The BGS Lexicon of Named Rock Units — Result Details

Pen-Y-Gadair Volcanic Formation

Computer Code: PGA Preferred Map Code: PgV
Status Code: Pending Upgrade
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Massive, pillowed and autobrecciated basalt lavas with intercalated crystal tuffs and subordinate felsic ash-flow tuffs, locally interbedded with mudstones.
Definition of Lower Boundary: Conformably overlies and interdigitates laterally with the Ty'r Gawen Mudstone Formation to the southwest, and with the Benglog Formation to the northeast.
Definition of Upper Boundary: Conformably overlain by mudstones of the Ty'r Gawen Formation.
Thickness: To 240m
Geographical Limits: Cadair Idris and Dolgelly areas, North Wales.
Parent Unit: Aran Volcanic Group (AVG)
Previous Name(s): Upper Basic (Volcanic) Group (-2976)
Pen-Y-Gader Volcanic Group (-4255)
Alternative Name(s): none recorded or not applicable
Type Area  Crags, on and to west of Penygadair, Cadair Idris area, North Wales. Pratt, W T, Woodhall, D G and Howells, M F. 1995. 
Pratt, W T, Woodhall, D G and Howells, M F. 1995. Geology of the country around Cadair Idris. Memoir of the British Geological Survey, Sheet 149. (England and Wales). (London: HMSO), 111pp 
Cox, A H and Wells, A K, 1927. The geology of the Dolgelley district, Merionethshire. Proceedings of the Geologists' Association, Vol.38, 265-318. 
Cox, A H. 1925. The geology of the Cadair Idris Range, (Merioneth). Quarterly Journal of the Geological Society of London, Vol.81, p.539-592. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: