The BGS Lexicon of Named Rock Units — Result Details

Wilmslow Sandstone Formation

Computer Code: WLSF Preferred Map Code: WlS
Status Code: Full
Age range: Olenekian Age (TO) — Olenekian Age (TO)
Lithological Description: In the Cheshire Basin and northwards into Cumbria, the formation comprises red-brown to brick-red, fine- to medium-grained, generally pebble-free, cross-bedded sandstones, with sporadic siltstones. The sand grains are well rounded and indicate an aeolian origin; in Cumbria, they are coarse- to very coarse-grained. There are thin units of fluvial sandstones that have subangular to subrounded sand grains and more common beds of mudstone. Southwards, these pass into bright orange-red to dark brick-red, generally silty or argillaceous, fine- to medium-grained, micaceous sandstones with subordinate siltstone and mudstone beds. The sand grains are subangular to subrounded and pebbles are rare.
Definition of Lower Boundary: The lower boundary, at the top of a sequence dominated by pebbly sandstones and conglomerates of the Chester Formation, is transitional. It may be taken at the highest occurrence of pebbles, either as a conglomerate or a pebbly sandstone. In Cumbria it is sharp and is taken at the upward change to typical aeolian sandstones from typical fluvial sandstones, which are finer grained and better cemented.
Definition of Upper Boundary: It is overlain unconformably by the Helsby Sandstone Formation. In Cumbria, it is placed at the top of a thick (40 to 50 m) fluvial sandstone unit that is well-cemented and overlain by coarser, less well-cemented aeolian sandstones of the Helsby Sandstone Formation. It is not a formational boundary with characteristic features on borehole geophysical logs.
Thickness: Thicknesses are variable across the country. In Cumbria the Sellafield boreholes proved 469 to 529 m. In the West Midlands and the Worcester Basin it is up to 284 m thick. In the Cheshire Basin, in the Knutsford Borehole, pebbles indicative of the Chester Formation were encountered at 1870 to 1878 m depth, giving a thickness of about 920 m for the Wilmslow Sandstone; this includes 325 m of strata below the ‘Top Silicified Zone’ which, in the EISB and regions 8 and 9, has been used to mark the base of the Wilmslow Sandstone Formation (Jackson et al., 1987).
Geographical Limits: The Wilmslow Sandstone is exposed from just south of Stourport, across the West Midlands to Stoke-on-Trent and Lichfield, from Macclesfield to Manchester and Liverpool, and as far north as Ormskirk. In Lancashire, north of Ormskirk, it cannot be distinguished from the Helsby Sandstone and Chester formations. In Cumbria it is a distinctive unit of aeolian facies with thin fluvial interbeds. It is present in the subsurface in the Worcester and Needwood basins but absent in the Wessex and Somerset basins. There is some uncertainty about its presence between the West Midlands and the Needwood Basin. It is absent to the east of the Worcester Basin and up the eastern side of England to Doncaster. North of Doncaster, the SSG is undifferentiated and the Wilmslow Sandstone Formation cannot be distinguished.
Parent Unit: Sherwood Sandstone Group (SSG)
Previous Name(s): Upper Mottled Sandstone [Obsolete Name And Code: See WLSF And WRS] (UMS)
Calder Sandstone Formation [Obsolete Name And Code Use: WLSF] (CSA)
Alternative Name(s): St Bees Sandstone Member
Smith Bank Formation
Bunter Sandstone Formation
Stratotypes:
Reference Section  Wildmoor (Wildmoor Sandstone Member), north of Bromsgrove, Worcestershire (Warrington et al., 1980). 
Reference Section  Bottom part, Sellafield Borehole 10B, Cumbria. BGS Registered No. NY00SW/40, 22.22 to 190.35 m. 
Reference Section  Sellafield Borehole 13B, Cumbria. BGS Registered No. NY00SW/42, 176.42 to 295.70 m. 
Type Area  Wilmslow-Alderley Edge area, north-east Cheshire (Taylor et al., 1963, p.61-62; Thompson, 1970; Warrington and Thompson, 1971). 
Reference(s):
Taylor, B J, Price, R H and Trotter, F M. 1963. Geology of the country around Stockport and Knutsford. Memoir of the Geological Survey of Great Britain. 
Thompson, D B, 1970. Itineries X and XI, Alderley Edge, "in" Broadhurst, F M and others. The area around Manchester. Geologists' Association Guide No.7 (Revised edition). Benhan, Colchester. p.39-51. 
Warrington, G, Audley-Charles, M G, Elliott, R E, Evans, W B, Ivimey-Cook, H C, Kent, P E, Robinson, P L, Shotton, F W and Taylor, F M. 1980. A correlation of the Triassic rocks in the British Isles. Special Report of the Geological Society of London, No.13. 
Warrington, G and Thompson, D B, 1971. The Triassic rocks of Alderley Edge, Cheshire. Mercian Geologist, Vol.4, p.69-72. 
Ambrose, K, Hough, E, Smith, N J P and Warrington, G. 2014. Lithostratigraphy of the Sherwood Sandstone Group of England, Wales and south-west Scotland. British Geological Survey Research Report, RR/14/01. 
Bachmann, G H, Geluk, M C, Warrington, G, Becker-Roman, A, Beutler, G, Hagdorn, H, Hounslow, M W, Nitsch, E, Röhling, H-G, Simon, T, and Szulc, J. 2010. Triassic. 148–173 in Petroleum Geological Atlas of the Southern Permian Basin Area. Doornenbal, J C, and Stevenson, A G (editors). (Houten: EAGE Publications b.v.) 
Cameron, T D J, Crosby, A, Balson, P S, Jeffery, D H, Lott, G K, Bulat, J, and Harrison, D J. 1992. United Kingdom offshore regional report: the geology of the southern North Sea. (London: HMSO for the British Geological Survey.) 
Cameron, T D J. 1993. 4 Triassic and Permian of the central and northern North Sea, in Knox, R W O'B and Cordey, W G, (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. 
Chadwick, R A, Jackson, D I, Barnes, R P, Kimbell, G S, Johnson, H, Chiverell, R C, Thomas, G S P, Jones, N S, Riley, N J, Pickett, E A, Young, B, Holliday, D W, Ball, D F, Molyneux, S G, Long, D, Power, G M and Roberts, D H. 2001. Geology of the Isle of Man and its offshore area. British Geological Survey Research Report, RR/01/06. 
Jackson, D I and Johnson, H, 1996. Lithostratigraphic nomenclature of the Triassic, Permian and Carboniferous of the UK offshore East Irish Sea Basin, British Geological Survey, Nottingham. 
Jackson, D I, Mulholland, P, Jones, S M and Warrington, G, 1987. The geological framework of the East Irish Sea Basin. 191-203 in Brooks J and Glennie, K (editors), Petroleum Geology of North West Europe. [Graham and Trotman.] 
Johnson, H, Warrington, G and Stoker, S J. 1994. Permian and Triassic of the Southern North Sea. In Knox, R W O'B and Cordey, W G (editors), Lithostratigraphic nomenclature of the UK North Sea. [Nottingham: British Geological Survey.] 
Mitchell, G H, Pocock, R W, and Taylor, J H. 1962. Geology of the country around Droitwich, Abberley and Kidderminster. Memoir of the Geological Survey of Great Britain, Sheet 182 (England and Wales). 
Warrington, G. 2010. Alderley Edge district, Cheshire. 182–190 in Mineralisation of England and Wales. Geological Conservation Review Series, No. 36. (Peterborough: Joint Nature Conservation Committee.) 
Whitehead, T H and Pocock, R W. 1947. Geology of the country around Dudley and Bridgnorth. Memoir of the British Geological Survey, Sheet 167. (England and Wales). 
Hounslow, M W, and Ruffell, A H. 2006. Triassic: seasonal rivers, dusty deserts and saline lakes. 295–324 in The Geology of England and Wales (2nd edition). Brenchley, P J, and Rawson, P F (editors). (London: The Geological Society.) 
Jones, N S, and Ambrose, K. 1994. Triassic sandy braidplain and aeolian sedimentation in the Sherwood Sandstone Group of the Sellafield area, west Cumbria. Proceedings of the Yorkshire Geological Society, Vol. 50, 61–76. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E123 E151 E137 E096