The BGS Lexicon of Named Rock Units — Result Details

Warwickshire Group

Computer Code: WAWK Preferred Map Code: Wk
Status Code: Full
Age range: Duckmantian Substage (CB) — Autunian Stage (CUT)
Lithological Description: The group includes the red-bed formations and the relatively coal-poor, grey formations that overlie the Pennine Coal Measures Group. The succession is divided into formations, many of which can be correlated between coalfields; others are geographically restricted. In south Staffordshire, the typical succession is Etruria, Halesowen, Salop and Clent formations. In Warwickshire, where the Clent Formation is not developed, the Tile Hill Mudstone Formation rests conformably upon the Salop Formation. In Northern England the Whitehaven Sandstone Formation is recognised in north and west Cumbria. In the Canonbie Coalfield, a broadly upward-coarsening, primary red-bed succession is now considered to represent the Warwickshire Group and three new formations have been proposed, in ascending order: Eskbank Wood, Canonbie Bridge Sandstone and Beckless Sandstone formations. A geographically restricted barren red measures succession is present above the Cambriense Marine Band in both the east crop of the South Wales Coalfield (Deri Formation) and the Bristol Coalfield (Winterbourne Formation). A younger, barren red measures succession is present in the Forest of Dean (Trenchard Formation). The overlying Pennant Sandstone Formation extends across the South Wales, Bristol and Forest of Dean coalfields at outcrop and the subsurface Oxfordshire and Berkshire coalfields. The formation is subdivided into members using marker coal seams. The Grovesend Formation within the Bristol and Oxfordshire-Berkshire coalfields is associated with alternating thicknesses of coal-bearing grey measures and barren red measures, defined as separate members. Distinct sandstone- and mudstone-dominated formations cannot be recognised within the subsurface Kent Coalfield. Predominantly red, brown or purple-grey sandstone, siltstone and mudstone, some grey strata, coals not common, local conglomerates, localised beds of Spirorbis limestone. The Warwickshire Group ranges in age from Westphalian (Duckmantian) to Early Permian (Autunian).
Definition of Lower Boundary: The lower boundary is taken generally at the base of the lowest red-bed formation (generally Etruria Formation) of late Carboniferous age. There is commonly a passage by alternation from grey strata of the Coal Measures into red strata of the Etruria Formation. Locally, the base is erosional (Symon Unconformity) in Warwickshire, Coalbrookdale and Lincolnshire. In north and west Cumbria the group unconformably overlies the Pennine Coal Measures Group and comprises a red-bed succession. The base of the Warwickshire Group in the east crop of the South Wales Coalfield and the Bristol Coalfield is taken at the conformable and diachronous base of the barren red-bed successions of the Deri or Winterbourne formations, respectively. Farther to the north, within the Forest of Dean Coalfield, the base of the group is taken at the base of the Trenchard Formation, which rests unconformably upon Visean and older strata. Elsewhere within the South Wales, Somerset and Oxfordshire-Berkshire coalfields, the base of the Warwickshire Group is taken at the base of the Pennant Sandstone Formation. This boundary is markedly diachronous, placed at the base of the first thick sandstone of Pennant type, occurring at younger levels towards the north. In the South Wales Coalfield (except the east crop) the Somerset Coalfield and Berkshire Coalfield the Pennant Sandstone Formation rests conformably upon strata of the South Wales Coal Measures Group. In the Oxfordshire Coalfield, the Warwickshire Group rests unconformably upon strata of Devonian or older age. In the Kent Coalfield the group rests, above a non-sequence, on South Wales Upper Coal Measures; strata associated with the A. phillipsii Biozone are absent (Ramsbottom et al., 1978).
Definition of Upper Boundary: The upper boundary of the group is taken at the base of unconformable (post-Variscan) Permian, or younger strata.
Thickness: The group is about 1225 m thick in the Warwickshire Coalfield. In north and west Cumbria the group is at least 300 m thick, whereas in the Canonbie Coalfield the group is up to 500 m thick. The Warwickshire Group is thickest, up to 1600 m, in the Swansea area of the South Wales Coalfield, decreasing to less than 650 m in the east crop of the same coalfield and within the Forest of Dean Coalfield. The Warwickshire Group is about 1000 m thick near Bristol and in the concealed Oxfordshire Coalfield, thinning northwards toward the southern flank of the Wales-Brabant High. In the concealed Kent Coalfield the group is about 600 m thick.
Geographical Limits: The group is present along the southern margin of the Pennine Basin, notably in Warwickshire, the type area, the West Midlands and north Wales. The group is also proved in the subsurface in Lancashire, South Yorkshire, Nottinghamshire and Lincolnshire.
Parent Unit: Not Applicable (-)
Previous Name(s): Barren Measures Group [Obsolete Name and Code: Use WAWK] (BME)
Ardwick Group [Obsolete Name and Code: Use WAWK] (ARG)
Red Measures [Obsolete Name and Code: Use WAWK] (-599)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The Warwickshire Coalfield from Tamworth [SK 2203] to Warwick [SP 2865]. 
Reference(s):
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. 
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. 
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. 
Besly, B M and Cleal, C J, 1997. Upper Carboniferous stratigraphy of the West Midlands (UK) revised in the light of borehole geophysical logs and detrital compositional suites. Geological Journal 32, 85 - 118. 
Davies, J R, Wilson, D and Williamson, I T. 2004. Geology of the country around Flint. Memoir for 1:50 000 Geological Sheet 108. 
Eastwood, T, Dixon, E E L, Hollingworth, S E, and Smith, B. 1931. The geology of the Whitehaven and Workington District. Memoir of the Geological Survey of Great Britain, Sheet 28 (England and Wales). 
Eastwood, T, Hollingworth, S E, Rose, W C C, and Trotter, F M. 1968. Geology of the country around Cockermouth and Caldbeck. Memoir of the Geological Survey of Great Britain, England and Wales, Sheet 23. 
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. 
Butterworth, M A, and Smith, A H V. 1976. The age of the British Upper Coal Measures with reference to their miospore content. Review of Palaeobotany and Palynology, Vol. 22, 281-306. 
Clayton, G, Coquel, R, Doubinger, J, Gueinn, K J, Loboziak, S, Owens, B, and Streel, M. 1977. Carboniferous miospores of western Europe: illustration and zonation. Mededelingen Rijks Geologische Dienst, Vol. 29, 1-71. 
Cleal, C J. 1984. The recognition of the base of the Westphalian D Stage in Britain. Geological Magazine, Vol. 121, 125-129. 
Smith, A H V, and Butterworth, M A. 1967. Miospores in coal seams of the Carboniferous of Great Britain. Palaeontological Association, London, Special Papers in Palaeontology, Vol. 1, 1-324. 
Waters, C N, Glover, B W, and Powell, J H. 1994. Structural synthesis of south Staffordshire, UK: implications for the Variscan evolution of the Pennine Basin. Journal of the Geological Society of London, Vol. 151, 697-713. 
Waters, C N, Glover, B W, and Powell, J H. 1995. Discussion on structural synthesis of south Staffordshire, UK: implications for the Variscan evolution of the Pennine Basin. Journal of the Geological Society of London, Vol. 152, 197-200. 
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. 
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:
E084 E085 E097 E098 E108 E109 E121 E122 E123 E137 E138 E139 E152 E153 E154 E155 E166 E167 E168 E169 E183