The BGS Lexicon of Named Rock Units — Result Details
Clypeus Grit Member
| Computer Code: | CG | Preferred Map Code: | SaL |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Bajocian Age (JB) — Bathonian Age (JN) | ||
| Lithological Description: | Pale grey to pinkish brown fine- to coarse-grained ooidal, peloidal and shell-detrital packstone to grainstone, with large orange-skinned peloids/pisoids and aggregate grains; common whole shells especially in upper part. Characteristic fauna includes the large echinoid Clypeus ploti Salter, large myacean bivalves and terebratulid brachiopods (Stiphrothyris). From Stroud southwards, includes coral-rich limestone ('Upper Coral Bed') at base. | ||
| Definition of Lower Boundary: | Upward change from shelly coarsely shell-fragmental limestone (Upper Trigonia Grit Member), to limestone as described under Lithology. Commonly a non-sequence, marked by a hardground, though locally appears to be transitional. Where Upper Trigonia Grit Member absent, boundary is hardground capping Aston Limestone or Birdlip Limestone formations, or unconformity on older beds. | ||
| Definition of Upper Boundary: | Upward change to mudstone (Fuller's Earth Formation) in southwest or into fine- to medium-grained ooidal grainstone (Chipping Norton Limestone Formation) in northeast. Generally transitional, but locally marked by a hardground (Sumbler, M G, Barron, A J M and Morigi, A N, 2000). | ||
| Thickness: | Typically 10 to 12m. Type section 10.5 to 12m. Maximum c.16m (Colesbourne area). | ||
| Geographical Limits: | Horton, northeast Avon (Green, G W, 1992; see also Barron, A J M, et al, 1997, p.281, figs. 4 and 5), through Gloucestershire Cotswolds to north Oxfordshire west of a line from Hook Norton to Tackley where overlapped by Great Oolite Group (Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D, 1987, fig.26). | ||
| Parent Unit: | Salperton Limestone Formation (SALS) | ||
| Previous Name(s): | Clypeus Grit
(-770)
Pholadomya Grit (-771) Clypeus Grit and White Oolite [Obsolete Name and Code: Use CG] (-2073) Rubbly Beds and Upper Coral Bed [Obsolete Name and Code: Use CG] (-2074) |
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| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | North Cotswolds, Gloucestershire. | ||
| Reference Section | Harford railway cutting SSSI (Buckman, S S, 1887, sections 3 and 4; Richardson, L, 1929; Parsons, L F, 1976; Barron, A J M, 1999; Cox, B M, and Sumbler, M G. 2002). | ||
| Type Section | Notgrove railway cutting SSSI, 1km eastnortheast of Salperton, Gloucester. (Beds 1 to 4 of Buckman, S S, 1887, section 6 (first cutting west of Notgrave Station)). See also Woodward, H B, 1894, p.133; Barron, A J M, 1998, Locality Q; Cox, B M, and Sumbler, M G. 2002. | ||
| Reference(s): | |||
| Richardson, L. 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217 (England and Wales). | |||
| Parsons, C F, 1976. Ammonite evidence for dating some Inferior Oolite sections in the North Cotswolds. Proceedings of the Geologists' Association, 87, 45-63. | |||
| Green, G W. 1992. Bristol and Gloucester region (3rd). British Regional Geology. (London: HMSO for British Geological Survey.) | |||
| Richardson, L. 1907. The Inferior Oolite and contiguous deposits of the Bath-Doulting district. Quarterly Journal of the Geological Society of London, Vol. 63, 383-423. | |||
| Barron, A J M. 1998. Geology of the Hawling area: 1:10 000 Sheet SP02SE. British Geological Survey Technical Report WA/98/26. | |||
| Sumbler, M G, Barron, A J M and Morigi, A N, 2000. Geology of the Cirencester district. Memoir of the British Geological Survey, Sheet 235 (England and Wales). | |||
| Barron, A J M, Sumbler, M G and Morigi, A N. 1997. A revised lithostratigraphy for the Inferior Oolite Group (Middle Jurassic) of the Cotswolds, England. Proceedings of the Geologists' Association, Vol. 108, 269-285. | |||
| Barron, A J M. 1999. Geology of the Naunton area. British Geological Survey Technical Report WA/98/27. | |||
| Buckman, S S. 1887. The Inferior ooilte between Andoversford and Bourton-on-the-Water. Proceedings of the Cotteswold Naturalists' Field Club, Vol. 9, 108-135. | |||
| Hull, E, 1857. The geology of the country around Cheltenham. Memoir of the Geological Survey of Great Britain. Old Series Sheet 44. | |||
| Witchell, E, 1880. Notes on a section of Stroud Hill, and the Upper Ragstone Beds of the Cotswolds. Proceedings of the Cotswold Naturalists' Field Club, Vol.7. | |||
| Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D. 1987. Geology of the country around Chipping Norton. Memoir of the British Geological Survey, Sheet 218 (England and Wales). | |||
| Lycett, J, 1857. The Cotswold Hills. London. | |||
| Woodward, H B, 1894. The Jurassic Rocks of Britain, Vol.4. The Lower Oolitic Rocks of England (Yorkshire excepted). Memoir of the Geological Survey of the United Kingdom. | |||
| Parsons, C F, 1980. Aspects of the statigraphy and ammonite faunas of the Aaenian-Bajocian stages in Great Britain. Unpublished PhD thesis, University of Keele. | |||
| Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E218 E235 E236 E237 E252 | |||