The BGS Lexicon of Named Rock Units — Result Details

Tarn Hows Tuff Formation

Computer Code: THW Preferred Map Code: THw
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Andesitic coarse tuffs and lapilli-tuffs; massive to weakly stratified, with a very rough weathered surface exhibiting conspicuous surface holes.
Definition of Lower Boundary: Change from dacitic to acid andesitic tuffs; overlies Lincomb Tarns Tuff Formation.
Definition of Upper Boundary: Not seen; unconformably overlain by lowest formation of Windermere Supergroup.
Thickness: 0 - 420m
Geographical Limits: Area between the Coniston Fault (Tarn Hows) and Lake Windermere.
Parent Unit: Borrowdale Volcanic Group (BVG)
Previous Name(s): Tarn Hows Formation (-2485)
Alternative Name(s): none recorded or not applicable
Type Area  Tarn Hows - Iron Keld Plantation area. 
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: