The BGS Lexicon of Named Rock Units — Result Details

Cockley Beck Tuff Member

Computer Code: CKT Preferred Map Code: CkT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Garnetiferous eutaxitic dacitic lapilli-tuff with thin interbedded laminated garnetiferous tuff locally.
Definition of Lower Boundary: Base of garnetiferous, dacitic lapilli-tuff. Unconformable, in type area overlies volcaniclastic breccia and sandstone (Dale Head Member); elsewhere overlies a variety of basaltic, andesitic and dacitic lava.
Definition of Upper Boundary: Overlain by a variety of lavas that range in composition from basaltic andesite to dacite, and locally overlain by valcaniclastic sandstone.
Thickness: 0 to 60m
Geographical Limits: Duddon Valley - Eskdale; Cockley Beck to Dale Head and Foxbield Moss, Cumbria.
Parent Unit: Birker Fell Andesite Formation (BFA)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Between Cockley Beck and Dale Head Chase 
Reference(s):
Petterson, M G, Beddoe-Stephens, B, Millward, D and Johnson, E W, 1992. The Ordovician Lower Borrowdale Volcanic Group in the English Lake District. The construction of a pre-caldera volcanic field. Journal of the Geological Society of London, Vol.149, p.889-906. 
Millward, D, Johnson, E W, Beddoe-Stephens, B, Young, B, Kneller, B C, Lee, M K, Fortey, N J, Allen, P M, Branney, M J, Cooper, D C, Hirons, S, Kokelaar, B P, Marks, R J, McConnell, B J, Merritt, J W, Molyneux, S G, Petterson, M G, Roberts, B, Rundle, C C, Rushton, A W A, Scott, R W, Soper, N J and Stone, P. 2000. Geology of the Ambleside district. Memoir of the British Geological Survey, England and Wales, Sheet 38. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E038