| Computer Code: |
GNWF |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Hirnantian Age (OH)
— Hirnantian Age (OH) |
| Lithological Description: |
A heterogenous mixture of silty-mudstones, siltstones, fine- to coarse-grained feldspathic and non-feldspathic sandstones, greywackes and conglomerates. |
| Definition of Lower Boundary: |
On Foel Crochan (7706 1050) the lower boundary is transitional over 2.65m. Sandy bands (1-2m) thick occur separated by 10-20cm silty-mudstones. The boundary is taken as the base of the first sandstone band. |
| Definition of Upper Boundary: |
Not seen, probably transitional. |
| Thickness: |
1000m-3000m south-west to north east. |
| Geographical Limits: |
Passes west into Cardigan Bay, and south to the Pennal Fault. Outcrop Garnedd-Wen Formation crosses Sheet 149 diagonally from south-west to north east. |
| Parent Unit: |
Abercorris Group (ARO)
|
| Previous Name(s): |
Garnedd-Wen Beds [Obsolete Name And Code: Use GNWF]
(GWB)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
South of Corris on Mynydd Braichgoch and Bryn Llwyd, north of the Tyn-Y-Ceunant, Gaewern and Braich-Goch Quarries. |
| Reference(s): |
| 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 |
| Pugh, W J. 1923. The geology of the district around Corris and Aberllefenni, (Merionethshire). Quarterly Journal of the Geological Society, London, Vol.79, 508-541. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E149
|
