The BGS Lexicon of Named Rock Units — Result Details

Great Whinscale Dacite Member

Computer Code: GWD Preferred Map Code: GWD
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Extensive white-weathered aphyric, dacitic lava flow, platy-foliated with marginal autobreccias.
Definition of Lower Boundary: Base of distinctive lava flow; underlain by thin un-named units of volcaniclastic sandstone or by the Little Stand Tuff.
Definition of Upper Boundary: Top of distinctive lava flow; overlain by volcaniclastic sandstone sequence of the Blisco Member, or by the Grey Friar Tuff, or by un-named andesite lava flows of the Birker Fell Andesite Formation.
Thickness: Generally 75 - 85m; locally 20 - 65m.
Geographical Limits: Yoadcastle (SD 15 95) south of Devoke Water to Little Stand (NY 25 03), Harter Fell (SD 218 997) and around Seathwaite Tarn (SD 249 984), Cumbria.
Parent Unit: Birker Fell Andesite Formation (BFA)
Previous Name(s): Great Whinscale Rhyolite (-300)
Tongue House Member [Obsolete Name: Replaced By LIT, GWD, GY] (TNM)
Alternative Name(s): none recorded or not applicable
Type Area  Crook Crag, Great Whinscale, (Ulpha Fell, south of Eskdale). 
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. 
Kanaris-Sotiriou R, Millward, D and Rundle, C C, 1991. The Great Whinscale Dacite - an enigmatic lava flow from the Borrowdale Volcanic Group, English Lake District. Proceedings of the Yorkshire Geological Society, Vol.48, p.393-408. 
Firman, R G J, 1957. The Borrowdale Volcanic Series between Wastwater and Duddon Valley, Cumberland. Proceedings of the Yorkshire Geological Society, Vol.31, p.39-64. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: