The BGS Lexicon of Named Rock Units — Result Details

Lag Bank Tuff Formation

Computer Code: LBT Preferred Map Code: LBT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Dacitic lapilli-tuff, poorly sorted, massive, containing abundant white-weathered plagioclase-phyric dacite lapilli.
Definition of Lower Boundary: Base of dacitic lapilli tuff. Unconformably overlies Caw Formation (volcaniclastic breccia and sandstone) and Lickle Formation (rhyolitic and dacitic tuff).
Definition of Upper Boundary: Contact with overlying Seathwaite Fells Formation (volcaniclastic sandstone).
Thickness: 0 to 600m
Geographical Limits: Ulpha Basin and Coniston Fells. Postlethwaite Allotment (SD 240 930) to Pikes (SD 237 947) and northeast to Low Water (SD 270 980), Cumbria.
Parent Unit: Borrowdale Volcanic Group (BVG)
Previous Name(s): Lag Bank Tuff (-2892)
Lag Bank Formation (-1640)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  In the vicinity of Lag Bank (SD 246 943); Postlethwaite Allotment (SD 24 93) to Pikes (SD 237 947). 
Reference(s):
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. 
Mitchell, G H, 1956. (Undivided Lickle Rhyolites). The Borrowdale Volcanic Series of the Dunnerdale Fells, Lancashire. Liverpool and Manchester Geological Journal, Vol.1, p.428-449. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E038