The BGS Lexicon of Named Rock Units — Result Details

Lincomb Tarns Tuff Formation

Computer Code: LTA Preferred Map Code: LTa
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Dacitic lapilli-tuff, typically lithic rich with both silicic and mafic clasts; interpreted as welded ignimbrite; locally with thin tuff and volcaniclastic sandstone interbeds. Component members are recognised in some areas.
Definition of Lower Boundary: Base of dacitic lapilli-tuff. Unconformably overlies erosion surface on top of Seathwaite Fell Sandstone Formation (volcaniclastic sandstone). Basaltic andesite and andesite sills may intervene locally.
Definition of Upper Boundary: Base of overlying formations: Esk Pike Formation (mudstone and siltstone) and, in the southeast of the district, Tarn Hows Tuff Formation (andesitic tuff and lapilli).
Thickness: 170 to more than 800m
Geographical Limits: Lincomb Tarns - Scafell - Rossett Pike - High Raise, Easdale - Grasmere - Scandale - Wansfell - Ambleside - Skelwith Bridge - Yewdale - Coniston - Torver High Common, Brothers Water to Shap area, Cumbria.
Parent Unit: Borrowdale Volcanic Group (BVG)
Previous Name(s): Lincomb Tarns Formation (-4772)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Threshthwaite Cove 
Reference Section  Pass of Dunmail Raise to Seat Sandal 
Type Area  Ridge from Glaramara to Allen Crags, along which lie the Lincomb Tarns (NY 241 093). 
Reference Section  Torver Beck. 
Reference(s):
Woodhall, D G, 1998. The geology of the Wythburn, Thirlmere and Fairfield areas of the north-east Lake District. British Geological Survey Technical Report WA/98/07. 
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. 
Oliver, R L, 1961. The Borrowdale Volcanic and associated rocks of the Scafell area, English Lake District. Quarterly Journal of the Geological Society of London, Vol 117, p. 377-417 
McConnell, B J, 1993. The Lincomb Tarns and Esk Pike formations. British Geological Survey Technical Report, WA/93/44. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E038 E029 E030 E039