| Lithological Description: |
| Pale grey to brown rubbly, fine- to coarse-grained ooidal, peloidal and finely shell-detrital packstone to grainstone (Clypeus Grit Member), generally with very shelly and coarsely shell-detrital ooidal grainstone and packstone (Upper Trigonia Grit Member) at base. |
| Definition of Lower Boundary: |
| Disconformity: hardground capping various members of Aston Limestone or Birdlip Limestone formations, or correlative disconformity on Lias Group. |
| 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 15m. Type section 13m. Maximum c.20m (Colesbourne area). |
| Geographical Limits: |
| Horton, northeast Avon (Green, G W, 1992; see also Barron, A J M, et al, 1997, p.281, fig.4), 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). |
| Reference(s): |
| Arkell, W J. 1933. The Jurassic System in Great Britain. [Oxford: Clarendon Press.] |
| 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. |
| Buckman, S S, 1901. Bajocian and contiguous deposits in the north Cotswolds: the main hill-mass. Quarterly Journal of the Geological Society of London, Vol.57, 126-155. |
| 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 Unpublished PhD thesis, University of Keele. |
| 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. |
| Barron, A J M, 1998. Geology of the Hawling area: 1:10 000 Sheet SP02SE. British Geological Survey Technical Report WA/98/26. |
| Buckman, S S, 1905. A monograph of the ammonites of the Inferior Oolite Series, Pt.13, Supplement pp.clxix-ccix. |
| Parsons, C F, 1976. Ammonite evidence for dating some Inferior Oolite sections in the North Cotswolds. Proceedings of the Geologists' Association, 87, 45-63. |
| Richardson, L, 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217, (England and Wales). |
| Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic stratigraphy. Geological Conservation Review Series, Vol.26. (Peterborough: Joint Nature Conservation Committee.) |
| 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). |
| Green, G W, 1992. British Regional Geology: Bristol and Gloucester region. (3rd edition). (London: HMSO for British Geological Survey). |
