The BGS Lexicon of Named Rock Units — Result Details

Pen-Y-Gader Group [Cf Upper Basic Volcanic Group]

Computer Code: PYGA Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Abereiddian Stage (O2) — Caradoc Series (O4)
Lithological Description: Spilitic pillow lavas with subordinate pyroclastic bands to the east and central parts of the Cader Idris Range and dominantly pyroclastic rocks to the west. (Correlative of Pen-Y-Gader Group = Upper Basic Volcanic Group).
Definition of Lower Boundary: Drawn at base of Pen-y-Gader Group where it rests conformably on pyroclastics of the Llyn-y-Gader Mudstones Group.
Definition of Upper Boundary: Drawn at conformable upward passage from spilitic lavas, mudstone, ash and chert of the Pen-y-Gader Group to mudstones of the Llyn Cau Mudstones.
Thickness: Approx. 120 to 150 metres.
Geographical Limits: Mid-Wales.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Upper Basic Volcanic Group
Stratotypes:
Type Area  Pen-y-Gader, Cader Idris, Gwynedd. 
Reference(s):
Davies, R G, 1959. The Cader Idris Granophyre and its associated rocks. Quarterly Journal of the Geological Society, London. Vol.115, 189-216. 
Cox, A H and Wells, A K, 1916. The Ordovician sequence in the Cader Idris district (Merioneth). British Association for the Advancement of Science Report for 1915 (Manchester), p.424. 
Wells, A K. 1925. The geology of the Rhobell Fawr district (Merioneth). Quarterly Journal of the Geological Society of London, Vol.81, 463-538. 
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:
none recorded or not applicable