| Computer Code: |
CGYG |
Preferred Map Code: |
CgF |
| Status Code: |
Full |
| Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
| Lithological Description: |
Calcareous mudstones. (Well stratified rhyolitic and calcareous ash, and pale blue bedded limestone; with calcareous shale and calcareous, blue mudstone and shale). |
| Definition of Lower Boundary: |
Not seen. |
| Definition of Upper Boundary: |
In faulted contact with mudstones of Llangynog Formation of Carodocian age. |
| Thickness: |
Greater than 300m in the Lwrch inlier. |
| Geographical Limits: |
Limited to fault bounded inliers in the central Berwyn Hills, Lwrch inlier (137), Llwyn-Onn inlier (136) (ca SJ 073 264), Garwallt inlier (136) (ca SJ 091 281). |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
Craig-Y-Glyn Group [Obsolete Name and Code: Use CGYG]
(-2078)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
The Lwrch inlier in the valley of Afon Lwrch around Pen-y-graig. Wedd, C B et al. 1929. |
| Type Area |
Craig-y-Glyn, near Llanrhaiadr, Powys, Wales. |
| Reference(s): |
| Wedd, C B, Smith, B, King, W B R and Wray, D A. 1929. Geology of the country around Oswestry. Memoir of the Geological Survey of Great Britain, Sheet 137. |
| MacGregor,A R. 1958. The Llandeilo limestone of the Central Berwyns and a comparison with rocks of the same age in north-western Europe. Unpublished PhD thesis, Cambridge University. |
| Cantrill,T C, and others. 1914. Denbighshire and Shropshire district. Summary of Progress of the Geological Survey of Great Britain, for 1914, p.7. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E136
E137
|
