The BGS Lexicon of Named Rock Units — Result Details

Rhayader Mudstones Formation

Computer Code: RHS Preferred Map Code: RhS
Status Code: Full
Age range: Aeronian Age (SA) — Telychian Age (ST)
Lithological Description: Thinly interbedded green and grey turbidite mudstones and burrowed hemipelagites. Sparse thin packets of thinly interbedded turbidite mudstones and laminated hemipelagites. Scattered thin packets with turbidite sandstones. NOTE: Overlain by the Caeran Mudstones and underlain by the Derwenlas Formation. Locally underlain by the Caban Conglomerate Complex.
Definition of Lower Boundary: Taken at base of a prominent thick packet of thinly interbedded turbidite mudstones and laminated hemipelagites overlying thinly interbedded turbidite mudstones and burrowed hemipelagites of the Derwenlas Formation.
Definition of Upper Boundary: Gradational, but taken at the base of the incoming of abundant packets of thinly interbedded turbidite mudstone and laminated hemipelagites.
Thickness: c.460 metres.
Geographical Limits: Central Wales.
Parent Unit: Claerwen Group (CLAE)
Previous Name(s): Rhayader Shales (-493)
Cwmsymlog Formation [Obsolete Name And Code: See RHS] (CSF)
Rhayader Pale Shales Formation (-4861)
Alternative Name(s): none recorded or not applicable
Type Section  Bed of River Wye at Rhayader. 
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: