List of geological groups of Great Britain

This is a sortable list of the groups into which the rock succession of Great Britain and surrounding seas is formally divided. Rock sequences are described by geologists by dividing them hierarchically thus: individual 'beds' of rock (or in the case of certain volcanic rocks, 'flows') are grouped into 'members', members are grouped into 'formations', formations into 'groups' and groups occasionally into 'supergroups'. Some groups are also subdivided into 'subgroups'. Not all of these hierarchical layers are necessarily present or defined within a particular rock succession. Many of these groups will be encountered as 'series' in older geological literature or indeed simply as the proper name e.g. 'Dalradian' or 'Millstone Grit' though care needs to be exercised as many of the names have or have had other meanings which may not coincide with the assemblage of rocks referred to formally through designation as a 'group'.

Note that with all such stratigraphical terms as 'groups', 'formations' and 'members' it is standard practice to capitalise both the proper name and the 'term-word' as per the recommendation of the International Commission on Stratigraphy e.g. Wentnor Group and not Wentnor group.[1]

Notes:

Column 1 indicates the name of the geological group. Those marked with an asterisk are no longer formally recognised but are included as they occur widely in literature.
Column 2 indicates during which geological period the rocks of each group were deposited. Note that where more than one period is indicated deposition stretched across the period boundary in at least a part of the group's geographical extent but not necessarily across the whole of its extent.
Column 3 permits sorting by period in chronological order ie Quaternary Period is 01; Neogene,03; Palaeogene,05; Cretaceous,07; Jurassic,09 Triassic,11; Permian,13; Carboniferous,15; Devonian,17; Silurian,19; Ordovician,21; Cambrian,23; Ediacaran,25; Cryogenian,27; Tonian,29; Stenian, 31; and Ectasian, 33 - the last five being some of the periods into which the Proterozoic Eon is divided.
Column 4 indicates in which of the three nations of Great Britain, the group is known to occur, followed by which of the surrounding sea areas (if any), including specifically: Atlantic Ocean, Celtic Sea, English Channel, Irish Sea, North Sea. (At present, for the purposes of this table 'Celtic Sea' also includes the Bristol Channel whilst 'Atlantic Ocean' includes all sea areas off the west coast of Scotland.) Note that the Isle of Man is not a part of Great Britain but is included here for convenience.
Group Period Period sequence Country/sea area
Aberystwyth Grits Group Silurian 19 Wales
Albion Glacigenic Group Quaternary 01 England, Scotland, Celtic Sea
Ancholme Group Jurassic 09 England
Appin Group Cryogenian 27 Scotland
Appleby Group Permian 13 England, Scotland
Aran Volcanic Group Ordovician 21 Wales
Arbuthnott Group* Devonian 17 Scotland
Arbuthnott-Garvock Group Devonian 17 Scotland
Ardmillan Group Ordovician 21 Scotland
Ardvreck Group Cambrian 23 Scotland
Arfon Group Ediacaran 25 Wales
Argyll Group Ediacaran 25 Scotland
Avon Group Carboniferous 15 England, Wales
Aylesbeare Group* Triassic 11 England
Aylesbeare Mudstone Group Triassic 11 England
Bacton Group Triassic 11 North Sea
Balcreuchan Group Cambrian/Ordovician 22 Scotland
Banks Group Jurassic 09 North Sea
Barr Group Ordovician 21 Scotland
Barton Group Palaeogene 05 England
Bathgate Group Carboniferous 15 Scotland
Benton Volcanic Group Cryogenian 27 Wales
Bisat Group Carboniferous 15 Irish Sea
Blackbrook Group Ediacaran 25 England
Border Group Carboniferous 15 England, Scotland
Borrowdale Volcanic Group Ordovician 21 England
Bowland High Group Carboniferous 15 England
Bracklesham Group Palaeogene 05 England
Brand Group Cambrian 23 England
Brent Group Jurassic 09 North Sea
Britannia Catchments Group Palaeogene/Neogene/Quaternary 04 England, Scotland, Wales, Irish Sea
British Coastal Deposits Group Quaternary 01 England, Scotland, Wales, Irish Sea
Builth Volcanic Group Ordovician 21 Wales
Caerbwdy Group Ediacaran 25 Wales
Caerfai Group Cambrian 23 Wales
Caithness Flagstone Group Devonian 17 Scotland
Caledonia Glacigenic Group Quaternary 01 England, Scotland, Wales, Irish Sea
Cementstone Group* Silurian 19 Scotland
Chalk Group Cretaceous 07 England, Atlantic Ocean, North Sea
Clackmannan Group Carboniferous 15 Scotland
Claerwen Group Silurian 19 Wales
Clair Group Devonian/Carboniferous 16 Atlantic
Clwyd Limestone Group Carboniferous 15 Wales
Coniston Group Silurian 19 England
Conybeare Group Carboniferous 15 North Sea
Corallian Group Jurassic 09 England
Cosheston Group Devonian 17 Wales
Crag Group Neogene/Quaternary 02 England
Craven Group Carboniferous 15 England, Isle of Man
Crawford Group Ordovician 21 Scotland
Cromer Knoll Group Cretaceous 07 England, Scotland, Atlantic Ocean, North Sea
Cumbrian Coast Group Permian 13 England, Scotland, Irish Sea
Cwmystwyth Grits Group Silurian 19 Wales
Dalby Group Silurian 19 Isle of Man
Dartmouth Group Devonian 17 England
Dent Group Ordovician 21 England
Drefach Group Ordovician 21 Wales
Dungavel Group Silurian 19 Scotland
Dunlin Group Jurassic 09 North Sea
Dunnottar-Crawton Group Silurian/Devonian 18 Scotland
Dunrobin Bay Group Jurassic 09 North Sea
Dunwich Group Quaternary 01 England
Durness Group Cambrian/Ordovician 22 Scotland
Eday Group Devonian 17 Scotland
Eriboll Group[2] Cambrian 23 Scotland
Exeter Group Permian 13 England
Exmoor Group Devonian/Carboniferous 16 England
Eycott Group* Ordovician 21 England
Eycott Volcanic Group Ordovician 21 England
Faroe Group Palaeogene 05 Atlantic Ocean
Farne Group Carboniferous 15 North Sea
Fishguard Volcanic Group Ordovician 21 Wales
Fladen Group Jurassic 09 North Sea
Forres Sandstone Group Devonian 17 Scotland
Gala Group Silurian 19 Scotland
Garvock Group* Devonian 17 Scotland
Garwood Group Carboniferous 15 Irish Sea
Girvan Group Silurian 19 Scotland
Glenbuck Group Silurian 19 Scotland
Glenfinnan Group Tonian 29 Scotland
Grampian Group Cryogenian 27 Scotland
Gray Sandstone Group Silurian 19 Wales
Great Estuarine Group Jurassic 09 Scotland
Great Oolite Group Jurassic 09 England, English Channel
Great Scar Limestone Group Carboniferous 15 England, Isle of Man
Gwna Group Ediacaran/Cambrian 24 Wales
Hagshaw Group Silurian 19 Scotland
Haisborough Group Triassic 11 North Sea
Harlech Grits Group Cambrian 23 Wales
Hawick Group Silurian 19 Scotland
Heron Group Triassic 11 North Sea
Holsworthy Group Carboniferous 15 England
Humber Group Jurassic/Cretaceous 08 Scotland, Atlantic Ocean, North Sea
Inferior Oolite Group Jurassic 09 England, Irish Sea, English Channel
Ingleton Group Ordovician 21 England
Inner Hebrides Group Cretaceous 07 Scotland
Inverclyde Group Carboniferous 15 Scotland
Inverness Sandstone Group Devonian 17 Scotland
Kendal Group Silurian 19 England
Kidston Group Carboniferous 15 Irish Sea, Celtic Sea
Kyle Group Devonian 17 North Sea
Lambeth Group Palaeogene 05 England
Lanark Group Silurian/Devonian 18 Scotland
Lias Group Triassic/Jurassic 10 England, Wales, Celtic Sea, English Channel, Irish Sea, North Sea
Llanbedrog Volcanic Group Ordovician 21 Wales
Llewelyn Volcanic Group Ordovician 21 Wales
Loch Maree Group Palaeoproterozoic 33 Scotland
Locheil Group Tonian 29 Scotland
Lower Greensand Group Cretaceous 07 England, English Channel
Lower Old Red Group Devonian 17 North Sea
Lower Old Red Sandstone Group Silurian/Devonian 18 England, Scotland, Wales
Manx Group Cambrian 23 Isle of Man
Maplewell Group Ediacaran 25 England
Marros Group Carboniferous 15 England, Wales
Mawddach Group Cambrian 23 Wales
Meadfoot Group Devonian 17 England
Menevian Group Cambrian 23 Wales
Mercia Mudstone Group Triassic 11 England, Scotland
Middle Old Red Group Devonian 17 North Sea
Milford Haven Group Silurian/Devonian 18 Wales
Millstone Grit Group Carboniferous 15 England, Isle of Man
Moffat Shale Group Ordovician/Silurian 20 Scotland
Monks Water Group Silurian 19 Scotland
Montrose Group Palaeogene 05 North Sea
Morar Group Stenian/Tonian 30 Scotland
Moray Group Palaeogene 05 Atlantic Ocean, North Sea
Mull Lava Group Palaeogene 05 Scotland
Nordland Group Neogene/Quaternary 02 Atlantic Ocean, North Sea
North Esk Group Silurian 19 Scotland
Ogofgolchfa Group Ediacaran 25 Wales
Papa Group Triassic 11 Atlantic Ocean
Peak Limestone Group Carboniferous 15 England
Peel Sandstone Group Devonian 17 Isle of Man
Pembroke Limestone Group Carboniferous 15 England, Wales
Penarth Group Triassic/Jurassic 10 England, Wales, Scotland, Irish Sea, English Channel, North Sea
Pennine Coal Measures Group Carboniferous 15 England, Isle of Man, Scotland, Wales
Penrhiw Group Cryogenian/Ediacaran 26 Wales
Portland Group Jurassic 09 England, English Channel
Priesthill Group Silurian 19 Scotland
Purbeck Group Jurassic/Cretaceous 08 England, English Channel
Ramsey Sound Group Ediacaran 25 Wales
Ravenscar Group Jurassic 09 England
Ravenstonedale Group Carboniferous 15 England, Isle of Man
Red Marl Group Silurian/Devonian 18 England, Wales
Residual Deposits Group Palaeogene/Neogene/Quaternary 03 England
Reston Group Silurian/Devonian 18 England, Scotland
Rhosson Group Ediacaran 25 Wales
Redbourne Group* Jurassic 09 England, Irish Sea, English Channel
Rhynie Group Devonian 17 Scotland
Riccarton Group Silurian 19 Scotland
Roch Rhyolitic Group* Ordovician 21 Wales
Rotliegendes Group Permian 13 England, North Sea
Sarclet Group Devonian 17 Scotland
Scottish Coal Measures Group Carboniferous 15 Scotland
Selborne Group Cretaceous 07 England, English Channel
Sherwood Sandstone Group Permian/Triassic 12 England, Scotland
Shetland Group Cretaceous/Palaeogene 06 Atlantic Ocean, North Sea
Skerry Group Jurassic 09 Atlantic Ocean
Skiddaw Group Ordovician 21 England
Skiddaw Slates Group* Ordovician 21 England
Skrinkle Sandstones Group Devonian 17 Wales
Skye Lava Group Palaeogene 05 Scotland
Sleat Group Stenian 31 Scotland
Snowdon Volcanic Group Ordovician 21 Wales
Solent Group Palaeogene 05 England
Solva Group Cambrian 23 Wales
South Wales Coal Measures Group Carboniferous 15 Wales
Southern Highland Group Ediacaran/Cambrian 24 Scotland
Stewartry Group Permian 13 Scotland
Stirling Group* Silurian 19 Scotland
Stockdale Group Silurian 19 England
Stockingford Shale Group Cambrian 23 England
Stoer Group Ectasian/Stenian 32 Scotland
Stonehaven Group Silurian 19 Scotland
Strathclyde Group Carboniferous 15 Scotland
Stratheden Group Devonian 17 Scotland
Strathmore Group Devonian 17 Scotland
Stretton Group Ediacaran 25 England
Stronsay Group Palaeogene 05 Scotland, Atlantic Ocean, North Sea
Sutherland Group Jurassic 09 Scotland
Tamar Group Devonian 17 England
Tappins Group Ordovician 21 Scotland
Tarskavaig Group Stenian 31 Scotland
Teign Valley Group Carboniferous 15 England
Thames Group Palaeogene 05 England, English Channel
Torridon Group Stenian/Tonian 30 Scotland
Tranearth Group Silurian 19 England
Trawden Limestone Group Carboniferous 15 England
Treffynnon Group Ediacaran/Cambrian 24 Wales
Treginnis Group Cryogenian/Ediacaran 26 Wales
Treglemais Group Cryogenian/Ediacaran 26 Wales
Unst Phyllite Group Ordovician/Silurian 20 Scotland
Upper Old Red Group Carboniferous 15 North Sea
Upper Old Red Sandstone Group Devonian/Carboniferous 16 England, Scotland, Wales, North Sea
Uriconian Group Ediacaran 25 England
Warwickshire Group Carboniferous/Permian 14 England, Scotland, Wales
Waterhead Group Silurian 19 Scotland
Wealden Group Cretaceous 07 England, English Channel
Wentnor Group Ediacaran 25 England
West Sole Group Jurassic 09 North Sea
Westray Group Palaeogene/Neogene 04 Scotland, North Sea
Whitehurst Group Carboniferous 15
Yesnaby Sandstone Group Devonian 17 Scotland
Yoredale Group Carboniferous 15 England, Scotland
Zechstein Group Permian 13 England, Atlantic, North Sea

Supergroups

The following 'supergroups', i.e. assemblages of 'groups', are recognised:

Subgroups

The following 'subgroups', i.e. subdivisions of 'groups', have been named:[3][4]

Albion Glacigenic Group:

Appin Group:

Ardmillan Group:

Argyll Group:

Britannia Catchments Group:

Grampian Group

Caledonia Glacigenic Group:

Lower Old Red Sandstone Group:

Pembroke Limestone Group:

Ogwen Group

References

  1. Definitions and procedures, section 4i
  2. Trewin, N.H. (ed) 2002 The Geology of Scotland, The Geological Society, London p72/3
  3. Appin, Argyll & Grampian subgroups after Trewin, N.H. (ed) 2002 The Geology of Scotland, The Geological Society, London p97
  4. Britannia catchments, Albion Glacigenic and Caledonia Glacigenic listings from: MCMILLAN, A A, HAMBLIN, R J O, and MERRITT, J W. 2005. An overview of the lithostratigraphical framework for the Quaternary and Neogene deposits of Great Britain (Onshore). British Geological Survey Research Report RR/04/04 38pp. ISBN 0 85272 516 7
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