The BGS Lexicon of Named Rock Units — Result Details

Craven Group

Computer Code: CRAV Preferred Map Code: notEntered
Status Code: Full
Age range: Chadian Substage (CI) — Yeadonian Substage (CY)
Lithological Description: Grey to dark grey, siliciclastic to calcareous mudstone, limestone packstone and wackestone in sharp-based beds, with localised sandstone, siltstone and chert and mudmound reef limestones. Formations are typically defined by variations in abundance of mudstone and limestone.
Definition of Lower Boundary: Not exposed or proved over most of its extent, although locally an unconformity above the limestone-dominated Bowland High Group in the Craven Basin or a disconformity above the limestone dominated Clwyd Limestone Group, marks a sharp boundary with the overlying mudstone dominated succession of the Craven Group.
Definition of Upper Boundary: Taken at the base of the lowermost thick feldspathic sandstone of the interbedded sandstone, siltstone, mudstone succession of the Millstone Grit Group. In Staffordshire, it is taken at the base of the lowermost quartzitic sandstone of the interbedded sandstone, siltstone, mudstone succession of the Morridge Formation.
Thickness: In the Craven Basin at least 1450m; across the Widmerpool half-graben 3000m known and 5000m from seismic; North Wales 400m thick.
Geographical Limits: Craven Basin, between Clitheroe and Skipton; northeast Wales; Derbyshire and the East Midlands.
Parent Unit: Not Applicable (-)
Previous Name(s): In Part: Worston Shale Group (-73)
In Part: Bowland Shale Group (-3323)
In Part: Dyserth Limestone Group (-161)
In Part: Gronant Group (-162)
Mallardale Shales [Obsolete Name And Code: Part Of CRAV] (MLDS)
Worston Shale Group [Obsolete Name And Code: Part Of CRAV] (WSG)
Gronant Group [Obsolete Name And Code: See CLWYD And CRAV] (GRN)
Alternative Name(s): none recorded or not applicable
Type Area  Craven Basin, Lancashire. See component Hodder Mudstone, Hodderense Limestone, Pendleside Limestone and Bowland Shale formations for reference sections. Earl et al., 1961; Fewtrell and Smith, 1980. 
Reference Section  Long Eaton No.1 Borehole (SK43SE/161) from 695 m to 2747 m depth (partially cored). 
Cossey, P J, Adams, A E, Purnell, M A, Whiteley, M J, Whyte, M A and Wright, V P. 2004. British Lower Carboniferous stratigraphy. Geological Conservation Review Series No.29. Joint Nature Conservation Committee, Peterborough. 
Riley N J. 1990. Stratigraphy of the Worston Shale Group (Dinantian) Craven Basin, north-west England. Proceedings of the Yorkshire Geological Society, Vol. 48, 163-187. 
Aitkenhead, N and Chisholm, J I. 1982. A standard nomenclature for the Dinantian formations of the Peak District of Derbshire and Staffordshire. Report of the Institute of Geological Sciences, No.82/8. 
Chisholm, J I, Charsley, T J and Aitkenhead, N. 1988. Geology of the country around Ashbourne and Cheadle. Memoir of the British Geological Survey, Sheet 124 (England and Wales). 
Whittard, W F and Simpson, S (editors). 1960. Lower Carboniferous "in" Lexique Stratigraphique International, Part 3A VII, Vol.1, p.91. 
Carney, J N, Ambrose, K and Brandon, A. 2001. Geology of the country between Burton, Loughborough and Derby. Description of 1:50k Sheet 141 (England and Wales). 
Waters, C N, Barclay, W J, Davies, J R and Waters, R A. In press. Stratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/05/06. 
Fewtrell, M D and Smith, D G, 1980. Revision of the Dinantian stratigraphy of the Craven Basin, N. England. Geological Magazine, Vol.117, p.37-49. 
Aitkenhead, N. 1977. The Institute of Geological Sciences borehole at Duffield, Derbyshire. Bulletin of the Geological Survey of Great Britain, No.59, 1-38. 
Davies, J R, Wilson, D and Williamson, I T. 2004. Geology of the country around Flint. Memoir for 1:50 000 Geological Sheet 108. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E059 E060 E067 E068 E069 E095 E096 E108 E123 E124 E125