The BGS Lexicon of Named Rock Units — Result Details

Gwastaden Group

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