The BGS Lexicon of Named Rock Units — Result Details

Crinkle Tuff Member

Computer Code: CRK Preferred Map Code: Crk
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Rhyolitic tuffs, lapilli-tuffs and pyroclastic breccias that are mostly very densely welded; rocks are conspicuously garnetiferous. Widespread intercalations of laminated rhyolitic tuff.
Definition of Lower Boundary: Base of high-grade rhyolitic pyroclastic rocks. Locally unconformable on older parts of Airy's Bridge Tuff Formation.
Definition of Upper Boundary: Contact with overlying formations comprising a mixed succession of bedded pyroclastic rocks and volcaniclastic sandstones, containing lavas and sills of andesite and basaltic andesite.
Thickness: 0 - 700m
Geographical Limits: Crinkle Crags to Scafell, Great Gable, Base Broan and Bell Crag. Yewbarrow, Illgill Head, Cumbria.
Parent Unit: Airy's Bridge Tuff Formation (AIB)
Previous Name(s): Crinkle Member (-4568)
Crinkle Tuffs (-3956)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Summit of Crinkle Crags between Long Top and Shelter Crags. 
Reference(s):
Branney, M J, Kokelaar, B P and McConnell, B J. 1992. The Bad Step Tuff: a lava-like rheomorphic ignimbrite in a calc-alkaline piecemeal caldera, English Lake District. Bulletin Volcanology, Vol.54, 187-199. 
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. 
Branney, M J, Davis, N C, Kokalaar, B P and McConnell, B J. 1993. The Airy's Bridge Formation in the central Fells. British Geological Survey Technical Report WA/93/41 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E038 E029