"453.833"^^ . "stable"@en . . "Tuff. Stratified bedrock. Occurs onshore. Deposited during the Soudleyan Substage (Ordovician Period) (455.167-453.833 Ma BP)."@en . "Overlies unnamed sandstones of the Llewellyn Volcanic Group and siltstones of the Nant Ffrancon Subgroup."@en . . . "Acidic ash-flow tuffs."@en . . "Total up to 340 m."@en . "Clogwyn Gottal Tuff"@en . "455.167"^^ . . "Capel Curig Volcanic Formation"@en . "Capel Curig Volcanic Formation"@en . "CCV"@en . . . . "Overlain by sandstones of the Cwm Eigiau Formation."@en . . . . . .