The BGS Lexicon of Named Rock Units — Result Details

Somerset Levels Formation

Computer Code: SLEV Preferred Map Code: notEntered
Status Code: Full
Age range: Ipswichian Stage (QI) — Holocene Epoch (QH)
Lithological Description: The formation encompasses the marine, estuarine and terrestrial deposits that were formed in the Somerset Levels area during the Holocene transgression. The deposits are dark blue-grey silty clays and silts with subordinate sands and beds of peat, submerged forests and gravel. The deposits rest on a rockhead platform intricately dissected by river valleys formed when sea levels were lower, and their upper surface is approximately level at c 4.6 to 6.7m OD. The river valleys are infilled with gravels and sands, which become shelly upwards. See also "Supplementary Information".
Definition of Lower Boundary: Rests on Triassic and Jurassic bedrock.
Definition of Upper Boundary: Surface.
Thickness: To c.35m
Geographical Limits: The Somerset Levels, from Clevedon to Langport, Somerset.
Parent Unit: British Coastal Deposits Group (COAS)
Previous Name(s): Estuarine Alluvium And Higher Estuarine Alluvium (-1185)
Alluvial Deposits And Peat (-1827)
Alternative Name(s): none recorded or not applicable
Type Area  The Somerset Levels. Kidson and Heyworth, 1976. 
Murray, J W and Hawkins, A B. 1976. Sediment transport in the Severn Estuary during the past 8000-9000 years. Journal of the Geological Society of London, Vol.132, 385-398. 
Kidson, C and Heyworth, A. 1976. The Quaternary deposits of the Somerset Levels. Quarterly Journal of Engineering Geology, Vol.9, 217-235. 
Allen, J R L. 2000. Sea level, salt marsh and fen: shaping the Severn Estuary Levels in the later Quaternary (Ipswichian-Holocene). Archaeology in the Severn Estuary, Vol.11, 13-34. 
Whittaker A and Green G W. 1983. Geology of the country around Weston-super-Mare. Memoir of the Geological Survey, England and Wales, Sheet 279 with parts of sheets 263 and 295. 
Godwin, H. 1943. Coastal peat beds of the British Isles and North Sea. Journal of Ecology, Vol.31, 199-247. 
Green, G W and Welch F B A, 1965. The geology of the country around Wells and Chedder. Memoir of the Geological Survey of England and Wales, Sheet 280. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E263 E264 E279 E280 E295 E296 E311