| Computer Code: |
LBA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full, pending ratification |
| Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
| Lithological Description: |
Calcareous ashy mudstones, dark blue silty mudstones, siltstones with fine-grained sandstones, ash, dark blue mudstones and subordinate siltstones with limestone. |
| Definition of Lower Boundary: |
Drawn at the base of the Derfel Limestone Member of the Nant Hir Mudstones Formation. The oldest rocks exposed in the area. |
| Definition of Upper Boundary: |
Drawn at the conformable upward passage of calcareous ashes of the Gelligrin Calcareous Ashes Formation where it is unconformably overlain by the Moelfryn Mudstones Formation. |
| Thickness: |
1505 metres approx. |
| Geographical Limits: |
The Arenig and Bala areas of North Wales. |
| Parent Unit: |
Not Entered (?)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
The area immediately surrounding Lake Bala. |
| Reference(s): |
| Williams, A and others, 1972. A correlation of Ordivician rocks in the British Isles. Geological Society of London Special Report No.3. |
| Bassett, D A, Whittington, H B, and Williams, A. 1966. The stratigraphy of the Bala district, Merionethshire. Quarterly Journal of the Geological Society of London, Vol. 122, 219-271. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
