| Computer Code: |
STCK |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Campanian Age (KC)
— Campanian Age (KC) |
| Lithological Description: |
Marl-free, soft chalk with large irregular flints. |
| Definition of Lower Boundary: |
The lower boundary is conformable at a marly bed with included marl, above which the chalk is marl-free in the Alum Bay/Scratchell's Bay section on the Isle of Wight and at "the lower horizon of yellow-stained chalk on Old Harry Rock" in Studland Bay, Dorset (Gale et al., 1987). It is not discernible from the published literature whether these two beds are in the same stratigraphical position. This doubt, together with the lack of exposure and geomorphological expression of the member, has led to the BGS reverting to the original concept of the Portsdown Chalk Member (Bristow, Mortimore and Wood, 1997). This is also the position stated in Rawson, Allen and Gale (2001) and thus the Portsdown Chalk Formation covers all of the chalk up to the sub-Palaeogene erosion surface. |
| Definition of Upper Boundary: |
The upper boundary is the sub-Palaeogene unconformity in the Southern Province. Relationship to the Upper Campanian and Maastrichtian chalks of the northeast "Transitional" Province is poorly understood due to poor exposure. |
| Thickness: |
Up to 23 m preserved beneath the sub-Palaeogene unconformity in Alum Bay on the Isle of Wight. |
| Geographical Limits: |
Limited to the Isle of Wight and the Swanage area of Dorset in the Southern Province. Might have lateral equivalents in Norfolk. |
| Parent Unit: |
Portsdown Chalk Formation (PCK)
|
| Previous Name(s): |
Studland Chalk [Obsolete Name and Code: Use STCK]
(-4902)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Within the cliff section in Studland Bay between Old Harry Rocks [SZ 055 825] and the Palaoegene contact [SZ 045 824]. Access difficult other than by boat. |
| Reference Section |
The cliff sections within Alum and Scratchell's Bay, Isle of Wight. Access by boat to Scratchell's Bay and traverse around Needles Headland only possible at exceptionally low tides. |
| Reference(s): |
| 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 |
| 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. |
| Gale, A S, Wood, C J and Bromley, R G. 1987. The lithostratigraphy and marker bed correlation in the White Chalk (Cenomanian-Campanian) of southern England. Mesozoic Research, Vol.1, 107-118. |
| Bristow, C R, Mortimore, R N, and Wood, C J. 1999. "Lithostratigraphy for mapping the chalk in southern England" by Bristow et al. (1997): discussion. Proceedings of the Geologists' Association, Vol. 110, 68-72. |
| Rawson, P F, Allen, P M and Gale, A. 2001. A revised lithostratigraphy for the Chalk Group. Geoscientist, Vol.11, p.21. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
