The BGS Lexicon of Named Rock Units — Result Details

Severn Valley Formation

Computer Code: SEVN Preferred Map Code: notEntered
Status Code: Full
Age range: Pleistocene Epoch (QP) — Holocene Epoch (QH)
Lithological Description: Fluvial terrace and alluvial deposits of the River Severn and tributaries excluding the Avon (see Warwickshire Avon Valley Formation) and possibly others, pending review. Mainly sand, gravel and mud; divided into six "terrace" members (Spring Hill, Bushley Green, Kidderminster Station, Holt Heath, Worcester, Power House members), plus Holocene alluvium (Elmore Member of Bowen, 1999) and with local named organic deposits. Includes contemporaneous head, colluvium and soil deposits. Gravels are principally composed of Palaeozoic, Triassic and (mainly below Avon confluence at Tewkesbury) Jurassic material from the local bedrock of the catchment, with an admixture of glacial material from the Anglian Wolston Formation, etc. and, in the younger terraces, a substantial admixture of "Irish Sea" glacial material from the Devensian Stockport Formation.
Definition of Lower Boundary: Unconformable, commonly channelled base on pre-Quaternary bedrock.
Definition of Upper Boundary: Ground surface.
Thickness: 0 to c.10m
Geographical Limits: Severn catchment (excluding Warwickshire Avon).
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  Lower Severn valley, Bridgnorth to Gloucester. Wills, 1938. 
Reference(s):
Barclay, W J, Ambrose K, Chadwick, R A and Pharaoh, T C. 1997. Geology of the country around Worcester. Memoir of the British Geological Survey, Sheet 199 (England and Wales). 
Dawson, M R. 1989. The Severn valley south of Bridgnorth. 78-100 in Keen, D H (Editor), The Pleistocene of the West Midlands. Field Guide. [Cambridge: Quaternary Research Association.] 
Maddy, D. 2002. An evaluation of climate, crustal movement and base level controls on the Middle-Late Pleistocene development of the River Severn Valley, UK. Netherlands Journal of Geosciences / Geologie en Mijnbouw, Vol.81, 329-338. 
Maddy, D and Lewis, S G. 2005. The lower Severn valley. 73-84 in Lewis, C A and Richards A E (editors), The glaciations of Wales and adjacent area. (Logaston Press). 
Whitehead, T H and Pocock, R W. 1947. Geology of the country around Dudley and Bridgnorth. Memoir of the British Geological Survey, Sheet 167. (England and Wales). 
Worssam, B C, Ellison, R A and Moorlock, B S P. 1989. Geology of the country around Tewkesbury. Memoir of the British Geological Survey, Sheet 216 (England and Wales). 
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
Keen, D H. 1989. The Pleistocene of the West Midlands. Field Guide. [Cambridge: Quaternary Research Association.] 
Maddy, D, Green, C P, Lewis, S G and Bowen, D Q. 1995. Pleistocene Geology of the lower Severn Valley, UK. Quaternary Science Reviews, Vol 14, 209 - 222. 
Wills, L J, 1938. The Pleistocene development of the Severn from Bridgnorth to the Sea. Quarterly Journal of the Geological Society, 94, 161-242. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E122 E123 E136 E137 E138 E139 E150 E151 E152 E153 E164 E165 E166 E167 E168 E180