| Computer Code: |
CAU |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Costonian Substage (OO)
— Soudleyan Substage (OY) |
| Lithological Description: |
[Obsolete] Mudstones, siltstones, sandstones and volcanic tuffs. |
| Definition of Lower Boundary: |
Drawn at the base of the Graitanog Sandstone of the Nantffrancon Formation unconformably rests upon the Carnedd-y-Filiast Grit of the Marchlyn Formation. |
| Definition of Upper Boundary: |
Drawn at the conformable upward passage of the Marian Mawr Mudstone Formation where mudstone is cross cut by ashflow tuffs of the Lower Crafnant Volcanic Formation. |
| Thickness: |
Up to 1800m. |
| Geographical Limits: |
The area around Capel Curig and Betws-y-Coed, 10kms squared, approximately. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
Glanrafon Beds
(-750)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
The area between Capel Curig, Betws-y-Coed and Dolwyddelan. |
| Reference(s): |
| Howells, M F, Francis, E H, Leveridge, B E and Evans, C D R, 1978. Classical areas of British Geology. Capel Curig and Betws-y-Coed. Description of 1:25 000 Sheet SH75. London: HMSO for Institute of Geological Sciences. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
