The BGS Lexicon of Named Rock Units — Result Details

Seathwaite Fell Sandstone Formation

Computer Code: SET Preferred Map Code: Set
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Predominantly bedded volcaniclastic sandstone and siltstone with interbeds of tuff, lapilli-tuff, volcaniclastic breccia and conglomerate. Host to penecontemporaneous andesite and basaltic andesite sills.
Definition of Lower Boundary: The base of the volcaniclastic sandstone succession. In the type area a facies transition or a sharp contact on underlying pyroclastic rocks of the Scafell Dacite Member. Markedly unconformable on many formations in the upper part of the Borrowdale Volcanic Group, including Airy's Bridge, Lingmell, Lag Bank, Low Water, Froswick and Woundale formations.
Definition of Upper Boundary: Usually marked by dacitic lapilli-tuff of the overlying Lincomb Tarns Tuff Formation [andesitic sills may intervene locally] or in the Kentmere area by the Kentmere Pike Formation.
Thickness: 30 to 1100m (excluding intrusive igneous rocks).
Geographical Limits: Extensive outcrop throughout the Lake District. From Seathwaite Fell (NY 230 100) to Grasmere (NY 33 07), Ambleside (NY 37 04), Coniston Fells (SD 29 99) and Broughton Moor (SD 25 94), Thirlmere (NY 31 13), High Street (NY 42 11) to Wet Sleddale (NY 53 10), Cumbria.
Parent Unit: Borrowdale Volcanic Group (BVG)
Previous Name(s): Seathwaite Fell Tuffs (-519)
Seathwaite Fell Formation (-2415)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Seathwaite Fell (Borrowdale). 
Reference Section  Walna Scar Quarries and Torver High Common. 
Reference Section  Great Intake to Holme Fell, includes Tilberthwaite and Quarries. 
Reference(s):
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 
Mitchell, G H, 1940. The Borrowdale Volcanic Series of Coniston, Lancashire. Quarterly Journal of the Geological Society of London, Vol.96, p.301-319. 
Kneller B C and McConnell, B J . 1993. The Seathwaite Fell Formation in the central Fells. British Geological Survey Technical Report WA/93/43 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E030 E039 E038 E029