The BGS Lexicon of Named Rock Units — Result Details

Carboniferous Limestone Supergroup

Computer Code: CL Preferred Map Code: CL
Status Code: Full
Age range: Tournaisian Age (CT) — Visean Age (CV)
Lithological Description: Dominated by typically bioclastic to micritic, bioturbated with common shelly, crinoidal and algal beds of limestone and coral biostromes which are darker grey, and commonly dolomitised in the lower part. The upper part is dominated by paler grey, thinner-bedded limestones with common palaeokarst surfaces, overlain by clay wayboards, which are possible weathered bentonites. Sandstone is locally common, particularly in the upper part of the Supergroup.
Definition of Lower Boundary: Typically rests with an angular unconformity above Lower Palaeozoic or older strata. Where the base of the limestone or dolostone succession rests directly upon the unconformity, the unconformity marks the base at the supergroup. Locally, red sandstones or conglomerates with common calcrete palaeosols or bedded and nodular anhydrite with subordinate dolostone and mudstone occur immediately above the uncomformity. In other circumstances the comformable base of the Supergroup is taken at the base of the lowermost bed of limestone or dolostone above a predominant succession of sandstone, conglomerate or anhydrite.
Definition of Upper Boundary: Typically a sharp conformable boundary with the top of the uppermost limestone bed succeeding a predominantly limestone-dominated succession, overlain by dark grey mudstone of the Craven Group, quartzitic sandstone of the Tenby Group, sandstone, or dark grey mudstone and dark grey, thinly bedded limestone of the Yoredale Group.
Thickness: The Supergroup comprises a single group in each tectonic province, and hence thickness is the same as for each component group; e.g. Peak Limestone Group about 800 m in the Peak District, the Great Scar Limestone Group attains about 800 m in northern England, and the thickest development is in the Stainmore Trough [NY]. The Clwyd Limestone Group of North Wales [SH and SJ] measures up to 900 m.
Geographical Limits: Extensive across England and Wales, including south and west Cumbria, the Yorkshire Dales, North and South Wales, the Peak District and the Bristol area.
Parent Unit: Not Applicable (-)
Previous Name(s): Carboniferous Limestone [Obsolete Name and Code: Use CL] (-4550)
Carboniferous Limestone [Obsolete Name and Code: Use CL] (-4550)
Alternative Name(s): none recorded or not applicable
Type Section  See component groups - Great Scar Limestone Group, Peak Limestone Group, Clwyd Limestone Group,and the Pembroke Limestone Group for respective type sections. 
Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. 
Waters, C N, Waters, R A, Barclay, W J, and Davies, J R. 2009. Lithostratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/09/01. 184pp. 
Waters, C N, Browne, M A E, Dean, M T and Powell, J H. 2007. Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore). British Geological Survey Research Report, RR/07/01. 
Dean, M T, Browne, M A E, Waters, C N and Powell, J H. 2011. A lithostratigraphical framework for the Carboniferous successions of northern Great Britain (onshore). British Geological Survey Research Report, RR/10/007. 165pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E232 E126 E263 E261 E262 E248 E247 E233 E231 E234 E089 E114 E127 E162 E188 E202 E273 E274