The BGS Lexicon of Named Rock Units — Result Details

Rosthwaite Rhyolite Member

Computer Code: RSR Preferred Map Code: RsR
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Pinkish weathered, crystal-poor, flow-banded, flow-folded rhyolite with autobreccia at its base and top. It is interpreted as a coulee-type lava and is connected to an underlying intrusion.
Definition of Lower Boundary: Taken at the base of the rhyolite or its autobreccia overlying volcaniclastic rocks of the main part of the Lingmell Formation.
Definition of Upper Boundary: Defined by the base of overlying volcaniclastic rocks; in the west of the outcrop by pyroclastic rocks of the Lingmell Formation, but in the central and eastern parts of the outcrop by volcaniclastic sedimentary rocks of the Seathwaite Fell Sandstone Formation.
Thickness: Up to 130m
Geographical Limits: Rosthwaite Fell, Borrowdale, Cumbria. The rhyolite has an outcrop length of 1.9km from NY 2518 0644 to NY 2708 1152.
Parent Unit: Lingmell Tuff Formation (LME)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Area  Rosthwaite Fell, Borrowdale, Cumbria. Kneller et al., 1993 
Kneller, B C, Kokelaar, B P and Davis, N C, 1993. The Lingmell Formation. British Geological Survey Technical Report, WA/93/43. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: