The BGS Lexicon of Named Rock Units — Result Details
Blisworth Clay Formation
| Computer Code: | BWC | Preferred Map Code: | BwC |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Bathonian Age (JN) — Bathonian Age (JN) | ||
| Lithological Description: | Silicate-mudstone, grey, commonly variegated purplish red, yellow and green, poorly bedded to blocky. Commonly contains fossil rootlets and sideritic ironstone nodules, and locally with impersistant beds and lenses of argillaceous limestone including (mainly in the south) shell fragmental wackestones, packstones and grainstones, and (mainly in the north) sandstone. Mudstone weathers to highly plastic clay. | ||
| Definition of Lower Boundary: | Sharp but generally more or less conformable contact: limestone of the Blisworth Limestone Formation (or locally, near its northern limit, bluish and greenish grey variably shelly mudstones of the Rutland Formation) overlain by grey or variegated mudstone. | ||
| Definition of Upper Boundary: | Sharp, generally disconformable contact: grey or variegated mudstone overlain by bioclastic limestone of the Cornbrash Formation or (very locally near its northern limit) by mudstone and sandstone of the Kellaways Formation. | ||
| Thickness: | 0 to c. 10 m; typically 2 to 4 m throughout most of its range. | ||
| Geographical Limits: | East Midlands Shelf, from just north of Milton Keynes, northwards to the Humber area where it is (probably) overstepped by the Cornbrash Formation. | ||
| Parent Unit: | Great Oolite Group (GOG) | ||
| Previous Name(s): | Glentham Formation
(GLF)
Great Oolite Clay [Obsolete Name And Code: See Blisworth Clay, BWC] (GOC) Blisworth Clay Member [Obsolete Name and Code: Use BWC] (-4507) |
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| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | Blisworth, Northamptonshire. See Sharp, 1870; Arkell, 1933 (NB: name derives from Sharp's description of a quarry near Blisworth, though in fact the unit he described is probably not the Blisworth Clay as currently defined.) | ||
| Reference Section | Ketton Quarry, 2.6 km north of Ketton, Rutland, near Stamford, Lincolnshire. Full sequence exposed, 5.07 m thick (Hudson and Clements, 2007, pp.254-257). | ||
| Reference Section | M1 Motorway cutting, southsoutheast of Portfields Farm, Newport Pagnell. See Horton and others, 1974. | ||
| Type Section | Thrapston Quarry, 1 km southsoutheast of Thrapston, Northamptonshire. Formerly fully exposed (2.5 m thick), now at least partly obscured. Cox and Sumbler, 2002, p.264; Cripps, 1986. | ||
| Reference(s): | |||
| Barron, A J M, Lott, G K, and Riding, J B. 2012. Stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf. British Geological Survey Research Report RR/11/06. | |||
| 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. | |||
| Arkell, W J. 1933. The Jurassic System in Great Britain (Oxford: Clarendon Press.) | |||
| Sharp, S. 1870. The Oolites of Northamptonshire, Part 1. Quarterly Journal of the Geological Society of London, Vol. 26, 354-391. | |||
| Hudson, J D and Clements, R G. 2007. The Middle Jurassic Succession at Ketton, Rutland. Proceedings of the Geologists' Association, Vol 118, 239-264. | |||
| Sumbler, M G. 2003. In Leicestershire and Rutland Geodiversity Action Plan. British Geological Survey Commissioned Research Report CR/04/063N. | |||
| Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] | |||
| Cripps, D W. 1986. A facies analysis of Upper Great Oolite Group in Central and Eastern England. (University of Aston in Birmingham: Unpublished PhD thesis.) | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E114 E103 E102 E115 E127 E128 E143 E144 E157 E158 E159 E171 E172 E186 E187 E188 E202 E203 E204 E217 E220 E089 | |||