The BGS Lexicon of Named Rock Units — Result Details

Peak Limestone Group

Computer Code: PKLM Preferred Map Code: PKLM
Status Code: Full
Age range: Courceyan Substage (CF) — Brigantian Substage (CX)
Lithological Description: A thick sequence of pale to dark grey, thinly to thickly bedded biosparite and cherty micritic limestone units displaying knoll-reefs, comprising fossiliferous, massive micrite with localised common spar-filled cavities, and grey-brown to dark grey dolomitic limestones. Subordinate partings and thin beds of calcareous mudstone and siltstone, basaltic lava, sills and pyroclastic rocks including tuff and volcanic breccia are common in the upper part of the Group, as well as pedogenic crusts, palaeokarstic surfaces and thin bentonite partings (known locally as "wayboards"), notably in Matlock [SK 20 60 to 30 60], and the Millers Dale to Buxton [SK 06 72 to 16 74] areas of the Peak District.
Definition of Lower Boundary: Generally rests unconformably upon deformed Lower Palaeozoic lava, volcanic breccias, pyroclastic rocks and mudstones, but locally the base of the Group rests conformably upon late Devonian to early Dinantian anhydrite, such as the Hathern Anhydrite Formation, or dolostone, like the Rue Hill Dolomite Formation. Locally, on the Hathern Shelf, the Group lies conformably upon sandstones of the Calke Abbey Sandstone Formation.
Definition of Upper Boundary: Taken at the conformable boundary at the base of predominantly mid to dark grey mudstones and turbiditic limestones of the Craven Group, above the limestone-dominated succession of the Peak Limestone Group. On the Hathern Shelf, strata of the Craven Group rest disconformably upon pale grey platform carbonate facies limestones of the Peak Limestone Group.
Thickness: About 800m thick in the Derbyshire Peak District, thinning southward over the Hathern Shelf to about 200m.
Geographical Limits: Seen at outcrop in the Peak District of Derbyshire and Staffordshire, but also exists largely in the subsurface on the Hathern Shelf of north Leicestershire, south Derbyshire and north Staffordshire; elsewhere in eastern England it is proved in the subsurface only.
Parent Unit: Carboniferous Limestone Supergroup (CL)
Previous Name(s): Carboniferous Limestone [Obsolete entry, see Supplementary Information] (-4550)
Carboniferous Limestone Series (-2703)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The Peak District of Derbyshire and Staffordshire - see component formations for reference sections. Aitkenhead and Chisholm, 1982. 
Reference(s):
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. 
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. 
Aitkenhead, N, Chisholm, J I and Stevenson, I P. 1985. Geology of the country around Buxton, Leek and Bakewell. Memoir of the British Geological Survey, England and Wales Sheet 111. 
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). 
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). 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E099 E111 E124 E125 E141 E112