal (Northumberland)
KWTH
Kale Water Till Formation
KWTI
Kennox Ell Coal
KXEL
Kennox Nine Foot Coal
KXNN
Kexbrough Rock
KXR
South Yorkshire, Barnsley area and to south.
Dominantly a thickly bedded, fine-grained sandstone, but locally flaggy and current-bedded, with impersistent sandy mudstone bands.
Kennox Seven Foot Coal
KXSV
Kennox Six Foot Coal
KXSX
Kennox Thirty-Inch Coal
KXTI
Kelty Blackband Ironstone (Comrie)
KYBC
Kelty Blackband Ironstone
KYBI
Keisley Limestone Formation
KYL
Formation seen only in core of anticline, base not reached.
Only seen in the Keisley area, Cross Fell Inlier, Cumbria.
Dark grey nodular limestone with siltstone partings overlain by grey massive beds of bioclastic limestone that are locally dolomitised; probably lowest part seen comprises dark grey siltstone with thin impure limestone beds. Thin unit of synsedimentary breccia and siltstone at top of Formation. Limestone is locally richly fossiliferous.
More than 50m
Taken at the base of black mudstones of overlying Silurian strata.
Kyle Group
KYLE
Kyle Limestone Unit
KYLI
Kynballoch Lava Member
KYLM
Kelty Main Coal (Fife)
KYMA
Kyle Mudstone Unit
KYMU
Kynachan Psammite Formation
KYPS
Gradational boundary with underlying Kynachan Quartzite Formation.
From Allt na Moine Buidhe near Mullinavadie [NN 713 611] via the south slopes of Creag Kynachan [NN 751 576] and the Allt Kynachan [NN 778 575] to the Loch Tay Fault [NN 802 598]. Also has small outcrop near the structural dome resulting from interference of the Clunes and Bohespic antiforms [NN 744 627].
Thickly-bedded schistose psammite. Relict bedding seen in lower few hundred metres, but more flaggy towards top. Cross-bedding well-developed, giving good younging directions. Minor quartzite units locally present.
Sharp, conformable boundary with Dunalastair Quartzite Formation.
Kynachan Quartzite Formation
KYQ
Gradational boundary with underlying Tummel Psammite Formation.
From Allt na Moine Buidhe [NN 720 611] via the main ridge of Creag Kynachan [NN 761 579] to the Loch Tay Fault near Blairbuie [NN 808 605]. Also has outcrop near the Torr Dubh structured dome resulting from interference of the Clunes and Bohespic antiforms [NN 745 632].
Massive, white to cream, granular impure feldspathic quartzite, probably forming a lensoid unit thickened by folding. Quartzite thins and becomes more schistose along strike from the type locality to the west.
Gradational boundary with overlying Kynachan Psammite Formation.
Kymah Quartzite Formation
KYQU
Lower limit of massive quartzite overlying either Laddder Hills Formation or Nochty Semipelite and Limestone Formation.
Southwest from the River Deveron, 6.5km west of Huntly, to Garbet Hill and thence from Scaut Hill southwards through Upper Strathdon to Glen Fenzie. Also SSE trending band from Delavorar in Glen Avon via Liath Beinn, Well of Don and Meikle Geal Charn to the Glen Gairn Granite. Also in the Lecht - Allargue - Carn Ealasaid - Carn Oighreag area of Upper Donside.
Quartzite, massive, gritty and cross-bedded in places. Basal part locally more psammitic. 'Boulder Bed' locally near base (with granite clasts in some outcrops). Amphibolitic pillow lavas and metavolcanic rocks near the base in Kymah Burn.
Generally 500 - 600m. Variable from 15m to 650m. Thin on Upper Donside (Allargue area).
Upper limit of massive quartzite below Culchavie Striped Formation.
Kyrre Formation
KYRE
Kingsley Sandstone
KYS
Kylnadrochit Semipelite Member
KYSP
At the top of the Glen Suie Limestone Member where limestone gives way to semipelite with thin limestone bands.
Kylnadrochit, Strath Avon, Glenlivet, Braes of Glenlivet, Glen Suie.
c. 230m in Braes of Glenlivet, up to 120m in type area (River Avon), possibly duplicated by minor/medium scale folding.
At the base of the Clashnoir Semipelite Formation, where laminated semipelite passes up into more weakly laminated, partly graphitic, semipelite.
Ryazanian To Barremian Rocks (Undifferentiated)
KZKB
Lewisian Complex
First Limestone To Second Limestone (Undifferentiated) (Cumbria)
L1L2
Third Limestone To Fourth Limestone (Undifferentiated) (Cumbria)
L3L4
Lower Four-Feet Coal (South Wales)
L4FCO
Fourth Limestone To Sixth Limestone (Cumbria)
L4L6
Fourth Limestone To Seventh Limestone (Undifferentiated) (Cumbria)
L4L7
Lower Five-Feet Coal (South Wales)
L5FC
Lower Five-Feet Coal And Gellideg Coal (Undifferentiated) (South Wales)
L5FGD
Fifth Limestone To Sixth Limestone (Undifferentiated) (Cumbria)
L5L6
Fifth Limestone To Seventh Limestone (Undifferentiated) (Cumbria)
L5L7
Lower Six-Feet Coal (South Wales)
L6FC
Sixth Limestone To Seventh Limestone (Undifferentiated) (Cumbria)
L6L7
Lower Seven-Feet Coal (South Wales)
L7FCO
Lower Nine-Feet Coal (South Wales)
L9FC
Lower Nine-Feet Coal (Lower Leaf) (South Wales)
L9FLL
Lower Nine-Feet Coal (Upper Leaf) (South Wales)
L9FUL
Re-Constituted Lewisian
Lacustrine Beach Deposits
LABD
Shingle, sand, silt and clay; may be bedded or chaotic; lacustrine beach deposits may be in the form of dunes, sheets or banks; formed fringing lakes. [Generic description].
Lacustrine Beach Deposits, 1
LABD1
Lag A'Bheith Formation
LABF
Laird's Burn Member
LABN
Locally, the top of the Duneaton Volcanic Formation.
New Cumnock 1:50 000 Geological Sheet 15 W.
Yellow-brown to pale buff volcaniclastic carbonate-cemented sandstones with some conglomerates.
The base of the purplish-brown to greenish cross-bedded volcaniclastic sandstones and siltstones, typical of the rest of the Auchtitench Formation.
Laminated Clays
LAC
Clay, generally brown and yellow, laminated. [Generic description: academic papers and BGS Memoirs]. Grain-thick silt laminae may be present.
Lacustrine Diatomite
LACDI
Langwell Conglomerate Member
LACO
Ladyha' Coal (North Ayrshire)
LADC
Lacustrine Deltaic Deposits
LADD
Typically sand and gravel; a delta within a lacustrine environment. [Generic description].
Loch Ard Grit Formation
LADG
Outgoing of coarse, chloritic and feldspathic arenites and wackes (at the top of the Ben Ledi Grit Formation) and incoming of pale arenaceous sandstones.
Ground southwest of Aberfoyle and west of the Loch Tay Fault zone, adjacent to the Highland Boundary Fault, through towards Loch Lomond.
Sandstone, pale buff to green-grey, clean to matrix-rich, coarse, locally gritty, interbedded with purple, grey and black slates.
Incoming of abundant black slate with chert (at base of Borfrishlie Slate Formation); contact may be tectonic.
Lady Coal (Warwickshire)
LADY
Dinantian To Westphalian Sills Of Lothians And Fife
LAFAS
Lancing Flint
LAFL
Ladygrange Coal (Glasgow, Airdrie; Central Coalfield)
LAG
Lochan An Aodainn Gabbro Intrusion
LAGB
Laig Gorge Limestone Member
LAGL
Unconformable on the Gribun Chalk Formation but considered absent in Mull and Morvern by Mortimore, Wood and Gallois (2001). This is the basal unit of the Strathaird Limestone Formation according to Braley (1990).
Known on the islands of Eigg and Skye.
Medium- to coarse-grained poorly sorted sandstones and conglomerates.
3.0 m at Laig Gorge, Eigg.
Unconformable at an erosion surface above a coarse very poorly sorted conglomerate with the grey micritic limestones of the remainder of the Strathaird Limestone Formation at Strathaird on Skye but apparently conformable at a burrowed horizon with the same limestones at Laig Gorge on Eigg.
Laggan Member
LAGN
Succeeds Benan Conglomerate; mudstone abruptly overlies coarse, pebble and boulder conglomerate.
Girvan area, Scotland.
Fossiliferous mudstone with well-preserved graptolite fauna obtained from the enclosed lime-rich nodules.
c.100m (estimate).
Succeeded by the Doon Hill Conglomerate Member of the Balclatchie Formation; boundary defined by abrupt overlying pebble conglomerate.
Laig Gorge Sandstone Member
LAGS
Laig Siltstone Member
LAGSL
Ladder Hills Formation
LAHI
Rapid transition from semipelite and pelite of the Glenfiddich Pelite Formation to micaceous and feldspathic psammite-dominated sequence.
Main development in the Ladder Hills. Thins northwards to flanks of Scaut Hill. Thins southwards to Donside (Carn Oighreag).
Micaceous and feldspathic psammites, semipelites and thin bands of pelite, the latter locally graphitic. Typically flaggy and commonly graded. Tuffaceous and rare metavolcanic beds. 'Boulder Bed' lithology with associated lenticular dolomite beds. Calc-silicate lenses in part. Quartzite bands.
0 to 1000m+. Probable duplication by folding in the Ladder Hills area.
Grades laterally and upwards into a semipelite/dark pelite/limestone sequence in Nochty Water-Upper Glenbuchat area. Elsewhere overlain by feldspathic quartzite and orthoquartzite of the Kymah Quartzite Formation.
Loch Ailsh Pluton
LAIL
Loch Ailsh Syenite S1
LAIL1
Loch Ailsh Syenite S2
LAIL2
Loch Ailsh Syenite S3
LAIL3
Loch Ailsh Ultramafic Rocks
LAILU
Lairg Intrusions
LAIRG
Lower Abdon Limestone Member
LAL
Llandovery Mudstone
LAM
Lamb Sill
LAMBS
Lady Morton Coal
LAMC
Loch A Mhoid Metagabbro Suite
LAMM
Lamington Conglomerate Member
LAMN
Lagan Mor Formation
LAMO
Ladder Hills Formation And Nochty Semipelite And Limestone Formation (Undifferentiated)
LAN
Lady Ann Coal (Glasgow; Central Coalfield)
LANC
Langdale Beds Member
LANG
Lanercost Limestone
LANL
Lanton Hill Vent And Plug
LANT
Lappathorn Member
LAPP
Lawsie Psammite Formation
LAPS
Lower Antiquatonia Band
LAQB
Laneast Quartzite Formation
LAQU
?Dinantian to ?Namurian
Not seen due to thrusting.
Between Otterham (SX 15 91) and Stoke Climsland (SX 36 74), north Cornwall. In the Otterham area (Sheet 322), the formation has been mapped as Crackington Formation (Mceown et al. 1973) and further investigation is needed to delimit the Formation.
Thick bedded, clean coarse-grained silica-cemented quartz sandstones with very subordinate dark grey to black mudstones, commonly containing plant debris.
Not known due to poor exposure and structure.
Lamb Rig Siltstone Member
LAR
Conformable: Laminated silty sandstones with rare bioclasts, directly overlying sandy siltstones and fine-grained sandstones with abundant bioclasts (Grain Heads Siltstones Member).
Olive-yellow, poorly fossilferous siltstones and fine-grained sandstones, with well-developed concretions.
Conformable: Olive siltstones underlying the lowest olive grey silty mudstone of the Baddingsgill Mudstone Member.
Lower Argillaceous Beds
LARG
Lark Formation
LARK
Larriston Sandstone Beds
LARS
Latterbarrow Sandstone Formation
LAS
Taken at the marked change to sandstone from silty mudstone containing an acritarch assemblage of Tremadoc to Arenig age (Skiddaw Group). Junction is nowhere exposed, but has been interpreted as an unconformity on mapping evidence.
Western part of the Borrowdale Volcanic Group outcrop, west of the Ennerdale Intrusion, Kinniside Common, Cumbria.
Sandstone (quartz-wacke) intercalated with mudstone in upper part.
Defined by the change to coarse volcaniclastic rocks at the base of the Devoke Water Member (Birker Fell Andesite Formation).
Laggan Sandstone Formation
LASA
Laisterdyke Shell Bed
LASB
Lealt Shale Formation
LASH
Sharp contact from Elgol Sandstone Formation.
The unit is divided into the Kildonnan and Lonfearn members, divided by a stromatolite bed. The Lealt Shale is argillaceous, with numerous thin limestone beds. A gradual coarsening upwards is apparent. Typically both members are fossil-rich with a restricted-range fauna of brackish-water bivalves, gastropods, ostracods and cochostracans. The first Jurassic footprint found in Scotland was discovered in the Trotternish region, Skye.
46m
Arbitrary to Valtos Sandstone Formation? According to references.
Langley Silt Member
LASI
Rests on sand and gravel River Terrace Deposits, with sharp base.
Thames Valley from Goring to Thames Estuary.
Varies from silt to clay, commonly yellow-brown and massively bedded. [Generic description].
1-5m, average 3m.
Lower Aisholt Limestone
LASL
Larkfield Shale Member
LASM
Lackagh Sandstone Formation
LAST
Lacustrine Alluvium
LAT
Normally soft to firm, consolidated, compressible silty clay, but can contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated, surface zone may be present. May be richer in clay and organic matter than "Alluvium" (of fluvial origin); of lacustrine origin. [Generic description].
Lacustrine Alluvium, First Level (Fermanagh)
LAT1
Normally soft to firm consolidated, compressible silty clay, but can contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated, surface zone may be present [generic description]; formed within a lacustrine environment.
Lacustrine Alluvium, Second Level (Fermanagh)
LAT2
Lacustrine Alluvium, Third Level (Fermanagh)
LAT3
Lacustrine Alluvium, Fourth Level (Fermanagh)
LAT4
Fifth Level Lacustrine Alluvium (Fermanagh)
LAT5
County Fermanagh.
Clay, blue-grey, soft, unconsolidated, deposit of formerly more extensive Upper Lough Erne, County Fermanagh.
Lower Alton Coal
LATC
Lacustrine Alluvium, High Level (Fermanagh)
LATH
Llandrindod Tuff Formation
LATU
Lauchlan Formation
LAU
Conformably overlies the Protovirgularia Grits.
Red-purple mudstone and thinly-bedded sandstone.
c.51m
Conformably overlain by the Drumyork Flags Formation.
Lower Acid Volcanic Group
LAV
Drawn at base of mainly tuffs of Lower Acid Volcanic Group which rest conformably on grits and sandy flags of the Basement Group.
Mid-Wales and Marches.
Tuffs and rhyolitic lavas (the latter may be recrystallized acid tuffs) interbedded slates also occur.
Approx. 150 to 300 metres.
Drawn at conformable upward passage from mainly tuffs of Lower Acid Volcanic Group to the Moelyn Slates of the 'Bifidus' Beds.
Llanelwedd Volcanic Formation
LAVO
Labour In Vain Vein
LAVV
Lady's Walk Shale Member [See Also Ldyw]
LAWA
Abrupt lithology change from sandstone of the Mains Formation to mudstone.
Inner Moray Firth Basin.
Sandy and shelly siltstones and mudstones with marine fauna, fining upwards as marine conditions deepened to open marine from shallow neritic conditions. Minor indicators of cyclicity, probably due to changing water depths and energy conditions.
Unrecorded.
Unconformity and erosion to Bathonian-age sandstones and coals of the Fladen Group.
Lochaline White Sandstone Formation
LAWS
[Late Cretaceous] Cenomanian; Turonian to Santonian in Mortimore et al. (2001).
Conformable (?) on the Morvern Greensand Formation.
Known from the Morvern district and the Isle of Mull.
Very pure white to pale yellow brown well-sorted medium-grained quartz sandstone. Massive with laminated and shelly beds to base. Most comprehensively described by Humphries (1961) at its type-site.
Up to 40 feet (12.2m) on the west side of Loch Aline according to Humphries (1961).
Unconformable beneath the Gribun Chalk Formation or Coire Riabhach Phosphatic Formation.
Law Sand And Gravel Member
LAWSG
Unconformably on bedrock and many older Quaternary strata including the Wilderness Till Formation and Bellshill Clay Member at Law and conformably on the Lochwinnoch Clay Member at Lochwinnoch.
Alluvium of the catchment of the River Clyde including all tributaries.
Massive, flat laminated and also cross bedded grey, fine- to coarse-grained sand with silt and traces of fine gravel, locally loose to dense, dark brownish grey, framework-supported, sub-angular to rounded fine to medium gravel with sand. Bedded silt with thin peat units and organic layers are intercalated. In places the member may encompass an even wider range of grain sizes including coarse gravel, cobbles and boulders.
Veneer to more than 18m.
The Law Sand and Gravel Member passes insensibly downstream into the estuarine and marine deposits of the Gourock Sand and Erskine Clay members of the Clydebank Clay Formation. It is widely exposed at the surface.
Laxfirth Limestone Formation
LAXF
Lower Bala Group
LBA
Drawn at the base of the Derfel Limestone Member of the Nant Hir Mudstones Formation. The oldest rocks exposed in the area.
The Arenig and Bala areas of North Wales.
Calcareous ashy mudstones, dark blue silty mudstones, siltstones with fine-grained sandstones, ash, dark blue mudstones and subordinate siltstones with limestone.
1505 metres approx.
Drawn at the conformable upward passage of calcareous ashes of the Gelligrin Calcareous Ashes Formation where it is unconformably overlain by the Moelfryn Mudstones Formation.
Low Barnsley Coal (West And South Yorkshire)
LBAC
Logie-Buchan (Albion) Glacigenic Subgroup
LBAG
Suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts derived predominantly from offshore of the Aberdeenshire coast (calcareous siltstone, limestone, red sandstone, shell fragments), including clayey diamictons (till), sand, gravel, silt and clay. Deposited from ice that pushed onshore from the North Sea Basin.
Unconformable contact with units of the Logie-Buchan and East Grampian Glacigenic subgroups.
Ludlow Bone Bed Member
LBB
Larry Bane Chalk Formation
LBC
Campanian. Belemnitella mucronata Zone.
Conformable at lower prominent erosion surface/marl resting on Boheeshane Chalk Formation.
Known throughout the North Antrim and east Antrim (Midland Valley) basins of Northern Ireland.
Limestone (chalk) with numerous flint bands. Shell debris abundant with distinct `pellet? or fragmentary limestone clasts evident on weathered surfaces. Three persistent erosion surfaces divide the Larry Bane Chalk Formation into two `Beds? (A and B). These surfaces may be treated as marl seams. Very large Belemnites are a prominent feature of this formation.
7.29m at type-site with Bed A 2.44m and Bed B 4.85m thick. This 1:2 ratio of bed thickness is considered to be characteristic of the whole Larry Bane Chalk Formation outcrop.
Conformable at an upper prominent erosion surface/marl beneath the Ballintoy Chalk Formation. Overlapped by younger members at margins of structural highs.
Leambreslen Conglomerate Member
LBCM
Linn Bed Coal (North Ayrshire)
LBCO
Logie-Buchan Glacigenic Subgroup
LBD
Unconformable on bedrock or older superficial deposits.
Coastal lowland north of Aberdeen (River Dee), east of Ellon and south of Peterhead.
Red clayey diamictons and gravels with a distinctive suite of clasts derived from the floor of the North Sea Basin, including calcareous siltstone, red sandstone and shell fragments.
Up to 20m known
At surface or beneath postglacial deposits.
Bringewood Beds And Lower Elton Beds
LBE
Lower Basalt Formation
LBF
Low Bright Floor Coal (Nottingham)
LBFC
Lugar Blackband Ironstone
LBI
Lockerbie Breccia Member
LBIE
Overlies Silurian strata with a marked angular unconformity north and west of the town of Lockerbie.
In the vicinity of Lockerbie, Lochmaben Basin, Dumfriesshire, southwestern Scotland [Southern Uplands].
Red-brown breccio-conglomerate interbedded with thin- to medium-bedded red sandstone. Lithic clasts have a distinctive local derivation and include reddened limestone, wacke sandstone, basic volcanic rocks, siltstone, mudstone and rounded quartz pebbles.
Proven by site investigations to be more than 11m thick.
Conformable lithostratigraphical boundary with the overlying undivided strata of the Hartfield Formation.
Ling Bank Formation
LBK
Overlain by the Fishes Formation with planar contact though sometimes eroded by pre-Forth or pre_Coal Pit Formation erosive phases. Basal surface is irregular, filling in an eroded topography.
Greenish grey micaceous silt with sand and clay interbeds. Sulphide-rich wisps and laminae and strong smell of hydrogen sulphide gas common. Shells increasing in abundance towards the base.
85.5m. Varies from ca 30m. to over 100 metres in deep erosive features.
Overlain by the Fishes Formation with planar contact though sometimes eroded by pre-Forth or pre-Coal Pit Formation erosive phases. Basal surface is irregular, filling in an eroded topography.
Lower Blackbird Coal (Lothian)
LBL
Loch Builg Diorite
LBLG
Lower Black Coal (South Wales)
LBLK
Llandovery Beds And Llandovery Mudstone (Undifferentiated)
LBLM
Lower Bluers Coal (South Wales)
LBLR
Lady Burn Formation
LBM
Conformably overlies the Quarrel Hill Formation (QHF).
Pale grey, poorly bedded nodular siltstones and mudstones with a locally rich shelly fauna.
Conformably overlain by the South Threave Formation (STHV).
Lower Bringewood Formation
LBN
Lacustrine-Bottom Deposits
LBOD
Typically organic material, clay, silt and sand; deposited on lake-bed by rain out, precipitation and inwash from the catchment. [Generic description].
Llanbedr Formation
LBR
Rests conformably on rocks of the Dolwen Formation; transitional boundary between dominantly sandstone and siltstone sequence of the Dolwen Formation and the mudstone dominated beds above.
Around the Dolwen Pericline; Harlech southwards towards Barmouth, where it is very poorly exposed.
Cleaved purple, green or bluish-grey mudstone with some siltstone and sandstone beds.
90m in the Dolwen pericline, 180m to the west, near Harlech.
Overlain conformably by sandstones of the Rhinog Formation. Boundary taken at the base of the first thick pale green turbiditic sandstone of the Rhinog Formation.
Lower Brampton Coal (Derbyshire)
LBRC
Little Brass Coal (South Wales)
LBRCO
Lower Brodini Coal (South Wales)
LBRO
Loch Borralan Pluton
LBRR
Long Bridge Sandstone
LBSA
Sharp upward change in a conformable succession from predominantly grey siltstone to sandstone - base of first sandstone bed above the Caw Mill Sandstone.
Sharp upward change in a conformable succession from sandstone to predominantly siltstone - top of last sandstone bed below the Hall Gill Sandstone.
Low Beamshaw Coal (South Yorkshire)
LBSW
The Low Beamshaw Coal of South Yorkshire is not the same as the Low Beamshaw Coal of West Yorkshire. Needs revision.
Lag Bank Tuff Formation
LBT
Base of dacitic lapilli tuff. Unconformably overlies Caw Formation (volcaniclastic breccia and sandstone) and Lickle Formation (rhyolitic and dacitic tuff).
Ulpha Basin and Coniston Fells. Postlethwaite Allotment (SD 240 930) to Pikes (SD 237 947) and northeast to Low Water (SD 270 980), Cumbria.
Dacitic lapilli-tuff, poorly sorted, massive, containing abundant white-weathered plagioclase-phyric dacite lapilli.
0 to 600m
Contact with overlying Seathwaite Fells Formation (volcaniclastic sandstone).
Low Bright Coal (Nottingham And Derby)
LBTC
Lower Bottom Coal (Lancashire)
LBTM
Lower Basic Volcanic Group
LBV
Drawn at base of mainly tuff and slate of Lower Basic Volcanic Group which rests conformably on massive, agglomeratic ashes of the Cefn-Hir Ashes.
Altered, pale green basic pillow lavas with intercalated bands of slate and acid and basic tuffs.
Approx. 450 metres.
Drawn at conformable upward passage from pillow lavas of the Lower Basic Volcanic Group to oolitic iron ore of the Llyn-y-Gader Mudstone and Ashes.
Lower Bath-House Wood Limestone
LBWL
Ledbury Formation
LBY
London Clay Formation
Rests unconformably on Woolwich and Reading Beds.
Fine, sandy, silty clay/silty clay. Glauconitic at base.
To 18m within Hitchin Sheet area but to 150m in London Basin (Essex).
Drawn at base of Bagshot Formation.
Lower Carboniferous Rocks (Undifferentiated)
LCA
Lower Cornbrash
LCB
Middle Jurassic, Upper Bathonian (Discus Zone).
Generally sharp, disconformable non-sequence: bioclastic limestone resting upon mudstones (and bioclastic ooidal limestones, locally) of Forest Marble Formation (Wessex Basin and south Midlands), Blisworth Clay Formation (East Midland Shelf east and north), or mudstone with minor sandstone beds of the Scalby Formation (Cleveland Basin).
Dorset Coast (Weymouth area) to Oundle-Fotheringay area, just south of Peterborough. Distribution in subcrop uncertain but probably restricted to Wessex and Worcester basins and southern parts of East Midland Shelf; absent over the London Platform.
"A high degree of lithological variation is observed ... very pale coloured bioclastic micritic and nodular limestones are characteristic". (Page, 1989). "Pale cream sparsely ooidal and peloidal, locally very shelly or with thin shelly mudstone partings and pseudonodular appearance" (Bristow, 1999).
[Compiler's Notes] This unit is apparently distinguished only on Sheet 297. This Lexicon entry has been compiled for this reason, but preferably the UCB and LCB should be expunged from maps and the lithostratigraphical database. Upper Cornbrash and Lower Cornbrash were originally, and certainly have become, chronostratigraphical terms (Douglas and Arkell, 1928, 1932). If they were to be extended to become lithostratigraphical units, then Page's (1989) terms Berry and Fleet members would be the appropriate ones to use, even though they are not absolutely precise synonyms. However, in my view (coloured particularly by my experience on Sheet 219) the Upper and Lower Cornbrash (or Berry and Fleet members) are indistinguishable (and so impossible to define) on the basis of lithology even in the broadest sense; this is why I have chosen to quote from Page and Bristow et al. in the Lithological Description. So I don't believe it is possible to map a boundary between the two, and it is unhelpful to pretend otherwise. It is true that some lithologies are more common in one unit rather than the other e.g. bedded sandy limestones are more or less restricted to the UCB, and may indeed comprise the bulk of the unit in some areas, but this does not enable a boundary to be drawn between UCB and LCB. Indeed, in many areas (e.g. sheets 219, 127) the UCB is of typical LCB lithology, see for example. Cox et al 1991. Despite the foregoing, it is possible to say that in certain areas much or all of the Cornbrash Formation is either UCB or LCB (e.g. Page, 1989, Fig.2), but this information should be shown on the chronostratigraphical GVS. [Condensed from notes provided by M G Sumbler 25/09/05.]
0 to c.4m; typically c.3m. Absent north of Peterborough.
Quasi-conformable or non-sequential contact with limestones of the overlying Upper Cornbrash or, where the latter is absent (eg, south Midlands), disconformable contact with mudstone of the succeeding Kellaways Formation.
London Clay Basement Bed [See Also Hwh]
LCBA
Lower Carboniferous Basal Breccia
LCBB
Laminated Clay Or Brickearth
LCBE
Clay, generally brown and yellow, laminated. [Generic description: academic papers and BGS Memoirs].
Little Cannel Coal
LCC
Lewes Nodular Chalk Formation, Seaford Chalk Formation, Newhaven Chalk Formation And Culver Chalk Formation (Undifferentiated)
LCCK
Loch Coire Granite
LCCO
Lower Clod Coal (North Staffordshire)
LCDCO
Lower Cemetery Beds
LCE
Lower Caithness Flagstone Subgroup
LCF
Lower Calcareous Grit Formation
LCG
Lower Calcareous Grit Formation And Coralline Oolite Formation (Undifferentiated) [Yorkshire]
LCGCO
Locharbriggs Sandstone Formation
LCH
Unconformable on Lower Palaeozoic turbidites; locally unconformable on probable Carboniferous strata.
Dumfries Basin and offshore extension within the North Solway Basin.
Aeolian dune sandstone; very well sorted unimodal sandstones exhibiting large scale dune cross-bedding.
Interdigitates with and overlain by the Doweel Breccia Formation.
Lamancha Conglomerate Formation
LCHA
Unconformably overlies Ordovician rocks of the Southern Upland Terrane.
The Peebles area of the Southern Uplands.
Purple and reddish brown conglomerates and breccias in a sandstone matrix, with pebbles and rounded boulders of local derivation, up to 0.4 m in diameter of wacke and local 'Haggis Rock'.
At least 50 m thick.
Not seen, as it is cut by the Southern Upland fault.
Lochinch Cherry Coal (Glasgow)
LCHC
Lincoln Hill Limestone Bed
LCHL
Change up from mudstone with limestone nodules of the Dry Doddington Nodule Bed; at 38.62m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands: north Leicestershire to Linclonshire. Not recognised in north Lincolnshire, or south Leicestershire, where it passes south either into part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or into part of the mudstone-dominated Charmouth Mudstone Formation.
Thin bed of grey, silty, shelly, ferruginous, bioclastic limestone. Fauna of forams, bivalves, gastropods, ammonites, bryozoans and echinoderms. Although mapped only locally, is thought to be laterally persistent.
Up to 0.3m; 0.12m in type section.
Change up into bluish grey, shaly mudstone of the undifferentiated Beckingham Member; at 38.50m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Lower Chamber Coal (South Lancashire)
LCHR
Lower Charles Coal (South Staffordshire)
LCHS
Lower Churnet Shales
LCHT
Lower Chalk Formation [Remains In Informal Use But Generally Regarded As Obsolete Onshore]
LCK
In Hitchin area, unconformity. Base of Cambridge Greensand resting on Gault Clay.
As defined above it is restricted to East Anglia, but the term can be applied more widely if defined differently. Limits necessarily vague.
A grey marly chalk with marl content decreasing upwards. No flint. Comprises a thin basal bed of glauconitic marl (Cambridge Greensand) overlain by more typical Lower Chalk sequence that is usually divided into a lower "Chalk Marl" with rhythmic alternations of chalk and marl, and an upper "Grey Chalk" separated by a distinctive hard band. (Totternhoe Stone).
45-80m in Hitchin area.
Sharp contact with overlying Middle Chalk the base of which is marked by Melbourn Rock, a hard nodular chalk. Top of Lower Chalk marked by a thin but distinctive yellowish marl (Plenus Marl).
Lunan Clay Member
LCL
Sharp conformable contact with gravel recorded by Rice (1960) at the former Anniston Brickworks.
Lower reaches of the Lunan and Brothock valleys, Angus, and possibly in northeast Fife.
Red plastic clay, typically laminated, with laminae of very fine-grained micaceous sand, locally with rhythmic, 2-3cm-thick cyclopels, thin beds of interlaminated fine- and medium-grained sand, sparse boulders and discoid calcareous concretions towards the base. Becoming more interbedded with sand inland. AMS radiocarbon dates of 17,065 and 17,720 ka BP on marine microfauna reported by McCabe et al (2007).
To 11m proved
Apparently sharp, unconformable contact at no higher than 23m OD with overlying glaciofluvial gravel of the Drumlithie Sand and Gravel Formation.
Loch Of Cliff Limestone Formation
LCLL
London Clay Formation And Lambeth Group (Undifferentiated)
LCLM
Lower Carriden Limestone
LCLS
London Clay Formation And Lower London Tertiaries (Undifferentiated)
LCLT
Longcleuch Vein
LCLV
Lower Comley Limestones Formation
LCML
Base of shelly glauconitic limestone, resting on glauconitic sandstone of the Lower Comley Sandstone.
Sandy glauconitic and phosphatic limestone overlain by phosphatic algal micrite.
Unconformable beneath Middle Cambrian sequence of pale grey-green calcareous sandstones and shales with thin limestones (Upper Comley Group).
Scottish Lower Coal Measures Formation
LCMS
Base of the Lowstone Marine Band, or its local correlative, or at the appropriate place of disconformity.
Scotland.
Sandstone, siltstone and mudstone in repeated cycles that most commonly coarsen upwards, but also fine upwards locally, with seatclay or seatearth and coal at the top. The mudstone and siltstone are usually grey to black, while the sandstone is fine- to medium-grained and off-white to grey. Coal seams are common and many exceed 0.3m in thickness.
90 to 340m
Base of the Vanderbeckei (Queenslie) Marine Band.
Lower Caerhedyn Coal (South Wales)
LCNC
Lodgement Coal (Central Ayrshire)
LCO
Lady Coal (Lancashire)
LCOL
Lower Coxtool Coal (Fife)
LCOX
Loch Caorach Quartz-Gabbro Ring-Intrusion
LCQGB
Lower Cretaceous Rocks [Obsolete Code Due To Duplication: Use Locr]
LCRE
Lower Camregan Grits Formation
LCRG
Disconformable junction with Pencleuch Shale Formation (Penwhapple South Group).
Fine- to medium-grained sandstone.
Conformably overlain by Wood Burn Formation.
Lower Crichton Limestone
LCRL
Low Carriteth Limestone
LCRT
Little Coal (South Derbyshire)
LCSD
Little Coal (South Lancashire)
LCSL
Lower Comley Sandstone Formation
LCSS
Base of sandstones and mudstones as described under Lithology, resting on grey quartzites of the Wrekin Quartzite; junction is sharp and may be disconformable locally.
Church Stretton, Lilleshall, Shropshire.
Interbedded green, glauconitic and phosphatic shales, sandy mudstones and fine- to coarse-grained calcareous sandstones.
Base of shelly glauconitic limestone of the overlying Lower Comley Limestones Formation. Locally an unconformity overlain by the Comley Breccia (bed).
Little Coal (In Swansea Member, South Wales)
LCSW
Longcarrow Cove Tuff Beds
LCTB
Lowca Till Member
LCTI
Sharp, irregular, unconformable contact with bedrock.
Coast of Cumbria between Whitehaven and Sellafield.
Reddish brown, gravelly sandy silty clay diamicton, massive, matrix-supported, very compact, containing angular to subrounded clasts up to boulder size of red sandstone, with some granite, granophyre, yellow sandstone, mudstone, limestone, Borrowdale Volcanic Group lithologies (rhyolite, welded tuff), greywacke sandstone and siltstone. Has well developed clast fabric and fissility typical of lodgement tills.
Ground surface or commonly a sharp, undulating, unconformable contact with sand and gravel of the St Bees Sand and Gravel Member of the Seascale Glacigenic Formation.
Logie Coldstone Intrusion
LCTO
North Britain Late Carboniferous Tholeiitic Suite
LCTS
Limestone Coal Formation And Upper Limestone Formation (Undifferentiated)
LCUL
Lower Crafnant Volcanic Formation
LCV
On Cwm Eigiau Formation sandstones.
Widespread in eastern Snowdonia (see Sheet 106).
Acidic ash-flow tuffs interbedded with siltstone, mudstone, hyaloclastite and thin basaltic tuffs.
Overlain by mudstones and siltstones at the base of the Middle Crafnant Volcanic Formation.
Linwood Blackband Ironstone
LDBI
Ledard Burn Member
LDBU
Outgoing of coarse clean, thick-bedded arenites and the incoming of finer-grained sandstones and siltstones.
Currently only defined between Loch Drunkie, Achray Forest, and ground around and to the west of Ledard Burn on Sheet 38E.
Metasandstone, pale to medium grey, and slaty metasiltstone, green-grey, rhythmically interbedded and interlaminated. Thin calcareous lenses and pelite beds.
c.1500m in the type section at Ledard Burn.
Incoming of coarser-grained arenites and wackes.
Lower Drumgray Coal (Central Coalfield)
LDC
Little Dilhorne Coal (Cheadle)
LDCO
Lower Dictyoclostus Teres Band
LDCT
Lake District Devonian Minor Intrusion Suite
LDDMI
Includes all dykes, sills and other minor intrusions in the Lake District of proved and inferred Lower Devonian age.
Within the Lake District Lower Palaeozoic inlier of Cumbria, and in the Cross Fell Inlier.
Quartz feldspar-phyric microgranite, plagioclase-biotite-phyric microgranodiorite, and rhyolite dykes and minor intrusions. Examples of these dykes in the Scafell area have the following radiometric ages: 393 +/- 9 Ma, 392 +/- 4 Ma ( Rb-Sr whole rock) (Al Jawadi, 1987).
Lacustrine Deposits
LDE
Silt and clay (can include organic and/or calcareous muds); of lacustrine origin. [Generic description: from East Anglian data].
Lacustrine Deposits, 1
LDE1
Silt and clay (can include organic and/or calcareous muds). Older than 'Lacustrine Deposits [undifferentiated]' in the same map area; of lacustrine origin. [Generic description: from East Anglian data.
Lacustrine Deposits, 2
LDE2
Lower Devonian Rocks (Undifferentiated)
LDEV
Lake District Ordovician Felsic Plutonic Suite
LDFP
Within the Lake District Lower Palaeozoic inlier in Cumbria, and concealed beneath the Askrigg Block.
Granite,microgranite (Eskdale and Ennerdale intrusions), granodiorite and microgranodiorite (Eskdale intrusions); garnet-bearing quartz-feldspar-phyric microgranite (Threlkeld Intrusion); dolerite,diorite and hybridised rocks (Ennerdale Intrusion). These all have Ordovician radiometric ages (see Millward, 2000, for summary and references).
To include all felsic plutonic intrusions in the Lake District and adjacent areas of proved and inferred Ordovician age which includes the exposed Threlkeld (THKD), Ennerdale (ENIN) and Eskdale (ESK) intrusions, and the concealed Wensleydale Intrusion (Kirby et al, 2000).
Loveden Gryphaea Bed
LDGR
Change up from mudstone with large argillaceous limestone nodules and small phosphatic nodules at some levels, of the undifferentiated Charmouth Mudstone Formation, into mudstone with abundant Gryphaea (as described under Lithology). In type section Copper Hill Borehole (SK94SE/56), base lies at change up from poorly fossiliferous sandstone, siltstone and mudstone beds at 147.30m depth.
East Midlands: north Leicestershire to Linclonshire. Not recognised in the Charmouth Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into part of the mudstone-dominated Charmouth Mudstone Formation. An assertion by Berridge et al, (1999) that the Loveden Bed (Raricostatum Zone) may correlate with the '70 Marker' (Jamesoni Zone) (Horton and Poole, 1977) of the Charmouth Mudstone Formation of the south Midlands is at odds with the biostratigraphy.
Grey mudstone beds with numerous Gryphaea maccullochii. Locally includes a thin shelly limestone bed. Fauna also includes corals, brachiopods, many other bivalve species, and belemnites. No feature, but Gryphaea conspicuous in clay soil.
1.5 to 2.2m; 2.22m in type section.
Change up from mudstone with numerous Gryphaea (as described under Lithology) into mudstone with thin (0.02m) limestone beds of undifferentiated Charmouth Mudstone Formation; at 145.08m depth in type section Copper Hill Borehole (SK94SE/56).
Little Dalby Head
LDHD
Loch Dhu Slate Member
LDHU
Lower Dalness Ignimbrite
LDI
Lower Diamond Coal (Tranent; Lothian)
LDIC
Lake District Batholith
LDIST
Lacustrine Deposits (Lough Neagh, First Level)
LDLN1
Lacustrine Deposits (Lough Neagh, Second Level)
LDLN2
Lacustrine Deposits (Lough Neagh, Third Level)
LDLN3
Lacustrine Deposits (Lough Neagh, Undifferentiated)
LDLNU
Linkhead Limestone
LDLS
Largoward Marl Coal
LDM
Lower Demesne Limestone
LDML
Lake District Ordovician Mafic Plutonic Suite
LDMP
Includes all mafic plutonic intrusions in the Lake District of proved and inferred Ordovician age which includes the Carrock Fell Complex (CFCO) and the Haweswater Intrusions (HAWS).
Within the Lake District Lower Palaeozoic inlier in Cumbria.
Gabbro, microgabbro and dolerite, with subordinate microgranite, microdiorite, rhyolite; and intrusive breccia.
Lake District Ordovician Minor Intrusion Suite
LDOMI
Dykes, plugs and other minor intrusions in the Lake District of known and inferred Ordovician age, including two formal lithodemic units, the Embleton microdiorite intrusions (EMBL) and the Bassenthwaite diorite intrusions (BADIN).
Cumbria, within the the Lake District and Cross Fell Lower Palaeozoic inliers.
Basalt, dolerite and gabbro; dacite, garnetiferous dacite, rhyolite; andesite and hybridised andesite; intrusive breccia; microdiorite; porphyritic horneblende diorite and microdiorite; hornblendite.
Lower Deep Coal (Cannock)
LDPC
Lower Dornoch Sandstone Unit
LDSA
Linwood Shell Bed
LDSB
Glasgow-Airdie (Central Coalfield).
Largoward Splint Coal
LDSP
Langland Till Member
LDTI
Lower Dunscome Goniatite Bed
LDU
Loch Dubh Formation
LDUBH
Loch Duich Gneisses
LDUI
Lower Devonian Slates
LDVS
Llandovery Rocks (Undifferentiated)
LDVY
Lower Dysart Coal
LDY
Lower Dykebar Coal
LDYC
Lady's Walk Formation [See Also Lawa]
LDYW
Corodale Gneiss
Leagram Mudstone Member
LEAM
The dark grey blocky mudstone of the Leagram Mudstone Member lies conformably upon limestones of the Limekiln Wood Limestone Member in the Clitheroe Anticline or upon the Whitemore Limestone Member of the Whitewell Anticline.
Restricted to the Clitheroe (SD 75 45), Slaidburn (SD 71 53) and Whitewell (SD 64 47) anticlines.
A dark grey, blocky, pyritic and calcareous mudstone, interbedded with thin, dark wackestones with diffuse bed boundaries.
Up to at least 50 m thick.
At the type locality, taken where there is a change from the dark grey blocky mudstone of the Leagram Mudstone Member to the overlying thin-bedded, laminated calcisiltites and dark grey, fissile mudstones of the Hodder Mudstone Formation (undifferentiated).
Leap Hill Vent
LEAP
Pyroclastic breccia or basaltic agglomerate in vent, intruded by trachyte and dolerite.
Vent, elongate, c.300m x 600m
Clach Leatad Pluton
LEAT
Lebberston Member
LEBB
Beeding Beds
LEBE
Beachy Head Beds
LEBH
Leigh Barton Limestone
LEBL
Caburn Beds
LECA
Cliffe Beds
LECF
Lewes Nodular Chalk Formation
LECH
Upper Cretaceous, Turonian to Coniacian. Top Terebratulina lata, Sternotaxis plana (now Plesiocorys plana) and Micraster cortestudinarium Zones.
Conformable at the base of Glynde Marl 1 in Sussex, but one of the higher marls elsewhere although invariably in the interval Glynde Marls to Southerham Marls in the Southern Province. The mapping boundary is placed at the appearance of nodular chalks and significant flint development within that range of marls. In the "Transitional" Province the formation is condensed in response to the later inception of nodularity and hardground development such that the lower boundary is diachronous here and placed below the "Chalk Rock Member" at the Reed Marl (the lateral equivalent of the Bridgewick Marls of the Southern Province).
Composed of hard to very hard nodular chalks and hardgrounds (which resist scratching by finger-nail) with interbedded soft to medium hard chalks (some grainy) and marls; some griotte chalks. The softer chalks become more abundant towards the top. Nodular chalks are typically lumpy and iron-stained (usually marking sponges). Brash is rough and flaggy or rubbly, and tends to be dirty. First regular seams of nodular flint, some large, commence near the base and continue throughout.
The formation is thickest in the basinal successions of the Southern Province in east Hampshire and Sussex where it attains c.35 to 60m in the east and up to 80m in west. The formation thins towards the margins of the outcrop and over synsedimentary structural highs.
Conformable at the Shoreham Marl 2, which is equivalent to the East Cliff Marl 2 in Kent and also identified at the Anstey Quarry [TL 395 329] south of Royston, in the "Transitional" Province. In the field, this is the most difficult boundary to place precisely because of the gradual upward transition in predominant lithology, with interbeds of hard chalk in soft chalk and vice versa. The most positive criterion is the incoming of abundant thick-shelled inoceramid debris (Platyceramus) in soft chalks, although this may not be applicable everywhere. The presence of a sequence containing carious flints within the low Seaford Chalk and high Lewes Chalk is a helpful field indicator of the boundary.
Leckhampton Member
LECK
Opalinum Zone to Scissum Zone.
Disconformity: change upward from Lias Group (mudstone/sand/shelly, ironshot marl and limestone) into the rock types described in the lithological description.
Cotswolds Hills from north Oxfrodshire (near Chipping Norton) to northeast South Gloucestershire District. Absent due to overstep by Salperton Limestone Formation in south Cotswolds and in Vale of Moreton area (see Barron, A J M, 1997, fig.4). Replaced in east Oxfordshire by Northampton Sand Formation (see Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D, 1987).
Grey, weathering yellow-brown, rubbly, highly bioturbated, ferruginous, possibly sideritic), finely shell-detrital, medium-grained peloidal and ooidal sandy muddy limestone, ironshot and very shelly in parts, with thin marl beds, basal bed conglomerate in places. In Wotton-under-Edge area includes 'ironshot' limestones of the Opaliniforme Bed at the base (Richardson, L, 1910).
Typically 2 to 6m. Type section; 5.3 to 5.6m. Maximum c.10m (Northleach area).
Upward transition from limestones as in lithological description into ooidal shell-detrital grainstone (Crickley Member), or hardground overlain by Salperton Limestone Member.
Lethen Bar Lethen And Clune Fish Bed
LECL
Lower Eday Sandstone Formation
LED
Lower Earthy Delf Coal (South Lancashire)
LEDC
Ledmorite Swarm
LEDD
Ledmore Nepheline-Syenite
LEDS
Leete Limestone Formation
LEEL
Holkerian to Early Asbian.
Lowermost porcellanous limestone overlying coarser-grained and thicker-bedded limestones of the Llanarmon Limestone Formation.
Crops out on Anglesey [SH5982] in northwest Wales; at Llandulas [SH9078] and along the western side of the Vale of Clwyd [SJ1252]; along the eastern side of the Vale of Clwyd in fault slices along the Vale of Clwyd Fault [SJ1267]; in its type area east of the Clwydian Range between Nannerch and Llanelidan [SJ1852]; and south of the Bala Fault Zone between Minera and Oswestry [SJ2722].
Lithologically varied comprising diagnostic porcellanous and fenestral limestones (wackestones and calcite mudstones) interbedded with dark, foetid argillaceous limestone (packstones), and pale skeletal peloidal limestones (packstones and grainstones) including beds rich in oncoids. Thin grey and green mudstone beds and rare coals are present locally. Lithologies are arranged in shoaling-upwards rhythms, each capped by a porcellanous limestone.
150 to 175m
Uppermost porcellanous limestone underlying rubbly and pseudobrecciated limestone of the Loggerheads Limestone Formation.
Lees Coal (South Staffordshire)
LEES
Leete Limestone Formation [Obsolete Code: Use Leel]
LEET
Lewes Tubular Flints
LEFL
Leitrim Group
LEG
Glynde Beds
LEGL
Leagarth Pelite Formation
LEGP
Leine Halite Formation
LEHA
Leet Hill Sand And Gravel Member
LEHI
Mid Pleistocene (MIS 16).
The lower boundary of the Leet Hill Sand and Gravel Member truncates either the diamicton facies of the Corton Till Member or older stratified sands of the Wroxham Crag Formation sediments. Locally, such as at the stratotype, the outwash and underlying fluvial sediments (Bytham Catchments Subgroup) form a gradational fluvial to glacial outwash continuum.
The deposit has been mapped extensively throughout the Yarmouth and Lowestoft districts.
Stratified and channelled proximal glaciofluvial outwash deposits. Lithologically, the gravels are rich in flint and quartzose clasts, and contain erratics of northern provenance including Old Red Sandstone, basaltic porphyry, dolerite and Carboniferous limestone. Palaeocurrent measurements reveal flow originally towards the northeast when constrained by the Bytham River valley, and then southwards as the river valley was infilled by outwash sediment.
The deposit thickens westwards from Corton (0.8m) to around 9m in the vicinity of Leet Hill.
The upper boundary of the Leet Hill Sand and Gravel Member with the overlying Corton Sand Member is abrupt but conformable.
Hope Gap Beds
LEHO
Loch Eil Group
LEIL
Land's End Intrusion
LEIN
Lower Eighteen-Feet Coal (South Wales)
LEIT
Kingston Beds
LEKI
Lower Elton Formation
LEL
Leete Limestone Formation And Loggerheads Limestone Formation (Undifferentiated)
LELH
Light Point Beds
LELP
Lewes Marl
LEMA
Lewisian Complex And Moine Supergroup (Undifferentiated)
LEMO
Leyland Formation
LEMU
Lenthay Limestone Bed
LEN
Transition from shell-detrital mudstone to shelly argillaceous limestone.
Lenthay Common, west of Sherborne, to c.1km northwest of Milborne Port.
Micritic limestone with a shelly and argillaceous base and an extensively bioturbated and argillaceous top. Contains abundant Sphaeroidothyris lenthayensis.
0 - c.1m; 0.32m in Purse Caundle Borehole.
Transition to calcareous mudstone from argillaceous limestone.
Navigation Beds
LENA
Lewes Nodular Chalk [Redundant Code: Use Lech]
LENO
St Leonard's Sill
LENS
Loxley Edge Rock
LER
Ringmer Beds
LERI
Lum Edge Sandstones
LES
The lower boundary is taken at the base of the first sandstone in the sandstone-dominated unit above black fissile mudstone that includes the highest Isohomoceras subglobosum Marine Band.
Oakenclough Brook [SK053 636] southeast to Archford [SK 080 605], Thorncliff [SK 020 585] area.
Thin to thick sharp-based turbiditic beds of fine- to coarse-grained protoquartzitic sandstone and silty mudstone.
Up to 47.52m
The upper boundary is taken below the black fissile mudstone of the Alportian Hudsonoceras proteum (H2a) Marine Band, at the base of a mudstone-dominated succession overlying the Lum Edge Sandstone.
Lewes Nodular Chalk Formation And Seaford Chalk Formation (Undifferentiated)
LESE
Lask Edge Shales
LESH
Letham Silt Member
LESI
Latest Loch Lomand Stadial to Holocene.
Unconformable and transgressive base on older units including the Bothkennar Gravel, Abbotsgrange Silt and Kinneil Kerse Silt members of the Forth Clay Formation and the Errol Clay Formation.
Forth valley west of Aberfoyle to the Forth estuary at Grangemouth.
Very fine- to coarse-grained sand, silt and clay, grey and brownish grey, well laminated to thin-bedded, some pebbles up to 4cm, finely micaceous, rooty near top below sub-Carse Peat (where developed), depending on location within the palaeo-estuary, the dominant material varies from sand to clay. The deposit forms a series of buried raised beaches/terraces related to transgressive and regressive cycles of sea-level change.
Overlain unconformably by the sub-Carse Peat (where present) and transgressive estuarine clay, silt and sand of the Carse of Stirling Clay Member.
Leighland Slates Member
LESL
Shoreham Beds
LESM
South Street Beds
LESO
Lessans Formation
LESS
Little Splint Coal (Fife)
LEST
Lewiston Beds
LEW
Lewis Member
LEWI
Lewis Till Formation
LEWTI
Rests on broken or striated rock surface.
Outer Hebrides and St Kilda.
Compact greyish brown, matrix-supported diamicton with cobble to boulder sized subangular clasts mainly of Lewisian gneiss lithogies in a silty sand matrix. Generally becomes more gravelly towards the base, with angular clasts, and interstratified with sand in the uppermost metre or so, where boulders up to 2m in diameter are common. Forms gently undulating sheets.
Generally capped by peat or alluvium deposits. Unconformably overlain by brown, matrix-supported, clast-rich diamicton of the Ruaival Diamicton Formation (Head) on St Kilda.
Leys Gravel Formation
LEY
Unconformable on diamicton of the Leys Till Formation.
Buchan, northeast Scotland. Mapped on Sheet 87W (Ellon).
Gravel, subrounded to rounded, up to boulder sized clasts, over 90% felsite.
Unconformable with rubbly felsitic "head" deposit, named as the "Kirkhill Gelifluctate I" by Hall and Connell, 1986.
Leys Till Formation
LEYST
As seen in geological test pits either sharply unconformable, planar, boundary on weathered bedrock or gradational glaciotectonised, boundary (over c.0.4m) showing incorporation of lenses and small rafts of weathered metasedimentary or mafic igneous rock types.
Buchan, northeast Scotland. This formation is currently only known from within the confines of Leys Quarry (disused) (centred on NK 0040 5250). Sheet 87W (Ellon). The unit might be regionally significant and present locally across northeast Scotland.
Non-calcareous, matrix supported, gravelly, slightly clayey, silty sand diamicton. Dominantly pale olive-brown and olive-brown (upper interval shows extensive yellowish brown and strong brown mottling). Non-calcareous, matrix supported, gravelly, slightly clayey silty sand. Clast types include quartzites, psammitic and pelitic metasedimentary rocks, felsite, mafic igneous rocks and grey granite. The lower intervals contain lenses and small rafts of kaolinised metasedimentary rocks and grussified mafic igneous rocks. Interpreted as a subglacial till.
As seen in geological test pits sharp, planar, erosive upper boundary with overlying felsite-rich gravels of the Denend Gravel Formation.
Lingula Flags Formation
Conformity and gradationally overlies mudstones of the Menevian Group.
1:50,000 Sheet 209 (St. David's) and adjacent Sheet 210, Pembrokeshire, South Wales.
Interbedded pale siliceous and feldspathic siltstones and greenish grey to buff micaceous mudstones, locally with abundant Lingulella davisii.
Generally faulted, but evidence locally of angular unconformity with various lithologies of Arenig age.
Lower Forest Beds
LFB
Loch Fad Conglomerate Formation
LFC
Not seen, as the formation is a fault-bounded slice within the Highland Boundary Fault system.
The eastern shore of Loch Fad, Isle of Bute, Scotland, restricted to 1:50 k sheet 29E, Dunoon.
A coarse conglomerate with clasts up to 1m, but more commonly in the 10-50 cm range, consisting mainly of gritty sandstone but with rare serpentinite, chert and 'epidiorite'. The sandy matrix and sporadic sandstone interbeds are strongly cleaved.
Little Flint Coal (Coalbrookdale)
LFCC
Lower Fireclays Of The Passage Formation
LFCL
Between Marine Bands Nos 2 and 3, Roman Cement Limestone and Netherwood Coal respectively.
Lower Florida Coal (South Lancashire)
LFCO
Lower Fuller's Earth Member
LFE
A rapid increase in shell-detritus in calcareous mudstones that pass into the uppermost limestone of the Inferior Oolite.
Bath area to English Channel; unit continues to Burford area, Oxon, but name used only where the Upper Fuller's Earth is also present.
Olive-grey, silty, calcareous mudstones with thin intervals of argillaceous limestone and oyster-rich mudstones (9 divisions: see principal reference).
12.85m in type section; 12.15m in Bath-Frome area, 68m in Purse Caundle Borehole and c.100m in South Dorset.
A similar increase in shell-detritus that passes into the massive limestones of the Fuller's Earth Rock.
Lower Follifoot Grit
LFG
Sharp contact between sandstone bed at the base of the unit and the underlying siltstone and mudstone.
Sandstone; fine-, medium- and coarse-grained.
Sharp contact between sandstone and the overlying mudstone.
Lower Fish Tooth Bed
LFI
Lower Fittleworth Member
LFIB
see Fittleworth Member FIB
Lower Fionchra Member
LFION
Lower Felltop Sandstone
LFLS
Lacoon Sandstone Member
LFM
Lower Flow Moss Lava Member
LFMLA
The nature of the base is unknown but it might be unconformable on Inverclyde Group or older strata.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton, limited in area between Neilston (NS 440 560) in the northwest and Darvel (NS 610 390) in the southeast.
The Lower Flow Moss Lava Member consists of alkali basalts and subordinate basanites and ankaramites.
The Member is overlain by and interbedded with the Moyne Moor Lava Member in the western part of the area of occurrence. Elsewhere where locally known, a thick bole is developed on the uppermost flow and the Upper Flow Moss Lava Member rests on this.
Lane Foot Sandstone
LFOS
Lower boundary taken where sandstone of Lane Foot Sandstone lies with a sharp base upon mudstone and siltstone of the Kirkbeck Member.
Known from the Bentham area, Lancashire. Not mapped east or south of SD66NE.
Coarse-grained, cross-bedded, gritty sandstone.
Up to 55m (in Bentham Station Borehole SD66NE/1); generally less than 10m.
Upper boundary taken where sandstone of the Lane Foot Sandstone has a sharp top, overlain by fissile, dark grey micaceous siltstone of the Kirkbeck Member.
Lower Findhorn Sandstone Unit
LFSA
Low Furness Basal Formation
LFSB
Basal unconformity on pre-Carboniferous strata.
South Cumbria, Ulverston (48) and Barrow (58), 1:50k sheets.
Conglomerate, sandstones, siltstones and mudstones with subordinate evaporites, presumed of terrigenous origin in lower part (Duddon Conglomerates). Upper part of limestones and siltstones, mostly red with interbedded conglomerates; all presumed of marine origin.
0 to more than 200m
Base of overlying Martin Limestone.
Lodge Farm Silt And Clay Member
LFSC
London Fields Sill
LFSI
Linfit Lousey Coal (West Yorkshire)
LFT
Lower Foot Coal (South Lancashire)
LFTC
Lower Felltop Limestone
LFTL
Landscaping For Site Formation (Generally Engineered)
LFU
Lower Foxton Limestone
LFXL
North Northumberland, particularly the area around Howdiemont Sands south of Howick.
Impure crinoidal limestone.
c.0.4m
Late-Glacial Alluvium
LGA
Flattish spreads of fine- to medium sand with silt and some gravel, with organic seams.Normally soft to firm consolidated, compressible silty clay, but can contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated, surface zone may be present [generic description]; late glacial.
Llanengan Formation
LGAN
Sharply overlies well-bedded muddy sandstones of the St Tudwal's Formation. Boundary is marked by a thin phosphatic conglomerate horizon at the top of St Tudwals Formation, possibly representing a non-sequence or minor disconformity.
Dark grey mudstone with thin laminae of sandstone and siltstone.
Amendments made to original entry.
Sharply overlain by oolitic ironstones of the Hen-dy-Capel Ironstone which are succeeded by undivided mudstones of the Nant ffrancon Subgroup.
Lower Gyffin Beds
LGB
Lacustrine Gravel Beach Deposits
LGBD
Shingle and sand, locally with silt or clay; may be bedded or chaotic; lacustrine gravel beach deposits may be in the form of dunes, sheets or banks; formed fringing lakes. [Generic description].
Lower Llangibby Beds [Obsolete Code: Use Llyb]
LGBL
Middle Llangibby Beds
LGBM
Upper Llangibby Beds [Obsolete Code: Use Ulyb]
LGBU
Llangibby Beds
LGBY
Lower Gasswater Coal
LGC
Lower Ganey Coal (Coalbrookdale)
LGCC
Lower Grovesend Coal (South Wales)
LGDC
Lang Geo Sandstone Member
LGE
Conformable on Hoy Volcanic Formation or unconformably resting on the Lower Eday Sandstone Formation.
Rhythmic pale greyish red sandstones with subordinate siltstone and mudstone; pale green reduction spots common throughout.
24m at Lang Geo (ND 1841 9912), Hoy Island, Orkney.
Gradational boundary with poorly-cemented pale greyish orange sandstones of the Lyre Geo Sandstone Member.
Llangynog Formation
LGF
Supposedly unconformable on mudstones of the Craig-y-gln Group [Oswestry Sheet 137].
Mudstones with intercalated tuffs, tuffites, lavas and limestones.
About 1750m
Conformably overlain by Pen Plaenau Siltstone Formation, the boundary being taken at the base of the Cwm Clwyd Tuff. Where the latter is absent, the boundary is gradational and taken at the point where mudstones pass into siltstones of the overlying Allt-tair-ffynnon Formation.
Late-Glacial Flood Gravel
LGFG
Gravel and sand, locally with silt and clay interbeds; sheet-like form; late glacial. [Generic description].
Lodge Farm Limestones Bed
LGFL
Change up from grey mudstone with phosphatic nodules of the undifferentiated Foston Member; at 30.90m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands: north Leicestershire to Lincolnshire. Not recognized in the Scunthorpe Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south either into part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or into part of the mudstone-dominated Charmouth Mudstone Formation.
Group of several thin (six of 0.04 to 0.14m thick in type section) probably impersistent limestone beds separated by mudstone beds (up to 0.3m thick). Limestones are hard, grey, brown-weathering, silty, bioclastic, fine- to medium-grained, with numerous bored Gryphaea and Pseudopecten. auna also includes gastropods, other bivalves, ostracods and echinoderms. Forms a weak feature.
1.0 to 3.5m; 1.39m in type section.
Change up from grey mudstone of the undifferentiated Foston Member; at 29.51m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Lower Gunnerton Fell Limestone
LGFLL
Lower Gwastaden Group [See Gwastaden Group, Gg]
LGG
Lower Glen Gairn Sheets
LGGI
Limekiln Gill Gravel Formation
LGGR
Unconformable, erosional, channelled contact with limestones and dolostones of the Zechstein Group (formerly Magnesian Limestone).
Partially cemented gravel typically containing a high (50-60%) proportion of locally derived limestone and dolomite pebbles of the Zechstein Group (formerly Magnesian Limestone) and a varied suite of far-travelled clasts including Carboniferous lithologies, andesite, granite, gneisse, schist, flint, quartz, quatzite and dolerite, together with unabraded shell fragments.
Up to 6m known
Generally a sharp, subhorizontal, planar to gently undulating contact with dark grey, stiff, sandy silty stony clay diamicton of the Blackhall Till Formation.
Loggerheads Limestone Formation
LGHL
Top of highest porcellanous limestone of underlying Leete Limestone Formation.
North Wales between Anglesey [SH5080] and Oswestry [SJ2723]; including the Corwen Outlier [SJ0542].
Thickly bedded, massive, pale grey shelly limestones (packstones and grainstones), locally mottled and pseudobrecciated, arranged in shoaling upwards cycles capped by calcretes, hummocky palaeokarstic surfaces and associated thin bentonitic clay seams (palaeosols) and rare coals. Locally dolomitised and with scattered chert nodules. The Loggerheads Limestone Formation records late Asbian platform carbonate deposition on the North Wales Dinantian shelf. Each cyclic sequence records a shoaling upwards unit developed in response to transgressive and regressive movements in sea level. Many regressions culminated in emergence of the platform surface and the formation of calcrete and karstic dissolution features. During these periods of emergence, wind blown volcanic ash accumulated on the platform surface to form thin bentonitic soils.
To 275m
Base of lowest sequence of thinly interbedded dark-grey limestones and mudstones of overlying Cefn Mawr Limestone Formation.
Loggerheads Limestone Formation (Knoll-Reef)
LGHLK
Lower Garscadden Blackband Ironstone (Glasgow)
LGI
Late-Glacial Beach Deposits
LGLB
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks; late glacial. [Generic description].
Lad Gill Limestone
LGLL
Late-Glacial Silt
LGLS
Silt and clay; late glacial. [Generic description].
Lower Graptolitic Mudstone
LGM
Langley Marine Band
LGMB
Late-Glacial Marine Deposits
LGMD
Variable lithology; any deposit from the marine environment; late glacial. [Generic description].
Lislea Granophyre
LGN
Lower Garscadden Coal (Glasgow)
LGNC
Limestone Group (Of South Lancashire)
LGP
Low Grit Sill
LGR
Lower Grinstead Clay
LGRC
A down-section change from silty mudstones to sandstone (Lower Tunbridge Wells Sand Formation, Ardingley Sandstone Member which may include at its top the Top Lower Tunbridge Wells Pebble Bed).
The member is present in the Chailey area west to Cuckfield and north-east to between Kingscote and East Grinstead (Sheet 302). It extends onto the Tunbridge Wells sheet (303) where it crops out between East Grinstead and Tunbridge Wells and again near Danehill. In the Sevenoaks/ Tonbridge district (sheet 287), the Lower Grinstead Clay Member is seen along the southern margin of the sheet between Wicken and Oakfield and in the north-eastern corner of sheet 318, north of Lunce's Common Fault (north of Burgess Hill).
The member comprises soft grey to greenish greg mudstones and silty mudstones with subordinate thin beds of siltstone, clay ironstone, sandstone and limestone. In some areas, where the Cuckfield Stone Member is absent the Upper and Lower Grinstead Clay members cannot be separated.
Up to 6.4m.
A down-section change from sandstones (Cuckfield Stone Member) to mudstones. Where the Cuckfield Stone Member is absent, the Upper and Lower Grinstead Clay members cannot be separated.
Lower Greensand Group
LGS
In southern England, erosional unconformity or disconformity at base of Atherfield Clay Formation: in most of area overlies Wealden Clay Formation, elsewhere Lower Greensand Group oversteps onto Jurassic rocks.
As described, circum-Weald. Also developed in the Isle of Wight, and less well in Wiltshire to Bedfordshire, Norfolk, Dorset, Lincolnshire and Yorkshire.
Mainly sands and sandstones (varying from well-sorted fine-grained to poorly sorted medium- to coarse-grained) with silts and clays in some intervals.
c.250m in south-western Weald
Base of Gault; specifically in the Wealden area, base of a short interval of condensed facies beds at the base of the silty clays of the Gault above the sands of the Folkestone Formation.
Glaciolacustrine Deposits (Loch Lomond Readvance)
LGSL
Lugasnaghta Shale Member
LGSM
Laggantuin Cornstone Member
LGT
Transition from grey silty mudstones with dolomitic limestones.
The vicinity of Laggantuin, northeastern coast of the Isle of Arran, Scotland.
White sandstones and red-brown mudstones with pedogenic carbonate.
Transition to white cross-bedded sandstones.
Lidget Coal (West And South Yorkshire)
LGTC
Lower Greensand And Upper Greensand (Undifferentiated) [Offshore Areas]
LGUG
Lower Gullane Head Sill
LGUHD
Little Gubbin Ironstone (South Staffordshire)
LGUI
Lagavarra Formation
LGV
Lligwy Sandstone Formation
LGY
Late Abian.
Rests unconformably on ?Devonian, Ordovician and Precambrian rocks (Mona Complex).
Between Llangefni [SH4675] and Lligwy Bay, [SH5087], Anglesey, North Wales.
Cross-bedded sandstones, pebbly sandstones and conglomerates with subordinate siltstone and mudstone beds. Records fluvial deposition along the margin of the North Wales Dinantian platform throughout the late Asbian.
Overlain and passes laterally into thick-bedded limestones of the Loggerheads Limestone Formation.
Lower Haslingden Flags
Lower Holcombe Brook Coal (South Lancashire)
LHBC
Lower Longhope Beds
LHBL
Lower Hartfell Shale Formation
LHBS
Conformable on Glenkiln Shale Formation.
Black hemipelagic mudstone.
22m
Conformably overlain by Upper Hartfell Shale Formation.
Upper Longhope Beds
LHBU
Lewisburn House Coal (Northumberland)
LHC
Predominantly the area around Lewis Burn, Northumberland.
The seam has been worked.
Lower Househill Clayband Ironstone
LHCI
Loggerheads Limestone Formation And Cefn Mawr Limestone Formation (Undifferentiated)
LHCM
Linney Head Formation
LHD
Taken at junction of massive dolomitised reef limestones of the Berry Slade Formation and the overlying dark limestones with thin mudstones and cherts of the Formation. Where the top of the Berry Slade Formation is in flank facies, the boundary is imprecise but taken at the increase in chert content at the base of the Linney Head Formation.
Castlemartin area [SR 95 98], southwest Pembrokeshire. Relationship to coeval Gully Oolite to north unknown.
Thin- to thick-bedded dark grey crinoidal wackestones with abundant chert beds interbedded with mudstones and nodular limestones. Packstones present in uppermost part. Deposited in a distal ramp setting.
30m at type section in southwest Pembrokeshire.
Taken at sharp junction between the dark limestones, cherts and mudstones of the Formation and the overlying thick-bedded coarsely crinoidal limestones of the Hobbyhorse Bay Limestone Formation.
Lower Heathen Coal (South Staffordshire) [Duplicate Code: Use Lhec]
LHEA
Lower Heathen Coal (South Staffordshire)
LHEC
Lower Howgate Edge Grit
LHEG
Lawns House Farm Sand Member
LHF
Nowhere exposed; details unknown.
This unit has a lobate form extending south from the Escrick Moraine for up to 15km, thinning gradually from a maximum of about 2.5m in the north. It is thought to extend across from River Ouse in the west to the River Foulness in the east. Its northern limit is believed to be the Escrick Moraine, and the southern extent reaches at least as far as Selby.
Characteristically reddish yellow very silty fine to medium sand with beds of silt or sand. Very sparse fine gravel and limited bands of fine dark detrital material are noted. Lawns House Farm Sand Member is commonly water saturated, supporting a weak hydrostatic head, and prone to "running".
Estimated to be approximately 2.5m maximum.
Sharp to gradational upwards transition (over several cms) via finely interbedded silty sand and clay into clays of the Thorganby Clay Member.
Leadhills Supergroup
LHG
Lying between the Glen App and Southern Upland Faults in the north and the Kingledores Fault in the south.
The Southern Uplands of Scotalns, and by extension into Longford-Down in Ireland.
Greywackes, shales, siltstones and mudstones with conglomerates.
Little Howgate Coal
LHGC
Lynch Hill Gravel Member
LHGR
Average 7m, range 1-12m.
The Liethies Sill
LHIES
Longmanhill Pluton
LHILL
Leahill Limestone
LHL
Lighthouse Nodular Band
LHN
Long Holme Row Limestone
LHRL
Little Hangman Member
LHS
Basal unit of 1m-thick bed with Myalina rests on rocks of the Sherrycombe Member (q.v.).
North Devon - west Somerset.
Grey heterolithic beds, dominantly fissile silty mudstone ("shale") and siltstone, alternating with cross-bedded, fine-grained sandstone.
Probably a transitional conformable junction with rocks of the Ilfracombe Slates Formation (q.v.); commonly faulted.
Little Hereford Sand And Gravel
LHSG
Sand and gravel, River Terrace Deposit; Middle Devensian (interstadial) in age. [Generic description: 1:50 k map margins].
Lime Hill Serpentinite
LHSP
Tectonic; contact with adjacent Corrie Burn Hornblende Schist.
Serpentinite, largely dolomitised and silicified, weathering grey-green to orange-brown where dolomitised, and jasper. Includes conglomerate with altered serpentinite matrix at Dounans, by Aberfoyle.
c.250m maximum (estimated).
Outgoing of thoroughly altered serpentinite and incoming of dolomitised and silicified limestone of Dounans Limestone Formation (probably an unconformity). Boundaries with upper units are tectonic in part.
Langholm Till Formation
LHTI
Unconformable on bedrock or older Quaternary deposits.
Stiff, pale yellowish brown to pale grey, stoney, sandy silty clay diamicton containing subangular to subrounded clasts of greywacke sandstone and siltstone, and other rocks cropping out in the Southern Uplands.
Less than 15m
At the land surface or conformable with younger Quaternary deposits.
Laght Hill Tonalite
LHTO
Rb-Sr whole rock 407 +/- 23 Ma (O'Connor et al., 1982); Rb-Sr whole rock 386 +/- 33 Ma and 388 +/- 4 Ma (Halliday et al., 1980).
Laverockhall Vein
LHV
Lower Hartfell Wrae Limestone
LHWL
Loch Humphrey Member
LHY
21.35 metres in IGS Loch Humphrey Borehole (NS47NE/1).
Airfall and bedded red-purple tuff with lapilli and blocks up to 0.3 metres; rooty with carbonaceous streaks near top in places, grey mudstone with fish scales in others. Overlies Markle type lava and underlies Dalmeny type lava.
Variable + 30 metres.
At NS 4600 4550.
Llwyneinion Half Yard Coal (North Wales)
LHYC
Lias Group
In some areas, markedly non-sequential on Penarth Group; at base of Blue Lias Formation, Scunthorpe Mudstone Formation or Redcar Mudstone Formation (q.v.).
Onshore and offshore United Kingdom, including Northern Ireland (see Cope, J C W, et al, 1980).
Predominantly grey, well bedded, marine calcareous mudstone and silty mudstone; thin tabular or nodular beds of argillaceous limestone, particularly in the lower part; thicker units of siltstone and sandstone, particularly in the upper part, and ironstone, particularly in the middle part. Marginal limestone facies also occur.
To c.1300m
Commonly an eroded surface at the base of lowest limestone or sandstone of the Inferior Oolite Group, Ravenscar Group or Dogger Formation.
Littlebeck Anhydrite Formation
LIA
Drawn at base of anhydrite of the Littlebeck Formation where it rests on red siltstone of the Sleights Formation.
Eastern England. (Yorkshire Province).
Pink-grey, finely crystalline and commonly unevenly laminated anhydrite with local discontinuous laminae of red-brown silty marl.
Approx. 1 to 2 metres.
Drawn at upward passage from anhydrite to red-brown mudstones and siltstones of the Roxby Formation.
Lianachain Complex
LIAN
Lianachain Complex, 1
LIAN1
Lianachain Complex, 2
LIAN2
Lianachain Complex, 3
LIAN3
Lianachain Complex, 4
LIAN4
Libishaw Sandstone
LIB
A sharp upward change in a conformable succession from predominantly grey mudstone to sandstone. The base of the first sandstone bed in an argilaceous succession above the Agill Sandstone where present, or the base of the first sandstone bed above the Cayton Gill Shell Bed.
The Pennines west of Masham.
A thinly to thickly bedded, grey, fine-grained, shelly sandstone.
From 0 to 55 m thick.
A sharp upward change in a conformable succession from sandstone to predominantly mudstone. The top of the last sandstone bed below the Ure Shell Bed.
Lisbellaw Conglomerate Formation
LIBC
Little Course Coal (Somerset)
LICC
Lickle Tuff Formation
LICK
Base of pyroclastic rocks of dacitic or rhyolitic composition that unconformably overlie the Duddon Hall Tuff (andesitic tuff), Dunnerdale Sandstone (volcaniclastic sandstone) or the Wallowbarrow Tuff (andesitic lapilli tuff) formations.
Ulpha Basin and Coniston Fells, Lickle Valley (SD 2493 to 2190) to Wallowbarrow Heald (SD 210 970) and Turner Hall (SD 230 960); Buck Pike (SD 260 970) to Knott Head (NY 300 020), Cumbria.
Massive unit of rhyolitic and dacitic welded tuff and lapilli-tuff with subordinate intercalated volcaniclastic sandstone; intruded by andesite and basaltic andesite sills.
Defined by base of overlying formations including Caw (volcaniclastic breccia and sandstone), Lag Bank (dacitic lapilli tuff) and Low Water (dacitic tuff) formations.
Little Coal (Bristol Area)
LICO
Liddaton Formation
LIDN
East Cornwall - West Devon.
Grey and greenish grey slate, siltstone and sandstone laminae. (This formation includes the Overwood Slate Member).
Thrust fault.
Lissan Conglomerate Formation
LIF
Little Fiery Coal (Bristol Area)
LIFI
Llanbedrog Volcanic Group
LIG
Underlain by sandstones and siltstones of the Dwyfach Formation.
Northwest Wales.
Basaltic trachyandesite-rhyodacite lavas and tuffs, with some ash flow tuffs and minor amounts of reworked sandstones, siltstones and conglomerates.
From about 300 to about 1100m
Overlain by mudstones and slates of the Nod Glas Formation.
Lias Group, Inferior Oolite Group And Great Oolite Group (Undifferentiated)
LIGO
Lion's Head Vent
LIHD
Lion's Haunch Vent
LIHH
Lias Group And Inferior Oolite Group (Undifferentiated)
LIIO
Lickbank Coal (Cumbria)
LIKB
Lillies Oil Shale
LIL
Lime Coal (New Cumnock, South Ayrshire)
LIM
Lighthouse Marls (One)
LIMA1
Lighthouse Marls (Two)
LIMA2
Limehillock Limestone Member
LIML
Base of first metalimestone bed above change from pale to dark pelites and semipelites at top of Tarnash Phyllite and Limestone Formation.
Occurs from Limehillock Quarry southwest to Nethermills [NJ 556 520 - 506 508], from Lurg Hill Plantation to north of Burnend [NJ 509 585 - 490 462] and from Goukstone to near Gallowhill Croft [NJ 480 560 - 482 533].
Crystalline pale to mid-grey metacarbonate rock, massive to flaggy and thin- to medium-bedded, with minor semipelite and pelite interbeds. Minor cherty and calc-silicate rock lenses and discontinuous thin layers.
c.100m at Limehillock Quarry and in Burn of Paithnick.
Sharp change from metalimestone to dark pelite or semipelite.
Lisnagrib Mudstone Member
LIMM
Little Main Coal (Cumbria)
LIMN
Linkim Formation
LIN
Massive, greywacke sandstone and thinly-bedded, laminated siltstone.
Linkbrae Limestone Member
LINK
Not seen in outcrop (blown sand), but observed in Sandend Bay borehole; sharp transition from psammite and semipelite, muscovite-rich, banded pale grey and greenish with some calc-silicate beds.
Extends southsouthwest from coast section in Sandend Bay [NJ 558 664] for c.400m. A limestone bed at Cairnton [NJ 544 635] may belong to this unit.
Metalimestone, white to grey, thin-bedded, with thin interbeds of calc-silicate rock.
Over 35m
Not seen (blown sand); probably sharp transition to muscovite-rich semipelite.
Linnhe Quartzite Member
LINN
Linnhe Semipelite Member
LINSP
Ling Sandstone Member
LISA
Lisgorman Shale Formation
LISG
Libishaw Shale
LISH
Little Sole Formation
LISO
Little Splint Coal (Midlothian)
LISP
Lista Formation
LIST
Little Stand Tuff Member
LIT
Base of tuff; overlies volcaniclastic sandstones and andesite sheets of the Birker Fell Andesite Formation (undivided).
West of Yoadcastle (SD 15 95) south of Devoke Water to Pike of Blisco (NY 27 04) and Seathwaite Tarn (SD 249 984), Cumbria.
White-weatherd, massive, crystal-rich (K-feldspar), welded rhyolitic tuff containing lithophysae-rich zones locally.
7 - 27m; ponded at one locality to 60m
Top of tuff; overlain by volcaniclastic sandstones of the Blisco Member or by the Great Whinscale Dacite.
Littlemore Member
LITC
Non-sequential upward change from sand or sandstone of the Beckley Sand Member of the Kingston Formation, to limestone and mudstone generally poor in quartz sands.
Kennington, Littlemore and Garsington, south and south-east of Oxford. The 1:50 000 sheet 237 (inset map), shows the north-eastern limit as a passage into the Wheatley Limestone or Oakley members. The southern and western extents are uncertain, but are believed to be restricted to the area above, beyond which it passes into the Wheatley Limestone or equivalent limestone facies (see Arkell, 1927; 1933).
Interbedded, alternating micritic, shell-fragmented wackestone and packstone limestones, with dark grey mudstones and variable shell fragmented marls, commonly containing Nanogyra nana.
Up to about 12 m thick.
Upward change to grey, more uniform and locally slightly sparsely shell-detrital mudstones of the Ampthill Clay Formation.
Little River Group
LITG
Llanddewi Till Formation
LITI
Linwood Clay Member
LIWD
The Linwood Clay Member of the Clyde Clay Formation rests with angular unconformity and conformity on older Quaternary sediments or bedrock. It normally rests conformably on the Paisley Clay Member of the Clyde Clay Formation or unconformably on the Wilderness Till Formation (WITI) of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
Recognised in the lower Clyde valley downstream from western Glasgow, in the Paisley-Linwood lowlands, in the estuary of the Clyde and Firth of Clyde and linked sea lochs, and in Loch Lomond. It is also present under the coastal plain of Ayrshire. (The use of this term in other estuaries such as the Forth, Tay and Earn on the east coast of Scotland awaits later consideration).
The typical lithologies are clayey silt and clay, mid grey, micaceous, very soft to soft consistency, firm with depth, medium to low plasticity and low plasticity index; sand is present especially at and near the top, in layers up to 3cm thick, with isolated stones of up to 2cm; seaweed and other plant remains are present together with foraminifera (Elphidium clavatum) and marine shells. Sequence at the base is thickly bedded to massive.
Veneer to more than 35m.
The Linwood Clay Member is overlain unconformably by younger Quaternary sediments, normally either the Clydebank Clay Formation of the British Coastal Deposits Group or the Clippens Peat Formation or Clyde Valley Formation of the Britannia Catchments Group (Clyde Catchments Subgroup). It passes upwards and laterally into the Killearn Sand and Gravel Member in some localities but in others is erosively overlain by the same unit. It is also extensively exposed at surface in the Lower Clyde valley below Shieldhall and in the low ground around Paisley and Linwood.
Lower Jurassic Rocks (Undifferentiated)
Little Jack Coal And Balls Coal (Undifferentiated) (South Wales)
LJBAL
Little Jack And Balls Coal (South Wales)
LJBC
Little Jack Coal (South Wales)
LJCO
Lower Johnstone Shell-Bed
LJSH
Lower Kinderscout Grit
Little Kilburn Coal (South Derbyshire)
LKBC
Lewisburn Kiln Coal (Northumberland)
LKC
Lickar Coal
LKCO
Lower Kent's Thick Coal (West And South Yorkshire)
LKEKC
Lerwick Sandstone Formation
LKF
Lickar Limestone
LKL
Limekiln Marine Band
LKMB
Leckenby Formation
LKNB
Limekiln Coal (North Staffordshire)
LKNC
Lower Knott Coal (Glasgow)
LKNO
Lackagh Till
LKT
Loch Katrine Volcaniclastic Formation
LKV
Outgoing of clean arenite and quartz arenite of the Ardnandave Sandstone Formation and the incoming of chloritic and epidotic, greenish silicaclastic sediments.
'Green Beds' that can be correlated with this formation crop out widely throughout the lower part of the Southern Highland Group in the Scottish Southern Highlands between Loch Lomond and Glen Clova and into Kintyre and Northern Ireland.
Metasandstone, arenite to wacke, pale to dark grey green and dark green ('Green Beds'), commonly orange- to pink-brown weathering. Fine- to very coarse-grained, graded to massive, interbedded with subsidiary semipelite and pelite. Contains locally abundant chlorite and epidote originally of volcanic origin.
1000m estimated
Outgoing of chloritic, greenish rocks and incoming of clean coarse arenites/quartz arenites (Creag Innich Sandstone) or more matrix rich arenites and wackes (Ben Ledi Grit Formation).
Lark Valley Formation
LKVY
Unconformable on Mid Pleistocene glacial deposits and on bedrock (Kimmeridge Clay to Chalk Group).
The entire catchment of the River Lark and its tributaries, from near Bury St Edmunds, Suffolk to Littleport, Cambridgeshire.
Formation encompasses the fluvial, lacustrine and organic deposits of the River Lark and its tributaries. Five terraces are identified. The terrace deposits comprise well bedded to rather poorly bedded sands and sandy gravels, deposited by braided rivers in a preglacial environment. The pebbles are dominantly angular to rounded flints up to about 100mm across, with a few glacial erratics. The three higher terraces are cryoturbated. The floodplain alluvium comprises silts, clays and fine sands, with bodies of peat, overlying sands and gravels.
Lincolnshire Limestone Formation
Lower Bajocian (Discites to ?Sauzei zones).
Quasi-conformable or more or less disconformable contact between sandstones and mudstones of the underlying Grantham Formation or, where the latter is absent (mainly in the north), ferruginous sandstone of Northampton Sand Formation, or mudstone of Lias Group, overlain by limestone of the Lincolnshire Limestone.
Market Weighton area (where overstepped by Cretaceous, Chalk Group, Hunstanton Formation) to the Kettering-Peterbogough area, where overstepped by the Rutland Formation. In subcrop, restricted essentially to onshore areas of the northern part of the East Midlands Shelf. Offshore passes eastwards into non-carbonate correlatives.
Limestone, typically calcilutites, and peloidal wackestones and packstones in the lower part (Lower Lincolnshire Limestone) and high energy ooidal and shell fragmental grainstones in the upper part (Upper Lincolnshire Limestone). Commonly includes sandy limestone in basal part and may contain substantial units of mudstone particularly from the Lincoln area northwards.
[Compiler's notes] Strangely, Ashton does not appear to have suggested a type section for the formation, but Ketton is an obvious Primary Reference being the only place where the whole formation is visible from bottom (dependent on transient excavations in quarry floor) to top. M D A Samuel's suggestion of Copper Hill is far less suitable as it shows little of the Lower Lincolnshire Limestone and is less well recorded in the literature. [M G Sumbler 25/09/05]
0-30m (south Lincolneshire) or more (see Ashton, 1980).
Disconformable, commonly markedly eroded and karstified top surface of limestone, overlain by non-calcareous, non-marine sandstones, siltstones and mudstones of the overlying Rutland Formation. Near its northern limit only, disconformable contact between limestone and ferruginous sandy calcareous sediments of the Hunstanton Formation above (Cretaceous).
Llyfnant Flags [See Extensus Flags]
LLA
Lower Llanbadoc Beds [Obsolete Code: Use Llcb]
LLBL
Llanberis Slates Formation
LLBS
On felsic tuff of the Bangor Formation or a conformable contact with sandstone of the Fachwen Formation.
Purple and blue-grey silty mudstones and subordinate coarse-grained turbiditic sandstones.
Formation not assigned to a group. Includes coarse sandstone units as members (Dorothea and Pen-y-bryn grits).
Silty mudstones of the Formation are sharply but generally conformably overlain by coarse-grained or conglomeratic sandstones of the Bronllwyd Grit Formation.
Upper Llanbadoc Beds [Obsolete Code: Use Ulcb]
LLBU
Llanishen Conglomerate
LLC
Lower Llanbadoc Beds
LLCB
Lancashire Ladies Coal (Coalbrookdale)
LLCC
Little Limestone Coal
LLCO
Llanddoget Disturbed Bed
LLD
Llanvirn To Ashgill Rocks (Undifferentiated)
LLDA
Llyn Dinas Breccias
LLDB
Llanvirn And Caradoc Rocks (Undifferentiated)
LLDC
Llyn-Y-Gader Mudstones And Shales
LLE
Little Coal (South Staffordshire)
LLEC
Lleyn Formation
LLEYN
Base not seen at type locality, but could potentially overlie pre-Late Devensian deposits (Young et al.,2002); locally the formation overlies bedrock and Devension head deposits (Gibbons and McCarroll, 1993). In Ceredigion and Pembrokeshire the base is unconformable on bedrock, head and regolith (Hambrey et al., 2001); near Llanrhystud it is on the Plynlimon Till Formation (Campbell and Bowen, 1989; Davies et al., 1997). Along Liverpool and Conwy bays the base overlies bedrock and, locally, tills of Welsh origin (Warren et al., 1984).
Coastal fringe of Ceredigion and Pembrokeshire approximately between Llanrhystud and St Brides Bay; Anglesey; north coast and western tip of Lleyn Peninsula as far east as Porth Neigwl; coastal fringe of Conwy and Liverpool bays, locally extending inland into the Cheshire-Shropshire Plain as far south as Shrewsbury.
Stiff, generally ill-sorted, massive to crudely stratified, variably pebbly, sandy clay, characteristically containing exotic clasts and shell fragments. Subordinate clayey gravels and stratified sand and gravel are locally present. Colour and dominant clast composition variable and generally reflect the local bedrock geology; in the Cheshire-Shropshire Plain the diamicton is red and red-brown and sparsely pebbly (see Thomas, 1985, p.322); in Ceredigion and Pembrokeshire it is generally green-grey with abundant Lower Palaeozoic rock clasts.
Highly variable: locally more than 17m in the Cardigan district (Maddison et al., 1994); more than 60m in the Dee Valley (Davies et al., 2004); and more than 30m on the Lleyn Peninsula (Gibbons and McCarroll, 1993).
Generally the ground surface or unconformable contact with West Wales or Cheshire-North Wales catchment subgroups. However, at the eastern end of the type section the upper boundary is defined by contact with the overlying Eryri Till Formation.
Llandeilo Flags Formation
LLF
Llynfi Member
LLFB
The base is placed at the base of the lowermost thick (over c.3m) bed of lithic arenite ("Pennant sandstone"). This lies immediately above the Cambriense (Upper Cwmgorse) Marine Band in the southwest of the South Wales Coalfield, where the sandstones rest on the underlying mudstones of the South Wales Upper Coal Measures Formation. The base is gradational and diachronous; northeastwards, the "Pennant sandstone" facies commences at a progressively higher level.
South Wales Coalfield, extending on the south crop from the Swansea district [SS 533 955] east to the Ferndale area [SS 9995].
Green-grey and blue-grey, feldspathic, micaceous lithic arenites ("Pennant sandstone") with thin mudstone/siltstone and seatearth interbeds and mainly thin coals.
Up to 420m in the Swansea district.
The top, as defined by Woodland et al. (1957), is placed at the base of the No.2 Rhondda Coal, which is overlain by lithic arenite and thin mudstones and siltstones that make up most of the Rhondda Member. The base of the coal rests on a mainly thin development of seatearth and mudstone at the top of the Member, which overlies thick lithic arenites.
Llanfallteg Formation
LLFT
Lower Limestone Formation (England And Wales)
LLG
Llangammarch Formation
LLGM
Loch Laggan Psammite Formation
LLGN
Transitional with underlying Coire nan Laogh Semipelite. Base marked by lowest thick (10 m +) grey psammite.
Central and southern Monadhliath Mountains, from Glen Roy to Strath Nairn and eastwards to Aviemore (Speyside).
Predominantly micaceous and feldspathic psammite with thin semipelite beds; turbiditic features. Abundant calc-silicate rock lenses and bands. Transitional upper and lower contacts.
variable 1.5 - 3.5 km
Transitional into overlying Ardair Semipelite - progressive increase in mica content.
Lower Limestone Formation
LLGS
Visean to Namurian (late Brigantian to early Pendleian).
Base of Hurlet Limestone.
Cyclic: includes marine limestones. NOTE: See lithological description note in entry for Limestone Coal Formation (LSC).
211m in type section
Top of Top Hosie Limestone.
Loch Linnhe Intrusion
LLINN
Landlake Limestone Member
LLKL
Thrust fault
Polyphant-South Petherwin area.
Greenish grey slate with thin bioclastic limestone beds.
Lower Lincolnshire Limestone Member
LLL
Lower Bajocian (Discites and Ovalis zones).
Quasi-conformable or more or less disconformable contact with sandstones and mudstones of the underlying Grantham Formation or, where the latter is absent (mainly in the north), ferruginous sandstone of the Northampton Sand Formation, or mudstone of Lias Group, overlain by limestone or sandy limestone of the Lower Lincolnshire Limestone Member.
Essentially as for the Lincolnshire Limestone Formation, ie, Market Weighton area (where overstepped by Cretaceous, Chalk Group, Hunstanton Formation) [probably] to the Kettering-Peterborough area (where overstepped by the Rutland Formation). Locally (or perhaps more generally) cut out by the Upper Lincolnshire Limestone south of Stamford. Extent in subcrop uncertain but probably more or less as for the Lincolnshire Limestone Formation, ie, onshore areas of the northern part of the East Midland Shelf.
Limestones, dominated by low-energy calcilutite, and peloidal wackestone and packstone. Commonly includes sandy limestone or calcareous sandstone in basal part (locally known as Collyweston Slate) and contains substantial units of mudstone, particularly from the Lincoln area northwards.
[Compiler's Notes] I have tended to use the term Lower Lincolnshire Limestone as an informal division, albeit of Member status, because of the existence of Ashton's and Gaunt et al's numerous members (which for most of Ashton's at least, are not generally correlatable members). Sproxton is chosen as a type section because, although not well-known like Ketton, it has just about the thickest and most complete LLL section exposed anywhere, although unfortunately the top is not seen, due to post-Mesozoic erosion. Because of the complication of the previous uses of the term Lower Lincolnshire Limestone (e.g. the exclusion by Ashton of his Middle Lincolnshire Limestone), if one really wanted this to be a formal member, a new name would perhaps be called for. So far I have been unable to identify an appropriate one which has not already been pre-empted for some part of Ashton's scheme (he has a Sproxton Member), or some other part of the Jurassic succession. Ketton Member would seem appropriate but for the Ketton Rhythm (Rutland Formation) and Ketton Stone (building stone in Upper Lincs Limestone). As with the ULL, it would be useful to have a thorough account of the definition of this unit, its type and reference section and its lateral variation. This is particularly so north of Lincoln (which hasn't been reviewed recently and where some problems remain relating to the top) and south of Stamford where relationships are not so clear (to me at least). See also my comments on Upper Lincolnshire Limestone [M G Sumbler 25/09/05]
0 to c.20m (south Lincolnshire).
Disconformable, commonly channelled contact between calcilutites, wackestones and packstones below and the high energy ooidal limestones of the overlying Upper Lincolnshire Limestone Member. Near the northern limit only, disconformable contact with ferruginous sandy calcareous sediments of the Hunstanton Formation (Cretaceous).
Lower Lancashire Ladies Coal (Coalbrookdale)
LLLC
Lower Llwydcoed Coal (South Wales)
LLLD
Llanarmon Formation, Leete Formation And Loggerheads Limestone Formation (Undifferentiated) (Knoll-Reef)
LLLK
Llanarmon Formation, Leete Formation And Loggerheads Limestone Formation (Undifferentiated)
LLLL
Lower Little Limestone
LLLM
Llandeilo Limestone Formation
LLLS
Llanymawddwy Formation
LLM
Lower Main Coal (Lower Seam) (Leicestershire)
LLMC
Lochlundie Pluton
LLND
Lower Linn Limestone
LLNL
Loch Lurgainn Till Member
LLNN
Unconformable on bedrock, predominantly Torridon Group sandstone.
Patchy, discontinuous extent across Coigach, Stoer headland, Handa Island and between Kinlochbervie and Cape Wrath, northwest Sutherland. Occurs predominantly on Torridon Group sandstone.
Orange-brown, red-brown or dull brown poorly sorted, sandy, matrix-rich diamicton with boulders. Clay content is usually very low. The till shows evidence of subglacial deposition; namely edge-rounded, striated, clasts and high consolidation. Clasts are predominantly Torridon Group sandstone, but may also include Lewisian gneiss. Eriboll Formation sandstone (quartzite), Moine Supergroup rocks and/or various igneous rocks to greater or lesser degrees. However, in certain areas the till is autochthonous and is comprised entirely of Torridon Group sandstone that has undergone little transportation. The till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older.
Variable; 0.5 to 6m (maximum observed thickness); possibly up to 10m.
Llanelen Sandstone
LLNS
Llanbabo Formation
LLO
Lower Lobster Member
LLOB
Lower Longcraig Limestone
LLOL
Llanarmon Limestone Formation, Loggerheads Limestone Formation And Prestatyn Limestone Formation (Undifferentiated)
LLPL
Llynfi Member, Rhondda Member And Brithdir Member (Undifferentiated)
LLRB
Lyoncross Limestone
LLS
Glasgow and adjacent area, Central Coalfield.
Lower Long Sands Sandstone Member
LLSA
Mapped on Plymouth (348) Sheet. May occur on sheets 349, 350, 355 and 356.
Dominantly sandstone in sedimentary cycles with mudstone, siltstone and subordinate limestone. Sporadic packets of quartzitic sandstone present.
Passes conformably up into slaty mudstone of the undivided Bovisand Formation where sandstone cycles die out.
Lillie's Shale Coal
LLSC
Lamlash Sandstone Formation
LLSF
Llandeilo Shales
LLSH
Lillie's Sandstone
LLSS
Local development between the two leaves of the Lillie's Shale Coal in the area around Paisley.
Flaggy sandstone.
c.8.5m
Lower Limestone Member
LLST
Llanstadwell Formation
LLSW
The base of the Formation is placed at the base of the lowest primary-coloured green siltstone at the western end of the railway cutting in the naval depot at Newton Noyes, Pembrokshire [SM9150 0530] This is a 0.32m-thick greenish grey, coarse-grained, parallel laminated siltstone 21.7m above the base of the section logged by Thomas et al (2006), which lies conformably on red mudstones of the underlying Gelliswick Bay Formation (formerly Red Marl Group).
Confined to the northern side of the Daugleddau estuary, Milford Haven, except for a small area east of Hobbs Point [SM 971 043] on the south side of the estuary from Llanion [SM 97 04] to Waterloo [SM 98 04]. On the north side, an outcrop extends from west of Newton Noyes [SM 92 05] to the east of Weir Point [SM 940 043]; the main outcrop extends from Llanstadwell [SM 950 050] eastwards to near Burton [SM 990 052], and from there northnorthwestwards around the axis of the Burton Anticline to the Benton Fault east of Rosemarket [c. SM 960 080]. (See Thomas et al, 2006, Figure 1).
Predominantly grey-green very fine- to medium-grained, plant bearing sandstones, with some intraformational conglomerates, red-brown and purple-brown siltstones; the facies are mainly arranged in fining-upwards cyclothems; up to 20% of the formation is affected by soft sediment deformation.
435 to 550m
The upper boundary of the Formation is placed at the base of an 11.8m-thick multistorey complex of interbedded grey-green intraformational conglomerates and sandstones with a few siltstones at the base of the overlying Mill Bay Formation. The boundary at Burton Cliff [SM 98967 05258] is placed northeast of Burton Hawn at a low-relief scour surface by the lowermost intraformational conglomerate of the Mill Bay Formation (see Thomas et al, 2006, Figure 9 for a detailed log of the beds above and below the boundary).
Loch Loyal Syenite Complex
LLSY
Lower Leintwardine Formation
LLT
Lower London Tertiaries
LLTE
Llyn Teifi Member
LLTI
Lluest-Y-Graig Member
LLUE
Lower Ludlow Shales Group
LLUS
Transitional with Much Wenlock Limestone (not formally defined).
Silty mudstones and siltstones.
220m to 240m in Malvern Hills.
Transitional with Aymestry Limestone (not formally defined).
Llewelyn Volcanic Group
LLV
Where one of the constituent formations rests on sediments of the undivided Nant Ffrancon Group; at base of the Capel Curig Volcanic Formation.
Acid ash-flow tuffs, with some basic and intermediate volcanic rocks. Note: see also the descriptions of the Capel Curig Volcanic, Conwy Rhyolite, Braich Tu Du, Gwern Gof, Foel Fras and Foel Grach formations.
1400m approx.
At top of Capel Curig Volcanic Formation. d tuffs of the Cwm Eigiau Formation.
Lower Level Vein Coal (Pembrokeshire)
LLVC
Llanvirn Rocks (Undifferentiated)
LLVN
Llanwrtyd Volcanic Formation
LLVO
Llanfwrog Formation
LLW
Unconformity on Silurian seen in stream section at Llanfwrog (SJ 1049 5782) and at Lady Bagots Drive (SJ 1022 5952).
North Denbighshire, Vale of Clwyd, Dyserth.
Red and green mudstone, marl, sandstone and cornstone with sporadic thin, impure limestone beds.
Overlain by lagoonal-peritidal limestones at Lady Bagots Drive (SJ 1026 5975).
Llanelly Formation
LLY
The base is placed at a major palaeokarstic surface truncating the ooidal grainstones of the underlying Gilwern Oolite Formation and overlain by green clay and micritic limestones (Clydach Halt Member) of the Llanelly Formation.
Northeast crop of the South Wales Coalfield, from the Hepste Valley [SN 971 129] east to the Clydach Gorge [SO 214 125] and southwards down the east crop on the west side of the Afon Lwyd Valley to about 1km south of Blaenavon [SO 261 077].
Well bedded peritidal, cyclic micritic to grainstone limestones with green clay interbeds at base, overlain by ooidal grainstone and capped by green and red-mottled clay palaeosol.
20m at type locality.
The top is a sharp unconformity at which the topmost green-red mottled clay (the Gilwern Clay) of the Llanelly Formation is overlain by dark grey limestones of the Dowlais Limestone Formation.
Lower Llangibby Beds
LLYB
Lindley Moor Grit
First Limestone (Cumbria)
LM1
Second Limestone (Cumbria)
LM2
Third Limestone (Cumbria)
LM3
Fourth Limestone (Cumbria)
LM4
Fifth Limestone (Cumbria)
LM5
Sixth Limestone (Cumbria)
LM6
Seventh Limestone (Cumbria)
LM7
Low Main Coal (Derby)
LMAC
Low Maid Coal (Cumnock)
LMAI
Lower Miller's Dale Lava Member
LMB
The base of the Lower Miller's Dale Lava Member, evident at Tideswell Dale (SK 154 740), is rubbly, resting directly upon about 1 m of red clay with columnar or prismatic structures up to 6 cm in diameter, possibly weathered basalt, believed to rest upon thermally altered limestone of the Bee Low Limestone Formation.(Waters, 2003).
Northern parts of the Peak District inlier, south-east of a line between Dove Holes (SK 08 77) to Ox Low (SK 12 80), and north-west of a line from Grin Low (SK 05 71) to Tideswell Dale (SK 15 73). Also, there is an isolated area to the north at Cave Dale (SK 14 82). The southern outcrops tend to be lenticular in plan.
Olivine basalt, usually very amygdaloidal with calcite-zeolite-and chlorite-filled vesicles. The central parts of flows may be non-vesicular. The lava is typically very weathered. Intervening beds of clay, tuff and limestone are locally present.
About 30 m thick at Wormhill (SK 123 741), decreasing in thickness rapidly to the north.
Vesicular lava of the Lower Miller's Dale Lava Member is overlain by limestone of the Miller's Dale Limestone Member.
Lamba Formation
LMBA
Lambeth Group
LMBE
At base of Upnor Formation; an unconformable burrowed contact with the Thanet Sand Formation in much of the London Basin; a burrowed contact with the Chalk in the west of the London Basin; burrowed contact with Ormesby Clay Formation in East Anglia.
London Basin, Hampshire Basin, East Anglia. In the Hampshire Basin the Lambeth Group is represented only by the Reading Formation.
Variable: the component formations are Upnor Formation, Reading Formation and Woolwich Formation. (See appropriate entry for their lithologies).
Up to 27m in the west of the London Basin.
At base of Thames Group at an upward change in lithology to marine sands (Oldhaven Beds), pebble beds (Blackheath Beds) or fine-grained sands with tuffs (London Clay Formation).
L'Homme Mort Conglomerate
LMCG
Lower Chalk Formation And Middle Chalk Formation (Undifferentiated) [Terms Remain In Informal Use But Are Generally Regarded As Obsolete]
LMCK
Lower Mottled Clay
LMCL
Lower Main Coal (South Derbyshire)
LMCO
Lingmell Tuff Formation
LME
Base of diverse sequence of tufflapilli-tuff that usually unconformably overlies the Crinkle Tuff Member (high-grade rhyolitic tuff) in the Airy's Bridge Tuff Formation.
Lingmell - Scafell - Longdale; Great Gable - Borrowdale - Rosthwaite; Yewbarrow - Illgill Head, Cumbria.
Pale-weathered, stratified sequence of garnetiferous silicic tuff, lapilli-tuff and pyroclastic breccia with intercalated volcaniclastic sedimentary rocks. Includes dacite (Scafell Dacite) and rhyolite (Rosthwaite) lavas.
0 to 450m
Defined by unconformable base of overlying Seathwaite Fell Sandstone Formation (volcaniclastic sandstone).
Little Meldrum Tuff Member
LMEL
Taken at the base of the lowest bed of volcaniclastic rock overlying mudstones of the Skiddaw Group
Restricted to the area at the base of the Borrowdale Volcanic Group northwest of Ullswater, Cumbria
Coarse tuff, lapilli-tuff and lapillistone with abundant pyroclasts from the Skiddaw Group, massive to crudely bedded
Lower Metagabbro (Shetland Ophialite)
LMGB
Lough Mourne Grit Formation
LMGR
Low Mill Gravel Member
LMGV
Generally erosional contact on older members of the Gosforth Glacigenic Formation. At its type section it rests on the Rothersyke Till Member.
1:50k Sheet 37 Gosforth. Egremont - Beckermet area, and Lower Wasdale area (seaward of the "Gosforth Oscillation Limit"), Western Cumbria.
Typically clast-supported, poorly sorted cobble gravel forming glaciofluvial terraces. Clasts are generally rounded to well rounded and comprise Borrowdale Volcanic Group rocks, slate, red, yellow and white sandstones, granophyre and granite.
Typically 2 to 4m thick
Generally occurs at the ground surface.
Lower Millgrit Coal (Bristol Area)
LMIC
Lower Millerhill Limestone
LMIL
Lower Jurassic And Middle Jurassic Rocks (Undifferentiated)
LMJ
Limekiln Wood Limestone Member
LMKL
The base is not seen at the type locality. Taken at the base of the succession of lithoclast breccias and boulder beds, packstones, floatstones, grainstones resting unconformably upon mainly pale grey packstones, wackestones and floatstones of the Clitheroe Limestone Formation.
Western part of the Craven Basin, including Cow Ark (SD 65 46), Plantation Farm (SD 66 43), Thornley (SD 60 40) and Slaidburn (SD 71 53) anticlines and the southern limb of the Whitewell Anticline (SD 64 47).
Packstones, floatstones, grainstones, Waulsortian limestone, limestone-mudstone lithoclast breccias and boulder beds, thin to thick-bedded, interbedded with mudstones, some of which are lithoclastic. Laminated, erosive-based, graded beds occur at the type locality. Crinoidal debris is very conspicuous.
Up to 120 m; maximum thickness at the type locality.
Typically, conformable passage from the succession of lithoclast breccias and boulder beds, packstones, floatstones, grainstones into the overlying dark grey mudstones of the Phynis Mudstone Member.
Lower Mottled Mudstone Member
LMM
Contrasts with the ribbon-banded silty mudstones of the Nantglyn Flags.
Calcareous siltstone, dark grey to black mudstone and irregular mottled mudstone. Shelly fauna. Massive bedding.
Lower Meltham Coal (West Yorkshire)
LMMC
Lochmaben Formation
LMN
Apparently conformable lithostratigraphical boundary with underlying coarse, red sandstone of "millet seed" grains of Corncockle Sandstone Formation as noted in the log of borehole NY08SE/1 at the Princes Street Dairy, Lochmaben.
Red, irregularly bedded siltstone and fine-grained sandstone that may be cross-bedded. It includes beds of coarse-grained sandstone with well-rounded frosted grains in a fine matrix, slump structures, small gypsiferous nodules, breccio-conglomerate and near-horizontal gypsum-cemented veins.
More than 54m proven in the Lochmaben Hospital Trial Borehole.
Not seen; any rocks deposited over the Lochmaben Formation are no longer preserved.
Lower Maesmelyn Coal (South Wales)
LMNC
Little Morven Conglomerate Member
LMOCO
Taken where conglomerate of the Little Morven Conglomerate Member rests unconformably on sandstone of the Ousdale Arkose Formation.
Occurs only in outliers overlying basement rocks within the area of 1:50K sheet (Scotland) 109E (Kildonan).
Taken where conglomerate of the Little Morven Conglomerate Member is overlain by sandstone of the Maiden Pap Sandstone Formation.
Lower Mountain Coal (South Lancashire)
LMOM
Lamplugh Formation
LMPL
Limplum Sill
LMPLM
Lampert Sandstone
LMPS
Loch Maree Group
LMR
Drawn at base of interdigitated schists and gneisses of Loch Maree Group which rests unconformably on high grade acid gneisses of Badcallian age (Archaean).
Gairloch and north-east of Loch Maree, north-west Highlands, Scotland.
Hornblende and quartz-mica schists with minor graphitic, quartz-magnetite, quartz-carbonate and garnet-cummingtonite schists with sulphide horizons.
Drawn at unconformable upward passage from schists of the Loch Maree Group to clastic rocks of the Torridonian including the Torridon Sandstone.
Leman Sandstone Formation
LMS
Little Minch Sill-Complex
LMSC
Lossiemouth Sandstone Formation
LMSF
Around Lossiemouth the base of the formation is the base of the predominantly aeolian sandstones above the waterlain sandstones of the Burghead Sandstone Formation. To the south, around Spynie, the base of the formation is the unconformity with the Upper Devonian "Rosebrae Beds".
Moray Firth area including exposures near Golspie.
White, yellow and pink, fine- to coarse-grained sandstones, siliceous at the top and calcareous towards the base. Some massive; some cross-bedded. Sandstone with a bimodal grain-size ("sago pudding" sandstone). Largely aeolian in origin but partly water-lain.
The unit includes subsidiary "millet-seed" sandstone and "sago-pudding" sandstone (see lithological description) and a trace amount ofgrey, brown and violet calcareous siltstone.
The top of the formation is the base of the pedogenic beds belonging to the Stotfield Cherty Rock Formation.
Lummaton Shell Bed
LMSH
Longmountain Siltstone
LMSI
Littleham Mudstone Formation
LMU
Rests on lenticular sandstone developed at the top of the underlying Exmouth Mudstone and Sandstone Formation.
Extends from south Devon coast between Littleham Cove (SY 040 802) and Budleigh Salterton, northwards through Exeter district to near Aylesbeare. Not recognised as separate formation north of Aylesbeare (SY 030 923). But Littleham Mudstone named from Taunton district by Edmonds and Williams (1985); correlation with the south Devon succession uncertain.
Reddish brown silty mudstone with sporadic thin (< 0.6m) beds of silt and silty sand. Sporadic gypsum present in Venn Ottery Borehole (SY 0659 9111) - not seen at outcrop.
c.200m in Exeter district. 275m on coast (Selwood and others, 1984).
Sharply overlain by the Budleigh Salterton Pebble Beds.
Lower, Middle And Upper Crafnant Formations (Undifferentiated)
LMUCV
Lammington's Vein
LMV
Moelwyn Volcanic Formation, Lower Member
LMVO
Lethemwell Coal
LMW
Within the range ?Yeadonian to Langsettian. Yeadonian might be appropriate rather than Namurian, but there is no real evidence. It is likely that the seam is no older than this. Note the Eskmouth Extra Coal is described in similar loose fashion and is at about the same position in the Passage Formation. On balance it is likely that both coals are Langsettian, but the key 6 Group Marine bands are difficult to identify as such in Fife and the Lothians.
Ness Assemblage
Long Nab Member
LNAB
Lynton Formation [Obsolete Code: Use Lnsl]
LNB
Long Crag Grit
LNC
Laggan Cementstone Formation
LNCF
Transition from Millstone Point Sandstone.
Grey mudstone with thin beds of dolomitic limestone.
c.20 metres.
Unconformably overlain by Laggan Cottage Mudstone.
Lochwinnoch Clay Member
LNCH
Windermere Interstadial to Holocene.
This laminated clay and silt member rests unconformably on the Wilderness Till Formation (at a depth of 24.4 m in the Lochwinnoch Borehole).
Known currently only in the Lochwinnoch area, southwest of Johnstone and Paisley in the upper valley of the Black Cart Water.
The Lochwinnoch Borehole (Browne and McMillan, 1989, Figure 25) contains the standard section in the Lochwinnoch Clay Member (20.08 to 24.4m in depth). The typical lithological association is of silty clay with many layers of silt and locally of sand. Bands relatively rich in organic detritus also occur, typically about 20 units per metre. Grains and flecks of vivianite are common except in the lowest metre of the unit. In the basal 50cm or so the deposit is almost all minerogenic and thinly colour-laminated in shades of orange, brown and grey. In general the clays are dark brown, of a firm consistency and medium plasticity, locally displaying folded slumped bedding. The base of the unit is a 10cm-thick ripple-laminated sand. The lithofacies association is typical of lake bottom muds, the presence of vivianite supporting this interpretation. The presence of dark organic-rich bands perhaps suggests seasonal banding.
Veneer to over 4m
Unconformity below younger Quaternary strata including the Law Sand and Gravel Member.
Langness Conglomerate Formation
LNCO
Carn Llundain Formation
LND
Unconformity [local] on Middle Cambrian sediments [Trwyn Llundain Formation - Solva Group].
Massive to thinly bedded and laminated, rhyolitic, ash-flow and turbiditic lapilli tuffs and tuffaceous sediments, including a basal conglomerate.
Lonsdaleia Duplicata Band
LNDB
Lough Neagh Clays Group
LNG
Lewisianoid Gneiss Complex
LNGN
Longman Gravel Formation
LNGR
An undulating, channelled and erosional unconformable contact with the underlying clayey silt and fine-grained sand of the Kessock Bridge Silt Formation.
The area around the Inner Moray Firth and Beauly Firth, Inverness. Sheet S87W (Fortrose).
A cobble gravel with a little sand and clay, and sparse shell fragments.
The present ground surface or a sharp, generally planar, erosional and unconformable contact with the overlying Flandrian raised beach deposits.
Larne Halite
LNH
Longton Hall Coal (North Staffordshire)
LNHAC
Lanark Group
LNK
Unconformity with the Wenlock - (probably) Ludlow inliers of the southern Midland Valley (or the equivalent disconformity in the case of the south central inliers of the Midland Valley).
Southern part of the Midland Valley of Scotland (cf the Lanark basin of Bluck, 1978, and cf Smith, R A, 1995).
Mainly terrestrial red-bed sequence of sandstones and conglomerates with intercalated calc-alkaline volcanic extrusive rocks.
Up to 2700m in Lanarkshire and 2400m in Lothian.
Unconformity with the overlying Stratheden or Inverclyde groups (Late Devonian - Early Carboniferous age).
Luxton Nodular Limestone Formation
LNL
Lenham Formation
LNM
Pliocene; ?contemporary with Coralline Crag Formation.
Unconformable on rocks of the White Chalk Subgroup, commonly preserved in dissolution hollows.
Restricted to the North Downs northeast of Lenham, Kent, above +180m OD.
Ferruginous sands, brightly coloured red, pink, yellow, orange and pale grey, fine-grained, micaceous and glauconitic. Beds of small, black, well-rounded, flint pebbles near base. Commonly occurring as infills of dissolution pipes in Chalk. Marine origin, disturbed by dissolution of the underlying Chalk.
Llanarmon Limestone Formation
LNML
East of the Clwydian Range, the base is taken at lowest massive, thick-bedded packstones and grainstone above thinner bedded, heterolithic sequences of the Foel Formation. West of the Clwydian Range, the Llanarmon Limestone Formation rests conformably on red beds of the Ffernant Formation, or sits unconformably on older Silurian rocks.
Crops out on the Great Orme at Llandudno [SH7683] and along the west side of the Vale of Clwyd [SJ1060]; in fault slices along the Vale of Clwyd Fault [SJ 1267]; in its type area east of the Clwydian Range between Dyserth [SJ0779 and Llandegla [SJ1852].
Predominantly pale, thick-bedded, locally cross-stratified, shelly limestones (packstones and grainstones), subordinate thinner bedded dark grey limestones (packstones) and oolitic limestones. Upper parts (of early Asbian age), which interdigitate with the Leete Limestone Formation, include limestones rich in peloids, plates of dasycladacean algae, oncoids and reworked micrite intraclasts. On the Great Orme, the formation is extensively dolomitised. The Llanarmon Limestone Formation records the intoduction of carbonate depositional environments across North Wales during a major and sustained Arundian marine transgression. The initial distribution of facies suggests a ramp-like setting, with darker off-shore limestones deposited in the north and east (of the Clwydian Range) and shallower, inner ramp facies to the west (Vale of Clwyd). Subsequently, during the late Arundian, these high energy, inner ramp limestones prograded northwards and eastwards to establish a low-gradient carbonate platform. During the early Asbian, these shoal facies withdrew to the outer edge of the platform to form a protective barrier to the peritidal facies of the Leete Limestone Formation.
Ranges from 75m in the Vale of Clwyd to 280m in the Dyserth-Caerwys area.
Where overlain by the Leet Limestone Formation, the top is taken at the lowest porcellaneous limestone diagnostic of this formation; however, east of the Clwydian Range, the Leete Limestone Formation passes laterally northwards into the Llanarmon Limestone Formation so that north of Nannerch the top of the latter is taken at the entry of pseudobrecciated and mottled packstone of the Loggerheads Limestone Formation.
Llanarmon Limestone Formation (Knoll Reef)
LNMLK
Lonan Formation
LNN
Not seen, but probably faulted.
A pale to dark grey mudstone, with a variable proportion of siltstone in laminae to thin beds, and sandstone in thin to medium beds becoming locally dominant.
At least 2,500 m thick.
In stratigraphical contact with the Mull Hill and Creg Agneash Formations, and marked by a change from a mudstone- to a sandstone-dominated facies.
Lintrathen Tuff Member
LNP
The unconformable base of the quartz-feldspar-biotite-bearing vitric tuff of dacitic composition, or at the incoming of similar rocks towards the top of the Crawton Volcanic Formation.
Dunkeld to Glenbervie.
A quartz-feldspar-biotite-bearing, vitric tuff of dacitic composition, locally partially welded.
Up to 150m thick.
The top of the quartz-feldspar-biotite-bearing vitric tuff of dacitic composition in the Crawton Volcanic Formation, overlain by strata or lavas of the Arbuthnott-Garvock Group.
Lenton Sandstone Formation
LNS
Gradational, upward passage by interdigitation, from mudstone of Edlington Formation. Overlaps successively onto Cadeby Formation and Basal Breccia to south of Nottingham.
Crops out from Nottingham to south Yorkshire, identifiable in subsurface to east. Lower part is a sandy facies of upper Permian, Edlington Formation.
Sandstone, very fine- to medium-grained. Argillaceous, red-brown with buff mottles, cross-stratified; subordinate beds of red-brown mudstone and conglomerate.
Marked but gradual upward increase in grain size and pebble content into overlying Nottingham Castle Sandstone Formation.
Lenton Sandstone Formation [Obsolete Code: Use Lns]
LNSF
Leen Sand And Gravel
LNSG
Lynton Formation
LNSL
Devonian (Late Emsian - ?Early Eifelian.
Sheets 277 and 278 (north Devon and west Somerset).
Finely-laminated sandstones and mudstones, slates, siltstones. Trace fossil Chondrites abundant. Thin shell beds.
Overlain conformably by Hangman Sandstone Formation (Hollowbrook Member) - ie. where sandstones become dominant in the succession.
Laminated Silt
LNST
Silt, laminated. [Generic description].
Laggan Cottage Mudstone Formation
LNT
Overlies white sandstones of the Millstone Point Sandstones (member of the Clyde Sandstone Formation).
Northeast Arran (Arran Special Sheet).
Grey mudstones and sandstones with fossil plant material.
Contact with overlying lavas and tuffs of the Clyde Plateau Volcanic Formation.
Llangelynin Till Member
LNTI
Longmyndian Supergroup
Loam
LOAM
Organic-rich sand, silt and clay. [Generic description]. A class of soil texture composed of sand, silt and clay, which produces a physical property intermediate between the extremes of the three components. [Earth science dictionaries in the BGS library].
Lathkill Lodge Lava Member
LOB
Not seen at outcrop. In the Haddon Fields Borehole tuffs of the Lathkill Lodge Lava Member rest upon grey and dark grey bioclastic limestone, included within the Fallgate Volcanic Formation.
Present at outcrop in the lower part of Lathkill Dale, north of Alport. Also proved in Boreholes at Alport (SK 23 65). Occurs about 27m (Shirley, 1950) or 19m (Aitkenhead, et al., 1985) below the Conksbury Bridge Lava Member.
At Lathkill Dale, basalt lava includes marmorised limestone fragments. In the Haddon Fields Borehole the member mainly comprises, in upward sequence: 20m of bedded tuff, 8m of partly brecciated basalt, 40m of hyaloclastite and 17.5m of amygdaloidal basalt.
In the Haddon Fields Borehole the member is 85.5m thick. At Lathkill Dale there is about 5m of lava.
In the Haddon Fields Borehole basalt of the Lathkill Lodge Lava Member is overlain by pale grey and cherty limestones with some calcilutites, included within the Fallgate Volcanic Formation.
Loch Ba (Centre 3) Suite
LOBA
Lower Bench Coal (North Wales)
LOBC
Lochaber Subgroup And Ballachulish Subgroup (Undifferentiated)
LOBH
Lower Brimham Grit
LOBM
Sharp upward change in a conformable succession from predominantly grey mudstone to sandstone - base of first sandstone bed in an argillaceous succession above the Ure Shell Bed.
Pennines foothills southwest and east of Masham [SE2230 8080].
A thickly bedded, trough cross-bedded, grey, coarse-grained, feldspathic sandstone and pebbly sandstone; locally, ganister at top.
10 to 30m
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of last sandstone bed below the Upper Brimham Grit.
Low Bottom Coal (Lancashire)
LOBO
Lobbs Sand And Gravel Formation
LOBSG
Generally an erosional, unconformable boundary on olive grey, sandy, silty, clayey, stony diamicton (Threlkeld Till Formation).
Northeast Lake District, Cumbria.
Forms both moundy and terraced spreads of glaciofluvial sand and gravel in the northern Lake District.
Mainly sand and gravel with subordinate beds of silt and clay, containing clasts mainly of "Borrowdale Volcanic Group" lithologies, slate and Threlkeld microgranite. Forming both moundy and terraced spreads of glaciofluvial sand and gravel in the northern Lake District.
Mostly ground surface or overlain unconformably by Flandrian deposits.
Lower Bent Coal (South Lancashire)
LOBT
Locherben Breccia Formation
LOC
Rests on thin sequence of Carron Basalt Formation.
Locherben Outlier approximately 2km sq.
Well sorted sandy breccia with clasts of bladed greywacke, argillite and purple amygdaloidal basalt.
Passes up by alternation into aeolian desert dune sandstone of the Thornhill Sandstone Formation.
Low Camlarg Coal (Dalmellington)
LOCA
Lower Cracker Coal
LOCC
Loch Coire Formation
LOCE
Lower Camphill Limestone
LOCH
Lockington Limestone Formation
LOCL
Much of the Formation is Asbian, but it might extend into the Brigantian.
The base of the lowest thick, pale brown turbiditic limestone package, where it rests on grey-brown calcareous mudstones and limestones of the Long Eaton Formation.
Does not appear at outcrop, limited to the Widmerpool half-graben in the subsurface [SK 53].
Packages between 15 and 30m thick of pale brown, argillaceous to sandy limestone, displaying turbiditic facies, normal graded with sharp bases, interbedded with thinner sequences of pyritic and carbonaceous mudstone and thin sandstone beds.
From 143 to 185m
Where the top of the uppermost thick limestone of the pale brown Lockington Limestone Formation, is overlain by the base of the overlying Widmerpool Formation, consisting of grey-brown mudstone with thin beds of argillaceous limestone.
Lower Old Red Sandstone Conglomerate (Undifferentiated)
LOCO
Lower Cretaceous Rocks (Undifferentiated)
LOCR
Lochend Sill
LOCS
Lowcray Tuff Formation
LOCY
Not seen but mapped at the change from densely welded andesitic tuff of the Fleming Hall Formation to a mixture of lithic lapilli-tuff and crystal rich tuff.
Restricted to the area west of the Thistleton Fault (Lake District Boundary Fault Zone), Cumbria.
Crystal-rich parataxitic tuff and lith-rich coarse lapilli-tuff, locally with a weak eutaxitic fabric, much hematised and silicified.
About 650m
Defined by the base of the overlying rhyolitic welded tuff of the Blengdale Formation.
Lodgedale Member
LOD
Drawn where conglomerates become common in a sandstone sequence.
Area south-east of Cheadle, Staffordshire.
Pebbly sandstones and conglomerates.
Up to 32m
Where conglomerates cease to be common in the sandstone sequence.
London Delf Coal (South Lancashire)
LODC
Lower Dements Limestone
LODL
Long Eaton Formation
LOE
The base is not proved by borehole, although known locally in the Long Eaton No. 1 Borehole to pass down to nodular anhydrite and interbedded dolostone, possibly a lateral equivalent of the Hathern Anhydrite Formation.
Does not appear at outcrop, but lies at depth within the Hathern Shelf and possibly the Widmerpool Half-Graben, in the Long Eaton No. 1 Borehole (SK43SE/161) [SK 4640 3166].
Dark grey or brown calcareous mudstones and siltstones, with thin beds of bioclastic limestone, graded calcisiltite, packstone and grainstone (description from borehole chip samples).
At least 2060m, and possibly up to 4000m thick in the Widmerpool Half-Graben.
The base of lowest, thickly bedded turbiditic limestone of the Lockington Limestone Formation.
Lower Etive Rhyolite
LOER
Loess
LOES
Mostly silt-grade material with little or no stratification; wind transported. [Generic description].
Longville Flags
LOF
Longlands Farm Tuff Member
LOFA
At base of homogeneous lapilli-tuff - sharp contact on thin bed of volcaniclastic sandstone at top of reworked, underlying ignimbrite or on pyroclastic breccia of Sides Farm Member.
Sellafield boreholes 2 (NY00SE/28), 4 (NY00SE/29), 5 (NY00SE/30), 8A (NY00SE/38), 10A (NY00SW/38) , RCF1 (NY00SE/35), RCF2 (NY00SE/36), RCF3 (NY00SE/37), RCM1 (NY00SE/41), RCM2 (NY00SE/40) and RCM3 (NY00SE/39).
Vitric tuff and lapilli-tuff; massive homogeneous andesitic ignimbrite; some intercalated pyroclastic breccia.
380m+ in type section - total thickness unproved because of eroded top. (Thickness not corrected for strutural dip or borehole deviation from the vertical).
Lower Five Coal (Bristol Area)
LOFI
Coal seam(s)
Lonfearn Member [Duplicate Code: Use Lonfn]
LOFN
Fissile dark grey shaly mudstones with abundant bivalves.
Lower Foot Rock
LOFO
Lowestoft Formation
LOFT
Pleistocene (Anglian).
The Lowestoft Formation unconformably overlies a large range of Mesozoic, Palaeogene, Neogene and early Pleistocene bedrock formations, and in eastern East Anglia also unconformably overlies the older glacigenic Happisburgh Formation (formerly Corton Formation on some maps) and the fluvial sands and gravels of the Dunwich Group. The tills within the Lowestoft Formation typically contain a significantly higher percentage of chalk than the underlying tills. The gravels in the Dunwich Group contain a significant amount of quartzose lithologies and only very minor quantities of erratics and chalk, whereas the gravels in the Lowestoft Formation contain common erratics from Scotland and northern England, and abundant chalk where not decalcified.
There is some debate as to the extent of the Lowestoft Formation. It is extensive over East Anglia having its southern limit near Romford, Essex. It is probable that most of the chalky tills in central East Anglia are also part of the Lowestoft Formation. In northern East Anglia the very chalky tills commonly referred to informally as the "marly drift" were generally included within the Lowestoft Formation, but recent work has indicated that these may belong to a younger glaciation. Likewise, chalky tills in the south and east Midlands have commonly been linked with the Lowestoft Formation, but these may also be younger. It is also uncertain how the pre-Devensian tills in Lincolnshire relate to the Lowestoft Formation.
The Lowestoft Formation forms an extensive sheet of chalky till, together with outwash sands and gravels, silts and clays. The till is characterised by its chalk and flint content. The carbonate content of the till matrix is about 30%, and tills within the underlying Happisburgh Formation have less than 20%.
Extremely variable. It is thickest in buried valleys where locally up to 60m may be present. Thick accumulations are also more generally present beneath much of northern Essex and south Suffolk.
The Lowestoft Formation is overlain unconformably by deposits of the Britannia Catchments Group and in northeastern East Anglia by the Sheringham Cliffs Formation. Where the uppermost part of the Lowestoft Formation comprises sand and gravel, it is not always easy to determine its upper boundary if overlain by younger sand and gravel, but in general the younger sand and gravel is better sorted and chalk free.
Lower Group (Of South Lancashire)
LOG
Logan's Bands
LOGB
Logan Formation
LOGF
Conformable transition from greenish grey sandstones and siltstone of Slot Burn Formation.
Greyish red or pale brown sandstones and beds of greyish red silty mudstone.
Unconformable junction with overlying conglomerate of the Middlefield Conglomerate Formation.
Loganhouse Gravel Member
LOGG
Erosional contact with the underlying Chapelknowe Till Member of the Gretna Till Formation.
Dense, reddish brown, silty gravel with clasts of red sandstone, greywacke sandstone and siltstone.
Either a conformable contact with the overlying Plumpe Farm Sand Member of the Plumpe Sand and Gravel Formation or a sharp, glacitectonic contact with the overlying Plumpe Bridge Till Member of the Gretna Till Formation.
Logie Head Quartzite Member
LOGQ
Fairly sharp change from very thickly-bedded quartzite of Findochty Quartzite Member.
Along coast section from Toshie's Long Craigs [NJ 4970 6835] to the east side of Logie Head [NJ 5310 6810]; cannot be differentiated inland.
Quartzite, flaggy, thin- to thick-bedded, with thin partings of micaceous psammite. Minor semipelite in upper part, in part with calc-silicate lenses.
Rapid transition to semipelite with thin psammitic ribs of Dicky Hare Member.
Lochnagar Pluton
LOGR
Lochnagar Pluton, Phase 1
LOGR1
Lochnagar Pluton, Phase 2
LOGR2
Lochnagar Pluton, Phase 3
LOGR3
From Rb-Sr whole rock isochron ages: 415 +/- 6Ma, equivalent to Ludlow to Pridoli (Harland), or Ludlow to Praghian (Gradstein and Ogg). Taken as Ludlow to Early Devonian for convenience.
Loanhead No.1 Coal
LOHC
Longskelly Sill
LOKLY
Lower Oakwood Limestone
LOL
Little Orme Limestone Member
LOLS
Entry of massive "reef" limestones above well-bedded Loggerheads Limestone Formation; also passes laterally into Loggerheads Limestone Formation.
Little Orme, Llandudno, (SH 81 82) North Wales.
Knoll reef limestones comprising highly fossiliferous, massive, pale, fine-grained, recrytallised and locally dolomitised limestones with abundant calcite-lined former cavities with internal geopetal sediment (stromatactis). Contains a rich brachiopod and goniatite fauna. During the time of late Asbian carbonate platform development in North Wales a series of knoll reefs formed along, and serve to define, the platform margin. The knoll reef facies interdigitate with platformal facies on one side, and resedimented basinal facies of the Craven Group on the other.
Not seen, but was probably overlain unconformably by red beds of the late Westphalian Warwickshire Group, or by Permo - Triassic strata (? Kinnerton Sandstone Formation).
Lower Old Mill Limestone
LOM
Lowstone Marine Band
LOMB
Lower Monkey Coal
LOMC
Lomvi Unit
LOMV
Lonfearn Member
LONFN
Longthorpe Member
LONG
The base of the limestones described, overlying limestones with Kallihynchia sharpi, of the Roade Member.
The Kettering to Stamford area.
Pale grey to off-white or brownish, more or less argillaceous packstones and wackestones, with grainstone intercalations, thin marls and mudstones, generally fossiliferous notably with Praeexogyra hebridica (Forbes),and bivalves such as Modiolus.
Typically from about 4 m to 7m thick (Cripps, 1986).
Generally a sharp boundary with mudstone of the Blisworth Clay Formation.
Lonachan Member
LONL
Lower Old Red Group
LOOR
Lochore Parrot Coal
LOPA
Lower Old Red Sandstone (Undifferentiated)
LOR
Lower Rigfoot Coal (New Cumnock)
LORC
Lower Old Red Sandstone Extrusive Rocks
LORE
Lower Old Red Sandstone
LORS
Longnor Sandstone
LOS
The lower boundary is taken at the base of the first sandstone-dominated unit above fissile mudstones that include a Reticuloceras reticulatum Marine Band.
Stanley Moor reservoir [SK042 710]; Hulme end [SK 106 590]; Swythamley [SJ971 647].
Sandstone, medium-grained, massive, sporadic mud-pellets, sub-arkosic, feldspathic; argillaceous in lower part. Sourced from the northwest.
200 to 240m
The upper boundary is taken at the base of a mudstone-dominated succession with black fissile mudstone including a Bilinguites gracilis Marine Band overlying the Longnor Sandstone.
Lower Stinking Coal (North Wales)
LOSC
Lossiehead Formation
LOSD
Louise Member
LOSE
Lochton Sand And Gravel Formation
LOSG
Unconformable on bedrock or conformable on Banchory Till Formation or Glen Dye Silts Formation.
Sand and gravel composed predominantly of clasts of Neoproterozoic metamorphic rocks and Caledonian igneous rocks.
Very variable, generally 3 to 5m; 14m proved in boreholes.
At ground surface or unconformably overlain by Flandrian deposits.
Lower Slatyband Ironstone
LOSI
Loch Treig Group
LOTR
Drawn at base of banded psammitic granulite of the Corrour Granulite where it rests conformably on mica-schist of the Monadhliath Schist.
Highlands, north-west Scotland.
Red and green-grey mica schist, banded psammitic granulite with micaceous laminae as well as quartzite.
Drawn at conformable upward passage from quartzite of the Stob Quartzite to fine-grained quartzite of the Eilde Quartzite.
Lousey Coal (West Yorkshire)
LOUC
The Lousey Coal is a reasonable quality coal that has been worked generally in the area between Bradford and Huddersfield. Correlation with other seams is problematical.
Lochnell Vein
LOV
Low Coal (South Wales)
LOWC
Low Main Coal (Midgeholm)
LOWM
Lower Permian Rocks (Undifferentiated)
LOWP
Lower Yard Coal (Lancashire)
LOYD
Lacknakilly Plug
Langport Member And Blue Lias Formation (Undifferentiated)
LPBL
Langport Member, Blue Lias Formation And Charmouth Mudstone Formation (Undifferentiated)
LPBLC
Langport Member And Blue Lias Formation (Undifferentiated) (Littoral Facies)
LPBLL
Leverburgh Belt
LPBT
Lewes Nodular Chalk Formation, Seaford Chalk Formation, Newhaven Chalk Formation, Culver Chalk Formation And Portsdown Chalk Formation (Undifferentiated)
LPCK
Lepton Edge Rock
LPE
Regionally the Lepton Edge Rock (also referred to as the Gomersal Rock) is a fine-grained, cross-bedded flaggy sandstone that forms prominent features. On the Huddersfield Sheet (see Addison et al. 2005 p16-17) the Lepton Edge Rock is fine- to very fine-grained, thinly bedded to flaggy sandstone.
Ranges from 2 to 11m in the Huddersfield Sheet area, with the thickest development at Gomersal (which provides the unit's alternative name).
Lower Peacock Coal (South Wales)
LPEAK
Lower Pentre Coal (South Wales)
LPEC
Ladyport Formation [Obsolete Code: See Lpt]
LPF
Lower Plompton Grit
LPG
Sharp gradation with underlying un-named mudstone sequence recorded in the Stockeld Borehole SE34NE/16, [SE 3803 4945].
North of Leeds 70 Sheet and west of Harrogate 62 Sheet onto Pateley Bridge 61 Sheet.
Sandstone, medium- to very coarse-grained, locally pebbly, locally micaceous with mudstone partings.
Sharp contact with overlying mudstones which include the Eccup Marine Band. Recorded in Stockeld Borehole SE34NE/16.
Llandudno Pier Dolomite Formation And Great Orme Limestone Formation (Undifferentiated)
LPGO
Lower Pigeon House Coal (South Lancashire)
LPHC
Light Point Hardgrounds
LPHG
Lower Pinchin Coal (South Wales)
LPIC
Lower Plateau Beds
LPLB
Lower Plompton Grit [Duplicate Code: See Lpg]
LPLG
Light Point Marls
LPMA
Langport Member
LPMB
Lower Palaeozoic Rocks (Undifferentiated)
LPRU
Linn Of Pattack Silt Formation
LPSI
Conformable on Pattack Till Formation.
Catchments of the rivers Pattack and Mashie (at least).
Silty clay and clayey silt, thinly laminated, pale olive grey. Some dropstones. Coarsening upwards into ripple cross-laminated sand.
Unconformable with Ardverikie Till Formation.
Ladyport Formation
LPT
Faulted with the Glen Dhoo Formation, distinguished by a change from a mudstone-dominated facies to a siltstone/sandstone-dominated facies in the overlying Glen Dhoo formation.
Isle of Man
A dark grey mudstone, with pale siltstone laminae and sandstone as thin to medium beds locally forming packets up to several tens of metres; debrite (pebbly mudstone) is well developed locally.
About. 250 m thick.
Langavat Belt
LPV
Lorn Plateau Volcanic Formation
LPVO
The base of the lava pile interfingering with the Kerrera Sandstone Formation below.
Mainly basalts, including orthopyroxene-bearing types, with rare rhyolites, dacites, tuffs, agglomerates and some intercalated conglomerate.
Up to 800m thickness is preserved.
The top of the lava pile, which has been partly removed by erosion.
Langport Member And Wilmcote Limestone Member (Undifferentiated)
LPWC
Lapworthella Limestone
LPWL
Lickey Quartzite Formation
Not seen, fault-bounded inlier.
West Midlands (South Staffordshire).
Quartzite, pale grey and purple (ranging from lithic arenite, subarkose to quartzite) and thin beds of fissile mudstone and possibly tuff.
Not fully proved - no reliable estimate
Unconformable boundary with the overlying Rubery Formation (Llandovery) or Halesowen Formation (Carboniferous).
Lower Queen's Cairn Breccias
LQCB
Lower Quarried Limestone Member
LQL
Base of lowest regularly bedded limestone in 2-3m transitional zone with underlying Coalbrookdale Formation.
West Midlands.
Limestone, grey, bioclastic, micritic, with abundant shelly fossils and thin calcareous mudstone partings; reefs (bioherms) locally present.
12.2-16.2m at Dudley (Wren's Nest)
Gradational passage taken at the transition from limestone-dominated beds to calcareous mudstone and nodular limestone beds of the overlying Nodular Member.
Landscaping Associated With Archaeological Sites
LQU
Lower Rhyolitic Tuff Formation
Overlies sandstones and silty mudstones of Cwm Eigiau Formation.
Acid ash-flow tuff, welded and non-welded, volcanic breccias and rhyolite intrusions.
Overlain by basic volcanic deposits of Bedded Pyroclastic Formation.
Lower Ardross Limestone
LRA
Little Rams Coal (South Lancashire)
LRAMS
Lower Matlock Lava Member
LRB
Generally, the basalt lava of the Lower Matlock Lava Member rests upon thickly bedded limestones of the Monsal Dale Limestone Formation. At Hoptonwoodstone Quarry (SK 277 557) the basal c.3m comprises amygdaloidal basalt, thoroughly altered to grey and yellow clay, with lenses of pink limestone (Smith, 1967). The base of the lava, here, has been interpreted as a palaeokarstic surface with pits up to 10m deep filled by weathered blocks of lava, tuff and limestone in a clay matrix (Walters, 1981). South of Bonsall the formation thins markedly and around Golconda Mine (SK 249 551) a thin lava rests upon pale grey calcarenites of the Bee Low Limestone Formation.
The Member has a poorly exposed outcrop from west of Gratton Dale (SK 198 604) to Masson Hill (SK 286 587) and the Bonsall area (SK 27 58). Present as inliers in the Derwent Valley at Matlock (SK 249 589) and Matlock Bath (SK 293 579). Also crops out around Aldwark (SK 23 57) in the Buxton district, where exposures are rare. From Aldwark the Member thins toward the west and south and cannot be traced beyond Minninglow Hill (SK 209 573), Curzon Lodge (SK 234 560) and Golconda Mine (SK 249 551).
Dark green, grey or brown basalt lava with interbedded tuff and locally, in the Masson Hill (SK 286 587) - Bonsall area (SK 2758), interdigitations of limestone and tuffaceous limestone (Chisholm et al., 1983; Walters and Ineson, 1981). At Masson Hill three distinct lava flows are recognized, characterised by vesicular upper and lower surfaces, separated by tuff or decomposed clay (Walters and Ineson, 1981), with the lower two flows containing abundant marmorised limestone and angular basaltic fragments. Typically amygdaloidal towards the top of the lava flows and may include haematite veinlets. Locally, the lavas include vertical wedges of clay representing partial weathering of the basalt (Smith et al., 1967). In places the weathering of the basalt to a grey or brown clay is complete, although the presence of amygdales indicates origin as a lava.
Maximum of 99m at Masson Hill (SK 286 587); about 50m thick in boreholes north of Winster.
Lavas and tuffs of the Lower Matlock Lava Member are overlain by thickly bedded limestones of the Monsal Dale Limestone Formation. At Hoptonwoodstone Quarry (SK 277 557) the uppermost 0.3m-thick bed of the Member comprises brecciated limestone in a matrix of clay with vestiges of amygdales (weathered basalt).
Largoward Black Coal (East Fife)
LRBC
Lower Cambrian Rocks (Undifferentiated)
LRC
Lower Cardenden Smithy Coal (Fife)
LRCS
Lower Red Coal (North Wales)
LRED
Latrigg Formation
LRG
Conformably overlies the Gawthwaite Formation.
Interlaminated hemipelagite, siltstone and fine-grained sandstone.
Conformably overlain by the Poolscar Formation.
Lower Rivergreen Limestone (Northumberland)
LRGL
Lower Hirst Coal (Stirling)
LRH
Langar Head
LRHD
Lower Jersey Coal (Fife)
LRJ
Lower Kimmeridge Clay
LRKC
Loughor Little Coal (South Wales)
LRLC
Llanfawr Mudstone Formation
LRM
North limit: near Cellws Farm (SO 0745 6345). West limit: Llanfawr Quarries. South limit: near Llandrindod Hall (SO 0642 6110), and East limit: near New Barn (SO 0958 6213).
Grey mudstone (few interbedded tuffs).
Lower Matlock Limestone
LRML
Loch Ryan Formation
LRN
Unconformable over Carboniferous strata.
Stranraer area, suoth west Scotland.
Coarse breccia - conglomerate of greywacke clasts in a red sandstone matrix. Thin, discontinuous interbeds of sandstone.
No younger strata preserved.
Lower Rowhurst Coal (North Staffordshire)
LROHC
Lower Possil Ironstone (Glasgow Area; Central Coalfield)
LRPI
Lower Red Sandstone (Triassic)
LRS
Lower Red Sandstone (Wenlock Series)
LRSA
Laira Shales
LRSH
Long Ridge Sandstone
LRSS
Largoward Thick Coal (East Fife)
LRTH
Landscaping For Recreational Purposes (Generally Not Engineered)
LRU
Scourian Gneisses
Lower Swansea Six Feet Coal (South Wales)
LS6FC
Leanach Sandstone Formation.
LSA
Conformable boundary with Nairnside Sandstone Formation below.
Red sandstones of mixed fluvial and aeolian origin.
50 metres +.
Conformable boundary with Inshes Flagstone Formation above.
Lees Bottom Lava Member
LSBB
Basalt lava of the Lees Bottom Lava Member is underlain by pale and medium grey limestone, locally tuffaceous, of the Monsal Dale Limestone Formation.
Restricted to the area west of Ashford (SK 19 69), in the Peak District inlier.
Vesicular and non-vesicular basalt.
A thickness of 8.5 m is proved at the type locality.
Basalt lava of the Lees Bottom Lava Member is overlain by pale and medium grey limestone of the Monsal Dale Limestone Formation.
Lacustrine Shoreface And Beach Deposits
LSBD
Typically sand and gravel; lacustrine deposits from within the active wave and beach zones. [Generic description].
Lower Leintwardine Formation [Obsolete Code: Use Llt]
LSBN
Lindsayston Burn Member
LSBU
Mapped as a conformable contact on NS20SE in the type section at (NS 2824 0080) but not actually exposed. Defined as the lithological change from the yellow sandstone with grey silty mudstone of the underlying Drumwhirn Member to red-purple sandstone with conglomerate and pedogenic carbonate.
NS20SE, NS20SW, NS30SW near Dailly, South Ayrshire. The full lateral extent of the unit is not yet confirmed.
Between (NS 2821 0082) and (NS 2272 0089), the strata are characterized by buff-white-grey, hard, flaggy sandstone, interbedded soft red-green sandstone with pedogenic carbonate nodules and pipes, and rarer red-green siltstone and mudstone with pedogenic carbonate nodules. Thick channelised sandstone and conglomerate a few metres thick and tens of metres wide are observed at several localities. In the northwestern part of the Lindsayston Burn section (NS 2272 0089) to (NS 2749 0097) the upper part of the member records a gradational change. Medium- to coarse-grained sandstone interbedded with red-grey siltstone with pedogenic carbonate are common, but intercalations of grey calcareous siltstone and mudstone and thinly bedded fine-grained sandstone in packages up to about 0.7m thick are also observed.
Approximately 200m at the type section with 134m proven by logging where exposed, interpreted to be laterally variable and up to 285m in other parts of NS20SE.
Mapped as a conformable contact on NS20SE in the type section at (NS 2735 0112) but not actually exposed. Defined as the lithological change from red-purple sandstone with conglomerate and pedogenic carbonate to the grey-green mudstone with thin non-marine limestones and sandstone that is typical of the Ballagan Formation in the Midland Valley of Scotland.
Limestone Coal Formation
LSC
Cyclic: includes coal seams.NOTE: Passage, Upper Limestone, Limestone Coal and Lower Limestone formations were defined for use on Scottish maps by MacGregor, 1960, based, except for the top of the Passage Formation, on the correlation of marine bands. The top of the Passage Formation is defined on the base of the overlying Lower Coal Measures, drawn at an arbitrary line that varies in horizon from basin to basin. The various positions are shown by Ramsbottom and others, 1978. It is proposed that these positions and the marine bands (considered as lithological markers) defining the other formational boundaries be followed here. It is proposed that the divisions be retained but with rank revised from Group to Formation, as these are the units that are mapped in practice and displayed on published 1: 50k maps.
530.2 metres in type section.
Base of Index Limestone.
Little Sulphur Coal (Coalbrookdale)
LSCC
Loch Scridain Sill Complex
LSCR
Longsleddale Member
LSD
Unconformable upon strata of the Borrowdale Volcanic Group.
Conglomerates and sandstones with subordinate red and green siltstones and shaly mudstones.
Maximum of 70m, thins to less than 2m at Kentmere Hall (4km to the west).
At base of Applethwaite Formation or of Stile End Formation where present.
Lower Limestone Shale Group And Dowlais Limestone (Undifferentiated)
LSDW
Lower Stromness Flagstone Formation
LSF
Drawn at unconformity where flagstones overlie Yesnaby Sandstone Group or pre-Devonian basement.
Laminated, carbonate-rich siltstones and shales with subordinate fine-grained, thinly bedded sandstones.
c.250m
Drawn at confromable upward passage to the Sandwick Fish Bed, upward passage being from sandstone and shale into limestone.
Lacustrine Shoreface Deposits
LSFD
Typically sand and gravel; lacustrine deposits from within the active wave zone. [Generic description].
Lysfaen Limestone
LSFL
Lower Siltstone Group
LSG
Longshank Gneiss Formation
LSGN
Landscaped Ground (Undivided)
LSGR
Variable composition. Man-made superficial deposit. Areas where the original surface has been extensively remodelled, but where it is impracticable or impossible to delineate separate areas of 'Worked Ground' or 'Made Ground'. [Generic description].
Lower Shafton Coal (West Yorkshire)
LSHC
Lower Shiaba Psammite Formation
LSHP
Lower Stanhope Coal (South Derbyshire)
LSHPE
Lowstone Ironstone
LSI
Inverian
LSIN
Lower Skateraw Limestone
LSKL
Silkstone Coal, Lower Leaf (West And South Yorkshire)
LSLKC
Linns Limestone
LSLS
Listeri Marine Band
LSMB
Lewes Nodular Chalk Formation, Seaford Chalk Formation And Newhaven Chalk Formation (Undifferentiated)
LSNCK
Lower Soap Coal (South Wales)
LSOAP
Lower Splint Coal
LSP
Little Splint Coal
LSPC
Little Strickland Limestone
LSRL
Lester Slates And Sandstones Member
LSS
Lower Coal 'Series' (Bristol/Somerset)
LST
Limestone Coal
LSTC
Littlestone Till Formation
LSTI
Wolstonian to Early Devensian.
Sharp, irregular contact with bedrock, with relief amplitude of 7.5m, part controlled by faults in the bedrock.
Probably widespread in west central Scotland.
Silty, sandy, stony clay diamicton ("lodgement till"), very stiff, dark grey, containing clasts of mainly local Westphalian lithologies (sandstone, mudstone, limestone, coal), and dolerite. Locally enclosing deformed sheets of sand up to 7.5m thick.
Sharp, undulose contact with overlying clay-rich gravel or clayey sand of the Lawthorn Diamicton Member.
Lower Stinking Coal (Cannock)
LSTK
Lower Stonesdale Limestone
LSTL
Lower Stockport Marl
LSTM
Latheron Formation
LSU
Lower Silurian Volcanic Rocks (Undifferentiated)
LSV
Lower Siller Willie Coal (Midlothian)
LSW
Lower Spilsby Sandstone Member
LSYS
Pending definition see information relating to the Spilsby Sandstone Formation [SYS]
Llyn Shear Zone Complex
LSZ
Not applicable. The shear zone involves Neoproterozoic rocks.
Lleyn Peninsula, but may connect offshore with the Berw Shear Zone Complex of Anglesey. Boundaries are tectonic and either gradational with, or locally faulted against rocks of the Gwna Group and the Sarn Complex.
Fine-grained, siliceous schists and phyllitic rocks containing porphyroclasts and larger bodies of sheared limestone, red phyllite and metamorphosed basaltic lavas.
Not applicable. Mostly involves pre-Arenig rocks but associated brittle faults penetrate the adjacent outcrops of Ordovician rocks.
Litton Tuff Member
The tuff at the base of the member is underlain by dark to medium grey limestones of the Monsal Dale Limestone Formation.
The member can be traced from Tideswell Moor (SK 152 766), Litton (SK 168 751), Cressbrook Dale (SK 172 749) and Wardlow Hay Cop (SK 180 738).
At the type locality the member is dominated by a volcanic breccia (agglomerate) with clasts, including some limestone, up to 13 cm diameter (Stevenson and Gaunt, 1971). In the Longstone Edge boreholes (e.g. SK 2144 7367) the member comprises one to three leaves of grey and green banded tuff with some limestone grains. The thickest development in these boreholes is associated with a well-sorted tuff, with coarser bands of fine lapilli (Aitkenhead et al., 1985). In the Eyam Borehole the member is a 1.1 m thick, fine-grained, grey-green, pyritic tuff (Dunham, 1973).
Maximum thickness of in excess of 30 m to the north-east of Litton.
The tuff at the top of the member is overlain by dark grey cherty limestones of the Monsal Dale Limestone Formation.
Lincomb Tarns Tuff Formation
LTA
Base of dacitic lapilli-tuff. Unconformably overlies erosion surface on top of Seathwaite Fell Sandstone Formation (volcaniclastic sandstone). Basaltic andesite and andesite sills may intervene locally.
Lincomb Tarns - Scafell - Rossett Pike - High Raise, Easdale - Grasmere - Scandale - Wansfell - Ambleside - Skelwith Bridge - Yewdale - Coniston - Torver High Common, Brothers Water to Shap area, Cumbria.
Dacitic lapilli-tuff, typically lithic rich with both silicic and mafic clasts; interpreted as welded ignimbrite; locally with thin tuff and volcaniclastic sandstone interbeds. Component members are recognised in some areas.
170 to more than 800m
Base of overlying formations: Esk Pike Formation (mudstone and siltstone) and, in the southeast of the district, Tarn Hows Tuff Formation (andesitic tuff and lapilli).
Lower Turbot Anhydrite Unit
LTAN
Loch Tay Limestone Formation
LTAY
Base of calcareous lithologies above dominantly semipelitic rocks of the Ben Lui Schist Formation.
Campbeltown to Glen Isla.
Schistose calcareous psammite and semipelite with units of blue-grey, crystalline meta-carbonate rock up to 10m thick.
Top of highest metacarbonate rock unit below the Mount Blair Psammite and Semipelite Formation or undivided Southern Highland Group.
Leintwardine Group
LTB
Lothbeg Shale Member
LTBS
Lower Tealby Clay Member
LTC
The erosional base separates blue-grey clay, glauconite-rich at some horizons and silty and oolitic in the lower part [Lower Tealby Clay Member] from clayey, oolitic ironstone [Claxby Ironstone formation]
Southern and central Lincolnshire. Mudstones equivalent to the Lower Tealby Clay Member are present below the Wash, although the upper boundary of the member cannot be accurately defined due to the absence of the Tealby Limestone Member.
Lower Tealby Clay Member comprises blue-grey clay, glauconite-rich at some horizons and silty and oolitic in the lower part.
Up to 13m proved, but an estimated 18m at North Willingham Owen and Thurrell, 1968]
In much of Lincolnshire, sandy limestones and thin oolitic clays [Tealby Limestone Member] overlies blue-grey clay, silty and glauconite-rich at some horizons [Lower Tealby clay Member]. In southern-most Lincolnshire, in the Skegness Borehole, and below the Wash, the Tealby Limestone Member is missing and the Lower Tealby Clay Member cannot be satisfactorily separated from the Upper Clay Member. In northern Lincolnshire, between Audleby and Clixby, the arenaceous Carstone Formation rests on mudstones of the Lower Tealby Clay.
Little Coal (West Yorkshire)
LTCO
The Little Coal is identified only in the area around Hunsworth and Westgate Hill in Bradford. It forms a split seam above the Shertcliffe Coal, merging with it to the east.
Lower Two Foot Coal (New Cumnock)
LTF
Lower Two Foot Coal (Dungannon)
LTFC
Lower Trigonia Grit Member
LTG
Discites Zone (and locally basal Ovalis Zone).
Disconformity: upward change from peloid and ooid limestone (Scottsquar Member) or sand, clay and sandy limestone (Harford Member) where present (both of Birdlip Formation) into limestone as described in lithology. Generally marked by a hardground.
North and mid-Cotswolds, Gloucestershire: west of Northleach, Cold Aston and Condicote, northeast of Stroud, south of Blockley. Absent between Birdlip and Cirencester. (Barron, A J M, et al, 1997, fig.4).
Grey speckled with orange brown very shelly and shell-detrital moderately sandy peloid wackestones, packstones and grainstones with thin marl and sand beds, some shelly; some of the peloids are ferruginous ('ironshot'); commonly pebbly at the base, thins and becomes more marly, ironshot and conglomeratic northwards; the fauna includes bivalves (notably trigoniids), brachiopods, corals and the colonial serpulid Sarcinella (See Sumbler, M G, Barron, A J M and Morigi, A N, 2000).
Typically 1 to 2m, maximum c.3m: type section (Leckhampton Hill); 1.5m (British Geological Survey files; Cox, B M, and Sumbler, M G. 2002) to 2.2m (Richardson, L, 1906).
Upward transition from limestone as described in lithology into sandier, more coarsely shell-detrital, less ironshot limestones (Gryphite Grit Member) or hardground overlain by Salperton Formation.
Littlegate Limestones Bed
LTGL
Change up from grey mudstone with phosphate nodules of undifferentiated Foston member; at c 3.3m depth in type section Fulbeck Airfield Borehole F/B1 (SK85SE/25).
East Midlands: north Leicestershire to Linclonshire. Not recognised in the Scunthorpe Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south either into part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or into part of the mudstone-dominated Charmouth Mudstone Formation.
Group of one to three, typically two, limestone beds, separated by mudstone. Lower limestone is hard grey, very shelly, including ammonites, bioclastic and about 0.25m thick. Upper limestone is less shelly, fine, very sandy, ferruginous limestone, with pectiniids. Fauna (mainly from the lower limestone bed) also includes forams, gastropods, brachiopods, belemnites (lowest recorded in area), ostracods, echinoderms, and Chondrites burrows. Forms a strong feature.
0.2 to 1.5m; c1.5m in type section.
Change up from grey mudstone of undifferentiated Foston member; at c 1.8m depth in type section Fulbeck Airfield Borehole F/B1 (SK85SE/25).
Lightspout Formation
LTGP
Drawn at the base of the Lightspout Formation where the grey mudstones and siltstones rest conformably upon dominantly purple mudstones and siltstones in the Synalds Formation.
Lightspout Hollow, Cardingmill Valley, northwest of Church Stretton, Shropshire.
Mainly flaggy, greenish grey siltstones and sandstones with massive sandstone beds. The top c.122m is mainly purple in colour.
c.670m
Drawn at the conformable upward passage of the Lightspout Formation to the overlying purple shaly mudstone and siltstone with bands of coarse purplish grey sandstone of the Huckster Conglomerate.
Letchworth Gravels Formation
LTH
Unconformable on Lower Chalk.
Capping hill top above c.65m OD around Fairfield Hospital, near Letchworth, with smaller spreads along the Pix Brook and to the southwest of Lower Wilbury Farm. Possibly underlying till-covered ground, south of the Hospital.
Pebbly sand and sandy gravel with a high proportion (commonly 50% or more) of rounded quartzose pebbles (quartz, quartzite and sandstone).Quartzose gravel and sand - [Generic description: 1:50 k map margins].
3.55m proven in borehole TL23NW/113 (TL 2048 3540). May be up to 5m elsewhere.
Mostly found at surface. Overlain in part by (Anglian) chalky till.
Lower Thick Coal (South Staffordshire)
LTHC
Lytham Formation
LTHM
Probably variably underlain by bedrock or deposits of the Caledonia Glacigenic Group.
Cumbria, Lancashire and north Cheshire. It includes all estuarine deposits of the rivers Lune, Ribble and Mersey.
Sand, clay and silt with gravel and peat. Gravel becomes dominant in the outer parts of the Mersey Estuary.
Includes the Scrobicularia and Lower Cyclas clays, Leasowe Marine Bed, Preesall Shingle and coastal peat beds.
5 to 25m
At the ground surface.
Lodgement Till
LTILL
Lilstock Formation
LTK
Placed at base of Cotham Member, sharp, commonly channeled on the Westbury Formation.
Present throughout the United Kingdom.
Includes Cotham Member (grey and grey-green shales and siltstones) and Langport Member (porcellanous limestone below, calcareous mudstone above).
Placed at top of Langport Member, where there is a sharp but conformable junction with the overlying 'paper shale' of the "Blue Lias".
Lilstock Formation (Marginal Facies)
LTKM
Low Tipalt Limestone
LTL
Little Coal (North Wales)
LTLC
Little Coal (In South Wales Middle Coal Measures Formation)
LTLE
Little Limestone
LTLS
Little Coal (In South Wales Lower Coal Measures)
LTLSW
Little Marine Band [Local Name: See Cwmb]
LTMB
Local name applied to the Clown Marine Band (National Standard Name) in the Durham and Northumberland coalfield areas.
Lawthorn Diamicton Member
LTND
Sharp undulose contact with underlying dark grey stony clay diamicton of the Littlestone Till Formation.
Clay-rich gravel, unstratified, passing laterally into clayey sand. Interpreted as an "ablation deposit".
Sharp, irregular, erosional contact with overlying sand and gravel of the Armsheugh Sand and Gravel Formation with relief amplitude of about 3.5m.
Lower Threequarters Coal (Cumbria)
LTQ
Lower Trap
LTR
Lower Trenchard Coal (Forest Of Dean)
LTRC
Lower Three Sisters Ignimbrite
LTSI
Loch Treig Schist And Quartzite Formation
LTSQ
Long Top Tuff Member
LTT
Base of rhyolitic pyroclastic rocks. Unconformable, on slumped surface of Whorneyside Tuff Formation and locally on the underlying Birker Fell Andesite Formation, but locally interbedded.
Crinkle Crags and Scafell area, extending to Coniston Fells, Duddon Valley, Eskdale, Wasdale, Borrowdale and Langdale.
Bedded units of massive, eutaxitic rhyolitic tuff and lapilli-tuff. Intercalations of bedded and laminated tuff widespread. Localized units of pyroclastic breccia.
Defined by the bases of overlying Crinkle Tuff Member of the Airy's Bridge Tuff Formation.
Little Coal (Cumbria)
LTTC
Low Tupton Coal (Derbyshire And South Yorkshire)
LTUC
Lower Tunbridge Wells Sand Formation
LTW
Interbedded silty sandstones and subordinate siltstones rest with a sharp contact on red stained mudstones [Wadhurst Clay Formation] and a spring line is also associated with the junction.
The formation is widespread in the Weald of South Eastern England, although where the Grinstead Clay and Ardingly Sandstone are missing, it is not possible to distinguish the Lower and Upper Tunbridge Wells Sand Formations, which have incorporated into the "Tunbridge Wells Sand". The formation can be traced across the Sevenoaks-Tonbridge [sheet 287], Maidstone [sheet 288], Horsham [sheet 302] and Tunbridge Wells [sheet 303] districts, but the Tunbridge Wells Sand is indifferentiated on the Tenterden sheet [304]. It is again present in the Northern part of the Brighton and Worthing district [sheet 318/333] and onto the Lewes sheet [319], but it is again indifferentiated "Tunbridge Wells Sand" in Eastern part of Lewes district and in the Hastings district [sheet 320/321].
The formation comprises; (i) A lower unit of thinly interbedded silty fine-grained sandstones and frequent, though subordinate, siltstone and rare beds of clay or silty clay. (ii). An upper unit of largely massive and thickly bedded, fine- and medium-grained sandstone [Aringly Sandstone Member]. It is cross-bedded and festoon-bedded in part. In much of the Horsham district it is composed of "sandrock", a clean white or greyish white, soft quartzose sandstone that forms crags. It becomes finer-grained towards the south of the Horsham district. Locally, in the East Grinstead area, stringers of quartz and quartzite pebbles are common. The pebbles become larger towards Tunbridge Wells.
Up to 33m
The upper boundary is taken at the base of the Top Tunbridge Wells Pebble Bed, which is situated at the base of the mudstones of the Grinstead Clay Formation. Where the pebble bed fails, as in the Tunbridge Wells district, the base is placed at the junction between the Grinstead Clay Formation above the Ardingly Sandstone Member below. Locally ripples of coarse-grained sand separate these two units. In some districts, however, such as Tenterden [304] Hastings [320/321] and Lewes [319] where the Ardingly Sandstone Member and the Grinstead Clay Formation thin out, the sands between the Wadhurst Clay Formation and the Weald Clay Formation are indifferentiated and termed "Tunbridge Wells Sand" in BGS Memoirs and maps.
Littleworth Beds
LTWB
Lower Trichwart Coal (South Wales)
LTWCO
Lanty Crag Breccia Member
LTY
Taken at the abrupt change from mudstone of the Skiddaw Group to volcaniclastic rocks. The Member lies at the base of both the Birker Fell Andesite Formation and the Borrowdale Volcanic Group in the area.
From Barton Fell, Ullswater, to Bampton, north-eastern Lake District, Cumbria.. Also present in the Tarn Moor Tunnel [Wadge et al., 1972].
A heterogeneous succession of volcaniclastic breccia and conglomerate, with some bedded volcaniclastic sandstone.
Overlain by aphyric andesite within the Birker Fell Andesite Formation.
Lubhair Beag Semipelite Formation
LUBE
Luccombe Breccia Formation
LUBR
Probably Triassic.
Unconformable: rests on Hangman Sandstone (Eifelian).
Porlock Basin, west Somerset. Sheet 278 (Minehead).
Breccia, sandy breccia, pebbly sandstone and sandstone, reddish brown, commonly calcareous; calcite-veined in places, and locally well-cemented-clasts in breccias; mainly angular platy slate, shale, sandstone and quartz. Thin unit of conglomerate with rounded boulders of Devonian sandstone. Near base, reddish brown, weakly cemented, silty, fine- to medium-grained sandstone unit, up to 70m.
Up to 650 m. estimated.
Probably unconformable: overlain with probable angular discordance by Mercia Mudstone Group (Triassic).
Loch Urigill Carbonatite
LUCB
Lurgaboy Dolomite
LUD
Ludgbridge Conglomerate
LUDG
Ludlow Rocks (Undifferentiated)
LUDL
Lower Forest Beds And Upper Forest Beds (Undifferentiated)
LUFB
Lugate Group
LUG
River Terrace Deposits, 1 (Lugg)
LUG1
River Terrace Deposits, 2 (Lugg)
LUG2
River Terrace Deposits, 3 (Lugg)
LUG3
River Terrace Deposits, 4 (Lugg)
LUG4
Longhaugh Sand And Gravel Member
LUGH
The Longhaugh Sand and Gravel Member of the Clydebank Clay Formation rests with angular unconformity on older Quaternary sediments or on bedrock. It most commonly rests on the Wilderness Till Formation (WITI) of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup).
The Longhaugh Sand and Gravel Member of the Clydebank Clay Formation is recognised in the lower Clyde in the estuary of the Clyde around Longhaugh.
The Member consists mainly of grey, loose, fine- to medium-grained, locally silty sand containing some comminuted shell debris. Gravel with shells is recorded below the sand units in the Longhaugh 20 Borehole [NS 4291 7319].
The Longhaugh Sand and Gravel Member of the Clydebank Clay Formation is overlain by younger Quaternary sediments belonging to the same Formation.
Lower Leintwardine Formation And Upper Leintwardine Formation (Undifferentiated)
LULT
Lulworth Formation
LULW
First occurrence of finely laminated, ostracod-rich limestones above the more massive, shelly limestones of the Portland Limestone.
Mapped within the South Dorset area, covered by British Geological Survey 1:50 000 scale sheets 341, 342 and 343. The unit can be defined elsewhere in southern England (e.g. Wessex Basin and south-east England), separated from the Durlston Formation above by the Cinder Bed. Occurs in the subcrop throughout southern Britain (Wessex Basin). Away from the type area of Dorset, the presence of the formation can be interpreted from described outcrops from the Weald and to the west in Wiltshire (Vale of Wardour). It is presently identified on mapsheets E328 [Lulw], (E341/342 [Lulw] and E342/343) [Lulw]. It is also likely to be present at depth but not depicted on E283, E284, E286, E301, and part of the Purbeck group shown on the following sheets E219 [Pb], E220 [Pb], E237 [Pb], E252 [g14], E270 [Pb], E271 [Pb], E285 [PB], E287 [g14], E288 [shown in GVS but not symbolised], E289 [shown in GVS but not symbolised], E297 [Purbeck Formation shown but only Oakley Marl Member symbolised], E298 [Pb, and Formations to be released late 2004], E299 [Pb], E300 [Pb], E302 [g14], E303 [g14], E304[g14], E305/6 [g14], E316 [pb], E317/332 [Pb], E318/333 [shown in GVS but not symbolised], E319 [g14], E320/321 [g14], E327 [g14].
Dominated in the lower part by pale-weathering, ostracod-rich calcarenites that are commonly rippled. Stromatolitic or algal, micritic limestone, with evaporitic material, is also common (particularly in east Dorset). The upper part of the formation comprises monotonous, interbedded dark grey mudstones and white-weathering micrites. Detrital quartz is common at several levels. The Lulworth Formation comprises three members in Dorset, namely in ascending order the Mupe Member, the Ridgway Member and the Worbarrow Toout member. Elsewhere the formation is undivided or is itself incorporated into an undivided Purbeck Limestone Group. The formation includes the informal Lower Purbeck Beds and the lower part of the Middle Purbeck Beds (up to the base of the Cinder Bed) of the traditional scheme. Within the Weald an equivalent of the Cinder Bed has been identified thus allowing the succession there to be considered within the formal terminology.
In Dorset, 27 to 63m
Top of the Cherty Freshwater Bed, comprising thick-bedded, chert-rich micrites. Overlain by the Cinder Bed at the base of the Durlston Formation.
Lugar Main Coal (Cumnock And Muirkirk, South Ayrshire)
LUM
Lubcloud Microgranite
LUMG
Not applicable, but the microgranite occupies a northwest-trending subvertical sheet, up to 9m wide, the actual contacts being obscured by vegetation. It is emplaced into grey, cleaved, thinly bedded to laminated volcaniclastic strata of the Charnian Supergroup (Ives Head Formation).
The intrusion follows a northwesterly trend and is exposed discontinously from about 350m westnorthwest of Ives Head trig point, to a narrow wooded ridge about 400m east of Lubcloud Farm, the latter being now much overgrown.
Brick-red, fine-grained microgranite with a saccharoidal, quartzo-feldspathic groundmass in which are set larger idiomorphic plagioclase crystals. Plagioclase and lath-shaped chlorite form c.2mm size phenocrysts; the latter are concentrated in the central part of the intrusion, where they comprise up to 15% of the rock.
Not applicable. (see Lower Boundary discussion.)
Lower Mottled Mudstone Member And Upper Mottled Mudstone Member (Undifferentiated)
LUMM
Lumphanan Intrusion
LUMP
Lunde Unit
LUND
Lune Valley Formation
LUNV
Cumbria and Lancashire within the river valley and tributaries of the River Lune.
Dominantly silty and sandy alluvial sediments with gravel and sporadic cobbles and boulders. River Terrace deposits are mainly sand and gravel.
Generally less than 10m.
Loch Ussie Red Sandstones And Shales
LUR
Lusa Limestone Member
LUSA
This formation marks the local base of the Jurassic on Skye and generally unconformably overlies Neoproterozoic ("Torridonian") strata.
Typically in the northern part of Skye, east of Breakish, but part of the Breakish Formation, which is found within the Sea of the Hebrides Basin.
Alternating fossiliferous wackestones, packstones and micritic limestones with interbedded calcarenites.
25 to 30m
The unit is a member within the Breakish Formation and the upper boundary is marked by a transition from carbonate facies of the unit to overlying massive sandstone.
Luachair Sandstone Member
LUSM
Wenlock Rocks And Ludlow Rocks (Undifferentiated)
LUW
Lower Veins Coals (Undifferentiated) (Pembrokeshire)
LVCO
Llandrindod Volcanic Formation
LVF
Llanrian Volcanic Formation
LVG
Drawn at the base of the Llanrian Volcanic Group where it rests conformably upon the Tetragraptus Shales.
1:50 000 Sheet 209 (St Davids). Llanrian, Pembrokeshire, south-west Wales.
Rhyolitic tuffs with interbedded mudstone.
Drawn at the conformable upward passage of the Llanrian Volcanic Group where it cross-cuts the Didymograptus Bifidus Beds.
Levencorroch Mudstone Formation
LVM
Lavernock Shales Member
LVN
Laverton Sandstone
LVS
A sharp upward change in a comformable succession from predominatly grey mudstone to sandstone, at the base of the first sandstone above the Cancelloceras cumbriense (G1b1) Marine Band.
The pennine foothills between Masham, Kirkby Malzeard Moor and Winksley, North Yorkshire.
A medium to thickly bedded, grey, medium-to coarse-grained, cross-bedded sandstone with beds of grey siltstone and a lingula band in parts.
From 10 - 25 m thick.
A sharp upward change in a conformable succession from sandstone to predomantly mudstone to top of the last sandstone below the subcrenatum Marine Band (where recognised) or below the Winkesley Sandstone.
Laverton Shales
LVSH
Lledr Valley Tuffs Member
LVT
Local members within Capel Curig Volcanic Formation.
Ash-flow tuffs, welded.
Landscaping Associated With Raised, Covered Structures
LVU
Langwathby Bed
LWBB
Lawrenny Cliff Formation
LWC
?Emsian.
The base of the Formation is a conformable, gradational junction with the Mill Bay Formation. It lies 139.91m above the base of the section in the eastern section of Mill Bay (Mill Bay East) measured by Thomas et al, (2006), at the base of the first extraformational conglomerate, which is 0.09m thick and contains over 10% of exotic clasts of the total clast population. It lies above an irregular erosion surface with up to 0.07m relief, and forms part of a 0.48m thick unit of interbedded sandstones and extraformational conglomerates (see Thomas et al, 2006, Figure 14B).
The Formation occupies most of the southern half of the Lawrenny peninsula [c. SN 015 065] south of the Benton Fault. It also crops out on the west side of the Daugleddau estuary in a small area north of Williamston Pill [SM 995 065] to the Benton Fault [SM 995 075] northwest of Benton Castle in the core of the Lawrenny Syncline. It is also present in a small, fault-bounded outlier at the southern end of Williamston Cliff [SN 002 054]. The main outcrop lies south of the Lawrenny peninsula, south of the Carew River and east of Cosheston [SN 00 04] from near Paskeston [SN 025 035] north to the Carew River near Mount Pleasant [SN 016 059].
The Formation consists of very fine- to coarse-grained, grey-green sandstones 46.1%), extraformational conglomerates (18.6%), interlaminated fine- to medium-grained to very fine-grained sandstones and red-brown siltstones (22.5%), red-brown siltstones (10.4%) and intraformational conglomerates (2.4%). The rocks are arranged predominantly in 0.4 to 11.0m-thick, fining-upward rhythms. Abundant exotic detritus in the extraformational conglomerates characterize the Formation and differentiate it from the underlying Mill Bay Formation. The Formation is prediminantly grey-green (68.1%), the remainder (mainly siltstones) are red-brown or red-purple; reddish colouration increases upwards in the Formation.
The upper boundary is a conformable transition from the grey-green sandstones and conglomerates at the top of the Formation into the red-brown, coarser extraformational conglomerates of the overlying New Shipping Formation. The actual boundary is not exposed.
Late Weichselian Channel Fill Deposits, Undifferentiated (Offshore)
LWCFU
Late Weichselian.
Low Coal (Machrihanish)
LWCM
Lower Welsh Coal (South Wales)
LWCO
Little Woodfield Coal (South Derbyshire)
LWDC
Late Weichselian Diamicton, Firm To Hard (Offshore)
LWDFH
Late Weichselian Deposits, Undifferentiated (Offshore)
LWDU
Late Weichselian Diamicton, Very Soft To Soft (Offshore)
LWDVS
Low Estheria Band
LWE
Lowton Estheria Band
LWEB
Lower Wee Coal (Glasgow Area; Central Coalfield)
LWEC
Kilwinning Lower Wee Coal (North Ayrshire)
LWEE
Loweswater Formation
LWF
The boundary is gradational with the underlying Hope Beck Formation and crops out on the east side of Dodd (NY 171 233). Jackson (1961) used "the presence of arenites 3 inches or more in thickness" as the criterion for separating the two units.
Occurs within the western part of the Skiddaw inlier, underlain by the Hope Beck Formation and overlain by the Kirk Stile Formation. It also occurs in a small inlier at Mungrisdale [NY 164 209].
Mainly sandstone with minor mudstone and quartz-rich greywacke. Basal beds are mainly thin, fine-grained sandstones interbedded with siltstones and mudstone. Bed thickness increases towards the middle of the Formation. Bed thickness decreases through the upper part of the Formation.
900m in the northwest Lake District; 450m around Jonah's Gill [NY 190 343]; unknown in faulted inlier at Mungrisdale.
In a small quarry on Whiteside End [NY 1660 2169] bedding thickness reduces rapidly and the proportion of mudstone increases forming a laminated facies of sandstone and mudstone with sporadic thin beds of quartz-rich greywacke. The top of the Formation is taken at the highest thin sandstone bed in the dominantly sandstone part of the succession.
Lower Fireclay Coal (Cumbria)
LWFC
Loweswater Formation (Hornfelsed)
LWFH
Late Weichselian Gravel (Offshore)
LWGRV
Little Whickhope Coal
LWHC
Little Whin Sill
LWHIN
Taken at the sharp intrusive contact of the sill, where it is in contact with sedimentary strata below.
Weardale, County Durham.
A very fine to fine-grained porphyritic dolerite, with finer grained 'chilled' contact rock. Sills are typically columnar jointed, and emplaced into the Three Yard Limestone. The literature on this sill is listed, referred to and discussed in Stephenson et al., 2003.
Up to 13 m thick.
Lower Winter Hill Terrace Deposits
LWHT
Definition as for "Winter Hill Gravel" elsewhere in Lexicon. [Generic description].
Little Wenlock Basalt Member
LWKB
Geological log of the Dinantian sequence at Lilleshall (Bridge and Hough, 2002) shows a sharp junction between basalt overlying limestone (formerly 'Lower Limestone') of the Sylvan Limestone Formation.
Little Wenlock, [SJ6470 0700], Lilleshall [SJ73 15] and Coalbrookdale [SJ64 08].
Microporphyritic olivine-basalt lava.
25 to 60m in the Little Wenlock area.
The basalt is overlain by sandstone, limestone or mudstone (formerly 'Upper Limestone') of the Sylvan Limestone Formation. The upper part of the Little Wenlock Basalt is locally marked by a weathered bole.
Lower Wenlock Limestone
LWL
Lawmuir Formation
LWM
Rests on volcanic detritus (Kirkwood Formation) in type section; on Clyde Plateau Volcanic Formation in some areas.
Neighbourhood of Lawmuir, Clydebank, Strathclyde, Scotland.
Cyclothemic sequence of mudstone, siltstone, sandstone with seatearths, coals and marine limestones. Marine bands in upper part, conglomerate in lowest part in some areas.
254.52m in type section.
At base of Hurlet Limestone (base of Lower Limestone Formation) as in type section.
Late Weichselian Mud And Sand, Interbedded (Offshore)
LWMAS
Late Weichselian Mud, Firm To Hard (Offshore)
LWMFH
Lesmahagow Main Gas Coal
LWMG
Low Main Coal (Warwickshire)
LWMN
Late Weichselian Mud, Very Soft To Soft (Offshore)
LWMVS
Late Weichselian Sediment, Undifferentiated, Affected By Mass Wasting And Iceberg Scour (Offshore)
LWMWS
Little Wonder Coal (Northumberland)
LWOC
Lower Parkhouse Marine Band
LWPM
Low Scales Beck Member
LWS
Base of volcanogenic sedimentary succession that overlies various parts of the Millom Park Formation (Borrowdale Volcanic Group).
Local basal conglomerate on south east side of Millom Park, the outcrop (exposed parts) extends from Beck Wood [SD 1584 8073] to Waterblean [SD 1744 8247] Millom Park, Cumbria.
Mixed succession of volcanogenic siltstone, mudstone, sandstone and conglomerate. Overall fining upwards succession that is capped by a palaeosol.
Up to 170m
Base of overlying calcareous siltstone (Kirkley Bank Formation).
Lawston Limestone
LWSL
Late Weichselian Sand (Offshore)
LWSND
Low Wath Till Member
LWTI
Not seen at its type or reference sections but assumed to be unconformable on bedrock.
1:50k Sheet 37 Gosforth. Cleator Moor - Egremont area (Seaward of the 'Gosforth Oscillation Limt'), Western Cumbria.
Stony sandy clay diamicton, matrix-supported, massive, very stiff, weak red, dark greyish brown to yellowish brown, with sand (? as lenses) locally. Typical lodgement till, with angular to subrounded clasts up to boulder size. Clasts derived from the northwest of the Lake District (olive brown ?Latterbarrow Sandstone, slate, limestone and granophyre) but locally dominated by clasts of the underlying red sandstone bedrock.
c.1.8m exposed at type section, but up to 20m thick in adjacent boreholes.
At its type section it is unconformably overlain by glaciofluvial gravel and at its reference section (at Rothersyke Scar river cliff) it is overlain by the Catgill Wood Sand and Gravel Member of the Seascale Glacigenic Formation.
Ludlow Rocks And Wenlock Rocks (Undifferentiated) [Obsolete Code: Use Luw]
LWU
Low Water Tuff Formation
LWW
Formation unconformably overlies the Paddy End Tuff Member of the Lickle Tuff Formation for most of its outcrop; at the southern end it overlies the Lag Bank Tuff Formation. The base is defined at the lowest extent of homogneous, fine, lapilli-tuff of dacite composition or, where present, the base of the underlying volcaniclastic sandstones.
Low Water (SD 275 982) to Greenburn Beck (NY 310 030), Coniston Fells, Lingmoor Fell (NY 300 035), Cumbria.
Welded dacitic lapilli tuffs with subordinate interbedded volcaniclastic sandstone and tuff.
Overlain by Seathwaite Fell Sandstone Formation; abrupt change to volcaniclastic sandstone.
Lower Weald Clay Member
LWY
Lowery Coal (Forest Of Dean)
LWYC
Lyndhurst Member
Lletty Member
LYB
Lynslie Burn Beds
LYBB
Lochty Back Coal
LYBC
Lochgelly Blackband Ironstone
LYBI
Lybster Flagstone Formation
LYBR
Lynebain Basic Volcanic Member
LYBV
Base of lowest metabasalt of the Blackwater Formation. In most of area this coincides with the faulted and/or sheared lower boundary of the Blackwater Formation.
500m-wide outcrop extending along NW side of River Deveron Valley and SE side of Black Water from 1 km S of Blackwater Lodge [NJ 3327] to opposite Tammies Burn [NJ 421 355], Cabrach area, Moray District. 1:50 000 sheet 75E and 85E.
Amphibolite/metabasalt, mostly aphyric, locally with fragmented pillow structures. Interbedded with greywacke grits and slaty to phyllitic pelites.
c. 300 to 400m (based on outcrop width with no allowance for probable folding).
Base of lowest recognisable sheet of fine-grained ultramafic rock in the Blackwater Formation.
Lyoncross Coal (Glasgow Area; Central Coalfield)
LYC
Lynecrook Limestone
LYCL
Part of the White Lyne valley, near Lynecrook, Cumbria.
Litley Coal (Cheadle)
LYCO
Lower Yard Coal (South Lancashire)
LYD
Lyons Delf Coal (South Lancashire)
LYDC
Lydford Formation
LYDD
West Devon.
Dark grey and black shale and sedimentary breccia beds.
Lochty Fore Coal
LYF
Llwyn-Y-Fran Sandstone Member
LYFS
Taken as corresponding to the entry of calcareous sandstone 13m above the base of the Llanarmon Limestone Formation in the Alyn Valley Borehole..
Llanarmon-yn-Ial area [SJ1958], east of the Clwydian Range, northeast Wales.
Calcareous sandstones and sandy limestones (grainstones), locally cross-bedded and dolomitised. Records high energy, near shore bar deposition during the early stages of the Arundian transgression of North Wales, at a time when siliciclastic detritus was still actively being supplied to the developing carbonate ramp margin.
20 to 30m
Entry of dark brown-grey, less sandy, crinoidal limestones (packstones) of the overlying part of the Llanarmon Limestone Formation.
Llyn Y Gafr Volcanic Formation
LYG
Conformably overlies the dark grey mudstones of the Cregennan Formation (Cefn Hir Member in places). Passes laterally into the Brithion Formation.
The Cadair Idris District, Gwynedd, North Wales.
Massive pillowed basalt lavas with reddened tops, and intercalated mafic tuffs with subordinate felsic tuffs and mudstones.
To 360m
Unconformably or disconformably overlain by he Ty'r Gowen Mudstone Formation, commonly represented by an oolitic ironstone (the Fron Newydd Member).
Lyon's Gate Bed
LYGB
Upward change from clay or sandy clay to sandstone or limestone. Commonly a spring line at base.
In the southwest corner of the Shaftesbury Sheet 313. Possibly a correlative of the Preston Grit of the Dorset coastal succession.
Calcareous, commonly oolitic, shelly, ferruginous sandstone or very sandy limestone.
Change from sandstone or limestone to grey clay.
Lochgelly Blackband Ironstone And Coal
LYIC
Lundy Island Intrusion
LYIN
Leny Limestone
LYL
Leny Limestone And Slate Member
LYLS
Rapid transition from dominantly pale grey arenites of Keltie Water Grit Formation into dominantly grey to black slates.
Keltie Water southwest to River Teith, adjacent to the Highland Boundary Fault, north of Callander, Perthshire.
Slate, black, dark and pale grey, locally graphitic, semipelite and pelite with trilobite-bearing limestone, pale to dark grey, fine-grained.
c.50m (estimated)
Transition into arenites of the upper part of the Keltie Water Grit Formation.
Laundry Mudstone Formation
LYMD
The lower boundary is marked by the change in lithology from the underlying Powys Castle Conglomerate.
Widespread on the Welshpool sheet (151) west of the river Severn. Also occurs in the south of Oswestry (137), in the Meifod area and in the north of Montgomery (165).
Mudstone, silty, grey, weathers buff, bioturbated, thinly interbedded with sandstones (< 15cm). The basal few metres comprise beds of fine-grained sandstone about 0.5m thick.
160 to 170m
Upper boundary gradational with pale grey-green mudstones of the Dolgau Formation.
Lytchett Matravers Sand Member
LYMS
Lynebank Member
LYN
Alternations of thin limestones, dolomitic limestones (cementstones) and mudstones with sandstone beds towards top of sequence.
c.430m (Bewcastle)
Conformable upper boundary at base of the Bogside Limestone (Bewcastle Member).
Lynch Coal (South Wales)
LYNC
Lyne Formation
LYNE
Comformable on the Ballagan Formation (Kirkbean, Annandale). At Bewcastle the base is not seen; elsewhere it may be unconformable on Devonian or older strata.
The Solway Basin, Northumberland. Mapped from Kirkbean Sheet S5E/6, to Roxburghshire Sheet S11/17, and Bewcastle Sheet E12.
Cyclical sequences of sandstone, siltstone, mudstone and thin limestones, with localised dolomitic cementstones and distinctive algal beds.
At least 900m thick, measured in the Bewcastle area.
A diachronous upper boundary with the Fell Sandstone Formation, locally defined as the base of the Whitberry Marine Bed at Bewcastle.
Lynn Mudstone Formation
LYNF
Lynavoir Semipelite Formation
LYNS
Lyon Coal
LYON
Lochgelly Parrot Coal
LYPA
Lyre Geo Sandstone Member
LYR
Gradational contact with Lang Geo Sandstone Member.
Poorly-cemented pale greyish-orange sandstone with thin pale olive mudstones.
65m at Lyre Geo HY 265 023, Hoy Island, Orkney.
Unconformably overlain by Haist Pebbly Sandstone Member.
Lydebrook Sandstone Formation
LYS
The lower boundary is taken at the base of sandstone, resting unconformably on, and overstepping, limestone (Jackie Parr Limestone Formation), and mudstone and sandstone (Silurian and Cambrian strata).
Coalbrookdale [SJ 64083]; Lilleshall [SJ 7315].
Orange-brown, fine- to coarse-grained sandstone, locally pebbly, with subordinate mudstones.
c.20 to 37m in the Lilleshall [SJ7315] and Coalbrookdale [SJ6408] areas.
The upper boundary is taken at the base of calcreted limestones of the overlying Sylvan Limestone Formation.
Lochgelly Splint Coal (Fife)
LYSP
Lletty Grit (Letty Beds)
LYT
Lyne Water Intrusion
LYW
Leaze Formation
Transition from greenish grey sandstones with beds of greenish-grey siltstone of Dunside Formation.
Greyish red fine-grained sandstones in beds 0.3 to 1.6m thick, interbedded with red-brown silty mudstone.
Passage into yellow-brown sandstones of Birkenhead Sandstone.
Leziate Sand Member
LZB
Down-section change from incoherant, moderately clean, pale grey locally green, yellow or orange], fine-to-medium-grained, cross-bedded quartz sands with subordinate bands of silt or clay [Leziate Sand Member] to glauconitic, clayey, grey and green sands with bands and "doggers" of brown weathering clay-ironstone and seams of phosphatic nodules [Mintlyn Sands Member].
The Leziate Member occurs in boreholes in The Wash and in Norfolk, and extends from Heacham Southwards to Denver. North of King's Lynn it forms a steep feature capped by the sandstones of the Dersingham Formation, but South of King's Lynn, the feature is subdued beneath the Carstone. It occurs in the heathland areas of Dersingham Heath, Sandringham Warren, Roydon Common, Leziate Heath and Shouldham Warren. It is known from a number of boreholes in West Norfolk, including Hunstanton and Gayton boreholes. It passes into the Claxby Formation to the North West.
Incoherent, moderately clean, pale grey locally green, yellow or orange], fine-to-medium-grained, cross-bedded quartz sands with subordinate bands of silt or clay. Pyrite nodules are present and glauconite is locally abundant.
In the King's Lynn district, the upper boundary is defined by a down-section change from thinly bedded, fine-grained, silty sands and sandstones [Dersingham Formation] to incoherant, moderately clean, pale grey, locally green, yellow or orange], fine-to-medium-grained, cross-bedded quartz sands with surbordinate bands of silt or clay. Locally medium to dark grey clay [?Snettisham Clay] rests on the sands of Leziate Sand Member [Gallois, 1994]. In the Gayton-Marham area, pebbly, ferruginous sandstones [Carstone Formation] oversteps the incoherant, moderately clean, pale grey Leziate Member.
Lezant Slate Formation
LZSL
Not seen/faulted.
Greenish grey slate.
Lenzie-Torphichen Dyke
LZTOR
Moine Supergroup
Mickley 1 Coal (Nottingham)
M1C
Mickley 1 And Mickley 2 Coal (Vale Of Belvoir)
M1M2
Mickley 2 Coal (Nottingham)
M2C
Mickley 3 Coal (Nottingham)
M3C
M3 Limestone
M3LM
Mickley 4 Coal (Nottingham)
M4C
Mickley 4 Sill
M4S
Main Algal One
MA1
Main Algal Ten
MA10
Main Algal Twelve
MA12
Main Algal Fourteen
MA14
Main Algal Eight
MA8
Marine Alluvium
MAAL
Variable lithology; sand, silt and clay, with gravel and possible peat, formed in the marine environment. [Generic description].
Manaccan Beds
MAB
Maiden Bower Flint
MABF
Flint. NOTE: Lowermost flint band in the Chalk; forms a bed in the lowest part of the Middle Chalk.
Mabel Seam
MABL
Basal Pelite Formation
MABP
Marchbank's Vein
MABV
Manson Coal
MAC
?Arnsbergian, possibly younger.
Metamorphic Aureole, Cornubian Batholith
MACB
Metamorphic Aureole, Cairnsmore Of Carsphairn Intrusion
MACC
Metamorphic Aureole Around The Criffel-Dalbeattie Pluton
MACD
Outer boundary of the aureole is gradational but mapped at the first occurrence of rocks of mauvish-brown colour that are indurated by growth of biotite.
Aureole rocks are exposed along the northern margin of the Criffel-Dalbeattie intrusion from Lochanhead [NX 92 72] to Loach Burn [NX 79 58] where it merges with the thermal aureole around the older Bengairn intrusion. Aureole rocks are exposed along the southern margin of the Criffel-Dalbeattie intrusion at Almorness Point [NX 84 52] and along the coast from Castlehill Point [NX 85 53] to the River Nith [NX 99 66].
Rocks of the Carghidown and Ross Formations (Hawick Group) and Siluro - Devonian minor intrusions are metamorphosed to biotite- or hornblende-diopside hornfels within the thermal metamorphic aureole of the Criffel-Dalbeattie Pluton.
Mapped as between 1 and 3.2km in width.
Margin of the Criffel-Dalbeattie Pluton.
Metamorphic Aureole, Cairnsmore Of Fleet Pluton
MACF
Outer boundary of the aureole is mapped at the first observation of a purple tint to sandstone, caused by the development of microscopic biotite in the matrix.
Aureole rocks are exposed all around the Cairnsmore of Fleet Pluton from Creetown in the south [NX 47 58], Blackcraig in the west [NX 64 44], Loch Ken to the east [NX 65 73] and St Johns Town of Dalry to the north [NX 62 80].
Ordovician strata of the Moffat Shale Group, Shinnel and Glen Lee formations, Silurian strata of the Gala Group and Siluro-Devonian minor intrusions are metamorphosed to biotite hornfels or, locally, calc-silicate skarn within the thermal metamorphic aureole of the Cairnsmore of Fleet Pluton.
Mapped as between 800m and 6km in width.
Margin of the Cairnsmore of Fleet Pluton.
Marsco Summit Gabbro (Skye Western Red Hills Centre)
MACG
Margate Chalk Member
MACK
Santonian to basal Campanian. Micraster coranguinum, Uintacrinus socialis, Marsupites testudinarius and Uintacrinus anglicus Zones
Conformable at the surface immediately above the Barrois Sponge Bed in Thanet (Robinson, 1986).
Confined to the Thanet area of Kent and possible northwards into Essex and southern East Anglia
Marl-free smooth white chalk with little flint, weakly developed indurated iron-stained sponge beds. There are no formal subdivisions, but informally includes a number of laterally persistent flint and marl beds named in Robinson (1986) which can be traced outside Kent in the Southern and Transitional provinces where they are correlated with the named beds of Mortimore (1986)
Up to 24m in the North Foreland to Foreness Point and Palm Bay sections on the Isle of Thanet in north Kent.
Limited by sub-Palaeogene erosion surface in the Isle of Thanet.
Main Coal (Dungannon)
MACL
Maggie Coal
MACO
Main Coal (Somerset)
MACS
Marine Deltaic Deposits
MADD
Manton 'Estheria' Band
MAEB
Marchlyn Formation
MAF
Conformable and gradational from mainly coarse-grained sandstones of the underlying Bronllwyd Grit Formation.
Northern Snowdonia and Arfon.
Grey siltstones and sandstones with rare ironstones near the base. Top marked by coarse-grained quartzose pebbly sandstone.
Includes the Carnedd-y-Filiast Grit at the top, as a member.
240 to 500m
Unconformable upper contact with overlying late Cambrian,Tremadoc or basal Arenig strata, (Dolgellau, Dol-cyn-afon or Allt Llwyd formations). The base of the overlying Arenig is characterized locally by sandstones.
Magpie Clay
MAGC
Main Hosie Limestone
MAHO
Generally seen as a conformable change from a marine mudstone within the Lower Limestone Formation.
Throughout most of the outcrop of the Lower Limestone Formation in the Midland Valley of Scotland; but locally difficult to recognize in Ayrshire and Lanarkshire where the Hosie limestones join together as the McDonald Limestone in the shelf setting. Also locally difficult to recognise in Fife, in the on-delta setting, where it is equivalent to the Seafield Marine Band.
A pale to dark grey, argillaceous, crinoidal and shelly bioclastic limestone.
From 0.05 m to 2.2 m thick in the Airdrie, Falkirk and Glasgow districts. This limestone fuses with the Mid Hosie Limestone at Petershill in the Bathgate Hills.
Generally seen as a change to marine mudstone within the Lower Limestone Formation.
Maid Coal (Cumnock And Muirkirk, South Ayrshire)
MAI
Maich Shell Bed
MAIB
Main Coal (North Wales)
MAIC
Main Coal (Ayrshire)
MAIN
Main Limestone Member (Ballycastle, Northern Ireland)
MAL
Rapid change from massive red and white sandstones of Ballyvoy Sandstone Formation to grey shale of the member.
Grey shale (marine fossils), limestone, sandstone.
Shales succeeded by white, massive calcareous and micaceous sandstones.
Malling Conglomerate Member
MALC
A transitional contact with the siltstone facies of the undivided Cromlix Mudstone Formation, especially in the lower part where interbeds of siltstone, sandstone and conglomerate show a diffuse boundary.
The north-west limb of the Strathmore Syncline from Kelty Water to a ridge north-east of Ben Gullipen, probably equivalent to the conglomerate in Keltie Water, Callander, 500 m above the Bridge of Brackland.
A fine- and coarse-grained, cobbly, poorly sorted, matrix supported conglomerate, with clasts of vein quartz, quartzite and some igneous lithologies, coarsening north-eastwards, and clast supported around Beinn Dearg.
About 120m at Beinn Dearg [NN 589 038]. 50 m near Malling, thinning south-westwards to about 15 m at Carse of Shannochill [NS 5385 9850], and to just 1m in Kelty Water [NS 4973 9504].
A sharp contact with the siltstone facies of the undivided Cromlix Mudstone Formation, which is commonly seen as a pronounced topographical feature.
Malin Complex
MALI
Mall Formation
MALL
Malham Formation
MALM
Drawn at the base of pale grey limestone of the Cove Limestone Member (of the Malham Formation) where is rests conformably (but gradationally and slightly diachronously) on the mid dark-grey limestone of the Scaleber Quarry Member (of the Kilnsey Formation) or, locally, unconformably on Lower Palaeozoic strata.
Southern part of the Askrigg Block, North Yorkshire, north of Settle [SD 77 to SD 97].
Massive to weakly bedded, pale grey to very pale grey, medium- to coarse-grained calcarenite packstones and grainstones, and well bedded, thick to very thick-bedded, mid-pale to very pale calcarenite packstones, wackestones and subordinate grainstones.
220m south of the Middle Craven Fault to about 140m north of the North Craven Fault.
Drawn at the conformable upward passage from pale grey limestone of the Gordale Limestone Member (of the Malham Formation) to darker grey limestone of the Lower Hawes Limestone at the base of the Alston Formation, Yoredale Group. However, in the Cominco S11 Borehole (SD 8590 6340) (SD86SE/5) the upper boundary of what is probably the Malham Formation is unconformable beneath rocks of the Bowland Shale Formation, Craven Group.
Malham Formation (Apron-Reef)
MALMA
Malin Formation
MALN
Overlies either rockhead or Skerryvore Formation.
Very stiff, dark grey gravelly, gritty clay.
66 metres.
Erosive in part.
Lower Morar Psammite Formation
MALP
Markle Mains Plugs
MAMNS
Morar Schists Formation
MAMS
Main Algal Member
MAN
Main Algal One is conformable on Bewcastle Member (Lyne Formation) of Bewcastle.
Rhythmic alternations of limestone and mudstone with 14 well developed nodular algal horizons.
87m (Bewcastle).
Top of Main Algal Fourteen is conformable with overlying Lower Antiquatonia Bed of the Cambeck Member (Lyne Formation) of Bewcastle.
Man-Made Ground Not Mapped Or Information Not Available [Digital Maps Only]
MANAB
Mansley Beds
MANB
Main Coal (Ballycastle, Northern Ireland)
MANC
Rests on pink sandstones of Ballyvoy Sandstoen Formation.
Overlain by sandstone of Ballyvoy Sandstone Formation.
Metamorphic Aureole, Northern Granite Pluton, Arran
MANG
Man-Made Theme Not Available [Digital Maps Only]
MANNA
Man-Made Theme Not Mapped [For Digital Map Use Only]
MANNM
Mains Formation
MANS
Manse Gelifluctate Bed
MANSE
The basal boundary of the bed is a planar, subhorizontal, unconformity resting on either the Hythie Till or Rottenhill Till formations in Kirkhill Quarry. In Leys Quarry the periglacial sediments and structures of this bed merge downward into (and are in part derived from) the red, felsitic Denend Gravel Formation where this is exposed near to the surface due to later erosion.
Buchan, northeast Scotland. The bed is only known within the immediate vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) and Leys Quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon).
Gravel with some sand and diamicton. Crudely bedded, pale olive-brown and pale pinkish brown, pebble to boulder gravel-grade, clast supported with a matrix of medium to coarse quartzose and felsitic sand. Clasts are typically angular to subangular and dominated by felsite. Less common clast lithologies include psammitic and quartzitic metasedimentary rocks, grey granite, mafic igneous rocks, red stained quartzite and pelitic metasedimentary rocks. Some thin sand beds and thin beds of brown gravelly clayey sand, diamicton. Close to the present ground surface frost shattered and erected clasts, poorly developed involutions and ice wedge clasts have been observed. Interpreted as periglacial gelifluctate deposits.
The upper boundary of the bed is generally the present ground surface.
Manx Group
MANX
A typically dark grey to black mudstone, commonly with pale siltstone laminae and sandstone dispersed as thin to medium beds; locally predominant thin- to thick-bedded, wacke and quartz arenite sandstone, and debrite (pebbly mudstone), which is well-developed in places.
At least 3000 m thick..
Stratigraphical boundaries not seen, the top is probably unconformiable with the Dalby Group against which exposed contacts are elsewhere faulted. It is distinguished by a change from a mudstone-dominated facies in the Manx Group to a sandstone-dominated facies in Dalby Group.
Manx Granite Suite
MANXG
Marr Bank Formation
MAR
Unconformably overlies Aberdeen Ground and Coal Pit formations.
Sand, fine-grained, poor- to well-sorted, soft to firm, grey to red brown with abundant lithic granules and pebbles. Locally silty.
16 metres. (Thickness varies 10 metres - 25 metres).
Unconformably overlain by Forth Formation or seabed sediments.
Margery Coal (South Lancashire)
MARC
Marsh Farm Formation
MARF
Rests on Earnley Sand Formation. Boundary marked by the sharp upward change from glauconitic sands of the Earnley Sand Formation to the thinly bedded clays and silts with glauconitic sand laminae of the Marsh Farm Formation.
Laminated clay; wavy to lenticular-bedded sand interbedded with clay in equal proportions; and fine- to medium-grained sparsely glauconitic sand with laminae and intercalations of clay.
Overlain by Selsey Sand Formation whose base is sharply marked by glauconitic sandy silts with a few flints on a burrowed surface.
Margie Formation
MARG
"Green Conglomerate" in North Esk section is unconformable on metabasalts of the North Esk Formation. All other contacts are faulted.
Occurs in several fault-bounded pods just north of the Highland Boundary Fault between Glen Sannox (Arran) and Garron Point (Stonehaven).
Poorly sorted, feldspathic, gritty psammite with calcareous cement dominant in North Esk section, but grey-blue slates dominate in Margie Burn. North Esk section contains a 2m limestone ("Margie Limestone") at NO 5685 7330. Basal conglomerate with metabasalt clasts to 0.3m ("Green Conglomerate") at NO 5875 7315.
Southern belt in North Esk section is 500m wide. Exposed thickness in North Esk probably no more than 300m.
Not seen: contacts faulted.
Markie Gneisses
MARK
Central part of 63E extending 10km. north-east in a number of fault blocks close to the Markie Fault from Loch Crumachdan [NN 545 928] to Meallan Dubh [NH 000 815].
Gneissose micaceous psammite with lenses and sheets of locally agmatitic psammite. Subsidiary psammite and gneissose semipelite.
Overlain by semipelite correlated with the Coire nan Laogh Semipelite Formation which in turn is overlain by the Loch Laggan Psammite Formation. Boundary with the semipelite is inferred to be an unconformity.
Markle Plug
MARKL
Markham Coal (Nottingham)
MARKO
Marros Group
MARR
The base is taken at the base of 35m of dark grey fissile mudstones with thin cherts and siliceous mudstones (Aberkenfig Formation), which gradationally overlie the interbedded dark grey argillaceous limestones and mudstones of the Oystermouth Formation. In the type section at Ragwen Point the base is not seen.
The group crops out in a narrow belt around the periphery of the South Wales Coalfield and its extension in Pembrokeshire. The outcrop around the main coalfield extends from near Kidwelly [SN 360 050] on the north crop eastnortheast to near Brynmawr [SO 20 11] and south to near Caerphilly [ST 20 86] and west to Swansea Bay [SS 79 84]; in Gower from Bishopston to Mumbles; and in the Pembroke Peninsula from Druidston [SM 860 169] to Marros [SN 198 076]; and on the southern limb of the syncline from Tenby [SN 135 010] northwest to near the Cleddau River [c.SN 012 085].
Fissile dark grey siliceous mudstones and cherts (Aberkenfig Formation); grey, commonly fossiliferous mudstones (Bishopston Formation); quartzitic sandstones and conglomerates (Twrch Sandstone Formation), occupying the basal half of the Group on the northeastern crops and eastern crops of the South Wales Coalfield, and quartzitic sandstones (Telpyn Point Sandstone Formation) occupying the highest part of the Group locally.
20m on the east crop of the South Wales Coalfield to 750m in Gower.
The top is taken at the base of the Subcrenatum Marine Band, where mudstones or sandstones are overlain by fossiliferous marine mudstones containing the index goniatite Gastrioceras subcrenatum (as for the base of the Coal Measures Group, as defined by Stubblefield and Trotter, 1957).
Marnock Sandstone Unit
MARS
Marsden Formation
MARSD
The sharp conformable base of the formation is taken at the base of the dark grey fissile mudstone of the Bilinguites gracilis Marine Band, with eponymous fauna where the formation overlies the Hebden Formation. In the southern part of the Askrigg Block, where the marine band is absent, the base of the formation is taken at the base of the Wandley Gill Shale, described by Wilson and Thompson (1965) as 3 m of shale with a Lingula Band at the base, overlying a seatearth at the top of the Upper Brimham Grit. In the Stainmore Trough the base of the formation is taken at the base of a 6 m thick shale with Productus carbonarius, which overlies a 0.15 m-thick shaly coal (Owens and Burgess, 1965). In the southern part of the Central Pennine Basin the base of the formation is taken at the base of the first thick quartz-feldspathic sandstone of Marsdenian age present above the Bowland Shale Formation.
Lancashire and west Yorkshire between Lancaster [SD 47 61] and Harrogate [SE 30 55], extending southward to north Staffordshire [SK06], and north to the Askrigg Block and Stainmore Trough.
Fine- to very coarse-grained and pebbly feldspathic sandstone, interbedded with grey siltstone and mudstone, and subordinate marine black shales, thin coals and seatearths.
Up to 600m thick between Preston and Macclesfield; Bradford 275m; north Derbyshire 450m; 15m thick in the Kirkby Malzeard area of the Askrigg Block; 40m thick in the Stainmore Trough.
The sharp conformable base of the dark grey, fissile mudstone of the Cancelloceras cancellatum Marine Band with eponymous fauna, overlain by a dark grey mudstone-dominated succession in the lower part of the Rossendale Formation. In the Stainmore Trough, the equivalent of this marine band, but lacking the diagnostic ammonoid fauna, was referred to as the Swinstone Bottom Marine Band (Owens and Burgess, 1965).
Margaret's Vein
MARV
Marsett Sandstone Formation
MASA
Though the formation is probably Tournaisian, finer age details are uncertain. In Ravenstonedale, the Marsett Formation, though poorly constrained palaeontologically, was judged by Holliday, Neves and Owens (1979) as "late" Courceyan, being bracketed by the Pinskey Gill Beds with Courceyan conodonts, below, and the late Chadian Stone Gill Limestone Formation, above.
Mass Movement Deposits Not Mapped Or Information Not Available [Digital Maps Only]
MASAB
Manson Shell Bed
MASB
?Arnsbergian; possibly younger.
Mathon Sand And Gravel Formation
MASG
Placed at base of gravels where they rest on bedrock or the Bray Silts.
Cradley Valley and Glynch Brook.
Basal gravels overlain by red cross-bedded sands with coal debris on foresets; locally overlain by an upper gravel. Gravels consist:- 50% local pebbles, 50% exotic pebbles, including c.25% Bunter pebbles.Sand and gravel, locally with lenses of silt, clay or peat -[Generic description].
Up to c.10 metres.
Placed at top of sand or gravel, where overlain by White House Silts or Coddington Till.
Manganese Shales And Equivalents
MASH
Mass Movement Deposits
MASMD
Mass Movement Theme Not Available [Digital Maps Only]
MASNA
Mass Movement Theme Not Mapped [For Digital Map Use Only]
MASNM
Offshore Mass Movement Theme Not Mapped [For Digital Map Use Only]
MASOF
Malpas Sandstone Member
MASS
Conformable, within a gradational, interdigitating transition from the interbedded brown sandstone, siltstone and mudstone of the underlying Tarporley Siltstone Formation (undivided) to the red sandstone with abundant millet seed grains of the Malpas Sandstone Member.
A locally developed sandstone-rich facies of the Tarporley Siltstone Formation, occurring in the upper part of that formation. The member occurs at outcrop at Malpas, west Cheshire; it is also proved at depth to the east in the Wilkesley Borehole (SJ64SW/7) [SJ 6286 4144], Cheshire (Stephens, 1961).
Sandstone, red, fine- to medium-grained, with abundant rounded "millet seed" grains. Sandstone is cross-stratified and weakly cemented. Subordinate beds also occur of sandstone and coarse siltstone, brown, fine-grained, micaceous, laminated; these resemble sandstones of the parent Tarporley Siltstone Formation.
Up to 180m at outcrop in the Malpas area.
Conformable, with an abrupt transition to interbedded red mudstone and pink micacesous siltstone of the Bollin Mudstone Member of the Sidmouth Mudstone Formation.
Metamorphic Aureole, Tincorn Hill Pluton
MATH
Maclurea Beds
MAU
Maudlin Coal (Northumberland And Durham)
MAUD
Bottom Maudlin Coal (Durham)
MAUDB
Maud Pluton
MAUDP
Top Maudlin Coal (Durham)
MAUDT
Upper Morar Psammite Formation
MAUP
Maureen Formation
MAUR
Mavis Coal (Lothian)
MAV
Margareta Volcanics Formation
MAVO
March Wood Formation
MAWO
The base of the predominantly sandstone succession on the southern side of the Eastfield Inlier, faulted against the Lanark Group (Siluro-Devonian).
Eastfield (or Tinto ) Inlier, south of Tinto, Lanarkshire.
Reddish brown, green and purple thinly bedded fine-and medium- grained sandstone with a few small silty mudstone clasts in some beds. Local green and grey mottled siltstones and mudstones and conglomerate beds including quartzite pebbles.
c.750m
The top of the predominantly sandstone succession in the Eastfield Inlier where it is overlain by thick conglomerate belonging to the Greywacke Conglomerate Formation
Maxwellston Mudstone Formation
MAX
Conformably overlies the Wood Burn Formation.
Purple mudstones.
Conformably overlain by the Upper Camregan Grits.
Mayfield Member
MAY
Mount Battock Pluton
MBAT
Main Non-Porphyritic Granite (Mount Battock Pluton)
MBAT1
Main Porphyritic Granite (Mount Battock Pluton)
MBAT2
Water Of Feugh Granite (Mount Battock Pluton)
MBAT3
Cock Cairn Granite (Mount Battock Pluton)
MBAT4
Fungle Granite (Mount Battock Pluton)
MBAT5
Clachnaben Granite (Mount Battock Pluton)
MBAT6
Water Of Dye Granite (Mount Battock Pluton)
MBAT7
Mongour Granite (Mount Battock Pluton)
MBAT8
Morth Brentor Beds
MBB
Canal Embankment
MBCA
Murlough Bay Coal B (Ballycastle, Northern Ireland)
MBCB
Murlough Bay Coal C (Ballycastle, Northern Ireland)
MBCC
Murlough Bay Coal D (Ballycastle, Northern Ireland)
MBCD
Murlough Bay Coal E (Ballycastle, Northern Ireland)
MBCE
Murlough Bay Coal F (Ballycastle, Northern Ireland)
MBCF
Murlough Bay Coal G (Ballycastle, Northern Ireland)
MBCG
Murlough Bay Coal H (Ballycastle, Northern Ireland)
MBCH
Murlough Bay Coal X (Ballycastle, Northern Ireland)
MBCX
Marine Beach Deposits
MBD
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks; in association with the marine environment. [Generic description].
Dam Or Barrage
MBDA
Moulzie Burn Intrusion
MBDI
Flood Defence Embankment
MBFL
Moine, Metamorphosed Basic Igneous Sills (Within The)
MBIS
Lochailort Pelite Formation
MBLA
Unidentified Marine Band (Pennine Lower Coal Measures Formation)
MBLCM
Middle Bluers Coal (South Wales)
MBLR
Unidentified Marine Band (Pennine Middle Coal Measures Formation]
MBMCM
Meall Buidhe Mor Granite Intrusion
MBMG
Meall Buidhe Mor Quartz-Gabbro Intrusion
MBMQG
Mount Blair Psammite And Semipelite Formation
MBPS
Top of the highest metacarbonate rock unit of the Loch Tay Limestone Formation.
Schistose psammite and semipelite. Locally gneissose semipelite in north.
Not known because of folding.
Base of thick green-bed unit that separates the formation from the overlying Cairn Gibbs Formation.
March Burn Quartzite Formation
MBQU
Middle Band Rock
MBR
The Middle Band Rock is a thin and relatively impersistent thinly bedded rubbly sandstone notable mainly in the north of the district and around Huddersfield.
Rail Embankment
MBRA
Road Embankment
MBRO
Reservoir Embankment
MBRV
Meikle Busbie Sandstone Formation
MBS
Lying within the Courceyan to Chadian Inverclyde Group, the unconfirmed age of the Meikle Busbie Sandstone Formation is given the same range pending more detailed information.
Monk's Bay Sandstone Formation
MBSA
Sewer Outfall Or Raised Pipe Embankment
MBSE
Mulindry Bridge Slate Formation
MBSL
Screening Embankment
MBSR
Middle Band Stone
MBST
Middle Basaltic Formation
MBT
Main Bright Coal (Nottingham, Derby And South Yorkshire)
MBTC
Marine Beach Deposits And Tidal Flats
MBTF
Composite: Marine Beach Deposits: shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks; in association with the marine environment. Tidal Flat Deposits: normally a consolidated soft silty clay, with layers of sand, gravel and peat; characteristically low relief; from the tidal zone. [Generic description].
Engineered Embankment (Undivided)
MBU
Unidentified Marine Band (Pennine Upper Coal Measures Formation)
MBUCM
Mill Bay Formation
MBY
The base of the Formation is conformable on the underlying Llanstadwell Formation. It is defined at Burton Cliff northeast of Burton Hawn [SM 98967 05258], at the base of an 11.8m-thick multistorey complex of green-grey, interbedded intraformational conglomerates, horizontally or low-angle parallel-laminated F/M to VF sandstones and a few thin siltstones, (see Thomas et al, 2006, figures 9 and 10). The base (at 110.34m above the base of the section measured by Thomas et al, 2006) is a low relief (?0.2m) scour surface overlain by a 0.05m-thick intraformational conglomerate.
On and adjacent to the shores of the Daugleddau estuary, Milford Haven, Pembrokeshire around the axial trace of the Burton Anticline. This encompasses an area around Cosheston village [SN 00 04] from Cosheston Pill [SM 995 035] northwards to Mill Bay [SN 00 05], and on the west side of the Daugleddau from east of Burton [SN 000 055] northwest to the Burton Fault in the Houghton [SM 983 073] - Williamson [SM 990 070] area (see Thomas et al., 2006, Figure 1).
Coarse- to very fine-grained green-grey sandstones (68.2%), interlaminated/thinly interbedded medium- to very fine-grained sandstones and red-brown siltstones (14.9%), intraformational conglomerates (9.7%) and red-brown siltstones (7.3%). All three sandstone categories in the Cosheston Group - litharenite, sublitharenite and subarkose - are present, but the last is restricted to this Formation. c.30% of the Formation is affected by synsedimentary deformation structures.
540 to 600m
The upper boundary is a conformable, transitional one with the overlying Lawrenny Cliff Formation. The 139.91m-thick section at Mill Bay (east) starts a few metres below the high water mark on the northeast side of Mill Bay inlet, at the base of a 1.59m-thick, fine-grained, horizontally and low-angle parallel-laminated sandstone [SN 0026 0491], and ends in the Lawrenny Cliff Formation, this being the only section that exposes the boundary (see Thomas et al, 2006, Figure 14B), which intersects the high water mark 60m southwest of the quay [SN 00570 05260].
Middle Cambrian
Mullaghcarn Formation
MCA
Gradational boundary with underlying Glengawna Formation.
North County Tyrone, Northern Ireland; southern foothills of the Sperrin Mountains and Lack Inlier, Northern Ireland.
Quartz and albite psammite and semi-pelites (mixed).
Max c.3km
Faulted off by Omagh Thrust.
Macbeth Formation
MCBT
Muirkirk Claud Coal (Ayrshire)
MCC
Meall Cos Charnan Pelitic Gneiss Member
MCCH
Macduff Formation
MCD
Change from calcareous semipelite to non-calcareous lithologies at top of Whitehills Grit Formation; commonly marked by change to locally coarsely gritty psammite of Knock Head Grit Member.
From Moray Firth coast [NJ 6514 6564-NJ 776 643], southwards to northern margin of Insch intrusion [NJ 650 325-NJ 725 305].
Metagreywacke: interbedded psammite and semipelite with subsidiary pelite. Contains major units of pebbly psammite, particularly in basal part (Knock Head Grit Member). Metamorphosed to slates, phyllites and mica-schists. Contains Boulder Bed at Macduff (glaciomarine diamicton). Minor calc-silicate pods. Contains andalusite, cordierite and locally staurolite porphyroblasts.
Up to 5.5km, but could be less, as there is repetition by folding.
Not seen - highest beds are in centre of Turriff Syncline.
Mcdonald Coal (Mauchline/Cumnock Area; South Ayrshire)
MCDC
Mcdonald Limestone
MCDL
Meeching Flints
MCFL
Middle Calcareous Grit
MCG
Machroes Member
MCH
Gradational contact taken at the base of the first prominent sandstone lying above muddy sandstones of the Penrhyn Du Member.
Well-bedded sandstone with mudstone interbeds. A thin phosphatic conglomerate horizon at the top.
<8m
Sharply overlain by dark grey mudstones with sandstone and siltstone laminae of the Llanengan Formation. The boundary is taken at the top of a districtive phosphatic conglomerate bed within the Machroes Member. The contact may be a disconformity or non-sequence.
Machrins Arkose Formation
MCHA
Marchburn Formation
MCHB
Faulted (against Afton Formation by Carcow Fault).
Wacke sandstones, siltstones and sporadic conglomerates (turbidite succession).
Faulted (by Southern Upland Fault).
Middle Charles Coal (South Staffordshire)
MCHS
Middle Churnet Shales
MCHT
Middle Chalk Formation [Remains In Informal Use But Generally Regarded As Obsolete Onshore]
MCK
Rests on Plenus Marls (topmost Lower Chalk). Coincides with the base of the Melbourn Rock.
Essentially East Anglia by above definition, but has been applied across the whole of Southern England.
White pure chalk with some flint seams and very shelly beds. Comprises from base: hard indurated chalk with flaser marls (Melbourn Rock) to exceptionally shelly chalk with flints into chalk with well defined marl seams.
75 - 95m in the Hitchin area.
At the base of the Chalk Rock (lowermost Upper Chalk).
Mackerel Formation
MCKL
Marble Cliff Limestone Member
MCLB
U. hermanni-cristatus to L. Asymmetricus Biozone
Conformable with Trevose Slate Formation.
Trevose Head - Trevone - Rock, north Cornwall.
Turbiditic limestone beds interbedded with dark grey mudstone.
Conformable with the Trevose Slate Formation.
Midland Valley Early Carboniferous Felsic Sill Suite
MCLFS
Middle Carriden Limestone
MCLS
Meeching Marls (One)
MCMA1
Meeching Marls (Two)
MCMA2
Meeching Marls (Three)
MCMA3
Middle Coal Measures (Dungannon, Northern Ireland)
MCMI
Scottish Middle Coal Measures Formation
MCMS
Sandstone, siltstone and mudstone in repeated cycles that most commonly coarsen upwards but also fine upwards locally, with seatclay or seatearth and coal at the top. The mudstone and siltstone are usually grey to black, while the sandstone is fine- to medium-grained and off-white. Coal seams are common and many exceed 0.3m in thickness.
The conformable and transitional boundary from the Scottish Middle Coal Measures Formation to the Scottish Upper Coal Measures Formation is drawn at the base of the Aegiranum (Skipsey's) Marine Band. The original definition (MacGregor, 1960) placed the boundary at the top of this marine band. The revision was made by Forsyth et al (1996).
Mcneish Coal
MCN
Main Coal (South Derbyshire)
MCO
Midland Valley Carboniferous To Early Permian Alkaline Basic Dyke Suite
MCPAD
Midland Valley Carboniferous To Early Permian Minor Alkaline Intrusions (Other Than Dykes, Sills And Plugs)
MCPAI
Midland Valley Carboniferous To Early Permian Alkaline Basic Sill Suite
MCPAS
Dinantian Dykes (Within Mcpad)
MCPDD
Early Permian Dyke (Within Mcpad)
MCPDP
Silesian Dyke (Within Mcpad)
MCPDS
Dinantian Intrusion (Within Mcpai)
MCPID
Early Permian Intrusion (Within Mcpai)
MCPIP
Silesian Intrusions (Within Mcpai)
MCPIS
Malvern Quartzite Formation
MCQ
Unconformable or in faulted contact with the Precambrian Malverns Complex.
Malvern Hills area, Hereford and Worcester.
Pale grey, quartz-cemented sandstones and interbedded conglomerates. Conglomerates contain mainly quartz pebbles, but also Malverns Complex and volcanic lithologies.
Difficult to estimate, but possibly up to 60m (Worssam and others, 1989).
Conformable junction with Hollybush Sandstone.
Mynytho Common Microgranite
MCRM
Granophyric microgranite with aligned poikilitic riebeckite crystals.
Murton Crags Sandstone Member
MCSA
Contact of sandstone with underlying mudstone and siltstone of the Fell Sandstone Formation (undifferentiated).
In the area southwest of Berwick-upon-Tweed the Fell Sandstone Formation consists of several sandstone members separated by variable thicknesses of mudstone and siltstone. The Murton Crags Sandstone is the upper of three members and crops out in the region of Shoreswood and Thornton in north Northumberland.
Medium- to thick-bedded, medium- to coarse-grained, planar and trough cross-bedded sandstone. In places the bedding is disturbed. Some thin mudstone beds towards top and base. Some granule-sized conglomeratic beds. Sandstone consists mainly of sub-rounded quartz grains with some interstitial quartz and calcite cements.
0 to 60m, with the greatest thickness near Shoreswood Farm [NT 3940 6465].
Contact of sandstone with overlying mudstone and siltstone of the Fell Sandstone Formation (undifferentiated).
Mancetter Shale Formation
MCSH
Sedimentary break. Basal conglomerate with mudstone clasts and quartz pebbles rests on dark grey mudstone of Abbey Formation.
Extends from Nuneaton, northwestwards to the southern suburbs of Atherstone (SP 3630 9171 - SP 3063 9715).
Grey to dark grey, sporadically greenish, micaceous and pyritic mudstone with common current ripple-bedded sandy wisps. Common beds of grey, fine-grained, disturbed, glauconitic sandstone.
General range 30 - >75m. 58m in reference section.
Gradational with Outwoods Formation. Taken at level below which dark pyritic mudstone, typical of Outwoods Formation, becomes insignificant.
Middle Crafnant Volcanic Formation
MCV
On Lower Crafnant Volcanic Formation, dominated by ash-flow tuffs.
Eastern Snowdonia, around Betws-y-Coed. Farther north is not readily separated from the Upper Crafnant Volcanic Formation.
Tuffs, tuffites and sedimentary rocks.
Under Upper Crafnant Volcanic Formation.
Mcgildowney's Shale Member
MCYS
Massive sandstones overlying Main Coal, typical of Ballyvoy Sandstone Formation.
Shales, mudstones, sandstone (lenticular), ironstone, limestone.
Junction with non-marine shale, sandstone and coals.
Marine And Coastal Zone Deposits
MCZD
Lithologically diverse. Sand, silt and clay, with gravel and possibly peat, formed in the coastal or marine environment. [Generic description].
Miller's Dale Limestone Member
MDA
Limestone of the Miller's Dale Limestone Member overlies vesicular lava of the Lower Miller's Dale Lava Member. Locally, the basal part of the limestone is tuffaceous.
Only recognised as a separate unit where the underlying Lower Miller's Dale Lava Member is present, restricting the Miller's Dale Limestone Member to the Wye Valley area near Buxton, in the north of the Peak District Dinantian inlier.
A massive, pale grey to grey, fine-grained calcarenite with common fossils, particularly corals, brachiopods and crinoid debris. Rare cherts occur locally in the middle part of the Member. Locally the limestones are pure white and/or have a more bedded character. Oolitic beds are present locally. The Dove Holes Tuff, 2.2m thick, occurs about 15m above the base of the Member and comprises pyritous greenish grey clay with limestone lapilli, resting on a palaeokarstic surface.
Reaches 43m near Dove Holes (SK 08 77).
The pale grey, massive limestone of the member is separated from the generally darker limestones of the Monsal Dale Limestone Formation by a palaeokarstic surface. The Upper Miller's Dale Lava Member or a laterally equivalent bed of altered clay may intervene locally.
Middle Band Coal (West And South Yorkshire)
MDBC
West and south Yorkshire.
The Middle Band Coal is a thin and impersistent seam that has seldom been worked economically. It rests on a fireclay in places and is overlain by the Honley Marine Band
Mid Drumgray Coal (Central Coalfield)
MDC
Mid Coal (Machrihanish)
MDCM
Mangotsfield Coals
MDCO
Monzodiorite Facies, Cruachan Intrusion
MDCRU
Middle Dodd Dacite Formation
MDD
Incoming of dacite above volcaniclastic sedimentary rocks of Esk Pike Sandstone Formation.
Middle Dodd and Little Hart Crag, on north side of the Kirkstone Pass, Cumbria.
Dacite lava flow: porphyritic, flow-banded, locally autobrecciated, white-weathered.
Top not seen in Type Area or Reference Section. Probable equivalent lithologies to the north are overlain by the Helvellyn Tuff and Deepdale Sandstone formations.
Middle Coal (Radstock Member, Somerset)
MDDC
Taken at the base of the coal, resting on mainly grey mudstone of the underlying undivided Radstock Member.
Identified across the North Somerset Coalfield, in the Radstock and Pensford basins and may extend as far north as Brislington, although it is not exposed at the surface. It has been mined at the Radstock and Clandown collieries, where it has a certain uniformity of thickness. It may correlate with the similarly appearing Grovesend Formation, logged as Upper Coal Measures in the Apley Barn borehole SP31SW/3 (434370, 210660), near Witney, in the concealed Oxfordshire Coalfield.
Coal, with a high clastic content, containing thick dirt partings where it splits in two, in the east of the subcrop.
A thin coal, from about 36 cm around Timsbury [366862 158 974], to 66 cm thick in the west of the Somerset Coalfield, near where it dips below the sub-Triassic outcrop, and also around Radstock [367195 153 272] in the south of the coalfield. To the east of the coal basin, the seam splits in two, and attains a combined thickness of about 75cm.
Taken at the top of the coal, overlain by a hard mudstone and sandstone both of the undivided Radstock Member. Elsewhere the unit is capped by a shale roof.
Maiden Coal (Lancashire)
MDEN
Middle Devonian (Undifferentiated)
MDEV
Melgund Sandstone Member
MDF
The top of the highest fine-grained member in the Dundee Flagstone Formation in the Melgund Castle-Finavon area, between Forfar and Brechin.
In the Forfar-Brechin area, on the south-east limb of the Strathmore Syncline, on Sheets 57E and 57W.
The base of the Finavon Conglomerate Member, except where the conglomerate is absent, this unit may not be distinguishable from theTannadice Sandstone Member.
Micheldean Flint
MDFL
Main Donegal Granite
MDGR
K-Ar 357-384 Ma (Pitcher and Berger, 1972).
Middle House Member
MDHO
Mindork Formation
MDK
Thick-bedded to massive, medium to coarse-grained greywacke, of variable, often pyroxenous composition.
From about 2 km to 3 km thick.
Middle Limestone
MDL
Middleton Little Coal (West Yorkshire)
MDLC
The Middleton Little Coal or Green Lane Coal is of variable thickness and quality such that it has been inconsistently worked. It was extracted mainly in the Morley district and around Gildersome.
Meall Dubh Limestone Formation And Meall Dudh Graphitic Schist Formation (Undifferentiated)
MDLGS
Methil Dock Mussel Bed
MDMB
Middleton Main Coal (West Yorkshire)
MDMC
The Middleton Main Coal, Cromwell or New Hards Coal is a good quality bituminous coal that has been worked extensively in the district around Batley, Gomersal and Gildersome. its roof measures are rich in fish remains.
Mugdock Dyke
MDOCK
Middop Limestone
MDPL
Middleton Quarry Member
MDQY
Mearns Glacigenic Subgroup
MDR
Unconformable: base of Mill of Forest Till Formation.
Strathmore, east of Perth and as isolated spreads along the coast between Stonehaven and the mouth of the River Dee.
Till, sand and gravel and laminated silt composed principally of decomposed Silurian and Devonian rocks and associated with deposition from glacial ice of the Strathmore ice-stream.
Very variable, generally 5 to 10m, but in excess of 24m proved in boreholes.
Unconformable: top of Drumlithie Sand and Gravel Formation.
Middle Shales
MDS
Mid Splint Coal
MDSP
Meadfoot Group
MDT
Drawn at base of Meadfoot Group where it rests conformably on non-marine or brackish water deposits called Dartmouth Beds.
South-west England.
Dark shales and siltstones with sporadic grey-brown sandstones and beds of decalcified shell debris. Upper part exhibits red coloration in places.
Drawn at conformable upward passage from commonly reddened sandstone of Meadfoot Group to sandstones and shales of the Staddon Grits.
Marine Deposits
MDU
Variable lithology; gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell). [Generic description: from East Anglian data].
Middle Devonian Limestone
MDVL
Middle Devonian Slates
MDVS
Mordybank Formation
MDY
Yell Sound 'Division'
Medway River Terrace Deposits 1
ME1
Pleistocene to Recent.
Overlies bedrock.
Royal Tunbridge Wells district.
Sand and gravel, locally with lenses of silt, clay or peat. [Generic description]. Gravel characterized by clasts of Wealden sandstone, siltstone and, sporadically, flint.
Overlain by head and brickearth.
Medway River Terrace Deposits 2
ME2
Sand and gravel, locally with lenses of silt, clay or peat. [Generic description]. Gravel characterized by clasts of Wealden sandstone, siltstone and, sporadically, flint. Includes locally derived silt horizons.
Around 1.8m
At surface, or locally overlain by head and brickearth.
River Terrace Deposits, 2 To 3 (Medway)
ME2T3
Medway River Terrace Deposits 3
ME3
Sand and gravel, locally with lenses of silt, clay or peat. [Generic description]. Gravel, characterized by well bedded, well rounded clasts of Wealden sandstone, siltstone and sparse flint.
Around 2.4 to 2.7m
Medway River Terrace Deposits 4
ME4
Marine Or Estuarine Alluvium
MEA
Variable lithology; sand, silt and clay, with gravel and possible peat, formed in the marine or estuarine environment. [Generic description].
Marine And Estuarine Alluvium, Mainly Clay
MEAC
Clay with gravel, sand, silt and possible peat, formed within tidally-influenced estuaries. [Generic description].
Mearns (Albion) Glacigenic Subgroup
MEAG
Strathmore, Angus.
Suite of glacial, glaciofluvial and glaciocustrine deposits that contain clasts derived predominantly from Strathmore (red sandstone and mudstone, conglomerate and andesite), including sandy diamictons (till), sand, gravel, silt and clay. Deposited from ice that radiated from the Western Grampian mountains northeastwards through Strathmore to the coast.
Currently unknown.
Unconformable contact with units of the Mearns Glacigenic Subgroup.
Marine And Estuarine Alluvium, Mainly Sand And Gravel
MEAS
Sand and gravel, with silt, clay and possible peat, formed within tidally-influenced estuaries. [Generic description].
Meadowtown Formation [Duplicate Code: Use Mtn]
MEB
Melville Group Of Coals (Lothian)
MEC
Mealfuorvonie Formation
MECO
Middle Eday Sandstone Formation
MED
Meall Dubh Metabasite Formation
MEDB
Meall Dubh Limestone Formation
MEDL
Boundary with Meall Dubh Striped Pelite Formation probably transitional over a few metres.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically as far west as Allt na Moine Buidhe [NN 708 612] and as far east as Allt Kynachan [NN 7790 5725]. Not present east of the Loch Tay Fault in Sheets 55E and 64E, where it is tectonically excised, but possibly equivalent to Baddoch Burn Dolomite in Sheet 65W; however some of the rocks of the 'Banvie Burn Series' may be equivalent.
Yellow-weathering, grey dolomitic metalimestone, striped calcareous schist, tremolite-actinolite schist with biotite or phlogopite porphyroblasts and rosettes of tremolite.
3 - 15m in Sheet 55W; much tectonic thinning compared with Ballachulish Limestone.
Gradational boundary with the Meall Dubh Graphitic Schist Formation with admixture of graphitic and calc-schists is poorly exposed.
Meall Dubh Striped Pelite Formation
MEDP
Apparently transitional boundary with Beoil Schist highly tectonised.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically as far west as Allt na Moine Buidhe [NN 708 612] and as far east as Allt Kynachan [NN 7790 5725]. Not present east of the Loch Tay Fault, where it may have been tectonically excised; however some of the rocks of the 'Banvie burn Series' may be equivalent.
Schistose muscovite-biotite pelite with delicately striped alternations of fine-grained psammite; becomes slightly calcareous near top.
3 - 30m in Sheet 55W; much tectonic thinning compared with Leven Schist.
Boundary with Meall Dubh Limestone Formation probably transitional over a few metres.
Meall Dubh Quartzite Formation
MEDQ
At base of transitional facies, c.2 - 3m thick, of finely-bedded fine-grained silty quartzite with black graphitic laminae which occurs just above contact with Meall Dubh Graphitic Schist Formation.
From Allt Druidhe [6424 5694] sporadically to Allt na Moine Biudhe [NN 7077 6112] and then continuously to south bank of Allt Kinardochy [7789 5727]. Not present east of the Loch Tay Fault, where its place is taken by the Beinn a'Ghlo Quartzite Formation.
Quartzite, feldspathic, with heavy-mineral laminae, originally pebbly but now strongly recrystallised and flattened; cross-bedding visible in places.
10 - 180m in Sheet 55W; shows much tectonic thinning compared with Beinn a'Ghlo/Appin Quartzite.
Sharp boundary to finely-laminated semipelite of Strath Fionan Banded Semipelite Formation.
Meall Dubh Graphitic Schist Formation
MEDS
Gradational boundary with the Meall Dubh Limestone Formation with admixture of graphitic and calc-schists is poorly exposed.
Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically as far west as Allt na Moine Buidhe [NN 708 612] and as far east as Allt Kynachan [NN 7790 5725]. Not present east of the Loch Tay Fault, where its place is taken by the Beinn a'Ghlo Graphitic Schist Formation; some of the 'Banvie Burn Series' may be equivalent.
Graphitic pelite with semipelite ribs, containing porphyroblasts of kyanite (up to 100mm), biotite, garnet and rare staurolite and albite.
0 - 50m in Sheet 55W; much tectonic thinning compared with Beinn a' Ghlo Graphitic Schist/Ballachulish Slate.
Graphitic kyanite-bearing semipelite merges with 1m of transitional muscovitic, rusty-weathering quartzite with graphitic seams which forms the base of the Meall Dubh Quartzite Formation. This transitional quartzite is possibly equivalent to the Beinn a'Ghlo Transition of Smith, R A and Harris, A L (1976).
Meenymore Formation
MEF
Metal + Five-Quarter Coal (Northumberland)
MEFQ
Meall Gruaim Pluton
MEGRU
Meiklehill Coal (Central Coalfield)
MEIC
Meikle Bin Vent
MEIKB
Melmerby Scar Limestone Formation
MEL
Alston Block.
Fine-grained, pale grey limestones with pseudobreccias and calcite mudstones, and some bands of shaly mudstone and sandstone. The uppermost part of the formation is the Robinson Limestone (bed), which comprises alternations of limestone, shaly mudstone and sandstone.
From 35 to c.107m. The uppermost (Robinson Limestone) bed is generally 4 to 6m thick, but reaches 25m as it approaches the Stainmore Trough.
Middle Elton Formation
MELB
Meltonfield Coal (South And West Yorkshire)
MELC
Meldon Intrusion
MELD
Aplite.
Megg's Linn Sandstone
MELS
The area around Megg's Linn (Lewis Burn), Northumberland.
Massive sandstone.
Melville Formation
MELV
Meltonwood Coal (South Yorkshire)
MELWC
Meiklehill Main Coal (Glasgow Area; Central Coalfield)
MEM
Meads Marls (One)
MEMA1
Meads Marls (Two)
MEMA2
Meads Marls (Three)
MEMA3
Meads Marls (Four)
MEMA4
Meads Marls (Five)
MEMA5
Meads Marls (Six)
MEMA6
Milngavie Marine Band
MEMB
Menevian Group
MEN
Conformable and gradational on the sandstones of the Solva Group.
Pembrokeshire; 1:50 000 Sheet 209 (St.David's).
Dark grey, laminated, commonly pyritous mudstones, with paler tuffaceous horizons locally, passing upwards into coarse turbiditic sandstones and interbedded mudstones in the upper part of the Group.
Conformable and gradational with the interbedded sandstones and mudstones of the Lingula Flags Formation.
Meon Formation
MEON
The catchment of the River Meon and its tributaries, in the Fareham to East Meon area.
Floodplain alluvium and river terrace deposits. The floodplain alluvium comprises overbank deposits of brown organic silty clay and peaty clay, yogether with peat, overlying sand and gravel. The surviving river terrace deposits comprise sand and gravel, commonly cross-bedded, locally overlain by overbank deposits of clayey sandy silts and silty clays. These fine-grained deposits may be partly aeolian in origin. The major gravel lithology is flint, dominantly sub-rounded to sub-angular, some of it well rounded. The sand fraction is composed of well rounded quartz grains and subangular flint. The older, higher terraces are commonly cryoturbated.
Marine, Estuarine And Raised Beach Deposits (Undifferentiated)
MERB
Variable lithology; gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell); from the marine and estuarine environments, the 'Raised Beach Deposits' are now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Meadie Schist Formation
MESC
Mungle Shale
MESH
Within the Range Asbian to Brigantian.
Menai Straits Formation
MEST
Rests unconformably on Ordovician rocks (Nant Ffrancon Formation) and Precambrian rocks of the Monian Supergroup.
Menai Straits area (SH 5571), North Wales.
Varied sequence of breccias, conglomerates, sandstones, siltstones and silty mudstones including veriegated yellow and purple "loam". Spherical ferruginous (goethite) ooids are abundant in both the mudstones and the mudstone matrix of the breccias. The formation records the accumulation of late Asbian terrestrial screes and alluvial deposits along the local margin of the Dinantian carbonate platform. The goethite ooids are the product of pedogenic processes.
To 43m
Conformably overlain by thick-bedded limestones of the Loggerheads Limestone Formation.
Methlick Formation
METH
Metal Coal (Northumberland And Durham)
METL
Merioneth And Tremadoc Rocks (Undifferentiated)
METR
Meldon Volcanic Beds
MEV
Medway Valley Formation
MEVA
Valley of the River Medway and its tributaries from Tunbridge Wells to Sheerness, north Kent.
River Terrace deposits comprising sand and gravel, characterised by clasts of Wealden sandstone, siltstone and sporadic flints, and Alluvium comprising silt, sand and gravel.
Meiklehill Wee Coal (Glasgow Area; Central Coalfield)
MEW
Mey Flagstone Formation
MEY
Middleton Eleven Yard Coal (West Yorkshire)
MEYC
The Middleton Eleven Yard Coal was previously equated with the Wheatley Lime but correlations now place it below that horizon. It is a thin coal of poor quality.
Mey Sandstone Member
MEYS
Margery Flags
Melby Fish Beds
MFB
Mell Fell Conglomerate
MFC
Middlefield Conglomerate Formation
MFD
Unconformable contact of conglomerate on sandstones and siltstone of Logan Formation.
Boulder conglomerate with well rounded quartzite, quartz, jasper, and igneous rock clasts, and sandstone with beds of conglomerate.
Top of highest important conglomerate bed below Plewlands Sandstone.
Mercia Mudstone (Marginal Facies) And Dolomitic Conglomerate (Undifferentiated)
MFDC
Monkey's Fold Formation
MFF
Muirkirk Four Foot Coal
MFFC
Muirkirk Fifty Fathom Coal (Ayrshire)
MFI
Moelfre Limestone Formation
MFLF
Meadow Farm Marine Band
MFMB
Moelfryn Mudstones Formation
MFN
Pale grey, brown-weathering burrow-mottled mudstones with thin siltstone and locally, sandstone beds. A thin, muddy, bioclastic limestone member [Rhiwlas Limestone] occurs at the base of the Formation in places.
Conformably overlain by the Foel y ddinas Mudstone Formation, but in the Corwen District is unconformably overlain by the the sandstones and siltstones of the Bron-y-graig Formation.
Muirkirk Forty Fathom Coal (Ayrshire)
MFO
Moffat Shale Group
MFS
Conformably overlies Kirkton Formation of Crawford Group.
Southern Uplands of Scotland and Longford-Down Inlier, Ireland.
Black shale, grey shale, bentonite, tuff
Up to c.110m
Overlain by various Ordovician and Silurian wacke units.
Mill Of Forest Till Formation
MFT
Unconformable: on pre Late Devensian deposits or bedrock.
Sandy diamicton, red-brown with clasts predominantly of Devonian rocks.
Very variable, generally 5 to 8m, up to 7m exposed at type section.
Generally conformable, overlain by Ury Silts Formation and Drumlithie Sand and Gravel Formation.
Millstone Grit Group [See Also Migr]
A conformable base, defined at the base of the lowermost thick feldspathic sandstone in a sequence of Namurian strata; e.g. Mam Tor Sandstones, Longnor Sandstones, Ashover Grit, and Pendle Grit lying above the dark grey mudstone-dominated succession of the Bowland Shale Formation (Craven Group).
Central Pennines and the Midlands.
Fine- to very coarse-grained feldspathic sandstones, interbedded with grey siltstones and mudstones, with subordinate marine shaly mudstone, claystone, coals and seatearths.
Thickest in the north of the Central Pennine sub-basin, with 1225 m in Wharfedale, Bradford. The unit broadly thins towards the southern part of the basin, with 150 m thickness in North Staffordshire.
A conformable top, located at the incoming of thick coal-bearing Coal Measures facies, at the top of the Rough Rock, or more precisely at the base of dark grey shaly mudstone of the Subcrenatum Marine Band, with eponymous fauna where present (Earp and others, 1961, p.104).
Margadale Member
MGAD
Main Gasswater Coal
MGC
Unnamed Sandstone Of Pendleian Age (In Millstone Grit Group)
MGCE
Unnamed Sandstone Of Arnsbergian Age (In Millstone Grit Group)
MGCG
Unnamed Sandstone Of Arnsbergian To Alportian Age (In Millstone Grit Group)
MGCGO
Unnamed Sandstone Of Kinderscoutian Age (In Millstone Grit Group)
MGCK
Meall A' Ghrianan Conglomerate
MGCO
Monzogranite Facies, Cruachan Intrusion
MGCRU
Unnamed Sandstone Of Yeadonian Age (In Millstone Grit Group)
MGCY
Unnamed Sandstone Of Marsdenian Age (In Millstone Grit Group)
MGCZ
Maughold Formation
MGD
Stratigraphical contacts at the base with the Creg Agneash and Mull Hill fms. It is distinguished by a transition from sandstone-domainated to mudstone-dominated facies.
A dark grey mudstone with pale siltstone laminae and sparse sandstone in thin-to thick beds.
The top is faulted against the Barrule Fm, from which it is distinguished by a lack of any sandstone or siltstone in the latter.
Middle Grovesend Coal (South Wales)
MGDC
Mangotsfield Member
MGF
Base of the lower most lithic arenite "Pennant" sandstone of the Mangotsfield Member, resting sharply upon the Mangotsfield Coal, present at the top of the Downend Member
Bristol, Somerset and Severn Coalfields
Predominantly cross-bedded, lithic arenite, "Pennant" sandstone in the lower part, and an upper part with thick grey fissile mudstone beds, interbedded with sandstone and sparse coal seams. The sandstone weathers to a distinctive red to purple colour
Up to c. 580m at Iron Acton [ST 67 84] to Engine Common [ST 70 84]; 450m proved in the type area
Top of member taken at the top of the Rudge Vein Coal in the Somerset Coalfield: top of the High Vein Coal in the Bristol Coalfield; top of the Avonmouth No. 2 Coal in the Severn Coalfield. Overlain by grey mudstone of the Farrington Member
Midgley Grit
MGG
West Yorkshire area (Midgeley Moor, near Halifax].
Generally coarse-grained sandstone, commonly with a significant shaly mudstone parting to 6m in thickness.
Mullach Geal Gabbro Intrusion
MGGB
Magherameena Limestone Member
MGHM
Appears to be slide plane associated with down slope movement of an allochthonous limestone mud mound into laminated micrites and alternating limestone/shales of the Ballyshannon Limestone Formation.
Restricted to three isolated knolls in the Belleek area of County Fermanagh in the northwest Carboniferous basin of Ireland.
Limestone, medium to pale grey, micrite, vuggy, fossiliferous, Waulsortian build-up.
c.12m
At the leading edge of the mass, the 'nose' of the allochthonous mud mound disrupts the host shales and limestones of the Ballyshannon Limestone Formation.
Magnesian Limestone Formation (Northern Ireland And Northwest England)
MGL
Millstone Grit Group And Lower Coal Measures Formation (Undifferentiated)
MGLC
Mousegill Marine Beds
MGMB
Unnamed Sandstone Of Marsdenian To Yeadonian Age (In Millstone Grit Group)
MGMY
Bottom Marshall Green Coal (Northumberland And Durham)
MGN
Marshall Green Coal (Northumberland And Durham)
MGNC
Maggot Coal (South Wales)
MGOT
Unnamed Sandstone Of Pendleian To Alportian Age (In Millstone Grit Group)
MGPA
Meall Garbh Psammite And Semipelite Formation
MGPS
Undefined, not yet mapped.
Crianlarich Sheet 46W (Scotland).
An undifferentiated, regularly bedded sequence of banded to laminated psammite, with thick units of semipelite and some pelite. Decimetre-scale beds of impure quartzite are common close to the base of the overlying unit, seen as part of the transitional change upwards. Pebbly and gritty beds are uncommon, and cross-lamination is rarely seen.
Boundary defined on first occurrence of grey to white quartzite.
Made Ground (Undivided)
MGR
Variable composition. Man-made superficial deposit (generic). Areas where the ground is known to have been deposited by Man, eg. embankments, flood defences, spoil heaps. Many types: BGS recognises many different categories. [Generic description].
Middle Gyffin Shale
MGS
Magnus Sandstone Member
MGSA
Mynydd-Y-Gader Rhyolitic Group [See Lower Acid Volcanic Group]
MGV
Drawn at the base of the Lower Ashes Formation where it rests conformably upon basement beds of Arenig age.
Dolgelly, North Wales.
Rhyolitic lavas and pyroclastic rocks.
Drawn at the conformable upward passage of the China Stone Ashes Formation to the Moelyn Slates Formation of Llanvian age.
Mangaster Voe Intrusion
MGVO
Mainsgate Wood Sand And Gravel Member
MGW
Sharp, undulating, erosional boundary with underlying moderate to reddish brown thinly interbedded clay and silt of the Holmeside Clay Member of the Aikbank Farm Glacigenic Formation.
Sand and gravel, coarsening upwards from pale brown fine-grained sand, with low-angle cross stratificationand ripple-drift cross lamination, to pebbly sand disposed in planar deltaic foresets (dip towards the south), and capped by gravel deltaic topsets. Clasts comprise local Lake District igneous and metamorphic rock-types together with some red and yellow sandstone, and coal. Forming flat-topped plateaux some 20m above the surrounding, poorly drained ground underlain by the Holmeside Clay Member.
About 9m
Mealy Grey Coal (South Staffordshire)
MGYC
Manor Hotel Beds
MHB
Marehill Clay Member
MHC
Upward change to silty clay (or clayey sand) from mostly well-sorted fine-grained sands (locally iron-cemented at top) of Pulborough Sandrock Member.
South-western and western Weald.
Dark grey, locally glauconitic, silty clay.See notes by D.Aldiss attached to application.
Upward change to well-sorted medium to coarse sands of the Folkestone Formation. Contact generally sharp, but rarely exposed.
Lower Marehill Clay [Informal Unit]
MHCL
see Marehill Clay Member MHC
Upper Marehill Clay [Informal Unit]
MHCU
Mains Hill Agglomerate Formation
MHF
Not seen: cut out by the Stinchar Valley Fault.
Ballantrae area, Ayrshire, southwest Scotland.
Volcanic agglomerate with subordinate tuff and chert. The volcanic lava clasts are remarkable in containing large and abundant phenocrysts of clinopyroxene and plagioclase, with some olivine.
At least 500m
Not seen: faulted against serpentinite of the Ballantrae Ophiolite Complex.
Mull Hill Formation
MHL
The stratigraphical with the Lonan Formation at the base, is marked by a change from a mudstone-dominated facies to a sandstone-dominated facies
A pale grey, thin to thick-bedded quartz arenite sandstonr, peripheral parts with interbedded laminated mudstone and siltstone
The stratigraphical contact at the top is marked by a change from a sandstone-dominated facies to mudstone-dominated facies.
Mill Hill Marine Band
MHMB
Moorhowe Formation
MHO
Conformably overlies the Poolscar Formation.
Interbedded siltstone and laminated hemipelagite.
Conformably overlain by the Yewbank Formation.
Munday's Hill Phosphatic Sandstone Formation
MHPS
May Hill Sandstone Group
MHS
Drawn at base of sandstone and conglomerate of the Huntley Hill Formation, - base not seen in type area: drawn at base of Cowleigh Park Formation in the Malverns.
Gloucestershire and Herefordshire.
Grey and brown sandstones and conglomerates with subordinate mudstone, as well as flaggy, fine-grained sandstone and siltstone with impersistent, grey limestone.
Drawn at conformable upward passage from calcareous siltstone and massive limestone of the Yartleton Formation (= Wyche Formation in the Malverns) to limestone and calcareous mudstone of Woolhope Limestone.
Maiden's Hall Sand And Gravel Formation
MHSG
Sharp, erosional contact on bedrock or very compact, fissile, dusky yellowish brown to dark olive grey, gravelly sandy silty clayey diamicton (lodgement till) containing angular to well-rounded clasts up to cobble size of yellow and white sandstone, dolerite, porphyritic lavas, limestone, coal, greywacke sandstone, 'haggis' rock, vein quartz, jasper, flint, granitic gneiss, numerous shell fragments and metamorphic rock of possible Scandinavian origin (Warren House Till Formation).
Northeast England.
Sandy gravel, yellowish brown with orange staining, with angular to well rounded clasts up to cobble size mainly of yellow, red and white sandstone, black fissile mudstone and coal. Sand mainly coarse-grained with shell fragments. Horizontal to trough cross stratification with palaeocurrent towards the north. Locally passes upwards into granule gravel and sand with 10-15mm thick laminae of silt.
Sharp, planar contact with dark olive grey, very stiff, gravelly sandy silty clayey diamicton with angular well rounded clasts up to boulder size mainly of yellow and white sandstones, greywacke sandstone, porphyritic lava and shell fragments (Blackhall Till Formation?).
Meadowhead Vein
MHV
Middle Hope Volcanic Member
MHVO
The boundary is placed at a sharp conformable boundary where bioturbated wackestones and packstones of the Black Rock Limestone Subgroup, are overlain by multi-coloured tuffs
Middle Hope at ST 322 659, north Somerset.
The lower part of the member comprises upward-coarsening multi-coloured mainly red-brown and green tuffs, with bioclastic material. Lapilli-rich beds, 3 to 5 cm thick, within this unit also increase in grain size upwards. Associated with the tuffs are thin-bedded limestones, some planer stratified or showing symmetrical ripples. The multi-coloured tuffs are overlain by green, graded and ungraded lapilli-tuffs, with clasts of devitrified amygdaloidal basalt and bioclastic material. Calcite vein networks are prominent locally. Within the upgraded lapilli-tuffs there are matrix- and clast-supported conglomerates, with clasts of chert nodules and limestones. Also associated with the lapilli-tuffs are beds of bioclastic limestones and both cross-stratified and laminated sandstones. Within the lapilli-tuffs is a prominent, laterally impersistent basaltic pillow lava [3.5 to 4.3 m thick], very weathered with abundant calcite-filled amygdales up to 10 cm across. The upper surface of the basalt is very irregular and highly amygdaloidal.
From 37 m thick at Swallow Cliff in the west, to 4 m in the east of the site, at ST 348 669.
The upper boundary is taken at a sharp, erosive boundary where red nodular limestones with green tuff laminae and beds are overlain by cross-bedded, bioclastic grainstones of the Black Rock Limestone Subgroup.
Milldale Limestone Formation
Mainly Chadian, but probably ranging from Ivorian (late "Courceyan") to early Asbian (Aitkenhead and Chisholm, 1982).
Only seen in the Caldon Low Borehole, where fine-grained pale grey-white dolostones comprising the Rue Hill Dolomite, of Tournaisian age, pass up rapidly into a predominantly limestone sequence of the Milldale Limestone Formation, with the base of the Milldale Limestone Formation taken at the base of a 2cm-thick black fissile mudstone overlying 2.35m of very fine-grained dolostone. In the Hathern No.1 Hydrocarbon Borehole (SK52SW 3) [SK 5158 2416] limestones interpreted as the Milldale Limestone Formation are underlain by anhydrite, limestone and dolostone of the Hathern Anhydrite Formation.
Staffordshire to Derbyshire, and at depth across northwestern Leicestershire.
In the type area, comprises well-bedded mid-grey, crinoidal "biosparites" and dark grey cherty micrites of an inter-reef facies, passing vertically and laterally into knoll reef mud-mounds of poorly bedded grey micrite, which are locally partially or completely dolomitised. In the Loughborough area, comprises grey to buff, thin to thickly bedded, fine- to coarse-grained, locally pebbly dolostones, whereas altered tuff and vesicular basaltic lava are recorded in the Gun Hill Borehole (SJ96SE 18), [SJ9723 6182] between depths at 709 and 770.5m.
From 305m in the type area, 470m in the Caldon Low Borehole (SK04NE 36) [SK 0804 4823], at least 380m at Breedon Hill, and 791.55m recorded in the Gun Hill Borehole (SJ96SE 18) [SJ 9723 6182], located 13km northwest of the Manifold Valley inlier.
Seen as a rapid upward transition, from dark cherty micritic limestones to: a) grey coarsely bioclastic conglomeratic limestones of the Hopedale Limestone Formation; b) to thicker bedded, paler peloidal and crinoidal bioclastic limestone of the Ecton Limestone Formation; c) poorly sorted conglomerate of reef limestone pebbles at the base of the Kevin Limestone Formation; or d) a sharp discomformity at the base of dark to pale brown and grey calcareous mudstone and thinly bedded argillaceous limestones of the Widmerpool Formation.
Milbuie Arkose Formation
MIA
Milton Abbot Formation
MIAB
Mafic volcanic rocks, subordinate slate, and olistostrome.
Minn Beds
MIB
Minnivey Coal (Dalmellington)
MIC
Millgrit Coal (Bristol Area)
MICO
Middleton Dale Anhydrite Formation
MIDA
Unconformable, with grey-green and red sandstone of the Middleton Dale Anhydrite Formation overlying grey and purple mudstone of Ordovician age.
Proved in the subsurface only, in the northern part of the Peak District [SK27].
Bedded and nodular anhydrite interbedded with dark grey mudstone and thin beds of dolostone. A thin grey-green and red sandstone marks the base of the formation, with dark grey dolostone and thin dolomitic mudstone beds dominant in the lower part of the unit.
Measured as 73.6 m thick in the Eyam Borehole.
Sharply unconformable, and defined as the base of the lowermost thick, dark grey dolostone bed of the Woo Dale limestone Formation, overlying anhydrite of the Middleton Dale Anhydrite Formation.
Middles Coal (South Staffordshire)
MIDC
Mid (Bowhousebog) Fireclay
MIDF
Milldale Limestone Formation (Dark Lithofacies)
MIDK
Middle Etive Rhyolite
MIER
Mill Formation
MIF
Conformably overlies the Myoch Formation.
Girvan area, south west Scotland.
Mottled shale, dark shale, calcareous flags, mudclast conglomerate.
Conformably overlain by Shalloch Formation.
Migdale Pluton
MIGD
Millstone Grit Formation (Offshore) [See Also Mg]
MIGR
Middle Grain Vein
MIGV
Milford Haven Group
MIH
Drawn at base of green marls and conglomerate to north, and of red marls and breccia to the south of Milford Haven where they rest conformably on the Benton Rhyolitic Group to the north and Gray Sandstone Group to the south.
Southwest Wales.
Hard, red calcareous marls with sporadic red and green sandstones. Basal beds of green marl, conglomerate and breccia are also present. (Correlative of Milford Haven Group-Red Marl Group).
About 1500m
Drawn at conformable and unconformable upward passage from red marls to sandstone and marls of the Cosheston Group, north of Milford Haven and to the Ridgeway Conglomerate, south of the Haven respectively.
Mid Hosie Limestone
MIHO
Generally seen as a change from marine mudstone within the Lower Limestone Formation.
Distributed throughout most of the outcrop of the Carboniferous of the Midland Valley of Scotland, but locally difficult to recognize in Ayrshire and Lanarkshire where the Hosie limestones join together as the McDonald Limestone in the shelf setting.
A pale to dark grey, argillaceous locally concretionary, crinoidal and shelly, bioclastic limestone, interpreted to be of marine origin.
0.35m to 1.15m thick, or locally less, in the Airdrie, Falkirk and Glasgow districts. This limestone fuses with the Main Hosie Limestone at Petershill in the Bathgate Hills.
Milldale Limestone Formation (Knoll-Reef)
MIK
Millerhill Limestone
MIL
Milton Coal (Fife)
MILC
Mill Coal (Central Coalfield)
MILL
Milngavie Dyke
MILND
Milngavie Sills
MILNS
Mill Coal (South Lancashire)
MILSL
Milltown Conglomerate Formation
MILT
Millbuie Sandstone Member
MIM
Conformable lower contact on Killen Burn Mudstone Member.
Red sandstones, largely of fluvial origin.
250 metres +.
Upper contact not seen.
Minch Formation
MIN
Lies on a rockhead.
Defined as a seismic formation, apparently till-like.
Thinly developed adjacent to Scottish mainland.
Overlain by Jura Formation.
Minge Coal (Leicestershire)
MINC
Minginish Conglomerate Formation
MINCO
Minffordd Formation
MINF
Unconformably overlies rocks of the Padarn Tuff Formation.
Snowdonia, North Wales.
Coarse- to fine-grained epiclastic rocks intercalated with pyroclastic and mixed pyroclastic and epiclastic rocks, comprising laminated siltstones, felsic air-fall tuffs and tuffites, volcanogenic sandstones and conglomerates (particularly in the lower part) and thin ash-flow tuffs.
Unconformably overlain by rocks of the Bangor Formation.
Minto Hills Vents
MINT
Pyroclastic breccia or agglomerate in vents.
Twin circular vents, c.500m in diameter, 200m apart.
Miocene Rocks (Undifferentiated)
MIOC
Lower Miocene Rocks (Undifferentiated)
MIOCL
Early Miocene.
Upper Miocene Rocks (Undifferentiated)
MIOCU
Late Miocene.
Middle Old Red Group
MIOR
Main Ironstone Seam
MIRS
Main Ironstone (Carron)
MIS
Middle Till Coal
MITC
Mill Vein
MIV
Major Coal (South Lancashire)
MJCO
Middle Johnstone Shell Bed
MJSH
Muck-Ardnamurchan Swarm
MKARD
Mickledore Breccias Member
MKB
Muck Dyke
MKDY
Muirkirk Ell Coal
MKEC
Mirk Fell Ganister
MKFG
Mirk Fell Ironstone
MKFI
Muschelkalk Halite Member
MKHA
Markhams Hole Formation
MKMH
Monkerton Formation
MKN
Overlies thin sequence of Heavitree Breccia in Hill Barton [SX 956 928], Exeter, with fairly sharp upward passage from breccia into a mainly clayey sequence. Around [SX 965 940], the Monkerton Formation rests directly on Whipton Formation.
Small area northeast of Exeter, Devon, from Hill Barton [SX 956 928] in the west, through Monkerton [SX 965 938], to just beyond the M5 Motorway in the east [SX 974 939].
Clayey fine-grained sandstone (locally medium- or coarse-grained); sandstone, sandy mudstone, silty mudstone, thin breccia beds. The formation passes laterally and downwards into the Heavitree Breccia.
Overlain by Dawlish Sandstone: the passage from clayey silty sandstones of the Monkerton Formation takes place within about 1m of strata.
Monkcastle Sandstone Formation
MKS
Taken at the lithological change channel-fill, upward-fining sandstones to the cyclical, upward-coarsening sequence of clastic strata with marine limestones in the underlying Upper Limestone Formation
Presently used within north Ayrshire
A medium- to coarse-grained sandstone, with seatearth and seatclay; subsidiary siltstone and mudstone
About 45 m thick.
Taken at the base of the Troon Volcanic Formation; defined by the lithological change from basaltic lavas to clastic strata of the underlying Monkcastle Sandstone Formation
Market Stance Meta-Igneous Complex
MKST
Monks Water Group
MKW
Base of Hareshaw Conglomerate.
Hagshaw Hills Lower Palaeozoic Inlier. Sheets 23W, 23E and 15W.
Conglomerate of well rounded quartzite pebbles (see Hareshaw Conglomerate) and reddish-brown to greyish-brown medium-grained sandstones (see Quarry Arenite). NOTE: Reference Sections; see component formations (Hareshaw Conglomerate and Quarry Arenite).
c. 520m
Base of overlying Greywacke Conglomerate.
Main Limestone
Millport Cornstones Member
MLC
The base is described as "transitional", indicating that it is likely to be interbedded, with grey mudstone and dolomitic limestone of the Ballagan Formation (Paterson and Hall, 1986), and occurs at crop in Millport Bay [NS 1561 5416]. The lower boundary is conformable (Monro, 1999).
Grey sandstone and red-brown silty mudstone with pedogenic limestone.
The top is not seen, but is presumed to be overlain by the Eileans Sandstone Member that crops out on The Eileans in Millport Bay (Paterson and Hall, 1986; Monro, 1999).
Mulloch Hill Conglomerate Formation
MLCG
Unconformably overlies the High Mains Sandstone Formation (HMS) and Drummuck Group (DKG).
Craighead Inlier, Girvan
A massive conglomerate with well-rounded pebbles, 2-3 cm in diameter. Some clast blocks are more than 15 cm across. Also some lenses of fossiliferous sandstone.
Conformably overlain by the Mulloch Hill Sandstone Formation (MLHS).
Lough Derg Group
MLD
Marldon Limestone Member
MLDL
Middle Coal (Farrington Member, Somerset)
MLEC
The base of the bed is taken at the base of the coal resting upon about 9 m of hard mudstone of the underlying undivided Farrington Member.
No.5 Vein, comprising the Dabchick and Peacock veins at Greyfield Colliery; Bromley No.4, -Possible correspondence; Smith's Vein.
Coal, although where the deposit splits into two seams, it is separated into two by by a band of seatearth around Old Mills Colliery (364500, 155500), whereas further away from the divide this, becomes 12 m of hard mudstone and fireclay, near Greyfield Colliery (364000, 158700).
A thin coal, about 46 cm thick at Dunkerton in the northeast of the Somerset Coalfield, to 71 cm thick at Farrington in the southwest of the coalfield.
The top of the coal is overlain by sandstone, which forms a hard roof, of the Middle Vein Greys. Elsewhere a planty shale developed between the coal and the sandstone of the surrounding Farrington Member.
Mulfran Formation
MLF
Middle Limestone Formation
MLG
Drawn at the base of the Oxford Limestone Member where it rests conformably upon the Crosshill Limestones Member. Boundary defined on palaeontological grounds only.
Limestones, sandstones, shales and coals. Fossiliferous.
Drawn at the conformable upward passage of the Middle Limestone Group with the base of the Great Limestone.
Mulloch Hill Sandstone Formation [Sensu Stricto]
MLHS
Conformably overlies the Mulloch Hill Conglomerate (MLCG).
Green to buff, ochreous-weathered sandstones, siltstones and mudstones.
Up to 240m thick.
Conformably overlain by the Glenwells Shale Formation (GWSH).
Merlin Limestone
MLL
Mill Lane Limestones Bed
MLLL
Change up from grey mudstone with large limestone nodules of undifferentiated Foston Member; at 19.58m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17)
Two grey, weathering brown, sandy, shelly limestone or highly calcareous siltstone beds up to c 0.3m thick, separated by up to 1m of mudstone. Limestone/siltstone becoming nodular in south of range. Fauna includes gastropods, brachiopds, bivalves (including numerous pectiniids and common Gryphaea), ammonites, belemnites, ostracods and echinoderms. Forms a variably strong feature.
0 to 1.1m; 1.07m in type section.
Change up into grey mudstone with thin impersistent limestone beds of undifferentiated Foston Member; at 18.51m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17)
Lower Main Coal (Middle Seam) (Leicestershire)
MLMC
Mull Of Logan Formation
MLN
Medium to thick-bedded greywacke and silty mudstone including very thickly bedded massive sandstone sequences and a unit of 'blocky arenite'.
Middle Lount Coal (Leicestershire)
MLOC
Meall Odhar Intrusion
MLODR
Middle Longcraig Limestone
MLOL
Millepore Bed
MLP
Milnrow Sandstone
MLRS
Marl Slate Formation
MLSL
Sharp, unconformable contact on either the aeolian Yellow Sands Formation or on Carboniferous, usually Coal Measures, strata: represents a rapid marine transgression with the incoming of marine, bituminous, silty, argillaceous dolostone.
Durham and Yorkshire provinces of the English Zechstein. Equivalent to the Kupferschiefer Formation in the North Sea, Dutch and German provinces.
Laminated, bituminous, silty, argillaceous dolostone with an unusually high concentration of metallic minerals and a distinctive fish fauna.
To 5.48m. (18 ft.) in the Durham Province.
Taken at the base of the overlying dolostones and limestones of the Raisby Formation in the Durham Province or the equivalent Cadeby Formation in the Yorkshire Province.
Milton Sand
MLTS
Artificial Lagoon (Undivided)
MLU
Middle Llangibby Beds And Upper Llangibby Beds (Undifferentiated)
MLUL
Morley Lane Volcanic Formation
MLV
Not known at outcrop.
Porphyritic metadacite lavas interbedded with greenish-grey 'tuffs' that may in part represent highly sheared fault-rocks.
Apparent thickness of 294m
Sharply overlain by Ives Head Formation at 541m depth in Morley Quarry Borehole. Ives Head Formation basal bed, is a grey, laminated volcaniclastic siltstone/sandstone.
Manchester Marls Formation
Conformable upward change from red sandstones (Collyhurst Sandstone) into red marls; a pebbly bed was included in the base of the Manchester Marls at Stockport by Taylor and others, 1963, p.53.
Lancashire, Cheshire.
Red marl (calcareous mudstone and siltstone) with thin beds of fossiliferous marine limestone and dolomite; locally green; sandy in places especially in top part; local breccias and pebbly beds. (Tonks and others, 1931, p.165; Taylor and others, 1963, p.53).
45 - 60m in Manchester; more in Stockport; dies out west of St. Helens.
Conformable upward passage into red sandstones of the Sherwood Sandstone Group.
Mercia Mudstone Unit 1
MM1
Mercia Mudstone Unit 2
MM2
Mercia Mudstone Unit 3
MM3
Mercia Mudstone Unit 4
MM4
Mercia Mudstone Unit 5
MM5
Mercia Mudstone Unit 6
MM6
Muirkirk Major Coal (Ayrshire)
MMA
Mottled Mudstone Member [Llandovery Age]
MMB
Muirkirk Musselband Coal (Ayrshire)
MMC
Maesmelyn Coal (South Wales)
MMCO
Mauld's Meaburn Edge Limestone
MMEL
Mercia Mudstone Group
MMG
Additional information about the age.
Gradational on Sherwood Sandstone Group, taken where mudstone and siltstone become dominant over sandstone; incoming of pseudomorphs after halite.
British Isles.
Description of landforms. Edited by sci expert.
Lacustrine. Edit by curator.
Dominantly red, less commonly green-grey, mudstones and subordinate siltstones with thick halite-bearing units in some basinal areas. Thin beds of gypsum/anhydrite widespread; sandstones are also present.
Named for the Saxon kingdom of Mercia.
Red-brown mudstone with thin grey, greenish or red-brown siltstone or fine-grained sandstone beds and thin to thick evaporite beds at some levels.
Supplementary information.
Overlain sharply by Penarth Group (incoming of marine lithologies).
Melton Mowbray Granodiorite
MMGD
Mid Hosie Limestone And Main Hosie Limestone (Undifferentiated)
MMHL
This is a composite or generalised description of MAHO and MIHO Hosie Limestones, used where the indvidual limestones cannot be recognised.
Midlands Minor Intrusive Suite
MMI
Not seen; no information on depth extent of the intrusive complex.
Most westerly occurrences are at the Wrekin, Shropshire. Easterly surface limit is the Nuneaton inlier, between Bedworth (SP 369 875) and Atherstone (SP 300 976).
Numerous thin sills of grey-green spessarite, lamprophyre and thicker composite sills of hornblende diorite, commonly melanocratic at the base, intruded into strata ranging from Precambrian to Ordovician (Tremadoc) age.
The individual sills range from c. 1m (lamprophyre), to about 60m (diorite). An aggregate thickness of 100 - 150m is probable
Taken at the unconformity between the sills and their host rocks and overlying strata of Devonian, Carboniferous and Triassic age.
Mauld's Meaburn Limestone
MML
Moyne Moor Lava Member
MMLA
The base is possibly unconformable on the sedimentary strata of the Ballagan Formation (Inverclyde Group), but the contact is not seen because of faulting.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton, irregular shaped but continuous outcrop from Balgray Reservoir (NS 510 570) to Over Auchentibber Farm (NS 459 498).
The Moyne Moor Lava Member consists of plagioclase porphyritic trachybasalts (hawaiites) with discrete subordinate alkali basalt and rare basaltic trachyandesites (mugearites) near the top of the Member. These might herald the initiation of trachytic magma generating the trachytes of the overlying Harelaw Lava Member.
The Member is overlain by the geographically separate (and laterally equivalent) alkali basalts of the Eaglesham and Neilston Lava members. The contacts are considered conformable but also locally unconformable.
Mammal Bed
MMMB
Mercia Mudstone Group (Marginal Facies)
MMMF
Markedly unconformable, at the abrupt base of conglomerates of the Marginal Facies, which infill a buried topography on Palaeozoic or late Proterozoic rocks of variable lithology.
Deposits occur on the flanks of the Mercia Mudstone Group outcrop, where the latter oversteps onto Palaeozoic or Proterozoic rocks; the thickest deposits lie unconformably on Carboniferous limestones in Somerset, Avon and South Wales, and around the flanks of the Charnwood Forest in Leicestershire.
Variable, typically consisting of conglomerate and/or breccia with clasts derived locally from rocks lying immediately below the unconformable base of these deposits. The matrix generally consists of finer-grained rock fragments or, less commonly, siltstone, sandstone or micritic limestone. Where these deposits overlie Carboniferous limestones, such as in the Bristol and Mendip areas, both the matrix and limestone clasts are commonly dolomitized ("Dolomitic Conglomerate"). Individual clasts can range up to several cubic metres in size. Fenestral and algal carbonates interdigitate with conglomerates and breccias in exposures to the south of Cardiff (Tucker, 1977; Waters and Lawrence, 1987).
Highly variable due to interdigitating relationship with the Mercia Mudstone Group; ranges from 1m or less at some exposures to over 100m where these deposits fill "buried valleys" in the underlying pre-Triassic topography.
Conformable and gradational, interdigitating with reddish-brown mudstone of the Mercia Mudstone Group (or its constituent formations).
Millin Mudstone Formation
MMN
Marchfield Moraine Member
MMO
Not exposed, but probably a gradational contact on till of the Gretna Till Formation.
Extends from Cargenbridge [NX 955 745], northnortheastwards to the vicinity of "The Grove" [NX 986 796] Dumfries, Dumfriesshire.
Large recessional moraine forming discontinuous mounds and ridges typically rising 10-15m above the level of the surrounding glaciofluvial sand and gravel deposits; a large mound at Cargenbridge rises up to 22m above the glaciofluvial deposits on the western bank of the river Nith.
Interstratified sequence dominated by Sand and Gravel. Subsidiary lithologies: Reddish brown glacial Diamicton(till), Silt and Clay. Lithologically very heterogeneous. Gravel and diamicton dominate at the type section; fine-to medium-grained sand and silt dominate in many surface exposures. These show extensive small-scale normal faulting and some low-angle glacitectonic thrusting.
At least 12m thick at type section; at least 7.4 to 11.3m proved in adjacent boreholes.
Normally the ground surface; locally overlain by Holocene peat in hollows in the moraine surface.
Mercia Mudstone Group And Penarth Group (Undifferentiated)
MMPN
Mullaghmore Sandstone Formation
MMS
Lower boundary, represented by base of Dromore Sandstone Member; is sharply conformable on Bundoran Shale Formation.
Sandstone, brown to grey, fine- to coarse-grained, silty, bioturbated interbedded with micaceous, carbonaceous mudstone and siltstone; immediately overlying basal Dromore Sandstone Member, are thin stromatolitic limestones, black ostracodal packstones and bituminous pyritous shales.
Conformable at sharp base of Drumchorick Siltstone Formation.
Maesgwm Slates
MMSL
Monument Formation
MMT
Transitional from greenish grey sandstones, siltstones and silty mudstones of Dippal Burn Formation.
Greyish red, medium-grained sandstones and silty mudstones.
Transitional to greenish-grey sandstones, siltstones and silty mudstones of Slot Burn Formation.
Middleton Main Top Coal (West Yorkshire)
MMTC
Mottled Mudstone Member [Wenlock Age]
MMU
Middleton Grit
Drawn at the base of the coarse-grained sandstone where it rests on shales (containing Nuculoceras nuculum) above the Nesfield Sandstone.
West Yorkshire area [Middleton, 2.5km northwest of Ilkley, Yorkshire.].
Coarse-grained sandstone (grit).
Drawn where the coarse-grained sandstone is overlain by shales (containing Homoceras beyrichianum) below the Brocka Bank Grit.
Mintlyn Sand Member
MNB
Glauconitic, clayey, grey and green sands with bands and "doggers" of clay-ironstone and phosphatic nodules (Mintlyn Member) overlies green, glauconitic, clayey sands with abundant phosphatic nodules (Runcton Sand Member)
The member is known from the east of Gaywood: King's Lynn By-Pass (where it is up to 15m thick, e.g. the cutting at Mintlyn Wood); South of Middleton Stop Drain to the North Runcton area;and south as far as the West Dereham area. Several boreholes have penetrated the member, includind Hunstanton Borehole (9.7m thick), Marham Borehole (10.3m thick) and Severals House Borehole (0.5m thick-the southward truncation being due to the overstepping Carstone). The member has been traced beneath The Wash (Borehole 72/77B) and apparently passes laterally into the Upper Spilsby Sandstone/ Basal Claxby formations. The "Surites levels" are represented in the Upper Spilsby Sandstone Formation of South Lincolnshire; Casey and Gallois (1973).
Glauconitic, clayey, grey and green sands with bands and "doggers" of brown weathering clay-ironstone and seams of phosphatic nodules (picking out erosion surfaces). A prominent band of phosphatic nodules occurs at the base. Ammonites present. Casey & Gallois (1973) stated that the member can be divided into two, a lower "Hectoceras Beds" and an upper division "in which Surites and allies predominate".
Up to c. 15m
Incoherent, moderately clean, pale grey (locally green, yellow or orange), fine-to medium-grained, cross bedded quartz sands with subordinate bands of silt or clay (Leziate Sand Member) overlies glauconitic, clayey, grey and green sands with bands and "doggers" of brown weathering clay-ironstone and seams of phosphatic nodules (Mintlyn Sand Member).
Main Chert
MNC
Meall Nan Con Gabbro Intrusion
MNCG
Main Coal (Northumberland)
MNCL
Meall Nan Con Net-Veined Dolerite Roof Zone
MNCND
This entry is at informal rank 7, in which "Zone" is an accepted lithodemic term.
Main Coal (Northumberland And Durham)
MNCO
Monadhliath Pluton
MNDL
Central Monadhliath Highlands, Scotland, near Aviemore, Speyside.
Pink, coarse-grained prophyritic biotite-granite and fine- to medium-grained leucogranite. Subsidiary microgranite and marginal granodiorite bodies. Aplitic microgranite veins.
Monadhliath Pluton, Phase 1
MNDL1
Monadhliath Pluton, Phase 2
MNDL2
Monadhliath Pluton, Phase 3
MNDL3
Monadhliath Pluton, Phase 4
MNDL4
Main Estheria Band
MNEB
Marton Formation
MNF
Muirkirk Nine Foot Coal
MNFC
Mourne Mountains Granite
MNG
Mourne Mountains Granite (G1)
MNG1
Mourne Mountains Granite (G2)
MNG2
Mourne Mountains Granite (G3)
MNG3
Mourne Mountains Granite (G4)
MNG4
Mourne Mountains Granite (G5)
MNG5
Maidenhead Formation
MNHD
Unconformable on glacigenic deposits of the Anglian stage or on older Pleistocene strata or bedrock. Individual terrace deposit members rest unconformably on older Pleistocene strata or bedrock.
The valley of the mainstream River Thames downstream of the Goring Gap, including the deposits of the valleys of the Blackwater, Lodden, Lea, Wandle, Mole, Godalming Wey, Bramley Wey, Darent and Cray. Deposits of the Kennet valley are referred to the Kennet Valley Formation.
Mainly river terrace sand and gravel, Brickearth silt and alluvial floodplain silt, silty clay and sand. The formation includes interbedded units (representing Interglacials) of locally fossiliferous silty sand, silt, together with organic clay, tufa and peat. River terrace deposits of the middle and lower Thames contain gravel clasts mainly composed of flint, vein quartz and local bedrock lithologies including chert. The terrace deposits are depicted on British Geological Survey maps using numbered terrace symbols. Modern British Geological Survey maps also show the terrace deposits as named units which are here interpreted as members of the Maidenhead Formation. The main terrace deposit members are the Black Park Gravel, Boyn Hill Gravel, Lynch Hill Gravel, Hackney Gravel, Taplow Gravel, Kempton Park Gravel, Shepperton Gravel and Staines Alluvium. Brickearth silt beds include the Enfield Silt, Roding Silt, Langley Silt, Dartford Silt, Crayford Silt and Ilford Silt.
Single terrace aggradations range from 3 to 12m. Interglacial beds (eg Trafalgar Square Beds) up to 12m.
Main Ironstone (Cadder)
MNI
Minuntion Member
MNN
Forms base of Confinis Formation, rests on Kirkland Conglomerate Formation,
Sandstone, reddened, cross stratified, medium- and coarse-grained.
0.5 to 8m
Succeeded by fossiliferous calcareous sandstone of the Confinis Formation.
Manor Coal Of The Forth
MNRC
Minn Sandstones
MNS
Main Smut Coal (Nottingham And Derby)
MNSC
Monadhliath Semipelite Formation
MNSP
Overlies Glen Doe Psammite and Loch Laggan Psammite Formations. Marked by gradual increase in semipelite beds in top of psammite formations.
Central and south-western Monadhliath Highlands, Loch Killin to Fort Augustus district.
Interbedded thin micaceous psammites and semipelites with subordinate feldspathic and siliceous psammite and quartzite. Quartzite is more common in the basal part of the formation.
Up to 2km in type area, west of the Corrieyairack Pass.
With increase in micaceous psammite and feldspathic psammite passes up transitionally into Carn Leac Psammite Formation (Foyers District - Haselock et al, 1982. Sheet 73E) and the Auchivarie Psammite Formation (Glen Roy district - Key et al, 1997. Sheet 63W). See May and Highton (1997).
Main Smut Sandstone
MNSS
Merion Till Member
MNTI
Money Head Formation
MNY
Tectonic contacts. Lower contact faulted against the Sinniness Formation.
Greywacke, thickly bedded for the most part but interbedded with sporadic units of thinly-bedded greywacke and siltstone. The greywacke composition is variable from bed to bed.
About 500 metres.
Tectonic contacts. Upper boundary faulted against the Shinnel and Mindork Formations.
Monsal Dale Limestone Formation
A sharp unconformable boundary with the lowest bed of dark limestone, commonly marked by abundant Girvanella or Saccamminopsis, above the pale grey limestones of the Bee Low Limestone Formation. Elsewhere, the boundary is marked by the base of the Upper Millers Dale Lava, Winstermoor Lava or Lower Matlock Lava.
Northern and eastern parts of the Peak District.
Pale to medium grey, thickly-bedded and bioturbated well-sorted biosparites and pelsparites, to poorly sorted biomicrites. The limestone contains sporadic chert nodules, and emergent surfaces are marked by pedogenic tubes and crusts of brown laminated micrite. The lower part at Cressbrook Dale - Millers Dale and all around Litton, comprise dark grey thinly-bedded, cherty limestone containing dark argillaceous partings, the limestone being typically a poorly sorted bioclastic calcisiltite with a micritic matrix, and includes several volcanic members of basaltic lava and tuff.
Appears 143 m thick in the Cressbrook Dale section (200m at Ashford on the Water [SK 19 69], and 359 m at Longstone Edge [SK 20 73].
Taken at the base of the dark grey - grey-brown limestones of the overlying Eyam Limestone, which locally overlies an erosive surface and clay wayboard above the pale to medium grey limestone, of the Monsal Dale Limestone Formation.
River Terrace Deposits, 1 (Mole)
MO1
River Terrace Deposits, 1 To 2 (Mole)
MO1T2
River Terrace Deposits, 2 (Mole)
MO2
Morag Anhydrite Unit
MOAN
Moat Coal (New Cumnock, South Ayrshire)
MOAT
Morecambe Bay Formation
MOBAY
Overlies extensive deposits of till probably equivalent of the Kirkham Glacigenic Formation (Irish Sea Coast Glacigenic Subgroup).
Cumbria, offshore in Morecambe Bay.
Glaciofluvial and glaciolacustrine sediments including sand, silt and laminated clay with subordinate gravel.
0 to 18m
Gradational with overlying post-glacial sequence of clay, silt and sand.
Morton Banks Coal (West Yorkshire)
MOBC
Moss Coal (New Cumnock)
MOC
Morag Carbonate Unit
MOCA
Moss Cannel Coal (North Staffordshire)
MOCC
Marsco Hybrids (Skye Western Red Hills Centre)
MOCH
Meall Odhar Conglomerate
MOCO
Malton Oolite Member And Coral Rag Member (Undifferentiated)
MOCR
Moorcock Sandstone
MOCS
At top of Claughton Moor Siltstone. Boundary drawn where sandstone more than 10% of beds. Boundary gradational through c.1m.
Caton Moor, Lancaster.
Interbedded flaggy fine-grained sandstones and siltstones.
Top not exposed on Caton Moor.
Monsal Dale Limestone Formation (Dark Lithofacies)
MODK
Monadh Dubh Sandstone Formation
MODS
Direct, unconformable contact on Torridonian sandstones.
Isle of Rum
The Monadh Dubh sandstone Formation consists of 4 members, but was shown as one unit on the 50k maps. From the base these members are Shellesder, A'Mharagach, Sgaorishal and Allt Dubh.The base of the unit lies directly on the Torridonian and comprises coarse, continental-derived conglomerates. Gradually the succession fines upwards and the top 25m (two members) are dominated by fine sand and lacustrine carbonate rocks with ostracods.
Jurassic transgression - change from continental derived sediments - not seen?
Moorside Farm Tuff Formation
MOF
Only seen in Sellafield BH No.2 (NY00SE/28)
Welded massive tuff and lapilli-tuff grading into polymict pyroclastic breccia.
114.5m minimum; base not proved (uncorrected for structural dip or borehole deviation).
Overlain by Broom Farm Formation - marked by change to volcaniclastic sandstone (bedded).
Mochrum Fell Intrusion
MOFE
Moira Grits
MOG
Morar Group And Glenfinnan Group (Undifferentiated)
MOGL
Morvern Greensand Formation
MOGR
Unconformable on various Jurassic and Triassic strata.
Glauconitic calcareous sandstone, white to pale greenish. Some gritty beds and calcareous inclusions up to cobble size. Conspicuously shelly (mainly oysters) in parts.
0.3 to 13.4m, according to Rawson et al. (1978).
[?]Conformable contact with the overlying Lochaline White Sandstone Formation. However Braley (1990) and Lowden et al. (1992) regarded the Lochaline White Sandstone Formation as a member within this formation and considered the upper boundary as unconformable with the Gribun Chalk Formation.
Mortlach Graphitic Schist Formation
MOGS
At the top of the Pitlurg Formation where interbedded thin limestones, calc-silicate beds and semipelites and psammites pass up into either graphitic schist or massive limestone.
From the coast at Sandend, SW through the Keith and Dufftown area into Glen Rinnes, thence continuing into Glenlivet, to the Bridge of Avon area west of Tomintoul and then in the Allnack Gorge, running SE into Glen Avon.
Semipelitic and pelitic schist, commonly graphitic, with calc-silicate lenses and metalimestone in lowermost part.
c. 970m, including any thickening due to folding in the type section; thinned and thickened considerably by deformation elsewhere.
At the base of the Corriehabbie Quartzite Formation where the schists pass up into flaggy psammites, phyllites and quartzite.
Moel Hebog Sandstone Member
MOH
Conformable within the Cwm Eigiau Formation.
Well-bedded microconglomerates locally containing larger clasts of felsic tuff, coarse-grained sandstones and subordinate thinner silty sandstones. Many sedimentary structures including large-scale cross-bedding, ripple lamination, grading and channels as well as convolute lamination and slump structures.
Conformably overlain by the felsic ash-flow tuffs of the Pitts Head Tuff Formation.
Mouldy Hills Gravel Formation
MOHI
Generally conformable boundary with the underlying Langholm Till Formation; otherwise unconformable contact with bedrock.
Very poorly-sorted, matrix-rich gravel with boulders comprising angular to subrounded clasts mostly of greywacke sandstone and siltstone with a matrix of yellowish brown, clayey sand. Subordinate beds of both clast-and matrix-supported, stratified diamicton, and lenses of silty sand.
Generally at the ground surface, locally a conformable boundary with overlying Flandrian deposits.
Moira Formation
MOI
An irregular unconformity surface on rocks of Precambrian to Palaeozoic age.
The unit is widely distributed at the base of the Triassic or Permian of the East Midlands, extending from Measham northwards as far as the Chesterfield area.
Typically a subangular conglomerate with locally-derived clasts in a red, sandy mudstone matrix. Buff sandstones interbedded with mudstones constitute a distal facies.
Highly variable, generally 0-15m but can range up to 55m.
Sharply and in places unconformably overlain by sandstones or mudstones of Permian to Triassic age.
Monsal Dale Limestone Formation (Knoll-Reef)
MOK
Middle Oakwood Limestone
MOL
Mollusca Band
MOLB
Mormeal Member
MOM
Morley Muck Coal (Nottingham And Derby)
MOMC
Mains Of Mause Lavas Member
MOML
Monkey Coal (Dungannon)
MONC
Montrose Group
MONT
Moorland Coal (Northumberland)
MOOR
Mosedale Peat Bed
MOPT
Sharp, uneven, unconformable contact with underlying extremely compact, silty sandy gravelly diamicton of the Thornsgill Till Formation containing clasts mainly of slate, "Borrowdale Volcanic Group" lithologies and Threlkeld microgranite.
Keswick-Thelkeld area of the northern Lake District.
Peat, highly compressed containing pollen and macroscopic plant remains dominated by willow. The peat bed is tentitively assigned to an early Devensian interstadial.
To 1m
Disturbed, locally gradational contact with remobilized till similar to that occurring below (landslip or head deposit), or a sharp, erosional, unconformable contact with overlying gravel forming a river terrace.
Middle Old Red Sandstone (Undifferentiated)
MOR
Moray Group
MORA
Morainic Deposits
MORD
Middle Ord Sandstone Member
MORDS
In the area southwest of Berwick-upon-Tweed the Fell Sandstone Formation consists of several sandstone members separated by variable thicknesses of mudstone and siltstone. The Middle Ord Sandstone Member is the lower of three members and is found in the region of Newburn Farm, north Northumberland.
Medium-grained, upward fining sandstone.
0 to 15m
More Coal (Fife)
MORE
Morag Member
MORG
Morlas Coal (North Wales)
MORL
Morpeth Group
MORP
Morar Group
MORR
Morridge Formation
MORRI
Conformable base of the first thick quartzitic sandstone of the Morridge Formation above the dark grey mudstone and siltstone of the Craven Group.
Goyt Trough of North Staffordshire and the Widmerpool half-graben of the East Midlands.
Interbedded dark grey, shaly mudstones and pale grey protoquartzitic siltstones and sandstones.
To 600m, thinning northwards.
Conformable base of the lowermost thick quartz-feldspathic sandstone of the Millstone Grit Group above the quartzitic sandstone and siltstone or dark grey, shaly mudstone of the Morridge Formation.
Morston Formation
MORS
Rests upon till of the Lowestoft Formation.
The coast of north Norfolk.
Interglacial raised beach deposits, gravel of rounded flint cobbles and pebbles overlying finely laminated mud. Pollen from the finely laminated mud suggests warm climate conditions.
c.2.3m
Overlain by till of the Holderness Formation.
Morven Conglomerate Formation
MORV
Meall Odhar Sandstone
MOS
Moreseat Sandstone Formation
MOSA
Not exposed. Probably unconformable on granite, or crystalline basement. Basal unit usually a strongly weathered siltstone.
The Buchan Ridge of Flett and Reed, 1921; Moss of Cruden. 1:10,000 sheets NK04SW, NK03NW. 1:50k geological sheet 87W (Ellon) and 87E (Peterhead).
Sandstone, fine-grained, silty, glauconitic, very dark grey. Bioturbated with moulds of mollusca.
About 12m. Not seen at one exposure.
Unconformable, overlain by the Buchan Ridge Gravel Member.
Moss Coal (North Staffordshire)
MOSC
Moss Side Member
MOSI
Muckle Ossa Sandstone
MOSSA
This comprises shelf sandstones within the Lower Nordland Unit. The reference sections for the Muckle Ossa Sandstone are in BGS boreholes 77/07, 77/09 and 90/03
Moelfre Tuff Formation
MOT
Conformable within the upper part of the Nant Ffrancon Subgroup.
Basaltic tuff.
To 165m
Melt Out Till
MOTIL
Mountain Coal (South Wales)
MOUC
Mountstewart Formation
MOUN
Mousa Formation
MOUS
Moylgrove Group
MOY
Moy Pluton
MOYG
Moy Sandstone Formation
MOYS
Onshore Republic of Ireland (Sligo - Leitrim)
Marchup Grit
West Yorkshire area [Low Marchup, eastsoutheast of Skipton, Yorkshire].
Mid Pentre Coal (South Wales)
MPEC
Mount Pleasant Group
MPG
Drawn at the base of the nodular limestones and Calcareous Shales Formation where it rests conformably upon the Kiln Wood Beds.
Chudleigh, south Devon.
Nodular limestones and nodular calcareous shales, purple and green slates with nodules, siliceous green slates with nodules.
Drawn at the conformable upward passage of the Siliceous Green Slates with nodules formation to the Winston Chert Formation of Upper Famennian age.
Magpie Coal (Dungannon)
MPIE
Maggot's Pike Limestone
MPIL
Mynydd Penarfynydd Layered Sill
MPLS
Hornblende gabbro.
Mohuns Park Mudstone Bed
MPMU
Middle Jurassic - Lower to Middle Callovian (Calloviense Zone to Jason and ?Coronatum Zone).
Arbitary boundary drawn at the top of highest substantial sandstone or sandy mudstone of underlying Kellaways Formation, above which the succession is predominantly mudstone.
Trudoxhill (Somerset) to Holwell (Dorset).
Silicate mudstone, medium grey, weakly calcareous, slightly pyritous, shelly, with sporadic beds of argillaceous limestone nodules.
[Compiler's Notes] Interestingly, on the original Lexicon form by C R Bristow this unit has the status of a Bed, also probably (though slightly ambiguously) on the Shaftesbury map (1994). It was upgraded to Member in the Shaftesbury Memoir (1995) and we regrettably (by default) stuck with this for the GCR volume and Correlation chart. I have not seen this unit on the ground, but reading the descriptions in the two memoirs it strikes me as a natural part of the Peterborough Member - it seems to contain typical Peterborough lithologies in places and passes into it laterally in a rather indefinite way. It is indicative of the rather vague characterization that the depths quoted for both top and base of the unit in Combe Throop on the original Lexicon form have been changed by several metres in the Shaftesbury Memoir. Neither version corresponds with that of B M Cox in a BGS internal Palaeontology Department report. Nevertheless, for this form I have stuck with the published account (Memoir). I suspect that this unit might have been separated off predominantly because there is a feature-forming cementstone band "near" (or at?) the top at the type locality, or because of some peculiarity of the weathering profile (dependent on all sorts of factors), rather than because of any particularly distinctive lithology - admittedly it is consistently described as "very shelly" but that could also apply to much of the Peterborough Member, when seen fresh in boreholes. So really, I doubt that this unit even merits a separate name, let alone Member status, and I would recommend that it be downgraded [Agreed by AJMB, 21/10/2005]. I think it is a bogus complication of the stratigraphical framework, albeit affecting only two BGS sheets. [M G Sumbler, 25/09/2005.]
Arbitary boundary within upward transition from grey mudstone to predominantly brownish grey, generally more fissile and organic-rich ("bituminous") mudstone of overlying Peterborough Member.
Methley Park Rider Coal (West Yorkshire)
MPRC
Millstone Point Sandstone Member
MPS
Conformably overlies the Laggantuin Cornstone Member, which comprises sandstone and red-brown silty mudstone in fining-upward cycles with nodules and beds of concretionary limestone. Boundary seen at [NR 9995 4875].
Laggan shoreline of the island of Arran, Scotland.
Mainly white, cross-bedded sandstone with thin beds of red-brown or grey mudstone (BGS, 1987).
From about 150 to 200m
Not seen, but is interpreted to be either faulted or unconformably overlain by grey mudstones with plant remains of the Laggan Cottage Mudstone of the Strathclyde Group.
Maiden Pap Sandstone Formation
MPSA
Unconformable on the Breamore Mudstone Formation and Ousdale Arkose Formation; basal conglomerate (Little Morven Conglomerate Member) locally developed.
BGS Scotland Sheet 109E (Kildonan).
Sandstone, flaggy, felspathic, red.
Overlain by conglomerate and sandstone of the Morven Conglomerate Formation.
Monks Park Shale Formation
MPSH
Passage from underlying Moor Wood Formation marked by incoming of silty micaceous laminae and thin sandstone beds.
From the area west of Mancetter Quarry, extending northwestwards to just north of Merevale Hall (3072 9490 - 2954 9765).
Grey micaceous shaly mudstones in lower part. Black, locally calcareous and phosphatic mudstones in upper part.
75 to 80m in general. 38m minimum in Merevale No.2 Borehole. 82m minimum in Merevale No.1 Borehole.
At the upper limit of a transition zone of alternating black and greenish grey mudstones, into overlying, predominantly black, Merevale Shales.
Boulby Potash Member
MPT
Martley Quartzite
Meldon Shale And Quartzite Formation
MQF
The lower boundary is taken at the incoming of black mudstones with abundant thin beds and laminae of quartzite above the dark brown hornfelsed mudstones with scattered thin beds and lenses of pale green feldspathic siltstone of the underlying Meldon-Slate-with-Lenticles Formation. The Meldon-Slate-with-Lenticles Formation exhibits early ?D1 isoclines deformed by later more open D2 structures. As the Meldon Shale and Quartzite Formation exhibits only open folds, it is possible that the boundary between the two formations is a thrust. Further investigation is needed.
Mainly limited to the Meldon Anticline of the Okehampton area (SX 59 94), central Devon. Mapped as far west as Launceston (SX 33 84) in thrust slices (BGS 1993) but the status of this crop needs further investigation.
Much of the outcrop occurs in the metamorphic aureole of the Dartmoor Granite with dark brown hornfelsed mudstone. The Formation comprises black shaly mudstones with variably abundant (locally exceeding 50%) thin beds (up to 15cm) and laminae of white and reddish brown quartzite. Radiolaria are abundant in the quartzites in the upper part of the Formation. A 26 to 61m-thick unit of thin-bedded to massive, locally cross bedded "keratophyric" tuffs and agglomerates is present in the upper part of the Formation.
126 to 161m
The upper boundary is taken at the incoming of internally structureless black argillaceous limestone beds, with subordinate black cherts and siliceous mudstones and mudstones of the overlying Teign Chert Formation above the thin-bedded mudstones and quartzites of the Meldon Shale and Quartzite Formation.
Archaeological Raised Ground (Undivided)
MQU
Melbourn Rock Member
Upper Cretaceous, Cenomanian to Turonian. Metoicoceras geslinianum, Neocardioceras juddi and basal Mytiloides spp. zones.
Conformable on the highest marl seam of the Plenus Marls Member. This is the Foyle Marl of Mortimore (1986).
Known throughout the Southern and Transitional provinces and forms the most readily identifiable geomorphological features in unexposed ground.
Hard to very hard off-white, blocky fractured chalk with numerous nodular chalk beds and thin anastomosing marls.
About 3m in the classic Chiltern area but noted in the Hitchin Memoir to be between 2 and 7m (Hopson et al., 1996). A range of 2.7 to 4m is given in Mortimore (1986).
Conformable but difficult to place in the `Transitional? Province where it is usually considered to be at a horizon of less hard flaggy chalks with significant anastomosing marls. This is probably equivalent to the Meads Marls sequence of the Southern Province and Mortimore (1986) places the boundary at the Meads Marl 1 in Sussex.
Marlstone Rock Formation
MRB
At downward change to mudstone/siltstone of the Dyrham Formation, or (in East Midlands Shelf north) mudstone of Charmouth Mudstone Formation; base typically erosive and conglomeratic. Locally may rest on a sandstone bed at the top of the Dyrham Formation, which it may be impractical to map separately from the Marlstone Rock.
East Midlands Shelf and Worcester Basin (Mendip to Market Weighton).
Sandy, shell-fragmental and ooidal ferruginous limestone interbedded with ferruginous calcareous sandstone, and generally subordinate ferruginous mudstone beds. Locally any of these lithologies may pass by increase in iron content into generally ooidal ironstone, and in places any of these may dominate. The iron content (as ooids, altered shell material or in the groundmass) is berthierine (dark green iron-rich layered silicate formed in low-oxygen marine conditions), altering to siderite. Fossil content variable throughout but locally abundant especially in limestone beds.
See also the Lexicon entry for the "Marlstone Rock Member (Wessex Basin)" [of the Beacon Limestone Formation] - MRWB.
To about 10m
At upward change to mudstone/nodular limestones of the Whitby Mudstone Formation.
Middle Rigfoot Coal
MRC
March Gravel
MRCG
Gravel; beach deposit; possibly Ipswichian in age. [Generic description: 1:50 k map margins].
Main Rider Coal (South Derbyshire)
MRCO
Land Raising Mine Fill (Colliery)
MRCY
Minera Formation
MRF
Base of the lowest, laterally extensive and mappable sandstone above the Cefn Mawr Limestone Formation, but diachronous as the formation passes laterally into the Cefn Mawr Limestone Formation in North Flintshire.
Northeast Wales between Oswestry [SJ2825] and Halkyn Mountain [SJ1970]
Interbedded limestones and calcareous sandstones. Limestone components compare with those of the underlying Cefn Mawr Limestone Formation and include both thick-bedded to massive pale grey limestones [packstones and grainstones], and sequences of thinly interbedded dark grey limestone [packstones and wackstones] and mudstone arranged in shoaling upwards cycles with the calcareous sandstones typically forming the upper parts of the cycles. The sandstones include oolitic units composed of radial fibrous ooids with sand-grain cores. Chert beds and nodules are common at some levels, and coral biostromes are present locally. The Minera Formation records late Brigantian, mixed carbonate-siliciclastic shallow marine deposition at a time of increased supply of siliciclastic detritus to the North Wales Dinantian platform. Each cycle represents a shoaling upwards sequence formed in response to transgressive and regressive movements in sea level. The diagnostic calcareous sandstones principally record the progradation of nearshore siliciclastic facies over transgressive off-shore limestone facies. Many regressions culminated in emergence of the platform surface, but, since sandstones commonly occupy the tops of the cycles, calcrete and karstic dissolution features, which are a common feature in the Cefn Mawr Limestone Formation, are only poorly developed in the Minera Formation.
c.50m in the type area, thickening to 180m north of the Bala Lineament.
Top of the highest laterally extensive and mappable limestone beneath thick, sandstone dominated sequences of the Cefn-y-fedw Sandstone Formation.
Moor Grit Member
MRG
Blue Lias Formation (Marginal Facies)
MRGF
Main Ravenhead Coal (South Lancashire)
MRHC
Land Raising Quarry Fill (Hard Rock)
MRHR
Merope Island Beds
MRI
Land Raising Industrial Fill
MRID
Land Raising Inert Fill
MRIT
Mickley Rock
MRK
Mardale Sandstone Formation
MRL
Taken at the abrupt change from silicic tuff and lapilli-tuff of the Whelter Knotts Formation, to generally well bedded volcaniclastic rocks.
Between Ullswater and Haweswater, and Nan Bield Pass to Wet Sleddale, northeastern Lake District.
A mixed succession of predominantly bedded volcaniclastic rocks, comprising detritus mainly of andesitic composition with bedded volcaniclastic sandstone as the main lithofacies, and subsidiary units of volcaniclastic breccia, tuff and lapilli-tuff, of which significant units of volcaniclastic breccia and pyroclastic rocks are given member status, the whole intruded by many contemporaneous andesite sills.
Probably up to 980m, but much faulted and greatly inflated by sills.
Defined by the sharp base of tte Froswick Tuff Formation.
Land Raising Domestic Refuse Fill
MRLA
Marchup Marine Beds
MRM
Land Raising Mine Fill (Metalliferous Mineral)
MRME
Mariner Formation
MRN
Lower boundary is an off-lapping/disconformable boundary with the underlying Shackleton Formation.
A sequence of sandy, silty clays with sand and clay layers interspersed. Pebbly and shelly sequences within the strata. Base of unit is largely silty sand, well sorted but with clayey partings. Unit below is sandy, as is the base of the Mariner Formation - faunal changes indicate boundary is in off-lapping sequence. Upper boundary is also sandy with a very marked erosion surface.
110 metres at Borehole 78/9. Thins to the south and southwest. Thickens to the north. May be largely eroded away in the southern parts of the Norwegian Trench.
Upper boundary is a marked erosion surface underlying the Ferder Formation.
Land Raising Mine Fill (Non-Metalliferous Mineral)
MRNO
Offshore Dumping Grounds
MROF
Marlstone Rock Formation, Whitby Mudstone Formation, Inferior Oolite Group, Great Oolite Group And Oxford Clay Formation (Undifferentiated)
MROX
Land Raising Pit Fill (Superficial Deposit)
MRPI
Mynydd-Rhiw Rhyolitic Tuff Member
MRRT
Overlies mudstones and siltstones with coarse sandstone interbeds.
Pwllheli district, northwest Wales.
Fine-grained, purple weathering, welded rhyolitic tuff.
Overlain by mudstones and siltstones with coarse sandstone interbeds.
Middle Red Sandstone
MRS
Mylor Slate Formation
MRSL
Maucher Sandstone Member
MRSM
Meriden Formation And Tile Hill Mudstone Formation (Undifferentiated)
MRTM
Raised Fill (Undivided)
MRU
Warp Land
MRWA
Marlstone Rock Member (Wessex Basin)
MRWB
See also the Lexicon entry for the "Marlstone Rock Formation" [of the Lias Group] - MRB.
Mythop Halite Member
MSA
Conformable, at the gradational upward transition from structureless reddish brown mudstones (Sidmouth Mudstone Formation, undifferentiated) to the halite-rich, reddish-brown mudstones of the Mythop Halite Member.
Fylde peninsula, Lancashire, and adjacent parts of the East Irish Sea Basin (Jackson et al., 1997).
Mudstone, reddish brown, with abundant halite veins, halite-mudstone rock ("haselgebirge") and common mudstone breccias.
Originally referred to simply as the Mythop Salts, the term was given Formation status by Warrington et al. (1980), and is now retained as a local member within the nationally recognized Sidmouth Mudstone Formation (Howard et al., 2008).
59m to 101m (Wilson and Evans, 1990).
Conformable, at the gradational upward transition from the halite-rich mudstones of the Mythop Halite Member to structureless reddish brown mudstones (Sidmouth Mudstone Formation, undifferentiated).
Strathy Complex
MSC
East boundary - fault. Small fault also approximately coincides with west boundary. Generally grades rapidly into highly migmatitic psammites and semi-pelites.
Quartzose banded gneisses, locally magnetite-rich. Orthopyroxene recorded in parts. Garnets common. Rare semi-pelitic and calc-silicate bands. Geochemically distinct - depleted in K, Rb, Cs, Th, La, B.
Main Sulphur Coal (Coalbrookdale)
MSCC
Mans Coal (Cheadle)
MSCO
Midland Valley Siluro-Devonian Felsic Intrusion Suite [Obsolete Code: Use Mvfei]
MSDFI
Midland Valley Siluro-Devonian Mafic Intrusion Suite [Obsolete Code: Use Mvmai]
MSDMI
Muirkirk Seventeen Fathom Coal (Ayrshire)
MSE
Muirkirk Seven Fathom Coal
MSEV
Meldon Slates-With-Lenticles Formation
MSF
Missenden Fish Beds
MSFB
Muirkirk Seven Foot Coal
MSFC
Millbuie Sandstone Group
MSGR
Drawn at the base of the sandstone of the Millbuie Sandstone Group where it rests conformably upon conglomerate of Devonian age.
Millbuie Moor, Black Isle, Ross-shire.
Red grey and yellow sandstones sometimes lightly friable, and reddish marly clays; included on horizon of Silurian calcareous shale with fossils.
900 metres approx.
The group is unconformably overlain by Pleistocene deposits.
Mesograptus Shales
MSH
Main Shale Bed (Llangollen Area)
MSHA
Middle Shafton Coal (West Yorkshire)
MSHC
Magilligan Sill
MSI
Muirkirk Six Foot Coal
MSIX
Morte Slates Formation
MSL
Moher Shale Member
MSM
Malling Street Marls
MSMA
Marine Sediments, Holocene (Undifferentiated)
MSQH
Marine Sediments, Pleistocene (Undifferentiated)
MSQP
Mountsorrel Complex
MSRL
Not seen; the Complex is intruded into hornfelsed slaty mudrocks believed to be correlatives of the Stockingford Shale Group (Cambrian to Ordovician).
Extends from Brazil Wood northeastwards into Mountsorrel Village.
An association of coarse grained igneous rocks, principally consisting of granodiorite and occurring within a roughly circular intrusive body.
Vertical thickness unknown; the surface outcrops extend over 2.5km, with probable extensions at depth on all sides.
Unconformably overlain by Triassic strata and Quaternary superficial deposits.
Mansfield Red Sandstone
MSRS
Mauchline Sandstone Formation
MSS
Sandstone of the Mauchline Sandstone Formation overlies with apparent conformity tuffs of the Mauchline Volcanic Formation. In the Redcraig Borehole the lower boundary is picked at the top of the uppermost occurrence of conglomeratic sandstone with many large pebbles and blocks, up to 25cm [10 inches], of vesicular and non-vesicular basalt in a sandstone matrix and is considered by Mykura [1965] to be diachronous.
The Mauchline Sandstone Formation is present only within the Permian Mauchline Basin, in the vicinity of Mauchline, Ochiltree and Tarbolton in Ayrshire, southwest Scotland.
Brick red to bright orange sandstone characterised by a predominance of quartz grains of which the larger are wind-rounded and almost free from mica. In the cored Redcraig Borehole (NS42NE/15) thin layers of coarse-grained sandstone alternate with more fine-grained material descibed as "clayey sand". Although dune bedding is characteristic of the Formation this is not seen at the base where it is exposed near Howford Bridge (Weedon and Mykura, 1992; Williamson, 2003, Fig.4.12).
The rocks of the Mauchline Sandstone Formation occupy the centre of the Mauchline Basin and the maximum deposited thickness is not known. However, minimum proven thicknesses are known from boreholes; 229m [700feet] in the Auchinweet Borehole at [NS 4554 2863] and 370m [1130 feet0 in the Middletonhill Borehole two and a half miles east of Tarbolton. A minimum thickness of 311m [948feet] is proven in the Redcraig Borehole.
The Mauchline Sandstone Formation is delimited by erosion; the top of the Formation is not seen. There is no evidence for any previous presence of younger overlying strata.
Mashie Semipelite Formation
MSSP
Tectonic contact with the Glen Banchor Succession.
In Spey Valley adjacent to Laggan Village in Dalwhinnie district. [Scotland sheet 63E].
Semipelite, schistose to gneissose.
Unknown. May be up to 100m
Gradational boundary into the Fara Psammite Formation placed where psammite becomes the dominant lithology.
Monograptus Sedgwickii Shale Member
MSW
Mansfield White Sandstone
MSWS
Maudsyke Till Member
MSYT
Generally a sharp, undulating to uneven, unconformable contact with bedrock, but locally a sharp, probably planar contact with extremely stiff, reddish brown, gravelly sandy clay diamicton of the Drigg Till Formation.
At depth in Lower Wasdale, western Lake District, Cumbria.
Extremely dense, moderate to pale reddish brown (Munsell Soil) cobbly sandy clay diamicton, mainly matrix-supported, with clasts predominantly of Borrowdale Volcanic Group lithologies (rhyolite, welded tuff, slate).
Sharp, draped, unconformable contact with overlying thinly laminated (varved) silt and clay of the Stubble Green Silt Member of the Carleton Silt Formation.
Mersey Valley Formation
MSYVA
Probably unconformable, irregular and in places strongly incised into lithologically variable sediments of the Caledonia and Albion Glacigenic groups or into bedrock.
Cheshire and south Lancashire within the river valley and tributaries of the River Mersey west of the Peak District.
Probably silt, sand and clay (with peat in places) Alluvial sediments grading to gravel at base. River terraces are composed of gravel or gravelly sand.
Generally less than 10m but locally in excess of 20m.
At the ground surface or unconformable below artificial deposits.
Mam Tor Beds
A sharp upward change in a conformable succession from predominatly grey mudstone to sandstone. The base of the first sandstone bed above the Reticuloceras reticulatum Marine Band.
Mam Tor, Hope Valley, upper Derwent Valley and Woolands Valley.
Thinly to medium-bedded, upward-fining turbiditic cycles of grey-brown, very fine-to fine-grained, massive and laminated, micaceous sandstone overlain by grey, laminated siltstone and dark grey mudstone; bases of sandstones show a variety of sole marks and some trace fossils
Up to 135 m thick.
A sharp upward change in a conformable succession from sandstone to predominantly mudstone. The top of the last fine-grained sandstone bed immediately below the first massive, coarse-grained sandstone of the overlying Shale Grit.
Metal Coal (Cumbria)
MTAL
Mary Tavy Beds
MTB
Mickley Thin Coal (Nottingham And Derby)
MTC
Muirkirk Three Dirt Coal (Ayrshire)
MTD
Muirkirk Ten Fathom Coal (Ayrshire)
MTE
Muirkirk Twenty Fathom Coal (Ayrshire)
MTF
Muirkirk Three Foot Coal
MTFC
Mynydd Tir-Y-Cwmwd Microgranite
MTGM
Porphyritic microgranite composed of perthite phenocrysts with lesser plagioclase and minor green biotite in an equigranular, unfoliated, granophyric groundmass
Middle Thick Coal (South Staffordshire)
MTHC
Mickley Thin Sill
MTHS
Marsh Till
MTIL
Used informally, in the sense of Straw (1964), on the 1999 edition of the Louth (103) sheet, to distinguish Devensian tills from older, pre-Devensian, tills.
Muirkirk Thirty Inch Coal
MTIP
Mickley Thick Coal (South Yorkshire)
MTKC
Martin Limestone Formation
MTL
Tournaisian to late Chadian
Not exposed. Taken where limestone becomes dominant over shale (Rose and Dunham, 1977, p.28). In practice, taken in boreholes at first significant shale parting, beds below there being assigned to `Basement Beds', now renamed `Low Furness Basal Formation'.
South Cumbria, West Cumbria.
Mainly carbonate mudstones, but with significant grainstones, locally cross-bedded, and oolites in upper part; ranges from peritidal to marine. Extensively dolomitized.
Base of "Red Hill Oolite", now redefined as the Red Hill Limestone Formation.
Maltby Marine Band
MTMB
Meadowtown Formation
MTN
Overlies Betton Shale Formation.
Variable sequence of calcareous sandstones and shales.
Underlies Rorrington Shale Formation.
Martin Sand And Gravel Member
MTNSG
Middle Pleistocene (MI Stage 12 or 10).
Unconformable, commonly channelled base, resting on Anglian Wragby Till (Lowestoft Formation) or (locally) Middle to Upper Jurassic bedrock.
Distributed mainly along the southwest side of the present Witham valley from Heighington [TF 04 69] to Billinghay [TF 14 55]; less well developed on the east side of the Witham valley (where it might be represented by the Tattershall Airfield Member (see Reference Section); distribution elsewhere uncertain; that indicated by Straw, 1958, Figure 4, is as yet unconfirmed. (BGS Sheets 114, 115 and ?102 and ?128).
Predominantly cold-phase sands and gravels that underlie the Martin Terrace of the lower Witham valley. At surface, dominated by rounded pebbles of "Bunter" quartz/quartzite with subordinate subangular flint, etc. Terrace preserved as extensive dissected remnants at c.+18m in the Type Area, i.e about 16m above the Witham Floodplain there. Correlated with the Eagle Moor Sand and Gravel west of the Lincoln Gap.
0 to c.7m
Malton Oolite Member
MTOL
Moreton Member
MTON
Sand with gravel layers, sandy clay and sandy gravel; quartz/quartzite-rock gravels. [Geol Soc Lond Special Publication Report 4, 2nd edition].
Muirkirk Thirty Six Fathom Coal (Ayrshire)
MTS
Marton Scars Limestone
MTSL
Meall An Tarmachain Summit Quartz-Gabbro Intrusion
MTSQG
Muirkirk Twenty Three Fathom Coal (Ayrshire)
MTT
Moine Thrust Zone Mylonites Complex
MTZM
Protolith Archaean to Cambrian. Formation of mylonite Silurian (c.430 to 420Ma).
Melau Formation
Conformably overlies the volcaniclastic sandstones of the Allt Lwyd Formation and passes laterally into the undivided siltstones and mudstones of the Aran Volcanic Group; locally, conformably overlies the felsic tuffs of the Offrwm Volcanic Formation.
Harlech and Bala districts, North Wales.
Mafic agglomeratic tuff, tuffite and thin mafic pillowed lava flows with interbedded silty mudstones.
To 220m
Conformably overlain by silty mudstones of the Aran Volcanic Group over much of the Harlech district, but locally overstepped by the Benglog Formation with apparent unconformity/disconformity.
Murchisoni Beds
MUB
Dark grey mudstones, locally with interbedded tuffs.
Melau Formation And Brithion Formation (Undifferentiated)
MUBR
Mull Central Complex
MUCC
Middle Chalk Formation And Upper Chalk Formation (Undifferentiated) [Terms Remain In Informal Use But Are Generally Regarded As Obsolete]
MUCK
Middle Crafnant Volcanic Formation And Upper Crafnant Volcanic Formation (Undifferentiated)
MUCV
Musselburgh Diamond Coal
MUD
Middle And Upper Devonian Limestones
MUDL
Musselburgh Fifteen Foot Coal
MUFF
Musselband Ironstone
MUI
Muirhouse Marine Band
MUIR
Musselburgh Jewel Coal
MUJ
Murrayshall Limestone
MUL
In the Stirling area for example where its base is taken as the base of the Lower Limestone Formation.
Mull Central Lavas Formation
MULC
Mull Dyke-Swarm
MULD
Mulderie Intrusion
MULDI
Mulgrave Shale Member
MULG
Mull Lava Group
MULL
Mull Plateau Lavas Formation
MULP
Mullynagowan Sandstone Member
MULY
Abrupt contact - possibly disconformable on grainstones of Newtownbutler Limestone Member at top of Ballyshannon Limestone Formation.
Newtownbutler area of south Co. Fermanagh, Northern Ireland.
Sandstone, bedded, pale to dark grey, fine- to medium-grained suborkose, bioturbated, calcareous, silty.
About 2m
At rapid change from calcareous sandstones of this member, to dark grey argillaceous limestones of the parent Bundoran Shale Formation.
Mullach Nan Coirean Pluton
MUNC
Musselburgh Nine Foot Coal
MUNF
Muness Phyllites Formation
MUNP
Mupe Member
MUP
South Dorset area, covered by British Geological Survey 1:50 000 scale Sheets 341, 342 and 343.
Across Dorset, in the lower part, comprises white-weathering marls and micrites containing algal laminations and some evaporitic material, with interbedded carbonaceous mudstones (caps, dirt beds) and localised brecciated limestone pockets (broken beds). Limestones, particularly in the upper part of the member (lower part of Cypris Freestones), are commonly Ostracod-rich micrites and sparites. Detrital quartz is rare. The Ostracod-rich limestones contain abundant parallel laminations and ripples, particularly higher in the member. The member may show a crude coarsening-upwards sequence, for example, at Stair Hole, Lulworth and Worbarrow Tout.
11m in west Dorset, increasing steadily to 16m in east. Anomalously thin at Stair Hole (7m).
Last occurrence of thickly bedded, Ostracod-rich limestone (Cypris Freestones) beneath Ridgeway Member mudstones.
Musselburgh Rough Coal
MUR
Mupe Member And Ridgeway Member (Undifferentiated)
MURI
Muckle Roe Intrusion
MURO
Musselburgh Splint Coal (Midlothian)
MUS
Muckross Sandstone Formation
MUSA
Musters Coal (Nottingham)
MUSCO
Musselburgh Seven Foot Coal
MUSF
Murlough Shale Formation
MUSH
Overlying green tuffaceous mudstones and vitric tuffs of Glenshesk Tuff Formation.
Shale, coal, sandy limestone, seatearth
Overlain by red sandstones and thin siltstones of Ballyvoy Sandstone Formation.
Multeadh Sandstone Member
MUSM
Mullach Sgar Dolerite-Microgranite Intrusion-Swarm
MUSR
Murton Formation
MUTN
Occurs within the Cross Fell inlier as a narrow strip almost 11km long between Hilton Beck and Knock Ore Gill, bounded to the east by the sub-Carboniferous unconformity and to the west by the Dufton Pike and Swindale Beck faults.
Pale to dark grey siltstones with subordinate, interbedded, pale grey sandstone. Many exposures show complex polyphase folding with abundant sheared folds and shear planes suggestive of slumping. The sequence is also folded tectonically.
Not known because neither base nor top of the Formation is exposed.
The upper contact with the Kirkland Formation is faulted.
Muir's Vein
MUV
Moelwyn Volcanic Formation
Caradoc (pre-Costonian).
Conformable within silty mudstones of the undivided Nant Ffrancon Subgroup.
Volcaniclastic debris-flow deposits, felsic tuffs and tuffites.
Upper up to 200mwith a Lower and Upper Member each up to 100m
Malverns Complex
MVC
Not seen, apart from local thrust slices in tectonic contact with Palaezoic cover rocks.
Malvern Hills, Hereford and Worcester; small outliers at Cowleigh Park and Martley.
Mainly diorite, tonalite and hybridised and sheared derivatives of these protoliths (Lambert and Holland, 1971; Barclay, W J, Ambrose, K, Chadwick, R A and Pharoah, T C. 1997].
Unconformity or faulted contact with Palaeozoic cover rocks.
Morven-Cabrach Pluton
MVCA
Merthyr Vein Coal (South Wales)
MVCO
Montrose Volcanic Formation
MVF
Conformable, diachronous to some extent. Lower boundary at the base of the base of the lowest lava of the thick succession of andesitic lavas that separate the conglomerate and sandstone of the Deep Conglomerate Formation (above) and the Catterline Conglomerate Formation (below) in the area to the north of the River North Esk. Oversteps Barras Conglomerate Member, St John's Knap Sandstone Member and the Catterline Conglomerate Formation from north to south.
North-eastern Midland Valley, between Stonehaven and Montrose.
Andesite, basaltic andesite, other andesitic rocks, volcaniclastic conglomerate and sandstone.
Up to 560 m thick in the type area, thinning out towards the west and south-west where it interfingers with lithic and volcaniclastic sandstone.
At the eroded top of the thick succession of andesitic lavas, in the area to the north of the River North Esk, where these are conformably and somewhat diachronously overlain by the clast-supported Deep Conglomerate Formation, or cross-bedded sandstone of the Scone Sandstone Formation.
Biglees Hill Sill
MVFBH
Caldron Hill Sill
MVFCH
Craigmuschat Sill
MVFCM
Clyde Plateau Subsuite (Of Mclfs)
MVFCP
Midland Valley Siluro-Devonian Felsic Intrusion Suite
MVFEI
East Lothian Subsuite (Of Mclfs)
MVFEL
Glentane Hill Sill
MVFGL
Goldenberry Hill Sill
MVFGO
High Corby Knowe Sill
MVFHC
Rye Water Head Sills
MVFRW
Southern Midland Valley Felsite Sills
MVFSI
Tweed Subsuite (Of Mclfs)
MVFTW
Midland Valley Glacigenic Subgroup
MVG
Sharp, unconformable contact with bedrock. Pre-Ipswichian Quaternary deposits are not proven within the Midland Valley of Scotland.
The Midland Valley of Scotland (most of Strathclyde, Stirlingshire, the Lothians and Fife) excluding Arran and the Strathmore Basin south of the Highland Boundary Fault (Aberfoyle, Strathallan and Strathmore districts). Approximately bounded to the south by the line of the Southern Upland Fault. Units of the subgroup may occur locally beyond these geographical boundaries and beyond the approximate surface boundaries with adjacent glacigenic subgroups. Units may also extend offshore (see stratotype classification).
Suite of glacial, glaciofluvial and glaciolacustrine deposits including sand diamictons (till), sand, gravel, silt and clay. The sediments were deposited by or are the deglaciation products of ice that eminated from the western Grampian Highlands and streamed generally eastwards across the Midland Valley of Scotland. The deposits contain clasts derived predominantly from Carboniferous to Permian sedimentary rocks (sandstone, siltstone, mudstone) and volcanic and intrusive rocks (basalt, microdiorite) of the Midland Valley of Scotland with varying but minor proportions of Dalradian metasedimentary rocks (metasandstone, metapelite) and Caledonian igneous rocks (granite, granodiorite, gabbro). In contrast to the Mearns Glacigenic Subgroup, with red tills dominated by clasts and matrix of Devonian origin of the Strathmore Basin, the Midland Valley Glacigenic Subgroup tills have characteristically grey matrices. However, locally they can be red where the diamictons are derived from red or reddened measures (e.g. Upper Coal Measures, Permian strata, small outcrops of Devonian rocks).
Unconformable contact with unit of the Britannia Catchments Group (Forth Catchments Subgroup, Tay Catchments Subgroup, Clyde Catchments Subgroup) and the British Coastal Deposits Group.
Mauchline Volcanic Formation
MVL
Plant remains in a bed of fine-grained tuffaceous sediment between two lava flows are probably of earliest Permian age (Wagner, 1983). This is supported by radiometric dates obtained from the Mauchline Volcanic Formation and associated volcanic necks that are around 290 Ma, just younger than the currently accepted date for the Carboniferous-Permian boundary of 292 Ma. Previous interpretation of the plant materials was used to suggest an uppermost Carboniferous age for the Formation (Mykura, 1965, 1967).
The basal strata, commonly tuff or sandstone, are between 3-88m thick and conformably overlie reddened sedimentary rocks of the Upper Coal Measures but with no marked discordance (Williamson, 2003). The boundary is taken at the lowest occurrence of either bright red sandstone with some wind-rounded grains or a sedimentory rock containing lava fragments. Lithologies in the basal strata are varied and can include siltstone, sandstone, mudstone, marly tuff and marl (Mykura, 1967).
The Mauchline Volcanic Formation is present only within the Permian Mauchline Basin, in the vicinity of Mauchline, Ochiltree and Tarbolton in Ayrshire, southwest Scotland.
Basic lavas with intercalated tuff, tuff breccia, agglomerate, sandstone and mudstone. The lavas are mainly olivine-microphyric and olivine-clinopyroxene-microphyric basalt with some nepheline basanities, analcime basanities and olivine nephelinities (Eyles et al., 1949). Most lava flows appear to be altered and colour varies between grey and purplish-red (Williamson, 2003).
The rocks of the Mauchline Volcanic Formation crop out around the Mauchline Basin with thicknesses known from boreholes; between 98m and 180m [300 to 550 feet] along the western and southwestern margins of the basin, generally greater than 197m [600 feet] in the east and northeast. The maximum thickness recovered is 252m [770 feet] in the Redcraig Borehole towards the northern margin of the basin.
Tuff and basalt lava of the Mauchline Volcanic Formation are interbedded with conglomerate of lava clasts and red sandstone towards the top of the Formation and overlain conformably by the Mauchline Sandstone Formation. The boundary is picked in borehole core at the top of the uppermost occurrence of conglomeratic sandstone with many large pebbles and blocks, up to 25cm [10 inches], of vesicular and non-vesicular basalt in a sandstone matrix and is considered by Mykura [1965] to be diachronous.
Midland Valley Siluro-Devonian Mafic Intrusion Suite
MVMAI
Midland Valley Namurian To Westphalian Plugs And Vents Suite
MVNWV
Mealfuarvonie Sandstone Member
MVS
Midland Valley Sill-Complex
MVSC
Meadow View Sand And Gravel Member
MVSG
Devensian (probably the early part of the Late Devensian).
Unconformable on pre-Quarternary bedrock.
Sand and gravel forming part of the infill of the buried valleys of the Ehen and Calder. Clasts are generally of Borrowdale Volcanic Group rocks, granite and olive brown ?Latterbarrow Sandstone.
Typically between 2.7 and 5.0m thick.
Overlain by gravelly diamictons of the Low Wath Till Member of the Seascale Glacigenic Formation.
Merevale Shale Formation
MVSH
Gradational passage down to Monks Park Shale Formation, by increase in content of black carbonaceous mudstone.
Extends from Outwoods north-westwards to just north-east of Woodlands Farm (SP 2978 9620-2849 9870).
Greyish green to dark grey mudstone with pale buff dolomitic bands and lenticles. Becomes darker and more carbonaceous downwards.
About 90m in general area. About 5.05m true thickness in Merevale No.2 Borehole.
Erosional unconformity. Overstepped by younger arenaceous beds.
Maybole-Straiton-Dalmellington Mafic Intrusions
MVSMI
Maentwrog Formation
Late St David?s to Merioneth.
Underlain by black mudstones of the Clogau Formation. Sharp contact, possible a non-sequence or disconformity.
Northern, eastern and southern flanks of the Harlech Dome.
Interbedded mudstones, coarse-grained sandstones and fine-grained turbiditic sandstones. The upper part of the Formation is dominated by mudstones.
Locally the Vigra and Penrhos members are distinguished (Pratt, Woodhall and Howells, 1995).
Unknown in detail, 500 to1200m
Conformable and gradational up into sandstones and mudstones of the Ffestiniog Flags Formation, with change in mudstone colour from pale to dark grey.
Micklewood Beds
MWB
Mine Waste Tip (Colliery)
MWCY
Moor Wood Sandstone Formation
MWF
Transition, with decreasing content of arenaceous beds, from dark mudstones of the underlying Outwoods Formation.
From Purley Chase Golf Course, extending northwestwards to just northeast of Merevale Hall (SP 3093 9451-2972 9764).
Massive to convoluted sandstone and siltstone, with interbedded wavy-bedded micaceous and shaly mudstone.
c. 15m (15.25m in reference section)
Upwards transition into grey micaceous mudstone of Monks Park Formation.
Mawddach Group
MWG
Base of the Clogau Formation as originally proposed, but under discussion.
Harlech Dome and southern Snowdonia.
Mudstone (including dark grey of black mudstone), siltstone and sandstone. For details of specific lithologies refer to entries for the Dol-cyn-Afon, Dolgellau, Ffestiniog Flags, Maentwrog and Clogau formations.
Top of the Dol-cyn-Afon Formation.
Meadow House Clay Member
MWHO
Late Devensian (Lateglacial - older than 14,623 C14 years BP).
At its type section it overlies the Lowca Till Member of the Seascale Glacigenic Formation (18.7m depth in Nirex Borehole QBH19 [BGS Registered borehole NX91SE251], as defined in Auton and Merritt, 2004).
1:50k Sheet 28 (Whitehaven) beneath the alluvium of the Pow Beck, but can also be applied to any similar Late Devensian varved sequences found in boreholes along the western Cumbrian coast.
Graded finely laminated silt-clay varves, soft to firm; finely colour-banded, yellowish red, reddish brown and dark greyish brown.
As now defined this unit equates with the lower 5.1m of the Meadow House Clay Member of the Gosforth Glacigenic Formation as defined in Norex Geoscience Report SA/97/045 (Issue 2).
5.1m exposed at type section.
Overlain with a gradational contact by the Fern Bank Silt Member of the Hall Carleton Formation, 13.68m depth in Nirex borehole QBH 19 (as defined in Auton and Merritt, 2004). The Fern Bank Silt Member is only weakly laminated and contains fossil assemblages of marine microplankton.
Quarry Waste Tip (Hard Rock)
MWHR
Industrial Waste Tip
MWID
Inert Waste Tip
MWIT
Maidenway Limestone
MWL
White Lyne valley and adjacent areas, Cumbria.
Massive grey limestone, locally dolomitic or sandy, with interleaved slaley mudstones.
Landfill Waste Tip (Domestic Refuse)
MWLA
Muirkirk Wee Limestone
MWLS
Mwmffri Sandstone Member
MWM
Mine Waste Tip (Metalliferous Mineral)
MWME
Mine Waste Tip (Non-Metalliferous Mineral)
MWNO
Pit Waste Tip (Superficial Deposits)
MWPI
Marine Warp And Sand
MWS
Artificially induced marine deposits and sand. [Generic description: 'TMOS' Procedures].
Mwmffri Sandstone Member [Obsolete Code: Use Mwm]
MWSA
Note: This entry and Code were generated in error due to incorrect spelling of the Unit name (now corrected). The associated Code [MWSA] should therefore NOT be used, but the Code MWM (which has precedence) should be used instead.
Mount Wise Shell Bed
MWSB
Waste Tip (Undivided)
MWU
Manx Glacigenic Subgroup
MXGL
Mainly the central uplands of the Isle of Man, but also present on low ground around the coast. (50k sheets,36, 45, 46, 56, 57).
Head, scree and slope wash deposits, covering upland areas (Snaefell Formation). These include boulder scree, and some "redeposited" gravels and diamictons.
The ground surface or overlain by Holocene sediments.
Mexborough Rock
MXR
Mytton Flags Formation
Mynydd Bach Formation
MYBA
Mickley Coal (Derbyshire)
MYCO
Mydrim Limestone Formation
MYD
Melby Sandstone Formation
MYF
Latest Eifelian to Givetian.
On the Walls Peninsula, faulted contact along the Melby Fault, against the Sandness Formation. However, basal relationships are complex and the sandstone may locally be disconformable on the lower leaf of the Melby Rhyolite Member [see also boundary definitions of Papa Stour Volcanic Formation].
Northwest portion of the Walls Peninsula, Mainland Shetland, northwest of Lerwick. May also extend onto the offshore islands of Foula (but may not be the same unit) and Papa Stour, c.40km northwest of Lerwick.
Sandstone, siltstone and mudstone, generally flaggy, buff and red; two pale grey siltstone units (Melby Fish Beds) near the base of the sequence.
c.760m on the Walls Peninsula.
Highest unit in the local sequence: top contact not preserved.
Moel-Y-Gest Beds
MYG
Mynydd-Y-Gareg Limestone
MYGL
Maydown Limestone Formation
MYLF
Mcgildowneys Marine Band
MYMB
Mynydd Myddfai Sandstone Formation
MYMY
Mynyddislwyn Coal (South Wales)
MYNC
Myoch Formation
MYO
Conformably overlies the Penwhapple Formation.
Red and green silty mudstones with sandstone and siltstone lenses.
30 m thick.
Conformably overlain by the Mill Formation.
Methley Park Coal (West Yorkshire)
MYPC
Mynheer Coal (Fife)
MYR
Melby Rhyolite Member
MYRH
Latest Eifelian.
The lower unit displays a faulted contact along the Melby Fault, against the Sandness Formation of the Lower ORS on the Walls Peninsula. The upper unit displays a highly irregular contact with the 'blocks and tongues' of rhyolite that penetrated the underlying grey, micaceous, ripple laminated sandstone with rhyolite clasts, of the Melby Sandstone Formation, to a distance of about 60 cm whilst it was unconsolidated sediment.
The northern portion of the Walls Peninsula, Mainland Shetland, about 32 km NW of Lerwick, BGS Scotland Sheet 127 Western Shetland.
Silicified rhyolite or ignimbrite, typically brecciated, purple when fresh, pale pink, greenish or brown mottled on weathered surfaces. The rock contains sparse euhedral phenocrysts of feldspar and locally exhibits well developed flow banding. Vesicles lined with quartz and calcite are commonly present in the upper 1.5m. The unit occurs as two lenticular bodies: one interstratified within the lower part of the Melby Sandstone Formation, and the second at the base of the Melby Sandstone Fm, at the NE end of its outcrop.
The upper unit is at least 70 m thick, whereas mapping suggests that the lower unit is at least up to 150 m thick.
The upper unit shows a disconformable irregular brecciated contact against fine-to medium-grained planar bedded pink sandstone, with partings of flaggy sandstone and siltstone and containing scattered rhyolite clasts of the Melby Sandstone Formation. The contact with the lower unit is not exposed but mapping suggests that it is disconformably overlain by similar sediments of the Melby Sandstone Formation to those overlying the upper unit.
Melbury Sandstone Member
MYS
Upper Cretaceous, Cenomanian. Mantelliceras mantelli Zone, Neostlingoceras carcitanense Subzone.
Above the highest bed of chert of the Boyne Hollow Chert.
Known for Dorset and Wiltshire. From Iwerne Courtenay (ST 860 130) northwards towards the limit of the Shaftesbury sheet (313). Northwards, beyond the mapped area, the Melbury Sandstone probably continues as the Rye Hill Sand and, farther north, as the Warminster Greensand.
Richly fossiliferous, glauconitic, fine-grained sand and weakly cemented sandstone.
0-6m (1.22m at type locality)
The incoming of marl is taken as the basal bed of the overlying remainder of the West Melbury Marly Chalk Formation. This can frequently be a minor erosion surface.
Mundesley Sand Member
MYSA
Erosional lower contact with the chalky diamicton of the Walcott Till Member. The upper surface of the latter is slightly undulatory in form with the topographic lows filled by chalk-rich gravel before passing up into the silty sands of the Mundesley Sand Member.
The Mundesley Sand Member crops out between Bacton and Sidestrand.
Dull yellow-orange to dull yellowish brown stratified silty sands with a high abundance of detrital chalk in the lower horizons, and opaque heavy minerals. Typical bedding structures include planar cross-bedding, horizontal bedding, massive beds, climbing ripples and convolute bedding.
The Mundesley Sand Member reaches a maximum observed thickness of 9m in its stratotype area.
The upper boundary of the Mundesley Sand Member is variable. Where the deposit is overlain by the Bacton Green Till, such as between Bacton and Mundesley, the contact is gradational and marked by a zone of horizontally-bedded sands and diamicton. Alternatively, where the Ivy Farm Laminated Silt Member overlies the Mundesley Sand Member, the boundary is unconformable (?tectonic).
Mydrim Shales Formation
MYSH
Mynydd-Tarw Group
MYT
Drawn at base of shale and mudstone with ash and grit of the Mynydd-Tarw Group where it rests conformably on the Gardden-Fawr Ash of the Gwern-Feifod Group.
Clwyd, Wales.
Blue-grey, cleaved mudstones and shales with silt or grit laminae, sporadic ashes or ashy grit as well as dirty blue grits or sandstones.
Drawn at conformable upward passage from flaggy mudstones and shales of the Mynydd-Tarw Group to the Cwm-Clwyd Ash of the Allt-Tair-Ffynnon Beds.
Millyeat Member
MYTB
Top of highest major channel sandstone unit in the Bransty Cliff Sandstone Member.
Purple/red mudstone, sandstone, marl and thin coals with thin beds of limestone with Spirobis sp.
180m maximum
Basal Permian unconformity.
Mynydd-Tarw Tuff Member
MYTT
Underlain by mudstones of the Llangynog Formation.
Central Berwyn Hills of Oswestry (137) and Bala (136).
Massive, pale grey, fine-grained tuff.
c. 3.5m at Blaen-y-cwm, thins eastward (Wedd et al., 1929).
Overlain by mudstones of the Llangynog Formation.
Mynytho Volcanic Group
MYV
Maize Beck Limestone
MZBL
Dark argillaceous limestone.
c.1m
Monian Supergroup
No. 0 Marine Band
No.0 Marine Band Limestone
N0LS
No.1 Marine Band
No.10 Coal (Somerset)
N10C
No.1 Llantwit Coal
N1LC
No.1 Marine Band Limestone
N1LS
No.1 Rhondda Coal (South Wales)
N1RC
No.1 Rhondda Rider Coal (South Wales)
N1RR
No.2 Marine Band
No.2 Llantwit Coal
N2LC
No.2 Marine Band Limestone
N2LS
No.2 Rhondda Coal (South Wales)
N2RC
No.3 Marine Band 'Group'
No.3 Llantwit Coal
N3LC
No.3 Rhondda Coal (South Wales)
N3RC
No.4 Marine Band 'Group'
No.5 Marine Band 'Group'
No.6 Marine Band 'Group'
Nameless Coal (Douglas)
New Aberdour Siltstone Formation
NAB
Nant Brianne Formation
NABR
Naburn Sand Member
NABS
Commonly sharply erosive, and characterised by a thin (<10mm) bed of coarse sand with rare gravel directly overlying mottled reddish brown and grey stiff laminated clay of the Hemingbrough Glaciolacustrine Formation
The Naburn Sand Member is distributed radially from Fulford, south of York to the east where it pinches out to the west of Elvington. The northern limit is marked by the York Moraine Member to the south of York. The southern limit is marked by the southwest to northeast trending Escrick Moraine Member [SE 584 407].
Mottled brownish yellow, yellowish brown, brown and grey silty, sporadically clayey fine to coarse sand. Characteristically poorly sorted and locally laminated. Grains dominated by quartz with sporadic plagioclase feldspar. Commonly shows a fining upwards sequence from lower boundary with underlying laminated clay.
Varies from <0.5m to 2.5m at Naburn flood alleviation pit [SE 59840 45280].
This unit is typically exposed at surface, or the upper boundary is represented by a gradational contact with fine-grained aeolian sand of the Sutton Sand Formation. This unit is inferred to thin and pinch out eastwards to the west of Elvington.
Nant Achlas Silstones
NAC
Nant Cerdin Tuff Member
NACE
New Accommodation Coal (South Lancashire)
NACO
Niveo-Aeolian Deposits
NAEOL
Navigation Flint
NAFL
Nant Hir Formation
NAH
Not defined. NOTE: Details as for Nant-Hir Shales. Name only modified.
Navigation Hardgrounds
NAHG
Navigation Marls (One)
NAMA1
Navigation Marls (Two)
NAMA2
Nanhoron Suite
NAN
Nansen Formation
NANN
Nant Coal (North Wales)
NANT
Napton Coal
NAP
Nar Valley Formation
NARC
Unconformable on Mid Pleistocene glacial deposits, and on bedrock.
The entire catchment of the Nar River and tributaries, in Norfolk.
The Nar Valley Formation encompasses the fluvial, lacustrine, organic and marine deposits of the Nar River and its tributaries. Floodplain alluvium comprises soft clay, silts and fine sands, with bodies of peat, overlying sands and gravels. River terrace deposits (Wormegay Member, Pentney Member and Marham Member of Lewis, 1999) comprise sands, gravelly sands and gravels, with the pebbles dominantly of angular to sub-rounded flint, and Chalk. Marine deposits ("Nar Valley Clay") comprise blue-grey finely laminated shelly silty clays; the underlying Nar Valley Freshwater Bed comprises grey fine-grained silty sands and silts and a compressed wood peat.
The Nar Valley Formation as defined here is taken to include the Nar Member, Wormegay Member, Pentney Priory Bed, Pentney Member and Marham Member as included in the Nar Valley Formation of Lewis (1999). The Nar Member includes both the marine Nar Valley Clay and the Nar Valley Freshwater Bed. Note that the Tottenhill Member of the Nar Valley Formation of Lewis (1999) is transferred to the Britons Lane Formation.
To c.5m
New Abbey Till Member
NATI
North Atlantic Igneous Superprovince
NATIG
Navigation Coal (Kilsyth)
NAV
Navan Group
NAVN
Nayley Coal (South Lancashire)
NAYC
Neilston Blackband Ironstone
NBBI
New Cumnock Blackband Coal (South Ayrshire)
NBC
Nettlebed Formation
NBED
Nab End Sandstone
NBES
West Yorkshire area [Nab End, near Mytholmroyd, Yorkshire].
Fine- and medium-grained sandstone, flaggy in its lower part and "gritty" above
Noblehouse Lava Member
NBL
Prestwick-Mauchline Sill-Complex
NBPSP
North Berwick Pyroclastic Member
NBPY
The base is conformable on the underlying Ballagan Formation (Strathclyde Group). The change is transitional by interbedding of tuff and lapilli tuff into the underlying siliciclastic and carbonate rocks.
East Lothian outcrop of the Garleton Hills Volcanic Formation around North Berwick, East Linton, Garleton Hills, Stenton and in the subcrop farther west in the BGS Spilmersford Borehole near Pencaitland, and south to the Lammemuir Fault.
The North Berwick Pyroclastic Member consists of green (lower part in the north) and red coloured (all in the south) tuffs and lapilli-tuffs and agglomerate locally with sedimentary intercalations of a lacustrine limestone, the Sunnyside Limestone, up to 2.9m thick. These are commonly well bedded and waterlain and interbedded with volcaniclastic sedimentary rocks including thin dolostones and siliciclastic mudstones with sandstones showing ripplemarks.
0 to 220m
The Member is overlain by the basaltic flows of the East Linton Lava Member to south of the Dunbar-Gifford Fault where the somewhat younger siliciclastic Gullane Formation rests directly on it. The contact is conformable and locally unconformable.
Nettleber Sandstone
NBS
North Berwick Abbey Plug
NBWKA
North Berwick Law Plug
NBWKL
Niarbyl Formation
NBY
The visible contacts are all faulted against Manx Group and the Peel Formation. It is likely that both lower and upper stratigraphical contacts are unconformable - the lower on the Manx Group where distinguished by being sandstone-dominated facies as opposed to mudstone, the upper probably with overlying Permian or Triassic red-bed facies.
A thin- to medium-bedded wacke sandstone, interbedded with siltstone and mudstone, locally including laminated carboniferous siltstone and thin beds of meta-bentonite.
Not seen, see above.
Newfaulds Coal
North Campsie Linear Vent-System
NCAMP
Non-Carbonate Salts
NCARB
Northumbria Catchments Subgroup
NCAT
Unconformable contact with units of the North Pennine and North Sea Coast Glacigenic subgroups, and with bedrock.
Northumberland, County Durham and northern Richmondshire east of the Pennine watershed.
A suite of fluvial, lacustrine, mass movement, periglacial and aeolian deposits that contain clasts derived from rocks cropping out in northeastern England (mainly sandstone, gritstone, mudstone, limestone and coal), including alluvium, river terrace deposits, peat, head and blown sand.
Nairnside Sandstone Formation
NCB
Conformable lower contact with Daviot Conglomerate Formation.
Red sandstones largely fluvial with grey-green siltstones, calcareous mudstones and fish-bearing limestone lenses and nodules.
Conformable upper contact with Leanach Sandstone Formation.
Norwich Crag Formation
NCG
Pliocene to Early Pleistocene.
Rests with discontinuity on the Red Crag Formation and oversteps onto Coralline Crag Formation, Palaeogene formations and Chalk Group bedrock.
Restricted to East Anglia. Well defined throughout Suffolk and north Essex, as far as Stanstead Mountfichet. It continues north into Norfolk area and Ludham, but farther north it is cut out beneath the base of the Wroxham Crag Formation.
The formation comprises a widespread sheet of well sorted, fine- to medium-grained micaceous, glauconitic, locally shelly sands (Chillesford Sand Member in southeast Suffolk), with localized beds of laminated silty clays (Chillesford Clay and Easton Bavents Clay members) and rounded flint gravels (Westleton Beds). The formation is marine, with the clay members being estuarine and the Westleton Beds representing beach-face gravels.
Overlain disconformably by Wroxham Crag Formation, unconformably by Kesgrave Valley Subgroup and Mid Pleistocene glacigenic deposits.
Nechells Breccia
NCHB
North Charnwood Diorite
NCHD
Margins generally cut Charnian bedding at high angles and show chilling within c.5-10m of contact.
Locally exposed northwards from Ulverscroft to the southern outskirts of Shepshed.
Coarse-grained inequigranular diorite, comprising a dark grey matrix with c.40-50% of white, subhedral plagioclase crystals. Fine-grained and equigranular at chilled margin.
c.60m, sheet like bodies.
None.
Newhaven Chalk Formation
NCK
Santonian to Campanian. Uintacrinus socialis, Marsupites testudinarius, Uintacrinus anglicus and Offaster pilula Zones.
Conformable at the Buckle Marl 1 in the Sussex succession (Mortimore, 1986). In typical sections, the boundary is the lower limit of chalk with numerous marl seams above several tens of metres of chalk without marl seams (the Seaford Chalk Member). The incoming of common Zoophycos flints and the presence of the zonal Uintacrinus socialis crinoid at the base of the Newhaven Chalk Formation are useful indicators in the field.
Known throughout the Southern Province northward to the Pewsey/Kingsclere structure and as limited outliers north of this structure. Its presence within the Chilterns and northward into East Anglia in the Transitional Province is not well known.
Composed of soft to medium hard, smooth white chalks with numerous marl seams and flint bands, including abundant Zoophycos flints (notably at levels near the base). The formation is known to contain distinct phosphatic chalks of limited lateral extent. Equivalent beds, the Margate Chalk of north Kent, are marl-free and contain little flint.
45 to 75m in the basinal sequences of the Southern Province. Limited by sub-Palaeogene erosion over large areas of Southern Britain.
Placed at the Castle Hill Marl 2 in the type locality at Seaford Head, Sussex where there is some evidence of a reduction in marl thickness over a structural high. In expanded trough areas a higher set of marls, the Pepper Box Marls, are well developed and the boundary is taken at this level.
Norwich Crag Formation And Red Crag Formation (Undifferentiated)
NCRC
Composite: Norwich Crag Formation: mainly reddish to yellow (oxidised) sand above watertable, green where saturated. Glauconitic, fine- to coarse-grained, micaceous, locally shelly. Includes gravels and clay layers particularly towards top of sequence. Commonly decalcified. Basal stone bed composed of flint, overlain by shelly sand; cross-bedded, overlain by sand and green-brown clay; flasar-bedded, overlain by quartz-quartzite gravel (outwash suite). Red Crag Formation: shelly sand, silt and clay. [Generic description].
New Coal (South Lancashire)
NCSL
Nettle Crags Tuff Member
NCT
Base of dacitic lapilli-tuff above dacite lavas (and/or sills) within the Birker Fell Andesite Formation.
Nettle Crags - Bootle Fell in the Borrowdale Volcanic Group outcrop between the Skiddaw Group and Eskdale Granodiorite.
Massive, eutaxitic to parataxitic dacitic lapilli-tuff.
Non-sequence at top of dacitic lapilli-tuff. Overlain by dacite and volcaniclastic sandstone in the Birker Fell Andesite Formation.
New Cumnock Diamond Coal
Netherwood Coal (Central Coalfield)
NDC
Northern Drift Formation
NDR
Quartzose and quartz gravel in a clay matrix. [Generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
Neath Valley Formation
NEATH
Sharp, unconformable and locally channelised, predominantly on bedrock and Late Devensian head and glacigenic deposits (e.g. Brecknockshire Formation). Interdigitates in a complex manner with Tidal Flat Deposits (Gwynllwg Formation of Bowen, 1999) in the estuary.
The valley of the River Neath and its tributaries (west Glamorgan, mid Glamorgan and Powys), Wales.
Unconsolidated, stratified gravels, sands, silts and clays forming the alluvial deposits of the River Neath (Afon Nedd) and its tributaries. Includes contemporaneous head, colluvium and pedogenic deposits within the catchment area. Clasts consist exclusively of Old Red Sandstone and Carboniferous limestone, sandstone and coal sourced either directly from the bedrock or via the reworking of Late Devensian glacigenic deposits (e.g. Brecknockshire Formation). Aggradational river terraces and major alluvial fans are dominated by pebble cobble gravels and medium- to coarse-grained sand (Strahan et al., 1932); the modern floodplain is dominated by silt and clay, or poorly sorted gravel (Barclay et al., 1988, p.39). Locally the deposits include lenses of peat.
Generally to around 10m; 6m of (fluvial) gravel over 15m (?glaciofluvial) sand were recorded in a borehole near Resolven at [SN 8346 0313] (Strahan et al., 1932).
North-East Grampian Basic Suite
NEBAS
Newton Clay Member
NEC
Rests with a sharp junction on the Sturminster Pisolite.
Across the whole of the Shaftesbury Sheet (313) and the southern part of the Wincanton Sheet (297).
Clay, oolitic; thin limestone beds or concretions. In the southern part of the outcrop, sand is only a minor component; in the north, sandy clay is common, and beds of fine-grained sand occur.
0 - 15m: (12.24m in the East Stour Borehole - ST82SW/9; 6.7m at the type locality; 3.65m in the Sturminster railway cutting).
Passes up into micritic oolitic limestones of the Todber Freestone.
Necropolis Sill
NECRO
Northern England Dinantian Intrusions Suite
NEDI
Northern England Devonian Plutonic Suite
NEDP
Includes all granite plutonic intrusions of Early Devonian age in Northern England, including the exposed Shap Pluton (SHAP), the Skiddaw Pluton (SKID) and the concealed Weardale and Crummock Water intrusions. The Shap Pluton is the type pluton for this Suite.
Cumbria, Northumberland and Durham, northern England.
A potassium feldspar-phyric granite, biotite granite and muscovite-quartz rock, interpreted as greisen.
Neeans 'Group'
NEE
Needs Law Plug
NEED
New Cumnock Eight Foot Coal
NEF
Newry Granodiorite Complex
NEGD
Newry Granodiorite Complex Phase 1
NEGD1
Newry Granodiorite Complex Phase 2
NEGD2
Newry Granodiorite Complex Phase 3
NEGD3
North-East Grampian Granitic Suite (Ordovician)
NEGRA
Netley Heath Deposits
NEHE
Neals Ing Formation
NEI
Taken at the sharp conformable base of sandstone resting on siltstones of the Horton Formation.
Parallel, thick-bedded, turbiditic, arkosic, medium-grained sandstone.
At least 250m
Not seen; unconformably overlain by Carboniferous rocks.
Neilead Semipelite Formation
NEIL
Newton Manor Sandstone Formation
NEM
Not present in either borehole
Sellafield boreholes 7A (NY00SE/36) and 14A (NY00NW/451).
Dominantly a bedded sequence of coarse- to fine-grained sandstone with some siltstone; massive and bedded lapilli-tuff, pumice lapilli-tuff and tuff, particularly towards top of formation.
Sellafield borehole No.7A: 137m+ (not corrected for structural dip nor borehole deviation); Sellafield borehole No.14A: 166m+
Taken at the change from bedded volcaniclastic deposits to massive rhyolitic welded tuff (base of Sella Park Member of Yottenfews Formation). (Not present in borehole 14A).
Nene Valley Formation
NENE
Definitely Pleistocene to Holocene, probably Hoxnian to Flandrian.
Neogene Rocks (Undifferentiated)
NEOG
Neogene And Quaternary Rocks (Undifferentiated)
NEOQ
Neptune Formation
NEPT
Neriby Formation
NERI
Newmead Sandstone Formation
NESA
Uretus Beds
NESE
Ness Formation
NESS
Neilston Steam Coal (Kilsyth)
NEST
Northern England Late Carboniferous Tholeiitic Dyke-Swarm
NETD
Nethybridge Psammite Formation
NETH
Presumed gradational boundary with underlying siliceous psammites, quartzites and graded psammites, semipelites and pelites of Pityoulish Formation.
In a large, irregular triangular area of the Abernethy Forest and the Spey Valley around Cromdale. To the northwest the formation extends across the Ericht - Laidon Fault (Spey Valley) and terminates against the Grampian Shear Zone and the Grantown Pluton (granite). To the south it is underlain by the Pityoulish Formation that crops out east of Loch Pityoulish and on Craigowrie and Meall a' Bhuachaille Hills. It is also truncated by the Cairngorm Pluton and to the east passes up into higher units of the Grampian Group in the Water of Ailnack section, the Braes of Abernethy and the Haughs of Cromdale.It is probably equivalent to the Coylumbridge Formation to the southwest. To the northeast it passes laterally into a thicker succession that includes much of the Dallas Psammite Formation, the Knockando Quartzite Formation, and parts of the Tormore Psammite Formation (the Rynaballoch Psammite Member and parts of the Cromdale Hills Quartzite Member).
Pale to dark grey, buff weathering, flaggy, feldspathic psammite, with subsidiary micaceous psammite, semipelite and quartzite. Locally more micaceous in parts and also contains thick quartzite beds. Lenticular calc-silicate pods widespread but not abundant in the psammites.
Grades upwards and laterally into siliceous psammites and quartzites of the Knockando Quartzite Formation, and into psammite and quartzite members of the Tormore Psammite Formation.
Netherly Diorite
NETY
Newington Coal
NEW
New Coal (Somerset)
NEWC
Newforte Breccia Formation
NEWF
Newlands Subgroup
NEWL
Unconformity at the base of the Mulloch Hill Conglomerate Fomation or the equivalent Craigskelly Conglmerate Formation on the Ardmillan Group.
Flaggy wacke sandstones, siltstones, and mudstones, plus conglomerate, grit and subsidiary thin limestones.
1370 m thick.
Unconformably overlain by the Lower Camregan Grits Formation of the Dailly Subgroup.
New Mains Intrusion (?Sill)
NEWMN
Newstead Rock
NEWR
Newtownbutler Limestone Member
NEWT
Not exposed - transition (probable) from dark grey crinoidal limestones (packstones) of parent Ballyshannon Limestone Formation.
Grainstones, pale to medium grey, fine- to coarse-grained, oolitic, peloidal, bioclastic, quartz-clastic, bedded.
Abrupt (probably disconformable) change from limestones to sandstone bed representive base of Mullynagowan Sandstone Member (basal member of Bundoran Shale Formation).
Nant-Y-Moch Formation
Thinly interbedded turbiditic mudstones and sandstones with units of laminated hemipelagic mudstone.
Conformable and sharp junction with the disturbed mudstones of the overlying Drosgol Formation.
Netherfield Coal
NFC
New Cumnock Five Foot Coal (South Ayrshire)
NFF
Newton Fells Grit
NFG
New Cumnock Four Foot Coal (South Ayrshire)
NFO
Nant Ffrancon Subgroup
NFR
Tremadoc-Arenig unconformity which lies at the top of the Dol-Cyn-Afon Formation (Mawddach Group) or top of Marchlyn Formation. Basal unit is Allt Lwyd Formation where present, otherwise undivided Nant Ffrancon Subgroup.
Northern and central Snowdonia, east of the Harlech Dome.
Mudstones, silty mudstones and sandstones; bioturbated, finely laminated, graptolitic: some volcanic units named as formations. Note that most of the Subgroup is not divided into formations. The named volcanic formations "float" within the undivided sedimentary Subgroup.
Originally proposed as a formation (Howells et al., 1983) and raised to group status by Howells and Smith, 1997, the Nant Ffrancon was reduced to a subgroup of the Ogwen Group by Rushton and Howells, 1998. It includes the Aberdaron Bay Group of Gibbons and McCarroll (1993).
>2km, variable
Base of the Capel Curig Volcanic Formation (where present), otherwise the base of the Cwm Eigiau Formation.
Nantglyn Flags Formation
NGF
Nanhoron Microgranite
NGM
Granophyric microgranite
Ny Garvain Member
NGN
Stratigraphical with undivided Lonan Formation.
Thin to medium-bedded sandstone, interbedded with laminated mudstone and siltstone. The sandstone is more abundant and more thickly bedded than in the units above and below.
Stratigraphical with Maughold Formation.
Nantglyn Flags Formation And Nant-Ysgollon Mudstone Formation (Undifferentiated) [Duplicate Term: Use Nyng]
NGNY
Northern Granite Pluton, Arran
NGPA
North Grimston Cementstone Member
NGRC
Notgrove Member
NGRV
Laeviuscula Zone.
Upward transition from very shelly, shell-detrital limestone (Gryphite Grit Member) into limestone as described in lithology.
Mid and north Cotswolds: north of Colesbourne and Chedworth, and west of Cold Aston and Condicote. Barron, A J M, et al, 1997, fig.4.
Pale brownish grey, poorly sorted medium- to coarse-grained peloidal and ooidal grainstone, typically poorly sorted or bimodal; medium-bedded and cross-bedded, shells and shell debris rare, except in lowest beds.
0 - 13m. Type section (Notgrove Cutting); 3.9m (Buckman, J, 1887).
Hardground: limestone as described in lithology overlain by shelly, sandy, ironshot limestone (Rolling Bank Member), or by Salperton Limestone Formation.
Nattrass Gill Hazle Sandstone
NGS
Nor Gill Sandstone Formation
NGSA
Nothe Grit Member
NGT
The sharp, probably non-sequential, boundary with the underlying Oxford Clay Formation. This is marked by the upward change from the mudstone of the Oxford Clay to the sandstone of the Nothe Grit Member.
Sandstone, grey to yellow to brown, fine-grained, sub-rounded grains, fairly well-sorted, argillaceous, in thick beds, with pervasive bioturbation (including Thalassinoides and Rhizocorallium). A bed with abundant sponge spicules forms a prominent calcareous cemented unit near the middle of the member. Large calcareous concretions (up to 1m) are common in many beds. Oysters, ammonites and serpulids occur in the sandstone. The uppermost part of the member (sensu BGS) is a 1.5m-thick bed of shelly, calcareous, medium-grained sandstone (Preston Grit Member of Wright, 1986), which is separated from the underlying succession by a sharp erosion surface, interpreted as a minor unconformity by Coe (1995).
10.5m (including the Preston Grit Member of Wright, 1986.
Gradational boundary, over several centimetres, from calcareous sandstone of the uppermost Nothe Grit (= topmost Preston Grit Member of Wright, 1986) to sandy mudstone of the overlying Nothe Clay Member.
New Glencrieff Vein
NGV
Gwna Group
NGW
Drawn at the base of the Gwna Group where it rests conformably on the Church Bay Tuffs.
Grit, phyllite, quartzite, limestone, jasper, graphitic phyllite, spilitic pillow lavas and tuffs.
Probably several hundred metres.
Drawn at the conformable upward passage of the Gwna Group to the base of the Fydlyn Group: diabase passing into chlorite epidote schist.
Newhey Mudstone
Amlwch Beds
NHAB
Bodelwyn Formation
NHBB
Northern Highlands And Argyll Catchments Subgroup
NHC
Unconformable contact with units of the Northwest Highlands Glacigenic Subgroup, the Central Grampian Glacigenic Subgroup, the Banffshire Coast and Caithness Glacigenic Subgroup, and with bedrock.
The Northern and Western Highlands, and Argyll.
A suite of fluvial, lacustrine, mass movement, periglacial and aeolian deposits that contain clasts derived from rocks cropping out in the northern Highlands and Argyll, including alluvium, river terrace deposits, peat, head and blown sand.
Celyn Beds
NHCB
New Pit Chalk Formation And Holywell Nodular Chalk Formation (Undifferentiated) [Redundant Code: Use Hnck]
NHCK
North Hill Dacites
NHD
North Holm Gneiss Formation
NHGN
Holy Island Group
NHI
Lynas Formation
NHLB
Newhill Coal (South And West Yorkshire)
NHLC
Holyhead Quartzite
NHQ
New House Limestone
NHS
Ashy Cleugh area, White Lyne valley, Cumbria.
Micritic limestone with some ooidal and algal layers.
To c.3m
Soldiers' Point Beds
NHSP
Newton Heath Sandstone
NHSS
Niand(T) Limestone
New Inn Sand And Gravel Member And Ailstone Sand And Gravel Member (Undifferentiated) (Warwickshire Avon)
NIAT
Sand and gravel: New Inn Terrace Deposits: gravel includes 'Bunter' type clasts, and mammalian bones; Ailstone Terrace Deposits: glacial and interglacial features and fossiliferous; third and fourth terraces of the River Avon; part of the Avon Valley Formation. [Generic description: academic papers and BGS Memoirs].
Nine Foot Coal (North Wales)
NIFC
Nine Feet Coal (Warwickshire)
NIN
Nidderdale Shale
NISH
New Inn Sand And Gravel Member
NIT
Late Pleistocene [MI Stage 5e to ?5b or ?4).
Unconformable, commonly channelled base, resting on Lower Jurassic or Triassic bedrock.
Avon Valley from Wasperton (just downstream of Warwick) to Tewkesbury.
Predominantly cold phase sands and gravels that underlie the Avon Third Terrace of Tomlinson (1925) and of BGS maps. Dominated by clasts of "Bunter" quartz/quartzite lihtologies with subordinate flint. Locally includes organic Eckington Bed (or New Inn Fossil Bed) at base, which is assigned to MIS 5e. Correlation with members of Severn Valley Formation problematical. See Compiler's Notes under Supplementary Information.
(A) The unit is referred to here as the New Inn Sand and Gravel Member though in Bowen (1999), and in previous BGS use it was simply New Inn Member. (B) The terrace surface is some 15m above the modern Avon alluvial floodplain (e.g at type locality) apparently decreasing to perhaps 10m downstream. (C) The terrace is not well defined morphologically and it seems too high and close to Terrace 4 (Cropthorne). Moreover, on the basis of elevation, it looks as if some supposed Terrace 3 downstream might actually be Terrace 2 (or less probably, vice versa). It might actually include head or tributary fluvial gravels, perhaps equivalent to older parts of the Wasperton (2) Member which is quite probably composite. Correlation with the Severn is a problem: Terrace 3 (Holt Heath) of the Severn also apparently has 5e organic material beneath, but is outwash from the main Devensian Icesheet, which is supposedly stage 2. In any case, as mapped, the Holt Heath looks too low to meet with the Avon?s New Inn, but could just about relate to the Avon?s Wasperton Member. (D) The upper boundary is given as ?ground surface? though head, colluvium or soil deposits may intervene. (E) As stated above, the Avon and Severn terraces need reviewing in their entirety and classification of some outcrops on existing maps is highly suspect. Hence information relating to Previous Names is necessarily an approximation.
New Jet Amber Coal (South Lancashire)
NJAC
New Jordan Hill Blackband Ironstone
NJBI
Skerries Formation
Drawn at the base of the Skerries Formation where it rests conformably upon pelites and semipelites with pillow lavas of the New Harbour Group.
Anglesey, north Wales.
Massive greenish-grey schistose greywackes, coarse and often pebbly, followed by unstratified dull greenish-grey pyroclastic rocks of intermediate composition.
500 metres approx.
Drawn at the conformable upward passage from the top of the Church Bay Tuff Formation to the limestone, graphitic pelite and other quartzite;- triple formation of the Gwna Group.
Norfolk Chalk
NKCK
Skerries Conglomerates
NKSC
Skerries Grits
NKSG
Tyfry Beds
NKTB
Naworth Limestone
North Leigh Member
NLE
Nellfield Marl
NLFM
Scottish Central Coalfield, typically around Nellfield, Lanarkshire.
Variegated red, purple and green "marls" (calcareous mudstone) alternating with gritty sandstone, with a hard, ferruginous basal conglomerate.
Between the Productus giganteus (Hollybush) Limestone above and the Fiddler Shell Bed (Dykebar Limestone) below.
c.4m
Northumberland Low Main Coal (Northumberland)
NLM
Nether Lount Coal (Leicestershire)
NLOC
Nash Scar Limestone
NLS
Knighton area of mid-Wales.
Lywn Beds
NLW
New Lynch Coal (South Wales)
NLYC
New Cumnock Musselband Coal (South Ayrshire)
New Main Coal (Leicestershire)
NMAC
Nordmarkite Swarm ('Nordmarkite' Swarm)
NMARK
Newmill Breccia Formation
NMBR
New Mine Coal (North Staffordshire)
NMC
New Mine Coal (Coalbrookdale)
NMCC
Nether Main Coal (South Derbyshire)
NMCO
New Mine Coal Rock
NMCR
Meeching Beds
NME
New Mine Fireclay
NMFC
Mona Gneiss Suite
NMG
Neoproterozoic Metamorphosed Granitic Suite Of Shetland
NMGS
New Mine Coal (South Staffordshire)
NMIC
New Mine Ironstone (South Staffordshire)
NMII
Newby Mill Limestone
NML
Neoproterozoic Metamorphosed Mafic And Ultramafic Minor Intrusion Suite Of Shetland
NMMUS
Nantmor Group
NMR
New Main Rider Coal (Leicestershire)
NMRC
Namurian Rocks (Undifferentiated)
NMRN
North Meadow Sandstone
NMS
New Moss Coal (North Staffordshire)
NMSC
Norham Till Formation
NMTI
Northmaven Pluton
NMVN
Newbury No.1 Coal (Somerset)
NN1C
Newbury No.2 Coal (Somerset)
NN2C
New Harbour Group
NNH
Drawn at the base of the New Harbour Group where it rests conformably upon the Rhoscolyn Formation (turbidites).
Western and northern parts of Anglesey and eastern Holy Island.
Fissile green mica schist, gritty green mica schist, with bedded jasper, jaspery phyllite and pelitic lava.
Drawn at the conformable upward passage from the top of the New Harbour Group to the overlying Skerries Formation of the Skerries Group.
Neilston Lava Member
NNLA
The base is apparently conformable on the Moyne Moor Lava Member, which consists predominantly of trachybasalt, but it might locally be unconformable.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton, in the western part of the area between Neilston (NS 480 570) and Stewarton (NS 430 480).
The Neilston Lava Member consists of alkali basalts with minor basanite in the lower part and trachybasalt in the upper.
The Member is overlain by the trachytic Harelaw Lava Member. The contact is unconformable.
Nuculoceras Nuculum Marine Band [See Also: E2c2, E2c3, E2c4]
NNMB
Nantannog Formation
NNN
Neilson Shell Bed
NNSB
Northmoor Sand And Gravel Member
Late Pleistocene (MI Stage 5 to 2).
Unconformable, commonly channelled base, resting on Jurassic bedrock, or very locally, on gravels of Summertown-Radley Member.
Upper Thames Catchment, i.e. River Thames and most tributaries (excluding River Thame) upstream of the Goring Gap. Fairly well developed along the Upper Thames itself, the Ock, and (somewhat less well) along the lower Evenlode and the lower Cherwell.
Predominantly cold phase sands and gravels that underlie the Northmoor or First Terrace of BGS Maps. Dominated by clasts of Middle Jurassic limestone, but also containing a small proportion of "Bunter" quartz/quartzite and a varying proportion of flint, the latter increasing downstream below the confluence with the River Ock near Abingdon.
(A) The unit is referred to here as the Northmoor Sand and Gravel though in Bowen (1999), and in previous BGS use, it was simply Northmoor Member. (B) Parent was originally Upper Thames Valley Formation. Despite correlation problems at Goring, I am happy with this as the member names in the Upper Thames remain discrete. (C)Terrace surface is up to 3m above modern alluvial floodplain, with Northmoor deposits of at least two phases (MIS 5?a and Late Glacial MIS 2). Locally, upper (c 2-3m) and lower (c 1m) ?facets? have been recognised (1b and 1a of BGS maps); these do not necessarily relate to the two phases of aggradation suggested by these organic beds. (D) The upper boundary is given as ?ground surface? though head, colluvium or soil deposits may intervene. (E) Recent work on sections shows that some deposits mapped as Summertown-Radley are in fact Northmoor, and the primary reference locality is mapped as alluvium (this could be correct, as the gravels extend beneath the alluvium, but in this case it is probably wrong). (F) There do not appear to be equivalents on the Upper Evenlode (Sheets 218, 235) and in the Upper Windrush (also on Sheet 235) a different name (Rissington Member) is used because of the lack of positive correlation. The name is (probably) applicable in the Cherwell valley on Sheet 218.
0 to c 6 or 7m, typically c 3m.
Ground surface or floodplain alluvium.
Northmoor Sand And Gravel Member, Lower Facet
NO1A
Sandy limestone gravel; terrace of the Thames. [Generic description: 1:50 k map margins].
Northmoor Sand And Gravel Member, Upper Facet
NO1B
No.5 Coal (Somerset)
NO5C
No.7 Coal (Somerset)
NO7C
No.9 Coal (Somerset)
NO9C
Nothe Clay Member
NOC
Base is a gradational boundary with medium-grained calcareous sandstone of the uppermost 1.5m of the Nothe Grit (=Preston Grit Member of Wright, 1986) passing to sandy mudstone of the basal Nothe Clay Member.
Grey mudstone and sandy mudstone, containing scattered ooids, interbedded with about eight limestone horizons. The limestones are variously iron-rich, ooidal, sandy and bioclastic, and there is a distinctive white-weathering shelly micrite, with extensive borings, near the base of the succession. Locally abundant bivalves.
12m at Osmington; 13.5m at Rodwell (Sandsfoot).
The top is a gradational boundary marked by an increase in quartz sand in the mudstones of the topmost part of the Nothe Clay Member, passing into the argillaceous sandstone of the Bencliff Grit Member. Crushed specimens of the bivalve Modiolus are common at this horizon.
No Coal (Forest Of Dean)
NOCO
North Esk Formation [Not Same As Nes]
NOE
No lower stratigraphical boundary identifiable.
Three lithologies with oceanic affinities are juxtaposed: (i) metabasalt, commonly spilitised, locally retaining pillows, metamorphosed to chlorite-schist over much of the outcrop; (ii) chert, brownish, pyritic in places, with cavities filled with yellow limonite; (iii) black slaty pelite rich in iron oxides, weathering reddish away from stream sections.
Outcrop belt 600m wide: thickness unknown.
Unconformably overlain by Margie Formation.
Nod Glas Formation
NOG
Caradoc (Longvillian to Onnian).
As conventionally defined, lower boundary is a conformable transition over 1.5m, from paler, silty mudstones of Ceiswyn Formation (and equivalents), to coal black soft mudstones of Nod Glas Formation. However, elements of Nod Glas lithostratigraphy (anoxic pelagic beds) appear in the underlying Ceiswyn Formation (Craig Hen-gae Member) at least 200-300m below the junction. The Cadnant Shales (=Llanrychwyn Slates) of the Dolgarrog area, considered to be equivalent to the Nod Glas, are likewise up to 400m thick. See also the Supplementary Information Description.
Extends discontinuously from the coast of Cardigan Bay in the southwest to the Conwy area in the north.
Black, pyritous, graptolitic mudstone. Rusty weathering, soft, very well cleaved and coal-like.
Biostratigraphy is ambiguous. Coventionally the Nod Glas Formation spans the clingani and linearis biozones of the Caradoc, but multidens faunas have been reported from the lower parts of the Cadnant Shales and Craig Hen-gae Member.
Generally 20m to 30m, but up to 400m recorded in Cadnant Shales of North Wales.
Upper boundary is transitional or possibly a non-sequence locally, from coal black mudstones into pale-bluish grey, bioturbated silty, mudstones of the Broad Vein Formation. Transition occurs over less than 2m but is not exposed.
North Greens Coal (Lothian)
NOGC
Nothe Grit Member [Redundant Code: Use Ngt]
NOGR
North Greens Sandstone
NOGS
North Head Member
NOHE
Numerous siltstone and claystone beds, massive or parallel laminated, desiccation cracks common. Sheetflood facies.
Nodular Limestone Member
NOL
Gradational passage taken at the base of the first predominantly calcareous mudstone and nodular limestone overlying the bedded, limestone-dominated Lower Quarried Limestone Member.
Limestone, grey, buff, nodular, interbedded with green-grey, calcareous mudstone; sporadic beds of bioclastic limestone and sparse bentonitic tuffs; sparse limestone bioherms (reefs).
31.1 - 37.8m at Wren's Nest, Dudley.
Base of the limestone-dominated Upper Quarried Limestone Member, overlying limestone with grey calcareous mudstone partings.
Norton Marine Band [Local Name: See Ammb]
NOMB
Local name applied to the Amaliae Marine Band (National Standard Name) in parts of the Derbyshire, Nottinghamshire and Yorkshire coalfield areas.
Old Nore Beds
NON
North Coal (Lothian)
NOR
Norber Formation
NORB
Taken at the irregular base of the conglomerate in Douk Ghyll, Horton, unconformably overlying sandstones of the Ingleton Group. Elsewhere, the base of the formation is not seen.
Calcareous siltstones and argillaceous limestones with a shelly fauna. There is a siliceous conglomerate at the base.
Defined by the base of the overlying Sowerthwaite Formation.
Nordland Group
NORD
Lower Nordland Unit
NORDL
This unit comprises the lower part of the Nordland Group. The Lower Nordland Unit includes a subdivision known as the Muckle Ossa Sandstone. The reference sections for the Lower Nordland Unit are in wells 202/8-1 and 208/15-1A
Middle Nordland Unit
NORDM
This unit comprises the mid part of the Nordland Group. The reference sections for the Middle Nordland Unit are in BGS boreholes 82/10 and 84/04 and well 208/15-1A
Upper Nordland Unit
NORDU
This unit comprises the upper part of the Nordland Group. The reference sections for the Upper Nordland Unit are in BGS boreholes 77/07, 84/04 and 85/01
Norwick Graphitic Schist Formation
NORG
Norwick Hornblendic Schist Type 1
NORH1
Tectonic base - imbricate thrust zone.
The main mass is about 1.5 km long and extends inland from Norwick, a small lens crops out on the coast at The Clifts, Norwick, Unst
Albite-porphyritic metablast, locally deformed to a phyllite.
Tectonic top - imbricate thrust stack.
Norwick Hornblendic Schist Type 2
NORH2
A tectonic slice, having a faulted base.
Occur in several locations in Fetlar - most outcrops are of limited extent up to 1 km long and up to several hundred metres wide.
A green hornblende-rich schist with an S-tectonite fabric, which commonly has fine closely-spaced feldspar-rich laminations. At Virva, it grades into greenschists of volcanic origin.
A tectonic slice up to several hundred metres thick.
Norwick Hornblendic Schist Type 3
NORH3
Not applicable, -chilled margins.
Occurs locally in small outcrops on Fetlar. Outcrops are typically lenses or small sheets. The main locations are opposite 'The Clett', at Dempster's Geo, southwest of the Virva section and at Honga Ness.
Clinopyroxene, garnet, brown hornblende schist forming basic intrusive lenses and sheets.
Up to several metres thick.
Norwick Phyllite Formation
NORP
Nook House Sandstone
NOS
Nook House Shale
NOSH
Nordon Formation
NOSL
Nottage Crag Grit
NOT
Sharp base to the coarse-grained sandstone of the Nottage Crag Grit overlying siltstones with fine-grained sandstone beds of the Claughton Member.
Claughton area of Lancaster Fells.
Sandstone, pale orange-brown, coarse- to very coarse-grained, very thick-bedded; typically low-angle tabular planar-bedded; feeble parallel laminations; sporadic trough cross-stratification. NOTE: Nottage Crag Grit is a very prominent feature-forming delta top sandstone within a siltstone/fine-grained sandstone interbedded, slumped delta slope formation.
Not exposed; sandstones of the Nottage Crag Grit are overlain by siltstone of the Claughton Moor Siltstones.
Nordelph Peat
New Pit Beds
NPBE
Neoproterozoic Basic Minor Intrusion Suite
NPBMI
New Pit Chalk Formation
NPCH
Upper Cretaceous, Turonian. The greater part of the Terebratulina lata Zone.
Conformable at the bedding plane immediately below the Gun Gardens Main Marl (the Lulworth Marl of Gale, 1996) in the standard Sussex succession. The mapping boundary is placed at the highest shell-detrital chalk and at the incoming of sporadic flints. In the `Transitional? Province the top of these shell-detrital chalks is at the Odsey Marl (See Hopson et al., 1996).
Known throughout the Southern Province, within the Chilterns and northward into East Anglia in the Transitional Province. A number of laterally persistent and named marl and flint beds in Mortimore (1986) can be recognised over much of southern England.
Principally blocky, white firm to moderately hard chalk with numerous marls or paired marl seams. Flint occurs sporadically in the upper part in the deeper basin areas of the Southern Province. In some localities flint, in seams, occurs to the base of the formation most notable over structural highs, towards the margins of the outcrop and within the `Transitional? Province.
Typically between 35 and 50 m but is as little as 10 to 25m metres thick in Wiltshire, north Hampshire and Berkshire over synsedimentary structural. The formation expands in the `Transitional? Province where it is thought to be up to 75 to 80m thick.
Conformable at the base of Glynde Marl 1 in Sussex, but one of the higher marls elsewhere although invariably in the interval Glynde Marls to Southerham Marls in the Southern Province. The mapping boundary is placed at the appearance of nodular chalks and significant flint development within that range of marls. In the `Transitional? Province the formation expands in response to the later inception of nodularity and hardground development (characteristic of the Lewes Nodular Chalk Formation) such that the upper boundary is diachronous here and placed below the `Chalk Rock Member? at the Reed Marl (the lateral equivalent of the Bridgewick Marls of the Southern Province).
Peacehaven Beds
NPE
North Pennine Glacigenic Subgroup
NPEG
Unconformable on bedrock or older superficial deposits including previous valley deposits, outwash deposits and laminated clays formed in front of the advancing glacier.
East of the Pennines from the southern margin of the Cheviot Hills in the north to the southern edge of the Escrick Moraine in the south.
Dominantly glacial till (clay, sandy clay and clayey sand with gravel and boulders) with interbedded sand, gravel and laminated clay, plus more substantial areas of those individual lithologies incorporated in the till sheet, moraines and eskers.
To about 50m on moraines and eskers, generally 10-30m
Varies between the present land surface and the contact with later deposits such as glacial lake deposits, outwash and blown sand.
Northern Porphyritic Felsite (Skye Western Red Hills Centre)
NPF
New Pit Marls (One)
NPMA1
New Pit Marls (Two)
NPMA2
New Pit Marls (Three)
NPMA3
Net Pool Mudstone
NPMU
Upper Holywell Beds
NPUH
Nob End Rock
North Denes Formation
NRD
The North Denes Formation rests unconformably mostly on the silts, clays and sands of the Breydon Formation, but also on the sands and gravels of the Crag Group, and to a lesser extent on the glacigenic deposits of the Happisburgh Formation.
The formation comprises a coastal barrier, 1km wide by 8km long, between Caister-on-Sea and Gorleston-on-Sea. The present coastline is taken as an arbitary eastern limt.
The North Denes Formation consists of an elongate, wedge-shaped body of sand with subordinate gravel and thin layers of silty clay.
Surface, or else covered by blown sand.
New Red Sandstone Supergroup
NRS
See definitions of base of component formations of the Exeter Group and Aylesbeare Mudstone Group. Rests unconformably on folded Devonian and Carboniferous Rocks.
Originally in Scotland; range extended as described. All red-bed sequences of Permian and Triassic age in southwest England. Probably applicable also to northwest England and Scotland, but in northeast England can only be applied to beds overlying the Magnesian Limestone. See Conybeare and Phillips, 1822.
Breccias, sandstones, mudstones (red-beds) component groups: Mercia Mudstone Group, Sherwood Sandstone Group, Aylesbeare Mudstone Group and Exeter Group. NOTE: In northeast England New Red Sandstone included only Sherwood Sandstone and Mercia Mudstone groups: the Magnesian Limestone was used as a term of equal status. In the northwest the map clearly shows the unit extended down to the unconformable contact with Coal Measures, and so included the Permian red beds. In the south-west likewise.
Up to c.2000m
Overlain by Penarth Group. (Triassic/Jurassic).
Norton Coal (Leicester, South Derbyshire, Nottingham, Derby, South Yorkshire)
NRTN
Narrow Vein Mudstone Formation
NRV
The lower boundary can be examined at Aberllefenni Quarry, where the contact is transitional, over 0.5m, from the pale-blue of the Broad Vein Mudstone Formation to a medium-blue, laminated silty mudstone of the Narrow Vein Mudstone Formation.
Passes west into Cardigan Bay. The outcrop of the Narrow Vein Mudstone Formation crosses Sheet 149 diagonally from southwest to northeast (Tywyn-Aberllefenni).
Medium blue, silty mudstone. Homogenous or finely laminated (0.5-1cm).
The upper boundary of the Narrow Vein Mudtone Formation is taken at the base of the first sand band seen in an air shaft on Foel Crochan (7706 1050). The boundary is transitional over 2.65m, where sandy bands 1-2cm thick, occur separated by 10-20cm silty mudstones.
Northampton Sand Formation
A sharp, unconformable contact with mudstones of the Whitby Mudstone Formation (Lias Group), commonly marked by a pebble bed containing phosphatic nodules and derived fossils from the underlying Whitby Mudstone.
North Lincolnshire from just south of the Humber, where the unit is apparently overstepped by the Grantham Formation (according to Gaunt et al.,1992), to the Chipping Norton area, where it passes laterally into the 'Scissum Beds' of Horton et al.,1987, now known as the Leckhampton Member of the Birdlip Limestone Formation. East and south-eastwards from the outcrop, the Northampton Sand is overstepped by the Grantham Formation in the north, and the Rutland Formation in the south.
Sandy, berthierine-ooidal and sideritic ironstone, greenish grey where fresh, weathering to brown limonitic sandstone, typically displaying a box-stone structure. The basal part, is commonly muddy and less ferruginous. The uppermost beds are generally more or less ferruginous sandstone. The unit includes lenses of mudstone and limestone in places, and contains a fairly abundant marine fauna of bivalves, brachiopods and ammonites, which are not generally evident in weathered sections.
Up to about 21m thick (Thompson, 1921, and Hollingworth and Taylor,1951), typically in the range from 4m to 8m.
Generally a sharp erosional, or in some places apparently transitional boundary, with, to the north of the Kettering-Peterborough area, a generally less ferruginous sandstone, siltstone or mudstone of the Grantham Formation, which in some places contains pebbles of reworked Northampton Sand, or to the South of Kettering-Peterborough, a sharp erosional contact with essentially non-ferruginous interpreted non-marine sandstone, siltstone or mudstone of the Stamford Member of the Rutland Formation or in the Brackley district the equivalent Horsehay Sand Formation.
Nochty Semipelite And Limestone Formation
NSAL
Rapid transition downwards to banded psammite-semipelite sequence (Ladder Hills Formation); south of River Don overlies Tornahaish Formation semipelite with carbonate.
Ladder Hills area. Extends from Kymah Burn section southwest to Littleglen Burn and Water of Nochty, then SSE to Ernan Water, Donside and Glen Fenzie (Sheet 75E only).
Striped/banded semipelite and pelite, part calcareous, with numerous limestone bands. Calc-silicate lenticles common in north. Thin dolomite bands also. South of River Don flaggy semipelites and micaceous psammites dominant and carbonate rare.
Maximum 1310m. Probably duplicated by folding - more likely thickness c. 500m.
Lower limit of quartzite of Kymah Quartzite Formation or gradation to banded psammite-semipelite sequence (+ volcaniclastic horizons) of Ladder Hills Formation.
Newton St Cyres Breccia Formation
NSBR
Correlates with Heavitree Breccia of Exeter area. Rests on Crediton Breccia, locally with a scarp at the junction. Distinguished from Crediton Breccia by more sandy matrix, greater degree of cementation and presence (increasing towards the top) of potassium feldspar (murchisonite).
Present in the eastern Crediton Trough around the limbs of a synclinal structure from Newton St Cyres in the south, to Trobridge House. [SX 835 979] in the west, to near Shute [SS 890 001] in the north.
Reddish brown, mainly fine-grained breccia; clasts (mostly < 5cm) of shale, slate, hornfels, chert, potassium feldspar (murchisonite), vein quartz, quartz-porphyry, acid lava and tuff, microgranite and tourmalinised igneous rocks. Locally well cemented. Local sandstone beds. Sub-vertical sandstone bodies.
180m southwest of Newton St Cyres, 10m at Creedy Barton (SX 865 995).
Passes gradationally upwards and laterally into the Shute Sandstone.
Coeden Formation
NSC
North Sea Coast (Albion) Glacigenic Subgroup
NSCA
The North Sea coast and coastal plains of northeastern and eastern England between Berwick-upon-Tweed and north Norfolk.
Suite of glacial, glaciofluvial, glaciolacustrine and possibly glaciomarine deposits that contain clasts predominantly from northeast England (yellow, grey and white sandstones, mudstone, limestone, coal, dolerite), southern Scotland (greywacke sandstone and mudstone, granite, andesite, red sandstone) and offshore (marl, gypsum, chalk and sparse Scandinavian erratics). Including clayey diamictons (till), sand, gravel, silt and clay. Deposited by ice sourced mainly in the Scottish Borders and central Scotland that flowed southeastwards along the eastern coast of England (but mainly offshore) as far as north Norfolk.
Unconformable, mainly planar contact with units of the North Sea Coast Glacigenic Subgroup. Possible lateral interdigitation with units of the North Pennine (Albion) Glacigenic Subgroup.
Nesfield Sandstone
NSFS
The base is gradational. with an upward coarsening succession of dark grey silty mudstone and grey siltstone with thin beds of sandstone that become more common upwards. The base of the Nesfield Sandstone is placed where sandstone becomes predominant over siltstone.
West Yorkshire area [Nesfield, near Ilkley].
Fine-grained sandstone (quartz arenite), well-sorted, thinly planar bedded and laminated, cross-bedded and ripple cross-laminated in places, with wave and current ripples. In the Steeton [SE04SW] and Cowling [SD94SE] areas the sandstone is medium-grained, medium-bedded and feldspathic.
To 20m: thickest near Addingham [SE 09 05].
Sharp transition from Nesfield Sandstone quartz arenite to overlying dark grey mudstone with up to three marine bands, the Nuculoceras nuculum marine bands (E2C 2-4) between 10 and 20m above the top of the sandstone.
North Sea Coast Glacigenic Subgroup
NSG
Sharp, unconformable, mainly planar contact with units of the North Sea Coast (Albion) Glacigenic Subgroup, or with bedrock.
A suite of glacial, glaciofluvial, glaciolacustrine and possibly glaciomarine deposits that contain clasts derived predominantly from northeast England (yellow, grey and white sandstones, mudstone, limestone, coal, dolerite), southern Scotland (greywacke sandstone and mudstone, granite, andesite, red sandstone) and offshore (marl, gypsum, chalk). Including clayey diamictons (till), sand, gravel, silt and clay. Deposited by ice sourced mainly in the Scottish Borders and central Scotland that flowed southeastwards along the eastern coast of England (but mainly offshore) as far as north Norfolk.
Ground surface or unconformable contact with various units of the Brittania Catchments Group or British Coastal Deposits Group. Lateral interdigitation with units of the North Pennine Glacigenic Subgroup.
Northampton Ironstone
NSI
North Esk Group
NSK
Regressive sequence passing up from turbidite mudstones, siltstones and sandstones, through laminated mudstones and siltstones to sandstones and conglomerates.
At least 2500m
Not exposed - Unconformably overlain by Greywacke Conglomerate Formation (Lower 'Old Red Sandstone') and faulted against Kinneswood Formation (Inverclyde Group).
Nant Saethon Keratophyric Dykes
NSKD
Stack Moor Beds
NSM
New Smiths Coal (Bristol Area)
NSMC
Splash Point Beds
NSP
Rhoscolyn Formation
NSR
South Stack Formation
NSS
Western parts of Holy Island and part on north-central Anglesey, north of the Carmel Head Thrust system.
Schistose greywackes with partings of mica-schist, or interbedded metasandstones, pelites and subordinate quartzites.
Approx. 360m to >1000m
Drawn at conformable upward passage from grits of the Llwyn Beds to pelites, semi-pelites and metabasic rocks of the New Harbour Group.
North Sannox Lava Formation
NSX
Not seen, underlain by sandstone of the Stratheden Group (undivided).
Basaltic lava.
About.30 m thick.
Not seen, overlain by sandstone of the Stratheden Group.
Norwegian Trench Formation
Partially unconformable on the underlying Cape Shore Formation.
Stiff to hard sandy silty clay, commonly with a till-like appearance. Seismic texture indicates the presence of sand and clay lenses or layers. Pebbles, including chalk fragments are common and shell fragments are also present. It is underlain by a geotechnically weaker and more uniformly textured clay and overlain by a soft, silty clay.
40 metres +. Thins to 0 on the west side of the Norwegian Trench and to the north within the Norwegian Trench area.
Overlain by the accoustically well-bedded soft clays of the Kleppe Senior Formation.
Nottingham Castle Sandstone Formation
NTC
Marked but gradual upward increase in grain size and pebble content; overlies Lenton Sandstone Formation.
Crops out in Nottinghamshire and south Yorkshire; pebbles die out north of Doncaster and hence formation not recognisable. Probably correlates with Kidderminster Formation etc. of central England.
Sandstone, pinkish red or buff-grey, medium- to coarse-grained, pebbly, cross-bedded, friable; subordinate lenticular beds of reddish brown mudstone.
70-170m (thickens to NE) in Nottinghamshire.
Sharp, non-sequence; marked by mudstone of thin conglomerate at base of Mercia Mudstone Group.
New Cumnock Three Foot Coal
NTF
Netherhill Coals (Bewcastle)
NTHC
Nitshill Sandstone
NTHS
Nantmel Mudstones Formation
NTM
Gradational incoming of sequence, dominated by burrow mottled mudstones, above the black laminated mudstones of the St Cynllo's Church Formation.
Silty mudstones with dark burrow mottles. Several thick units of laminated hemipelagite. Scattered packets with thin sandstones. Thick unit of interbedded conglomerates, sandstones, pebbly mudstones and mudstones known as Doldowlodd Conglomerate (Member) locally present.
Sharp incoming of coarse silty mudstones with silt laminae or slumped mudstones, above burrowed mottled mudstones of the Doldowlod Conglomerate (Member).
Nantmel Mudstones (Formation) (Laminated Hemipelagites Unit, 1)
NTM1
Nantmel Mudstones (Formation) (Laminated Hemipelagites Unit, 2)
NTM2
Nantmel Mudstones (Formation) (Laminated Hemipelagites Unit, 3)
NTM3
Nantmel Mudstones (Formation) (Laminated Hemipelagites Unit, Undifferentiated)
NTMU
Netherton Breccia Formation
NTN
Newton Coal (Northumberland)
NTNC
Nursling Sand Member
Nun Volcanics Formation
NUNV
Nurseries Formation
NURS
Rests upon Permo-Triassic and Palaeozoic bedrock.
Full extent highly uncertain pending further work, but likely to be fairly widespread in and to the south of the Birmingham area (Sheet 168, 182, 183) beyond the limit of the Devensian Stockport Formation, both beneath the Ridgacre Formation and beyond its limits of that unit. Currently positively identified only in sections at Quinton and Nechells, where it underlies the temperate (Hoxnian) Quinton Beds. Remnants may be present inside the Devensian limit beneath the Stockport Formation.
Comprises the older of the two pre-Devensian glacial successions identified in the Birmingham area. Predominantly tills, sands and gravels and laminated glaciolacustrine clays. Characteristically lacks Scottish and Lake districts erratics (which characterise the Stockport Formation), and northern and eastern (e.g. Cretaceous) erratics (which are found in the pre-Devensian Wolston Formation). At the type locality it comprises brown till with abundant erratics (mainly local Upper Carboniferous rocks but including rocks of western derivation such as North Welsh rhyolite), together with sands and gravels and laminated clays. Represented by sand and gravel and laminated clay at Nechells. At both localities underlies the organic Quinton Beds ("Hoxnian"). Full geographic exent and thus full range of lithology uncertain.
(A) Name follows Bowen et al. (1999) and the provisional BGS Framework, but should it be Nurseries Glacigenic Formation? (B) There is little dispute about its Stage 12 Anglian age. That it lies below ?Hoxnian? organics is an important part of the argument for two pre-Late Devensian glaciations - see also comments on Ridgacre Formation - but this is largely dependent on the exact age of the organics, which is still contentious. (C) By definition this is the older of the two pre-Devensian glacial successions identified in the Birmingham area. It was separated by Kelly in his sections of M-way boreholes, which suggest it is quite extensive beneath the Ridgacre in north Birmingham. Neither he nor Horton give sufficient data to characterise it fully lithologically so it is not possible to state the full range of lithology nor its lateral extent. Survey of the Birmingham district (Powell et al, 2000) threw no further light on the problem, except that most of the tills are described as reddish and Trias-rich, which sounds more like the younger Ridgeacre Formation. (D) Glacigenic deposits are widespread beyond the Devensian limit in the Midlands but they have not been separated into two phases (except perhaps where stratigraphy is clear in the Wolston Formation). If there is a southern or eastern limit to the Ridgacre within the area (see Maddy et al., 1995) and the Nurseries Formation extends beyond it, it would mean that the latter is widespread at surface and constitutes much of the western older drift to the west of obvious northern and eastern Wolston Formation. Much more work is needed. (E) This unit is not yet distinguished on any maps, so the information related to 50K maps indicates where the Nurseries Formation (and/or Ridgacre) might occur.
Up to c 20 to 25m at type locality and Nechells.
At type locality and at Nechells, overlain by the organic Quinton Beds ("Hoxnian"). Elsewhere and more generally, inferred to be overlain by the Ridgacre Formation, or depending on lateral extent, younger Quaternary deposits (head, fluvial deposits) or ground surface. Remnants may be present inside the Devensian limit beneath the Stockport Formation.
Nar Valley Clay [Obsolete Code: Use Narc]
Silt, clay and silty clay, finely laminated, with a sporadic basal shell bed; marine. [Generic description: 1:50 k map margins].
Niddrie Vexhim Coal (Lothian)
NVC
Nar Valley Freshwater Beds
NVFB
Silty sand, fine-grained, and silt, grey; freshwater. [Generic description: 1:50 k map margins].
Newside Arenite Member
NWA
Incoming of predominantly sandstone succession belonging to the Newside Arenite Member above the greenish grey conglomerate forming the Fence Conglomerate Member of the Westgate Formation.
Mainly pale olive-grey to brownish grey arkosic medium-grained sandstones.
c.365m
The transitional top of the predominantly sandstone succession belonging to the Newside Arenite Member of the Westgate Formation below interdigitating lenses of conglomerate containing a high percentage of quartzite pebbles which constitutes the Kirk Hill Conglomerate Member.
Newside Arenite Member And Eastgate Sandstone Member (Undifferentiated)
NWAE
Aber Geirch Phyllites And Grits
NWAP
Naworth Bryozoa Band
NWBB
Bodafon Moor Flags
NWBM
Bodafon Quartzite
NWBQ
Newton Coal (Glasgow)
NWC
Ceinwen And Llanddwyn Spilitic Formation
NWCL
Porthdinllaen Spilitic Formation
NWDS
Engan Spilitic Formation
NWES
Newlands Farm Formation
NWF
Conformably overlies the Glenwells Conglomerarte Formation (GWC).
Blue-grey, weathering bright yellow-buff, calcareous siltstone, with a locally rich shelly fauna.
About 185 m thick.
Conformably overlain by the Glenshalloch Shale Formation (GLSH).
Great Quartzite
NWGQ
North-West Grampian Granitic Suite (Ordovician)
NWGRA
Northwest Highlands (Albion) Glacigenic Subgroup
NWHAG
The Northwest Highlands north of the Great Glen and the Inner Hebrides from Mull northwards, but excluding Caithness, the hinterland of Inverness and the Western Isles.
A suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts derived predominantly from Lewisian, Torridonian, Cambrian, Caledonian igneous and Moine psammitic rocks of the northern Highlands. Including sandy diamictons (till), sand, gravel, silt and clay. Deposited by ice that radiated outwards from an ice divide positioned inland of the western seaboard of the Northern Highlands.
Unconformable contact with units of the Northwest Highlands Glacigenic Subgroup, or Flandrian deposits, predominantly peat.
North-West Highlands Alkaline Plutonic Suite
NWHAP
Northwich Halite Member
NWHF
Conformable at the base of the lowest substantial halite in the member.
Halite with partings of mudstone.
To 286m
Conformable at the top of the highest substantial halite in this member.
Northwest Highlands Glacigenic Subgroup
NWHG
The Northwest Highlands north of the Great Glen, and the Inner Hebrides from Mull northwards, but excluding Caithness, the hinterland of Inverness and the Western Isles.
Ground surface or unconformable contact with various Flandrian deposits, predominantly peat.
North-West Highlands Minor Intrusion Suite
NWHIM
Newton Limestone
NWL
New Mine Coal (Birmingham)
NWMN
Netherwitton Coals (Northumberland)
NWNC
Netherwitton Limestone
NWNL
New Orleans Conglomerate Formation
NWO
The top of the Glenramskill Formation where volcanic conglomerate overlies sandstones and mainly quartzitic conglomerate.
Conglomerates and breccias composed of mainly lava boulders, with beds of red sandstone and siltstone, and localised tuff.
About 890 m thick.
The base of the Bastard Sandstone Formation, where quartz-rich sandstone overlies predominantly volcanic conglomerate.
Porth Orion Limestone
NWPL
New Shipping Formation
NWS
The lower boundary is a gradational boundary with the underlying Lawrenny Cliff Formation and placed where red-purple beds succeed the green beds of the underlying Lawrenny Cliff Formation. The actual junction is nowhere exposed.
The Formation occupies a small area around New Shipping [SN 035 043] in the upper reaches of the Carew River east of Milford Haven, Pembrokeshire. It is present in a small outcrop east of Ford Point [SN 0346 0404]. On the west side of the River Carew, it crops out west of Ford Pill from near Paskeston [SN 028 035] north to Hakin Point [SN 033 043]. It is also present in a small area in the northeast of the Lawrenny peninsula 500m south of Lawrenny [SN 019 066]; in a faulted block on the western shore of Cosheston Pill [SM 982 040] near Waterloo; and in a partially faulted block on the northern shore of Cosheston Pill [SM 996 035] 500m southwest of Cosheston.
The formation consists of red-purple extraformational conglomerates (40.7%) with a wide range of exotic pebbles, red-purple very fine- to very coarse grained sandstones (35.1%), and sandy, coarse-grained siltstones (24.1%), principally arranged in 1 to 10m-thick, fining-upward units, with a few coarsening upward sequences up to 7m thick.
320 to 400+m
The boundary is not seen, the Formation being unconformably overlain by strata of the Avon Group (formerlt "Lower Limestone Shales") of Early Carboniferous age. This junction is seen on the shore on the east side of the Carew River [SN 03852 04105] southsoutheast of New Shipping Point. It is a scour surface with up to 2cm relief cut in medium- to coarse grained purple sandstone overlain by a bed of quartz grit up to 4cm thick with shell fragments.
Triple Group Formation
NWTG
Trwyn Glas Spilites
NWTS
Church Bay Tuffs
NXCT
Nant-Y-Big Formation
NYB
Conformably overlies red-brown-green siltstones and subordinate sandstones of the Ceiriad Formation.
St Tudwal's Peninsula, northwest, Wales.
Dark grey and blue-grey siltstones with thin beds of pale sandstone/quartzose siltstone in upper part, and local bentonite horizons.
At least 110m
Unconformity defined by irregular erosion surface, commonly with stromatolites, above which lie conglomeratic sandstones of the Maentwrog Formation.
Nant-Ysgollon Mudstone Formation
NYG
Centrifugus Biozone.
Overlies the palr grey-green mudstones of the Dolgau Mudstone Formation.
Northern and central Wales.
Mudstones.
30 to 125m
Overlain by thinly bedded mudstones and siltstones of the Nantglyn Mudstones Formation.
Nant Y Gledryd Member
NYGD
Oxidised and reddened top of the rhyodacite lavas of the Foel Ddu Rhyodacite Formtion.
Crystal-lithic tuffs with variable characteristics, locally strongly welded towards the top.
Overlain by coarse crystal-lithic tuffs of the Bodgadle Member, or by volcanoclastic sediments of the Yoke House Formation.
Nant-Y-Gamar Limestone Member
NYGL
Early Asbian.
Not seen, but presumed to be a contact between massive, bryozoan-rich, reef limestones and underlying well-bedded, extensively dolomitised liestones (peloidal and skeletal grainstones) of the Llanarmon Limestone Formation
Nant-y-Gamar, Llandudno (SH 8081)
Massive, bryozoan-rich reef limestone (bafflestone/framestone). Early Asbian buildup of trepostome bryozoan rich limestones at the margin of the North Wales Dinantian carbonate platform.
At least 35m
Contact between "massive reef" limestones and well bedded, extensively dolomitised limestones (peloidal and skeletal grainstones) of the Llanarmon Limestone Formation.
Nant-Ysgollon Mudstone Formation And Nantglyn Flags Formation (Undifferentiated)
NYNG
Nieuw Zeeland Gronden Formation
NZG
Orchard Beds
Generally seen as a change from fluvial sandstone and overlying seatearth or coal, if present, to marine mudstone within the Upper Limestone Formation.
Distributed throughout most of the outcrop and subcrop of the Upper Limestone Formation in the Midland Valley of Scotland.
A thick marine mudstone and siltstone, with the the Orchard Limestone near the base.
Up to 20m in the Stirling, Airdrie, Falkirk and Glasgow districts.
Generally seen as a change to upward-coarsening arenaceous strata within the Upper Limestone Formation.
Ousdale Arkose Formation
Old Accommodation Coal (South Lancashire)
OACO
Oakeley Mynd Formation
OAK
Passage from underlying Aston Mudstones - trench: (SO 3494 8817) to (SO 3481 8810).
Eastern environs of Bishops Castle.
Mudstones, bedding-fissile with much graptolitic hemipelagite and thin siltstone laminae.
Overlain by Bailey Hill Formation.
Oakdale Clay Member
OAKC
Oakdale Sand Member
OAKS
Older Alluvium [Continued Use Not Recommended: See Alv1]
OAL
Normally soft to firm consolidated, compressible silty clay, but can contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated surface zone may be present. [Generic description]. Older than "Alluvium" in the same map area.
Oldbury And Avonmouth Levels Formation
OALEV
Rests unconformably on Triassic Bedrock.
The Oldbury and Avonmouth Levels, from Berkeley, Gloucestershire, to Portishead, Somerset.
The formation excompasses the marine, estuarine and terrestrial deposits that were formed in the Oldbury and Avonmouth Levels area during the Holocene transgression. The deposits are dark blue-grey silty clays and silts with subordinate sands and beds of peat, submerged forests and gravel. The deposits rest on a rockhead platform intricately dissected by river valleys, and their upper surface is approximately level at c 4.5 to 7m OD. The river valleys are infilled with gravels and sands that become shelly upwards. Typically two beds of peat are included, up to 0.6m thick; the lower of these forms the lowest unit in the formation except where it rests upon the valley-fill sands and gravels, and was formed c.8500-8000 years BP when a birch forest was inundated by the rising sea. The other formed c 5000-4500 years BP during a slowing down of the rising sea level, and is now found resting horizontally at OD.
c.10 to 13m, increasing to c.21m in buried channels.
Ordovician Rocks And Silurian Rocks (Undifferentiated)
OASR
Oystermouth Formation
Taken at the palaeokarstic surface seperating the thick-bedded mottled and pseudobrecciated skeletal packstones of the Oxwich Head Limestone Formation and the overlying thin- to medium-bedded argillaceous limestones, cherts and mudstones of the Formation.
South Pembrokeshire [SM 99 01], Gower [SS 50 90], northwestern crop of the South Wales Coalfield [SN 63 17], and western Vale of Glamorgan [SS 80 80].
Thin- to medium-bedded dark grey argillaceous limestones and mudstones. Chert nodules and beds, and silicified limestones common. Interbedded argillaceous limestones and mudstones commonly deeply weathered to decalcified rottenstone and pale grey, white and yellow clay. In western Gower and south Pembrokeshire, units of medium- to thick-bedded skeletal packstones and oolitic limestone with cherts occur in the lower part of the Formation.
61m on the Gower, thinning northwards to a feather edge on the northwestern crop of the South Wales Coalfield.
Taken at the top of the last limestone in the gradational junction between the interbedded limestones and mudstones of the Formation and the overlying thin-bedded banded cherts and mudstones and silaceous mudstones of the Aberkenfig Formation.
Old Bridge Coal (Northumberland)
OBC
Northumberland, especially the area centred upon Lewis Burn.
Observatory Sandstone Formation
OBG
Drawn at base of siltstone and mudstone of the Furse Argillaceous Beds at the base of the Observatory Sandstone Formation, where they rest conformably on sandstone of the Ward Hill Sandstone Formation.
Sandstone with thick beds of dolomitic siltstone and mudstone.
c.950m
Drawn at the conformable upward passage from sandstone of the North Haven Beds (of the Observatory Sandstone Formation) into sandstones, pebbly sandstones and conglomerates of the Vaasetter Sandstone Formation.
Baron Hill Rocks [Obsolete Code: Use Bah]
OBH
Old Bridge Limestone
OBL
Northumberland; type area around Lewis Burn.
Group of thin limestones and subordinate calcareous shaly mudstones.
c.4m in total.
Bodwrog Marble
OBM
Oddicombe Breccia Formation
OBR
Old Bridge Sandstone
OBRS
The area around Lewis Burn, Northumberland.
Orebank Sandstone
OBS
Bryn-Teg Volcanic Formation
OBTV
Late Precambrian or Comley.
Formation not assigned to a group. Not exposed, but seen in the Bryn-teg Borehole. Underlies the Harlech Grits Group.
Ormesby Clay Formation
Ockran Sandstone Formation
OCKS
Careg Onen Formation
OCO
Neoproterizoic to Early Cambrian.
Unknown, but Greenly [1919] supposed that it overlay the Gwna Melange (now the Gwna Group)] of Anglesey. There is some doubt about this, given current uncertainties on the age of these divisions.
Anglesey. The formation represents part of the Arfon Group of the mainland that extends onto Sheet 105 Caernarfon.
Fine- to coarse-grained, locally micaceous greywacke ["high-matrix"] sandstones, conglomeratic in places, with igneous and metamorphic clasts, interbedded with sandy mudstones, locally ferruginous.
Unknown, but probably overlain unconformably by Ordovician strata.
Oakenshaw Rock
OCR
West Yorkshire area [Oakenshaw, south of Bradfrod, Yorkshire].
False-bedded, fairly coarse-grained sandstone. Top part, known locally as the Shertcliffe Seatstone, may be separated from the lower sandstone by up to 15m of shaly mudstone.
Octofad Sandstone Formation
OCSA
Oxford Clay (Skye)
OCSK
Odhar Gravel Formation
ODGR
Sharp, erosional, undulating contact with underlying sandy clayey diamicton of the Suidheig Till Formation.
Sheet 84W (Fortrose), southest of Inverness.
Cobble gravel with lenses of finer gravel and sand, dense, mainly clast-supported, containing subangular to rounded clasts of pink granite with psammites, gneiss and schist. All but psammite clasts commonly weathered. Iron-pan commonly developed.
Conformable contact with overlying compressed peat of the Allt Odhar Peat Formation.
Orkney Devonian Minor Intrusion And Volcanic Suite
ODMIV
Ordley Sandstone
ODS
Odin Sandstone Member
ODSA
Oadby Member
ODT
Typically the bedrock surface below the deposit; other deposits may, however, intervene.
East Midlands.
Diamicton, grey, weathering brown, characterised by Cretaceous and Jurassic rock fragments; subordinate lenses of sand and gravel, clay and silt.Clay, brown to grey, and silty clay, with chalk and flint fragments - [Generic description: 'TMOS' Procedures].
Variable up to 20m; typically 1-7m
Typically the present-day surface; can, however, be overlain by later river terrace deposits or glacigenic deposits, or head.
Oadby Member (Lias-Rich)
ODTL
Clay, brown to grey, and silty clay, with chalk and flint fragments; rich in 'Lias' rock fragments. [Generic description: 'TMOS' Procedures].
Oadby Member (Trias-Rich)
ODTT
Clay, brown to grey, and silty clay, with chalk and flint fragments; rich in Triassic rock fragments. [Generic description: 'TMOS' Procedures].
Offrwm Volcanic Formation
Conformably overlies the siltstones and sandstones of the Allt Lwyd Formation or the conglomerates of its highest subdivision, the Aran Boulder Bed Member in the Harlech area and western part of the Cadair Idris district, but is disconformable on the Dol-cyn-afon, Dolgellau and Ffestiniog Flags formations in the south and east.
Cadair Idris and Harlech districts, North Wales.
Thick- to thin-bedded, locally welded, felsic ash-flow tuffs, subordinate rhyolitic lavas and dark grey mudstones.
0 to 290m
Conformably overlain by the Cregennen Formation (locally the Bryn Brith Member) over much of the Cadair Idris district, but unconformably overlain by the Ty'r Gawen Mudstone Formation (Fron Newydd Member) in the southwest. In the Harlech district it is variably overlain by the Cregennen, Melau and Benglog formations, with possible unconformity/disconformity.
Offa Formation
OFFA
Oldbury Farm Sandstone Formation
OFS
Conglomerate with subordinate sandstone layers rests with sharp base on reddish purple shaly mudstone of the Merevale Shale Formation.
From just south of Outwoods (SP 2975 9614) southeastward to just southeast of Moor Wood Farm (SP 3133 9417).
Greyish green conglomerates, sandstones, siltstones and reddish brown and green silty and sandy mudstones. Typically in upward-fining cycles.
152m true thickness in Merevale No.2 Borehole.
Greyish green massive siltstone with mudstone fragments and large roots in the top 15cm (Oldbury Sandstone Formation) is sharply overlain by pale grey sandstone with carbonised woody fragments (Millstone Grit).
Orton Group
Conformable base of lowest limestone unit overlying Carboniferous Basal (Basement) Beds, Ravenstonedale Group or Cockermouth Lavas.
Ravenstonedale area, Cumbria.
Limestone, sandstone, mudstone.
Approximately 40m
Overlain by Alston Group.
Orton Group And Alston Group (Undifferentiated)
OGAG
Overton Gas Coal
OGC
Oldham Great Coal (South Lancashire)
OGCO
Older Glacial Deposits
OGD
Gwddel Felsitic Formation
OGF
Older Glaciofluvial Deposits
OGFD
Sand and gravel, locally with lenses of silt, clay and organic material; of glaciofluvial origin; older than "Glaciofluvial Deposits [undifferentiated]" in the same map area. [Generic description].
Ogof Hen Formation
OGH
Unconformable.
Sandstones and sandy mudstones; basal conglomerate locally.
Up to 400 metres.
Oolite Group
OGP
Drawn at the base of the Oolite Group where it rests conformably upon the Lower Limestone Shales Formation.
Clydach Valley, Powys.
Wellsorted richly fossilferous crinoidal oolites with much secondary dolomite.
About 50 m thick.
Drawn at the unconformity upwards from the Oolite Group to the base of the Calcite-Mudstone Group.
Oolite Group Dolomite
OGPD
Older Glaciolacustrine Silt And Clay
OGSC
Silt and clay, interbedded, commonly laminated; of glaciolacustrine origin; older than 'Glaciolacustrine Silt and Clay' in the same map area. [Generic description].
Old Glencrieff Vein
OGV
Ogwen Group
OGW
Base of the Allt Lwyd Formation, at unconformable boundary overlying the Mawddach Group and Rhobell Volcanic Group.
Gwynedd, North Wales
Mudstones and siltstones, but including basal sandstone units and other sandstones, tuffs and oolitic ironstones.
c.1000m Pwllheli District.
Top of the Nod Glas Formation .
Ogwr Limestone
OGWR
Oldhaven Beds [See Also Hwh]
The term "Oldhaven Beds" was introduced by William Whitaker (1866). He named the unit for a locality to the east of Herne Bay, Kent, where it is exposed in the sides of a gully cut through the cliffs, and in the adjacent parts of the cliffs. This gully was then known as "Oldhaven Gap" but on later maps appears as "Bishopstone Haven" (1898 to 1938), or as "Bishopstone Glen" (current 1:10 000 scale topographic maps) or "Bishopstone Gap". The mouth of the "gap" is at National Grid reference 620715, 168730. It is about 3.5km east of the Pier at Herne Bay. The cliffs east of Herne Bay are a reference section for the Harwich Formation, which supersedes the term Oldhaven Beds, at least locally. See HWH.
Ord Hill Conglomerate
OHC
Oxwich Head Limestone Formation
OHL
In the Vale of Glamorgan the base is taken at the sharp contact, defined by a palaeokarstic surface, between the heterolithic lithologies of the underlying Stormy Limestone Formation and the overlying partially dolomitised sandy skeletal packstones and calcareous sandstones of the Pant Mawr Sandstone Member. On the northwestern crop of the South Wales Coalfield, it is taken at the sharp junction of the calcareous sandstone of the basal Honeycombed Sandstone Member and the underlying dark bituminous skeletal/peloidal grainstone/packstone/wackestone of the Dowlais Limestone Formation. In Gower and Pembrokeshire it is taken at the palaeokarstic surface separating the heterolithic lithologies of the underlying Hunts Bay Oolite Subgroup from the mottled and pseudobrecciated skeletal packstones of the Formation. In the Bristol/Mendip area the Formation overlies the Clifton Down Limestone Formation. The base here needs further work but is generally taken at the gradational change from calcite mudstones and ooidal limestones of the Clifton Down Limestone Formation to ooidal and skeletal limestones of the Formation. In the north of the Bristol area the Formation overlies the middle tongue of the Cromhall Sandstone Formation, the base being taken at the incomming of the ooidal and skeletal limestones above the sandstones of the Cromhall Sandstone Formation.
Western and central Vale of Glamorgan [ST 00 74], Gower [SS 50 90], northwest crop of the South Wales Coalfield [SN 90 13] and Bristol/Mendip Hills area [ST 50 65]. Present but unmapped in south Pembrokeshire [SM 99 01]. Interfingers with and passes northwards into the Cromhall Sandstone Formation in the Bristol area [ST 67 03].
Thick bedded fine- to coarse-grained, recrystalised, bioturbated skeletal packstones with distinctive pale to dark grey mottling and pseudobrecciation and ooidal limestones. Units of dark grey, irregularly bedded skeletal packstones with shaly partings are developed at intervals. Thin unit of calcareous sandstone and sandy skeletal packstone [Pant Mawr Sandstone Member and Honeycombed Sandstone Member] at base in the Vale of Glamorgan and northwest crop of the South Wales Coalfield respectively. Unit of ooidal limestone in lower part [Penderyn Oolite Member] on northwest crop of the South Wales Coalfield. Palaeokarstic surfaces, overlain by red and grey clay palaeosols, punctuate the Formation; thin coals developed in palaeosols in Gower.
125m in the central Vale of Glamorgan thickening southwards to 183m in the Mendip Hills.
Taken at the palaeokarstic surface separating the thick-bedded mottled and pseudobrecciated skeletal packstones of the Formation and the overlying thin- to medium-bedded argillaceous limestones, cherts and mudstones of the Oystermouth Formation.
Owl Head Marine Band
OHMB
Old Hythe Till Member
OHT
Gradational contact with underlying diamictons (including rafts) of the Whitehills Glacigenic Formation, or unconformable contact with Boyne Craig Till Formation, or on bedrock.
Scotland Sheets 95 (Elgin) and 96W (Portsoy).
Diamicton, silty, clayey, stony, dark yellowish brown to dark grey, angular to well rounded clasts of psammite, quartzite, pink granite, Devonian and Triassic sandstone, amphibolite and (importantly) fresh gabbro and troctolite.
>10m
Generally the land surface or overlain conformably by glaciofluvial or glaciolacustrine deposits.
Outer Hebrides Thrust Zone Mylonites Complex
OHTZ
Protolith Archaean (Lewisian) with Proterozoic deformation. Mylonitisation Proterozoic (1700 to 1100Ma; see Fettes et al, 1984, 151-152.
River Terrace Deposits (Undifferentiated) (Ouse, Kent)
River Terrace Deposits, 1 (Ouse, Kent)
OK1
River Terrace Deposits, 1-2 (Ouse, Kent)
OK1T2
River Terrace Deposits, 2 (Ouse, Kent)
OK2
River Terrace Deposits, 3 (Ouse, Kent)
OK3
River Terrace Deposits, 3-4 (Ouse, Kent)
OK3T4
River Terrace Deposits, 4 (Ouse, Kent)
OK4
Oak Bank Grit
OKB
Oakwood Coal (Northumberland)
OKC
Oakwood Limestone
OKL
Oakley Member
OKLY
A marked, and generally sharp, non-sequential, lithological change from sand or sandstone of the Beckley Sand or Arngrove Spiculite members of the Kingston Formation, or silty mudstones of the West Walton Formation.
Around Wheatley to Westcott, north-east of Oxford, restricted to 1:50 000 sheet 237 (see inset map for south-west limit). Similar facies which occur at the same horizon farther north-east; e.g. sheets 219, 220 and 203 are not Oakley Member, but should be treated as part of the West Walton Formation.
Interbedded pale grey marls, silty, argillaceous micritic limestones, siltstones and silty to sandy mudstones, commonly containing scattered ferruginous ooids, and locally rich in Nanogyra nana and serpulids.
Up to about 5 m thick.
An upward change to mudstones of the West Walton Formation or Ampthill Clay Formation.
Oakport Limestone Formation
OKPT
Okraquoy Gritty Quartzite (Formation)
OKRA
Oaktrow Sandstone
OKS
Oakshaw Coal (Bewcastle)
OKSC
Ockbrook Sand And Gravel
OKSG
Probably to 4m
Oakshaw Limestone
OKSL
Oakshaw Sandstone
OKSS
Oakshaw Tuff
OKST
Oakwood Glacigenic Formation
OKWDG
Anglian OIS 12 to ?Wolstonian OIS 6.
Irregular, unconformable contact with bedrock.
A mixed glacigenic sequence of till (sandy, gravelly clay with cobbles and boulders) and silt, sand and gravel possibly correlated with the Ridgacre Formation of the Birmingham area.
Unknown but probably <5m.
Overlain unconformably by sand of the Chelford Sand Formation (Irish Sea Coastal Glacigenic Subgroup).
Oakley Marl Member
OKY
Upward change from either dominantly micritic limestones of the Wockley Member, or fine-grained oolites of the Chilmark Member, to marls and clays. In sections, base taken below lowest "Dirt Bed"; in the field, micritic limestone above the Dirt Bed is probably mapped with the underlying Member.
Fonthill Gifford [ST 923 316] eastwards to beyond Chilmark [ST 980 310] (limit of current mapping).
Variable, but dominantly marls or clays, with thin beds of micritic limestone.
Upward change fron a dominantly marly sequence to micritic limestones of the "Middle Purbeck".
Old Lawrence Rock
Olive Coal (South Lancashire)
OLCO
Old Coal (South Lancashire)
OLDC
Older Lacustrine Deposits [Continued Use Not Recommended: See Lde1]
OLDE
Silt and clay (can include organic and/or calcareous muds). Older than 'Lacustrine Deposits [undifferentiated]' in the same map area; of lacustrine origin. [Generic description: from East Anglian data].
Old Harbour Vent
OLDH
Oldhamstocks Sill
OLDM
Older Head
OLHD
Polymict deposit: comprises gravel, sand and clay depending on upslope source and distance from source. Poorly sorted and poorly stratified deposits formed mostly by solifluction and/or hillwash and soil creep. Essentially comprises sand and gravel, locally with lenses of silt, clay or peat and organic material. In the Bristol area: red or brown silt and stony clay with cobbles of hard rock, eg. Carboniferous limestone or sandstone. Older than "Head" in the same map area. [Generic description].
Old Hythe Semipelite Member
OLHL
Sheared boundary with migmatitic semipelite and minor psammite of Cowhythe Psammite Formation.
From Moray Firth coast (Old Hythe to Boyne Bay) [NJ 6140 6630 - NJ 6155 6625] to Hill of Chattie [NJ 5900 6250].
Finely interbedded semipelite and micaceous psammite with lenses of quartzite and white to cream metalimestone.
c.150m on coastal section; progressively overstepped southwards by Whitehills Grit Formation. Sheared and tightly folded on coast.
Base of lowest massive metalimestone bed of Boyne Castle Limestone Member.
Oligocene Rocks (Undifferentiated)
OLIG
Ollaberry 'Series'
OLLY
Orchard Limestone
OLS
Generally seen as a change from a marine mudstone within the Upper Limestone Formation Orchard Beds.
Distributed throughout most of the outcrop and subcrop of the Upper Limestone Formation in the Midland Valley of Scotland, although it can be locally difficult to recognize in Fife, for example, in on-delta settings, where thick mudstones only of the Orchard Beds are present.
A pale to dark grey, fine-grained, argillaceous, crinoidal, bioclastic, locally shelly limestone.
From 0.15m to 1.2m, or locally less, in the Airdrie, Falkirk and Glasgow districts, but reaches over 5m thickness in shelf settings in Ayrshire.
Generally seen as a change from limestone to thick marine mudstone within the Orchard Beds of the Upper Limestone Formation.
Older Littoral Sand And Gravel
OLSG
Sand and gravel, formed within the littoral zone (between high and low water); older than modern littoral deposits in the same map area. [Generic description].
Oldbury Shales
OLSH
Old Lizard Head Series
OLZH
Unpublished data give a U-Pb zircon age of intrusion for a granodioritic sheet in the Old Lizard Head Series as c.500 Ma (Nutman et al. 2001. JGSL, Vol.158, 809-820).This would imply that the minimum age of the Old Lizard Head Series is Late Cambrian, on the basis of most recent chronostratigraphical compilations, unless the zircons are inherited.
Ousdale Mudstone Formation
Over Main Coal (South Derbyshire)
OMCO
Older Marine And Estuarine Alluvium
OMEA
Variable lithology. Sand, silt and clay, with gravel and peat locally, formed in the marine and estuarine environment. [Generic description].
Old Mine Fireclay
OMFC
Ormskirk Sandstone Formation
OMS
In the Reference Section (Sellafield Bh 13B), it is taken where aeolian sandstones overlie a thick fluvial sandstone sequence assigned to the Calder Sandstone. Geophysically, it is marked by a rapid upward decrease in gamma-ray values and an increase in sonic interval transit times.
Sellafield to Drigg on West Cumbrian coast; East Irish Sea Basin (offshore). Parts of North Lancashire in the same basin.
Fine- to coarse-grained (generally medium-) cross bedded and flat bedded sandstones, generally friable. In West Cumbria sandstones are aeolian, but offshore the Ormskirk Sandstone is dominated by fluvial sandstones, with aeolian interbeds. Details of lithology in the type area are not known, other than a description of 'coarse sandstone'.
176.42m+ onshore in Cumbria. Average 250m elsewhere. Up to 275m offshore.
Not seen onshore in West Cumbria, offshore it is overlain by the Mercia Mudstone Group. Awaits formal definition offshore in East Irish Sea Basin.
Omagh Sandstone Group
OMSG
Unconformity on Dalradian Supergroup metamorphic rocks.
The Kesh-Omagh area of the northwest Carboniferous basin in Ireland.
Predominantly clastic sediments; at the base are red-bed conglomerates and coarse sandstones, overlain by deltaic sandstones, siltstones and carbonaceous shales; highest beds are dark grey peritidal carbonates, serpulid limestones and shales.
Overlain unconformably by clastic sediments of the Claragh Sandstone Formation.
Ousel Nest Grit
Ouse-Nene Catchments Subgroup
ONCA
Formations of the Ouse-Nene Catchments Subgroup rest with marked unconformity on Middle Pleistocene glacial deposits and on Cretaceous and Jurassic bedrock.
The entire catchments of the rivers Nene and Ouse and their tributaries including the Nar, Cam, Lark, Slea and Witham.
The Ouse-Nene Catchments Subgroup encompasses all the fluvial, lacustrine and organic deposits of the rivers that occupy the catchment area of the rivers Ouse and Nene and their tributaries. Floodplain alluvium comprises soft silts and clays, commonly with beds of peat and a basal bed of sand and gravel. River terrace deposits are largely sand and gravel, the constituents of the gravel components reflecting the source rocks in each catchment. Lacustrine deposits are dominantly soft silts and clays. Minor marine deposits are included where they are intercalated in dominantly fluvial formations.
Old Nore Marl
ONMA
Onecote Sandstones
ONS
Old Park Coal (South Staffordshire)
Orionastraea Placenta Band
OPB
Openshaw Sandstone
OPS
The lower boundary is taken at the base of a sandstone-dominated unit directly overlying the Openshaw Coal.
The Bradford district of East Manchester [SJ864 988].
A dark reddish brown sandstone and subordinate mudstone.
24 m thick.
The upper boundary is taken at the base of the mudstone-dominated succession of the Pennine Upper Coal Measures Formation above the sandstones of the Openshaw Sandstone.
Openshaw Coal (South Lancashire)
OPSC
Oaks Rock
Ornatella Beds
ORB
Orchard Coal
ORC
Orcadia Formation
ORCA
Ordovician Rocks (Undifferentiated)
ORD
Ord Fundlie Pluton
ORDF
Older River Gravel
ORG
Gravel and sand; of fluvial origin; older than "River Gravel" in the same map area. [Generic description].
Organic Deposits
ORGD
Oronsay Greywacke Formation
ORGW
Orknagable Formation
ORKG
Orkney Swarm
ORKY
Rivers Mouth Formation
ORMF
Arenig And Llanvirn Rocks (Undifferentiated)
OROV
Orroland Member
ORR
Coastal section from Port Mary to Castle Muir.
Conglomerates, conglomeratic sandstones, red siltstones, marls and cornstones.
Biostratigraphical correlation with the Southerness Limestone Member (Lyne Formation) places the Orroland Member (of the Ballagan Formation) within the Chadian Stage (see Lintern and Floyd, 2000).
c.280m
Orrisdale Formation
ORRIS
Unconformably overlies the glacially tectonically deformed complex of diamictons, gravels and shelly sands of the Shellag Formation.
Stratigraphically complex sequence of stratified coarse-grained diamictons, sands and gravels. It is dominated by material derived from offshore within the Irish Sea basin. The Formation includes tills that are thought to have been formed subglacially or by glaciomarine deposition, and some of sands and gravels show extensive flow folding.
As now defined the Formation includes the nine members (Orrisdale Head, Bishop's Court, Trunk, Ballavarkish, Ballacottier, Ballaquark, Cranstal, Kinlough and Dog Mills members) originally assigned to it by Thomas (1999) and it also includes the Ballaleigh Member, which was originally assigned to the Ballaugh Formation by Thomas (1999).
Up to at least 60m
At the base of the stratigraphically complex sequence of laminated and massive muds with dropstones, gravel, sand and muddy diamicton comprising the Jurby Formation.
Orrin Formation
ORRN
Old Red Sandstone Supergroup
ORS
Older River Sand And Gravel
ORSG
Sand and gravel, of fluvial origin; older than "River Gravel" in the same map area. [Generic description].
Oreton Limestone Formation And Lower Limestone Shale Group (Undifferentiated)
ORSH
Upper Old Red Sandstone Group
ORSU
Oreton Limestone Formation
ORTL
The base of the lowermost ooidal or crinoidal limestone-dominated sequence of the Oreton Limestone Formation, underlain conformably by calcareous mudstone and impure limestone of the Avon group in the southern crop near Cleehill [SO 571 750]. This boundary has not been mapped on the Ludlow (181) Sheet. In the north crop near Oreton [SO 665 806]] , the Oreton Likestone Formation is shown resting directly upon conglomeratic sandstone, interpreted to be the basal unit of the Avon Group.
Clee Hills Outlier, between Cleehill [SO 571 750] and Oreton [SO 665 806].
The lower part is dominated by hard grey crystalline Limestones, crinoidal limestones and ooidal limestones. The upper part of the succession comprises mudstone with thin nodular limestones.
About 45 m thick in the northern outcrop between Oreton and Farlow [SO 646 803], and 20 m thick in the southern crop at Clee Hill [SO 571 750].
Mudstone and nodular limestones of the Oreton Limestone Formation are overlain with an angular unconformity by quartzitic sandstone of the Cornbrook Sandstone Formation.
Orval Member
ORVAL
Older River Deposits
ORVD
Normally soft to firm, consolidated, compressible silty clay, but can contain layers of silt, sand, peat and a basal gravel. A stronger, desiccated surface zone may be present; older than "Alluvium" in the same map area. [Generic description].
Otter Sandstone Formation
Rests sharply on ventifact bed at top of Budleigh Salterton Pebble Beds, in area between coast and Hill Head (Uffculme). Base difficult to identify in Taunton district owing to upward passage from conglomerate to sandstone (Edmonds and Williams, 1985).
Extends from south Devon coast between Budleigh Salterton and Sidmouth, northwards to near Minehead on the north Somerset coast.
Fine- to medium-grained sandstone, weathering to sand near surface. Sandstones locally micaceous and cross-bedded. Thin units of hard intraformational conglomerate; lenticular beds of reddish brown clay or mudstone locally; calcretes at some horizons. Lenticular pebble bed units mapped in the Exeter district.
Coast and Exeter district: c.160m. Taunton district: 30 to 60m
In coastal exposures (SY 110 8663), transitional into overlying Mercia Mudstone.
Osborne Beds
OSB
Osgodby Formation
OSBY
Osmington Oolite Formation And Clavellata Formation (Undifferentiated)
OSCL
Osdale Formation
OSDA
Overlies the Bracadale Formation and older lavas of the Skye Lava Group. Sporadic plant beds or plant fragments are locally present at the base of the unit.
Mugearite and basalt lavas. The initial work on this formation strongly implied that tholeiitic (sub-alkali) basalt dyke intrusion immediately post-dated the extrusive phase.
Uppermost lava flow. Overlain by superficial deposits or landslide material.
Onny Shales Formation
OSH
Olive green and grey mudstones
0 to 30m
Ordan Shuas Psammite Formation
OSHP
Base of the fairly massive shelfal psammites in the Ordan Shuas (NN 702 957) - Creagan a Choin area (NN 703 955), south of Newtonmore, taken at the incoming of thick quartzose psammites with channels, cross-bedding and slumped sedimentary structures.
Newtonmore area, south of Ralia and between the Glen Truim and Ericht-Laidon faults.
Mostly pale grey massive psammite intercalated with thin biotite-rich semipelite and pelitic layers, some quartoze psammite intervals. In parts slumped and channelled sedimentary structures are preserved.
Not seen; cut out to the southeast by the Ericht-Laidon Fault
Osborne Limestone
OSL
Osgodby Formation And Oxford Clay Formation (Undifferentiated)
OSOX
Outer Silver Pit Formation
OSP
Osmington Oolite Formation
OSS
An erosive, burrowed junction marks the boundary between the argillaceous sandstones and siltstones of the Bencliffe Grit Member (uppermost Redcliff Formation) and the argillaceous, sandy and ooidal limestones of the basal Osmington Oolite Formation.
South Dorset. Equivalent to the upper part of the Stour Formation of north Dorset. Probably no physical continuity due to pre-Cretaceous erosion.
The lower part predominantly comprises a regularly bedded series of ooidal limestones, sandy limestones and argillaceous limestones, overlain by mudstones with calcareous concretions, becoming sandy upwards (Upton Member of Wright and Cox, 2001). These are overlain, locally with an erosional contact by laterally variable cross bedded and bioturbated ooidal limestones with generally subordinate mudstone beds (dominant at Sandsfoot)(Shortlake Member of Wright and Cox, 2001). Shelly calcilutites are also developed at East Fleet. The Shortlake Member is overlain sequentially by irregularly bedded limestone and calcareous mudstone, with locally developed calcareous concretions (Nodular Rubble Member of Wright and Cox, 2001). The Formation contains a diverse ichnofauna, including Thalassinoides, Diplocraterion, Gyrochorte and Rhizocorallium, and macrofossils are represented particularly by ammonites, bivalves and gastropods.
Variable, but up to about 22m in the cliffs and foreshore between Bowleaze Cove and Ringstead. About 12m at East Fleet.
An irregular unconformity marks the contact of the uppermost Osmington Oolite Formation with the overlying Clavellata Formation. A change, from nodular limestone (below) to sandy limestone (above) occurs at this unconformity.
Outer Porphyritic Monzogranite Facies, Starav Intrusion
OSTAR
Older Storm Beach Deposits
OSTB
Gravel (shingle) and rare sand, often in a bank-like form; older than 'Storm Beach Deposits' in the same map area. [Generic description: academic papers and BGS Memoirs].
Oldstead Oolite Member
OSTD
Ordovician Shales (Undifferentiated)
OSU
Outwoods Breccia Member
OTB
Probably sharp upon Buck Hills Member, latter comprising blue-grey, thinly bedded volcaniclastic mudstones and siltstones.
Mainly occurs in the Outwoods Nature Area and possibly feathers out southwards, on the Charnwood Forest Golf Course.
Grey volcaniclastic sandstones and sediment-clast breccias interbedded with subordinate volcaniclastic mudstone and siltstone.
About 115m in Type Area, thinning to south.
Sharply overlain by Bradgate Formation, of blue-grey, laminated volcaniclastic rocks and tuffites.
Otter Bank Formation
OTBA
Trefdraeth Conglomerate
OTC
Oatlands Pluton
OTD
Older Tidal Flat Deposits
OTFD
Normally a consolidated soft silty clay, with layers of sand, gravel and peat. Characteristically low relief; from the tidal zone. [Generic description].
Older Till
OTIL
Variable lithology,usually sandy, silty clay (possibly chalky in southeast England) with pebbles, but can contain gravel-rich, or laminated, sand layers; varied colour and consistency; older than "Till" in the same map area. [Generic description].
Old Town Marl
OTMA
Outlet Mudstone Member
OTMM
Otterswick Psammite Formation
OTPS
Oatland Sandstone
OTS
Otley Shell Bed
OTSB
Oughtboy Burn Member
OUB
Probably conformable, with the normal Glenelly Formation schist lithologies.
Dark green chloritic schists.
Oulton Clay Member
OULT
Anglian (MIS 12).
The basal contact of the Oulton Clay Member with the underlying Lowestoft Till Member is sharp, and represented by an abrupt transition from clay-rich till, to laminated silts and clays.
Cliff sections between Corton Woods, Corton, north Norfolk. The deposit has been traced westwards inland in a series of shallow boreholes for some 400m.
Composed of horizontally laminated pale grey sandy silts and grey clays with sporadic isolated pale grey sand lenses.
Maximum thickness of 2.2m observed at stratotype.
The upper contact of the Oulton Clay Member with the overlying Pleasure Gardens Till Member is diffuse and represented by the interdigitation of beds of silt and clay with lenses of chalky till.
Ouse Valley Formation (Bucks, Beds, Cambs And Norfolk)
OUSE
Oulart Villa Limestone Formation
OUVF
Overwater Siltstone Formation
Unconformity with Skiddaw Group rocks below. (Angular discordance seen in places).
Limited to exposure of the base of the Eycott Volcanic Group. (Entirely within 1:50k Sheet 23, Cockermouth)
Grey, laminated siltstones and tuffaceous fine-grained sandstones; channels of sedimentary breccia composed of platy siltstone clasts at base. Formation is intruded by sills of Eycott Volcanic Group age.
c.8m at type section; up to 10m elsewhere; absent in some areas.
Overlain by conglomerate or by basaltic andesite and andesite lavas and sills forming main part of the Eycott Volcanic Group.
Ovenstone Coal
OVENC
Ochil Volcanic Formation
OVF
The base is not seen, because the unit interdigitates laterally with the siliciclastic rocks of the Dundee Flagstone Formation.
The bridge of Allan to Tayport and Coupar Angus, central Scotland.
Pyroxene andesite and olivine basalt lavas and rhyodacite, trachyandesite, hornblende andesite and volcaniclastic rocks.
Up to 2400 m thick.
The top of the lavas and associated volcaniclastic rocks of the Ochil Volcanic Formation, overlain by sandstones of the Scone Sandstone Formation.
Ovingdean Marl
OVMA
Overtoun Sandstone Member
OVS
The lower boundary is unconformable and overlies strata of the Ballagan Formation, that are characterised by grey mudstone and dolomitic limestone (cementstone). In the Barnhill Borehole, the base of the member is picked at the top of an interval dominated by grey mudstone with gypsum veins, at 161.48m depth, and overlain by a sequence dominated by thick intervals of sandstone.
The area around Overtoun House, north of the River Clyde near Dumbarton in Strathclyde, Scotland.
The lower part of the unit is about 36m thick, and is dominated by grey, fine-grained, thin-bedded or partly concretionary sandstone. There are also intervals of mudstone, up to 3.32m thick, commonly with calcareous concretions and uncommon beds of concretionary limestone or dolomitic limestone (cementstone). The upper part, which is about 20m thick, largely comprises of pale grey, mostly fine-grained sandstone with clasts of carbonate. Unlike the lower part of the member, sandstones with concretions and mudstones are uncommon.
56.6m at the Type Section.
The boundary is sharp and picked at a marked change from grey sandstone and mudstone to grey tuff, with volcanic lapillae of the overlying Clyde Plateau Volcanic Formation at 104.89m depth in the Barnhill Borehole. Correlation with the Greenock district, demonstrates that the base of the Clyde Plateau Volcanic Formation is unconformable.
Overwood Slate Member
OVSL
Greenish grey silty slate.
Overthorpe Coal (Oxfordshire)
OVTH
Owenkillew Sandstone Group
OWSA
Outwoods Shale Formation
OWSH
Transitional passage, with decreasing proportion of bioturbated, erosionally-truncated beds in upper part.
Extends from eastern suburbs of Bedworth, northwest to just east of Merevale Hall. (SP 3688 8633-2986 9758)
Interbedded grey burrowed, and dark-grey or greenish grey pyritic, mudstone. Beds of siltstone and sandstone increase in upper part.
300m in general: 87m minimum in Merevale No.1 borehole; 158m minimum in Merevale No.3 borehole.
Transitional passage into the Moor Wood Sandstone Formation by increase in silty and sandy beds and decrease in dark-grey, pyritic and carbonaceous material.
Oxbow Coal (West Yorkshire)
OXBC
According to Tragheim (1991), Godwin and Calver (1974, fig 4) thought that the Middleton Little, Third Brown Metal and Second Brown Metal coals merged to form the 'Oxbow Coal' near the opencast site of that name. It now appears that only the Middleton Little and Third Brown Metal coals effectively merge, but with a dirt parting, and this pairing was previously referred to solely as the 'Middleton Little Coal'.
Oxford Clay Formation
OXC
Middle to Upper Jurassic, Lower Callovian to Lower Oxfordian (Calloviense Zone to Cordatum Zone).
Generally a fairly sharp but generally conformable junction with silicate-sandstone or sandy mudstone of the underlying Kellaways Formation or, in the Cleveland Basin, sandstone of the underlying Osgodby Formation, overlain by silicate-mudstone. In thicker, expanded successions (Wessex Basin) arbitary boundary drawn at the top of highest substantial silicate-sandstone or sandy mudstone above which the succession is predominantly silicate-mudstone.
Dorset coast (Weymouth area) to North Yorkshire coast. Extensive in onshore subcrop, though absent above the interior of the London Platform.
Silicate-mudstone, grey, generally smooth to slightly silty, with sporadic beds of argillaceous limestone nodules. Over most of the outcrop (except the Cleveland Basin, where only the upper part is present) it comprises a tripartite succession: lower part (Peterborough Member) silicate-mudstone, mainly brownish-grey, fissile, organic-rich ("bituminous"), with subordinate beds of pale to medium grey, blocky mudstone; middle part (Stewartby Member) silicate-mudstone, mainly pale to medium grey, smooth to slightly silty, blocky, with subordinate beds of silty shell-debris-rich mudstone; upper part (Weymouth Member) mudstone, mainly pale grey, calcareous, smooth, blocky. For more detail see Peterborough, Stewartby and Weymouth members.
To 185m (perhaps in south Dorest); typically 50 to 70m over much of the East Midlands Shelf.
Upward transition from silicate-mudstone to silty mudstone of the overlying West Walton Formation (Oxford to Market Weighton) or sandy mudstones and calcareous sediments (Dorset to Oxford, and Yorkshire, north of Market Weighton) of the Corallian Group. In Market Weighton area, sharp disconformable contact with chalk (Chalk Group, Hunstanton Formation). In the Westbury to Longleat area, Wiltshire, sharp disconformable contact with sandy micaceous mudstone (Cretaceous, Gault Formation).
Oxford Clay Bituminous Member
OXCB
Oxford Clay Silty Member
OXCS
Oxford Clay Top Member
OXCT
Oxfordian Deposits
OXFD
Kellaways Formation And Oxford Clay Formation (Undifferentiated) [Obsolete Code: Use Klox]
OXKL
Oxford Limestone Member
OXL
Taken at the generally conformable, sharp base of the first bed of limestone that overlies measures of the Alston Formation. This typically displays a coal or seatearth immediately below the limestone.
Widespread limestone member occurring throughout the Northumberland Trough in northern England and the Scottish Borders within the Alston Formation, lying stratigraphically below the Eelwell Limestone.
Limestone, thick bedded at base, becoming thin bedded at top; grey to dark grey with numerous red-weathered Osagia (an alga) haloes; particularly rich in corals and brachiopods.
Some authors correlate the Oxford Limestone with the Jew Limestone of the Alston Block and north of the Lake District (George and Black, 1971) and with the Bridge Limestone in the Bewcastle and Langham area (Day, 1970).
Taken at the top of the uppermost limestone bed that is overlain by a coarsening upwards sequence of dark grey mudstones, siltstone and sandstone, the first containing ironstone nodules.
Oxendale Tuff
OXT
Base of rhyolitic, lava-like, welded tuff overlies parallel bedded, andesitic tuff (Whorneyside Tuff Formation). Essentially conformable but with angular discordances where the andesitic tuffs are slumped.
Oxendale, Great Langdale and Coniston Fells, Cumbria.
Pink weathered rhyolitic, lava-like, welded tuff.
At base of overlying main part of the Long Top Tuff Member: rhyolitic tuff and lapilli-tuff that is of lower-grade (less densely welded).
Oxford Clay Formation And West Walton Formation (Undifferentiated)
OXWW
Oakley Upper Coal
OYU
Plean No.1 Limestone
P12 Coal (South Derbyshire)
P12
P13 Coal (South Derbyshire)
P13
P14 Coal (South Derbyshire)
P14
P15 Coal (South Derbyshire)
P15
P16 Coal (South Derbyshire)
P16
P17 Coal (South Derbyshire)
P17
P18 Coal (South Derbyshire)
P18
P19 Coal (South Derbyshire)
P19
Plean No.1 Coal
P1C
Plean No.2 Limestone
P20 Coal (South Derbyshire)
P20
P21 Coal (South Derbyshire)
P21
P22 Coal (South Derbyshire)
P22
P23 Coal (South Derbyshire)
P23
P23 And P24 Coal, (South Derbyshire) (Undifferentiated)
P24 Coal (South Derbyshire)
P24
P25 Coal (South Derbyshire)
P25
P26 Coal (South Derbyshire)
P26
P27 Coal (South Derbyshire)
P27
P27 And P28 Coal, (South Derbyshire) (Undifferentiated)
P28 Coal (South Derbyshire)
P28
P29 Coal (South Derbyshire)
P29
Plean No.3 Limestone
P30 Coal (South Derbyshire)
P30
P31 Coal (South Derbyshire)
P31
P32 Coal (South Derbyshire)
P32
P33 Coal (South Derbyshire)
P33
P33 And P34 Coal, (South Derbyshire) (Undifferentiated)
P34 Coal (South Derbyshire)
P34
P35 Coal (South Derbyshire)
P35
P35 And P36 Coal, (South Derbyshire) (Undifferentiated)
P36 Coal (South Derbyshire)
P36
P37 Coal (South Derbyshire)
P37
P38 Coal (South Derbyshire)
P38
P39 Coal (South Derbyshire)
P39
P39 And P40 Coal, (South Derbyshire) (Undifferentiated)
P40 Coal (South Derbyshire)
P40
P41 Coal (South Derbyshire)
P41
P42 Coal (South Derbyshire)
P42
P42 And P43 Coal, (South Derbyshire) (Undifferentiated)
P43 Coal (South Derbyshire)
P43
P44 Coal (South Derbyshire)
P44
Pemberton Four Foot Coal
P4FT
Prescot Five Foot Coal (South Lancashire)
P5FT
Paxford Gravel Member
Limestone gravel, bedded. [Generic description: 1:50 k map margins].
Platyschisma Bed [Obsolete Code: Use Pty]
PAB
Pabay Shale Formation
PABS
Abrupt facies change from Ardnish Formation sandstones to dark mudstones.
Sea of Hebrides Basin (mainly Skye and Raasay).
Basal beds consist of fine-grained, dark, micaceous fissile mudstones. The remainder of the Formation consists of silty and micaceous mudstones. The unit is rich in infaunal and epifaunal benthic faunas, ammonites and belemnites. The unit coarsens upwards to the Scalpay Sandstone Formation, with thin, local, clastic coarsening cycles.
200m maximum
Diachronous and transitional to the Scalpay Sandstone Formation.
Patna Coal
PACO
Locally the Patna Coal can comprise Lower, Middle and Upper coals. See also the Supplementary Information concerning the Patna Coal Group [= Patna group of coals].
Park Farm Clay Member
PAF
Observed in boreholes, this unit rests on either a sand and gravel lag deposit or directly on bedrock.
Vale of York, south of the Escrick Moraine between the rivers Ouse, Foulness and Humber where the Lawns Farm Sand Member is present, and extending northwards beneath the Escrick Moraine, the York Moraine and the tills of the Vale of York Formation.
Greyish brown to dark grey, slightly fissured, laminated, soft (0.2-2cm varves) silt and clay with rare fine sand layers. Horizons of fine-grained sand to 1m thick occur within the unit.
To 16m
The Park Farm Clay Member is succeeded by the Lawns House Farm Sand Member, The contact with the Lawns House Farm Sand Member is typically sharp.
Park Hill Member
PAH
At base of first bed to show cross bedding and an undulatory top surface. Lower sandstones are massive, with planar or only gently undulatory tops.
From Nuneaton town centre, extending northwest for 3.5km to just east of Cherry Tree Farm (SP 3548 9220-3262 9521)
Grey medium-grained sandstone with thin breccia layers in basal 17m: main part in beds 0.2-0.8m thick showing herringbone cross-bedding. Very rare mudstone beds or drapes.
30 - 56m. 35m in type section (min), 34m in reference section (min).
Bedding plane beneath first significant development of mudstone with thin, sharp-based sandstone beds. Mudstone drapes ubiquitous in beds above this.
Paisley Clay Member
PAIS
The Paisley Clay Member of the Clyde Clay Formation rests with angular unconformity or disconformity on older Quaternary sediments or bedrock. It normally rests on the Wilderness Till Formation of the Caledonia Glacigenic Group (Midland Valley Glacigenic Subgroup). However, under the deeper part of the Quaternary sedimentary basin adjacent to the River Clyde it is underlain by the Bridgeton Sand Member of the Clyde Clay Formation.
The Clyde Clay Formation is recognized in the lower Clyde valley north of Lanark, in and around the estuary of the Clyde and the Firth of Clyde and linked sea lochs, and in Loch Lomond. It is also present under the coastal plain of Ayrshire. The Paisley Clay Member has a distribution similar to the parent formation up to the elevations of 35 to 40m above sea level.
The Linwood Borehole (Browne and McMillan, 1989a, Figure 17) is the standard section for the Paisley Clay Member in the Clyde valley west of Govan, and Loch Lomond. Stratigraphical relationships and geographical distribution are in ibid (Figures 2c, 3, 4). The lithofacies are: Clay and silt, finely colour banded in shades of greyish brown and grey; sparse marine fauna (26.5-28.14m in depth). Silt with clay bands, grey, well-bedded; sparse marine microfauna (28.14 - 29.20m). Clay with silt layers, very finely colour laminated in shades of reddish brown and grey (29.20 - 30.23m). Silt with some sand and clay bands; grey, well bedded (30.23 - 31.10m). The succession is thicker and subdivided into three east of Govan. In the Bridgeton Borehole (ibid, Figure 18): Clay, silty, with many silt laminae; colour banded in shades of brownish grey and sometimes reddish brown; rarely fossiliferous (6.9 - 16.23m). Clay, silty, with many silt laminae; colour banded in shades of brownish grey and reddish brown; bands of finely colour laminated clay in shades of reddish brown and grey; rarely fossiliferous (16.23 - 21.77m). Silt with clayey silt and clay bands; thinly laminated to thinly bedded; brownish grey, reddish brown and grey; rarely fossiliferous (21.77 - 29.31m).
Veneer to over 25m.
The Paisley Clay Member is overlain conformably or unconformably by younger Quaternary sediments. Normally the Linwood Clay Member of the Clyde Clay Formation (of the British Coastal Deposits Group) is in conformable contact but the Clydebank Clay Formation and Clyde Valley Formation of the Britannia Catchments Group (Clyde Catchment Subgroup) is unconformable. It is also extensively exposed at surface in the lower Clyde valley.
Park Hill Limestone Member
PAL
The base of the Member coincides with the top of the "Algal Layer" (Coldbeck Limestone Formation) in the Ravenstonedale area.
Limestone and dolostone, fine-grained grainstone and packstone, dark grey to buff, wavy bedded, interbedded with sandstone, siltstone and mudstone. The limestone lacks the common occurrence of corals typical of the overlying Coupland Sike Limestone.
The top occurs beneath the more regularly bedded and fossiliferous overlying Coupland Sike Limestone Member. The junction is marked by a 5m interbedded sandstone and mudstone unit that forms a topographical depression.
Palaeogene Rocks (Undifferentiated) [Obsolete Code Due To Duplication: Use Pgu]
PALG
Patna Limestone
PALS
Upper Cretaceous And Palaeogene Rocks (Undifferentiated)
PALUC
Pasture Coal (South Lancashire)
PAMC
Pant Formation
PANT
Rests unconformably on Ordovician mudstones and tuffaceous sandstones of the Allt-tair-ffynnon Formation.
Pant area (SJ 28 22), south of Oswestry, North Wales.
Pale, greenish-grey mudstones, darker in uppermost 3m with thin beds of dark grey sandy limestone. The formation records the accumulation of alluvial and lagoonal (restricted marine) muds along the local margin of the North Wales Dinantian platform.
Conformable and gradational contact with porcellanous or coarser-grained limestones of the Leete Limestone Formation.
Pant Limestone
PANTL
Papa Group
PAPA
Palaeozoic Or Quaternary Rock And Sediment (Undifferentiated) [Offshore Only]
PAQU
Parrot Coal (Bristol Area)
PARC
Parade Vent
PARD
Peralkaline Rhyolite Swarm
PARH
Park Coal (South Lancashire)
PARK
Parrot Rough Coal (Limestone Coal Formation)
PARP
Parrot Rough Coal (Coal Measures) (Lothian)
PARW
Pattison Sill
PAS
Ptarmigan Sandstone Member
PASA
Pastures Coal (South Lancashire)
PASC
Palaeosol (Quaternary Only)
PASO
Soil formed in an earlier period of pedogenesis during the Quaternary. [Generic description: earth science dictionaries in the BGS library].
Pandy Tuff Formation
PAT
Conformable sharp junction with underlying siltstones and mudstones of the Teirw Siltstone Formation.
Welded and non-welded felsic ash-flow lapilli crystal tuffs and thin mudstones.
To 37m
Conformable gradational junction with the Bryn Siltstone Formation.
Pattack Gneisses
PATK
Port An T-Seilich Member
PATS
Pattack Till Formation
PATT
Unconformable, on bedrock.
Valley of the River Pattack.
Gravelly sandy clay diamicton with angular to rounded clasts of micaceous psammite, grey granite, porphyry and quartzite. Pale olive brown and slightly weathered.
<4m
Generally unconformable with the Ardverikie Till Formation, but locally conformable with overlying Linn of Pattack Silt Formation.
Pavey Ark Breccia Member
PAV
Base of the unit of pebbly sandstone and volcaniclastic breccia. Mildly unconformable on volcaniclastic sedimentary rocks within the Seathwaite Fell Sandstone Formation.
Langdale Pikes (NY 280 075) to Bell Crags (NY 298 142), Cumbria.
Pebbly sandstone and volcaniclastic breccia; brown weathered, massive to poorly bedded; in the type area contains abundant ragged, vesicular andesite spatter.
Generally overlain by fine-grained sandstone and siltstone within the Seathwaite Fell Sandstone Formation.
Purbeck Limestone Group
First occurrence of finely laminated, ostracod-rich limestones above the more massive, shelly limestones of the Portland Group.
Occurs in a number of sub-basins across north Europe. In England, occurs in south Dorset (between Weymouth and Swanage), in the Weald (largely in sub-crop), and as several inliers in the Vale of Wardour and Vale of Pewsey. Likely also to occur as inliers beneath cover across much of southern England. Occurs in the subcrop throughout southern Britain (Wessex Basin) as far west as Wiltshire and Dorset, and as far north as Berkshire, Oxforshire and Buckinghamshire. It outcrops within the core of the Weald and as outliers on Oxfordshire, Buckinghamshire and Bedfordshire. It is presently identified on mapsheets E219 [Pb], E220 [Pb], E237 [Pb], E252 [g14], E270 [Pb], E271 [Pb], E285 [PB], E287 [g14], E288 [shown in GVS but not symbolised], E289 [shown in GVS but not symbolised], E297 [Purbeck Formation shown but only Oakley Marl Member symbolised], E298 [Pb, and Formations to be released late 2004], E299 [Pb], E300 [Pb], E302 [g14], E303 [g14], E304[g14], E305/6 [g14], E316 [pb], E317/332 [Pb], E318/333 [shown in GVS but not symbolised], E319 [g14], E320/321 [g14], E327 [g14]. E328 [formations and members shown], E331 [Pu], E341/342 [formations and members shown], E342/343 [formations and members shown]. It is also likely to be present at depth but not depicted on E283, E284, E286, E301.
Interbedded mudstones, limestones and evaporites of marginal freshwater, brackish and marine origin; detrital quartz occurs in parts. The group (Purbeck Beds), was traditionally divided into Lower, Middle and Upper units ('beds') with a key marker, the Cinder Bed placed within the middle part of the Middle Purbeck Beds. At the type site in Dorset, the Group is now formally divided into the Lulworth Formation, below and the Durlston Formation above with the base of the Durlston Formation placed at the base of the Cinder Bed. This formal terminology can now be applied throughout the outcrop and subcrop of the Group.
45 to 120m in south Dorset. 77 to 186m in the Weald. Succession incomplete in the Vale of Wardour.
Last occurrence of significant limestone before monotonous Wealdon Group sandy mudstones. Highest Limestone rich in Viviparus and Unio.
Permian Basal Breccia
PBB
Sharp; unconformable on reddened Carboniferous rocks.
Eastern and north-east England, patchily distributed (Smith, 1989, fig.3). Associated with aeolian sandstone in Yorkshire.
Conglomerate, matrix supported; matrix of grey-brown, dolomitic or calcareous sandstone with rounded to angular grey, green, purple or red clasts of mudstone, sandstone, ironstone, limestone and less common igneous and metamorphic rocks.
Generally less than 2m
Sharp; upward passage into late Permian mudstones (Marl Slate), dolostone or dolomitic siltstone (Cadeby Formation) or sandstone (Lenton Sandstone Formation).
Portnaloub Coal (B)
PBCB
Preshal Beg Conglomerate Formation
PBCO
Pontybodkin Divided Coal (North Wales)
PBDC
Plann Blackband Ironstone
PBI
Potts Beck Limestone Formation
PBK
Latest Holkerian to early Asbian.
Where medium to dark grey, medium- and coarse-grained limestones and shaly limestones of the Potts Beck Limestone overlie pale, grey-brown, flaggy, fossiliferous limestone of the Ashgill Limestone.
Predominantly limestone but with interbedded sandstone and possibly mudstone. Limestones not only include pale grey biosparites etc, as in Knipe Scar Limestone, but also dark grey, platy beds.
70 metre. (Thins slightly westward to c.60m north of Orton).
Where pale grey limestone and dark grey limestone and sandstone of the Potts Beck Limestone is overlain by pale grey, scar-forming limestone (mostly thick-bedded biosparites and biopelsparites commonly pseudobrecciated) of the Knipe Scar Limestone.
Pepper Box Marls (One)
PBMA1
Pepper Box Marls (Two)
PBMA2
Pontybodkin Mountain Coal (North Wales)
PBMC
Porthleven Breccia Member
PBR
Pulborough Sandrock Member
PBS
At upward change from poorly sorted sands, typically pebbly, limonitic and/or clayey (locally at a pebbly sandy clay), of the Fittleworth Member or the Rogate Member, to dominantly fine-grained, well-sorted sands.
South-west Weald; eastern limit is Storrington, West Sussex [TQ 07 14]; northern limit not known.
Uniformly fine-grained, friable, well-sorted, fossiliferous sandstone; rarely cross-bedded, grey when fresh, yellowish-brown when weathered. Sparse coarse grains can be present near base. Coarse ferruginous sand locally present at top. Thin clay beds in places.
In the type area, the top of a thin cemented ironstone beneath the clays and silts of the Marehill Clay Member; around Petersfield at the change from mainly sand to mainly grey silty clay in a short gradational sequence.
Permian Basal Sandstone Formation (Tyrone)
PBSA
Lower Pulborough Sandrock
PBSL
see Pulborough Sandrock Member PBS
Upper Pulborough Sandrock
PBSU
Pen Bwlch Tuff Member
PBT
Conformable Member of the Teirw Siltstone Formation.
Two thin units of lapilli tuff separated locally by 5m of mudstone and siltstone.
Conformably overlain by mudstones and siltstones of the Teirw Siltstone Formation.
Port Beag Till Formation
PBTI
Irregular, unconformable contact with underlying deposits of organic sand and silt belonging to the Mid-Devensian Tolsta Head Member of the Lewis Formation of Bowen (1999).
Northern Lewis, northeast of a prominent lateral moraine.
Reddish brown, matrix-supported diamicton with a notable proportion of clasts of Torridonian sandstone and, at the type section, blocks of the underlying organic sand and silt. Generally occurs as an interbedded and locally glacitectonically deformed sequence of shelly diamicton, silt, sand and gravel.
Up to 25m
Ground surface or unconformably overlain by glaciofluvial sand and gravel.
Penwhapple Burn Shale Member
PBU
A conformable contact of this prominent mudstone with sandstone of the enclosing Saugh Hill Grits Formation.
Limited to Penwhapple Burn, near Girvan, but may correlate with the Glenshalloch Shale Formation (GLSH) in the Craighead Inlier. May not be able to see outcrop on the map at this scale.
A bedded grey mudstone, probably of turbiditic origin.
Persabus Member
PBUS
Benton Volcanic Group
PBV
Unknown, possibly faulted.
South west Wales, Pembrokeshire, Haverfordwest district.
Spherulitic and autobrecciated lavas of sodic rhyolite and trachyte with subordinate red and green sillicic tuffs.
Polygenetic Conglomerate
Penchrise Burn Beds
PCB
Port Calliagh Chalk Formation
PCC
Maastrichtian. Belemnella lanceolata Zone.
Conformable on the Tanderagee Chalk Formation at the lowest `separation plane? immediately beneath the `belt of complex flints? seen in the Ballycastle section.
Outcrops in the Southern Uplands area (in isolated areas), the North Antrim Basin and in the southern part of the Londonderry Shelf. Absent in the East Antrim Basin, the Highland Border High and northern Londonderry shelf due to pre-Palaeogene erosion.
Limestone (chalk) with numerous flint bands displaying large, tabular and complex habit.
12.40m at the type-site.
Conformable at a prominent weathered-out bedding plane at the top of `Bed? F with the Ballycastle Chalk Formation,
Peacock Coal (South Lancashire)
PCCK
Pot Clay Coal (West And South Yorkshire)
PCCL
West and south Yorkshire area.
The Pot Clay Coal is a thin coal of little value, but it overlies a valuable fireclay that has been widely extracted for bricks and pottery.
Penclawdd Coal (South Wales)
PCDD
Praetiglian To Cromerian Complex Interglacial 1 Deposits, Undifferentiated (Offshore)
PCDU
Praetiglian to Cromerian Complex Interglacial 1.
Pont-Y-Ceunant Ash
PCE
Impersistent basal Member of the Gelli-grin Calcareous Ash Formation. Conformably overlies mudstones of the Ceiswyn Formation, but base is extremely irregular.
Coarse rhyolitic tuff.
Passes conformably and gradationally upwards into the main part of the Gelli-grin Calcareous Ash Formation.
Pitlurg Calcareous Flag Formation
PCFL
Ardonald Anticline, from Blackhillock and Alehousehillock, in the Cairnie area, SW to Achmore, Glen Rinnes. And around Keith from Drummuir to Ardrone (Sheets 85E and 86W). Above Keith Shear Zone - equivalent stratigraphically to Cairnfield Calcareous Formation below the Keith Shear Zone.
Calcareous, banded psammite and semipelite, grey and pale green, normally flaggy. Some beds of impure metalimestone locally.
>50 - 1200m (based on outcrop width and average dip). Real thickness is probably closer to lower estimate, owing to prevalent open folds.
Patna Coal Group
PCG
The Patna Coal Group is not be a "group" in the lithostratigraphical sense. Depending upon context its use might be restricted to covering the Upper, Middle and Lower Patna coals, which underlie the Patna Sandstone, or might also include the 5 or 6 thin (<10") coals beneath the Black Metals Member and the underlying 2 to 5 leaves of the Diamond Coal (Patna). These are all within the Limestone Coal Formation and of Pendleian age. The most common use of the term "Patna Coal Group" would be the former option, referring to the three Patna Coals (Upper, Middle and Lower) and so is the equivalent of and alternative to Patna Coal in areas where more than one seam is recognised.
Polcrebo Gravels
PCGR
Pre-Caledonian Granites (Informal Suite)
PCGRA
Pencleuch Shale Formation
PCH
Conformably overlies Saugh Hill Grits Formation.
Lower grey shale unit and upper black shale unit.
Disconformably overlain by Lower Camregan Grits Formation (Penwhapple North Group).
Portsdown Chalk Formation
PCK
Campanian. Topmost Gonioteuthis quadrata and Belemnitella mucronata Zones.
Conformable at the Portsdown Marl 1in the Farlington Redoubt on Portsdown and at Whitecliff Bay, Isle of Wight (Mortimore, 1986).
Limited to Sussex, Hampshire, Wiltshire and Dorset close to the Palaeogene cover in the Southern Province. Its possible occurrence and distribution beneath the Quaternary deposits of East Anglia in the Transitional Province is not well known.
Composed of white chalk with marl seams (particularly in the lower part) and flint bands, although less flinty than the Culver Chalk Formation. The lowest part (up to and including the Farlington Marls at the base of the mucronata Zone) contains several belts rich in inoceramid shell debris, as well as isolated marl seams and pairs of marl seams that likewise contain much inoceramid shell debris. The highest part is essentially marl-free and termed the Studland Chalk `Member? of Gale, Wood and Bromley (1987).
62m at Whitecliff Bay. Thought to be thicker elsewhere, but limited by the sub-Palaeogene erosion surface.
IAs defined the upper boundary of the Formation is the sub-Palaeogene erosion surface. The boundary with the Studland Chalk Member (sensu Gale et al., 1987) is conformable at a marly bed with included marl above which the chalk is marl-free in the Alum Bay/Scratchell?s Bay section on the Isle of Wight and at ?the lower horizon of yellow-stained chalk on Old Harry Rock? in Studland Bay, Dorset (Gale et al., 1987). In the `Transitional? Province the upper boundary is undefined but it is noted (Mortimore, Wood and Gallois, 2001) that the ?highest chalk of the Isle of Wight and Dorset? is equivalent to beds within the Weybourne Chalk Member as formalised by Johansen and Surlyk (1990). These higher beds are informally termed the `Norwich Chalk? and `Trimmingham Chalk?.
Piper's Cross Limestone
PCL
Bluish grey crinoidal limestone with corals and giganteid productids.
Pettycur Limestone
PCLS
Pennine Coal Measures Group
PCM
The base of the mudstone of the Gastrioceras subcrenatum Marine Band (=Subcrenatum Marine Band) or at the base of the lowest coal within the coal-bearing sequence if this marker band cannot be identified.
Central and Northern England and North Wales.
Alternation of sandstone, grey siltstone and grey mudstone, with frequent coal seams and seatearth horizons. Note that, definitions for the base of the Pennine Coal Measures Group and the bases of the Middle and Upper Formations are those of Stubblefield and Trotter (1957), but the top of the Pennine Coal Measures Group is newly defined here on a purely lithostratigraphical basis.
Up to 1600m thick in the Potteries Syncline of Stoke, 900m thick in the Northumberland-Durham Coalfield, 300-400m thick in West Cumbria, 100-200m thick in the South Staffordshire-Warwickshire Coalfield.
Taken at the base of the lowest conformably overlying red-bed formation, - Etruria Marl or lateral equivalent of the Warwickshire Group in North Wales and Central England, or the Whitehaven Sandstone Formation in West Cumbria, and elsewhere taken at the sub-Permian unconformity.
Praetiglian To Cromerian Complex Interglacial 1 Mud And Sand, Interbedded (Offshore)
PCMAS
Praetiglian To Cromerian Complex Interglacial 1 Mud, Very Soft To Soft (Offshore)
PCMVS
Pennine Coal Measures Group And Warwickshire Group (Undifferentiated)
PCMWK
Pre-Cambrian To Ordovician Rocks (Undifferentiated)
PCOR
Pen-Ychain Rhyolitic Complex
PCR
Overlies sandstones, tuffs and siltstones of the Cwm Eigiau Formation.
Rhyolitic domes, sills and tuffs associated with the Pitts Head Tuff and Llwyd Mawr Tuff.
Up to 700m (including the Pitts Head Tuff).
Overlain by sandstones, tuffs and siltstones of the Cwm Eigiau Formation or ash-flow tuffs and breccias of the Lower Rhyolitic Tuff Formation.
Piper's Cross Coal
PCRC
Widely developed in Northumberland.
Worked seam. Roofed by an impure calcareous band rich in ostracods.
c.0.75 to 1.2m locally.
Portencorkrie Intrusion
PCRK
South end of Rhins of Galloway.
Zoned granitic intrusion, granitic core, dioritic envelope.
c. 5 square km in area
Pebbly Clay And Sand
PCS
Clay, pebbly, locally with gravel, sand and silt lenses. [Generic description].
Praetiglian To Cromerian Complex Interglacial 1 Sand (Offshore)
PCSND
Princess Coal (Northumberland)
PCSS
Powderhouse Corner Sandstone
PCST
Penrhyn Du Member
Conformably overlies thickly bedded pale weathering sandstones of the Trwyn yr Wylfa Member.
Fine-grained bioturbated muddy sandstones.
Conformable and gradationally overlain by well-bedded sandstones of the Machroes Member.
Pathhead Formation
PDB
The conformable base of the Formation lies in a transitional sequence from the Sandy Craig Formation, the boundary being drawn at the base of the West Braes Marine Band. The boundary was originally drawn at a slightly lower level in the type section; the change was made by Browne (1986, fig.2).
Central and East Fife.
Predominantly of mudstone and siltstone with beds of dolomite and limestone; sandstone is subordinate to the argillaceous rocks: overall pattern of sedimentation is cyclic with marine influence (marine bands common).
Maximum thickness is about 220m in East Fife
The upper boundary is at the base of the Hurlet Limestone (base of Lower Limestone Formation).
Pendine Conglomerate
PDC
Pentland Hills Volcanic Formation
PDH
The base of the volcanic rocks overstepping from the Swanshaw Sandstone Formation to the Greywacke Conglomerate Formation.
The Pentland Hills in east-cental Scotland.
Acid and basic lavas and associated pyroclastic rocks including basalts, andesites, trachytes, rhyolites, acid and basic tuffs and intercalated conglomerates, sandstones and minor constituent sediments.
About 1800 m thick.
The unconformity with the Inverclyde Group (Carboniferous).
Pendleside Limestone Formation
PDL
In the type section, the base is defined at the base of the first grey mudstone bed lying above the pale olive and blue-grey nodule-bearing wackestones that characterize the Hodderense Limestone Formation.
Occurs throughout the Craven Basin, roughly between Lancaster [SD46], Skipton [SD95] and Preston [SD52].
Grey, fine- to coarse-grained, bioclastic, commonly graded, erosive-based and bioturbated cherty packstones, interbedded with wackestone, sporadic intraformational and extraformational limestone conglomerate, and especially in the lower part, dark to pale olive- and blue-grey mudstone (Rad Brook Mudstone Member). Locally dolomitized, especially in the packstones, and rare sandstones.
The junction with the overlying Bowland Shale Formation is marked by the absence of bioturbation, and by a colour change from pale olive- and blue-grey, to dark blue and black, as mudstones and interbedded limestones become fetid and petroliferous. This colour change commonly corresponds to the entry of limestone breccias.
Pared Mawr Member
PDM
Underlain unconformably by interlaminated sandstone and mudstone of the Ceiriad Formation (Mawddach Group).
Dominantly coarse-grained, locally conglomeratic, bioturbated sandstones, with minor mudstone.
15 to 37m
Overlain gradationally by thickly bedded pale-weathering sandstones of the Trwyn yr Wylfa Member (St Tudwals Formation).
North Britain Palaeogene Dyke Suite
PDNB
Barrmill Dyke
PDNBR
Cumbrae-Stevenston Dyke
PDNCS
Eskdalemuir Dyke
PDNEM
Middleton Dyke
PDNMD
Moneyacres Dyke
PDNMO
Penderyn Oolite Member
PDO
The base is placed at the junction of pale grey, massive ooidal limestone of the Penderyn Oolite Member with calcereous sandstone of the underlying Honeycombed Sandstone Member, or with the dark grey, bituminous skeletal/peloidal grainstones/packstones/wackestones of the Dowlais Limestone Formation.
North crop of South Wales Coalfield, extending eastwards from near Crwbin [SN 467 125] to near Ponsticill [SO 072 112].
Pale grey, massive ooidal limestone, lenticular sandstone, rubbly limestone and shelly mudstone, locally with coal streaks and seatearth, at top.
13m at type locality, 25 to 33m elsewhere.
The top is placed at the top of ooidal limestone or at the top of lenticular sandstone and mudstone of the Member, above which dark grey, cyclic shelly and crinoidal grainstones of the undivided part of the Oxwich Head Limestone Formation enter.
Pickwell Down Sandstones Formation
PDS
Pentland Shale
PDSH
Midlothian coalfield basin.
Oil-shale.
Padarn Tuff Formation
PDT
?Late Neoproterozoic. According to Rushton and Howells (1998) its age "might be Precambrian", though it was listed by them as being of Cambrian age.
Unknown. Base not seen.
North Wales, Snowdonia, Bangor and Caernarfon districts.
Strongly welded rhyolitic ash-flow tuffs with abundant phenocrysts of quartz and sodic plagioclase, subordinate air-fall tuffs and rhyolite lavas.
800m to 2000m
Conformably overlain by volcaniclastic sediments and rhyolitic air-fall tuffs of the Minfordd Formation. Details of the boundary are unknown.
Penbedw Formation
PDW
Rests unconformably on cleaved and folded Silurian mudstones,siltstones and sandstones.
The formation comprises a series of disconnected bodies occurring beneath the Clwyd Limestone Group along the eastern side of the Clwydian Range (SJ 17 67) northeast Wales.
Red and green mottled mudstones, sandstones, conglomerates and basal breccias. The Penbedw Formation represents localised accumulations of terrestrial scree and alluvial deposits in palaeovalleys and embayments along the margin of the North Wales Dinantian platform
Conformable contact with limestones of the Foel Formation
Plateau Edge Formation
Overlies clay of the Tampen or Norwegian Trench Formations with a marked unconformity.
Coarsening upwards sequence of sand and gravel deposits, frequently with shell fragments. Distal parts of the (coastal) deposit are frequently finer grained. Underlain by a stiff to hard clay and overlain by fine, reworked. Holocene sand in some places.
40 metres. Thins and coarsens to north and northwest, on North Sea Plateau. Thins and fines to south east and east in deeper waters in the Norwegian Trench.
Underlies thin Holocene sand sedimentation.
Peacock Coal (Lothian)
PEA
Peacock Coal (Somerset)
PEAC
Peacock Coal (South Wales)
PEAK
Peat
PEAT
Two main lithologies: 'brushwood' (freshwater) peat and 'phragmites' (brackish water) peat; may be an organic-rich clay; humic deposits - [generic description: from East Anglian data] - accumulation of wet, dark brown, partially decomposed vegetation. [1:50k map margins].
Pentamerus Sandstone Formation
PEB
Peacock Coal (North Staffordshire)
PECC
Pentre Chert Formation
PECH
Conformable or disconformable contact between the chert lithologies of the Pentre Chert Formation and mudstones of the Teilia Formation around Prestatyn, or, to the south, with limestones of the Cefn Mawr Limestone Formation.
Northeast Wales between Prestatyn (SJ 09 83) and Halkyn Mountain (SJ 21 69).
Banded glassy cherts and siliceous (cherty) mudstones with subordinate thin siltstone and silicified crinoidal limestone beds, and scattered beds of pebbly quartzose sandstone, arranged in thickening-upwards cycles. Petrographic studies suggest that recrystalised radiolaria tests and rod-shaped sponge spicules are locally abundant in some of the cherts. The Pentre Chert Formation represents an offshore to basinal early Namurian facies deposited across the northern sector of the former Dinantian limestone platform, in a setting isolated from coarser grade siliclastic contamination, but in which sponges and radiolaria where abundant. The formation also exhibits the effects of extensive secondary silicification.
Chert/mudstone contact taken as the base of the Bowland Shale Formation.
Pentre Coal (South Wales)
PECO
Permian To Cretaceous Rocks (Undifferentiated)
PECR
Penmaen Dewi Shale Formation
PED
1:50,000 Sheet 209 (St.Davids) and adjacent areas.
Dark blue cleaved mudstones.
c.300 metres.
Portree Shale Formation
PEE
Lower Toarcian
Abrupt lithological change from sandstone of the Scalpay Sandstone Formation to anoxic mudstone.
Dark grey/black mudstones of anoxic deposition dominate the succession, which is locally laminated, organic-rich and contains few benthic fossils. Poorly exposed.
2m+
Gradational transition to limestone of the Raasay Ironstone Formation.
Peel Group
PEEL
Palaeocene And Eocene Flint Gravels
PEFG
Penstrowed Grits Formation
PEG
Diachronous within the lower Wenlock; closes with the upper boundary near the lateral margins of the turbidite basin. Underlying formation: Nant-ysgollon Shales.
Erected in 1969 in isolation, for the Newtown area only. Subsequent mapping has joined the outcrop to that of the Denbigh Grits in Clwyd via the Llangadfan Syncline, Potter (1971), Cummins (1967), BGS 1:50k sheet 150 (Bala), Alder (1976), Campbell (1983), BGS 1:50k sheet 120 (Corwen), and GS 1" Old Series Sheet 60 (Montgomery).
Mudstones with greywacke sandstones, medium- to coarse-grained in thick beds, many isolated, but commonly in packets, forming 20%-100% of the packet.
Various, 0- >100m
Diachronous within the lower Wenlock (see lower boundary). Overlying formation : Nantglyn Flags.
Pickersett Edge Grit
PEGR
Penstone Ironstone
PEI
Pennyearth Ironstone
PEIR
Permian To Jurassic Rocks (Undifferentiated)
PEJU
Pelaw Clay Member
PELC
Generally a planar, subhorizontal to undulating, gradational, glaciotectonic boundary with underlying dark grey, laminated silt and clay of the Tyne-Wear Glaciolacustrine Formation, or on brown or purplish brown, stony silty sandy clay diamicton of the Wear Till Formation. Locally rests on bedrock.
Lowlands of County Durham and southern Northumberland.
Reddish-brown to dark brown silty clay containing well dispersed pebbles ad cobbles (locally abundant), and commonly, small, buff to grey, grotesquely shaped calcareous concretions towards the base of the weathering zone. Clasts mainly of Carboniferous lithologies (sandstone, mudstone, limestone, coal). Typically has closely spaced, subvertical, prismatic jointing that formed during dry periglacial conditions.
Generally 1-2m, but reaching 4.5m
Peltura Punctata Beds
PELP
Dark blue-grey mudstones with subordinate beds of conglomerate and sandstone, more common in the upper part of the sequence.
Peacehaven Marl
PEMA
Pembroke Limestone Group
PEMB
Conformable and taken in southern settings at the incoming of dark grey fine to coarse skeletal packstones with scattered mudstone partings of the Black Rock Limestone Subgroup above the interbedded mudstones and skeletal packstones of the Avon Group. Along the north crop of the South Wales Coalfield, taken at the gradational incoming of the dolomitised skeletal packstones [Sychnant Dolomite Formation] of the Clydach Valley Subgroup above the interbedded mudstones and skeletal packstones of the Avon Group.
South Wales [SN 99 02], Bristol and the Mendip Hills area [ST 50 65].
Skeletal and ooidal limestones with some calcite- and dolomite-mudstones, sandstones and mudstones, and a few coals and cherts. Waulsortian reef limestones occur in the south. Extensively dolomitised on the east crop of the South Wales Coalfield. Interfingers with fluvial sandstones in the Monmouth, Chepstow and Bristol areas. Deposited in a ramp setting that, with time, became a platform.
To 1025m
Conformable and gradational in south Pembrokeshire, Swansea and Bristol/Mendip areas and taken at the incoming of banded cherts, silaceous mudstones and mudstones [Aberkenfig Formation] of the Marros Group above the interbedded limestones and mudstones and cherts [Oystermouth Formation] of the Group. Elsewhere, overlain unconformably by the Marros Group.
Pentre 'Series' (Group)
PEN
Pensford No.1 Coal (Bristol Area)
PEN1
Pensford No.2 Coal (Bristol Area)
PEN2
Pensford No.3 Coal (Bristol Area)
PEN3
Penyscallen Coal (South Wales)
PENC
Pencraig Sill
PENCG
Penda Formation
PEND
Pendleton Formation
PENDL
Taken at the base of the first thick quartz-feldspathic sandstone of Pendleian age, present above the dark grey, carbonaceous, fissile mudstone of the Bowland Shale Formation, which in the north Lancashire area and Bradford-Harrogate districts, is at the base of the Pendle Grit, and on the Askrigg Block, taken at the base of the Grassington or Lower Howgate Edge Grit.
The Craven Basin of north Lancashire and north Yorkshire between Lancaster [SD 47 61], Pendle Hill [SD 80 41], Skipton Moor [SE 00 50] and Harrogate [SE 30 55], and also present across the southern part of the Askrigg Block, and in the Masham district [SE 29].
Fine to very coarse-grained and pebbly, feldspathic sandstone, interbedded with grey siltstone and mudstone, with subordinate marine black shales, thin coals and seatearths.
Lancaster 800 m, Bradford 600 m, Askrigg Block up to 45 m thick.
Sharp conformable base of the dark grey, fissile mudstone of the Cravenoceras cowlingense Marine Band with eponymous fauna, which is commonly underlain by a thin, fine-grained, calcareous and phosphatic sandstone of the Pendleton Formation. Locally, in the absence of the Cravenoceras cowlingense Marine Band, the top of the formation is taken at the top of the Warley Wise Grit.
Penllwyn Oolite Member
PENO
The base is placed where the bioclastic grainstone forming the base of the Member lies sharply on and truncates the underlying limestone or calcrete forming the topmost bed of the Cheltenham Limestone Member.
Ooidal limestone and bioclastic limestone, bioturbated, locally ripple-marked and cross-bedded; oncoids are present at the base and stromatolites are present at the top. The limestone is a grainstone, with some local fining up to packstone and wackestone.
3 to 5m
The top is placed at a palaeokarstic surface that truncates the Member and is overlain by the green clay forming the lowermost part of the overlying Gilwern Clay Member.
Hiw 'Series'
PENR
Pencnwc West Formation
PENW
Peveril Point Member
PEP
First occurrence of thickly bedded, coarse biosparite (base Broken Shell Limestone Bed) above muds and finer-grained biosparites or micrites at the top of the Stair Hole Member.
Upway to Swanage in Dorset.
Calcarenites and calcirudites (rich in bioclastic material) interbedded with carbonaceous clays. The base is defined by thickly bedded, commonly massive limestones containing fragmented shells (upper broken Shell Limestone Bed). This passes (and fines) upwards into a biomicrite and carbonaceous mud-dominated sequence with glauconite-rich beds, which, in the west, are commonly rich in detrital quartz (Unio Bed, Upper 'Cypris' Clays and Shales Beds). The limestones in this part of the Member contain abundant Unio and Viviparus.
Between 7 and 17m in Dorset
Last occurrence of significant limestone beds (containing Unio and Viviparus) beneath monotonous sandy mudstones of the Wealden Group.
Port Ellen Phyllite Formation
PEPH
Pen-Plaenau Siltstone Formation
PEPL
Conformable passage from underlying Cwm Clwyd Tuff Formation, the boundary being taken at the base of the epiclastic sandstones and mudstones that overlie the highest tuff of the latter formation.
Mudstones and interbedded thinly laminated, ripple-marked siltstones and sandstones.
150 to 350m
Conformable upward passage from mudstones and siltstones into flaggy volcaniclastic sandstones of the Swch Gorge Tuff Formation.
Paddy End Tuff Member
PER
Base of rhyolitic tuff, overlies an erosion surface within the Lickle Tuff Formation resting on volcaniclastic sandstone and Kiln Bank Tuff Member dacitic tuff in the Ulpha Basin and with marked unconformity on the andesitic bedded tuff of the Duddon Hall Tuff Formation or silicic pyroclastic rocks of the Airy's Bridge Tuff Formation in the Coniston Fells.
Ulpha Basin and Coniston Fells. Great Stickle (SD 211 915) to Turner Hall (SD 230 960) and Appletree Worth (2442 9250); Buck Ake (SD 260 970) to Knott Head (NY 300 020), Little Langdale, Cumbria.
Pink-weatherd rhyolitic tuff, densely welded and locally rheomorphic.
Ulpha Basin 30 - 100m. Coniston Fells 150 - 170m
Overlain by younger parts of the Lickle Tuff Formation in the Ulpha Basin (volcaniclastic sandstone and rhyolitic tuff (Stickle Pike Member) or by the Lag Bank Formation (dacitic tuff) or Low Water Formation (dacitic tuff) in the Coniston Fells.
Pentre Rider Coal (South Wales)
PERC
Peat Rig Formation
PERG
Presumed conformable base on Cat Cleugh Formation.
Diverse porphyritic autobrecciated lavas, volcanic tuffs, breccias and agglomerates; hawaiite/mugearite in composition.
Faulted locally; otherwise top of the Bail Hill Volcanic Group, overlain conformably by Kirkcolm Formation.
Perpetual Coal (Lothian)
PERP
Specifically the Peebles area; fullest extent not recorded.
Pershore Sand And Gravel Member
PERT
Mid Pleistocene (MI Stage 9 to 8).
Unconformable, commonly channelled base on Lower Jurassic or Triassic bedrock.
Lower Avon valley, Stratford-upon-Avon to Tewkesbury. (BGS Sheets 199, 200, 216).
Predominantly cold phase sands and gravels that underlie the Avon Fifth Terrace of Tomlinson (1925) and of BGS maps (sheets 199, 200 and 215). Dominated by clasts of "Bunter" quartz/quartzite lithologies with subordinate flint.
(A) Here named the Pershore Sand and Gravel Member though in Bowen (1999) and also in the previous BGS list of computer codes it is simply Pershore Member. (B) Terrace surface some 40m above modern Avon alluvial floodplain at type locality, where it includes the organic Allesborough Bed (the Pershore Fossil bed of Maddy et al., 1991) at base, which is assigned to MIS 9. Probably equates with Frog Hall Member of the upstream Avon/Leam, and with Bushley Green Member of the Severn Valley Formation. (C) Upper Boundary is given as ?ground surface? though there may be head, colluvium or soil deposits intervening. (D) The Avon, and also Severn, terraces need reviewing in their entirety and the classification of some outcrops on existing maps is suspect, so the list of Previous Names is necessarily an approximation. It is likely that some deposits classified as Pershore (Terrace 5) on existing maps are too low and should actually be classified as Cropthorne (4). That aside, despite some problems of correlation with other terraces, on the basis of elevation, it seems that the correspondence of the Pershore and Bushley Green members between the Avon and Severn, is fairly good.
0 to c 7m
Pennant Sandstone Formation
PES
The base of the Formation is placed at the base of the first thick (c. over 3m) "Pennant" sandstone bed. Generally sharp and non-gradational, the base overlies grey mudstones/siltstones of the South Wales Coal Measures Group.
Crops out widely in the South Wales Coalfield, from near Llanelly [SN 40 00] in the west to Pontypool [SO 25 03] in the east. It is also present in the Forest of Dean and Bristol coalfields, and in the subsurface in the Oxfordshire and Berkshire coalfields.
Green-grey and blue-grey, feldspathic, micaceous, lithic arenites ("Pennant" sandstones) of southerly provenance, with thin mudstone/siltstone and seatearth interbeds and mainly thin coals; the lithologies are commonly arranged in fining-upwards channel-fill sequences.
c.275m in the east of the coalfield [c.SO 25 03] to c.1350m in the Swansea area [SS 73 94].
The top is placed at the base of the Grovesend Formation (base of Swansea Four-Feet/Mynyddislwyn Coal), where the coal lies between massive "Pennant" sandstones of the underlying Swansea Member and the grey mudstones of the overlying Grovesend Formation. In the eastern part of the coalfield, the coal appears to lie at an unconformity, with the Swansea Member apparently absent and the coal resting on "Pennant" sandstones of the Hughes Member.
Peterlee Sand And Gravel Formation
PESG
Generally sharp, erosional and forming broad depressions on underlying dark grey, stony silty sandy clay diamicton of the Blackhall Till Formation. Lower unit mainly restricted to depressions whereas the upper unit commonly oversteps directly onto the Blackhall Till Formation.
Typically comprises a unit of horizontally bedded, red, fine-grained sand with beds of silt, clay, coarse sand and fine gravel, overlain by a more laterally extensive unit of gravel, coarseing upwards and locally cemented. Beds of red and grey diamicton may occur throughout, representing intercalation with underlying and overlying tills. Clasts are mainly limestone and dolostone from the upper divisions of the Zechstein Group (fprmerly Magnesian Limestone), together with Carboniferous lithologies, Cheviot andesite and sparse shell fragments.
Generally planar, subhorizontal contact with overlying dark brown to purplish brown, stony silty sandy clay diamicton of the Horden Till Formation. Contacts may be sharp or gradational with glacitectonic intercalation.
Peterel Shell Beds
PESH
Type locality is at Dipton Burn, Hexham, Northumberland.
These comprise shell beds (?limestone) in shale above sandstone mapped as the lowest grit of the 'Millstone Grit'. The name is an alternative one for the Dipton Foot Marine Beds.
Peterborough Member
PET
At top of highest sandstone of underlying Kellaways Formation (this is the best definition for mapping purposes and consistency; a boundary based on the lowest mudstone is more subjective and arbitrary. This boundary is also the lower boundary of the Oxford Clay Formation.
Dorset to Humberside.
Mainly brownish-grey, fissile, organic-rich (bituminous) mudstones; shelly fauna dominated by crushed aragonitic ammonites and bivalves, including nuculoid and meleagrinella shell-beds. Subordinate beds of pale-medium grey, blocky mudstone. Several bands of cementstone nodules/concretions. Basal beds commonly silty, with Gryphaea-rich shell beds.
At top of highest brownish-grey, organic-rich mudstone within thinly interbedded lithological transition (up to c.3m thick) to pale grey, calcareous mudstones of overlying 'Middle Oxford Clay' (see Stewartby Member). Inevitably, more or less arbitrary in field mapping.
Petrockstow River Terrace Deposits, 1 Member
PET1
Unconformable on bedrock of Palaeogene and Late Carboniferous age.
The Petrockstow Basin, Devonshire.
The deposits of the first terrace are largely gravels of Carboniferous sandstone with scattered flints, with thin seams of clayey sand and sandy clay, 1.5 to 7m thick. The clasts are up to 20mm in diameter, increasing to 130mm at the base.
To about 7m
At the land surface.
Petrockstow River Terrace Deposits, 2 Member
PET2
Petrockstow River Terrace Deposits, 3 Member
PET3
Petrockstow River Terrace Deposits, 4 Member
PET4
Petrockstow River Terrace Deposits, 5 Member
PET5
Petester Granite
PETR
Petrockstow River Terrace Deposits, 1 Member [Duplicate Code: Use Pet1]
PETR1
Petrockstow Valley Formation
PETRO
Unconformable on bedrock of Paleogene and Late Carboniferous age.
The formation includes the deposits of five river terraces. The deposits of the first terrace are largely gravel of Carboniferous sandstone with scattered flints, with thin seams of clayey sand and sandy clay, 1.5 - 7m thick. The pebbles are up to 20mm in diameter, increasing to 130mm at the base. Deposits of the higher terraces are less gravelly, and dominantly comprise clay with gravel seams.
Up to c.8m
Permian Evaporites (Undifferentiated)
PEV
Penistone Flags
Pathhead Four Foot Six Inch Coal (New Cumnock)
PFC
Penny Farm Gill Formation
PFD
Pinkie Four Foot Coal (Lothian)
PFF
Pittencrieff Blackband Ironstone (Fife)
PFFI
Portfield Formation And Haverford Mudstone Formation (Undifferentiated)
PFHD
Possil Fourteen-Inch Coal (Glasgow Area; Central Coalfield)
PFI
Possil Fourteen-Inch Ironstone (Glasgow Area; Central Coalfield)
PFII
Possil Fourteen Inch Under Coal (Glasgow Area; Central Coalfield)
PFIUC
Thin coal or seat earth bed overlies Ashfield Coking Coal within Limestone Coal Formation.
Glasgow region of Midland Valley, Scotland.
Thin, impersistent but easily recognisable coal seam in the Glasgow-Stirling region. Occasionally found in Kilsyth and Stirling area. Forsyth, 1962, states that: "when absent as coal, a prominent seat earth is found and the overlying shale (fissile mudstone) is thicker than found with adjacent coals".
Possil Fourteen Inch Under Coal is overlain by thin "cyclothem" containing Possil Fourteen Inch Coal (PFI), Limestone Coal Formation.
Portfield Formation
PFLD
Apparently conformable on the underlying Slade and Redhill Formation, but contact nowhere seen.
Interbedded dark grey carbonaceous mudstones [Cuckoo Shale Member; Scotchwell Shale Member] and well-sorted, fine-grained, grey and buff sandstones [Cethings Sandstone Member]. Local conglomerates at, or near, the base of the Formation.
At least 65m
Conformably and gradationally overlain by the Haverford Mudstone Formation.
Peat Flow
PFLO
Mass movement of peat resulting from a bog-burst. [Generic description: 'TMOS' Procedures].
Penchford Limestone
PFLS
Plumpe Farm Sand Member
PFS
Conformable contact with the underlying Chapelknowe Till Member of the Gretna Till Formation or with the Loganhouse Gravel Member of the Plumpe Farm Sand and Gravel Formation.
Reddish brown, silty sand with subordinate beds of silt, clay and gravel. Locally dominantly silt and clay.
Commonly a gradational, glacitectonic contact with the overlying Plumpe Bridge Till Member of the Gretna Till Formation. Otherwise unconformable on bedrock.
Pendle Grit Member
Commonly a gradational coarsening upwards change from the underlying mudstone and siltstone of the Bowland Shale Formation means that the base is taken at the point in the sequence where sandstone becomes predominant.
Widespread in the Craven Basin in Lancaster, Settle, Garstang, Clitheroe, Bradford sheet areas.
Medium- to coarse-grained feldspathic sandstone with subordinate interbedded siltstone and mudstone. Commonly in sharp based beds from 0.2 to 4.5m thick, which are distinctly massive internally.
From c.200m at the northern margin of the Lancaster district to c.475m on Longridge Fell, and an average of 457m in the Clitheroe district.
Taken at the point in the sandstone succession where cross-bedded sandstones of the Warley Wise Grit become evident.
Pen-Y-Gadair Volcanic Formation
PGA
Conformably overlies and interdigitates laterally with the Ty'r Gawen Mudstone Formation to the southwest, and with the Benglog Formation to the northeast.
Cadair Idris and Dolgelly areas, North Wales.
Massive, pillowed and autobrecciated basalt lavas with intercalated crystal tuffs and subordinate felsic ash-flow tuffs, locally interbedded with mudstones.
To 240m
Conformably overlain by mudstones of the Ty'r Gawen Formation.
Ponfeigh Gas Coal (Douglas)
PGAS
Post-Glacial Beach Deposits
PGBD
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks; postglacial. [Generic description].
Palacecraig Blackband Ironstone
PGBI
Parkgate Coal (West And South Yorkshire And Nottingham)
PGC
Composed of several component seams. No known alternative names.
Powgavie Clay Member
PGCL
The relationship of the Powgavie Clay to the Errol Clay Formation is not clearly demonstrable at any known locality. At the type section the member rests unconformably on glaciofluvial sand and gravel. This relationship is assumed to have come about by mass movement on the sea floor causing removal of the Errol Clay before deposition of this member.
Catchment of the River Tay east of Perth adjacent to the Tay estuary.
Marine clay containing sub-angular ice-rafted clasts (dropstones) characterized by graded units from 2cm to 10cm thick consisting of a thin basal layer of pale coloured silt or sand passing up into dark brownish grey clay. Sporadic laminae and thicker beds are stained black by sulphide. The deposit is considered to be prodeltaic in origin.
20m known at Powgavie.
Diachronous transitional top with and passing laterally into the Culfargie Sand Member.
Palacecraig Coal (Airdrie; Central Coalfield)
PGCO
Pen-Y-Garnedd Limestone Formation
PGD
Overlies mudstones of the Allt-tair-ffynnon Formation.
The Pen-y-garnedd Limestone Formation and overlying Nod Glas Formation in much of the Ordovician of North Wales, in particular in the Llantyllin syncline at Oswestry (137) and around Meifod (151) and Dinas Mawddwy (150).
Limestone and dolomite.
c. 17m at Pen-y-garnedd, (Wedd et al., 1929).
Overlain by black phosphatic mudstones of the Nod Glas Formation, locally unconformably overlain by mudstones and siltstones of the Laundry Mudstone Formation.
Proglacial Deposits
PGDEP
Pen-Y-Glog Grit
PGG
Pegmatitanhydrit Formation
PGHY
Peghorn Limestone
PGL
Productus Giganteus Limestone
PGLS
Post-Glacial Marine Deposits
PGMD
Variable lithology. Gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell); postglacial. [Generic description: from East Anglian data].
Pwll Glas Mudstone Member
PGMU
Conformable within sandstones of the Dinas Island Formation.
Interbedded grey turbiditic mudstones and laminated hemipelagic mudstones.
Passage Formation
PGP
Top of Castlecary Limestone.
Cyclic: including coarse sandstones and seatearths. See NOTE relating to lithological description of Lower Limestone Formation [LLGS].
357.1m in type section.
Base of Coal Measures (base of Lowstone Marine Band in type section).
Pea Grit Facies
PGR
Penistone Green Coal (South Yorkshire)
PGRC
Parkgate Sill
PGS
Known only beneath the Vale of Belvoir.
Plynlimmon Grey Shales
PGSH
Pen-Y-Graig Tuff Member
PGT
Base of tuff succeeds siltstones of the Bryn Siltstone Formation.
North side of Berwyn Hills of Oswestry (137) and Wrexham (121). Overstepped by Dolhir Formation.
Laterally discontinous acid tuff. (coarse ash of Wedd et al., 1929).
Uncomformably overlain by Ashgill, grey-green muds of the Dolhir Formation.
Pitlurg Farm Till Formation
PGTI
Generally unconformable on bedrock or older tills, such as the Bellscamphie Till Formation.
A very dark to dark grey clayey, silty, pebbly, slightly calcareous, diamicton. Besides local rock types, it includes red (Devonian) sandstone, white, probably Mesozoic, sandstone, and shell fragments.
At least 7m
Generally unconformable with the Hatton Till Formation.
Palaeogene Rocks (Undifferentiated)
PGU
lower tertiary rocks where not differentiable in east anglian boreholes.
Portgower Boulder Beds Member
PGW
Pendle Grit Member And Warley Wise Grit Member (Undifferentiated)
PGWWG
Rhindaston And Gignog Group
Drawn at the base of the rhyolitic and keratophyric tuffs and lavas where it rests conformably upon rhyolitic tuffs of the Pont Yr Hafod Group.
Haycastle, west Wales. (Dyfed).
Rhyolitic and keratophyric tuffs and lavas.
Drawn at the conformable upward passage from tuffs and lavas of the Rhindaston and Gignog Group to basal conglomerate of the lower Cambrian Caerfai Group.
Parkhouse Beck Limestone
PHBL
Limestones and shaly mudstones.
Pennyvenie High Coking Coal
PHC
Pathhead Blackband Ironstone
PHDB
Pule Hill Grit
PHG
West Yorkshire [Pule Hill, near Marsden] and westwards into Lancashire.
Coarse- to fine-grained sandstone.
Pen Hill Head
PHHD
Pike Hill Limestone
PHL
Pittenweem Harbour Lingula Band
PHLB
Mudstone with ribs of clayband ironstone, fish remains, ostracods and Lingula.
0.45m in type section.
Phillips Member
PHLP
Pittendreich Limestone
PHLS
Parishholm Conglomerate Formation
PHM
Lowest occurrence of conglomerate above the Ree Burn Formation (greywackes).
Lower Palaeozoic inlier of the Hagshaw Hills, Scotland. (50k sheets, 23E, 23W and 15W).
Reddish-grey unsorted pebble conglomerate, roughly bedded, clasts to 120mm but usually less than 30mm, angular to subrounded, probably matrix supported; many clasts are of igneous rocks.
Top of topmost bed of conglomerate, below the red and yellow sandstones of the overlying Douglas Water Arenite.
Parkhouse Marine Band
PHMB
Phynis Mudstone Member
PHS
At the type locality and also in the Whitewell Anticline, the dark grey mudstones rest conformably upon crinoidal packstones of the Clitheroe Limestone Formation. Elsewhere, the mudstones are underlain conformably by lithoclast breccias and boulder beds, packstones, floatstones and grainstones of the Limekiln Wood Limestone Member.
The western part of the Craven Basin, including Cow Ark (SD 65 46), Plantation Farm (SD 66 43), Slaidburn (SD 71 53) and Whitewell (SD64 47) anticlines. Not shown on published maps.
Dark grey, laminated mudstones, finely micaceous, silty and calcareous, interbedded with dark grey, laminated, blocky and calcareous siltstones.
Up to 350 m, with the thickest development in the Plantation Farm Anticline.
In the Slaidburn and Whitewell anticlines the dark grey mudstones are overlain conformably by pale blue-grey wackestones and packstones of the Whitemore Limestone Member. Elsewhere, the mudstones are overlain by non-micaceous, laminated mudstones interbedded with laminated calcisiltites of the Hodder Mudstone Formation (undifferentiated).
Parkhead Sandstone
PHSA
Po House Tuff Formation
PHT
Base of Dog Crag Tuff Member - a thin pyroclastic flow deposit - which rests on a non-sequence that occurs at the top of the Whinney Bank Formation (an interbedded succession of siltstone and andesitic lapilli-tuff).
Whicham Valley:- between Park Head (SD 172 834) and Lacra Bank (SD 145 815).
Thin and medium parallel bedded andesitic tuff and lapilli-tuff.
Up to c.400m
Base of Waberthwaite Formation (dacitic tuff and lapilli-tuff).
Peasah Wood Limestone
PHWD
Pundeavon Ironstone
Pishlinn Burn Gravel Formation
PIBG
Portknockie to Troup Head.
Gravel, cobbly, clast or matrix-supported mass movement or waterlain deposit. Clasts angular to subrounded; matrix silty sand.
Upper limit defined by base of Whitehills Glacigenic Formation or Crovie Till Formation.
Pibroch Member
PIBR
Pilkembare Coal (Fife)
PIC
Pistyll Gwyn Mudstones Formation
PIG
Gradational but taken at base of first thick mudstone unit above the Allt-y-Clych Conglomerate.
Interbedded grey turbidite mudstones and laminated hemipelagites. Scattered thin turbidite sandstones.
Up to 400m.
Pisgah Hill Limestone
PIHL
Pilkin Coal (Fife)
PILK
Pillmour Vent
PILL
Pigdon Limestone
PILS
Pilot Inn Marl
PIMA
Pinbain Lava Formation
PIN
Succeeds and locally interdigitates with Kilranny Hill Formation (KRY). Distinguished by incoming lava facies.
Area between Girvan and Ballantrae, southwest Scotland.
Thick, massive and pillowed, porphyritic and aphric basalt lavas, partly brecciated. Rare beds of lithic arenite, siltstone, mudstone and polymict basalt lava breccia.
c.475m
Succeeded by Slockenray Hyaloclastite and Lava Formation (SLO). Distinguised by incoming of hyalocastite and basalt lava with large bladed plagioclase phenodrysts.
Pin And Crown Coal (North Wales)
PINC
Pindale Tuff
PINT
Piper Formation
PIPR
Pecten Ironstone Seam
PIRS
Pistyllgwyn Member
PIST
Pityoulish Formation
PITY
Not exposed - considered to rest with apparent conformity on Dava succession rocks.
Central Highlands of Scotland [sheets 74W, 74E, 75W], in a mainly east-west zone [ca. 2 - 3 km wide] through Aviemore.
Interbanded psammite and semipelite with distinctive bands of siliceous psammite and quartzite.
Not exposed but presumed to be transitional up into Coylumbridge Formation.
Patrick Burn Formation
PKB
Presumed transitional with underlying Ponesk Burn Formation, but actual boundary is a fault.
Alternating beds of grey feldspathic, medium-grained turbiditic sandstone and grey siltstone with beds of grey laminated siltstone and silty mudstone. Sandstone beds carry washed fossil debris, mainly of molluscs.
Base of lowest thick fine-grained greywacke bed of the Castle Formation.
Parkstone Clay Member
PKC
Perrink Coal (Somerset)
PKCO
Park End Breccia Formation
PKE
Base of the Formation not seen but faulted against Lower Ordovician igneous rocks in Ballantrae harbour.
Red breccio-conglomerate with rare thin silty sandstone lenses. Clasts are predominantly [90%] of "greywacke" sandstone of pebble to cobble size, the remainder are of mudstone, chert, basalt and various granitic and gabbroic coarse-grained igneous rocks. No serpentinite clasts are recorded, either in the primary survey by Peach and Horne in 1894 or in recent survey, which is in contrast to the publications of Pringle and Brookfield. The clasts are mostly subrounded to subangular, are contained in a siltstone or fine sandstone matrix and crudely imbricated indicating deposition from a palaeocurrent flowing towards the northwest.
>250m
Upper boundary with the overlying Corseclays Sandstone Formation is concealed but inferred to be conformable.
Penkill Mudstone Formation
PKF
Conformable on Upper Camregan Grits.
Purple and green banded shale.
Conformably overlain by Protovirgularia Grits.
Peak Forest Sill
PKFS
Park Limestone Formation
PKL
Point where sharp (this change can extend over 1 or 2m. Rose and Dunham, 1977, p.29, South Cumbria Memoir) upward change occurs from the dark grey bedded packstones of the Dalton Formation to the pale unbedded grainstones of the Park Limestone.
Around Dalton-in-Furness in the west, to near Carnforth in the east.
Unbedded or poorly bedded, pale grey or pale yellowish grey bioclastic and peloidal grainstone or biocalcarenite. NOTE: type area is south Cumberland - Furness area.
120 to 130m
Upward change from massive cream-white to thickly bedded grey pseudobrecciated limestone of overlying Urswick Limestone Formation.
Penkill Formation (Sensu Stricto) [See: Pkf]
PKLC
Penkill Flags
PKLF
Penkill Greywackes
PKLG
Peak Limestone Group
PKLM
Generally rests unconformably upon deformed Lower Palaeozoic lava, volcanic breccias, pyroclastic rocks and mudstones, but locally the base of the Group rests conformably upon late Devonian to early Dinantian anhydrite, such as the Hathern Anhydrite Formation, or dolostone, like the Rue Hill Dolomite Formation. Locally, on the Hathern Shelf, the Group lies conformably upon sandstones of the Calke Abbey Sandstone Formation.
Seen at outcrop in the Peak District of Derbyshire and Staffordshire, but also exists largely in the subsurface on the Hathern Shelf of north Leicestershire, south Derbyshire and north Staffordshire; elsewhere in eastern England it is proved in the subsurface only.
A thick sequence of pale to dark grey, thinly to thickly bedded biosparite and cherty micritic limestone units displaying knoll-reefs, comprising fossiliferous, massive micrite with localised common spar-filled cavities, and grey-brown to dark grey dolomitic limestones. Subordinate partings and thin beds of calcareous mudstone and siltstone, basaltic lava, sills and pyroclastic rocks including tuff and volcanic breccia are common in the upper part of the Group, as well as pedogenic crusts, palaeokarstic surfaces and thin bentonite partings (known locally as "wayboards"), notably in Matlock [SK 20 60 to 30 60], and the Millers Dale to Buxton [SK 06 72 to 16 74] areas of the Peak District.
About 800m thick in the Derbyshire Peak District, thinning southward over the Hathern Shelf to about 200m.
Taken at the conformable boundary at the base of predominantly mid to dark grey mudstones and turbiditic limestones of the Craven Group, above the limestone-dominated succession of the Peak Limestone Group. On the Hathern Shelf, strata of the Craven Group rest disconformably upon pale grey platform carbonate facies limestones of the Peak Limestone Group.
Peel Knowe Sandstone Member
PKNS
In the area southwest of Berwick-upon-Tweed the Fell Sandstone Formation consists of several sandstone members separated by variable thicknesses of mudstone and siltstone. The Peel Knowe Sandstone Member is the middle of three members and is found in a northeast - southwest band between Longridge Towers and Grievestead Moor.
Medium-grained, locally coarse-grained in upper 10m, medium- to thick-bedded, cross-bedded sandstone. Some thin mudstone beds (0 to 3m).
20 to 75m
Pink Pool Limestone
PKPL
Bewcastle sheet area.
Limestones with interbedded "marly" layers.
Parkgate Rock
PKR
Parker Mine Coal [Manchester Area]
PKRMC
Parkstone Sand Member
PKS
Peckmill Sand Member
PKSA
Late Devensian (Lategacial).
Unconformable on older-Quaternary deposits, including the more thickly bedded Gutterfoot Sand and Gravel Member of the Gosforth Glacigenic Formation (in the St Bees Moraine), the coarse-grained, cross-bedded Peel Place Sand and Gravel Member of the Gosforth Glacigenic Formation, at Seascale, and the Fishgarth Wood Till Member of the Gosforth Glacigenic Formation, at Ravenglass.
Coastal cliff sections between St Bees and Ravenglass on 50k sheets 28 (Whitehaven) and 37 (Gosforth).
Thinly interbedded sand, sandy silt, pebbly silty sandy clay, diamicton and gravel, typically red-brown in colour. The member typically drapes older glacial and glaciofluvial deposits, and thickens into hollows and kettleholes in their surface. Synsedimentary small-scale normal faulting and collapse structures are common within the unit.
Typically between 1.0 and 3.0m
Overlain by Holocene deposits such as peat and blown sand.
Park Style Limestone Member
PKSL
Taken at the base of the lowermost normal-graded packstone overlying a black mudstone-dominated succession of the Bowland Shale Formation (undifferentiated).
The member is mainly found in the Garstang district, located in the western part of the Craven Basin.
Packstones and wackestones predominate, interbedded with dark grey fissile and blocky mudstone. At the type locality, the lower 17 m comprises equal proportions of limestone and mudstone. The limestone is dark bluish grey, typically with sharp bases and flute and groove casts. The limestones form graded beds (8 to 70 cm thick), with medium-to coarse-grained packstone fining upwards to calcisiltite and argillaceous wackestone. The beds have an undulatory parallel lamination. The interbedded mudstones are cherty, calcareous and platy or fissile. Thin beds of bioclastic debris, mainly crinoid, brachiopod and coral fragments, occur in places. The upper 67 m has a proportion of 70 to 90% limestone to mudstone. The limestones are grey wackestones, locally weathering to pale brownish grey. Beds range from 8 cm to 80 cm thickness, with sharp, slightly undulatory bases and tops. Faint parallel lamination is visible in some beds. The interbedded mudstone is dark grey, calcareous, blocky and strongly bioturbated.
At the type locality the member is 84 m thick.
Taken at the top of the uppermost wackestone in a limestone-dominated succession, overlain by black mudstones and siltstones of the Bowland Shale Formation (undifferentiated).
Park Limestone Formation And Urswick Limestone Formation (Undifferentiated)
PKUL
Park Yard Coal (South Lancashire)
PKYD
Portland Group
In the type area traditionally, but not unanimously, taken at the base of the Massive Bed, which also marks the Portlandian/Kimmeridgian stage boundary. In other areas taken at upward change from silty/sandy mudstones (Kimmeridge Clay) to argillaceous sandstones/siltstones (possibly marked by a spring-line) or, where non-sequential, at the base of the Upper Lydite Bed.
Dorset, Wiltshire, Oxfordshire, Buckinghamshire.
Upper part predominantly limestone (micrites, wackestones, packstones and grainstones) including good freestones; lower part predominantly argillaceous, dolomitic sandstones/sands; some mudstones/shales, and thin beds or nodular layers of micrite.
To c.75m
The most practical definition is at the top of the highest, massive marine limestone of the Portland Stone. In the type area, the overlying beds are thin algal limestones and palaeosols (`Dirt Beds') of the Purbeck Group.
Porth Llauog Formation
PLA
1:50 000 Sheet 209 (St. Davids).
Dark mudstones with abundant debris flows.
500 metres.
Plashetts Coal
PLAC
Widely developed in Northumberland; named from the area around Plashetts.
The thickest and most valuable coal seam in the former "Scremerston Coal" unit, and worked widely across the area of its occurrence.
To c.1.2m
Plateau Beds
PLB
Plas Brereton Formation
PLBR
Plumpe Bridge Till Member
PLBT
Commonly a gradational, glacitectonic contact with underlying Plumpe Farm Sand and Gravel Formation [or members thereof], or Chapelknowe Till Member. Otherwise unconformable on bedrock.
Reddish brown, sandy silty, clayey diamicton with clasts of greywacke, red sandstone, siltstone and grey granodiorite. Uppermost 3m generally quite variable in lithology and compactness, with lenses of sand, gravel, silt and clay.
At surface or overlain conformably by glaciofluvial/glaciolacustrine or Flandrian sediments.
Priestland Clay
PLC
Pennine Lower Coal Measures Formation
PLCM
At the base of the dark grey, fissile mudstone of the Subcrenatum Marine Band with eponymous fossils, or at the base of the lowest coal of the coal-bearing sequence if this marker cannot be recognised. Typically, the formation rests conformably upon the Rossendale Formation (Millstone Grit Group). However, in north, west and east Cumbria, the Solway Basin (except the Canonbie area), the Stainmore and Northumberland troughs, on the Alston Block and in northeast Northumberland, the formation overlies conformably the repetitive mudstones, siltstones, sandstones, thin limestones and thin coals of the Stainmore Formation (Yoredale Group). In the Canonbie Coalfield, the formation is underlain unconformably by the Alston Formation (Yoredale Group).
Central and northern England, North Wales and the north Isle of Man.
Interbedded grey mudstone, siltstone and pale grey sandstone, commonly with mudstones containing marine fossils in the lower part, and more numerous and thicker coal seams in the upper part.
Up to 650m thick in the North Staffordshire (Potteries) Coalfield, and 720m thick in Lancashire.
At the base of the mudstone of the Vanderbeckei Marine Band with eponymous fossils.
Palaeocene Rocks (Undifferentiated)
PLCU
Peldar Dacite Breccia
PLD
All exposed boundaries are faulted.
Extends from Whitwick Quarry northwards and is last seen in the railway cutting north-west of Whitwick Church. Occurs again in Bardon Quarry, to the south.
Breccia consisting of enclaves of fine-grained, porphyritic dacite and green-grey microdiorite, in black medium-grained crystal-vitric matrix: locally rafts of volcaniclastic siltstone.
Plashetts Dun Limestone
PLDL
Northumberland; type area around Plashetts.
Ferruginous, yellow-weathering, brown crinoidal limestone.
0.6 to 1.8m
Plattendolomit Formation
PLDO
Plean Limestones
PLE
Pleurotomaria Beds
PLEU
Unnamed Extrusive Rocks, Palaeocene
PLEX
Plantinhead Member
PLF
Not seen, thought to rest on Craighead Limestone Formation.
Grey and purple flaggy calcareous and dark siltstone (with graptolites).
50m+ (estimate).
Plateau Gravel
PLG
Flint pebbles, sub-angular, with clasts of rounded flint, sarsen sandstone, vein quartz, in a clay-rich quartz matrix; fluviatile in origin, laid down on erosional shelves. [Generic description: 1:50 k map margins].
Powley's Hill Tuff Member
PLH
Taken at the abrupt change from andesite or volcaniclastic sandstone of the Birker Fell Andesite Formation to bedded silicic pyroclastic rocks.
Haweswater, eastern Lake District.
A markedly garnetiferous, heretogenous succession of crystal, pumice and lithic-rich massive beds, bedded silicic tuff and lapilli tuffs.
To 65m
Defined by the base of the Pinnacle Howe Member.
Pliemont Formation
PLIE
Pliocene Rocks (Undifferentiated)
PLIO
Peel Limestone
PLL
Peel Fell and adjacent areas, Cumbria.
Impure limestone. The lower part is oolitic and contains algal nodules and fragments of a broken algal crust; the upper part contains abundant microfossils, including pellets.
Pontar-Llechau Formation
PLLE
Plungar Limestone Formation
PLLS
The unconformable base is taken where dolomitic, locally ooidal limestone of the Belvoir Limestone Formation is overlain by grey , pebbly sandstone of the Plunger Limestone Formation.
The base of the Formation comprises a 6m-thick bed of grey, pebbly sandstone. This is overlain by dolomitic limestones with two thinner sandstones in a 15m thickness of strata. White to buff, crystalline limestones, ooidal in part, occur above the youngest sandstone.
199m at the type locality.
The top is taken where the white to buff, crystalline limestone of the Plunger Limestone Formation is overlain by grey mudstone, siltstone or sandstone of the Millstone Grit Group.
Plodder Coal (South Lancashire)
PLM
Plenus Marls Member
PLMA
Upper Cretaceous, Cenomanian (Metoicoceras geslinianum Zone).
Northern Province: An uneven erosion surface that may be stained with iron minerals and glauconite, at the top of a succession of marly chalk (the Ferriby Formation). This member and the newly proposed Black Band Member, generally form a topographical slack at outcrop, which facilitates the mapping of the base of the Welton Formation, and can also be recognised from its higher gamma-ray geophysical log signature in boreholes. Southern Province: Conformable beneath the lowest marl on the underlying Zig Zag Chalk Formation. Sequence constitutes the lowest member of the Holywell Nodular Chalk Formation and the White Chalk Subgroup.
Widespread within the Southern, Transitional and Northern provinces and offshore in the North Sea area. Forms the most characteristic downhole geophysical signature in the whole of the Chalk Group. In the Northern Province the distribution is not known in detail but it is suspected that this member forms part of the succession formerly identified as the Black Band in boreholes and seismic sections.
Northern Province: Thinly bedded dark-coloured calcareous mudstone (marl) overlain by rubbly limestone and calcareous silty beds followed by a higher calcareous mudstone siltstone (marl). Southern Province: Interbedded coloured marl and chalk. In the southern Province, the Plenus Marls was defined by Jefferies (1963) and, herein, treated at member level. It marks the basal unit of the Holywell Nodular Chalk Formation. The Plenus Marl Member in the Northern Province, as defined in Sumbler (1999), included beds A to H of Dodsworth (1996) and thus contained the Black Band. The term was redefined by Hopson (BGS Research Report RR/05/02) to include only beds A and B of Dodsworth with the higher beds C to H forming the newly proposed formal term Black Band Member. In so doing the Plenus Marl Member as defined in the Northern Province is the direct equivalent of the member as described for the Southern Province. No formal subdivisions are recognised, but the unit has been finely divided into eight beds of widespread geographical distribution in the southern Province by Jefferies (1963).
Northern Province: About 1.15 at type-site but to as little as 0.25 m elsewhere. Southern Province: Usually in the range 1 to 1.5m but known to be up to 3.0 m at the Holywell Cafe cliff section in Eastbourne.
Northern Province: Conformable at the base of the Black Band ss (the `Main Black Band? of Wood et al., 1997), the lowest unit of the Black Band Member. Southern Province: Conformable at the bedding plane above the highest marl and below the hard nodular limestone of the Melbourn Rock Member
Pathhead Lower Marine Band
PLMB
Pennine Lower Coal Measures Formation And Pennine Middle Coal Measures Formation (Undifferentiated)
PLMC
Plenus Marls Member (Northern Province)
PLMN
Port Logan Formation
PLN
Medium to thick-bedded greywacke with laminated silty mudstone units up to 120 metres thick.
Portland Formation (Wiltshire, Oxfordshire And Buckinghamshire)
PLND
Conglomeratic and glauconitic coarse-grained sand, sandstone and limestone (Upper Lydite Bed) resting disconformably on mudstones, siltstones or fine-grained argillaceous sands and/ sandstones of the Kimmeridge Clay Formation.
Outliers from Swindon to Aylesbury in north Wiltshire, Oxfordshire and Buckinghamshire, and possibly an outlier in the Vale of Pewsey near Devizes, though this is currently rather poorly known (Wimbledon, 1980). A separate description applies to the Portland of the Vale of Wardour in south Wiltshire and Dorset.
Fossiliferous marine limestones, calcareous and commonly glauconitic, sandstones and sands.
Upwards change from fully marine limestones with large molluscan fossils to lagoonal fine-grained limestones and marls of the Purbeck Formation, the base of which is commonly marked either by laminated, ostracod-bearing 'Pendle' or oyster-bearing marl, or by a sharp nonsequential junction overlain by generally non-calcareous and commonly ferruginous sands and sandstones of the Lower Greensand or Whitchurch Sand Formation, or by calcareous mudstones of the Gault Formation.
Portland Group And Purbeck Limestone Group (Undifferentiated)
PLPB
Peldar Porphyritic Dacite
PLPD
Bardon Hill Quarry, Western Charnwood Forest.
A highly porphyritic dacite, with abundant large phenocrysts of white plagioclase and less commonly, green-grey quartz in a dark grey, fine-grained groundmass.
At least 50 m, possibly up to 200 m thick.
Grades upwards to peperite breccia, interleaved with volcaniclastic sandstone of the Bardon Hill Volcanic Complex.
Plateau Beds And Quartz Conglomerate Group (Undifferentiated)
PLQC
Portland Sand Formation [Obsolete Code: Use Posa]
PLS
Plankey Shell Band
PLSB
Palaeo-Landslip, Mid-Devonian
PLSDM
Plumpe Sand And Gravel Formation
PLSG
Sand and gravel, typically reddish brown and silty, containing clasts of red sandstone, greywacke sandstone and siltstone, and grey granodiorite.
Commonly a gradational, glacitectonic contact with overlying Plumpe Bridge Till Member of the Gretna Till Formation.
Palm Lodge Shales
PLSH
Plains Skerry (Informal Term)
PLSK
Peel Sandstone
PLSS
Portland Stone [Obsolete Code: Use Post]
PLST
Palaeo-Landslip, Age Unknown
PLSU
Pilton Mudstone Formation
PLT
At the coast, the lower boundary is taken at the incoming of interbedded mudstones, siltstones and sandstones of the Pilton Mudstone Formation above a prominent slumped unit overlain by cross-bedded, medium-grained sandstones of the underlying Baggy Sandstone Formation. Inland, the boundary is taken above the highest, sugary, buff-brown, fine- to medium-grained feldspathic and micaceous sandstone, typical of the Baggy Sandstone Formation.
Between Croyde and Wellington, north Devon (SS 70 28).
Grey mudstones and siltstones with thin- to thick-bedded, locally calcareous sandstones and beds and lenses of limestone. Sandstones are thickest and predominate in the lower half of the formation, whereas mudstones predominate in the upper half. Rish shelly neritic fauna occurs in the mudstones and limestones.
Between Brushford and Wellington the upper boundary is taken at the incoming of hard black finely laminated rarely fossiliferous cherty mudstones of the Doddiscombe Formation above the soft medium to dark grey mudstones with scattered very thin fossiliferous limestones, siltstones and sandstones of the underlying Pilton Mudstone Formation. West of South Molton, the upper boundary is taken at the gradational incoming of dark grey to black rarely fossiliferous, slightly siliceous, finely laminated mudstones of the overlying Doddiscombe Formation (Unit D of the Pilton Beds of Prentice (1960), above the fossiliferous mudstones with thin sandstones and siltstones of the underlying Pilton Mudstone Formation. The Doddiscombe Formation has not been mapped by BGS west of South Molton, instead it has been included in the Pilton Mudstone Formation and/or the Coddon Hill Chert Formation; further work is needed.
Palate Bed
PLTB
Widely but patchily developed in the area around Bristol.
Thin limestone, phosphatic in part, locally conglomeratic, crinoidal and crowded with fish remains.
Taken as the local base of the undivided Avon Group where this overlies the Bryozoa Bed at the top of the Shirehampton Formation (qv).
Poolvash Limestone
PLVL
Southern Isle of Man.
Possil Lower Wee Coal (Glasgow Area; Central Coalfield)
PLW
Polesworth Formation
PLWF
Taken at the contact with the underlying, crudely-bedded mudstones and breccias of the Hopwas and Moira Breccias.
Mapped at surface, and proven by borings in the Hinckley Basin. (East Warwickshire/west Leicestershire).
Poorly cemented, reddish-brown sandstone with thin beds of red mudstone and conglomerate.
140-200m near type area; may exceed 200m in deepest parts of Hinckley Basin.
Taken at the junction between the conglomerate dominated Polesworth Formation and the sandstone and mudstone dominated Bromsgrove Formation.
Plewland Sandstone Formation
PLWS
Taken at top of highest conglomerate bed in underlying formation (Middlefield Conglomerate).
Sandstone, greyish red or pale brown, medium- to fine-grained, cross-bedded with a few partings of red-brown siltstone.
To 1400m
Taken at base of overlying conglomerate formation (Greywacke Conglomerate).
Plessey Coal (Northumberland)
PLY
Plynlimon Till Formation
PLYNT
Generally unconformable on bedrock or regolith/head (e.g. Davies et al., 1997). At Broughton Bay it overlies the Gower Formation unconformably (Campbell and Bowen, 1989, 52-54).
Mid and west Wales, Welsh Borderlands, Usk Valley east of Talybont, southwest Wales approximately north of Black Mountain and east of St Clears and Llandysul.
Generally stiff, blue-grey, stony, sandy and silty clay and clayey gravel, characteristically containing clasts of Lower Palaeozoic rocks (derived from the Cambrian Mountains). Subordinate stratified sand and gravel are locally present. Colour and dominant clast composition are variable and generally reflect the local bedrock geology; in the Usk valley and the Wye valley east of Llyswen it can be pink and contain abundant Old Red Sandstone material; in central and west Wales it is generally grey and the clasts are exclusively Lower Palaeozoic. In Broughton Bay it contains shell fragments (Bowen, 1999).
Highly variable, locally in excess of 30m.
Generally the ground surface or contact with overlying peat, head (Severn and Avon and West Wales catchment subgroups), Kenfig Formation or Ynyslas Formation. Near Llanrhystud it is overlain by the Lleyn Formation (Campbell and Bowen, 1999; Davies et al., 1997) and in the Shropshire lowlands by the Shrewsbury Glacigenic Formation (Thomas, 1989).
Pemberton Two Foot Coal (South Lancashire)
PM2FT
Pemberton Five Foot Coal (South Lancashire)
PM5FT
Possil Main Coal (Glasgow Area; Central Coalfield)
PMA
Pittenweem Formation
PMB
The conformable base of the Formation lies in a transitional sequence up from the Anstruther Formation and is drawn at the base of the Cuniger Rock Marine Band.
Mudstone and siltstone with thin beds of limestone and dolomite; sandstone is subordinate; pattern of sedimentation cyclic with non-marine origin dominant over marine.
Maximum thickness is 220m+ in East Fife
The conformable top of the Formation lies in a transitional sequence to the Sandy Craig Formation and is taken at the top of the St. Andrews Castle Marine Band.
Pennine Middle Coal Measures Formation
PMCM
The base of the dark grey, fissile mudstone of the Vanderbeckei Marine Band, with eponymous fauna and/or other marine fossils.
Central and northern England, North Wales.
Interbedded grey mudstone, siltstone, pale grey sandstone and commonly coal seams, with a bed of mudstone containing marine fossils at the base, and several such marine fossil-bearing mudstones in the upper half of the unit.
See the Lexicon entries for the bounding marine bands for details of local alternative names.
Up to 600m thick across the North Staffordshire Coalfield; about 650m thick in Lancashire; 200m thick in northwest England and in the northwest of the Canonbie Coalfield.
The top of the dark grey, fissile mudstone of the Cambriense Marine Band, with eponymous fauna and/or other marine fossils. This definition is extended to the Scottish Solway area, which formerly used the top of the Aegiranum (Skelton) Marine Band to define the top of the formation.
Prescot Main Delf Coal (South Lancashire)
PMDC
Poole Formation, Marsh Farm Formation And Earnley Sand Formation (Undifferentiated)
PMFE
Permian Marls
PMLS
Pittenweem Marine Band
PMMB
Penmaen Tuff Formation
PMN
Overlies mudstones and sandstones of the Dwyfach Formation.
Basaltic trachyandesite lavas and tuffs and derived sediments.
Upward change from andesitic lavas and tuffs into rhyodacitic lavas and tuffs of the Foel Ddu Rhyodacitic Formation.
Port More Formation
PMO
Pumphouse Member
PMP
Mid Ordovician, mid Caradoc, Burrellian Stage, foliaceus Zone (see Fortey and others, 2000, column 78).
Where seen, the mudstone unit overlies the Doon Hill Conglomerate Member of the Balclatchie Formation.
Estimated at about 10m
The mudstone unit is overlain by the Burn Side Conglomerate Member of the Balclatchie Formation (where seen).
Pemberton Rock
PMR
The lower boundary is believed to be partly erosional. The base is taken at a sharp, well-defined surface which is erosional in parts, seperating mudstones below the boundary and sandstones and pebbly sandstones above the boundary. The base is taken at the base of the first sandstone-dominated unit above the higher Florida Coal in the Runcorn [SJ 50 80] and the south Wigan [SD 00 60] areas, and the base of the first sandstone unit above the Pemberton 5' Coal in the North Wigan [SD 60 10] area, and the base of the first sandstone unit above the Bargain Delf Coal at Bradley Hall Colliery (SD 5730 1106).
Adlington [SD 59 12] to Rainhill [SJ 49 91].
A yellow, cross-bedded sandstone, with subordinate mudstone. Pebbly sandstone noted at the base of the unit at Bradley Hall Colliery, Standish borehole SD51SE/53.
Up to 61 m thick.
The upper boundary is taken at the base of the mudstone, coal and fireclay-dominated succession of the Pennine Middle Coal Measures Formation above sandstones of the Pemberton Rock
Pant Mawr Sandstone Member
PMSA
Taken at the sharp contact, defined by a palaeokarstic surface, between the calcite mudstones and skeletal/peloidal/ooid packstone/grainstones of the underlying Stormy Limestone Formation and the overlying, partially dolomitised, sandy skeletal packstones and calcareous sandstones of the Member.
Western Vale of Glamorgan [ST 00 74]. May pass north into the coeval Honeycombed Sandstone Member on the north crop of the South Wales Coalfield [SN 97 13].
Partially dolomitised, sandy,skeletal packstone in lower part, and thin-bedded, cross bedded fine-grained calcareous sandstone in upper part. Represents transgressive shoreface deposits.
1.5 to 4m
Taken at the sharp junction at the top of the calcareous sandstones of the Member and the overlying thick-bedded, fine- to coarse-grained , mottled and pseudobrecciated skeletal packstones of the remainder of the Oxwich Head Limestone Formation.
Pumpherston Shales
PMSH
Permian Siltstone Member
PMST
Porth Meudwy Formation
PMU
Conformable on the siltstones of the Wig Bach Formation, the boundary being taken at the base of the first coarse-grained turbidite sandstone or slumped unit of the Porth Meudwy Formation.
Not yet entered.
Coarse-grained turbiditic sandstones interbedded with very coarse matrix-supported conglomerates, the latter representing mass-flow deposits containing boulders up to 1m of phyllitic and schistose mylonites comparable to those of the Llyn Shear Zone. Subordinate mudstone beds.
25 to 35m
Conformably overlain by the ferruginous siltstones, sandstones and ironstones of the Trygarn Formation, the boundary being taken at the top of the highest coarse clastic bed.
Porth Maen Melyn Volcanic Formation.
PMV
1:50,000 Sheet 209 (St.Davids) and adjacent Sheet 210.
Rhyolitic and dacitic lavas, tuffs and agglomerates, locally with interbedded sediments and debris flows.
80-100 metres.
Pemberton Yard Coal (South Lancashire)
PMYD
Pebidian Supergroup
St. Davids Sheet 209.
Trachytic and andesitic tuffs, with locally conglomeratic tuffaceous sediments. NOTE: The definition follows the usage on British Geological Survey 1:25 000 Special Sheet SM72 (St Davids), 1973, which in turn derives from Green, JFN. 1908.The computer code PV already exists for 'Pebidian Volcanic Series (undifferentieated)'.
At least 2000m.
Stratigraphical top uncertain/undefined (see Ogofgolchfa Group); ?overlain unconformably by Lower Palaeozoic rocks.
Pensarn Basaltic Andesite
PNBA
Intrusive contact coincident with the base of the Nod Glas Formation (qv).
Feldspar porphyritic and highly vesicular basaltic andesite.
Within the Nod Glas Formation (qv).
Pinstane Conglomerate Member
PNC
Enclosed within wacke sandstone of the Mindork Formation.
Irregular packets and lenses of pebble and boulder conglomerate within wacke sandstone. Clasts include vein quartz, quartzite, rhyolite, microgranite, granophyre, granite, chert and mudstone.
Several packets of beds, some packets up to 100m thick.
Penton Coals
PNCS
Pendleside Sandstone Member
PNDS
Point where sandstones start to dominate the Lower Bowland Shales, going up sequence.
Widely, but discontinuously cropping out in the Craven Basin in Clitheroe, Settle, Lancaster and Garstang districts and probably farther afield.
Sandstone turbidite facies comprising mainly fine- to medium-grained, thin to thickly bedded, grey to pale brown sandstones, interbedded with shaly mudstones and siltstones, calcareous in part.
c.300m maximum.
Point, going up sequence, where sandstones cease to dominate the Lower Bowland Shales sequence.
Pistyllion Formation
PNF
Penarth Group
PNG
At base of Westbury Formation, usually erosional, on the Blue Anchor Formation of the Mercia Mudstone Group.
United Kingdom, including Northern Ireland.
Grey to black mudstones with subordinate limestones and sandstones; predominantly marine in origin.
0- >12m.
At base of lowest formation in the Lias Group: Scunthorpe Mudstone Formation, Blue Lias Formation, Redcar Mudstone Formation etc; or 'Lower Lias'.
Portnagree Conglomerate
PNGC
Pinnacle Howe Tuff Member
PNH
Taken at the sharp change to vitrophyric tuff from underlying units that include andesite and volcaniclastic sandstone of the Birker Felll Formastion, or bedded garnetiferous tuff and lapilli tuff of the Powley's Hill Member (Whelter Knotts Fomration).
Eastern Lake District, from Pinnacle Howe to Naddle Beck, Haweswater, Cumbria.
A foliated, vitrophyric, rhyodacitic tuff containing a diagnostic population of angular, grey felsic clasts, in white to pink weathered exposures.
Up to 70 m thick.
Taken at the abrupt change to eutaxitic lapilli-tuff of the main part of the Whelter Knotts Formation.
Pennan Hill Vent
PNHI
Subvolcanic explosion breccia pipe 75 x 50 m, of mainly wacke breccia, with little or no igneous component.
Thickness, not known, 75 x 50 m in areal extent
Pins Ironstone
PNIR
Pinskey Gill Formation
PNKG
Mid Courceyan.
Penton Limestone [Obsolete Code: Use Pnls]
PNL
Penarth Group And Lias Group (Undifferentiated)
PNLI
Penlan Coal (South Wales)
PNLN
Penton Limestone
PNLS
Penarth Group (Marginal Facies)
PNMF
Markedly unconformable, at the abrupt base of sandstones of the Marginal Facies; these may overlie mudstones of the Penarth Group or Mercia Mudstone Group, or locally they overstep onto older Palaeozoic or Proterozoic rocks.
Deposits occur at the surface on the flanks of the Penarth Group outcrop in the Bridgend area of South Wales (Wilson et al., 1990) and in the subsurface in central-southern England (Oxfordshire, Berkshire), around the flanks of the London Platform (Horton et al., 1987).
Variable, typically consisting of pale grey or yellowish grey sandstone, calcareous or dolomitic, locally with pebble-sized clasts of limestone or quartzitic sandstone derived from nearby Palaeozoic rocks. These lithologies interdigitate with the typical grey to black mudstones with thin sandstones and limestones of the Penarth Group or its constituent formations.
Highly variable due to interdigitating relationship with the Penarth Group; ranges from 1m or less at some exposures to over 10m.
Conformable and gradational, interdigitating with mudstones, sandstones and limestones of the Penarth Group (or its constituent formations).
Pennan Sandstone Formation
PNN
Base of red pebbly sandstone sequence conformably overlying the mixed siltstones and minor sandstones of the Gamrie Bay Sandstone.
Gardenstown - Cuminestown - Sandy Haven at NJ 8592 6553.
Red sandstone.
Everywhere an unconformity overlain by the middle Devonian Conglomerates of the Inverness Group, i.e. Gardenstown Conglomerate.
Penrhos Member
PNR
Locally recognisable member of the Maentwrog Formation (Pratt, Woodhall and Howells, 1995).
Penrhiwmoch Member
PNRH
Pumpherston Shell Bed
PNSB
Penamnen Tuff Formation
PNT
Caradoc (?Soudleyan).
Eastern central Snowdonia.
Felsic tuffs with siltstone intercalations.
Pentland Formation
PNTL
Pennystone Coal
PNY
Pennyhill Coal (Northumberland And Durham)
PNYH
Pennystone Ironstone (South Staffordshire)
PNYI
Porthkerry Member
Point Of Ayre Formation
POA
Generally unconformably overlying glacigenic diamicton or sand and gravel, or Lateglacial sediments (head gravels or humic sands, silts and clays), or bedrock.
Applies to all onshore coastal/marine deposits on the Isle of Man.
Coastal marine and brackish water deposits, including shingle beach ridges, beach deposits, blown sand dunes (Ayre Member), diatomite, fen-peat, lagoonal and lake mud (brackish and fresh water) (Lough Cranstall Member) and submerged forest peat, laminated silt and palaeosols (Phurt Member).
Unrecorded but probably commonly exceeds 5m locally.
Porthtowan Formation
POAN
?Eifelian to Frasnian.
Transition above Grampound Formation of Meadfoot Group.
West Cornwall.
Interbedded slaty mudstone, grey and grey-green, and sandstone. Subordinate sandstone beds are up to 2m thick, typical turbidites.
2.8km
Transition with Mylor Slate Formation.
Portishead Formation
POB
Unconformable contact on the underlying Black Nore Sandstone (Brownstones Formation of South Wales) or on Silurian Volcanics.
Bristol - Mendip area. Splits laterally into Tintern Sandstone and Quartzite Conglomerate in Forest of Dean.
Red-green mudstones and marls, red siltstones and red-yellow, hard, fine-grained quartzose sandstones, with conglomerate locally.
Incoming of shales and thin limestones of the Lower Limestone Shale Formation which rest conformably on the Portishead Formation.
Port Of Brims Sandstone Member
POBS
Conformable on the top of the uppermost green siltstone of the underlying Tang Sandstone Member.
Onshore and immediately offshore of the Dounreay area, Caithness, Northern Scotland. Geographical Map Scotland Sheet 115E.
Prominent thick (>4m), cross-bedded sandstone units in a generally sandy sequence with lenticular bedding.
c.30m
Faulted against the Crosskirk Bay Formation by the Bridge of Forss Fault at Port of Brims.
Portobello Vein
POBV
Poneil Coal
POC
Powis Castle Conglomerate Formation
POCA
Portland Cherty Member
POCH
Pocklington Gravel Formation
POCKG
Sandy gravel of the Pocklington Gravel Formation rests unconformably on Mesozoic bedrock with a sharp to variably disturbed (cryoturbated, soliflucted, reworked) basal content.
The Pocklington Gravel Formation exists as a blanket deposit at the eastern limit of the Vale of York, The gravel is known to extend beneath the Breighton Sand Formation to the west of Bielby. To the north and south the gravel flanks the elevated ground into the York and Beverley areas.
Matrix to clast supported clayey sandy medium to coarse gravel. Clast composition is typically polymodal, domiated by chalk and flint. Average clast composition is 75% well-rounded chalk, 15% sub-angular flint, plus 10% accessory lithologies including ironstone and oolitic limestone. Clast composition varies in extreme cases to 100% chalk or 100% flint, increased flint content may be due in part to different dissolution of chalk clasts. Matrix material is characterized by reddish brown clayey sand to sandy clay with varying degrees of partially decomposed chalk.
In excess of 1m (1.2m observed in temporary excavation [480417, 448013]).
The upper contact with the Breighton Sand Formation is proved in auger holes to be relatively sharp with minor intercalation due to local reworking. Elsewhere, the Pocklington Gravel Formation is known to be overlain by alluvial, aeolian and artificial deposits with varying degrees of incision and disturbance.
Portland Clay
POCL
Argillaceous dolomite [dolomite-mudstone].
Currently (09/02/2007) treated as an informal Bed within the Portland Sand Formation, though it might be elevated to Member status in the light of ongoing framework/correlation considerations.
Potato Coal (South Lancashire)
POCO
Portencross Sandstone Formation
POCR
Faulted inlier near Portencross, Sheet 21/22W.
Brown and chocolate-brown, hard, compact, massive, cross-bedded and thinly bedded sandstone with conglomerate patches and lenses.
From 450 m to 550 m thick.
Portland Freestone Member
POFR
Potts Ghyll Tuff Formation
POG
Lower boundary not exposed in detail; taken at upward change from dominantly andesite to volcaniclastic deposits, within the Eycott Volcanic Group
Northern flanks of Caldbeck Fells from Branthwaite Beck (NY301 367) to just west of Birket (NY329 363)
Massive vitroclastic and lithic-rich lapilli tuff and tuff of acid andesite/dacite composition.
Overlain unconformably by Carboniferous strata
Powell Group Of Coals (North Wales)
POGC
Pomeroy Granite
POGR
Portree Hyaloclastite Formation
POHY
This is the earliest of the Paleocene volcanic formations and is typically unconformable on the underlying Jurassic strata. Plant-bearing beds are also common at this juncture.
Predominantly tuffs, with fragments of glassy and devitirified olivine basalt and also accretionary lapilli. The tuffs are interspersed with thin amygdaloidal basalt flows and pillowed basalts. Interflow sediments are sporadically present as typically plant-bearing volcaniclastic sandstones and siltstones.
Overlain by the Beinn Edra Formation in northeastern Skye and by the slightly younger Ramasaig Formation farther west.
Polyphant Intrusion
POIN
Porcellaneous Limestone (Carboniferous, North West)
POL
Found across much of the southern Askrigg Block between Kingsdale in the west and Malham in the east, though may be absent locally. Also found in Westmorland. In both areas the bed marks the approximate local top of the Holkerian Stage.
Polglaze Formation
POLG
Faulted against the Portscatho Formation, comprising predominantly turbiditic sandstone beds.
Mevagissey Sheet 353 (England and Wales), but is known to extend northwards onto the Bodmin and St. Austell Sheet (347), for which no modern mapping is available.
A dark grey, slatey cleaved mudstone, which has a marked absence of coarser lithologies, and showing low grade (anchizone) regional metamorphism.
Unknown, as obscured by complex folding, but probably at least 500m.
Faulted against the Hallane Formation, seen as a mudstone with siltstone and limestone.
Polshill Pluton
POLL
Polquhairn Limestone
POLS
Known in the subsurface in south-central Ayrshire.
Poltallan Member
POLT
Appearance of lava clasts in sandstone-siltstone succession.
Breccia of amygdaloidal lava clasts in a clastic or tuffaceous matrix with intercalations of dark silty mudstone.
Last occurrence of lava clasts.
Poltimore Mudstone Member
POM
Sharp lower boundary on fine-medium and coarse-grained, locally pebbly, sandstone.
Outcrop extends from around Poltimore village [SX 966 970], northeastwards to near Hay House, [SX 986 988], Broadclyst.
Reddish brown mudstone, sandy mudstone and clayey fine-grained sandstone, weathering to clay and clayey sand.
Change from predominantly clayey Poltimore Mudstone to overlying sandstones; marked by pronounced feature.
Portsdown Marl
POMA
Polhote Marine Band
POMB
Pontefract Rock
PONR
Poole Formation
POOL
Poppleton Glaciofluvial Member
POPP
Unconformable on glacial till (Vale of York Formation).
Vale of York, in York area north of York Moraine.
Dominantly glacio-fluvial sand and gravel in esker ridges, outwash fans and less definite spreads of sand and gravel.
Portavo Formation
POR
Porteous Band
PORB
The base of this marine horizon marks the local base of the (Scottish) Coal Measures Group in the Douglas outlier.
Portskerra Psammite Formation
PORK
Portscatho Formation
PORO
Carrick Thrust.
Gramscatho Basin, South Cornwall.
Interbedded sandstone beds (up to 2m) and slaty mudstone.
Up to 5.4km.
Veryan Thrust.
Portsmouth Sand Member
PORT
Posidonia Beds
POS
Boundary with main part of Teign Chert taken at level where well-bedded cherts become predominant.
Middle Teign Valley, Devon.
At the top of the Teign Chert, shales containing Posidonia becheri are overlain by interbedded shales, cherts and thin limestones. A band with spirally striate goniatites is present above the beds containing Posidonia.
30-45 metres.
Conformably succeeded by the Ashton Shale (basal member of the Crackington Formation). The boundary is reflected in the topography, with the Teign Chert (including the Posidonia Beds) forming prominent features.
Portland Sand Formation
POSA
Powillimount Sandstone Member
POSD
Gradational with the Gillfoot Sandstone Formation.
Powillimount shore, Southerness, Kirkcudbrightshire, south-western Scotland (Southern Uplands).
Interbedded bioturbated sandstone, sandy limestone (some oncolite beds) and mudstone, sparsely fossiliferous.
Taken at top of the Thirlstane Sandstone Member, which lies conformably under the Arbigland Limestone Formation.
Pontesford Shales Formation
POSH
Basal conglomerate overlies Uriconian Group (Precambrian) volcanic rocks with marked unconformity.
Black pyritous mudstones overlie a basal conglomerate and are succeeded by buff weathering, greenish grey, silty micaceous mudstones and siltstones.
Portland Stone Formation
POST
Pot Coal (Bristol Area)
POTC
Penfro Till Formation
POTI
Powell Coal (North Wales)
POWC
Portsmouth Sand Member And Whitecliff Sand Member (Undifferentiated)
POWH
Pitscow Sand And Gravel Formation
POWSG
Anglian (MIS 12) to Wolstonian (?MIS 8).
In Kirkhill quarry (infilled) southeast face A and east face at the base of the unit rests unconformably on unweathered felsite bedrock. In southeast face B the formation in part both overlies and interdigitates with felsitic rubble of the Kirkton Gelifluctate bed. To the southwest at Leys quarry (disused), northeast face, a sand and gravel body interpreted to be the Pitscow Sand and Gravel Formation, unconformably overlies the Denend Gravel Formation. Here the Pitscow Formation rests in a -2m deep erosive channel feature.
Buchan, northeast Scotland. The formation is currently only known within the immediate vicinity of Kirkhill quarry (infilled) and Leys quarry (disused) on Sheet 87W (Ellon). The unit may be regionally significant and present locally across northeast Scotland.
Sand with subsidiary beds of gravel. Dominantly pale olive-brown and pale pinkish brown quartzose and felsitic medium to coarse sand. Typically horizontally stratified with some planar and trough cross beds indicating transport towards the west. The gravel component diminishes upwards and is typically of pebble-cobble grade. Angularity varies significantly from rounded to angular. Clast lithologies are dominated by felsite, with smaller quantities of quartzite, psammite, hornfels and red and grey granites. Interpretated as a periglacial fluvial deposit (possibly glaciofluvial in part).
At both Kirkhill Quarry (infilled) southeast face A and east face, and Leys Quarry (disused), northeast face, the upper boundary of the unit is gradational, undulatory boundary with the overlying bleached, podzolic Kirkhill Palaeosol Bed.
Penny Pieces Coal (South Wales)
PPCO
Portpatrick Formation
PPF
Conformably overlies the Lower Hartfell Shale Formation.
Wacke and siltstone turbidite succession.
Pliocene-Pleistocene Gravels And Crags
PPGC
Including (all/part/none of) Glacial Sand and Gravel, Kesgrave Formation, Westleton Gravels, Norwich Crag, Red Crag and Coralline Crag.
Portpatrick Formation And Glenwhargen Formation (Undifferentiated)
PPGW
Pinder Park Ironstone
PPI
North Britain Palaeogene Plug Suite
PPNB
Pipe Rock Member
PPR
Conformable and gradational boundary with underlying Basal Quartzite Member.
The Eriboll Formation (including the Pipe Rock Member) forms a narrow belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt, Dundonnell, Kinlochewe and Kishorn, to Skye.
Mature bioturbated, predominantly white quartz arenite with Skolithos burrows.
75 m - 100 m thick.
Defined at the distinct boundary with the overlying Fucoid Beds Member of the An t-Sron Formation.
Poppingstone Sandstone
PPS
Peel Place Sand And Gravel Member
PPSG
Generally conformable on the Fishgarth Wood Till Member of the Gosforth Glacigenic Formation in the Drigg Hall Carleton area; on the How Man Till Member between St Bees and Braystones and on the Rothersyke Till Member in the Ehenside area.
Western Cumbria within (seaward of) the limit of the Gosforth Oscillation. Typically on the coastal lowlands between Gosforth, Seascale and Drigg. 1:50k Sheet 37 Gosforth.
Well bedded cross-stratified gravel and sand that typically forms upward coarsening sequences. Clasts are generally rounded to well rounded and comprise a mixture of Permo-Triassic and Carboniferous rocks, as well as igneous and metamorphic rocks derived from the Lake District. Deposit fines downwards into horizontally bedded sand with horizontal and climbing ripple lamination.
Unconformably overlain by Holocene deposits such as Blown Sand and by Late Glacial to Holocene peats near its type site.
Pumpquart Coal (South Wales)
PQCO
Peach Quarry Limestone Member
PQL
Conformable passage from poorly exposed dark grey fissile mudstones and packstones of the "Upper Coplow Shales" to packstones and grainstones of the Peach Quarry Limestone Member.
Lenticular unit restricted to the southern limb of the Clitheroe Anticline (SD 74).
Packstone and grainstone, clean washed, fine-to coarse-grained, pale grey, with thin to thick, massive and multi-storey beds, wavy bedded and chert with abundant crinoid, algal and pellet grains, interbedded with subordinate dark to brownish grey, calcareous mudstones, platy with bedding planes crowded with brachiopods and ostracods. Many limestones contain intraformational lithoclasts and show erosive bases. Grading and cross-bedding occur, together with high-angle, imbricate shell-lags.
Up to 70m thick.
Gradational passage from the packstones and grainstones into the Waulsortian limestones of the Bellman Limestone Member.
Pumpquart (Lower) Coal (South Wales)
PQLC
Pre-Quaternary Rocks (Undifferentiated)
PQU
Weathered Pre-Quaternary Rocks (Undifferentiated)
PQUW
Peel Hall Rock
Port Edgar Ash
PRA
Lower Perton Beds
PRBL
Upper Perton Beds
PRBU
Portrush Chalk Member
PRC
Conformable, on the Garron Chalk Formation, at a bedding plane beneath a prominent continuous tabular flint.
Found consistently throughout the province but is generally absent from much of the East Antrim (Midland Valley) Basin due to pre-Palaeogene basalt erosion. Oversteps onto older strata over the Londonderry Shelf.
Limestone (chalk) with many tabular flint bands and Inoceramus debris in upper part. In the south Antrim area (Southern Uplands High) there are important hardground non-sequences of green-coated chalk pebbles called the South Antrim Hardgrounds (of member? status).
14.28m in the type section.
At a prominent bedding plane above Inoceramus-rich chalk with tabular flint.
Pretoria Coal (South Wales)
PRCO
Pantrhydydwr Coal (South Wales)
PRDC
Redoubt Beds
PRE
Pre-Devonian Complex (Basement) (Undifferentiated)
PRED
Premier Coal (North Wales)
PREM
Prestwich Rock
PRER
Flinty Rhyolites
PRFR
Paisley Ruck Fault Zone
PRFZ
This unit represents the spatial extent of the Paisley Ruck (fault) crush zone.
Priesthill Group [Cf Hagshaw Group]
PRH
Drawn at base of greywackes of the Patrickburn Formation where it rests on the Ordovician.
Midland valley, Strathclyde, Scotland.
Greywackes, sandstones, siltstones and mudstones with sporadic carbonaceous silty layers. (Correlative of Priesthill Group = Hagshaw Group.)
Drawn at conformable upward passage from sandstones of the Dunside Formation to sandstone of the Passage Formation of the Waterhead Group.
Preesall Halite Formation (Offshore)
PRHA
East Irish Sea Basin and (as the Preesall Halite Member, q.v.) in adjacent onshore areas of West Lancashire.
Primrose Hill Metamorphic Complex
PRHM
The Wrekin, Shropshire and the Welsh Borderlands.
Granitic and amphibolitic gneisses, altered tuffs, intrusive granite and pegmatite.
Poor Robin Ironstone (South Staffordshire)
PRI
Pridoli Rocks (Undifferentiated)
PRID
Possil Rider Coal (Glasgow Area; Central Coalfield)
PRIDC
Primrose Bank Sill
PRIM
Prismatic Clay Member
PRIS
Generally a planar, subhorizontal to undulating gradational boundary with dark brown or purplish brown, stony silty sandy clay diamicton of the Horden Till Formation. Where thin deposits of sand and gravel intervene locally, the Prismatic Clay forms pipes and load structures into the underlying sand and gravel. Locally conformably overlies reddish brown sandy silty clay formerly assigned to the Pelaw Clay by Smith (1994), but containing chalk and flint.
Generally a dull brown or reddish brown, sandy silty clay with well dispersed fine pebbles and sparse ironstone nodules. The Prismatic Clay derives its name from the closely spaced, subvertical, prismatic jointing that formed during dry periglacial conditions.
Generally about 0.5m but up to 1.5m
Generally the ground surface. Locally concealed by blown sand.
Prince Rock Member
PRK
Basal mudstones conformably succeed the Faraday Road Member.
Coxside area of Plymouth (geological sheet 348) and Prince Rock area of Plymouth (geological sheet 349).
Thin- to medium-bedded, fine- to medium-grained skeletal wackestone and packstone with stylolitic mudstone partings and interbeds. Coarser crinoidal lithologies occur in lower part and form basal lags of graded and cross-stratified packstone beds that are common in upper part. The limestone is typically dark grey and foetid.
Succeeded by red and black reef limestone of late Givetian age of the undivided Plymouth Limestone Formation.
Prestatyn Limestone Formation
PRL
Not exposed, but presumed to be a conformable contact between thicker bedded limestones (packstones and grainstones) of the underlying Llanarmon Limestone Formation and thinner bedded Prestatyn Limestone facies.
Prestatyn area of North Wales (SJ 07 81).
Thin bedded limestone turbidites (packstones and wackestones), occurring as fining-upwards graded beds, with mudstone interbeds; local thick-bedded units of resedimented fine-grained limestone (grainstones) and isolated rolled blocks of knoll reef limestone; scattered chert nodules.The formation formed as an apron of late Asbian limestone turbidites, resedimented carbonate detritus and fallen blocks of "reef" limestone derived from the adjacent North Wales Clwyd Limestone Group platform.
Over 120m
Conformable contact with interbedded mudstones and dark argillaceous limestones of the Teilia Formation.
Prestonlinks Offshore Dyke
PRLO
Raploch Sandstone
PRLS
Permian Rocks And Triassic Rocks (Undifferentiated)
PRMT
Penyraber Mudstone Formation
PRMU
Perna Member
PRNA
Nant-Y-Coy (Cae) Beds
PRNC
Protovirgularia Grits Formation
PRO
Conformably overlies the Penkill Formation.
Grey-green, gritty sandstone and shale.
165 m thick.
Conformably overlain by the Lauchlan Mudstone Formation.
Proterozoic Rocks (Undifferentiated)
PROT
Purple Sandstone Member
PRS
Unconformity. Lowest occurrence of purple sandstone, locally conglomeratic, resting on rocks of the Highland Border Complex.
Medium-grained, purple, quartzo-feldspathic sandstone, pebbly in places in lower part.
93m
At the base of the lowest metre-thick red siltstone bed in the overlying Castle of Cowie Member.
Preesall Halite Member
PRSA
Conformable, at the gradational upward transition from the laminated reddish brown and greenish grey mudstones (formerly referred to the Thornton Mudstone Member, now undifferentiated Kirkham Mudstone Member) to the halite of the Preesall Halite Member.
Preesall Saltfield, north Fylde peninsula, Lancashire, and (as the Preesall Halite Formation, q.v.) in adjacent parts of the East Irish Sea Basin.
Halite, with thin partings of reddish brown and dark greenish grey mudstone. Breccias formed by dissolution are common at shallow depth.
Originally referred to simply as the Preesall Salt, the term was given Formation status by Warrington et al. (1980), and is now retained as a local member within the nationally recognized Sidmouth Mudstone Formation (Howard et al., 2008).
100m to 150m (Wilson and Evans, 1990).
Conformable, at the gradational upward transition from the halite of the Preesall Halite Member to the predominantly greenish grey laminated mudstone at the base of the overlying undifferentiated Kirkham Mudstone Formation (formerly referred to the now Obsolete Coat Walls Mudstone Member).
Prestonpans - Seton Dyke
PRSE
Princes Risborough Sand And Gravel
PRSG
Sand and gravel, rich in flint and chalk clasts; crops out in the dry gap in the Chilterns (the 'Princes Risborough Gap'). [Generic description: 1:50 k map margins].
Parsonage Sandstone
PRSS
Priestlaw Intrusion
PRST
Parrot Coal (Northumberland)
PRTC
Poortown Intrusion
PRTN
Prescot Yard Coal (South Lancashire)
PRYD
Penrith Sandstone Formation
Unconformable base on Carboniferous rocks.
BGS sheets 23, 24, 30, and 31
Coarse-grained cross-bedded aeolian sandstone.
Conformably overlain by Eden Shale Formation.
Prenteg Sandstone Member
PSA
Conformably overlies ash-flow tuffs and subordinate sediments of the Capel Curig Volcanic Formation.
Fine- to coarse-grained, locally magnetitic sandstones with abundant sedimentary structures.
100 to 200m
Sharply but conformably overlain by thinly interbedded siltstones and mudstones and siltstones of the undivided Cwm Eigiau Formation.
Pathhead Soft Coal (New Cumnock)
PSC
Pinkie Six Foot Coal (Lothian)
PSF
Passage Formation (Wenlock Series)
PSG
Sands And Gravels, Pleistocene
PSGU
Including (all/part/none of) Glacial Sands and Gravels, Kesgrave Formation, Westleton Gravels.Sand and gravel, locallt with silt, clay and peat; of Pleistocene age. [Generic description].
Purley Shale Formation
PSH
Sharp contact of red mudstone on grey, massive or bioturbated glauconitic sandstone of the Woodlands Member (Hartshill Formation). Some sediment mixing along junction.
From Nuneaton, extending northwestwards to the southern suburbs of Atherstone (SP 3629 9197 - 3064 9712).
Blocky to shaly red or maroon mudstone and siltstone at the base; green and grey fissile mudstones in the middle and red and green interbedded shaly mudstones at the top.
200m in type area.
Gradational passage upwards into Abbey Shales. Faunal definition not specified.
Portskerra Conglomerate Member
PSKA
The unit rests unconformably, directly on Caledonian igneous or Precambrian Moine (basement) rocks as the basal unit of the Bighouse Formation on the Middle Old Red Sandstone unconformity.
A pebble and boulder conglomerate, typically containing rounded to subangular clasts of Moine psammite, Reay diorite and some granitic rocks in a matrix of greenish grey fine- to medium-grained sandstone. The unit is locally intercalated with thin beds of grey nodular limestone of the Aryleive Limestone Bed.
Typically 5 - 10m, and locally more than 40m
Overlain by an interbedded, sandstone-dominated rhythmic sequence of sandstones, siltstones and laminated carbonate mudstones (fish beds) of the Baligill Limestone Member of the Bighouse Formation.
Ponesk Burn Formation
PSKB
Not seen, formation occurs in core of anticline.
Alternating beds of grey, medium-grained, turbiditic sandstone (greywacke) with washed-in fossil debris of brachiopods, molluscs, trilobites etc; and grey siltstones - in some cases laminated with silty mudstone.
Presumed transitional with overlying greywacke/siltstone sequence of Patrick Burn Formation, but everywhere faulted.
Pennine Lower Coal Measures Formation And South Wales Lower Coal Measures Formation (Undifferentiated)
PSLCM
Port Na Spaniagh Member
PSM
Pennine Middle Coal Measures Formation And South Wales Middle Coal Measures Formation (Undifferentiated)
PSMCM
North Britain Palaeogene Sill Suite
PSNB
Portland Sand Member (Wiltshire, Oxfordshire And Buckinghamshire)
PSND
Conglomeratic and glauconitic coarse-grained sand, sandstone and limestone (Upper Lydite Bed) resting non-sequentially on mudstones, siltstones or fine-grained argillaceous sands and sandstones of the Upper Kimmeridge Clay.
Outliers from Swindon to Aylesbury in north Wiltshire, Oxfordshire and Buckinghamshire, and possiblly an outlier in the Vale of Pewsey near Devizes, though this is currently rather poorly known (see Wimbledon, 1980). A separate description applies to the Portland of the Vale of Wardour in south Wiltshire or Dorset.
Calcareous sandstones and sands, commonly glauconitic (Glauconitic Beds) and conglomeratic sandstones, sands, marls and limestones (Upper Lydite Bed).
Up to 6 m thick.
Either seen as a transition from calcareous sandstones and sands, commonly glauconitic (Glauconitic Beds), to limestone of Portland Stone Member, which is probably diachronous, or as a sharp, non-conformable junction with generally non-calcareous and commonly ferruginous sands and sandstones of the Lower Greensand, or Whitchurch Sand Formations, or by calcareous mudstones of the Gault Formation.
Pennyvenie Splint Coal
PSP
Poolscar Formation
PSR
Conformably overlies the Latrigg Formation.
Sandstone with subordinate siltsone and mudstone.
Conformably overlain by the Moorhowe Formation.
Spy Rigg Sandstone
PSRS
Plantation Sike Sandstone
PSS
Possil Subgroup
PSSG
Port Seton - Spittal Dyke
PSSP
Patna Sandstone
PST
Pollock Stone Coal
PSTC
Portland Stone Member (Wiltshire, Oxfordshire And Buckinghamshire)
PSTN
Upward transition from variable calcareous and glauconitic sand or sandstone such as the Portland Sand Member, to variable sandy limestone.
Outliers from Swindon to Aylesbury, in north Wiltshire, Oxfordshire and Buckinghamshire, and possibly an outlier in the Vale of Pewsey near Devizes, though this is currently rather poorly known (see Wimbledon, 1980). A separate description applies to the Portland in the Vale of Wardour, south Wiltshire andf Dorset.
Variable sandy marine limestones commonly with large and robust molluscan macrofauna, such as the Aylesbury Limestone, Rubbly Limestone, Cockly Bed, Creamy Limestone and Town Gardens Limestone) and variable calcareous sands and sandstones, generally non-glauconitic such as the Crendon Sand, Swindon Sand and Swindon Sandstone.
Up to, and locally greater than 11 m thick.
Upward change from fully marine limestones with large molluscan fossils of Portland Stone Member to lagoonal fine-grained limestones and marls of Purbeck Formation (the base of which is commonly Marked either by laminated, ostracod-bearing 'Pendle' or oyster-bearing marl, or by a sharp non-sequential contact with overlying, generally non-calcareous and commonly ferruginous sands and sandstones of the Lower Greensand or Whitchurch Sand Formation, or by calcareous mudstones of the Gault Formation.
Power House Terrace Deposits (River Severn)
PSTT
Bridgnorth (Shropshire) to Worcester - Severn Basin.
Pebbly, silty sand/sandy silt; sandy gravel, silty clay and peat.
To 6.5m
Papa Stour Volcanic Formation
PSV
Latest Eifelian
In the type area, there is an unconformable contact upon sandstone and tuffaceous sandstone of the Melby Sandstone Formation. In the Melby area, it is in faulted contact along the Melby Fault against the Sandness Formation (Lower ORS] on the Walls Peninsula, or along a highly irregular contact with 'blocks and tongues' of rhyolite, that penetrated the underlying grey, micaceous, ripple laminated sandstone with rhyolite clasts of the Melby Sandstone Formation, to a depth of about 60 cm whilst it was an unconsolidated sediment.
The island of Papa Stour is about 2 km off the western coast of Mainland Shetland, about 36 km NW of Lerwick and the northern portion of the Walls Peninsula, BGS Scotland Sheet 127 Western Shetland.
Comprises principally rhyolite lava, rhyolitic tuff and agglomerate and basalt. In its type area on Papa Stour, the lava is largely devitrified. It occurs in two thick flows with intercalations of tuff, basalt and sandstone. The rhyolite is strongly banded. The basalt, which is intensly weathered locally, occurs in up to four flows. These have thick scouriaceous upper zones with chaledony-, calcite-barytes- and zeolite-filled vesicles. Similar rhyolite and pyroclastic rocks , such as the Melby Rhyolite Member, occur on the Walls Peninsula on Mainland Shetland.
Up to at least 200 m in the type area.
In the type area, the rock at the top of the Papa Stour volcanic sequence is the youngest exposed bedrock. In the Melby area, the top of the upper unit of the Melby Rhyolite Member is a disconformable, irregular, brecciated contact against fine-to-medium-grained, planer bedded pink sandstone, with partings of flaggy sandstone and siltstone, and containing scattered rhyolite clasts of the Melby Sandstone Fm. The upper boundary of the lower unit is not exposed, but mapping suggests that it is disconformably overlain by similar sediments of the Malby Sandstone Fm to those overlying the upper unit.
Pitts Head Tuff Formation
Overlies sandstones and mudstones of the Cwm Eigiau Formation.
From Llwyd Mawr to Dolgarrog, central Snowdonia.
Acid ash-flow tuff; variably welded, rhyolitic. Two main facies - intra caldera tuffs and out-flow tuffs.
700m intra caldera facies, 0-100m outflow facies
Overlain by sandstones and siltstones of the Cwm Eigiau Formation or tuffs of the Lower Rhyolitic Tuff Formation.
Peat And Alluvium (Undifferentiated)
PTAL
Protalus Reef Deposits
PTALR
Petit Tor Breccia Member
PTBR
Pathhead Thick Coal
PTC
Pinkie Three Foot Coal (Midlothian)
PTF
Pennyvenie Two Foot Seven Inch Coal
PTFS
Pennyvenie Two Foot Three Inch Coal
PTFT
Ptilograptus Shales
PTG
Point Garry Sill
PTGRY
Peterhead Pluton
PTHD
Potholes Limestone
PTHL
Protolenus Limestone
PTL
Petershill Limestone
PTLS
Pencerrigtewion Member
PTM
Pathhead Marine Bands
PTMB
Pitmain Semipelite Member
PTMN
Transitional contact. Quartzose psammites and semipelites at base contrast with underlying striped micaceous psammites / semipelites of the Loch Laggan Psammite Formation.
Central Monadhliath Highlands: Speyside, Kingussie - Newtonmore area. Possibly extending southwest to Crubenmore area.
Gneissose semipelite with quartzose psammites and micaceous psammites, distinctive garnetiferous calc-silicate bands and pods.
270m in type area.
Transitional contact, marked in places by quartzose psammites and semipelite passing up into overlying micaceous and feldspathic psammites of the Loch Laggan Psammite Formation.
Plastirion Member
PTN
Conformable and gradational with the underlying mudstones and sandstones of the Bodwrog Member. It is the presence of the latter that has allowed the Plastirion Member to be named thus. Where the Bodwrog Member is absent, the Plastirion Member overlies the Allt Fawr Rhyolitic Tuff Formation and forms the whole of the Dwyfach Formation. It is for this reason that it should be more aptly regarded as "Dwyfach Formation (undivided)".
Pwllheli and Nefyn areas, North Wales.
Fossiliferous grey calcareous mudstone and siltstone with fine- to medium- to coarse-grained sandstones.
100 to 120m
Overlain by andesitic tuffs of the Penmaen Formation. The boundary is generally sharp but probably conformable, and is heralded by a marked coarsening at the very top of the Plastirion Member.
Partan Craig Vent
PTNCG
Pecten Ironstone (Bed)
PTNI
Pysgotwr Grits Formation
PTR
Base of lowest thick argillaceous sandstone bed above the lower tongue of the Glanyrafon Formation.
Thinly interbedded turbidite sandstones and mudstones with abundant thicker beds of argillaceous coarse sandstone.
Top of highest thick argillaceous sandstone bed below the upper tongue of the Glanyrafon Formation.
Parkgate And Tupton Roof Coal (Vale Of Belvoir)
PTRC
Pentre Formation
PTRE
Fossiliferous argillaceous fine-grained sandstones and silty mudstones.
Probably unconformable base of overlying Henfryn Formation.
Pentre Formation [Obsolete Code: Use Ptre]
PTRF
Pentire Slates
PTRS
Priest Sandstone
PTSA
Portrush Sill
PTSI
Portsoy Limestone Formation
PTSL
First limestone bed above Castle Point Pelite Formation.
Coast section in western part of Portsoy [NJ 584 665-586 662], together with isolated inliers and xenoliths in Portsoy basic intrusion. Some equivalent strata may have been included within the Castle Point Formation in the poorly exposed ground in the south of Sheet 96W and the north of Sheet 86W.
Interbedded units of semipelite with graphitic pelite, beds of crystalline metalimestone, quartzite and minor dolomite. Distinctive kyanite after andalusite in graphitic pelite of basal Sandy Pots Limestone Member. Some pebbly quartzite and psammite.
Probably c.200m+, but much disrupted by Portsoy basic intrusion and movement along Portsoy Shear Zone.
Not seen at type section: upper part cut out by Portsoy basic intrusion and Portsoy Shear Zone. Screens and rafts of semipelite and metalimestone in basic body.
Portsoy Igneous Complex
PTSOY
Portoto Vein
PTV
Platyschisma Shale Member
PTY
Pottery Clays (Member)
PTYC
At the top of the Hill Farm Sandstone, or floor of P40 coal seam where Hill Farm Sandstone not present.
The area between Swadlincote, Church Gresley and Moira, south Derbyshire.
Interbedded thin coal seams, seatearth clays, siltstones and sandstones.
Unconformity at base of Etruria Formation, latter consisting of red-yellow mottled mudstone and siltstone.
Pott Yeats Sandstone
PTYS
Publow Member
PUB
The base is taken at the Top of the Withy Mills Vein Coal in the Radstock Basin; top of the Forty Yard Vein Coal in the Pensford Basin. Underlain conformably by grey mudstones of the Radstock Member.
Restricted to the Somerset Coalfield (ST 66).
Mainly a grey mudstone and siltstone, with subordinate sandstone and rare thin coals. The sandstones are typically of lithic 'Pennant' type, but also include massive quartzose sandstones.
A maximum thickness of 600 m is recorded in the Pensford Basin.
The top of the grey mudstone and siltstone of the Publow Member is truncated by the Permo-Triassic unconformity, overlain by the red mudstones of the Mercia Mudstone Group.
Pubil Melange Member
PUBL
Sharp change from the typical psammite, micaceous psammite and garnetiferous semipelite of the Auchlyne Formation to schistose muscovite-chlorite-talc calcsilicate- rock with included fragments.
Only localized development in Upper Glen Lyon, Allt Phubuill to Allt Camaslaidh.
Muscovite-chlorite-talc schist with included fragments of carbonate, psammite and siliceous semipelite; with a melange-type appearance. Fragments have a variety of shapes from rounded/flattened to angular and range in size from 5-30cm up to 8m. Irregular bodies of crystalline quartz locally developed - ?metachert.
Sharp upward change from melange-type lithology back to the typical psammite, micaceous psammite and garnetiferous semipelite of the Auchlyne Formation.
Pennine Upper Coal Measures Formation
PUCM
Defined by Stubblefield and Trotter, 1957 as the top of the dark grey fissile mudstone with marine fossils of the Cambriense Marine Band. In the Scottish Solway area the base of the Upper Coal Measures was formerly taken at the base of the Aegiranum (Skelton) Marine Band but is now proposed to be taken at the top of the Cambriense Marine Band to conform with the position elsewhere in the Pennine Basin.
Interbedded grey mudstone, siltstone and pale grey sandstone, commonly with coal seams, but no mudstones containing marine fossils are present.
To 350m in the North Staffordshire (Potteries) Coalfield; 800m thick in the Canonbie Coalfield.
At the point in the conformable sequence where red or brown mudstones of primary origin, typically assigned to the Warwickshire Group, become predominant over the grey beds, or at the base of the sub-Permian unconformity.
Pulsford Member
PUL
Pulchella Coal (Yorkshire)
PULC
Pathhead Upper Marine Band
PUMB
Permian Rocks (Undifferentiated)
PUND
Purple Shales Formation
PUS
Punt Sandstone Member
PUSA
Push Moraine
PUSHM
Permian Rocks (Undifferentiated) And Sherwood Sandstone Group
PUSSG
Caerbwdy Group
PVC
Unknown; appears to be conformable on Lower Pebidian strata (undivided).
St David's area, Pembrokeshire.
Fine- to coarse-grained, feldspathic and porcellanitic ("halleflinta") crystal lithic tuffs, with volcaniclastic conglomerates in the lower part.
Unknown; appears to be conformably overlain by the Ramsey Sound Group.
Rhosson Group
PVH
Appears to overlie the Ramsey Sound Group conformably.
Pembrokeshire: 1:50 000 Sheet 209. (St Davids).
Andesitic, trachytic and basaltic autobrecciated lavas and scoriaceous debris.
At least 550m
Appears to be overlain conformably by the Ogofgolchfa Group.
Pebidian Supergroup [Obsolete Code: Use Pn]
PVL
St Davids Sheet 209.
Trachytic and andesitic tuffs and tuffaceous sediments, locally conglomeratic. NOTE: The definition follows the usage on British Geological 1:25 000 Special Sheet SM72 (St Davids), 1973, which in turn derives from GREEN, JFN, 1908.The computer code PV already exists for 'Pebidian Volcanic Series (undifferentiated)'
Base of Caerbwdy Group of Pebidian Volcanic Complex.
Pennyvenie Low Coking Coal
PVLC
Ogofgolchfa Group
PVO
Appears to overlie the andesitic and basaltic tuffs and lavas of the Rhosson Group conformably.
Pembrokeshire: 1:50,000 Sheet 209 (St.David's).
Dark green and purple chloritic slates, felsic tuffs and tuffaceous sedimentary rocks.
At least 100m
Overlain unconformably by Cambrian strata.
Penrhiw Group
PVP
Drawn at base of halleflinta of Penrhiw Group. (Base not seen). (Penrhiw Group = part of Pebidian Complex).
Red and green trachytic and andesitic tuffs as well as halleflinta and porcellanites. Feldspathic grit with fragments of felsite and vesicular andesites.
At least 310 metres.
Drawn at conformable upward passage from feldspathic grit of the Penrhiw Group to green grit with trachyte fragments of the Treginnis Group.
Ramsey Sound Group
PVR
Appears to overlie the feldspathic tuffs and tuffaceous conglomerates of the Caerbwdy Group conformably.
Pembrokeshire: 1:50 000 Sheet 209 (St Davids) extending onto Sheet 210 (Fishguard).
Fine- to coarse-grained silicic ash-flow tuffs, locally welded, including soft chloritic and sericitic fine-grained tuffs with some porcellanitic tuffs.
At least 200m
Appears to be overlain conformably by the andesitic and basaltic tuffs and lavas of the Rhosson Group.
Port Vasgo Microdiorites
PVSG
Treginnis Group
PVT
Drawn at base of green grit with trachyte fragments where it rests conformably on feldspathic grit of the Penrhiw Group.
Fragments of vesicular trachyte, augite andesite and quartz rhyolite in red matrix as well as fragments of reddish trachyte in green gritty matrix.
180 - 220m approx.
Drawn at conformable upward passage from red grit of the Treginnis Group to green grit and clegyr conglomerate of the Caerbwdy Group.
Petherwin Formation
PWB
Local to type area.
Nodular and bedded limestone, greenish-grey slate and fine-grained sandstone.
Pwll-Y-Cwm Oolite Formation
PWCO
The base is placed at an irregular, palaeokarstic surface cut in underlying dolostones of the Sychnant Dolomite Formation, which is overlain by ooidal grainstones of the Pwll-y-Cwm Oolite Formation.
Northeast crop of the South Wales Coalfield, correlation at Cwar-yr-Hendre [SO 090 146] is uncertain, but the basal 2-4m of ooidal grainstone of the sequence there is the Pwll-y-Cwm Oolite, it extends eastwards from there to Craig-yr-Hafod [SO 2720 1001] where it is dolomitized.
Pale grey ooidal grainstone.
c.7m; 7.6m at Type Section.
The top is a sharp, planar boundary at which the topmost ooildal limestones of the Pwll-y-Cwm Oolite Formation are overlain by buff dolostones of the Pantydarren Formation.
Possil Wee Coal (Glasgow Area; Central Coalfield)
PWEE
Pendower Formation
PWER
Mid to Late Eifelian.
Roseland Peninsula, south Cornwall.
Slaty mudstone with interbedded sandstone, limestone and chert.
430m in Type Section.
Conformable with the Carne Formation.
Portway Formation
PWG
Drawn at the base of the Huckster Conglomerate where pebble horizons with coarse sandstone rest conformably upon purple mudstone, siltstones and sandstones of the Lightspout Formation.
The Port Way on the Longmynd, west of Church Stretton, Shropshire.
Purple and greenish grey shaly mudstones and siltstones with sandstone bands, sandstones are locally massive particularly near the base.
Averages 625m
Drawn at the conformable upward passage of purple and green shaly siltstones and sandstones of the Portway Group into more massive coarse-grained purple and grey sandstones of the Bayston-Oakswood Formation.
Pwll-Y-Glo Group
PWGP
Drawn at the base of the Pwll-Y-Glo Group where it rests conformably upon the Trilobite Dingle Shales.
Welshpool.
Shales and mudstones with bands of green micaceous grit.
100 metres approx.
Drawn at the conformable upward passage from the Pwll-Y-Glo Group to the micaceous grits of the Gaerfawr Group.
Penwhapple Formation
PWH
Conformably overlies the Threemile Formation.
Grey flaggy siltstone and mudstone with a mudstone conglomerate unit.
Conformably overlain by the Myoch Formation.
Pesah Wood Limestone
PWL
Pwll Little Coal (South Wales)
PWLC
Penny's Wood Limestone Member
PWLM
Pickwell Down Sandstones [Obsolete Code: Use Pds]
PWS
Powis Coal
PWSC
Parwyd Gneiss
PWYD
Sheet 133 (Aberdaron).
Strongly sheared and retrogressed hornblende-garnet amphibolites and subordinate felsic gneisses.
Unknown, except unconformably overlain by lower Ordivician (Arenig) sediments.
Pont-Yr-Hafod Group
Drawn at the base of the coarse purple and green Feldspathic Tuff Formation where underlying rocks are not seen.
South west Wales between Haycastle and Tre-Rhos, Dyfed.
Highly feldspathic tuffs varying in texture from conglomeratic to fine-grained, and in colour from pink and green to maroon and purple.
Drawn at the conformable upward passage from the Rhyolitic Tuffs Formation of the Pont-Yr-Hafed Group to the rhyolitic and keratophyric tuffs and lavas of the Rhindaston and Gignog Group.
Paleocyclus Band
PYB
Pen Y Bedw Tuff Member
PYBT
Member at top of Llyn Conwy Formation. Basal contact marked by acid ash-flow tuff.
Northeast flanks of Harlech Dome.
Acid ash-flow tuffs interbedded with silty calcareous mudstone.
75m
Below mudstones of undivided Nant Ffrancon Group.
Pylle Clay Member
PYC
Upward change from alternating thin limestones and mudstones, to a thick mudstone sequence.
From at least as far west as Pylle (limit of current mapping on 1:50k sheets 296 and 297)in an arc southeastward to just west of Milton Clevedon [ST 655 370]
Dark grey shaly mudstone.
Upward change to micritic limestones, or, where absent, to silty and fine-grained sandy clay.
Pottery Coal (South Lancashire)
PYCO
Pant Y Darren Formation
PYDN
The base is a sharp, planar boundary on which the basal dolostone of the Pantydarren Formation overlie ooidal grainstone of the underlying Pwll-y-Cwm Formation.
Northeast crop of the South Wales Coalfield, from Darren Disgwlfa [SO 217 145] southeast to around Craig-yr-Hafod [SO 2720 1001].
Fine-grained, thinly bedded dolostones with minor mudstone layers.
The top is a sharp junction where dolostones of the Pantydarren Formation are overlain by ooidal grainstones of the Blaen Onnen Oolite Formation.
Pusey Flags Member
PYF
Base taken at change up from shelly ooidal limestone (Highworth Limestone Member) into sandy ooidal limestone or ooidal calcareous mudstone of the Pusey Flags Member.
Southwest Oxfordshire: Faringdon to Garford, where overstepped by Stanford Formation. May be present at Highworth (Arkell, 1939, p.502). Pusey Flags mapped with underlying Highworth Limestone (g11a orange) on BGS 1:50 000 sheet 253 Abingdon, 1971 edition.
Cross-bedded fissile sandy ooidal limestone passing to ooidal calcareous mudstone in the Highworth area. Common lignite fragments and bivalves, rare ammonites.
To 6m in the type area.
Top taken at change up from sandy ooidal limestone or calcareous mudstone of the Pusey Flags Member into grey or brown sandy mudstone (Highworth Clay Member, where present) or sand or sandstone with ooids (Highworth Grit Member).
Pen-Y-Gelli Formation
PYG
Pen-Y-Gader Group [Cf Upper Basic Volcanic Group]
PYGA
Drawn at base of Pen-y-Gader Group where it rests conformably on pyroclastics of the Llyn-y-Gader Mudstones Group.
Mid-Wales.
Spilitic pillow lavas with subordinate pyroclastic bands to the east and central parts of the Cader Idris Range and dominantly pyroclastic rocks to the west. (Correlative of Pen-Y-Gader Group = Upper Basic Volcanic Group).
Approx. 120 to 150 metres.
Drawn at conformable upward passage from spilitic lavas, mudstone, ash and chert of the Pen-y-Gader Group to mudstones of the Llyn Cau Mudstones.
Lower Pen-Y-Graig Mudstone Member
PYGML
Conformable upward passage from sandstone-dominated part of the Dinas Island Formation.
Conformable upward passage into sandstone-dominated part of the Dinas Island Formation.
Upper Pen-Y-Graig Mudstone Member
PYGMU
Conformable with sandstones of the Dinas Island Formation.
10 to 15m
Pwllygranant Mudstone Member
PYGT
Pen-Y-Holt Limestone Formation
PYHL
Taken at sharp junction between dolomitised crinoidal packstones at the top of the underlying Hobbyhorse Bay Limestone Formation and the crinoidal packstones with mudstone partings of the Pen-y-holt Limestone Formation. This boundary is unsatisfactory [Simpson and Kalvoda, 1987] but has not been changed as it defines the base of the Arundian Stage and needs further work.
Castlemartin area [SR 95 98], southwest Pembrokeshire. Relationship with the coeval High Tor Limestone Formation to the northeast is uncertain and needs further investigation.
Dark grey, thin- to medium-bedded crinoidal wackestones and calcareous mudstones. Scattered chert nodules and bands, together with silicified fossils. Local dolomitization. Crinoidal packstones with regular stylolitic partings comprise the basal 5m. Wackestones represent storm generated deposits on a muddy distal carbonate ramp.
To 280m
Taken at the gradational boundary between the dark grey interbedded wackestones and mudstones of the Formation and the pale grey thick-bedded skeletal and oolitic limestones of the overlying Stackpole Limestone Formation. Top taken at the base of the first oolitic limestone in the Stackpole Limestone Formation.
Plymouth Limestone Formation
PYL
Mapped within the city of Plymouth (Sheet 348). Extending eastwards onto the Ivybridge (349) sheet. Discontinuous reef type deposits.
Comprises irregular masses of fine-grained pale grey stromatoporoid boundstone that pass laterally and vertically into coarse-grained crinoidal packstone and grainstone with scattered stromatoporoids and corals. Erosive floatstone and rudstone beds of reworked and broken coral and stromatoporoid colonies are also present. Beds of fine-grained skeletal packstone interdigitate with normal facies. Red argillaceous calcite mudstone and breccia are found as fissure fill.
Not known. (This is a reef, which varies from 0 where not developed).
Porth Y Mor Beds
PYMB
Age data based upon Figure 7, p.43 in House et al., 1977.
Pen-Y-Lan Mudstone
PYN
Paynes Coal (South Wales)
PYNC
Pyotshaw Coal (Central Coalfield)
PYO
Pennyland Sandstone Member
PYSM
Polzeath Slate Formation
PZS
Late Frasnian to Mid Famennian.
Faulted where seen on coast, inland rests conformably on Harbour Cove Slate Formation.
Padstow Bay to west of St Tudy, north Cornwall.
Cleaved purple mudstone with pale green and grey beds and laminae, and thin sandstone and laminated siltstone horizons. Thicker beds of green mudstone occur in association with dark grey mudstone, which is sporadically fossiliferous.
Estimates vary between 240-320m.
Quarry Coal (Lothian)
Located in the Lower Coal Measures of MIdlothian just below the Cowpits Five Foot.
Quaternary Diamicton, Firm To Hard (Offshore)
Q1DFH
Quaternary Deposits, Undifferentiated (Offshore)
Q1DU
Quaternary Deposits, Undifferentiated, Less Than 5m Thick (Offshore)
Q1DU5
Quaternary Mud And Sand, Interbedded (Offshore)
Q1MAS
Quaternary Mud, Firm To Hard (Offshore)
Q1MFH
Quaternary Mud, Very Soft To Soft (Offshore)
Q1MVS
Quarry Intrusion
QARRY
Qui Ayre Sandstone Formation
QAS
Faulted against Harra Ebb Formation.
Lower unit of rusty-weathering, well-graded sandstone, overlain by pebbly bioturbated sandstone.
150 metres on Qui Ayre coastline, Mainland Orkney NY 220 153.
Unconformably overlain by the Lower Stromness Flags Formation.
Quartzite Breccia
QBR
Queensberry Formation
QBY
Silurian, mid-Landovery, (post-acuminatus Biozone to halli Biozone].
Sedimentological boundary with rocks of the Moffat Shale Group.
Sandstone, typically medium- to coarse-grained but ranging from fine- to very coarse-grained, locally pebbly. Generally medium- to very thick-bedded or massive over thicknesses of tens of metres, units up to few metres thin-bedded. Interbedded siltstone or silty mudstone generally thin to medium beds but silstone units range up to several tens of metres locally. Rare conglomerate and intraclast-rich sandstone occur locally. Sandstone siltstone typically bluish grey when fresh, darker grey when weathered. Although of similar facies, the mid-Llandovery Queensberry Formation is younger then the adjacent early Llandovery Mindork Formation. Sandstone in both formations is predominantly quartzo-feldspathic, but is distinguished by accompanying volcanic debris; the Mindork Formation sandstone commonly contains sparse intermediate volcanic lithic debris and associated mafic crystal material (typically pyroxene); volcanic debris may be more common in the Queensberry Formation and tends to be more basic (spilitic) in character, mafic crystal material occurs locally but is relatively rare.
minimum 100m, may be substantially more.
Faulted, no stratigraphical evidence preserved.
Quartz Conglomerate Formation (Forest Of Dean)
Queen's Cairn Conglomerate
QCC
Quartz Conglomerate Group (South Wales)
QCG
Drawn at the base of lenticular quartz-conglomerate beds with sandstones, grits and quartzites, where they rest unconformably on Early Devonian sandstones of the Brownstones Formation.
South Glamorgan, Cardiff, South Wales.
An upper portion of sandstones with alternations of marl, and a lower portion of lenticular quartz-conglomerate beds with sandstones, grits and quartzites.
c.77m
Drawn at the conformable upward passage from sandstones and marls of the Quartz Conglomerate Group into limestones and calcareous mudstones of the "Carboniferous Limestone" [generally the Lower Limestone Shale Group or its lateral equivalents].
Quilichan Granodiorite Vein Complex
QCHAN
Queen Coal
QCO
Queensferry Cements
QCS
At least two beds of "cementstone" close below the Pumpherston Shell Bed.
Queensbury Grit And Grieston Shales
QGG
Queen's Hill Formation
On Sheet 65E, top of Balnacraig Metabasite Formation (Easdale Subgroup); not seen on sheets 66W, 66E, 76W and 76E.
Forms a 4-6km wide strip on Sheet 65E from Gallows Hillock (NO295 797) to Pannanich Hill (NO390 950), and a belt up to 6km wide on Mid-Deeside (Sheets 66W, 66E, 76W, 76E) from near Tombae (NO425 970) at least as far as Banchory (NO695 953).
Mixed psammite, semipelite and pelite, with rare beds of calc-silicate rock.In the Balnagowan Hill - Queen's Hill area, discrete units of psammite and pelite can be mapped out.
Approximately 1700m in northern Sheet 65E, but this may be an overestimate, due to tectonic thickening.
Incoming of dominantly calcareous material at the base of the Deeside Limestone Formation (Sheet 66W) / Water of Tanar Limestone Formation (Sheet 65E) (Tayvallich Subgroup).
Quarrel Hill Formation
QHF
Conformably overlies the Auldthorns Formation. The boundary is taken at the change from the alternating sandstone (dominant) and silty mudstone succession of the Auldthorns Formation to the fossiliferous green purple-stained bedded mudstones with thin subsidiary sandstones of the Quarrel Hill Formation.
Craighead Inlier, Girvan, southwest Scotland.
Green, purple-stained, bedded mudstones with thin subsidiary sandstone beds, conglomerate and mass-flow deposits with olistoliths.
Conformably overlain by the Lady Burn Formation. The poorly defined boundary is taken at the change from fossiliferous green, purple-stained bedded mudstones with thin subsidiary sandstones of the Quarrel Hill Formation into the more massive, nodular pale grey unbedded silty mudstones of the Lady Burn Formation.
Quien Hill Grit Member
QHGR
Quarry Hill Sandstone Formation
QHI
Transitional, marked by incoming of rhythmically graded siltstone/sandstone units, disappearance of conglomerate bands, and lightening of colour.
Pink to white, well sorted sandstone, with graded siltstone/sandstone units averaging 10 metres in thickness occurring at regular intervals.
400 metres at type locality; thins northwards, probably to zero by NJ 523 281; reaches approx. 700 metres without top being reached at Wester Clova (NJ 451 194).
Change to argillaceous sedimentation (not exposed).
Quarry Hazle Sandstone
QHS
Medium-grained white or brown micaceous sandstone with carbonaceous streaks and plant impressions.
Lies close above the Four Fathom Limestone towards the top of the Alston Formation.
Holocene Deposits (Undifferentiated)
QHU
Quarried Limestone Member, Lower [Obsolete Code: Use Lql]
QLL
Quarried Limestone Member, Upper [Obsolete Code: Use Uql]
QLU
Queen Coal (Northumberland)
QNC
Pleistocene Sediments (Undifferentiated)
QPSED
Quarry Arenite Formation
QRY
Upper surface of uppermost bed of conglomerate in the Hareshaw Conglomerate.
Lower Palaeozoic Inlier of the Hagshaw Hill, Scotland. (50k sheets 23W, 23E and 15W).
Reddish-brown, greyish-brown, medium-grained, slightly micaceous sandstones, in beds 0.5 to 1.2m thick; large-scale cross-bedding. Shaly intraclasts occur. Soft, red and friable with reduction spots at top.
Lower surface of lowest bed of conglomerate in the overlying Greywacke Conglomerate.
Quaternary Sediments (Undifferentiated)
QSEDU
Quartzitic Sandstone Formation
QSG
Incoming of mudstones and sandstones at the top of the Carboniferous Limestone [Pembroke Limestone Group].
Bristol area. (Wells- Bath - Bristol - Wickwar).
Hard pale grey quartzitic sandstones with grey mudstones, seatearths and thin carbonaceous or coaly beds.
Ashton Vale Marine Band. (Gastrioceras subcrenatum Marine Band).
Quarrelton Thick Coal
QTC
Quarry Three Limestone
QTHL
Quarry Two Limestone
QTWL
Quartz Conglomerate Formation
QTZC
Quarella Sandstone
Quaker Coal (North Wales)
QUAC
Quarry Coal
QUC
Quarry Coal (Milford, South Wales)
QUCO
Queyhouse Flags Formation
QUHF
Easter Glen Quioch Psammite
QUIO
Queen's Rock Member
QURK
Quarry Sandstone Member
QURY
Quarrel Sands Vent
QUSND
Quaternary Deposits (Undifferentiated)
QUU
Queyfirth Group
QYFH
Quarry Sandstone
QYS
Massive and flaggy sandstone with some beds of sandy, shaly mudstone.
Quartzite Conglomerate
QZT
Hodsonites Magistrorum Marine Band
R1A1
Reticuloceras Circumplicatile Marine Band
R1A2
Reticuloceras Subreticulatum Marine Band
R1A3
Reticuloceras Todmordenense Marine Band
R1A4
Reticuloceras Dubium Marine Band
R1A5
Reticuloceras Eoreticulatum Marine Band
R1B1
Reticuloceras Nodosum Marine Band
R1B2
Reticuloceras Stubblefieldi Marine Band
R1B3
Reticuloceras Reticulatum Marine Band [1 Of 3]
R1C1
Reticuloceras Reticulatum Marine Band [2 Of 3]
R1C2
Reticuloceras Reticulatum Marine Band [3 Of 3]
R1C3
Reticuloceras Coreticulatum Marine Band
R1C4
Bilinguites Gracilis Marine Band
R2A1
Bilinguites Bilinguis Marine Band [1 Of 3]
R2B1
Bilinguites Bilinguis Marine Band [2 Of 3]
R2B2
Bilinguites Bilinguis Marine Band [3 Of 3]
R2B3
Bilinguites Eometabilinguis Marine Band
R2B4
Bilinguites Metabilinguis Marine Band
R2B5
Bilinguites Superbilinguis Marine Band
R2C1
Verneulites Sigma Marine Band
R2C2
Rhondda Member
The base of the Member is placed at the base of the No.2 Rhondda Coal in the type area of the Rhondda valleys; the seam is named the Llwydcoed Seam in the Ammanford district and the Wernddu in the Swansea district. The coal rests conformably on lithic ("Pennant") sandstones and thin mudstones/siltstones of the underlying Llynfi Member.
South Wales Coalfield; on north crop from Burry Port [SN 42 02] to the Bargoed Taff Valley [SO 115 054] and on the south crop from the Loughor estuary [SS 535 957] to Risca [ST 24 92].
Green-grey, lithic arenites ("Pennant sandstones") with thin mudstone/siltstone and seatearth interbeds and mainly thin coals.
Up to 320m in the Swansea - Port Talbot district [c.SS 775 940].
The top is placed at the base of the Brithdir Coal, where the coal overlies thin mudstone/seatearth at the top of the Member and is overlain by lithic ("Pennant") sandstone and thin siltstone/mudstone of the Brithdir Member.
Raasay Granite
RAAG
Raise Beck Volcaniclastic Member
RABK
Indistinct contact with vitric (welded) tuff of the Thirlmere Tuff Member.
North Lake District immediately east of Thirlmere.
Massive and bedded fine- to coarse-grained tuff, some volcaniclastic sandstone at top. There is some uncertainty over whether the rocks are primary ptroclastic or reworked and resedimented.
Sharply overlain by lapilli-tuff of the Lincomb Tarns Tuff Formation (undivided).
Randle Coal (Coalbrookdale)
RACC
Rag Coal (Bristol Area)
RACO
Radstock Member
RAD
In the Radstock Basin the base of the member is taken at the base of the Nine Inch Seam. In the Pensford Basin the base is taken at the base of the Number Eight Seam (Kellaway, 1993). Underlain by red and grey mottled mudstone of the Barren Red Member.
Restricted to the Somerset Coalfield (ST66)
Grey mudstone and numerous thin, muddy coal seams.
Up to 315m in the Pensford Basin; 250m in the Radstock Basin.
In the Radstock Basin the top of the member is taken at the top of the Withy Mills Seam. In the Pensford Basin the top occurs at the top of the Forty Yard Seam (Kellaway, 1993). Overlain by grey mudstone and siltstone of the Publow Member.
Radley Coal (South Lancashire)
RADC
Radernie Duffie Coal
RADD
Radernie Main Coal
RADM
Raebeg Sandstone Formation
RAES
Sedimentary transition into Delnabo Conglomerate Formation.
North-east of the Conglass Water in the north-east part of Tomintoul ORS outlier, upper Banffshire; a 50 km2 outlier, 15 x 5 km in extent, that is totally separated from other ORS outcrops of the north-east Grampian area.
Micaceous sandstone and siltstone, red-brown to fawn, flaggy, well-bedded, immature, commonly weathered, soft and friable. Pebbly beds common near base.
ca. 100 m.
Junction with Conglass Sandstone Formation, not exposed.
Ravenscar Group
RAG
The lower boundary is taken at the base of the Saltwick Formation where sandstone, siltstone or mudstone, commonly with plant fragments, rest unconformably or disconformably on the heterolithic, marine, Dogger Formation (ferruginous sandstone; ironstone; limestone; calcareous mudstone) or, where the Dogger Formation is absent, on grey, shelly mudstone or siltstone of the Lias Group.
The Cleveland Basin, including the North York Moors, Cleveland Hills, Hambleton Hills, Howardian Hills and the North Yorkshire coast. Equivalent strata offshore comprise the West Sole Group (Lott and Knox, 1994).
Fluvial, fluvio-deltaic and paralic mudstone, siltstone and sandstone, intercalated with relatively thin marine units comprising calcareous sandstone, calcareous mudstone, calcareous siltstone, limestone and ironstone. Thin coal seams and seatearth mudstones occur in the paralic lithofacies.
Generally about 240m thick on the North Yorkshire coast (Ravenscar to Scarborough) thinning westward to 114m in the Hambleton Hills.
The upper boundary is taken at the unconformable or disconformable upward passage from sandstones, siltstones and mudstones, commonly with plant fragments, of the Scalby Formation to calcareous, bioturbated mudstone and nodular, shelly limestone of the Cornbrash Formation.
Ragman Coal (North Staffordshire)
RAGC
Red Ash Coal (Goyt Trough)
RAGT
Ramsden Heath Member
RAH
Raise Coal (North Ayrshire)
RAIS
Raliabeg Psammite Formation
RALP
Ramasaig Formation
RAMA
Overlies the Beinn Edra Formation in northeastern Skye; might overlie the Portree Hyaloclastite Formation farther west.
Alkali basalt flows comprise the majority of this unit. Some flows are olivine- and/or plagioclase-phyric.
To 760m
Overlain by the Beinn Totaig Formation.
Rams Coal (South Lancashire)
RAMS
Rannoch Moor Pluton
RANH
Rannoch Formation
RANN
Rascarrel Member
RASC
Faulted and unconformable contacts with Lower Palaeozoic Ross Formation (Hawick Group). In the Rerrick Outlier the strata are faulted against the Orroland Formation (Lower Carboniferous).
Rascarrel Bay (Rerrick Outlier); Castlehill Point to Gutcher's Isle and Portling to Portowarren shores (Colvend Outlier), Kirkcudbrightshire, south-western Scotland (Southern Uplands).
Conglomeratic sandstone interbedded with thin beds of marl and siltstone.
>360m
Raasay Ironstone Formation
RASI
Dark siltstone (shale), ironstone 8' 0" and oolitic siltstone (shale).
8' 0".
Racks Tuff
RAT
Ratagain Plutonic Complex
RATG
Raik Vein
RAV
Ravine Coal (South Lancashire)
RAVCO
Ravensheugh Sill
RAVH
Rattray Volcanics Member
RAVL
Raven Gill Formation
RAVN
Southern Uplands of Scotland, Leadhills area.
Lava, tuff and mudstone.
Overlain by Kirkton Formation.
Ratcliffe Volcanic Member
RAVO
At base of the lowest tuff bed at 631m depth in Ratcliffe on Soar borehole.
Does not crop out.
Chip samples indicate a sequence of olive green to brown silty carbonaceous mudstones and limestones with beds of bluish grey, pyritous tuff.
At top of the highest tuff bed, at 507m depth in Ratcliffe on Soar borehole
Reading Formation
London Basin: the base is generally well defined although may be diffuse due to the translocation of clay into the underlying sand of the Upnor Formation during pedogenesis. In the Hampshire Basin, the Reading Formation rests unconformably on chalk.
Dominantly clay, mottled by pedogenetic processes in a humid environment (Buurman, 1980). Red hues dominate with a more or less equal proportion of blue-grey and brown. Red sediments decrease towards the east where there were shorter periods of subaerial weathering, and reducing conditions in ephemeral lagoons. The proportion of sand beds varies greatly, and may constitute more than half the formation, dominantly in the basal part (eg Crane and Goldring, 1991).
Maximum 27m, generally 12 to 16m; in two leaves in Central London.
The top is sharp, at an upward change from mottled clay to glauconitic sands and sandy clays of the Harwich Formation.
Red Bay Formation
RBAY
Rosebrae Beds
RBB
Raeberry Castle Formation
RBC
Raised Beach Deposits, 1
RBD1
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks - [generic description}; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; older than 'Raised Beach Deposits' in the same map area. [Generic description: earth science dictionaries in the BGS library].
Raised Beach Deposits, 2
RBD2
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks - [generic description}; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; older than 'Raised Beach Deposits' and 'Raised Beach Deposits 1' in the same map area. [Generic description: earth science dictionaries in the BGS library].
Raised Beach Deposits, 3
RBD3
Raised Beach Deposits, Late-Glacial
RBDLG
Raised Beach Deposits Older
RBDO
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks - [generic description]; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; older than 'Raised Beach Deposits' in the same map area. [Generic description: earth science dictionaries in the BGS library].
Raised Beach Deposits, Post-Glacial
RBDPG
Raised Beach Deposits
RBDU
Shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks - [generic description]; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Earth science dictionaries in the BGS library].
Raised Beach Deposits Younger
RBDY
Shingle, sand, siilt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks - [generic description]; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; younger than 'Raised Beach Deposits' in the same map area. [Generic description: earth science dictionaries in the BGS library].
Rough Brow Flint
RBFL
Roughband Ironstone (Central Coalfield)
RBI
Roeburndale Member
RBL
Base is top surface of the Brennand Grit, where present. This is typically a sandstone rootlet bed (ganister), overlain sharply by siltstone and fine-grained sandstone of the Roeburndale Member. Where the Brennand Grit is absent, gradational above the Pendle Grit Member, with boundary where siltstones of the Roeburndale Member become predominant above massive turbiditic sandstones of the Pendle Grit Member.
Lancaster, Garstang and Settle, 1:50,000 sheets.
Predominantly grey, sandy, micaceous, shaly siltstones with bunches of interbedded, generally fine-grained, sharp-soled sandstone lenses locally developed; includes three thin marine bands; rare clean quartzitic sandstones.
(nb previously defined at the base of the Caton Shale Formation).The base of the sandstone of the Ward's Stone Sandstone is typically sharp and erosional, and rests upon siltstones and fine-grained sandstones of the Roeburndale Member.
Rutland Formation, Blisworth Limestone Formation And Blisworth Clay Formation (Undifferentiated)
RBLBC
Reading Formation And London Clay Formation (Undifferentiated)
RBLC
Raised Brackish Lagoon Deposits (Undifferentiated)
RBLDU
Generically: Dominantly silt and clay, locally with lenses of sand and gravel.
Redhouse Burn Lower Limestone
RBLL
Rib Mudstone
RBM
Redhouse Burn Middle Limestone
RBML
Ree Burn Formation
RBN
Taken at the lowest occurrence of a persistent greywacke turbidite in the Ree Burn Formation to Smithy Burn Siltstone sequence.
Medium-grey greywacke, sub-greywacke, siltstones, mudstones and shales. Greywackes are mainly thin (<0.3 m ) except at top of formation where there is about 11 metres of thickly bedded greywackes. The middle part consists of firmly laminated silty mudstones and mudstones.
Base of the overlying Parishholm Conglomerate.
Ruabon Till Member
RBNTI
Raised Bog Peat
RBPT
Rubery Sandstone Member
RBS
Basal sandstone bed, locally with clasts of Lickey Quartzite, unconformably overlying Lickey Quartzite (Wills and others, 1925)
Two or tthree small, faulted outcrops at Rubery, West Midlands.
Sandstone, yellow, grey, locally pebbly at base, and mudstone, red, purple, grey, buff with sporadic pale grey limestone beds.
32m in type area; c.43m in Walsall Borehole (Butler, 1937)
Base of `Rubery Shale', where buff, grey and purple 'shales' with `fucoids' overlie predominantly sandstone beds of the `Rubery Sandstone' (Wills and others, 1925).
Rubery Shale Member
RBSH
Base of buff, grey, and purple mudstone-dominated beds (shales), overlying predominantly sandstone beds of the underlying `Rubery Sandstone' (Wills and others, 1925).
Small area around Rubery, West Midlands.
Mudstone, buff, grey, blue and purple (`shales') and thin beds of fine-grained fossiliferous sandstone and thin white and purple limestone.
c.23m in type area; c.73m in Walsall Borehole.
Unconformable base of the Halesowen Formation (Carboniferous) in type area. Base of mudstone with thin limestone bands (bed M of Butler, 1957) in Walsall Borehole (base of Buildwas Formation).
Rubha Sandstone Member
RBSM
Rouen Bay Sandstone Member
RBT
The base of the lowest bed of the poorly-sorted volcaniclastic conglomerate with angular clasts, where this conformably overlies a clast-supported conglomerate with rounded clasts of lava and quartzite, of the undivided Catterline Conglomerate Formation.
Northern Midland Valley, between Braidon Bay [NO 866 773] and Whistleberry [NO 860 753].
A coarse sand to boulder-sized, massive, angular, very poorly-sorted, conglomerate with clasts of vesicular lava and rare clasts of quartzite and metabasic rock interbedded with a coarse- to very coarse-grained, typically massive, volcaniclastic sandstone. One flow of andesitic lave seen at Whistleberry.
From 75 m to 115 m thick.
The top of the highest bed of very coarse-grained volcaniclastic sandstone with angular clasts, where this is conformably overlain by a clast-supported conglomerate with rounded clasts of lava and quartzite of the undivided Catterline Conglomerate Formation.
Redhouse Burn Upper Limestone
RBUL
Roanburn Vein
RBV
Rhiw Bach Volcanic Formation
RBVO
Conformably overlies or is intruded into undivided mudstone of the Nant Ffrancon Subgroup immediately above the top of the Allt Lwyd Formation, and passes laterally into them.
Southern Snowdonia and northeast of the Harlech Dome, North Wales.
Felsic ash-flow tuffs, fine-grained dust tuffs and tuffites with interbedded silty mudstones and, locally, conglomerates, as well as intercalated high-level intrusions and extrusions of both dioritic and rhyolitic composition.
Overlain conformably by undivided mudstones of the Nant Ffrancon Subgroup.
Robeston Wathen Limestone
RBW
Rubery Formation
RBY
Sandstone, yellow and grey, locally pebbly at base, siltstone, and mudstone with thin limestone beds in upper part.
c.55m in type area (top is erosional), c.117m in Walsall Borehole (Butler, 1937).
Erosional, unconformable base of the Halesowen Formation (Carboniferous) at Rubery. Base of Buildwas Formation, bed (M) at 265.2m in Walsall Borehole (Butler, 1937).
Roundhill Clay
Roosecote Anhydrite
RCA
Roman Camp Beds
RCB
Lower Roman Camp Beds
RCBL
Upper Roman Camp Beds
RCBU
Rob's Cove Conglomerate Member
RCC
Stonehaven to Inverbervie area.
An angular to sub-rounded, poorly sorted conglomerate with cllasts up to 1m across with a diverse range of lithologies from a 'flysch-terrane' to the south-east.
Up to at least 100 m thick.
The top of the uppermost bed of the described conglomerate within the Gourdon Sandstone Formation.
Red Chalk And Carstone Formation (Undifferentiated)
RCCA
Roosecote Dolomite
RCD
Red Crag Formation
RCG
Rests unconformably on the Coralline Crag Formation, Palaeogene formations and Chalk Group bedrock.
Widespread in the Southern North Sea basin and onshore at depth beneath Norfolk and northeast Suffolk. Crops out in southeast Suffolk and extends into northern Essex. Can be traced farther inland in boreholes as far west as Stansted Mountfitchett and beyond in an isolated outlier at Rothampstead.
Coarse-grained, poorly sorted, cross-bedded, abundantly shelly sands (in East Anglia). Dark green and glauconitic when unoxidised, but typically oxidised to yellow or reddish brown with ferruginous concretions (iron pan). Basal bed of rounded flint pebbles. Offshore, fine- to medium-grained, muddy, calcareous, glauconitic sands.
70m maximum offshore (Flemish Bight Sheet). Onshore commonly to 20m but thicker in coastal areas of east Norfolk and Suffolk and within the Stradbroke Trough, locally reaching c.40 to 45m.
Onshore overlain unconformably by sands of the Norwich Crag Formation, which are less coarse-grained, better sorted, less shelly and generally paler in colour. Offshore overlain unconformably by early Pleistocene or Holocene sediments.
Rough Craig Intrusion
RCGG
Red Conglomerate Group
RCGP
Red Craig Gravels Formation
RCGR
Not seen, but probably rests directly on bedrock.
Gravel, clast-supported but locally matrix-supported with matrix of reddish-brown sandy mud. Angular clasts of sandstone and psammite.
Sharp, gently undulating erosion surface. Overlain by Kincurdy Silts Formation.
Red Chalk
RCK
Rock Coal (South Wales)
RCKC
Rockey Coal (Forest Of Dean)
RCKY
Rockdale Limestone Formation
RCLF
Roman Cement Limestone
RCLS
Riccarton Group
RCN
Faulted contact with Carghidown Formation at NX 4528 3414.
Greywackes (dominantly less than 0.5 metres thick) with interbedded mudstones including dark grey, finely laminated, fossiliferous siltstone beds. NOTE: Riccarton Group not subdivided in Wigtownshire. See Warren, 1964, for subdivision to east.
c.500 metres of folded and faulted, steeply dipping strata.
Rock Creep
RCRP
Variable lithology. In-situ or nearly in-situ rock debris of mountainous areas. Openwork, clast-supported accumulation of blocks (>64 mm) without a cliff or steep slope above as an apparent source. May be active or inactive. [Generic description: 'TMOS' Procedures].
Roseland Breccia Formation
RDBR
?Late Givetian to ?Frasnian
No details yet provided.
Roseland and Meneage, south Cornwall.
[Olistostrome] Grey slaty mudstone with framework and matrix breccias/conglomerates, interbedded sandstone, felsic and mafic tuffs/lavas and metamorphic rock breccias. Olistoliths of Ordovician quartzite, Silurian and early to mid Devonian limestone, sandstone, breccia, metamorphic and mafic/ultramafic igneous rocks.
The Roseland Breccia Formation is the major Palaeozoic olistostrome of Europe. It can be considered as a slaty mudstone matrix host with clasts (sedimentary, metamorphic, igneous) up to 1.3km across with and local in situ sequences (sedimentary - sandstones, breccias, and igneous - tuffs, lavas, breccias). See the coded lithologies for a fuller list of components.
To 1.5km
Richmond Chert
RDC
Radcliffe Coal (Northumberland)
RDCC
Radcliffe Member
RDCF
Gradational and conformable; taken at the top of highest significant sandstone bed of the underlying Tarporley Siltstone Formation.
Mappable at the surface in south Nottinghamshire and Leicestershire. Upper boundary coincides with a widespread geophysical log marker traceable throughout the East Midlands and northeast England.
Mudstone, siltstone and very fine-grained sandstone, finely interlaminated; pinkish red or red-brown, subordinately green.
12 to 19m (16m in the Cropwell Bridge Borehole, SK63NE/28)
Gradational; taken at the transition from the laminated beds of the Radcliffe Member into blocky, deformed mudstone of the Gunthorpe Member.
Red Cliff Hole Member
RDCH
Roker Formation And Concretionary Limestone (Undifferentiated)
RDCL
Roddam Dene Conglomerate Formation
RDCO
Not seen, but thought to overlie rocks of the Cheviot Volcanic Formation unconformably.
Eastern flanks of the Cheviot massif, Northumberland.
Conglomerate, typically coarse in massive thick and very thick beds; reddish coloured; subangular to subrounded clasts of pebble to boulder size set in a clay-rich sandstone matrix; matrix supported to clast supported. Clasts predominantly of andesite, derived from the Cheviot Volcanic Formation, but also rare clasts of Silurian mudstone and greywacke sandstone, Cheviot Granite. Minor intercalations of mudstone and sandstone, and sandstone and siltstone at the top.
About 170m seen.
Not seen, but believed to be overlain by rocks of the Ballagan Formation (formerly the "Cementstone Group") of Northumberland.
Rhuddnant Grits Formation
RDD
Base of lowest thick argillaceous sandstone bed overlying Caeran Mudstones.
Top of highest thick argillaceous sandstone bed below lower tongue of Glenyrafon Formation.
Red Down Sand Member
RDDI
Base is taken at change up from mottled grey, yellow and brown mudstone of undifferentiated Ampthill Clay Formation or grey, shelly, ferru-ooidal mudstone or ironstone of the Marston Ironstone Member (where present) into fine- to medium-grained, ferruginous sand or sandstone.
Area between Hillmarton and Lyneham, Wiltshire and Swindon, Wiltshire and Faringdon, Oxfordshire. Pinches out laterally into undifferentiated Ampthill Clay. May be lateral equivalent of the Red Down Sand of Westbury, Wiltshire. (not defined here).
Sand and sandstone, fine- to medium-grained, reddish brown to yellow, ferruginous.
0 to 4.5m (Swindon-Faringdon area); 0-1.5m (Lyneham area).
Top marked by change up from fine- to medium-grained ferruginous sandstone or sand into mudstone of the undifferentiated Ampthill Clay Formation.
Residual Deposits
RDEPS
Raddery Sandstone Formation
RDF
Red sandstones largely of fluvial origin with lensing conglomerate members and muddy lacustrine members with fish fragments.
+ 1000 metres.
Upper contact not established.
Rudford Member
RDFD
Generally interpreted as where fluvial deposits rest on bedrock or older superficial deposits.
The valley of the River Leadon.
Variable, up to 5 m thick.
The present day river terrace upper surface, which may be overlain by alluvium.
Readycon Dean Flags
RDG
Riding Coal (South Lancashire)
RDGC
Reclaimed Ground
RDGR
Redhall Marine Band
RDH
Redesdale Ironstone (Shale)
RDI
Northumberland; type area around Redesdale
Dominantly shaly mudstone, with ironstone nodules.
c.7.5m
Redesdale Limestone
RDL
Widespread in Northumberland.
Red Marl Group
RDM
Drawn at base of green-yellow sandstones of Green Beds where they rest unconformably on sandstones and siltstones of Ludlow age.
South Wales and Gloucestershire.
Red siltstones and mudstones with subordinate sandstones. Correlative of Red Marl Group is the Milford Haven Group.
1100m approx.
Drawn at conformable upward passage from red marls to green and red sandstone of the Senni Beds.
Raydale Dolostone Formation
RDO
Red Sandstone Member
RDS
At the top of the highest coarse-grained bed in the underlying Cowie Harbour Conglomerate Member.
Red, lithic, medium-grained, trough cross-bedded sandstone and massive or thinly planar-bedded sandstone farther west.
The top is taken at the base of the lowest grey sandy siltstone bed in the Cowie Harbour Siltstone Member, overlying the red lithic sandstones.
Ringstead Sand And Gravel Member
RDSG
The Ringstead Sand and Gravel Member rests unconformably on the Holkham Till Member and a variety of Cretaceous formations. In places it can be difficult or impossible to distinguish the Ringstead Sand and Gravel from the sand and gravel of the older Sheringham Cliffs Formation in adjacent outcrops.
Restricted to the northern part of Norfolk from Heacham to the Holkham area.
Glaciofluvial sediments that are associated with the Holkham Till Member in the area around Heacham, Ringstead, Hunstanton and Holkham. Landforms associated with meltwater deposition include the Hunstanton Esker in Old Hunstanton Park [TF 206 940]. Mainly sand and flint gravel, locally with chalk clasts. Also typically contains a minor component of igneous clasts.
Of very variable thickness, generally less than 5m, but potentially greater in the Hunstanton Esker.
The Ringstead Sand and Gravel Member is overlain by the Holkham Till Member and Head, and silt and clay of the British Coastal Deposits Group.
Ravensdale Tuff Member
RDT
Not seen, but defined as the transition from tuffs of the Ravensdale Tuff Member to underlying limestones of the Bee Low Limestone Member.
Restricted to the lower part of Cressbrook Dale (SK 17 74), in the northern part of the Peak District inlier.
A banded tuff with lapilli, including vesicles infilled with analcite.
Up to 20 m thick.
Not seen, but defined as the transition from tuffs of the Ravensdale Tuff Member to overlying limestones of the Bee Low Limestone Member.
Ridgeway Conglomerate Formation
RDWC
Roadwater Limestone
RDWL
Redmires Flags
The base of a main sandstone between the Chatsworth Grit and Rough Rock, and below the Cancelloceras Marine Band.
South Yorkshire & Derbyshire.
Fine to coarse grained massive and thinly bedded sandstone.
Up to 15 m thick.
The top of the first sandstone below the Cancelloceras Marine band. Where present, it is the second main sandstone below the top of the Millstone Grit Group, about 60m below the top and above the Chatsworth Grit.
Reading Formation [Obsolete/Duplicate Code: Use Rb]
REA
Reay Diorite
REAY
Rebecca Sandstone Member
REB
Probably conformable: at base of sandstone in silty mudstone sequence of undivided Ashgill Formation.
Furness Lower Palaeozoic Inlier.
Coarse sandstone, locally pebbly.
Up to 50m
Probably conformable: at top of sandstone in silty mudstone sequence of undivided Ashgill Formation.
Reay Burn Till Formation
REBU
Caithness and Sutherland mainly east of a line between Reay and Berridale (1:50 000 sheets 115E and W, and sheet 100).
Diamicton, clayey and sandy, typically reddish brown to pale yellowish brown, boulder-sized clasts mainly of Orcadian Devonian sandstones, conglomerates, siltstones and mudstones where overlying Devonian strata, otherwise mainly of Caledonian igneous and Moine metamorphic rocks (Thormaid Till Member) when overlying or near basement outcrops.
Overlain by Holocene strata.
Reagill Coal
REC
Redcliff Formation
RECF
Base is a sharp, probably non-sequential, boundary with the underlying Oxford Clay Formation. This is marked by the upward change from the mudstone of the Oxford Clay to the sandstone of the Nothe Grit Member.
South Dorset. Equivalent to the Hazelbury Bryan and lower part of the Stour Formation of north Dorset. Probably no physical continuity due to pre-Cretaceous erosion.
Lower and upper units of thick-bedded fine-grained sandstone and argillaceous sandstone (respectively the Nothe Grit and Bencliffe members), locally with large calcareous concretions, separated by an interval of mudstone and sandy mudstone with interbedded limestones (Nothe Clay Member). Pervasive bioturbation is evident in the Nothe Grit, and conspicuous cross stratification in the Bencliff Grit. There are common shelly and bioclastic-rich intervals, comprising particularly bivalves and ammonites.
29.2m at Osmington, about 28m at Sandsfoot.
The top is a sharp, planar, burrowed erosion surface at the top of the sandstone of the Bencliff Grit Member, which marks the upward change to thin argillaceous limestones and mudstones of the basal Osmington Oolite Formation.
Rehiran Cryoturbate Member
RECR
Gradational contact over 10 to 20cm with weathered clayey cobble gravel of the Craig an Daimh Gravel Formation below.
Clayey, sandy,silty gravel (diamicton), matrix-supported, very dense, very pale grey to white, with disseminated black charcoal and peaty material. Gravel similar in composition to that occuring in the Craig Daimh Gravel Formation below, but bleached white or pale yellow.
Gradational with the white peaty sandy clayey gravel of the Drummournie Biogenic Member above.
Red Coal
RED
Red Arch Formation
REDA
Red Coal (North Wales)
REDC
Red Coal (South Wales)
REDCO
Eastern Red Hills Centre (Skye Central Complex)
REDHE
Western Red Hills Centre (Skye Central Complex)
REDHW
Red Island Formation
REDI
Redhythe Quartzite Member
REDQ
Base faulted out in coast section.
Coast section from Red Haven to Foul Hole [NJ 5660 6660 - 5780 6675]; not exposed inland.
Quartzite, grey to off-white, with minor psammite, thick-bedded.
c.60m at coast.
Change from thick-bedded quartzite to interbedded psammite and semipelite.
Reisgill Burn Till Formation
REDR
Unconformable on bedrock or on the Dunbeath Till Formation.
Caithness and Sutherland northeast of a line between Reay and Berridale (1:50 000 Sheets 115E and W, 116 E and W, 110). Note that this unit does not equate with the Quaternary Lybster Formation of Hall and Whittington (1989) and the term Lybster [Flagstone] Formation is pre-used by the BGS to include rocks of Mid Devonian age.
Dominantly calcareous glacial diamicton containing clasts of Orcadian Devonian rocks, Mesozoic erratics and Quaternary shells. Note that the partially synonymous term Lybster Formation (Hall and Whittington, 1989) was pre-used by the BGS to cover Middle Devonian strata (Lybster Flagstone Formation). The unit defined by Hall and Whittington included Late glacial peats and gellifluctates, but only true glacial sediments are included in the Reisgill Burn Till Formation. To date only one Member, the Forse Till Member, has been recognised, but further survey work in Caithness may reveal more.
Taken at the base of overlying Holocene strata.
Red Vein Coal (South Wales)
REDV
Reeker Coal
REEK
Reelan Formation
REEL
Rest Gill Tuff
REG
Taken at the base of bedded silicic tuff overlying parataxitic and lava-like tuff of the Bad Step Tuff
Cumbria. Langdale area of Lake District
Brown and tourquoise-weathered, bedded, fine-grained tuff with common scour and fill structures that forms a prominent marker unit overlying the Bad Step Tuff.
Up to 3.5m, but is typically less than 1m
Defined by the overlying parataxitic lapilli-tuff of the Crinkle Tuff Member
Rempstone Granodiorite
REGD
Glas Bheinn Mhor Granite (Skye Eastern Red Hills Centre: Phase 1)
REHE1
Beinn Na Cro Granite (Skye Eastern Red Hills Centre: Phase 2)
REHE2
Beinn An Dubhaich Granite (Skye Eastern Red Hills Centre: Phase 3)
REHE3
Creag Strollamus Granite (Skye Eastern Red Hills Centre: Phase 4)
REHE4
Ben A Caillich Granite (Skye Eastern Red Hills: Phase 5)
REHE5
Glamaig Granite (Western Red Hills Centre: Phase 1)
REHW1
Glen Sligachan Granite (Western Red Hills Centre: Phase 2)
REHW2
Southern Porphyritic Granite (Western Red Hills Centre: Phase 3)
REHW3
Marsco Granite (Western Red Hills Centre: Phase 4)
REHW4
Beinn Deag Mhor Granite (Western Red Hills Centre: Phase 5)
REHW5
Loch Ainort Granite (Western Red Hills Centre: Phase 6)
REHW6
Maol Na Gainmhich Granite (Western Red Hills Centre: Phase 7)
REHW7
Meall Buidhe Granite (Western Red Hills Centre: Phase 8)
REHW8
Eas Mor Granite (Western Red Hills Centre: Phase 9)
REHW9
Reeker Limestone
REKL
Red Wharf Limestone Formation
REL
Not exposed, but assumed to be a contact between massive sandy limestones with abundant chert nodules and lithologically more varied limestone sequence of the underlying Cefn Mawr Limestone Formation. The contact is likely to be taken at a palaeokarstic surface developed at the top of the uppermost Cefn Mawr Limestone cycle.
Western side of Red Wharf Bay on Angelsey [SH5381], and Great Orme at Llandudno [SH7483], North Wales.
Massive or irregularly bedded skeletal limestones (packstones and grainstones), commonly sandy, with abundant chert nodules. The formation comprises a series of shoaling upwards cycles capped by palaeokarstic surfaces commonly overlain by beds of sandstone infilling karstic pipes, or by channel-filling sequences of conglomerate, sandstone and silty mudstone. The Red Wharf Limestone Formation records late Brigantian, mixed carbonate-siliciclastic shallow marine deposition at a time of increased supply of siliciclastic detritus to the North Wales Dinantian platform. Each cycle represents a shoaling upwards sequence formed in response to transgressive and regressive movements in sea level. Many regressions culminated in emergence of the platform surface and the formation of karstic dissolution feartures and of channels that were filled by fluvial conglomerates and sandstone and estuarine mudstones.
In its type section, the Red Wharf Limestone Formation is overlain by a 6m-thick unit of bedded cherts, which was previously included in the Formation as the Castell Mawr Chert Member, but which may now be viewed as a local representive of the Pentre Chert Formation.
Rosemarkie Metamorphic Complex
REM
Lewisian hornblende rocks interleaved with Moinian acidic gneisses, cross-cut by porphyritic granite veins.
Reticuloceras Reticulatum Marine Band [See Also: R1c1, R1c2, R1c3]
REMB
Rempstone Formation
REMP
Redheugh Mudstone Formation
REMU
Unconformable upon folded Llandovery rocks, well exposed at Siccar Point [NT 812 710].
Southern Uplamnds Terrane of Scotland.
Mainly reddish sandy mudstones intercalated with sandstones and subsidiary siltstones. The local basal breccia of conglomerate is exposed at Siccar Point.
Estimated to be about 200 m thick.
The base of a predominantly sandstone succession belonging to the Greeenheugh Fomration.
Redmain Formation
REN
Not exposed, presumed to overlie Skiddaw Group.
Well sorted, thickly bedded, reddish purple protoquartzite; rare shale partings in lower and middle parts, reddish-purple shale beds + 1 metre at top.
100 metres in Tommy Gill, the only occurrence of the formation.
Unconformably overlain by Carboniferous sandstone.
Reidh Psammite Formation
REP
Reppachie Semipelitic Schist Formation
REPS
Redhouse Sandstone Formation
RES
Not seen, but probably unconformable upon pre-Carboniferous strata.
Off-shelf to the Derbyshire High and Staffordshire Shelf, in the Ashbourne and Cheadle District, but in the subsurface only.
Pebbly sandstone, conglomerates especially near the base, fine- to medium- sandstone, siltstone and mudstone, typically red-brown with minor green mottling.The formation is broadly upward fining, with individual beds internally upward fining too, the cycles average 6.7 m thick, and diminish in thickness upwards. Carbonate concretions of calcrete may be present at the top of some cycles.
Measured as 170.3 m thick in the Caldon Low Borehole, although the base is not proved.
Conformable passage, with the base of the overlying Rue Hill Dolomite Formation taken at the base of the lowest dolostone bed containing bioclasts, and underlain by reddish-brown pebbly sandstone of the Redhouse Sandstone Formation.
Redcliffe Sandstone Member
RESA
Unconformable, at the abrupt base of the red sandstones of the Redcliffe Sandstone Member overlying sandstones and mudstones of Late Carboniferous age.
Crops out in the Bristol area between Bedminster and Winterbourne (Barton et al., 2002).
Sandstone, distinctive fine- to medium-grained, deep red, calcareous and ferruginous. Commonly decalcified at shallow depths below the surface, giving rise to an uncemented sand.
For a time this unit was treated as an informal local unit within the locally undivided Mercia Mudstone Group succession. Subsequently (see Howard et al., 2008) considered as a local member of the Sidmouth Mudstone Formation.
Up to 65m (Kellaway and Welch, 1993).
Conformable and gradational, with interdigitation between red sandstone of the Redcliffe Sandstone and reddish-brown mudstone of the Sidmouth Mudstone Formation (undivided).
Reservoir Flags
RESF
Resipol Striped Formation
RESI
Residual Deposits Group
RESID
Irregular and unconformable contact with bedrock of Neogene age or older. In the case of Clay-with-Flints, dissolution of underlying chalk has resulted in local development of pipes and hollows that are infilled with the residual deposit.
Southern Britain across the Chalk outcrop and northeastern Scotland [Buchan] [for grid references see Stratotype details].
Includes remanie deposits formed by weathering and solifluction of original Palaeogene bedrock and Neogene to Early Quaternary superficial deposits. Typical deposits include the Clay-with-Flints of southern Britain and the Buchan Gravels Formation of northeastern Scotland. For the latter see stratotypes of constituent members: Buchan Ridge Gravel, Windy Hills Gravel. Clay-with-Flints lithologies include reddish brown clay with large unworn flint cobbles, yellow fine-to-medium-grained sand, reddish brown clayey silt and sandy clay. Buchan Gravels lithologies include well rounded gravel and cobbles of quartzite and flint with sand, silt and kaolinitic clay.
Clay-with-Flints: 2 to 10m; Buchan Gravels Formation: 25m+
Generally at the ground surface or overlain unconformably by Quaternary deposits.
Reservoir Schists Member
RESS
Reston Group
REST
Unconformably overlying the Lower Palaeozoic rocks of the Southern Uplands.
The Scottish Southern Uplands Terrane, bounded by the Southern Upland Fault to the north-west.
Conglomerates, sandstones,siltstones, mudstones and volcanic rocks of terrestrial, subaerial facies.
2350 m maximum thickness.
Unconformably overlain by the Stratheden Group (Upper Devonian).
Retreat Siltstone Formation
RETR
Reid's Vein
REV
Rough Rock Flags
The Rough Rock Flags are generally fine- to medium-grained, flaggy sandstone.
Reading Formation Basement Bed
RFBB
Rhengog Fach Coal (South Wales)
RFCH
Rhasfach Coal (South Wales)
RFCO
Reform Coal (South Lancashire)
RFMC
Ryhope Five Quarter Coal (Northumberland And Durham)
RFQ
Roof Soft Coal (Nottingham And Derby)
RFSC
Rhengog Fawr Coal (South Wales)
RFWR
Raglan Mudstone Formation
Conformable junction with underlying Downton Castle Sandstone Formation.
Red mudstones and silty mudstones with calcretes and sandstones. Townsend Tuff Bed 100m from top; Bishop's Frome Limestone at top.
To c.800m
Drawn at top of Bishop's Frome Limestone.
Raised Gravel Beach
RGB
Shingle with sand; beach deposits may be in the form of dunes, sheets or banks - [generic description]; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description: earth science dictionaries in the BGS library.
Rivergreen Coal (Northumberland)
RGC
Rubha Gaidheaiach Grit Formation
RGGT
Red Gill Formation
RGI
Raughton Gill Limestone
RGL
River Gravel
RGR
Gravel and sand of fluvial origin. [Generic description].
Rogenstein Member
RGST
Raven's Gulley Tuff
RGT
Rogate Member
RGTB
Top of the Hythe Formation; incoming of pebbles (including pebbles of polished limonite), usually set in a slightly clayey, glauconitic sandy matrix.
Western Weald; outcrop extends from Stedham, West Sussex, to north of Liss.
A heterogeneous sequence of coarse-grained pebbly sands, very glauconitic clayey pebbly sands, glauconitic pebbly and sandy clays, calcareously cemented pebble beds and coarse-grained pebbly sands with many polished limonite pebbles.
Base of Pulborough Sandrock Member: top of a glauconitic pebbly sandy clay where present, otherwise at change from pebbly sands to the fine-grained, well-sorted Pulborough Sandrock (but nb, scattered coarse grains occur in basal metre or so of Sandrock).
Rhaetian Rocks (Undifferentiated)
Rockingham Sandstone Member
RHAM
Ruthery Head Breccia
RHBR
Rova Head Conglomerate Member
RHC
Rownham Hill Coral Bed
RHCB
Rickets Head Coal (Milford, South Wales)
RHCO
Rue Hill Dolomite Formation
RHD
The top of a red-brown sandstone, pebbly sandstone and conglomerate of the Redhouse Sandstone Formation, displaying a sharp passage into grey dolostone of the overlying Rue Hill Dolomite Formation.
Off-shelf, to the Derbyshire High and the Staffordshire Shelf, in the subsurface of the Ashbourne and Cheadle district.
Grey, thinly bedded, very fine-grained dolostone, with subordinate beds of dark grey limestone comprising calcilutite and calcisiltite, mudstone, in which fenestral cavities are common, breccias and several thin beds of coarse-grained quartzitic sandstone. The variably bedded argillaceous limestone or dolostone, has a marine fauna of crinoids and brachiopods, alternating with dolostone containing penecontemporaneous breccias, sparse gastropods, serpulid and ostracod fauna.
Measured as 84.47 m thick in the Caldon Low Borehole.
A conformable passage into medium grey biosparites or dark grey cherty micrites of the Milldale Limestone Formation, with the boundary at the top of unfossiliferous porcellaneous dolostone above the highest occurrence of the ostracod-gastropod fauna.
Robbery Head Subgroup
RHE
Red Head Sandstone Member
RHF
The top of the uppermost fine-grained unit of the Dundee Flagstone Formation.
The coastal area between Monifieth and Lunan Bay/Red Head, and the south-east limb of the Sidlaw Anticline.
Red-brown ro purple-grey, fine- to coarse-grained sandstone, the lower part contains red mudstones and siltstones with small calcareous concretions with local pebbly sandstones, including concretionary limestone clasts.
About 455 m thick.
The base of the Auchmithie Conglomerate Member of the Scone Sandstone.
Rhobell Volcanic Group
RHG
Drawn at the base of the Rhobell Volcanic Group where mixed compound and multiple basaltic flows unconformably rest upon banded dark grey mudstone of the Dol-Cyn-Afon Member.
The area from Nannau-Uwch-Afon in the south to Rhobell-y-big in the north.
Basalt with flow autobreccia and epiclastic breccias; laharic flows at base; rare fluviatile intercalations.
960 metres approx.
Drawn at the conformable upward passage of the Rhobell Volcanic Group where it is unconformably overlain by grey volcanic sandstone with interbedded black siltstone and sandstone with quartzose sandstone of the Allt Lwyd Formation.
Rhinns Complex
RHIN
Rigghead Limestone
RHL
Locally in and around the White Lyne valley, Cumbria.
Alternating limestones, cementstones and calcareous shales.
To c.4.5m
Central Intrusion (Rum Layered Suite) [Obsolete Code: Use Rlc]
RHLC
Dornabac Member (Central Intrusion, Rum Layered Suite) [Obsolete Code: Use Rlc1]
RHLC1
Long Loch Member (Central Intrusion, Rum Layered Suite) [Obsolete Code: Use Rlc2]
RHLC2
Ruinsival Member (Central Intrusion, Rum Layered Suite) [Obsolete Code: Use Rlc3]
RHLC3
Eastern Layered Intrusion (Rum Layered Suite) [Obsolete Code: Use Rle]
RHLE
Western Layered Intrusion (Rum Layered Suite) [Obsolete Code: Use Rlw]
RHLW
Harris Bay Member (Western Layered Intrusion, Rum Layered Suite) [Obsolete Code: Use Rlw1]
RHLW1
Transitional Member (Western Layered Intrusion, Rum Layered Suite) [Obsolete Code: Use Rlw2]
RHLW2
Ard Mheall Member (Western Layered Intrusion, Rum Layered Suite) [Obsolete Code: Use Rlw3]
RHLW3
Rhymney Grit Member
RHM
Rhynie Group
RHN
Conglomerate, shale, sandstone and siltstone, with intercalated andesitic and rhyolitic lava and ash, and thin chert bands. Comprises entire Old Red Sandstone of Bogie outlier, and possibly also the Cabrach outlier.
970 metres in type localities for each formation; maximum thickness probably 2100 metres in Kildrummy (NJ 46 18) area.
Rhynie Chert Member
RHNC
Lower boundary is where cherty material overlies weathered shales.
Chert with plant remains, with minor interbedded cherty sandstones.
2.23 metres in Trench No.3; 2.36 metres in Trench No.1.
Upper boundary where succeeded by argillaceous and arenaceous rocks.
Rubha Na H-Earba Formation
RHNE
Northern Marginal Zone (Rum Central Complex) [Obsolete Code: Use Runm]
RHNM
Northern Marginal Zone, Am Mam Breccias (Rum Central Complex) [Obsolete Code: Use Runma]
RHNMA
Red Hill Limestone Formation
RHO
Early Arundian. The base of the unit is coincident with the Arundian/Chadian boundary
Taken at base of Algal Band in type locality and elsewhere; otherwise at upward change from fine-grained oolites/grainstones/carbonate mudstones of Martin Limestone to coarse-grained unbedded grainstone.
Carbonate bioclastic, intraclastic and peloidid grainstones, coarse-grained and virtually structureless following bioturbation.
20 to 60m
Base of overlying Dalton Formation.
Rough Holden Coal (West Yorkshire)
RHOC
Rougholme Point Conglomerate
RHP
Unconformity; in type section it overlies Millstone Grit Group (Namurian) sandstone and mudstone with seatearths.
Cark Peninsula, South Cumbria, to the south of the Cark Fault and west of the Humphrey Head Fault, extending southwards off-shore into Morecambe Bay.
Limestone conglomerate - granule to cobble sized clasts with interbeds of red sandstone and some siltstone near base.
At least 257m
Top not seen, present-day erosion surface.
Ravenhead Rock
RHR
The lower boundary is taken at a well-defined erosional surface. The base is taken at the base of the first sandstone unit above the Wigan 4 foot Coal, or where this is absent, the base of the first sandstone unit overlying the Wigan 5 foot Coal.
Southern and western parts of the South Lancashire Coalfield.
Sandstone and pebbly sandstone, part-reddened, medium-to-coarse-grained, micaceous, with well-defined soft hematic partings, and subordinate mudstone. A basal pebbly sandstone may be present, comprising clasts of mudstone and ironstone up to 2 feet in diameter.
From 21m to 46m
The upper boundary is taken at the base of a mudstone-dominated succession of the Pennine Lower Coal Measures Formation above the sandstone of the Ravenhead Rock.
Rhayader Mudstones Formation
RHS
Taken at base of a prominent thick packet of thinly interbedded turbidite mudstones and laminated hemipelagites overlying thinly interbedded turbidite mudstones and burrowed hemipelagites of the Derwenlas Formation.
Thinly interbedded green and grey turbidite mudstones and burrowed hemipelagites. Sparse thin packets of thinly interbedded turbidite mudstones and laminated hemipelagites. Scattered thin packets with turbidite sandstones. NOTE: Overlain by the Caeran Mudstones and underlain by the Derwenlas Formation. Locally underlain by the Caban Conglomerate Complex.
c.460 metres.
Gradational, but taken at the base of the incoming of abundant packets of thinly interbedded turbidite mudstone and laminated hemipelagites.
Rookhope Shell Beds
RHSB
Rhayader Mudstone Formation (Green Beds)
RHSG
Southern Mountain Zone (Rum Central Complex) [Obsolete Code: Use Rusm]
RHSM
Rum Subswarm [Obsolete Code: Use Rum]
RHUM
Rum Central Complex [Obsolete Code: Use Rumc]
RHUMC
Rum Layered Suite [Obsolete Code: Use Ruml]
RHUML
Western Granite (Rum Central Complex) [Obsolete Code: Use Rwg]
RHWG
Western Granite, Fine-Grained Phase (Rum Central Complex) [Obsolete Code: Use Rwg1]
RHWG1
Western Granite, Medium-Grained Phase (Rum Central Complex) [Obsolete Code: Use Rwg2]
RHWG2
Rough Hills White Ironstone (South Staffordshire)
RHWI
Rhynchonellid Sandstone
RHY
Rhydings Formation
RHYD
Ryhope Sand Member
RHYS
Sharp, erosional contact with underlying dark greyish brown to dark yellowish brown, stony sandy silty clay diamicton of the Wear Till Formation, infilling channels cut in the latter.
Cross-bedded sand with subordinate silt, clay and gravel, mainly composed of limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone), Carboniferous lithologies (sandstone, gritty sandstone, limestone, mudstone, ganister, coal), and far-travelled clasts from Scotland and the Lake District (greywacke sandstone and siltstone, granite and granodiorite). Includes some clasts of till, shell fragments and locally much coal. Locally cemented. Mainly southeastward palaeocurrent.
Generally a sharp, unconformable contact with reddish-brown stony clay of the Horden Till Formation. Ice-wedge casts reported in the top of the member, truncated by overlying till.
Raesgill Ironstones
The Crossbasket or Raesgill Ironstones of Carluke lie within the Lower Limestone Formation. They lie below the Hosie Sandstone and are of Brigantian age.
Riabhach Banded Formation
RIAB
River Brickearth
RIB
Varies from silt to clay, commonly yellow-brown and massive; of fluvial origin. [Generic description].
Ribbon Coal
RIBC
Ribble Valley Formation
RIBV
Lancashire and adjacent areas within the river valley and tributaries of the River Ribble.
Silt, sand and clay in Alluvium grading into gravel at base. River Terraces are dominated by gravel grading upwards into silt and sand.
Generally less than 5m but locally up to 12m.
Ringslade Clay Member
RICL
Rider Coal (Cheadle)
RICO
Ridgeway Member
RID
First significant occurrence of dark grey or brown muds above thickly bedded, ostracod-rich limestone of the Mupe Member.
In west Dorset, comprises dark greyish brown, carbonaceous muds and pale marls and micrites, commonly containing thin detrital quartz laminations that form isolated ripples. The mudstones are replaced in east Dorset by micritic limestone, and at Durlston Bay, where the sequence becomes very monotonous, it is difficult to define the Member.
3 to 7m
Top of thicker mudstone beds beneath thick-bedded, ripple cross-laminated, quartz-detrital limestone of the overlying the Worbarrow Tout Member.
Rider Coal (Derbyshire)
RIDC
Ridge Conglomerate Unit
RIDCO
Ridgacre Formation
RIDG
At type locality and Nechells, overlies the organic Quinton Beds ("Hoxnian"). More generally, inferred to rest upon Nurseries Formation or Permo-Triassic or Palaeozoic bedrock.
Full extent highly uncertain pending further work, but likely to be widespread in and to the south of the Birmingham area beyond the limit of the Devensian Stockport Formation, and probably makes up the great bulk of the pre-Devensian glacigenic deposits there, and possibly in adjoining districts. Currently positively identified only in sections at Quinton and Nechells where it overlies the temperate (Hoxnian) Quinton Beds. Possibly also represented by till at Stourport beneath Holt Heath Member of Severn Valley Formation(Dawson, 1988; Maddy et al., 1995), and by gravels farther upstream in the Stour valley (Maddy et al., 1995). Remnants may be present inside the Devensian limit beneath the Stockport Formation.
Comprises the younger of the two pre-Devensian glacial successions identified in the Birmingham area. Predominantly sands and tills, which characteristically lack Scottish and Lake districts erratics (which characterize the Devensian Stockport Formation), and northern and eastern (e.g. Cretaceous) erratics (which are found in the pre-Devensian Wolston Formation). At type locality comprises glacigenic reddish-brown and orange sand with clay partings, overlain by reddish brown till with Trias (mainly Bunter quartz/quartzite) and Upper Carboniferous erratics; similar deposits of sand and gravel occur at Nechells. At both localities overlies the organic Quinton Beds ("Hoxnian"). Full geographic extent and thus full range of lithology uncertain. Precise age and correlation contentious.
(A) As in Bowen et al (1999) and new BGS scheme. Should it be Ridgacre Glacigenic Formation? (B) Age left vague. Overlying ?Hoxnian? organics it is part of support for two pre-Late Devensian glaciations. Those envisaging a 2-phase Anglian put the unit in MIS 10, with the Oadby Till. Others put it in 6, based on relationship with Severn terraces, mirroring arguments based on the Avon/Severn/Thames that imply a Stage 10 Oadby Till (+ Ridgacre)! Avon/Severn relationships must be sorted out. Ridgacre at Quinton and Nechells could be Upper Pleistocene 4, or even 12, as the ?Hoxnian? beds age is uncertain. (C) This is the younger of two pre-Devensian glacial sequences at Quinton and Nechells. Not separated by BGS but Kelly?s (1964) sections suggest Ridgacre must be widespread, at least in north Birmingham. Neither Kelly nor Horton give enough lithological data to characterize the unit fully. Until lateral extent is known, full range of lithologies is unknown; a Catch 22! (D) Widespread glacigenic deposits beyond Devensian limit in the Midlands are not separated into two phases (except in Wolston Formation). As representing the later episode it might be safe to say most pre-Devensian glacial deposits on Birmingham area maps are Ridgacre, and that Nurseries might be limited to buried pockets, as at Quinton and Nechells. Birmingham area survey (Powell et al, 2000), shed little light ? most tills reddish and Trias rich, more like Ridgeacre than Nurseries. Ridgacre?s southern limit could be within the area and Nurseries extend beyond, with both at outcrop. Other problems are deciding Ridgacre?s eastern limit, where it becomes part of Wolston Formation, and how far north it goes. Maddy?s model suggests not far but, if contemporaneous with the Wolston, it could be widespread. This could be settled by more research and study of lithologies beyond the Devensian limit. (E) The unit is not distinguished on BGS maps, so the list of 50K maps shows where the Ridgacre MIGHT occur.
c.8m at type locaity; elsewhere may be represented by up to 50m of deposits.
Ground surface or various younger Quaternary deposits (head, fluvial deposits). Remnants may be present inside the Devensian limit beneath the Stockport Formation.
Reclaimed Intertidal Deposits
RIDS
Deposits from the intertidal zone: variable lithology - gravel through to clay, may be rich in organic matter; originally deposited in the intertidal coastal zone but reclaimed by Man. [Generic description].
Rillage Limestone
RIL
Rimarsin Limestone Formation
RIML
Rissington Member
RIN
Limestone gravel; a terrace of the River Windrush. [Generic description: 1:50 k map margins].
Ringinglow Coal (North Derbyshire)
RING
Rinn Point Limestone Formation
RIPO
Raasay Ironstone And Portree Shale Formation (Undifferentiated)
RIPS
Raised Intertidal Deposits And Raised Marine Deposits (Undifferentiated)
RIRM
Composite deposit: 'Raised Intertidal Deposits': variable lithology - gravel through to clay, may be rich in organic matter; from the intertidal coastal zone, but now above the level of the present shoreline as a result in earth movement or a general fall in sea level. 'Raised Marine Deposits': also a variable lithology - gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell) now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Ringsbury Spiculite Member
RIS
Base is a change up from interbedded yellowish fine quartz sand, clayey in parts and locally cemented into calcareous sandstone, and sandy mudstone of undifferentiated Hazelbury Bryan Formation into grey sandstone with siliceous sponge spicules of the Ringsbury Spiculite Member.
Area between Purton and Wootton Bassett, Wiltshire. Pinches out laterally into undifferentiated Hazelbuty Bryan Formation. May be lateral equivalent of the Arngrove Spiculite Member of the Kingston Formation of east Oxfordshire.
Pale grey to brownish grey sandstone, mainly composed of abundant siliceous spicules of Rhaxella perforata (tetractinellid sponge), with scattered ferruginous ooids. Notably low density (highly porous?). Weathers in soil to angular blocks
The top is a change up from grey sandstone with siliceous sponge spicules of Ringsbury Spiculite Member, into interbedded yellowish fine quartz, calcareous sandstone, and sandy mudstone of undifferentiated Hazelbury Bryan Formation or, where absent, into bedded, finely bioclastic limestone of the Stanford Formation.
Ribble Sandstone Member
RISA
Ridgeway Member And Worbarrow Tout Member (Undifferentiated)
RIWO
Rubha Gaidheaiach Grit Formation, Kilchiaran Phyllite Formation And Eilean Liath Grit Formation (Undifferentiated)
RKE
Rock Fach Coal (South Wales)
RKFC
Rock Glacier Deposits
RKGLA
Rosskit Limestone Member
RKIT
Rookwood Limestone Member
RKLM
Rad Brook Mudstone Member
RKM
The base of the first mudstone above the characteristic pale noduliferous wackestones of the Hodderense Limestone Formation.
Limited to the southern part of the Craven Basin; absent north of the Clitheroe (SD82 44) and Whitwell (SD64 47) anticlines.
A dark to pale olive-and blue-grey, calcareous, bioturbated mudstone, interbedded with dark, laminated, micromicaceous, calcareous siltstones andsporadic fine-grained, grey-blue packstones and wackestones.
Taken at the base of the lowest packstone of the Pendleside Limestone Formation with less than 50% interbedded mudstone.
Ravensholme Limestone Member
The limestone of the Ravensholme Limestone Member either conformably overlies dark mudstones of the Bowland Shale Formation (undifferentiated) or rests directly on the relatively fine-grained limestones of the Pendleside Limestone Formation.
Occurs at scattered localities in the Craven Basin, including the northern slopes of Pendle Hill [SD 81 43] and the Brennand Inlier [SD 65 54].
Coarsely bioclastic, shelly and crinoidal limestones, conglomeratic in places, with subordinate shaly mudstone beds and partings.
Top is overlain conformably by the predominantly mudstone sequence of the Bowland Shale Formation (undifferentiated).
Rhyddlan Formation
RLAN
Rubers Law Vent And Plug
RLAW
Redhill Beds
RLB
Central Intrusion (Rum Layered Suite)
RLC
Dornabac Member (Central Intrusion, Rum Layered Suite)
RLC1
Long Loch Member (Central Intrusion, Rum Layered Suite)
RLC2
Ruinsval Member (Central Intrusion, Rum Layered Suite)
RLC3
Rutland Formation
RLD
Generally a sharp unconformable boundary of sandy beds of the Stamford or Thorncroft Sand members overlying: in Lincolnshire, Rutland and north Northants, limestones of the Lincolnshire Limestone Formation, commonly marked by the "Ironstone Junction Bed"; or in mid Northants, north Buckinghamshire and Bedfordshire, by ironstone or ferruginous sandstone of the Northampton Sand Formation, or mudstones of the Lias Group; and across the London Platform subcrop by Palaeozoic strata. In the southwest, the lower boundary is an upwards gradation from limestones of the Taynton Limestone Formation to mudstone of the reduced Rutland Formation (see Lithological Description).
The Cherwell Valley, around Northbrook [SP 49 22], where the reduced Formation passes westward into the Hampen Formation, (Horton et al., 1987, fig.8), northeast and north, to the Market Weighton High around North Newbald [SE 91 37], where the unit is overstepped by Cretaceous rocks.
Interpreted as a succession of up to seven shallowing upward, essentially delta-type rhythms, comprising ideally of a grey marine mudstone passing up into non-marine mudstone and siltstone, with a greenish-grey rootlet bed at the top. The basal beds comprise mainly fluviatile and lacustrine sandstones, designated the Stamford Member in the south, passing north in central Lincolnshire into the Thorncroft Sand Member. Subordinate sandstone beds occur higher in the sequence locally, as well as typically shelly and shell-detrital marine limestones and calcareous mudstones, notably in the mid part, the Wellingborough Limestone Member, in Northamptonshire. In southwest Northants and north Oxfordshire only the upper part of the Formation is represented, by largely argillaceous strata, and the lower part is replaced by the Horsehay Sand, Chipping Norton Limestone, Sharp's Hill and Taynton Limestone formations.
Typically from about 8 to 12m, and up to about 15m thick, measured as about 12m at the type section, and, where reduced in the southwest, typically from 2m to 4m thick.
A gradational boundary from argillaceous beds of the Rutland Formation into limestones of the Blisworth Limestone Formation or, in the southwest on Sheets 218,219,236,237, into limestones of the White Limestone Formation.
Eastern Intrusion (Rum Layered Suite)
RLE
Eastern Layered Intrusion, Unit 1 (Rum Layered Suite)
RLE1
Eastern Layered Intrusion, Unit 10 (Rum Layered Suite)
RLE10
Eastern Layered Intrusion, Unit 11 (Rum Layered Suite)
RLE11
Eastern Layered Intrusion, Unit 13 (Rum Layered Suite)
RLE13
Eastern Layered Intrusion, Unit 14 (Rum Layered Suite)
RLE14
Eastern Layered Intrusion, Unit 15 (Rum Layered Suite)
RLE15
Eastern Layered Intrusion, Unit 2 (Rum Layered Suite)
RLE2
Eastern Layered Intrusion, Unit 3 (Rum Layered Suite)
RLE3
Eastern Layered Intrusion, Unit 5 (Rum Layered Suite)
RLE5
Eastern Layered Intrusion, Unit 7 (Rum Layered Suite)
RLE7
Eastern Layered Intrusion, Unit 8 (Rum Layered Suite)
RLE8
Eastern Layered Intrusion, Unit 9 (Rum Layered Suite)
RLE9
Ruchill Flagstone Formation
RLF
In the Callander-Crieff area, taken as the top of the Craig of Monievreckie Conglomerate, which is the volcanic conglomerate of Frances, Forsyth, Read and Armstrong, 1970, south-west of Aberfoyle the Ruchill Formation is faulted against Dalradian and Highland Border Complex rocks.
The Highland border between Balmaha and Crieff, north-west limb of the Strathmore Syncline.
Grey to reddish grey, fine- and medium- to locally coarse-grained sandstones with thin interbeds of mudstone and siltstone and the locally impersistent Inchmurrin, Callander Craig and Gartartan conglomeratic members.
Between 400m and 1750 m thick.
In the Callender-Crieff area, the top is taken at the base of the Cromlix Mudstone Formation, which is strongly diachronous, whereas in the Aberfoyle area, the Ruchill Flagstone Formation is locally overlain by the Shannochil Sandstone Member of the Cromlix Mudstone Formation.
Rotliegendes Group
RLG
Unconformable base resting on older strata ranging from Devonian to Late Carboniferous.
Northern England, southern and northern North Sea, Holland, Germany.
Succession of terrestrial aeolian, fluvial and inland lacustrine sandstones and conglomerates with mudstone and subordinate halite.
Unconformable top overlain by the Kupferschiefer or Marl Slate (or younger strata).
Raised Lacustrine Gravel Beach Deposits
RLGB
Typically sand and gravel; lacustrine deposits from the littoral zone; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Regolith
RLITH
Rhobell Ganol Formation
RLL
Rough Limestone (Cumbria)
RLM
Rugby Limestone Member
RLS
Conformable on Saltford Shale Member - placed at base of an argillaceous limestone above which such limestones are common; at type section boundary placed at limestone below Bed 8 of Clements (1977).
Central and southern Midlands.
Alternating grey, argillaceous limestones and mudstones.
36m at type section; up to 40m elsewhere.
Placed at top of highest limestone of the limestone/mudstone sequence. At the type section, placed at Bed 53c of Clements (1977).
Red Lion Till Member
RLTI
Western Intrusion (Rum Layered Suite)
RLW
Harris Bay Member (Western Intrusion, Rum Layered Suite)
RLW1
Transitional Member (Western Intrusion, Rum Layered Suite)
RLW2
Aed Mheall Member (Western Intrusion, Rum Layered Suite)
RLW3
Rosemarket Formation
RMB
Raised Marine Beach Deposits
RMBD
Typically sand and gravel; marine deposits from the littoral zone; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Raised Marine Beach Deposits, Late Devensian
RMBDD
Sharp, unconformable, generally planar, shelving contact on various older superficial deposits, most commonly till.
Britain to the north of the Tees-Ribble.
Gravel and sand, commonly silty. Gravel typically cobble grade, poorly sorted, clast supported with subangular to rounded clasts. Sand mainly medium-grained.
Up to 10 m.
Ground surface, or sharp, undulating, conformable contact with younger superficial deposits, peat and blown sand.
Raised Marine Beach Deposits Of Flandrian Age
RMBDF
Sharp, unconformable, generally planar, gently shelving contact on various older superficial deposits (most commonly till) or rockhead.
Gravel and sand, commonly shelly. Gravel typically cobble grade, well sorted, clast supported with well-rounded clasts. Sand mainly medium-grained and shelly.
Ground surface, or sharp, undulating, conformable contact with younger superficial deposits, including peat and blown sand.
Raised Marine Beach Deposits, 1 (Rathlin)
RMBR1
Raised Marine Beach Deposits, 2 (Rathlin)
RMBR2
Raised Marine Beach Deposits, 3 (Rathlin)
RMBR3
Red Mine Coal (North Staffordshire)
RMC
Roger Coal (South Lancashire)
RMCO
Raised Marine Deposits
RMD
Variable lithology. Gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell); now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description: from East Anglian data].
Raised Marine Deposits,1
RMD1
Raised Marine Deposits,2
RMD2
Raised Marine Deposits,3
RMD3
Raised Marine Delta Deposits
RMDD
Typically sand and gravel; marine deltaic deposits; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Raised Marine Deltaic Deposits, Devensian
RMDDD
Raised Marine Deposits Of Flandrian Age
RMDF
Variable lithology. Gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell); now above the level of the present shoreline as a result of earth movement or a general fall in sea level; of Flandrian age. [Generic description: from East Anglian data].
Raised Marine Deposits Of Flandrian Age, 1
RMDF1
Mainly uncomformable on till or bedrock.
Northern England and Scotland.
Mainly sand and gravel underlying shelving raised shoreface (beach) features, but commonly passing landwards, and downwards, into interbedded sand,silt, clay and organic mud underlying flat-lying ground.
up to 25m.
Raised Marine Deposits Of Flandrian Age, 2
RMDF2
Up to 25 m thick.
Raised Marine Deposits Of Flandrian Age, 3
RMDF3
Raised Marine Deposits Of Flandrian Age, 4
RMDF4
Raised Marine Deposits, Devensian
RMDV
Variable lithology. Gravel (shingle), sand, silt and clay; commonly charged with organic debris (plant and shell); now above the level of the present shoreline as a result of earth movement or a general fall in sea level; of Devensian age. [Generic description: from East Anglian data].
Raised Marine Deposits, Late Devensian, 1
RMDV1
Mainly sand, gravel and cobbles, poorly sorted, underlying shelving raised shoreface features, commonly passing landwards, and downwards, into interbedded sand, silt and clay underlying flat-lying ground.
Raised Marine Deposits, Late Devensian, 2
RMDV2
Mainly unconformable on till or bedrock.
Mainly silty sand, gravel and cobbles, poorly sorted, forming shelving raised beaches. The deposits commonly pass landwards into interbedded sand, silt and clay underlying raised tidal flats and lagoons.
Ruabon Marl Formation And Erbistock Formation (Undifferentiated)
RMER
Raisby Formation And Ford Formation (Undifferentiated)
RMFM
Rag Mine Coal (North Staffordshire)
RMIC
Raised Marine Intertidal And Subtidal Deposits
RMIS
Composite deposit: 'Raised Marine Intertidal Deposits': variable lithology - gravel through to clay, may be rich in organic matter; from the marine intertidal coastal zone, but now above the level of the present shoreline as a result of earth movement or a general fall in sea level. 'Raised Subtidal Deposits': also a variable lithology - any deposit laid down in the subtidal zone ie. below mean low water, but now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Raisby Formation
RML
Typically sharp, taken at the incoming of dolostone and limestone above the laminated, bituminous, silty, argillaceous dolostone of the Marl Slate Formation and, where this is absent, either above the aeolian Yellow Sands Formation or unconformably on Carboniferous (usually Coal Measures ) strata.
Durham Province of English Zechstein; County Durham, Tyne and Wear, Cleveland and northernmost North Yorkshire.
Cream, brown and grey, fine-grained dolostone with grey, fine-grained limestone.
48m at type locality; ranges from 20 to 40m but, locally up to 73m in east Durham.
At the incoming of oolitic and pisolitic or equivalent reef dolostone of the Ford Formation.
Redmarley Member
RMLY
Interpreted generally as where fluvial deposits rest on bedrock, or older superficial deposits.
The River Leadon and tributary valleys, including Glynch Brook, Gloucestershire and Worcestershire.
The upper surface of the present day river terrace, which may be ovelain by alluvium.
Rossmore Mudstone Formation
RMM
Reticuloceras Moorei Marine Band
RMMB
Raglan Mudstone Formation And St Maughans Formation (Undifferentiated)
RMSM
Ruddington Moor Till
RMT
Clay, unconsolidated and dark grey, with chalk and flint pebbles and lenses of sand and gravel. [Generic description: 1:50 k map margins].
Redcar Mudstone Formation
RMU
Where grey, silty mudstone with thin beds of limestone and calcareous sandstone rest with sharp and irregular contact on grey-green soft mudstone with thin siltstone laminae of Penarth Group (Lilstock Formation, Cotham Member); in the British Geological Survey Felixkirk Borehole, this is at depth 288.87m.
Cleveland Basin, North Yorkshire and Cleveland.
Grey, fossiliferous, fissile mudstones and siltstones with subordinate thin beds of shelly limestone in lower part, and fine-grained carbonate-cemented sandstone in upper part; argillaceous limestone concretions occur throughout.
To c.283m
Gradational contact with overlying sandstones and siltstones of Staithes Sandstone Formation, but defined at the base of the "Oyster Bed" (highly fossiliferous calcareous and ferruginous sandstone).
Rhinog Formation
Late Comley.
Conformably overlies mudstones of the Llanbedr Formation, base being taken at the first pale green sandstone overlying the mudstones.
Grey to bluish grey, thick bedded turbiditic sandstones, conglomerates and laminated sandstones, with thin siltstone and mudstones intercalations.
400 to 780m
Conformable below siltstones of the Hafotty Formation.
Runcton Member
RNB
Round How Breccia Member
RND
Rests sharply on andesite or breccia of the Haystacks Andesite Member. Locally overlies Birker Fell Andesite Formation (undivided andesite lavas and volcaniclastic rocks).
Poorly to well bedded volcaniclastic sandstone and breccia, some accretionary lapilli-tuff and tuff.
Overlain by undivided lavas (andesites) and volcaniclastic rocks of the Birker Fell Andesite Formation (undivided).
Randerston Limestone
RNDL
Rain Gill Limestone Member
RNGL
Not seen at type locality. Upward passage of underlying laminated calcisiltites and mudstones of the Hodder Mudstone Formation (undifferentiated) into wackestones and floatstones of the Raingill Limestone Member.
Restricted to the Ashnott [SD 69 48], Middop [SD 83 45], Slaidburn [SD 97 53] and Whitewell [SD 64 47] anticlines.
Wackestones, floatstones and subordinate packstones, fine- to coarse-grained, cherty, muddy, dark-grey, thin- to thick-bedded, commonly with diffuse bed boundaries, interbedded with thin mudstones. Slumping is common.
To 170m
Not seen at type locality. Passage of wackestones and floatstones of the Raingill Limestone Member into overlying laminated calcisiltites and mudstones of the Hodder Mudstone Formation (undifferentiated).
Rubha Na H'Airde Moire Phyllite Formation
RNHM
Robinson Limestone
RNL
The Robinson Limestone is the uppermost part of the Melmerby Scar Limestone.
Generally 4 to 6m, but reaches 25m adjacent to the Stainmore Trough.
Robinson Member
RNM
The Robinson Member is locally conformable with the underlying Goat Gills Member (breccia) [NY 1895 1624], but the lowest beds are highly disturbed and in Goats Gills [NY 1914 1630] they are truncated against the underlying unit.
Occurs in the south of the Skiddaw inlier within the Buttermere Formation and bounded to the north by the Causey Pike Fault.
A series of large sandstone-rich olistoliths ranging in size up to 1km across. Mainly quartz-rich lithic wackes and granule conglomerates interbedded with siltstone amd mudstone.
The Robinson Member is surrounded by an envelope of sandstone-rich Buttermere Formation rocks.
Raeburn Shell Bed
RNSB
Ruallan Till Member
RNTI
Generally a gradational contact over 10 to 20cm, but locally a sharp, planar contact and change in colour from dark yellowish brown to "strong brown" (Munsell Soil), with underlying stony sandy clay diamictons of the Cantray Till Member.
Stony sandy clay diamicton, matrix-supported, dark yellowish brown, fissile, massive, extremely compact, containing angular to sub-rounded clasts of gneissose psammite and semipelite, pink and grey granite and some Devonian sandstone and siltstone. Typical lodgement till with well developed north-easterly fabric and containing concavo-convex discontinuities that are commonly sand-filled.
Erosional contact with gravel of the Carn Monadh Gravel Formation at the Allt Odhar Interstadial site, otherwise overlain by various younger deposits or boundary at the ground surface.
Rosenum Formation
RNUM
Conformable on the Tempellow Slate Formation.
Locally south of Liskeard (Burton, C J and Tanner, P W G) and westwards towards Bodmin (British Geological Survey Sheet 335 and 336).
Dull grey and black slate.
Not recorded
Conformable below the Milepost Slate Formation.
River Terrace Deposits, 1 (Rother, Kent)
RO1
River Terrace Deposits, 2 (Rother, Kent)
RO2
River Terrace Deposits, 3 (Rother, Kent)
RO3
River Terrace Deposits, 4 (Rother, Kent)
RO4
Roade Member
ROAD
The base of the described limestones, overlying mudstones of the Rutland Formation.
From the Towcester district, Northants (Sheet 202) to the Stamford district (Cripps,1986) passing south- west into the Shipton Member of the White Limestone Formation and north into the Blisworth Limestone Formation which cannot be separated from the Longthorpe Member, notwithstanding the presence of K sharpi in the lower part of the Blisworth Limestone Formation in north Lincolnshire (see Cripps,1986).
A pale grey to off-white or brownish, more or less clayey or sandy shell fragmental, bioturbated wackestone and packstone, characteristically containing Kallirhynchia sharpi (Muir-Wood) and other brachiopods and bivalves such as mussels and oysters with thin marls and mudstones.
Typically about 1m thick in the type area, elsewhere from about 3m, foe example the 2.51 m recorded by Torrens, 1967, to 2.99 m measured by Cripps,1986, at the type section.
Generally a sharp boundary with beds of limestone, marl or mudstone lacking K sharpi,commonly a marl or mudstone bed at this level which may prove a reliable marker compared to the mudstone at the base of the Ardley Member of the White Limestone in Oxon.
Rosyth Algal Dolostone
ROAL
Rolling Bank Member
ROBA
Laeviuscula Zone to Sauzei Zone.
Upward change, locally a hardground, from ooidal and peloidal limestone (Notgrove Member) into limestone of Witchellia Grit as described in lithology.
North Cotswolds: Cleeve Hill - Andoversford area, Gloucestershire (Barron, A J M, et al, 1997, fig.4).
Grey rubbly limestones: in lower part (Witchellia Grit) yellowish, shelly, sandy, ooidal and ironshot with brachiopods and rare ammonites including Witchellia; in middle part (Bourguetia Beds) very shelly with bivalves and gastropods including Bourguetia saemanni (Oppel); in upper part (Phillipsiana Beds) hard, sandy and shelly with brachiopods, including 'Terebratula' phillipsiana (Walker).
Type section very approximately 8.5m.
Disconformity/hardground: limestone as in lithology overlain by Salperton Limestone Formation.
Robb Coal
ROBB
Robie's Coal
ROBIE
Rowton Brook Sandstone Member
ROBR
Robin Sandstone
ROBS
Rock Coal
ROC
Rock Coal (Somerset)
ROCC
Rosses Centred Complex
ROCE
K-Ar 382-404 Ma (Pitcher and Berger, 1972).
Rosses Centred Complex Phase 1
ROCE1
Rosses Centred Complex Phase 2
ROCE2
Rosses Centred Complex Phase 3
ROCE3
Rb-Sr whole rock 404 +/- 3 Ma (Halliday et al., 1980).
Rosses Centred Complex Phase 4
ROCE4
Rosehall Croft Limestone
ROCL
Roker Formation
ROD
Drawn at diachronous base of dolostone of the Roker (Dolomite) Formation where it rests conformably on and interdigitates with the Concretionary Limestone Formation. Gradational contact with the underlying Hartlepool Anhydrite Formation offshore and with the equivalent dissolution residue that overlies the Ford Formation onshore.
Durham Province, onshore and offshore, of the English Zechstein Group: County Durham, Tyne and Wear, Cleveland and northernmost North Yorkshire.
Cream, oolitic dolostone with subordinate thin beds of fine-grained dolomite. Breccias also present.
Up to approx. 80m (offshore); [Smith, et al. 1986].
Above and to the west of the Ford Formation reef; by incoming of reddish brown mudstone and siltstone at the base of the overlying Edlington Formation. East of the Ford Formation reef-edge it is overlain by the Seaham Residue, (dissolution residue of Fordon Evaporite Formation) overlain offshore by the Fordon Evaporite Formation.
Roddlesworth Formation
RODD
Conglomerate or sandstone overlying an angular unconformity above Lower Palaeozoic purple slates, or conformably upon white, pink to red and green, fine- to medium-grained sandstone of the Old Red Sandstone Group.
Not proved at outcrop. Proved in the subsurface over the Central Lancashire High, a SW-NE structure extending from Chorley [SD 60 20] to Bradford [SE 10 30], bounded to the northwest by the Pendle Fault and the Bowland Basin, and to the southeast by the Rossendale Basin.
At the stratotype, the formation comprises in ascending order: a pale green, grey and red conglomerate with quartz pebbles in a medium-grained chloritic sandstone matrix; medium to dark grey dolomitic siltstone, with beds of white to buff fine-grained dolostone, anhydrite and red siltstone; pale grey, medium-grained sandstone with siliceous and dolomitic cement, interbedded with medium to dark grey, fine-grained sandstone with an argillacous and dolomitic matrix.
140m in the Roddlesworth borehole, and 28m in the Holme Chapel borehole.
The pale to dark grey, green or red, fine- to medium-grained sandstone with siliceous and dolomitic cement of the Roddlesworth Formation is overlain unconformably by dolostone or limestone of the Trawden Limestone Group. The top of the formation is taken at the base of the lowermost limestone or dolostone of the predominantly carbonate succession of the Trawden Limestone Group.
Rødby Formation
RODY
Rødby Formation lithology.
Roerwater Intrusion
ROER
Roe Valley Group
ROEV
The Roe Valley Group unconformably succeeds Dalradian rocks of both the Argyll and Southern Highland groups.
East side of the Dalradian Supergroup outcrop in the Sperrin Mountains and fringing the south side of Lough Foyle. Located west of the western edge of the basalt lavas of the Antrim Plateau.
Consisting of two formations (qv), the basal Spincha Burn Conglomerate Formation and the succeeding Barony Glen Formation.
In this sheet area the Roe Valley Group is overlain unconformably by a succession of rocks including the Triassic Sherwood Sandstone and Mercia Mudstone groups, the late Cretaceous Hibernian Greensands and Ulster White Limestone formations and the Palaeogene Lower Basalt Formation of the Antrim Lava Group.
Rousay Flags Member
ROF
Roach Formation And Fulletby Beds (Undifferentiated)
ROFU
Roaches Grit
ROG
The unit is poorly defined. In the field and in stratigraphic logs, the lower boundary is taken at the base of a sandstone-dominated succession overlying a mudstone interval of Millstone Grit Group that in turn overlies sandstones of either the Five Clouds Sandstone or the Corbar Grit, or mudstone of undifferentiated Millstone Grit Group.
Chinley, Derbyshire (SK 045 825) to Upper Hulme, Staffordshire (SK 01 61) to Rainow, Cheshire (SJ 95 76).
Medium-to coarse-grained or fine-grained, feldspathic, massive, rarely cross-bedded sandstone, with sole marks and load casts, and turbiditic mudstone. The sandstone is interpreted to have been deposited in a delta-top setting.
From 60 m to-375 m thick.
The upper boundary is taken at the base of a mudstone-dominated succession overlying the Roaches Grit, 10 m to 61 m below fissile black mudstone, that includes a Bilinguites superbilinguis Marine Band.
Rothley Grits
ROGT
Roach Formation
ROH
In northern Lincolnshire, near Brigg, oolitic and ferruginous mudstones, sandstones and limestones [Roach Formation]. In Southern Lincolnshire, the base is a minor erosion surface where the oolitic and pebbly mudstones and very fine sandstones [Roach Formation] rest on the smooth, fossiliferous clays [Upper Tealby Clay Member of the Tealby Formation]. In Norfolk the erosion surface separates the Roach Formation from underlying interbedded, fine-grained sands, ferruginous sandstones, silts and clays [Dersingham Formation].
In Norfolk the Roach is seen on the coast at Hunstanton and in boreholes, but it disappears farther south [it is not present in the Gayton Borehole]. It increases its thickness under The Wash and is again known from a number of boreholes in Lincolnshire and locally at outcrop, although it apparently disappears in northern Lincolnshire and is absent at Nettleton Bottom [TF 1257 9856] and Acre House [TF 1117 9701].
Sandy, bioturbated, oolitic-mudstones and very fine-grained, very clayey, bioturbated, partly oolitic sands. Calcite-cemented, oolitic ironstones occur locally. At Hunstanton, sandy, phosphatic ironstone nodule horizons contain shelly fossils. In Lincolnshire, the Formation has been divided informally into "Upper Roach" and "Lower Roach", separated by an indurated calcareously cemented, oolitic sandstone known as "Roach Stone". Boreholes at Hunstanton, Skegness and The Wash Borehole 72/78 show a rhythmic sequence of interburrowed and interbedded clay, "chamosite" mud, chamosite ooliths, quartz sand and small pebbles of quartz and ironstone. In northern Lincolnshire it comprises ferruginous, sandy limestone and ferruginous, oolitic quartz and ironstone. In northern Lincolnshire it comprises ferruginous, sandy limestone and ferruginous, oolitic mudstones.
Up to c. 22m
In Norfolk, the upper boundary is marked by an erosion surface seperating the very pebbly, oolitic clay at the base of the Carstone Formation, from the fine-grained clayey sand of the Roach Formation. Burrows extend down into the top c.30cm of the Roach Formation. Boreholes at Skegness and The Wash prove the junction between medium and dark grey mudstone with Prodeshayesites bodei and iridescent fragments of other ammonites [Skegness Clay] and the oolitic mudstones of the underlying Roach Formation. Farther north, pale grey, fossiliferous, calcareous mudstones [Sutterby Marl Formation] are separated from the oolitic mudstones of the Roach Formation by an erosion surface.
Rowhurst Coal (North Staffordshire)
ROHC
Ronas Hill Granite
ROHG
Rot Halite Member
ROHL
Rodhuish Limestone
ROL
Roddymoor Marine Band
ROMB
Ross Of Mull Pluton
ROMG
Ross Of Mull Pluton, Phase 1
ROMG1
Ross Of Mull Pluton, Phase 2
ROMG2
Ross Of Mull Pluton, Phase 3
ROMG3
Rosneath Conglomerate Formation
RON
Unconformable upon the Dalradian basement.
Rosneath Point to Helensburgh and Southern Loch Lomond, sheets 30W, 38W.
A conglomerate with clasts up to 40 cm in size of quartz, quartzite, metamorphic, igneous and volcanic rocks with minor sandstone and pebbly sandstone interbeds.
In excess of 1000 m thick.
Not exposed, presumed to pass upwards and laterally into the Stockiemuir Sandstone Formation.
Rona Formation
RONA
Rushindoo Oolite Member
ROOM
Not exposed but by analogy with its lateral equivalent the Gortnaree Sandstone Member, it succeeds conformably, and abruptly, the Termon River Limestone Formation.
Confined to the Kesh area of the northwest Carboniferous basin of Ireland.
Limestone, brown-grey, arenaceous biosparite, oolite, interbedded with calcareous, fine-grained, cross-bedded and parallel laminated feldspathic sandstone.
Maximum exposed is 3.5m
Not exposed but by analogy with its lateral equivalent, the Gortnaree Sandstone Member, it probably grades upwards gradually into argillaceous and bioclastic packstones of the normal Ballyshannon Limestone Formation.
Rora Tonalite
RORA
Rowhurst Rider Coal (North Staffordshire)
RORC
Rogart Pluton
RORT
Rogart Pluton, Phase 1
RORT1
Rogart Pluton, Phase 2
RORT2
Rogart Pluton, Phase 3
RORT3
Rodway Beds
ROS
Rottington Sandstone Member
ROSA
Rosebush Formation
ROSB
Roding Silt Member
ROSI
Rests on Kempton Park Gravel river terrace deposit and older bedrock strata.
Thames Valley, restricted to River Roding tributary valley from South Woodford, upstream to Passingford Bridge. May be present farther upstream but none mapped; lateral limits are limits of deposition.
Typically 2-3m
At surface, and may be overlain by alluvium.
Royal Sovereign Formation
ROSO
Ross Formation
ROSS
Rossendale Formation
ROSSE
The sharp conformable base of the formation is taken at the base of the dark grey, fissile mudstone of the Cancelloceras cancellatum Marine Band with eponymous fauna, where the formation overlies the Marsden Formation. It typically overlies quartz-feldspathic sandstone of the Huddersfield White Rock (Yorkshire), Holcombe Brook Grit (Lancashire), Chatsworth Grit (Derbyshire).
Central Pennine Basin from Lancashire and West Yorkshire, between Lancaster [SD 47 61] and Harrogate [SE 30 55], extending southward to north Staffordshire [SK06], the Askrigg Block [SE 10 80] and Stainmore Trough [SD 85 15] and locally on the north of the Isle of Man [NX 46 00].
A fine- to very coarse-grained and pebbly, feldspathic sandstone, interbedded with grey siltstone and mudstone, and subordinate marine black shales, thin coals and seatearths. Typically, the formation comprises a lower mudstone-dominated succession including two prominent marine shales, the Cancelloceras cancellatum and Cancelloceras cumbriense marine bands, and an upper sandstone-dominated succession, including the Rough Rock and Rough Rock Flags.
Rochdale (Rossendale) 130m thick; Bradford and north Derbyshire 75m; Stainmore Trough and Askrigg Block 45m; north Isle of Man 26m.
The sharp conformable base of the dark grey, fissile mudstone of the Subcrenatum Marine Band with eponymous fauna present at the base of the Pennine Coal Measures Group. Typically rests upon coarse- or very coarse-grained and pebbly sandstone of the Rough Rock.
Rottenhill Till Formation
ROTIL
In Kirkhill Quarry (infilled) the basal boundary of the unit is a sharp, planar, subhorizontal unconformity. The till rests on units from the Camphill Gelifluctate Bed, the Swineden Sand Bed, the Kirkhill Palaeosol Bed down to the Pitscow Sand and Gravel Formation. It is also seen to unconformably overlie unweathered felsite bedrock close to the margins of channels/basins. In Leys Quarry (disused) the till has been observed to have a sharp, planar, subhorizontal, unconformable basal boundary on the West Leys Sand and Gravel Formation and the Camphill Gelifluctate Bed.
Buchan, northeast Scotland. The formation is currently only known within the immediate vicinity of Kirkhill Quarry (infilled) (centred on NK 0120 5285) and Leys Quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon). The unit might be regionally significant and present locally across northeast Scotland.
Diamicton, dominantly yellowish brown, very stiff non-calcareous, matrix supported, gravelly, slightly clayey, silty sand. Clast types include pebbles and cobbles of quartzitic and psammitic and pelitic metasedimentary rocks, phylite/slate, felsite, grey and red granites,mafic igneous rocks, red sandstone and red-stained quartzite. Clast fabric indicates glacial transport from the northwest. In the northwest and northeast faces of Leys Quarry (disused) thin beds of deformed and attenuated silty fine to medium sand are present. Interpreted as a subglacial till.
In Kirkhill Quarry (infilled) the upper boundary of the unit is a sharp, planar, subhorizontal, unconformity overlain by gravelly, sandy, silty diamicton of the Corsend Gelifluctate Bed. The uppermost part has undergone pedogenesis to form the Fernieslack Palaeosol Bed. In Leys Quarry (disused) the upper boundary of the unit is a sharp, undulatory, unconformity overlain by the Corse Diamicton Formation/Hythie Till Formation.
Roughband Limestone
ROUL
Ron Volcanics Member
ROVL
Rowe Chalk Formation
ROWE
Basal flint band of thick unit of flint-bearing chalk above thick flint-free unit of Flamborough Formation; recognised on the basis of downhole geophysical logs.
Southern North Sea region; onshore, present only in eastern Holderness, Yorkshire (from approximately Barmston near Bridlington, to Withernsea; see Sumbler, M G, 1999, Fig.1), where it is entirely concealed beneath thick superficial deposits.
White, flint-bearing chalk with sporadic marl bands.
About 80m preserved onshore; up to c.380m offshore.
Upper limit of Chalk Group onshore, where unconformably overlain by Quaternary deposits; offshore succeeded by clastic Palaeogene deposits or by the Ekofisk Formation, resedimented chalks of Palaeocene age (Lott, G K and Knox, R W O'B, 1994).
Rowlington Coal (Northumberland)
ROWL
Roxby Formation
ROX
Diachronous; taken at top of highest anhydrite (Littlebeck Anhydrite) in subsurface, and at top of Brotherton Formation at outcrop.
Eastern England; dies out in south Nottinghamshire.
Mudstone and siltstone, reddish brown, with subordinate sandstone. Sulphates (gypsum, anhydrite) common towards base.
0-130m (129m in Staithes S20 borehole - Smith et al, 1986).
Conformable; taken at gradational and diachronous transition into sandstones of Sherwood Sandstone Group.
Royston Coal (West Yorkshire)
ROYC
Randy Pike Member
RPE
Rushy Park Coal (South Lancashire)
RPKC
Rottingdean Pair Marls (One)
RPMA1
Rottingdean Pair Marls (Two)
RPMA2
Roffey Park Sandstone
RPS
Rhayader Mudstones [Duplicate Code: Use Rhs]
RPSL
Rough Rock
The base of the Rough Rock is sharp and erosional, in part undertlain by mudstones with the Gastrioceras cumbriense Marine Band; locally present are fine-grained sandstones (Rough Rock Flags, Upper Haslingden Flags).
Central Pennines.
Coarse-grained feldspathic sandstone, cross-bedded.
To about 30m
The sandstone of the Rough Rock is commonly overlain sharply by a seatearth clay (Pot Clay), thin coal (Pot Clay Coal) and dark grey mudstones with the Gastrioceras subcrenatum Marine Band.
Rora Mudstone Formation
RRAM
The lower boundary is not seen. May possibly overlie the Tavy Formation but further investigation is needed.
Liverton area (SX79 75), south Devon.
Purple, green and greyish green mudstones. Scattered siliceous and calcareous nodules developed at some levels. A prominent 10m-thick unit of buff-weathering calcareous laminated siltstone capped by 2m of interbedded grey silty mudstones and siliceous black mudstones is present at the top of the Formation.
Uncertain, but probably not more than 200m exposed.
The upper boundary is taken at the sharp incoming of the black mudstones of the "Ararat Slate" (Teign Chert Formation) above the buff-weathering calcareous laminated siltstones capped by 2m of interbedded grey silty mudstones and siliceous black mudstones at the top of the underlying Rora Mudstone Formation.
Ruler Coal (Northumberland And Durham)
RRCO
Roch Volcanic Formation
RRH
Fine-grained, highly silicified, pale greenish - blue rhyolites weathering white; thin bands of blue - green and pale mauve banded flinty tuffs with interbedded sediments.
At least 180m
Not seen, but generally faulted.
Rowley Regis Lopolith
RRLO
Rorrington Shale Formation
RRR
Overlies Meadowtown Formation.
Grey shaly mudstone.
Underlies Spy Wood Sandstone Formation.
Rough Rock Shales
RRS
Ragman And Rough Seven Feet Coal (North Staffordshire)
RRSFC
Rorrington Shale Formation And Spy Wood Sandstone Formation (Undifferentiated)
RRSW
Rushton Schist
Unknown - base not seen.
The Welsh Borderlands, in Shropshire, and the Wrekin area.
Quartz-feldspar-garnet-mica schists.
Unconformably overlain by younger strata of various ages.
Sussex Rother Terrace Deposits, 1 Member
RS1
Chichester and Bognor district.
Sand, sandy gravel and gravel, locally clayey. Gravel is predominantly subangular flint with subordinate debris of chert, polished quartz grain and larger fragments of pebbly ferruginous sandstones derived from Lower Cretaceous sequences to the north.
Generally up to 4m thick, locally up to 10m.
Sussex Rother Terrace Deposits, Facet 1a
RS1A
Sand and sandy gravel, locally clayey. Gravel component is predominantly subangular flint with subordinate debris of chert, polished quartz grains, and larger fragments of pebbly ferruginous sandstone derived from Lower Cretaceous sequences to the north.
Sussex Rother Terrace Deposits, Facet 1b
RS1B
Sussex Rother Terrace Deposits, 2 Member
RS2
Devensian: IOS 2-4.
Sussex Rother Terrace Deposits, 3 Member
RS3
Wolstonian: OIS 6-8.
Sussex Rother Terrace Deposits, Facet 3a
RS3A
Sussex Rother Terrace Deposits, Facet 3b
RS3B
Chichester and Bognor region.
Sussex Rother Terrace Deposits, 4 Member
RS4
Anglian: IOS 12
Sussex Rother Terrace Deposits, 5 Member
RS5
Anglian or older Pleistocene: IOS 12-14?
Rossall Halite Member
RSA
Conformable, at the gradational upward transition from laminated reddish brown and greenish grey mudstones (Sidmouth Mudstone Formation, undifferentiated) to the halite-rich, reddish-brown mudstones of the Rossall Halite Member.
Mudstone, reddish brown, with abundant halite veins and nodules, and common mudstone breccias.
Originally referred to simply as the Rossall Salts, the term was given Formation status by Warrington et al. (1980), and is now retained as a local member within the nationally recognized Sidmouth Mudstone Formation (Howard et al., 2008).
0 to 12m (Wilson and Evans, 1990)
Conformable, at the gradational upward transition from the halite-rich mudstones of the Rossall Halite Member to structureless reddish brown mudstones (Sidmouth Mudstone Formation, undifferentiated).
Rhiwlas Beds
RSB
Raised Storm Beach Deposits, 1
RSB1
Gravel and rarely sand; commonly with a bank-like form; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; older than 'Raised Storm Beach Deposits' in the same map area. [Generic description].
Raised Storm Beach Deposits, 2
RSB2
Gravel and rarely sand; commonly with bank-like form; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; older than 'Raised Storm Beach Deposits' and 'Raised Storm Beach Deposits 1' in the same map area. [Generic description].
Raised Storm Beach Deposits
RSBD
Gravel and rarely sand; commonly with bank-like form; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Rookhope Shell-Beds Limestone
RSBL
Raised Storm Beach Deposits, Older
RSBO
Gravel and rarely sand; commonly with bank-like form; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; older than 'Raised Storm Beach Deposits' in the same map area. [Generic description].
Raised Storm Beach Deposits, Late Devensian
RSBQD
Generally an uncomformable contact with till or bedrock.
Gravel, sandy, silty, partly clast-supported, poorly sorted, mainly of cobble to boulder grade with subsidiary beds of finer gravel and sand.
Raised Storm Beach Deposits Of Flandrian (Holocene) Age
RSBQF
Generally an unconformable contact with till or bedrock.
Gravel, clast-supported, openwork, well sorted, mainly of cobble to boulder grade with subsidiary beds of finer gravel and sand.
Raised Storm Beach Deposits, Younger
RSBY
Gravel and rarely sand; commonly with bank-like form; now above the level of the present shoreline as a result of earth movement or a general fall in sea level; younger than 'Raised Storm Beach Deposits' in the same map area. [Generic description].
Riddle Scout Rock
RSC
Raebeg Sandstone Formation And Conglass Sandstone Formation (Undifferentiated)
RSCS
Rusland Member
RSD
Incoming of sandstone into the Bannisdale sequence. Interdigitates with siltstones.
Southern Lake District.
Sandstone beds to 75cm thick within siltstone and mudstone sequence of the Bannisdale Formation.
Transitional into Bannisdale Formation, siltstone and mudstone.
Roof Soft + Deep Soft Coals (Nottingham)
RSDS
Raveagh Sandstone Formation
RSF
Supposedly diachronous with and transitional from conglomerates and sandstones of underlying/contemporaneous Gortfinbar Conglomerate Formation.
Interbedded sandstones, siltstones and mudstones with thin conglomerates.
Not exposed; probably faulted; also probably an unconformity as rocks are unconformably overlain by basal Carboniferous (inter alia) Ballyness Formation
Rough Seven-Feet Coal (North Staffordshire)
RSFC
Red Scar Grit
RSG
Overlies interbedded shaly mudstones and sandstones above the Cockhill Limestone.
Coarse-grained feldspathic sandstone ["grit"], usually coloured red on weathered surfaces.
Overlain by the Colsterdale Marine Band.
Raeburn Shale
RSH
Red Shagg Coal (North Staffordshire)
RSHC
Rodway Siltstone Formation
RSI
At the type locality the base of the formation is faulted against mid to pale grey oolitic limestone of the Pembroke Limestone Group. A non-tectonized base of the Formation has not been recorded at crop or in boreholes, suggesting that the formation was displaced to its current location above a low-angle lag fault, (Whittaker, 1975).
The outcrop is restricted to the Rodway Inlier [ST 244 398] and Swang Farm Inlier [ST 231 392], located northwest of Cannington, Somerset. The Formation is also proved in boreholes to occur beneath the Sherwood Sandstone and Mercia Mudstone groups within the vicinity of the inliers.
Dark grey, locally red, purple and green stained, micaceous siltstone with subordinate thin beds of pale grey or purple-stained, fine- to medium-grained, locally bioturbated sandstone. Near the base there are small-scale rhythmic cycles of sandstone, siltstone and black shale.
More than 138m, with 138m exposed (top not seen) at the type locality.
The grey siltstones of the Rodway Silstone Formation are overlain unconformably by red, yellow and buff mottled, fine- to medium-grained sandstone of the Otter Sandstone Formation (Sherwood Sandstone Group).
Redside Vent
RSIDE
Rilbury Siltstone Member
RSM
Riddings Marine Band
RSMB
Rosthwaite Rhyolite Member
RSR
Taken at the base of the rhyolite or its autobreccia overlying volcaniclastic rocks of the main part of the Lingmell Formation.
Rosthwaite Fell, Borrowdale, Cumbria. The rhyolite has an outcrop length of 1.9km from NY 2518 0644 to NY 2708 1152.
Pinkish weathered, crystal-poor, flow-banded, flow-folded rhyolite with autobreccia at its base and top. It is interpreted as a coulee-type lava and is connected to an underlying intrusion.
Up to 130m
Defined by the base of overlying volcaniclastic rocks; in the west of the outcrop by pyroclastic rocks of the Lingmell Formation, but in the central and eastern parts of the outcrop by volcaniclastic sedimentary rocks of the Seathwaite Fell Sandstone Formation.
Ross Sand Member
RSSA
Uncomformity on bedrock or more commonly on older Quaternary strata, particularly the Wilderness Till Formation of the Midland Valley Glacigenic Subgroup. Conformably with the Bellshill Clay Member.
Central Scotland; Glasgow area in the lower Clyde valley below Lanark and in tributary valleys.
The lithological association consists of flat and ripple-laminated medium- to fine-grained sand with laminae and thin bands of silt. It is moderately dense. Sedimentary structures were formerly visible at Ferniegair Gravel Pit [NS 734 543] and at Bothwell [NS 708 589]. At Ferniegair the dominant structures were large-scale trough cross-bedding in sands and gravelly sands and horizontal bedding in finer sands. At Bothwell, the sedimentary structures were largely horizontal lamination and ripple lamination. The climbing ripples preserved rose southwards (sediment transport up the Clyde valley). Thin beds of reddish brown silty clay were also present. The sedimentological features of the Member are consistent with deposition by glaciodeltaic processes. At Ferniegair, the Avon was probably building a lateral delta into the ice-dammed "Lake Clydesdale". It also seems likely that the Bothwell deposit was deltaic, with the interfingering bands of laminated clay passing laterally southwards into the Bellshill Clay Member.
The Ross Sand Member is named from the Ross House Borehole (Browne and McMillan. 1989a, Figure 21), the standard section being that between 17.2 and 19.53m depth. However, the deposit elsewhere exceeds 20m. Generalized stratigraphical relationships and geographical distribution are shown in ibid (Figures 2b, 3D and 4A).
Veneer to about 20m.
Unconformity below younger Quaternary strata such as the Clyde Clay Formation but also exposed at the surface. Locally passes conformably laterally and upwards with the Bellshill Clay Member.
Rothersyke Till Member
RSTI
Unconformable on older-Quaternary deposits and its base is commonly repeated by small-scale thrusting. At its type section and other sites within the buried valleys of the Ehen, Calder and Lower Uldale, the Rothersyke Till Member overlies the Ehen Valley Sand and Gravel Member of the Seascale Glacigenic Formation.
Gravelly sandy clay diamicton, compact and massive, matrix-supported, generally reddish brown. The diamicton contains well dispersed angular to well rounded clasts of red sandstone, Borrowdale Volcanic Group rocks, Skiddaw Group slates, limestone and yellow and white Coal Measure sandstones, coal, granophyre, granodiorite (?Criffel) and greywacke sandstone. The member also contains "rip-up" clasts of underlying deposits and its composition can vary considerably locally (being largely determined by the nature of the underlying sequences from which it is mainly derived).
Typically 1.0 to 2.0m
Commonly the ground surface, but at its Type Section the Member is overlain by the Low Mill Gravel Member of the Gosforth Glacigenic Formation, and at other localities, by the Peel Place Sand and Gravel Member of the Gosforth Glacigenic Formation or by Holocene deposits such as peat and alluvium. At its Reference Section the upper surface of the till (the ground surface) displays a polygonal pattern of thermal contraction cracks (relict tundra patterned ground). In the coastal area north of Sellafield, the gravelly reddish brown Rothersyke Till Member is overlain (or is cut out by) the sandy and clayey How Man Till Member of the Gosforth Glacigenic Formation.
Reservoir Formation
RSVR
Mudstones and shales interbedded with siltstones and fine-grained sandstones.
At least 1080m in North Esk Inlier. c.800m exposed in Bavelaw Castle Inlier.
Conformable below Deerhope Formation: at top of highest sandy siltstone bed showing internal structures typical of Bouma sequence.
Sussex Rother Formation
RSX
Sands, sandy gravels, gravels, some being clayey. The gravel component is predominantly subangular flint with subordinate debris of chert, polished quartz grains and larger fragments of pebbly ferruginous sandstone derived from the Lower Cretaceous sequences to the north. Subrounded flint nodules are also present in places. Locally clayey and sandy silt and silty clay mask the sands and gravels, perhaps indicating preservation of overbank or aeolian deposits at the top of the fluvial cycle.
Each terrace averages 4m thick, reaching to 8 to 10m in places.
At surface or locally overlain by younger deposits including head and alluvium.
Rosy Coal (South Wales)
RSYC
Ragleth Tuff Formation
Late Neoproterozoic
Welsh Borderlands, Shropshire, Church Stretton area.
Pink, brown, purple and green, tuffaceous mudstones, siltstones and sandstones, with beds of fine-grained lithic felsic tuff.
More than 450m
Uncertain. Considered by Greig et al (1968) to be an unconformity, but Cobbold and Whittard (1935) and Pauley (1991) suggested a conformable contact with the Helmeth Grits, based on lithological similarities with the latter.
River Terrace Deposits, 11
RT11
River Terrace Deposits, 11a
RT11A
River Terrace Deposits, 11b
RT11B
River Terrace Deposits, 12
RT12
River Terrace Deposits, 12a
RT12A
River Terrace Deposits, 12b
RT12B
River Terrace Deposits, 13
RT13
River Terrace Deposits, 14
RT14
River Terrace Deposits, 15
RT15
River Terrace Deposits, 16
RT16
River Terrace Deposits
RTD
River Terrace Deposits, 1
RTD1
River Terrace Deposits, 1a
RTD1A
River Terrace Deposits, 1b
RTD1B
River Terrace Deposits, 1c
RTD1C
River Terrace Deposits, 2
RTD2
River Terrace Deposits, 2a
RTD2A
River Terrace Deposits, 2b
RTD2B
River Terrace Deposits, 3
RTD3
River Terrace Deposits, 3a
RTD3A
River Terrace Deposits, 3b
RTD3B
River Terrace Deposits, 4
RTD4
River Terrace Deposits, 4a
RTD4A
River Terrace Deposits, 4b
RTD4B
River Terrace Deposits, 5
RTD5
River Terrace Deposits, 5a
RTD5A
River Terrace Deposits, 5b
RTD5B
River Terrace Deposits, 5c
RTD5C
River Terrace Deposits, 6
RTD6
River Terrace Deposits, 6a
RTD6A
River Terrace Deposits, 6b
RTD6B
River Terrace Deposits, 7
RTD7
River Terrace Deposits, 8
RTD8
River Terrace Deposits, 9
RTD9
River Terrace Deposits (Undifferentiated)
RTDU
River Terrace Deposits, 10
RTDX
River Terrace, Erosional, 1
RTE1
Commonly misinterpreted on topographical grounds as depositional terraces, these erosional features may be cut into any superficial deposit or bedrock lithology. Examples such as those in the lower Wharfe valley between Ilkley and Wetherby are cut into Pleistocene glacial deposits comprising alternations of flow and/or meltout till (diamicton) and sand and gravel, overlying lodgement till (diamicton).
Retford Member
RTF
Slightly unconformable, at an abrupt upward change from red-brown pebbly sandstones of the Sherwood Sandstone Group to the greenish grey mudstones at the base of the Retford Member. In north Nottinghamshire, the Retford Member is separated from the Sherwood Sandstone Group by a tongue of reddish brown mudstone and siltstone that thickens towards the northeast.
Mapped at outcrop in central and north Nottinghamshire, and proved in boreholes in the adjacent subcrop to the east.
Mudstone and siltstone, greenish grey, intercalated with subordinate reddish-brown mudstone; thin beds of varicoloured fine- to medium-grained sandstone, laminated and micaceous, are common throughout. Veins and nodules of gypsum are common locally. A thin calcareous conglomerate occurs locally at the base.
Maximum 21m in northeast Nottinghamshire, thinning to 6m south of Ollerton, pinches out at the northern outskirts of Nottingham.
Conformable, within a gradational, upward transition from greenish-grey mudstones and siltstones of the Retford Member to the predominantly brown mudstones, siltstones and fine-grained micaceous sandstones of the overlying undifferentiated Tarporley Siltstone Formation.
Raised Tidal Flat Deposits
RTFD
Normally a consolidated soft silty clay, with layers of sand, gravel and peat. Characteristically low relief; from the tidal zone, but now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Raised Tidal Flat Deposits, Late Devensian
RTFDD
Sharp, unconformable, generally planar contact on various older superficial deposits, most commonly till.
Britain to the north of the Humber-Ribble.
Silt, clay and fine-grained sand with lenses of gravel.
Raised Tidal Flat Deposits Of Flandrian Age
RTFDF
Raised Tidal Flat Deposits Of Flandrian Age, 1
RTFF1
Sharp unconformable, generally planar boundary with older superficial deposits, commonly till. Locally, rests unconformably on clast-supported gravel of raised beaches.
Cumbria.
Pale yellowish brown sandy clayey silt (loam) or grey sandy clay, locally with lenses of gravel, peat and disseminated organic material.
Ground surface or gradational undulating boundary with younger superficial deposits such as peat and blown sand. Locally,a sharp unconformable contact with clast-supported gravel of raised beaches.
Raised Tidal Flat Deposits Of Flandrian Age, 2
RTFF2
Sharp, unconformable, generally planar boundary with older superficial deposits, commonly till. Locally, rests unconformably on clast-supported gravel of raised beaches.
Ground surface or gradational, undulating boundary with younger superficial deposits such as peat and blown sand. Locally, a sharp unconformable contact with clast-supported gravel of raised beaches.
River Terrace Loam
RTL
Silty clay; usually overlies 'River Terrace Deposits'. [Generic description: 1:50 k map margins].
Rattler Coal (Cumbria)
RTLR
Rotton Marl Formation
RTM
Roedean Triple Marls (One)
RTMA1
Roedean Triple Marls (Two)
RTMA2
Roedean Triple Marls (Three)
RTMA3
Rottal Schist Formation
RTS
River Terrace Sand And Gravel
RTSG
Sand and gravel. [Generic description].
Roter Salzton Formation
RTSZ
Rumbles Coal (Lothian)
Rubble Coal (South Staffordshire)
RUBC
Rubha Ruadh Granite
RUBR
One sample has been dated at 1854 +/- 13 Ma (Friend and Kinny, 2001).
The Rubha Ruadh Granite is intrusive into the Inchard Gneiss.
The granite and pegmatitic granite sheets of the Rubha Ruadh Granite Suite occur within the Lewisian Gneiss Complex in Sutherland. They are especially abundant in a 2km-wide WNW-ESE trending zone near the Laxford River, stretching from Rubha Ruadh in the WNW, to Loch Stack in the ESE. Further, smaller intrusions occur north of the Laxford River; e.g. near Rhiconich and Kinlochbervie. A body of Rubha Ruadh granite also occurs in the Moine Thrust Zone, south of Achfary. The suite occurs on Sheets 113 (Cape Wrath), 107E (Loch Glencoul), 108W (Ben Hee) and the Assynt Special Sheet.
Comprises granite, which is commonly foliated; granite gneiss and pegmatitic veins and pods. The granite is generally pink, coarse-grained and fairly homogenous, consisting of K-feldspar, plagioclase (oligoclase), quartz, minor biotite and accessory titanite and epidote. Intrusions belonging to this suite occur as WNW-ESE sheets in a zone along the Laxford Front, and have been variably deformed during the Laxfordian event at about 1750 Ma.
From 1m to about 200m
Rumer Coal (South Staffordshire)
RUCO
Runton Cliffs Sand And Gravel Member
RUCSG
The Runton Cliffs Sand and Gravel Member rests upon the upper surface of the Bacton Green Till Member. The contact is abrupt and scoured and marked by a lithological change from till to sand and gravel. An additional geometric complexity is that the deposit has been loaded (gravitationally) into the Bacton Green Till Member.
Coastal sections between East Runton and Sheringham.
The Runton Cliffs Sand and Gravel Member is composed of planar cross-bedded, rippled, channelised and horizontally-bedded yellow to olive brown sands with sporadic beds of massive or cross-bedded gravel. The flint gravel content (c.82%) is low compared to other outwash lithofacies in north Norfolk, but it contains a high content (c.3-4%) of far travelled erratics including Carboniferous limestone, micaceous schist, quartz-schist, granodiorite, felsic porphyry and andesite.
The upper boundary of the deposit is truncated by the ground surface.
Rudge Coal (Somerset)
RUDC
Rubh' An Dunain Formation
RUDUN
Ruperra Limestone
RUL
Rum Subswarm
RUM
Rum Central Complex
RUMC
Rum Layered Suite
RUML
Northern Marginal Zone (Rum Central Complex)
RUNM
Northern Marginal Zone, Am Mam Breccias (Rum Central Complex)
RUNMA
Ruadh-Phort Beag Member
RUPB
Roxham Member And Runcton Member (Undifferentiated)
RURO
Rushall Formation
RUS
Southern Mountain Zone (Rum Central Complex)
RUSM
Runton Till Member
RUTI
The Runton Till Member rests unconformably upon preglacial marine deposits of the Wroxham Crag Formation. The boundary is sharp and planar and in places resembles a surface of decollement. The boundary is represented by a lithological change from sands and gravels to diamicton.
The Runton Till Member crops out between East Runton and Sheringham on the north Norfolk coast.
The Runton Till Member consists of a dark grey to greyish brown matrix-supported diamicton that contains highly attenuated lenses and laminations of sand, chalk and reworked inclusions of older and more chalky till (Walcott Till Member).
Up to 9m at stratotype locality.
The Runton Till Member exhibits a gradational upper boundary with the Bacton Green Till, with a transition from massive, highly consolidated diamicton, to stratified diamicton.
Ruthven Semipelite Formation
RUVN
Marked lithological contact with underlying arkosic psammites of the Glenshirra Subgroup, commonly attenuated locally, possibly unconformable.
Strath Nairn and north-western part of Monadhliath Mountains, Central Highlands, 1:50 K sheets 73E and 74W.
Coarsely foliated, migmatic semipelite and pelite with subordinate striped psammites with bands of calcsilicate rock. Minor amphibolite pods and lenses.
In excess of 200 m - difficult to estimate due to complex fold patterns.
Poorly exposed, incoming of well-bedded psammites [turbiditic] of the Loch Laggan Psammite Formation.
Roineval Formation
RVAL
Raventhorpe Beds
RVB
Quasi-conformable or more or less disconformable contact between sandstone and mudstone of the underlying Grantham Formation or, where the latter is absent, ferruginous sandstone of the Northampton Sand Formation, or mudstone of Lias Group and the overlying interbedded limestone, calcareous mudstone and calcareous siltstone of the Raventhorpe Beds.
BGS 1:50 000 sheets 72, 80, 89, and possibly 102; North Lincolnshire to Market Weighton.
Limestone, predominantly calcilutitic and more or less argillaceous, interbedded with calcareous mudstone and calcareous siltstone.
[Compiler's notes] This entry defines the unit thus called on sheets 72, 80 and 89. However it should not be perpetuated in any formal lithostratigraphical review of the Lincolnshire Limestone. Whilst it may remain a valid stratigraphical unit, the Member status is inappropriate. Following stratigraphical revision of the Lincolnshire Limestone Formation, it forms part of the Lower Lincolnshire Limestone Member which (with Upper Lincolnshire Limestone) is one of the two constituent members of the Formation. Because of this mis-use of the member status I have indicated the "parent" unit to be Lincolnshire Limestone Formation, though as an informal unit it should be Lower Lincolnshire Limestone Member [agreed - AJMB].The Member suffix should be dropped, and the name revert to the informal Raventhorpe Beds. However, the Raventhorpe Beds/Member sensu Gaunt et al., incorporates the Cleatham and Ellerker limestones, which together more or less equate with the Hydraulic Limestones of previous authors which were excluded from the Raventhorpe Beds. Hence there is scope for confusion over the use of the name. I haven?t really seen enough of this unit to judge whether or not it is a useful entity. I have only seen it at Manton where the top is fairly obvious because of the development of "Santon Oolite". It is not clear to me how one would differentiate this unit from the overlying Kirton Cementstones in the absence of a mudstone at the base of the latter. Southern limits and correlation are also somewhat uncertain. [M G Sumbler 25/09/05]
Conformable contact between interbedded limestone, calcareous mudstone and calcareous siltstone of the Raventhorpe Beds and the mudstone-rich succession of the overlying Kirton Cementstone Beds or with peloidal and ooidal limestone of the Santon Oolite (where present).
Ronas Voe Breccias
RVBR
Ravenscraig Sandstone
RVC
Rock Vein Coal (Pembrokeshire)
RVCO
Reservoir Formation [Obsolete Code: See Rsvr]
RVF
Rivelin Grit
RVG
Ravenstonedale Group And Great Scar Limestone Group (Undifferentiated)
RVGS
Raventhorpe Beds And Kirton Cementstone Beds (Undifferentiated)
RVKC
Ravelston Sandstone
RVN
Only known for certain in Edinburgh area.
A brown or locally black, often thickly bedded with trough cross bedding, typically fine-grained, siliceous, sandstone, containing little mica or carbonaceous material, and famous building stone.
Up to 40 m thick in the City of Edinburgh.
Transitional by upward fining into mainly non-marine siltstone and mudstone of the Gullane Formation.
Reservoir Quartzite Member
RVQU
Ravenfield Rock
RVR
Sharp upward change in a conformable succession from predominantly grey mudstone to sandstone - base of first sandstone above the fine- to medium-grained Wickersley Rock.
Eastnortheast of Rotherham, around the village of Ravenfield [SK4850 9515], South Yorkshire.
A medium to thickly bedded, grey, fine- to medium-grained, ripple cross-laminated, yellowish brown sandstone, with some red staining and iron-rich concretions.
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of the last sandstone bed below the Permian unconformity, marked by the occurrence of the Yellow Sands Formation (formerly Basal Permian Sand).
Ravenstonedale Group
RVS
Within the Stainmore Trough the unit is Tournaisian in age whereas on the northern margin of the Askrigg Block it is Chadian to early Holkerian.
Drawn at the base of the Pinskey Gill Formation (formerly Pinskey Gill Beds) where it rests unconformably upon the Silurian Bannisdale Slates.
Ravenstonedale, near Brough, Cumbria.
Limestones and oolites with some sandstones and shales.
Maximum of about 380m in the Stainmore Trough.
Drawn at the conformable upward passage from the Coldbeck Limestone Formation to the Scandal Beck Limestone Formation of the Orton Group.
Ravenglass Till Member
RVTI
Not seen in sections, but probably mainly a sharp, irregular, unconformable contact with bedrock. Locally a sharp, unconformable contact with a sequence of reddish or yellowish brown sand, silt and clay of the Barn Scar Sand and Silt Member of the Seascale Glacigenic Formation.
The coast to the west of the Lake District inland of the limit of the "Gosforth Oscillation" between Cleator and Ravenglass.
Moderate brown sandy silty gravelly diamicton, very compact, matrix-supported, generally massive, containing moderately well dispersed, subangular to subrounded clasts of granophyre, granite, Borrowdale Volcanic Group rocks (rhyolite, welded tuff, slate), with some red sandstone, ironstone and shell fragments.
Sharp, undulating, unconformable contact with overlying sand and gravel deposits or till units of the Gosforth Glacigenic Formation.
Raised Warp
Artificially induced alluvium at a raised level. [Generic description: 'TMOS' Procedures].
Ringstead Clay Member
RWC
A sharp, non-sequential boundary, marked by the upward change from ferruginous, bioturbated sandstone or sandy mudstone of the underlying Sandsfoot Grit, or ferruginous oolite of the Westbury Ironstone Member (Wilts), to grey, calcareous mudstone.
Dorset: Weymouth to Abbotsbury, Mappowder to Bourton. Wiltshire: Westbury and Steeple Ashton; northeast limit uncertain. NB: Because of poor exposure and landslipping, the Ringstead Clay Member has been included in the mapped outcrop of the Kimmeridge Clay Formation in Dorset.
Pale to dark grey mudstone, variably calcareous, with locally numerous, fine calcareous laminae. The upper part of the member is reddish silty mudstone with siltstone lenses and is characterised by red-weathering, lens-shaped sideritic concretions. Poorly fossiliferous, with echinoids, bivalves and rare ammonites.
Dorset coast: 3.5-5m at outcrop, up to 18m in boreholes at Kimmeridge. Inland Dorset: up to 9m. Westbury, Wilts: 6.3m.
Either: Sharp change up from reddish mudstone with siderite nodules of Ringstead Clay into shelly, ferru-ooidal calcareous mudstone or limestone (Osmington Mills Ironstone Member, including Ringstead Coral Bed), or: Non sequence; overlain by dark grey mudstone (Kimmeridge Clay Formation), with basal bed of very dark grey shelly bioturbated mudstone with ferruginous ooids and phosphatic pebbles (Inconstans Bed).
Western Granite (Rum Central Complex)
RWG
Western Granite, Fine-Grained Phase (Rum Central Complex)
RWG1
Western Granite, Medium-Grained Phase (Rum Central Complex)
RWG2
Rhiwlas Limestone Member
RWL
Locally unconformable on various Caradoc strata.
Data not available.
Impersistent, locally honeycombed, fine-grained, pale grey, muddy bioclastic limestone with mudstone partings.
Conformable upward passage into the mudstones of the main part of the Moelfryn Mudstone Formation.
Rawns Member
RWN
?Conformable on rocks of the Trentishoe Member (q.v.).
Coarse-grained, pebbly sandstone with angular exotic clasts; the uppermost 22m are mainly fine-grained and lacking in exotic materials.
148m (Tunbridge, 1978).
Abrupt boundary with overlying transgressive grey mudstones of the Sherrycombe Member (q.v.).
Rawney Limestone
RWNL
Locally developed in the Bewcastle district.
Dominantly cementstone and shaly limestone.
Robeston Wathen Limestone And Sholeshook Limestone (Undifferentiated)
RWSL
Rowantreethwaite Tuff Member
RWT
Taken at the abrupt change from bedded volcaniclastic sandstone to bedded pyroclastic rocks.
Southeast of Haweswater Reservoir, Cumbria, between Rowantreethwaite Beck and Woof Crag.
A well-bedded dacitic tuff and lapilli-tuff, with some pyroclastic breccia and accretionary lapilli-tuff, more thinly-bedded, finer grained and better sorted upwards, with abrupt intra-bed changes in grain size common.
Intruded by andesite sills at the base of the overlying Mardale Formation.
Rhiw Volcanic Group
RWV
Drawn at the base of the metasomatised tuff/manganese ore where it rests upon possibly dolerite, but the underlying rocks are not seen.
Around Rhiw, near Porth Neigwl, Lleyn Peninsula, Caernarvonshire.
Rhyolitic lavas and tuffs, spilitic and basic lavas, and manganese ash occuring within the hirundo and bifidus zones.
Drawn at the conformable upward passage of the Rhiw Volcanic Group into the overlying Tal-y-fan argillites.
Roxham Sand Member
RXB
A down-section change from sands, with a pebbly base, to mudstones (Kimmeridge Clay Formation). An erosion surface separates the two units.
The member crops out between the banks of the Babingley River, southwards to near Southery, where it disappears beneath the Methwold Fens. It has been penetrated by a number of boreholes at Hunstanton, North Wootton, Gayton, Mundford and Little Ouse. The member extends under The Wash and has been recognised in borehole 72/77B, but passes laterally into the lower pat of the Spilsby Sandstone Formation.
Grey and yellow-green, pyritic, silty sands with an indurated basal pebbly sandstone with black chert phosphatic nodules and derived Kimmeridgian debris. Bioturbation and burrows occur in the unit and may extend down into the top of the underlying Kimmeridge Clay.
Up to 6m.
Green, glauconitic, clayey sands with abundant phosphatic nodules (Runcton Sand Member) overlies grey and yellow-green, pyritic, silty sands (Roxham Sand Member).
Ruabon Yard Coal (North Wales)
RYC
Rotherby Member
RYCL
Ryder Coal
RYD
Ryder Coal (Warwickshire)
RYDC
Rushy Knowe Limestone
RYKN
Ryhope Little Coal (Northumberland)
RYL
Rothesay Limestone
RYLS
Rynelrich Limestone Member
RYNL
Rynaballoch Psammite Member
RYNP
Royley Sandstone
RYSA
Sharp upward change in a conformable succession from predominately grey mudstone/siltstone to sandstone - base of first sandstone above the Arley Coal.
Between Royton [SD 9150 0750] and Lees [SD 9550 0450] near Oldham, Lancashire.
A medium-bedded, very fine- to mediium-grained, trough cross-bedded and part ripple cross-laminated, micaceous, buff to pale brown sandstone.
Sharp upward change in a conformable succession from sandstone to predominantly grey mudstone - top of last sandstone bed below the New Coal (South Lancashire).
Ryazanian And Valanginian Rocks (Undifferentiated)
RYVA
Rozel Conglomerate
RZCG
Palaeozoic Rocks (Undifferentiated)
RZRU
Swansea Two Feet Coal (South Wales)
S2FC
Swansea Three Feet Coal (South Wales)
S3FC
Swansea Four Feet Coal (South Wales)
S4FC
Skelmersdale Four Foot Coal (South Lancashire)
S4FT
Swansea Five Feet Coal (South Wales)
S5FC
Skelmersdale Five Foot Coal (South Lancashire)
S5FT
Swansea Six Feet Coal (South Wales)
S6FC
Skelmersdale Seven Foot Coal (South Lancashire)
S7FT
St Agnes Formation
?Oligocene.
Sandgate Formation
SAB
At base of Easebourne Member, Fittleworth Member or Rogate Member, where present. Otherwise, base of condensed sequence at base of heterogeneous sediments of Sandgate Formation, overlying uniform Hythe Formation sequence. Note that in much of Sussex the Sandgate Formation cannot be separated from the Hythe Formation with confidence (Young and Lake, 1988).
The Weald
Fine sands, silts and silty clays, commonly glauconitic; some sands limonitic or calcareous; some soft sandstones.
50-100m in West Sussex
At top of Marehill Clay Member (where it is present): upwards change to well-sorted, medium to coarse sands of the Folkestone Formation. Generally sharp, but rarely exposed.
Sandside Bay Formation
SABA
Top of the Fresgoe Sandstone Member [qv] of the Bighouse Formation.
Sandstone-dominated cyclic sequence with siltstone and calcareous (fish bed) laminite limestones.
Top of uppermost medium-grained cross-bedded sandstone, below the Dounreay Shore Formation [qv].
Shoreface And Beach Deposits (Undifferentiated)
SABD
Composite deposit: variable lithology. Any deposit laid down on the shoreface, ie. the area between low water and the wave base (Shoreface Deposits) and in the littoral environment (Beach Deposits). [Generic description: earth science dictionaries in the BGS library].
Bennan Intrusion (South Arran)
SABNI
Baoileig Sill (South Arran)
SABS
Saccammina Beds
SAC
Severn And Avon Catchments Subgroup
SACA
Formations of the Severn and Avon Catchments Subgroup rest unconformably on glacial and periglacial deposits and on a wide range of Palaeozoic and Mesozoic bedrock.
The entire area covered by the catchments of the River Severn, the Warwickshire Avon, the Bristol Avon, those rivers which flow from Wales into the Bristol Channel as far west as Port Talbot, and all of their tributaries.
The Severn and Avon Catchments Subgroup encompasses all the fluvial, lacustrine and organic deposits of the rivers that occupy the catchment areas of the River Severn, the Warwickshire Avon, the Bristol Avon, those rivers which flow from Wales into the Bristol Channel as far as Port Talbot, and all their tributaries. Floodplain alluvium comprises soft silts and clays, commonly with beds of peat and a basal bed of sand and gravel. River terrace deposits are largely sand and gravel. The gravels include a wide range of Palaeozoic and Mesozoic rocks, and much glacial material. Peat is a minor component, and minor marine deposits are included where they are intercalated in dominantly fluvial formations.
Saltern Cove Formation
SACO
Sandy's Creek Mudstone Formation
SACR
Faulted inlier near Portencross,Sheet 21/22W.
Siltstones, silty mudstones and greenish grey, contorted bedded sandstones.
30m thickness seen.
Clauchland Sill (South Arran)
SACS
Saddle Hill Granite
SADHI
Drumadoon Intrusion (South Arran)
SADRI
Dippin Sill (South Arran)
SADS
Sandness Formation
SAF
Sale Fell Minette
SAFE
Stratheden Group
SAG
Angular unconformity. Base of Stockiemuir Sandstone (Gargunnock Sandstone) Formation in Dumbarton-Stirling area, where this rests on Strathmore Group. Base of Burnside Sandstone Formation in Fife and Kinross, where this rests on the Arbuthnott Group. Stratheden Group rests on Strathmore Group in Arran. The 'Upper Old Red' at Milton Ness (Montrose area) is probably the Kinnesswood Formation and of Carboniferous age, although the Strathededen Group may be present in the subsurface.
Midland Valley of Scotland, Arran to north-east Fife. Sheets 12, Arran 21, 22, 29, 30E, 30W, 38W, 38E, 39E, 39W, 39E, 40W, 40E, 48W, 48E, 49.
Sandstone, mainly red-brown and yellow, partly pebbly; subordinate red-brown siltstone and mudstone; local thick conglomerates in the west.
Up to about 1500m thick.
At base of Kinnesswood Formation (incoming of common pedogenic carbonate); boundary normally transitional, locally unconformable in west of Midland Valley, marking base of Inverclyde Group.
Glenashdale Sill (South Arran)
SAGAS
St Agnes Intrusion
SAGI
St Asaph Glacigenic Formation
SAGL
Suballuvium Gravel
SAGR
Gravel-rich lag commonly found at the base of alluvial deposits. [Generic description].
Garbad Sill (South Arran)
SAGS
Sanaig Greywacke Formation
SAGW
Saltash Formation
SAH
The lower boundary is mainly thrust out in the east where it is assumed to overlie the Staddon Formation. In the west, on the north Cornish coast, it is taken at the incoming of dark and pale grey mudstones with scattered thin sandstones of the Saltash Formation above the sandstones and siltstones with subordinate mudstones of the underlying Bedruthan Formation.
From Trevose Head area (SW 86 76), north Cornwall to Torquay area (SX 93 65), south Devon.
Dark grey and grey silty mudstone with variable but very subordinate amounts of laminae and thin beds of siltstone and sandstone. Bioturbation is locally present, especially in the lower part. There are scattered units of thin- to thick-bedded limestone (eg: Marble Cliff Limestone Member), thin- to thick-bedded sandstone (eg: Wearde Sandstone Member), basaltic lava (spilite), massive and bedded hyclastite, and bedded tuff (eg: St Germans Tuff Member).
3900m on the north Cornwall coast. Comparable thicknesses are expected elsewhere.
The upper boundary is predominantly tectonic, except in the east in the Tamar valley, where it is taken at the incoming of dark grey cherts and siliceous mudstones of the Winstow Chert Formation above the mid grey silty mudstones of the Saltash Formation.
Sandy Haven Formation
SAHA
Sarn Hill Basalt
SAHB
Spilitic and peperitic basalt, with evidence of load structures ["pillowing"] on an unconsolidated, unstable substrate.
Holy Island Sill (South Arran)
SAHIS
St Ann's Hill Pebble Bed Member
SAHP
Sandgate Formation And Hythe Formation (Undifferentiated)
SAHY
St Austell Intrusion
SAIN
1. Coarse granite withlarge megacrysts common and sparse;2. Medium granite with lithium mica;3. Fine granite with large megacrysts common and sparse.
'S Airde Beinn Plug
SAIRB
Kilpatrick Intrusion (South Arran)
SAKPI
Kingscross Sill (South Arran)
SAKS
Salop Formation
SAL
Conformable, transitional-gradational boundary taken at the base of the first, at least 1 m thick, red-bed stratum, overlying the grey mudstone-dominated Dark Slade Member of the underlying Halesowen Formation. Where this is also red, the boundary is drawn arbitrarily, above the top of the highest litharenite sandstone.
Staffordshire, Shropshire and Warwickshire.
Red and red-brown mudstone, and red-brown (mostly sublitharenite) sandstone containing beds of pebbly sandstone and conglomerate itself containing Carboniferous limestone and chert clasts, and thin 'Spirobis' limestone beds and caliche in the lower part of the unit.
From 200 m to 360m thick in Shropshire, and 625 m thick in Warwickshire.
In the type area at the boundary occurs at the base of the Clent Formation. The boundary is an unconformable or disconformable sharp junction, in the Clent Hills where the Clent Formation is a red-brown breccia; or is a gradational boundary where there is red mudstone-dominated Clent Formation; but is taken at the base of red sandstone with Uriconian volcanic clasts in the Gospel End area of the West Midlands. In Warwickshire, the boundary is conformable below the red-brown mudstone-dominated succession of the Tile Hill Mudstone Formation.
Salachan Formation
SALA
Salridge Coal (Bristol Area)
SALC
Salen Pelite Formation
SALP
Salperton Limestone Formation
SALS
Garantiana Zone to Zigzag Zone.
Disconformity: hardground capping various members of Aston Limestone or Birdlip Limestone formations, or correlative disconformity on Lias Group.
Horton, northeast Avon (Green, G W, 1992; see also Barron, A J M, et al, 1997, p.281, fig.4), through Gloucestershire Cotswolds to north Oxfordshire west of a line from Hook Norton to Tackley where overlapped by Great Oolite Group (Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D, 1987, fig.26).
Pale grey to brown rubbly, fine- to coarse-grained ooidal, peloidal and finely shell-detrital packstone to grainstone (Clypeus Grit Member), generally with very shelly and coarsely shell-detrital ooidal grainstone and packstone (Upper Trigonia Grit Member) at base.
Typically 10 to 15m. Type section 13m. Maximum c.20m (Colesbourne area).
Salters Coal (Lothian)
SALT
Salsburgh Volcanic Formation
SALV
Visean (?Asbian).
Base is unconformable on supposed Lower Devonian rocks in the Salsburgh No.1A Oilwell (BGS Reg. No.NS86SW/89).
Unknown, the formation is only known from the Salsburgh 1A borehole.
Greenish tuffs and basaltic lavas interbedded with strata of the West Lothian Oil-Shale Formation.
The upper boundary is a transition into sedimentary strata.
Sandstone And Marl Group
SAM
Drawn at base of feldspathic grits and breccias and grey shales of the Sandstone and Marl Group where they rest conformably on purple marl of the Lower Marl Group.
Red or green siltstones (marls). Red, sometimes nodular mudstones, very fine- to fine-grained, bright green or purple sandstones and intra-formational conglomerates. (Sandstone and Marl Group = division of Red Marls).
Approx. 200 metres - 275 metres.
Drawn at conformable upward passage from red marls of the Sandstone and Marl Group to siltstones of the Upper Marl Group.
Saltoun Marine Band
SAMB
Saltmarsh Deposits
SAMD
Sand, silt and clay with organic debris. [Generic description].
Samlesbury Formation
SAML
The sharply conformable base of the formation is taken at the base of the dark grey shaly mudstone of the Isohomoceras subglobosum Marine Band with eponymous fauna, where the formation overlies the interbedded sandstone, siltstone and mudstone succession of the Silsden Formation. Where the marine band is absent from the interval, the base of the formation is taken at the top of the Lower Follifoot Grit in the southern part of the Askrigg Block, or the base of a mudstone succession with Lingula in the Stainmore Trough. In the southern part of the Central Pennine Basin it is taken at the base of the first thick quartz-feldspathic sandstone of Chokierian to Alportian age, present above the Bowland Shale Formation.
The Craven Basin of north Lancashire and north Yorkshire, between Lancaster [SD 47 61], Pendle Hill [SD 80 41], Skipton Moor [SE 00 50] and Harrogate [SE 30 55] and the southern part of the Askrigg Block and the Stainmore Trough.
A dark grey mudstone, common thin shaly mudstones, subordinate sandstone and siltstone, and locally in the Bradford area, a thick, coarse-grained, cross-bedded sandstone (Brocka Bank Grit).
Lancaster 64m; Bradford 75m; less than 30m thick along the southern part of the Askrigg Block, and in the Stainmore Trough the succession is no more than 20m thick.
The sharp conformable base, of the dark grey shaly mudstone of the Hodsonites magistrorum Marine Band, including eponymous fauna, overlain by the siltstone-dominated lower part of the Hebden Formation, underlain by the mudstone-dominated succession of the Samlesbury Formation. Where the marine band is absent from the interval, the top of the formation equates with the base of the Cayton Gill Shale in the south of the Askrigg Block (Wilson, 1977) and the base of the Mousegill Marine Beds in the Stainmore Trough (Owens and Burgess, 1965).
Monamore Sill (South Arran)
SAMS
St Saviour's Andesite Formation
SAN
Sandside Sandstone Formation
SAND
Shiaba Pelite Formation
SAPE
Sanaigmore Phyllite Formation
SAPH
Saddle Point Member
SAPO
Sarclet Group
SAR
Drawn at base of Sarclet Conglomerate which rests unconformably on rocks of the Moine Supergroup.
Northeast Highlands, Scotland.
Dark or pale red sandstones, conglomerate, with red and pale green mudstones.
480m approx.
Drawn at conformable upward passage from the Ulbster Sandstone of the Sarclet Group to the Ellens Goe Conglomerate of the Wick Flagstone Group.
Sandringham Sand Formation, Roxham Member And Runcton Member (Undifferentiated)
SARR
South Arthurlie Coal
SARTC
Sandringham Sand Formation
SAS
A down-section change from sands, with a pebbly base, to mudstones [Kimmeridge Clay Formation]. An erosion surface separates the two formations.
The Sandringham Sand Formation is confined to Norfolk and extends beneath The Wash where it apparently merges with the Claxby Ironstone Formation and Spilsby Sandstone Formation [Casey & Gallois, 1973; Wingfield et al. 1978, Gallois, 1994]. Its outcrop has been traced from the Hunstanton area South to near West Dereham.
The formation comprises silty and clayey sands, sporadic clay ironstones, with cleaner quartz sands at the top. Four members are recognised [Casey & Gallois, 1973; Gallois, 1984, 1994]: Incoherant, moderately clean, pale grey [locally green, yellow or orange]. fine-to-medium-grained, cross-bedded quartz sands with surbordinate bands of silt or clay. Pyrite nodules are present and glauconite is locally abundant. [Leziate Sand Member]. Glauconitic, clayey, grey and green sands with bands and "doggers" of brown weathering clay-ironstone and seams of phosphatic nodules [picking out erosion surfaces]. A prominent band of phosphatic nodules occurs at the base. [Mintlyn Sand Member]. Green, glauconitic, clayey sands with abundant phosphatic nodules [Runcton Sand Member]. Grey and yellow-green, pyritic, silty sands with an indurated basal pebbly sandstone with phosphatic nodules and derived Kimmeridgian debris [Roxham Sand Member].
Up to c. 50m
South of Gayton, the pebbly sands of the Carstone Formation overstep the silty and clayey sands and clean sands [Sandringham Sand Formation], resting progressively on the Roxham and Runcton members, the Mintlyn Member and finally the Leziate Member. In Northern Norfolk the upper boundary is defined by the down-section change from the clayey sands [Dersinham Formation] to incoherent, generally clean quartz sands [Leziate Member, Sandringham Sand Formation]. Beneath The Wash, the Leziate Member passes into the Claxby Ironstone Formation and the overlying Dersingham Formation passes laterally into the Tealby Formation [Gallois, 1994].
Sub-Alton Sandstone
SASA
Saltford Shale Member
SASH
Placed at the base of mudstones resting on the highest limestone of the underlying Wilmcote Limestone. Placed at top of Bed 26 at type section (Donovan, 1956).
Mostly grey, fissile or blocky, fossiliferous calcareous mudstones; a few limestones.
4.27m at type section, 20-30m over most of Midlands.
Placed at the base of an interbedded argillaceous limestone ('cementstone') and mudstone sequence. At base of Bed 22 at type section. (Donovan, 1956).
South Arran Sills
SASS
Satturland Coal
SATC
Tighvein Sills (South Arran)
SATVS
South Arran.
South Alwyn Valley Formation
SAV
Lower limit : unconformity upon sediments of the Ferder and Cape Shore Formations.
Usually a very soft to soft, highly plastic silty clay with shell fragments and containing lenses/layers of sand, gravelly sand, gravel and sandy mud up to 10cm thick.
4 metres +. Up to 15 metres thick on seismic sections.
Sawdde Sandstone Formation
SAWD
Senni Formation
Central South Wales.
St Baldred's Plug
SBAL
St Abbs Formation
SBB
Base of formation lies unconformably on the surface of the Wee Bankie Formation, or directly on rockhead.
Mud, locally silty, soft to stiff, red-grey to grey-brown, with sporadically distributed pebbles up to several centimetres diameter.
c.6 metres. Generally <10 metres but occurs locally up to 20 metres in thickness.
Top of unit unconformably overlain by younger sediments.
Stabba Pelite Member
SBBA
Sandy Boulder Clay
SBC
Sandy, silty, pebbly clay, locally with sand and gravel lenses. [Generic description].
Shields Bed Limestone
SBD
Soft Bed Coal (West And South Yorkshire)
SBDC
Storm Beach Deposits, Gravel
SBDG
Gravel and rarely sand; commonly with bank-like form. [Generic description].
St Bees Evaporite Formation
SBE
Taken at the point where the "basal breccia" or brockram passes up into grey carbonate-rich siltstones.
West and south Cumbria, north Lancashire and east Irish Sea Basin.
Anhydrite and/or gypsum, with subordinate dolomite and siltstone, interbedded in cyclical sequences.
21m in the type section with general range of 0 - 100m in west and south Cumbria.
Taken at the base of the overlying red clastic sequence (St. Bees Shales) where red mudstones become predominant over evaporites.
Belle Tout Beds
SBEL
Soft Bed Flags
SBF
The Soft Bed Flags are generally fine-grained, thinly-bedded and cross-bedded to flaggy sandstone interbedded with mudstone
Short Brow Flint
SBFL
Slievebane Group [Superfluous Entry: Use Sli]
SBG
Conglomerates form upper part of group. Thin formation of mudrocks occur at base of group.
c. 1080 metres.
Storm Beach Gravel, Flint
SBGF
Flint-rich gravel and rarely sand; commonly with bank-like form. [Generic description].
Storm Beach Gravel, Limestone
SBGL
Limestone-rich gravel and rarely sand; commonly with bank-like form. [Generic description].
Spout Of Ballagan Sandstone
SBGS
Formerly included within the Downie's Loup Sandstones or Downie's Loup Sandstone Formation (which terms are now Obsolete).
Sheep Bught Bed
SBH
Coastal section at Sheep Bught.
Fining upward cycles of white to grey sandstone sometimes conglomeratic (65% of succession), siltstone and shale.
Succoth-Brown Hill Type Ultramafic Intrusion
SBHT
Sarclet Group And Black Isle Sandstone Group (Undifferentiated)
SBKI
Shell Band Limestone
SBLS
Sutterby Marl Formation
SBM
The base is taken at the erosion surface immediately below a phosphatic nodule horizon. In the type section the base is marked by a downward change from pale grey, fossiliferous, calcareous clay to sandstones (Roach Formation). In southern Lincolnshire and below The Wash, there is a downward change from pale grey, fossiliferous, calcareous mudstone to medium to dark grey, sparsely fossiliferous, clay with irridescent ammonite fragments (Skegness Clay).
Southern Lincolnshire and The Wash. The Sutterby Marl Formation extends as far north as the Oxcombe-Scamblesby area and disappears below The Wash, approximately 2km north of the Norfolk coast.
The formation comprises a thin, poorly exposed, pale grey calcareous clay. It is usually strongly bioturbated and contains a rich and diverse macrofauna, including ammonites, belemnites, bivalves, brachiopods, rare echinoids and corals, together with coccoliths, foraminifera and ostracods.
Up to c. 3.14m in boreholes, but 1-2m at outcrop in the type area.
The upper boundary is placed at an erosion surface where there is a downward change from sandstones (Carstone Formation) to calcareous mudstones.
Subcrenatum Marine Band
SBMB
Slot Burn Formation
SBN
Transition from greyish-red sandstones, siltstones and mudstones of Monument Formation.
Dark greenish-grey mudstones, siltstones and sandstones, mainly flat laminated.
Transitional into greyish-red sandstones, siltstones and mudstones of Logan Formation.
Sand Beck Nodule Bed
SBNB
Change up from mudstone with sparse argillaceous limestone nodules of undifferentiated Charmouth Mudstone Formation into mudstone with ironstone nodules (as described under Lithology); at 181.5m depth in type section Copper Hill Borehole (SK94SE/56).
East Midlands: north Leicestershire to Linclonshire. Not recognised in the Charmouth Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south into the mudstone-dominated Charmouth Mudstone Formation.
Grey mudstone beds with numerous ovoid sideritic ironstone nodules 0.05 to 0.1m across, weathering to reddish brown. Fauna includes gastropods, bivalves (Gryphaea), ammonites and belemnites.
3 to 5m; c 4.0m in type section.
Change up from mudstone with ironstone nodules (as described under Lithology) into mudstone with sparse limestone nodules of undifferentiated Charmouth Mudstone Formation; at c 177.2m depth in type section Copper Hill Borehole (SK94SE/56).
Scandal Beck Peat Bed
SBPT
Note that this bed is a raft of Ipswichian peat, now lying within the Early Devensian Gillcambon Till Formation.
Not observed, but lying stratigraphically above yellowish brown, sandstone-rich diamicton.
The Vale of Eden, Cumbria.
Organic mud passing upwards into interbedded organic sand, gravel and compressed peat containing twigs of hazel and pine.
At least 4m
Sharp, planar, unconformable contact, or intercalated glacitectonic junction with overlying yellowish brown, sandstone-rich diamicton correlated with the Gillcambon Till Formation.
Slack Bank Rock
SBR
Sharp upward change in a conformable succession from predominantly grey mudstone to sandstone - base of first sandstone above the Blocking and/or Middleton Eleven Yards Coal. Erosive base washing out Middleton Eleven Yard Coal in Leeds area.
Extensive area covered by east Leeds/Garforth [SE3700 3300] to southwest of Wakefield [SE3000 1800], West Yorkshire.
A medium-bedded, medium- to fine-grained, ripple cross-laminated, grey sandstone.
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of last sandstone bed below the Middleton Main/Wheatley Lime Coal.
Sub-Brooch Coal (Cannock)
SBRC
Sudbury Formation
SBRY
Formation is restricted to the Thames Valley, Essex and Suffolk. It does not extend into Norfolk (Hamblin and Moorlock, 1995).
Formation encompasses fluvial, lacustrine and organic deposits of the pre-diversionary River Thames. Most of the surviving deposits are fluvial gravels, with sedimentary structures indicating deposition by a braided river. Lacustrine silts and clays and organic peats are uncommon. The formation represents the first significant input of far-travelled materials into the Thames river sediments, and is characterised by quartz and quartzite from the Triassic, Carboniferous and Devonian rocks of the West Midlands, Welsh Borderland and possibly southwestern Pennines, and felsic volcanic rocks from northern Wales. The presence of mega-erratics and glacially fractures sand grains indicate glacial erosion in the headwater regions of the river. The fluvial gravels occupy terrace levels and the members are defined on the basis of altitude and pebble clast content. The members comprise bodies of cross-bedded and massive, moderately sorted sand and gravel. The aggradations are generally entrenched into bedrock with a difference in surface elevation of at least 10m.
c.18m. Individual terrace aggradations typically 5-10m thick.
St Bees Sandstone Formation
SBS
Taken at the base of the lowest main/significant sandstone in the beds transitional with the underlying St Bees Shale Formation. The base is sharply marked on the gamma-ray log; an abrupt change from a highly serrated signature in the lowermost St Bees Sandstone to a much more subdued signature with higher values in the St Bees Shales.
South and west Cumbria, Solway Basin, Vale of Eden. Also includes the 'Lower' St Bees Sandstone of the East Irish Sea Basin.
Red-brown, very fine- to medium-grained, commonly micaceous sandstones, generally cross bedded, some parallel lamination; mudstone clasts locally common, subordinate thin beds of greenish grey sandstone.
340 - 627m proved in UK NIREX Sellafield boreholes.
Taken at the sharp upward change from generally fine-grained, well cemented sandstones, with features typical of fluvial deposition, to coarser, more friable sandstones with common well rounded aeolian grains (Calder Sandstone Formation). Marked also by an abrupt decrease in gamma ray values and increase in sonic interval transit time.
Smith Bank Sandstone Unit
SBSA
Sharnberry Shell Bed
SBSB
Sutterby Marl Formation And Skegness Clay Formation (Undifferentiated)
SBSC
St Bees Sand And Gravel Member
SBSG
Gradational, conformable contact with laminated fine-grained sand, silt and clay of the St Bees Silt Member.
Cumbrian coast between St Bees and Sellafield seaward of the limit of the "Gosforth Oscillation" between Cleator and Ravenglass.
Sand and gravel, coarsening upwards from pebbly sand to boulder gravel, dense, composed of angular to subrounded clasts of red (Permian) sandstone, white and yellow (Carboniferous) sandstone and ganister, black (Carboniferous) mudstone and coal, with some Borrowdale Volcanic Group rocks (rhyolite, welded tuff), greywacke sandstone and siltstone, limestone and grey (Criffel) granite. Top of unit commonly cemented by calcite. Palaeocurrents directed between NW and SW.
Sharp, undulating, unconformable contact with grey sandy pebbly silt diamicton of the St Bees Till Member of the Gosforth Glacigenic Formation.
St Bees Shale Formation
SBSH
'The base of the main red clastic sequence', where red mudstones become predominant over the evaporites that characterise the underlying formation (St. Bees Evaporites).
West and south Cumbria, north Lancashire, East Irish Sea Basin.
Mainly red siltstones and silty mudstones, with some sandstone, millet-seed sand grains, mudstone breccias and gypsum.
62m in type section with range of 0 - 215m in Cumbria generally.
Taken where sandstone, which characterises the overlying formation (St. Bees Sandstone), becomes predominant over red siltstone and mudstone.
St Bees Silt Member
SBSI
Not exposed, but BGS-registered borehole NX91SE5 near the type section indicates that it rests unconformably on stiff, reddish brown diamicton, probably the Lowca Till Member of the Seascale Glacigenic Formation.
Thinly interlaminated calcareous, bluish grey silty clay, reddish brown clay and yellowish brown silt passing upwards into ripple-drift cross laminated sand with much finely disseminated coal. Palaeocurrents mostly directed towards the northwest.
At least 3.7m
Gradational, conformable contact with sand and gravel of the St Bees Sand and Gravel Member of the Seascale Glacigenic Formation above.
Strathaird Beds (Skye)
SBSK
Sandside Bay Sandstone Member
SBSM
South Brentor Formation
SBT
Thrust bounded.
Area around South Brentor, East Dartmoor, Devon.
Black, sandy micaceous slates and pale greenish grey slates with nodular limestones. More rarely thick siltstone and fine sandstone horizons.
Passes upwards into the Lydford formation. Lithology changes to shale with breccia.
Scale Beck Till Member
SBTI
Western side of Lake District, inland of the limit of the "Gosforth Oscillation".
Reddish brown cobbly sandy clay diamicton, very compact, generally massive and matrix-supported, containing clasts mainly of Borrowdale Volcanic Group rocks (rhyolite, welded tuff, slate), granite and granophyre from the Lake District. Has tightly clustered clast fabric typical of a lodgement till.
To at least 6m
Ground surface, or sharp, undulating, unconformable contact with overlying glaciolacustrine laminated silt and clay (Bark Butts Silt Member); glaciofluvial cobble gravel (Whin Garth Gravel Member); or by various Flandrian deposits such as peat and alluvium.
St Bernard Tuff Member
SBTU
Not seen, probably on undivided beds of Charnwood Lodge Volcanic Formation. Member is characterised from latter by increased abundance of fine- to medium-grained, well-bedded lithologies.
Crags to east of Mount St. Bernard Monastery.
Varied, massive thick to thinly bedded sequence of graded volcaniclastic sandstones and siltstones and massive lithic-crystal tuff.
Scors Burn Schist Formation
SBUS
Unknown - lozenge-shaped outcrop between two major faults of the Portsoy Lineament.
NNW/SSE-trending outcrop, to 1.25km wide, from Allt na Craoibhe-caorainn [NJ 321 257] to Leadensider Burn [NJ 343 197]. Blackwater - Glenbuchat area, Moray and Gordon Districts. Sheet 75E.
Semipelitic mica-schist, usually grey or olive, knotted in parts, commonly staurolite bearing.
Up to 900m (based on maximum observed outcrop width with no allowance for probable folding and other tectonic thickening or thinning).
Stewartby Member
SBY
At top of highest brownish-grey, organic rich mudstone within thinly interbedded transition (to c.3m thick) to brownish-grey, fissile mudstones of underlying 'Lower Oxford Clay'(Peterborough Member). More or less arbitrary in field mapping.
Predominantly pale to medium grey, commonly smooth, variably silty, calcareous, poorly fossiliferous, blocky mudstones. Subordinate beds of silty mudstones packed with immature shells of the bivalve Bositra buchii (Roemer). Thin, calcareous siltstones, particularly in upper part, commonly with Gryphaea. Ammonites and other macrofauna generally pyritised.
At the top of the Lamberti Limestone (where present) or an equivalent shell bed or siltstone. The horizon is clear on geophysical logs. Change in Gryphaea faunas (G.lituola, below to G. dilatata, above) and ammonite faunas. (Kosmoceras, below: Cardioceras, above) useful supportive indicators. Base of Weymouth Member.
Salisbury Craigs Sill
SBYC
Swallowcraig Coals (Sanquhar)
Scart Grits Formation
SCA
Conformable on the Woodland Formation.
Conglomerate (pebbles of vein quartz, lava, dolerite, chert and red jasper) and coarse sandstone.
Scaat Craig Beds
SCAA
Scaraben Quartzite Formation
SCAB
Scalpay Granite
SCAG
South Campsie Linear Vent-System
SCAMP
Scaphites Bed (2)
SCAP
Scatsta Quartzitic Formation
SCAT
Scaur Group
SCAU
Southern Uplands of Scotland, between Leadhills and Fardingmullach Faults.
Faulted (Leadhills Fault).
Scar Vein
SCAV
Sandy Craig Formation
SCB
The conformable base of the formation lies in a transitional sequence from the Pittenweem Formation and is taken at the top the St. Andrews Castle Marine Band.
Central and east Fife.
Mudstone and siltstone with thin beds of non-marine limestone and dolomite; sandstone is subordinate; pattern of sedimentation both upward coarsening and upward fining cycles of non-marine origin.
Maximum thickness is about 670m in East Fife.
The conformable top of the Formation lies in a transitional sequence up into the Pathhead Formation and is taken at the base of the West Braes Marine Band. This is slightly higher in the sequence than in the original definition, having been altered by Browne (1986, fig.2).
Scandal Beck Limestone Formation
SCBL
Chadian to early Arundian.
Scot's Brook Member
SCBR
Tournaisian to Visean (older than Asbian).
At the top of a medium- to coarse-grained pebbly sandstone, overlain by green, slickensided, smectite-rich mudstone with about 4mm ferruginous concretions of the Arch Farm Sandstone Formation, sharply overlain by pale grey to white calcareous sandstone of the Scot's Brook Member.
Not identified at the surface.
Green to grey, medium- to coarse-grained pebbly argillaceous sandstones with subordinate calcareous mudstones and layers of white, nodular, micritic limestone. The Member contains marine fossils (brachiopods and algae).
3.5m in the Ticknall Borehole.
Sharply overlain by grey, nodular limestone of the Cloud Hill Dolostone Formation ('Carboniferous Limestone').
Scobbiscombe Sandstone
SCBS
Scatsta Division And Boundary Zone (Undifferentiated)
SCBZ
St Cynllo's Church Formation
SCC
Black, locally laminated, pyritic mudstones with scattered thin bentonites and sandstones. Packets of thin- to thick-bedded sandstones with subordinate mudstones locally developed.
Gradational but taken at incoming of sequence dominated by burrow mottled mudstones.
Scarba Conglomerate Formation
SCCO
Scafell Dacite Member
SCD
Base of dacite; unconformable - overlies older parts of the Lingmell Tuff Formation, and locally rests on the Airy's Bridge Tuff Formation (rhyolitic tuffs).
Between Little Narrowcove (NY 2250 0675) and Aaron Crags (NY 2293 1038), Cumbria.
Pale-weathered dacite, locally flow-banded and folded, with garnet phenocrysts; marginal autobreccia.
Overlain by the Seathwaite Fell Sandstone Formation (volcaniclastic sandstone and breccia).
Scremerston Formation
SCF
Scremerston Coal Member
SCG
Scattergate Sandstone
SCGS
Scout Hill Formation
SCH
Sligachan Formation
SCHAN
South Charnwood Diorites
SCHD
Where intrusive contacts are exposed (eg Cliffe Hill Quarry), the diorite fines progressively in grain size over about 10m, eventually developing a selvage 1.5m wide consisting of dark grey porphyritic andesite. The contact sharply truncates bedding in adjacent volcaniclastic rocks of the Charnian Supergroup, the latter developing thermal spots that are locally attenuated within the plane of a later cleavage. Many contacts are sheared and faulted.
The intrusion crops out discontinuously in Leicestershire, from beneath Triassic cover, from Stanton under Bardon [SK 457 108] southeastwards to the Groby Quarries [SK 526 082], and thence northeastwards to Bradgate Park [SK 535 102].
A grey to pink, medium- to coarse-grained granophyric diorite with a distinctive "mottled" appearance caused by the clumping together of dark grey ferromagnesian minerals (mainly hornblende and chlorite) and grey-green hypidiomorphic plagioclase crystals. Both components are surrounded by a pink to grey granophyric mesostasis. The texture coarsens in places, but true pegmatites are rarely developed; green-grey aplite sheets cross the diorite in some quarries.
Intrusive, as for the Lower Boundary; in places overlain unconformably by Triassic strata.
Scolt Head Formation
SCHE
Scalp Hill Granite
SCHG
Scour Hollow Deposits
SCHO
Variable lithology; deposits infilling scour hollows. [Generic description].
Stockiemuir Sandstone Formation
SCK
Passes downwards and laterally into the Rosneath Conglomerate Formation in the Inverclyde-Loch Lomond area. Further east in the Kippen area, Francis, Forsyth, Read and Armstrong (1970) record Gargunnock Sandstones (~SCK) resting on the Teith Sandstone Formation.
The Firth of Clyde and Stirling areas, on sheets 30W, 30E, 39W.
Red and bright red, cross-bedded sandstones with scattered mudstone clasts and a few quartz pebbles in the lower part, overlain by purple, yellow and pink sandstones with sporadic cornstones of the Kinnesswood Formation in the upper part, which has scattered quartz pebbles near the base. The unit is faulted against the underlying grey and red-purple sandstones and mudstones of the Lower Devonian, Arbuthnott-Garvock Group.
In excess of 400m thick.
The base of the Kinnesswood Formation.
Sand In Creekmoor Clay Member
SCKM
Scar Limestone Member
SCL
Taken at the sharp base of limestone overlying measures within the Alston Formation; directly underlain locally by dark mudstone, seatearth sandstone or by a coal seam.
Member within the Alston Formation of the Alston and Lake District blocks in Cumbria, Northumberland and Durham, lying stratigraphically between the Tynebottom (below) and the Five Yard (above limestone members. The limestone is well exposed along the Pennine escarpment, in Teesdale and Weardale.
Limestone, pale to medium-grey, wavy bedded, crinoidal with fissile uppermost part and shaly partings; styolitic. Fossiliferous, with bands of Siphonodendron junceum, but comparatively unfossiliferous in the south though a bed rich in brachiopods is present at the base in the southern part of the Brough district (Burgess and Holliday, 1979). Nodules of chert are commonly found in this limestone. In the Longcleugh No 1, Allenheads No 1, and Rookhope boreholes an interbedded unit of black pyritic fossiliferous mudstone with sporadic small ironstone nodules in the upper part of the member. Goniatites of the P2a biozone are found in mudstone just above the limestone at Bowlees in Teesdale.
4 to 14.6m.
Taken at the base of overlying measures within the Alston Formation.
Spring Cove Lava Member
SCLA
The base is irregular and channelled up to 1.2 m into the underlying limestone of the High Tor Limestone Formation.
Spring Cove, north Somerset.
A typically fine grained, chocolate-brown, massive and highly amygdaloidal olivine basalt, with imperfect pillow structures and red oolitic limestone fragments in all stages of alteration and assimilation, which in places appear to occupy spaces between pillows. In the centre of the member, cindery lava is mixed with broken limestone fragments. Calcite veins are common throughout.
A sharp boundary forms the upper boundary between basalt and overlying reddish-fawn, dolomitised limestone of the High Tor Limestone Formation, containing tuffaceous debris in the bottom 1.5m, decreasing upwards from the base.
Sessiagh-Clonmass Formation And Lower Falcarragh Pelite Formation (Undifferentiated)
SCLF
Scratchell's Marls (One)
SCMA1
Scratchell's Marls (Two)
SCMA2
Scratchell's Marls (Three)
SCMA3
St Andrew's Castle Marine Band
SCMB
Seacombe Sand Formation
SCMBS
Details unknown.
North Wirral and the Liverpool Bay coast.
At Seacombe, a shell-rich sand with fine gravel, this deposit contains boulders and cobbles of till; developed as a foraminifera-rich till at Crosby and Blackpool.
Possible correlative offshore of glaciomarine sediments of the Dog Mills Member (Orrisdale Formation), Isle of Man.
0 to 45m
Overlain unconformably by till at the type locality at Seacombe.
Scremerston Main Coal
SCMC
Scone Sandstone Formation
SCN
Transitional with the Dundee Flagstone and Ochil Volcanic Formations in the Dundee-Arbroath area, and transitional with the Craighall Conglomerate Formation in the Blairgowrie area.
Purple-brown and purple-grey, fine- to coarse-grained, commonly cross-bedded sandstones with subsidiary siltstone, mudstone, conglomerate, sparse andesitic lava flows and some calcareous beds with concretionary limestones towards the top.
Locally over 2000 m thick.
The base of Cromlix Mudstone Formation.
Schooner Formation
SCNR
Stack Cleugh Oolite
SCO
Local development in the area around Stack Cleugh, near Bewcastle, Cumbria.
Flaggy limestone, generally fine-grained with abundant pellets, ooliths and algal beads.
To c.1.5m
Scott Beds
SCOT
Scoughall Vent
SCOU
Scourie Dyke Swarm
SCOUR
Scotland Carboniferous-Permian Alkaline Suite
SCPA
Probably extends from late Visean (c. 326 Ma) to Late Permian (250 Ma).
Scoor Pelite Formation
SCPE
Scottish Late Carboniferous To Early Permian Plugs And Vents Suite
SCPPV
Scarlett Point Member
SCPT
Taken at the lowest black claystone, which is about 0.12m thick, overlying the fine-grained, pale mottled limestone (wackestone) of the Hodderense Limestone Formation at Scarlett Point [SC 2583 6633].
The southern part of the Isle of Man, in the Castletown area, from Scarlett Point [SC 2583 6633] northwestwards to Poyllvaaish [SC 2440 6761]. Dinantian rocks in the northern part of the island are entirely concealed and hence it is unknown whether the unit is present in the north.
The member is characterised by tabular beds of pale wackestone and calcisiltite. These beds, which can be cherty and pyritious, have gradational (locally dolomitised) boundaries with the interbedded black fissile, blocky claystones. 'Chondritiform' and Helminthoides burrows are common in the limestones. Inadunate crinoid lags and scattered ammonoids (Beyrichoceras or Bollandoceras) also occur, some preserved in a semi-buoyant resting position, with the venter resting on the former sea bed. Deposition was in a deep marine hemi-pelagic environment, but with periodic fine clastic and carbonate supply (gravitational).
14m
This is not exposed, so the nature of the upper boundary is therefore unknown. The overlying succession comprises black hemipelagic mudstones of the Bowland Shale Formation.
Scarborough Formation
SCR
The lower boundary is conformable, or disconformable, at the abrupt upward transition from plant debris-rich, mudstone with plant rootlets, or cross-bedded sandstone of the upper part of the Cloughton Formation (Gristhorpe Member) and well laminated calcareous mudstone, or limestone of the Scarborough Formation (Bate, 1965, p.83; Parsons, 1977; Gowland and Riding, 1991; Powell et al., 1992).
Present throughout the North Yorkshire Moors, Cleveland Hills, Hambleton Hills and Howardian Hills, and is well exposed in several coastal cliff sections near Hundale Point [TA 026 948] between Cloughton Wyke and Long Nab, northwest of Scarborough, and at Black Rocks [TA 050 870] to the south of Scarborough. Equivalent strata in Humberside and Lincolnshire are dominated by limestones (Lincolnshire Limestone, Cope et al., 1980). Offshore, the formation is equivalent, in part, to the Strangways Formation of the West Sole Group (Lott and Knox,1994).
Forms steep cliff and rock platforms on the North Yorkshire coast. Inland, throughout the North York Moors, it forms a small positive topographical feature, especially where the Brandsby Roadstone and Crinoid Grit members are present in the Hambleton and Howardian Hills.
A fully marine unit that represents the most widespread marine transgression over the fluvio-deltaic deposits of the Middle Jurassic, Ravenscar Group.
Variable lithology comprising: fossiliferous argillaceous limestone (peloidal micrite and wackestone), calcareous mudstone, calcareous siltstone, calcareous medium-grained sandstone, calcareous concretions and ironstone. Peloidal limestones are locally cross-bedded.
Up to 30m in the type coastal section at Hundale Point [TA 026 949] Gowland and Riding, 1991); thins westward to between 9-14m in the Hambleton Hills [SE 477 898] (Powell et al., 1992, p.46); at Yons Nab [TA 085 841] south of Scarborough it is only 3m thick (Rawson and Wright, 1992).
The upper boundary is disconformable, at the abrupt upward transition from grey shelly mudstone or shelly sandstone of the Scarborough Formation to cross-bedded sandstone with plant fragments of the lower part of the Scalby Formation (Moor Grit Member) (Bate, 1965, p.83; Parsons, 1977; Gowland and Riding, 1991; Powell et al., 1992).
Scrag Coal (Bristol Area)
SCRC
Scree
SCRE
Clast-supported accumulation of angular rock fragments derived from a cliff or steep rocky slope. May be active or inactive. [Generic description: 'TMOS' Procedures].
Scalpay Sandstone Formation
SCS
Diachronous coarsening upwards from fissile mudstone of the Pabay Shale Formation.
The Scalpay Sandstone Formation comprises siltstones and sandstone, in a gradually coarsening-upwards succession to massive fine-grained sandstone. Locally cross-bedded and bioturbated. Fossiliferous horizons of Pseudopecten and other bivalves exist. The top of the formation is characterised by thin beds, ferriginous material and of chamosite-rich oolidal ironstone.
10m exposed
Abrupt lithological change to fissile mudstone of the Portree Shale Formation.
Scaladale Sandstone Member
SCSA
Scarle Sand And Gravel Member
SCSG
Upper Pleistocene (MI Stage [5e to] 4). Formerly stated to be Devensian in the original Code_Only Lexicon entry provided by J Carney, 28/03/2002.
Currently only known in Type Area (on Sheet 114; see Brandon and Sumbler, 1988, Fig.1): possibly remnants might occur elsewhere on BGS Sheet 113 and possibly on sheets 114 and 102.
Predominantly cold-phase sands and gravels that underlie the Scarle Terrace. Gravel dominated by rounded pebbles of "Bunter" quartz/quartzite with subordinate subangular flint, and rarer Triassic sandstone, Lias limestone, etc. Infills a shallow channel diverging from the Trent at Collingham and extending northnortheastwards to North Scarle where it is apparently truncated by the Kirkstead Sand and Gravel Member. Surface is c.3 to 4m above the Trent floodplain, and up to c.2m above the adjoining Kirkstead/Holme Pierrepont Terrace. Correlated with Beeston Sand and Gravel Member (Trent Valley Formation), and Fulbeck Sand and Gravel Member (Proto-Trent).
Stockdale Group [Redundant Code: Use Stk]
SCSH
Unconformably overlies the Red Gill Formation of the Dent Group.
Includes Skelgill and Browgill Formations as separately defined: dominantly mudstone.
About 50 metres.
Stump Cross Limestone
SCSL
Scarden Sandstone Member
SCSM
Spencroft Coal (North Staffordshire)
SCT
Lower Spencroft Coal
SCTL
Upper Spencroft Coal
SCTU
Cuckmere Beds
SCU
Scotland Late Carboniferous - Permian Lamprophyric Subsuite
SCUPL
Scarlett Volcanic Member
SCV
The base is clearly seen on the foreshore below Close-ny-Clollagh Point [SC 245 671], where volcaniclastic tuffs rest with a sharp, baked contact on underlying claystones of the Bowland Shale Formation.
The southern part of the Isle of Man, in the Castletown area, from Scarlett Point [SC 257 661] to Close-ny-Clollagh Point [SC 245 671].
The member is dominated by waterlain tuffs, basaltic lavas, submarine volcaniclastic debris flows and gravity slides. Olistoliths of older Dinantian carbonates and claystones also occur.
The top is not exposed, so the nature of the upper boundary is unknown.
Scalehow Tuff Formation
SCW
Taken at the sharp change from andesite and dacite sheets of the Birker Fell Andesite Formation to a dominantly pyroclastic sequence, along a conformable contact.
Patterdale Common, Martindale and Riggindale, south-east of Ullswater, Cumbria.
Andesitic and dacitic lapilli-tuff, and intercalated tuff, with some bedded volcaniclastic sandstone in the upper part of the formation, and some accretionary lapilli-tuff in the tuff sequence.
0 - 340 m thick.
Defined by the base of silicic ignimbrites of the Whelter Knotts Formation.
Sand In Clay With Flints
SCWF
Sand-rich unit within [generic description] reddish brown clay or sandy clay with abundant flint pebbles and rare sarsen sandstone. Originates possibly as an insoluble residue after dissolution of chalk and/or from Palaeogene sediments. [generic description]. Residual deposits of chalk areas. [BGS Procedures].
Scalby Formation
SCY
The lower boundary is disconformable or unconformable, at the abrupt upward transition from grey, shelly mudstone or shelly sandstone of the Scarborough Formation to grey, cross-bedded and planar laminated sandstone with sporadic plant fragments of the lower part of the Scalby Formation (Moor Grit Member) (Gowland and Riding, 1991; Nami and Leeder, 1978; Powell et al., 1992). The boundary is commonly a scoured, erosional surface.
North Yorkshire Moors, Cleveland Hills, Hambleton Hills and Howardian Hills, and is well exposed in several coastal cliff sections (Scalby Cliff) between Long Nab [TA 028 943] and Scalby Ness [TA 037 907], and south of Scarborough between South Bay [TA 046 875] and White Nab [TA 058 864] (Black, 1929; Hemingway and Knox, 1973; Nami and Leeder, 1978). Equivalent strata in Humberside and Lincolnshire are represented by the Redbourne Group (Gaunt et al., 1992). Offshore, the formation is equivalent, in part, to the Hudleston Formation of the West Sole Group (Lott and Knox, 1994).
Forms steep cliffs on the North Yorkshire Coast, and generally a steep scarp slope in the North York Moors. The lowermost Moor Grit Member forms a prominent bench-like feature in the coastal cliff, and a positive topographical feature in the Cleveland, Hambleton and Howardian hills. The overlying Long Nab Member is mudstone-dominated with thin channel sandstones, and generally forms less prominent topographical features.
The formation comprises paralic ("coal measure") lithofacies, and was deposited in fluvial, fluvio-deltaic and coastal plain environments (Nami and Leeder, 1978; Leeder and Nami, 1979; Livera and Leeder, 1981; Riding and Wright, 1989; Fisher and Hancock, 1985; Powell et al., 1992; Butler et al., 2005).
The lower part of the formation (Moor Grit Member) is dominated in coastal exposures by grey, medium- to coarse-grained, sporadically pebbly, trough cross-bedded sandstone, with thin siltstone and mudstone beds; plant fragments and fossil wood casts are common. Inland, in the Hambleton Hills (Powell et al., 1992) this member is represented by grey to white, fine-grained, orthoquartzitic sandstone, with low-angle cross stratification and planar bedding. The uppermost Long Nab Member comprises laminated grey mudstones and siltstones with yellowish grey, fine- to medium-grained, planar bedded and cross-stratified sandstones. Plant fragments and rootlets are common in both members, together with sporadic thin coals and grey mudstone seatearths.
Up to 60m on the North Yorkshire coast; 32 to 48m in the Hambleton Hills in the west of the outcrop.
The upper boundary is conformable or disconformable, at the boundary between siltstone, mudstone or cross-bedded sandstone with plant fragments of the Long Nab Member (Scalby Formation) and the Cornbrash Formation, which at Cayton Bay [TA 078 841], comprises red-brown, sandy, nodular, bioturbated limestone with oysters and other bivalves; u-shaped burrows extend down from the base of the Cornbrash Formation into the underlying grey siltstone and silty sandstone of the Scalby Formation (Wright, 1977). Inland in the Hambleton Hills and Howardian Hills, the Cornbrash Formation (limestone) is generally absent (Powell et al., 1992, p.53) and the upper boundary is taken at the base of the yellow-brown, calcareous medium-grained sandstone with bivalves (Kellaways Rock Member, Osgodby Formation). The Kellaways Rock Member is referred to as the Redcliff Rock Member by Page (1989).
Slisgallow Dolerite
Seafield-Deans Ash
SDA
Shetland (Albion) Glacigenic Subgroup
SDAG
The Shetland archipelago, Foula and Fair Isle.
A suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts derived predominantly from rocks cropping out on the Shetland archipelago, including sandy diamictons (till), sand, gravel, silt and clay. Deposited by ice that radiated outwards from an ice divide positioned along the axis of the archipelago.
Unconformable contact with units of the Shetland Glacigenic Subgroup or Flandrian deposits, predominantly peat.
Sodbury Coal (Bristol Area)
SDBY
Stairhead Coal (Lothian)
SDC
North Britain Siluro-Devonian Calc-Alkaline Dyke Suite
SDCAD
Scottish Highland Siluro-Devonian Calc-Alkaline Minor Intrusion Suite (Other Than Dykes)
SDCAM
Carlandcheek Vent
SDCAV
Sedbergh Conglomerate Formation
SDCO
Southdean Plug
SDEA
Smiddy Ganister
SDG
Sandhurst Gravel
SDGR
Gravel with sand. [Generic description: academic papers and BGS Memoirs].
Stapleford Head
SDHD
St David's Head Gabbro
SDHI
Quartz gabbro and microgabbro.
Sandholes Coal (Glasgow)
SDHS
St David's Granophyre
SDIN
Intruded into Neoproterozoic rocks.
St David's Peninsula, Pembrokeshire.
Not applicable: unconformably overlain by Cambrian sandstones.
Sraduffy Member [Duplicate Code: Use Srad]
SDM
Seafield Marine Band
SDMB
Mochrum Hill Vent
SDMHV
Seisdon Sand And Gravel Formation
SDNSG
Sharp, erosive, unconformable contact with bedrock. Strongly channelised.
Narrow, linear belt between Seisdon and Trysull, Staffordshire.
Yellowish red sand or sandy gravel with sporadic cobbles. Gravel and cobbles are dominated by well-rounded Sherwood Sandstone derived quartzite but with some rounded erratics of granite, felsite and Coal Measures sandstone. Fossiliferous in part.
3 to 34m
Either the ground surface or the basal surface of red silt of the Trysull Silt Formation or till and sand and gravel of the Stockport Glacigenic Formation.
North Britain Siluro-Devonian Plug And Vent Suite
SDPV
Silurian And Devonian Rocks (Undifferentiated)
SDRU
Studfold Sandstone Member
SDS
Taken at the sharp base of thick-bedded sandstone within the sequence of laminated sandy siltstones of the Horton Formation.
Poorly sorted arkosic fine-grained sandstone, mostly thickly bedded.
Defined by the change to dominantly laminated siltstones within the main part of the Horton Formation.
Sleaford Sand And Gravel
SDSG
Sabden Shales
SDSH
The lower boundary is taken at the base of fissile black mudstones of the Reticuloceras reticulum Marine Band, or where this is absent, at the base of the mudstone-dominated succession overlying the sandstones of the Warley Wise [Wilpshire] Grit
Longridge [SD 60 35] to Bailey Hall [SD 68 37] on the Ribchester Syncline, eastwards to approximately Foulridge [SD 88 42].
A fossiliferous mudstone with subordinate beds of locally pebbly sandstone and thin argillaceous limestone and ironstone.
Note that the beds comprising the "informal" Sabden Shales form parts of the three adjacent Silsden, Samlesbury and Hebden formations, within the Millstone Grit Group.
The upper boundary is taken at the base of a sandstone-dominated succession of the Todmorden (Parsonage) Grit, overlying the mudstone-dominated Sabden Shales
Sandsting Pluton
SDSTG
Sandsfoot Formation
SDT
Upper Oxfordian (Serratum Zone to ?lower Rosenkrantzi Zone).
Upward change from limestones of the Clavellata Formation into silicaclastic beds or limonitic oolite.
Dorset to Wiltshire, and probably other areas too.
A variable unit ranging from sand-free clay through clayey fine-grained sand, to sand, ferruginous sandstone and limonitic oolite.
2 to 12m
Upward change from sands, clayey sands and, locally, limonitic oolite to smooth mudstone of the Ringstead Waxy Clay/Ampthill Clay/Kimmeridge Clay.
Stud Vein Coal (Pembrokeshire)
SDVC
Sand Voe Group
SDVO
Sands Of 25-Foot Drift Of Vale Of York
SDVY
Sand; some aeolian in origin. [Generic description].
St Erth Formation
Late Pliocene based on foraminerfera (Millett, 1895, 1895; Reid, 1890; Mitchell et al. 1973).
Base of sands not seen but presumed to be Mylor Slate Formation (Late Devonian). Sections recorded by H Dewey (unpublished IGS records) in the north part of Vicarage Pit indicate shelly clay resting unconformably on bedrock.
Isolated outlier, 0.3 x 1.4km, 1km east of the village of St Erth, Cornwall.
Fossiliferous clay and sandy clay on ferruginous and quartzose sands. The clays have yielded abundant marine mollusca and foraminifera.
Deposit greater than 4m comprising c.4m of highly fossiliferous shelly clay on pebbly fine sand.
Overlain by and in irregular contact with Head.
River Terrace Deposits, 1 (Solway Esk)
SE1
Sharp undulating, erosional contact on reddish brown, clayey, sandstone-rich diamicton of the Gretna Till Formation or bedrock.
Valley of the River Esk.
River terrace deposits. The 1st terrace is divisible into three sub-terraces.
Grey pebbly sand (less than 3m thick)on reddish brown, interbedded silty sand, silt and clay (less than 4m thick), on reddish brown sand and gravel.
Up to 7m (see lithology description).
Ground surface, generally up to 3.5m above the floodplain.
River Terrace Deposits, 1a (Solway Esk)
SE1A
River Terace Deposits (Solway Esk), 1a-C
SE1AC
A sharp, undulating erosional contact, mainly on reddish brown, clayey, sandstone-rich diamicton of the Gretna Till formation, or elsewhere, upon bedrock.
The valley of the River Esk, downstream of Canonbie, Dumfrieshire.
A reddish brown clayey gravel, overlain by interbedded reddish brown silty sand, silt and clay, which in turn, is overlain by a grey pebbly sand. Unit name and code refers to three separate outliers each of which may be a part of SE1, though no vertical succession A-C is implied.
Up to 8 m thick.
The present ground surface, generaly up to 4 m above floodplain level.
River Terrace Deposits, 1b (Solway Esk)
SE1B
River Terrace Deposits, 1c (Solway Esk)
SE1C
River Terrace Deposits (Solway Esk), 2
SE2
Sharp, undulating, erosional contact, mainly on reddish brown, clayey, sandstone-rich diamicton of the Gretna Till Formation or on bedrock.
The valley of the River Esk downstream of Mumbie Cottages, Canonbie, Dumfries-shire.
River terrace deposits.
Sand and gravel, well sorted, brown. reddish brown clayey sand and gravel, commonly passing upwards into reddish brown, pebbly silty sand.
Up to 12 m thick.
The present ground surface, generally up to 6m above floodplain level.
River Terrace Deposits (Solway Esk), 3
SE3
The valley of the River Esk, downstream of Mumbie Cottages, Canonbie, Dumfries-shire.
Sand and gravel on pebbly silty sand, reddish brown.
The present ground surface, generally up to 9 m above floodplain level.
Seat Coal
SEAC
Seacliff Plug
SEAF
Seascale Glacigenic Formation
SEAG
Generally a sharp, irregular, unconformable contact with bedrock, or locally a sharp, undulating, unconformable contact with stony clay diamicton of the Holmrook Till Member of the Blengdale Glacigenic Formation.
West Cumbrian coast to the west of the Lake District and west of the limit of the 'Gosforth Oscillation' between Cleator and Ravenglass.
Interbedded sand, gravel, silt, clay, pebbly clay diamicton and gravelly sandy clay diamicton, typically reddish brown, containing clasts mostly derived from the northwestern valleys of the Lake District (granophyre, red sandstone, greywacke, welded tuff), the West Cumbrian Coalfield (yellow and white sandstone, coal), but with some from Scotland (greywacke, granodiorite).
Variable, but commonly the ground surface or a sharp, planar, unconformable contact with reddish brown pebbly sandy clay diamicton units of the Gosforth Glacigenic Formation.
Seatown Sandstone Member
SEAS
Seacliff Tower Vent
SEAT
Second Ell Coal (South Yorkshire, Nottingham And Derby)
SEC
Decomposes into thin, un-named coals elsewhere.
Seaford Chalk Formation
SECK
Coniacian to Santonian. Micraster coranguinum Zone.
Conformable at the base of Shoreham Marl 2 in Sussex that marks the change from regularly spaced nodular and grainy chalk beds of the upper Lewes Nodular Chalk Formation to smooth white chalks. This marl is equivalent to the East Cliff Marl 2 in Kent and which is also identified at the Anstey Quarry [TL 395 329] south of Royston, in the `Transitional? Province. In the field, this is the most difficult boundary to place precisely as it falls in the sequence where the predominance of interbeds of hard chalk reduces in favour of soft chalk. The most positive criterion is the incoming of abundant thick-shelled inoceramid debris (Platyceramus) in soft chalks, although this may not be applicable everywhere. The presence of a sequence containing carious flints within the low Seaford Chalk and high Lewes Chalk is a helpful field indicator of the boundary. Geomorphologically the formation characteristically forms long even dipslope crests.
Firm white chalk with conspicuous semi-continuous nodular and tabular flint seams. Hardgrounds and thin marls known from the lowest beds. Some flint nodules large to very large.
Generally in the range 50 to 80m in the basinal successions of Sussex and Hampshire within the Southern Province. Equivalent beds in Kent are in the range 55 to 60m. Over considerable areas of Southern England the thickness of this unit is limited by erosion beneath the sub-Palaeogene unconformity.
Conformable at the Buckle Marl 1 in the Sussex succession (Mortimore, 1986). Typically, at upward change from white flinty chalks with no marl seams to less flinty chalk with numerous marl seams (the Newhaven Chalk Member). The incoming of common Zoophycos flints and the presence of the zonal Uintacrinus socialis crinoid at the base of the Newhaven Chalk Formation are useful indicators in the field.
Sedgwickii Grits Facies (Caban Conglomerate Formation)
SED
Seend Ironstone Formation
SEEI
Seeley Formation
SEEL
Strathmore Group
SEG
At base of bright red, massive, poorly-sorted siltstone and silty sandstone of Cromlix Formation and its correlatives, where this overlies coarser-grained sandstone or conglomerate of Arbuthnott-Garvock Group. Locally diachronous in areas adjacent to Highland Boundary Fault where conglomerate and sandstone interfingers with Cromlix Mudstone Formation.
Northern Midland Valley, Arran to Stonehaven.
Interbedded sandstone and siltstone. These interfinger with clast-supported conglomerate containing well-rounded boulders, cobbles and pebbles predominantly of psammite, quartzite and lava in areas adjacent to the Highland Boundary Fault. Siltstone and mudstone are interbedded with the sandstone, particularly in Strathallan.
1800-2400m over much of the outcrop.
Not seen. Base of Upper Devonian succession in the northern Midland Valley is unconformable.
Seaham Formation
SEH
Sharp, conformable contact with the underlying Fordon Evaporite Formation (gypsum, anhydrite and halite) offshore and the laterally equivalent Seaham Residue and Edlington Formation onshore. Marked by the incoming of thinly bedded limestone above evaporite and laterally equivalent mudstone
Durham Province of the English Zechstein: County Durham, Tyne and Wear, Cleveland and northernmost North Yorkshire (equivalent to the Brotherton Formation in the Yorkshire Province).
Predominantly thin-bedded limestone (calcite mudstone/wackestone with some interbedded coquina, packstone, grainstone, mudstone and concretionary limestone) with some dolostone.
1 to 31.5m.
The base of the overlying Billingham Anhydrite Formation, or where the latter has been dissolved, at the base of the overlying mudstones and siltstones of the Roxby Formation.
Seascale Hall Tuff Member
SEHA
Sharp base within the Brown Bank Tuff Formation at upward change from andesitic lapilli-tuffs to rhyodacitic lapilli-tuff; pyroclastic breccia at base in Sellafield borehole No.10A. Seascale Hall Member oversteps other (unnamed) members of the Brown Bank Tuff Formation and in Sellafield borehole No.5 rests on the Bleawath Tuff Formation.
Seen in Sellafield boreholes 2 (NY00SE/28), 4 (NY00SE/29), 5 (NY00SE/30), 10A (NY00SW/38) and RCF1 (NY00SE/35).
Eutaxitic and parataxitic rhyodacitic lapilli-tuff containing small abundance of pale acid lithic clasts. Interpreted as a welded ignimbrite sheet.
Overlain by thin, andesitic, lithic rich lapilli-tuff-grade ignimbrite within the Brown Bank Tuff Formation.
Seaham Residue
SEHR
Stratheden Group And Inverclyde Group (Undifferentiated)
SEIC
Sgurr Of Eigg Pitchstone Formation
SEIG
Seisdon Formation
SEIS
Variable lithology; glaciogenic sequence beneath the Tryssul Beds. [Generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
Sedg(E)Ley Limestone
SEL
Selborne Group
SELB
Sele Formation
SELE
Slingstane Limestone
SELS
Sub-Ell Marine Band
SEM
Stile End Formation
SEN
Taken at change in lithology from siltstones to sandstones of Longsleddale Formation below, or locally at unconformity with Borrowdale Volcanic Group.
Grey, calcareous, fossiliferous siltstones.
Maximum of c.50m, wedges out laterally over a distance of 3km.
At base of Applethwaite Formation or Stockdale Rhyolite Formation where present.
Selcoth Formation
SEO
Silurian, Llandovery, guerichi Biozone to Early turriculatus Biozone.
Conformable sedimentary boundary with rocks of the Moffat Shale Group.
Sandstone, typically fine- to medium-grained but ranging from very fine- to coarse-grained. Generally medium- to thick-bedded over thicknesses of tens of metres interspersed with units up to few metres very thin to thin-bedded. Interbedded siltstone or silty mudstone generally in thin beds; sandstone and siltstone typically greenish grey when fresh, pale brown weathering. The Selcoth Formation is of broadly similar character to the Glendearg Formation, although it lacks the very thick-bedded parallel laminated sandstone units typical of the latter and has a very restricted age range in comparison.
Few hundred metres to 2000m
Faulted, no stratigraphical contact preserved.
Sella Park Tuff Member
SEP
Taken at the sharp change from bedded tuff, lapilli-tuff and sandstone of the Newton Manor Sandstone Formation.
Sellafield borehole 7A (NY00SE/36) only.
Spherulitic and silicified welded rhyolitic tuff.
91m (uncorrected for structural dip or borehole deviation from vertical).
Overlain by other members of the Yottenfews Tuff Formation: immediately by laminated fine-grained sandstone.
Pre-Late Devensian Quaternary Sequence At Depth [See Description For Limitations Of Use]
SEQ
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. Hence, all pre-Late Devensian Pleistocene ages encountered in this area are potentially included.
Originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. Note that on the related Quaternary Domains map, this category was described as: "POSSIBLE PRE-LATE DEVENSIAN QUATERNARY SEQUENCE AT DEPTH (generally restricted to areas where drift thickness isopachs are >15m; or are inferred to be >15m; shown in conjunction with surficial domain, eg GLD/SEQ or ALV/SEQ".
Skrinkle Sandstone Formation
SES
Solway Esk Valley Formation
SESKV
A sharp, undulating, erosional contact, mainly on reddish brown, clayey, sandstone-rich diamictons of the Gretna Till Formation, or yellowish brown, greywacke-rich diamictons of the Langholm Till Formation.
The valley of the River Esk and its tributaries, Dumfries-shire.
Mainly comprises sand and gravel, forming river terraces, and silty, clayey sand forming floodplains, and concealing sand and gravel. Includes units of sand, silt and clay, which are typically reddish brown.
At the present ground surface or, locally, covered by peat.
Seathwaite Fell Sandstone Formation
SET
The base of the volcaniclastic sandstone succession. In the type area a facies transtion or a sharp contact on underlying pyroclastic rocks of the Scafell Dacite Member. Markedly unconformable on many formations in the upper part of the Borrowdale Volcanic Group, including Airy's Bridge, Lingmell, Lag Bank, Low Water, Froswick and Woundale formations.
Extensive outcrop throughout the Lake District. From Seathwaite Fell (NY 230 100) to Grasmere (NY 33 07), Ambleside (NY 37 04), Coniston Fells (SD 29 99) and Broughton Moor (SD 25 94), Thirlmere (NY 31 13), High Street (NY 42 11) to Wet Sleddale (NY 53 10), Cumbria.
Predominantly bedded volcaniclastic sandstone and siltstone with interbeds of tuff, lapilli-tuff, volcaniclastic breccia and conglomerate. Host to penecontemporaneous andesite and basaltic andesite sills.
30 to 1100m (excluding intrusive igneous rocks).
Usually marked by dacitic lapilli-tuff of the overlying Lincomb Tarns Tuff Formation [andesitic sills may intervene locally] or in the Kentmere area by the Kentmere Pike Formation.
Setter Quartzite (?Formation)
SETQ
Seven Feet Coal (Warwickshire)
SEV
Severn Valley Formation
SEVN
Unconformable, commonly channelled base on pre-Quaternary bedrock.
Severn catchment (excluding Warwickshire Avon).
Fluvial terrace and alluvial deposits of the River Severn and tributaries excluding the Avon (see Warwickshire Avon Valley Formation) and possibly others, pending review. Mainly sand, gravel and mud; divided into six "terrace" members (Spring Hill, Bushley Green, Kidderminster Station, Holt Heath, Worcester, Power House members), plus Holocene alluvium (Elmore Member of Bowen, 1999) and with local named organic deposits. Includes contemporaneous head, colluvium and soil deposits. Gravels are principally composed of Palaeozoic, Triassic and (mainly below Avon confluence at Tewkesbury) Jurassic material from the local bedrock of the catchment, with an admixture of glacial material from the Anglian Wolston Formation, etc. and, in the younger terraces, a substantial admixture of "Irish Sea" glacial material from the Devensian Stockport Formation.
(A) The name may need changing if it is decided that the Upper Severn should be excluded. Obviously Lower Severn would seem appropriate. The Upper Severn is entirely within the Devensian limit - in pre-Devensian times it was probably a tributary of the Dee.This is a common problem with rivers that have had major diversions during the Pleistocene e.g. Thames and Trent. (B) The list of members relates to the ?lower Severn? below Bridgnorth but even there might not be fully comprehensive if ?awkward? rivers like the Teme (see below) are included. (C) It is impractical to give a fully comprehensive definition of the base in lithological terms. (D) The Upper Boundary might need modification if head etc is not included in this type of Formation. (E) Thickness estimates are subject to possible modification. (F) Listed 50K sheets are those that include a portion of the entire Severn catchment. More work might be needed to decide if some rivers like the Teme (the valley of which includes pre-Devensian terraces related to the River Wye!), or indeed the Upper (later Devensian) Severn (see above) should be included.
Scotland Flags
West Yorkshire area [Scotland Quarries, Midgley, near Halifax].
Flaggy bedded sandstone.
Sandwick Fish Bed Member
SFB
Strath Fionan Banded Semipelite Formation
SFBS
Sharp boundary from lineated quartzite with feldspathic laminae at top of Meall Dubh Quartzite Formation.
From Allt na Moine Buidhe [NN 7076 6110] to south bank of Allt Kinardochy [NN 7789 5727]. Not present east of the Loch Tay Fault, where its place is taken by the lower part of the Monzie Limestone and Schist Formation.
Rusty-weathering interbedded semipelite and pelite, with muscovite and biotite; cross-lamination and graded bedding well-preserved on 10-100mm scale; calcareous beds occur in places.
0 - 60m in Sheet 55W; probably some tectonic thinning.
Transitional boundary to limestone of Strath Fionan Pale Limestone Formation.
Sandsfoot Clay Member
SFC
Shoreface Deposits
SFD
Variable lithology, commonly sand and gravel; any deposit from the subtidal coastal zone between low water mark and the wave base, ie. the part of the sea-floor affected by wave action. [Generic description: earth science dictionaries in the BGS library].
Scalford Sandstone Formation
SFDS
Late Devonian to Early Dinantian.
The base has has not been proved, is likely to be an unconformity upon Lower Palaeozoic strata.
Only proved at the type locality, but may occupy other eastern parts of the Hathern Shelf.
Redish-brown, brown or green, fine- to medium-grained calcareous sandstone, brown, red and purple, blocky to fissle siltstone and grey, blocky mudstone.
At least 123.7m
The top is taken at the type locality where the calcareous sandstones, siltstones and mudstones of the Scalford Sandstone Formation are in tectonic contact with the overlying mudstone and thin limestone of the Widmerpool Formation.
Southerham Fingerflints
SFFL
Sandsfoot Grit Member
SFG
Shunner Fell Limestone
SFL
Scaleber Force Limestone Member
SFLM
Base of Scaleber Force Limestone Member is drawn where the dark limestones of the Member rest sharply and conformably on paler grainstone of the Chapel House Limestone Formation.
Bioturbated, well-bedded, fine- to coarse-grained dark limestones (packstones and subordinate wackestones), generally argillaceous, with common detrital quartz and common mudstone partings and interbeds to 1.8m thick.
North of Middle Craven Fault the Member ranges from 22m to 58m thick. South of Middle Craven Fault the Member is 61.6m thick at the type locality (Stockdale Farm (Cominco S7) Borehole).
The top is taken where the dark grey limestones of the Scaleber Force Limestone Member are overlain by the mid dark grey limestone of the Scaleber Quarry Limestone Member.
Scrabster Flagstone Member
SFM
Shafton Marine Band
SFMB
The correlation of a marine band found in Central Ayreshire and one recorded at Bothwell Bridge in Lanarkshire with the Shafton Marine Band is tentative, and hence so is the potential relationship to the Scottish Upper Coal Measures [Ramsbottom and others, 1978, Fig.14 and associated notes].
Seventy Fathom Post Member
SFP
Strath Fionan Pale Limestone Formation
SFPL
Transitional boundary from semipelite to pelite of Strath Fionan Banded Semipelite Formation.
From streams draining towards Lochan an Daim [NN 7156 5811] to south bank of Allt Kynachan [NN 7776 5720]. Not present east of the Loch Tay Fault, where its place is taken by one of the limestones in the Monzie Limestone and Schist Formation.
White, dolomitic limestone with tremolite, containing thin siliceous ribs and laminae with muscovite and phlogopite.
0 - 20m in Sheet 55W; probably some tectonic thinning.
Sharp contact with semipelite of the Tullochroisk Semipelite Formation.
Shunner Fell Sandstone
SFS
Strath Fionan Banded Semipelite Formation, Strath Fionan Pale Limestone Formation And Tullochroisk Semipelite Formation (Undifferentiated)
SFSFT
Staffin Shale Formation
SFSH
St Fergus Silt Formation
SFSI
A sharp, undulating, unconformable contact with underlying till, comprising grey, pebbly clay diamicton, yellowish brown gravelly clayey sand diamicton, and reddish brown gravelly silty sandy clay diamicton.
Buchan, northeast Scotland, on Sheets 97 (Fraserbugh) amd 87E (Peterhead).
A dark grey, silty clay with laminae of sand and well dispersed gravel dropstone clasts, containing boreal to boreal arctic marine microfossils; interpreted as a glaciomarine deposit.
A gradational contact with overlying organic silts and clays, interpreted as lacustrine alluvium.
Seafield Tower Limestone
SFT
Seafield Tower Sandstone
SFTS
Shale Grit
Shotts Gas Coal (Central Coalfield)
SGA
Sand And Gravel Of Uncertain Age And Origin
SGAO
Sand and gravel with rare lenses of clay. [Generic description: from East Anglian data].
Sgaorishal Member
SGAOR
Cross-stratified conglomerate mark the base of the Member, above poorly-sorted conglomerates of the A'Mharagach Member.
Cross-stratified conglomerates, containing cornstone, quartzite and Torridonian sandstone clasts predominate. Channels, cross-bedding and a high degree of sediment sorting indicate that fluvial deposition was likely, indicating a gradual transition to the marine conditions of the overlying Allt Dubh Member. Clasts reach a maximum size of 150mm. Not shown on 50K maps.
Below marine fossil-rich sandstone beds of the Allt Dubh Member.
Snebro Gill Beds
SGB
Storm Gravel Beach Deposits
SGBD
Standing Coal (Somerset)
SGCO
Slieve Gullion Complex
SGD
Seggholm Micaceous Flagstones
SGF
Stoke Goldington Member And Felmersham Member (Undifferentiated)
SGFM
Probable Wolstonian (Saalian) to Devensian.
Stricegill Grit
SGG
Stragglethorpe Grange Limestone Bed
SGGL
Change up from grey shelly mudstone of the undifferentiated Foston Member; at 10.91m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands: north Leicestershire to Lincolnshire. Not recognised in the Scunthorpe Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes southwards into part of the mudstone-dominated Charmouth Mudstone Formation.
Grey, weathering pale brown, silty, finely sandy, shelly limestone in one or two closely-spaced 0.1 to 0.35m-thick beds. Upper part may include fine ferruginous peloids. Fauna includes forams, serpulids, gastropods, bivalves (including numerous pectiniids and Gryphaea), ammonites, belemnites, ostracods, fish debris and palynomorphs. Forms a weak feature.
0.1 to 1m; 0.19m in type section.
Change up into grey mudstone of the undifferentiated Foston Member; at 10.72m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Slieve Gallion Granite
SGGR
U-Pb 466 +/- 3.3 Ma (Noble et al., 2004); Rb-Sr whole rock 418 +/- 26 Ma (O'Connor et al., 1982).
Scargill Grit
SGGT
Screes Gill Formation
SGI
Below the first sandstone bed above the laminated siltstone of the Wray Castle Formation.
Unit, as defined, is recognised in the southern and central Howgill Fells (Sheet SD69). Correlation with lower part of Coniston Group in the northern Howgills is probable, but as yet unproven.
Thin, medium or thick beds of fine-grained sandstone grading up to mudstone, intercalated with thin-bedded siltstone-mudstone couplets, and laminated siltstone units.
About 280m in the type section.
Below a 70m thick siltstone-dominated unit, forming the basal division of the 'Undivided Coniston Group'.
Studgill Tuff Formation
SGIL
Lower boundary is nowhere seen becouse of faulting
In the Cross Fell Inlier, Cumbria
Rhyolitic lapilli-tuff and volcaniclastic sandstone
Defined by the base of the overlying silicic tuff of the Knock Pike Formation
Saughland Sill
SGLND
Sangomore Formation
SGM
Conformably overlies the dark grey, chert-rich dolostones of the Sailmhor Formation.
The Durness Group, which contains the Sangomore-Formation, forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye.
Fine-grained, granular dolostones, pale to dark grey in colour, although commonly pale cream coloured. Chert nodules and layers are common near the base. Towards the top there are bands of pink and cream limestone.
Up to 180 m thick, measured as 60 m thick at Balnakiel Bay.
Conformably overlain by dolomitic limestones of the Balnakiel Formation.
Sub-Glenfuir Marine Band
SGMB
Sgurr Marcasaidh Formation
SGMC
Staosnaig Phyllite Formation
SGP
Salterella Grit Member
SGQ
Conformably overlies the Fucoid Beds Member of the An t-Sron Formation.
The An t-Sron Formation, including the Salterella Grit Member, forms a narrow, discontinuous belt, extending along the North-western side of Scotland from the Durness-Eriboll area, through Assynt, Dundonnell, Kinlochewe and Kishorn, to Skye.
White quartz arenite and quartzite, characterised by small conical Salterella shells.
Up to 20 m thick, but generally less than 15 m thickness.
St Ann's Grit
SGR
Sunderland Ground Formation
SGRD
Stubble Green Silt Member
SGSI
Gradational, conformable contact with dark brown, calcareous, laminated silt and clay of the Carleton Hall Clay Member of the Glannoventia Formation.
West Cumbria, within the Wasdale basin (around Holmrook).
Brownish grey (Munsell Soil) sandy silt with shell fragments and diverse assemblages of cold water marine dinoflagellate cysts and foraminifera.
To 2.3m
Sharp, conformable contact with overlying grey, laminated silty sand of the Kokoarrah Shelly Sand Member of the Glannoventia Formation.
Swch Gorge Tuff Formation
SGT
Conformably overlies mudstones and siltstones of the Pen-plaenau Siltstone Formation.
Grey porcellanous felsic ash-flow tuffs and interbedded volcaniclastic sandstones, with local thin mudstones.
30 to 90m
Conformably overlain by mudstones of the Allt-tair-ffynnon Formation or Teirw Siltstone Formation.
Allt Sgiathaig Till Member
SGTI
Unconformable on bedrock, predominantly Eriboll Formation sandstone.
Patchy, discontinuous extent within the outcrop of the Moine Thrust Belt, between Ullapool and Loch Eriboll. Occurs exclusively to the west of the Moine Thrust and predominantly on Eriboll Formation sandstone.
Pinkish off-white, pale grey to mid grey, poorly sorted, sandy, clast-rich diamicton with boulders. The till has a quartz-sand matrix devoid of clay. Clasts are typically angular and densely packed. Clasts are predominantly of Cambrian Eriboll Formation sandstone (Basal Quartzite and Pipe Rock Member), although rare Lewisian gneiss, Torridon Group sandstone, Moine Supergroup and local igneous clasts may occur. The till is typically autochthonous, being derived from the local quartzite bedrock. Local underlying lithological variations (eg. Assynt imbricate zones) may be reflected by clast lithologies (eg. Salteralla Grit, Durness Limestone, Fucoid Beds, etc.).
Variable; 0.2-5m (maximum observed thickness).
St Germans Tuff Member
SGTU
Conformable with slate and mudstone of undivided Saltash Formation below.
Liskeard to Plymouth.
Carbonate cemented basic lava and hyaloclastite fragments, massive basic lava and bedded lithic tuffs.
Up to 175m.
Conformable with slate and mudstone of undivided Saltash Formation above.
Sand And Gravel Of Unknown Age
SGU
Sand and gravel with rare lenses of clay. [Generic description].
Sand And Gravel Of Unknown Origin
SGUO
Shale Group [May Be Obsolete = Part Of Millstone Grit]
Drawn at base of sandstone of the shale group where it rests conformably on shale of the basal grit.
North Crop of South Wales Coalfield.
Dark grey, blue and black shales with bands of grit, sandstone and quartzite. The sandstones are lenticular.
About 100 metres thick.
Drawn at conformable upward passage from dark shales of the Shale Group to brown, green and yellow sandstones and quartzites of the Farewell Rock.
First Shale Member
SH1
Third Shale Member
SH3
Fourth Shale Member
SH4
Fifth Shale Member
SH5
Sixth Shale Member
SH6
Seventh Shale Member
SH7
Shale Coal (North Ayrshire)
SHA
Shale Coal (Glasgow Area; Central Coalfield)
SHAC
Shanmullagh Formation
SHAN
Not exposed: unconformable, in the east on Sheet 34 (Pomeroy) on Lower Palaeozoic sediments and on varied igneous/metamorphic lithologies of Tyrone Volcanic Complex (Palaeozoic).
The Irvinestown segment of the Fintona Block, Northern Ireland.
Sandstone, purple-brown, fine- to medium-grained, thin to very thick beds; and purple-red siltstones and mudstone; ripples.
Not known; probably >1000m
Not exposed; overlain unconformably by Lower and Upper Carboniferous sediments.
Shap Pluton
SHAP
Shap Fells, Cumbria.
Potassium feldspar-megaphyric granite. Radiometric age: 397 +/- 7 Ma (K-Ar, biotite) (see Rundle, 1992).
A steep-sided, cylindrical pluton, with an outcrop area of about 8 km2.
Not present.
South Harris Meta-Igneous Complex
SHAR
Shannochill Sandstone Member
SHAS
The sharp contact at the top of the Gartartan Conglomerate Member of the Ruchill Flagstone Formation.
The north-west limb of the Strathmore Syncline, from Shannochill [NS 542 992] to north-east of Lochan Balloch, probably re-appearing in Keltie Water, north-east of Callander.
Sandstone, grey-brown to reddish brown to purple., fine- to medium-grained, lithic, locally micaceous, commonly planar bedded, rare sandy siltstone beds, coarsening north-eastwards from Glenny Burn [NN 5700 0213].
Up to 300 m near Arntamie [NN 565 010].
North-east of Malling [NN 5625 0065], seen as a diachronous transition to the Malling Conglomerate Member, south of Malling, there is a diachronous transition to the undivided Cromlix siltstone facies.
Haven Brow Beds
SHAV
Shirehampton Formation
SHB
Gradational, but taken for convenience at the top of the Sneyd Park Fish Bed, a conglomeratic fish-bearing sandstone at the top of the red sandstones, mudstones, siltstones and conglomerates of the underlying Portishead Formation. Above the Sneyd Park Fish Bed grey mudstones and limestones of the Formation appear interbedded with red sandstones and mudstones. This boundary is in need of work.
Bristol area [ST 60 74]. There is considerable confusion over the exact geographical extent. Thought to pass southwards into the undivided Avon Group. Locally included mistakenly within the Portishead Formation on BGS maps.
Interbedded, thin- to medium-bedded red, green and grey mudstone, limestone, sandstone and siltstone with a thick red crinoidal limestone, known as the Bryozoa Bed, developed at the top. Mainly deposited in a marine influenced lagoonal environment.
30 to 50m
Taken at the irregular erosive contact between the red crinoidal limestone [Bryozoa Bed] of the Formation and the overlying pebbly phosphatic limestone [Palate Bed], the basal bed of the interbedded limestones and mudstones of the undivided Avon Group.
Shiaba Group
SHBA
Shape Burn Limestone
SHBL
Sheiling Burn Vein
SHBV
Salt Hill Cap Beds
SHCB
Shepherd's Chine Member
SHCH
Shank Castle Limestone
SHCL
Sherrycombe Member
SHCM
Sharp transgressive base on rocks of the Rawns Member (q.v.).
Mainly upward-coarsening sandstones above a scoured base. Naticopsis, Myalina and, very rarely, fragments of Thamnopora are found in thin shelly mounds above the scoured surfaces. These sequences give way to grey lenticular-bedded mudstones with sporadic Chondrites and, in the highest beds, Diplocraterion. Cross-bedded sandstones follow to complete the uplands-coarsening sequence.
Overlain by the basal 1m-thick bed at the base of the Little Hangman Member (q.v.), which contains Mylina (mostly in life position) and bryozoans.
Shining Coal (Dungannon)
SHCO
Shank's Castle Formation
SHCS
Shellesder Member
SHDER
Unconformable base on Torridonian sandstone (quartzite).
Basal member of the Monadh Dubh Sandstone Formation, exposed as a thin alluvial fan infilling Torridonian topography. The Member commences with cornstones, overlain by extensive Torridonian-clast-rich conglomerates and laterally discontinuous interbedded sandstones. Not shown on 50K maps.
16m
Contact overlain by 'red beds' of the Sgaorishal Member.
Strath Halladale Migmatite Complex
SHDL
Sherborne Member
SHE
Shertcliffe Coal (West Yorkshire)
SHEC
Shetland Granitic Suite
SHEGR
Shell Bank
SHEL
Shenley Limestone Member
SHEN
Overlying silty beds at the top of the Woburn Sands is a thin, gritty ironstone ("carstone"), which passes up into a sandy mudstone associated with lenticular beds of a pale brown phosphatic limestone with scattered polished goethite ooliths (Shenly Limestone) (Owen 1972; Smart, 1997).
Restricted to the area around Leighton Buzzard. Leighton Buzzard Sheet 1:50k sheet number 220.
Lenticular beds of a pale brown, phosphatic limestone with scattered polished goethite ooliths (Owen 1972; Smart, 1997). It may be slightly limmonitic and glauconitic. Brachiopods common.
Up to c. 0.1m.
Lenticular beds of a pale brown phosphatic limestone with scattered polished goethite ooliths (Shenley Limestone) are overlain by a 1.2m thick fissile, red mudstone informally called "Red Clay" or "Cirripede Bed".
Shearwater Salt Formation [Obsolete Code: Use Shwt]
SHES
Shettleston Sandstone
SHET
Shetland Glacigenic Subgroup
SHETG
Sharp, unconformable contact with bedrock or with units of the Shetland (Albion) Glacigenic Subgroup.
Scar House Beds
SHF
Shafton Coal (West And South Yorkshire And Derbyshire)
SHFC
Sharp's Hill Formation And Fullers Earth Formation (Undifferentiated)
SHFE
Shotts Furnace Coal (Central Coalfield)
SHFU
Stonehaven Group
SHG
Angular unconformity on meta-igneous and metasedimentary rocks of the Highland Border Complex.
Fine- to medium-grained lithic sandstone interbedded with minor amounts of conglomerate and siltstone.
Variable, up to maximum of 1800m. Presumed to lap onto basement (Highland Border Complex and possibly Dalradian) and to be overlapped by younger groups.
Base of Downie Point Conglomerate Member (Dunnothar Castle Conglomerate Formation), where thickly-bedded or massive conglomerate overlies planar bedded or cross-bedded pebbly sandstone of the Carron Sandstone Formation.
Shingly Geo Limestone
SHGL
Shinnel Formation And Glenlee Formation (Undifferentiated)
SHGN
Shepperton Gravel Member
SHGR
Erosional surface cut into Tertiary-Cretaceous bedrock.
Thames Valley, Abingdon-London.
Gravel with clay and sand.
0-8m, locally 12-14m
Lies beneath Thames floodplain alluvium (Staines Alluvial Deposits).
Shaftoe Grits
SHGT
Sharp's Hill Formation
SHHB
Non-sequential, on the Chipping Norton Limestone Formation, where present or the Horsehay Sand Formation. The base, which may be marked by an uneven junction, is taken as the first mudstone (commonly carbonaceous), marl, sand or micritic limestone (commonly richly fossiliferous or pebbly), above the ooidal limestones of the Chipping Norton Limestone Formation (Horton, 1987, p.74), or the barren sands of the Horsehay Sand Formation.
North Oxfordshire north-east of Milton-under-Wychwood and Minster Lovell, where it passes south-west (on BGS 1:50000 sheet 236) into the marine mudstones of the Fuller's Earth Formation; north-west Buckinghamshire; Northamptonshire south-west of Eydon and Wappenham (on BGS 1:50000 sheet 202) where the overlying Taynton Limestone Formation is succeeded to the north-east by the Wellingborough Member of the Rutland Formation (unpublished BGS data), and the Sharp's Hill Formation is undifferentiated, passing into lithologically similar unnamed mudstone beds of the Rutland Formation.
Varied sequence of greenish grey, silty, moderately shelly and calcareous mudstones, pale greenish grey shelly marls and fine-grained shelly limestones with marine and freshwater faunas. Rootlets are common, and some mudstones display seatearth textures and more variegated colours, also indicating shallow, proximal conditions. Subordinate siltstone and sandstone beds are present near the base of the formation.
Up to 5 m thick.
Conformably overlain by ooidal and shelly detrital limestones of theTaynton Limestone Formation, where present, otherwise, the formation is difficult to distinguish from the lithologically similar Rutland Formation.
Shilburnhaugh Coal
SHHC
Shoal High Formation
SHHI
Shiels Coal (Central Coalfield)
SHI
Shilbottle Coal (Northumberland)
SHIC
Shinnel Formation
SHIN
Conformably overlies Moffat Shale Group (Lower Hartfell Shale).
Wacke sandstone and siltstone turbidite succession.
Faulted (against Silurian rocks by the Kingledoors Fault).
Shipton Member
SHIP
The base of the peloidal wackestone/packstone/grainstone, overlies marls and fine-grained ooidal grainstones of the Hampen Formation or Rutland Formation.
From the Stroud to Cirencester area of Gloucestershire, where passes westwards into the Athelstan Oolite Formation, north-eastward through Oxon and Buckinghamshire to the Brackley area, where it passes north-eastward into the Roade Member of the Blisworth Limestone Formation.WhL is the code for White Limestone Formation. On some sheets (219,235), because the Signet Member (Si) or Bladon Member (Bl) of the White Limestone Formation is separated, WhL is described as 'Shipton and Ardley Members, undivided' but the Shipton Member has not been, nor is likely to be separated on any 1:50k or 1:10k map.
Pale grey to off-white or yellowish limestone, peloidal wackestone and packstone with subordinate ooidal and shell fragmental grainstone, and re-crystallised limestone with beds of argillaceous limestone, marl and mudstone or clay.
From 3 m to 10 m thick, increasing to the south-west, about 4 m thick in type section.
A generally sharp, erosive boundary, and commonly a bored and oyster-encrusted hardground,at the top of the Excavata Bed, which is a peloidal packstone at the top of the Shipton Member, and generally succeeded by a sandy mudstone or sandy limestone at the base of the Ardley Member.
Spy Hole Limestone
SHL
Shellag Formation
SHLAG
The base of the Shellag Formation rests on sand, gravel and diamicton of northern origin forming the top of the Kindroughad Formation.
The Isle of Man (50K sheets 36, 45, 46 and 56).
Glacially technically deformed complex sequence of diamictons, gravels and shelly sands. It is dominated by material derived from offshore within the Irish Sea basin, and the Formation includes rafts of marine sediment.
c.50m (but glacitectonically thickened by folding and repeated by faulting) at its type section.
Overlain unconformably by the Orrisdale Formation.
Shellband Coal
SHLB
Sharlston Low Coal (West Yorkshire)
SHLC
Sand Hole Formation
SHLE
Second Hosie Limestone
SHLS
Generally seen as a conformable change from marine mudstone within the Lower Limestone Formation, underlain by Lillie's Shale Coal in the Glasgow area. Not uncommon for Second and Top Hosie limestone to be separated by only marine strata or even to become fused together.
Located throughout most of the outcrop of the Lower Limestone Formation of the Midland Valley of Scotland, but locally difficult to recognize in Ayrshire and Lanarkshire where the Hosie limestones join together as the McDonald Limestone in a shelf setting.
A pale to dark grey, argillaceous, crinoidal, shelly bioclastic limestone, interpreted to be of marine origin. Thicker occurrences consist of calcareous mudstone and lime mudstone with a dolomitic top.
Generally up to 0.38m, and locally up to 2.10m in the Airdrie, Falkirk and Glasgow districts. This limestone fuses with the Top Hosie Limestone in the west Glasgow district and at Wairdlaw [NS 995 731] in the Bathgate Hills. In shelf settings, such as in Midlothian, it can be as much as 15m thick.
Generally seen as a conformable change to marine mudstone within the Lower Limestone Formation.
Slate Hill Andesite
SHM
Shoreham Marls (One)
SHMA1
Shoreham Marls (Two)
SHMA2
Sandwich Marine Band [Local Name: See Htmb]
SHMB
Local name applied to the Haughton Marine Band (National Standard Name) in the Canonbie Coalfield area.
Sharlston Muck Coal (West Yorkshire)
SHMC
Shackleton Formation
SHN
Unconformable on Pliocene and older strata of varied lithology and competence.
Predominantly a sandy sequence with pebbles and shell fragments. Some clayey partings but generally a well-sorted fine-grained to silty sand. Similar in lithology to base of Mariner Formation above it, but base of unit rests on a variety of lithologies, especially in the west of the area where it onlaps to, or offlaps from, a variety of older strata.
40 metres approximately at Borehole 80/1, 90 metres approximately at Borehole 81/18. Thickens to north, east and northwest on North Sea Plateau. May be absent in parts of the Norwegian Trench where it has been eroded away.
Unconformable/disconformable or apparently conformable with the sandy material of the overlying Mariner Formation.
Stair Hole Member
SHO
First occurrence of very shelly micrite (Cinder Bed) above more pure micrites of the Warbarrow Tout Member.
Characterised by calcarenites and calcirudites. These are thicker and dominant lower in the succession; the Cinder Bed at the base of the member comprises a package of biomicrites, with abundant oysters, and can be easily correlated across the region. This passes up into a sequence of interbedded biosparites, biomicrites and mudstones (Intermarine and Scallop beds). The limestone may contain cross-stratification, particularly in the east. Thicker, carbonaceous mudstones, with numerous "beef" (fibrous calcite) veins, become more common towards the top of the member (Corbula and Chief Beef beds), again, particularly in the east. The middle part of the member, across Dorset, contains detrital quartz. The upwards decrease in shelly limestone defines a crude fining-upwards sequence.
Ranges from 10m in west Dorset to 40m in the east.
Top of thicker mudstones and finer grained biosparites or micrites beneath thickly bedded, coarse biosparite (base Broken Shell Limestone Bed) at the base of the overlying Peveril Point Member.
Shetland Ophiolite Complex [Redundant Code: Use Shop]
SHOC
Shetland Ophiolite Complex
SHOP
The base of the complex is marked by a thrust.
The Shetland Ophiolite covers the eastern half of Unst, and the central and eastern parts of Fetlar.
The unit is composed of two ophiolitic nappes, the upper and lower nappes, which are separated and underlain by imbricate zones composed of metasedimentary strata, including ophiolitic erosional debris, acid and basic metavolcanic rocks, ophiolitic rocks and hornblende schist.
At least 8 km thick.
The top of the upper nappe is not seen.
Scawt Hill Plug
SHP
Stanhope Coal (South Derbyshire)
SHPE
Sharkham Point Member
SHPT
Shane's Hill Rhyodacite
SHRD
Shrewsbury Glacigenic Formation
SHREW
Unconformably on the Stockport Formation (sensu Bowen, 1999) at the stratotype locality, and locally on the Plynlimon Till Formation within the Shrewsbury area (Thomas, 1989). At some locations farther north, it interdigitates with Irish Sea Ice derived deposits in a complex manner (Worsley, 2005); Cannell, 1982). Locally, it overlies bedrock unconformably.
Shropshire lowlands to the west of Shrewsbury and Dorrington, extending north of Four Crosses (see Pocock et al.,1938; Cannell, 1982) in a narrow band (5 to 10km wide) as far as Wrexham (Worsley, 1991).
Stratified sand and gravel with interbeds of laminated clay, silt and diamict (till), all characteristically containing Lower Palaeozoic clasts derived from the Welsh massif.
To c.6m at the stratotype locality.
Irregularly overlain at the stratotype locality by Late Glacial solifluction deposits and thence Windermere interstadial peat (Worsley, 1991). Elsewhere provides the present ground surface or is overlain unconformably by deposits of the Severn and Avon Catchments subgroup.
Shepshed Sandstone Member
SHSA
Unconformable on Precambrian rocks of Charnian Supergroup, and on Carboniferous rocks north and east of Charnwood Forest.
Mainly restricted to northern part of Charnwood Forest, between Newhurst Quarry and Whitwick. May also occur farther west, near Coleorton.
Red to brown, angular or subangular, fine- to medium-grained sandstone, generally parallel-bedded, with concentrations of angular Charnian clasts forming matrix-supported conglomerates. Siltstones and mudstones in upper part.
0-30m, may be 60m locally in palaeovalley situation in Charnwood Forest.
Gradational, by increase in siltstones and mudstones, into the Sneinton Formation (Mercia Mudstone Group). Probably also grades laterally into the main part of the Bromsgrove Formation.
Saugh Hill Grits Formation
SHSG
Conformably overlies the Tralorg Shale Formation.
Grey-green, thickly bedded, gritty sandstone and shale.
180 - 365 m thick.
Conformably overlain by the Pencleuch Shale Formation.
Shineton Shale Formation
SHSH
Tremadoc (Cressagian to Migneintian).
Grey or green shaly mudstones with interbedded sandstones at some levels.
At least 1000m locally.
Taken at the conformable transition into the black, flaggy micaceous siltstones of the overlying Habberley Formation, the junction being taken at the first appearance of black siltstone.
Shatterford Sill
SHSI
Shops Sandstone Member
SHSM
Slate Hill Trachyte
SHT
Sharlston Top Coal (South And West Yorkshire)
SHTC
Sharlston Thin Coal (West Yorkshire)
SHTH
Shiant Isles Sills
SHTS
Shute Sandstone Formation
SHU
In the western part of the outcrop, overlies and is partly laterally equivalent to the Newton St Cyres Breccia; in the eastern outcrop, overlies Crediton Breccia and Yellowford Formation; some interdigitation of silty sandstone with breccia is present at the top of the Yellowford Formation.
Outcrops around the limbs of a syncline between Upton Pyne, Newton St Cyres, and then eastwards to the River Exe.
Predominantly reddish-brown, silty, very fine-grained sandstone and sandy siltstone, weathering to silty sand and sandy silt. Breccia lenses occur at a few localities. Beds of intraformational breccia locally present.
Gradational boundary with the Dawlish Sandstone.
Shuttle Coal (Lancashire)
SHUC
Strumble Head Volcanic Formation
SHV
1:50 000 Sheet 209 (St. Davids) and adjacent Sheet 210.
Basaltic pillow lavas, spilitic breccias, ashes and intercalated sediments.
Up to 1500 metres.
Soundwell Hard Venture Coal (Bristol Area)
SHVC
Shap Village Limestone Formation
SHVI
Algal band at the top of the Stone Gill Limestone Formation, or the base of the first significant limestone bed above the Marsett Formation mudstone conglomerate.
Between the Anne's Well Fault in the south, and the Kirk Rigg Fault to the north, in the Shap and Penrith district of Edenside.
Comprises grainstone, oolite, calcarenite, dolostone, sandstone, siltstone, mudstone and conglomerate lithologies.
From 40 to 150m
Disconformity at the base of the overlying Ashfell Sandstone Formation.
Shales With Beef Member
SHWB
Base of bed 50, of Lang, W D, et al, 1923. Taken at sharp lithological change from limestone-shale interbeds of the Blue Lias Formation, to predominantly shales. Conformable boundary.
Southwest Dorset and southeast Devon, United Kingdom, mapped on Sheets 326 (Sidmouth) and 327 (Bridport). Northern limit not yet proved.
Dark grey laminated organic-rich shaly mudstone and dark grey mudstones with sporadic concretionary and tabular limestone bands. Abundant vertically oriented fibrous calcite of diagenetic origin ('Beef').
Top of bed 75 (Birchi nodules) of Lang, W D, et al, 1923).
Shap Wells Conglomerate Formation
SHWC
Shapwick Member
SHWK
Top of mineralised surface (Whitecliff Hardground).
Devon and West Dorset. Recorded on Sheets 326 (Sidmouth), 327 (Bridport) and 311 Wellington).
Calcareous sandstones and calcarenites with several chert horizons in lower part; glauconitic at most levels.
Erosion surface at base of Cenomanian Limestone.
Shearwater Salt Formation
SHWT
Sharlston Yard Coal (South And West Yorkshire)
SHYC
St Helen's Yard Coal (South Lancashire)
SHYD
Sub-Hartley Lingula Band
SHYL
Occurs persistently below the Hartley Coal in the Stirling/Clackmannan Coalfield and intermittently in the Airdrie district, e.g. around Kirkintilloch.
Shaftesbury Sandstone Member
SHYS
Sharp feature break, presumably coinciding with the incoming of beds of sandstone above the Cann Sand.
Main outcrop from Fontmell Magna (ST865 170) northwards across the Shaftesbury Sheet (313) and onto the Wincanton Sheet (297). Some small irregular outcrops (eg Dogbury Gate ST660 048), beneath unconformable Lower Chalk in the southwest of the Shaftesbury Sheet.
Alternating sequence of fine- to medium-grained glauconitic sand and sandstone. At the top, a massive, 2-3m thick, shelly calcareous sandstone. (Ragstone).
0 - 25m (3.9m exposed at type locality, of a total thickness of about 15m).
At the top of the Ragstone.
Signet Member
Base of rock types as described in lithological description, resting on (generally) hardground or eroded surface of white carbonate mudstone or wackestone at top of underlying Ardley Member of White Limestone Formation.
Churn Valley west of Cirencester area of Gloucestershire (westwards of which the member cannot be recognised consistently) eastwards to Shilton, near Burford, Oxon (eastwards of which it passes into the Bladon Member of the White Limestone Formation).
Typically brownish grey sandy or clayey peloidal wackestone, commonly with shell-fragments and lignite, associated with green and brown mudstone/clay; also shell-fragmental ooidal grainstones, brown sandy limestone and white carbonate mudstone and coralliferous marl.
Generally sharp, erosive boundary with cross-bedded shell-fragmental ooidal limestone, or mudstone of Forest Marble Formation.
Sillyhole Coal (Dalmellington)
SIC
Sitwell Coal (Derbyshire And South Yorkshire)
SICO
Siddick Seam
SIDK
Sides Farm Breccia Member
SIFA
At downward change from coarse polymict deposits to welded vitric tuff and lapilli-tuff of the Town End Farm Member. In reference section (RCM3) basal beds include 13m of bedded tuff and lapilli-tuff; and poorly sorted lithic-rich lapilli-tuff.
Sellafield boreholes 5 (NY00SE/30), 8A (NY00SE/38), RCF1 (NY00SE/35), RCF2 (NY00SE/36), RCF3 (NY00SE/37) and RCM3 (NY00SE/39).
Unbedded, poorly sorted sheets of pyroclastic breccia, lithic-rich lapilli-tuff; locally pumice-rich. Generally polymict, but with dominant dacite/andesite clasts in places.
68m in type section; 43m in RCF3. Thicknesses are uncorrected for structural dip or borehole deviation from vertical. Thickness in RCM 3 (reference section) not calculated.
At sharp upward change in lithology from polymict deposits to welded vitric tuffs of Longlands Farm Member.
Silchester Gravel Member
SIGR
Erosional contact on Cretaceous-Tertiary bedrock.
Kennet Basin.
Terrace surface around Silchester, Sulhampstead and correlatives.
Simonstone Limestone
SIL
Silesian Rocks (Undifferentiated)
SILA
Silsden Formation
SILS
A sharp base of dark grey fissile claystones of the Cravenoceras cowlingense Marine Band with diagnostic eponymous fauna, commonly underlain by a thin, fine-grained, calcareous and phosphatic sandstone of the Pendleton Formation. Elsewhere the boundary is taken at the base of the first thick quartz-feldspathic sandstone of Arnsbergian age, present above the dark grey, carbonaceous mudstone of the Bowland Shale Formation. It is taken at the base of the Mirk Fell Ironstones in the Stainmore Trough or the top of the Lower Howgate Edge Grit in the northern part of the Askrigg Block.
The Craven Basin of north Lancashire and north Yorkshire, between Lancaster [SD 47 61], Pendle Hill [SD 80 41], Skipton Moor [SE 00 50] and Harrogate [SE 30 55]. Also present across the southern part of the Askrigg Block, in the Masham district [SE 29].
Fine- to very coarse-grained pebbly feldspathic sandstone, interbedded with grey siltstone and mudstone and subordinate marine black shales, thin coals and seatearths. The lower part of the formation is dominated by thinly bedded sandstone, siltstone and mudstone forming sharp-based, normal graded beds of interpreted turbiditic origin.
Lancaster 1000m; Bradford 400m; Askrigg Block and Stainmore Trough up to 190m.
The base of the dark grey fissile claystones of the Isohomoceras subglobosum Marine Band, with diagnostic eponymous fauna. Where the Marine Band is not proven, the boundary is taken at the base of a thick, medium or dark grey mudstone succession, with numerous marine bands of the Samlesbury Formation.It is taken at the top of the Lower Follifoot Grit in the southern part of the Askrigg Block, or the base of a mudstone succession with Lingula in the Stainmore Trough.
Silurian Rocks (Undifferentiated)
SILU
Siller Willie Coal (Midlothian)
SILW
Sidmouth Mudstone Formation
SIM
The boundary is both gradational and conformable, and is drawn arbitrarily within an upward-fining, interdigitating succession where mudstones of the Sidmouth Mudstone Formation predominate over the siltstones and fine-grained sandstones of the underlying Tarporley Siltstone Formation; the junction is diachronous. Where the underlying Tarporley Siltstone Formation is absent or not differentiated (including at the type section), the boundary is marked by a rapid upward transition from sandstone- to mudstone-dominated lithologies immediately above the Sherwood Sandstone Group. At outcrop, the boundary is associated with a change from the brown sandy soils of underlying formations to the clayey, distinctively reddish brown soils of the Sidmouth Mudstone Formation. A concave break of slope is associated with the boundary in some areas.
The surface outcrop extends from the South Devon coast east of Sidmouth northwards into Somerset, Avon, Worcestershire, Warwickshire, Leicestershire, Nottinghamshire and North Yorkshire; and westwards into Derbyshire, Staffordshire, Cheshire and Lancashire. The formation occurs in the subsurface below much of southern England, the south Midlands and eastern England. Equivalents occur below the southern North Sea and eastern Irish Sea.
The formation consists of dominantly mudstone and siltstone, red-brown with common grey-green reduction patches and spots. The mudstones are mostly structureless, with a blocky weathering habit, but intervals up to 15m thick of interlaminated mudstone and siltstone occur within parts of the formation, notably in the Bollin and Byley Mudstone members of the Cheshire Basin (Wilson, 1993) and in the Radcliffe Member of the East Midlands (Charsley et al., 1990). Heterolithic units consisting of several thin beds of grey-green dolomitic siltstone and very fine-grained sandstone, interbedded with mudstone, occur at intervals throughout the formation. These units range from a few centimetres up to 4m thick, and locally form mappable cuesta features. Named examples include the Cotgrave Sandstone Member and Clarborough Member of the East Midlands (Charsley et al., 1990; Smith et al., 1973; Warrington et al., 1980) and the Weatheroak Sandstone Member of the Redditch area (Old et al., 1991). Units of halite up to 400m thick are present at several stratigraphical levels in the thicker basinal sequences of the East Irish Sea, Cheshire, Staffordshire, Cleveland, Worcestershire, Somerset and Dorset, though are most prevalent towards the top. Breccias produced by contemporaneous dissolution of salt are common throughout the formation. In Cheshire, more recent salt dissolution (some induced artificially by brine pumping activities) gives rise to dissolution hollows and collapse breccias associated with the halite members. Gypsum/anhydrite also occurs throughout the formation as nodules and veins.
165m at the type section (Gallois, 2001). Elsewhere, it ranges from 120-130m in the East Midlands, to 1600m in the Cheshire Basin.
Placed at a rapid upward transition from red mudstones or siltstones to the dominantly grey or green, partly or largely arenaceous beds of the overlying Arden Sandstone Formation. In the Cheshire Basin and parts of the Wessex Basin, where the Arden Sandstone Formation cannot be differentiated within thick halite deposits, the boundary is drawn immediately above the highest halite beds of the Sidmouth Mudstone Formation, which is conformable in all areas. At outcrop, the boundary is typically marked by a change from the reddish-brown clayey soils of the Sidmouth Mudstone Formation to the grey, slightly sandy clay soils of the overlying Arden Sandstone Formation. Where the latter forms a marked cuesta feature, the boundary typically lies at a slight concave break in the scarp slope. In the Cheshire Basin, where the Arden Sandstone Formation is absent, the boundary is mapped at the approximate down-dip limit of subsidence hollows and collapse breccias, which are associated with near-surface solution of halites (Wilkesley Halite Member) at the top of the Sidmouth Mudstone (Taylor et al., 1963).
Shide Marl
SIMA
Simmondley Coal
SIMM
Sinniness Formation
SIN
Conformable on Moffat Shale Group at Gillespie Burn (NX 257 540).
Medium- to thick-bedded greywacke, with thin mudstone beds, including very thick-bedded massive sandstone pockets and thick mudstone beds (to 2 metres).
Singing Coal (South Staffordshire)
SINC
Sandrock Formation
SIOW
The lower boundary is defined by a down-section change from upward coarsening rhythmical sequence of pebble beds, fine- to coarse-grained, generally cross-bedded sandstone and ["Group XIV" sensu Fitton, 1847, of the Ferruginous Sands Formation]. The boundary is drawn below the basal mudstone, which forms the lowest unit of "Group XV", the "Upper Clays and Sandrock" of Fitton [1847] and "clay band of the Group XV" of Casey [1961].
Isle of Wight and in the neighbourhood of Punfield Bay, Dorset. The unit is not mapped separately on the mainland, having been incorporated into an undivided Lower Greensand Group.
The Sandrock Formation comprises up to four upward coarsening sedimentary rhythms. Although rarely complete, a full rhythm comprises: 3. Well-sorted fine- to coarse-grained, commonly cross-bedded, sands the top of which is scoured. 2. Very dark grey mudstone and finely laminated, fine-grained sands and silts. Bioturbated. 1. Pebble beds overlying a scoured surface. The sands with small-scale cross-bedding are believed to have been deposited as migrating shoals in shallow water, estuarine conditions, whereas the large scale cross-bedded sands are considered to be subtidal channels [Wach and Ruffell, 1990; Insole, Daley and Gale, 1998; Ruffell and Wach, 1998a,b].
The top of the formation is an eroded surface where there is a change from gritty, reddish-brown sandstone with pebbles and phosphatic nodules ["Carstone Formation of the Isle of Wight"] and the underlying rhythmical sequence of fine- to coarse-grained, generally cross-bedded sands, dark grey mudstones and pebble beds. This depositional break is called the "Mid tardefurcata Break" by Casey [1961].
Side Pike Volcanic-Complex
SIPI
Base faulted, passes into more coherant stratigraphy
Restricted to the area between Great Langdale and Wrynose Pass, Lake District, Cumbria.
A chaotic, coarse volcanotectonic megabreccia comprising successions of tuff, lapilli-tuff, volcaniclastic sandstone, andesite and rhyolite. Some megablocks may be assigned to established formations, but other blocks are not recognizably parts of formations. The volcanic-complex passes laterally into more coherent stratigraphy
Faulted, passes into more coherant stratigraphy
Sitwell Rock (Derbyshire)
SIRO
Selham Ironshot Sands Member
SIS
Well-defined junction with lower part of Fittleworth Member (sandy clay which includes some limonite grains at this level).
West Sussex:, from Cowdray Park in the north, possibly as far as Ambersham Common in the south, possibly also as far as the Stedham area in the west, to about 1km east of Selham in the east.
Sand, purplish-reddish-brown, poorly-sorted, medium- to coarse-grained, with polished dark brown to black limonite grains to granule size locally. Cross bedded. Secondary iron-pan concretions in parts. From about 9km from Stedham, West Sussex (NGR SU 86 22) to east of Selham, West Sussex (NGR SU 94 20) the Fittleworth Member is divided by the Selham Ironshot Member. Samuel (1994) proposed the name 'Upper Fittleworth Beds' for the upper division (c.2m thick). This is here re-named informally the 'upper Fittleworth Member', with the lower division (to c.8m) named the 'lower Fittleworth Member'.
0-24.4m (passes laterally into 'loams', Fittleworth Beds or Rogate Beds to west).
Sharp junction of sand with upper part of Fittleworth Member (pale sandy clay without limonite, becoming strong greenish-grey where thinning out) or of hardground-like ferruginous sandstone with fine-grained well-sorted sand of Pulborough Sandrock, where Fittleworth Member absent.
Siliceous Tufa
SITU
Inorganic or organic silica deposited at or near springs and seepages. [Generic description: 'TMOS' Procedures].
Sixteen-Inch Coal (Dungannon)
SIXC
Sir John Coal (South Lancashire)
SJCO
St John's Knap Sandstone Member
SJKS
Passes diachronously and conformably downwards and laterally to the south into the conglomerates of the Catterline Conglomerate Formation; taken at the point where sandstone becomes predominant in the upward sequence.
Between Law of Lumgair (NO 8525 8180), and Moor of Auchendreich (NO 833 770).
Sandstone, pebbly sandstone and conglomerate.
From 230 to 345m
Passes diachronously and conformably upwards and laterally to the north into the Barras Conglomerate Member, taken at the point at which conglomerate becomes predominant.
Smith's Knoll Formation
Unconformably overlies early Lower Pleistocene Westkapelle Ground Formation.
Fine to medium-grained, muddy marine sands, with clay intercalations in the east. In the south and west it is characterised by gently-dipping prograding reflectors, mostly inclined eastnortheast; in the east its internal reflectors are sub-parallel. It passes laterally eastwards into thick, overlapping westward-prograding units of the Ijmuiden Ground Formation.
40 metres. (20 - 50 metres).
Unconformably overlain by Yarmouth Roads Formation or Winterton Shoal Formation, or by Upper Pleistocene or Holocene sediments.
Skaterigg Coal
SKA
Skelmersdale Albert Coal (South Lancashire)
SKAC
Skade Formation
SKAD
Skagerrak Formation
SKAG
Skadan Sandstone Member
SKAS
Skaw Intrusion
SKAW
Silurian-Devonian (c.400Ma).
Skelgill Formation
SKB
Laminated mudstone with calcareous laminae. Thin, impure limestone at base.
Conformably overlain by the Browgill Formation.
South Kent Catchments Subgroup
SKCAT
Pre-Cromerian (Middle Pleistocene) to Holocene.
Unconformable on Cretaceous bedrock.
The entire area covered by the catchments of south Kent (Stour, Rother and other rivers) that flow southwards from the North Downs to the English Channel.
Mainly river terrace sand and gravel and alluvial floodplain silt, silty clay and sand, together with related organic and mass movement deposits of the rivers Stour and Rother (Kent).
Saltwick Formation And Cloughton Formation (Undifferentiated)
SKCH
Skipton Castle Limestone
SKCL
Stink Coal (Milford, South Wales)
SKCO
Skiddaw Group (Undifferentiated) (Crummock Aureole)
SKCW
Contact metamorphism probably Early Devonian.
Shankend Beds
SKD
Skelmersdale Dam Coal (South Lancashire)
SKDC
Skerry Band
SKE
Skea Sandstone Member
SKEA
Conformable distally, resting on soft multi-coloured clays that lie on top surface of Ballyshannon Limestone Formation. Proximally, lower contact is deeply erosional into underlying limestone formation.
Kesh-Omagh area of the northwest Carboniferous basin in Ireland.
Sandstone, pale grey to blue-grey, medium-grained, calcareous, sparsely bioturbated, fossiliferous. Proximally is a channel (palaeovalley) fill conglomerate with mainly metamorphic clasts.
0 - 4.5m (measured), probably 10 - 12m in area of main palaeovalley conglomerate fill.
Abrupt change, in distal location, from sandstone up into conformable silty mudstones, shales and thin sandstones of normal Bundoran Shale. Proximally, top of member is not exposed.
Skelmersdale Earthy Delf Coal (South Lancashire)
SKED
Skegness Clay Formation
SKEG
In the type section, the base is defined by a downward change from medium and dark grey mudstone with partially pyritised and phosphatised ammonites to black, pyritous upper Roach Formation. The boundary is apparently conformable, although the junction is bioturbated and the top of the underlying Roach is burrowed.
Confined to The Wash and southern part of Lincolnshire, but not known at outcrop. The formation occurs only in the Skegness Borehole and BGS Borehole 72/78 in The Wash. It has not been recognised in Norfolk, but it appears to extend under the Wash to within two kilometres of Hunstanton (Wingfield et al., 1978). Swinnerton (1935), mentioned 1.83m of a similar lithology below the Sutterby Formation in the Alford and Maltby boreholes, and although he made no reference to the fauna, this deposit may be the Skegness Formation.
The Formation comprises medium and dark grey mudstone with Prodeshayesites bodei and iridescent fragments of other ammonites, some of which are partially pyritised and phosphatised. In borehole 72/78 the formation becomes brownish grey in the lower part of the formation, with scattered, cream-coloured phosphatic nodules. Burrows occur, sometimes filled with limonite ooliths.
1.98m in the type section.
The upper boundary is defined by a downward change from pale grey, calcareous, mudstone (Sutterby Formation) to medium and dark grey mudstone with ammonites, some of which are partially pyritised and phosphatised.
Skipperton Fireclay
SKFC
Late Namurian, no older than Arnsbergian.
Skiddaw Group
SKG
Late Tremadoc to Early Llanvirn.
The Skiddaw Group crops out in the Skiddaw, Ullswater, Bampton, Black Combe and Furness inliers in the English Lake District. Also in the Cross Fell and Teesdale inliers in northern England and it is recognised in boreholes in the Alston Block (northern England). The Skiddaw Group is unconformably overlain by volcanic rocks of the Eycott Volcanic and Borrowdale Volcanic groups or by Carboniferous limestones.
Laminated siltstone and mudstone with sporadic greywacke beds and one thick sequence of greywackes (Loweswater Formation), overlain by the Eycott Volcanic Group of volcanic and sedimentary rocks. Base of Skiddaw Group not seen.
Skiddaw inlier <5000m; Black Combe inlier 1000m+
In the northern part of the Skiddaw inlier, the youngest siltstones and mudstones (Kirk Stile Formation) of the Skiddaw Group are unconformably overlain by volcanogenic mudstones and andesites of the Eycott Volcanic Group. In the Tarn Moor Tunnel, the youngest known strata of the Tarn Moor Formation (Skiddaw Group) are mudstones unconformably overlain by andesite lavas and volcaniclastic rocks of the Borrowdale Volcanic Group.
Skeagh Plug
SKGH
Skella Dale Burn Gneiss Formation
SKGN
Skiddaw Pluton
SKID
Grainskill Beck and the River Caldew [NY 298 300 to 326 331], and Sinen Gill [NY 229 281], Cumbria.
Biotite granite and potassium feldspar-phyric biotite granite, with a zone of muscovite-quartz rock, interpreted as greisen. Radiometric age: 399 +/- 8 Ma (recalculated using later constants from Shepherd et al., 1976).
A steep-sided cylindrical pluton, with an outcrop area less than 3 sq. km.
Skillicore Member
SKIL
21 to 46m
Skinnisfield Metagabbro
SKIN
Skipperton Coal [Airdrie-Falkirk]
SKIP
Skipwith Sand Member
SKIS
Sharp to gradational transition (over several tens of cms) to underlying sands and clays of Hemmingbrough Glaciolacustrine Formation. A moderate to well developed dark brown peat (Skipwith Peat Bed) is present at some localities.
Skipwith Common Sand Member is known to extend across the Vale of York from the River Ouse in the west to beyond the River Derwent in the east. The northern limit is marked by the Escrick Moraine [SE 595 396]. The sands are known to extend beyond Selby. Lateral boundaries vary from a gradual thinning over several hundred metres, to an abrupt thinning of the sands giving rise to a strong topographic feature.
Dominantly yellow to pale brown slightly clayey sand. Typically composed of moderately well sorted medium quartz grains with minor bands of finer, coarser or poorly sorted material, including finely comminuted flint and lithic clasts. Thin laminae of clayey sandy peat and poorly developed fine to medium slightly gravelly clayey sand are noted towards base of the member.
Maximum thickness in excess of 2.4m, as proven in borehole SE64NE/14 [466220 439530].
The Skipwith Sand Member is largely exposed at surface, beneath a thin (0.2-0.6m) development of well drained light brown sandy soil. This unit is also present beneath alluvial and aeolian deposits.
Sholeshook Limestone Formation
SKL
Base is diachronous, unconformably overlying the Mydrim Shales Formation.
Thick to thin-bedded and nodular, dark blue-grey limestone, fissile calcareous siltstones and mudstones, locally richly fossiliferous.
To 57m
Disconformably overlain by limestones of the Slade and Redhill Formation.
Skelton Coal (Canonbie)
SKLC
Skelmorlie Conglomerate Formation
SKM
Conformable, but scoured, resting on the Wemyss Bay Sandstone Formation.
Sheet 29, Wemyss Bay-Skelmorlie area.
Conglomerate with clasts of quartz, schist, quartzite and lava and interbeds of pebbly sandstone.
From 20 m to 60 m thick.
Passes upwards into the Kelly Burn Sandstone Formation.
Skipwith Peat Bed
SKPE
Sharp to bioturbated (principally by root development) contact between red to black peat and clayey sandy peat with underlying sands and clays of the Hemingbrough Glaciolacustrine Formation.
Skipwith Peat Bed is known to occur discontinuously across the Vale of York between the River Ouse in the west and the River Derwent in the east. The maximum northern extent is limited by the termination of the overlying Skipwith Common Sand Member at the Escrick Moraine [SE 585 395]. Auger holes prove the southerly extent as far as North Duffield.
Very dusky red to black compressible peat to clayey sandy peat.
To 0.2m
Where preserved, the Skipwith Common Peat Bed is overlain by a sharp to gradational (reworked) contact with sands of the Skipwith Common Sand Member.
Skittering Rock Shale
SKR
Skerry Rock [Igneous Intrusion]
SKRK
Skroo Sandstone Member
SKRS
Skerry Group
SKRY
Skibeden Shales
SKS
Skiff Sandstone Member
SKSA
Skiddaw Group (Undifferentiated) (Skiddaw Intrusion Aureole)
SKSK
Skudiburgh Formation
SKU
Late Bathonian.
Skerryvore Formation
SKV
Lies on rockhead.
Very stiff, silty, micaceous, dark grey clay.
Less than 10m in 81/10A, although only 0.3m recovered. Thickness exceeds 40m locally in Skerryvore Trough.
Undulating and erosive.
St Kilda Western Gabbro Pluton
SKWGB
Skerrywhirry Plug
SKWY
Skye Central Complex
SKYC
Skye Dyke Swarm
SKYED
Skye Lava Group
SKYL
Sloanstone Coal (Dalmellington)
Slab Horizon
SLAB
Slate Coal (Warwickshire)
SLAT
Sulby Flags
SLBF
Sandwell Coal (Fife)
SLC
Slochd Psammite Formation
SLCD
Poorly exposed, metamorphic fabrics dominant in parts, no way-up criteria, therefore stratigraphic succession unknown.
Central Highlands of Scotland. Slochd area extending eastwards and northwards across Dava Moor.
Gnessose to migmatitic psammite and siliceous psammite, potash feldspar rich, thin bands of quartzite.
As above - unknown, overall possible unconformable relationship with overlying Grampian Group units.
Stanllyd Coal (South Wales)
SLCO
South Leicestershire Diorite Complex
SLED
Where not in mutual contact, the intrusions are believed to have been emplaced into mudrocks of Cambrian to Ordovician (possibly Tremadoc) age, correlatives of the Stockingford Shale Group.
Forms isolated and generally quarried outcrops extending from southeast of Sapcote (SP 497 931) northwards to near Enderby (SP 998 535).
An association of coarse-grained igneous rocks, mainly quartz diorites, occurring as a complex of circular to elongate, roughly overlapping intrusive bodies.
Vertical thickness unknown; boreholes show the complex is approximately 16km in diameter.
Where not roofed by their host rocks, the intrusions are unconformably overlain by Triassic strata or Quarternary superficial deposits.
Starslee Coal
SLEEC
Somerset Levels Formation
SLEV
Rests on Triassic and Jurassic bedrock.
The Somerset Levels, from Clevedon to Langport, Somerset.
The formation encompasses the marine, estuarine and terrestrial deposits that were formed in the Somerset Levels area during the Holocene transgression. The deposits are dark blue-grey silty clays and silts with subordinate sands and beds of peat, submerged forests and gravel. The deposits rest on a rockhead platform intricately dissected by river valleys formed when sea levels were lower, and their upper surface is approximately level at c 4.6 to 6.7m OD. The river valleys are infilled with gravels and sands, which become shelly upwards. See also "Supplementary Information".
The following generalised succession was noted in boreholes for the M5 Motorway (Whittaker and Green, 1983):c 4.3m of grey-brown mottled clay, silty, peaty at the base; "Roman Clay", formed during a period of rising sea levels from 4500 years BP to the Romano-British period; 0.61-2.13m of peat, horizontal at OD, formed 5000-4500 years BP; 1.83-7.93m of grey silty clay with peaty clay (saltmarsh deposits); up to 14m of grey silty clay with fine sand intercalations (intertidal deposits); up to 16.8m of grey uncemented sand; 0.15-0.61m of Basal Peat, formed 8500-8000 years BP, when a birch forest was inundated by the rising sea. Additionally, blue-grey and grey-brown clay and loam overlying gravel are found marginal to the Levels at up to 18m OD; these are believed to pre-date the youngest estuarine clay of the Levels.
Stinchar Limestone Formation
SLF
Conformably overlies Confinis Flags and Auchensoul Bridge Mudstone.
Rubbly, sandy and massive limestone.
64m
Part conformable, part erosive, overlain by Benan Conglomerate.
Slag Coal (Midgeholm)
SLGC
Shalloch Formation
SLH
Conformable on the Mill Formation.
Flaggy wacke and siltstone turbidites.
Conformably overlain by the Auldthorns Formation, which is part of the Drummock Subgroup.
Slievebane Group
SLI
Probably faulted.
Clastic sediments predominantly coarse-grained, red-bed facies, conglomerates and pedogenic mudstones, palaeosols.
Definitely faulted.
Slishwood Division
SLID
Landslide Deposits
SLIP
Debris slide of rock and soil, including mud flows; commonly lies unconformably on bedrock. [Generic description]. Variable material, dependent on the nature of the upslope material and the type of slip failure. [Generic description].
Silkstone Four Foot Coal (South Yorkshire)
SLK4
Silkstone Coal (West And South Yorkshire And Derbyshire)
SLKC
Sub-Lodgement Lingula Band
SLL
Slack Lane Coal [Manchester Area]
SLLAC
Slaty Law Plug
SLLAW
Slieve League Formation
SLLE
Shell Marl
SLM
Soft, calcareous deposit formed in rivers and freshwater lakes mainly from shell debris and plant encrustions. [Generic description: 'TMOS' Procedures].
Stallion Hill Formation
SLN
Unconformable on Raglan Mudstone (Siluro-Devonian).
Purplish-grey to green-grey fine- to coarse-grained cross-bedded sandstone; basal conglomerate contains cobbles of Silurian and igneous, possibly Malvernian rocks.
80m. Thinning to 0 within 2km to northwest; cut out by faulting within 0.5km to east of type locality.
Overlain by Westphalian D Coal Measures.
Slockenray Hyaloclastite And Lava Formation
SLO
Succeeds Pinbain Lava Formation (PIN). Distinguished by incoming of hyaloclastite and basalt lava with large bladed plagioclase phenocrysts.
Massive, porphyritic and aphyric hyaloclastites and porphyritic and aphyric massive basalt lavas, distinguished by large (to 2cm) bladed plagioclase phenocrysts.
Succeeded by Brandy Craig Lava Formation (BCG). Distinguished by the incoming of reddened horizons - suggestive of subaerial weathering.
Solport Coal
SLP
Silverpit Evaporite Member
SLPE
Slade And Redhill Formation
SLR
Sloop Sandstone Member
SLSA
Shawell Sand And Gravel
SLSG
Not seen, probably sharp and locally erosional on the underlying Oadby Till.
Patchy outcrops extend from around Newton (SK 53 78) northwards to around Lutterworth (SK 53 86).
Yellow,orange and grey medium- to coarse-grained cross-bedded sand with subordinate lenses or sheets of flinty gravel.
Variable, locally at least 11m around Shawell.
Sharp contact with an overlying sheet of the Oadby Till.
Surgill Shale
SLSH
Top of highest mappable thick coarse-grained sandstone of Pendle Grit, or top of unit containing thick massive coarse-grained sandstones where individual sandstones not mapped.
Grey, shaly, commonly sandy, finely micaceous siltstones and mudstones with thin subordinate sharp-soled sandstones.
To 245m. Commonly absent.
Overlain by sharp base of Grassington Grit, Brennand Grit or Warley Wise Grit; commonly an unconformity.
Skerries (Siliceous)
SLSK
Sleights Siltstone
SLST
Llandovery Rocks And Wenlock Rocks (Undifferentiated)
SLSW
Selsey Sand Formation
SLSY
Rests on the Marsh Farm Formation at a sharp contact on a burrowed surface overlain by glauconitic sandy silt with a few pebbles.
Silty sand, silty clay and sandy clayey silt, glauconitic, bioturbated, locally calcareous.
Overlain by Barton Clay Formation. Boundary based a distinction of sand content from fine- to very fine-grained sandstone of the Tellina Bed (topmost Selsey Formation) to the olive grey glauconitic sandy clays of the Barton Clay Formation.
Silt
SLT
Silt. [Generic description].
Slatog Coal (South Wales)
SLTG
Slaty Coal (Cumbria)
SLTY
Silver Coal (North Staffordshire)
SLVC
Silverpit Formation
SLVP
Silver Hills Sandstone
SLVS
Sandstone sharply overlies relatively thinly bedded and fine-grained sandstones and siltstones (Claughton Member or Keasden Flags).
Fine- to very coarse-grained sandstone with thin coals and seatearths.Trough cross-bedding in sets up to 0.5m thick. Planar cross-bedding, small-scale cut-and-fill structures, syndepositional faults and slump structures have been recorded.
Kettles Beck 15.2m (50ft); Knott Copy Borehole c 34m; up to 90m on Settle (60) Sheet.
Sandstone is overlain sharply by mudstones with marine fauna (Crossdale Mudstone) including Isohomoceras subglobosum Marine Band in Crossdale Beck.
Slea Valley Formation
SLVY
Unconformable on Middle Pleistocene glacial deposits, and on Jurassic bedrock.
The entire catchment of the River Slea and its tributaries, Lincolnshire.
The formation encompasses the fluvial, lacustrine and organic deposits of the River Slea and its tributaries. It includes floodplain alluvium, river terrace deposits, and the Sleaford Sands and Gravels of Berridge et al (1999). The floodplain comprises soft clays, silts and fine sands, with bodies of peat, overlying sands and gravels. The terrace deposits comprise sands, gravelly sands and sandy gravels, deposited by braided rivers in a periglacial environment. The pebbles include much buff ooidal limestone from the Lincolnshire Limestone Formation, and flint, ironstone and sandstone, and are up to c.40mm in diameter.
To c.7m
Slyving Coal (Somerset)
SLYC
Skipton Moor Grit
Smith Bank Formation
SMBA
Smithy Burn Siltstone Formation
SMBS
Faulted
Dark grey, homogeneous siltstones, silty mudstones and shales, very weakly bedded.
>122m
The base of the overlying Ree Burn Formation.
St Martin's Cemetery Beds
SMC
Sheringham Cliffs Formation
SMCL
Two different stratigraphical associations of the lower boundary of the formation can be observed. Firstly, where the Mundesley Sand Member rests upon the upper surface of the Walcott Till Member (Lowestoft Formation) it exhibits a slightly scoured, erosional contact, and lithological transition from till to sand. Secondly, where the Runton Till Member truncates shallow marine sediments of the Wroxham Crag Formation. The contact is commonly marked by a sharp plane of decollement.
The Sheringham Cliffs Formation has been mapped extensively in northern Norfolk and crops out in the Cromer, Aylsham and Wells districts.
Consists of a thick glacigenic sequence that contains several distinctive lithofacies. The basal member is the Mundesley Sand Member, which consists of stratified fine-grained sands; this is overlain by the laminated silts and clays of the Ivy Farm Laminated Silt Member. Overlying these waterlain sediments are the Runton Till and Bacton Green Till members; these are matrix-supported diamictons, which in turn, are overlain by thin units of clay (Trimingham Clay Member) and sand (Trimingham Sand Member). These deposits are truncated by the chalky Weybourne Town Till Member, a highly consolidated matrix-supported diamicton, and finally by the Runton Cliffs Sand and Gravel Member which forms the highest stratigraphical unit within the Formation.
Variable - up to 40m
Sharp, erosional boundary at the base of the overlying Briton's Lane Formation. The lithological change is from till to sand and gravel.
Scunthorpe Mudstone Formation And Charmouth Mudstone Formation (Undifferentiated)
SMCM
Smalley's Coal (South Derbyshire)
SMCO
Scunthorpe Mudstone Formation
SMD
Where lowest grey mudstone (may be laminated) of the Lias Group rests with sharp contact on bluish and greenish grey to (less commonly) reddish brown mudstone of the Cotham Member (Lilstock Formation, Penarth Group) or on grey porcellanous limestone of the Langport Member (Lilstock Formation, Penarth Group) where locally present.
East Midlands Shelf (north) (Leicester to Market Weighton).
Grey, variably calcareous and silty, blocky or fissile mudstone with thin beds of argillaceous limestone (bioclastic or micritic) and calcareous siltstone, particularly near base and in upper part, which is ferruginous in the type area.
To c.128m
In type area, at top of Frodingham Ironstone (Gaunt, G D, Fletcher, T P and Wood, C J, 1992); elsewhere, at erosive base of thin pebbly ferruginous oolite (Glebe Farm Bed), which marks the base of the Charmouth Mudstone Formation.
St Mellion Formation
SME
Not seen; all observed contacts are tectonic.
St Mellion area (SX 39 65), between Bodmin Moor and Dartmoor, east Cornwall. The area mapped as Crackington Formation on Sheets 338 (Reid et al. 1912; BGS, 1995) and 339 (Selwood et al, 1984) between Holne (SX 715 695) and Haytor Vale (SX 770 770), southeast of Dartmoor may also be St Mellion Formation, but further work is needed.
Interbedded dark grey sandstone and mudstone with scattered siltstone beds. Sandstones tend to be concentrated in packets are are medium- to thick- bedded. Rare polymict conglomerate sandstones and argillaceous sandstones are locally present.
In excess of 500m, but may be more or less, due to thrusting.
Smeorail Formation
SMF
St Maughans Formation
SMG
Placed at top of Bishop's Frome ('Psammosteus') Limestone Member of the Raglan Mudstone Formation.
Interbedded purple, brown and green sandstones and red mudstones with intraformational conglomerates containing calcrete clasts.
At base of Brownstones and (locally) Senni Beds, where sandstone-dominated sequences begin.
Stainmore Formation
SMGP
Conformable: taken at the top of the uppermost limestone beds of the Great Limestone Member, which are overlain by a sequence of dark grey siltstones and mudstones at the base of the Stainmore Formation.
Cyclical repetition of sandstones, siltstones, mudstones, thin limestones and some coals.
Conformable: base of Subcrenatum Marine Band or equivalent.
Smaull Greywacke Formation
SMGW
Sailmhor Formation
SMH
Conformably overlies pale grey flaggy dolostones of the Eilean Dubh Formation.
The Durness Group, containing the Sailmhor Formation, forms a narrow, discontinuous belt, extending along the north-western side of Scotland from the Durness-Eriboll area, through Assynt and Kishorn, to Skye.
Dark grey, massive granular dolostones with dark and pale mottling and conspicuous developments of white and pink diagenetic chert nodules and layers.
About 130 m thick.
Conformably overlain by fine-grained, pale cream coloured dolostones of the Sangomore Formation.
Somerset Halite Member
SMHF
Conformable, at gradational upward transition from reddish brown mudstone (Sidmouth Mudstone Formation, undivided) to mudstone with abundant halite of the Somerset Halite Member.
Subsurface, north Somerset, not present at outcrop. Probably equavalent to thick halites in the upper part of the Sidmouth Mudstone Formation in Dorset (Gallois, 2001) and offshore below the English Channel (Hamblin et al. (1992).
Mudstone, reddish brown, with abundant beds and veins of halite, and common beds of brecciated mudstone, formed by salt dissolution.
154m at type section
Conformable, at gradational upward transition from mudstone with abundant halite of the Somerset Halite Member to the reddish brown mudstone of the Branscombe Mudstone Formation.
Summerhouse Sandstone
SMHS
Smithy Coal (North Ayrshire)
SMI
Smithy Coal (Warwickshire)
SMIC
Smiddy Limestone
SML
Stanley Main (Lower) Coal (West Yorkshire)
SMLC
Small Rider Coal (South Wales)
SMLR
Swinstone Middle Marine Band
SMMB
Smithy Coal (Mid And East Lothian)
SMMI
Smoile Coal (Leicestershire)
SMOC
Sionascaig Meta-Olivine-Gabbro Subswarm
SMOG
One dyke of the Subswarm has been dated at 1992 +3/-2 Ma by U-Pb methods (Heaman and Tarney, 1989), and a further two have been dated at 2031 +/- 62 and 2015 +/- 42Ma using Sm-Nd methods (Waters et al., 1990).
The dykes of the Sionascaig Meta-olivine-gabbro Subswarm are part of the Lewisian Gneiss Complex and only occur within it. They have been mapped as a separate subswarm only in the Assynt area (between Geln Canisp in the north and Loch Lurgainn in the south).
The Sionascaig Meta-olivine-gabbro Subswarm comprised the Fe-rich members of the Scourie Dyke Swarm. The dykes of the Subswarm are most abundant within the Lewisian Gneiss Complex in the Assynt region, where they are found to the south of the Canisp Shear Zone. Typically they have a broadly E-W trend. The dykes of the Subswarm are typically coarse-grained and texturally heterogeneous. They have the primary mineralogy olivine - clinopyroxene - orthopyroxene - plagioclase - kaersutite - biotite - Fe-Ti oxide. The plagioclases are typically heavily altered so that they appear black in hand-specimen, and this led to these dykes originally being mapped as ultramafic. The dykes of the Sionascaig Meta-olivine-gabbro Subswarm appear to post-date all but a few late metadolerites of the Scourie Dyke Swarm.
Sgurr Nam Meann Quartz-Dolerite Ring-Dyke
SMQD
Sandy Mouth Shale
SMS
Smallburn Sandstone Formation
SMSA
Not exposed. Almost certainly unconformable on granite, and crystalline basement.
Buchan Ridge, of Flett and Read, 1921; 1:10 000 sheets NK04SW, 1:50 000 sheets 87W (Ellon) and 87E (Peterhead) (on join).
Sandstone, arkosic, micaceous, medium- to coarse-grained, scattered pebbles, dark red-brown.
Not exposed. Locally overlain by Moreseat Sandstone Formation (Cretaceous), or Buchan Ridge Gravel Member.
St Mary's Bay Member
SMSB
Smiths Coal (North Wales)
SMSC
Shanmaghery Sandstone Formation
SMSF
Shouldham Sand And Gravel Formation
SMSG
Deposits occupy the valley of the pre-Glacial Bytham River from Shouldham Thorpe, Norfolk, southwards along the eastern margin of the Fens, as far south as High Lodge, Mildenhall.
The formation encompasses fluvial, lacustrine and organic deposits of the pre-Glacial Bytham River, At the type site, yellowish red to brownish yellow cross-stratified sands, with minor beds of pebbly sand, overlie sands and gravels. In the lower unit, massive and planar cross-stratified gravels alternate with planar cross-stratified, thick bedded massive pebbly and trough-bedded sands. Clast analysis of the gravels (11.2-16.0mm fraction) indicated 60.1% quartz and quartzite, 19.0% flint, 12.1% chert and 7.0% ironstone, and quartzite is derived from Triassic pebble beds to the west, chert from the Carboniferous, and flint from the local Chalk.
Smith Coal (Titterstone Clee)
SMTC
Smith Coal (Bristol Area)
SMTH
Smith Coal (South Lancashire)
SMTHC
Superstes Mudstone Formation
SMU
Interfingers with Benan Conglomerate. Also rests conformably on Stinchar Limestone.
0 to 25m
Overlain/interfingers with Benan Conglomerate.
Stanley Main (Upper) Coal (West Yorkshire)
SMUC
St Monans White Limestone
SMW
Strichen Formation
Top of Aberdeen Formation, where dominantly psammitic and semipelitic lithologies pass up into lithologies dominated by semipelite but including psammite and pelite, greywacke, grits, calc-silicates and some limestones.
Eastern parts of Aberdeenshire between the eastern margin of the Insch Basic Intrusion and the eastern margin of the Strichen Granite.
Semipelite with pelite and psammite (including greywacke) with subordinate quartzite, amphibolite, calc-silicate rocks and rare limestones. The calc-silicate rocks and limestones are characteristic.
Incoming of lithologies dominated by psammites, greywackes and grits, but including conglomerates and very rare thin calc-silicate layers.
Sherburn (Anhydrite) Formation
SNA
Drawn at base of anhydrite of the Sherburn Formation where it rests on magnesite of the Upgang Formation or mudstones and siltstones of the Carnallitic Marl Formation.
Eastern England (Yorkshire and Durham); provinces.
A formation within the Staintondale Group of the English Zechstein. The group is not formally defined. It comprises the deposits of the Zechstein evaporite cycle EZ4.
Approximately 2-15 metres (thins eastwards).
Drawn at upward passage from anhydrite to halite, with anhydrite laminae of the Sneaton Formation (at depth) or to mudstone of Roxby Formation (at outcrop).
Snaefell Formation
SNAEF
Generally unconformable on bedrock, except where the head and scree deposits interdigitate with glacigenic sediments of the Orrisdale Formation.
Mainly the central uplands of the Isle of Man, but also present on low ground around the coast. (50k sheets 36, 45, 46, 56, 57).
Head, scree and slope wash deposits, covering upland areas. These include boulder scree, and some "redeposited" gravels and diamictons. The head and scree deposits intercalate with glacigenic sediments of the Orrisdale Formation at low elevations around the island margin. Head, scree and slope wash deposits, covering upland areas. These include boulder scree, and some 'redeposited' gravels and diamictons. The head and scree deposits intercalate with glacigenic sediments of the Orrisdale Formation at low elevations around the island margin.
Unrecorded, probably <10m
The ground surface or overlain by Holocene fluvial and organic sediments.
Snarravoe Pelite Member
SNAP
Snarra Ness 'Group'
SNAR
Snettisham Clay Member
SNC
The base is probably an erosion surface. In the Leziate, Ashwicken and East Winch areas the Snettisham Clay appears to have cut out the lower and middle parts of the Dersingham Formation and rests on the clean sands of the Leziate Sandstone Member, Sandringham Sands Formation. At Heacham and Snettisham, silts and clays of the Snettisham Clay Member rest on pale yellow sands of the Dersingham Formation. At Dersingham Common, silty clay rests on a pebble bed comprising quartz, quartzite, chert, limestone and phosphate, which in turn rests on soft, brown and white, fine-to medium grained sands.
The member crops out between Heacham and Ashwicken and is present in boreholes (e.g. Gayton Borehole).
At Heacham Jackson (1911) recorded greyish brown clay with a seam of fossiliferous clay ironstones in the upper part and ironstone concretions scattered throughout. Sand partings are present and, in the Gayton Borehole, bioturbation is represented by tracks, trails and burrows (Gallois, 1994). A rich shelly fauna has been recovered from the Snettisham Clay Member. Locally (between Heacham and Appletone), a pebble bed is present at the base and at Snettisham Brickworks, a hard clay ironstone occurs in the lower part of the member.
At Dersingham Common, Snettisham and in the Gayton Borehole, pebbly, ferruginous sands (Carstone Formation) rests on clay and silty clay (Snettisham Clay Member) with an erosion surface between. At Dersingham Common a spring line picks out the Carstone/Snettisham Clay boundary. The boundary appears to be conformable in the Hunstanton Borehole where oolitic, silty and sandy mudstones (Roach Formation) rest on red-brown mudstone (Snettisham Clay).
Srath Na Creitheach Centre [Skye Central Complex]
SNCC
Meall Dearg Granite [Srath Na Creitheach Centre]
SNCC1
Ruadh Stac Granite [Srath Na Creitheach Centre]
SNCC2
Blaven Granite (Srath Na Creitheach Centre)
SNCC3
St Non's Sandstone Formation And Caerfai Bay Shale Formation (Undifferentiated)
SNCF
Seaford Chalk Formation And Newhaven Chalk Formation (Undifferentiated)
SNCK
Sandhills Lodge Member
SND
Not exposed, probably conformable on blue-grey interbedded fine- to coarse-grained tuffites of the Beacon Tuff Member.
From near Sandhills Lodge, south of The Home Farm, it extends northwards and is last seen north-west of The Home Farm (SK 5036 1688).
Grey coarse-grained volcaniclastic sandstone and sediment-clast breccia.
Not exposed, probably sharply succeeded by Buck Hills Member, comprising beds of grey, graded volcaniclastic siltstone and sandstone.
Sandend Harbour Limestone Member
SNDL
Sharp change from tremolitic flags of Garron Point Tremolitic Flag Member to interbedded graphitic pelite, metalimestone and semipelite.
From coast between Garron Point and Sandend village [NJ 5550 6700 - 5575 6665], as far inland as fault at [NJ 535 632], south of which it is covered by Devonian sedimentary rocks.
Semipelite and pelite, slaty to schistose, partly graphitic, containing beds of metalimestone. In basal part thick folded metalimestone and pyritic graphitic pelite. In upper part, pale grey banded metalimestones and pelite partings.
c.150m on coast section; not measurable inland.
Top of highest thick metalimestone bed.
Sandringham Sands [Duplicate Code: Use Sas]
SNDS
Sandwich Coal (Canonbie)
SNDW
Stone Coal (South Lancashire)
SNEC
Strathlethan Sandstone Member
SNF
At the base of the lowest volcaniclastic sandstone bed resting on the Downie Point Conglomerate Member.
A grey, fine-grained, cross-bedded sandstone, volcaniclastic sandstones and pebbly sandstones.
Up to 350 m thick, according to Armstrong and Paterson 1970.
The base of the lowest coarse conglomerate bed in the Castle Haven Conglomerate Member.
Snowdrop Flints
SNFL
Sneaton (Halite) Formation
SNH
Drawn at base of halite with anhydrite laminae where it rests on anhydrite of the Sherburn Formation.
Variously almost pure halite, halite with anhydrite laminae, halite with potash minerals and halite with abundant fine-grained red clastic material.
Approx. 55 metres, (thins westwards).
Drawn at upward passage from halite to red siltstones of the Sleights Formation or to the Roxby Formation.
Senhouse Seam
SNHS
Sandersdean Limestone
SNLS
Singleton Mudstone Member
SNM
Originally referred to as the Singleton Mudstones (Wilson and Evans, 1990) and raised to Formation status by Warrington et al. (1980) the unit is retained but with Member rank as part of the nationally recognized Sidmouth Mudstone Formation (Howard et al., 2008).
Santon Oolite
SNO
Conformable or mildly disconformable contact between underlying silty limestone, calcareous siltstone and mudstone (of the Raventhorpe Beds sensu Gaunt et al., 1992), and peloidal and ooidal limestones of the Santon Oolite.
BGS 1:50 000 sheets 80, 89 and possibly 102; North Lincolnshire, ?from the Hibaldstow area to the Humber.
Limestone: peloidal and ooidal packstones, with some grainstones and locally interbeds of wackestone and lime-mudstone.
[Compiler's Notes] This entry defines the Santon Oolite as mapped on sheets 80 and 89. However it should not be perpetuated in any formal lithostratigraphical review of the Lincolnshire Limestone. Whilst it may remain a valid stratigraphical unit, the Member status is inappropriate. Following stratigraphical revision of the Lincolnshire Limestone Formation, it forms part of the Lower Lincolnshire Limestone Member which (with Upper Lincolnshire Limestone) is one of the two constituent members of the Formation. I recommend that the status of the unit be downgraded to Santon Oolite or Santon Oolite Beds (formal or informal). As with many of these Lincs. Limestone subdivisions, the term is not terribly tightly defined, and is somewhat compromised by varied usage in the literature, e.g. Ashton (1975; 1980) included "oolites" lower in the succession within his Santon Oolite Member, which at Manton, is split by his Raventhorpe Member. This makes me wonder if the name now has any value - it just comprises one or more thin beds of oolite in the Lower Lincs Limestone. [M G Sumbler 25/09/05]
Conformable, contact between peloidal and ooidal limestones of the Santon Oolite and the argillaceous and mudstone-rich succession of the overlying Kirton Cementstone.
Sheen Sandstones
SNS
The lower boundary is taken at the base of the first sandstone-dominated unit above fissile black mudstone that includes a Bilinguites bilinguis (R2b1) Marine Band.
Restricted to the area around Sheen, Staffordshire, SK 11 62.
A grey and pale brown, fine-grained, feldspathic, sandstone, thinly-to thickly-bedded with subordinate beds of mudstone with sideritic ironstone; ripple-laminated in upper part.
25 m thick.
The upper boundary is taken at the base of a mudstone-dominated succession (Millstone Grit Group, undivided) overlying the uppermost leaf of the Sheen Sandstones.
Stretton Shale Formation
SNSH
Uncertain, formerly taken at the base of the Helmeth Grit Member (Greig et al, 1968), although more recent work (Pauley, 1990) suggests that the latter forms part of the apparently underlying Ragleth Tuff Formation. Alternatively, it may underlie or form part of the Ragleth Tuff. The boundary between the Helmeth Grit Member and the Stretton Shale Formation has been variously interpreted as conformable (Greig et al, 1968 and other authors) or unconformable (Pauley, 1990).
Welsh Borderland, Shropshire, Church Stretton and Long Mynd.
Greenish grey, laminated mudstones and siltstones.
Over 900m thick.
Generally taken at the relatively sharp, conformable contact with the base of the Buxton Rock Member, the lowest division of the Burway Formation. However the transition from the mudstone dominated Stretton Shale Formation into the sandstone dominated Burway Formation takes place over several metres.
St Non's Sandstone Formation
SNSS
Unconformable on Neoproterozoic volcanic and intrusive rocks.
Pembrokeshire, St David's Peninsula.
Dark green, buff weathering planar and cross-laminated micaceous sandstones with up to 50m of basal conglomerate.
Up to 190m (including up to 50m of basal conglomerate).
Conformable and transitional with the overlying mudstones of the Caerfai Bay Shale Formation.
Solent Catchments Subgroup
SNTCA
Unconformable on Jurassic to Cretaceous strata.
The entire area covered by the catchments of the Hampshire Basin, the Isle of White and Dorset. The subgroup includes deposits of the valleys of the rivers Meon, Hamble, Itchen, Test, Hampshire Avon, Dorset Stour and Frome-Piddle and tributaries draining southwards from the Hampshire Basin and Dorset to the English Channel.
Mainly river terrace sand and gravel and alluvial floodplain silt, silty clay and sand, together with related organic and mass movement deposits of the "Solent River" (Frome, Piddle, Stour and Avon) of the Hampshire Basin and Dorset. The Subgroup includes interbedded units of river terraces comprising fossiliferous silty sand, silt, together with organic clay, tufa and peat, which are biostratigraphically correlated with interglacial (warm) stages. The terrace deposits are depicted on British Geological Survey maps using numbered terrace symbols.
Santon Member
SNTN
A thin to medium-bedded sandstone, interbedded with laminated mudstone and siltstone; sandstone predominantly wacke but includes quartz arenite. The unit contains more abundant sandstone and is more thickly bedded, distinguishing it friom the units above and below.
At least 600 m thick.
Southacre Clay And Lignite Member
Conformable upon the Abbrook Clay and Sand Member, from which lignites and brown carbonaceous clays are absent.
Bovey Basin, Devon.
Lignites and brown and black carbonaceous clays, with subordinate grey to greyish brown silty clays and rare sands.
30 to 67m
Passes upwards into the undifferentiated upper parts of the Bovey Formation, marked by the absence of lignite beds and a considerable increase in fine sand and stiff, silty clay beds.
Soap Coal (South Wales)
SOAP
Soap Rider Coal (South Wales)
SOAPR
Soar Valley Formation
SOARV
Middle Pleistocene to Holocene (Post-Anglian: MI stages 12 or 10 to 1)
Unconformable, commonly channelled base on Anglian glacial deposits (Wolston Formation) or on pre-Quaternary bedrock.
Catchment of the modern Soar (including Wreake).
Mainly post-Anglian fluvial terrace and alluvial deposits of the River Soar of Leicestershire and those of its tributaries such as the Wreake, but excluding Anglian/pre Anglian deposits of the so-called Proto-Soar or Bytham River. Mainly sand, gravel and mud; divided (in type area) into six principal "terrace" members (Eagle Moor, Knighton, Birstall, Wanlip, Syston, and Hemington members), plus Holocene alluvium (the Soar Member of Bowen, 1999). Includes contemporaneous head, colluvium and soil deposits. Gravel is generally dominated by "Bunter" pebbles and flints in roughly equal proportions, plus other components including Charnian material.
Soay Basic Magmatic Breccia Intrusion
SOAY
Scotsman Office Beds
SOB
Solan Bank Formation
SOBA
Lower Sleaves Oak Beds
SOBL
Upper Sleaves Oak Beds
SOBU
Somerset Catchments Subgroup
SOCA
Formations of the Somerset Catchments Subgroup rest unconformably on bedrock varying in age from Devonian to Cretaceous.
Somerset, constrained by the watersheds formed the the Quantock Hills to the west, the Mendip Hills to the north and the Blackdown Hills to the south.
The Somerset Catchment Subgroup encompasses all the fluvial, lacustrine and organic deposits of the rivers whose catchments fall between the Mendip, Quantock and Blackdown hills. The deposits comprise gravels, sands, silts, clays and peats. Floodplain alluvium comprises soft silts and clays, commonly with beds of peat and a basal bed of sand and gravel. River terrace deposits are largely sands and gravels. The gravels are composed of locally-derived rocks, variously Devonian sandstones, Carbonifeous sandstones and limestones. Triassic sandstones, Jurassic limestones and Cretaceous chert and flint. Minor marine deposits may be included where they are intercalated in dominantly fluvial formations.
Surface, or locally overlain by clays, silts and peats of the Somerset Levels Formation.
Shoulder O' Craig Vent
SOCG
The intrusive contacts with the country rock of Llandovery Turbidites is poorly exposed, which together with diffuse internal structures, makes field relationships difficult to define.
Kirkcudbright Sheet 5W (Scotland)
Subvolcanic explosion-breccia composite vent, comprising: carbonated vent agglomerate of wacke clasts in a fine-grained comminuted igneous matrix, altered bioitite-bearing olivine basaltic intrusion and kersantite intrusions.
Thickness not known, but individual vents vary from 5 x 50 m, to 250 x 100m. This unit may be one vent with two small subsidiary vents.
Pridoli To Mid Devonian Volcanic Rocks (Undifferentiated)
SODMV
Shaftoe Coal (Northumberland)
SOEC
South Street Flints
SOFL
Southern Highland Group
SOHI
The age range is now known to extend beyond the Neoproterozoic, at least as far as the early Mid Cambrian] (fide C W Thomas, 28 March, 2001).
The top of the highest limestone recorded in the Tayvallich Subgroup
South Sperrin Mountains and Lack Inlier, Northern Ireland. Southern Highlands, Scotland
A thick pile of psammitic and pelitic greywackes and associated rocks, some volcanic.
>5000m
Gradual transition into overlying, less deformed, probable Ordovician rocks of lower metamorphic grade.
Soil
SOIL
Organic rich; interbedded silt, sand and clay. [Generic description].
Bedrock At Or Near Surface [See Descriptions For Limitations Of Use]
SOL
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. Hence, all pre-Quaternary ages encountered in this area are potentially included. See also SOLX and SOLC.
Originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future.
Bedrock (Pre-Carboniferous Rocks) At Or Near Surface [See Descriptions For Limitations Of Use]
SOLC
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. Hence all pre-Carboniferous ages encountered in this area are potentially included. See also SOLX and SOL.
Note that on the related Quaternary Domains map, this category was described as: "Sedimentaary cover, ie Carboniferous, Permo-Trias".
Southerness Member
SOLM
Not exposed, probably gradational with the Kirkbean Cementstone Formation.
Southerness shore, Southerness, Kirkcudbrightshire, south-western Scotland (Southern Uplands).
Interbedded fossiliferous marine limestone, mudstone, siltstone with thick beds of bioturbated sandstone and prominant algal horizons.
>135m
Gradational contact with strata of the Gillfoot Sandstone Formation.
Solent Group
SOLT
Bedrock (Sedimentary Cover) At Or Near Surface [See Descriptions For Limitations Of Use]
SOLX
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. Hence, all pre-Quaternary ages relating to sedimentary bedrock units encountered in this area are potentially included. See also SOL and SOLC.
Note that on the related Quaternary Domains map, this category was described as: "Pre-Carboniferous rocks, mostly igneous and metamorphic".
Sandford Orcas Marls
SOM
South Street Marl
SOMA
Sutton Marine Band
SOMB
South Parrot Coal (Lothian)
SOP
Solva Group
SOS
Drawn at the base of the Solva Group where it rests conformably upon the Caerfai Group.
1:50,000 Sheet 209 (St.David's) and probably the adjacent Sheet 210. (Pembrokeshire, west Wales).
Greenish grey sandstones, locally coarse and pebbly, and interbedded mudstones.
Drawn at the conformable upward passage of the Solva Group to the Menevian Group: separated on palaeontological grounds.
Sourlie Organic Silt Formation
SOSI
Sharp, conformable contact with sand and gravel of the Armsheugh Sand and Gravel Formation at 10.82m above OD.
Mainly dark brown, laminated organic silt and clay containing fragments of bone, antler and plant debris, with lenses of pebbly sand, pale and dark brown silt, black silty clay and about 30cm of pale grey to white clay at the base. Containing a rich fauna and flora of Middle Devensian age, including bone of woolly rhinoceros and reindeer. Radiocarbon dates on antler fragments range between 33.5 and 29.0 ka BP.
Sharp unconformable, planar to gently undulating contact with pinkish brown shelly clayey diamicton of the Eglinton Shelly Till Member at 11.10m above OD.
South Coal (Lothian)
SOU
Sowerthwaite Formation
SOW
Taken at the base of the volcaniclastic rocks of the Dam House Bridge Tuff Member or at the base of the tuffaceous sandstone of the Jop Ridding Sandstone Member.
Restricted to the Craven inliers of North Yorkshire.
Siltstone and mudstone with interbedded tuff (Dam House Bridge Tuff Member) and sandstone (Jop Ridding Sandstone Member). A 2m-thick conglomerate (Wharfe Conglomerate) lies towards the top of the succession.
Defined by the base of the overlying Silurian strata.
Southrey Sand And Gravel Member
SOYSG
Middle Pleistocene (MI Stage 7 to 6). The chronology is based on the assumed correlation with the Balderton Sand and Gravel. Organic deposits are associated with the Southrey at at least two sites, but it is not clear if they are beneath the Southrey or in earlier or later unrelated channels. This is not likely to be resolved in the near future.
Unconformable, commonly channelled base, resting on Anglian Wragby Till (Lowestoft Formation).
Distributed along the east side of the present Witham valley from Southrey [TF 13 66] to Kirkstead [TF 19 60] (where it passes onto the Thorpe Member of the Bain). Distribution elsewhere uncertain but correlatives probably present northwest (upstream) of Southrey along the Barlings Eau or River Langworth, to the Langworth area [TF 06 76 (BGS sheets 102, 114, 115, ?128). Correlatives up the Langworth River are unlikely to be quartzite-rich and more probably are like the Thorpe Sand and Gravel of the Bain, so it is questionable if they should be included as Southrey Sand and Gravel Member per se.
Predominantly cold-phase sands and gravels that underlie the Southrey Terrace. At surface, dominated by rounded pebbles of "Bunter" quartz/quartzite (c.60%) with subordinate subangular flint, etc. (c.40%). Terrace surface highly dissected but rises to c.6 to 7m above the Witham floodplain in the Type Area. Associated silts yielding a temperate flora and fauna occur at at least two sites; these might occur at the base of the unit but relationships are uncertain. Correlated with the Balderton Sand and Gravel Member (Trent Valley Formation, west of the Lincoln Gap) and the Egginton Sand and Gravel Member (Trent Valley Formation).
Sanquhar Parrot Coal (Sanquhar)
SPA
Spa Beds
SPAB
Spango Pluton
SPAN
Sanquhar area.
Minor pluton of granodiorite intruded into wackes of the Leadhills Supergroup (Ordovician).
Elliptical pluton c.5km x 2.4km, orientated NE - SW.
Spotted Limestone
SPB
Speeton Beck Member
SPBK
Spirorbis Limestone Bed
SPBL
Sampford Peverell Member
SPBR
Spincha Burn Conglomerate Formation
SPBU
Unconformably succeeds Dalradian rocks of both the Argyll and Southern Highlands groups.
Alternating beds up to 1m thick of conglomerate, very coarse-grained matrix with self-supporting clasts of very well rounded pale greenish grey quartzite and white vein quartz and sandstone, coarse- to very coarse-grained.
Concealed, but succeeded by non-conglomeratic rocks of the Barony Glen Formation.
Spelsbury Member
SPBY
Gravel with sand; interpreted Fourth terrace of the Thames; part of the Thames Valley Formation. [Generic description: academic papers and BGS Memoirs].
Speeton Clay Formation
SPC
Grey and black clays [D Beds of the Speeton Clay Formation] rest on a thin, but prominent, pyritized and phosphatized basal bed [E Bed]. The underlying dark grey to black mudstones [Kimmeridge Clay] have an eroded upper boundary.
The Formation is exposed along the coast at the southern end of Filey Bay. The outcrop is rarely exposed inland, but extends as a narrow strip along the northern edge of the Chalk Wolds to Granton, East Heslerton, West Heslerton to south of Knapton [1;50K sheets 54 and 55]. It has been penetrated in several boreholes, located on the Chalk Wolds, including the Fordon 1 Borehole [TA05834 75713], North Fordon G1 borehole [TA 04138 76860], Fordon G2 [TA 04724 75377], Fordon G3 [TA 02027 76395], Reighton Borehole [TA 1465 7581] and Hunmanby [TA 1301 7588]. It is also said to have been penetrated in boreholes on the Great Driffield Sheet [1:50K sheet 64]. The formation was recognized in the North Sea by Rhys [1974], but the offshore succession has since been divided into the Carrack and Valhall formations [Johnson and Lott, 1993; Lott and Knox, 1994].
The Speeton Clay Formation comprises mudstones, cementstones and sporadic bentonites. It was divided into five units [A-E from the top down] by Lamplugh [1889] and this division is still maintained. E Bed: the basal bed comprises rolled and fragmented, pyritized and phosphatized bivalves, ammonites and bone and is usually referred to as the Copralite Bed. D Beds: black shale is overlain by greenish-brown, brown and grey clays and includes The Blue Bed [D6], The Lingula Bed [D5] and The Astarte Bed [D4]. A compound nodular bed [Bed D1] occurs at the top of the D beds.
To 100m at outcrop, but possibly up to c.400m in boreholes [Rawson et al., 1978].
Chalk, commonly nodular and almost entirely red [one bed near the base is white] comprising the Hunstanton Chalk Formation, overlies the brown and grey-green, glauconitic and calcareous clays, with horizons of phosphatic nodules, that form the A Beds of the Speeton Clay.
Spetisbury Chalk Member
SPCH
Campanian. Gonioteuthis quadrata Zone
Conformable. Inferred to be at the Whitecliff Wispy Marls (at Whitecliff Bay) at the boundary between the Sompting and Whitecliff beds of Mortimore (1986).Taken just below a marked feature break that is thought to be formed by either a hardground or a thick bed of flints.
Limited to Sussex, Hampshire, Wiltshire and Dorset and as widely spaced outliers to the north of the Pewsey/Kingsclere structure in the Southern Province. It possible occurrence and distribution beneath the Quaternary deposits of East Anglia in the Transitional Province is not well known.
Firm White flint with regular large flint seams, some tabular in lower part and of Zoophycus type in the upper part.
30m at Whitecliff Bay thought to be as thick as 45m in Dorset and around 35m in Hampshire
Conformable at the Portsdown Marl 1 in the Farlington Redoubt on Portsdown and at Whitecliff Bay, Isle of Wight.
Splint Coal (Ballycastle, Northern Ireland)
SPCL
Coal and coaly shale.
Overlain by carbonaceous shale.
Stonepit Coal (Milford, South Wales)
SPCO
Sapling Clough Sandstone
SPCS
Not exposed but as delta top sandstone overlies delta slope deposits of the Roeburndale Member, likely to be sharp and erosional on siltstones with thin sandstones.
Known currently only from the north and east sides of Ward's Stone Hill, Forest of Bowland, Lancashire.
Sandstone, grey, mostly weathered orange-brown, fine- to medium-grained siliceous with ganister levels particularly near top. Delta top sandstone. 0.2m coal at reference section, c 12m from top of unit.
12m+ in Sapling Clough (basal part not seen). c.12m in tributary to Foxdale Beck (basal and top parts not seen).
Sharp with c 0.5m grey micaceous sandy siltstone overlain by claystones of the Eumorpoceras yatesae Marine Band.
Spouty Dennans Bed
SPD
Coastal section at Spouty Dennans.
Purple and grey conglomeratic sandstones passing upwards into red siltstones, marls and cornstones.
Sperus Formation
SPE
Lower boundary is a strong seismic reflector in otherwise parallel or sub parallel reflectors above and below in the Cape Shore Formation with which it is apparently conformable.
Soft to firm to very stiff, highly to moderately plastic, sandy, silty clay with shells and pebbles. Some clay and numerous sand/silt lenses may give a laminated appearance. Similar in geotechnical strength to underlying clay but more uniform colour/less streaky and has more pebbles and shells. Geotechnically weaker and more uniform than overlying till-like unit.
40 metres from seismic sections. Thins to west where it crops out. Absent in the Norwegian Trench area where it has been eroded or never deposited.
The upper boundary is also apparently conformable with the Tampen Formation.
Speke Formation
SPEK
Strath Spey Formation
SPEY
Sharp, undulating, erosional contact, mainly on yellowish brown tills (diamicton) of the Central Grampian, East Grampian or Banffshire Coast and Caithness Glacigenci subgroups, or on bedrock.
The valley of the River Spey and its tributaries, Grampian Highlands.
Mainly sand and gravel forming river terraces and silty, clayey sand forming floodplains and concealing sand and gravel. Including units of silty sand, silt, clay and peat.
Ground surface, locally covered by peat,
Spirifer Furcatus Band
SPF
Slemish Plug
SPG
Spernal Gypsum
SPGY
Spring Hill Sand And Gravel Member
SPHT
Mid Pleistocene, late Anglian (MI Stage 10).
Recognised from near Holt Heath (between Stourport and Worcester, Sheet 182) downstream. Currently mapped by BGS only on Sheets 182, 199 and 216. Possibly also present both farther downstream (Sheet 234) and farther upstream (Sheet 167) and also in the lowermost part of the Warwickshire Avon. (Sheet 200).
Predominantly cold phase sands and gravels that underlie the Severn Sixth Terrace of BGS Maps (Sheets 199, 216 and ?234). Dominated by clasts of "Bunter" quartz/quartzite lithologies with subordinate flint (c 20% below Avon confluence), with an argillaceous sandy matrix.
(A) Now named the Spring Hill Sand and Gravel Member, though in Bowen 1999 and also the BGS computer codes list have Spring Hill Member. (B) Terrace surface some 55m above modern Severn alluvial floodplain in the Worcester area, descending to about 45m downstream, at type locality, in the southern part of Sheet 216. Probably represents downstream equivalent of the Dunsmore Gravel Member of the Wolston Formation, ie. Anglian outwash terrace (and younger than the Woolridge Gravel Member, which occurs in the lower Severn valley). (C) Upper Boundary given as ?ground surface? though there may be head, colluvium or soil deposits intervening. (D) Severn terraces, particularly the older ones, need reviewing and the classification of some outcrops on existing maps is suspect ? hence the section of Previous Names is necessarily an approximation. The Spring Hill as such was not recognised prior to BGS work on sheet 216, although some outcrops of ?Sixth Terrace?, which (mostly) seem to be Spring Hill, were mapped on Sheet 182. On Sheet 234 some high gravels are classified as Wills? Woolridge Terrace, which is now (as Woolridge Member) included in the Wolston Formation (outwash gravels) but some look more likely to be Spring Hill on the basis of elevation. (E) According to the compiler?s favoured scheme for a two-phase Anglian (believed to be the only one that fits the evidence, despite the so-far missing stage 11 interglacial) the Spring Hill is Stage 10 distal outwash and the Woolridge Stage 12, probably more proximal, outwash. This accords with the ages assigned in Bowen (1999).
Up to 7m
Spital Flagstone Formation
SPI
Second Piper Coal (South Yorkshire, Nottingham And Derby)
SPIC
Aith - Spiggie Pluton
SPIG
Spirean Mor Granite Sheet-Complex
SPIR
Splent Coal (Leicestershire)
SPLC
Spilmersford Intrusion
SPLFD
Spargrove Limestone
SPLI
Upward change from thick mudstone sequence to a dominantly limestone sequence.
From just southwest of Ditcheat [ST 620 361] in an arc northeastward through Spargrove to just north of Stoney Stratton (limit of current mapping on 1:50 000 sheets 296 and 297).
Interbedded muddy limestones and thin silty mudstones.
Upward change from a dominantly limestone sequence to silty and fine-grained sandy clays.
Spilmersford Beds
SPMF
Spengill Member
SPN
Base of lowest nodular limestone or massive mudstone above the laminated mudstone of the Ashgill Formation.
Howgill Fells, the Lake District, Cross Fell and the Craven Inliers.
Nodular limestone and pale grey mudstone.
Base of the black graptolitic mudstone of the main part of the Skelgill Formation.
Swinton Pottery Coal (West Yorkshire And Nottinghamshire)
SPOC
Found in southern Yorkshire and northern Nottinghamshire; might also the present in adjacent parts of Derbyshire.
Spothfore Member
SPOT
At the base of the predominantly rudaceous beds containing intrabasinal clasts of greywacke, chert, black mudstone and volcanic rock, within the Kirkcolm Formation.
North east of Bail Hill Volcanic Group, within the Kirkcolm Formation, north of Sanquhar, Dumfries, Scotland.
Intrabasinal rudite.
The top of the predominantly rudaceous beds, within the Kirkcolm Formation.
Springpool Sandstone Bed
SPPS
Sprinkling Tarn Sandstone Member
SPR
The gradational base is taken at the first appearance of pyroclastic rocks in the sandstone succession
From High Raise to Scafell and Langdale, probably also present in the Tiberthwaite, Coniston area, Lake District, Cumbria
Interbedded coarse-grained pebbly volcaniclastic sandstone, planar bedded and cross-bedded. Includes units of banded andesitic tuff (pyroclastic fall-out deposits) and a succession of silicic tuff and lapilli-tuff (pyroclastic fall-out and density current deposits (the Glaramara Tuff). The facies associated separates this from the underlying Cockley Pike Member
Up to 70m
Defined by the base of the overlying silicic pyroclastic rocks of the Lincomb Tarns Formation. The contact varies from conformable and with angular discordance
Stoke Park Rock Bed
SPRK
Conformable, at abrupt or near abrupt upward change from the reddish brown mudstone of the Mercia Mudstone Group (undivided) to the greenish grey dolomitic sandy mudstone of the Stoke Park Rock Bed.
Crops out in northern part of Bristol area and in south Gloucestershire.
Mudstone, greenish grey, silty, sandy, dolomitic, well indurated; nodules of celestite (strontium sulphate) common, especially towards top.
0.5 to 2m
Conformable, at gradational upward transition from greenish grey mudstone with celestite of the Stoke Park Rock Bed to reddish brown and greenish grey mottled mudstone of the Mercia Mudstone Group.
Sprotbrough Member
SPRO
Drawn at base of pale grey oolitic dolomite where it rests on the Wetherby Member; overlies the lower dolomite of the Hampole Beds.
Eastern England, (Yorkshire Province), near outcrop.
Pale cream and grey to buff, sparsely fossiliferous and commonly cross-stratified, finely oolitic dolomite.
Up to approx. 40 metres.
Drawn at base of mudstones of the Edlington Formation.
Shelley Plain Sandstone
SPS
Scapa Sandstone Member
SPSA
Saltpetre Coal (South Lancashire)
SPTR
Spy Wood Sandstone Formation
SPW
Overlies Rorrington Shale Formation.
Calcareous quartz mudstone.
Underlies Aldress Shale.
Whitecliff Beds
SPWH
Spey Conglomerate Formation
SPY
Conglomerate at base of conglomeratic sequence generally unconformably resting upon metamorphic basement. (Local Aulrothie Sandstone Member at base near Whiteash Hill).
Coarse red-bed conglomerate sequence with sporadic thin pebbly sandstone beds.
At diachronous change to the essentially sandstone sequence (Fochabers Sandstone Formation) typically developed in the Fochabers area.
Spynie Clay Member
SPYCL
A sharp, unconformable, undulating contact with underlying deposits of either glaciofluvial sand and gravel, or brown, gravelly clayey sand, and gravelly sandy clay diamictons, interpreted as till.
Sheet 95 (Elgin).
A dark bluish grey to yellowish-red, commonly laminated clay containing well-dispersed clasts and lenses of sand, gravel and diamicton, and low diversity, high-Arctic microfossils, indicative of a glaciomarine environment.
A sharp, planar, erosional, unconformable contact with late-glacial raised beach deposits, or at the present ground surface.
Scottsquar Member
SQAR
Bradfordensis Zone.
Upward change from ooid grainstone (Cleeve Cloud Member) to marl or limestone as described in lithology; junction marked by hardground.
Cotswolds Hills: north of Nailsworth and Cirencester, west of Stow-on-the-Wold and Northleach. (Barron, A J M, et al, 1997, fig.4).
Pale grey and brown medium- to coarse-grained peloid, ooid and shell fragment packstone and grainstone ('Upper Freestone'), with beds and lenses of grey to white, commonly highly fossiliferous marl/carbonate mudstone ('Oolite Marl'). These occur throughout the succession, though particularly in the lower part. Fauna dominated by brachiopods; characteristic fossils include the plicate terebratulid brachiopod Plectothyris.
Typically 5 to 10m. Type section; 2.4m (Mudge, D C, 1978a) to 3.6m (Baker, P G, 1981). Maximum c.30m (Colesbourne area).
Upward rapid transition to Harford Member generally by increasing sand and decreasing calcareous content, or: hardground overlain by Aston Limestone Formation or Salperton Limestone Formation.
South Quarry Breccia Member
SQBR
Member locally developed at the top of the Ives Head Formation; planar and probable conformable base on grey, laminated, volcaniclastic siltstones and sandstones of the Ives Head Formation (undivided).
Charnwood Forest area, Central England.
Volcaniclastic slump-breccia, composed of folded and contorted fine-grained laminated siltstone rafts in a coarse, grey, crystal-rich volcaniclastic matrix.
About 31m
Overlain by the Blackbrook Reservoir Formation, consisting in its lower part of greenish grey, laminated volcaniclastic siltstone.
Scaleber Quarry Limestone Member
SQLM
The base is taken where grey limestone of the Scaleber Quarry Limestone Member overlies dark grey limestone and mudstones of the Scaleber Force Limestone Member. This boundary is typically gradational and for convenience the base is taken at top of highest prominent mudstone.
Well-bedded, thin and thick beds of mid and mid dark grey, fine- to coarse-grained limestone, with minor mudstone beds. Bioclastic packstones characterize the lower part of the Member, passing up to packstones and grainstones. Bands and nodules of black chert occur locally in the lower part of the Member. The member contains an abundant macrofauna, characterized by cerioid and fasciculate lithostrotionids.
To 134m thick at the type locality, decreasing to 29m at outcrop at Kilnsey Crag.
The top of the Member is drawn at the conformable, gradational and slightly diachronous upward passage from mid dark-grey limestone of the Scaleber Quarry Limestone Member to the pale grey limestone of the Cove Limestone Member.
Sacquoy Sandstone Member
SQS
Transgressive sandstone base in flagstone sequence of siltstones.
Pebbly sandstone with medium to thick-bedded, predominantly fluvial sandstones in four bodies.
17m on Sacquoy Head, Rousay Island, Orkney.
Base of blackish laminite mudstone at base of lacustrine rhythm number 36 of Astin, 1990.
Silkstone Rock
Scrach Formation
SRA
Gradational with underlying Tridwr or Yr Allt Formations. Taken at entrance of abundant thin sandstones.
Mudstones with numerous thin sandstones; packets of thick-bedded sandstone and conglomerate locally present. Flaser and lenticular bedding common in thin sandstones. NOTE: In type area overlain by Bronydd, Coldbrook or Goleugoed Formations and underlain by Tridwr Formation. In the Rhayader district overlies the Yr Allt Formation. Top not seen.
Up to 150 metres.
Sharp entrance of mudstone dominated sequences of the Bronydd, Coldbrook or Golengoed Formations in the type area. Top not seen at Rhayader due to local disconformity at base of Telychian Formations.
Sraduffy Member
SRAD
Strath Rannoch Beds
SRB
Serpent Brae Coal
SRBC
Known in the area around Megg's Linn (Lewis Burn), Northumberland.
c0.5m
Serpent Brae Limestone
SRBL
Rusty-weathering sandy, micaceous limestone, with polyzoans and large productoids.
Strath Rannoch Conglomerate
SRC
Strathendrick Formation
SRCK
Unconformity on older Quaternary deposits and bedrock.
Recognised in the Clyde catchment area as the fluvial and lacustrine deposits of the valley of the Endrick Water.
In addition to alluvium of the present day floodplain and river terrace deposits, the Strathendrick Formation includes a wide range of lithologies encompassing pebbles, fine to coarse gravel, cobbles and boulders in a sandy matrix and coarse- to fine-grained sand, silt and clay. Beds rich in organic remains occur as well as peat (in the floodplain deposits).
St Raven's Edge Tuff Member
SRE
Taken at the base of eutaxitic lapilli-tuff resting on volcaniclastic sandstone or bedded tuff of the Glaramara Tuff.
Kirkstone Pass to Troutbeck and south of Hayeswater, eastern Lake District, Cumbria.
A massive, eutaxitic, lithic-rich, andesitic lapilli-tuff.
Up to 40 m thick.
Taken at the abrupt change from massive lapilli-tuff to volcaniclastic sandstone.
Sheriffmuir Sandstone Member
SRF
Diachronous over the top of the Ochil Volcanic Formation lavas, except in the Bridge of Allan area where volcaniclastic conglomerate is overlain.
The Stirling to Alloa area, on the south-east limb of the Strathmore Syncline.
Grey and brown, locally pebbly sandstones, with subsidiary mudstones.
From 300 m to 500 m thick.
The base of the Buttergask Flagstone Member within the Scone Sandstone Formation.
Strath Rory Group [See Also Strr]
SRG
Drawn at base of conglomerate of the Strath Rory Group where it rests unconformably on siltstone and mudstone of the Struie Group.
Fluvial sandstones with thick conglomerates and subordinate calcareous fish-bearing shales. (Lenticular basal conglomerates).(Correlative of Strath Rory Group = Millbuie Sandstone Group).
Approx. 1350m seen.
Drawn at unconformable upward passage from sandstones of the Strath Rory Group to yellow and red sandstone of the Balnagown Group.
Sron Garbh Semipelite Formation
SRGA
Lower boundary not exposed. Probably tectonic boundary with Grampian Group rocks.
Eastern part of Ardverikie Forest between the Allt Cam [NN 50 78] and the Allt Mhainisteir [NN 542 860]. On sheet 63E [Dalwhinnie].
Gneissose semipelite with local gradations towards micaceous psammite. Typically magnetite-rich and hence notably magnetic. Thin amphibolites occur locally throughout.
Where magnetite semipelite is succeeded (rapid / sharp transition) by tremolite schist of the Iubhair Beag Calcareous Formation.
Sranagross Member
SRGM
Red Marls (Saliferous)
SRM
Springwood Marine Band
SRMB
Sand Rock Coal (South Lancashire)
SRMC
Sarn Complex
SRN
Lleyn Peninsula, Sheet 113 (Aberdaron and Bardsey Island), although the complex probably extends offshore. The boundaries of the intrusive complex are largely sheared along the Lleyn Shear Zone.
Locally foliated granites, granodiorites, diorites and hornblende gabbros with garnetiferous gneiss in places.
Sronbane Coal (Ballycastle, Northern Ireland)
SRNC
Rests on seatearth.
Coal and coaly seatearth.
Overlain by fireclay.
Sron Nan Dias Pelite And Limestone Formation
SRND
Remains to be defined in regional context.
Not yet known.
Dark grey pelite with garnet and biotite, graphitic, schistose with subsidiary semipelite. Contains beds of dark metalimestone, some grading into calcareous pelite and calc-silicate rock. The sequence contains at least two units of relatively pure metacarbonate rock; the thicker beds of metalimestone are up to 10-15m thick.
Sralahan Shale Member
SRSM
Sarrowcole Vein
SRV
Lead-zinc veins cutting Ordovician greywacke.
Sherwood Sandstone Unit 1
SS1
Sherwood Sandstone Unit 2
SS2
Sherwood Sandstone Unit 3
SS3
Sherwood Sandstone Unit 3 Type (A)
SS3A
Sherwood Sandstone Unit 3 Type (B)
SS3B
Sherwood Sandstone Unit 3 Type (C)
SS3C
Shirdley Hill Sand Formation
SSA
Late Devensian to Flandrian.
Variably overlies sediments of the Caledonia Glacigenic Group.
Discontinuous distribution in Lancashire and Merseyside between Wigan, Liverpool and Southport.
Moderately to well-sorted, fine-grained sand with peat layers in the lower part. Sand grains are dominated by rounded to sub-rounded quartz grains. The formation is divisible into an upper "white" sand and a lower "brown" sand that is olive grey and brown. The sediments are interpreted as coastal blown sands, possibly a coastal facies of the Seacombe Sand Formation.
<1 to 5m.
Either the ground surface or basal surface of overlying peat deposits.
Sulby Slump Breccia
SSB
St Sunday Crag Tuff Member
SSC
Basal bedded tuffs are conformable on sandstone of the Deepdale Sandstone Formation.
St Sunday Crag, Bannerside, Gavel Pike, Lord's Seat, Coldcove and adjacent to Trough Head, all in northeastern Lake District, Cumbria.
Dacitic ignimbrite in the form of lapilli-tuff, mostly with a eutaxitic foliation due to welding, and with bedded tuffs at the base and top (some with accretionary lapilli, top only) which represent pyroclastic fall and surge deposits.
Typically 45-55m
Bedded tuffs are overlain by andesite - probably a sill.
South Of Scotland Granitic Suite
SSCGR
Seaford Chalk Formation, Newhaven Chalk Formation And Culver Chalk Formation (Undifferentiated)
SSCK
As for lower boundary of Seaford Chalk Member.
Chalk, firm, white, flinty. See the also the Lithology descriptions for the component formations.
As for upper boundary of Spetisbury Chalk Member.
Lothian Subsuite [Of Ssdpv]
SSDLO
Clyde Plateau Subsuite [Of Ssdpv]
SSDPC
Southern Scotland Dinantian Plugs And Vents Suite
SSDPV
South of Scotland.
Suite of plugs and vents in southern Scotland.
Seven Sisters Flint
SSFL
Sherwood Sandstone Group
SSG
Gradational on the Roxby Formation (formerly the Permian Upper Marls) in type area and similar relationship elsewhere, but sharp and unconformable on Carboniferous or older rocks locally. In Devon, taken at the base of the Budleigh Salterton Pebble Beds Formation.
Sandstone, red, yellow and brown, part pebbly; subordinate red mudstone and siltstone.
Variable, maximum >1500m
Gradational into Mercia Mudstone Group where mudstone/siltstone becomes dominant over sandstone. In Devon taken at top of the Otter Sandstone Formation.
Stockingford Shale Group
SSH
Sharp contact of mudstone on massive grey, glauconitic sandstone of the Woodlands Member (Hartshill Sandstone Formation). Some sediment mixing and flame structures at junction.
Extends from Bedworth, northwestwards to just northeast of Woodlands Farm (SP 3688 8633 - 2849 9870).
Pale to medium grey or dark grey to black micaceous mudstone, locally calcareous and pyritic, with silty or organic laminae and bands. Burrowed and bioturbated intervals. Some intercalated grey quartzose sandstone beds.
775m in type area (maximum aggregate of partial type sections).
Hard, grey, commonly fractured mudstone overlain with unconformity by beds that may comprise: Devonian sandstone or conglomerate, Carboniferous mudstone, sandstone and Triassic breccia or mudstone.
Sheena Shale Member
SSHM
Scrabo Sill
SSI
Stonesfield Slate
SSL
Strath Suardal Formation
SSLL
Sunnyside Limestone
SSLS
Shass Shale Member
SSM
Swinstone Bottom Marine Band
SSMB
Second Smalley Coal (Leicester And Derby)
SSMC
Heads Of Ayr Vent
SSPHA
Southshore Formation
SSR
Conformably overlies the Ardwell Formation.
Limestone flysch.
Conformably overlain by the Threemile Formation.
Seaton Sluice Sandstone
SSSA
Staffin Shale Formation And Staffin Bay Formation (Undifferentiated)
SSSB
Stammers Vein Coal (Pembrokeshire)
SSVC
Staithes Sandstone Formation
STA
Gradational contact with underlying mudstones of the Redcar Mudstone Formation, but defined at base of "Oyster Bed" (highly fossiliferous calcareous and ferruginous sandstone), which apparently persists as a continuous horizon throughout the Cleveland Basin.
Silty sandstone, more or less argillaceous, typically intensely bioturbated and/or showing bedding structures of many types.
Upward transition from sandstone/siltstone to shaly mudstone with scattered sideritic nodules of the Cleveland Ironstone Formation.
St Abbs Vent
STAB
Stanhope Coal (Warwickshire)
STAC
Seatallan Dacite Member
STAD
Junction with underlying unnamed andesite sheets in the Birker Fell Andesite Formation.
Seatallan - Haycock area, west of Wasdale, Cumbria.
Dacite lava flow. Porphyritic, flow laminated, white to pink-weathered.
Junction with overlying tuffs or ignimbrites of the Craghouse Member.
Staffa Lava Formation
STAF
Stanah Member
STAH
Stainby Member
STAI
Generally a sharp boundary resting on sandstone or sandy mudstone, often developed as a seatearth, forming the lower part of the Grantham Formation.
According to Kent (1975 fig 1), the unit is more or less restricted to the type area, although it is more likely that it is much more widespread, particularly to the north, such as identified by Gaunt et al. (1992), in North Lincolnshire.
A dark grey to brownish, fissile, laminated mudstone and siltstone, and more massive laminated mudstone, locally containing marine bivalves such as Gervillella and Modiolus, and the brachiopod Lingula, succeeded by a rootletted seatearth in the upper part of the unit, where it forms the basal interpreted marine part, of a second shallowing-upward rhythm of the Grantham Formation.
Up to about 1.5 m thick, typically about 1 m thick in the type area,and 1.42 m thick in the type section.
A transitional, and somewhat arbitrary boundary, with interpreted non-marine mudstones, siltstones and sandstones forming the upper part of the Grantham Formation, which in some places is overlain directly by limestones of the Lincolnshire Limestone Formation.
Stamford Member
STAM
In the north, this junction is identified by a sandstone/siltstone/mudstone lithology, sharply and unconformably overlying an uneven channelled surface of marine ooidal limestones of the Lincolnshire Limestone Formation, commonly marked by a secondary limonitic 'Ironstone Junction Bed', and in a presumed narrow zone beyond the limit of the Lincolnshire Limestone-Kettering-Peterborough by similar sandstone, siltstone and mudstone sediments of the Grantham Formation, although in most of Northants, this boundary is seen as an ironstone or ferruginous sandstone of the Northampton Sand Formation or mudstones of the Lias Group, and across the London Platform subcrop the sediments overlie Palaeozoic strata.
North Lincolnshire,arbitrarily taken at the northern margin of 1:50 000 Sheet 102 where the unit passes northward into the Thorncroft Sand Member of the Rutland Formation, which is more sandy and includes marine intercalations, with an additional sedimentary cycle at the base, south and south-westwards to Bucks, approximating to the southern boundary of Sheet 202, and in subcrop, the western boundary of Sheet 220, where the unit passes into the Horsehay Sand Formation, which is more sandy, interpreted to be of deltaic facies.
A pale greenish grey to yellowish and white, generally massive, fine-grained, generally friable, quartzose, unfossiliferous sandstone or siltstone, interpreted as mainly swamp and lacustrine, seen particularly in the upper part of the succession and in thicker successions as a sandy silty mudstone with plant debris, rootlets and thin lignite lenses, especially near the top, locally including interpreted lacustrine carbonaceous mudstones in hollows at the base and at the top.
Up to 12m, but typically 4m to 5m thick, measured as 4.5 m in the type section.
The top of the andstone/siltstone/mudstone as above, often strongly rootletted or with more or less well-developed mudstone seatearth, generally sharply and erosively overlain by marine beds of typically mudstone or sandy mudstone of the succeeding rhythm.
Stanton Formation
STAN
Unconformably on Canna Formation or older.
Stiff silty clay with sporadic pebbles.
91 metres, found throughout most of the deep basins in the sea of the Hebrides, up to 120 metres thick.
Upper boundary is a major erosion surface.
Starfish Bed [Eocene]
STAR
Statfjord Formation
STAT
Staunton Member
STAU
The River Leadon and tributary valleys including Glynch Brook, Gloucestershire and Worcestershire.
Sand and gravel, or pebbly, sandy, clayey silt, with pebbles of quartz, quartzite, granite and limestone.
Variable, up to 5 m.
Strathtay Formation
STAY
Recognized in the Tay catchment area as the alluvial deposits of the Tay and all its tributaries, from highest to lowest order, includes valleys of the Earn, Eden, Almond, Isla, Tummel and Garry.
A wide range of lithologies encompassing pebbles, fine to coarse gravel, cobbles and boulders in a sandy matrix and coarse- to fine-grained sand, silt and clay. Peat and beds rich in organic remains occur in the floodplain deposits.
Veneer to several metres
Stourscombe Formation
STB
Late Famennian.
Staffin Bay Formation
STBA
Stobs Castle Beds
STBC
Stubton Limestones Bed
STBL
Change up from bluish grey, shaly mudstone with numerous phosphatic nodules of uppermost 1m of the undifferentiated Beckingham Member; at 34.65m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
East Midlands: north Leicestershire to Lincolnshire. Not recognised in the Scunthorpe Mudstone Formation of north Lincolnshire, or south Leicestershire, where it passes south either into part of the more argillaceous Rugby Limestone Member of the Blue Lias Formation or into part of the mudstone-dominated Charmouth Mudstone Formation.
Group of two to four limestone beds separated by mudstone. Uppermost bed is typically brown and grey mottled, highly bioturbated, shelly, bioclastic, ferru-ooidal, packstone with numerous bored Gryphaea, weathering to orange brown, and 0.61m thick in the type section. Below are one to three thinner, non-ooidal argillaceous limestone beds. Rich fauna including forams, serpulids, corals, brachiopods, gastropods and ammonites. Forms a strong scarp feature with a dip slope.
1.0 to 2.4m; 1.14m in type section.
Change up into grey, mudstone of the undifferentiated Foston Member; at 33.51m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Stob Quartzite Member
STBQ
Stubbs Coal (South Lancashire)
STBS
St Bees Till Member
STBT
Generally conformable contact (but with evidence of glacitectonic shearing) on the St Bees Sand and Gravel Member of the Seascale Glacigenic Formation.
Part of the St Bees Moraine on 50k Sheet 28 (Whitehaven).
Pebbly silty clay diamicton, calcareous, very still, massive, matrix-supported; dark greyish brown. It contains well dispersed subangular to rounded pebbles of red sandstone, white and yellow Coal Measure sandstones, coal, greywacke, slate, limestone and Borrowdale Volcanic Group rocks. It is typically thinly interlaminated with dark yellowish orange silt towards its base; locally a dense, thickly interlaminated bed (<3m thick) of fine-grained sand and silt (showing ripple-drift lamination) occurs at the base of the Member.
3.0m thick at its Type Section, 2.0m thick at its Reference Section.
Gradational contact with the base of the overlying Gutterfoot Sand Member of the Gosforth Glacigenic Formation.
Straight Brae Vein
STBV
Saltby Volcanic Formation
STBY
Sarclet Conglomerate
STC
Stotfield Calcrete Formation
STCA
Stiddlehill Calcareous Beds
STCB
Seaton Carew Member
STCF
Slightly unconformable, at the abrupt transition from sandstone of the underlying Sherwood Sandstone Group to deformed mudstone and sandstone of the Seaton Carew Member.
Proved in the subsurface only, Teesside area.
Mudstone, red-brown and grey-green mottled, and sandstone, coarse-grained, sporadically pebbly, brown or grey-green. Sandstone occurs within convoluted soft sediment injection structures and sandstone dykes.
Conformable, at the abrupt transition from deformed mudstone and sandstone of the Seaton Carew Member to red-brown "blocky" mudstone of the undifferentiated Sidmouth Mudstone Formation.
Strichen Pluton
STCH
Studland Chalk Member
STCK
Campanian. Belemnitella mucronata s.l. Zone
Conformable at a marly bed with included marl, above which the chalk is marl-free in the Alum Bay/Scratchell?s Bay section on the Isle of Wight and at ?the lower horizon of yellow-stained chalk on Old Harry Rock? in Studland Bay, Dorset (Gale et al., 1987). It is not discernible from the published literature whether these two beds are in the same stratigraphic position. This doubt together with the lack of exposure and geomorphological expression of the member has led to the BGS reverting to the original concept of the Portsdown Chalk Member (Bristow, Mortimore and Wood, 1997). This is also the position stated in Rawson, Allen and Gale (2001) and thus the Portsdown Chalk Formation covers all of the chalk up to the sub-Palaeogene erosion surface.
Limited to the Isle of Wight and the Swanage area of Dorset in the Southern Province..
Marl-free, soft chalk with large irregular flints.
Up to 23m preserved beneath the sub-Palaeogene unconformity in Alum Bay on the Isle of Wight.
The sub-Palaeogene unconformity in the Southern Province. Relationship to the Upper Campanian and Maastrichtian chalks of the northeast `Transitional? Province poorly understood due to poor exposure.
Compact Limestones
STCL
Stockings Coal (South Derbyshire)
STCO
Saltom Dolomite
STD
Stonedelph Coal (South Lancashire)
STDC
Supratidal Deposits
STDU
Variable lithology. Any deposit laid down in the supratidal zone, ie. the area of tidal flat above the mean high water for spring tides. This zone is only inundated by exceptional tides augmented by a storm surge. [Generic description: earth science dictionaries in the BGS library.]
Stone Gill Limestone Formation
STE
At depth of 49.73 metres in Wyegarth Gill No.1 Borehole (NY 7201 0355).
Can be informally divided into a lower unit of interbedded porcellanous limestones, argillaceous limestones, sandstones and mudstones c.25 metres thick and an upper unit of mostly porcellanous limestone with some flaggy dolomites c. 55 metres + thick. Overlying Coldbeck Limestone comprises dark grey, fine-grained limestones with interbedded mudstone and flaggy dolomite in which algal macrostructures are common. Underlying Shap Conglomerate comprises green/brown/red sandstones, siltstones mudstones and conglomerates.
Estimated thickness in Ravenstonedale area (based on Wyegarth Gill No.1 Borehole and Stone Gill) is about 100m. It thins slightly westward to c.80m on NY60NW.
Overlain by Coldbeck Limestone Formation.
Stone Coal (North Wales)
STEC
Strathtummel Subgroup
STEL
Gradational boundary with Bruar Psammite Formation at base of Tummel Quartzite Formation.
From closure of Errochty Synform [NN 710 671] north-east to A9 road near Dalnamine [NN 750 700, then due east to Loch Tay Fault at [NN 880 700], then along Loch Tay Fault to Loch Tummel [NN 802 598], and thence back to the closure of the Errochty Synform via the northern boundary of the Dunalastair Formation. Possible extension of this area to north-west not defined.
Interbedded psammite and quartzite units, mostly thickly-bedded, with internal features suggesting deposition in a shallow marine shelf environment.
1000 - 3800m on limbs of Meall Reamhar Synform; lower limit probably involves tectonic thinning, but upper limit may involve tectonic thickening.
Sharp, conformable boundary at top of Kynachan Psammite Formation with Dunalastair Quartzite Formation (Lochaber Subgroup, Appin Group).
Stenton Sill
STEN
Stewartry Group
STEW
Plant materials preserved within the Stewarty Group in the Mauchline Basin indicate an Early Permian age. K-Ar dating of lavas in the Mauchline Basin indicates an age of around 290 Ma, just younger than the currently accepted estimated age of the Carboniferous?Permian boundary of 292 Ma. Both techniques corroborate an earliest Permian age for the Stewarty Group. K/Ar dating of the Glas Eilean Lava Formation gives a similar age: 285 +/- 5 Ma. Strata of the Stewarty Group appear to be of Early Permian age. Application of internationally defined chronostratigraphical subdivisions for the Permian to strata in the western UK places the Appleby Group [and equivalents] within the Mid Permian and the Cumbrian Coast Group [and equivalents] within the Late Permian.
Unconformable, with basal lithologies of breccia or basaltic lava, overlying Carboniferous or Lower Palaeozoic rocks in south and west Scotland.
In the isolated basins in south and west of Scotland [Stranraer, Mauchline, Thornhill, Dumfries, Lochmaben and Moffat basins and in the Sound of Islay] within the counties of Argyll, Ayrshire and the Dumfries and Galloway region and the eastern part of Borders region.
Thick and very thick sequences of red sandstone and sedimentary breccias, some with evidence of basaltic lavas at or near the base of the sequence, deposited within separate fault-defined or fault-controlled basins e.g. Stranraer [Stone, 1988]. Breccia formations may be present at the base of the Stewartry Group. They are either overlain by sandstone formations or breccia and sandstone formations occur in an intertonguing relationship. Basaltic lava may also be present at or near the base of the Group. The Stewarty Group sequences are thick, c.1400m in the Dumfries and Lochmaben basins, but cannot be correlated between the adjacent depositional basins. The Waterbeck and North-East Axial faults, that are aligned northeast and lie along the line of the Solway Firth, bound the southerly extent of the Stewarty Group. South of the Waterbeck and North-East Axial faults the sequences of Permian strata are relatively thin, around 500m in the Annan and Carlisle basins and up to 550m in west Cumbria, and lithostratgraphical units are laterally extensive and correlated between basins. Lithostratigraphical formations within the Appleby and Cumbrian Coast groups can be correlated from west Cumbria to the Carlisle Basin.
The proven preserved thickness of the Stewarty Group is up to 610m in the Mauchline Basin, 270m in the Thornhill Basin, and >98m in the Moffat Basin [BGS water borehole records]. Where the thickness is not proven by drilling or exposure, estimates of thickness have been derived from modelling of the Upper Palaeozoic strata from gravity anomaly data as being around 1400m in the Dumfries and Lochmaben basins and 1.5 to 2.0km in the Stranraer Basin.
The upper boundaries are not seen; Triassic strata are not preserved in onshore basins in Scotland unlike Permian sequences in the adjacent Carlisle, Solway, Irish Sea and Larne basins. The preserved upper surface is the present day level of erosion and there is no evidence for the previous presence of Triassic strata.
Stonesty Tuff
STF
Taken at the base of bedded silicic tuff overlying andesitic tuff of the Whorneyside Formation; in places including in the reference section, there is an angular discordance at the base.
Cumbria. Thirlwell to Scafell and Stonesty Pike, central Lake District, occurring at the base of the Long Top Tuff Member except where the Oxendale Tuff is present.
White-weathered, flinty, bedded and cross-bedded rhyodacitic tuff and accretionary lapilli-tuff
Stockdale Farm Formation
STFA
Not seen, but possibly an angular unconformity above Lower Palaeozoic sandstone, siltstone and mudstone.
The southern margin of the Askrigg Block, in the transition zone to the Craven sub-basin.
A lower member comprises thinly interbedded laminated dolostones, dolomitic-siliciclastic siltstone, mudstone and laminated anhydrite. This is overlain by interbedded sandstone, siltstone, mudstone and thin limestone. The sandstones are arkosic, pale grey, fine-grained, micaceous and carbonaceous. Limestones are dark grey micrites with subordinate packstones and wackestones.The upper member comprises interbedded limestone, siltstone and mudstone, lithologically similar to the middle member, but lacking sandstones.
At least 165m
A deeply fissured top surface marking a significant non-sequence, overlain by conglomerates of the Chapel House Limestone Formation and underlain by limestone, siltstone and mudstone of the Stockdale Farm Formation.
Starfish Bed [Ashgillian]
STFB
Stafford Coal
STFC
Stanford Formation
STFD
Top of highest sandy lithology of underlying Kingston Formation (or silty mudstone of West Walton Formation, where the former is absent) above which succession is dominated by (non-sandy) limestone and/or marl; generally sharp and non-sequential boundary, commonly marked by pebble bed.
Westbury, Wilts (where overstepped by Lower Cretaceous) to Waddesdon, near Aylessbury, Bucks (where wedges out into Ancholme Group; Horton et al., 1995).
Shell detrital limestones, ooidal limestone, coralline limestone, fossiliferous marls, and interbedded limestone, marl and mudstone.
0 to 26 m (Oxford area); up to c. 15 m (Calne-Swindon area).
Top of limestone and/or marl-dominated succession succeeded by grey mudstones and silty mudstone of Ampthill Clay Formation; generally a sharp, non-sequential boundary. Locally unconformably succeeded by Lower Cretaceous (Lower Greensand Group).
Steel Fell Diabase
STFE
St Fergus Pluton
STFG
Styford Limestone
STFL
Staddon Formation
STG
Faulted out: lower part of sequence adjacent to fault is transitional to slaty mudstone, thin sandstone beds and sporadic thin limestone beds of the Bovisand Formation.
Staddon Grit Formation mapped on Plymouth (348) Sheet. Known to occur between north Cornwall coast at Trenance Point and south Devon coast south of Berry Head.
Medium to thick beds (1-4m) of fine- to medium-grained sandstone, thickening and coarsening upwards with thin interbedded grey mudstone and siltstone.
Faulted out: Staddon Formation thrust over Saltash Formation.
Straiton Grit Formation
STGC
Conformable on the Knockgardner Sandstone Formation.
The Girvan to Straiton area of south-west Scotland.
The lower part is composed of green, thinly-bedded, grits and siltstones, whereas the upper part is composed of red, massive, coarse grits and conglomerates.
About 90 m thick.
Unconformably overlain by the Inverclyde Group.
Stricegill Limestone
STGL
Strand Gneiss Formation
STGN
Stoke Goldington Member
STGO
Original entry stated "Wolstonian (Saalian)", but this was subsequently revised to Pleistocene (DJLO - 16/10/2006)
0 to 8m
Stanmore Gravel Formation
STGR
Early Pleistocene; ?contemporary with the Red Crag Formation.
Rests unconformably on London Clay bedrock, base of deposit at 105-128 above O.D.
Thames Valley and Colne and Lea valleys region; plateau cappings from Stanmore, Middlesex to Billericay, Essex, and Shooter's Hill, Kent.
Gravel and sand, clayey near base. Gravel mostly composed of flints, up to 150mm in diameter, with a little quartz, quartzite and Lower Greensand chert in the fine fractions. Matrix of orange-brown, pale grey, red mottled clay and sandy clay, with pockets of coarse sand. Locally with layers of silt, clay or peat. Interpreted as offshore or beach gravels (Ellison et al 2004), or possibly fluvial (Bridgland 1994).
To 7m; average 3m
Overlain in places by till of the (Anglian) Lowestoft Formation, but generally at surface.
Strandhall Beds
STH
Stassfurt Halite Formation
STHA
Strathfinella Hill Conglomerate Member
STHC
A diachronous, gradational, conformable boundary, interfingering with and passing down into the Teith Sandstone Formation and the Cromlix Mudstone Formation, taken from where conglomerate becomes the predominant lithology in the upward sequence.
Strathfinella Hill [NO 6878].
A poorly sorted, clast-supported conglomerate with clasts of semi-pelite, psammite, quartzite, lava and feldspar porphyry in a medium-grained, lithic sandstone matrix.
Up to 1700 m thick.
The top of the predominantly conglomerate member, below the overlying part of the Teith Formation.
Strath Halladale Migmatite Complex And Strath Halladale Granite (Undifferentiated)
STHD
Stafford Halite Member
STHF
Strath Halladale Granite
STHL
Stone House Shale Formation
STHO
Stanners Hill Pebble Bed Member
STHP
Start Horneblende Schists
STHS
Stow Hill Sand And Gravel Member
STHSG
The Stow Hill Sand and Gravel Member rests unconformably on the upper surface of the Bacton Green Till Member between Bacton Green [TG338345] and Mundesley [TG319361], and on the Weybourne Town Till Member within large, tectonically-controlled synclines between Trimingham [TG279389] and Sidestrand [TG265397].
Coastal sections between Paston and Sidestrand.
The Member consists of beds of matrix-supported gravel separated by thick beds of horizontally bedded sand. Up to 92% of the clast content is flint, with a small (c.6%) subsidiary quartzose content.
The maximum observed thickness of the deposit is 8m, in the Trimingham area.
The sand and gravel deposit is truncated by the ground surface which forms its upper boundary.
South Threave Formation
STHV
Conformably overlies the Lady Burn Formation. Taken at the change from the massive, nodular pale grey largely unbedded silty mudstones of the Lady Burn Formation into the bedded green mudstone, sandstone and siltstone of the South Threave Formation.
Bedded green mudstones, sandstones and siltstones, but with some units of unbedded grey silty mudstone.
Conformably overlain by the High Mains Formation. The boundary is taken at the change from bedded greyish-green muddy siltstone of the Waterfall Member of the South Threave Formation into the fine- to medium-grained grey sandstone of the High Mains Sandstone.
Silver Threads Ironstone (South Staffordshire)
STI
Stinking Coal (South Staffordshire)
STIC
Struie Formation [See Also Stru]
STIE
Starston Till Member
STIL
The basal boundary of the Starston Till Member is abrupt and commonly erosional. The Member overlyies Bytham River (Bytham Catchment Subgroup) deposits at the stratotype locality, where a lithological change from sand and gravel to till can be observed.
Buried beneath Lowestoft Formation till at depth within the Diss and Harleston districts, southern Norfolk.
Brown clayey-sand matrix-supported diamicton with flint and sporadic chalk pebbles. Laminations are common.
The upper boundary of the Starston Till Member with overlying glaciofluvial outwash (un-named) is erosional. Hollows on the upper surface of the till are commonly infilled by a coarse gravel lag.
Stockdale Group
STK
As for base of Skelgill Formation: unconformably overlies the Red Gill Formation of the Dent Group or conformable (but with local non-sequence) at base of graptolitic black mudstone and siltstone above calcareous and bioturbated siltstone of the Dent Group (Ashgill Formation).
Southern Lake District and Lower Palaeozoic Inliers of Northern England.
Includes Skelgill and Browgill Formations as separately defined: dominantly mudstone and siltstone.
Conformable, at top of pale green oxic siltstones (Browgill Formation); overlain by laminated siltstone (Brathay Formation).
Stenkrith Brockram
STKB
Stinking Coal (South Wales)
STKC
Stinking Coal (Ne Bristol)
STKG
St Kilda Centre
STKI
Stinking Rider Coal (South Wales)
STKR
Starkey Coal (Forest Of Dean)
STKY
Skelton Limestone
STL
St Tudwal's Formation And Llanengan Formation (Undifferentiated)
STLE
Staplehill Gravel Member
STLG
Sandy Till
STLL
Shetland Group
STLN
Strathavon Lodge Calcareous Semipelite Member
STLO
Storakaig Limestone Member
STLS
St Mary's Well Bay Member
STM
St Magnus Bay Group
STMA
Stanley Main Coal (West Yorkshire)
STMC
St Martins Gravel
STMG
Subangular gravel of Chalk flints and Greensand chert.
Stony Coal (Lothian)
STMI
St Monans Little Limestone
STML
St Michael's Mount Intrusion
STMM
Medium- and coarse-grained biotite granite.
Start Mica Schists
STMS
Stanhope Coal [Obsolete Code: See Shpe And Stac]
STNC
Stone Coal (West Yorkshire)
STNE
Straiton Subgroup
STNG
Conformable junction with the Blair Shale Formation, the topmost unit of the underlying Dailly Subgroup.
Flaggy sandstones, gritty sandstones and conglomerates.
About 270 m thick.
St Ninian Formation
STNI
Stinking Coal
STNK
Stanningley Rock
STNR
The Stanningly Rock, or 36 Yard Rock, is a fine-grained, thinly bedded, commonly ganisteroid sandstone.
Stanley Sandstones
STNS
Strathnaver Granite
STNV
Stobswood New Coal (Northumberland)
STNW
Storm Beach Deposits
STOB
Storm Beach Deposits, 1
STOB1
Storm Beach Deposits, 2
STOB2
Stone Coal (Kilmarnock - Glasgow)
STOC
Stoodfold Member
STOD
Interbedded within Kirkcolm Formation.
Bail Hill area, Sanquhar, Southern Uplands of Scotland.
Tuffaceous sandstone turbidites.
<30m
Stocked Head Quartz Porphyry
STOHD
Stone Coal (Ayrshire)
STON
Stanton Coal (Northumberland)
STONC
Stone Coal (Northumberland And Durham)
STONE
Stotfield Cherty Rock Formation
STOT
Base of the pedogenic sedimentary rock (after calcrete) above the Lossiemouth Sandstone Formation or, where the latter is absent, the Burghead Sandstone Formation.
Moray Firth Basin, Scotland.
Sedimentary rock comprising massive pale grey chert, sandy limestone, calcareous sandstone and silicified sandstone of pedogenic origin. Includes red and green mudstones with carbonate concretions in Sutherland.
The unconformity with the Jurassic conglomerate, mudstones, siltstones and sandstones above.
Stour Formation
STOU
Incoming of ooliths, generally accompanied by a significant drop in, or elimination of, sand.
From the eastern edge of the Yeovil Sheet (312), across the Shaftesbury Sheet (313) and the northern part of the Wincanton Sheet (297).
Alternating sequence of oolitic limestone and clay, commonly oolitic, with generally only a minor sand content.
At the top of the non-bioclastic or evenly graded bioclastic limestone.
Sturminster Pisolite Member
STP
Usually sharply defined by an abrupt incoming of large numbers of pisoliths/oncoliths.
Across the Shaftesbury Sheet (313) and southern part of Wincanton Sheet (297).
Pisoliths or oncoliths, about 6mm diameter, varying from spherical to oblate, in a coarse-grained oolitic matrix; locally the matrix is an oolitic clay. In places the pisoliths/oncoliths form a grain-supported concentrate.
Usually sharply defined by the abrupt disappearance of pisoliths/oncoliths.
Stockport Conglomerate
STPC
Stronachullin Phyllite Member
STPH
Stickle Pike Tuff Member
STPI
At base of rhyolitic lapilli-tuff in the Lickle Tuff Formation that usually overlies volcaniclastic sandstone and locally rests on the Paddy End Tuff Member.
Within the Ulpha Basin southeast of the River Duddon. Turner Hall (SD 230 960) to Great Stickle (SD 211 915) and Lickle Valley (SD 240 920), Cumbria.
Rhyolitic lapilli-tuff, pale-weathered, eutaxitic to parataxitic.
Base of overlying Caw Sandstone Formation (volcaniclastic breccia and sandstone) or, locally, the Lag Bank Tuff Formation (dacitic lapilli tuff).
Stackpole Limestone Formation
STPL
?Arundian to Holkerian.
Taken at the gradational boundary between the dark grey interbedded wackestones and mudstones of the underlying Pen-y-holt Limestone Formation and the pale grey thick-bedded skeletal and oolitic limestones of the Formation. Boundary taken at base of first oolitic limestone.
Castlemartin area [SR 95 98], southwest Pembrokeshire. Its relationship with the coeval Hunts Bay Oolite Subgroup to north and east is uncertain and needs further investigation.
Pale grey, thick-bedded skeletal and oolitic limestones; scattered cherts and silicified fossils; local dolomitisation. Dark grey, thinner-bedded limestones are common in the lower part. Pale grey oncolitic limestones and calcite mudstones are common in the uppermost part. Deposited in front barrier, barrier and back barrier settings.
260m at type locality in southwest Pembrokeshire.
Taken at the outgoing of pale grey calcite mudstones of the Formation and the incoming of mottled [pseudobrecciated] skeletal packstones and palaeokarstic surfaces of the overlying Oxwich Head Limestone Formation.
Sticklepath Slate
STPS
Stockport Glacigenic Formation
STPTG
Unconformable and in places heavily incised contact with bedrock.
Cheshire, Staffordshire and south Lancashire approximately corresponding to the area between the Kirkham Moraine (near Kirkham [SD420 300] ) in the north and the Ellesmere Moraine (Wood Lane Quarry, Ellesmere [SJ 4220 3280] ) in the south.
A mixed glacigenic sequence of till (sandy, gravelly clay with cobbles and boulders), sand, gravel and laminated clay and silt. Erratics are dominated by Lake District (Borrowdale Volcanic rocks and Eskdale Granite), and Carboniferous derived rock fragments but include Irish Sea derived material in places.
Highly variable from 3m to locally in excess of 100m.
Either the ground surface or various units of the Britannia Catchments Group or other formations or subgroups of the Caledonia Glacigenic Group.
Stiperstones Quartzite Formation
STQ
Strathpeffer Group
STRA
Drawn at base of olive shales and calcareous bands of the Ord Beds where they rest conformably on conglomerate and breccia of the Kilmorack Group.
Highland, Scotland.
Red shales and sandstone, olive shales and fetid, calcareous, bituminous beds.
Drawn at unconformable upward passage from red shales and sandstones of the Strathpeffer Group to the Knock Farril Conglomerate.
Starav Intrusion
STRAV
Stringocephalus Beds
STRB
Strathan Conglomerate Member
STRC
Stronchreggan Formation
STRCH
Strathspey Granite
STRG
Granite and granodiorite, pale grey, medium-grained, contains muscovite and biotite. Petitic inclusions common in its western part, psammitic in its eastern part.
Glen Sanda Facies [Strontian Pluton]
STRGS
Strinds Formation
STRI
Unknown; contacts are generally faulted.
Welsh Borderlands. Old Radnor, Radnorshire.
Pale greenish grey, purple and brown, fine- to medium- grained, massive, micaceous sandstones, with beds of conglomerate containing clasts of vein quartz, rhyolite and mica schist.
Unknown - unconformably overlain by Dolyhir Limestone (Wenlock).
Stockbridge Rock Member
STRK
Santonian (?). Micraster coranguinum Zone.
Conformable at the change from soft white smooth chalk to very hard chalk. Placed within the higher part of the Seaford Chalk Formation.
Occurs in the high part of the Seaford Chalk Formation in the Winchester, Stockbridge area of Hampshire and westwards within the Bourne and Avon valleys near Salisbury. Central Hampshire and Wiltshire in the Southern Province. May extend northwards into Berkshire.
Very hard, locally porcellanous, creamy white chalk, grainy in part with abundant sponge spicules.
Not known in detail estimated to be 2 to 3m. Member may be a number of such beds of hard chalk between 5 and 10m below the mapped base of the Newhaven Chalk Formation.
Conformable at the top of the uppermost bed of very hard chalk.
Strathaird Limestone Formation
STRL
Unconformable upon the Gribun Chalk Formation and Feorlin Sandstone Formation.
Throughout the Inner Hebrides islands but poorly represented in Morvern.
Dark grey micritic limestone and two clastic members. A basal Laig Gorge Sandstone member and the Clach Alasdair Conglomerate Member.
2 to 6m on Eigg, 2.5m on Skye and 2m of the Clach Alasdair Conglomerate Member on Mull.
Unconformable below the Beinn Iadain Mudstone Formation or at an erosion surface beneath the Palaeogene basalts.
Loch Sunart Facies [Strontian Pluton]
STRLS
Stroma Member
STRM
Strokestown Group
STRO
Strontian Pluton
STRON
Strath Ossian Granitic Complex
STROS
Strathavon Psammite Member
STRP
Strath Rory Formation [See Also Srg]
STRR
Inner and outer Moray Firth.
Strensham Sand And Gravel Member
STRSG
Unconformable channelled base, resting on Triassic bedrock.
Only currently recognised at Upper Strensham SO905 395 (BGS Sheets 199, 216).
Predominantly cold phase sands and gravels that underlie a terrace supposedly intermediate in height between the Cropthorne (4) and Pershore members (5) of the Avon Fourth Terrace of Tomlinson (1925) and of BGS maps. Dominated by clasts of "Bunter" quartz/quartzite lithologies with subordinate flint. Terrace surface at type locality approximately 40-42m OD, ie, some 30m above the modern Avon. Overlies the organic Strensham Court Bed (Bowen, 1999), = the Strensham Bed of de Rouffignac (1995), assigned to Stage 7. (See Supplementary Information Description).
(a) This unit may be superfluous in the Avon scheme. (b) The "terrace" top and deposit base at the type locality lie within the 4th/Cropthorne envelope, suggesting the deposits should be classified as Cropthorne Member. Supposed MIS 7 organic deposits beneath it strengthen the case. (c) However, it has been mapped as Terrace 5/Pershore Member. It does indeed lie 6m or so above a nearby terrace outcrop mapped as Terrace 4/Cropthorne. If it were Pershore Member MIS 9 organics might be expected beneath it. "Dating" to MIS7, based solely on "aminostratigraphy", could be wrong - apparently C fluminalis (to strengthen the Stage 7 case) has not been found. (d) Thus an extra Member is not needed: the unit should be reclassified as Cropthorne (ie BGS maps are wrong) or as Pershore Member. The former is most likely: probably it is a dissected remnant of a valley-side head fan, derived from Pershore gravels, but contemporaneous with the Cropthorne, and somewhat higher than the true Cropthorne terrace flat. Such fans extending uphill from the Cropthorne terrace are commonplace in the upper Avon. (d) Terrace surface at type locality c.40-42m OD, ie, c.30m above the modern Avon. (e) Upper boundary described as ?ground surface? but head might intervene.[Precis of notes from MGS]
0 to c.4m
Start Complex
STRT
Strangways Formation
STRW
Stronsay Group
STRY
Sarclet Sandstone
STS
Stretton Sand
STSA
Start Schists
STSC
Shakenhurst Sand And Gravel
STSG
Stack Skerry Formation
STSK
Shothouse Spring Tuff Member
STT
The tuffs of the Shothouse Spring Tuff Member rest upon thickly bedded limestones of the Monsal Dale Limestone Formation.
Outcrop is localised to the vicinity of Shothouse Spring (SK 242 589). Proved in a borehole at Bottom Leys Farm, Bonsall SK25NE/41, at SK 2587 5795.
A green tuff containing beds of coarse lapilli in a calcareous cement. To the east of Grangemill (SK 244 578) the tuffs interdigitate with limestone in the Bottom Leys Farm Borehole (SK25NE/41) (SK 2587 5795). In the latter, the tuffs include medium-to coarse-grained, angular to subrounded fragments of mudstone and limestone in a fine-grained grey to dark grey or green matrix.
Unknown in the type area. Seen as 3 leaves, in ascending order 6.90, 0.32 and 4.93 m thick.
The tuffs of the Shothouse Spring Tuff Member are overlain by thickly bedded limestones of the Monsal Dale Limestone Formation.
Allt An T-Strathain Till Member
STTI
Unconformable on bedrock, predominantly Moine Supergroup psammite.
Relatively widespread across Moine Supergroup rocks in Assynt and northwest Sutherland. Also occurs on Torridon Group sandstone bedrock around Ullapool. May occur locally on other lithologies (eg. Eriboll Sandstone, Durness Limestone, Lewisian Gneiss) in structurally complex terrain.
Pale brown to mid grey, poorly sorted, clay-rich, matrix-supported diamicton with boulders. The till shows good evidence of subglacial deposition; namely edge-rounded and bullet-shaped striated clasts set within a stiff, highly consolidated muddy matrix. In places the diamict exhibits a strong subhorizontal fissility, is overconsolidated, and was most likely deposited by subglacial lodgement processes. Clasts are predominantly Moine Supergroup rocks, with minor amounts of Eriboll sandstone (quartzite). Sporadic clasts of Torridon Group sandstone, Lewisian gneiss and various local igneous rocks are also present. The till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older.
Variable; 0.5-8m (maximum observed thickness), probably >10m locally.
Stafford Tonstein (North Staffordshire)
STTO
Stumpy Coal
STU
Steelend Upper Blackband Ironstone
STUB
Blackband ironstone (sandy) : 36", Blaes : 9", Blackband ironstone (wandering) : 8".
4'5" (135 cm).
St Tudwal's Formation
STUD
Transgressive boundary and unconformable contact with underlying mudstones and siltstones of the Mawddach Group or Harlech Grits Group.
Coarse- to medium-grained well-bedded and bioturbated muddy sandstone.
60 to 130m
Is overlain by the mudstones of the Llanengan Formation. The sharp contact with the latter is a transgressive boundary, possibly a non-sequence, with a horizon of phosphatic conglomerate at the top of the St Tudwals Formation. (Machroes Member).
Stumpy Coal (Warwickshire)
STUM
Straitstep Vein
STV
Stornoway Formation
STW
Stobswood Coal (Northumberland)
STWD
Stewartby Member And Weymouth Member (Undifferentiated)
STWE
Stwrin Coal (South Wales)
STWR
Sty Head Tarn Member
STY
Stanbury Coal (West Yorkshire)
STYC
Stormy Limestone Formation
STYL
Holkerian to ?Asbian.
Taken at the base of the first bed of calcite mudstone occuring above the ooid grainstones and the subordinate skeletal packstones of the underlying Cornelly Oolite Formation.
West and central Vale of Glamorgan [ST 00 74]. Present also in Gower [SS 50 90] and the Pembroke/Tenby [SM 99 01] area but has not been mapped. Passes laterally eastwards into the Hunts Bay Oolite Subgroup, that cannot be subdivided into Cornelly Oolite and Stormy Limestone formations.
Interbedded cryptalgal and fenestral, calcite mudstones, coquinoid limestones, skeletal, peloid, intraclast, ooid packstone/grainstones, ooid grainstones and the characteristic oncolitic grainstones. Scattered algal bioherms. Deposited in a peritidal enviroment.
55 to 65m in the central and western Vale of Glamorgan.
In the Vale of Glamorgan the top is taken at the sharp contact, defined by a paleokarstic surface, between the heterolithic lithologies of the Formation and the overlying partially dolomitised sandy skeletal packstones and calcareous sandstones of the Pant Mawr Sandstone Member [Oxwich Head Limestone Formation]. In Gower and Pembrokeshire it is taken at the palaeokarstic surface separating the heterolithic lithologies of the Formation from the mottled and pseudobrecciated skeletal packstones of the Oxwich Head Limestone Formation.
Sub-Oolite Bed
SUB
Courceyan to ?Chadian.
Taken at the junction between the dolomitised packstones of the underlying Black Rock Limestone Subgroup and the undolomitised crinoidal limestones of the Bed. The boundary needs further investigation.
Bristol area [ST 60 74], Tytherington area [ST 67 88] and Monmouth and Chepstow area [ST 53 93].
Pale grey well-sorted crinoidal limestone, oolitic in upper part. Deposited in a shallow marine setting.
6m at Southmead, near Bristol, to 21m in the Tytherington area.
Taken at the junction of crinoidal limestone of the Bed and the oolites of the overlying Gully Oolite Formation. Boundary needs further investigation.
Succoth-Brown Hill Intrusion
SUBH
Subcrenatum Sill
SUBS
Sump Coal (Glasgow-Airdrie)
SUC
Suffolk Catchments Subgroup
SUCA
Formation of the Suffolk Catchment Subgroup rest unconformably upon glacial and periglacial deposits, and upon Crag Group, London Clay Formation and Chalk Group bedrock.
Restricted to that area of Suffolk and Essex that lies between the catchments of the River Thames and the River Waveney and their tributaries, on BGS 1:50 000 Sheets 176, 189-191, 205-208, 222-225, 240-242, 259.
The Suffolk Catchments Subgroup encompasses all the fluvial, lacustrine and organic deposits of the rivers of Suffolk and Essex which flow into the North Sea south of the River Yare and north of the River Thames. Floodplain alluvium comprises soft silts and clays, commonly with beds of peat and a basal bed of sand and gravel. River terrace deposits are largely sand and gravel. The gravels are dominantly composed of subrounded to angular flint, including large cobbles, also rounded pebbles of quartz and quartzite, northern British erratics of glacial derivation, and a little chalk. Marine deposits are included where they are intercalated in dominantly fluvial formations.
Southern Uplands Glacigenic Subgroup
SUDR
Diamicton, gravel, sand, silt and clay containing clasts predominantly of greywacke sandstone and siltstone with some granite, granodiorite, porphyry and dolerite. Deposits locally dominated by granite or granodiorite. Typically yellowish brown but locally reddish brown.
Ground surface or conformable contact with Flandrian sediments.
Submerged Forest
SUF
Peat and organic rich silty clay, commonly with fossil trees preserved in 'life' positions. [Generic description].
Sulby Glen Formation
SUGL
Generally unconformably overlying glacigenic diamictons and outwash debris flows and alluvian fan sediments or bedrock.
The Isle of Man. (50k sheets 36, 45, 46, 56, 57).
Well sorted, stratified alluvial gravel, sand, silt and clay, forming floodplains and river terraces.
Note that as now defined this does NOT equate with the Sulby Member of the Ballaugh Formation of Thomas (1999).
Terraces up to 6m high are recorded.
Suie Hill Formation
SUH
Transition from mixed psammite, semipelite and pelite without gritty units to more uniform semipelite with gritty units: overlies Craigievar Formation (right way up).
(i) Western: Bounded to north by Boganclogh Intrusion, to east by Rhynie Devonian outlier and to west and south by Craigievar Formation. (ii) Central: Bounded to north by Insch Intrusion, to west by Rhynie outlier, to south by Craigievar Formation, and to east by Bennachie Granite. (iii) Eastern: Small area near Hillbrae (NJ 684 246), bounded to northwest by a ductile shear zone at the margin of the Insch Intrusion, to east by a continuation of fault marking the eastern boundary of the Bennachie Granite and to south by the Bennachie Granite. (iv) Kist Hill: Small area around NJ 6415 bounded to east and west by faults, to south by the Tillyfourie Tonalite and to north by the Bennachie Granite.
Dominantly semipelite, muscovite-rich, typically with andalusite, but with mappable units of poorly-sorted, gritty psammite becoming dominant towards the top; also contains a mappable unit of strongly magnetic pelite.
Maximum of c.4000m to the east of the Rhynie Devonian outlier, but only 800-1000m west of the outlier.
Not seen: cut off by Insch and Boganclogh intrusions.
Surrey Hill Gravel Member
SUHG
Windsor and Bracknell, and Basingstoke districts.
Gravel characterised by clasts of the following lithologies: abundant angular flint (65-79%), common rounded flint (12.8-29.6%), sporadic Lower Greensand (4.6-12.2%) and very sparse quartz and quartzite (up to 0.8%).
Suisgill Semipelite Formation
SUIS
Sullom Formation
SULM
Sugar Loaf Member
SULO
Superstes Mudstone Formation [Duplicate Code: Use Smu]
SUM
Southerham Marls (One)
SUMA1
Southerham Marls (Two)
SUMA2
Sutton Manor Marine Band [Local Name: Use Vdmb]
SUMB
Local name applied to the Vanderbeckei Marine Band (National Standard Name) in part(s) of the Lancashire Coalfield area.
Sumburgh Group
SUMH
Summit Pelite Member
SUMP
Sun Vein Coal (South Wales)
SUNC
Sunkir Marble Member
SUNK
Sunnyside Psammite Member
SUNS
Faulted against Dicky Hare Member on coast.
From coast at Sunnyside Bay [NJ 5340 6765 - 5370 6740] as far as a line from the southeast side of Crannoch Hill [NJ 521 664] to [NJ 528 600], just north of the A98.
Quartzite and feldspathic quartzite, medium- to thickly planar bedded, well-sorted, with tabular cross-bedding.
c.350m on coast section; appears to thicken slightly inland.
Sharp change to micaceous, schistose semipelite of West Sands Mica Schist Member of Findlater Flag Formation.
Superficial Deposits
SUPD
Any deposit, natural or man-made, overlying bedrock (generic description).
Superficial Theme Not Mapped [For Digital Map Use Only]
SUPNM
Offshore Superficial Theme Not Mapped [For Digital Map Use Only]
SUPOF
Sulphur Rock
SUR
Summertown-Radley Sand And Gravel Member
SURA
Mid (?to Late) Pleistocene (MI Stage ?8 to 5 or 4).
Upper Thames catchment, ie. River Thames and most tributaries (excluding River Thame) upstream of the Goring Gap. Fairly well developed along the Upper Thames itself, the Ock, and (somewhat less well) along the lower Evenlode and the lower Cherwell.
Predominantly cold phase sands and gravel that underlie the Summertown-Radley or Second Terrace of BGS maps. Dominated by clasts of Middle Jurassic limestone, but also containing "Bunter" quartz/quartzite and a proportion of flint, the latter increasing downstream below the confluence with the River Ock near Abingdon.
(A) Here named the Summertown-Radley Sand and Gravel Member, though simply Summertown-Radley Member in Bowen 1999 and in the previous BGS list of computer codes. (B) Parent was originally Upper Thames Valley Formation. Despite correlation problems at Goring, this is OK as the member names in the Upper Thames remain discrete. (C) Terrace surface some 8m above modern alluvial floodplain at the type locality and (apparently) elsewhere. Locally extends below the level of the Northmoor Terrace. Includes the Stanton Harcourt Bed (organic muds, MIS 7) and the Eynsham Beds (fossiliferous gravel, MIS5e). Locally, upper and lower "facets" have been recognised (2b and 2a of BGS maps), these do not necessarily relate to the two phases of aggradation suggested by the organic beds. (D) Upper boundary is given as ?ground surface? though head, colluvium or soil deposits might intervene. (D) A different type locality (Summertown) to that specified in Bowen, 1999 (Radley) is specified for several reasons. However, this is of merely historical interest as the Primary Reference section is much more significant and much better described. (E) Relatively recent work on sections shows that some deposits mapped as Summertown-Radley are in fact Northmoor, and probably the converse is also true. (F) There do not appear to be equivalents on the Upper Evenlode (Sheets 218, 235) and in the Upper Windrush (also on Sheet 235) a different name (Sherborne Member) is used because of the lack of positive correlation. The name is (probably) applicable in the Cherwell valley on Sheet 218.
0 to c 6m
Ground surface or (locally) Northmoor Sand and Gravel Member.
Summertown-Radley Sand And Gravel Member, Lower Facet
SURAL
Summertown-Radley Sand And Gravel Member, Upper Facet
SURAU
Surface Sands Formation
SURF
Unconformable erosion surface (the "Y" seismic unconformity of Akhurst et al, 1997) proved by seabed cores, lying upon the Western Irish Sea Formation.
Dominantly sands, with subordinate mud, peat and some basal lag gravel, together with a rich fossil assemblage of present day species.
Generally from 0.5m to 2m, reaching 40m in sandbanks and up to 100m in channel infills.
Present day sea-bed surface.
Sugar Sands Limestone
SUS
Sunninghill Sand Member
SUSA
Sule Skerry Formation
SUSK
Sutherland Group
SUTH
Unconformity at the top of the Triassic Stotfield Cherty Rock Formation.
Moray Firth Basin, Geological Sheets 109, 103, 94 and 95 (Scotland).
Interbedded grey-green mudstone, siltstone and sandstone all of which are locally carbonaceous/bituminous, thin sandy limestones, ironstones, a thin coal, a basal conglomerate and boulder beds towards the top.
At least 1400 m.
Top of the Helmsdale Boulder Beds Formation (not exposed onshore).
Suidheig Till Formation
SUTI
Uneven, unconformable contact with bedrock.
Stony sandy clay diamicton, matrix-supported, moderate yellowish brown, extremely compact, containing clasts of Devonian sandstone and siltstone with some psammite, granite and schist. Many clasts are decomposed, especially petitic rocks and granite, with orange weathering rinds.
Erosional, undulating, unconformable contact with the Odhar Gravel Formation at the Allt Odhar Interstadial site, the Craig an Daimh Gravel Formation at the Dalcharn Interglacial site, or unconformable, planar contact with the Athais Till Formation elsewhere.
Sutton Sand Formation
SUTN
Unconformable on older superficial deposits, mainly Devensian glacial lake deposits (eg, Alne Formation at type locality) and glacial till or underlying bedrock.
Vale of York from near Hutton Sessay [448707 475623], to Sutton-on-the-Forest, southwards into the area east of Doncaster and in Lincolnshire to the west of Scunthorpe [Gaunt, 1994].
Fine-grained silty sand.
Present land surface.
Susanna Vein
SUV
Sulphur Coal (Wyre Forest)
SUWF
Snowdon Volcanic Group
At base of volcanic formations resting on sedimentary rocks of Cwm Eigiau Formation.
Snowdonia.
Acidic ash-flow tuffs with a major basaltic division.
Not exceeding 1800 metres.
At base of Cadnant Shales Formation.
Stinkard Vein Coal (Pembrokeshire)
SVCO
Strathaven Formation
SVF
Sheepcote Valley Flint
SVFL
Skomer Volcanic Group
SVG
Drawn at the base of the Skomer Volcanic Group (which is never seen) where it unconformably overlies Ordovician rocks.
Skomer Island off the Pembrokeshire coast.
Subaerial lava flows with breccias, conglomerates, quartzites and red clayrocks. Mafic to felsic, including felsite, albite-trachyte, keratophyre, skomerite, marloesite, mugearite and olivine basalt.
1000 metres approx.
Drawn at the conformable upward passage of the Skomer Volcanic Group where it is unconformably overlain by upper Llandovery shales and sandstone.
Seven Linns Coal
SVLC
Seven Linns Sandstone
SVLS
Sealyham Volcanic Formation
SVO
Gradational passage from shales of underlying Rosebush Formation. Boundary is drawn where volcanic rocks become dominant over shales.
The lower part of the formation comprises green-grey, pillowed, andesitic or dacitic hyaloclastites (Bevins et al, 1992; cf. Thomas and Cox, 1924) The upper part of the Formation comprises rhyolitic tuffs.Geochemical investigations undertaken by Bevins et al (1992) confirm the calc-alkaline chemistry of these rocks, indicating that they are the continental-side products of island arc magmatism.
Unconformable contact with the base of the Aber Mawr Shale Formation.
Saxa Vord Pelite Formation
SVP
Spean Viaduct Quartzite Formation
SVQU
Svarte Formation
SVRT
Swansea Member
The base is placed at the base of the Golden Seam (Swansea Three Feet or Graigola) (Woodland et al., 1957), where the coal rests on mudstone seatearth within a predominantly arenaceous sequence of the Pennant Sandstone Formation.
Western part of the South Wales Coalfield, from Llanelli [SN 49 01] to the Neath area [c.SS 75 97].
Green-grey, lithic arenites ("Pennant sandstones") with thin mudstone/siltstone and seatearth interbeds, and mainly thin coals.
274m to 290m
The top is placed at the base of the Wernffraith Seam (correlated with the Mynyddislwyn Seam of the eastern part of the South Wales Coalfield) where the coal overlies mudstone seatearth with a predominantly arenaceous sequence of the Pennant Sandstone Formation, and is overlain conformably by the mudstone-dominated succession of the Grovesend Formation.
Sandwith Anhydrite
SWA
Swansea Member [Redundant Code: Use Sw]
SWAM
At the base of the Golden (Swansea Three Feet or Graigola) seam (Woodland et al., 1957), where the coal rests on its underlying seatearth.
The western part of the South Wales Coalfield, in the Swansea - Gorseinon - Gower area, and extending eastwards to the Margam - Tondu - Bettws area.
Green-grey Pennant sandstones, seen as lithic arenites, with thin mudstone, siltstone and seatearth interbeds, and mainly thin coals.
From 274 m to 290 m thick.
The base of the Wernffraith (Mynyddislwyn) Seam, (Woodland et al., 1957).
Swanage Group
SWAN
Swanshaw Sandstone Formation
SWAS
The top of the Greywacke Conglomerate, which is a massive coarse conglomerate over 25 m thick comprising mainly greywacke pebbles.
Between the Ayrshire and Douglas Carboniferous basins, continuing north-east into the Pentland Hills in Ayrshire and Lanarkshire, Scotland.
Red-brown, grey-green and chocolate-brown, medium and coarse-grained terrestrial sandstones with subordinate pebble beds and conglomerates, minor fine-grained sandstones, siltstones and mudstones.
Estimated to be at least 750 m thick.
The base of an andesite volcanic sequence, such as the Duneaton Volcanic Formation around New Cunnock, within the Lower Old Red Sandstone.
Shacklow Wood Lava Member
SWB
Basalt lava of the Shacklow Wood Lava Member is underlain by pale and medium grey limestone of the Monsal Dale Limestone Formation.
Restricted to the area west of Ashford (SK 19 69), Peak District inlier.
A dark greenish grey, locally purplish grey, basalt, variably amygdaloidal or compact, locally doleritic, in part autobrecciated.
Up to 20 m thick at outcrop at least 50 m thick in the Mogshaw Borehole (SK 16 NE 19) (SK 1889 6778).
Basalt lava of the Shacklow Wood Lava Member is overlain by mainly dark and medium grey limestone, thinly bedded and cherty, of the Monsal Dale Limestone Formation.
Swarte Bank Formation
SWBK
Swindon Clay
SWC
Saalian To Weichselian Channel Fill Deposits, Undifferentiated (Offshore)
SWCFU
Saltwick Coal (Northumberland)
SWCK
Swinley Clay Member
SWCL
South Wales Coal Measures Group
SWCM
The base is placed at the base of the Subcrenatum Marine Band, either in a sequence of mudrocks at the point where a marine fauna makes its first appearance, or where marine mudstone of the Subcrenatum Marine Band overlies quartzites of the underlying Telpyn Point Sandstone Formation of the Marros Group.
South Wales Coalfield; from Pembrokeshire [SM 86 15] in the west eastwards to Abersychan, Monmouthshire [SO 29 02]. It extends from the Black Mountain [SN 670 215] in the north, southwards to Swansea - Port Talbot [SS 80 85] and crops out in a peripheral belt around the coalfield, concealed below the Pennant Sandstone Formation over most of the coalfield.
Grey (productive) coal-bearing mudstones/siltstones with seatearths and minor sandstones.
c.240m on the east crop of the coalfield to c.900m in the Swansea area.
The top is taken at the base of the Pennant Sandstone Formation (Warwickshire Group), where grey, productive coal-bearing mudrocks of the South Wales Coal Measures Formation are overlain conformably either by the first substantial development of Pennant sandstones or by red beds of the Deri Formation.
Shallow Coal (South Staffordshire)
SWCO
Sandwith Dolomite
SWD
Swineden Sand Bed
SWDEN
Wolstonian (?MIS 6 - 7).
The basal boundary of the bed is a sharp undulatory erosion surface with an amplitude of up to 0.2m developed on white sand of the Kirkhill Palaeosol Bed.
Buchan, northeast Scotland. The bed is only known within the immediate vicinity of Kirkhill Quarry (infilled) (centres on NK 0120 5285) on Sheet 87W (Ellon).
Weakly organic sands. Greyish brown, silty, fine-medium-coarse grained, weakly stratified, containing rare granules and pebbles of weathered felsite and charcoal fragments. A seam of black to dark brown, laminated, organic mud (0.01-0.05m) occurs at the base of the unit and drapes the eroded surface of the underlying Kirkhill Palaeosol Bed. A C 14 date of >47, 360 BP (SRR-2416) has been obtained from the organic mud. Palynological analysis indicates that the bed contains recylcled arboreal pollen (probably derived from earlier soil horizons) together with the pollen of grasses and heather suggesting that the bed was formed under cool climatic conditions in an open treeless environment. Interpreted as slope wash deposits derived from contemporaneous surface soils.
To 0.7m
The upper boundary of the bed is typically gradational over c.0.05m with the overlying Camphill Gelifluctate Bed. On the margins of the channels/basins cut into bedrock seen in Kirkhill Quarry (infilled), units up to the Rottenhill Till Formation may rest conformably on the Swinedon Sand Bed.
Saalian To Weichselian Diamicton, Firm To Hard (Offshore)
SWDFH
Swinden Limestone
SWDL
Spy Wood Sandstone Formation [Duplicate Code: Use Spw]
SWG
Scatterigg Wandering Gas Coal
SWGC
Satwell Gravel Formation
SWGR
Saalian To Weichselian Gravel (Offshore)
SWGRV
Sandwick Member
SWIK
c.46m
Swindon Coal
SWINC
Swillington Sandstone
SWIS
Saltwick Formation
SWK
Shandwick Siltstone
SWKSI
Balintore area, eastern Scotland.`
Swindale Limestone Formation
SWL
Taken at the base of limestone unconformably overlying mudstone of the Dufton Shale Formation. The extent of the unconformity is appreciated only from the faunal evidence
Grey nodular limestone with intercalations of pale grey mudstone with limestone nodules
About 19m
Taken at the base of mudstones belonging to the unconformably overlying Ashgill Formation
South Wales Lower Coal Measures Formation
SWLCM
The base is taken at the base of the Subcrenatum Marine Band (as defined by Stubblefield and Trotter, 1957), where marine, fossiliferous mudstones at the base of the marine band conformably overlie the topmost mudstones or sandstones of the Marros Group. The Formation rests unconformably on Dinantian or Devonian strata in the Berkshire and Kent coalfields.
South Wales Coalfield; from Pembrokeshire [SM 86 15] in the west eastwards to Abersychan, Monmouthshire [SO 29 02]. The Formation extends from the Black Mountain [SN 670 215] in the north, southwards to Swansea - Port Talbot [SS 80 85] and crops out in a peripheral belt around the coalfield. Probably also represented in the subsurface in the Berkshire and Kent coalfields.
Grey, (productive) coal-bearing mudstones/siltstones, with seatearths and minor sandstones.
c. 80m on the east crop of the South Wales Coalfield to c.300m in the Swansea area.
The top is taken at the base of the Vanderbeckei (Amman) Marine Band (as defined by Stubblefield and Trotter, 1957), where basal fossiliferous, marine mudstone of the marine band comformably overlies the top of the Amman Rider Coal (and its equivalents).
South Wales Lower Coal Measures Formation And South Wales Middle Coal Measures Formation (Undifferentiated)
SWLMC
Swallowdrum Coal
SWM
Saalian To Weichselian Mud And Sand, Interbedded (Offshore)
SWMAS
Stobswood Marine Band
SWMB
Swallowdrum Coal Of Comrie
SWMC
South Wales Middle Coal Measures Formation
SWMCM
The base is taken at the base of the Vanderbeckei (Amman) Marine Band (see Stubblefield and Trotter, 1957), where grey, marine, fossiliferous mudstones at the base of the marine band conformably overlie the Amman Rider Coal or the local equivalent where the Amman Rider amalgamates with the underlying coals. In the stream exposures in Cwm Gwrelych - Nant Llyn Fach, the boundary [SN 9010 0533] lies at the top of a 0.18m thick coal, at the base of 0.10m of grey mudstone with lingulids and fish fragments (the Vanderbeckei Marine Band).
The Formation crops out in a peripheral belt around the coalfield, extending from south of Little Haven, Pembrokeshire [SM 850 124] in the west to near Pontypool [SO 263 020] in the east; and from near Llandybie [SN 610 149] in the north to Swansea - Port Talbot area [c.SS 780 840] in the south.
c.120m on east crop [SO 20] of the coalfield to 240m in the Swansea area [SS 88].
The top is taken at the top of the Cambriense (Upper Cwmgorse) Marine Band (Stubblefield and Trotter, 1957), where grey marine mudstones at the top of the marine band are conformably overlain by non-marine mudstones marking the base of the South Wales Upper Coal Measures or by Pennant sandstones marking the base of the Pennant Sandstone Formation.
Saailian To Weichselian Mud, Firm To Hard (Offshore)
SWMFH
Southwest England Minor Intrusive Suite
SWMI
Sweeney Mountain Sandstone
SWMS
Saalian To Weichselian Mud, Very Soft To Soft (Offshore)
SWMVS
Saalian To Weichselian Sediment, Undifferentiated, Affected By Mass Wasting And Iceberg Scour (Offshore)
SWMWS
Shotto Wood Limestone
SWOL
Swordly Pelite Member
SWOR
Stornoway Phyllite Formation
SWPH
Shank Wood Sandstone
SWS
Spurlswood Shell Beds
SWSB
Swindale Shale Formation
SWSH
Swithland Formation
SWSL
Passes down to coarse-grained greywackes interbedded with silty mudrocks, of the Brand Hills Formation.
From The Brand/Swithland Wood area, north to Charnwood Forest Golf Course; last seen at Nanpantan.
Purple to grey slaty meta-mudstones and greywackes with thin conglomeratic sandstones.
Not seen or proved in this area.
Saalian To Weichselian Sand (Offshore)
SWSND
Swatchway Formation
SWT
Base : smooth reflector often uncertain.
Muddy sands with sporadic gravel or mud layers.
35 metres - 0.
Upper: seabed or ice scoured surface beneath Witch Ground Formation.
South Wales Upper Coal Measures Formation
SWUCM
The base of the Formation is placed at the top of the Cambriense (Upper Cwmgorse) Marine Band. Mid-grey mudstones or siltstones conformably overlie darker grey, fossiliferous mudstones of the Cambriense Marine Band, which mark the top of the underlying South Wales Middle Coal Measures (Stubblefield and Trotter, 1957).
Widespread throughout the South Wales Coalfield, from the Twyi estuary [SN 38 01], west of Pembrey, east to the Rhymney area [SO 120 058] on the north crop of the coalfield and to Risca [ST 24 92] on the south crop.
Grey (productive) coal-bearing mudstones/siltstones with seatearths and minor grey, quartz-rich sandstones, coals and ironstones.
Up to a maximum of 184m, southwest of Ammanford [SN 58 09].
The top of the formation is placed at the incoming of the first thick (over c.3m) lithic arenite ("Pennant Sandstone"), where the arenite rests conformably but diachronously on grey mudstones/siltstones at the top of the South Wales Upper Coal Measures Formation. On the east crop of the coalfield, the top is placed at the diachronous incoming of red/green mottled mudstones, which mark the base of the Deri Formation.
Swallow Wood Coal (West And South Yorkshire)
SWWC
Solway Marine Band [Local Name: See Vdmb]
SWYMB
Local name applied to the Vanderbeckei Marine Band (National Standard Name) in the Cumbrian Coalfield area.
Sussex Catchments Subgroup
SXCAT
The entire area covered by the catchments of Sussex (Ouse, Arun, Rother and Cuckmere and other rivers) that flow southwards from the Weald to the English Channel.
Mainly river terrace sand and gravel and alluvial floodplain silt, silty clay and sand, together with related organic and mass movement deposits of the rivers Ouse (Sussex), Arun, Rother (Sussex) and Cuckmere.
Six Inch Coal (South Lancashire And Goyt Trough)
SXMC
Six Quarters Coal (Cumbria)
SXQ
Sannox Siltstone Formation
SXS
The top of the Glen Sannox Conglomerate Member of the Am Binnein Sandstone Formation.
The Isle of Arran.
Red-brown siltstones and silty mudstones, with beds of sandstone and quartzite conglomerate.
About 350 m thick.
The base of the sandstone, unnamed on Arran sheet GVS, but referred to as the North Sannox Sandstones by Morton (1979)(Fig.1), and correlatable with the Teith Sandstone Formation.
Six Yard Limestone
SXYL
Swannington Yard Coal (Leicestershire)
Swannymote Breccia Member
SYB
Not seen, unit may be wholly enclosed within Sharpley Porphyritic Dacite.
The unit is discontinuous and poorly exposed; the quoted type section and Ratchet Hill reference section are the only known exposures outside Whitwick Quarry.
Volcanic block-breccia, angular to sub-rounded blocks of porphyritic (quartz-feldspar) dacite in a crystal-rich coarse tuff matrix.
Sharp contact with overlying Sharpley Porphyritic Dacite; contact is either stratigraphical or the latter unit is intrusive into member.
Smithy Coal (Fife)
SYC
Sandway Cellar Conglomerate Member
SYCC
Lies unconformably on the rocks of the Staddon Formation.
Sandway Cellar beach area.
Fine to coarse reddish brown conglomero-breccia with coarse- to very coarse-grained sandstone with dispersed clasts of Lower Devonian sandstone and penecontemporaneous rhyolite.
Overlain by rhyolites of the Kingsand Rhyolitic Formation.
Sycarham Member
SYCM
Sychnant Dolomite Formation
SYCN
The lower boundary is gradational, with thinly bedded grey mudstones and skeletal packstones of the underlying Cwmyniscoy Mudstone Formation, interbedded with thin, fine-grained dolostones of the Sychnant Dolomite Formation. The base of the latter is placed at the base of the dolostone overlying the highest grey mudstone bed.
Northeast crop of the South Wales Coalfield, from near Pontsticill in the Taff Fechan Valley [SO 059 108] eastwards to the Blorenge [c.SO 268 110].
Buff, fine-grained, bedded dolostones (dolomitised skeletal packstones).
The top is placed at an irregular palaeokarstic surface cut in buff dolostone of the Formation, overlain by pale grey ooidal grainstones of the Pwll-y-Cwm Oolite Formation.
Skelmersdale Yard Coal (South Lancashire)
SYDC
Solway Catchments Subgroup
SYDR
Generally a comformable boundary with formations and members of the Irish Sea Coast Glacigenic Subgroup.
The catchment of the Solway Firth, as defined by McMillan and Hamblin [2000].
Alluvial, organic and mass movement deposits typical of the Solway Lowlands, but also including the entire catchment area of the Solway Firth bordering the coast between Stranraer and St Bees Head [McMillan and Hamblin, 2000].
30 m
Ground surface or contact with "overlying" man-made deposits.
Strathclyde Group
SYG
In west at base of Clyde Plateau Volcanic Formation; in east at base of Gullane Formation or Arthur's Seat Volcanic Formation. Conformable or (locally) unconformable.
Sandstone, siltstone, mudstone and seatrock, with some coal seams, ironstones and limestones; non-marine faunas common; marine faunal bands rare except in top part.
To c.1500m
Conformable at base of Lower Limestone Formation.
Syringothyris Limestone
SYGL
Synalds Formation
SYGP
Drawn at the base of the Synalds Formation where purple shaly mudstones and siltstones rest conformably upon the Carding Mill Grit of the Burway Formation.
Within the Church Stretton district. Longmyndian rocks of the Long Mynd Massif, Shropshire.
Mainly purple shaly mudstones and siltstones with subordinate sandstone bands; locally some greenish grey mudstones and sandstones with volcanic tuff.
About 670m
Drawn at the conformable upward passage of the Synalds Formation where dominantly purple shales and sandstones pass into greenish grey flaggy siltstones and sandstones of the Lightspout Formation.
Scawby Limestone
SYL
Quasi-conformable or more or less disconformable contact with mudstone-dominated succession of the underlying part of the Kirton Cementstones, overlain by the limestone-dominated sequence of the Scawby Limestone.
BGS 1:50 000 sheets 80 and 89, North Lincolnshire from the Humber, possibly as far south as the Lincoln area.
Limestone, predominantly lime-mudstone and shelly, peloidal and oncoidal wackestone, with some thin interbeds of calcareous mudstone.
[Compiler's Notes] This entry defines the Scawby Limestone as mapped on sheets 80 and 89. However it should not be perpetuated in any formal review of the Lincolnshire Limestone. Whilst it may remain a valid stratigraphical unit, the Member status is inappropriate. Following stratigraphical revision of the Lincolnshire Limestone Formation, it forms part of the Lower Lincolnshire Limestone Member which (with Upper Lincolnshire Limestone) is one of the two constituent members of the Formation. Scawby Limestone was formerly ranked as a Member in the BGS Lexicon, but it was not perceived as such even by Gaunt et al. It is a constituent part of their Kirton Cementstone [Member]. As an informal unit it should be included within the Lower Lincolnshire Limestone Member, or within the Kirton Cementstone Beds. Certainly the Member suffix should be dropped, and the name revert to the informal Scawby Limestone. However, I am unconvinced of the integrity of this unit even as an informal lithostratigraphical item; as Gaunt et al. (who seem to have invented it) admit, "the range of lithologies differs little from those in the underlying strata" and I have had some difficulty deducing any distinctive characteristics from their account and so the basis of the correlation tie-lines on their Fig. 20 is a mystery! I suspect it is merely something that they were able to map on the ground as a predominantly limestone unit within an otherwise predominantly mudstone Kirton Cementstone. On this basis, it doesn't really warrant a separate name - on the maps I would key it as as "Limestone in Kirton Cementstone Beds" [M G Sumbler, 29/09/2005]
Conformable contact between the Scawby Limestone's limestone-dominated sequence and the mudstone-rich succession of the overlying part of the Kirton Cementstone.
Syllavethy Pluton
SYLL
Stanley Limestone
SYLS
Sylvan Limestone Formation
SYLV
The lower boundary is taken at the base of lowermost limestone resting, probably unconformably, on sandstone/mudstone sequence of the Lydebrook Sandstone Formation.
Lilleshall [SJ 73 15], Coalbrookdale [SJ 64 08], Little Wenlock, [SJ 6470 0700].
Limestone (typically rubbly calcrete) with subordinate mudstone and sandstone, and basaltic lava(s) including the Little Wenlock Basalt.
Full thickness of 19.68m at stratotype but c.105m in expanded section of Little Wenlock Basalt at Little Wenlock [SJ 6470 0700].
Upper boundary taken at conformable base of lowermost sandstone of the overlying Pennine Lower Coal Measures Formation (where present). Elsewhere unconformable junction with overlying mudstone and sandstone of the Pennine Lower Coal Measures Formation.
Sharpley Porphyritic Dacite
SYP
Sharp, possibly intrusive contact with Swannymote Breccia Member. Other contacts seen are faulted.
Exposed between High Sharpley and Whitwick Quarry.
Grey to pale purple, massive, fine-grained matrix porphyritic (quartz and feldspar) dacite. Quartz phenocrysts commonly rounded and green in colour.
Spilsby Sandstone Formation
SYS
A downsection change from grey sandstone with phosphatic nodules [the "Basement Beds" of the Lower Spilsby Sandstone Member] to mudstone of the Kimmeridge Clay Formation.
Onshore, the Spilsby Sandstone Formation is restricted to the southern part of Lincolnshire. It extends offshore into The Wash, but its extent is unknown as within a short distance it passes laterally into the lower part of Sandringham Sand Formation [Wingfield et al., 1978]. Offshore in the Southern North Sea, the Formation has been recognized in quadrants 47, 48, and 51-54. In the offshore region it forms the basal part of the Cromer Knoll Group [Lott and Knox, 1994]. It is not clear how the Spilsby Sandstone Formation [offshore] relates to the Spilsby Sandstone Formation and the Sandringham Sand Formation [onshore].
The Formation comprises two members that are further divided: Upper Spilsby Sandstone Member. Thin, coarse-grained, grey or brown pebble sandstone with iron ooliths [Ferruginous Grit of Swinnerton, 1937]. Underlain by fine-to medium-grained, buff, yellow and white sands with sparse calcareous "doggers" [the upper part of Swinnerton's 1937, "Glauconitic Sands"]. The latter sands become coarser and greener towards the base of the Member. A bed of phosphatic nodules and small [generally chert] pebbles occurs at the base [the Mid Spilsby Nodule Bed of Casey [1963, 1973]. Lower Spilsby Sandstone Member. Coarse-grained, pebbly, glauconitic sands and sandstones with calcareous "doggers" and sporadic phosphatic nodules towards the Top [this unit equates with the lower part of Swinnerton's, 1937, "Glauconitic Sands"]. The base of the Member comprises a thin grey sandstone with phosphatic nodules [the "Basement Beds" of Swinnerton, 1937, and Beds A and D of Swinnerton, 1935.
To c.24m
Down-section change from purple-grey and brown mottled mudstones with sporadic iron ooliths [Hundlsby Clay Member, Claxby Ironstone Formation] or argillaceous oolitic ironstone [Claxby Ironstone Formation] to pale yellow, medium-grained sand and sandstone [Upper Spilsby Sandstone Member]. Offshore in the Southern North Sea Basin, the upper boundry is recognised by a down-section change from calcareous mudstones [Valhall Formation] to sandstones. It corresponds to a reduction in gamma-ray values and increase in sonic log.
Spilsby Sandstone Formation And Sandringham Sand Formation (Undifferentiated)
SYSA
Syston Member
SYSG
The bedrock surface, beneath the deposit.
Soar Valley.
Typically to 6m
Top of sand and gravel, usually corresponding to terrace surface.
Stapeley Shales
SYSH
Stapeley Volcanic Member
SYV
Overlies Mytton Flags Formation.
Volcaniclastic members and two basaltic-andesite lava/pyroclastic members - the Todleth and Llan Fawr members, (Lynas, 1983).
Very variable.
Underlies Weston Flags Formation, Middleton Group.
River Terrace Deposits, 1 To 2
T1T2
River Terrace Deposits, 1 To 3
T1T3
River Terrace Deposite, 1 To 4
T1T4
Top First Waterloo Coal (Derby)
T1WC
River Terrace Deposits, 2 To 3
T2T3
River Terrace Deposits, 2 To 4
T2T4
Top Second Waterloo Coal (Derby)
T2WC
River Terrace Deposits, 3 To 4
T3T4
Top Three Yards Coal (South Lancashire)
T3YD
River Terrace Deposits, 4 To 5
T4T5
River Terrace Deposits, 4 To 6
T4T6
River Terrace Deposits, 4 To 7
T4T7
Newbury 50k Sheet.
River Terrace Deposits, 5 To 6
T5T6
River Terrace Deposits, 5 To 7
T5T7
River Terrace Deposits, 6 To 7
T6T7
River Terrace Deposits, 6 To 8
T6T8
Seventh To Ninth River Terrace Deposit
T7T9
Unconformable on various pre-Quaternary formations.
Ringwood, Hampshire (Sheet E 314).
From 3 m to 6 m thick.
Present-day ground surface.
River Terrace Deposits, 8 To 9
T8T9
Stoer Group
Drawn at base of massive breccias of the Stoer Group where it rests unconformably on Lewisian gneisses.
Northwest Highlands, Scotland.
Breccia-conglomerate, sandstone and a volcanic mudflow, with sandstones and mudstones, and grey shaly mudstone.
Drawn at unconformable upward passage from sandstones of the Stoer Group to grey shaly mudstone of the Diabaig Formation of the Torridon Group.
Thanet Sand Formation
TAB
Drawn at base of unworn, glauconite-coated flint of the Bullhead Bed; it rests unconformably on micritic limestone of the Chalk Group.
London Basin, as far north as Ipswich.
Glauconite-coated, nodular flint at base, overlain by pale yellow-brown, fine-grained sand that can be clayey and glauconitic. Rare calcareous or siliceous sandstones.
Drawn at unconformable boundary marked by upward change from fine-grained sands of the Thanet Formation to glauconitic sand of the Woolwich and Reading Beds.
Bastion Steps Beds
TABS
Target Coal (Sanquhar)
TAC
Castle Hill Beds
TACA
Tops And Cracklers Coal (South Staffordshire)
TACC
Tarrant Chalk Member
TACH
Conformable. As defined Mortimore (1986), the base of the Culver Chalk lies low in the quadrata Zone, at the Castle Hill Marl. Strong marls commonly occur for several metres above the Castle Hill Marls, up to and including the Pepper Box Marls which are now taken as the base. Approximately coincident with the Arundel Sponge Beds.
Limited to Sussex, Hampshire, Wiltshire and Dorset and as widely spaced outliers to the north in the Southern Province. It occurrence and distribution beneath the Quaternary deposits of East Anglia in the Transitional Province is not well known.
Soft white chalk with relatively widely spaced but large flint seams.
35-45 m in Sussex, about 30 m in Dorset, but can be considerably reduced where synsedimentary channelling occurs.
Conformable (but see note below on thickness). Inferred to be at the Whitecliff Flint at the boundary between the Sompting and Whitecliff beds of Mortimore (1986).
Meall Dearg Formation
TAD
Torr An Fhuich Psammite
TAFH
Tai-Herion Member
TAH
Gradational from the underlying and overlying mudstones of the Afon Gam Formation.
Unevenly bedded flaggy, micaceous siltstones and mudstones. Locally irregularly laminated. Strong bioturbation.
Locally recognised member of the Dol-cyn-afon Formation.
c 50m.
Taking Head Sill
TAKI
Tealby Limestone Member
TAL
Sandy limestones and oolitic clays [Tealby Limestone Member] rest on blue-grey clay, glauconite-rich at some horizons and silty and oolitic in the lower part [Lower Tealby Clay Member].
Confined to Lincolshire. It was not seen in Skegness Borehole or beneath the Wash. According to Owen & Thurrell [1968] it is present between Belchford and Cawkwell and in the south and is 3.4m thick at Thorseway. It thins and disappears to the north of Audleby.
Comprises sandy limestone with oolitic clays. The limestones are thicker and more indurated in northern Lincolnshire, becoming thinner, softer and more argillaceous towards the south.
Generally up to c. 4m, but estimated to be 6m at North Willingham [Owen & Thurrell, 1968]
In much of Lincolnshire, grey and buff clays,silty at some horizons and locally glauconitic [Upper Tealby Clay Member], rest on sandy limestones with oolitic clays [Tealby Limestone Member]. In the Brigg District, to the North of Normandy, ferruginous, oolitic limestone [Roach Formation] rests on sandy limestones [Tealby Limestone Member]. In the Audleby-Nettleton Top area, pebbly sandstone [Carstone Formation] rest on Tealby Limestone Member.
Thanet Sand Formation And Lambeth Group (Undifferentiated)
TALM
Talnotry Intrusion
TALN
Taliaris Formation
TALS
In the type area, the formation rests upon grey, burrow-mottled mudstones of the Nantmel Mudstones Formation. The lower boundary is typically gradational and is taken where the proportion of thin beds of turbidite sandstone exceed approximately 15% of the formation, which generally coincides with the incoming of thick sandstone beds or, more rarely, conglomerate beds. The contact is not exposed.
The Taliaris Formation crops out principally on the rugged hilltops flanking the Dulais valley, north of the town of Llandeilo in Carmarthenshire. It is preserved in the hinge and limbs of a northeast-trending anticline.
The Taliaris Formation comprises locally slumped and destratified, thin to thick bedded, medium- to coarse-grained turbidite sandstone with subordinate turbidite and hemipelagic mudstone and impersistant conglomeratic units.
To 370m
The formation is overlain by grey, burrow-mottled mudstones of the Nantmel Mudstones Formation. The upper boundary is gradational and is taken where beds of turbidite sandstone makes up less than 15% of the formation, generally coincident with the last thick bed of turbidite sandstone or conglomerate. The contact is not exposed.
Talisker Formation
TALSK
Talus
TALU
Talus, Active
TALUA
Talus, Inactive
TALUI
Tampen Formation
TAM
Lower boundary apparently conformable or disconformable on the Sperus Formation.
Soft to firm, to stiff, moderately to slightly plastic, pebbly and shelly, sandy, silty clay. Sand partings common, gravel also present. General till-like texture and moraine-like distribution. Underlain by a more uniform and geotechnically weaker clay unit.Lithologically variable, sandy, pebbly clay, shelly; overconsolidated - [generic description: Geol Soc Lond Special Publication Report 4, 2nd edition].
Up to 50 metres from seismic section.
Upper boundary is an erosional, partly winnowed surface, mantled by thin holocene sedimentation.
River Terrace Deposits, 1 (Tamar)
TAM1
River Terrace Deposits, 2 (Tamar)
TAM2
River Terrace Deposits, 3 (Tamar)
TAM3
River Terrace Deposits, 4 (Tamar)
TAM4
River Terrace Deposits, 5 (Tamar)
TAM5
River Terrace Deposits, 6 (Tamar)
TAM6
River Terrace Deposits, 7 (Tamar)
TAM7
River Terrace Deposits, 8 (Tamar)
TAM8
Tamar Group
TAMA
The lower boundary is everywhere tectonic, but the Tamar Group is assumed to overline the Meadfoot Group.
South Devon (SX 80 60) to north Cornwall (SX 00 80).
Mudstones with variable amounts of very subordinate thin siltstone, sandstone and limestone beds. Component mudstone formations are characterised either by grey, purple and red, or green and grey green colourations. The mudstone formations locally contain scattered units of thin- to thick-bedded limestone or sandstone. Intertonguing with the grey mudstones are thick, geographically separated formations of thick-bedded to massive shallow water bioclastic and reef limestone, locally capped by condensed nodular limestones and mudstones. Thick units of basaltic lava (spilite), massive and bedded hyaloclastite, and bedded tuff are also present in the Group.
In excess of 6700m on the north Cornish coast; possibly thicker elsewhere.
The upper boundary is rarely seen due to tectonics but taken at the incoming of dark grey to black mudstones and or thin-bedded cherts of the Chudleigh Group above the grey, purple and green mudstones of the Tamar Group.
River Terrace Deposits (Undifferentiated) (Tamar)
TAMU
Tang Sandstone Member
TANG
Conformable on the uppermost dolomitic laminite-limestone of the Brims Castle Dolomitic Limestone Member.
Onshore and immediate offshore of Dounreay area, Caithness, Northern Scotland.
Alternating quartzose, medium-grained sandstone units less than 1m thick with greenish siltstone interbeds; minor grey silty mudstone (not laminated) with fossil fish (Millerosteus minor).
Conformable beneath Port of Brims Sandstone Member at the base of the first thick (>4m), cross-bedded sandstone unit.
Tan Hill Coal
TANHC
Tantallon Vent
TANT
Tappins Group
TAP
Faulted (Glen App Fault).
Girvan area and Southern Uplands, south west Scotland.
See constituent Formations: Marchburn, Corsewell, Dalreoch, Currarie, Traboyack, Downan Point Lava. Alternating greywackes and shales, red mudstones, sandstones, lava breccias and conglomerates.
Total of constituent formations is c.7000m
Faulted (Stinchar Fault).
Tarvie Psammite Formation
TAPS
Overlies the Ben Wyvis Pelite Formation along the western boundary, where predominant pelites pass into predominantly psammitic lithologies.
The northern limit lies immediately west of Struie Hill, on the south side of Dornoch Firth, where it terminates against the faulted Old Red Sandstone (ORS) unconformity. The eastern margin is defined by the ORS unconformity/fault, which continues to the south-west across Strath Rusdale and Glen Glass through Strathpeffer and the eastern end of Strathconon. South of Strathconon it forms a broad outcrop, and extends west to the Orrin Reservoir, continuing south through Strathglass. South and east of Strathglass, the outcrop widens, and the eastern margin extends southwards to Fort Augustus, where it forms the ground between Strathglass and Glen Moriston. The outcrop to the south and west is unclear, but probably does extend further in this direction.
Well bedded, flaggy, fawn to brown and white quartzose psammite with minor semipelite bands.
At least 2.5 km thick, up to about 5 km.
Tarbert Formation
TARB
Tarff Banded Formation
TARF
Conformable transition from underlying Glen Doe Psammite to semipelite/micaceous psammite-dominated sequence. Locally marked by appearance of impersistent quartzite beds and striped psammites.
South-western Monadhliath Mountains in Central Highland of Scotland (SE of Great Glen).
Interbedded semipelite and micaceous psammite, contains distinctive garnets with snowball and spiral inclusion patterns in semipelites near shear zones. Quartzite and pelite interbeds, notably in basal part.
Minimum 2.7km up to c. 3km.
Not seen - faulted and sheared with Glen Buck Pebbly Psammite Formation.
Tarannon Mudstone Formation
TARO
Tarskavaig Group
TARS
Bay Of Stoer Formation
TAS
Stac Fada Member
TASF
Sompting Beds
TASO
Poll A' Mhuilt Member
TASP
Clachtoll Formation
TAT
Tamar Valley Formation
TAVA
Early Pleistocene to Holocene
Unconformable on bedrock of Carboniferous and Devonian age, and on intrusive igneous rocks.
The entire catchment of the River Tamar and its tributaries, including the rivers Ottery and Thrushel, from near Holsworthy to the sea near Plymouth, Devonshire.
The formation encompasses the fluvial, lacustrine and organic deposits of the River Tamar and its tributaries. It includes floodplain alluvium and the deposits of eight terraces. The floodplain alluvium comprises soft poorly sorted clays, silts and fine-grained sands, with bodies of peat, overlying sands and gravels. The terrace deposits dominantly comprise silty and sandy pebbly clays but include sands and gravels, and silts. The clays are largely derived from Upper Carboniferous and Devonian mudstone bedrock. Gravels are dominantly formed of rounded pebbles up to 50mm diameter of Upper Carboniferous sandstone but also include vein quartz and Lower Carboniferous and Devonian limestone and chert. Tin ore (cassiterite) occurs in the deposits near the Bodmin Granite.
Up to c.10m
Taw Valley Formation
TAW
Unconformable upon bedrock of Late and Early Carboniferous and Permian age and upon the Dartmoor Granite.
The entire catchment of the River Taw and its tributaries, including the rivers Mole and Bray, from Dartmoor and Exmoor to Barnstaple, Devonshire.
The formation encompasses the fluvial, lacustrine and organic deposits of the River Taw and its tributaries. It includes floodplain alluvium and the deposits of ten terraces. The floodplain alluvium comprises soft poorly sorted clays, silts and fine-grained sands, with bodies of peat, overlying sands and gravels. The terrace deposits dominantly comprise silty and sandy pebbly clays but include sands and gravels and silts. The clays are largely derived from Upper Carboniferous mudstone bedrock. Gravels are dominantly formed of rounded pebbles up to 50mm diameter of Upper Carboniferous sandstone but also include vein quartz and Lower Carboniferous limestone and chert. Boulders of Dartmoor Granite and quartz-feldspar-tourmaline rock are common in the upper reaches. All the terraces contain alluvial tin ore (cassiterite).
Up to 22.5m recorded in the buried sub-drift valley of the 7th terrace.
Taw River Terrace Deposits, 1 Member
TAW1
Taw River Terrace Deposits, 10 Member
TAW10
Taw River Terrace Deposits, 11 Member
TAW11
Taw River Terrace Deposits, 2 Member
TAW2
Taw River Terrace Deposits, 3 Member
TAW3
Taw River Terrace Deposits, 4 Member
TAW4
Taw River Terrace Deposits, 5 Member
TAW5
Taw River Terrace Deposits, 6 Member
TAW6
Taw River Terrace Deposits, 7 Member
TAW7
Taw River Terrace Deposits, 8 Member
TAW8
Taw River Terrace Deposits, 9 Member
TAW9
Tawnyunshinagh Limestone Member
TAWN
Tay Catchments Subgroup
TAYCA
Unconformable contact with units of the Mearns, Central Grampian and East Grampians Glacigenic subgroups and bedrock.
The present physical catchments of the River Tay and tributaries, the Firth of Tay and the Montrose Basin. The catchments extend across Perthshire and Angus (Strathmore).
A suite of fluvial (river terrace sand and gravel and alluvium) and related lacustrine (silt and clay) and organic (peat) deposits derived from bedrock and glacigenic sediments. Clast rock types of the fluvial sands and gravels include Devonian strata (sandstone, siltstone), volcanic (andesite and basalt) together with intrusive igneous rocks (granite and microdiorite) and metasedimentary rocks of the Grampian Highlands. In the valley of the Tummel and the higher reaches of the Tay, Earn, Almond, Isla, north and south Esk clasts are dominantly of Dalradian metasedimentary rocks and Caledonian intrusive igneous rocks.
Tayport Formation [Obsolete Code: Use Typo]
TAYP
Tay Sandstone Member
TAYS
Sleat Group
Drawn at base of breccia and sandstone of the Rubha Guail Formation where it rests unconformably on Lewisian Gneisses.
Isle of Skye and northwest Scotland.
Slightly metamorphosed cross-bedded grey sandstones and shaly mudstones. The sandstones are poorly sorted and resemble feldspathic greywackes.
3500m approx.
Drawn at conformable upward passage from grey sandstone and shale of the Kinloch Formation to grey shale of the Diabaig Formation of the Torridon Group.
Tower Wood Gravel, Buller's Hill Gravel And Aller Gravel (Undifferentiated)
TBAG
Turbot Anhydrite Formation
TBAN
Torbay Group
TBAY
Tim Bobbin Rock
TBBR
Trub Coal (West Yorkshire)
TBC
Tidal Bank Deposits
TBD
Typically gravel, sand and mud; deposited in tidal rivers and between barrier islands. [Generic description].
Rubha Guail Formation
TBE
Top Bensham Coal (Northumberland)
TBEN
Tealby Formation
TBF
The base is an erosion surface where there is a downsection change from blue-grey clay, glauconite-rich at some horizons and silty and ooidal in the lower part [Lower Tealby Clay Member] to clayey, ooidal ironstone [Claxby Ironstone Formation].
The Tealby Formation is present in Boreholes in The Wash, the southern-most sections being in BGS boreholes 72/77 and 72/78 [Wingfield et al., 1978]. Further south, it apparently passes laterally into the Roach and Dersingham Formations [e.g. in Hunstanton Borehole]. The Tealby Formation occurs beneath the Lincolnshire Wolds disappearing north of the Audleby area in northern Lincolnshire. Its presence around Elsham, northern Lincolnshire, recorded in early publications, is due to the erroneous correlation of Neocomian deposits with the kimmeridgian Elsham Sandstone and Kimmeridge Clay Formation.
Brown and grey clays, ooidal and glauconitic in part, with a sandy limestone in the middle part of the formation. It can be divided into three units. Lower unit. Blue-grey clay, glauconite-rich at some horizons and silty ooidal in the lower part [Lower Tealby Clay Member] Middle unit. Comprises sandy limestones and oolitic clays [Tealby Limestone Member]. The limestones are thicker and more indurated in northern Lincolnshire, becoming thinner, softer and more argillaceous towards the south. Upper unit. Grey and buff clays, silty at some horizons and locally glauconitic [Upper Tealby Clay Member]. Locally, ooidal horizons occur at the top.
Up to c. 31m.
In southern Lincolnshire and The Wash a rhythmic succession of interburrowed and interbedded clay, "chamosite" mud, chamosite ooids, quartz sand and small pebbles of quartz and ironstone [Roach Formation] rest on grey and buff clays, silty at some horizons, locally glauconitic or ooidal [Upper Tealby Clay Member]. In central to northern Lincolnshire ferruginous, sandy limestone and ferruginous, oolitic mudstones [Roach Formation] rest on grey and buff clays, silty at some horizons, locally glauconitic or ooidal [Upper Tealby Clay Member] In northern Lincolnshire, between Nettleton Top and Audleby, sandstones of the overstepping Carstone Formation rest on the limestones of the Tealby Limestone Member, and between Audleby and Clixby the arenaceous Carstone Formation rests on mudstones of the Lower Tealby Clay.
Ten Bands Ironstone
TBI
Kinloch Formation
TBK
Tynebottom Limestone Member
TBL
Taken at the sharp base of limestone overlying measures within the Alston Formation, in places comprising sandstone, elsewhere mudstone.
So-called because it crops out in, or closely underlies, the bed of the River South Tyne between Alston and Tynehead. Well exposed along the Pennine escarpment, in Teesdale and Weardale.
Limestone, blue-grey, thick-bedded, planar to wavy-bedded, stylolitic, in part fissile with intercalated thin mudstone beds. Fossiliferous, particularly with abundant corals, brachiopods and crinoid debris. It commonly has a Saccamminopsis band 1.5 to 2m from the top. A bed near the top is characteristically argillaceous and "slaggy" (Johnson and Dunham, 1963).
7.6 to 14.6m
Taken at the base of overlying measures within the Alstone Formation, here usually comprising up to about 10m of compact, hard, dark grey mudstone colloquially referred to as the Tyne Bottom Plate.
Loch Na Dal Formation
TBLN
Tirfergus Glen Limestone
TBLS
Trewern Brook Mudstone Formation
TBM
Termon River Limestone Formation, Bin Mountain Sandstone Formation And Ballyshannon Limestone Formation (Undifferentiated)
TBMB
Top Beaumont Coal (Northumberland)
TBMN
Top Bench Coal (Warwickshire)
TBNC
Currently it is uncertain whether Top Bench is synonymous with Upper Bench (UBNC) or whether the Top Bench represents the top leaf of the Bench Coal (where split) and is in turn overlain locally by the Upper Bench Coal.
Troutbeck Palaeosol
TBPS
A gradational boundary with relatively unweathered dark grey diamicton or decomposed slate bedrock.
Vale of Threlkeld, Cumbria.
Extremely compact, silty sandy gravelly diamicton derived from the Thornsgill Till Formation containing clasts mainly of slate. "Borrowdale Volcanic Group" lithologies and Threlkeld microgranite. Dark grey at base becoming increasingly weathered upwards to yellowish brown with olive brown, orange and white mottling where it had been cryoturbated. Most clasts are decomposed towards top and are commonly bleached. It is the deeply weathered zone of the unit that constitutes the Troutbeck Palaeosol.
Generally a sharp, planar, or gradational glacitectonic boundary with overlying greyish brown stony clay diamicton (Threlkeld Till Formation).
Teignmouth Breccia
TBR
Top Brockwell Coal (Northumberland And Durham)
TBRO
Beinn Na Seamraig Formation
TBS
Tubbrid Sandstone Formation
TBSF
Not exposed but considered to be conformable with underlying Benbulben Shale Formation.
Kesh-Omagh area, northwest Carboniferous basin of Ireland.
Sandstone, fawn to pale grey, medium- to coarse-grained, micaceous with plant debris; calcareous horizons weathering rusty brown and friable, very fossiliferous and crinoidal.
Not exposed or preserved due to post Carboniferous to Pleistocene erosion.
Turbot Anhydrite Formation (A) [Obsolete Code: Use Tban]
TBSH
Top Beamshaw Coal (South Yorkshire)
TBSW
Tailbert Formation
TBT
Taken at the lithological change from mudstones of the Tarn Moor Formation, to a dominantly sandstone succession.
The Bampton Inlier of the Skiddaw Group, west of Shap, Cumbria.
Dominantly thick, massive bedded, well sorted, medium-grained sandstone, with some thin, dark grey mudstone interbeds.
Not seen, but presumed to be overlain unconformably by the Borrowdale Volcanic Group.
Top Brass Thill Coal (Northumberland And Durham)
TBTC
Top Busty Coal (Northumberland And Durham)
TBU
Tremuda Bay Volcanic Formation
TBVF
The base of lowest lava flow overlying the Dunnottar Castle Conglomerate Formation.
Tremuda Bay to Thornyhive Bay, Stonehaven area.
Olivine-basalt hawaiite lavas.
Not less than 170 m thick.
Tillybrex Sand And Gravel Formation
TBXSG
A sharp, erosional, undulating contact with very compact, yellowish brown sandy clay diamicton of the Bellscamphie Till Formation, containing clasts of psammite, metagreywacke and quartzite derived from the west.
A clayey gravel and yellowish brown sand, with subrounded to well-rounded pebbles of psammite, metagreywacke and quartzite, with some gneiss and slate, the latter two rock types being particularly strongly weathered.
A sharp, planar, unconformable contact with an unnamed brown till, containing clasts of psammite, metagreywacke and quartzite derived from the west, or with dark grey pebbly clay diamicton of the Pitlurg Till Formation, with sparse erratics and fossils derived from Jurassic strata beneath the Moray Firth to the northwest.
Torridon Group
Drawn at the base of the Diabaig Formation (Torridon Group) where it rests unconformably on the Stoer Group.
Rum to Cape Wrath, west Scotland.
Unmetamorphosed red beds with subordinate grey shaly mudstones.
7km
Drawn where the Cailleach Head Formation is overlain by superficial deposits.
Applecross Formation
TCA
Bheinn Bhreac Member
TCAB
Mullach Nan Carn Member [Obsolete Code: Use Tcdc]
TCAC
Leac Nam Faoileann Member
TCAF
Sithean Glac An Ime Member
TCAI
Leac-Strearnan Member
TCAL
Allt Mor Na H-Uamha Member
TCAM
Base (NM 4205 9722): the "first" (stratigraphically lowest) thickly-bedded,cross-stratified and/or convoluted fine- to medium-grained sandstone bed greater than 2m in thickness.
Isle of Rum, Allt Mor Na H-Uamha.
Cyclically interbedded "siltstones" and fine- to medium-grained cross-bedded sandstones (the "siltstones" actually consisting of siltstone and very fine- to fine-grained sandstone with subordinate mudstone); the fine- to medium-grained cross-bedded sandstone beds increase in abundance towards the top of the Member.
415m. in type locality.
Top,(NM 4108 9751): the 'first'(stratigraphically lowest) thickly-bedded, cross-stratified and/or convoluted coarse-grained sandstone (arkose) bed containing 'exotic' pebbles characteristic of the Applecross Formation.
Rubha Dubh Ard Member
TCAR
Scresort Sandstone Member
TCAS
The 'first' (stratigraphically lowest) thickly-bedded, cross stratified and/or convoluted coarse-grained sandstone (arkose) bed containing 'exotic' pebbles characteristic of the Applecross Formation. (NM 4108 9751 or NM 4155 9905).
Isle of Rum, Loch Scresort.
Medium- to coarse-grained sandstones containing "exotic" pebbles, and displaying abundant cross-stratification and soft-sediment convolution structures; fine-grained sandstones, siltstones and mudstones are subordinate.
Total thickness (from NG 4230 0014 to NG 3270 0200) of c.2000m +/- 500m (allowing for uncertainty in fault displacements).
Marked by the disappearance of 'exotic' pebbles characteristic of the Applecross Formation (NM 3769 9147 or NG 3360 0247).
Aultbea Formation
TCAU
Tremadoc Beds
TCB
Brochel Member
TCBL
Cailleach Head Formation
TCC
Top Coal (Coalbrookdale)
TCCC
Cape Wrath Sandstone Member
TCCW
Diabaig Formation
TCD
Slattadale Member
TCD1
Horrisdale Waterfalls Member
TCD2
Dubh Loch Member
TCD3
Bla-Bheinn Member
TCDB
Mullach Nan Carn Member
TCDC
Dibidil Grit Member
TCDD
Fiachanis Gritty Sandstone Member
TCDF
NM 3720 9366. Unconformable contact with Lewisian Gneiss.
Isle of Rhum, Fiachanis.
Predominantly coarse-grained sandstone, with subordinate granular sandstone and basal breccia; breccias and granular sandstones occur at the base of the member, on or near the underlying Lewisian Gneiss; the coarse sandstones gradually become medium-grained towards the top of the member.
35m-70m in type locality (highly variable elsewhere).
NM 3730 9366. Highly variable gradational and/or interdigitating transition into overlying Laimhrig Shale Member, which may occur over several tens of metres of stratigraphical thickness, eg NM 3695 9905.
Laimhrig Shale Member
TCDL
Highly variable gradational and/or interdigitating transition from the underlying Fiachanis Gritty Sandstone Member. (NM 3730 9366 or NM 3695 9905).
Isle of Rhum, Laimhrig.
Laminated dark-grey "shales" (actually consisting of laminated mudstone, siltstone, and very fine- to fine-grained sandstone), with intercalated beds of pale grey fine-grained sandstone that increase in thickness and abundance towards the top of the member.
275m minimum in type-locality (stratigraphical base not visible).
The 'first' (stratigraphically lowest) thickly-bedded, cross-stratified and/or convoluted fine- to medium-grained sandstone bed greater than 2 metres thick. (NM 4186 9604).
Sgurr Na Stri Member
TCDS
Trambley Cove Formation
TCF
Late Visean.
The lower boundary is taken at the sharp contact of the finely banded dark to pale grey mudstones with thin siltstones of the Trambley Cove Formation with the underlying tuffs, lavas and agglomerates of the Tintagel Volcanic Formation.
Tintagel area (SX 06 89) to the south of Launceston (SX 32 77), Cornwall. The outcrop in the Launceston area (BGS 1993) needs further investigation.
Pale to dark grey and black, finely colour-banded mudstone with thin beds of commonly cross-bedded siltstone. The siltstone and locally the mudstone are silicified, giving the succession a cherty appearance. Greenish brown tuffaceous mudstones are locally present, especially towards the base.
The upper boundary is faulted. However, it is thought that as the formation is locally silicified, it may orignally have passed up into the Teign Chert Formation. (Freshney et al. 1972).
Top Crag Limestone
TCGL
Teign Chert Formation
TCH
In the Teign valley and Ilsington area the lower boundary is taken at the incoming of interbedded cherts and siliceous mudstones of the Teign Chert Formation above the bluish black and black mudstones of the underlying Combe Mudstone Formation. Boundary taken at the base of the first bedded chert. South of Ilsington, it is taken at the sharp boundary of the black mudstones of the "Ararat Slate" (Teign Chert Formation) or the buff weathering calcareous laminated siltstones at the top of the underlying "Rora Slate" (?Torpoint Formation). In the Okehampton area it is taken at the incoming of black argillaceous limestones with subordinate black cherts and siliceous mudstones and mudstones of the Teigh Chert Formation above the thin bedded mudstones and quartzites of the Meldon Shale and Quartzite Formation. Along the rest of the south crop of the Teign Valley Group, between Dartmoor and Bodmin moor and the north Cornish coast, the formation occurs in thrust slices and basal contacts are tectonic.
Thin to medium bedded cherts varying from white, grey and green to bluish black; rarely jasper red. Beds range from a few millimetres to 0.6m, generally separated by siliceous mudstone beds and partings. Radiolaria are locally abundant in the cherts and siliceous mudstones. Also present are bluish black mudstone and thin to medium-bedded argillaceous limestones. Some areas are dominated by mudstone, others by chert or limestone. Manganiferous beds are present in the Teign valley. Various volcanic rocks are present in the Teign valley and Ilsington area, south Devon and in the St Mellion area of east Cornwall. They include quartz-keratophyre tuffs, basic spilitic, and felsitic lavas. The spilitic lavas occur near the base of the formation in the Teign valley and are up to 12m thick; units of tuff up to 12m thick occur throughout. In the Teign valley the succession comprises interbedded cherts and subordinate mudstones and is capped by the 30 to 45m-thick Posidonia Beds, a distinctive unit of thin bedded cherts, limestones and shales with abundant pectinoid bivalves and spirally striated goniatites. South of Ilsington, south Devon, a 10m-thick unit (the "Ararat Slate") of black siliceous slatey mudstones, locally containing decalcified nodules, is present at the lowermost part of the formation. In the Okehampton area, north Dartmoor, the formation comprises interbedded cherts, limestones and mudstones. Locally limestones and mudstones are dominant and reported to occur in mappable lenticular units. This suggests that some cherts might be silicified limestones. The Posidonia Beds have not been mapped but their fauna occurs in the limestone lenses. In the St Mellion area of east Cornwall, the lower part of the formation comprises siliceous mudstone with or without scattered cherts beds and the upper part comprises cherts with thin mudstone interbeds. The Posidonia beds are present. In the Boscastle area, north Cornwall, the formation is dominated by mudstone; the Wilsey
150 to 230m in the Teign valley. South of Ilsington about 70m+ thick; in the Okehampton area it is 73m; a structural thickness of 100m has been calculated in the St Mellion area, east Cornwall.
In the Teign valley the upper boundary is taken at the incoming of bluish grey micaceous mudstones with scattered thin sandstones and siltstones of the overlying Aston Mudstone Member of the Dowhills Mudstone Formation above the fossiliferous interbedded cherts, limestones and mudstones (Posidonia beds) of the Teign Chert Formation. In the Okehampton and Ilsington areas, the Dowhills Mudstone Formation has not been recognized, Crackington Formation being mapped overlying the Teign Chert Formation. Further work is needed in these areas at this level. Along the rest of the south crop of the Teign Valley Group, the formation occurs in thrust slices and the upper contact is tectonic.
Thin Coal (Hanwood)
TCHW
Tom Croft Limestone Formation
TCL
Temple Cloud Coal (Somerset)
TCLC
Loch An Uach Member
TCLU
Tobaireach Conglomerate Member
TCM
Tobar Ceann Siltstone Member
TCN
Talus Cone
TCON
Clast-supported accumulation of angular rock fragments derived from a cliff or steep rocky slope. May be active or inactive. Cone-like landform. [Generic description: 'TMOS' Procedures].
Talus Cone, Active
TCONA
Talus Cone, Inactive
TCONI
Thick Coal Rock
TCR
The Crackers Member
TCRS
Tinklers Crag Sandstone
TCS
Thorncombe Sand Member
TCSA
Top of the Margaritatus Stone.
Yellow-weathering silty very fine-grained sands, locally bioturbated and with hummocky cross-bedding. Impersistent 0.3m limestone in middle. At base 'Blue Band' - 1.8m of blue-grey mudstone - overlies Margaritatus Stone. At top 2.3m of grey mudstone occurs between the Thorncombiensis Bed and the Beacon Limestone Formation
23m
Base of Beacon Limestone Formation (formerly termed Junction Bed).
Sgor Mhor Sandstone Member
TCSM
Base: (eg NM 3769 9147 or NG 3360 0247) : marked by the disappearance of 'exotic' pebbles characteristic of the Applecross Formation.
Isle of Rhum, Sgor Mhor.
Fine- to medium-grained sandstones containing no "exotic" pebbles, and displaying an abundance of horizontal-stratification (in addition to cross-stratification and soft-sediment convolution structures); detrital heavy minerals of silt to fine-grained sand grade occur commonly as dark laminae or as prominent dark beds up to 2m thick.
Minimum thickness (from NM 3698 9106 to NM 3659 9172) of 175m. (Stratigraphical top is nowhere visible; in the type locality the stratigraphical base and top are not visible).
Top: not seen (nor defined) on Rhum.
Thorncliff Sandstones
TCSS
Staffordshire [Thorncliff Quarry, 2 miles northeast of Leek].
Tron Church Sandstone
TCST
Torran Member
TCTN
Top Coatyards Coal
TCYD
Torrisdale Vein-Complex
TDALE
Tanderagee Chalk Member
TDC
Maastrichtian. Belemnella lanceolata Zone?
Conformable, on the Ballymagarry Chalk Formation, at a bedding plane immediately below the thick continuous tabulate Long Gilbert Flint Band where this exists. Or at the same bedding plane marking the faunal change from the Ballymagarry Chalk Formation fauna.
Outcrops in the Southern Uplands area, the North Antrim Basin and in the southern part of the Londonderry Shelf. Absent in the East Antrim Basin, the Highland Border High and northern Londonderry shelf due to pre-Palaeogene erosion.
Limestone (chalk) with flint bands. Divided into five `Beds? (A to E). Abundant belemnites in lower `Bed? A and by an acme of crinoid debris in `Bed? C. Elsewhere asteroid and crinoid debris common.
7.63m at type-site.
Conformable, with the overlying Port Calliagh Chalk Formation, at a bedding plane below a `belt of complex flints?.
Tom Dubh Conglomerate Member
TDCO
A sharp, diachronous contact with poorly sorted mudstones and sandstones of the undivided Cromlix Mudstone Formation.
The north-west limb of the Strathmore Syncline, between Lake of Menteith and Meall Leathan Dhail [NN 667 117].
A poorly sorted, coarse conglomerate, with cobble-sized clasts of vein quartz and quartzite.
Measured as 110 m thick near Tom Dubh [NN 64 09], 300m north of Port of Menteith.
A transitional, diachronous contact with sandstones and pebbly sandstones of the Teith Sandstone Formation.
Tardree Rhyolite Complex
TDER
Torduff Hill Volcanic Formation
TDF
Todmorden Grit
TDG
Torduff Hill Volcanic Member
TDH
Aphanitic, fine-grained, pale grey, rarely porphyritic trachyte. Flow- banding common.
Not seen: Faulted against Warklaw Hill Volcanic Member to west, Bonaly Volcanic Member to east and Ballagan Formation to north, unconformably overlain by Kinneswood Formation to south.
Twecher Dirty Coal [Redundant Code: Use Twd]
TDIC
The Twechar Dirty Coal was inadvertantly re-coded due to the mis-spelling that is preserved in this entry. The original code (TWD) is retained for future use.
Top Durham Low Main Coal (Northumberland And Durham)
TDLO
Tweeddale Member
TDM
Tidcombe Sand Member
TDS
Tornahaish Dark Schist And Limestone Formation
TDSL
At top of calcareous semipelite of Cock Burn Calcareous Schist Formation.
In Upper Donside west of Tornahaish to Delnadamph and Dunandhu. Also SSE adjacent to A939 road to Mammie Hill. Includes as large hornfelsed pendants and xenoliths in east part of Glen Gairn Granite.
Grey to black, thinly banded to laminated, semipelites and subsidiary pelites. Micaceous psammites noted. Thin limestone interbeds. Beds slaty to schistose. To south schistose semipelites. Prominent crystalline limestone member. Graphitic pelite generally present at base.
100-150m. Possibly up to 200m west of Tornahaish.
Upper limit of pelites, thin limestones and/or calcareous beds below semipelite and micaceous psammite of the Nochty Semipelite and Limestone Formation.
25-Foot Drift Of Vale Of York
TDVY
Sand with subordinate silt and clay; some of the sand is of aeolian origin. [Generic description: 1:50 k map margins].
Third Waterloo Coal (Nottingham And Derby)
TDWC
Trough Edge End Sandstone
Teasses Main Coal
TEA
Teal Sandstone Member
TEAS
Temeside Shales Formation [Obsolete Code: Use Tsh]
TEB
Glacitectonic Thrust Terrain [See Descriptions For Limitations Of Use]
TEC
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future.See also TECF, TECG and TECS. Note that on the related Quaternary Domains map, this category was described as: "GLACITECTONIC THRUST TERRAIN (recognised at surface as organised, elongated kettle-ridge topography".
Glacitectonic Thrust Terrain, Mostly Fines [See Descriptions For Limitations Of Use]
TECF
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area.To avoid potential confusion it should be used only for similar purposes in future. See also TEC, TECG and TECS. Note that on the related Quaternary Domains map, this category was described as: "GLACITECTONIC THRUST TERRAIN (recognised at surface as organised, elongated kettle-ridge topography, Mostly fines".
Glaciotectonic Thrust Terrain, Mostly Gravels [See Descriptions For Limitations Of Use]
TECG
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also TEC, TECF and TECS. Note that on the related Quaternary Domains map, this category was described as: "GLACITECTONIC THRUST TERRAIN (recognised at surface as organised, elongated kettle-ridge topography, Mostly gravels".
Glaciotectonic Thrust Terrain, Mostly Sands [See Descriptions For Limitations Of Use]
TECS
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also TEC, TECF and TECG. Note that on the related Quaternary Domains map, this category was described as: "GLACITECTONIC THRUST TERRAIN (recognised at surface as organised, elongated kettle-ridge topography, Mostly sands".
Temple Cowley Member
TECY
An upward transition from mudstone and silty mudstone of the West Walton Formation to coarser grained predominantly arenaceous sediments.
the Oxford to Abingdon area from Wheatley south-westwards. The north-eastern limit which passes into the Arngrove Spiculite Member shown on 1:50000 sheet 237 (inset map). The south-western limit is uncertain, but probably extends at least as far as Faringdon and possibly as far as the Swindon to Calne area.
Fine-grained silty sands, calcareous sandstones and clayey silts and siltstones, commonly thinly or ripple bedded, may show pronounced bioturbation.
Up to at least 13 m thick.
An upward transition from fine-grained silty sands and clayey silts to coarser grained, calcareous possibly spiculitic sand or sandstone of the Beckley Sand Member, Arngrove Spiculite Member, or very locally, mudstone and limestone of the Littlemore Member.
Tir Edmond Coal (South Wales)
TEDC
Tedd Formation
TEDD
The Tedd Cross Roads segment of the Fintona Block.
Red Beds: Interbedded sandstone, very coarse-grained, pebbly with pebble bands, purple-grey, sandstones and siltstone, fine-grained, cross-bedded, ripple laminated, purple-red mudstones.
Not exposed, faulted out, but probably is gradational with base of finer grained Shanmullagh Formation.
Tempar Dolomitic Member
TEDO
Sharp change from quartzite to calc-semipelite and non-calcareous semipelite.
Discontinuous occurrence from closure of Errochty Synform [NN 7131 6655] to near Loch Kinardochy [NN 7750 5440]. Occurs sporadically east of Loch Tay Fault near Loch Tummel [NN 8334 6005] and Kincraigie [NN 892 678].
Calcareous and non-calcareous semipelite at base passes upwards into well-bedded tremolitic dolomite. At top dolomite passes upward into semipelite and fine-grained psammite before upper boundary with Schiehallion Quartzite is reached.
Change from finely-bedded semipelite to well-bedded quartzite.
Teenie Coal (Lothian)
TEE
Tannadice Sandstone Member
TEF
Conformable, diachronous to some extent. The base of the member is placed at the top of the highest lava of the Montrose Volcanic Formation in the Montrose area where this is overlain by cross-bedded sandstones. It is underlain by and interdigitates laterally with the Deep Conglomerate Formation, the base being taken at the top of the highest bed of conglomerate in the underlying formation. In the Blairgowrie area the base occurs at the top of the highest bed of conglomerate in the Hatton Conglomerate Member.
A fine- to medium-, locally coarse-grained and pebbly, generally cross-bedded, sandstone, containing lenses and rarely more extensive beds of siltstone, mudstone and conglomerate and rare flows of andesitic lava. Thin carbonate beds are rarely developed in the siltstone or mudstone beds. Distinctive pedogenic carbonate (calcrete) clasts occur in the pebbly sandstone and conglomerate.
Up to 880 m thick in Kincardineshire, typically 1500-2000 m in northern Midland Valley, passing laterally into the Deep Conglomerate Formation towards the north-east.
Generally conformable, locally diachronous to some extent. Placed at the base of poorly-sorted, massive or laminated red siltstone of Cromlix Mudstone Formation, where this overlies fine- to medium-grained cross-bedded sandstone. Upper boundary may be locally interfingered with the Cromlix Mudstone Formation or the Campsie Limestone Member near Pittendreich.
Tay-Earn Gravels Member
TEGR
Latest Windermere Interstadial to Loch Lomand Stadial.
Markedly erosive base cut into the Errol Clay Formation and the Culfargie Sand Member of the Forth Clay Formation. This supposedly fluvial unit is usually found in a deep channel cut into pre-existing deposits but is recognized on the flanks too.
River Tay just northwest of Perth, River Earn from Bridge of Earn eastwards to the Tay bridges at Dundee adjacent to the Tay/Earn estuary.
Gravel, rounded to sub-angular up to 10cm, and fine- to coarse-grained sand; gravel recorded as composed of vein quartz, quartzite and other metamorphic rocks, Lower Devonian lavas, and dolerite.
Veneer on the flanks of channels and up to 25m.
Overlain unconformably by the transgressive estuarine sand, silt and clay of the Carey Silt Member (Carse Clay Formation) and also by younger units including the sub-Carse Peat (Flanders Moss Peat Formation) and Carse of Cowrie Clay Member (Carse Clay Formation); also exposed at the surface locally.
Teifi Valley Formation
TEIFI
Sharp, unconformable and locally channelised on bedrock, Devensian head deposits and Late Devensian glacigenic deposits (particularly the Plynlimon Till Formation and, west of Llanysul [SN 4190 4043], the Teifi Clay Formation and Lleyn Till Formation). In Tregaron Bog it overlies the Tregaron Formation. Interdigitates in a complex manner with Tidal Flood Deposits (Gwynllwg Formation of Bowen, 1999) in the estuary.
The valley of the River Teifi and its tributaries (Dyfed, Wales).
Unconsolidated, stratified gravel, sands, silts and clays forming the alluvial deposits of the River Teifi (Afon Teifi) and its tributaries. Includes contemporaneous head, colluvium and pedogenic deposits within the catchment area. Clasts principally consist of local Lower Palaeozoic turbidites but, west of a line approximately running between Talgarreg [SN 4267 5096] and Pentrecagel [SN 3385 4030] a substantial mixture of "Irish Sea" material derived from the Lleyn Formation can be present. Aggradational river terraces and major alluvial fans are dominated by pebble cobble gravels and medium- to coarse-grained sand, the modern floodplain is dominated by silt and clay, and locally includes lenses of peat.
Generally 4 to 5m, but ranging up to 10m.
Generally the present ground surface, or, locally, overlain by peat.
Teist Unit
TEIS
Tenuis Limestone
TELM
Telpyn Point Sandstone Formation
TELPP
The base is placed at the base of the lowermost quartzitic sandstone of the formation, where it overlies a sharp surface or erosion surface cut in the underlying mudstones of the Bishopston Mudstone Formation. At the type section at Telpyn Point, the boundary is placed at the base of a fine-grained quartzitic sandstone at 27.66m (90' 9") below the top of the section measured by Archer (1965).
Around the margins of the Pembrokeshire Coalfield, and on the east crop of the main South Wales Coalfield, from the Clydach Valley south to Blaenserchan.
Fluvial, fine- to coarse-grained, locally pebbly and conglomeratic, pale grey, quartzitic sandstones with thin argillaceous mudstone/siltstone and seatearth interbeds; sporadic, thin coals in the argillaceous beds.
18.97m at type section to 21.3m at Settling Nose.
The top is placed at the top of the highest quartzitic sandstone of the Formation, immediately or close below the base of the dark grey fossiliferous mudstones of the Subcrenatum Marine Band. Note that, for practical mapping purposes, any development of thin non-marine beds between the top of the highest quartzite and the base of the Subcrenatum Marine Band are included in the Telpyn Sandstone Formation. There are 8.7m of these at Telpyn Point and 7.62m at Settling Nose.
Tombstone Limestone [Obsolete Code: Use Tmbl]
TELS
Telscombe Marls (One)
TEMA1
Telscombe Marls (Two)
TEMA2
Telscombe Marls (Three)
TEMA3
Telscombe Marls (Four)
TEMA4
Terschellingerbank Member
TERB
Tetragraptus Shales Formation
TESH
Teign Valley Group
TEVY
On the north crop in north Devon and west Somerset, the lower boundary is taken at the incoming of black, locally siliceous mudstones of the Teign Valley Group (Doddiscombe Mudstone Formation) above the soft mid to dark grey mudstones with scattered very thin fossiliferous limestones, siltstones and sandstones of the underlying Exmoor Group (Pilton Mudstone Formation). On the south crop in south Devon, the lower boundary is taken at the incoming of black, locally siliceous mudstones of the Teign Valley Group (Combe Mudstone Formation) above the olive green and pale grey mudstones of the Trusham Mudstone Formation. Elsewhere on the south crop the base is thrust out.
Between Bideford (SS 45 27), north Devon and Westleigh (ST 06 17), west Somerset. Between the north Cornish coast at Boscastle (SX10 91) and east Dartmoor (SX 84 87), south Devon, including the Launceston area (SX 33 84), the St Mellion area (SX 39 65), Okehampton area (SX 59 94), Teign Valley area (SX 84 84), Ilsington area (SX78 76) and south of Ilsington (SX 79 74).
Predominantly comprises black commonly pyritic mudstones, siliceous mudstones, bedded cherts and some thin limestones. Formations dominated by limestone or sandstone turbidites are locally developed. Shallower water formations comprising greenish mudstones with thin limestones and black mudstones with quartzitic sandstones are confined to north Cornwall. Scattered formations and units of basaltic tuff and lava locally are present on the south crop of the group.
100 to 720m
Due to thrusting along the south crop of the Group, the upper boundary is seen only between Okehampton (SX 59 54) and the Teign Valley (SX 84 84), east Dartmoor, Devon. The top is gradational and taken at the incoming of dark grey mudstones with abundant thin- to medium-bedded turbidite sandstones of the overlying Holsworthy Group (Crackington Formation) above the dark grey mudstones with sparse scattered thin turbidite sandstones of the Teign Valley Group (Dowhills Mudstone Formation). On the north crop of the Group, between the Bideford area (SS 45 27), north Devon, and the Westleigh area (ST 06 17), west Somerset, the base is taken at a similar level. However, in the Bideford area, the top needs further investigation as the Dowhills Mudstone Formation (Limekiln Beds of Prentice, 1960), was included in the Crackington Formation by Edmonds et al. (1979). Between Bodmin and Dartmoor the group occurs in tectonic slices and no top is seen. The top here is thought to be an unconformity where the overlying Holsworthy Group (Bealsmill Formation) rests unconformably on rocks of the Teign Valley Group, which had already been deformed by D1.
Teign Valley Group And Tintagel Group (Undifferentiated)
TEVYT
Two Foot Coal (South Derbyshire)
Treffgarne Bridge Beds
TFB
Two Foot Coal (Glasgow Area; Central Coalfield)
TFC
Three Foot Coal Of Kilmux
TFCK
Tidal Flat Deposits
TFD
Tidal Flat Deposits, 1
TFD1
Normally a consolidated soft silty clay, with layers of peat, sand and a basal gravel. A stronger, desiccated surface zone is sometimes present. Older than "Tidal Flat Deposits" in the same map area. [Generic description].
Tranent Four-Foot Coal
TFF
Ten Fathom Grit
TFG
Toft Hill Limestone And Shales
TFH
Restricted to the Swinden Anticline [SE 86 54], about 2km south of Hellifield, North Yorkshire.
Top Fourth Waterloo Coal (Derby)
TFHWC
Torrance Four Inch Coal
TFIC
Teifi Clay Formation
TFICL
Unconformable on bedrock or contact with ?Late Devensian regolith, head and fluvial deposits.
South Ceredigion, north Pembrokeshire and north Carmarthenshire (Wales). Predominantly within pre-glacial valley systems.
Brown and grey clay and silt laminated clay, with interbeds of grey/yellow stratified silt and fine sand, which locally increases in abundance towards the top. Dropstones are locally abundant and form thin beds of diamicton. Clasts are dominated by local bedrock lithologies but characteristically include shell fragments.
Bowen (1999) considered the Teifi Formation (his Llechryd Member) to have formed during retreat and, therefore, to overlie fluvioglacial gravels. Hambrey et al. (2001) have shown the oppositeto be the case. Further, Bowen (1999) placed his Llechryd Member in the Plynlimon Till Formation (his Elenid Formation) but, based on the presence of Irish Sea Ice derived shell fragmants it is here placed in the Lleyn Formation.
Up to 75m in a borehole at Llwynpiod [SN14NE/156]
Ground surface (sheared) contact with overlying Lleyn Formation, or unconformable with fluvioglacial deposits of the Lleyn Formation and Plynlimon Till Formation, West Wales Catchments Subgroup (peat and fluvial deposits).
Ten Foot Measures Ironstone
TFIR
The Fara Psammite Formation
TFPS
Base of dominantly psammitic succession above an underlying semipelite. Change to dominantly psammites.
Central Highlands of Scotland between Loch Ericht, Ardverikie Forest and the Upper Spey Valley.
Micaceous and feldspathic psammites, in graded beds with thin semipelite bed tops. Minor semipelite beds.
1km to 1.5km
Top Five Quarter Coal (Northumberland And Durham)
TFQ
Two Foot Rock
TFR
Tidal Flat And Raised Beach Deposits (Undifferentiated)
TFRB
Composite deposit: (Tidal Flat Deposits) normally a consolidated soft silty clay, with layers of sand, gravel and peat; characteristically low relief; from the tidal zone, with (Raised Beach Deposits) shingle, sand, silt and clay; may be bedded or chaotic; beach deposits may be in the form of dunes, sheets or banks; now above the level of the present shoreline as a result of earth movement or a general fall in sea level. [Generic description].
Thorny Force Sandstone
TFS
The Flats Stone Band
TFST
Two Foot Coal (Nottingham And Derby)
TFT
Two-Foot Coal (West And South Yorkshire)
TFTC
Two Foot Coal (Wyre Forest)
TFWF
Two Foot Coal (West Lothian)
TFWL
Thornbrough Grit
Tremoge Glen Granite
TGGR
U-Pb 487 +/- 14 Ma (Noble et al., 2004).
Throstle Garth Basalt Member
TGH
Rests on andesitic and dacitic rocks of the Birker Fell Andesite Formation (undivided).
Green How, Horn Crag, Lingcove Beck, Hard Knott, (NY 195 068 - 243 050 - 235 015) Upper Eskdale, Cumbria.
Compound lava flows of dark greenish grey aphyric to sparsely olivine-phyric basalt/basaltic andesite and interbedded volcaniclastic rocks.
Overlain by andesitic and dacitic rocks of the Birker Fell Andesite Formation (undivided) or by the andesitic lapilli-tuff of the Whorneyside Tuff Formation.
Todingill How Formation
TGHO
Trygarn Formation
TGN
Early Llanvirn.
Overlies the sandstones and mudstones of the Bryncroes Formation, possibly with disconformity or non-sequence, the boundary being taken at the base of the first ooidal ironstone within the Tregroes Formation.
Mudstones and siltstones with coarse-grained sandstone interbeds containing ferruginous ooids.
Conformable, gradational boundary where ferruginous sandstones of the Trygarn Formation pass upwards into undivided micaceous siltstones of the Nant Ffrancon Subgroup.
Tintagel Group
TGP
Drawn at base of grey-black slates of the Barras Nose Formation where they rest apparently conformably on grey slates of the Yeolmbridge Formation.
Southwest England.
Grey-black slates with siltstones and carbonate nodules, and limestone; coarse- and fine-grained tuffs also occur with agglomerate and lavas.
About 135m
Drawn at unconformable upward passage from grey-black banded slates of the Trambley Cove Formation to green slates and limestone of the Buckator Formation.
Trentishoe Member
TGR
?Conformable on rocks of the Hollowbrook Member (q.v.).
Thick sequence mainly of grey, purple and green quartzitic fine- to medium-grained sandstone, commonly parallel laminated and convolute-bedded, with shale and silty shale interbeds. Abundant scoured surfaces and silty drapes. Scattered scarce remains of Psilophyton sp. and a calamitid-like stem. Local distictive facies of deformed laminae of red siltstones and very fine-grained sandstones in which desiccation cracks alternate with convolute laminae.
c.1250m (Tunbridge, 1978).
Overlain ?conformably by rocks of the Rawns Member (q.v.)
Trowie Glen Sandstone Member
TGS
Gradational contact with laminated sandstone at top of pebbly sandstones characterising the Haist Pebbly Sandstone Member.
Non-pebbly sandstone.
1300m at Haist [HY 2320 0218] on Hoy Island, Orkney.
Youngest unit in Orkney Old Red Sandstone sequence, no younger beds known in the area.
Tongwynlais Formation
TGW
A thin unit [3 to 4m] of red, sparsely shelly, calcareous sandstones, sandy limestones, and mudstones with calcrete caps the red fluvial sandstones of the underlying Quartz Conglomerate Group. The sharp base of the Tongwynlais Formation is taken at the top of this thin unit at the incoming of restricted marine or peritidal, green or grey mudstones, micrites, calcisiltites and skeletal packstones/grainstones.
Vale of Glamorgan [ST 00 74]. The formation is overstepped northwards by the Castell Coch Limestone Formation. Present but not mapped in the southeast crop of the South Wales Coalfield [ST 17 85], Gower [SS 50 90], Pembrokeshire [SM 99 01] and Chepstow areas [ST 53 93].
Lower part comprises thin- to thick-bedded skeletal, peloidal, ooidal and sandy grainstones and packstones with subordinate grey mudstones, calcite mudstones, calcretes and ironstones. Upper part comprises thin- to medium-bedded skeletal packstones and grey mudstones. The lower part represents deposition in ooidal shoal, embayment and peritidal environments. The upper part represents deposition on a storm-influenced, open marine, nearshore shelf.
Up to 50m in the south of the Vale of Glamorgan, thinning northwards to a feather edge in the Risca area on the east crop of the South Wales Coalfield.
Interbedded thin- to medium-bedded grey skeletal packstones and mudstones forming the upper part of the Tongwynlais Formation thicken upwards and pass up quickly, but gradationally, into the medium- to thick-bedded ooidal and skeletal grainstones of the Castell Coch Limestone Formation. The top of the Tongwynlais Formation is taken at the top of the last mudstone bed.
Thames Group
THAM
In both the Hampshire and London Basins the boundary is placed at the erosion surface below the glauconitic sands and sandy clays of the Oldhaven Formation of King (1981), which rest on the Woolwich and Reading Beds (King, 1981), or the Lambeth Group (Ellison et al, 1994).
Silty clay/mudstone, sandy silts and sandy clayey silts of marine origin.
c.110-115m in the Hampshire Basin.
In the Hampshire Basin the boundary is placed at the erosion surface at the base of the Wittering Formation of the Bracklesham Group, where the dark grey bioturbated silty clay of the London Clay gives way upwards to the glauconitic sands and silty clays of the Wittering Formation.
Thornbury Formation
THB
Townhead Boulder Gravel Member
THBG
Steep erosional (channelled) base against well bedded units of the St Bees Sand and Gravel Member of the Seascale Glacigenic Formation.
Nethertown area of 1:50k Sheet 28 (Whitehaven) only.
Clast-supported, very poorly sorted boulder gravel, with clasts up to >2.5m in diameter. Clasts are generally angular to subrounded and mainly comprise red Permian sandstone, yellow and white Coal Measure sandstones, black Coal Measure mudstone, together with some coal, green Borrowdale Volcanic Group lavas, grey Criffel granite, ironstone, greywacke and limestone.
Planar unconformable base of the How Man Till Member of the Gosforth Glacigenic Formation.
Thorneyburn Limestone
THBN
Top Hard Coal (Nottingham And Derby)
THC
Thames Catchments Subgroup
THCAT
Unconformable on glacigenic deposits of the Anglian stage or on older Pleistocene strata or bedrock. Individual terrace deposit members rest unconformably on older Pleistocene strata.
The valley of the mainstream River Thames and tributaries (Upper Thames Valley Formation, Maidenhead Formation). Separate formations are established for the deposits of some of the major tributaries of the Thames (eg: Kennet). The terrace deposits of the Medway Valley Formation (in the valley of the Medway) are also included within the subgroup. The Kesgrave Catchment Subgroup (Dunwich Group) includes all terrace deposits of the pre-Anglian, pre-diversionary ancestral River Thames.
Mainly river terrace sand and gravel, brickearth silt and alluvial floodplain silt, silty clay and sand. The subgroup includes interbedded units of locally fossilferous silty sand, silt, together with organic clay, tufa and peat that are biostratigraphically correlated with interglacial (warm) stages. The subgroup is currently divided into the Upper Thames Valley Formation and the Maidenhead Formation (middle and lower Thames valley) for deposits of the main valley and some tributary valleys. The Kennet Valley Formation is established to terrace deposits of that valley. Terrace deposit gravel clasts are mainly limetone lithogies (upper Thames) and flint, vein quartz and local bedrock lithologies including chert (middle and lower Thames). The terrace deposits are depicted on British Geological Survey maps using numbered terrace symbols. Modern British Geological Survey maps also show the terrace deposits as named units that are here interpreted as members of the relevant valley formation.
Single terrace aggradations range from 3 to 12m. Interglacial units (eg: Trafalgar Square Member) up to 12m.
Thorncliffe Coal (South Yorkshire)
THCC
Not equivalent to the 'Thorncliffe' of Wakefield, which is lower in the stratigraphy. It probably equates to the 'Middleton Main Top' Coal of Wakefield. Note variable spellings of 'Thornclffe' and 'Thornecliffe'.
Townhead Coal (Northumberland)
THDC
Top Hebburn Fell Coal (Northumberland)
THEB
Teith Sandstone Formation
THF
At the base of the lowest bed of purple sandstone or locally conglomerate overlying the Cromlix Mudstone Formation, except in the Glen Shee district where the boundary is not seen due to faulting.
Strathmore, Northern Midland Valley.
A reddish-brown, grey, purple and brown, cross-bedded sandstone, locally interbedded with siltstone and mudstone intercalations, conglomerate members and interbeds are common in the Highland Border area.
At least 1800 m thick on the north-west limb of the Strathmore Syncline.
Faulted out or locally unconformably overlain by the Stratheden group near Stirling.
Tan Hill Grit
THG
Tan Hill Grit Coal
THGC
Thatcham Gravel
THGR
Terrace surface modified by erosion: Thatcham (+8 - 10m) Terrace in Kennet.
Lower Thatcham Gravel
THGRL
Upper Thatcham Gravel
THGRU
Subdivision of Thatcham Gravel based on morphology, by break-of-slope only.
Thornsgill Till Formation
THGTI
Generally an uneven, unconformable boundary with slate bedrock, but locally a thin unit of weathered sand and gravel intervenes. Bedrock commonly decomposed.
Vale of Thelkeld, Cumbria.
Extremely compact, silty sandy gravelly diamicton containing clasts mainly of slate. "Borrowdale Volcanic Group" lithologies and Threlkeld microgranite. Dark grey at base becoming increasingly weathered upwards to yellowish brown with olive brown, orange and white mottling where it has been cryoturbated. Most clasts are decomposed towards top and are commonly bleached. The deeply weathered zone of the unit is named formally as the Troutbeck Palaeosol.
Generally a sharp, planar, or gradational glacitectonic boundary with greyish brown stony clay diamicton (Threlkeld Till Formation).
Thurstaston Hard Sandstone Bed
THHB
Taken at the base of a maximum 3m thick pebbly sandstone bed (the Thurstaston Hard Sandstone Bed), overlying pebble-free reddish-orange sandstone (Wilmslow Sandstone Formation).
Wirral Peninsula, west of the Woodchurch Fault (Cheshire Basin).
Sandstone and pebbly sandstone, greyish-brown. Fine- to medium-grained, moderately- to poorly-sorted. Laterally impersistent. Very well cemented in comparison to sandstone units immediately above (Thurstaston Sandstone Member) and below (Wilmslow Sandstone Formation).
Taken at the top of a maximum 3m thick pebbly sandstone bed (the Thurstaston Hard Sandstone Bed), underlying pebble-free reddish-orange sandstone (Thurstaston Sandstone Member).
Thornhill Sandstone Formation
THHS
Rests unconformably on Carboniferous strata or on basal Permian breccias.
Thornhill Basin and Locherben, Dumfriesshire, south-western Scotland (Southern Uplands).
Fine- to coarse-grained, well sorted, red quartz sandstpone with large scale aeolian cross bedding.
200m+ on geophysical evidence
The Thornhill Sandstone Formation is stratigraphically the highest unit in the district.
Thick Coal (South Staffordshire)
THIC
Thin Coal (Warwickshire)
THIN
Thick Coal Rock (South Staffordshire)
THIR
Thick Coal (Birmingham And South Staffordshire)
THKC
Threlkeld Intrusion
THKD
Low Rigg [NY 305 230],Threlkeld Knotts [NY 328 238], around White Pike [NY 339 229] and in Bramcrag Quarry, east of Keswick,Cumbria.
A garnet-bearing, alkali feldspar-quartz-plagioclase-phyric microgranite. Age: 451.0 +/- 1.1 (2-sigma) Ma (U-Pb, zircon), Millward, D and Evans, J A, 2003.
A laccolith 0.5 to 1km thick and with an area of about 12 sq. km intruded into the Skiddaw Group and lowermost part of the Borrowdale Volcanic Group.
Thornbrough Limestone
THL
Tollhouse Mudstone Bed
THM
In its type section, the base is taken at the contact between the mudstone and underlying dolomitised limestones (formerly part of the Llandudno Pier Dolomite, but now included in the Loggerheads Limestone Formation).
Anglesey (SJ 50 87) and the Great Orme (SJ 77 83), northwest Wales.
Fossiliferous, dark grey, calcareous mudstone and highly argillaceous limestone. The Tollhouse Mudstone is a widely recognised bed of marine mudstone occurring within the late Asbian platform carbonate succession of North Wales. Recognised on Anglesey and at Llandudno, it appears to record a temporary cessation of limestone deposition and (or caused by) an increase in the volume of terrigenous mud supplied to this northwestern portion of the platform.
In its type section, the top is taken at the entry of overlying, pale, thick-bedded limestones.
Top Haigh Moor Coal (West Yorkshire)
THMC
Top High Main Coal (Northumberland And Durham)
THMN
Top High Main Coal (Derby)
THMNC
Till, Thin, On Bedrock [See Descriptions For Limitations Of Use]
THN
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also THNC and THNX. Note that on the related Quaternary Domains map, this category was described as: "Thin till on rock (generally <5m)".
Till, Thin, Overlying Sedimentary Cover [See Descriptions For Limitations Of Use]
THNC
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future.To avoid potential confusion it should be used only for similar purposes in future. See also THN and THNX. Note that on the related Quaternary Domains map, this category was described as: "Thin till on rock (generally <5m), Overlying sedimentary cover, ie Carboniferous, Permo-Trias".
Till, Thin, Overlying Pre-Carboniferous Rocks [See Descriptions For Limitations Of Use]
THNX
The code was originated for use in describing Quaternary Domains in the Sellafield (Cumbria) area. To avoid potential confusion it should be used only for similar purposes in future. See also THN and THNC. Note that on the related Quaternary Domains map, this category was described as: "Thin till on rock (generally <5m), Overlying pre-Carboniferous rocks, mostly igneous andd metamorphic".
Thornthwaite Crag Tuff Member
THO
Thorr Pluton
THOP
K-Ar 390-392 Ma (Pitcher and Berger, 1972).
Thorganby Clay Member
THOR
The Thorganby Clay Member is shown in boreholes and sections to rest directly on the Lawns House Farm Member. The contact can be sharp or gradational with interbedded sand, silt and clay layers. The Thorganby Clay Member only occurs where the Lawns House Farm Sand Member is present. Outside of this area, the equivalent clay is part of the undivided Hemingbrough Formation.
The Thorganby Clay Member occurs south of the Escrick Moraine [SE703 450] between the rivers Ouse and Foulness. In south of district deposit is likely to merge with other members of of the Hemingbrough Glaciolacustrine Formation.
Greyish brown soft, locally fissured, laminated silt and clay. The top metre of this member commonly contains a higher percentage of silt and sand, is reddish yellow to grey colour-mottled and the laminated structure has been destroyed by periglacial and soil processes. This unit can contain gravel dropstones and glaciotectonic structures, particularly near the Escrick Moraine.
1 to 3.5m. (Proved in auger holes).
The Thorganby Clay Member is typically exposed at surface, or concealed beneath the Breighton Sand Formation. The upper boundary may not be preserved where Skipwith Peat Bed has formed directly on silted up or dried up lake bed. Where the base of the overlying Breighton Sand Formation is represented by sandy facies, the upper boundary is typically sharp and erosive. In most places the upper boundary is disturbed by periglacial and soil processes.
Tuttle Hill Member
THQ
Base of beds with abundant mudstone-draped top surfaces. Sandstones beneath (of Park Hill Member) predominantly grey, with herringbone cross-bedding in main part.
From Nuneaton town centre, extending north-west for 5.2km to Worthington Farm, Mancetter.(SP 3541 9205-3192 9572).
Pink to maroon, medium- to fine-grained glauconitic sandstone. Subordinate mudstone beds and near-ubiquitous mudstone drapes. Tabular-planar and compound cross-bedding common. Summary of typical lithologies in Type Section:(i) Sandstone, maroon, fine, glauconitic and micaceous. Smooth, flat-topped beds, parallel-sided with horizontal lamination. Many bed tops bioturbated (56m). (ii) Sandstone, pink to maroon, glauconitic. Undulatory, smooth-topped beds with mudstone drapes. Compound cross-bedding with highly lenticular bed forms (39m). (iii) Sandstone, maroon to pinkish grey, glauconitic. Parallel-sided, smooth-topped beds with horizontal or gently dipping lamination; mudstone beds locally constitute 50% of succession (10.5m). (iv) Sandstone, maroon to pale pink, glauconitic. In thick tabular-planar cross-bedded sets, showing unimodal current directions, or in lenticular compound cross-bedded sets. Ubiquitous mudstone drapes (39m). (v) Sandstone, grey, coarse to pebbly. In lenticular, thick beds with tabular-planar cross-bedding showing bimodal current directions. Mudstone interbeds are lenticular, locally to 0.7m thick (7.5m). (vi) Horizontally laminated sandstone, mudstone dominant at base (5.3m).
157m in type section.
Incoming of variegated fine-grained sandstone and siltstone beds of Jees Member. Bimodal cross-bedding and trough cross-bedding becomes well-developed.
Threequarters Coal (South Yorkshire, Nottingham And Derby)
THQU
Thornhill Rock 1 (Lower)
THR1
West Yorkshire area [Thornhill, Yorkshire].
Thornhill Rock 2 (Middle)
THR2
Thornhill Rock 3 (Upper)
THR3
Thin Rider Coal (Warwickshire)
THRI
Top Harvey Coal (Durham)
THRV
Three Yard Coal (North Wales)
THRY
Thorncroft Sand Member
THS
Passage up from the ooidal limestone-dominated succession of the Lincolnshire Limestone Formation into a predominantly sand-dominated, generally non-calcareous succession, which in places comprises a dark sooty mudstone, accentuated in the weathered zone by the development of a secondary limonitic bed at the base, known as the 'Ironstone Junction Bed' which lies at the base of the Thorncroft Sand, although elsewhere, there may be up to 2 m of interdigitated ooidal limestone and sandstone strata, or indications of a non-sequence, such as limestone pebbles or oxidation of the top of the Lincolnshire Limestone.
North Lincolnshire and the East Riding of Yorkshire (Humberside).The northern limit is located around North Newbald near Market Weighton (Sheet 72), where the unit is overstepped by the Cretaceous.The southern limit is uncertain, although it is perhaps defined by the absence of the lower cycle, (see note above) either by passage into the Lincolnshire Limestone facies and/or by overstep through downcutting of the upper (Stamford) cycle into the Lincolnshire Limestone, which can be seen in the area between the Grantham district (Sheet 127) and the Brigg district (89), and probably also to the north of Lincoln. Provisionally the arbitrary boundary is taken at the southern edge of Sheet 89.
A grey to yellow, locally bioturbated massive parallel or cross-bedded fine-grained, patchily iron-cemented but otherwise friable sandstone with plant debris, rootlets and thin lignite lenses, with thinly bedded and laminated locally sphaerosideritic and pyritic sandstone, siltstone and mudstone, seatearths and thin coals, which may include a median unit of marine fossiliferous calcareous mudstone or siltstone.
Up 18 m or more thick.
A sharp often rootleted contact with the mudstone-dominated upper part of the Rutland Formation described as the Priestland Clay Member of Gaunt et al, 1992.
Thorverton Sandstone Formation
THSA
Rests on Cadbury Breccia, apparently fairly sharply, possibly unconformably; exact nature of contact uncertain.
Main outcrop between West Raddon (SS 895 014), Thorverton, and Silverton. Fault-bounded outcrop around the Killerton area between Heazille (SS 947 005) in the west and Budlake (SS 985 001) in the east.
Predominantly reddish brown fine- to very fine-grained sandstone, with local thin beds and partings of reddish brown clay. Lenticular breccia bed south of Raddon (c.SS 915 016); possibly other thin breccias present. Basaltic lavas at various levels. May correlate with Knowle Sandstone.
Overlain, apparently fairly sharply and unconformably west of Thorverton by Crediton Breccia, and by Yellowford Formation elsewhere.
Thirlstane Beds
THSD
Sharp base on marine mudstones of the Powillimount Sandstone Formation.
Fine-grained, well sorted, pale grey quartz sandstone characterised by large-scale cross-bedding and soft sediment liquefaction structures.
The Thirlstane Sandstone Member lies conformably under the Arbigland Limestone Formation.
Thorpe Sand And Gravel Member
THSG
Unconformable, commonly channelled base, resting on Anglian Wragby Till in the Type Area but possibly locally on Upper Jurassic mudstone bedrock if present elsewhere.
Bain valley; upstream limits unknown but possibly represented in the Upper Bain. To the northwest, merges with correlative Southrey Sand and Gravel in the Witham valley.
Predominantly cold-phase sands and gravels that underlie the Thorpe or Second Terrace of the River Bain. Dominated by clasts of flint with up to 50% chalk (though decalcified near ground surface) and a smaller proportion of Upper Jurassic and Lower Cretaceous lithologies plus minor exotics, notably Carboniferous sandstone and "Bunter" quartz/quartzite pebbles (mostly derived from Anglian tills). It forms a rather degraded terrace surface typically some 3 to 4m above the modern alluvial floodplain, and c.2m higher that the adjacent Castle Terrace, though deposits extend beneath the level of the latter. Sections show intraformational and epigenitic ice wedge casts, and upper part locally incorporates a rubified palaeosol (Hykeham Soil; Ipswichian). Locally includes cold-phase organic silts and peats, but channel-filling organic silts at the base (Kirkby Bed) yield a temperate flora and fauna assigned to MIS 7. Correlated with the Southrey and Balderton Sand and Gravel members and Egginton Sand and Gravel Member (all in the Trent Valley Formation).
0 to c.8m
Ground surface or (locally) overlain by the Castle Sand and Gravel Member.
Thornton Shales With Limestone (Knoll-Reef)
THSK
Thornton Shales-With-Limestone
THSL
Telegraph Hill Sands Member
THSS
Thrussington Member
THT
Typically bedrock surface below deposit; other deposits may, however, intervene.
Diamicton, brown to reddish-brown with stones and matrix derived primarily from Upper Carboniferous and Triassic rocks; subordinate sand, gravel and stoneless clay and silt.Red pebbly clay and silty clay with rock fragments - [generic description: 'TMOS' Procedures].
Typically the present-day surface; can, however, be overlain by latter glacigenic or fluvial deposits or head.
Thormaid Till Member
THTI
Caithness and Sunderland west of a line between Reay and Berridale (1:50 000 sheets 115 E and W, and sheet 110).
Diamicton, gravelly and sandy, typically light brown with clasts of predominantly Caledonian igneous and Moine metamorphic rocks.
Up to 5m thick.
Thornton Limestone Member (Knoll-Reef)
THTK
Thornton Limestone Member
THTL
Overlies the Chatburn Limestone Group.
Confined to the Craven Basin of Lancashire and Yorkshire.
Packstones, wackestones and subordinate grainstones predominantly wavy-bedded, muddy, pale to dark grey, bioclastic and locally cherty, interbedded with variable amounts of dark-grey calcareous mudstone and siltstone. Bioturbation is common.
Overlain unconformably by the Hodder Mudstone Formation in the Worston Shale Group.
Top Hutton Coal (Durham)
THUC
Thurstaston Sandstone Member
THUN
Taken at base of a maximum 3m thick pebbly sandstone bed (the 'Thurstaston Hard Sandstone Bed'), overlying pebble-free reddish-orange sandstone of the Wilmslow Sandstone Formation.
Sandstone, reddish-orange and rare pebbly sandstone, reddish-grey. Predominantly fine-grained; well-sorted with spherical to sub spherical grains. Rare laterally impersistent pebbly sandstone beds up to 3m thick in lower part. Soft sediment deformation common in pebble-free units. Less well-cemented in comparison to overlying Delamere Sandstone Member.
58m in Hoylake Water Works No.2 Borehole (SJ28NW/5). Wirral. 62m in Hoylake Water Works No.1 Borehole (SJ28NW/4). Wirral.
At boundary of weakly-cemented, pebble-free sandstone and overlying pebbly sandstone of the Delamere Sandstone Member (Helsby Sandstone Formation).
Thurfer Coal
THUR
Tarn Hows Tuff Formation
THW
Change from dacitic to acid andesitic tuffs; overlies Lincomb Tarns Tuff Formation.
Area between the Coniston Fault (Tarn Hows) and Lake Windermere.
Andesitic coarse tuffs and lapilli-tuffs; massive to weakly stratified, with a very rough weathered surface exhibiting conspicuous surface holes.
Not seen; unconformably overlain by lowest formation of Windermere Supergroup.
Thwaites Coal (West Yorkshire)
THWC
Tryddyn Half Yard Coal (North Wales)
THYC
Tankersley Ironstone
Twenty Inch Coal (Sanquhar)
TIC
Tilmanstone Coal
TICO
Ticknall Limestone Formation
TIL
The lower unconformable boundary is taken at the base of the lowest palaeosol, recognised by 1- 2 m of heterogeneous, friable siltstone and sandstone with carbonate nodules, above fine- to coarse-grained dolostones containing shaly mudstone partings, of the Cloud Hill Dolostone Formation.
South Derbyshire to north-west Leicestershire, between Ticknall [SK 35 24] and Thringstone, near Grace Dieu [SK 42 17].
Buff to pale grey, fine- to medium-grained massive to thinly bedded dolostone and limestones, with shaly mudstone interbeds, common palaeosols and karstic surfaces with green clayey drapes, and bioclastic grainstones and calcaeous mudstones where undolomitised. Some sandy dolostones and dolomitic sandstones are present at the base of the formation.
Estimated to be 60 m thick in the type area, and possibly up to 90 m between the Worthington Borehole and Cloud Hill Quarry.
The highest bed of limestone or dolostone in the Peak Limestone Group, is overlain rapidly by grey mudstone, siltstone or sandstone of the Millstone Grit Group or red-bed Permo-Triassic breccia of the Moira Formation.
Till, Devensian (Irish Sea Ice)
TILDI
Till, Devensian (Welsh Ice)
TILDW
Till
TILL
Group of sediments laid down by the direct action of glacial ice. [Generic description: earth science dictionaries in the BGS library]. Variable lithology, usually sandy, silty clay (possibly chalky in southeast England) with pebbles, but can contain gravel-rich, or laminated sand layers; varied colour and consistency. [generic description].
Till, 1
TILL1
Group of sediments laid down by the direct action of glacial ice. Variable lithology, usually sandy, silty clay (possibly chalky in southeast England) with pebbles, but can contain gravel-rich, or laminated sand layers; varied colour and consistency; older than "Till" in the same map area. [Generic description].
Till, 2
TILL2
Group of sediments laid down by the direct action of glacial ice. Variable lithology, usually sandy, silty clay (possibly chalky in southeast England) with pebbles, but can contain gravel-rich, or laminated sand layers; varied colour and consistency; older than "Till" and "Till 1" in the same map area. [Generic description].
Till, Anglian
TILLA
Till, Devensian
TILLD
Till (Irish Sea Ice)
TILLI
Till, Mid Pleistocene
TILMP
"Mid Pleistocene" or of uncertain pre-Devensian age from Cromerian to Oxygen Isotope Stage 6.
Tibbie Pagan's Limestone
TILS
Tilley Coal (Northumberland And Durham)
TILY
Till And Morainic Deposits (Undifferentiated)
TIMO
Twelve Inch Coal (South Derbyshire)
TINC
Tinto Felsic Intrusion
TINTO
Tirnaskea Formation
TIR
Tirabad Formation
TIRA
Tillybrachty Sandstone Formation
TIS
Red, friable sandstone with conglomerate bands and thin intercalated lava flows.
250 metres at type section (possibly incomplete due to faulting); increases southwards to approx. 1400 metres around Kildrummy Castle (NJ 455 164); decreases northwards to approx. 100 metres near Boghead (NJ 521 278).
Tilestones Formation
TIST
Tissington Volcanic Member
TIVO
Taken at the first bed of slumped, laminated dark grey to grey dolomitised limestone containing angular lapilli of amygdaloidal basalt lava (in Lees Farm Borehole, SK 15 SE/12); depth 182.02m.
The principal outcrop extends from a locality 250m NW of Pethills (SK 207 493) to about 100m SE of Crakelow Farm (SK 177 535).
Mainly a hyaloclastite, composed of highly amygdaloidal and partly carbonated basaltic rock fragments. Minor basaltic lavas also occur.
Up to 44m recorded.
Taken at the last occurrence of calcitic igneous rock and mudstone, or of hyaloclastite. This is overlain by calcareous mudstones and thin limestones of the Widmerpool Formation (in Tissington 1 and 2 Boreholes, SK 15 SE/13 and 14).
Tisbury Member
TIY
Upward change from clayey sands and sandy clays of the Wardour Formation to bioclastic calcareous sandstone and sandy limestone.
West Tisbury [ST 910 290] to Chilmark [ST 975 310]
Fine-grained, glauconitic, bioclastic sandstones and limestones.
Upward change from glauconitic calcareous sandstones and sandy limestones to non-glauconitic micrites of the Wockley Member.
Mesozoic (Triassic To Cretaceous) Rocks (Undifferentiated)
Tickwood Member
TKB
Transitional on mudstones of the underlying Coalbrookdale Formation. Base taken beneath first bed of coalesced limestone nodules.
Greenish-grey siltstones with bands of prominent limestone nodules.
24m
Base of reef facies limestones within the Much Wenlock Limestone Formation.
Tea Kettle Hole Formation
TKH
Trosk Plug
TKP
Thick Rock
TKR
Thick Stone
TKS
The Thick Stone is generally a fine-grained sandstone, split in places into two leaves. It lies between the Black Bed Coal and the Better Bed Band Coal but in some sections coalesces with a sandstone above the Better Bed, cutting out the Better Bed Band.
Threlkeld Till Formation
TKTI
Generally an unconformable boundary on bedrock. Locally a sharp, planar, or gradational glacitectonic boundary with yellowish brown sandy gravelly clay diamicton (Thornsgill Till Formation).
Very compact, olive grey, sandy, silty, clayey, stony diamicton containing clasts mainly of "Borrowdale Volcanic Group" lithologies, slate and Threlkeld microgranite. Locally includes masses of weathered diamicton (Thornsgill Till) at base. Commonly weathered to yellowish grey.
Mostly ground surface or overlain unconformably by glaciofluvial sand and gravel.
Thick Coal (Wyre Forest)
TKWF
Tanhouse Limestone
Local to the area around Yate, Gloucestershire.
Fossiliferous limestone and calcareous shaly mudstone forning a wedge within the upper part of the Cromall Sandstone Formation.
Tyne Limestone Formation And Alston Formation (Undifferentiated)
TLA
Teilia Formation
TLB
Entry of thicker mudstones and dark limestones above conformable contact with thin-bedded limestones of the Prestatyn Limestone Formation; locally rests on"knoll reef" limestones.
Prestatyn area, northeast Wales [SJ 0781]
Interbedded calcareous mudstones and dark grey, tabular-bedded, argillaceous limestones containing a pectinoid bivalve and goniatite fauna. The Teilia Formation represents a basinal, turbiditic and hemipelagic marine mudstone facies, which onlapped the northern margin (including knoll reefs) of the North Wales Dinantian platform during the Brigantian.
Conformable contact with bedded cherts of the Pentre Chert Formation.
Town Lane Coal (South Lancashire)
TLCO
Thornylee Formation
TLEE
Silurian, Llandovery, guerichi Biozone.
Interbedded turbidite (wacke) sandstone and mudstone/siltstone passing locally to massive sandstone. Sandstone typically fine- to medium-grained but ranging to coarse-grained especially in massive units; commonly medium- to very thick bedded (up to 2m) with sparse units up to a few metres thick that are very-thin to thin-bedded, usually with thin siltstone or silty mudstone interbeds; massive sandstone units tens of metres thick and massive siltstone units a few metres thick occur locally. Sandstone and siltstone are typically grey to greenish grey when fresh, weathering olive green to pale brown. The sedimentological character is transitional from the Gala Group to the north, but the Thornylee Formation is distinguished by its younger age range, abundant garnet in coarse-grained sandstone and relatively low Sr and Ni content in whole rock sandstone composition. To the south, the adjoining Selcoth Formation (Ettrick Group) lacks the very thick massive units of coarse-grained sandstone and siltstone and generally has a higher proportion of interbedded mudstone; garnet is rare in the Selcoth Formation. However, the Thornylee and Selcoth formations are the same age and have similar whole rock sandstone composition; they are therefore closely related if not facies variants.
Tralorg Shale Formation
TLG
Disconformable junction with Shalloch Formation (Ordovician).
Grey, brown and black mudstones, and thin beds of gritty sandstone.
Conformably overlain by Saugh Hill Grits Formation.
Traeth Lligwy Beds
TLL
Tile Hill Mudstone Formation
TLM
At the first red-brown mudstone, above the highest mappable persistent red-brown sandstone of the Salop Formation.
Extensive outcrops in the southern part of the Warwickshire Coalfield.
Red-brown mudstones with subordinate thin red-brown and green, flaggy, fine- to coarse-grained sandstones with rare thin conglomeratic lenses.
280 m thick.
At the change from red-brown mudstone, to the predominantly red-brown sandstone of the Kenilworth Sandstone Formation.
Tircorran Limestone-Mudstone Member
TLMM
Tile Hill Mudstone Formation And Meriden Formation [Obsolete Code: Use Mrtm]
TLMR
Top Lousey Coal (West Yorkshire)
TLOU
Top Limestone
TLS
Marks the top of the Upper Limestone Formation (at least) in south-central Ayrshire.
Top Little Limestone
TLTL
Tillyfourie Pluton
TLYF
Tullyskeherny Member
Tait's Marine Band
TMB
Tombstone Limestone
TMBL
Tom's Cove Shale
TMCS
Dark grey to black shaly mudstone with calcareous nodules and coprolitic pellets.
Tarn Moor Formation
TMF
Not yet proved, probably unconformable on the Buttermere Formation.
Occurs within the southeast part of the Skiddaw inlier, bounded to the north by the Causey Pike Fault. It forms all of the Ullswater and Bampton inliers. It is unconformably overlain by the Borrowdale Volcanic Group, the youngest part of the Formation is in the Tarn Moor Tunnel.
The lower part comprises laminated and thickly laminated mudstone with subordinate siltstone beds. The middle part is mudstone and locally, siltstone with up to 5% tuffaceous beds. The highest part comprises dark grey to black mudstones.
Not seen as it is unconformably overlain by rocks of the Borrowdale Volcanic Group.
Top Marshall Green Coal (Northumberland And Durham)
TMGN
Threemile Formation
TML
Conformably overlies the Southshore Formation.
Sandstone flysch.
45 metres.
Conformably overlain by the Penwhapple Formation.
Trusham Mudstone Formation
TMMU
The lower boundary is taken at the gradational incoming of pale grey and green micaceous shales of the Trusham Mudstone Formation above the dark blue-grey or bluish green-grey mottled shales and calcareous beds of the underlying Hyner Mudstone Formation. Commonly this boundary cannot be detected in the metamorphic aureole of the Dartmoor Granite.
Middle Teign Valley and Ilsington areas, eastern Dartmoor (SX 84 85), south Devon.
Olive green, soapy "shales" exhibiting a conchoidal fracture and pale grey "shales" with calcareous micaceous laminae. The small bivalve Sanguinolites? ellipticus is locally abundant in the upper part of the Formation. Sparse shelly benthos and pelagic ostracods are locally present.
65m
The upper boundary is taken at the incoming of bluish black and black mudstones of the overlying Combe Mudstone Formation above the olive green and pale grey mudstones of the Trusham Mudstone Formation.
Top Main Coal (Northumberland And Durham)
TMNC
Temple Newsam Sandstone
TMNS
Tomnaverie Intrusion
TMNV
Top Moorland Coal (Northumberland)
TMOR
Thirlmere Tuff Member
TMR
Mostly faulted but locally rests conformably on bedded pyroclastic rocks at the base of the Lincomb Tarns Tuff Formation, or unconformably on sandstone (Seathwaite Fell Sandstone Formation) or andesite lavas (Birker Fell Andesite Formation).
North Lake District, around Thirlmere Reservoir, including Watson's Dodd and Stybarrow Dodd.
White to pink-weathered, parataxitic, garnetiferous rhyo-dacitic lapilli-tuff and vitric tuff, locally lithic-rich and with breccia.
At least 300m
Conformably overlain by tuff and volcaniclastic sandstones of the Raise Beck Member (Lincomb Tarns Tuff Formation), or by undivided parts of the Lincomb Tarns Tuff Formation.
Tormitchell Conglomerate Member
TMS
Ordovician (Caradoc)
Discrete lenticular pebbly and conglomeratic member within the flaggy sandstones, siltstones and mudstones of the Ardwell Farm Formation and located about 150m above the base of the formation.
Coarse, buff-weathering, medium-grey pebbly grit with scattered boulders of dolerite, spilite lava and red granite. Some intercalated mudstones and siltstones yielding a brachiopod fauna.
0 to 73m
Tormynydd Coal (South Wales)
TMYD
Twente Formation
In type section rests on marine sands of Eem Formation (Eemian Interglacial). In Flemish Bight Sheet, rests on the Eem Formation or on brackish-marine early Weichselian clays of the Brown Bank Formation.
Fine-grained, well-sorted, wind-blown periglacial sands, evidence of cryoturbation in onshore exposures in the Netherlands.
1 - 25 metres
Overlain by early Holocene peat or brackish marine sand (Elbow Formation) or marine sand (Bligh Bank Formation).
Tresglen Formation
TNB
North and south of Llandovery, mid to south Wales.
183 to 213m
Trwyn Cam Member
TNC
Conformable and gradational with dark grey siltstones that form the main part of the Wig Bach Formation.
Not yet recorded.
Grey, bioturbated, fine-grained laminated sandstones and subordinate siltstones, with large calcareous nodules that weather out. A structureless grey siliceous siltstone, possible representing a tuff, occurs in the upper part of the sequence.
Conformably overlain by dark grey siltstones of the Wig Bach Formation.
Trigloin Coal (South Wales)
TNCO
Tarn Crags Tuff Member
TNCR
Taken at the base of pyroclastic sequence unconformably overlying bedded sandstone of the Seathwaite Fell Sandstone Formation or andesite of the Birker Fell Andesite Formation.
North Lake District around Thirlmere Reservoir.
Bedded coarse-grained dacitic tuff and lapilli-tuff, sparsely garnetiferous.
Up to about 8m, except on Great Howe and Castle Rock, Thirlmere, where up to 280m
Conformable contact with welded lapilli-tuff of the Thirlmere Member, or with that of the Lincomb Tarns Formation (undivided).
Top Neddy Coal (South Lancashire)
TNED
Ten-Feet Coal (North Staffordshire)
TNFC
Tarring Neville Flint
TNFL
Ten-Feet Rock (North Staffordshire)
TNFR
Tincorn Hill Intrusion
TNHL
Ty-Nant Limestone Formation
TNL
At junction with underlying Basement Beds.
Llangollen-Minera district, east Wales.
Regular cyclic alternations of dark grey bioclastic limestone and porcellaneous limestone (birdseye micrite).
At junction with overlying Eglwyseg Limestone Formation, which comprises sedimentary cycles of calcareous shale, cross bedded biosparite and massive pale grey biosparite.
Torr Na Moine Trachyte Plug
TNMT
Tarnash Phyllite And Limestone Formation
TNPL
At upper limit of quartzite of the Corryhabbie Quartzite Formation, where present. Otherwise at lowest appearance of white limestone or muscovite-rich semipelite above Mortlach Graphitic Schist Formation.
Extends southsouthwest from coast section in eastern half of Sandend Bay [NJ 559 664], to Stripeside [466 518], and south of the River Isla around the Herricks and Birken Burns [NJ 45 48]. Farther southwest, equivalent unit is termed the Ailnack Phyllite and Limestone Formation.
Semipelite, commonly thinly bedded, with white to pale grey metacarbonate and green-grey calc-silicate rocks. Prominent white limestone (Linkbrae Limestone Member) near base well developed on coast. Dolomitic metalimestone developed in lower part in Tarnash area. Less calcareous in the Grange area (River Isla).
240m from Deskford ORS outlier to Sandend Bay; c.400m in Grange area; c.250m in Tarnash area.
Rapid gradation from calcareous semipelite and limestone to graphitic pelite/semipelite and dark-grey limestone of Fordyce Limestone Formation.
Ten Quarters Coal (Cumbria)
TNQ
Tranearth Group
TNTH
As for the base of the Brathay Formation: conformably overlies the grey siltstone of the Browgill Formation (Stockdale Group).
Northwest England: Southern Lake District, Cumbria; Howgill Fells, Cumbria inlier, Cumbria; Craven inliers, Yorkshire.
Laminated hemipelagite is the characteristic lithology. In upward succession in the southern Lake District type area: the Brathay Formation consists largely of hemipelagite, the Birk Riggs Formation contains in addition, an abundance of turbidite sandstone, the Coldwell Formation comprises two units of calcareous siltstone separated by hemipelagite, the Wray Castle Formation comprises hemipelagite with some turbidite siltstone.
Child Unit names: Southern Lake District: Brathey, Birk Riggs, Coldwell and Wray Castle formations; Cross Fell: Brathay Formation; Craven inliers: Brathay, Austwick and Arcow formations.
About 500 to 1000m
Conformably overlain by turbidite sandstone at the base of the Coniston Group.
Top Nether Witton Coal (Northumberland)
TNWC
Tortworth Beds
TOB
Tortworth - Tites Point Inlier, north of Bristol.
c.61m
Torbay Breccia Formation
TOBR
Top Coal (Somerset)
TOCO
Todburn Limestone
TODL
Tom Dunan Schist Member
TODU
Town End Farm Tuff Member
TOEF
At base of homogeneous welded lapilli tuff, at the base of the lithic rich basal breccia if it is present. This is the basal member of the Fleming Hall Formation; it rests on the Brown Bank Ignimbrite Formation.
Sellafield boreholes Nos 2 (NY00SE/28), 4 (NY00SE/29), 5 (NY00SE/30, 10A (NY00SW/38), RCF1 (NY00SE/35), RCF2 (NY00SE/36), RCF3 (NY00SE/37), RCM1 (NY00SE/41), RCM2 (NY00SE/40) and RCM3 (NY00SE/39).
Massive, homogeneous, pumice-rich to pumice-poor eutaxitic and parataxitic lapilli-tuff with "autobrecciated" zones and basal lithic breccia.
155m in type section (120m - bh4; 150m in RCF3)
At sharp upward change to pyroclastic breccia of the Sides Farm Member.
Todber Freestone Member
TOF
At the base of the lowest ooidal limestone.
Across the northern half of the Shaftesbury Sheet (313).
Oolitic limestone, fine- to medium-grained, well sorted, commonly cross bedded, sparingly fossiliferous.
At the top of the non-bioclastic, or evenly bedded, ooidal limestone.
Two-Foot Coal (North Staffordshire)
TOFC
Tobar Fuar Limestone Member
TOFU
Lower limit of limestone overlying graphitic semipelitic to pelitic schist of the Badenyon Schist and Limestone Formation.
South of the Lecht in the valleys of the Loinherry/Camore Burn, west of the Lecht Road (A939) and east of the road in the valley of the Milltown Burn. Upper Donside, Aberdeenshire.
Crystalline limestone, grey, lenticular, bedded, originally fragmental, commonly with pyrite, locally with tight folding. Calcite segregations in parts. Generally blocky (massive to flaggy).
To c.20m
Upper limit of limestone overlain by semipelite and highly micaceous psammite, slaty, blue-grey, of the Badenyon Schist and Limestone Formation.
Torbanehill Gas Coal
TOGC
Top Hosie Limestone
TOHO
Generally seen as a conformable change from marine mudstone underlying the Top Hosie Limestone above a thin coal or seatearth within the Lower Limestone Formation that forms the top of the second Hosie Limestone cycle. It is not uncommon for Second and Top Hosie limestones to be separated only by marine strata, or even to become fused together.
Throughout most of the outcrop of the Carboniferous of the Midland Valley of Scotland, but locally difficult to recognize in Ayrshire and Lanarkshire where the Hosie limestones join together as the McDonald Limestone in the shelf setting, and in the on-delta setting in Fife, where it may have been removed by erosion, or simply undeveloped.
A grey, fine-grained, very argillaceous, slightly crinoidal bioclastic "cementstone" type of limestone, interpreted to be of marine origin.
Generally between 0.11m and 1.30m, or less, in the Airdrie, Falkirk and Glasgow districts. This limestone fuses with the Second Hosie Limestone in the west Glasgow district and at Wairdlaw [NS 995 731] in the Bathgate Hills.
Generally seen as a conformable change to marine mudstone that passes up into deltaic arenaceous deposits of the Limestone Coal Formation.
Tormore Psammite Formation
TOM
Tom Anthon Mica Schist Formation
TOMA
Tom Na Fianaig Formation
TOMF
Tomintoul Group
TOMI
Tonga Granite
TONG
Toomebridge Sandstone Formation
TOOM
Gradational with red mudstones and sandstones at the top of the underlying Drumcullen Formation.
Sub-surface on the northwest shore of Lough Neagh.
Sandstone, orange-red, up to medium-grained with some coarse sand grains, sub-angular to well rounded, weakly cemented; thin siltstone and mudstone layers, brick-red.
Sharp contact with red mudstones and siltstones at the base of the succeeding Mercia Mudstone Group.
Toories Pluton
TOOP
Top Rock
TOP
Top Bright Coal (Vale Of Belvoir)
TOPB
Top Furnace Coal (South Lancashire)
TOPF
Top Rock (Birmingham)
TOPR
Tor Formation
TOR
Torridge River Terrace Deposits, 1 Member
TOR1
Torridge River Terrace Deposits, 2 Member
TOR2
Torridge River Terrace Deposits, 3 Member
TOR3
Torridge River Terrace Deposits, 4 Member
TOR4
Torridge River Terrace Deposits, 5 Member
TOR5
Torridge River Terrace Deposits, 6 Member
TOR6
Torridge River Terrace Deposits, 7 Member
TOR7
Torridge River Terrace Deposits, 8 Member
TOR8
Torridge River Terrace Deposits, 9 Member
TOR9
Top Robins Coal (South Staffordshire)
TORC
Tore Hill Pluton
TOREH
TONALITE, PORPHYRITIC TO GRANODIORITE, PORPHYRITIC
Torulian Limestone Member
TORL
Torphins Intrusion
TORP
Torridge Valley Formation
TORR
Unconformable upon bedrock of Early and Late Carboniferous and Permian age and upon the Dartmoor Granite.
The entire catchment of the River Torridge and its tributaries, including the rivers Okement and Waldon, between Dartmoor and Bideford, Devon.
The formation encompasses the fluvial, lacustrine and organic deposits of the River Torridge and its tributaries. It includes floodplain alluvium and the deposits of eight river terraces. The floodplain alluvium comprises soft poorly sorted clays, silts and fine-grained sands, with bodies of peat, overlying sands and subrounded gravels. The terrace deposits dominantly comprise silty and sandy pebbly clays but include sands and gravels and silts. The clays are largely derived from Upper Carboniferous mudstone bedrock. Gravels are dominantly formed of rounded pebbles up to 50mm in diameter of Upper Carboniferous sandstone but also include vein quartz and Lower Carboniferous limestone and chert. Boulders of Dartmoor Granite and quartz-feldspar-tourmaline rock are common in the upper reaches of the River Okement and its tributaries. The terraces contain alluvial tin ore (cassiterite).
Townhouse Sandstone
TOS
Tabular Or Sheet Deposits
TOSD
Variable lithology. Any deposit with a tabular or sheet-like form. [Generic description].
Tonlegee Shale Member
TOSM
Tottenhill Gravel Member
TOTL
The Tottenhill Sand and Gravel Member unconformably overlies silts and clays of the Nar Valley Clay and the Nar Valley Freshwater Beds with a sharp lithological change. Elsewhere it locally overlies chalky till of uncertain affinity (but probably Lowestoft Formation or Sheringham Cliffs Formation).
Limited to the area around Tottenhill, Norfolk.
The Tottenhill Sand and Gravel Member is a complex sequence of sands and gravels, dominated by flint. They were formerly well exposed in the Tottenhill Gravel Pit, where two units were evident. A lower unit up to 5m thick consists of medium to coarse, poorly sorted, mostly angular gravels with cross-bedding dipping steeply (20 to 25 degrees) to the southeast, and with frost wedge and cryoturbation structures. The gravels contain numerous pebbles of woody and reedy peat, soft brown clay, varved clay and Jurassic and Lower Cretaceous erratics. The upper unit is about 3.5m thick and consists of fine- and medium-grained gravels, which are better sorted than the lower gravels, and have a planar cross-bedding dipping westwards at 8 to 15 degrees. The junction of the two units is marked by a well-defined, slightly uneven surface along which the upper gravels truncate cryturbation and bedding structures in the lower gravel. The lower unit has no known outcrop.
Up to 14m
The Tottenhill Sand and Gravel Member is locally overlain by a cryturbated mixture of dull red-brown, sparsley stony, sandy clay and gravelly sand. This might be a till, although Lewis and Rose (1991) have interpreted this as evidence of a period of temperate-climate soil formation, followed by cold climate disturbance.
Tormentil Volcanics
TOVO
Terrace Of Warp
TOW
Terrace deposit of artificially induced alluvium. [Generic description: 'TMOS' Procedures].
Littlebeck Formation
TPA
Tyrone Plutonic Group
TPG
Mid-Ulster, Co.Tyrone c.10km west of Cookstown.
Hornblende gabbro and diorite with cross-cutting invasive dyke systems.
Taplow Gravel Formation
TPGR
Rests with sharp base on bedrock geology, eg London Clay.
Average 5m, locally to 9m
Third Post Limestone
TPLS
Top Plessey Coal (Northumberland)
TPLY
Tumulites Pseudobilinguis Marine Band [Obsolete Code: Use E1b2]
TPMB
Topped Mountain Sandstone Formation
TPMS
Not seen; everywhere faulted.
Southern sector of the Fintona Block, Northern Ireland.
Sandstone, cross-laminated, grey, pink-purple stained, fine- to coarse-grained, subarkose with interbedded grey-red and green siltstones and mudstones; carbonate nodules.
First appearance of conglomerates and pebbly sandstones marks change to Ballyreagh Conglomerate Formation.
Trwyn Pendalfa Mudstone Member
TPMU
Templepatrick Rhyolite
TPR
Tarfside Psammite Formation
TPS
Top of Deeside Limestone Formation - change from dominant calc-silicate rock to dominant psammite.
(i) Deeside: North of Mount Battock Granite, south of Deeside Limestone Formation [NO 420 957 to 560 955] (ii) Tarfside: South of Mount Battock Granite, north of Glen Effock Schist Formation [NO 405 846 to 570 817]. (iii) Sheet 65E. Strip bounded to east by Water of Tanar Limestone Formation, to west by the Glen Effock Schist Formation [NO 415 952 to 370 800]. Southern boundary is lateral transition to Cald Burn Gneiss Formation.
Psammite, much of it quartzitic, and calcareous psammite, with minor pelite and semipelite, passing up into mixed psammite and semipelite: beds of meta-limestone and calc-silicate rock throughout.
(i) Probably no more than 500m north of Mount Battock Granite (top not seen): (ii) 1250 - 2750m south of Mount Battock Granite; upper figure probably overestimate, due to tectonic thickening of Glen Turret Member.
Base of Glen Effock Schist Formation - change to semipelite with much psammite and pelite: marked by incoming of magnetic horizons within the semipelites.
Top Soft Coal (Nottingham And Derby)
TPSC
Tarporley Siltstone Formation
TPSF
The boundary is diachronous, in most areas interdigitating with the underlying Sherwood Sandstone Group. Within individual sections the boundary is drawn arbitarily within an interbedded, generally upwards-fining gradation from the coarse-grained, cross-stratified sandstone of the underlying Sherwood Sandstone Group to the micaceous mudstone, siltstone and fine sandstone of the Tarporley Siltstone (Warrington et al., 1980). In the Nottingham area, the base of the unit is abrupt and unconformable; it is marked by a patchily distributed basal conglomerate up to 1m thick with a strong calcareous cement (Howard et al., in press; Howard, 2003). At outcrop, the boundary is typically marked by a change in soil type from the sandy soils of the Sherwood Sandstone Group to the more clayey, slightly reddish brown soils (commonly containing fragments of fine-grained micaceous sandstone) associated with the Tarporley Siltstone Formation. A concave break of slope may mark the boundary in some areas.
The outcrop extends northwards from Warwickshire through Staffordshire, Cheshire, Leicestershire and Nottinghamshire; the formation is also proved by numerous boreholes in the adjacent subcrop. To the south of a line between Wolverhampton and Coventry, the formation passes laterally by interdigitation into the uppermost part of the Sherwood Sandstone Group and has not been differentiated by mapping. To the north of the outcrop, the formation passes laterally into mudstone-dominated facies. It appears to be absent in north and west Lancashire and the central part of the East Irish Sea Basin (Jackson et al., 1987; 1995), where the Sherwood Sandstone Group is directly overlain by a silt- and sand-poor sequence typical of the bulk of the Mercia Mudstone Group farther south. However, in the Solway and Carlisle Basins, a "Waterstones lithology" has been tentatively identified (Jackson et al., 1995) and may correlate with a grey siltstone facies in adjacent offshore areas. On the East Midlands Shelf, although the formation is identified in boreholes in the Grantham and Grimsby districts (Berridge et al., 1999; Berridge and Pattison, 1994), it cannot be identified confidently farther north in the Kingston-upon-Hull district (Gaunt et al., 1992). The lateral transition into mudstone-dominated facies in Eastern England has been described by Smith and Warrington (1971). Coeval strata in the Southern North Sea Basin are in mudstone- and halite-dominated facies (Johnson et al., 1994).
Heterolithic, comprising interlaminated and interbedded siltstones, mudstones and sandstones in approximately equal proportions. The siltstones are micaceous and interlaminated with mudstones or sandstones; most of the mudstones appear structureless with a blocky habit. The sandstones are mostly very fine- to fine-grained, well sorted, and micaceous. They are typically cemented by ferroan calcite or dolomite. Sandstone beds are commonly less than 0.5m thick, though composite units, consisting of several individual sandstone beds, may reach over 5m thick. Intraformational mudclast conglomerates are common, with mudclasts concentrated at the bases of sandstone beds. Conglomerates with extraformational pebbles are rare and tend to be less than 1m thick; the "Waterstones Conglomerate" of Nottinghamshire is a notable example [Elliott, 1961]. Most mudstone and siltstone beds are reddish brown, though green-grey mottles and laminae are common. Gypsum occurs sporadically in the mudstones as small nodules. The sandstones are grey-brown and substantially paler than the siltstones and mudstones. Bedding is generally planar. Most beds are tabular and laterally extensive, though channel sandstones occur and typically have incised, erosional bases. The upper surfaces of sandstones and coarse siltstones are commonly wave or current rippled; in section the sandstones are usually planar or ripple-laminated, and exhibit sporadic rootlets.
Varies from 20 to 60m in the East Midlands, 50 to 70m in Staffordshire to a maximum of 220m in Cheshire. The 276m-thick succession logged in the Ashley Borehole, Cheshire (Taylor et al., 1963) probably includes a substantial thickness of the overlying Sidmouth Mudstone Formation.
The boundary is diachronous, and interdigitates with the overlying Sidmouth Mudstone Formation. Within individual sections the boundary is drawn arbitrarily within an upwards-fining, interbedded succession at the level where mudstones of the overlying Sidmouth Mudstone Formation predominate over the siltstones and sandstones of the Tarporley Siltstone Formation. At outcrop, the boundary is typically marked by a change in soil type from the brown, sandy clay soils of the Tarporley Siltstone Formation to the clayey, markedly reddish brown soils of the Sidmouth Mudstone Formation. A concave break of slope is associated with the boundary in some areas.
Torpoint Formation
TPT
The Torpoint Formation dies out in the Liskeard area on the west side of the Plymouth 348 Sheet but continues eastward onto the Ivybridge (349) Sheet.
Brownish purple to purplish red cleaved mudstone and fine-grained siltstone, yellowish to blue-green, fine- to coarse-grained siltstone and fine-grained sandstone. Colour mottling and transposition of colour by fluids may occur near faults. Green reduction spots are sporadically formed.
In the Tavy Basin: A transition from the purplish red slaty mudstone of the Torpoint Formation into the greenish grey slaty mudstone of the Tavy Formation. Also interdigitates with the Saltash Formation in the South Devon Basin.
Three-Quarter Coal (Northumberland And Durham)
Threequarters Coal (Leicestershire)
TQC
Three Quarter Coal (Midgeholm)
TQCO
Toward Quay Grit Member
TQGR
Torquay Limestone Formation
TQL
Three Quarter Coal (Titterstone Clee)
TQTC
Thornhill Rock
Generally a fine-grained, thickly-bedded and cross-bedded sandstone, commonly split with a thin coal and mudstone around Batley
To c.40m
Traboyack Formation
TRA
Faulted contacts.
Red-purple sandstones, mudstones and conglomerates with high magnetic susceptibility.
Up to about 1200 m thick.
Transition Member
TRAN
Traprain Law Laccolith
TRAP
Trichrug Formation
TRB
South Llandovery area, southern Wales.
Traeth Bach Beds
TRBB
Trawenagh Bay Pluton
TRBP
Rb-Sr whole rock 405 +/- 3 Ma (Halliday et al., 1980); U-Pb monazite 411 +/- 2 Ma (Halliday et al., 1980).
Trencherbone Rock
TRBR
Trecoed Beds
TRBS
Tupton Roof Coal (Nottingham)
TRC
Triscombe Beds
TRCB
Trimingham Chalk
TRCK
Trencher Coal (Warwickshire)
TRCO
Tidal River Or Creek Deposits
TRD
Variable lithology. Mainly silt and clay; locally may contain peat, sand and gravel; infilling tidal rivers or creeks. [Generic description].
Trendrean Mudstone Formation
TRDN
Trefawr Formation
TRE
Trench Coal (Bristol Area)
TREC
Trefechan Formation
TREF
Tregaron Formation
TREGN
Defined by the base of bed 3 (Hibbert and Switsur, 1976) where peats replace Late Devensian muds and lacustrine clay. Corylus is first represented continuously in the profile, and a C14 date of 9750+/-220 (11 6000 cal)BP was obtained. Locally unconformably overlies Late Devensian Head deposits (Godwin and Mitchell, 1938) and Plynlimon Till Formation.
Tregaron Bog, Ceredigion (Wales).
Peat; the margins of the formation are more silt-rich.
Bowen (1999) applied the name/definition to all peat deposits in Wales; here the term is redefined toinclude only the peats of Tregaron Bog.
Ground surface, locally unconformably overlain by deposits of the Teifi Valley Formation.
Tremadoc Rocks (Undifferentiated)
TREM
Trecoed Sandstone Member
TRES
Treffgarne Volcanic Formation
TREV
Drawn at base of Treffgarne Volcanic Group where it rests unconformably on green/grey micaceous shales, sandy mudstones and grits of the Treffgarne Bridge Beds.
Cleddau Valley, south-west Dyfed.
Blue-green keratophyric or andesitic lavas, basaltic andesite, purple, red and green andesitic tuffs and volcanic agglomerate.
Drawn at conformable upward passage from tuffs and volcanic agglomerate of Treffgarne Volcanic Formation to shales, tuff, ashy sandstone and rhyolitic tuff of the Brunel Beds.
Treffynnon Group
TRF
Late Neoproterozoic to Early Ordovician.
Not defined - contacts mostly faulted.
Felsic pyroclastic and extrusive rocks interbedded with shallow water sediments. Lithologies comprise volcanastic breccias, crystal tuffs, porphyritic rhyolitic lavas and thinly interbedded quartzose sandstones, tuffs, lapillistone and mudstone.
Unknown - at least 15m proved in boreholes around Llandeloy.
Unknown - unconformably overlain by mudstones and sandstones of the Solva Group (Cambrian)
Top Ryhope Five Quarter Coal (Northumberland)
TRFQ
Transition Group (Devonian-Carboniferous)
TRG
Trenchard Formation
TRGP
The basal conglomerate of the Trenchard Formation rests unconformably upon the quartzitic sandstone of the Cromhall Sandstone Formation.
Restricted to the northern part of the Forest of Dean coalfield, approximately north of a line from Mailscott Wood, Coleford (SO 562 142) to Ruspidge, Cinderford (SO 649 119).
Grey or pinkish grey quartzose sandstone. Quartzose conglomerate beds are common at the base of the formation, increasing in thickness and clast size towards the north.
Up to 120 m thick in the north of the Forest of Dean Coalfield.
Taken at the base of the lowermost sandstone of "Pennant"- type (lithic arenite) of the Pennant Sandstone Formation, resting conformably above coarse-grained sandstone of the Trenchard Formation. This is a significant change to the Trotter (1942), who included all strata below the Coleford High Delf as part of his Trenchard Group.
St John's Rhyolite Formation [Redundant Code: Use Bjr]
TRH
Triassic Rocks (Undifferentiated)
TRIA
Tridwr Formation
TRID
Triffleton Group
TRIF
Trimingham Clay Member
TRIMC
The lower boundary of the Trimingham Clay Member is gradational with the Bacton Green Till Member, representing a lithological change from stratified sandy diamicton to laminated silts and clays.
Coastal cliff sections between Trimingham and Sidestrand, northern Norfolk.
The Trimingham Clay Member consists of rhythmically laminated clays and pale grey silts.
Up to 2.2m have been observed at the stratotype.
The nature of the upper boundary between the laminated silts and clays (Trimingham Clay Member) and the overlying sandy facies of the Trimingham Sand Member is sharp and irregular.
Trimingham Sand Member
TRIMS
Erosional contact with the underlying Trimingham Clay Member, represented by a lithological change from clay to sand.
Coastal cliff sections between Trimingham and Sidestrand, north Norfolk.
Horizontally bedded and massive sand with sporadic ripple structures.
A maximum of 0.3m is exposed at the stratotype locality.
The sand facies of the Trimingham Sand Member is truncated by the till facies of the Weybourne Town Till Member. In places that sands have been sheared and dragged into small isoclinal fold structures.
Tregonning Intrusion
TRIN
Lithium-mica granite.
Triassic Rocks And Jurassic Rocks (Undifferentiated)
TRJ
Top Rock Bed
TRK
Uppermost Turonian to Coniacian. P (S) plana to M cortestudinarium zones
Conformable within the Kensworth Nodular Chalk Member at an indistinct boundary marking a significant increase in nodularity between 2 and 3 m above the uppermost hardground of the Chalk Rock Member.
The Chilterns within Hertfordshire and possibly Buckinghamshire.
Hard cream limestone with scattered brownish phosphatic nodules commonly green-coated at the top. Mineralised hardground or chalkstone bed.
0.8 to 1.0m in Cambridgeshire. 0.3m to 1.0m in Chilterns to where it is essentially confined.
Conformable at the hardground surface marked by the change from mineralised hard chalkstone to soft white smooth chalk.
Tarland Intrusion
TRLD
Termon River Limestone Formation
TRLF
Abrupt, but conformable change from deltaic facies, clastic sediments at the top of the underlying Claragh Sandstone Formation to peritidal carbonates and thin shales of the Termon River Limestone Formation.
The Kesh-Omagh area of the northwest Carboniferous basin of Ireland.
Limestone, blue-grey, sparsely bioclastic, crinoidal, fine- to medium-grained containing pellets, micritised bioclasts, oncolites and ooliths, interbedded with dark grey to grey-green shale and brown, medium-grained sandstone.
Change from 'clean' peritidal carbonates of the Termon River Limestone Formation, to sandstones and sandy limestones of the Gortnaree Sandstone Member of the Ballyshannon Limestone Formation.
Trawden Limestone Group
TRLI
A conformable base of argillaceous dolostone (Holme Chapel Borehole) or dark grey to black blocky claystone ,grading upward into medium to dark grey micritic limestone of the Trawden Limestone Group, above pale grey medium-grained sandstone with siliceous and dolomitic cement ,interbedded with medium to dark grey fine-grained sandstone, with an argillaceous and dolomitic matrix of the Roddlesworth Formation (Roddlesworth Borehole). Evident as a sharp change from highly serrated and high gamma responses below, and generally lower and more subdued gamma ray responses above the boundary.
Not proved at outcrop, but proved in the subsurface over the Central Lancashire High, a SW-NE structure extending from Chorley [SD 60 20] to Bradford [SE 10 30], bounded to the NW by the Pendle Fault and the Bowland Basin, and to the SE by the Rossendale Basin.
A pale to dark grey, typically darker towards the base, micritic to crystalline limestone, with subordinate partings and thin beds of calcareous mudstone, locally abundant chert, crinoid and brachiopod debris. A pale grey, fine- to medium-grained dolostone is locally present, near the base of the group.
Thickest development of 1055 m in the type locality, and 422 m in the Holme Chapel Borehole.
A conformable base of overlying dark brown to black, calcareous and carbonaceous claystone to siltstone, of the Bowland Shale Formation above pale grey limestone of the Trawden Limestone Group.
Trostrey Limestone Member
TRLS
Trefriw Mudstone
TRM
Trencherbone Coal (South Lancashire)
TRMC
Thornilee Slates
TRN
Troughton Beck Member
TRO
Trochrague Vent
TROC
Volcanic breccia.
Trolley Coal (Bristol Area)
TROL
Trossachs Group
TROS
Tresham Rock Formation
TRR
Sharp change up from grey mainly calcareous mudstone of the Fuller's Earth Formation (locally known as theHawkesbury Clay) or, where absent, erosive non-sequence, with a sharp upward change from bioclastic limestone of the Dodington Ash Rock Member (Fuller's Earth Formation) into fine-grained limestone.
Outcrop: Dodington, Gloucestershire, where the Tresham Rock passes into the Fuller's Earth Formation, to Kingscote, Gloucestershire, where it passes into the Athelstan Oolite Formation. Subcrop: Biddestone to Milbourne (Malmesbury), Wiltshire (Wyatt, 1996).
Limestone, calcilutite, pale grey, bioturbated, silici-muddy, poorly fossiliferous; passing up into whitish grey, less silici-muddy calcilutite. Lenses of ooidal limestone occur in places, at the base (Hen's Cliff Oolite of Arkell and Donovan, 1952) and in the upper part. Subordinate calcareous mudstone beds occur in places. Passes laterally by interdigitation southwards into the predominantly mudstone sequence of the Fuller's Earth Formation, and by increase in ooid content northeastwards into the Athelstan Oolite Formation.
0 to about 17m.
Rapid passage up from calcilutite with ooidal limestone lenses into massive ooid-limestones of the Athelstan Oolite Formation or, locally, where that formation is absent, well-bedded ooid-limestone of the Chalfield Oolite Formation, or in the south, a sharp upward change into grey mudstone of the Lansdown Clay (Fuller's Earth Formation).
Trilobite Dingle Shales
TRS
Treworgans Sandstone Member
TRSA
Conformable within the Grampound Formation.
Present at least along the northern margin of the Mevagissy (353) sheet and in the northeast corner of the Falmouth (352) sheet areas.
Sandstone beds to 6m (grainflows) with interbeds of grey slaty mudstone and yellow-green laminated siltstone.
Triassic Sandstone
TRSD
Trinucleus Shales
TRSH
Tircrevan Sandstone Member
TRSM
Table Rocks Sandstone
TRSS
Trefriw Tuff Formation
TRT
?Caradoc. Younger than the youngest Caradoc sedimentary rocks in the area (Nod Glas Formation) and overlain by the Ashgillian Conwy Mudstone Formation.
Conformably overlies black mudstones of the Nod Glas Formation.
Highly weathered, medium to coarse basaltic tuff, hyaloclastite and agglomerate with interbedded volcaniclastic sediments.
Overlain by grey mudstones and siltstones of the Conwy Mudstone Formation.
Traligill Till Member
TRTI
Unconformable on bedrock, predominantly on Durness Group limestone and An-t Sron Formation, sandstone and mudstones.
Patchy, discontinuous extent across the outcrop of the Moine Thrust Belt, between Ullapool and Eriboll. Occurs exclusively to the west of the Moine Thrust (except on north edge of Cromalt Hills [NC 20], and predominantly on Durness Group limestone.
Orange-brown to dull grey, poorly sorted, sandy, clay-rich, matrix-supported diamicton with boulders. The till shows some evidence of subglacial deposition; namely edge-rounded, striated clasts and high consolidation. Clasts are lithologically diverse; but typically include Eriboll Formation sandstone (Cambrian quartzite), An-t Sron Formation sandstone and mudstone, Moine Supergroup rocks and/or various minor igneous rocks to greater or lesser degrees. Clasts of Durness Group limestone are rare but may exist near the till-bedrock boundary. Much of the clay-rich matrix is probably derived from local muddy dolostones and mudstones. Sporadic clasts of Torridon Group sandstone and Lewisian gneiss may also be present, particularly in the River Traligill catchment. The till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older.
Variable; 0.2 to 8m. (maximum observed thickness).
Trentham Tonstein (North Staffordshire)
TRTO
Trelowgoed Volcanic Formation
TRV
From approximately 200m west of Upper Trelowgoed Farm (SO 0845 6312) to 200m south east of Alpine Bridge (SO 0905 6313), and northwest to north of New Barn Farm (SO 0958 6213).
Volcanic breccia and tuff.
Sharp - unconformably overlain by late Llandovery mudstones.
Trent Valley Formation
TRVA
Middle Pleistocene to Holocene (Post-Anglian; MI Stages ?11 or 9 to 1).
Unconformable, commonly channelled base on pre-Quaternary bedrock or glacial deposits (mostly Anglian Wolston Formation, or, in the uppermost Trent, Devensian Stockport Formation).
Modern Trent catchment (excluding the Soar [and the Idle]).
Fluvial terrace and alluvial deposits of the River Trent from its source to the Humber, and those of its tributaries excluding Soar [and Idle], and possibly others, pending review. The formation includes deposits of an older course via the Lincoln Gap. Mainly sand, gravel and mud; divided (in type area) into six principal "terrace" members (Eagle Moor, Etwall, Egginton Common, Beeston, Holme Pierrepont and Hemington members), plus Holocene alluvium (the Trent Member of Bowen, 1999) and with local named organic deposits. Includes contemporaneous head, colluvium and soil deposits. Gravel composition varies substantially throughtout the catchment but is generally dominated by "Bunter" pebbles derived ultimately from the Triassic Sherwood Sandstone Group, together with a proportion of material from local bedrock sources and from glacial deposits of the Anglian Wolston Formation and, in the youngest terraces, from the Devensian Stockport Formation.
Note that the Idle, which now meets the Trent just below Gainsborough, was a tributary of the Don before artificial drainage works. Hence it is excluded from the Trent catchment for the purposes of this definition. Also for the purposes of this and related definitions the Upper Trent is taken as being above the confluence of the Dove and the Lower Trent is that part downstream of Newark. The section between these tow limits is the Middle Trent.
Trent-Witham Catchments Subgroup
TRWCA
Unconformable contact with units of the Albion Glacigenic Group and bedrock.
The catchments of the valleys of the rivers Trent and Witham, Soar and Bain and their tributaries south and east of the Peak District and including Lincolnshire.
The Trent-Witham Catchments Subgroup comprises a suite of fluvial, lacustrine, mass movement (head), periglacial and organic (peat) deposits. The subgroup includes the alluvium and river terrace deposits of the Trent and Witham valleys and pre-diversionary valleys (Trent Valley Formation), the Soar valley (Soar Valley Formation) and the Bain valley (Bain Valley Formation) and their respective tributaries, including the Derwent (Derbyshire), Dove and Devon. The fluvial deposits contain clasts derived from rocks cropping out in the Midlands of England (mainly Triassic "Bunter" sandstone, ironstone and chert, Carboniferous sandstone, Lias siltstone, limestone and ironstone).
Generally less than 5m. Individual terrace deposits up to 9m thick.
Generally the ground surface, but units of this group interfinger locally with units of the Great Britain Coastal Deposits Group.
Top Ryhope Little Coal (Northumberland And Durham)
TRYL
Top Shuttles Coal (South Lancashire)
TSC
Tarrant Chalk Member And Spetisbury Chalk Member (Undifferentiated)
TSCH
Tullos Clay Member
TSCL
Sharp, draped, undulating, unconformable contact with underlying massive, gravelly, silty, sandy, clay diamicton of the Hatton Till Formation.
The coast between Newburgh and Aberdeen on 1:50K Sheet 77.
Silt and clay, reddish brown and olive-brown, mainly massive, but with some laminae of sand.
The present ground surface, or gradational, conformable contact with younger alluvial deposits, but not capped by till as are parts of the parent Formation.
Teesside Clay Formation
TSDC
Varves in these laminated clays have been tentatively "wriggle-matched" with the late glacial Greenland ice core record, and dated very approximately by thermoluminescence to 18,365 cal ka BP.
Uneven, conformable, draped contact with underlying dark brown, stony silty sandy clay diamicton of the Blackhall Till Formation (possibly of the Horden Till Formation).
Widespread beneath the Teesside Lowlands to an altitude od about 92m OD.
Red or reddish brown pebbly sandy silty clay containing well dispersed pebbles mainly of limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone), with some Carboniferous lithologies (sandstone, mudstone, limestone, coal), typically overlying thinly laminated silts and clays, or locally overlying sand. Varves in these laminated clays have been tentatively "wriggle-matched" with the late glacial Greenland ice core record, and dated very approximately by thermoluminescence to 18,365 cal ka BP.
To 9.1m
Unevem, erosional contact with overlying alluvial or estuarine sands, silts and clays.
Ton Siltstone Formation
TSF
Tintern Sandstone Formation
TSG
Drawn at base of Tintern Sandstone Group where it rests conformably on quartz conglomerate of the Quartz Conglomerate Group. (Correlative of Tintern Sandstone Group and Quartz Conglomerate Group- Portishead Beds).
Forest of Dean, Gloucestershire.
Buff-yellow sandstone with local lenticles of pebbles and subordinate marl partings.
Up to 75m approx.
Drawn at conformable upward passage from buff-yellow sandstone of Tintern Sandstone Group to limestone of Lower Limestone Shale Group.
Temeside Mudstone Formation
TSH
The base of the mudstones and siltstones resting conformably on Downton Castle Sandstone.
Wales Borders and South Staffordshire.
A green to olive mudstone and siltstone with subsidiary green to brown micaceous sandstone and locally developed vertebrate bone beds.
Ranging from 12 to 27 m thick at Ludlow, and 10 to 13 m thick South Staffordshire.
The base of the red mudstones and siltstones of the overlying Ledbury Formation.
Threshthwaite Crag Tuff Member
TSHC
Top Hosie Limestone And Second Hosie Limestone
TSHL
This is a composite or generalised description of TOHO and SHLS Hosie Limestones, used where the indvidual limestones cannot be recognised.
Teirw Siltstone Formation
TSI
Conformably overlies rocks of the Swch Gorge Tuff Formation (qv).
Grey, thinly laminated to pervasively bioturbated siltstones and interbedded mudstones, with local massive, lenticular sandstones and channelised intraformational mudstone conglomerates and a localised tuff member, the Pen Bwlch Tuff.
210 to 250m
Conformably overlain by rocks of the Pandy Tuff Formation (qv).
Tanderagee Siliceous Ironstone Formation
TSIF
Three Sisters Ignimbrite Member
TSIG
Tredorn Slate Formation
TSL
U. Palmatolepsis marganifera to L. Velifer Biozone.
From Tregardock to south of South Petherwin, north Cornwall.
Greenish grey quartz-chlorite-mica slate, locally interbedded with thinly bedded, commonly lenticular bioclastic limestone and dolomite beds, up to 0.15m thick, and with sandstone, siltstone and rare tuff beds.
500-800m (estimated structural thickness).
Thanet Sand Formation, Lambeth Group And Harwich Formation (Undifferentiated)
TSLH
Trysull Silt Formation
TSLSI
Unconformable on sand and gravel of the Seisdon Sand and Gravel Formation.
A heterogeneous, fossiliferous sequence of silt, clay, sand, clayey sand, gravel and organic-rich horizons. Strong iron and manganese staining along some horizons.
2.8 to 5m
Either the ground surface or underlies till of the Stockport Glacigenic Formation.
Tullyclevaun Shale Member
TSM
Tranent Splint Coal
TSP
Temeside Mudstone Formation And Raglan Mudstone Formation (Undifferentiated)
TSRG
Trehills Sandstone Member
TSS
Transitional to slaty mudstone of undivided Tavy Formation.
Restricted to Plymouth (348) Sheet, east of the River Tamar.
Medium- to fine-grained sandstone interbedded with mudstone and micaceous laminated siltstone.
Top Saltwick Coal (Northumberland)
TSWC
36 Yard Coal (West Yorkshire)
TSYC
The Thirty Six Yard Band Coal is thin and worked only locally, although the associated fireclays are widespread, thick and of high economic importance.
Througham Tilestone Formation
Three Tarns Sandstone Member
TTA
Taken at the sharp base of bedded volcaniclastic sedimentary rocks where these overlie pyroclastic rocks of the Lingmell Formation, and locally, the Airy's Bridge Tuff Formation and Scafell Dacite. The contact is gradational and arbitrary where the upper part of the Lingmell Formation has been reworked subaqueously
Bell Crags, Thirlmere to Seathwaite (Borrowdale) Fell, and from Pike de Bield to the Langdale Pikes, Cumbria
White-weathered laminated and thinly bedded fine-grained volcaniclastic sandstone and siltstone
Up to 80m
Defined by the base of overlying volcaniclastic rocks including the Cam Crags and Bell Crags members
Terrington Beds
TTB
Mainly silt and clay (Salt Marsh and Tidal Creek Deposits). [Generic description: 1:50 k map margins].
Tupton Coal (Nottingham And Derby)
TTC
Tranent Three-Foot Coal
TTF
Triton Formation
TTHY
Tottlebank Member
TTK
Top Tilley Coal (Northumberland And Durham)
TTLY
Top Three-Quarter Coal (Northumberland And Durham)
TTQ
Tetragraptus Beds
TTRA
Torr Na Truim Semipelite Formation
TTRS
Not seen, cut out to the southeast by the Glen Truim Fault Zone
Southwest of Newtonmore, between the Creag Liath Fault and Glen Truim Fault Zone (Sheet 64W).
Semipelite, composed mainly of muscovite, biotite, quartz and feldspar, schistose and locally gneissose, with subordinate thin psammite, quartose semipelite and micaceous psammite bands. The psammite bands become more common towards the overlying Creag Dhubh Psammite Formation.
To 750m
Base of the Creag Dhubh Psammite Formation, where a predominantly schistose semipelite belonging to the Torr na Truim Semipelite Formation.
Twiston Sandstone Member
TTS
Lower boundary taken at sharp base of sandstone of the Twiston Sandstone Member where it rests conformably on mudstones and thin calcisiltites of the Hodder Mudstone Formation (undifferentiated) and unconformably on limestones of the Embsay Limestone Member in the Lothersdale Anticline.
Southern limb of Clitheroe Anticline [SD 82 44], and the Lothersdale Anticline [SD 93 44] and Skipton Anticline [SE 00 54] within the Craven Basin, northwest England.
Pale to dark grey, locally bioclastic siliceous, calcareous, thin- to thick-bedded, fine- to medium-grained sandstone.
To 4m.
Top is a conformable upward passage from sandstone of the Twiston Sandstone Member to mudstones and thin calcisiltites of the Hodder Mudstone Formation (undifferentiated). Upper boundary taken at the base of the lowermost mudstone in a succession dominated by mudstone.
Totternhoe Stone Member
TTST
Commonly indistinct conformable boundary with the underlying Lower Chalk (Chalk Marl) but there may be an erosion surface with concentration of phosphatic pebbles in base of Totternhoe Stone. May be difficult to locate, even in sections.
Known from Berkshire, Hertfordshire and Cambridgeshire where the Southern Province and Transitional Province overlap. Thickest development through Bedfordshire, Hertfordshire and Cambridgeshire, thinning again in Suffolk and Norfolk.
A distinctly harder unit in the Grey Chalk Subgroup (Lower Chalk). Typically brownish-grey, fine-grained calcarenite. Has been described as "sandy" because of coarse fossil fragments - not because of quartz sand grains. Thin to thickly bedded. Phosphatic in part with dark brown pellets a few mm across, up to nodules several cm across. Fossiliferous. Locally used as building stone.
0.3 - 6.0m in Hitchin district. Typically 1-2 metres thick but expanded sequences in synsedimentary channels may be up to 6m thick.
Commonly indistinct conformable boundary with the overlying strata of the Zig Zag Chalk Formation (Lower Chalk, Grey Chalk unit). Upward reversion to softer, finer grained more typical chalk or marly chalk. May be difficult to locate, even in sections.
32 Yard Coal (West Yorkshire)
TTYC
Turbot Anhydrite Formation (B) [Obsolete Code: Use Tban]
TUAN
Turbot Carbonate Unit
TUCA
Tufa
TUFA
Inorganic or organic calcium carbonate or silica deposited at or near springs and seepages. [Generic description: 'TMOS' Procedures].
Tullanaglare Mudstone Formation
TUG
Mudstones, laminated mudstones, siltstones, sandstones, quartz-clastic palaeosols, sandy palaeosols, calcareous, grey and green-grey, commonly mottled purple-red.
Defined by top of Drumgivery Limestone Member; abruptly overlain, probably disconformably, by Drumlish Conglomerate Formation.
Tullykevin Formation
TULL
Tullochroisk Semipelite Formation
TULS
Sharp contact with pale limestone of Strath Fionan Pale Limestone Formation.
Intermittently from closure of Errochty Synform [NN 713 670] to the south bank of Allt Kynachan [NN 7778 5722]. Not present east of the Loch Tay Fault, where its place is taken by the upper part of the Monzie Limestone and Schist Formation.
Lower part - rusty weathering pyritic semipelite with psammitic beds, non-graphitic; Upper part - semipelite, moderately graphitic, with biotite porphyroblasts.
0 - 200m in Sheet 55W; probably some tectonic thinning.
Sharp boundary with graphitic limestone at base of Blair Atholl Dark Limestone and Dark Schist Formation.
Tummel Quartzite Formation
TUMQ
Gradational boundary with underlying Bruar Psammite Formation.
From west of Meall a'Chataidh [NN 737 680] via Drumcroy Hill [NN 72 63] to core of Meall Reamhar Synform [NN 76 59]. On southern side of Meall Reamhar Synform outcrop continues via Creag nan Caisean [NN 783 605] to River Garry at Tomban [NN 825 654]; and on northern side of Meall Reamhar Synform via Craig of Tulloch [775 625] to An Teampan [787 653]. This limb is faulted out in the River Garry section, but the formation reappears north of Clunes and may continue as far as Dalinturaine [NN 76 69].
Dominantly white quartzite, in mappable layers up to 30m thick, interbedded with thicker units of laminated cleaved psammite rich in dune-bedding, ripple cross-lamination and soft-sediment deformation structures.
Gradational bundary with overlying Tummel Psammite Formation.
Twecher Upper Coal [Redundant Code: Use Twu]
TUPC
The Twechar Upper Coal was inadvertantly re-coded due to the mis-spelling that is preserved in this entry. The original code (TWU) is retained for future use.
Tullagh Point Pluton
TUPP
Unknown; likely to be one of c.400 Ma suite (O'Connor et al., 1987).
Tupton Rock
TUPR
Tummel Psammite Formation
TUPS
Gradational boundary with underlying Tummel Quartzite Formation.
On southern side of Meall Reamhar Synform from near Trinafour [NN 728 645] via north flank of Creag Kynachan [NN 769 579] to River Garry east of Tomban [NN 829 654]; on northern side of Meall Reamhar Synform from Meall a'Chataidh [NN 745 680] via Over Bohespic [NN 758 611] to Kinaldy [761 645]; also probably in River Garry around [NN 787 667].
Regularly and thick-bedded psammite, with dune-bedding and ripple marks. Minor schistose pelite.
Gradational boundary with Kynachan Quartzite Formation.
Turkeyland Member
TURK
18 to 25m
Tulaichean Schist Formation
TUSC
Top of Sron nan Dias Pelite and Limestone Formation.
Glen Shee district: north-west part of Sheet 56W, south-west part of Sheet 65W, south-east part of Sheet 64E and north-east part of Sheet 55E.
Schistose semipelite to psammite, garnetiferous, with graded bedding. Some layers and lenses of calcareous schists, calcsilicate rocks and quartzite.
Top of dominantly semipelitic rocks below the dominantly calcareous and graphitic rocks of the overlying Gleann Beag Schist Formation.
Top Usworth Coal (Northumberland And Durham)
TUSW
Tutbury Gypsum
TUT
Tutbury Gypsum [Obsolete Code: Use Tut]
TUTG
Tullyard Conglomerate Member
TUY
Within Bin Mountain Sandstone: Change from orange-weathering, fine-grained sandstones, below, to coarse conglomerate.
The Omagh area of the northwest Carboniferous basin of Ireland.
Conglomerate, matrix-clast supported, calcareous, very coarse sand (grit) matrix. Clasts up to 6cm, unsorted, rounded/subrounded, exclusively of white, milky and clear vein quartz.
Within Bin Mountain Sandstone: Top of conglomerate marked by 0.04m of black coaly shale and orange-weathering medium- to coarse-grained decalcified pebbly sandstone.
Thames Valley Formation
Sand and gravel; comprising the various river terrace deposits of the Thames. [Generic description: academic papers and BGS Memoirs].
Timber Vein Coal (Pembrokeshire)
TVCO
Timber Vein Coals (Undifferentiated) (Pembrokeshire)
TVCU
Tintagel Volcanic Formation
TVF
The lower boundary is taken at the sharp contact of tuffs, lavas and agglomerates of the Tintagel Volcanic Formation with the siltstone-striped mudstones of the underlying Barras Nose Formation.
Tintagel area (SX 06 89) to south of Launceston (SX 32 77), Cornwall.
Poorly sorted green fine-to coarse-grained basaltic calcareous tuffs with subordinate agglomerates and recrystallised carbonate-rich basaltic lavas. A few thin pink limestones occur scattered throughout the Formation.
The upper boundary is taken at the sharp contact of the finely banded dark to pale grey mudstones with thin siltstones of the overlying Trambley Cove Formation with the tuffs, lavas and agglomerates of the Tintagel Volcanic Formation.
Tyrone Volcanic Group
TVG
Faulted off.
Central Co. Tyrone, Northern Ireland.
Heterogeneous volcanic sequence: tuff, agglomerate, chert, with pillow lava horizons. Outcrop tectonised and metamorphosed in greenschist facies.
Estimated 4-5km
Top Victoria Coal (Northumberland And Durham)
TVIC
Troon Volcanic Member
TVL
Taken at the lithological change from sandy clastic strata of the underlying parent Passage Formation to basaltic lava.
Presently used within north and central Ayrshire.
Olivine microporphyritic basalt (Dalmeny type).
Taken at the base of the Ayrshire Bauxitic Clay Member, and defined as the lithological change from olivine basalt to bauxitic clay. The boundary is described as normally gradational.
Trevose Slate Formation And Rosenum Formation (Undifferentiated)
TVRN
Trevose Slate Formation
TVS
Eifelian to early Frasnian.
Conformable on Bedruthan Formation in cliffs [SW 8487 6993] near Queen Bess rock.
West of Bodmin Moor, to Pentire Point, Trevose Head and Park Head.
Pale grey silty laminated dark grey slate with regular beds of structureless siltstone, from 0.03-0.10m thick, interbedded. Sporadic thin beds of sandstone and limestone also occur, the latter particularly in the upper part of the formation.
Conformable with the overlying Harbour Cove Formation in the cliff facing Lower Merope Island [SW 8943 7700].
Timber Vein String Coal (Pembrokeshire)
TVSC
Tavy Formation
TVY
A transition into the Torpoint Formation. Pale green slaty mudstone of the Tavy Formation passing into purplish red slaty mudstone of the Torpoint Formation.
Defined on Sheet 348 but similar lithologies occur on: 335/336 (Tredom Slate Formation), 337 (Kate Brook Slate Formation), 338 and 339 (Kate Brook Slate Formation), 349 (Upper Devonian Slate).
Pale green and grey-green slaty silty mudstone with minor thin fine-grained sandstone beds and lenses. Medium- to fine-grained sandstone interbedded with mudstone and laminated siltstone constitute the Trehills Member.
A transition between the Tavy Formation and the Burraton Formation (grey slate) is observed in the vicinity of North Hooc Mine [4254 6608], and Holes Hole [425 655] in an inverted sequence.
Twinhoe Beds
Thirlwall Coal
TWC
Trichwart Coal (South Wales)
TWCO
Twechar Dirty Coal (Central Coalfield)
TWD
Tweed Catchments Subgroup
TWEED
Devensian to Holocene/Flandrian.
Unconformable contact with units of the Borders Glacigenic Subgroup and Southern Uplands Glacigenic Subgroup, and with bedrock.
The catchment of the River Tweed in northern Northumberland and the Scottish Borders including the northern drainage of the Cheviot Hills, the valley of the River Till, Teviotdale, Ettrick, Yarrow and Tweed valleys, and southern drainage of the Lammermuir Hills.
A suite of fluvial, lacustrine, mass movement (head), periglacial and organic (peat) deposits. The subgroup includes the alluvium and river terrace deposits of the River Tweed and tributaries (Tweed Valley Formation). The fluvial deposits contain clasts derived from rocks cropping out within the catchment of the River Tweed in northern Northumberland and the Scottish Borders (mainly Devonian to Carboniferous sandstone, siltstone with limestone, Lower Palaeozoic wacke sandstone and siltstone and varying proportions of volcanic rocks including Devonian andesites of the Cheviot Hills and Carboniferous basalts of the Kelso district).
Generally less than 5m. Individual terrace deposits up to 5m.
Generally the ground surface, but units of this subgroup locally interfinger with units of the Great Britain Coastal Deposits Group.
Treiorworth Formation
TWF
Twelve Foot Sandstone
TWFS
Two Foot Coal (Cumbria)
TWFT
Tower Wood Gravel Member
TWGR
Junction with underlying Upper Greensand marked by a sandy flint-free bed up to 12.5cm thick containing well rounded quartz and schorl pebbles (Pickard, 1949).
Great and Little Haldon Hill, south Devon; also occurs within dissolution pipes and hollows near Kingsteignton (Brunsden and others, 1976).
Unbedded gravel of large, closely packed, unabraded flints in a matrix of white, locally brown-stained, clay and a little sand.
Overlain by the Buller's Hill Gravel (fluvial flint gravel).
Top Whinmoor Coal (South Yorkshire)
TWHN
Twist Coal (North Staffordshire)
TWIC
Tarnbrook Wyre Marine Beds
TWMB
Townburn Sandstone Member
TWN
Unconformable on Lower Palaeozoic turbidites; locally rests on Lower Carboniferous strata.
Thornhill basin at Closeburn, Keir, Eccles, River Nith (Drumlanrig), Hapland, Fellend, Townhead and Morton Wood.
Medium- to coarse-grained sandstone with conglomeratic bands.
41.55m in Crichope Linn Borehole.
Overlain by Lower Coal Measures strata.
Twrch Sandstone Formation
TWR
The lower boundary, which is generally an unconformity, is placed at the base of the major development of quartz arenite and quartz pebble conglomerate. The Twrch Sandstone Formation rests with discordance on the underlying limestones of the Pembroke Limestone Group. In the south of the type area it rests unconformably on rocks of the Oystermouth Formation, in the north on rocks of the Oxwich Head Limestone Formation.
On the northern limb of the Pembrokeshire Coalfield westwards from Ragwen Point [SN 220 071] to just east of Druidston [SM 877 170] and eastwards along the north crop of the main South Wales Coalfield to near Blaenavon [SO 270 110], southeast to Machen [ST 225 895].
Quartz arenites and quartz conglomerates with minor mudstones.
To c.190m
The top is placed at a sharp junction, generally a disconformity, where the lowermost grey mudstones of the Bishopston Mudstone Formation overlie the highest quartz arenites of the Twrch Sandstone Formation. This boundary is exposed at [SN 7719 1508] in the Afon Twrch section.
Tunbridge Wells Sand Formation
TWS
See Lower Tunbridge Wells Sand Formation and Upper Tunbridge Wells Sand Formation.
The Lower Tunbridge Wells Sand Formation and the Upper Tunbridge Wells Sand Formation are separated by the Grinstead Clay Formation. Where the last named formation thins and disappears, the Upper and Lower Tunbridge Wells Sand formation often cannot be separated. In maps and memoirs this undifferentiated sand unit has been called 'Tunbridge Wells Sand'. The 'Tunbridge Wells Sand' cannot be a formation in the way that it is sometimes treated. The term 'Tunbridge Wells Sand Formation' [coded TWS] should be concidered an informal unit. This seems to be the best pragmatic approach, because the problem remains when naming the combined Tunbridge Wells Sands unit when separation into the individual formations is not possible. The epithet 'Formation' should not be used. For descriptions and definitions, see Lower Tunbridge Wells Sand Formation and Upper Tunbridge Wells Sand Formation.
Three Wells Sandstone Member
TWSA
Passes conformably and diachronously downwards and laterally to the south into the conglomerate of the undivided Catterline Conglomerate Formation, taken at point where sandstone becomes predominant in the upward sequence.
Between Castle of Allardice (NO 818 741), and the foreshore at Narrows Cottage, by Johnshaven.
Sandstone, pebbly sandstone and conglomerate with thin andesitic lavas.
From 46m to 85 m thick, increasing south-eastwards to 360m
Passes conformably and diachronously upward into conglomerate, taken where conglomerate becomes predominant in the undivided Catterline Conglomerate Formation.
Townsend Tuff Bed
TWT
Drawn at base of crystal tuff at base of FALL A.
South Wales and Welsh Borders.
Composite unit of air-fall tuff with three recognisable tuff beds and intervening mudstones.
Drawn at top of dust tuff at top of FALL C.
22 Yard Coal (West Yorkshire)
TWTC
Twechar Upper Coal (Glasgow Area; Central Coalfield)
TWU
Top Wheatworth Coal (West Yorkshire)
TWWC
Trwyn Yr Wylfa Member
TWY
Gradational upward change from coarse-grained sandstones of the underlying Pared Mawr Member.
Thickly bedded pale weathering sandstones, bioturbated and fine-grained.
See Unit revisions.
Conformable contact with the overlying cross-bedded, bioturbated muddy sandstones with granular clasts, of the Penrhyn Du Member.
Two Yard Coal (Warwickshire)
TWYD
Taldwyn Coal (South Wales)
TWYNC
Twenty Yard Rock (South Staffordshire)
TWYR
Taynton Limestone Formation
Top of highest significant mudstone in Fuller's Earth Formation or Sharp's Hill Formation, or passage from finer grained limestone of the Eyford Member, where present.
Stroud, Gloucestershire (where passes westwards near Stroud into finer grained limestones of Througham Member (Fuller's Earth Formation) and succeeding Hampen Formation; Sumbler, M G, Barron, A J M and Morigi, A N, 2000. To Brackley, Northants (where passes northeast into Wellingborough Member (formerly Upper Estuarine Limestone) of the Rutland Formation (Horton et al, 1987)).
White to pale brown, typically well-sorted medium- to coarse-grained, moderately to highly shell-detrital ooidal grainstone, locally fine- to very coarse-grained; medium to thickly well-bedded and cross-bedded, with thin shell-detrital marl seams and locally calcareous sandstone beds.
0-11m, locally possibly up to 15m, type area 6 to 8m
Passage upwards into fine-grained ooidal limestone and marls of Hampen Formation or mudstone, siltstone and limestone of the Rutland Formation.
Tynet Burn Fish Beds
TYBF
Trwyn Y Bwa Mudstone Member
TYBM
Caradoc (? Onnian).
Ty-Brith Mudstone Member
TYBR
Tyneholm Beds
TYBS
Tycwtta Mudstones Formation
TYC
Sharp incoming of less silty mudstones, with units of burrowed and laminated hemipelagites, above the coarse silty micaceous mudstones of the Yr Allt Formation.
Turbidite mudstones, thinly interbedded within packets dominated either by laminated or burrowed hemipelagites. Sporadic thin turbidite sandstones. Locally slumped.
Taken at base of first pebbly mudstone or conglomerate of overlying Allt-Y-Clych Conglomerate.
Top Yard Coal (Northumberland)
TYCO
Top Yard Coal (South Lancashire)
TYDC
Tyladu Coal (South Wales)
TYDUC
Trwyn Y Fulfran Formation
TYF
Late Comley to early St David's.
Underlain by coarse- to medium-grained green sandstones and interbedded siltstones of the Hell's Mouth Formation.
Manganiferous siltstones with fine- to medium-grained sandstones in thin to medium beds.
37m
Overlain by coarse-grained, thickly bedded turbidites of the Cilan Formation.
Torry Four Foot Coal (Fife)
TYFF
Tal Y Fan Volcanic Formation
TYFV
Rests on mudstones associated with the Lower Crafnant Volcanic Formation.
Restricted to the area of Tal y Fan, 5km north west of Dolgarrog.
Basalt lavas and pillow breccias with hyaloclastite, basaltic tuff; mudstone intercalations.
Overlain by part of the Nod Glas (= Cadnant Shales).
Ty'r Gawen Mudstone Formation
TYGN
Caradoc (gracilis) to Caradoc (?multidens).
Regionally unconformable on the Allt Lwyd Formation, Offrwm Volcanic Formation and Cregennan Formation, and paraconformable on the Llyn y Gafr Volcanic Formation. Taken at the appearance of ooidal ironstones and phosphatic mudstones above these various formations. Passes laterally into the Pen y gadair Volcanic Formation.
Predominantly mudstones with subordinate siltstones and sandstones, locally tuffaceous, with a distinctive phosphatic and ooidal ironstone (the Fron Newydd Member) at its base.
To 1000m.
Overlain by ash-flow tuffs of the Craig Cau Formation and, in the extreme west of its occurrence, by mudstones of the Ceiswyn Formation, although the nature of the latter boundary is problematical.
Ty Gwilym Sandstone Member
TYGW
North Llandovery area, southern Wales.
Three Yard Limestone Member
TYL
Taken at the generally conformable, sharp base of the first bed of limestone that overlies measures of the Alston Formation. On the Alston Block, usually overlies above a major sandstone body referred to as the Six Fathom Hazle. This typically displays a seatearth below the limestone and in north Northumberland there is typically a coal, also, a few tens of centimetres of mudstone may intervene locally.
Widespread limestone member occurring throughout northern England and the Scottish Borders within the Alston Formation, stratigraphically lying below the Four Fathom Limestone and above the Five Yard Limestone on the Alston Block or the Eelwell Limestone in Northumberland.
Limestone, packstone, fine-grained, medium and dark grey, thickly bedded, fissile and nodular in part, with styolites, thin mudstone partings, particularly in north Northumberland. Crinoid debris and foraminifera are typically characteristic, but the member if not particularly fossiliferous on the Aslton Block. A goniatite indicative of the P2c biozone has been recorded from mudstones above the Three Yard Limestone. On the Askrigg Block, the limestone is split into two leaves by a ganister-like sandstone, which thickens to up to 8m westwards; a thin coal is shown at a similar horizon in the Barnard Castle district to the east.
1.8 to 4.6m on the Alston Block; 3 to 10m in the Whitehaven to Gilcrux district, north of the Lake District, an average of 2.7m on the Askrigg Block; 5 to 6m in Northumberland.
Taken at the top of the uppermost limestone bed that is overlain by a sequence of dark grey mudstones and siltstones, in north Northumberland containing ironstone nodules locally.
Tylacourt Coal (South Wales)
TYLAC
Tullymore Limestone Member
TYLM
Tyne Limestone Formation
TYLS
Conformable on Fell Sandstone Formation variably represented as base of Clattering Band, Kingbridge Limestone or Glencartholm Volcanic Member.
Fine- to medium-grained sandstone, siltstone, seatearth and thin limestone; locally thin coals are developed; local development of volcanic tuffs and basalt lavas.
Up to 850m
Conformable with Alston Formation. Top defined as base of overlying Low Tipalt or Callant Limestone.
Tal-Y-Gareg Member
TYM
Lower boundary, with mudstones of Bifidus Slate Formation, is not seen and is inferred at change in slope.
Extends from the coast north of Tywyn, inland to Castell Mawr, (5848 0492) where it is last seen. Length of outcrop c. 2km.
Mudstone matrix, volcanic debris flow. Comprises dominantly basaltic, angular clasts in a mudstone matrix-matrix-to clast-supported.
0 - approximately 6m.
Upper boundary, with mudstones of Bifidus Slate Formation, is not seen and is inferred at change in slope.
Ty-Mawr Formation
TYMA
Tyninghame Formation
TYN
The base is drawn at the incoming of significant thicknesses of grey mudstone and cementstone in or above a sandstone-cornstone sequence.
Lothians. Berwickshire.
Pale sandstones interbedded with grey, green, purple or brown siltstones and mudstones. Bands of dolomite/limestone (cementstone) and nodular carbonate (cornstone) are distributed irregularly through the sequence.
800m estimated in Edinburgh, 384m+ at East Linton; 209m at Birnieknowes and 263m at Spilmersford.
The top is drawn at the incoming of common seatrock, coal, sideritic ironstone, black mudstone or marine bands; or where the sequence becomes dominated by volcanic rocks.
Tyne Valley Formation
TYNE
Sharp, undulating, erosional contact, mainly of grey tills (diamicton) of the North Pennine or North Sea Coast Glacigenic subgroups, or on bedrock.
The valley of the River Tyne and its tributaries, northern England.
Tayport Formation
TYPO
Two Yard Coal (North Wales)
TYRD
Tyrie Coal (Fife)
TYRI
Tyrone Group
TYRO
Unconformable on metamorphic basement or Courceyan Omagh Sandstone Group.
The northwest Carboniferous basin of Ireland.
Mixed sequence of thin basal (red-bed) clastics, marine limestones (with mud mounds) and shales/mudstones; thin deltaic horizons. NOTE: Reference Sections: see component formations: Daltry, Glancar, Ballyshannon, Termon River Limestone, Tubbrid, Mullaghmore, Bin Mountain, Claragh Sandstone, Benbulben, Bundoran, Keeneghan Shale and Drumchorick Siltstone formations.
To 2400m
Overlain disconformably by predominantly shale sequence of the Leitrim Group.
Ty-Draw Slates Formation
TYS
Interbedded with underlying grey slates of the Fron-frys Formation.
Llangollen - Corwen area of east Wales.
Homogeneous pale green slates.
Overlain by dark grey slates of the "Denbighshire Series" (Wenlock) (Variously termed Denbigh Grits Group, Pen-y-glog Group etc).
Tyncoed Sandstone Member
TYSA
Trelydan Shale Formation
TYSH
Tyne And Wear Glaciolacustrine Formation
TYWE
Generally in irregular, draped, conformable contact with underlying dark grey, stony sandy silty clay diamicton of the Wear Till Formation.
Laminated greyish brown to brownish grey, silty clay and micaceous clayey silt with subordinate beds and laminae of fine-grained sand, pebbly clay diamicton and gravel. Complex interdigitation of units is common, especially towards the coast. Dropstones are common and worm traces can be seen locally on partings. The complex sequence was deposited in several lake basins including Glacial Lake Wear and Glacial Lake Edderacres where it tends to fine upwards and southwards with fine-grained units successively overlapping coarser ones northwards.
Up to 60m within buried channels.
Generally a planar, subhorizontal to undulating, gradational, glaciotectonic boundary with overlying reddish-brown to dark brown pebbly silty clay of the Pelaw Clay Member.
Tywi Valley Formation
TYWI
Sharp, unconformable and locally channelised, predominately on bedrock and Late Devensian head and Welsh glacigenic deposits (e.g Brecknockshire and Plynlimon till formations). Locally beyond the ice limit of the Late Glacial Maximum (e.g. north and west of Cwmduad [SN 3748 3125], it might overlie older alluvial, periglacial and glacial deposits. Interdigitates in a complex manner with Tidal Flat Deposits (Gwynllwg Formation of Bowen, 1999) in the estuary.
The valley of the River Twyi and its tributaries (Dyfed, Wales).
Unconsolidated, stratified gravels, sands, silts and clays forming the alluvial deposits of the River Towy (Afon Tywi) and its tributaries. Includes contemporaneous head, colluvium and pedogenic deposits within the catchment area. Clasts principally consist of local, Lower Palaeozoic turbidites, admixed to the west of Llandovery with Old Red Sandstone clasts. Aggradational river terraces and major alluvial fans are dominated by pebble cobble gravels and medium- to coarse-grained sand; the modern floodplain is domiated by silt and clay, and locally includes lenses of peat.
Bowen (1999) applied the term Tywi Formation to Holocene valley alluvium in all the ajor rivers of Wales, and in northwest Wales he included late glacial fluvial gravels.
Generally to about 10m; it might be locally thicker in the lower reaches of the Tywi.
Uriconian Group [Obsolete Code: Use Uo]
Upper Four-Feet Coal (South Wales)
U4FCO
Upper Five-Feet Coal (South Wales)
U5FCO
Upper Six-Feet Coal (South Wales)
U6FC
Upper Seven-Feet Coal (South Wales)
U7FCO
Upper Seven-Feet Coal And Yard Coal (Undifferentiated) (South Wales)
U7FYC
Upper Nine-Feet Coal (South Wales)
U9FC
Upper Abdon Limestone Member
UAL
Upper Antiquatonia Band
UAQB
Upper Argillaceous Beds
UARG
Upper Alton Coal
UATC
Upper Bringewood Beds
UBB
Upper Band Coal (Leicester And South To North Derbyshire)
UBC
Uamh Bheag Conglomerate Member
UBCO
The base of the youngest body of 'mixed conglomerate' on Uamh Bheag, north-east of Callander, which interdigitates partly with the Teith Sandstone and partly with the Cromix Mudstone formations.
The Callander to Highland Border area, on the north-west limb of the Strathmore Syncline.
Mostly a cobble conglomerate, containing clasts of basic or intermediate lavas, vein quartz, quartzite and other metamorphic rocks with lenses of pebbly sandstone.
Up to at least 233 m thick.
Strongly diachronous, overlain by and interfingered with sandstones of the Teith Sandstone Formations
Upper Bodenham Beds
UBD
Upper Basalt Formation
UBF
Bailey Hill Formation [Duplicate Code: Use Bai]
UBH
Upper Blackbird Coal (Lothian)
UBL
Upper Black Coal (South Wales)
UBLK
Upper Bluers Coal (South Wales)
UBLR
Upper Bench Coal (Warwickshire)
UBNC
Currently it is uncertain whether Upper Bench is synonymous with Top Bench (TBNC) or whether the Top Bench represents the top leaf of the Bench Coal (where split) and is in turn overlain locally by the Upper Bench Coal.
Upper Brodini Coal (South Wales)
UBRO
Upper Basic Volcanic Group [Cf Pen-Y-Gader Group]
UBV
Drawn at base of Upper Basic Volcanic Group where it rests conformably on pyroclastics of the Llyn-y-Gader Mudstones Group.
Spilitic pillow lavas with subordinate pyroclastic bands to the east and central parts of the Cader Idris Range and dominantly pyroclastic rocks to the west. (Correlative of Upper Basic Volcanic Group = Pen-y-Gader Group).
Drawn at conformable upward passage from spilitic lavas, mudstone, ash and chert of the Upper Basic Volcanic Group to mudstones of the Llyn Cau Mudstones Group.
Upper Bath-House Wood Limestone
UBWL
Upper Cambrian, Including Tremadoc
Upper Calmy Limestone
UCAL
Upper Cornbrash
UCB
Middle Jurassic, Lower Callovian (Herveyi Zone).
Quasi-conformable to non-sequential contact with limestones of the underlying Lower Cornbrash (Upper Bathonian) or mudstone of the the Blisworth Clay Formation (East Midland Shelf east and north), or with the mudstone with minor sandstone beds of the Scalby Formation (Cleveland Basin), overlain by limestone of the Upper Cornbrash.
Dorset coast (Weymouth area) to Yorkshire coast (Scarborough area) Absent locally, mainly in the south Midlands and in the Market Weighton area. Distribution in subcrop uncertain but probably similar to that of the Cornbrash Formation.
"A variable sequence of sandy limestones, calcareous sands and calcarenitic limestones" (Page, 1989). "Sparsely sandy peloidal biomicrite overlying fine-grained calcareous sandstone and sandy biomicrite" (Bristow, 1999).
[Compiler's Notes] In my view the UCB and LCB should be expunged from BGS maps and the lithostratigraphical database. Upper Cornbrash and Lower Cornbrash were originally, and certainly have become, chronostratigraphical terms (Douglas and Arkell, 1928, 1932). If they were to be extended to become lithostratigraphical units, then Page's (1989) terms Berry and Fleet members would be the appropriate ones to use, even though they are not precise synonyms. However, in my view (coloured particularly by my experience on Sheet 219), the Upper and Lower Cornbrash (or Berry and Fleet members) are indistinguishable (and so impossible to define) on the basis of lithology even in the broadest sense. Thus I quote from Page and Bristow et al. in section 2.1a. So I don't believe it is possible to map a boundary between the two, and it is unhelpful to pretend otherwise. It is true that some lithologies are more common in one unit rather than the other e.g. bedded sandy limestones are more or less restricted to the UCB, and may indeed comprise the bulk of the unit in some areas, but this does not enable a boundary to be drawn between UCB and LCB. In many areas (e.g. sheets 219, 127) the UCB does not generally include such distinctive lithologies and is of typical LCB lithology, see for example Cox et al., 1991. If it is found possible to separate off the "sandy limestones" in other areas, then either new member names would be needed, or they could be shown as a lithological variant within the undivided Cornbrash Formation. Despite the foregoing, it is possible to say that in certain areas much or all of the Cornbrash Formation is either UCB or LCB (e.g. Page, 1989, Fig.2), but this information is (or should be) shown on the chronostratigraphical GVS. [M G Sumbler, 25/9/2005]
0 to c.7m; thickest in the Wessex Basin, and (probably) absent in much of the south Midlands.
Taken at the base of the succeeding Kellaways Formation or Cayton Clay Formation (in the Cleveland Basin); comprising mudstone, commonly shelly at its base, resting generally sharply and conformably or non-sequentially on the limestone of the Cornbrash.
Raasay Upper Cornbrash
UCBR
Upper Cannel Coal (South Derbyshire)
UCC
Upper Cannel Coal (South Lancashire)
UCCO
Upper Clod Coal (North Staffordshire)
UCDCO
Upper Cemetery Beds
UCE
Upper Caithness Flagstone Subgroup
UCF
Drawn at the base of the Achanarras Formation, where limestone rests conformably upon sandstone and shale of the Robbery Head Formation.
Northern Highlands of Scotland.
Laminated carbonate rich siltstones and shales with subordinate fine-grained, thinly bedded sandstones.
Drawn at the conformable upward passage of lacustrine sandstone of the Mey Flagstone Formation to fluvial sandstone of the John O'Groats Sandstone Group.
Upper Calcareous Grit Formation
UCG
Upper Churnet Shales
UCH
Upper Charles Coal (South Staffordshire)
UCHS
Upper Chalk Formation [Remains In Informal Use But Generally Regarded As Obsolete Onshore]
UCK
At base of Chalk Rock, a hard basal unit. (Conventionally also taken at base of Holaster planus Zone).
As used here: The Chilterns, extending to South Norfolk and Suffolk: ie area of "Anglo-Brabant Massif". Definition breaks down where Chalk Rock disappears. Approximates to the "Transitional Province" of Mortimore (1983).
White chalks (microporous coccolithic limestone) with beds of flint, nodular chalks, hardgrounds and marl seams. NOTE: No type section has been established. See Chalk Rock for stratotypes of base of Upper Chalk.
Up to 60m preserved in the Hitchin district, more than 300m in parts of Norfolk.
In mainland Britain this is an unconformity overlain by post-Cretaceous formations.
Scottish Upper Coal Measures Formation
UCMS
The conformable and transitional boundary from Middle Coal Measures is drawn at the base of the Aegiranum (Skipsey's) Marine Band. The original definition (MacGregor, 1960) placed the boundary at the top of this marine band. The revision was made by Forsyth et al (1996).
Sandstone, siltstone and mudstone in repeated cycles, most commonly fining upwards; argillaceous rocks commonly as structureless beds and seatearth; commonly reddish brown or purple due to oxidation of originally grey strata; some reddening may be primary.
Maximum thickness probably exceeds 750m under the Firth of Forth
Not known at outcrop due to unconformity beneath Permo-Triassic rocks.
Upper Codshot Coal (South Wales)
UCOD
Upper Coxtool Coal (Fife)
UCOX
Upper Camregan Grits Formation
UCRG
Conformably overlies Maxwellston Mudstone Formation.
Massive pale green-brown sandstone turbidites.
33m
Conformably overlain by Penkill Formation.
Upper Comley Sandstone Formation
UCSS
Unconformable on the Lower Comley Sandstone Formation.
Welsh borderland, Shropshire.
Coarse- to fine-grained calcareous sandstones and interbedded shaly mudstones.
A non-sequence or unconformity with various Upper Cambrian mudstone formations, at least locally.
Upper Crafnant Volcanic Formation
UCV
Rests on mudstone and siltstone of the Middle Crafnant Volcanic Formation.
Eastern Snowdonia, around Betws-y-Coed. Farther north it is not readily separated from the Middle Crafnant Volcanic Formation.
Massive, acidic, grey, muddy, crystal tuffite.
Overlain by Nod Glas (= Cadnant Shales).
Udale Coal (Cumbria)
UDA
Unnamed Dyke, Late Neoproterozoic
UDA3
Unnamed Dyke [Age Unknown]
UDAU
Unnamed Dyke, Neoproterozoic
UDAZ
Upper Drumgray Coal (Central Coalfield)
UDC
Unnamed Dyke, Dinantian
UDCL
Upper Devonian Rocks And Lower Carboniferous Rocks (Undifferentiated)
UDCS
Unnamed Dyke, Westphalian
UDCW
Unnamed Dyke, Devonian
UDD
Upper Devonian Rocks (Undifferentiated)
UDEV
Unnamed Dyke, Palaeogene
UDG
Upper Dalness Ignimbrite
UDI
Upper Diamond Coal (Tranent; Lothian)
UDIC
Unnamed Dyke, Carboniferous
UDKC
Under Limestone Bed
UDL
Unnamed Dyke, Late Caledonian
UDLC
Upper Drumgray Musselband (Glasgow; Central Coalfield)
UDM
Upper Demesne Limestone
UDML
Udny-Pitmedden Intrusion
UDNY
Unnamed Dyke, Ordovician
UDO
Unnamed Dyke, Permian
UDP
Unnamed Dyke, Pre-Caledonian
UDPC
Unnamed Dyke, Late Carboniferous To Early Permian
UDPL
Unnamed Dyke, Late Palaeozoic
UDRU
Upper Dornoch Sandstone Unit
UDSA
Unnamed Dyke, Late Silurian To Early Devonian
UDSD
Upper Delabole Slates
UDSL
Upper Devonian Slates
UDVS
Upper Dykebar Coal
UDYC
Upper Eday Sandstone Formation
UED
Upper Eighteen-Feet Coal (South Wales)
UEIT
Upper Elton Formation
UELB
Upper Ell Marine Band
UEMB
Unnamed Extrusive Rocks Of Unknown Age
UEX
Unnamed Extrusive Rocks, Palaeoproterozoic
UEXAL
Unnamed Extrusive Rocks, Neoproterozoic
UEXAZ
Unnamed Extrusive Rocks, Carboniferous
UEXC
Unnamed Extrusive Rocks, Dinantian
UEXCL
Unnamed Extrusive Rocks, Namurian
UEXCN
Unnamed Extrusive Rocks, Silesian
UEXCU
Unnamed Extrusive Rocks, Devonian
UEXD
Unnamed Extrusive Rocks, Devonian To Carboniferous
UEXDC
Unnamed Extrusive Rocks, Cambrian
UEXE
Unnamed Extrusive Rocks, Cambrian To Ordovician
UEXEO
Unnamed Extrusive Rocks, Palaeogene
UEXG
Unnamed Extrusive Rocks, Cretaceous
UEXK
Unnamed Extrusive Rocks, Ordovician
UEXO
Unnamed Extrusive Rocks, Permian
UEXP
Unnamed Extrusive Rocks, Silurian
UEXS
Unnamed Extrusive Rocks, Silurian To Devonian
UEXSD
Upper Follifoot Grit
Upper Forest Beds
UFB
Unnamed Mineral Flat In Carboniferous Limestone [Age Of Emplacement Unspecified]
UFC
Mineralized country rock (dominantly limestone), containing lead and zinc ore minerals and gangue minerals such as fluorite, baryte and calcite.
Upper Fireclay Of The Passage Formation
UFCL
Associated with the Bowhousebog Coal.
Underfoot Coal (Machrihanish)
UFCO
Upper Fuller's Earth Member
UFE
Top of the limestones of the Fuller's Earth Rock .
Bath district, south to the Dorset coast (at crop).
Pale to medium olive-grey, calcareous silty mudstone with thin highly calcareous mudstones or argillaceous limestones and (in Bath-Frome area), a seam of montmorillonite-rich clay (Fuller's Earth).
24 to 28m in the Bath-Frome area, thin or absent between Baggridge and Purse Caundle, and 21m in the Mappowder Borehole.
The base of the lowermost argillaceous limestone of the Wattonensis Beds Member (Frome Clay Formation) marked by an increase in shell-detritus.
Upper Fish Tooth Bed
UFI
Upper Fittleworth Member
UFIB
Upper Fionchra Member
UFION
Upper Forest Beds And Lower Llanbadoc Beds (Undifferentiated)
UFLC
Upper Felltop Sandstone
UFLS
Upper Flow Moss Lava Member
UFMLA
The base is apparently unconformable on the Harelaw Lava Member, which consists of trachytic lavas, and the volcaniclastic rocks of the Gowk Stane Member. A thick bole formed on the top flow of the Lower Flow Moss Member marks the contact with this underlying member.
Dunlop-Eaglesham moors between Glasgow, Kilmarnock and Hamilton, widespread area between Neilston (NS 440 560) in the northwest and Darvel (NS 610 390) in the southeast.
The Upper Flow Moss Lava Member consists of alkali basalts and subordinate basanites and ankaramites.
The Member is overlain unconformably by the Kirkwood Formation (Strathclyde Group).
Upper Findhorn Sandstone Unit
UFSA
Upper Foot Coal (South Lancashire)
UFTC
Upper Felltop Limestone
UFTL
Upper Foxton Limestone
UFXL
Described as a "limy ironstone" by Carruthers et al., 1930.
Upper Gas Coal (New Cumnock)
Upper Garth Coal
UGA
Upper Ganey Coal (Coalbrookdale)
UGCC
Ugie Clay Formation
UGCL
Generally a sharp, undulating, draped, unconformable contact with the gravelly clayey sand diamictons (tills) of the East Grampian Glacigenic Subgroup, but locally a sharp, undulating, draped, unconformable contact with deposits of glaciofluvial gravel with erect pebbles at the top, probably formed in a periglacial environment.
Buchan, north-east Scotland, between Peterhead, Ellon and Aberdeen.
A typically reddish brown, but locally dark grey, black, brown and yellowish brown, laminated clay, silt and fine-grained sand, with localised black organic laminae formed of reworked Jurassic material.
Generally a sharp, undulating, draped, erosional and unconformable contact with glaciofluvial or alluvial sand and gravel. Locally the boundary is seen as a sharp, planar, unconformable glacitectonic contact with red clayey diamictons (deformation tills, glaci- tectonites) of the Logie-Buchan Glacigenic Subgroup towards the North Sea coast.
Upper Grovesend Coal (South Wales)
UGDC
Upgang Formation
UGF
Upper Gunnerton Fell Limestone
UGFL
Upper Gwastaden Group (See Gwastaden Group, Gg)
UGG
Upper Garscadden Blackband Ironstone (Glasgow)
UGI
Upper Garscadden Coal (Central Coalfield)
UGNC
Upper Garry Psammite Formation
UGPS
Upper Grinstead Clay
UGRC
Down-section change from mudstones [Upper Grinstead Clay Member] with a basal pebble bed [Cuckfield Pebble Bed] to fine-grained, silty, cross-bedded, buff sandstone with local thin mudstones and limestones [Cuckfield Stone Member].
The Upper Grinstead Clay Member is present at a number of localities on the eastern part of the Horsham district [sheet 302] from the Scaynes Hill area, east to the Cuckfield-Handcross-balcombe area and then north-east to East Grinstead. On the Tunbridge Wells sheet [287], it is present between East Grinstead and Royal Tunbridge Wells, with a further small outcrop near Danehill. On the Sevenoaks sheet [287] the member is restricted to a small area near Finch Green and it is again present along the north-eastern margin of the brighton & Worthing Sheet [318/333], where it is found in a small area north of the Lunce's Common Fault, north of Burgess Hill.
The member comprises soft grey mudstones and silty mudstones the pary of which weathers to a red colour. In some cases the Cuckfield Pebble Bed occurs at the base.
Up to 12.2m proved.
Down-section change fromsilt and sand rhythms [Upper Tunbridge Wells Sand Formation] mudstones [Upper Grinstead Clay Member].
Upper Greensand Formation
UGS
Albian (Upper) Inflatum Zone (varicosum Subzone) to Cenomanian (Mantelli Zone, Cartitianense Subzone) in the Wessex Basin. Mostly Dispar Zone elsewhere.
Upward change from sandy micaceous clay of the Gault to silt and/or sand.
Eastborne to Sevenoaks in the Weald; across the Wessex Basin and northwards to just northeast of Monks Riseborough in the Chilterns. SEE ALSO the definition for the now abandoned term "Upper Greensand Formation (Devon)".
Sand and sandstone, fine-grained, silt, glauconitic, shelly.
0 to 75m
Upward change from dominantly arenaceous sequence to dominantly marly or chalky sequence.
Upper Gyffin Shales
UGSH
Ugbrooke Sandstone Formation
UGST
?Brigantian to Namurian.
The base is taken at the incoming of dark grey and greenish grey mudstones with thin siltstones and fine- to coarse-grained sandstones of the Ugbrooke Sandstone Formation above the thin-bedded cherts, shales and limestones of the underlying Winstow Chert Formation.
Chudleigh (SX 870 784) and East Ogwell (SX 845 695) areas, south Devon.
Thick-bedded massive, grey, medium-to coarse-grained, locally pebbly and conglomeratic sandstones with impersistent thick units of pebble-cobble conglomerate, argillaceous sandstone and dark grey mudstones with thin sandstones and siltstones. Pebbly mudstones are also present. Conglomerate clasts include chert and granite.
Not known, but at least 500m.
The upper boundary is taken at an angular unconformity, where fine grained glauconitic sandstone at the Upper Greensand Formation rests upon thick-bedded to massive, locally pebbly to conglomeratic sandstone of the Ugbrooke Sandstone Formation.
Upper Gullane Head Sill
UGUHD
Upper Haslingden Flags
Upper Holcombe Brook Coal (South Lancashire)
UHBC
Upper Hartfell Shale Formation
UHBS
Conformable on Lower Hartfell Shale Formation.
Pale grey mudstone with rare laminae of black hemipelagic mudstone.
28m
Conformably overlain by Birkhill Shale Formation
Upper Househill Clayband Ironstone
UHCI
Upper Hall Coal (Northumberland)
UHCO
Upper Heathen Coal (South Staffordshire) [Duplicate Code: Use Uhec]
UHEA
Upper Heathen Coal (South Staffordshire)
UHEC
Upper Howgate Edge Grit
UHEG
Upper Hartfell Lowther Shales
UHLS
Upper Henshaw Siltstones
UHS
Unnamed Igneous Intrusion, Proterozoic
UIAP
Unnamed Igneous Intrusion, Neoproterozoic
UIAZ
Upper Interbasaltic Formation
UIB
Unnamed Igneous Intrusion, Dinantian
UICL
Unnamed Plugs And Vents, Carboniferous To Permian
UICPV
Unnamed Igneous Intrusion, Silesian
UICU
Unnamed Igneous Intrusion, Westphalian
UICW
Unnamed Igneous Rocks, Devonian To Carboniferous (Undifferentiated)
UIDCU
Unclassified Igneous Rock, Early Devonian
UIDL
Unnamed Igneous Rocks, Devonian (Undifferentiated)
UIDU
Unnamed Igneous Intrusion, Early Caledonian
UIEC
Unnamed Igneous Intrusion, Palaeogene
UIG
Uig Hills - Harris Igneous Complex
UIGH
Uig Hills - Harris Igneous Complex: Vein Complex [Central Zone]
UIGHC
Uig Hills - Harris Igneous Complex: Vein Complex [Marginal Zone]
UIGHM
Unnamed Igneous Intrusion, Palaeoproterozoic
UIIAL
Unnamed Igneous Intrusion, Carboniferous
UIIC
Unnamed Igneous Intrusion, Carboniferous To Permian
UIICP
Unnamed Igneous Intrusion, Devonian
UIID
Unnamed Igneous Intrusion, Devonian To Carboniferous
UIIDC
Unnamed Igneous Intrusion, Cambrian
UIIE
Unnamed Igneous Intrusion, Cambrian To Ordovician
UIIEO
Unnamed Intrusive Rocks, Cretaceous
UIIK
Unnamed Igneous Intrusion Of Unknown Age
UIIN
Unnamed Igneous Intrusion, Ordovician
UIIO
Unnamed Igneous Intrusion, Ordovician To Silurian
UIIOS
Unnamed Igneous Intrusion, Permian
UIIP
Unnamed Igneous Intrusion, Silurian
UIIS
Unnamed Igneous Intrusion, Late Caledonian
UILC
Unnamed Igneous Intrusion, Early Palaeozoic
UILRZ
Unnamed Igneous Intrusion, Type And Age Unspecified
UINT
Unclassified Igneous Rock, Ordovician
UIO
Unnamed Igneous Intrusion, Arenig
UIOR
Unclassified Igneous Rock, Ordovician To Silurian
UIOS
Unclassified Igneous Rock, Permian
UIP
Unnamed Igneous Intrusion, Pre-Caledonian
UIPC
Unnamed Igneous Intrusion, Pre-Caledonian To Early-Caledonian
UIPEC
Ulbster/Ires Geo Sandstone
UIS
Unnamed Igneous Intrusion, Late Silurian To Early Devonian
UISD
Uist Member
UIST
Often wedges within Stanton Formation, or adjacent to it.
Silty clays with sporadic pebbles.
83 metres. Generally developed as wedges within Stanton Formation. This represents near maximum thickness.
Upper Johnstone Shell Bed
UJSH
Upper Kinderscout Grit
Upper Kilburn Coal (South Derbyshire)
UKBC
Upper Kimmeridge Clay
UKC
Upper Kent's Thick Coal (West And South Yorkshire)
UKEKC
Urswick Limestone Formation
Point where poorly bedded limestones of the Park Limestone Formation pass upwards into well bedded limestones and "pseudobreccias".
South Cumbria - north Lancashire from Duddon Estuary to Carnforth area.
Mainly thickly and well-bedded pale grey grainstones or calcarenites, commonly with darker mottling (pseudobreccia) and a rubbly texture, especially adjacent to scattered partings and thin beds of grey and varicoloured clay.
Taken where the predominantly pale thickly bedded Urswick Limestones pass up into the predominantly dark thinner-bedded limestones of the Alston Formation (formerly Gleaston Formation).
Ulbster Sandstone Formation
ULBS
Upper Llanbadoc Beds
ULCB
Upper Limestone
ULE
Usk Limestone Formation
ULF
Upper Limestone Formation
ULGS
Cyclic: includes marine limestones. See NOTE relating to lithological description of Limestone Coal Formation (LSC).
435.3m in type section
Urswick Limestone (Knoll-Reef)
ULK
Upper Lincolnshire Limestone Member
ULL
Lower Bajocian (Laeviuscula to ?Sauzei zones).
Disconformable, commonly channelled contact between dominantly calcilutite, packstone and wackestone limestones of the Lower Lincolnshire Limestone Member, or (locally in the south) mudstone, sandstone and ironstone of the underlying Grantham Formation or Northampton Sand Formation, overlain by the ooidal and bioclastic grainstones of the Upper Lincolnshire Limestone.
Essentially as for the Lincolnshire Limestone Formation, ie, Market Weighton area (where overstepped by Cretaceous, Chalk Group, Hunstanton Formation) to the Kettering-Peterborough area (where overstepped by the Rutland Formation). Extent in subcrop is uncertain, but probably as for the Lincolnshire Limestone Formation, ie, onshore areas of the northern part of the East Midlands Shelf.
Limestone, overwhelmingly dominated by high-energy ooidal and shell fragmental grainstones, but includes secondarily recrystallized and micritized lithologies.
[Compiler's Notes] Having considered the Lincolnshire Limestone in some detail, I am fully convinced that a bipartite division of the unit is the only really workable scheme. However, I have [almost] always used the term Upper Lincolnshire Limestone as an informal division, albeit of Member status, because of the existence (in print) of Ashton's Sleaford and Clipsham members (which I don't consider to be discrete stratigraphical units, just lithological types). Discussion and decision making are needed as to whether to formalize ULL (and LLL) as members (and as a necessary consequence, downgrade the various existing Members), whether they should be sub-Formations (cf. sub-Phylum in biological taxonomy) or just informal but mappable formational subdivisions. On balance, I'd recommend the first option, for ULL to be a formal Member, in which case a new name would perhaps be called for. Ancaster Member (based on Copper Hill) seems entirely appropriate, the only complication being possible confusion with Ancaster Stone (building stone) although that is at least part of the ULL. Hibaldstow Member is not suitable because, like Upper and Lower Lincolnshire Limestone, that is tied up in confusion with the Crossi Bed. Furthermore, certain limestones included at the base of the Hibaldstow Beds are not necessarily ULL as defined here, though this complication is avoided in this definition. Actually, a simple way round this confusion would be to define ULL north of Lincoln as everything above the Kirton Cementstones. Or to have both an Ancaster Member and Hibaldstow Member. As with the Lower Lincolnshire Limestone, it would be useful to have a thorough account of the definition of this unit, its type and reference section and its lateral variation. This is particularly so north of Lincoln, as mentioned above. [M G Sumbler, 25/09/05]
Disconformable, commonly markedly eroded and karstified contact between ooidal and bioclastic grainstone of the Upper Lincolnshire Limestone and the non-calcareous non-marine sandstones, siltstones and mudstones of the overlying Rutland Formation. Near the northern limit only, disconformable contact between ooidal and bioclastic grainstone of the Upper Lincolnshire Limestone and ferruginous sandy calcareous sediments of the Hunstanton Formation (Cretaceous, Chalk Group).
Ullapool Gneiss
ULLA
The unit always occurs within the Moine Thrust Belt, and the lower structual boundary is always tectonic.
The Ullpool Gneiss occurs in thrust slices within the Moine Thrust Belt. The most northerly thrust slice occurs in Strathkanaird, just east of Langwell Lodge. A major thrust slice extends from Ullapool River (just west from Loch Achall), via Corry Point across Loch Broom to Loch Lagaidh. Similar gneisses have been identified in the Kinlochewe area by earlier mappers (see references).
The Ullapool Gneiss is a dark pink to white weathering, variably foliated and poorly layered, medium- to coarse-grained orthogneiss, rich in alkali feldspar. The gneiss has a broadly syenitic to granitic composition. Samples from the type locality typically comprise K-feldspar (perthite and microcline) + plagioclase + guartz + bluish green amphibole, with minor epitode and accessory titanite. The mafic minerals occur in clusters several millimetres across, which commonly gives the rock a pink-green speckled appearance. The felsic gneiss contains some pods of more mafic, amphibole-rich gneiss. The gneissic layering is considerably less well developed than in the typical Scourian Gneiss. Amphibolitic mafic dykes cross-cut the unit.
The upper structural boundary is formed by the Moine Thrust or by the unconformity with overlying Torridon Group sediments.
Upper Llanbadoc Beds And Llangibby Beds (Undifferentiated)
ULLB
Upper Lancashire Ladies Coal (Coalbrookdale)
ULLC
Upper Llwydcoed Coal (South Wales)
ULLD
Upper Llanbadoc Beds And Lower Llangibby Beds (Undifferentiated)
ULLLY
Upper Linn Limestone
ULLS
Lower Main Coal (Upper Seam) (Leicestershire)
ULMC
Upper Lobster Member
ULOB
Upper Lount Coal (Leicestershire)
ULOC
Upper Lount Rider Coal (Leicestershire)
ULOR
Ulpha Andesite Formation
ULP
Base of plagioclase-phyric andesite lava, unconformably overlying the Duddon Hall Tuff Formation (bedded air-fall tuff) and Holehouse Gill Mudstone Formation (mudstone and sandstone).
Duddon Valley from Seathwaite [SD 220 960] to Bleansley Bank [SD 200 890], Cumbria.
Andesite, plagioclase-phyric lavas with thin interbeds of volcaniclastic rocks.
Defined by bases of overlying formations including Wallowbarrow Tuff Formation (andesitic lapilli tuff) and Dunnerdale Sandstone Formation (volcaniclastic sandstone).
Upper Long Sands Sandstone Member
ULSA
Not exposed in type section or elsewhere. (Type section chosen because it is the only place where the lithology can be fully seen).
Mapped on geological sheet 348 (Plymouth). May also occur on sheets 349, 350, 355 and 356.
Sandstone of variable type, thin to thick beds, fine- to coarse-grained, fossiliferous with siltstone interbeds. Limestone beds up to 0.5m are present through the upper part of the member.
Ullstone Formation
ULSE
Ulster Canal Formation
ULST
Upper Leintwardine Formation
ULT
Upper Lodge Volcanic Group
ULV
Lies conformably on sandstones and siltstones, plus tuffs of the Cwm Eigiau Formation.
Basaltic trachyandesite with rhyolitic tuff.
Overlain by siltstones, sandstones and calcareous mudstones of the Dwyfach Formation.
Upper Llangibby Beds
ULYB
Upper Main Coal (Leicestershire)
Unnamed Metamorphic Rocks, Neoproterozoic
UMAZ
Upper Miller's Dale Lava Member
UMB
At the type section, basalt of the Upper Miller's Dale Lava Member rests upon dark grey, thinly bedded, fine-grained limestone of the Miller's Dale Limestone Formation. Outside of the Miller's Dale area the Member rests disconformably upon pale grey limestones of the Bee Low Limestone Formation.
Nearly continuous outcrop from Hurdlow Town (SK 112 669) and Miller's Dale (SK 134 731) and an isolated outcrop at Harpur Hill (SK 066 713) and Cressbrook Dale (SK 173 724).
An amygdaloidal olivine basalt with calcite and chlorite infilling vesicles. At the type locality the lava is brown-weathered with a flow banding and degraded lava blocks up to 0.6 m diameter. In Miller's Dale, where the member is thickest, the member was subdivided into a 5.2 m thick tuff with a thin amygdaloidal basalt, overlain by a 30 m thick lava, at least in part comprising non-vesicular, holocrystalline basalt with spheroidal weathering (Walters and Ineson, 1981).
Up to about 35 m thick in Miller's Dale (SK 140 730), decreasing markedly to the east toward the type locality.
At the type locality, an irregular upper surface of the lava is overlain by grey, fine-grained, irregularly bedded limestones of the Monsal Dale Limestone Formation, including rounded and decomposed fragments of lava immediately above the boundary.
Upper Metal Band Coal (Cumbria)
UMBC
Upper Chalk Formation And Middle Chalk Formation (Undifferentiated) [Obsolete Code: Use Muck]
UMCK
Upper Mottled Clays
UMCL
Upper Main Coal (North Wales)
UMCO
Upper Marl Group
UMG
Drawn at the base of the Upper Marl Group where it rests conformably on the Sandstone and Marl Group.
South Pembrokeshire (Dyfed), southwest Wales.
Red, locally nodular, mudstones, fine- to very fine-grained sandstones and intraformational conglomerates: lithology represents fining up sequences (cyclothems).
106 metres to 305 metres approx.
Drawn at the conformable upward passage from the top of the upper marl group to the base of the green flaggy sandstones formation of the Casheston Group.
Upper Metagabbro [Shetland Ophialite]
UMGB
Upper Millgrit Coal (Bristol Area)
UMIC
Unnamed Metamorphosed Igneous Rocks, Caledonian
UMIGC
Unnamed Metamorphosed Igneous Rocks, Pre-Caledonian To Caledonian
UMIGP
Upper Millerhill Limestone
UMIL
Upper Mottled Mudstone Member
UMM
Calcareous siltstone, dark grey to black mudstone and irregular mottled mudstone. Shelly fauna. Massively bedded.
Upper Meltham Coal (West Yorkshire)
UMMC
Ummoon Formation
UMMN
Upper Maesmelyn Coal (South Wales)
UMNC
Upper Mountain Coal (South Lancashire)
UMOM
Unnamed Metamorphic Rocks, Pre-Caledonian To Caledonian
UMPCC
Unnamed Metasedimentary Rocks, Neoproterozoic
UMSAZ
Moelwyn Volcanic Formation, Upper Member
UMVO
Underset Chert
UNC
Underbarrow Flag Formation
UND
Taken where the characteristic finer-grained "banded-facies" (Rickards, 1964) of the underlying Bannisdale Slate Formation passes vertically or laterally into ill-sorted siltstones.
Uniform succession of sediments consisting generally of ill-sorted, silt-size quartz grains irregularly distributed in a matrix of very fine silt and clay, with subordinate discontinuous units of well-sorted siltstone.
c.200m in type area: thin northwards to less than 50m in the Staveley Syncline; increase eastwards to a maximum of c. 900m.
The upper boundary is taken at the incoming of the massive siltstones of the Kirkby Moor Flags.
Under Dunnet Shale
UNDS
Underbarrow Formation And Kirkby Moor Formation (Undifferentiated)
UNKM
Unknown Stratigraphy Of Any Age [For Use In Borehole Logs Only]
UNKN
Unnamed E Seam (West Cumbria)
UNME
Unnamed F Seam (West Cumbria)
UNMF
Unnamed G Seam (West Cumbria)
UNMG
Unnamed H Seam (West Cumbria)
UNMH
Unnamed I Seam (West Cumbria)
UNMI
Unnamed J Seam (West Cumbria)
UNMJ
Unst Phyllite Group
UNPH
Under Vexhim Coal
UNVC
Uriconian Group
Generally not seen, but probably unconformable on schists and gneisses of Primrose Hill at the Wrekin.
Lavas and tuffaceous rocks ranging in composition from basalt through andesite and dacite to rhyolite.
c.2310m (Wrockwardine).
Varies, but unconformable beneath basal Cambrian quartzites at the Wrekin.
Upper Oakwood Limestone
UOL
Upper Old Mill Limestone
UOM
Upper Old Red Sandstone
UORS
Upper Ostrea Member
UOST
Sharp base, dark clay with plant fragments, thin shell beds of Neomiodon and Isognomon, mudstones and shell-rich beds - indicative of a gentle, lagoonal transgression.
This Member records the major Callovian transgression in Europe. Mudstone and siltstones predominate with a low-diversity bivalve fauna. "Ostrea" is anomalous as they are not the dominant fossils. Unit is present in the Staffin Bay area of northern Skye, but absent farther south.
Gradationally overlain by sandstone of the 'Belemnite Sands'.
Sherburn Anhydrite Formation [Obsolete Code: See Sna]
UPA
Unnamed Pluton, Neoproterozoic Iii
UPA3
Upper Brimham Grit
UPBM
Sharp upward change in a conformable succession from predominantly siltstone to sandstone - base of first coarse-grained sandstone bed above the Brimham Shale.
A thickly bedded, trough cross-bedded, grey, coarse-grained, feldspathic sandstone, fine-grained in upper 3m and with ganister top.
5 to15m
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of last sandstone bed below the Wandley Gill Sandstone.
Upper Cracker Coal
UPCC
Unnamed Pluton, Westphalian
UPCW
Unnamed Pluton, Devonian
UPD
Upper Dements Limestone
UPDL
Upper Dunnet Shale
UPDS
Upper Etive Rhyolite
UPER
Upper Plompton Grit
UPG
Sharp erosive base on underlying mudstones recorded in Farnham (British Geological Survey) Borehole [SE35NE/27].
West of Harrogate 62 Sheet, south onto Leeds (70) Sheet.
Sandstone, medium- and coarse-grained, quartzofeldspathic, pebbly in places.
Sharp top to sandstones conformably overlain by seatearth, very thin coal and then mudstone in the Farnham (British Geological Survey) Borehole.
Primrose Hill Gneiss
UPHG
Upper Halite
UPHL
Primrose Hill Schist
UPHS
Upper Pinchin Coal (South Wales)
UPIC
Upper Pinchin Rider Coal (South Wales)
UPIRC
Upware Limestone Member
UPL
Rests unconformably on Oxford Clay.
Western half of Cambridge (183) mapsheet, cropping out around Upware and Barway.
Cross-bedded ooidal limestones and coral rag.
Up to 11 m thick.
Overlain unconformably on Ampthill Clay.
Upper Plateau Beds
UPLB
Upper Plompton Grit [Duplicate Code: See Upg]
UPLG
Upper Matlock Limestone
UPML
Unnamed Pluton, Ordovician
UPO
Upper Orchard Limestone
UPOL
Upper Old Red Group [Offshore]
UPOR
Unnamed Pluton, Ordovician To Silurian
UPOS
Unnamed Pluton, Permian
UPP
Upnor Formation
UPR
Rests unconformably on the Thanet Sand Formation in the east of the London Basin, overstepping onto chalk in the west. The contact is well defined, with burrows extending up to 0.5m into the Thanet Sand. A basal flint pebble bed is usually present. In the far east of the London Basin bioturbation has produced a gradational junction. Where resting on chalk, the basal bed contains unworn nodular flints. In East Anglia, the formation rests on the Ormesby Clay Formation.
London Basin, thinning westwards. In north Kent the top was removed by erosion prior to deposition of the Oldhaven Beds.
Mainly variably glauconitic fine- to medium-grained sand with beds and stringers of well-rounded, black flint pebbles. When fresh, the sands are dark grey-brown to dark green depending on proportion of glauconite grains which may be more than 25%. In southeast London there is a persistent pebble bed at the top. The sands weather pale grey-brown to yellow-brown but the glauconite remains dark green. In the central and northern London Basin pedogenic processes during deposition of the overlying Reading Formation modified the sands, resulting in development of carbonate concretions, clay enrichment and colour mottling that exceptionally extend through the formation. Oysters are common in unweathered sections.
Maximum 7.5m. 5-6m in central London.
Generally well defined, being overlain by a variety of sediments ranging from mottled clays of the Reading Formation, or lignitic sands of the Woolwich Formation (Ellison, 1983).
Rhyolitic Grits And Tuffs
UPRT
Unnamed Pluton, Late Palaeozoic
UPRU
Basic Tuff (Lydol Hole) [Part Of Uo]
UPS
Upper Stinking Coal (North Wales)
UPSC
Upper Slatyband Ironstone
UPSI
Sneaton Potash Member
UPT
Upton Coal (West Yorkshire)
UPTC
Unapool Till Member
UPTI
Unconformable on bedrock, predominantly Lewisian gneiss.
Patchy, discontinuous extent across much of western Assynt and northwest Sutherland; almost exclusively occurs on Lewisian gneiss bedrock.
Grey-brown to dark grey, very poorly sorted, sandy, clast-rich diamicton with boulders. The till has a silty sand matrix with a low clay content. The till shows some evidence of subglacial deposition; with edge rounding and lodged clasts. Clasts are predominantly of Lewisian gneiss, but may also include sporadic Torridon Group sandstone, Eriboll Formation sandstone (quartzite) and Moine Supergroup clasts. The till is typically autochthonous, being derived from the local gneissose bedrock. However, the till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older. Local lithological variations within the Lewisian complex are reflected by till clast lithogies (eg. Laxford granite sheets; Scourie dykes; ultramafic zones, etc.).
Variable, 0.5 to 6m (maximum observed thickness).
Upton Formation
UPTN
Probably rests on weathered Crackington Formation; outcrops mainly fault-bounded.
Restricted to small area west of Clyst Hydon, Devon, and to a small outcrop around Chapelhaies Farm (SS 973 052), Bradninch, Devon.
Orange-brown to purplish brown gritty clay with scattered angular to subrounded culm sandstone fragments; locally clayey gravel. The clay matrix consists of angular fragments of weathered shale forming a "shale paste".
At least 10m
Upper Permian Rocks (Undifferentiated)
UPU
Upper Wee Coal
UPWC
Upper Wishaw Limestone
UPWL
Upper Yard Coal (South Wales)
UPYC
Upper Queen's Cairn Breccias
UQCB
Upper Quarried Limestone Member
UQL
Base of limestone-dominated beds overlying calcareous mudstone-dominated Nodular Limestone Member.
Limestone, grey, bioclastic, micritic with abundant shelly fossils and thin calcareous mudstone partings; reefs (bioherms) locally present.
8.6-10.4m at Wren's Nest, Dudley.
Base of pale grey silty calcareous mudstone with sporadic limestone nodules of the overlying Lower, Middle and Upper Elton formations (undifferentiated). These are equivalent to Lower Ludlow Shales.
Upper Rhyolitic Tuff Formation
Overlies Bedded Pyroclastic Formation.
Acid ash-flow tuffs, bedded tuffs, tuffites and tuffaceous siltstones.
Underlies black mudstones of Cadnant Shale.
Upper Ardross Limestone
URA
Upper Matlock Lava Member
URB
The basalt lava (or clay derived from weathered lava) of the Upper Matlock Lava Member rests upon thickly bedded limestones of the Monsal Dale Limestone Formation.
The Member has a more restricted outcrop in comparison with the Lower Matlock Lava Member, extending from Tearsall Mine (SK 262 600) in the west to Masson Hill (SK 286 587) and the Derwent Valley (SK 296 587) in the east. The southernmost extent is Groaning Tor adit, Via Gellia (SK 283 572).
Mainly vesicular and non-vesicular basalts. At Groaning Tor adit, Via Gellia (SK 283 572) the Member is seen as a 1m-thick clay wayboard (Walters and Ineson, 1981).
36m thick in boreholes at Cawdor Quarry, Matlock (SK 285 605) (Smith et al., 1967)
The basalt lava (or clay derived from weathered lava) of the Upper Matlock Lava Member is overlain by thickly bedded limestones of the Monsal Dale Limestone Formation.
Undifferentiated Red Beds
URBD
Upper Rags And Bath Oolite (Undifferentiated)
URBO
Upper Rigfoot Coal (New Cumnock, South Ayrshire)
URC
Upper Cardenden Smithy Coal (Fife)
URCS
Upper Red Coal (North Wales)
URED
Upper Fireclays Of Bonnybridge
URFC
Upper Rivergreen Coal (Northumberland)
URGL
Upper Hirst Coal (Glasgow-Stirling Area; Central Coalfield)
URH
Upper Jersey Coal (Fife)
URJ
Under Limestone
URLS
Ulbster/Riera Geo Mudstone
URM
Rushton Schist [Obsolete Code: Use Rs]
URN
Upper Rowhurst Coal (North Staffordshire)
UROHC
Upper Possil Coal (Glasgow Area; Central Coalfield)
URP
Upper Possil Ironstone (Glasgow Area; Central Coalfield)
URPI
Upper Red Sandstone
URS
Upper River Green Limestone Formation
URVG
Unnamed Sill, Late Neoproterozoic
USA3
Unnamed Sedimentary Rocks, Neoproterozoic
USAZ
Upper Skelgill Beds
USB
Upper Sulphur Coal (South Staffordshire)
USC
Unnamed Sill, Dinantian
USCL
Unnamed Sill, Westphalian
USCW
Unnamed Sill, Devonian
USD
Upper Stromness Flagstone Formation
USF
Drawn at the base of the Sandwick Fish Bed, where limestone rests conformably upon laminated siltstones and minor sandstones of the Lower Stromness Flagstone Formation.
Laminated carbonate-rich siltstones and shales with subordinate fine-grained thinly bedded sandstones.
c.560m
Drawn at the conformable upward passage from the flaggy siltstones of the Rousay Member to fluvial sandstone of the Lower Eday Sandstone Formation.
Unnamed Sill, Palaeogene
USG
Upper Shafton Coal (West Yorkshire)
USHC
Upper Shiaba Psammite Formation
USHP
Upper Stanhope Coal (South Derbyshire)
USHPE
Ury Silts Formation
USI
Generally conformable on Mill of Forest Till Formation.
Laminated silt and clay, generally red-brown.
Very variable, generally 3 to 4m; 7.7m proved in boreholes.
Generally overlain conformably by the Drumlithie Sand and Gravel Formation.
Upcott Slates Formation
USL
Under Smithy Lingula Band
USLB
Silkstone Coal, Upper Leaf (West And South Yorkshire)
USLKC
Unnamed Sill, Ordovician
USO
Upper Soap Coal (South Wales)
USOAP
Unnamed Sill, Ordovician To Silurian
USOS
Unnamed Sill, Permian
USP
Unnamed Sill, Late Carboniferous To Early Permian
USPL
Upper Spilsby Sandstone Member
USPS
Medium-grained, buff and green sands with sparse calcareous "doggers" and a basal bed of phosphatic nodules and small [generally chert] pebbles [Upper Spilsby Sandstone Member] rests on coarse-grained, pebbly, glauconitic sands and sandstones with calcareous "doggers" and sporadic phosphatic nodules towards the top [Lower Spilsby Sandstone Member]. An erosion surface separates the two members.
See Spilsby Sandstone Formation.
Upper Spilsby Sandstone Member. Thin, coarse-grained, grey or brown pebbly sandstone with iron ooliths (Ferruginous Grit of Swinnerton, 1937], underlain by fine-to medium-grained,buff, yellow and white sands with sparse calcareous "doggers" [the upper part of Swinnerton's, 1937,"Glauconitic Sands"]. The latter sands became coarser and greener towards the base of the member. A bed of phosphatic nodules and small [generally chert] pebbles occurs at the base [the Mid Spilsby Nodule Bed of Casey, 1963, 1973]. Offshore, in the Southern North Sea, the Upper Spilsby Sandstone Member has not been recognised.
To c.11.5m
Down-section change from purple-grey and brown mottled mudstones with scattered iron ooliths [Hundleby Clay Member, Claxby Ironstone Formation] or argillaceous ooidal ironstone [Claxby Ironstone Formation] to pale yellow, medium-grained sand and sandstone [Upper Spilsby Sandstone Member].
Unnamed Sill, Late Palaeozoic
USRU
Unnamed Sill, Late Silurian To Early Devonian
USSD
Upper Stinking Coal (Cannock)
USTC
Upper Stonesdale Limestone
USTL
Upper Siller Willie Coal (Midlothian)
USW
Usworth Coal (Northumberland And Durham)
USWO
Upper Turbot Anhydrite Unit
UTAN
Upper Tealby Clay Member
UTBC
Grey and buff clays, silty at some horizons and sporadically glauconitic (Upper Tealby Clay Member) rest on sandy limestones and ooidal clays (Tealby Limestone Member). In southern Lincolnshire (Skegness Borehole) and The Wash, the Tealby Limestone Member is missing and the Upper Tealby Clay Member rests on the Lower Tealby Clay Member. The base of the Member is difficult to define accurately in these areas.
Southern and central Lincolnshire. Mudstones equivalent to the Upper Tealby Clay Member are present below the Wash, although the lower boundary of the member cannot be accurately defined due to the absence of the Tealby Limestone Member.
Grey and buff clays, silty at some horizons and locally glauconitic. Ooidal horizons occur at the top in some areas. The member becomes more ferruginous north of Donnington-on-Bain and can be confused with the Roach Formation.
Up to c. 12 m.
In southern Lincolnshire and The Wash a rhythmic sequence of interburrowed and interbedded clay, "chamosite" mud, chamosite ooids, quartz sand and small pebbles of quartz and ironstone (Roach Formation) rest on grey and buff clays, silty at some horizons, locally glauconitic or ooidal (Upper Tealby Clay Member). In central to northern Lincolnshire ferruginous, sandy limestone and ferruginous, ooidal mudstones (Roach Formation) rest on grey and buff, silty, locally ooidal clays (Upper Tealby Clay Member).
Upper Two Foot Coal (New Cumnock)
UTF
Upper Two Foot Coal
UTFC
Upper Trigonia Grit Member
UTG
Garantiana Zone.
Hardground capping various members of Aston Limestone or Birdlip Limestone formations, or correlative disconformity on Lias Group, overlain by limestone as in lithological description.
Cotswolds: north Gloucestershire to east Avon. Absent east of a line Snowshill-Condicote-Southrop (modified after Barron, A J M, et al, 1997, fig.4). Possibly passes southwards into Maes Knoll Conglomerate (Arkell, W J, 1933, p.237-238).
Very hard poorly but thickly bedded grey and brown very shelly shell-detrital and moderately ooidal grainstone and packstone; characteristic fauna includes trigoniid bivalves, commonly as moulds, and brachiopods.
Typically 1 to 2.5m. Type section; 1.05 to 1.2m. Maximum c.5m (Colesbourne area).
Upward change from limestone as in lithological description, to fine- to coarse-grained ooidal, peloidal/pisoidal and shell-detrital packstone to grainstone (Clypeus Grit Member); commonly a non-sequence marked by a hardground.
Upper Thick Coal (South Staffordshire)
UTHC
Upper Thames Valley Formation
UTMS
Unconformable on glacigenic deposits of the Anglian stage or older Pleistocene strata or bedrock. Individual terrace deposit members rest unconformably on older Pleistocene strata or bedrock.
The upper part of the valley of the River Thames, upstream of Goring together with deposits of tributary valleys including the Thame, Ock, Cherwell, Evenlode and Windrush.
Mainly sand and gravel forming river terraces and silt, silty clay and sand forming floodplains and concealing sand and gravel. Including units of silty sand, silt, clay and peat. Terrace deposits of the upper Thames contain clasts mainly of limestone lithologies. The formation includes interbedded units of locally fossiliferous silty sand, silt together with organic clay, tufa and peat, which are biostratigraphically correlated with interglacial (warm) stages. The main terrace deposit members are the Freeland Sand and Gravel, Spelsbury Gravel, Hanborough Gravel, Daylesford Sand and Gravel, Wolvercote Sand and Gravel, Summertown-Radley Sand and Gravel, Northmoor Sand and Gravel and Alluvium. In the Thame and Windrush valleys terrace deposit member include the Tiddington Sand and Gravel, Chilworth Sand and Gravel, Blackditch Sand and Gravel, Shabbington Sand and Gravel, Sherbourne Sand and Gravel, Ickford Sand and Gravel, Rissington Sand and Gravel and Quarrendon Sand and Gravel.
Single terrace aggradations range from 3 to 12m.
Upper Threequarters Coal (Cumbria)
UTQ
Upper Trap
UTR
Upper Trenchard Coal (Forest Of Dean)
UTRC
Utsira Formation
UTS
Upper Three Sisters Ignimbrite
UTSI
Upper Tunbridge Wells Sand Formation
UTW
Down-section change from fine-grained sandstones and siltstones [Upper Tunbridge Wells Sand Formation] to mudstone [Grinstead Clay]. In some areas the boundary is sharp [e.g. Scayne's Hill, in the Horsham district, where a thick basal sandstone unit occurs].
The formation is widespread in the Weald of southeastern England, although where the Grinstead Clay and Ardingly Sandstone are missing, it is not possible to distinguish the Lower and Upper Tunbridge Wells Sand formations [which are then incorporated into the "Tunbridge Wells Sand"]. The Upper Tunbridge Wells Sand Formation can be traced across the Sevenoaks-Tonbridge sheet [287], Horsham sheet [302] and Tunbridge Wells sheet [301] where it is seen only in boreholes, and Tenterden sheet [304]. It is again present in the northern part of the Brighton and Worthing district sheet 316/333] and can be traced onto the northwestern part of the Lewes sheet [319], but it is again undifferentiated "Tunbridge Wells Sand" in much of the Lewes district and in the adjoining Hastings district [sheet 320/321].
The formation comprises a complex succession of interbedded deposits with both upward-fining and upward-coarsening cycles. Thinly bedded silty mudstones, siltstones, silty sandstones and fine-grained sandstones are laterally persistent over long distances. Sandstones, which form prominent scarp and dip slope features, are typically fine-grained and quartzose, weathering to a pale yellowish grey or brown colour. They are locally ferruginous in the St Leonard's Forest area, three sandstone beds are sufficiently persistent to be named Shelly Plain Sandstone, Colgate Sandstone and Roffey Park Sandstone [Gallois and Worssam, 1993]. Clay ironstone occurs locally, notably in the Horsham-Crawley area [Worssam, 1972]. In the Cuckfield area, silt is the dominant component [Lake & Thurrell], 1974]. Here, grey and greenish grey silty mudstones, red-mottled in part, dominate in the lower part of the Formation, whereas pale grey to yellowish grey sandstone mostly appear in the upper part. Channel and slump structures, together with cross- bedding occur in the sandstones. Siltstones are commonly bioturbated.
Up to c.100m [possibly up to 128m according to Gallois and Worssam, 1993].
Boundary is generally transitional. The mudstone of the Weald Clay Formation passes down into fine-grained sandstone and siltstones. The boundary is shown in the resistance log in the Cuckfield No1 Borehole [Lake & Thurrel, 1974]. In the Crawley area, at outcrop,"clayey sediments without sandstones" [Weald Clay Formation] pass down into "silty and clayey sediments with rare thin sandstone beds" [Upper Tunbridge Wells Sand Formation] [Gallois & Worssam, 1993]. The boundary is placed at the top of the highest sandstone. However, in the southern part of the Horsham district and the northern part of the Brighton district, the top of the Upper Tunbridge Wells Sand Formation is marked by a thick sandstone unit, locally capped by "very ferruginous, ripple marked sandstone" or by clay ironstone. The top is also a persistent sandstone bed in the Crawley-Lingfield area of the Tunbridge Wells district [Bristow and Bazley, 1972]. In some districts, however, such as Tenterden [304], Hastings [320/321] and Lewis [319] where the Ardingly Sandstone Member and the Grinstead Clay Formation thin out, the sands between the Wadhurst Clay Formation and the Grinstead Clay Formation thin out, the sands between the Wadhurst Clay Formation and the Weald Clay Formation are undifferentiated and termed "Tunbridge Wells Sand"in BGS memoirs and maps.
Upper Vexhim Coal
UVC
Upper Weald Clay Member
UWC
Upper Welsh Coal (South Wales)
UWCO
Upper Winter Hill Terrace Deposits
UWHT
Definition as for "Winter Hill Deposits"; see elsewhere in Lexicon. [Generic description].
Upper Western Irish Sea Formation
UWIS
Disconformity at top of underlying Cardigan Bay Formation or incised into pre-Quaternary rockhead surface.
Glaciomarine/marine clay and silt with local concentrations of sand. Seismically well-ordered character, exhibiting drape, onlap and progradation features.
10 to 20m, locally thickening to 60m in channel infills.
Unconformity at base of overlying Surface Sands Formation (the "Y" seismic unconformity surface of Akhurst et al,1997). Locally crops out at sea bed.
Ulster White Limestone Group
UWLF
Santonian to Maastrichtian. Uintacrinus socialis to Belemnitella occidentalis occidentalis (see Wood, 1967) zones.
Rests disconformably on various members of the Hibernian Greensands Formation and oversteps (unconformable) onto older pre-Cretaceous rocks. Internal overstep within the group principally at the level of the Post-Larry Bane White Limestone Subgroup (informal term defined below) places successively higher formations at the base of the group over structural highs at the margins of the principal basins
Throughout Northern Ireland. Fullest development in the North Antrim Basin with significant successions in the Midland Valley (East Antrim Basin) and the Southern Uplands as defined in Fletcher (1977).
Principally limestones (hardened chalks) with subordinate flint, marl, sponge bed, hardground, conglomeratic and fossil acme bands, with glauconite grains where formations become condensed over structural highs. Fletcher (1967, 1977) proposed fourteen members which are herein considered as formations, in ascending order; the Cloghfin Sponge Formation, Galboly Chalk Formation, Cloghastucan Chalk Formation, Creggan Chalk Formation, Boheeshane Chalk Formation, Larry Bane Chalk Formation, Ballintoy Chalk Formation, Glenarm Chalk Formation, Garron Chalk Formation, Portrush Chalk Formation, Ballymagarry Chalk Formation, Tanderagee Chalk Formation, Port Calliagh Chalk Formation and Ballycastle Chalk Formation. He informally divided the succession into a Pre-Larry Bane Chalk White Limestone, Larry Bane Formation and Post-Larry Bane Chalk White Limestone parts. The two divisions above and below the Larry Bane Chalk Formation are regarded as subgroups herein but their name is shortened to the by the omission of the white limestone descriptor.
Highly variable dependant on the position within structurally controlled basins (environments) of which five were named by Fletcher (1977) as the Hebridean Basin (presumably incorporating his Londonderry Shelf and North Antrim Basin), the Highland Border (also termed the Dalradian Massif), the Midland Valley (usually termed the East Antrim Basin) and the Southern Uplands. Up to 150m+ of `White Limestone? was encountered in the Aughrimderg Borehole [H 880 685] (Wilson , 1972, p 56) but the thickest and most complete development at outcrop is found on the North Antrim coast where 120m of beds are present, although not at any one locality. The Geological Society Special Report on the Cretaceous (Rawson et al., 1978) gives a value of 130m.
Eroded contact where the group is overlain by the Palaeogene Antrim Basalts or Quaternary deposits.
Upper Yard Coal (Cumbria)
UYD
Upper Yard Coal (North Wales)
UYDC
Uyea 'Group'
UYEA
Uyea Fault Zone
UYFZ
Amphibolite (Of Guernsey And Sark)
Valla Field Group
VAFD
Valla Field Gneiss Formation
VAFG
Valla Field Schist Formation
VAFS
Vaasetter Sandstone Formation
VAG
Drawn where rocks of the Vaasetter Sandstone Formation (see Lithology Description) rest conformably on sandstone of the North Haven Beds.
Conglomerate, sandstone and pebbly sandstone with lenses of conglomerate.
c.600m
Drawn at conformable upward passage from conglomerate of the Sheep Craig Sandstone to sandstone of the North Gavel Beds.
Valayre Gneiss Formation
VAGN
Vaila Formation
VAIL
Valhall Formation
VALH
Vaich Pelite Formation
VAPE
Overlies the Glascarnoch Psammite Formation at its eastern margin, where predominantly psammitic lithologies pass gradationally into predominantly pelitic lithologies.
The outcrop runs approximately north to south, continuing north from the western end of Loch Luichart (NH320860) through the south-eastern end of Loch Glascarnoch (NH320720), through Strathvaich Forest to the western end of Gleann Beag (NH300840). It then swings round to the east, forming a large outcrop in the northern part of Freevater Forest (NH350930), before the outcrop thins and swings to the south-east, terminating against a fault in Freevater Forest at (NH455883). To the southern end of Loch Luichart the outcrop runs south-west and thins out near Carn na Feith rabhain (NH225580)
Garnet-muscovite-biotite bearing, schistose pelite and semipelite, interbanded with psammitic units.
Overlain by the Crom Psammite Formation at its western maargin, where predominantly pelitic lithiloigies pass gradationally into predominantly psammitic lithologies.
Vexford Breccias
VBR
Underlain by the Wiveliscombe Sandstones. Boundary marked by lithology change form mainly sandstone to include breccia.
Taunton district, Somerset.
Angular and subangular fragments of sandstone, slate and quartz in a sandy matrix whose grains are mostly angular, but locally rounded. Locally rounded fragments are found including Carboniferous limestone. The breccias are generally well cemented. Interbedded sandstones are present up to 1m thick. The Breccias generally form a distinct scarp feature.
Overlain by the Littleham Mudstone. Boundary marked by change in lithology to mudstone.
Volcanic Conglomerate Member
Viger Coal (Coalbrookdale)
VCCC
Castle Cornet Gneiss
VCG
Ciger Coal Rock
VCR
Doyle Gneiss
VDG
Vanderbeckei Marine Band
VDMB
Vementry 'Group'
VEM
Valley Infill, Pre-Holocene [See Descriptions For Limitations Of Use]
VFL
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also VFLD, VFLF, VFLG and VFLS. The full description on the original map was "PRE-HOLOCENE VALLEY INFILL (mainly beyond Scottish Readvance)".
Valley Infill, Pre-Holocene, Mostly Till [See Descriptions For Limitations Of Use]
VFLD
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also VFL, VFLF, VFLG and VFLS. The full description on the original map was "PRE-HOLOCENE VALLEY INFILL (mainly beyond Scottish Readvance), Mostly till".
Valley Infill, Pre-Holocene, Mostly Fines [See Descriptions For Limitations Of Use]
VFLF
Pre-Holocene.
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also VFL, VFLD, VFLG and VFLS. The full description on the original map was "PRE-HOLOCENE VALLEY INFILL (mainly beyond Scottish Readvance), Mostly fines (glaciolacustrine)".
Valley Infill, Pre-Holocene, Mostly Gravels [See Descriptions For Limitations Of Use]
VFLG
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also VFL, VFLD, VFLF and VFLS. The full description on the original map was "PRE-HOLOCENE VALLEY INFILL (mainly beyond Scottish Readvance), Mostly gravels (sandar)".
Valley Infill, Pre-Holocene, Mostly Sand [See Descriptions For Limitations Of Use]
VFLS
This was originally used as part of the Sellafield Quaternary Domains Map. To avoid potential confusion it should be used only for similar purposes in future. See also VFL, VFLD, VFLF and VFLG. The full description on the original map was "PRE-HOLOCENE VALLEY INFILL (mainly beyond Scottish Readvance), Mostly sand (deltaic)".
Vobster Formation
Vigra Member
VGR
Locally recognisable member of Maentwrog Formation.
Virgin Coal (Central Coalfield)
Icart Orthogneiss
VIC
Victoria Coal (South Wales)
VICO
Victoria Coal (Northumberland And Durham)
VICT
Victory Formation
VICY
Vidlin Limestone Formation
VIDL
Village Farm Formation
VIFM
The lower boundary is taken at a sharp, well-defined unconformity. The base of the unit is taken at the lowermost pebbly sandstone unit overlying a pebble-free sandstone sequence. Rests on Lower Palaeozoic strata of the Lower Comley Sandstone or "Dolgelly Beds".
Lilleshall Inlier, Lilleshall, North Shropshire.
Polymictic conglomerate, sandstone and breccia.
40.35m maximum proved (incomplete thickness, top not present) from Lilleshall L8 Borehole (SJ71NW/34).
The upper boundary is assumed to be unconformable or transitional. It is taken at the uppermost sandstone below a sandstone and limestone-dominated sequence of the Jackie Parr Limestone Formation.
Virgin Under Coal (Central Coalfield)
VIU
Vallis Limestone Formation
Taken at the incoming of pale grey coarse crinoidal limestones of the Formation above the dolomitized packstones of the underlying Black Rock Limestone Subgroup. Little is known about this contact, which needs further investigation.
Eastern Mendips [ST 70 45]. Passes westwards into the Burrington Oolite Subgroup. The geometry of this Formation is problematical and needs further investigation.
Pale grey coarse-grained crinoidal limestone. Deposited in a shallow shelf/ramp environment.
152m in eastern Mendip, thinning westwards to a feather edge in the central Mendip Hills.
Taken at incoming of ooidal limestones and crinoidal/ooidal limestones of the overlying Burrington Oolite Subgroup above the coarse crinoidal limestone of the Formation. Little is known about this contact, which needs further investigation. At the type locality it is taken at the incoming of calcite mudstones and ooidal/crinoidal limestones of the overlying Clifton Down Limestone.
Valley Gravel
VLGR
Sand and gravel, locally with lenses of silt, clay or organic material. [Generic description].
Vicard Mudstone
Unnamed Volcanic Rocks Of Any Age
VOLC
Voylart Coal (South Wales)
VOYC
Perelle Gneiss
VPG
Pea Stack Gneiss
VPS
Quartz Breccia (Vein)
VQBR
Abundant in the Beinn Udlaidh - Ben Lui - Beinn Odhar area around Tyndrum in the nirthwest part of the Stirling District and adjacent parts of the Argyll District.
Quartz veins forming anastomosing networks of individual veins of varying orientation. The veins enclose or encircle generally angular patches and fragments of country rock. The vein-breccia itself lies within a discrete and normally sub-vertical or steeply-dipping vein.
Normally a few metres to tens of metres thick
Not applicable
Vein-Quartz Of Unknown Age And Affinity
VQU
Schists (Of Guernsey)
Victoria Shell Bed
VSB
Victoria Shell Bed Coal (Northumberland)
VSBC
Biotite-Quartz-Gneiss Of Sark
VSG
Vectis Formation
VTIS
Valtos Sandstone Formation
VTS
Virtuewell Coal
VWC
Victory Coal (Fife)
Vale Of York Formation
VYORK
Unconformable on bedrock or older superficial deposits such as valley deposits, outwash deposits and laminated clays formed in front to the advancing glacier.
Vale of York, northwards to Teeside, southwards to the Escrick Moraine.
Dominantly glacial till (sandy clay, clayey sand and clay with gravel and boulders) with interbedded sand, gravel and laminated clay, plus more substantial areas of those individual lithologies incorporated in the till sheet and moraines.
Up to about 50m in moraines, generally 10 to 30m.
Varies between the present land surface and the contact with later deposits such as glacial lake deposits, outwash deposits and blown sand.
Wealden Group
Base of non-marine silts and sands on soft calcareous mudstones of the Upper Purbeck (Peveril Point Member of Dorset), or unconformable contact on older formations.
Sandstones, siltstones, shales, limestones and clay ironstones of predominantly non-marine facies.
Up to about 800m
Grey or red clays of predominantly non-marine Weald Clay Formation overlain on sharp unconformable/disconformable contact by Atherfield Clay Formation (typically dark grey to black), or other marine deposits of the Lower Greensand Group, or younger formations.
White Four Feet Coal (South Wales)
W4FC
Worsley Four Foot Coal (South Lancashire)
W4FT
Wattonensis Beds Member
WAB
Base defined by an upward increase in shell-detritus in calcareous mudstone.
South of Mere Fault to Dorset coast (at crop).
Pale olive-grey argillaceous shelly limestones interbedded with medium olive-grey, bioturbated, shell-detrital silty mudstones. Distinctive fauna includes Rhynchonelloidella wattonensis.
The top of the uppermost argillaceous limestone marked by a decrease in shell-detritus.
Wall Coal (North Wales)
WACO
Wadbister Ness Formation
WAD
Drawn at base of psammite of the Wadbister Ness Formation where it rests conformably on the Girlsta Limestone.
Alternating bands of flaggy, micaceous psammite and semipelite with bands of calc-silicate rock and impure marble as well as some bands of hornblende schist.
Drawn at conformable upward passage from semi-pelite of the Wadbister Ness Formation to the Laxfirth Limestone.
Walbottle Dyke
WADY
Walls Sandstone Formation
WAF
Ward Hill Sandstone Formation
WAG
Drawn at the base of thr Dronga Conglomerate and Pebbly Sandstone. Base not seen, or faulted contact.
Basal conglomerate, sandstone and pebbly sandstone with beds of dolomitic siltstone and mudstone.
Drawn at conformable upward passage from the Ward Hill Sandstone to siltstone and mudstone of the Furse Argillaceous Beds at the base of the Observatory Sandstone Formation.
Wagtail Limestone
WAGL
White Ash Coal (Goyt Trough)
WAGT
Hall Hill Sandstones
WAH
Warton Halite Formation
WAHA
Warren House Gill Till Formation
WAHG
Unconformable, undulating erosional contact on limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone) within the floor of a buried valley at the mouth of Warren House Gill. Locally overlies limestone rubble-filled fissures in the "Magnesian Limestone".
Dark grey, very compact, pebbly sandy clay diamicton containing Scandinavian erratics to the exclusion of rocks from the British mainland excepting local limestone and dolostone of the Zechstein Group (formerly Magnesian Limestone). More than 80% of the erratics have been matched with igneous and metamorphic rocks occurring in the Oslo area pf southern Norway, including larvikite and nordmarkite. Chalk, flint, red sandstone, red and green (Triassic) marl and belemnite fragments constitute about 6% of the erratics, and, together with numerous marine shell fragments, have been derived from the North Sea Basin.
Sharp, conformable, draped contact with overlying pale brown, fine-grained sand and silt of the Warren House Gill Loess Bed.
Warren House Gill Loess Bed
WAHL
Sharp, conformable, draped contact with underlying dark grey, shelly, silty sandy gravelly diamicton of the Warren House Gill Till Formation.
Pale brown, massive, very fine-grained sand and silt, typically with vertical cracks, containing rounded concretions and sparse pebbles. Grading upwards into horizontally stratified, very fine-grained sand and silt, with thin beds of coarser sand and stringers of fine pebbles.
Planar, subhorizontal to gently undulating, gradational glacitectonic contact with overlying dark grey, stiff, sandy, silty stony clay diamicton of the Blackhall Till Formation.
Wallowbarrow Tuff Formation
WAL
Base of andesitic lapilli-tuff and pyroclastic breccia, unconformably overlying Duddon Hall Tuff Formation (bedded air-fall tuff), Ulpha Andesite Formation (andesitic lava) Holehouse Gill Mudstone Formation (mudstone and sandstone).
Grassguards Fault (SD 220 970) to Hutton (SD 204 902) and Holehouse Gill (SD 183 930) in the Duddon Valley, Cumbria.
Massive, andesitic lapilli-tuff and pyroclastic breccia.
Defined by bases of overlying formations; usually the Dunnerdale Sandstone Formation (volcaniclastic sandstone) but locally the Lickle Tuff Formation (rhyolitic and dacitic tuff).
Wallsend Coal
WALC
Wales Coal (Yorkshire, Nottingham)
WALE
First Wales Coal
WALE1
Second Wales Coal
WALE2
Wales Glacigenic Subgroup
WALES
Generally sharp, unconformable contact with bedrock. Locally on Head of Ipswichian or early Devensian age or on units of the Irish Sea Coast Glacigenic Subgroup (e.g. Stockport Glacigenic Formation).
South, southeast, mid and northeast Wales and Welsh Borderland.
Suite of glacial, glaciofluvial and glaciolacustrine deposits including sandy diamictons (till), sand, gravel, silt and clay. The sediments were deposited by, or are the deglaciation products of, ice that emanated from the Welsh mountains and radiated across Wales and the Welsh Border. The till deposits vary in colour and clast content reflecting local bedrock. Constituent formations include the Brecknockshire Till Formation containing clasts derived predominantly from the Devonian (Black Mountain, Fforest Fawr and Brecon Beacons) and Carboniferous sources (sedimentary rocks of the South Wales Coalfield), the Plynlimon Till Formation and Shrewsbury Glacigenic Formation containing Lower Palaeozoic clasts of the Cambrian Mountains and the Eryri Till Formation with Lower Palaeozoic volcanic clasts derived from Snowdonia. The till formations contain subordinate stratified sand and gravel. The principal centres of ice build-up were the Cambrian Mountains.
Unconformable contact with units of the Britannia Catchments Group (West Wales Catchments Subgroup and Cheshire-North Wales Catchments Subgroup) and the British Coastal Deposits Group.
Wall Coal (Fife)
WALL
Walls 'Division'
WALS
Walton Member
WAM
Waterloo Mudstone Formation
WAMU
Wandering Coal
WAN
Wasperton Sand And Gravel Member And New Inn Sand And Gravel Member (Undifferentiated)
WANIT
Wardour Formation
WAR
Upward change from dark grey, slightly sandy mudstones (of the Kimmeridge Clay) to clayey sands and sandy clays; boundary taken at the base of a glauconitic sand forming the top to a coarsening-upward cycle. Springs commonly mark the base.
West Tisbury [ST 906 290] to Tisbury [955 297].
Sandy clays and clayey sands, locally glauconitic, especially towards the base.
Upward change from sandy mudstones and clayey sands to fine-grained bioclastic sandstones and sandy limestones and/or (locally) shelly micrites (of the Tisbury Member).
Warras Coal (North Wales)
WARC
Warp
WARP
Artificially induced alluvium. [Generic description: 'TMOS' Procedures].
Wardie Sandstone
WASA
Status uncertain but likely to be erosive on underlying argillaceousand arenaceous rocks of the Gullane Formation.
A typically fine-grained, off-white, often thickly bedded with trough cross bedding, siliceous sandstone containing little mica or carbonaceous material, used locally as a building stone.
Between 10 m and 20 m thick, in the Granton and Wardie area of the City of Edinburgh.
Wasdale Head Granite
WASD
c.450Ma
Wanlip Member
WASG
Wardie Shales Member
WASH
Recognised locally in Midlothian; named after Wardie in Edinburgh.
Variable sequence of shales, calcareous mudstones, and thin sandstones, with thin calcareous and cherty bands.
Status uncertain; for now considered an informal member of the Gullane Formation.
To c.325m
Warren Sponge Bed
WASP
Wasperton Sand And Gravel Member
WAT
Late Pleistocene (MI Stage ?5a to 4, or 3 to 2).
Unconformable, commonly channelled base, resting on Wolston Formation or Baginton Formation in upper Avon or farther downstream (beyond Coventry) on Lower Jurassic or Triassic bedrock.
Avon Valley, Rugby to Tewskesbury (BGS Sheets 183, 184, 199, 200, 201, 216).
Predominantly cold phase sands and gravels that underlie the Avon Second Terrace of Tomlinson (1925) and of BGS Maps. Dominated by clasts of "Bunter" quartz/quartzite lithologies with subordinate flint. Locally includes the organic Fladbury Bed, which is "Mid Devensian" although the precise age is controversial. Probably correlates with Holt Heath Member of the Severn Valley Formation.
(A) Here named the Wasperton Sand and Gravel though it is simply Wasperton Member in Bowen 1999, and in the previous BGS list of computer codes. (B) Dating of this terrace is contentious; as yet the crucial Fladbury Bed beneath it has no age-diagnostic fauna and its C14 date of c.38K (within MIS 3) may be a minimum. (C) Terrace surface typically some 5m above modern Avon alluvial floodplain in the Rugby area, increasing downstream to c.9m near the confluence with the Severn at Tewkesbury. (D) All things being equal, one this unit might be expected to correspond with the Holt Heath (3) of the Severn (Late Devensian outwash terrace) but the latter seems a few metres lower at the Avon confluence (Tewkesbury) so this isn?t as might be hoped. On the other hand, the Wasperton is too high to meet the Worcester (Terrace 2) of the Severn too! Actually as both the Holt Heath and Wasperton are composite, age-wise, none of this is greatly surprising Nevertheless there might be a problem both with the classification of the Severn terraces, and those of the Avon. (E) The upper boundary is given as ?ground surface? though head, colluvium or soil deposits might intervene. (F) Avon and Severn terraces need reviewing in their entirety and classification of some outcrops on existing maps is highly suspect. Thus the Previous Names are necessarily an approximation. (G) Only 50K maps on the main course of the Avon are listed. Terrace 2 appears on several other maps in the catchment, up tributary steams and so on, (see Warwickshire Avon Valley Formation for complete list) but whether this is really the Wasperton Member is unclear.
Wasperton Sand And Gravel Member, Lower Facet (Warwickshire Avon)
WATA
Sand and gravel; gravel composed of a high proportion of flint, Jurassic limestone and 'Bunter' type clasts; beneath low rise within the Wasperton Member; part of the second terrace of the River Avon. [Generic description: academic papers and BGS Memoirs].
Wasperton Sand And Gravel Member, Upper Facet (Warwickshire Avon)
WATB
Sand and gravel, gravel composed of a high proportion of flint, Jurassic limestone and 'Bunter' type clasts; above a low rise within the Wasperton Member; part of the second terrace of the River Avon. [Generic description: academic papers and BGS Memoirs].
Wenallt Coal (South Wales)
WATC
Walcott Till Member
WATI
The lower boundary of the Walcott Till Member is irregular and erosional and lies upon either sandy Wroxham Crag Formation sediments or on laminated silts and clays of the Happisburgh Glacigenic Formation. Commonly these underlying sediments exhibit evidence of shearing. [See also the Stratotype information.]
Found in outcrops throughout the North Walsham and Cromer districts; occurs in coastal sections between Happisburgh and Overstrand, north Norfolk.
The lower boundary of the Walcott Till Member consists of an olive grey to olive brown silt-rich matrix-supported diamicton that is largely massive in structure. It has a moderate matrix calcium carbonate content of c.36% and contains an abundance of chalk and flint clasts.
A maximum of 2.2m has been observed.
The diamicton is generally overlain by the outwash sands of the Mundesley Sand Member. The junction between the two units is commonly sharp and erosional.
Water Of Tanar Limestone Formation
WATL
Watstone Musselband Ironstone
WATM
Wenallt Rider Coal (South Wales)
WATR
Waveney Valley Formation
WAVV
Unconformable upon glacial and solifluction deposits and upon Crag Group and Chalk Group bedrock.
Valley of River Waveney and its tributaries, from west of Diss, Suffolk, to its junction with the River Yare northwest of Lowestoft.
The formation encompasses the fluvial , lacustrine and organic deposits of the River Waveney and its tributaries. It includes floodplain alluvium and a restricted development of river terrace deposits. The floodplain alluvium comprises soft clays, silts and fine-grained sands, with bodies of peat, overlying fine- to coarse-grained sands and gravels. River terrace deposits are largely gravel and sand. The gravels are dominated by subangular to rounded flint, including large cobbles, also rounded pebbles of quartz and quartzite and a little chalk.
Warwickshire Group
WAWK
At gradational conformable base of the lowest red-bed formation, which is generally the red mudstones of the Etruria Formation above the Coal Measures, at the sharp unconformable base of red-beds of late Carboniferous age if the Coal Measures are absent, or locally at the base of grey beds, seen as grey-green sandstone of the Halesowen Formation.
The Pennine Basin in Staffordshire, Warwickshire, Shropshire, Lancashire, Nottinghamshire and South Yorkshire.
Predominantly red, brown or purple-grey sandstone, siltstone and mudstone, some grey strata, coals not common, local conglomerates, localised beds of Spirorbis limestone.
About 1225 m thick in Warwickshire, up to 1192 m thick in the Stoke-on-Trent area.
At the base of the unconformable (post-Variscan) Permian or younger strata.
White Axen Coal (Somerset)
WAXC
Waberthwaite Tuff Formation
At change from rhyolitic (of the Airy's Bridge Tuff Formation) to acid andesitic/dacitic welded tuffs; in part overlies andesites of the Birker Fell Andesite Formation, tuff and lapilli-tuff of the Whinny Bank Formation or the Po House Formation.
Whitfell, Burnmoor, Buck Barrow, Plough Fell, Waberthwaite, Millom Park, Cumbria. (SD 16 93; 14 90;16 90).
Acid andesitic to dacitic, welded lapilli-tuffs and tuffs; massive, poorly sorted, eutaxitic to parataxitic; intercalations of pyroclastic breccia.
Probably around 1100m. Not present east of Baskill Fault.
Defined by base of Duddon Hall Formation at the sharp change to andesitic bedded tuffs.
Wee Bankie Formation
WBA
Base of formation rests on an irregular pre-Quaternary rockhead surface.
Overconsolidated sandy and gravelly till with interbeds of fluvial sand and pebbly sand, and, less commonly, accumulations of coarse sand and gravel.
c.35 metres. Thickness generally varies from < 5 metres to 40 metres. Rarely it exceeds 40 metres.
Top of unit is unconformably overlain by younger sediments.
Whitberry Band
WBB
Calcareous and sandy shaly mudstones.
Local base of the Fell Sandstone Formation (previously the Middle Border "Group").
West Bay Cornstone Member
WBC
Probably Courceyan, being the uppermost part of the Kinnesswood Formation, which spans from Frasnian to Courceyan,
About 16m
Welton Chalk Formation And Burnham Chalk Formation (Undifferentiated)
WBCK
Woodhill Bay Congomerate
WBCO
Westbury Formation And Cotham Member (Undifferentiated)
WBCT
Westleton Beds
WBDS
Flint-rich gravel with sand; >90% gravel. [Generic description: academic papers and BGS Memoirs].
West Burra Firth 'Group'
WBFG
Walls Boundary Fault Zone
WBFZ
Woodbank Group
WBK
Drawn at the base of the Clee Sandstone Formation where it conformably rests upon the Abdon Limestone Formation.
Brown Clee Hill, Shropshire.
Dominant green sandstones, subordinate red siltstones and rare conglomerates and dolomitic rocks. In the upper parts comprising fine-grained to very coarse-grained sandstones with subordinate conglomerates.
225 metres approx.
Drawn at the conformable upward passage of the Monleys Fold Sandstone where it is unconformably overlain by basal conglomerate of the Farlow Group.
White Lias Formation And Blue Lias Formation (Undifferentiated)
WBL
White Lias Formation And Blue Lias Formation (Littoral Facies) (Undifferentiated)
WBLL
Whitebaulks Limestone
WBLS
West Braes Marine Band
WBMB
White Brae Mudstone Formation
WBMU
Watcombe Breccia Formation
WBR
Wellingborough Limestone Member
WBRO
Limestone or sandstone overlying marine mudstone or siltstone of the Rutland Formation,undifferentiated, forming the lower part of the Wellingborough Rhythm of Bradshaw (1978).
The Stamford district, where the unit thins, and passes northward into sandstone as at Ketton Quarry (Cox, B M, and Sumbler, M G. 2002), passing south-westwards into the Taynton Limestone Formation in the Silverstone area.
A massive argillaceous, sandy, shelly and shell-detrital limestone associated with rubbly oyster-rich limestone and marl and mudstones, passing northwards into sandstone.
Up to about 5 m thick, typically 3m to 4m, measured as 3.04 in type section.
The top of the limestone or sandstone overlain by rootleted siltstone or mudstone of the Rutland Formation, undifferentiated, forming the upper part of the Wellinborough Rhythm of Bradshaw,1978.
Woburn Sands Formation
WBS
Unconformably overlies Jurassic or older strata in boreholes. Jurassic strata predominantly mudstone such as Kimmeridge Clay, Ampthill Clay and Oxford Clay.
Outcrop Leighton Buzzard to Cambridge through Bedfordshire, Buckinghamshire and Cambridgeshire. In the area of the "Bedfordshire Straits" linking the Weald Basin (Folkestone Beds and Sandgate Beds) in the south to Eastern England Shelf (Carstone and Sutterby Marl) in the north.
Sandstone (or loose sand). Fine- to coarse-grained rounded marine quartz sand, glauconitic in part. Commonly silty with few clay wisps or seams. Locally clean silver sands. Locally cemented to iron pan or gritty carstone. Cross-bedded. Some pebbles and phosphatic nodules to base. Typically grey or greenish grey weathering to ochreous yellow-brown. Minor lignite and pyrite. Local developments of fuller's earth. Commonly barren but nodule layers to base fossiliferous as at Upware and Brickhill.
To 120m. Rapid variation, resulting from uneven underlying topography and pre-Gault erosion. Thins to southeast on to London Platform. 85m proved at Woburn, 60m proved east of Leighton Buzzard. Absent west of Leighton Buzzard.
Unconformity. Overlapped by Gault - a grey mudstone.
Woodbine Shale
WBSH
Westbury Formation
WBY
Usually non-sequential with underlying Blue Anchor Formation, locally transitional.
Present throughout United Kingdom outcrop area.
Dark grey mudstones or shales with subordinate thin limestones, sandstones and fossiferous arenaceous units ('bone beds').
Placed at locally transitional junction with overlying Cotham Member of the Lilstock Formation.
Weald Clay Formation
Base of clayey silts and silty clays (without sandstones) overlying highest sandstone of Tunbridge Wells Formation (within Hastings Beds (Subgroup)).
Mainly silty clay and clayey silt, with silts, sands, ironstones and clay ironstones; typically clays are grey, weathering to mottled orange/yellow or steel grey, or red, retaining that colour in weathered condition.
Overlain on sharp unconformable/disconformable contact by Atherfield Clay Formation (typically dark grey to black, weathering bluish grey to brown or orange, clay or silty clay).
White Corries Breccia
WCB
Whinneyhill Coppice Clay Member
WCC
Sharp, undulating, unconformable contact with pale red stony clay diamicton and cobble gravel of the Holmrook Till Member of the Blengdale Glacigenic Formation.
Dark brown (Munsell Soil colour) clay with laminae of silt and fine-grained sand, and sparse dropstone pebbles. Rhythmic graded lamination is common.
To 24.7m
Generally sharp, planar, glacitectonic, unconformable contact with dark reddish brown pebbly silty clay diamicton of the Green Croft Till Member of the Aikbank Farm Glacigenic Formation.
White Cliff Coral Band
WCCB
Weybourne Crag
WCG
Winstow Chert Formation
WCH
In the Chudleigh area the lower boundary is taken at the incoming of black sooty and siliceous mudstones of the Winstow Mudstone Member above the purple, green and grey mudstones of the underlying Whiteway Mudstone Formation. The contact is generally sharp. In the Plymouth area it is taken at the incoming of dark grey cherts and siliceous mudstones of the Winstow Chert Formation above the mid grey silty mudstones of the Saltash Formation.
Between Chudleigh (SX 870 784) and Kingsteignton (SX 88 74), south Devon and in the middle Tamar valley (SX 44 61) in the Plymouth area.
Thin- to medium-bedded green, grey-green, black and purple radiolarian cherts with interbeds of siliceous mudstones and "shales". In the Chudleigh area, there is a thin (to 14m) basal unit of black siliceous and sooty mudstones (the Winstow Mudstone Member). The uppermost part of the Formation, the Posidonia Beds, comprises 10m of thin-bedded cherts, shales and limestones with an abundant fauna of Posidoniid bivalves and spirally striated goniatites.
45m in the Chudleigh area; about 30m+ in the Plymouth area.
In the Chudleigh area the upper boundary is taken at the incoming of dark grey and greenish grey mudstones with thin siltstones and fine- to coarse-grained sandstones of the overlying Ugbrooke Sandstone Formation above the thin-bedded cherts, shales and limestones (Posidonia Beds) of the Winstow Chert Formation. In the Plymouth area the top of the formation is not exposed.
Welton Chalk Formation
WCK
Base of Plenus Marls Member, a unit of buff to green and grey marls and marly chalks, typically 0.5m thick but up to 1.4m in the Cleveland Basin. This rests on an uneven erosion surface that may be stained with iron minerals and glauconite, at the top of a succession of marly chalk (the Ferriby Formation). The marly basal beds generally form a topographical slack at outcrop, which facilitates the mapping of the base of the formation, and can also be recognised from their geophysical log signature in boreholes.
Scarp area of Yorkshire and Lincolnshire Wolds, and superficial deposit-covered area to the southeast, from Bempton Cliffs south to the Chapel St Leonards-Skegness area on the Lincolnshire coast (see Sumbler, M G, 1999, Fig.1).
White, massive or thickly-bedded rubbly-weathering chalk with common flint nodules ("burrow-form flints") but generally lacking tabular flint bands; sporadic marl seams including the Plenus Marls Member ("Black Band") at the base. Formal subdivision: Includes at its base the Plenus Marl Member and the Black Band Member both defined herein. There are many named marl and flint bands throughout the succession that are used to divide the formation. They are all of bed status.
About 53m in type area; thinner in south and over the Market Weighton High, but may expand towards the Cleveland Basin in the northernmost part of outcrop, being (reportedly) 68m in the Bempton/Buckton Cliffs.
Marked change from massive, rubbly-weathering chalks below, to harder, thinly bedded or nodular chalk (Burnham Formation) above. This horizon lies just below the Ravendale Flint, a tabular or semi-tabular flint up to 0.25m thick, which is the lowest such flint in the Chalk Group and the base of the chalk unit in which such flint bands are common.
Woodrow Clay Member
WCL
Change from sandy clay and clayey fine-grained sand to commonly ooidal, generally sand-free clay.
Across much of the Shaftesbury Sheet (313).
Clay; grey, locally ooidal, slightly sandy, patchily fossilferous.
0 - 5m (3 - 4m in the type area); 2.7m in the East Stour Borehole - ST82SW/9.
At the change to the dominantly limestone sequence of the Cucklington Oolite.
White Coral Limestone
WCLS
Whitehouse Conglomerate Formation
WCO
The base of the lowest conglomerate bed overlying the Gourdon Sandstone Formation.
Couts [NO 823 700] south of Gourdon to Thornyhive Bay [NO 878 826].
A massive, thickly bedded, or weakly cross-stratified, clast supported conglomerate, and pebbly sandstone, chiefly of 'Highland' provenance.
From 60 m to 300 m thick.
The base of the lowest lava in the Crawton Volcanic Formation.
Woodhead Crag Sandstone
WCS
Lyne valley and adjacent areas, Cumbria.
Hard, quatzitic, fine- to medium-grained wedge-bedded sandstone. Some layers are "curled" or slumped.
Wilmcote Limestone Member
WCT
Placed where limestone overlies sharp, irregular surface of pale grey-green silty mudstones of the Cotham Member (of Lilstock Formation).
Central and south Midlands of England.
Alternating limestones and mudstones.
6.4m at type locality; ranges from this up to 11.9m.
Placed at the top of the highest limestone and may be arbitrary; Saltford Shale Member lies above.
Waterfoot Dyke
Westfield No.1 Mine Coal
WD1
Westfield No.2 Mine Coal
WD2
Wadhurst Clay Formation
WDC
Down-section change from nodular clay-ironstone, silty mudstone and siltstone [Wadhurst Clay Formation] to sandstones [Ashdown Formation]. Locally the Top Ashdown Pebble Bed is situated at the base of the Wadhurst Clay Formation.
The Wadhurst Clay is widespread beneath the Weald, having been recorded in boreholes. It also crops out in several sheets in the Weald. Sevenoaks and Tonbridge [287]: southern quarter of the sheet from Dry Hill, east of Dormans Land, eastwards across the sheet south of Tonbridge to Brenchley. Maidstone [288]: South eastern corner of the district near Castle Hill to the east of Mount Easy. Horsham [302]: Eastern part of the sheet, south of East Grinstead to Horsted Keynes. Tunbridge Wells [303]: Extensive. East Grinstead to Tunbridge Wells and Lamberhurst-Rotherfield and Wadhurst areas. In the south of the district it is seen in the Danehill, Cackle Street and Buxted to Burwash areas. Tenterden [304]: Extensive in southern half of the sheet. Goudhurst-Benenden-Rolvenden-Tenterden areas; Ticehurst-Etchingham-Sandhurst-Newenden areas; and Staple Cross-Northiam-Peasmarsh-Iden areas. Brighton and Worthing [318/333]: Confined to a very small area on the very north eastern margin of the district, north of Burgess Hill. Lewes [319]: Sw of the Newick, Ridgewood, Framfield and Horam areas to the Dalington,Bodle Street Green and Boreham Street areas. Hastings and Dungerness [320/321]: Extensive in the western part of the sheet, west of a line drawn from Rye, Winchelsea and Fairlight.
Dark grey mudstones and silty mudstones, weathering to greenish grey and yellowish brown clays dominate the succession. Thin beds of shelly limestone, rich in Neomiodon and sometimes \viviparus, are present throughout. Nodular clay-ironstone occur particularly in the lower part of the formation, but also near the top. Thicker beds of siltstone and lenticular calcareous sandstone units are also present. In the Tunbridge Wells district a thicker sand in the lower part of the formation has been named Hog Hill sand Member [Allen, 1959; Bristow & Bazley, 1972]. Rare Equisetities fossil soils have been described. The base of the formation is often a thicker siltstone and in some area's a basal pebble bed[Top Ashdown Pebble Bed] is present.
Up to about 78m.
Down-section change from sandstones with interbedded siltstones -Lower Tunbridge Wells Sand Formation] to mudstones and siltstones [wadhurst Clay Formation].
Woodfield Coal (South Derbyshire)
WDCO
Woo Dale Dolomite
WDD
Wernddu Coal (South Wales)
WDDU
Woodend Coal (Northumberland)
WDEC
Woodend Limestone
WDEL
Washover Fan Deposits
WDEP
Variable lithology; typically sand and gravel; a fan-shaped body of sediment that is transported landward by marine waters flowing through or across a coastal barrier; formed especially during storms when barriers can be overtopped. [Generic description: earth science dictionaries in the BGS library].
Widmerpool Formation
WDF
Seen only in the Ratcliffe-on-Soar and Long Eaton boreholes, where it is taken at the top of the uppermost thick bed of pale brown argillaceous to sandy limestone, of the Lockington Limestone Formation. Overlain by dark green mudstone of the Widmerpool Formation, which might locally be unconformable on other units, such as the Milldale Limestone Formation.
Crops out discontinuously northwestwards from Wardgate to Kniveton [SK 20 50], Grindonmoor Gate and Butterton [SK 07 56] in Derbyshire. Restricted to the Widmerpool half-graben [SK53] and Hathern Shelf [SK52].
Dark to pale brown or grey, calcareous and locally carbonaceous, pyritic, fissile mudstone, thinly interbedded with turbidite, argillaceous cherty limestone and thin beds of quartzose siltstone, calcareous or quartzose sandstone and tuff. The proportion of limestone to mudstone increases northwards, with the formation passing laterally into the Hopedale Limestone Formation of the Derbyshire Platform.
Variable, from 741m in the Ratcliffe-on-Soar Borehole (SK52NW/72) at [SK 5081 2913], with attenuated development of 110-130m on the Hathern Shelf.
The base of dark grey fossiliferous, fissile mudstone of the Cravenoceras leion Marine Band, where present. Otherwise taken at the start of a dark grey mudstone and siltstone sequence, lacking limestones, of the Bowland Shale Formation, present above the top of the uppermost limestone bed of the Widmerpool Formation.
Woolridge Member
WDGE
Gravel overlying till correlated with the Thrussington Member, or bedrock.
Isolated outliers on high ground, 80-85 m above OD, near the River Severn, 10-13 km west of Cheltenham.
Sandy, clayey coarse-grained gravel, predominantly 'bunter' quartzite pebbles with 5-10% flints and rare Malvernian, Lower Palaeozoic and igneous clasts. Inferred to be glaciofluvial outwash.
Variable, up to 2 m.
Present day ground level.
Woodhouselee Volcanic Member
WDH
Conformable: where rhyolitic tuff and flow-banded rhyolite of the Caerketton Volcanic Member are overlain by, or locally interbedded with, pale lilac or pink trachytes and andesite.
Pale lilac or pink trachytes and andesites with phenocrysts of biotite and alkali-feldspars. Generally highly kaolinized.
Variable - 75-150m
Conformable: where pale lilac or pink trachytes and andesites are overlain by feldspar-phyric and fine-grained microporphyritic basalts and andesites of the Carnethy Volcanic Member.
Westward Ho! Member
WDHO
The lower boundary is taken at the incoming of channels overlain by syndepositionally disturbed units and thick, locally cross- bedded sandstones of the Westward Ho! Member above the regularly interbedded mudstones and turbidite sandstones of the underlying Crackington Formation. This boundary is not exposed on the coast at the type locality and has never been mapped, as the Westward Ho! Member was previously included in the Crackington Formation. Further investigation of this boundary is needed.
Westward Ho! area (SS 41 29), Bideford, north Devon. As the Member is unmapped it is not known how far east it extends, but it is possible that it occupies the lower part of the Bideford Formation as far as the eastern limit of the latter to 6km west of South Molton (SS 71 26), mid Devon.
Thin-bedded mudstones, siltstones and sandstones, some of which are turbiditic and others cross-laminated and wave rippled. The succession is cut by several channels filled from 3 to 25m deep by slumped and disturbed strata, or more rarely cross-bedded or cross-laminated sandstones
The upper boundary is taken at the incoming of coarsening-upwards cycles (mudstone, interbedded mudstone and sandstone, cross-bedded sandstone) of the main part of the Bideford Formation above the top of the Mermaid's Pool Sandstone, a thick, mappable, cross-bedded sandstone at the top of Westward Ho! Member.
Woo Dale Limestone Formation
WDL
Taken at the bottom of the basal breccia of the Dinantian limestone sequence in the Woo Dale Borehole, marking a prominent unconformity above pre-Carboniferous volcanic rocks. The conformable boundary in the Eyam Borehole, with anhydrite and thin mudstone and dolostone beds of the Middleton Dale Anhydrite Formation, is overlain by dolostone of the Woo Dale Limestone Formation.
The East Midlands, notably across the Peak District [SK].
In the Woo Dale Borehole, the base of the formation comprises a basal breccia of lava and pyroclastic rock fragments, overlain by grey and dark grey limestone, including thin calcilutite beds and shale partings. These are typically overlain by pale or medium grey crinoidal biosparites and pelsparites. However, at the type locality of Woo Dale, the overlying succession is dominated by dark grey to grey-brown and mainly dolomitised limestone, with subordinate limestone beds. The upper part of the formation is characterised by irregular beds of medium to pale grey and grey-brown micritic limestone, interbedded with peloidal calcarenitic limestone, comprising biopelsparites and pelsparites.
Measured as 402.26 m thick in the Woo Dale Borehole and Woo Dale outcrop, with 1324.52 m in the Eyam Borehole.
The base of the lowest pale grey limestone of the Bee Low Limestone Formation above the dark grey micrite or calcilutite beds of the Woo Dale Limestone Formation.
Woodlands Member
WDMB
Sharp, probably disconformable, contact on hardground surface developed on Home Farm Member limestone. Detritus from latter locally incorporated into basal bed.
From Nuneaton town centre, extending northwest for 5.2km to Worthington Farm, Mancetter (SP3192 9572)(SP3529 9197-3192 9572).
Grey to maroon, medium-grained glauconitic and micaceous sandstones. Faint cross-bedding but commonly appear massive and thick-bedded. Rare mudstone drapes.
19m in type section. 9-19m between Hartshill and Woodlands Quarries.
Sharp contact with basal mudstone of Stockingford Shale Group. Some intermixing between sandstone and mudstone along contact. Upper c.1m of is bioturbated and locally calcareous.
Woodmine Coal
WDMC
Worsley Delf Rock
WDR
The lower boundary is taken at the base of the first sandstone in the sandstone-dominated unit above fissile black mudstone of the Cambriense (Prestwich Top) Marine Band.
South and west Manchester.
Sandstone, cross-bedded, brown or yellow, rarely purplish, with subordinate beds of mudstone and sandy mudstone.
36 - 55 m thick.
The upper boundary is taken at the base of a mudstone-dominated succession of the Pennine Upper Coal Measures Formation above the sandstone of the Worsley Delf Rock.
Warmden Sandstone
WDS
Woodland Shell Beds
WDSB
Westfield Shale Coal
WDSC
Westfield Shale
WDSH
Westfield Thick Coal
WDT
Westfield Two Foot Coal
WDTF
Woodward Formation
WDWR
Woolley Edge Rock
West and south Yorkshire area [Woolley Edge, northwest of Barnsley].
Sandstone, coarse-grained in the north, becoming finer southwards.
Maximun c.50m near Normanton.
Agricultural Cutting
WEAG
Wear Valley Formation
WEAR
The valley of the River Wear and its tributaries, northern England.
Mainly sand and gravel forming river terraces and silty, clayey sand forming floodplains and concealing sand and gravel, including units of silty sand, silt, clay and peat. Clasts mainly sandstone, gritstone, mudstone, limestone and coal.
Weston Flags Formation [Duplicate Code: Use Wst]
WEB
Wardie Coal
WEC
Canal Cutting
WECA
Cut Away Landscape
WECU
Wee Drum Coal
WED
Dredged Or Drainage Channel
WEDR
Wee Coal (Ayrshire Limestone Coal Formation)
WEE
Wee Coal
WEEC
Wee Pit Coal
WEEP
Westing Gneiss Formation
WEGN
Westing Group
WEGP
Wellington Heath Member
WEH
Not exposed. Probably rapidly transitional.
Cyclical sequence of red-brown mudstones and purple-red-brown sandstones (latter from c.25 - 30% of the beds). Lack of calcretes except in transitional highest beds and many more sandstones distinguishes the member from the overlying Raglan Mudstone. The underlying Downton Castle Sandstone consists of yellow-brown sandstones and thin grey to brown siltstones.
c.200 metres.
Not exposed. Slowly transitional.
Weisdale Limestone Member
WEIL
Weir Coal
WEIR
Much Wenlock Limestone Formation
WEL
Pale grey nodular to thinly bedded limestones with reef bodies.
29m in type area.
Upward transition into alternating siltstones and limestones of the Elton Formation (ie lower part of Lower Ludlow Shale).
Well Ground Formation
WELG
Well Coal (South Derbyshire)
WELL
Westing Limestone Formation
WELS
Wemyss Bay Sandstone Formation
WEM
The Wemyss Bay area, Sheet 29.
Cross-bedded, fine-grained red-brown sandstone.
Disconformably succeeded by the Skelmorlie Conglomerate Formation.
Wellesley Marine Bed
WEMB
Artificial Pond Or Artificial Lake
WEML
West Moor Coal (Northumberland)
WEMR
Wenlock Rocks (Undifferentiated)
WEN
Woodend Serpentinite
WEND
Wensleydale Pluton
WENG
Rail Cutting
WERA
Road Cutting
WERO
Westbury Sands
WES
Westmuir Sandstone
WESA
West Sands Semipelite Member
WESD
Sharp change from feldspathic quartzite and psammite of the Sunnyside Sandstone Member (Cullen Quartzite Formation).Locally faulted (e.g. on coast section).
From coast at West Sands [NJ 5375 6740], as far as Easter Bogs [NJ 410 630] (Sheet 95), where it is unconformably overlain by Devonian sedimentary rocks.
Semipelite, micaceous, generally biotite-rich and garnetiferous.
c.100m on coast section and inland.
Transition to thin-bedded, flaggy psammite and semipelite within the Findlater Flag Formation.
Westerhouse Sandstone Member
WESS
Wedmore Stone
WEST
Westray Group
WESY
Wetherby Member
WETH
Drawn at base of buff dolomite where it rests on the highest finely laminated stratum of the Marl Slate or on basal Permian continental strata or carboniferous strata.
Eastern England, (Yorkshire Province).
Parallel bedded, buff coloured and moderately fossiliferous dolomite with scattered patch reefs and (in the southwest) calcitic and dolomitic mudstones.
Up to 40 metres (commonly 12 to 20 metres).
Drawn at base of pale grey ooidal dolomite of the Sprotbrough Member; also at the top of the lower dolomite of the Hampole Beds where present.
Wear Till Formation
WETI
Generally a sharp uneven contact on bedrock, but locally a complex gradational glaciotectonic contact with fractured or decomposed bedrock.
Dark greyish brown to dark yellowish brown, extremely compact, stony sandy silty clay diamicton with clasts dominated by Carboniferous lithologies (sandstone, gritty dandstone, limestone, mudstone, ganister, coal), but including Whin Sill dolerite and far-travelled clasts from Scotland and the Lake District (greywacke sandstone and siltstone, granite and granodiorite). Includes some large rafts of local rocktypes towards the base.
Generally 3-10m, locally to 30m
Generally irregular, draped, conformable contact with overlying thinly laminated, greyish brown to brownish grey, silty clay and micaceous clayey silt, or gravel of the Tyne and Wear Glaciolacustrine Formation.
Wet Sleddale Andesite Formation
WETS
Taken at the base of the lowest andesite sheet overlying the bedded volcaniclastic sandstone succession of the Seathwaite Fell Sandstone Formatrion.
Longsleddale to Wet Sleddale, eastern Lake District, Cumbria.
Andesite and basaltic andesite sheets with thin intercalations of bedded volcaniclastic rocks.
Possibly up to 1200m, much faulted.
Defined by the base of the overlying Lincomb Tarns Tuff Formation.
Engineered Excavation (Undivided)
WEU
Weymouth Member
WEY
Top of Lamberti Limestone (where present) or an equivalent shell bed or siltstone. This horizon can be clearly picked on geophysical logs. Change in Gryphaea faunas (G. lituola below to G. dilatata, above) and ammonite faunas (Kosmoceras, below; Cardioceras, above) useful supportive indicators.
Dorset to North Yorkshire.
Predominantly pale grey, blocky, smooth, calcareous mudstones, generally only slightly silty. Thin, dark grey, carbonaceous beds with striking interburrowing at intervals. Thin calcareous siltstones may occur. Poorly fossiliferous. Large Gryphaea are characteristic; ammonite fauna usually pyritised, locally associated with sideritic nodules.
At upward change to more silty lithologies of West Walton Formation or its more sandy correlatives (eg Nothe Grit); commonly transitional and necessarily arbitrary. Most easily positioned where minor disconformity present. Upward change in faunal preservation from three-dimensional pyritised forms, below, to crushed clay casts, above, where Gryphaea specimens are increasingly large.
River Terrace Deposits, 1 (Wey)
WEY1
Wytch Farm Breccia
WFB
Rests unconformably (in the type area) on Devonian rocks.
Probably confined to south Dorset.
Conglomerate composed of angular clasts of mudstone and well-foliated phyllite with quartz pebbles and very little matrix.
Up to about 50 m thick, 48 m in type section.
Change from conglomerates to mudstone with minor siltstones and sandstones.
Wharfe Member
WFC
White Flat Coal (Coalbrookdale)
WFCC
West Fenton Sill
WFENT
Wallingford Fan Gravels
WFGR
Variable lithology. Older scree and solifluction deposits in some chalk valleys. [Generic description: 'TMOS' Procedures].
No.1 Jersey Coal Of West Fife
WFJ1
No.2 Jersey Coal Of West Fife
WFJ2
Waterfall Sandstone
WFS
Whisby Farm Sand And Gravel Member
WFSG
Mid Pleistocene (??MI Stage 6).
Unconformable, commonly channelled base, resting on pre-Quaternary bedrock (at Type locality).
Currently only known around the Type locality but likely to be more widepsread flanking the Balderton Terrace between Newark-on-Trent and the Lincoln Gap (see Brandon and Sumbler, 1991, Fig.1) and perhaps elsewhere (BGS sheets 114, ?126).
Reddened sands and gravels dominated by rounded pebbles of "Bunter" quartz/quartzite with subordinate subangular flint. Underlies possible terrace remnants adjacent to the outcrop of the Balderton Sand and Gravel and with a terrace surface standing typically c.4 to 5m above the Balderton Terrace. Upper part locally includes a thin fluvio-aeolian coversand (Whisby Sand Bed, pre-Ipswichian) and rubified palaeosol (Hykeham Soil; Ipswichian). Tentatively correlated with the Etwall Sand and Gravel Member (Trent Valley Formation).
Weardale Grit Group
Wigan Two Foot Coal (South Lancashire)
WG2FT
Wigan Four Foot Coal (South Lancashire)
WG4FT
Wigan Five Foot Coal (South Lancashire)
WG5FT
Wigan Six Foot Coal (South Lancashire)
WG6FT
Westgate Formation
WGAT
Sharp incoming of conglomerate belonging to the Fence Conglomerate Member of the Westgate Formation above the predominantly mudstone member of the Carmichael Burn Formation
Carmichael Inlier, around Carmichael, Lanarkshire, Scotland.
Mainly pale olive-grey to brownish grey sandstones and dark greenish grey to pale red subgreywackes with local greenish grey or brownish grey conglomerate beds and members, up to 60m thick, containing variable contents of igneous, chert, quartz and quartzite pebbles in a coarse-grained sandstone matrix. Includes the Fence Conglomerate, Newside Arenite, Kirk Hill Conglomerate and Eastgate Sandstone members.
c.847 m
The top of the predominantly sandstone succession belonging to the Eastgate Sandstone Member of the Westgate Formation below the incoming greywacke-pebble bearing conglomerate of the Greywacke Conglomerate Formation.
Wig Bach Formation
WGB
Unconformable on rocks of the Gwna Melange, Sarn Complex and Dol-cyn-afon Formation.
Dark grey mudstones, laminated siltstones and fine-grained bioturbated sandstones, with a ferruginous pisolitic sandstone and conglomerate at the base.
Conformably overlain by the Porth Meudwy, Llanengan and Trygarn formations as well as by undivided mudstones of the Nant Ffrancon Subgroup.
Whitehill Great Seam Coal (Lothian)
WGC
Witch Ground Formation
WGD
Possible unconformity on ice-scoured surface.
Acoustically transparent, multilayered with pockmarks mainly muds, some sand/silt.
30 - 0 metres.
Seabed.
Fladen Member
WGDF
Underlain unconformably by an ice-scorned surface of Swatchway, Coal Pit and Fisher Formation.
Moderately sorted sandy mud, intermediate-high plasticity, sporadic dropstones and rare shell fragments.
10 metres. Lateral variations up to 15 metres.
Overlain conformably by Witch Member of Witch Ground Formation.
Glenn Member
WGDG
Conformable base on the Witch Member.
Silt rich (> 80%).
1 metre. Lateral variations 0.3 metres - 2.5 metres.
Seabed or seabed sediment is upper surface.
Witch Member
WGDW
Underlain conformably by Fladen Member of Witch Ground Formation.
Highly plastic, poorly sorted, slightly sandy mud, acoustically transparent with buried pockmarks.
10 metres (lateral variations up to 15 metres).
Overlain conformably by Glenn Member of Witch Ground Formation.
Wingfield Flags
WGF
The base of the first main sandstone above the Amaline Marine Band that forms part of a significant sandstone-dominated sequence. If the Amoline Marine Band is not proved, it is the base of the last main sandstone in the sandstone-dominant sequence below the Kilburn Coal.
South Yorkshire, Derbyshire, Nottinghamshire and Leicestershire.
Fine-grained sandstone with siltstone interbeds.
Up to 60 m thick.
The top of the first main sandstone that forms part of a significant sandstone-dominated sequence below the Kilburn Coal.
Westland Green Gravel
WGGR
Thames Valley and southern East Anglia.
Gravel variably sandy, clayey.
Terrace form.
Whin Garth Gravel Member
WGGV
Erosional contact on the Scale Beck Till Member or the Bark Butts Silt Member of the Blengdale Glacigenic Formation.
1:50k Sheet 37 (Gosforth), but could be applied to kame terrace gravels of the Central Cumbria Glacigenic Subgroup throughout western Cumbria.
Poorly sorted boulder and cobble gravel, matrix-rich, with poorly developed sub-horizontal stratification and thin interbeds of brown silt and red silty diamicton present in some exposures. Clasts are generally angular to subrounded and comprise locally derived igneous rocks from the Borrowdale Volcanic Group and metamorphic rocks. The gravel forms narrow kame terraces within the Bleng Valley area.
Generally the ground surface, but locally overlain by Holocene alluvium of the Ehen Alluvial Formation or peat of the Blelham Peat Formation.
Winghay Ironstone Coal
WGI
Wee Gillespie Coal (Lothian)
WGIL
West Greenland Province
WGLND
Woorgreen Coals (Forest Of Dean)
WGNC
Worked Ground (Undivided)
WGR
Areas where the ground is known to have been cut away by Man, eg. quarries, pits, cut-away landscaping, dredged channels. BGS recognises many different categories. [Generic description].
Wandley Gill Sandstone
WGS
A sharp upward change in a conformable succession from predominantly grey mudstone to sandstone. The base of the first sandstone above the Upper Brimham Grit.
The Pennine foothills between Masham and Pateley Bridge, North Yorkshire.
A, grey, fine-to coarse-grained, medium to thickly bedded, cross-bedded sandstone.
From 8 m to 30 m thick.
A sharp upward change in a conformable succession from sandstone to predominantly mudstone. The top of the last sandstone below the Cancelloceras cancellatum (G1a1) Marine Band
Wandley Gill Shale
WGSH
Whitchurch Green Slates
WGSL
Wrighthow Basalt Member
WGTB
Not exposed, but taken at the change from porphyritic andesite to scoriaceous basalt.
Wrighthow Crags and Foxbield Wood - 2km north of Santon Bridge, Cumbria.
Dark greenish grey scoriaceous pyroxene-phyric basalt lava flows and their autobreccias.
Not exposed/faulted.
Warren Gutter Shale
WGTS
Wool Gill Vein
WGV
Wiston Grey Volcaniclastic Sandstone Member
WGVS
Woodhead Hill Rock
Whittery Volcanic Formation [Duplicate Entry: Use Wty]
WHA
West Harbour Member
WHAB
Whatton Sand And Gravel
WHAT
Whistler Coal (North Ayrshire)
WHC
Whitecliff Chert Member
WHCH
Hardground surface on top of Foxmould Member, below which chert is absent and calcareous sandstone doggers/lenses are common.
Devon and West Dorset. Mapped on Sheets 326 (Sidmouth) and 327 (Bridport): continuation on Sheet 311 (Wellington).
Glauconitic and calcareous sandstones with numerous horizons of lenticular cherts; mineralised surfaces, pebble beds and shell brash at several levels.
Hardground surface (Whitecliff Hardground).
White Chalk Subgroup
WHCK
Upper Cretaceous, Cenomanian to Maastrichtian (onshore UK). Metoicoceras geslinianum to Belemnitella mucronata s.l. Zones and into Belemnella spp. Zones where the highest Campanian and Maastrichtian chalks are encountered. Up to basal Danian (Basal Paleocene) in North Sea Basin.
Conformable on the Grey Chalk Subgroup. Placed at the lowest bed in the Plenus Marls Member at the base of the Holywell Nodular Chalk Formation (Southern Province) and at the base of the same member in the Welton Chalk Formation (Northern Province). (Note that the Plenus Marls Member is now considered as part of this subgroup thus providing a consistent datum throughout the Chalk Group of England and the North Sea).
The Subgroup is known throughout the onshore outcrops in England and offshore in the Southern, Central and Northern North Sea areas.
Chalk with flints. With discrete marl seams, nodular chalk, sponge-rich and flint seams throughout. Typology of flints and incidence of marl seams is important for correlation.
Variable depending on degree of post-Cretaceous erosion and the relative development of its constituent formations. Onshore the thickest development is within the Hampshire/Sussex area of the Southern Province, where up to about 470 to 515m of strata are preserved; the most chronostratigraphically complete succession is in Norfolk but is thought there to be only some 350m thick; within the Northern Province up to 500m are preserved but the thickest succession is within the North Sea area where about 800 to 1100m are preserved.
Unconformable beneath Palaeogene/Quaternary basal unconformity onshore in the UK. Conformable beneath Danian age Maureen Formation in parts of the North Sea. Elsewhere unconformable.
Whickhope Coal
WHCO
Waterhead Group (Cf Glenbuck Group)
WHD
Drawn at base of sandstones of the Passage Formation where they rest conformably on sandstones of the Dunside Formation of the Priesthill Group.
Sandstones, mudstones, with fish beds. (Correlative of Waterhead Group - Glenbuck Group).
720m approx.
Drawn at conformable upward passage from sandstones of the Logan Formation to conglomerate of the Middlefield Conglomerate of the Dungavel Group.
Waterhead Group And Dungavel Group (Undifferentiated)
WHDG
Whitehouse Subgroup
WHE
Overlies the Ardwell Farm Formation, part of the Ardwell Subgroup.
Sandstones, mudstones, sandy limestones and shales. Conglomerate lenses. See also the definitions of the constituent (Southshore, Threemile, Penwhapple, Myoch, Mill and Shalloch) formations.
Conformably overlain by the Auldthorns Formation [AUT], part of the Drummuck Group [DKG].
Waterhead Central Volcanic-Complex
WHEAD
Whitecliff Flint
WHFL
Whitefield Formation
WHFS
Watch Hill Formation
WHG
Late Tremadoc to Arenig.
Boundary with underlying Bitter Beck Formation is gradational and marked by an increase in the proportion of sandstone and a decrease in the proportion of mudstone in the succession. Base taken at the level where sandstone and siltstone predominate.
Within the northwest part of the Skiddaw inlier, not known elsewhere. Eastern margin is faulted, the western margin is defined by the edge of the inlier. It is underlain by the Bitter Beck Formation and overlain by the Hope Beck Formation.
Interbedded lithic wackes (with subordinate lithic arenites), siltstones and mudstones. Sandstones are fine-grained to granular with abundant siltstone and mudstone intraclasts. Sedimentary structures are uncommon but include normal grading and sole structures.
55 to 800m
Not exposed but taken to lie between exposures of Watch Hill Formation and overlying Hope Beck Formation just north of Lorton Street Road Bridge.
West Highland Granite Gneiss Intrusion
WHGG
Neoproterozoic (870 +/- 7Ma).
Whitehills Glacigenic Formation
WHGL
On bedrock or overlying the Pishlinn Burn Gravel Bed.
Elgin to Ellon.
Dark blue-grey clayey till with erratics and rafts of Mesozoic strata, pre-Late Devensian glaciomarine shelly mud, shell fragments and rafts of sand and clay.
At the surface or overlain by the Crovie Till Formation (East Grampian Glacigenic Subgroup) or the Kirk Burn Silt Formation.
Well Hill Gravel Formation
WHGR
Rests unconformably on bedrock: Lambeth Group (Woolwich and Reading Beds).
Geographically isolated from other superficial deposits, at OD 155-167m, capping a hill at Well Hill, Kent.
Gravel and sandy gravel; sub-angular, partly water-rolled flints up to 0.3m across, Lower Greensand cherts up to 10%. Tertiary pebbles, many decomposed brown flints; matrix of coarse sand, mostly quartzose, some flint; rare lenses of clay.
2 to 4m
Whirl Howe Formation
WHH
Sub-Windermere Group unconformity - rests discordantly on the Borrowdale Volcanic Group.
Very variable volcaniclastic breccias, conglomerates and sandstones (Longsleddale Member) and overlying calcareous siltstone (Stile End Member).
70 metres (0 - 70 metres).
Defined by the base of the overlying Yarlside Volcanic Formation.
West Highlands - Hebrides Cluster
WHHB
Probably extends from late Visean (c.326 Ma) to Early Permian (c.290 or possibly 268 Ma).
Whitehurst Coal (North Staffordshire)
WHHC
Whitehurst Group
WHHU
Whitecliff Sand Member
WHI
White Hill Sandstone Formation
WHIL
The unconformity with the folded Wenlock strata of the Riccarton Group of the Southern Upland Terrane.
Jedburgh and the Cheviot Hills.
Red sandstone and mudstones with local beds of conglomerate containing clasts of red sandstone and volcanic rock.
From 0 m to 30 m thick.
The top of red clastic sedimentary rocks below the Cheviot Volcanic Formation.
Whin Sill Complex
WHINS
A locally pegmatitic quartz-dolerite, with finer grained 'chilled' contact rock. Sills are typically columnar jointed, and comprise up to three leaves are present in places. The component sills and associated dykes cut strata up to and including those of Carboniferous, Duckmantian (Westphalian B) age, and derived pebbles are reworked into breccias of Early Permian age. Radiometric dates (K-Ar, Ar-Ar and U-Pb) are in the range of 301-294 Ma. The large volume of literature on this sill-complex is listed, referred to and discussed in Stephenson et al., 2003.
Whitelaw Pluton
WHIP
White Ironstone Measures (Cakestone)
WHIR
Whiting Sandstone Unit
WHISA
Whitcliffe Formation
WHIT
Above lithological change from limestone to calcareous siltstone (at Ludlow) (Holland and others 1963); Top of highest nodular limestone of Aymestry limestone. (South Staffordshire)
West Midlands and Welsh Borders.
Grey to greenish grey, flaggy calcareous siltstone with shelly limestone beds (at Ludlow); upward passage from argillaceous, flaggy limestone to olive-buff shaly mudstone overlain by buff silty sandstone and mudstone (South Staffordshire).
9-55m: 9-15m South Staffordshire; 55m Ludlow.
Base of cross bedded sandstone of Downton Castle Sandstone; locally at base of Ludlow Bone Bed.
White Limestone Formation
WHL
The base of the described peloidal wackestone, packstone or grainstone, overlying marls or fine-grained ooidal grainstones of the Hampen Formation or Rutland Formation.
The Stroud to Cirencester area, where it passes south-westwards into the Athelstan Oolite Formation, and north-eastward through Oxon and Bucks to the Brackley area, where it passes north and east into the Blisworth Limestone Formation.
A pale grey to off-white or yellowish limestone, peloidal wackestone and packstone with subordinate ooidal and shell fragmental grainstones, recrystallised limestone and/or hardgrounds at some levels with rare sandy limestone, argillaceous limestone, marl and mudstone or clay.
Up to 30 m, and typically 20 m thick in the type area.
Generally a sharp, erosive boundary, with a cross-bedded shell-fragmental ooidal limestone of the Forest Marble Formation or mudstone of the Forest Marble Formation.
Wheatley Lime Coal (West Yorkshire)
WHLC
Well Hole Formation
WHLE
Whitehouse Limestone
WHLM
Walls Hill Member
WHLS
Whitby Mudstone Formation
WHM
In Cleveland Basin, base of mudstone resting upon ooidal limestone or sideritic mudstone nodules of the Cleveland Ironstone (see Cox, B M, et al, for more details). Elsewhere, at base of mudstone overlying ironstone of the Marlstone Rock Formation.
Cleveland Basin, East Midlands Shelf and Worcester Basin (i.e. Yorkshire coast to Mendip).
Medium and dark grey fossiliferous mudstone and siltstone, laminated and bituminous in part, with thin siltstone or silty mudstone beds and rare fine-grained calcareous sandstone beds; dense, smooth argillaceous limestone nodules very common at some horizons; phosphatic nodules at some levels. Nodular and fossiliferous limestones occur at the base in some areas.
In most areas, sharp, eroded boundary with limestones or sandstones of the Inferior Oolite Group (East Midlands Shelf) or the Ravenscar Group or Dogger Formation (Cleveland Basin). In Ravenscar area, and in much of Worcester Basin arbitrary boundary in transition to sandy sediments of the Blea Wyke Formation or Bridport Sand Formation respectively
Whitecliff Marl
WHMA
Well Hill Marine Band
WHMB
White Mine Coal (South Lancashire)
WHMC
Whinmoor Coal (West And South Yorkshire)
WHNC
Warren House Formation
WHO
Tectonic (thrust) contact with Proterozoic Malverns Complex.
Tinker's Hill (SO 767 401) to Hangman's Hill (SO 765 390), Malvern Hills, Hereford and Worcester.
Spilitic basalt lavas, altered intermediate lavas ('keratophyres'), altered rhyolitic lavas, felsic pyroclastic rocks, including ignimbrite.
Tectonic (East Malvern Fault) with Mercia Mudstone Group.
Warren House Coal (West And South Yorkshire)
WHOC
White Port Bed
WHP
Unconformable on Silurian turbidites.
Coastal section at White Port.
Fining upwards cycles of light grey to white sandstones (70% of succession) succeeded by purple siltstones, marls and shales.
Wharncliff Rock
WHR
South Yorkshire [Wharncliff Crags, 6 miles northnorthwest of Sheffield].
Warren House Rider Coal (West And South Yorkshire)
WHRC
Whitchurch Sand Formation
WHS
Discordant contact on limestone or calcareous mudstones of the Purbeck Formation, fossiliferous limestones or calcareous sandstones of the Portland Formation, or rarely mudstones or siltstones of the Kimmeridge Clay Formation.
Outliers in the Aylesbury to Oxford area, Swindon and in the Vale of Pewsey near Devizes, Wiltshire [Casey and Bristow, 1964; Horton et al., 1995].
White, buff, yellow, orange and red to dark brown, generally unconsolidated fine- to medium-grained sand, with seams and irregular masses of limonite-cemented sandstone and rare siliceous or calcareous concretions, localized beds of grey to white silt and clay or mudstone, and rare ooidal limonitic ironstone.
Discordant contact with coarse gritty sandstones of the Lower Greensand Group, or calcareous mudstones of the Gault Formation. Mostly occurs as outliers without succeeding strata.
Whitehills Grit Formation
WHSG
Local unconformity at incoming of first major psammite bed above thin-bedded calcareous semipelites of Boyne Limestone Formation.
From Moray Firth coast [NJ 655 652-NJ 789 635] southwards to northern margin of Insch intrusion [NJ 650 325 to NJ 725 305].
Coarse-grained psammites, commonly gritty, and quartzites, with subsidiary semipelite and pelite; gritty units and semipelites in part calcareous.
Probably c.1km, but coast section includes considerable repetition by folding.
Transition from partly calcareous semipelite and psammite to non-calcareous lithologies at top of Whitehills Grit Formation; commonly marked by change to graded coarse gritty psammite and semipelite.
Whittery Shale Formation
WHSH
White Stone Band
WHST
Wilkesley Halite Member
WHT
Conformable; base of lowest substantial salt (Evans and others, 1968, include several thin salts in the underlying Wych Mudstones).
Halite of varied purity with mudstone partings.
To 404m
Conformable: at top of highest substantial halite in Wilkesley and Prees boreholes.
Whitberry Vent
WHTB
White Coal (South Wales)
WHTC
Wheatley Trough Limestone
WHTL
Whittington Coal (Forest Of Dean)
WHTN
Whirl Howe Formation [Obsolete Code: Use Whh]
WHW
Whyntie Brae Limestone Member
WHYL
Top of highest massive metalimestone bed at the top of the Boyne Castle Limestone Member.
From Moray Firth coast (Old Hythe to Boyne Bay) [NJ 6165 6608 - NJ 6300 6580] to Auchmillie [NJ 5900 6370].
Calc-silicate rock, calcareous semipelite or thin impure metalimestone, laminated and striped, passing upward into mainly calcareous semipelite with minor thin metalimestone and lenses of reworked carbonate material.
c.500m on coastal section; progressively overstepped southwards by Whitehills Grit Formation.
Westbury Ironstone Member
Abrupt upward change from limestone of the Clavellata Beds into ferruginous oolite and ironstone.
Westbury (mainly) to Steeple Ashton [905 570].
Ironstone and limonitic oolite, yellowish brown, shelly.
Fairly rapid upward change from ironstone and ferruginous oolite to smooth grey clay of the Kimmeridge Clay.
Western Isles (Albion) Glacigenic Subgroup
WIAG
The Western Isles archipelago.
A suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts derived predominantly from Lewisian rocks of the Western Isles, including sandy diamictons (till), sand, gravel, silt and clay. Deposited by ice that mainly radiated outwards from an ice divide positioned along the western seaboard of the Western Isles archipelago.
Planar unconformable contact with units of the Western Isles Glacigenic Subgroup.
Wimblebury Coal (South Staffordshire)
WICO
Windlesham Formation
WIDS
Widdrington Five-Quarter Coal (Northumberland)
WIFQ
Wig Member
WIG
Arenig (Moridunian).
Conformable on sandstones of the Wig Bach Formation.
Dark grey silty mudstone containing phosphate nodules.
Conformable and gradational with dark grey mudstones of the undivided Wig Bach Formation.
Winghay Coal (North Staffordshire)
WIGC
Wigton Marine Bed
WIGM
Core recovery was poor, but the clays apparently rested on bedrock (Stanwix Shale) within a buried channel at about 46m depth. (-21m OD) at Wigton.
Found only at Wigton, north Cumbria.
Lenses of "drab" clay within red clay containing Turritella communis, foraminifera and ostracods, recovered from a borehole only. The fossilliferous deposits are possibly Ipswichian in age, but were probably transported as glacial rafts from the Solway Firth during the Early Scottish Glaciation.
Probably a few metres, but core recovery was poor.
Core recovery poor, but the fossilliferous deposits were found beneath "clay containing foreign erratics", presumably till.
Wigston Member
WIGS
Winter Hill Gravel
WIHG
Erosional contact with Tertiary-Cretaceous bedrock.
Terrace surface.
Wilsey Beck Sandstone Member
WIL
Wilgi Geos 'Group'
WILG
Winton Marine Band
WIM
Widdrington Main Coal (Northumberland)
WIMC
Windermere Supergroup
WIN
At base of black shales of the Skelgill Beds, overlying the Ashgill Shale Formation.
A sequence of silty mudstones and siltstones with units of sandstone.
At the unconformable base of the overlying Carboniferous strata.
Winter Coal (South And West Yorkshire)
WINC
Windyhills Intrusion
WINDY
Windy Hills Gravel Member
WING
Unconformable, on deeply weathered crystalline basement.
Well rounded gravel composed of white quartzite and vein quartz in white, micaceous silty sand matrix.
Unconformable, below till and 'head', or at the surface.
Winterbourne Formation
WINT
The base of the formation is taken at the top of the dark grey to black fisile mudstone of the Cambriense Marine Band (locally termed the Winterbourne Marine Band), overlain by grey and red mudstone, locally conglomerate and pebbly sandstone, of the Winterbourne Formation.
Northern limb of Kingswood Anticline and Coalpit Heath Basin of Bristol Coalfield [ST 70 80].
Grey and red mudstones with common thin and lenticular beds of quartz-conglomerate and pebbly sandstone.
The grey and red mudstone, locally conglomerate and pebbly sandstone, of the Winterbourne Formation is overlain with a sharp, slightly erosive base, by the first lithic sandstone of "Pennant" type of the Downend Member
Winpenny Coal (North Staffordshire)
WIPC
Winksley Sandstone
WIS
A sharp upward change in a conformable succession from a predominantly grey mudstone to sandstone. The base of the first sandstone bed above the Subcrenatum Marine Band (where present) or the coarse-grained, Laverton Sandstone.
The Pennine foothills between Masham and Winksley, North Yorkshire.
A medium to thickly bedded, grey fine-to coarse-grained, cross-bedded sandstone.
A sharp upward change in a conformable succession from sandstone, to predominantly mudstone. The top of the last sandstone bed below the Nook House Sandstone.
Wick Sandstone Formation
WISA
Western Isles Glacigenic Subgroup
WISG
Sharp, unconformable contact with bedrock or planar unconformity with units of the Western Isles (Albion) Glacigenic Subgroup.
Winksley Shale
WISH
Whitacre Member
WIT
Transitional. Defined in the field at the upwards change from grey measures of the Halesowen Formation to red beds. Defined on geophysical logs (in uncored boreholes) above a narrow zone of high gamma radiation.
Warwickshire Coalfield (northern part) Sheet 169. Also likely to extend in the subcrop across the southern part of the Warwickshire Coalfield (Sheet 184).
Red bed sequence; mudstone-dominated in lower part but increasingly arenaceous towards top. Thin Spirorbis limestones at some levels. Impersistent conglomerates in uppermost part.
Range 280 - 357m; mean 334m; based on geophysical well log data.
At the top of highest mappable sandstone unit (Arley and Exhall sandstones) beneath the basal argillaceous beds of the overlying Keresley Member.
Withycombe Formation
WITH
Wilderness Till Formation
WITI
Unconformity or glacial deformation boundary on bedrock or on older Quaternary strata, e.g. the Cadder Sand Formation.
Central Scotland, related to ice streams sourced in the Highlands (in contrast to the Southern Uplands) during the Dimlington Stadial; Glasgow area, Stirling, Clackmannan, Tayside, north and south Lanarkshire, Lothians and Edinburgh, Fife.
The typical lithology is a glacially organized diamicton composed of isolated boulders, cobbles, gravel and pebbles in a matrix of sandy silty clay. The more elongate clasts are preferentially oriented and the deposits usually has systematic sets of joints. It is of a hard to stiff consistency and low plasticity. The colour varies, depending upon that of the local bedrock and can be reddish brown (Devonian and Upper Coal Measures), brownish grey or black (Carboniferous) and also greenish grey (Highland Metamorphic rocks). Minor features include pockets and bands of medium-grained sand and laminated clay bands up to 10cm thickness. The the Cadder area, temporary sections revealed that the diamicton is locally graded, displaying both upward and downward coarsening of the dispersed pebble to boulder sized clasts. At Baillieston (ibid, Figure 13), the till showed slices of laminated clay, one of considerable size (tens of metres), including near the base of the formation and sandwiched between two dicordant planes, which are likely to be low angle thrusts.
The Wilderness Till Formation is named from the Wilderness Plantation [NS 605 720], north of Glasgow (Browne and McMillan, 1989a). It is a regional till sheet of the Main Late Devensian glaciation.
Veneer to over 30m
Unconformity below younger Quaternary strata, or a glacial deformation boundary that is partly represented by the upper surface of drumlinoid landforms. These landforms are commonly seen at surface but might also form buried features in the Glasgow conurbation.
Witham Valley Formation
WIVY
The entire catchment of the River Witham and its tributaries, from around Boston to around Claypole, Lincolnshire.
The formation encompasses the fluvial, lacustrine and organic deposits of the River Witham and its tributaries. It includes floodplain alluvium and deposits of three river terraces. The floodplain alluvium comprises soft clays, silts and fine sands, with bodies of peat, overlying sands and gravels. The terrace deposits are dominantly sands with some gravelly sands, sandy gravels and gravels. Sands are dominantly pale brown to orange brown, quartzose, fine- to medium-grained, clean and well sorted. Pebble fractions are dominantly bioclastic limestone, siltstone, ironstone and phosphatic nodules derived from the Lias Group and Lincolnshire Limestone Formation, with additionally some angular to subrounded quartz, "Bunter" quartzite, ironstone, chert and sandstone.
Widdrington Yard Coal (Northumberland)
WIYC
Whitehill Jewel Coal (Lothian)
WJC
Westkapelle Ground Formation
Unconformably overlies gently-folded and faulted Palaeogene or older sediments, unconformably overlies Red Crag Formation in southwest quadrant of Flemish Bight.
Marine clays with thin sandy laminae passing gradationally upwards to sand with thin clay laminae (shallowing upwards), characterised by strong, continuous, sub-parallel reflectors in seismic profiles.
20 - 75 metres. (45 metres in 81/50A).
Unconformably overlain by Lower, Middle and Upper Pleistocene formations, and by Holocene sediments in the southwest.
Warklaw Hill Volcanic Member
WKH
Not exposed: lowest flows faulted against Inverclyde Group sediments.
This formation is composed of four well-defined subdivision as follows in downward sequence: d) Several thin flows of macroporphyritic olivine-basalts with large feldspar phenocrysts up to 5mm long; c) Several flows of macroporphyritic olivine-basalt with large phenocrysts of olivine and feldspar; b) Several thick flows (to 27m) of microporphyritic olivine-basalt with fluxion texture. a) Thin flows of porphyritic olivine-basalt.
At least 175m
Not seen: highest flows seen are highly vesicular purplish-grey feldspar-phyric basalts, 3.0-3-7m thick.
Weaklaw Vent
WKLAW
Weatheroak Sandstone Member
WKSA
Where greenish grey mudstone or sandstone rests on red mudstone.
Longbridge to Redditch.
Sandstone, pale greenish grey, medium- to fine-grained, well cemented, flaggy, generally parallel laminated; local copper mineralisation, subordinate red sandstone and siltstone, and green silty to sandy mudstone.
Where red mudstone overlies greenish grey sandstone.
Wester Keolka Shear Zone
WKSZ
The shear zone is probably a thrust that has juxtaposed Sand Voe Group rocks , that may be equivalent of the Moine Supergroup, against the Wilgi Geos Group of the Lewisian Gneiss Complex.
The unit extends about 5 km from Garmus Taing on the north coast of Northmaven to Pettadale Water, and is then offset by faulting about 2 km to the east, then continues another 2 km until it abuts the Ronas Hill and Eastern granites.
Blastomylonite, derived from Wilgi Geos Group and Sand Voe Group rocks.
The blastomylonite is of mappable thickness.
Woolwich Formation
Rests either on red-brown, yellow-brown and blue-grey mottled clays (Reading Formation) or glauconitic sands (Upnor Formation). Base sharp, with burrows extending up to 0.5m into the underlying beds. The boundary with the Reading Formation in central and southeast London is very well defined and, as lithological and colour contrasts are pronounced, can be interpreted readily in most drillers' logs.
Variable: largely grey to grey-brown, interlaminated fine-grained sands, silts and clays (also known as "Striped loams" (eg Dewey and others, 1924). Common plant debris concentrated locally in thin allochthonous lignites. Sporadic burrows throughout; bioturbation more common in higher beds, where sparse glauconite has been recorded. Shelly beds, particularly in the basal 2m, dominated by brackish water shells in dark grey clay matrix ("Woolwich Shell Bed"). Other lithofacies of local occurrence are limestone beds such as the "Paludina Limestone" (eg Berry and Cooper, 1977) at the top of the formation, and ferruginous sand and pebble beds (Ellison, 1983). Woolwich Formation not shown previously on maps.
Maximum 14.5m; generally 11 to 12m in southeast London and north Kent; thins to the west and north as it passes into the Reading Formation.
Other than in central London, where the formation is overlain by the Reading Formation, the top is marked by a change to glauconite-bearing sands with a basal rounded flint pebble bed and a marine fauna (Harwich Formation).
Woodland Beds [Obsolete Code: Use Wdb]
WLB
Warp And Lacustrine Clay
WLC
Composite deposit: artificially induced alluvium (Warp) and clay of lacustrine origin (Lacustrine Clay). [Generic description: 'TMOS' Procedures].
Whitelady Formation
WLDY
Local to Lydford, West Devon.
Greenish-grey slate with thin quartzite and limestone beds and nodular cephalopod limestone.
Woodland Formation
WLF
Conformable on the Craigskelly Conglomerate.
Conformably overlain by Scart Grits.
Westmill Gravel Member
WLGR
Mid Pleistocene, Anglian; final pre-diversionary deposit of the Proto-Thames.
Rests unconformably on chalk bedrock of the Chalk Group or sands and clays of the Palaeogene formations.
Colne Valley, near Watford, at 60-70m OD; course of Proto-Thames (ancestral Thames) through the Vale of St Albans.
Gravel and sand, locally with lenses of silt, clay or peat and organic material. Gravel is 80 to 90% flint with relatively high percentage (10 to 15%) of quartz, and 1.5 to 6% chalk.
Overlain by till of the (Anglian) Lowestoft Formation in places; otherwise at surface. Cut by till at Aldenham [TQ 133 981].
Wall Hill Member
WLH
Coastal outcrop between White Port (NX 7234 4336) and Port Mary (NX 7550 4540).
Fining upwards cycles of light grey to white conglomerates and sandstones with thin purple siltstones, marls and shales.
360m (maximum)
Much Wenlock Limestone (Knoll-Reef)
WLK
Whickhope Linn Limestone
WLL
Wentlooge Level Formation
WLLEV
In the type area it lies unconformable on bedrock, fluvioglacial sand and gravel of Welsh Ice origin, and locally on Brecknockshire Formation.
Northern shore of the Severn Estuary between Cardiff and Gloucester. Includes Wentlooge Level, Caldicote Level, New Grounds and Minsterworth Ham, as well as tidal banks north of the main channel.
Soft to very soft, blue-grey clay, with scattered diffuse silt laminae and peats. A basal gravel and diachronous basal peat are commonly present.
Generally 9 to 12m, though locally more in the region of buried channels. 15m proved in borehole [ST58NW/2] at Sudbrook.
Generally the ground surface; locally overlain by deposits of the Severn and Avon Catchments Subgroup.
White Limestone
WLM
Wormistone Lower Marine Band
WLMB
Western limb of the Wormiston Syncline.
Limestone.
0.15m in type section.
Wether Law Linn Formation
WLN
Silty mudstone, mudstone, siltstone and fine-grained sandstones.
Conformable: highest red, poorly lithified shales below coarse-grained sandstones of the Henshaw Formation.
West Lothian Oil-Shale Formation
WLO
Base of the Humbie Marine Band (= lowest of the Macgregor Marine Bands).
Lothians, Fife, eastern Strathclyde.
Pale sandstones, interbedded with grey siltstones and mudstones, seams of oil-shale and of coal with beds of seatrock, ostracod-rich limestone/dolomite and sideritic ironstone.
Base of the Hurlet Limestone.
Waterside Limestone
WLS
Known in the subsurface around Dalmellington, Ayrshire.
Wilmslow Sandstone Formation
WLSF
Drawn where pebble-free sandstones become dominant over pebbly sandstones of Chester Pebble Beds.
Sandstone, fine- to medium-grained, red-brown to brick red, generally pebble-free, cross stratified, with sporadic siltstones.
Locally transitional into Bulkeley Hill Formation (laterally continuous sandstones and mudstones, commonly pebbly). Elsewhere overlain by erosional base of Helsby Sandstone Formation.
West Leys Sand And Gravel Formation
WLSG
The lower boundary of this unit is a sharp erosional unconformity on angular gravel of the Camphill Gelifluctate Bed. It represents a discontinuous channel, (up to 1m in depth) eroded into the underlying deposit.
Buchan, northeast Scotland. The formation is currently only shown from Leys Quarry (disused) (centred on NK 0040 5250) on Sheet 87W (Ellon). The unit might be regionally significant and present locally across northeast Scotland.
Sandy gravel and gravelly sand, very pale brown to pale brown pebble to cobble grade, clast-supported with quartzose medium to coarse sand matrix; locally sand with dispersed pebbles. Clast angularity is variable from subangular to rounded. Clast lithologies are dominated by psammitic and quartzite metasedimentary rock, with subsidiary felsite, mafic igneous rocks, pelites, red and grey granites and red sandstone. The sediments display tabular cross beds showing palaeocurrent from the northwest, and crude horizontal bedding. Interpreted as either a proglacial or subglacial glaciofluvial sediment.
The upper boundary of the unit is unconformable - a subhorizontal, planar, erosion surface at the base of the yellowish brown diamicton of the Rottenhill Till Formation.
White-Leaved-Oak Shales [Obsolete Code: Use Woa]
WLSH
Woodland Sands Member
WLSS
Washing Lodge Stone Band
WLST
Whelter Knotts Tuff Formation
WLT
Taken at the abrupt change to silicic pyroclastic rocks from andesite of the Birker Formation or the volcaniclastic rocks of the Scalehow Formation.
North-eastern Lake District, south and east of Ullswater to the Haweswater area.
A pale, yellowish grey, to grey-weathered, garnetiferous, massive silicic tuff and eutaxitic lapilli tuff, with subordinate foliated vitrophyric tuff, and bedded units of lithic-rich tuff and lapilli-tuff. Lithologically distinctive units have member status.
Defined by the base of the Mardale Formation.
Winstermoor Lava Member
WMB
Basalt of the Winstermoor Lava Member rests upon pale grey, massive limestones of the Bee Low Limestone Formation.
Restricted to the area between Gratton Dale, Winster and Bonsall Moors and the workings of Millclose Mine. Boreholes show the lavas to be lenticular in distribution and locally absent.
A dark grey basaltic lava, locally altered to green and brown clay with basalt fragments.
Up to 4.4 m thick proved in the Aldwark Borehole.
The basalt of the Winstermoor Lava Member is overlain by grey to dark grey, bituminous limestones of the Monsal Dale Limestone Formation.
Bell Pit
WMBP
White Mine Coal (Ballycastle, Northern Ireland)
WMC
Rest on fireclay.
Coal and shale.
West Melbury Marly Chalk Formation
WMCH
Upper Cretaceous, Cenomanian. Mantelliceras mantelli to Cunningtoniceras inerme Zones.
Unconformable. Base marked by erosion surface, frequently bored, at the base of the Glauconitic Marl Member (Southern Province), Melbury Sandstone Member (western Southern Province) or Cambridge Greensand Member (`Transitional? Province).
Throughout the Southern Province and the Transitional Province of England. Is known to be absent or attenuated over structural highs. Most notably the mid-Dorset Swell in Dorset.
Buff, grey and off-white, soft, marly chalk and hard grey limestone arranged in couplets.
In general between 15 and 25 metres of these beds are preserved but they are absent over the Mid-Dorset Swell (Drummond, 1970; Kennedy, 1970; Bristow et al., 1995) and thin over other syndepositional structural `highs?.
CConformable in `full? sequences at the erosional base of the overlying Cast Bed `Member? (bedC1 of Gale, 1995) of the Zig Zag Chalk Formation in the Southern Province and by the base of the Totternhoe Stone Member, its lateral equivalent, in the `Transitional? Province north of the Thames. This mid-Cenomanian erosional break marks the change from well-defined limestone marl couplets below to chalks with marls above and also the boundary between the `B? and `C? Chalk Marl couplets of Gale (1995). In full sequences the `Tenuis Limestone? is the bed immediately beneath the mid-Cenomanian break.
Waterloo Marker Coal (Derby)
WMCO
Windermere Clay And Silt Formation
WMCS
Devensian OIS 2 (Windermere Interstadial to Younger Dryas).
Overlies gravel and till of the Central Cumbria Glacigenic Subgroup (Caledonia Glacigenic Group).
Lacustrine and organic sediments infilling Lake Windermere, comprising upper (Upper Laminated Clay), and lower (Lower Laminated Clay) units of laminated clay separated by a sequence of silt or organic silt (Non-organic and organic silt unit). Sporadic rock fragments are present in the organic silt.
Cores of up to 6m have been sampled on the lake floor in water depths of 30m. Echo sounding in deeper water indicates 21 to 40m of sediment (Howell, 1971).
The Upper Laminated Clay passes conformably upwards into organic muds of the Cumbria-Lancashire Catchments Subgroup (Britannia Catchments Group) of Flandrian age.
Opencast (Colliery)
WMCY
Mine Entrance Excavation
WMEN
Infilled Ground
WMGR
Variable composition; man-made superficial deposit. Areas where the ground has been cut away and then had artificial ground deposited, eg, a backfilled quarry, landfill. [Generic description].
Western Mud Hole Member
WMH
Quarry (Hard Rock)
WMHR
Lower West Mills Marine Band
WMIL
Upper West Mills Marine Band
WMIU
Whitemore Limestone Member
WML
The base is defined at the base of the first pale blue-grey wackestones of the Whitemore Limestone Member overlying conformably the dark grey mudstones of the Phynis Mudstone Member.
Limited to the Slaidburn (SD 71 53) and Whitewell (SD 64 47) anticlines and the northern limb of the Plantation Farm Anticline (SD 66 43), from the western part of the Craven Basin.
Wackestones and packstones, pale blue-grey, thin-bedded, bioclastic, fine-to coarse-grained, graded, often erosive-based and containing intraformational lithoclasts, interbedded with similar amounts of pale blue-grey calcareous mudstone, commonly platy and blocky.
Up to 80 m thick.
In the Whitewell Anticline, taken at the base of the dark grey blocky mudstone interbedded with thin wackestones of the Leagram Mudstone Member, overlying conformably the pale blue-grey wackestones and packstones of the Whitemore Limestone Member. In the Slaidburn Anticline, the limestones of the Whitemore Limestone Member are overlain by non-micaceous, laminated mudstones interbedded with laminated calcisiltites of the Hodder Mudstone Formation (undifferentiated).
Waterman's Lodge Member
WMLO
Opencast (Metalliferous Mineral)
WMME
Opencast (Non-Metalliferous Mineral)
WMNO
Pit (Superficial Deposits)
WMPI
Westernmoor Coal (South Wales)
WMRC
Wambury Siltstones
WMS
White Metal Coal (Cumbria)
WMT
Mineral Excavation (Undivided)
WMU
Western Midland Valley Westphalian To Early Permian Sills
WMVAS
Crosshouse Sill
WMVCH
Caprington Sill
WMVCP
Hillhouse Sill
WMVHH
Inner Nebbock Sill
WMVIN
Lennoxtown Boss
WMVLT
Saltcoats Main Sill
WMVSC
Winterton Shoal Formation
Widespread unconformities. Overlies early Pleistocene Prodelta Beds, overlain by Yarmouth Roads Formation.
Presumed fine- or medium-grained sands with minor clay laminations (1 x 0.66 metres core sample only in British Sector). Mainly structureless in seismic profiles, but in some sections gently-dipping reflectors prograde westwards onto erosional base. Unconformably overlain by unit with chaotic reflector configuration, overlies eastward-prograding (Smith's Knoll Formation) or westward-prograding beds (Ijmuiden Ground Formation).
0 - 130 metres.
Whinny Bank Tuff Formation
WNB
Unconformity. Overlies erosion surface on Skiddaw Group.
Whicham Valley:- between Broadgate (SD 180 867) and Lacra Bank (SD 145 815), Cumbria.
Interbedded succession of silty mudstone and andesitic lapilli-tuff; the proportion of andesitic lapilli increases up the succession. Much of the silty mudstone occurs as abraded pellets and accretionary lapilli, suggesting a pyroclastic origin.
Base of overlying Po House Formation (bedded tuff) or Waberthwaite Formation (dacitic tuff and lapilli-tuff).
Wilsontown Gas Coal (Central Coalfield)
WNG
Warren Hill Sand Member
WNH
Woodland Limestone [Obsolete Code: Use Wldl]
WNL
Wilsontown Main Coal (Central Coalfield)
WNMA
Windmill Coal (South Lancashire)
WNML
West Melbury Marly Chalk Formation, Zig Zag Chalk Formation, Holywell Nodular Chalk Formation And Newpit Chalk Formation (Undifferentiated)
WNPCK
Windrush Member
WNR
In the type section, reddish brown, blue mottled mudstone with calcareous nodules of the Windrush Member, overlies conformably grey mudstone of the Burford Coal Member.
Oxfordshire Coalfield; although in the subsurface only.
Consists of approximately equal proportions of red and grey strata. The red intervals are dominated by red massive mudstone with beds of red silty mudstone with common dessication cracks. The grey intervals include upward-coarsening cycles of grey, locally reddened, mudstone to sandstone capped by seatearth and thin coal seams.
Up to 590 m in the Upton Borehole
The red and grey mudstones and sandstones of the Windrush Member are overlain unconformably by red mudstones of the Mercia Mudstone Group.
Wilsontown Smithy Coal (Central Coalfield)
WNS
Woofferton Sand And Gravel
WNSG
Whiteness Limestone Member
WNSL
Whorneyside Tuff Formation
WNY
Base of andesitic lapilli-tuff or, where that is absent, at base of bedded andesitic tuff. Markedly unconformable on the succession of Birker Fell Andesite Formation lavas that range in composition from basalt to dacite.
Whorneyside, Langdale to Scafell, Wasdale, Borrowdale; Coniston Fells, Hard Knott and Duddon Valley, Cumbria.
Brown-weatherd, massive eutaxitic andestic lapilli-tuff overlain by laminated and thinly bedded andesitic tuff. Intruded by many contemporaneous andesite sills in part.
Contact with overlying rhyodacitic rocks in the Airy's Bridge Tuff Formation.
White-Leaved Oak Shale Formation
WOA
Faulted junction with Hollybush Sandstone.
Southwest of Raggedstone Hill; west side of Midsummer Hill, both at south end of Malvern Hills; small proving in well at West Malvern.
Dark grey mudstones.
Nowhere exposed; probably conformable junction with Bronsil Shale.
Wood Burn Formation
WOB
Conformably overlies the Lower Camregan Grits Formation.
Pale sandstones, siltstones and mudstones.
Conformably overlain by the Maxwellston Mudstone Formation.
Wolston Clay
WOC
Clay and silt, grey; glacial. [Generic description: 1:50 k map margins].
Woodhead Coal (Cheadle)
WOCO
Wolf Crags Formation
WOCR
Unconformable on bedrock or disconformable on the Threlkeld Till Formation of the central Cumbria Glacigenic Group.
Central Lake District 1:50k Sheet 29, but probably could also be applied to Loch Lomond Stadial deposits of the Central Cumbria Glacigenic Subgroup on sheets 30, 38 and 39, and elsewhere in Cumbria.
Diamicton and gravel that form moraines, fluted hummocks and terraces laid down in the uplands of the central part of the Lake District by corrie glaciers and their associated meltwaters during the Loch Lomond Stadial. Two members are recognised: The Wolf Crags Till Member is a yellowish brown sandy diamicton, with clasts of Borrowdale Volcanic Group and Skiddaw Group rocks, and subordinate numbers of clasts of Threlkeld Microgranite. The Wolf Crags Gravel Member forms a series of terraces in the Mosedale Beck valley. It is composed of coarse gravel (with clasts up to 1m diameter) with subordinate amounts of finer gravel and sand. It contains clasts of Borrowdale Volcanic Group rocks and Threlkeld Microgranite.
c.15m at the type site.
Generally the ground surface, but locally overlain by Holocene peat.
Wood Coal (Douglas)
WOD
West Orkney Evaporite Formation
WOEV
Woolley Grit Member
WOG
Woodford Gravel Formation
WOGR
Tributary of pre-diversionary (ancestral) River Thames, Woodford - Epping area.
1-10m, average 5m
Overlain in part by Anglian till, otherwise at surface.
Wolford Heath Member
WOHE
Woodhouse Flags
WOHF
Woodhouse Flags And Midgley Grit (Undifferentiated)
WOHMG
Woolhope Limestone Formation
WOL
Conformable on Wyche Formation in Malverns; sharp lithological boundary with Upper Haugh Wood Beds in type area.
Woolhope Inlier, Malverns.
Thinly bedded nodular limestones and calcareous siltstone and mudstones; some bentonites.
6 - 75m; 39m in type area.
Conformably overlain by Coalbrookdale Formation; transitional junction.
Wolston Formation
WOLS
Mid Pleistocene (MI Stage 12 and/or 10).
Overlies the pre-glacial fluvial sands and gravels of the Baginton Formation or, more generally, bedrock (mainly Triassic and Jurassic).
English Midlands east of Birmingham, and as far south as the Moreton-in-Marsh and Tewkesbury areas. Precise limits in east and north somewhat uncertain and contentious, but essentially lies northwest of the Chalk scarp of the Chilterns and Norfolk and west of the Fens (including lower Witham of Lincolnshire) and Lincolnshire Limestone scarp or north Lincolnshire, and (mostly) south of the Trent.
Comprises the pre-Devensian glacial succession of much of the English Midlands. Predominantly tills, sands, gravels and laminated clays. In type area and elsewhere constitutes a succession including a basal reddish-brown Trias-rich till of essentially northern provenance (Thrussington Till Member), glacialacustrine muds ([Wolston or Grounds Farm Member and] Bosworth Clay Member), an upper grey, chalky till with Jurassic and Cretaceous material, essentially of northeastern provenance (Oadby Till Member), and flint-rich outwash gravels (Dunsmore Gravel Member). Characteristically lacks Scottish and Lake districts erratics (which characterise the Devensian Stockport Formation), and western (Welsh, etc.) erratics (which are found in the probably equivalent Nurseries and Ridgacre formations to the west of the Wolston Formation).
(A) The name follows Bowen et al (1999) and BGS provisional Framework document. (B) The consensus view in academia is that this unit is Stage 12 (as per Bowen 1999), but there is evidence to suggest it is younger Stage 10, or both 10 and 12. (C) The succession within the Wolston Formation is only touched upon; neither the Wolston Clay Member nor the synonymous Grounds Farm Member are mentioned. (D) The precise limits of the Wolston Formation are contentious. It could be taken to the Devensian limit in Lincolnshire but Lewis (in Bowen, 1999) excluded things such as the Wragby Till (putting it in the Lowestoft Formation), which could be included in the Wolston Formation. Thus the limit in the east is fairly arbitrary, and the northern limit is particularly vague, and probably best left as such until some primary work has been done on the older drifts of the south Pennines area. (E) As this unit is not actually distinguished on any BGS maps (locally its component members are) the listing of 50K sheets is actually superfluous, but a list is included to show the areas where the Wolston Formation should encompass the glacial deposits.
c.25m at type locality; elsewhere may be represented by up to 80m of deposits.
Ground surface or various younger Quaternary deposits (head, fluvial deposits).
Wood Coal (Midlothian)
WOMI
Woodhall Marine Band
WOO
Woogill Coal (Masham Area)
WOOG
Wormwood Formation
WORM
White Orr Limestone
WORRL
Worcester Member
WORT
Where river deposits overlie bedrock.
River Severn Basin - Bridgnorth To Chepstow.
Cross bedded gravels and sands; pebbles mostly Triassic quartzites, together with flints 'Irish Sea erratics' and others, including Jurassic and "Malvernian" clasts.
Up to 10m+
Woodhorn Sandstone
WOSA
Wolston Sand And Gravel
WOSG
Woolhope Shale
WOSH
Worbarrow Tout Member
WOT
First occurrence of significant, commonly ripple cross-laminated, quartz-detrital limestone (base Hard Cockle Beds) above mudstones of the Ridgeway Member.
In west Dorset, the lower part of the member contains prominent brown-weathering limestones containing detrital quartz (Hard Cockle Beds) and exhibiting abundant ripple cross-laminations. The rest of the member comprises characteristic, regularly interbedded, white-weathering micrite and dark grey mudstone (Soft Cockle and Marly Freshwater beds). Salt pseudomorphs, hard grounds and rare algal laminations are present in the micrites, particularly in the central part of the member. Algal lamination increases in significance in the east and may be associated with zones of multiple hardgrounds. Gypsum is present at Worbarrow Tout and Durlston Bay. The highest part of the member comprises thicker-bedded, chert-rich micrites (Cherty Freshwater Bed).
Ranges from 17m in west Dorset to 39m in the east.
Top of thickly bedded cherty pure micrites (Cherty Freshwater Beds) beneath very shelly micrite (Cinder Bed) at the base of the Stair Hole Member.
Woundale Tuff Formation
WOU
Taken at the change from massive, uniform, dacitic lapilli-tuff of the Froswick Tuff Formation, to variable andesitic tuff and lapilli-tuff lithofacies, at a generally conformable contact interpreted to be an erosion surface of low relief.
From Stock Ghyll, Ambleside to Troutbeck, Kentmere and Longsleddale to Mosedale and around High Street, eastern Lake District.
Heterogenous andesitic tuff and lapilli-tuff, with impersistent interbeds of volcaniclastic sandstone, particularly in the upper part of the Formation.
To 800m
Defined by the base of the overlying Seathwaite Fell Sandstone Formation, which here is an erosion surface overlain by well bedded volcaniclastic sedimentary rocks.
Wockley Member
WOY
Upward change from glauconitic bioclastic sandstone (of the Tisbury Member) to micrites.
Newtown area of Tisbury [ST 930 290] to Chilmark [ST 975 310].
Chalky micrites and dense porcellanous micrites, commonly very shelly.
Upward change from micrites to fine-grained oolites of the Chilmark Member.
Wemyss Parrot Coal
WPA
Warren Point Beds
WPB
Wernpistyll Coal (South Wales)
WPCO
West Park Farm Member
WPF
Wilpshire Grit
WPG
Woolpit Beds
WPIT
Silt, laminated. [Generic description: 1:50 k map margins].
Wee Post Limestone
WPLS
Whipton Formation
WPN
Rests directly and unconformably on Crackington Formation (Namurian), except where local patches of basalt intervene. A marked hiatus is present between the basalts at 290 Ma, and the Whipton Formation at c.260 Ma.
Outcrop extends from near Ide [SX 885 900], eastwards and northeastwards through Exeter to Whipton.
Reddish-brown silty, clayey, sand and weakly cemented sandstone, with some clayey silt, mudstone and breccia units.
20m (Ide area), 25m at least (Exeter City centre), c.60m (type section), 10m (Pinhoe [c.SX 970 943]).
Overlain mostly by Alphington Breccia; junction gradational over a vertical interval of about 10m, with upward passage into breccia. Overlain by Monkerton Formation around [SX 965 940].
Wernpistyll Rider Coal (South Wales)
WPRC
Wild Pear Slates Member
WPSL
Wrekin Quartzite Formation
Unconformable on Ercall Granophyre.
Quartzose sandstones (orthoquartzites) comprising rounded quartz grains, subordinate feldspar and some glauconite. Locally pebbly and conglomeratic at base, with clasts of Precambrian (Uriconian) volcanic material. Sporadic mudstone interbeds.
Sharp conformable junction with glauconitic sandstones of the overlying Lower Comley Sandstone Formation.
Archaeological Excavation (Undivided)
WQU
Warley Rock
Werraanhydrit Formation
WRAN
Woolwich And Reading Beds Formation
WRB
Drawn at base of glauconitic sand of the Woolwich and Reading Beds where it rests unconformably on fine-grained sands of the Thanet Formation.
Glauconitic sands at base (Bottom Bed), overlain by grey clays and sands with brackish fauna (Woolwich Beds), and interleaved red and variegated clays and sands (Reading Beds).
Approx. 12-20m
Unconformity, at boundary between clays and sands of the Woolwich and Reading Beds and sands and pebble beds of the London Clay Formation. (Blackheath and Oldhaven Beds intervene in the east of London and Essex).
Whitehill Rough Coal (Lothian)
WRC
Weather Castle Member
WRCA
Wroxham Crag Formation
WRCG
Pre-Pastonian to Cromerian.
Disconformable on the Norwich Crag, from which it can be distinguished by the generally coarser and less well sorted nature of the sediments and by the presence of significant quantities of quartz, quartzite and far-travelled clasts in the gravels. The formation cuts down through the Norwich Crag northwards and comes to rest on Chalk Group bedrock in north Norfolk.
Restricted to eastern Norfolk and northeastern Suffolk, at least as far south as Halesworth.
The formation comprises a sheet of interbedded gravels, sands, silts and clays. The gravels are dominated by flint (up to c.80%) and by quartz and quartzite (up to c.60%), with far-travelled minor lithogies including Carboniferous chert, Rhaxella chert, Greensand chert, Spilsby Sandstone and felsic volcanic rocks from North Wales. The deposits are interpreted as estuarine and near-shore marine.
Widely overlain by Mid Pleistocene glacial deposits, less widely by deposits of the Bytham Valley Subgroup and the Cromer Forest-bed Formation. It is distinguished from the latter units by sedimenrary, etc, features related to its marine origin.
Weardale Pluton
WRDG
Wray Castle Formation
WRE
Conformably overlies the Coldwell Formation.
Conformably overlain by the Gawthwaite Formation, which is the sandstone member of the Coniston Group.
Wearde Sandstone Member
WRG
Conformable transition with the slate and mudstone of the undivided Saltash Formation below.
Mapped over a strike length of 20km in the Plymouth area.
Channel sandstone: Thickly bedded massive sandstone beds with rare interbeds of mudstone and siltstone. Non-channel sandstone: Fine- to coarse-grained sandstone in parallel beds up to 1m thick with interbeds of interlaminated siltstone and mudstone. Mudstone with sandstone streaks, lenses, thin to thick laminae and thin beds. Associated basaltic lava and hyaloclastite form an important but subordinate facies of this division.
Conformable transition with the slate and mudstone of the undivided Saltash Formation above
Wolf Rock Intrusion
WRIN
Fine-grained, microporphyritic, soda-rich phonolite.
Woodmuir Jewel Coal (Central Coalfield)
WRJ
Wester Main Coal
WRMA
Woodmuir Main Coal (Central Coalfield)
WRMN
Warmwell Farm Sand Member
WRMS
Wroot Formation
WROT
Wildmoor Sandstone Formation
WRS
Transitional, at top of sequence dominated by pebbly sandstones and conglomerates of the Kidderminster Formation.
Stafford and Worcester Basins.
Sandstones, generally silty or argillaceous, fine- to medium-grained, bright orange-red to dark brick-red, with subordinate siltstone and mudstone; pebbles rare.
c.284m (Worcester area); c.200m (Sheet 123), 0-200m South Staffs and Worcestershire, 0-134m Redditch area.
Marked by normally disconformable base of Bromsgrove Formation.
Whiterigg Serpula Band
WRSB
Worston Shales [Obsolete Code: Use Wsg]
WRSH
Woodmuir Smithy Coal (Central Coalfield)
WRSM
Woodmuir Splint Coal (Central Coalfield)
WRSP
Ward's Stone Sandstone
WRST
Sharp, generally erosional, base on siltstones of the Roeburndale Member.
Lancaster Fells. Mapped but unnamed on Settle (60) and Garstang (67) sheets where included in top of Roeburndale Member (then termed Formation).
Feldspathic to quartzose, coarse-grained to fine-grained sandstones, commonly with ganisters; typically fines upwards; several thin coal seams in upper part.
c.15 - 200m; typically c.15 - 30m; unusually thick in Ward's Stone area.
Sharp upper boundary at base of dark grey mudstone of the Caton Shale.
Wrayslack Tuff Member
WRT
Taken at the base of the pyroclastic flow deposit, usually overlying volcaniclastic sandstone in the Waberthwaite Formation succession; basaltic sills may intervene.
Between Windy Slack (SD 172 888) and Boadhole (SD 190 878), west of Duddon Bridge near Broughton in Furness, Cumbria.
Top of pyroclastic flow deposit, usually overlain by volcaniclastic sandstone, which separates it from the overlying pyroclastic flow deposit (Barrow Tuff Member).
Whitehaven Sandstone Formation
Unconformable, base of lowest major reddened channel sandstone unit above unreddened Middle Coal Measures.
Red to purple-brown, cross-bedded sandstones with vari-coloured mudstone and siltstone. Thin coal seams, marls and limestone bed with spirorbis sp. present locally.
300m minimum
Warren Sandstones
WSA
Wee Stairhead Coal (Lothian)
WSC
Westoe Coal Formation
WSCO
Wet Side Edge Tuff Member
WSE
Base of andesitic lapilli-tuff. Markedly unconformable on the succession of basaltic to dacitic lavas in the Birker Fell Andesite Formation.
Watendlath, Borrowdale, to Scafell, Langdale, Wet Side Edge - Duddon Valley - Stainton Pike, Cumbria.
Brown-weathered, massive, eutaxitic andesitic lapilli-tuff.
At base of overlying unnamed bedded tuff, member of the Whorneyside Tuff Formation.
Wessex Formation
WSEX
Wellwood Seven Foot Coal (Fife)
WSF
White House Silts
WSI
Placed at junction of laminated clays and silts and the underlying Mathon Sand and Gravel.
Cradley Valley between Mathon and Eastnor and Glynch Brook Valley, Hereford and Worcester.
Laminated reddish brown clays, silts and fine-grained sands.
Up to c.23 metres proved.
Placed at erosion surface that truncates the beds and which is overlain by Coddington Till or Cradley Silts.
Wiley Sike Limestone
WSKL
Woodbury Shale Member
WSM
Weston Flags Formation
WSN
Underlain by Stapeley Volcanic Formation and Hope Group Shales.
Flaggy siltstones and fine-grained sandstones.
Overlain by Betton Shale Formation.
Whickhopenick Sike Coal
WSNC
Whitehill Splint Coal (Lothian)
WSPC
Walland Sandstone
WSS
Westleigh Limestone Formation
WST
Original Lexicon entry claimed "age" of Courceyan to Asbian. This level of precision is not considered reliable in the current definition.
Around Westleigh the lower boundary is taken at the incoming of thin-bedded fine-grained limestones of the (lower) Westleigh Limestone Formation above the black, hard cherty mudstones of the underlying Doddiscombe Formation. To the north it is taken at the incoming of thin to thick bedded coarse calcarenites and mudstones of the (upper) Westleigh Limestone Formation above the black hard cherty mudstones of the underlying Doddiscombe Formation.
Between Ashbrittle (ST 04 21), and Wellington (ST 13 20), Somerset.
Lower part (known informally as the Lower Westleigh Limestone) comprises thin-bedded, platy, fine-grained (mud and silt grade), commonly partly silicified limestones. Shaly mudstone interbeds are sparsely developed. Upper part (known informally as the Upper Westleigh Limestone) comprises thin to massive beds of coarse, locally conglomeratic, bioclastic/ooidal/pelloidal calcarenite interbedded with subordinate mudstones and calcilutites. Silicification is locally present. The Lower Westleigh Limestone is present only around Westleigh; to the north it passes into the Upper Westleigh Limestone.
Not known but probably c.100m.
The upper boundary is taken at the incoming of dark grey unfossiliferous finely laminated silty mudstones with scattered siltstones of the overlying Dowhill Mudstone Formation above the highest limestone bed of the Westleigh Limestone Formation.
Wester Coal (Scremerston)
WSTC
West Sole Group
WSTS
West Stayvoyage Vein
WSV
Wellsyke Coal (Midgeholm)
WSYK
West Angle Formation
WTA
Woodston Beds
WTB
Estuarine deposits of possible Hoxnian age. [Generic description: 1:50 k map margins].
Lower Wooton Beds
WTBL
Upper Wooton Beds
WTBU
Witney Coal Member
WTC
Seen in the type section as a grey mudstone with basal coal of the Witney Coal Member overlies conformably pale greenish grey, rooted, fine-grained sandstone of the Pennant Sandstone Formation.
Widespread in the Oxfordshire Coalfield, but proved only in the subsurface, and in a single borehole, Harwell No. 3 SU48NE92, (SU 46801 86441), in the Berkshire Coalfield (Foster et al., 1989).
A grey coal-bearing succession, with typical upward-coarsening cycles from mudstone to sandstone, capped by a seatearth and a coal.
Maximum thickness of 83 m in the type section.
Seen in the type section as a greyish blue, brown, yellow and red mudstone of the Crawley Member, overlies conformably dark grey, carbonaceous mudstone of the Witney Coal Member.
Whitsand Bay Formation
WTD
Base not seen on Sheet 348 or elsewhere in southwest England.
Sheet 348 (not mapped elsewhere).
Purple and green slaty mudstone and siltstone with thin to medium beds of grey green sandstones and sporadic packets of pale grey quartzite sandstone beds. Local mottling and blebbing due to bioturbation, dispersed sedimentary clasts and volcanic detritus.
Upper part comprises pale grey-green silty mudstone with fine-grained sandstone streaks, lenses, thick/thin beds of sandstone and lenticular quartzite beds. Boundary with Bovisand Formation marked by colour change to dark grey above. Above the boundary bioturbation, bioclasts and sandstone beds with load casting and cross lamination are progressively more common.
White Crag Member
WTE
White Limestone (Cumbria)
WTL
Watchlaw Coal (Northumberland)
WTLC
Watchlaw Limestone
WTLL
Water Coal (South Lancashire)
WTRC
Watergate Seam
WTRG
White Limestone And Rough Limestone (Undifferentiated)
WTRL
Wintertarn Sandstone Member
WTRS
At the base of the sandstone overlying the uppermost thick-bedded limestone of the Great Scar Limestone Group.
Northwest England.
From 3 to 7m
Base of the overlying Askham or Peghorn Limestone Member.
Whita Sandstone Beds
WTS
Conformable on Birrenswark Volcanic Formation (Langholm).
Northumberland - Solway Basin. Langholm district (Scotland, Sheets 10E, 11 and 17).
Medium to thickly bedded, fine- to coarse-grained white, grey and pink sandstones with a few thin siltstones and sandy cementstones.
c.300m (Langholm).
Passes upwards by alternation into interbedded sandstone, siltstone and and dolomitic limestone ('cementstone') facies of the Kirkbean Cementstone Member (Ballagan Formation).
Weeton Shales
WTSH
Wittering Formation
WTT
Rests on London Clay, a dark grey bioturbated clay below with marked lithological change to interbedded glauconitic fine-grained sand and very silty clay above.
Greyish brown laminated clay; wavy- to lenticular-bedded sand interbedded with clay in equal proportions; and fine- to medium-grained sparsely glauconitic sand.
Overlain by Earnley Sand Formation, well marked by the transgressive basal surface of glauconitic silty sands with pebbles.
Weybourne Town Till Member
WTTI
The lower boundary of the chalky diamicton facies of the Weybourne Town Till Member rests upon either the Wroxham Crag Formation or the Bacton Green Till Member. In the case of the Wroxham Crag Formation, the boundary is sharp and planar and in places resembles a plane of decollement, with till resting upon sand and gravel. In the latter case where it overlies the Bacton Green Till Member (brown sandy diamicton), the Bacton Green Till has been folded and incorporated into the Weybourne Town Till in a series of highly attenuated shear structures.
The Weybourne Town Till Member crops out in the Weybourne, Hanworth and Trimingham areas of north Norfolk. No stratigraphical link is made with 'Marly Drift' to the west of the Glavern Valley.
The Weybourne Town Till Member consists of a highly calcareous silt and chalk-rich matrix supported diamicton. It is generally massive in structure, but locally, such as at the unit's stratotype locality, the diamicton is highly stratified, consisting of highly attenuated and deformed inclusions of pre-existing till (Bacton Green Till Member).
Locally to 6m
The Weybourne Town Till Member is overlain and truncated by the sands and gravels of the Briton's Lane Formation.
Whittery Volcanic Formation
WTY
Overlies Hagley Shale Formation.
Underlies Whittery Shale Formation.
Wormistone Upper Marine Band
WUMB
West limb of the Wormiston Syncline.
Westing Ultramafic Zone
WUZ
Wolvercote Sand And Gravel Member
Mid Pleistocene (MI Stage ?10 to 8).
Upper Thames catchment (ie, River Thames and most tributaries (excluding the River Thame) upstream of the Goring Gap. Weakly developed along the Upper Thames and also weakly developed along the lower Evenlode and the lower Cherwell.
Predominantly cold phase sands and gravels that underlie the Wolvercote or Third Terrace of BGS maps. Dominated by clasts of Middle Jurassic limestone, but also containing "Bunter" quartz/quartzite and a proportion of flint.
(A) Here named Wolvercote Sand and Gravel though in Bowen (1999) and in the previous BGS list of computer codes it is Wolvercote Member. (B) Parent was formerly Upper Thames Valley Formation. Despite correlation issues at Goring, revision is acceptable as member names in the Upper Thames remain discrete. (C) Terrace surface c.12m above modern alluvial floodplain at type locality, and (apparently) elsewhere. At type locality, Wolvercote Channel Beds (temperature fauna, ?MIS 9) probably underlie the gravels (ie, older) but may be within them (contemporaneous) or incised into them (younger). (D) Dating depends only partly on Wolvercote Channel. More important is relationship with ?Moreton Drift? at the head of the Evenlode (see below). The presence of flint is critical to the interpretation - debate has arisen about whether or not it is the oldest terrace to contain ?significant? amounts of flint (Maddy et al., 1991). (E) Upper Boundary given as ?ground surface? but head, colluvium or soil may intervene. (F) Terrace is weakly developed and poorly defined, so recognition based on elevation is suspect in places; some mapping is dubious. Deposits mapped as ?Third terrace? are not necessarily Wolvercote. The feeble development of the terrace is rather surprising, particularly if it is primarily late Anglian outwash derived from the Moreton Drift. However, this all came down the Evenlode; whilst there is a fairly good flinty outwash terrace in the Upper Evenlode (Sheet 235, 218) where (as the correlation is contentiousness) the name Daylesford Member is used. The Lower Evenlode valley is narrow and incised where it cuts through the Great Oolite limestones (so-called Evenlode Gorge) and perhaps was cleaned out at a later stage. (G) The identity of Terrace 3 on Sheet 218 is questionable. Most of the Evenlode Terrace 3 seems to be Daylesford Member (which may or may not equate with Wolvercote). That in the Cherwell valley may be Wolvercote, but mapping is suspect.
0 to c,3m
Whitwick Volcanic Complex
WVO
All boundaries are probably intrusive or fault-controlled. Components include: Peldar Dacite Breccia, Sharpley Porphyritic Dacite, Grimley Andesite.
North-west Charnwood Forest between Whitwick Quarry, High Sharpley and Whitwick Village.
An assemblage with no obvious stratigraphy, consisting of massive porphyritic dacite, dacite breccia and andesite.
Weaver Valley Formation
WVRVA
Cheshire within the river valley and tributaries of the River Weaver.
Probably silt, sand and clay alluvial deposits grading to gravel at base. River Terraces are composed of gravel or gravelly sand.
Highly variable depending on the relative stratigraphical positions of each of the component units. In the major river valley the thickness may vary from between 2 and 5m, but probably does not exceed 10m.
Wiveliscombe Sandstones
WVS
West Walton Formation And Ampthill Clay Formation (Undifferentiated)
WWAC
West Wales Catchments Subgroup
WWACA
Unconformable and in places strongly incised into lithologically highly variable sediments of the Caledonia Glacigenic Group or bedrock.
Catchments of West and South Wales
River terraces and alluvial floodplain
Highly variable depending upon the relative stratigraphical positions of each of the component units. In the major river valleys the thickness may vary between 2 and 5m, but probably does not exceed 10m. For deposits flanking the major river valleys, the thickness probably varies between 1 and 3m.
Ground surface or overlain unconformably by artificial deposits.
West Walton Formation, Ampthill Clay Formation And Kimmeridge Clay Formation (Undifferentiated)
WWAK
Wern Watkin Formation
WWAT
Sharp, erosion surface cut in underlying Lower Devonian Brownstones or Upper Devonian Plateau Beds overlain locally in west by a fish-bearing basal conglomerate. [Lovell, 1978].
From west of Llangynidr, Powys, eastwards and southwards to Pontypool, Gwent, South Wales.
Pale greenish-grey and buff, fine-grained, parallel bedded sandstones with minor mudstone interbeds.
About 8m in the Llangynidr area to about 16m in the Pontypool area, Gwent, South Wales.
Top of a persistent rubbly or massive calcrete, overlain by conglomerates of the Craig-y-cwm Formation. [Lovell, 1978].
West Walton Formation
WWB
Late Jurassic; Early to Mid Oxfordian (Cordatum to Tenuiserratum zones).
Base of sediments as described under "Lithology" (generally the lowest dark grey, silty mudstone), resting, commonly with marked interburrowing, on pale grey, smooth-textured mudstones of the Oxford Clay Formation (Weymouth Member); commonly a marked colour change and break of slope at outcrop; change commonly well-marked on borehole geophysical (particularly gamma-ray) logs. Base of unit WW1 in type area (Cox and Gallois, 1979).
Oxford area (where it passes southwestward into the Corallian Group; Horton et al., 1995) to the Market Weighton area (Gaunt et al., 1980).
Calcareous mudstone, silty mudstone and siltstone, with subordinate fine-grained sandstones and argillaceous limestone (cementstone) or siltstone nodules; typically rhythmic alternations of dark grey, silty mudstone (rich in fine-grained shell and plant material) with pale grey mudstone; ooidal, and in some cases coralline marls and limestones developed locally (including Elsworth Rock Member; Upware Limestone Member), (Gallois and Cox, 1977; Cox and Gallois, 1979).
0 to c.20m; typically c.15m, 14.06m in type section.
Base of pale to mid grey, smooth-textured mudstones of the Ampthill Clay Formation; generally a marked colour change and break of slope at outcrop; change commonly well-marked on borehole geophysical (particularly gamma-ray) logs. Top of unit WW16 in the type area (Cox and Gallois, 1979).
Wheatworth Coal (West Yorkshire)
WWC
Warley Wise Grit
WWG
Sharp upward change in a conformable succession from predominantly grey mudstone to sandstone - base of first pebbly sandstone bed above the Pendle Grit Member.
Yorkshire and Lancashire Pennines south of the Craven Fault System and north of a line from Rochdale to Leeds.
A medium to thickly bedded, brownish grey, medium- to coarse-grained, sandstone and pebbly sandstone, which is massive to cross-bedded; beds of siltstone occur throughout and coals are locally developed.The unit is interpreted as a delta top sandstone.
40 to165m
Sharp upward change in a conformable succession from sandstone to predominantly mudstone - top of last coarse or pebbly sandstone below the synsedimentary slumped siltstones and sandstones of the Roeburndale Member and the Cravenoceras cowlingense Marine Band.
Winstow Mudstone Member
WWM
Original entry had "age" Courceyan, which is retained pro tem, although the 2005 application stated "Tournaisian".
The lower boundary is taken at the incoming of black, sooty and siliceous mudstones of the Winstow Mudstone Member above the purple, green and grey mudstones of the underlying Whiteway Mudstone Formation.
Between Chudleigh (SX 870 784) and Kingsteignton (SX 88 74), south Devon.
Black, siliceous and sooty mudstones.
The upper boundary is taken at the incoming of interbedded green-grey and black cherts and siliceous mudstones of the Winstow Chert Formation above the black, sooty and siliceous mudstones of the Winstow Mudstone Member.
Warley Wise Marine Band
WWMB
Whitwell Oolite
WWO
West Walton Formation And Oxford Clay Formation (Undifferentiated) [Obsolete Code: Use Oxww]
WWOX
Wells O'Wearie Sandstone
WWS
Whiteway Mudstone Formation
WWYM
The lower boundary is taken at the gradational incoming of red, purple and green mudstones with scattered limestone nodules of the Whiteway Mudstone Formation above the red and green nodular cephalopod limestones with subordinate mudstones of the underlying Luxton Nodular Limestone.
Between Chudleigh (SX 870 784), Bishopsteignton (SX 905 735) and East Ogwell (SX 845 695) areas, south Devon.
Consists predominantly of red and purple mudstone with subordinate green and grey-black, locally laminated mudstone. Calcareous nodules are common where the formation is condensed and near the base, but in thicker developments calcareous, siliceous and, rarely, sideritic nodules and laminae are sparsely present. The mudstones and calcareous nodules contain a rick planktonic fauna of ammonoids, ostracods and conodonts; benthic fauna include crinoid debris and brachiopods, amongst others. Thin units of basalitic (spilitic) lava are sparsely present in thicker developments.
The upper boundary is taken at the incoming of black sooty and siliceous mudstones of the Winstow Mudstone Member (basal Winstow Chert Formation) above the purple, green and grey mudstones of the underlying Whiteway Mudstone Formation. The contact is generally sharp.
Wyche Formation
Non sequence with underlying Cowleigh Park Formation.
Malvern Hills to Ankerdine Hill.
Grey, brown and pale green mudstones and siltstones with thin tabular green sandstones.
Conformably overlain by Woolhope Limestone.
Bych Beds
WYB
Wyrley Bottom Coal (South Staffordshire)
WYBC
Waverley Coal
WYC
River Terrace Deposits, 1 (Wye)
WYE1
Whitley Ironstone
WYI
Wheatley Limestone Member
WYLS
A sharp, upward non-sequential transition from sand and sandstone of the Beckley Sand Member of the Kingston Formation, to shell-fragmental limestone, generally with very little quartz sand, except in the reworked basal bed, which may otherwise be marked by a shelly conglomeratic bed with or without a shelly marl.
The Oxford area and from Wheatley to Cumnor as shown on 1:50 000 sheets 236 and 237. The southern and western extents are uncertain, but are likely to extend as far as Faringdon (sheet 253) ,and possibly towards Swindon and Calne too.
Shell-fragmental, biosparite grainstones interbedded with shell-fragmental marls, locally with rubbly coralliferous limestone with marls of the 'Coral Rag' facies.
Up to 26 m thick.
Sharp, upward non-sequential change to grey mudstones of the Ampthill Clay Formation.
Wych Mudstone Member
WYM
Top of highest greenish grey and reddish brown laminated unit of the Byley Mudstones.
Structureless reddish brown mudstones with anhydrite/gypsum nodules mostly in uppermost two thirds of Member.
186.44m in Wilkesley Borehole (611' 8").
Base of Wilkesley Halite. Some thin halite bands in Palmer Mann No.12 Borehole have been included in the Wych Mudstones.
Withy Mills Coal (Somerset)
WYMC
Wyddgrug Porphyritic Microgranite
WYPM
Porphyritic micrgranite with isolated phenocrysts and glomeroporphyritic clusters of oligoclase and perthitic alkali feldspar in a fine-grained quartz-feldspar groundmass.
Wickersley Rock
WYR
River Terrace Deposits, 1 (Wyre)
WYR1
River Terrace Deposits, 2 (Wyre)
WYR2
Wyre River Terrace Deposits, 1 Member
WYRE1
North Lancashire.
Gravel or sandy gravel.
Wyre River Terrace Deposits, 2 Member
WYRE2
Wyre Valley Formation
WYRV
Cumbria and Lancashire.
Probably dominantly silt, sand and clay with gravel and peat.
Highly variable depending on the relative stratigraphical position of the component units. In the major river valleys the thickness might vary between 2 and 5m, but probably does not exceed 10m.
Wyrley Yard Coal (South Staffordshire)
WYYC
West Melbury Marly Chalk Formation And Zig Zag Chalk Formation (Undifferentiated)
WZCK
Yr Allt Formation
Sharp incoming of mudstones with siltstone laminae and no burrows, above burrow mottled mudstones of the Nantmel Formation. Locally rests sharply on top of Doldowlod Conglomerate Member of Nantmel Formation.
Very silty mudstones with abundant siltstone laminae and scattered thin beds of sandstone. Units of thick-bedded sandstone locally present. Slump folding and destratification commonly present.
Up to 1200 metres.
Either gradational and taken at incoming of sandstone dominant sequence of Scrach Formation, or sharp, where overlain by mudstones lacking silt laminae of the Cwmere Formation or Tycwtta Mudstones.
Yard Coal (Dungannon)
YAC
Yard Coal (Cheadle)
YACO
Yateley Gravel
YAGR
Yate Hard Coal (Bristol Area)
YAHC
Yard Coal (Hanwood)
YAHW
Yate Little Coal (Bristol Area)
YALC
Yard Coal (South Wales; Langsettian)
YARC
Yard Coal (South Wales; Duckmantian)
YARCO
Yard Coal (Northumberland)
YARD
Yard Rock (Nottinghamshire Area)
YARR
Yawl Sandstone Member
YASA
Yr Arddu Tuffs Formation
YATU
Lies on sedimentary rocks of the Cwm Eigiau Formation.
Limited to an area around Yr Arddu, 6km east of Moel Hebog.
Welded acidic ash-flow tuffs with pyroclastic breccias.
Underlies part of the Cwm Eigiau Formation.
Yat Wood Formation
YAWO
Unknown, contacts generally faulted.
Welsh borderlands. Old Radnor.
Pale green laminated or massive siltstones, thinly laminated mudstones and fine-grained, generally massive, sandstones.
Unknown - generally faulted contacts.
Unknown in detail; unconformably overlain by the Dolyhir Limestone of Wenlock age.
Yewbank Formation
YBK
Conformably overlies the Moorhowe Formation of the Coniston Group.
Yard Coal (South Derbyshire)
Yare Catchments Subgroup
YCAT
Formations of the Yare Valley Subgroup rest unconformably on glacial and periglacial deposits and upon Crag Group, London Clay Formation and Chalk Group bedrock.
The entire catchment of the River Yare and its tributaries, and the whole of Norfolk to the north of that catchment.
The Yare Catchments Subgroup encompasses all the fluvial, lacustrine and organic deposits of the rivers which occupy the catchment area of the River Yare and its tributaries, and also the other minor rivers that flow into the North Sea along the coast of Norfolk. Floodplain alluvium comprises soft silts and clays, commonly with beds of peat and a basal bed of sand and gravel. River terrace deposits are largely sand and gravel. The gravels are dominantly composed of subrounded to angular flint, including large cobbles, also rounded pebbles of quartz and quartzite, northern British erratics of glacial derivation, and a little chalk. Peat is a minor component, and minor marine deposits are included where they are intercalated in dominantly fluvial formations.
Surface, or overlain by deposits of the Breydon Formation.
Yard Coal (Coalbrookdale)
YCCC
Yard Coal (Leicestershire)
YCL
Younger Coombe Deposits
YCOD
Variable lithology. Scree and solifluction deposits in some chalk valleys ('Coombe Rock' where cemented); younger than 'Coombe Deposits' in the same map area. [Generic description: 'TMOS' Procedures].
Yard Coal (Milford, South Wales)
YCOM
Yard Coal (South Lancashire)
YCSL
Yard Coal [Yd] (North Staffordshire)
YCYD
Yellow Downtonian
Yard Coal (South Yorkshire And Nottingham And Derby)
YDC
The Yard Coal (South Yorkshire) is not the same as the Yard Coal (Notts).
Yard Coal (South Staffordshire)
YDCO
Yard Coal (Goyt Trough)
YDGT
Yard Limestone
YDLS
Yard Rock (South Staffordshire)
YDR
Yedmandale Member
YED
Yellowford Formation
YEL
Rests on Thorverton Sandstone, probably unconformably, around Dunsmore (SS 957 015). Basalt at the top of the Thorverton Sandstone is directly overlain by basal Yellowford Formation clay. East of Poundsland (SS 961 013) change from Thorverton Sandstone to Yellowford Formation less clear, due to greater proportion of sand in the Yellowford Formation.
Crops out from near Berrysbridge (SS 917 010), about 1km south of Thorverton, eastwards through Yellowford, across the Exe Valley to near Ellerhayes (SS 980 020).
Reddish brown silty and sandy mudstone; clayey sandy siltstone; and silty clayey fine-grained sandstone. Laterally equivalent to the Crediton Breccia.
To 150m. Lower 75m penetrated in Yellowford Farm Borehole (SS9255 0089).
Overlain by Shute Sandstone; gradational boundary.
Yellow Craig Plug
YELCG
Yellow Man Dykes
YELMA
Yesnaby Sandstone Group
YES
Yate Evaporite Bed
YEV
Yeolmbridge Formation
The lower boundary is taken at the gradational incoming of silt laminated dark green-grey and black mudstones of the Yeolmbridge Formation above the dark green-grey and black mudstones with siliceous thin beds and nodules of the underlying Stourscombe Formation. This contact is not well documented and needs further work.
Launceston area (SX 33 84). Mapped as ?part of the Transition Group on the Holsworthy sheet (323). Might extend westwards to the north Cornwall coast where it has been mapped as Transition Group and eastwards to west Dartmoor, but further work is needed.
Dark green-grey, black and green mudstones with variably abundant siltstone laminae and scattered thin- to medium-bedded sandstones, limestone nodules and units of nodular cephalopod limestone. Lavas and thin tuff beds are sporadically present.
Not known due to structure, but unlikely to exceed 100m.
The upper boundary is not seen; everywhere tectonic.
Yard Floor Coal (Nottingham)
YFC
Yellow Farlow Sandstone Formation
YFS
Yorkshire Catchments Subgroup
YKC
Unconformable contact with older superficial deposits including units of the North Pennine, North Sea Coast and Central Cumbria Glacigenic subgroups, and bedrock.
Yorkshire, east of the Pennine watershed, including the valleys of the rivers Swale, Nidd, Aire, Ouse, Derwent and Wharfe and all their tributaries that flow from the north and west into the Humber.
The Yorkshire Catchments Subgroups include clay, silt, sand, gravel, boulders and peat deposited mainly by alluvial, aeolian and slope movement processes.
Alluvial and terrace deposits may reach up to a maximum of around 25m. The individual formations and members in the subgroup are highly variable in thickness.
Yoke House Formation
YKH
The clastic apron deposits lie on Carneddol Rhyolitic Tuff Formation, passing onto Foel Ddu Rhyodacite Tuff Formation. Locally overlies the Penmaen Formation.
Pwllheli area, north-west Wales.
Rhyolitic crystal-lithic tuffs, tuffaceous sandstones and breccio-conglomerates.
The clastic apron deposits pass upwards into dark grey graptolitic mudstones of the Nod Glas Formation, and part of the Carneddol Rhyolitic Tuff Formation.
Yorkley Coal (Forest Of Dean)
YKLY
Yellow Craig Plantation Plug
YLCPP
Yellow Craig Plantation Vent
YLCPV
Yarmouth Roads Formation
Unconformably overlies early Pleistocene Westkapelle Ground, Smith's knoll, Ijmuiden Ground or Winterton Shoal Formations.
Fine or medium-grained grey-green sands, typically non-calcareous, with variable clay lamination and local intercalations of reworked peat. Characteristic chaotic reflector configuration in seismic profiles, presumed mainly fluviatile, with possible shallow marine incursions.
0 - 100 metres.
Unconformably overlain by Middle and Upper Pleistocene formations, and subcrops below Holocene sands in parts of British Sector.
Yealm Formation
YMF
Ystrad Meurig Grits Formation
YMG
Ystrad Meurig Grits Facies [First Sequence]
YMG1
Ystrad Meurig Grits Facies [Second Sequence]
YMG2
Ystrad Meurig Grits Facies [Third Sequence]
YMG3
Chwarel Goch Facies [In Ystrad Meurig Grits Formation]
YMGCG
Henblas Facies [In Ystrad Meurig Grits Formation]
YMGH
Ynysarwed Coal (South Wales)
YNYSA
Ynyslas Formation
YNYSS
Commonly unconformable on Flandrian or Late Devensian superficial deposits. In the type area it overlies Flandrian storm beach gravels in the west and peat in the east; locally, it overlies bedrock (Godwin, 1943).
Cardigan Bay; principally at Morfa Bychan, Morfa Harlech, Morfa Dyffryn, Poppit Sands, Whitesands Bay and Freshwater West.
Stratified, unconsolidated, fine- to medium-grained, quartz sand with shell debris.
Exceptionally to 10.5m in the type area, but generally less and in accordance with the topographic expression of dune forms (Cave and Hains, 1986).
Generally the ground surface, but locally, contact with overlying Flandrian deposits. In the type area the formation is locally overlain by Tidal Flat Deposits (British Coastal Deposits Group).
Yoredale Coal (Barnard Castle Area)
YOC
Yoredale Formation [Offshore Areas]
YOF
Younger Head
YOHD
Red or brown silt and stony clay with cobbles of hard rock, eg. Carboniferous limestone or sandstone. Sand and gravel, locally with lenses of silt, clay or peat and organic material. Poorly sorted and poorly stratified deposits formed mostly by solifluction and/or hillwash and soil creep. Polymict deposit: comprises gravel, sand and clay depending on upslope source and distance from source. Younger than "Head" in the same map area. [Generic description].
Yoredale Group
YORE
York Moraine Member
YORKM
Unconformable on bedrock, or pre-existing superficial deposits such as fluvial and glacial deposits.
Yorkshire in the vicinity of York. The moraine ridge exists from just east of Bicketon [445197, 450188] in the west through York to Sand Hutton [471257, 459893].
Glacial till comprising sandy clay, clayey sand and clay with erratic pebbles, cobbles and boulders mainly of Carboniferous sandstone and limestone. The Member also includes local deposits of sand and gravel plus local deposits of clay and laminated clay incorporated into the sequence.
The present land surface, which forms an elongated moraine ridge, or unconformable contact with overlying deposits to north and south including the Alne Glaciolacustrine Formation and the Elvington Glaciolacustrine Formation respectively.
Yottenfews Tuff Formation
YOT
Taken at the base of the spherulitic, rhyolitic welded tuff that constitutes the Sella Park Member. This is a major change from dominantly volcaniclastic sandstones of the underlying Newton Manor Formation to the ignimbrite sequence of the Yottenfews Tuff Formation.
Sellafield borehole No.7A only.
Welded tuffs and lapilli-tuffs with intercalations of volcaniclastic sandstone; interpreted as two sheets of rhyolitic ignimbrite and one of dacitic ignimbrite.
194m+ (uncorrected for structural dip or borehole deviation from the vertical). Thickness includes a 49.3m-thick sill.
Not seen in its original form as the formation is unconformably overlain by Carboniferous strata.
Yell Pegmatite Swarm
YPS
Yorke Rock
Yard Coal (North Wales)
YRC
Yard Coal (Warwickshire)
YRCL
Yard Coal (Cumbria)
YRD
Yard Coal [Y] (Stoke)
YRDC
Younger River Gravels
YRG
Sand and gravel; younger than 'River Gravels' in the same map area. [Generic description].
Yarlside Volcanic Formation
YRL
Taken at the base of volcanic rocks (generally the felsite, but locally tuff and lapilli-tuff) overlying calcareous siltstone of the Stile End Formation. In part overlies andesite of the Borrowdale Volcanic Group.
In the northeastern Lake District, from near Stile End (NY 471 047) to Shap Wells (NY 577 096).
Pink to pale grey, flow banded rhyolitic vitrophyre (felsite), locally with beds of massive tuff and lapilli-tuff, particularly at the base.
Up to 325m
Defined by the base of the overlying Kirkley Bank Formation.
Burway Formation [Obsolete Code: Use Bugp]
YSB
Buxton Rock [Obsolete Code: Use Bur]
YSBB
Cardingmill Grit [Obsolete Code: Use Cddg]
YSBC
Ysguborwen Formation
YSG
Stretton Shale Formation [Obsolete Code: Use Snsh]
YSH
Helmeth Grit [Obsolete Code: Use Hlg]
YSHH
Lightspout Formation [Obsolete Code: Use Ltgp]
YSL
Portway Formation [Obsolete Code: Use Pwg]
YSP
Huckster Conglomerate [Obsolete Code: Use Hcg]
YSPH
Yell Sound Psammite Formation
YSPS
Synalds Formation [Obsolete Code: Use Sygp]
YSS
Batch Volcanics [Obsolete Code: Use Bv]
YSSB
Stretton Group
YST
Uncertain. Taken by some at base of Helmeth Grit Member (Cobbold 1935; Greig et al, 1968), but the latter was included by Pauley (1990) within the Ragleth Tuff Formation. The relationship of the latter to the Uriconian Volcanics is uncertain as all contacts are faulted.
Welsh Borderlands, Shropshire, Powys.
Interbedded purple and green mudstones, siltstones, sandstones and subordinate conglomerates, with several tuff units. The suffix 'Eastern Longmynd' is superfluous and it is also preferable not to ascribe a geographical extent to this division, given the uncertainties over its relationship to the much more extensive Wentnor Group that overlies it (i.e. whether their boundary is unconformable or not). It is possible that the term Stretton Group will become obsolete in the future, as there is already a formation of this name (the Stretton Shale Fmn). However, the term 'Stretton Group' is currently used and understood widely (eg. Pauley 1990), and it is suggested that this is retained as an informal name.
2700-4000 m thick.
Traditionally taken at the top of the Portway Formation by those who considered there to be an unconformity with the overlying Wentnor Group at this level (e.g. Greig et al, 1968). However, Pauley (1990) considered that no such unconformity exists, and the succession was one of prograding alluvial facies.
Ystog Formation
YSTOG
Unconformable on bedrock and Plynlimon Formation. Laterally it might interdigitate with Head deposits.
Upper Camlad Valley and Caebitra Valley, upper Mule Valley and lower Camlad Valley, Powys/Shropshire.
Grey, laminated and massive, silty clay and silt. Gravelly shoreline deposits and sandy deltaic deposits are present locally (Cave and Hains, 2001). Likely to contain dropstones and interbedded thin diamicts at depth.
Likely to be in excess of 10m. A railway cutting at [SO 1696 9105] exposes 7m of sand and fine gravel.
Generally the ground surface or unconformable contact with Flandrian alluvial deposits of the Severn and Avon Catchments Subgroup.
Ystradwalter Member
YSTW
Linley Formation
YSY
Not known. Occurs as fault slivers adjacent to Pontesford-Linley Fault.
Between Linley Big Wood and Knolls Farm, Norbury, Shropshire.
Greenish grey shales, siltstones and very fine- to fine-grained sandstones. Local interbedded lapilli tuffs. Sandstones as thick homogeneous beds with sporadic normal grading, also as isolated beds 10cm to 2m thick displaying upward-fining trends.
Yartleton Formation
Younger Till
YTIL
Group of sediments laid down by the direct action of glacial ice. Variable lithology, usually sandy, silty clay (possibly chalky in southeast England) with pebbles, but can contain gravel-rich or laminated sand layers; varied colour and consistency; younger than "Till" in the same map area. [Generic description].
Yat Wood Formation [Obsolete Code: Use Yawo]
YTW
Unknown -the contact is generally faulted.
Pale green, laminated or massive siltstones, thinly laminated mudstones, and fine-grained, generally massive sandstones.
Unknown in general, although it is overlain unconformably by the Dolyhir Limestone of Wenlock age.
Yare Valley Formation
Unconformable upon glacial and solifluction deposits and upon Crag Group, London Clay Formation and Chalk Group bedrock.
The valley of the River Yare and its minor tributaries, from near Shipdham to its mouth at Great Yarmouth, Norfolk, and also the offshore extensions of the buried valley of the River Yare, but not including the valleys of the rivers Bure and Waveney and their tributaries.
The formation encompasses the fluvial , lacustrine and organic deposits of the River Yare. It includes floodplain alluvium and a restricted development of river terrace deposits. The floodplain alluvium comprises soft clays, silts and fine-grained sands, with bodies of peat, overlying fine- to coarse-grained sands and gravels. These gravels are mostly composed of rounded flint pebbles and cobbles, with a little chalk, rarely shelly but commonly silty. The gravels commonly occur in buried channels overlain by the Breydon Formation. River terrace deposits are largely gravel and sand. The gravel is dominated by subangular to rounded flint, including large cobbles, with some pebbles of quartz and quartzite. Gravelly sediments belonging to this formation have been recorded in boreholes offshore.
Wentnor Group
Taken at the change from purple and green shaly mudstones and sandstones of the Portway Formation of the Stretton Group, into the more massive coarse purplish sandstones of the Bayston Formation of the Wentnor Group. It has been argued that the boundary is an unconformity by Greig et al. (1968), although there is no obvious angular discordance at this level. However, Pauley (1990) considered that no such unconformity exists, and the succession was one of prograding alluvial facies.
Welsh Borderlands, Shropshire, Longmynd.
Massive, purple and green, coarse-grained volcaniclastic sandstones with subordinate mudstones and siltstones, and beds of conglomerate. The suffix 'Western Longmynd' is superfluous and it is also preferable not to ascribe a geographical extent to this division, given the uncertainties over its relationship to the Stretton Group that underlies it; i.e. whether the boundary is unconmformable or not . It is possible that the term will become obsolete in the future, depending on the degree of acceptance of the stratigraphy proposed by Pauley (1990). However the term 'Wentnor Group' is currently used and understood widely, and it is suggested that it is retained as an informal name.
1800 m - 3600 m thick.
Bridges Formation [Obsolete Code: Use Brgp]
YWB
Haughmond Conglomerate Member
YWCH
Taken at base of lowermost bed of conglomerate within the Bayston-Oakswood Formation, immediately overlying the purple and grey mudstones of the Portway Formation. Believed to be an unconformable contact by certain authors.
Welsh Borderlands, specifically the Shrewsbury Sheet. Appears to pass laterally into the coarse sandstones of the Bayston-Oakswood Formation.
Purple and green micaceous pebbly sandstone and conglomerate containing abundant volcanic and metamorphic pebbles.
100 m thick.
Taken at the transition into coarse feldspathic sandstones and interbedded thin mudstones of the Bayston-Oakswood Formation.
Yellow Man Vent
YWMAN
Bayston-Oakwood Formation [Obsolete Code: Use Bagp]
YWO
Oakswood Conglomerate Member
YWOC
Taken at the transition from coarse sandstones into conglomerate within the Bayston-Oakswood Formation; about 270 m of these sandstones separate the conglomerate from the underlying Radlith Conglomerate.
Welsh Borders, specifically Sheet 152 (Shrewsbury). Disappears beneath younger strata southwest of type area, yet may pass laterally into sandstones of the Bayston-Oakswood Formation to the northeast.
A coarse volcaniclastic conglomerate, containing pebbles of purple rhyolite, felsite and quartzite.
60 m thick.
Taken at the transition from conglomerate into coarse sandstones of the Bayston-Oakswood Formation.
Darnford Conglomerate Member
YWOD
Taken at the transition from coarse sandstone into conglomerate within the Bayston Oakswood Formation. Represents the second conglomerate unit above the base of the Bayston Oakswood Formation, its base occuring about 250 m above the base of the formation.
Welsh Borderlands, Sheets 152 (Shrewsbury) and 166 (Church Stretton). Appears to pass laterally into the coarse sandstones of the Bayston-Oakswood Formation.
Purple and green pebbly sandstones and conglomerates, with clasts of quartzite and felsic igneous rock.
90 m thick.
Taken at the transition into coarse feldspathic sandstones and interbeded thin mudstones of the Bayston-Oakswood Formation.
Lawn Hill Conglomerate Member
YWOL
Taken at the transition from coarse sandstones into conglomerate within the Bayston-Oakswood Formation; about 550m of these sandstones separate the conglomerate from the underlying Oakswood Conglomerate Member.
Welsh Borderlandsm, specifically Sheet 152 (Shrewsbury), 165 (Montgomery) and 166 (Church Stretton). Disappears laterally due to faulting or is concealed by superficial deposits.
Coarse, pebbly sandstone and conglomerate with pebbles of quartzite, rhyolite and felsite.
From 75 m to 150 m thick.
Taken at the transition into coarse sandstones of the Bayston-Oakswood Formation.
Radlith Conglomerate Member
YWOR
Stanbatch Conglomerate Member
YWOS
Taken at the transition from coarse sandstones into conglomerate within the Bayston-Oakswood Formation. Represents the third conglomerate unit above the base of the Bayston-Oakswood Formation, its base occuring about 670 m above the base of the formation.
Welsh Borderlands, specifically 1:50 000 Sheets 152 (Shrewsbury) and 166 (Church Stretton).
Two beds of coarse, massive conglomerate, composed predominantly of quartzite pebbles, and an intervening bed of coarse-grained, often deeply weathered, purple sandstone.
75 m thick.
Yellow Sands Formation
YWS
Unconformity; erosion surface cut in Carboniferous, usually Coal Measures, strata.
In the Durham province; Durham, Tyne and Wear, Cleveland and northernmost North Yorkshire, South and West Yorkshire, it covers about two-thirds of the sub-Permian unconformity, [Smith, 1994].
Generally uncemented or weakly cemented, mainly medium- and fine-grained, cross-stratified, yellow aeolian sand or sandstone.
To 68.7m [Smith,1994].
Unconformity; transgression of marine, Late Permian, Zechstein Group strata; usually the Marl Slate Formation but locally where this is absent, over palaeotopographic highs or as a result of syndepositional slumping, the younger Raisby and Ford formations.
Lizard Complex
Eddystone Gneiss
ZEG
Zeeland Formation
ZELD
Zechstein Group
Unconformable base with the Kupferschiefer or Marl Slate (or younger strata) resting on the Rotliegend Group or Carboniferous strata.
Zechstein basin, Northern England, North Sea, Holland, Germany.
Cyclical succession of marine dolomite, limestone, evaporites, red mudstone and siltstone.
The term Zechstein comes from the German for "mine" and "stone", referring to the considerable number of mines in the German Permian sequence working salt, potash, gypsum, and anhydrite with the copper-bearing Kupferschiefer (copper-shale) at its base.
Gradational boundary taken at the base of the Sherwood Sandstone Group onshore and the base of the Bacton and Heron groups offshore.
Lizard Hornblende Schists
ZHS
Kennack Granite And Gneiss
ZKG
Landewednack Hornblende-Schist
ZLHS
Man Of War Gneiss (And Granite)
ZMG
Lizard Mica Schists
ZMS
Zechsteinkalk Formation
ZSTK
Zones Of Silicification And/Or Vein-Quartz Of Unknown Age And Affinity
ZSVQU
Traboe Hornblende-Schist (Lizard Complex)
ZTHS
Treleague Metaquartzite
ZTQ
Serpentine (Lizard Complex)
Zig Zag Chalk Formation
ZZCH
Upper Cretaceous, Cenomanian. Acanthoceras rhotomagense to Calycoceras guerangeri Zones.
Conformable in full sequences. The lower boundary is placed at the erosional contact at the base of the "Cast Bed" (Southern Province) or the Totternhoe Stone (Transitional Province) in southern England. The former is the direct equivalent of Bed C1 of Gale (1995). The formation oversteps onto older formations over the Mid-Dorset Swell where the preceding West Melbury Marly Chalk Formation is absent. The basal unit here is termed the Cenomanian Basement Bed (Drummond, 1970)
Throughout the Southern Province and the Transitional Province of England.
Mostly firm, pale grey to off-white blocky chalk with a lower part characterised by rhythmic alternations of marls and marly chalks with firm white chalk. Thin gritty, silty chalk beds act as markers in the sequence.
Generally in the range 35 to 50m in the Southern Province with the most expanded sequences (up to 75m exceptionally) in the area of West Sussex, East Hampshire and the Isle of Wight. Thins markedly to the west and is at its least over the Mid-Dorset Swell where as little as 10m may be preserved.
Conformable. The upper surface is redefined as the bedding plane beneath the lowest of the marls in the Plenus Marls Member in the overlying Holywell Nodular Chalk Formation. (Note that the Plenus Marls Member is now considered as part of the overlying formation, thus providing a consistent datum throughout the Chalk Group of England and the North Sea).
Not Available
Not Entered
Not Applicable
Ferruginous Limestone Series
5 Foot Vein
Bellingham Coal
Ben Lawers Schist
Bensham Coal
Beresford Seam
Big Coal [In Part]
Big Coal [South Wales Coalfield]
Big Mine Coal
Bin Mine Coal
Black And White Mine Coal
Black Cliff Vein
? Lateral Equivalent Of Glenfinnan Group
Black Coal [South Wales Coalfield]
Black Metals Marine Band
Black Mine Coal
Blackclose Coal
Blackhall Colliery Formation
Blackhall Member