The BGS Lexicon of Named Rock Units — Result Details

Coal Measures Group [Obsolete Except In Northern Ireland: Use PCM, SWCM, CMSC]
Computer Code: CM Preferred Map Code: CM
Status Code: Full
Age range: Westphalian Age (CW) — Westphalian Age (CW)
Lithological Description: Alternation of sandstone, grey siltstone and grey mudstone, with frequent coal seams and seatearth horizons. NOTE: Definitions for the base of the Coal Measures, and the bases of the Middle and Upper divisions, are those of Stubblefield and Trotter (1957), but the top of the Coal Measures in the Pennine Basin is newly defined on a purely lithostratigraphical basis, (Powell et al., 1999). In areas such as South Wales, where no significant Carboniferous red-beds overlie the coal-bearing measures, the top of the Coal Measures may be defined differently.
Definition of Lower Boundary: Base of Gastrioceras subcrenatum Marine Band (=Subcrenatum Marine Band) or at base of coal-bearing sequence if this marker band cannot be identified.
Definition of Upper Boundary: Base of lowest conformably overlying red-bed formation - Etruria Marl or lateral equivalent.
Thickness: Up to 1600m in the Potteries Syncline; to c.1900m in Lancashire.
Geographical Limits: Britain, except Devon and Cornwall, and parts of Ireland for the Group; England and Wales for divisions LCM, MCM and UCM.
Parent Unit: Not Applicable (-)
Previous Name(s): Productive Coal Measures (-1446)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  For base and lower part. Ridgeway Borehole (SJ85SE/14) from surface to 1806ft 10ins. 
Reference Section  For boundary between Middle and Upper Coal Measures. Parkhouse Colliery No.1 Underground Borehole (SJ85SW/19): top of Cambriense Marine Band, at 529ft depth in bore, is boundary. 
Reference Section  For top and upper part. Wolstanton Colliery No.3 Shaft (SJ84NE/29) from 1142ft 7ins to base of shaft. 
Reference Section  For boundary between Lower and Middle Coal Measures. Mirywood: Locality C on map SJ84NW: to become a designated RIGS; base of Vanderbeckei Marine Band is boundary. 
Type Area  Pennine coalfields. Full development in Potteries Syncline, with numerous borehole and shaft sections but few good exposures. (Rees and Wilson, 1998). 
Reference(s):
Rees, J G and Wilson, A A. 1998. Geology of the country around Stoke-on-Trent. Memoir of the British Geological Survey, Sheet 123 (England and Wales). 
Besley B M, 1988. Palaeogeographic implications of late Westphalian to early Permian red-beds, central England. "In" Sedimentation in a synorogenic basin complex. Besley B M and Kelling, G, editors. 
Powell, J H, Chisholm, J I, Bridge D M, Rees, J G, Glover, B W and Besly, B M, 1999. Stratigraphical framework for Westphalian to Early Permian red-bed successions of the Pennine Basin. British Geological Survey Technical Report, WA/99/101. 
Whitehead, T H and Pocock, R W, 1947. Dudley and Bridgnorth. Memoir of the Geological Survey of Great Britain. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E024 E261 E262 E245 E231 E232 E234 E233 E107 N35 E055 E065 E064 E072 E080 E089 E018 S013 E103 E115 E128 E201 E217 E235 E236 E237 E268 E167 S039 E273 E274 E246 E049
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