The BGS Lexicon of Named Rock Units — Result Details

Upper Cornbrash

Computer Code: UCB Preferred Map Code: notEntered
Status Code: Index Level
Age range: Callovian Age (JC) — Callovian Age (JC)
Lithological Description: "A variable sequence of sandy limestones, calcareous sands and calcarenitic limestones" (Page, 1989). "Sparsely sandy peloidal biomicrite overlying fine-grained calcareous sandstone and sandy biomicrite" (Bristow, 1999).
Definition of Lower Boundary: Quasi-conformable to non-sequential contact with limestones of the underlying Lower Cornbrash (Upper Bathonian) or mudstone of the the Blisworth Clay Formation (East Midland Shelf east and north), or with the mudstone with minor sandstone beds of the Scalby Formation (Cleveland Basin), overlain by limestone of the Upper Cornbrash.
Definition of Upper Boundary: Taken at the base of the succeeding Kellaways Formation or Cayton Clay Formation (in the Cleveland Basin); comprising mudstone, commonly shelly at its base, resting generally sharply and conformably or non-sequentially on the limestone of the Cornbrash.
Thickness: 0 to c.7m; thickest in the Wessex Basin, and (probably) absent in much of the south Midlands.
Geographical Limits: Dorset coast (Weymouth area) to Yorkshire coast (Scarborough area) Absent locally, mainly in the south Midlands and in the Market Weighton area. Distribution in subcrop uncertain but probably similar to that of the Cornbrash Formation.
Parent Unit: Cornbrash Formation (CB)
Previous Name(s): Fleet Member (-1884)
Alternative Name(s): none recorded or not applicable
Type Section  Berry Knap (cliff section) 2.5km southsoutheast of Abbotsbury, Dorset. Full sequence exposed; 6.2m thick. Page, 1989; Cox and Sumbler, 2002, p.22. 
Reference Section  Cliff section, Gristhorpe Bay, 6.6km southeast of Scarborough, North Yorkshire. Full sequence exposed, about 0.4m thick. Wright, 1977; Cox and Sumbler, 2002, p.326. 
Page, K N. 1989. A stratigraphic revision for the English Lower Callovian. Proceedings of the Geologists' Association, Vol.100, 363-382. 
Cox, B M, Hopson, P M and Sumbler, M G. 1991. A new record of the Upper Cornbrash near Buckingham. Proceedings of the Geologists' Association, Vol.102, 63-65. 
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Douglas, J A and Arkell, W J, 1928. The Stratigraphical Distribution of the Cornbrash: I. The southwestern area. Quarterly Journal of the Geological Society, Vol.84, 117-178. 
Douglas, J A and Arkell, W J, 1932. The Stratigraphical Distribution of the Cornbrash II. The northeastern area. Quarterly Journal of the Geological Society, Vol.88, 112-170. 
Wright, J K. 1977. The Cornbrash Formation (Callovian) in North Yorkshire and Cleveland. Proceedings of the Yorkshire Geological Society, Vol.41, 325-346. 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M and Woods, M A. 1999. The Wincanton district - a concise account of the geology. Memoir of the British Geological Survey, Sheet 297 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E188 E297