Computer Code: |
GG |
Preferred Map Code: |
notEntered |
Status Code: |
Full, pending ratification |
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 Entered (?)
|
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): |
Lapworth, H, 1900. The Silurian sequence at Rhayader. Quarterly Journal of the Geological Society, Vol.56, p.67-137. |
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. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
none recorded or not applicable |