The BGS Lexicon of Named Rock Units — Result Details

Bron Y Graig Formation

Computer Code: BGG Preferred Map Code: BGG
Status Code: Pending Upgrade
Age range: Llandovery Epoch (SL) — Llandovery Epoch (SL)
Lithological Description: Dark grey mudstones and yellow to light grey laminated siltstones, fine-grained grey to yellow sandstones, which are massive, graded or parallel and/or ripple laminated. Sporadic graptolites.
Definition of Lower Boundary: Base unconformable on Ashgill sediments e.g. Maerdy Mudstone Formation.
Definition of Upper Boundary: Top succeeded by pale grey siltstones of the Bettws Mudstone Formation.
Thickness: To 500m
Geographical Limits: Not defined.
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Corwen 120. 
Reference(s):
Campbell, S D G. 1983. The geology of an area between Bala and Betws-y-Coed, North Wales. Unpublished PhD Thesis, University of Cambridge. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E120