"Conwy Rhyolite Formation"@en . "Underlies mudstones of the Nant Ffrancon Subgroup. Interdigitates with the Foel Fras Volcanic Complex."@en . "To c.1000m, thins southwards."@en . . . "Conway Rhyolite Formation [Obsolete: use COR]"@en . . "Rhyolite with subsidiary mudstone, sandstone, tuff and volcaniclastic-breccia. Stratified bedrock. Occurs onshore. Deposited during the Caradoc Series (Ordovician Period) (458.2-449.75 Ma BP)."@en . . "stable"@en . "458.2"^^ . . . . "Conwy Rhyolite Formation"@en . . "Overlies mudstones of the Nant Ffrancon Subgroup. Interdigitates with the Foel Fras Volcanic Complex."@en . "Rhyolite lavas and inter-flow breccias, tuffs and intercalated sedimentary rocks."@en . "449.75"^^ . . "COR"@en .