The BGS Lexicon of Named Rock Units — Result Details

Bristol Avon Valley Formation

Computer Code: BAVON Preferred Map Code: notEntered
Status Code: Full
Age range: Anglian Stage (QA) — Holocene Epoch (QH)
Lithological Description: The formation encompasses the fluvial, lacustrine and organic deposits of the Bristol Avon river. It includes floodplain alluvium and deposits of three river terraces. The floodplain alluvium comprises soft clays, silts and fine sands, with bodies of peat, all overlying sands and gravels. The terrace deposits include gravels, sands, silts and clays; the gravel clasts are dominantly local Jurassic limestones, Triassic sandstones and Carboniferous limestone, but also include some glacially-derived erratics from northwest England and the Welsh Borders. Anglian to Holocene (MIS 12 - 1).
Definition of Lower Boundary: Rests unconformably on Jurassic, Triassic and Carboniferous bedrock.
Definition of Upper Boundary: Ground surface.
Thickness: Up to 10 m.
Geographical Limits: The entire catchment of the Bristol Avon river and its tributaries, from Malmesbury and Frome to the mouth of the river.
Parent Unit: Severn and Avon Catchments Subgroup (SACA)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The valley of the Bristol Avon river from Bathampton to the mouth of the Avon. Campbell et al., 1999. 
Reference(s):
McMillan, A A, Hamblin, R J O, and Merritt, J W. 2011. A lithostratigraphical framework for onshore Quaternary and Neogene (Tertiary) superficial deposits of Great Britain and the Isle of Man. British Geological Survey Research Report, RR/10/03. 343pp. 
Stoker, M S, McMillan, A A and Waters, C N. Quaternary Stratigraphical Chart: Southern Britain. British Geological Survey, 1 poster. 
Kellaway, G A and Welch, F B A. 1993. Geology of the Bristol district. Memoir of the British Geological Survey Special Sheet [England and Wales]. 
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:
E251 E252 E264 E265 E281