The BGS Lexicon of Named Rock Units — Result Details

Birdsall Calcareous Grit Member

Computer Code: BICG Preferred Map Code: BCG
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Sandstone, fine- to medium-grained, commonly bioturbated and shelly with ammonites, bivalves and sponge spicules, some beds cross-bedded, generally weathering to soft sandstone, but some beds more calcareous and harder, including in the upper part (at Filey Brigg) a shelly, bioclastic sandy limestone bed
Definition of Lower Boundary: Soft fine- to medium-grained calcareous sandstone of Birdsall Calcareous Grit Member sharply but conformably overlies shelly ooidal limestone (Hambleton Oolite Member, lower leaf) where present, or non-sequentially overlies generally well-cemented calcareous fine-grained sandstone, locally spicule-rich (Lower Calcareous Grit Formation) where present, or in the extreme south, grey mudstone (Oxford Clay Formation).
Definition of Upper Boundary: Sharp change upwards from fine-grained generally calcareous sandstone into variously shelly, sandy and ooidal limestone (Hambleton Oolite Member), or where this is absent, difficult to distinguish from Middle Calcareous Grit Member, or where this is absent, non-sequentially overlain by mudstone of Langton Clay Member (Upper Calcareous Grit Formation) or of Ampthill Clay Formation.
Thickness: 0 to 27m: 6.5 to 7m at Filey Brigg (Wright, 1983; Coe, 1995), 0 to about 20m in Hambleton Hills (Powell et al., 1992), thickening south, 18 to 20m in Howardian Hills, 27m in Brown Moor Borehole (SE86SW/4) (Gaunt et al., 1980).
Geographical Limits: Cleveland Basin, North Yorkshire: generally confined to the south side of the Vale of Pickering - the Hambleton Hills and Howardian Hills, east to Filey and as far south as Acklam area, where it is the only representative of the Corallian Group, and is overstepped by Cretaceous strata. Present in Brown Moor Borehole, SE86SW/4 [81266 62043] (Gaunt et al., 1980). Generally absent from the Tabular Hills.
Parent Unit: Coralline Oolite Formation (COO)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Rock platform and low cliffs at Carr Nase, Filey Brigg, Filey, North Yorkshire. Exposes entire thickness of member, 6.5 to 7 m thick, underlain by the lower leaf of the Hambleton Oolite Member, and overlain by the upper leaf of the Hambleton Oolite Member. Wilson (1949) and Wright (1972) regarded this interval as Middle Calcareous Grit, but it was later identified as Birdsall Calcareous Grit by Wright (1983). Wright and Cox, 2001, pp 139-144; Wilson, 1949; Coe, 1995; Rawson and Wright, 1995. 
Type Section  Old quarries in wood, Birdsall Grange Farm, Birdsall, North Yorkshire. Possibly in landslide. Exposed (1960s) a total of 1.5 m of calcareous sandstone on soft, shelly sandstone. Wright, 1972, p 249. 
Type Area  Birdsall, North Yorkshire Wright, 1972, p 228. 
Reference(s):
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.] 
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. 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. 
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.) 
Wright, J K. 1972. The stratigraphy of the Yorkshire Corallian. Proceedings of the Yorkshire Geological Society, Vol. 39, 225-266. 
Wilson, V. 1949. The lower Corallian rocks of the Yorkshire coast and Hackness Hills. Proceedings of the Geologists' Association, Vol. 60, 235-271. 
Gaunt, G D, Ivimey-Cook, H C, Penn, I E and Cox, B M. 1980. Mesozoic rocks proved by the Institute of Geological Sciences boreholes in the Humber and Acklam areas. Report of the Institute of Geological Sciences, No. 79/13. 
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). 
Rawson, P F and Wright, J K. 1995. Jurassic of the Cleveland Basin, North Yorkshire. 173-208 in Taylor, P D (Ed.) Field Geology of the British Jurassic. (London: Geological Society.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E052 E053 E054