| Computer Code: |
CFH |
Preferred Map Code: |
Cfn |
| Status Code: |
Full |
| Age range: |
Llanvirn Series (OE)
— Llanvirn Series (OE) |
| Lithological Description: |
Mafic and felsic tuffs and tuffites with interbedded mudstones and rare pillowed basalts. |
| Definition of Lower Boundary: |
Conformable within the mudstones of the Cregennen Formation. |
| Definition of Upper Boundary: |
Conformable within the mudstones of the Cregennen Formation and locally overlain conformably by the mafic lavas and tuffs of the Llyn y Gafr Volcanic Formation. |
| Thickness: |
To 90m |
| Geographical Limits: |
Cadair Idris district. |
| Parent Unit: |
Cregennen Formation (CREN)
|
| Previous Name(s): |
Cefn Hir Ashes.
(-766)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
The crags of Pared-y-Cefn Hir, east of Arthog. Pratt, W T, Woodhall, D G and Howells, M F. 1995. |
| Reference(s): |
| 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. 1921. The Lower Palaeozoic rocks of the Arthog-Dolgellau district (Merionethshire). Quarterly Journal of the Geological Society, London, Vol. 76, p. 254-324. |
| Pratt, W T, Woodhall, D G and Howells, M F. 1995. Geology of the country around Cadair Idris. Memoir of the British Geological Survey, Sheet 149. (England and Wales). (London: HMSO), 111pp |
| Jones, B, 1933. The geology of the Fairbourne-Llwyngwril district, Merioneth. Quarterly Journal of the Geological Society, Vol.89, 145-171. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E149
|
