. . "455.167"^^ . "452.5"^^ . "Allt-Tair-Ffynnon Formation"@en . "Mudstone and sandstone. Stratified bedrock. Occurs onshore. Deposited during the Soudleyan Substage - to - Longvillian Substage (Ordovician Period) (455.167-452.5 Ma BP)."@en . . . "ATF"@en . "Allt-Tair-Ffynnon Formation"@en . . "Mudstone and sandstone."@en . "stable"@en .