The BGS Lexicon of Named Rock Units — Result Details

Somerset Catchments Subgroup

Computer Code: SOCA Preferred Map Code: notEntered
Status Code: Full
Age range: Early Pleistocene Epoch (QPE) — Holocene Epoch (QH)
Lithological Description: 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.
Definition of Lower Boundary: Formations of the Somerset Catchments Subgroup rest unconformably on bedrock varying in age from Devonian to Cretaceous.
Definition of Upper Boundary: Surface, or locally overlain by clays, silts and peats of the Somerset Levels Formation.
Thickness: c.10m
Geographical Limits: 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.
Parent Unit: Britannia Catchments Group (BCAT)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Valley of the River Parrett and its tributaries between Martock and Westonzoyland. 
Reference(s):
McMillan, A A, Hamblin, R J O and Merritt, J W. 2005. An overview of the lithostratigraphical framework for the Quarternary and Neogene deposits of Great Britain (onshore). British Geological Survey Research Report RR/04/04. 
Hunt, C O. 1987. The Pleistocene history of the Langport-Chard area of Somerset. PhD Thesis, University College of Wales, Aberystwyth. 
Campbell, S, Hunt, C O, Scourse, J D, Keen, D H and Croot, D G. 1999. Southwest England. 66-78 in Bowen, D Q (Editor), A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report No.23. [London: Geological Society.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable