The BGS Lexicon of Named Rock Units — Result Details

Craig Hill Breccia Formation

Computer Code: CIL Preferred Map Code: CIL
Status Code: Full
Age range: Arenig Series (OR) — Arenig Series (OR)
Lithological Description: Polymict breccia of basalt, amphibolite and various granite clasts, interbedded with some basaltic pillow lavas and rare chert beds.
Definition of Lower Boundary: Base of the lowest breccia bed, overlying pillow lavas of the Balcreuchan Group (undivided).
Definition of Upper Boundary: Top of the highest breccia bed where it is overlain by pillow lavas of the Balcreuchan Group (undivided).
Thickness: About 100m
Geographical Limits: Northeast of Colmonell, Ayrshire, southwest Scotland.
Parent Unit: Balcreuchan Group (BCN)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Crags and roches moutonnees in moorland on the southern flanks of Craig Hill. There are two areas of exposure: one around Garnaburn, the other at Craig Farm. Stone and Smellie, 1988. 
Reference(s):
Stone, P and Smellie, J L, 1988. Classical areas of British Geology: The Ballantrae area: a description of the solid geology of parts of 1:25 000 sheets NX 08, 18 and 19. [London: HMSO for British Geological Survey.] 
Balsillie, D, 1937. Further observations on the Ballantrae igneous complex, south Ayrshire. Geological Magazine, Vol.74, 20-33. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S007