The BGS Lexicon of Named Rock Units — Result Details

Middle Calcareous Grit Member

Computer Code: MCG Preferred Map Code: MCG
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Sandstone, fine-grained, bedded, clayey in lower part passing calcareous and shelly upwards with scattered ooids, generally poorly fossiliferous; locally a sandy ooidal limestone with trigoniid bivalves, gastropods and ammonites is developed at the top (Newbridge Trigonia Bed; Coe, 1995, p. 169).
Definition of Lower Boundary: Conformable: sharp change upwards into calcareous fine-grained sandstone from sandy ooidal limestone (Hambleton Oolite Member). Where this is absent, difficult to distinguish from Birdsall Calcareous Grit Member.
Definition of Upper Boundary: Conformable or non-sequence: sharp change up from calcareous fine-grained sandstone or locally a sandy ooidal limestone (Newbridge Trigonia Bed) into generally non-sandy ooidal limestone (Malton Oolite Member), at the base of a black ooid-limestone bed at Newbridge Quarry (Coe, 1995).
Thickness: 12 to 15m in the Tabular Hills thinning to zero south of Malton and near Scarborough, less than 2m at Spiker's Hill Quarry.
Geographical Limits: Central and western Cleveland Basin, North Yorkshire, overstepped eastwards by Malton Oolite Member.
Parent Unit: Coralline Oolite Formation (COO)
Previous Name(s): Middle Calcareous Grit (-4183)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Love Lane Quarry, Pickering, North Yorkshire. 5m of massive, calcareous sandstone is currently seen with the Newbridge Trigonia Bed clearly visible near the top, with a conformable upward transition into the Malton Oolite Member. Formerly exposed up to 8.5m of strata but base not seen. Blake and Hudleston, 1877, pp 334-336; Arkell, 1933, pp 426-427. 
Reference Section  Spikers Hill Quarry, West Ayton, North Yorkshire. Exposes entire member, 1.17m thick, comprising bedded clayey fine-grained sandstone, underlain by Hambleton Oolite Member, non-sequentially overlain by Malton Oolite Member. Type Section proposed here; Wright, 1972, p.237; Wright and Cox, 2001, pp 157-161. 
Reference Section  Newbridge Quarry, Pickering, North Yorkshire. Exposes upper part of member, about 2.3m thick, comprising siltstone, overlain by sandy, shelly ooidal limestone and ooidal fine-grained sandstone (Newbridge Trigonia Bed), overlain by Malton Oolite Member. Nearby [SE 8017 8565], the lower part, bioturbated fine-grained sandstone beds are exposed. Coe, 1995 
Reference(s):
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.) 
Blake, J F and Huddleston, W H 1877. On the Corallian rocks of England. Quarterly Journal of the Geological Society of London, Vol.33, 260-405. 
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Wright, J K. 1972. The stratigraphy of the Yorkshire Corallian. Proceedings of the Yorkshire Geological Society, Vol. 39, 225-266. 
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, 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:
E043 E044 E052 E053 E054