The BGS Lexicon of Named Rock Units — Result Details

Worbarrow Tout Member

Computer Code: WOT Preferred Map Code: WoT
Status Code: Full
Age range: Berriasian Age (KR) — Berriasian Age (KR)
Lithological Description: In south central Dorset, the lower part of the member contains prominent brown-weathering limestones containing detrital quartz (Hard Cockle Beds) and exhibiting abundant ripple cross-laminations. The rest of the member comprises characteristic, regularly interbedded, white-weathering micrite and dark grey mudstone (Soft Cockle and Marly Freshwater beds). Salt pseudomorphs, hard grounds and rare algal laminations are present in the micrites, particularly in the middle part of the member. Algal lamination increases in significance in the east and may be associated with zones of multiple hardgrounds. Gypsum is present at Worbarrow Tout and Durlston Bay. The highest part of the member comprises thicker-bedded, chert-rich micrites (Cherty Freshwater Beds).
Definition of Lower Boundary: The base is conformable and is marked by the first occurrence of significant, commonly ripple cross-laminated, quartz-detrital limestone (base Hard Cockle Beds) above mudstones of the Ridgeway Member.
Definition of Upper Boundary: The top is conformable, at the top of thickly-bedded cherty pure micrites (Cherty Freshwater Beds) beneath very shelly micrite (Cinder Bed at the base of the Stair Hole Member).
Thickness: Ranges from 17m in west Dorset to 39m in the east.
Geographical Limits: Member defined in and limited to the Dorset coast region.
Parent Unit: Lulworth Formation (LULW)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Section  West side of Worbarrow Tout. Westhead, R K and Mather, A E, 1996. 
Westhead, R K and Mather, A E. 1996. An updated lithostratigraphy of the Purbeck Limestone Group in the Dorset area. Proceedings of the Geologists' Association, Vol.107, 117-128. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E341 E342 E343