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): | Alluvial deposits and peat [Obsolete Name and Code: Use SLEV]
(-1827)
Estuarine alluvium and higher estuarine alluvium [Obsolete Name and Code: Use SLEV] (-1185) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | The Somerset Levels. Kidson and Heyworth, 1976. | ||
| Reference(s): | |||
| 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. | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E263 E264 E279 E280 E295 E296 E311 | |||