The BGS Lexicon of Named Rock Units — Result Details

Ridgacre Formation

Computer Code: RIDG Preferred Map Code: notEntered
Status Code: Full
Age range: Pleistocene Epoch (QP) — Pleistocene Epoch (QP)
Lithological Description: Comprises the younger of the two pre-Devensian glacial successions identified in the Birmingham area. Predominantly sands and tills, which characteristically lack Scottish and Lake districts erratics (which characterize the Devensian Stockport Formation), and northern and eastern (e.g. Cretaceous) erratics (which are found in the pre-Devensian Wolston Formation). At type locality comprises glacigenic reddish-brown and orange sand with clay partings, overlain by reddish brown till with Trias (mainly Bunter quartz/quartzite) and Upper Carboniferous erratics; similar deposits of sand and gravel occur at Nechells. At both localities overlies the organic Quinton Beds ("Hoxnian"). Full geographic extent and thus full range of lithology uncertain. Precise age and correlation contentious.
Definition of Lower Boundary: At type locality and Nechells, overlies the organic Quinton Beds ("Hoxnian"). More generally, inferred to rest upon Nurseries Formation or Permo-Triassic or Palaeozoic bedrock.
Definition of Upper Boundary: Ground surface or various younger Quaternary deposits (head, fluvial deposits). Remnants may be present inside the Devensian limit beneath the Stockport Formation.
Thickness: c.8m at type locaity; elsewhere may be represented by up to 50m of deposits.
Geographical Limits: Full extent highly uncertain pending further work, but likely to be widespread in and to the south of the Birmingham area beyond the limit of the Devensian Stockport Formation, and probably makes up the great bulk of the pre-Devensian glacigenic deposits there, and possibly in adjoining districts. Currently positively identified only in sections at Quinton and Nechells where it overlies the temperate (Hoxnian) Quinton Beds. Possibly also represented by till at Stourport beneath Holt Heath Member of Severn Valley Formation(Dawson, 1988; Maddy et al., 1995), and by gravels farther upstream in the Stour valley (Maddy et al., 1995). Remnants may be present inside the Devensian limit beneath the Stockport Formation.
Parent Unit: Albion Glacigenic Group (ALBI)
Previous Name(s): Western Drift (-1097)
Upper Glacial Series (-494)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Site investigation boreholes and motorway cutting at Quinton, Birmingham. Horton, 1974, 1989. 
Reference Section  Nechells. See publications by Kelly, 1964; Shotton and Osborne, 1965. 
Reference(s):
Horton, A. 1974. The sequence of Pleistocene deposits proved during the construction of the Birmingham motorways. Report of the Institute of Geological Sciences, No.74/22. (London:HMSO). 
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
Old R A, Hamblin, R J O, Ambrose, K, and Warrington G. 1991. Geology of the country around Redditch. Memoir of the British Geological Survey, Sheet 183 (England and Wales). 
Kelly, M R. 1964. The Middle Pleistocene of North Birmingham. Philosophical Transactions of the Royal Society of London, Vol.B247, 533-592. 
Powell, J H, Glover, B W and Waters, C N. 2000. Geology of the Birmingham area. Memoir of British Geological Survey Sheet 168 (England and Wales). 
Shotton, F W and Osbourne, P J. 1965. The fauna of the Hoxnian interglacial deposits of Nechells, Birmingham. Philosophical Transactions of the Royal Society of London, Vol. B248, 353-378. 
Dawson, M R. 1988. Diamict deposits of pre-Late Devensian Glacial Age underlying the Severn Main Terrace at Stourport, Worcestershire; their origins and stratigraphic implications. Proceedings of the Geologists' Association, Vol.99, 125-132. 
Horton, A. 1989. Quinton. 69-76 in Keen, D H (editor), 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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E124 E125 E140 E141 E154 E155 E167 E168 E169 E183