| Computer Code: |
PYGA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Abereiddian Stage (O2)
— Caradoc Series (O4) |
| Lithological Description: |
[Obsolete: use PGA] 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: |
none recorded or not applicable
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Pen-y-Gader, Cader Idris, Gwynedd. |
| Reference(s): |
| 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. |
| 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, 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. |
| Davies, R G, 1959. The Cader Idris Granophyre and its associated rocks. Quarterly Journal of the Geological Society, London. Vol.115, 189-216. |
| Wells, A K. 1925. The geology of the Rhobell Fawr district (Merioneth). Quarterly Journal of the Geological Society of London, Vol.81, 463-538. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
