. "stable"@en . . "Sandstone and siltstone with subsidiary mudstone and trace tuff. Stratified bedrock. Occurs onshore. Deposited during the Soudleyan Substage (Ordovician Period) (455.167-453.833 Ma BP)."@en . "Conformable and gradational with mudstones of the Ceiswyn Formation, generally taken at the top of the Cefn Gwyn Tuff where the latter is present."@en . . "130m to 150m."@en . . "Glyn Gower Formation [Obsolete: use GYG]"@en . "Laminated siltstones and fine-grained sandstones with subordinate mudstones and rare thin tuffs."@en . . "Glyn Gower Siltstones Member"@en . . . "Conformable and gradational with mudstones of the Ceiswyn Formation, but generally taken at the base of the overlying Frondderw Tuff, where the latter is present."@en . "GYG"@en . "Glyn Gower Siltstones Member"@en . . "455.167"^^ . "453.833"^^ . . . "Glyn Gower Siltstones [Obsolete: use GYG]"@en .