The BGS Lexicon of Named Rock Units — Result Details
Windlesham Formation
| Computer Code: | WIDS | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Lutetian Age (GL) — Lutetian Age (GL) | ||
| Lithological Description: | The typical lithologies of the Windlesham Formation are bioturbated dark green to brown, fine- to medium-grained sands with sand-sized glauconite grains, silts and white, yellow or brown clay, overlain by organic dark grey clay with lenticles of fine sand, and then by glauconitic sand and sandy clayey silt. There are occasional layers of flint gravel, and a prominent gravel bed occurs at the top. Teeth and bones of marine vertebrates occur as do marine bivalve molluscs, although occurrences above the water table generally have been decalcified (Curry, 1958; Hawkins, 1954). Marine: inner shelf ranging up to marginal. Eocene (early to mid Lutetian) (King, in prep.). | ||
| Definition of Lower Boundary: | The base of the Windlesham Formation is taken at an interburrowed omission surface on the top of the Swinley Clay Member, or on sands of the Bagshot Formation, marking an upwards change from a dominantly sandy sequence without glauconite to a darker-coloured sandy sequence with glauconite. | ||
| Definition of Upper Boundary: | The top of the Windlesham Formation is marked by the upwards change from dark-coloured sand and sandy, clayey silt to fairly homogeneous, yellow-brown silty fine-grained sands of the Camberley Sand Formation, probably at an omission surface (King, in prep.). | ||
| Thickness: | Up to 25 m (Ellison and Williamson, 1999). | ||
| Geographical Limits: | The Windlesham Formation is present in the core of the western London Basin around the junction of Surrey, Berkshire and Hampshire. | ||
| Parent Unit: | Bracklesham Group (BRB) | ||
| Previous Name(s): | Bracklesham Beds [Obsolete Name and Code: Use WIDS, BRB]
(-2010)
Middle Bagshot Beds [Obsolete Name And Code] (BGBM) Bracklesham Beds [Obsolete Name and Code: Use WIDS, BRB] (-2010) |
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| Alternative Name(s): | Marsh Farm Formation Earnley Sand Formation |
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| Stratotypes: | |||
| Type Section | BGS Bracknell Borehole (SU86NE 42) [SU 8888 6547] between 16.2 and 28.9 m depth (Ellison and Williamson, 1999, fig. 6). | ||
| Reference Section | BGS Farnborough (Mytchett) Borehole 1 (SU85NE 184) [SU 8830 5541] 41.86 to 56.57 m (Ellison et al., 2002, fig. 6). | ||
| Reference Section | BGS Farnborough (Mytchett) Borehole 2 (SU85NE 185) [SU 8833 5539] 55.2 to 60.0 m (Ellison et al., 2002, fig. 6). | ||
| Reference(s): | |||
| King, C. in prep. A revised correlation of Palaeogene and Neogene deposits in the British Isles. Geological Society of London Special Report. | |||
| Hawkins, H L. 1954. The Eocene succession in the eastern part of the Enborne valley, on the borders of Berkshire and Hampshire. Quarterly Journal of the Geological Society, London, Vol. 110, 409-430. | |||
| Prestwich, J, 1847. On the main points of structure and the probable age of the Bagshot Sands and on their presumed equivalents in Hampshire and France. Quarterly Journal of the Geological Society, Vol.3, p.378-409. | |||
| 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. | |||
| Aldiss, D T. 2014. The stratigraphical framework for the Palaeogene successions of the London Basin, UK. British Geological Survey Open Report OR/14/008. 95 pp. | |||
| Curry, D. 1958. Part 3a XII Palaeogene. Lexique Stratigraphique International. Whittard, W F, and Simpson, S (editors). Vol. 1 Europe (Paris: Centre Nationale de la Research Scientifique.) | |||
| Dewey, H, and Bromehead, C E N. 1915. The geology of the country around Windsor and Chertsey. Memoir of the Geological Survey of Great Britain, Sheet 269 (England and Wales). | |||
| Edwards, R A and Freshney, E C. 1987. Lithostratigraphical classification of the Hampshire Basin Palaeogene Deposits (Reading Formation to Headon Formation) Tertiary Research, Vol.8, 43-73. | |||
| Ellison, R A and Williamson, I T. 1999. Geology of the Windsor and Bracknell district - a brief explanation of the geological map. Sheet Explanation of the British Geological Survey. 1:50 000 Sheet 269 Windsor (England and Wales). | |||
| Ellison, R A, Williamson, I T and Humpage, A J. 2002. Geology of the Guildford district - a brief explanation of the geological map. Sheet explanation of the British Geological Survey. 1:50 000 Sheet 285 Guildford (England and Wales). | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E284 E283 E269 E285 E268 | |||