Glossary of geological terms
ABCDEFGHI J KL
MN OP QRSTU VW X Y Z
Raglan Marl Group / Grŵp Marl Rhaglan
Former name for the Raglan Mudstone Formation
Raglan Mudstone Formation / Ffurfiant Carreg Laid Raglan
A thick succession (up to 1100m) of mudstones and siltstones laid down during the Pridoli Stage of the Silurian Period.
Redhill & Slade Beds / Gwelyau Redhill a Slade
A succession of mudstones and sandstones laid down during the Ashgillian Epoch of the Ordovician Period.
Red Marl Group / Grŵp y Marl Coch
Former name for the Raglan Mudstone Formation
Red Sandstone Formation / Ffurfiant y Tywodfaen Coch
Former name for the Brownstones and Senni Formations and the uppermost part of the St Maughan’s Formation.
Rhuddanian / Rhuddanaidd
Lowermost stage of the Silurian. See Silurian timechart.
rottenstone / carreg bwdr
Weathered limestone which was once quarried for use as an abrasive. The removal by natural processes of the calcium carbonate from the rock left a pumice-like material composed of silica. The largest deposits were worked in the C19th just to the northwest of Cribarth.