| Computer Code: |
GGTU |
Preferred Map Code: |
GGT |
| Status Code: |
Full |
| Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
| Lithological Description: |
Non- to weakly-welded acidic ash-flow tuffs with cross-laminated, well-bedded tuffaceous sandstone derived from the tuffs. |
| Definition of Lower Boundary: |
Rests on sandstones and mudstones intercalated in the Llewelyn Volcanic Group above the Foel Fras Volcanic Complex. |
| Definition of Upper Boundary: |
Underlies sandstone and siltstone in the Llewelyn Volcanic Group that underlies the Capel Curig Volcanic Formation.. |
| Thickness: |
About 30m |
| Geographical Limits: |
East of Carnedd Dafydd to east of Tryfan. |
| Parent Unit: |
Llewelyn Volcanic Group (LLV)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
East of Tryfan. |
| Reference(s): |
| Howells, M F, Reedman, A J and Campbell, S D G, 1991. Ordovician (Caradoc) marginal basin volcanism in Snowdonia (north-west Wales). (London: HMSO for the British Geological Survey). |
| Howells M F, Reedman A J and Leveridge B E. 1985. Geology of the country around Bangor: Explanation for 1:50 000 geological sheet 106 (England and Wales). British Geological Survey Sheet Explanation. [London: HMSO.] 34pp. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E106
|
