The BGS Lexicon of Named Rock Units — Result Details

Coral Rag Member (Cleveland Basin)

Computer Code: CLRG Preferred Map Code: CR
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Limestone, coralliferous, variably ooidal, shelly: member typically formed of two beds: a lower shelly, ooidal, bioclastic packstone/wackestone with coral debris, and an upper very fossiliferous calcilutite with many corals in life position, coral debris and a shelly fauna of bivalves, gastropods and echinoids. This passes laterally in places into a sparsely fossiliferous, laminated limestone facies.
Definition of Lower Boundary: Non sequence or erosional disconformity: generally a poorly to moderately shelly ooid-limestone (Malton Oolite Member, Coralline Oolite Formation) sharply overlain by a moderately to highly fossiliferous, moderately ooidal, lime-muddy, bioclastic limestone (Coral Rag Member); locally boulders of Malton Oolite may be set in Coral Rag limestone (Wright, 1972, p. 241).
Definition of Upper Boundary: Non-sequence: rubbly coralliferous shelly limestone (Coral Rag Member) sharply overlain by silty mudstone and fine-grained sandstone (Newbridge Member) or fine-grained calcareous sandstone (Spaunton Sandstone Member) or unfossiliferous fine-grained limestone (North Grimston Cementstone Member) or mudstone (Langton Clay Member) or sandstone (Limekiln Member), all of Upper Calcareous Grit Formation.
Thickness: Up to 12m: Tabular Hills 1 to 9m, Hambleton Hills 4.5 to 8m, Howardian Hills 0 to at least 12m.
Geographical Limits: Cleveland Basin, North Yorkshire: as far south as North Grimston, possibly overstepped southwards by the Upper Calcareous Grit.
Parent Unit: Coralline Oolite Formation (COO)
Previous Name(s): Coral Rag (-2706)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Wath Old Quarry, Hovingham, North Yorkshire: exposed (1997) lower part of the Coral Rag Member at least 3.4m thick resting on an eroded surface of the Malton Oolite Member, and comprising 1.75 m of variably ooidal shelly bioclastic packstone/wackestone, overlain by at least 1.65m of very fossiliferous calcilutite with many corals in life position, and coral debris and a shelly fauna of bivalves, gastropods and echinoids Wright and Cox, 2001, pp 179-182 
Type Section  Railway cuttings and quarries at Nunnington, North Yorkshire, exposing the full thickness of the member, ranging from 2.4 to 3.4m, underlain by the Malton Oolite Member, and overlain by the Upper Calcareous Formation. Strata forms two beds: a lower shelly coralliferous ooidal limestone, and an upper calcilutite with corals in life position. Type Section proposed here (strata at original Type Section at Hackness are now part of the Yedmandale Member). Wright and Cox, 2001, pp 173-179. 
Reference Section  Newbridge Quarry, Pickering, North Yorkshire, exposing the entire member, about 6.8m seen in an unusual, sparsely fossiliferous, laminated limestone facies, sharply overlying the Malton Oolite Member, and with a planed and bored top, non-sequentially overlain by the Upper Calcareous Grit Formation. Coe, 1995, pp 169-170; Wright and Cox, 2001, pp 161-164. 
Reference(s):
Hudleston, W H. 1878. The Yorkshire Oolites, Part 2, the Middle Oolites: section 2, the Coralline Oolites, Coral Rag and supracoralline beds. Proceedings of the Geologists' Association, Vol. 5, 407-494. 
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.) 
Hudleston, W H. 1876. The Yorkshire Oolites, Part 2, the Middle Oolites: introduction and section 1. Proceedings of the Geologists' Association, Vol. 4, 353-410. 
Wright, J K. 1972. The stratigraphy of the Yorkshire Corallian. Proceedings of the Yorkshire Geological Society, Vol. 39, 225-266. 
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. 
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.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E044 E053 E054 E063 E064