The BGS Lexicon of Named Rock Units — Result Details

Lower Lobster Member

Computer Code: LLOB Preferred Map Code: notEntered
Status Code: Full
Age range: Aptian Age (KP) — Aptian Age (KP)
Lithological Description: Pale blue grey mudstone with brown nodules (Bed 7) passing up into thin dark blue micaceous mudstone with yellow sand lenses (Bed 8), into brown sandy mudstone (Bed 9), dark blue micaceous mudstone with yellow sandy lenses (Bed 10), laminated and sporadically glauconitic brown sandy mudstone (Bed 11) and dark blue argillaceous sandstone (Bed 12).
Definition of Lower Boundary: The conformable boundary is placed (Simpson, 1985) at the base of his Bed 7, and is identified by the upward change from pale grey, poorly-laminated mudstone of the Chale Clay Member into pale blue grey mudstone with small brown nodules of the Lower Lobster Member.
Definition of Upper Boundary: Boundary placed at the upward conformable change from dark blue argillaceous sandstone of Simpson (1985) Bed 12 (top Lower Lobster Member) into the compact dark blue sandstone of Simpson (1985) Bed 13 (The Crackers Member). This boundary is gradational.
Thickness: 11.6m at the type site.
Geographical Limits: Distiguished at the type site but difficult to delimit in other outcrops.
Parent Unit: Atherfield Clay Formation (AC)
Previous Name(s): Lower Lobster Bed (-367)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  The coastal cliff section at Compton Bay [SZ 372 848], Isle of Wight. The full succession is generally visible in low cliffs at appropriate states of the tide. 
Reference Section  The coastal cliff section at Red Cliff, Sandown [SZ 626 855]. The full succession is discernable but generally it is considerably obscured by landslide. 
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(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. 
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.] 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable