| Computer Code: |
PNF |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Aurelucian Stage (OJ)
— Burrellian Stage (OK) |
| Lithological Description: |
Basaltic and andesitic lavas, with mudstone, mudflow breccias and crystal tuffs. |
| Definition of Lower Boundary: |
Oversteps the Craig y Ffynnon Formation northwards and rests on the Allt Lwyd Formation. |
| Definition of Upper Boundary: |
Overlain by the Aran Fawddwy Formation. |
| Thickness: |
To 300 m. |
| Geographical Limits: |
none recorded or not applicable
|
| Parent Unit: |
Aran Volcanic Group (AVG)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Pistyllion to Bwlch y Fign [SH 8225 1900 to 8220 1855] (Allen and Jackson, 1985, p. 43). |
| Reference(s): |
| Rushton, A W A and Howells, M F. 1998. Stratigraphical framework for the Ordovician of Snowdonia and the Lleyn Peninsula. British Geological Survey Research Report, RR/99/08. |
| British Geological Survey. 1986. Bala. England and Wales, Sheet 136. Provisional Solid Geology. 1:50 000 Series. (Keyworth, Nottingham: British Geological Survey.) |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E136
E135
|
