The BGS Lexicon of Named Rock Units — Result Details

Lower Calcareous Grit Formation

Computer Code: LCG Preferred Map Code: LCG
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Sandstone, fine-grained, quartzose, spiculitic, bedded, variably calcareous as hard beds or rows of sphaeroidal nodules ('doggers' or 'ball beds'), some beds highly bioturbated, diverse fauna notably of ammonites and bivalves; locally finer-grained sandstone beds, sponge spicule-rich beds ('chert') and ooidal limestone beds are developed (see Supplementary Information)
Definition of Lower Boundary: Gradational: passage up from silty mudstone (Weymouth Member, Oxford Clay Formation) by increasing siltiness and fine sand, including sponge spicules, necessarily arbitrary.
Definition of Upper Boundary: Non-sequence: generally well-cemented calcareous fine-grained sandstone, locally spicule-rich, sharply overlain by softer fine- to medium-grained calcareous sandstone (basal Yedmandale Member or Birdsall Calcareous Grit Member of Coralline Oolite Formation) or sandy ooidal limestone (Hambleton Oolite Member of Coralline Oolite Formation).
Thickness: 40 to 60m in Tabular Hills, 20-21m at Scarborough, 16m+ at Cayton Bay, thins west and south.
Geographical Limits: Cleveland Basin, North Yorkshire: as far south as Malton, where it is overstepped southwards by the lithologically similar Birdsall Calcareous Grit Member (Coralline Oolite Formation).
Parent Unit: Corallian Group (CR)
Previous Name(s): Calcareous Grit, Lower (-4752)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Rock platform and low cliffs at Carr Nase, Filey Brigg, Filey, North Yorkshire. Exposes upper part of formation, including part of Tenant's Cliff Member and Saintoft Member, totalling over 9m thick, overlain by Coralline Oolite Formation. TS proposed here; see Wright and Cox, 2001, pp 139-144; Wilson, 1949; Coe, 1995. 
Type Area  Coast between Filey and Scarborough Castle, North Yorkshire. Phillips, 1829 
Reference Section  Cliffs below Scarborough Castle on north-west side, North Yorkshire coast. Exposes upper part of formation, including part of Tenant's Cliff Member and Saintoft Member, totalling between 20 and 21m , overlain by the Yedmandale Member, Coralline Oolite Formation. Wright, 1983; Wilson, 1949. 
Reference Section  Faulted and in part landslipped cliff and rock platform exposures at Tenants’ Cliff, Cayton Bay, North Yorkshire. Contains substantial exposures of calcareous sandstone containing concretions with a prolific ammonite-bivalve fauna. Wright and Cox, 2001, pp 144-147. 
Reference(s):
Wright, J K. 1972. The stratigraphy of the Yorkshire Corallian. Proceedings of the Yorkshire Geological Society, Vol. 39, 225-266. 
Phillips, J. 1829. Illustrations of the geology of Yorkshire, or a description of the strata and organic remains. Part I, the Yorkshire Coast. (York.) 
Powell, J H, Cooper, A H C and Benfield, A C. 1992. Geology of the country around Thirsk. Memoir of the British Geological Survey, Sheet 52 (England and Wales). 
Wright, J K and Cope, J C W. In press. Oxfordian - Kimmeridgian Correlation Chart. In: A correlation of Jurassic rocks in the British Isles: Middle and Upper Jurassic. Cope, J C W (editor). Special Report of the Geological Society of London. 
Frost, D V. 1998. Geology of the country around Northallerton. Memoir of the British Geological Survey, Sheet 42 (England and Wales). 
Rawson, P F and Wright, J K (eds). 1992. The Yorkshire Coast. Geologists' Association Guide, No.34. 2nd Edition, 117pp. (Ongar: PSS Group.) 
Coe, A L. 1995. A comparison of the Oxfordian successions of Dorset, Oxfordshire and Yorkshire. 151-172 in Taylor, P D (Ed.) Field Geology of the British Jurassic. [Bath: The Geological Society.] 
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Wright, J K. 2009. The geology of the Corallian ridge (Upper Jurassic) between Gilling East and North Grimston, Howardian Hills, North Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 57, 193-216. 
Wilson, V. 1949. The lower Corallian rocks of the Yorkshire coast and Hackness Hills. Proceedings of the Geologists' Association, Vol. 60, 235-271. 
Wright, J K. 1983. The Lower Oxfordian (Upper Jurassic) of North Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 44, 249-281. 
Wright, J K, and Cox, B M. 2001. British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian). Geological Conservation Review Series. No. 21. (Peterborough: Joint Nature Conservation Committee/Chapman and Hall.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E042 E043 E044 E052 E053 E054 E063 E064