| Computer Code: |
GG |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Llandovery Epoch (SL)
— Llandovery Epoch (SL) |
| Lithological Description: |
Mudstones, shales, flags and grits. |
| Definition of Lower Boundary: |
Drawn at the base of the Gwastaden Group where mudstones rest conformably upon shales of the Blue Black Shales Formation. |
| Definition of Upper Boundary: |
Drawn at the conformable upward passage of grits of the Gwastaden Group where it is unconformably overlain by the Caban Group. |
| Thickness: |
552 metres approximately. |
| Geographical Limits: |
Rhayader district, Radnorshire and Breconshire. |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
North-western slope of Gwastaden Hill and valley of River Wye immediately south-east of Rhayader, Radnorshire. |
| Reference(s): |
| Roberts, R O, 1929. Geology of the district around Abbeycwmhir. Quarterly Journal of the Geological Society. Vol.85, p.661. |
| Davies, K A. 1928. Geology of the country between Rhayader and Abergwesyn. Proceedings of the Geologists' Association. Vol. 39, p. 162. |
| Lapworth, H, 1900. The Silurian sequence at Rhayader. Quarterly Journal of the Geological Society, Vol.56, p.67-137. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
