The Cwmystwyth Grits Group is a Silurian lithostratigraphic group in mid Wales. The name is derived from the village of Cwmystwyth near Devil's Bridge in Ceredigion. The Group comprises the Blaen Myherin Mudstones Formation, the Glanyrafon Formation, the Caerau Mudstones Formation, the Rhuddnant Grits Formation and the Pysgotwr Grits Formation.
The Llanbedrog Volcanic Group is an Ordovician lithostratigraphic group in northwest Wales. The name is derived from the village of Llanbedrog on the Llyn Peninsula where the strata are exposed.
The Snowdon Volcanic Group is an Ordovician lithostratigraphic group in Snowdonia, north-west Wales. The name is derived from Snowdon, the highest peak in Wales where it outcrops. This assemblage of rocks has also been referred to as the Snowdon Volcanic Series.
The Harlech Grits Group is a lower to middle Cambrian lithostratigraphic group in northwest Wales. The name is derived from the town of Harlech in Gwynedd.
The Mawddach Group is a middle to upper Cambrian lithostratigraphic group in Gwynedd, Wales. The name is derived from the river known as the Afon Mawddach.
The Sherwood Sandstone Group is a Triassic lithostratigraphic group which is widespread in Britain, especially in the English Midlands. The name is derived from Sherwood Forest in Nottinghamshire which is underlain by rocks of this age. It has economic importance as the reservoir of the Morecambe Bay gas field, the second largest gas field in the UK.
The Exeter Group is a Permian lithostratigraphic group which occurs through East Devon in southwest England. The name is derived from the city of Exeter in Devon which is partly underlain by rocks of this age.
The Aylesbeare Mudstone Group is an early Triassic lithostratigraphic group in southwest England. The name is derived from the village of Aylesbeare in east Devon. The Group comprises the Littleham Mudstone Formation, the Exmouth Mudstone and Sandstone Formation and the underlying Clyst St Lawrence Formation. The strata are exposed on the coast between Exmouth and Budleigh Salterton where the type section is defined. The rocks of the Aylesbeare Mudstone Group have also previously been known as the Aylesbeare Group and the Aylesbeare Mudstone Formation.
The Thames Group is an Eocene lithostratigraphic group which is widespread in southeast England, especially in the Hampshire Basin from Dorset through Hampshire to West Sussex and in the Isle of Wight and in the London Basin from Berkshire east through northern Hampshire, Surrey and Greater London to Essex and north Kent. It is encountered in older literature as the London Clay Group.
The Pennine Coal Measures Group is a lithostratigraphical term referring to the coal-bearing succession of rock strata which occur in the United Kingdom within the Westphalian Stage of the Carboniferous Period. In formal use, the term replaces the Coal Measures Group as applied to the succession of coal-bearing strata within the Pennine Basin which includes all of the coalfields of northern England and the English Midlands. It includes the largely concealed Canonbie Coalfield of southern Scotland and the coalfields of northeast Wales and the minor Anglesey coalfield. The sequence consists in the main of mudstones and siltstones together with numerous sandstones, the more significant ones of which are individually named. Some are laterally extensive, others are more restricted in their range. There are numerous coal seams, again with some being more laterally continuous than others. Those which were economically valuable were named though any individual seam may have attracted different names in different pits and different districts. Marine bands preserving distinctive and dateable marine fossils such as goniatites and brachiopods are widespread within the sequence and enable correlation to be made between sequences in one part of the basin and another and with other basins
The Bacton Group is a Triassic lithostratigraphic group beneath the southern part of the North Sea. The name is derived from Bacton on the Norfolk coast. These strata, which are up to 600 m thick are the offshore equivalent of the Roxby Formation and Sherwood Sandstone Group which occur in northeast England. The group comprises a lower Bunter Shale Formation of red and brown to grey mudstones and an upper Bunter Sandstone Formation of dolomitic sandstones with mudstone interlayers.
The Tamar Group is an early Devonian to early Carboniferous geologic group in south Devon and north Cornwall in southwest England. The name is derived from the valley of the River Tamar on the Devon/Cornwall border. The Group comprises the Torquay Limestone, Tavy and Burraton formations. Some of the rocks are fossiliferous.
The Cosheston Group is an early Devonian lithostratigraphic group in west Wales. The name is derived from the village of Cosheston in south Pembrokeshire. The Group comprises the Llanstadwell, Burton Cliff, Mill Bay, Lawrenny Cliff and New Shipping formations. The strata are exposed in the Milford Haven area of southern Pembrokeshire where several partial type sections are defined. The outcrop extends around the northern and southern shores of the Haven. It is bounded to the north by the Benton Fault between the villages of Rosemarket and Lawrenny, and extends east to New Shipping and west almost to the town of Milford Haven itself. The rocks of this group have also previously been known as the Cosheston Beds.
The Milford Haven Group is a late Silurian to early Devonian lithostratigraphic group in west Wales. The name is derived from the estuary and town of Milford Haven in south Pembrokeshire. The Group comprises calcareous marls with occasional sandstones along with conglomerates and breccias.
The Red Marl Group is a late Silurian to early Devonian lithostratigraphic group in south Wales and Gloucestershire. The Group which was first established in the early twentieth century, includes the modern-day Temeside Mudstone, Raglan Mudstone and St Maughans formations and forms the lower part of the Old Red Sandstone. The rocks of this group have also previously been known as the Red Marl.
The Teign Valley Group is a late Devonian to late/middle Carboniferous lithostratigraphic group in north Cornwall through Devon and into west Somerset in southwest England. The name is derived from the valley of the River Teign. The Group comprises the Barras Nose, Trambley Cove, Teign Chert and Dowhills Mudstone formations. It also includes the Brendon and St Mellion formations whose stratigraphical context is unclear since all known boundaries of these two unit are tectonic. The Brendon Formation slates extend from Tavistock west to Bodmin Moor. The St Mellion Formation sandstones, siltsones and mudstones are found from Holne northeastwards. The Teign Valley Group was formerly known as the Lower Culm Group or Lower Culm Measures.
The Holsworthy Group is a late Carboniferous lithostratigraphic group in north and east Cornwall and Devon in southwest England. The name is derived from the Devon town of Holsworthy. The Group comprises the Crackington, Bideford and Bude formations. In the Launceston area the group is represented by the Bealsmill Formation. It was formerly known as the Upper Culm Group.
The Exmoor Group is a late Devonian to early Carboniferous lithostratigraphic group in southwest England whose outcrop extends from Croyde in north Devon east across Exmoor to Minehead in west Somerset. The group comprises the following formations the:
The Craven Group is a lithostratigraphical term referring to the succession of mudstone and limestone rock strata which occur in certain parts of northern and central England and northeast Wales in the United Kingdom within the Chadian to Yeadonian sub-Stages of the Carboniferous Period. Other lithologies including sandstones, siltstones and chert occur within the group. The Group is subdivided into numerous formations, some of which previously enjoyed group status. In stratigraphic order, these are:
The Arbuthnott-Garvock Group is a Devonian lithostratigraphic group in central Scotland. The name is derived from the village of Arbuthnott in Aberdeenshire and the Hill of Garvock near Laurencekirk. The group comprises the previously separate overlying Garvock Group and the underlying Arbuthnott Group.
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