The BGS Lexicon of Named Rock Units — Result Details
Ridgacre Formation
| Computer Code: | RIDG | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Mid Pleistocene (QPM) — Mid Pleistocene (QPM) | ||
| 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 Glacigenic Formation), and northern and eastern (e.g. Cretaceous) erratics (which are found in the pre-Devensian Wolston Formation). At the type section it 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 Peat Formation (Hoxnian). More generally, inferred to rest upon Nurseries Glacigenic 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 Glacigenic Formation. | ||
| Thickness: | About 8 m at type locality; elsewhere may be represented by up to 50 m 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 Glacigenic 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 Peat Formation. Possibly also represented by till at Stourport beneath the Holt Heath Sand and Gravel Member of the 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 Glacigenic Formation. | ||
| Parent Unit: | Albion Glacigenic Group (ALBI) | ||
| Previous Name(s): | Upper Glacial Series [Obsolete Name and Code: Use RIDG]
(-494)
Western Drift [Obsolete Name and Code: Use NURS, RIDG] (-1097) |
||
| 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. Kelly, 1964; Shotton and Osborne, 1965. | ||
| Reference(s): | |||
| 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. | |||
| 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. | |||
| Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. | |||
| Stoker, M S, McMillan, A A and Waters, C N. Quaternary Stratigraphical Chart: Southern Britain. British Geological Survey, 1 poster. | |||
| 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. | |||
| 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). | |||
| 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. | |||
| 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). | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E124 E125 E140 E141 E154 E155 E167 E168 E169 E183 | |||