The BGS Lexicon of Named Rock Units — Result Details

Grange Crags Andesite Member

Computer Code: GCG Preferred Map Code: GCg
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Aphyric, fine-grained andesite lava, flow banded at base and autobrecciated at top.
Definition of Lower Boundary: Flow banded andesite lava rests sharply on volcaniclastic rocks; in part rests unconformably on the Skiddaw Group (mudstones).
Definition of Upper Boundary: Brecciated andesite lava overlain sharply by volcaniclastic rocks.
Thickness: Up to 200m
Geographical Limits: North Lake District near Borrowdale. (Ashness Wood to Dale Head).
Parent Unit: Birker Fell Andesite Formation (BFA)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Crags near and around village of Grange. 
Reference(s):
Beddoe-Stephens, B, 1997. The initiation of Borrowdale Volcanism in the Ordovician Lake District as indicated by basal volcaniclastic deposits. British Geological Survey Technical Report WG/97/14. 
Beddoe-Stephens, B, 1996. Mapping; petrology and geochemistry of the Borrowdale Volcanic Group on 1:10k sheets NY21NE and NY21NW. Part of the 1:50k Sheet 29 (Keswick). British Geological Survey Technical Report MPSR/96/16. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E029