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'.

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.Definitions and procedures, section 4i

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 areaAberystwyth Grits GroupSilurian19WalesAlbion Glacigenic GroupQuaternary01England, Scotland, Celtic SeaAncholme GroupJurassic09EnglandAppin GroupCryogenian27ScotlandAppleby GroupPermian13England, ScotlandAran Volcanic GroupOrdovician21WalesArbuthnott Group*Devonian17ScotlandArbuthnott-Garvock GroupDevonian17ScotlandArdmillan GroupOrdovician21ScotlandArdvreck GroupCambrian23ScotlandArfon GroupEdiacaran25WalesArgyll GroupEdiacaran25ScotlandAvon GroupCarboniferous15England, WalesAylesbeare Group*Triassic11EnglandAylesbeare Mudstone GroupTriassic11EnglandBacton GroupTriassic11North SeaBadenoch GroupTonian29ScotlandBalcreuchan GroupCambrian/Ordovician22ScotlandBanks GroupJurassic09North SeaBarr GroupOrdovician21ScotlandBarton GroupPalaeogene05EnglandBathgate GroupCarboniferous15ScotlandBenton Volcanic GroupCryogenian27WalesBisat GroupCarboniferous15Irish SeaBlackbrook GroupEdiacaran25EnglandBorder GroupCarboniferous15England, ScotlandBorrowdale Volcanic GroupOrdovician21EnglandBowland High GroupCarboniferous15EnglandBracklesham GroupPalaeogene05EnglandBrand GroupCambrian23EnglandBrent GroupJurassic09North SeaBritannia Catchments GroupPalaeogene/Neogene/Quaternary04England, Scotland, Wales, Irish SeaBritish Coastal Deposits GroupQuaternary01England, Scotland, Wales, Irish SeaBuilth Volcanic GroupOrdovician21WalesCaerbwdy GroupEdiacaran25WalesCaerfai GroupCambrian23WalesCaithness Flagstone GroupDevonian17ScotlandCaledonia Glacigenic GroupQuaternary01England, Scotland, Wales, Irish SeaCementstone Group*Carboniferous15ScotlandChalk GroupCretaceous07England, Atlantic Ocean, North SeaClackmannan GroupCarboniferous15ScotlandClaerwen GroupSilurian19WalesClair GroupDevonian/Carboniferous16AtlanticClwyd Limestone GroupCarboniferous15WalesConiston GroupSilurian19EnglandConybeare GroupCarboniferous15North SeaCorallian GroupJurassic09EnglandCosheston GroupDevonian17WalesCrag GroupNeogene/Quaternary02EnglandCraven GroupCarboniferous15England, Isle of ManCrawford GroupOrdovician21ScotlandCromer Knoll GroupCretaceous07England, Scotland, Atlantic Ocean, North SeaCumbrian Coast GroupPermian13England, Scotland, Irish SeaCwmystwyth Grits GroupSilurian19WalesDalby GroupSilurian19Isle of ManDartmouth GroupDevonian17EnglandDent GroupOrdovician21EnglandDrefach GroupOrdovician21WalesDungavel GroupSilurian19ScotlandDunlin GroupJurassic09North SeaDunnottar-Crawton GroupSilurian/Devonian18ScotlandDunrobin Bay GroupJurassic09North SeaDunwich GroupQuaternary01EnglandDurness GroupCambrian/Ordovician22ScotlandEday GroupDevonian17ScotlandEriboll GroupTrewin, N.H. (ed) 2002 The Geology of Scotland, The Geological Society, London p72/3Cambrian23ScotlandExeter GroupPermian13EnglandExmoor GroupDevonian/Carboniferous16EnglandEycott Group*Ordovician21EnglandEycott Volcanic GroupOrdovician21EnglandFaroe GroupPalaeogene05Atlantic OceanFarne GroupCarboniferous15North SeaFishguard Volcanic GroupOrdovician21WalesFladen GroupJurassic09North SeaForres Sandstone GroupDevonian17ScotlandGala GroupSilurian19ScotlandGarvock Group*Devonian17ScotlandGarwood GroupCarboniferous15Irish SeaGirvan GroupSilurian19ScotlandGlenbuck GroupSilurian19ScotlandGlenfinnan GroupTonian29ScotlandGrampian GroupCryogenian27ScotlandGray Sandstone GroupSilurian19WalesGreat Estuarine GroupJurassic09ScotlandGreat Oolite GroupJurassic09England, English ChannelGreat Scar Limestone GroupCarboniferous15England, Isle of ManGwna GroupEdiacaran/Cambrian24WalesHagshaw GroupSilurian19ScotlandHaisborough GroupTriassic11North SeaHarlech Grits GroupCambrian23WalesHawick GroupSilurian19ScotlandHeron GroupTriassic11North SeaHolsworthy GroupCarboniferous15EnglandHumber GroupJurassic/Cretaceous08Scotland, Atlantic Ocean, North SeaInferior Oolite GroupJurassic09England, Irish Sea, English ChannelIngleton GroupOrdovician21EnglandInner Hebrides GroupCretaceous07ScotlandInverclyde GroupCarboniferous15ScotlandInverness Sandstone GroupDevonian17ScotlandKendal GroupSilurian19EnglandKidston GroupCarboniferous15Irish Sea, Celtic SeaKyle GroupDevonian17North SeaLambeth GroupPalaeogene05EnglandLanark GroupSilurian/Devonian18ScotlandLias GroupTriassic/Jurassic10England, Wales, Celtic Sea, English Channel, Irish Sea, North SeaLlanbedrog Volcanic GroupOrdovician21WalesLlewelyn Volcanic GroupOrdovician21WalesLoch Maree GroupPalaeoproterozoic33ScotlandLocheil GroupTonian29ScotlandLower Greensand GroupCretaceous07England, English ChannelLower Old Red GroupDevonian17North SeaLower Old Red Sandstone GroupSilurian/Devonian18England, Scotland, WalesManx GroupCambrian23Isle of ManMaplewell GroupEdiacaran25EnglandMarros GroupCarboniferous15England, WalesMawddach GroupCambrian23WalesMeadfoot GroupDevonian17EnglandMenevian GroupCambrian23WalesMercia Mudstone GroupTriassic11England, ScotlandMiddle Old Red GroupDevonian17North SeaMilford Haven GroupSilurian/Devonian18WalesMillstone Grit GroupCarboniferous15England, Isle of ManMoffat Shale GroupOrdovician/Silurian20ScotlandMonks Water GroupSilurian19ScotlandMontrose GroupPalaeogene05North SeaMorar GroupStenian/Tonian30ScotlandMoray GroupPalaeogene05Atlantic Ocean, North SeaMull Lava GroupPalaeogene05ScotlandNordland GroupNeogene/Quaternary02Atlantic Ocean, North SeaNorth Esk GroupSilurian19ScotlandOgofgolchfa GroupEdiacaran25WalesOgwen GroupOrdovician21WalesPapa GroupTriassic11Atlantic OceanPeak Limestone GroupCarboniferous15EnglandPeel Sandstone GroupDevonian17Isle of ManPembroke Limestone GroupCarboniferous15England, WalesPenarth GroupTriassic/Jurassic10England, Wales, Scotland, Irish Sea, English Channel, North SeaPennine Coal Measures GroupCarboniferous15England, Isle of Man, Scotland, WalesPenrhiw GroupCryogenian/Ediacaran26WalesPortland GroupJurassic09England, English ChannelPriesthill GroupSilurian19ScotlandPurbeck GroupJurassic/Cretaceous08England, English ChannelRamsey Sound GroupEdiacaran25WalesRavenscar GroupJurassic09EnglandRavenstonedale GroupCarboniferous15England, Isle of Man Red Marl GroupSilurian/Devonian18England, WalesResidual Deposits GroupPalaeogene/Neogene/Quaternary03EnglandReston GroupSilurian/Devonian18England, ScotlandRhosson GroupEdiacaran25WalesRedbourne Group*Jurassic09England, Irish Sea, English ChannelRhynie GroupDevonian17ScotlandRiccarton GroupSilurian19ScotlandRoch Rhyolitic Group*Ordovician21WalesRotliegendes GroupPermian13England, North SeaSarclet GroupDevonian17ScotlandScottish Coal Measures GroupCarboniferous15ScotlandSelborne GroupCretaceous07England, English ChannelSherwood Sandstone GroupPermian/Triassic12England, ScotlandShetland GroupCretaceous/Palaeogene06Atlantic Ocean, North SeaSkerry GroupJurassic09Atlantic OceanSkiddaw GroupOrdovician21EnglandSkiddaw Slates Group*Ordovician21EnglandSkrinkle Sandstones GroupDevonian17WalesSkye Lava GroupPalaeogene05ScotlandSleat GroupStenian31ScotlandSnowdon Volcanic GroupOrdovician21WalesSolent GroupPalaeogene05EnglandSolva GroupCambrian23WalesSouth Wales Coal Measures GroupCarboniferous15WalesSouthern Highland GroupEdiacaran/Cambrian24ScotlandStewartry GroupPermian13ScotlandStirling Group*Silurian19ScotlandStockdale GroupSilurian19EnglandStockingford Shale GroupCambrian23EnglandStoer GroupEctasian/Stenian32ScotlandStonehaven GroupSilurian19ScotlandStrathclyde GroupCarboniferous15ScotlandStratheden GroupDevonian17ScotlandStrathmore GroupDevonian17ScotlandStretton GroupEdiacaran25EnglandStronsay GroupPalaeogene05Scotland, Atlantic Ocean, North SeaSutherland GroupJurassic09ScotlandTamar GroupDevonian17EnglandTappins GroupOrdovician21ScotlandTarskavaig GroupStenian31ScotlandTeign Valley GroupCarboniferous15EnglandThames GroupPalaeogene05England, English ChannelTorridon GroupStenian/Tonian30ScotlandTranearth GroupSilurian19EnglandTrawden Limestone GroupCarboniferous15EnglandTreffynnon GroupEdiacaran/Cambrian24WalesTreginnis GroupCryogenian/Ediacaran26WalesTreglemais GroupCryogenian/Ediacaran26WalesUnst Phyllite GroupOrdovician/Silurian20ScotlandUpper Old Red GroupCarboniferous15North SeaUpper Old Red Sandstone GroupDevonian/Carboniferous16England, Scotland, Wales, North SeaUriconian GroupEdiacaran25EnglandWarwickshire GroupCarboniferous/Permian14England, Scotland, WalesWaterhead GroupSilurian19ScotlandWealden GroupCretaceous07England, English ChannelWentnor GroupEdiacaran25EnglandWest Sole GroupJurassic09North SeaWestray GroupPalaeogene/Neogene04Scotland, North SeaWhitehurst GroupCarboniferous15Yesnaby Sandstone GroupDevonian17ScotlandYoredale GroupCarboniferous15England, ScotlandZechstein GroupPermian 13England, Atlantic, North Sea

Supergroups The following 'supergroups', i.e. assemblages of 'groups', are recognised: Carboniferous Limestone Supergroup Culm Supergroup Dalradian Supergroup Great Britain Superficial Deposits Supergroup Leadhills Supergroup Loch Ness Supergroup Longmyndian Supergroup Moine Supergroup - deprecated New Red Sandstone Supergroup Old Red Sandstone Supergroup Pebidian Supergroup Wester Ross Supergroup Windermere Supergroup

Subgroups