The BGS Lexicon of Named Rock Units — Result Details

Pennine Coal Measures Group

Computer Code: PCM Preferred Map Code: PCM
Status Code: Full
Age range: Westphalian Stage (CW) — Westphalian Stage (CW)
Lithological Description: The Pennine Coal Measures Group (Coal Measures facies) accumulated in the broad Pennine Basin. Subsequent tectonism separated the Coal Measures into smaller coalfields at outcrop, and at depth beneath the Permo-Triassic strata (Ramsbottom et al., 1978). Historically, 'Coal Measures' has been used as a chronostratigraphical term synonymous with the combined Westphalian and Stephanian strata. However, the name, Pennine Coal Measures Group, has recently been defined lithostratigraphically to describe the main body of coal-bearing strata in the Westphalian succession (Powell et al., 2000). The group is divided into three formations, Pennine Lower Coal Measures, Pennine Middle Coal Measures and Pennine Upper Coal Measures (following Stubblefield and Trotter, 1957). The group comprises cyclothems of alternating sandstone, siltstone and grey mudstone, with frequent coal seams, ironstone nodules or beds and seatearth (palaeosol) horizons. The base of the cycle is marked by grey mudstones, commonly recognised as nonmarine bands, or less commonly as marine bands. Both are of importance in correlation of the strata. Sandstones are typically very fine to fine grained, commonly overlain by leached ganisters or unleached grey seatearths. There is a general upwards decrease in the number and thickness of marine bands and contrasting increase in the importance of coals and seatearths from the Millstone Grit into the overlying Coal Measures. Marine bands are dominated by foraminifera, Lingula sp., fish remains and shallow marine benthic productid fauna. In the Northumberland-Durham Coalfield, the Millstone Grit facies with sheet-like coarse-grained sandstones (including the 'Third Grit'), common marine bands and thin coals persists into the Langsettian. The Pennine Upper Coal Measures of the Canonbie Coalfield is typically reddened secondarily. The fluviodeltaic Coal Measures facies represents wetland forest and soils (coal and seatrock), floodplain (plant-rich or rooted siltstone and mudstone), river and delta distributary channel (thick sandstones), prograding deltas (upward-coarsening sequences) and shallow lakes (mudstones with nonmarine faunas). Marine bands are less common generally than in the Millstone Grit facies. The Pennine Coal Measures Group is entirely Westphalian in age.
Definition of Lower Boundary: Over much of the Pennine Basin the group rests conformably upon the Millstone Grit Group. Along the southern margin of the basin, the Coal Measures overstep the Millstone Grit and lie unconformably upon pre-Carboniferous strata of the Wales-Brabant High. The base of the group is taken as the base of the Subcrenatum Marine Band or at the base of the coal-bearing sequence if this marker band cannot be identified, as defined by Stubblefield and Trotter (1957). The bases of the Pennine Middle and Pennine Upper Coal Measures are taken at the base of the Vanderbeckei and Cambriense marine bands, respectively. In Northern England, the base of the group generally rests conformably upon the Yoredale Group. However, in the Canonbie Coalfield there is an unconformity at the base of the group. In the north-west of this coalfield, the Pennine Upper Coal Measures also rest unconformably upon the Pennine Middle Coal Measures.
Definition of Upper Boundary: The top of the group has been defined as the base of lowest, conformably overlying, major red-bed formation of the Warwickshire Group (Powell et al., 2000), in the south of the Pennine Basin, or the Permo-Triassic unconformity, elsewhere.
Thickness: The thickest development of the group is up to 1900 m near Manchester, located in the depocentre of the Pennine Basin. Cyclic sequences in the Coal Measures are thinner (tens of metres) and more numerous than in the underlying Millstone Grit. The Pennine Coal Measures Group in the main area of the Northumberland-Durham coalfield is up to 900 m thick. In west Cumbria, the group is between 300 and 400 m thick, thickening offshore to the north-west into the Solway Basin. In the Canonbie Coalfield, the group is about 1000 m thick, with a westward thinning and overstep of the Coal Measures onto a structural high. About 800 m of this succession belongs to the Pennine Upper Coal Measures.
Geographical Limits: Central and Northern England and North Wales.
Parent Unit: Coal Measures Supergroup (COME)
Previous Name(s): Coal Measures Group (CM)
Bettisfield Formation [Obsolete Name and Code: Use PCM] (BTD)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Base and lower part: Ridgeway Borehole, Stoke-on-Trent (SJ85SE/14) from 1806 ft 10 ins (550.7 m) depth to the surface. 
Reference Section  Middle and Upper Coal Measures: Parkhouse Colliery No.1 Underground Borehole, Stoke-on-Trent (SJ85SW/19), where the top of the Cambriense Marine Band, at 529 ft (161.2 m) depth in the bore, marks the boundary. 
Type Area  Potteries Syncline, Stoke-on-Trent, North Staffordshire numerous borehole and shaft sections but few good exposures. 
Reference Section  Upper part and top: Wolstanton Colliery no.3 Shaft Stoke-on-Trent (SJ84NE/29), from 1142 ft 7 ins (348.2 m) to the base of shaft. 
Reference Section  Boundary between Lower and Middle Coal Measures: Miry Wood, Apedale, Stoke-on-Trent, listed as Locality C on map SJ84NW (Silverdale) 1991, with the base of the Vanderbeckei Marine Band as the boundary. Intended to become a designated RIGS site. 
Reference(s):
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. 
Chisholm, J I, Waters, C N, Hallsworth, C R, Turner, N, Strong, G E, and Jones, N S. 1996. Provenance of Lower Coal Measures around Bradford, West Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 51, 153-166. 
Guion, P D, and Fielding, C R. 1988. Westphalian A and B sedimentation in the Pennine Basin, UK. 153-177 in Sedimentation in a synorogenic basin complex: the Upper Carboniferous of north-west Europe. Besly, B M, and Kelling, G (editors). (Glasgow and London: Blackie.) 
Guion, P D, Fulton, I M, and Jones, N S. 1995. Sedimentary facies of the coal-bearing Westphalian A and B north of the Wales-Brabant High. 45-78 in European coal geology. Whateley, M K G, and Spears, D A (editors). Geological Society of London Special Publication, No. 82. 
Hallsworth, C R, and Chisholm, J I. 2000. Stratigraphic evolution of provenance characteristics in Westphalian sandstones of the Yorkshire Coalfield. Proceedings of the Yorkshire Geological Society, Vol. 53, 43-72. 
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. 
Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) 
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. 
Chisholm, J I, 1990. The Upper Band-Better Bed sequence (Lower Coal Measures, Westphalian A) in the central and south Pennine area of England. Geological Magazine, Vol.127, 55-74. 
Powell, J H, Chisholm, JI, Bridge, D M, Rees, J G, Glover, B W and Besly, B M. 2000. Stratigraphical framework for Westphalian to Early Permian red-bed successions of the Pennine Basin. British Geological Survey Technical Report WA/99/10. 
Ramsbottom, W H C, Calver, M A, Eagar, R M C, Hodson, F, Holliday, D W, Stubblefield, C J and Wilson, R B. 1978. A correlation of the Silesian rocks in the British Isles. Geological Society of London, Special Report No.10. 
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:
E009 E010 E011 E012 E014 E015 E018 E019 E020 E021 E022 E023 E026 E027 E028 E031 E032 E049 E050 E051 E052 E059 E060 E062 E068 E069 E070 E075 E076 E077 E078 E084 E085 E086 E087 E097 E098 E099 E100 E105 E107 E108 E110 E111 E112 E121 E123 E124 E125 E126 E137 E139 E141 E152 E153 E154 E155 E166 E167 E168 E169 E181 E182 E024