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'.
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 | |
| Badenoch Group | Tonian | 29 | Scotland | |
| 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 | Carboniferous | 15 | 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 | |
| Ogwen Group | Ordovician | 21 | 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 |
The following 'supergroups', i.e. assemblages of 'groups', are recognised:
The following 'subgroups', i.e. subdivisions of 'groups', have been named:[3] [4]
Ardmillan Group
Lower Old Red Sandstone Group