The BGS Lexicon of Named Rock Units — Result Details

Wrayslack Tuff Member

Computer Code: WRT Preferred Map Code: WrT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Andesitic lapilli-tuff, massive.
Definition of Lower Boundary: Taken at the base of the pyroclastic flow deposit, usually overlying volcaniclastic sandstone in the Waberthwaite Formation succession; basaltic sills may intervene.
Definition of Upper Boundary: Top of pyroclastic flow deposit, usually overlain by volcaniclastic sandstone, which separates it from the overlying pyroclastic flow deposit (Barrow Tuff Member).
Thickness: c.140-230m
Geographical Limits: Between Windy Slack (SD 172 888) and Boadhole (SD 190 878), west of Duddon Bridge near Broughton in Furness, Cumbria.
Parent Unit: Waberthwaite Tuff Formation (WB)
Previous Name(s): Wrayslack Tuffs And Lavas (-1286)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  On Wrayslack, c.1km west of Duddon Bridge, Cumbria. 
Reference(s):
Johnson, E W, Soper, N J, Burgess, I C, Ball, D F, Beddoe-Stephens, B, Carruthers, R M, Fortey, N J, Hirons, S, Merritt, J W, Millward, D, Roberts, B, Walker, A B and Young, B. 2001. Geology of the country around Ulverston. Memoir of the British Geological Survey, England and Wales, Sheet 48. 
Mathieson, N A, 1986 Geology, structure and geochemistry of the Ordovician volcanic succession in south west Cumbria. Unpublished Ph.D. thesis, University of Sheffield. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E048