"stable"@en . . "DGUU"@en . . . "Dolgau Mudstones Formation (Upper Tongue)"@en . "443.1"^^ . . "432.9"^^ . "Mudstone."@en . . "Dolgau Mudstones Formation (Upper Tongue)"@en . . . . "Mudstone. Stratified bedrock. Occurs onshore. Deposited during the Llandovery Epoch (Silurian Period) (443.1-432.9 Ma BP)."@en .