The BGS Lexicon of Named Rock Units — Result Details

The Crackers Member

Computer Code: TCRS Preferred Map Code: notEntered
Status Code: Full
Age range: Aptian Age (KP) — Aptian Age (KP)
Lithological Description: Dark blue well-packed sandstone (Bed 13), overlain by harder brown sandstone (Bed 14) with seams of phosphatic nodules near the base and top of the member. Both contain a single discontinuous seam of large, fossiliferous "doggers".
Definition of Lower Boundary: Boundary placed at the upward conformable change from dark blue argillaceous sandstone of Simpson (1985) Bed 12 of the Lower Lobster Member into the dark blue well-packed sandstone of Simpson (1985) Bed 13 of The Crackers Member. This boundary is gradational.
Definition of Upper Boundary: Boundary placed at the conformable upward change from hard brown sandstone (Bed 14) of The Crackers Member into sporadically glauconitic brown sandy mudstone (Bed 15) of the Upper Lobster Member.
Thickness: 6.0m at the type site.
Geographical Limits: Isle of Wight and Dorset with equivalent beds in the Weald.
Parent Unit: Atherfield Clay Formation (AC)
Previous Name(s): Crackers Group (-2478)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  The coastal cliff section at Compton Bay [SZ 372 848], Isle of Wight. Generally showing a full succession. 
Type Section  Defined as the coastal cliff section of Chale Bay, Isle of Wight between Shepherd's Chine [SZ 4466 7982] and Whale Chine [SZ 4684 7825]. 
Reference Section  The coastal cliff section at Red Cliff, Sandown [SZ 626 855]. Showing a full succession but generally obscured by landslide debris. 
Reference(s):
Simpson, M I. 1985. The stratigraphy of the Atherfield Clay Formation (Lower Aptian, Lower Cretaceous) at the type and other localities in southern England. Proceedings of the Geologists' Association, Vol.96(1), 23-45. 
Fitton, W H. 1847. A stratigraphical account of the section from Atherfield to Rocken-end on the south-west coast of the Isle of Wight. Quarterly Journal of the Geological Society of London, Vol.3, 289-327. 
Osborne White, H J. 1921 [1994 reprint]. A short account of the geology of the Isle of Wight. Memoirs of the Geological Survey of Great Britain. 235pp. [HMSO.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable