The BGS Lexicon of Named Rock Units — Result Details

Spetisbury Chalk Member

Computer Code: SPCH Preferred Map Code: SpCk
Status Code: Full
Age range: Campanian Age (KC) — Campanian Age (KC)
Lithological Description: Firm white chalk with regular large flint seams, some tabular in lower part and of Zoophycus type in the upper part.
Definition of Lower Boundary: The lower boundary is conformable (but see comments re. thickness). Inferred to be at the Whitecliff Wispy Marls (at Whitecliff Bay) at the boundary between the Sompting and Whitecliff beds of Mortimore (1986). In mapping terms taken just below a marked feature break that is thought to be formed by either a hardground or a thick bed of flints.
Definition of Upper Boundary: The upper boundary is conformable at the Portsdown Marl 1 in the Farlington Redoubt on Portsdown and at Whitecliff Bay, Isle of Wight.
Thickness: 30m at Whitecliff Bay; thought to be as thick as 45m in Dorset and around 35m in Hampshire.
Geographical Limits: Limited to Sussex, Hampshire, Wiltshire and Dorset and as widely spaced outliers to the north of the Pewsey/Kingsclere structure in the Southern Province. Its possible occurrence and distribution beneath the Quaternary deposits of East Anglia in the Transitional Province is not well known.
Parent Unit: Culver Chalk Formation (CUCK)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Equivalent To The Upper Part Of The Culver Chalk
Type Area  The member crops out over a wide area near Spetisbury, Dorset. 
Type Section  Within the quarry face of Bushes Pit, Bushes Farm, 1.25km northnorthwest of Winterborne Zelstone. 
Reference Section  Whitecliff Bay cliffs on the Isle of Wight. 
Barton, C M. 1991. Geology of the Blandford Forum district (Dorset). British Geological Survey Technical Report, WA/91/81. 
Bristow, C R. 1993. Geology of the Milborne St Andrew - Winterborne Kingston area (Dorset). British Geological Survey Technical Report, WA/93/18. 
Mortimore, R N. 1986. Stratigraphy of the Upper Cretaceous White Chalk of Sussex. Proceedings of the Geologists' Association, Vol.97(2), 97-139. 
Bristow, C R, Mortimore, R N and Wood C J. 1997. Lithostratigraphy for mapping the Chalk of southern England. Proceedings of the Geologists' Association, Vol.108(4), 293-315. 
Bristow, C R. 1987. The geology of sheets ST90SW and ST90SE (Shapwick-Pamphill, Dorset). British Geological Survey Technical Report, WA/93/86. Revised 1993. 
Rawson, P F, Allen, P M and Gale, A. 2001. A revised lithostratigraphy for the Chalk Group. Geoscientist, Vol.11, p.21. 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H C, and Taylor, R T. 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey, Sheet 313 (England and Wales). 
Hopson, P M. 2005. A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland, with statements on the Chalk of Northern Ireland and the UK Offshore Sector. British Geological Survey Research Report RR/05/01 102pp. ISBN 0 852725175 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E313 E314 E327 E341 E342 E343