| Computer Code: |
LGF |
Preferred Map Code: |
notEntered |
| Status Code: |
Pending Upgrade |
| Age range: |
Llanvirn Series (OE)
— Caradoc Series (O4) |
| Lithological Description: |
Mudstones with intercalated tuffs, tuffites, lavas and limestones. |
| Definition of Lower Boundary: |
Supposedly unconformable on mudstones of the Craig-y-gln Group [Oswestry Sheet 137]. |
| Definition of Upper Boundary: |
Conformably overlain by Pen Plaenau Siltstone Formation, the boundary being taken at the base of the Cwm Clwyd Tuff. Where the latter is absent, the boundary is gradational and taken at the point where mudstones pass into siltstones of the overlying Allt-tair-ffynnon Formation. |
| Thickness: |
About 1750m |
| Geographical Limits: |
none recorded or not applicable
|
| Parent Unit: |
Not Available (!)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| Reference(s): |
| British Geological Survey. 1986. Bala. England and Wales, Sheet 136. Provisional Solid Geology. 1:50 000 Series. (Keyworth, Nottingham: British Geological Survey.) |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E136
E137
|
