The BGS Lexicon of Named Rock Units — Result Details

Pennine Lower Coal Measures Formation and South Wales Lower Coal Measures Formation (Undifferentiated)

Computer Code: PSLCM Preferred Map Code: notEntered
Status Code: Full
Age range: Langsettian Substage (CA) — Langsettian Substage (CA)
Lithological Description: Interbedded grey mudstone, siltstone and pale grey sandstone, commonly with mudstones containing marine fossils in the lower part, and more numerous and thicker coal seams in the upper part.
Definition of Lower Boundary: At the base of the dark grey, fissile mudstone of the Subcrenatum Marine Band with eponymous fossils (as defined by Stubblefield and Trotter, 1957), or at the base of the lowest coal of the coal-bearing sequence if this marker cannot be recognised. Typically, the unit rests conformably upon the Rossendale Formation (Millstone Grit Group) in central and northern England. However, in north, west and east Cumbria, the Solway Basin (except the Canonbie area), the Stainmore and Northumberland troughs, on the Alston Block and in northeast Northumberland, the formation overlies conformably the repetitive mudstones, siltstones, sandstones, thin limestones and thin coals of the Stainmore Formation (Yoredale Group). In the Canonbie Coalfield, the formation is underlain unconformably by the Alston Formation (Yoredale Group). In South Wales and Bristol-Somerset coalfields the Subcrenatum Marine Band conformably overlies the topmost mudstones or sandstones of the Marros Group. The unit rests unconformably on Visean, Tournaisian, or Devonian strata in the Berkshire and Kent coalfields.
Definition of Upper Boundary: At the base of the mudstone of the Vanderbeckei Marine Band with eponymous fossils (as defined by Stubblefield and Trotter, 1957), where basal fossiliferous, marine mudstone of the marine band comformably overlies the top of the Pennine and South Wales Lower Coal Measures.
Thickness: Up to 650 m thick in the North Staffordshire (Potteries) Coalfield, and 720 m thick in Lancashire and 100 m in the Canonbie Coalfield. c. 80 m on the east crop of the South Wales Coalfield to c.300 m in the Swansea area and from about 160 m in the Bristol district to 200 m in the Somerset Coalfield and 63m thick in the Kent Coalfield.
Geographical Limits: The unit is present at crop and in the subsurface over extensive parts of central and northern England, North Wales and the north Isle of Man, the South Wales Coalfield and Pembrokeshire Coalfield, across the Bristol-Somerset coalfields and is present in the subsurface in the Berkshire and Kent coalfields.
Parent Unit: none recorded or not applicable
Previous Name(s): Grey Measures Of Yorkshire And Nottingham [Obsolete Name And Code: See PLCM And PMCM] (GRM)
Lower Coal Measures (-1759)
Alternative Name(s): Pennine Lower Coal Measures Formation
South Wales Lower Coal Measures Formation
Stratotypes:
none recorded or not applicable
Reference(s):
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. 
Stubblefield, C J and Trotter, F M, 1957. Divisions of the Coal Measures on Geological Survey Maps of England and Wales. Bulletin of the Geological Survey of Great Britain, No.13, p.1-5. 
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. 
British Geological Survey. 2007. Bedrock Geology UK North. 1:625 000 scale (Keyworth, Nottingham: British Geological Survey). 
British Geological Survey. 2007. Bedrock Geology UK South. 1:625 000 scale (Keyworth, Nottingham: British Geological Survey). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable