"Firedamp Coal (North Wales)"@en . . . . "319.0"^^ . . "Firedamp Coal (North Wales)"@en . . . "Coal. Stratified bedrock. Occurs onshore. Deposited during the Langsettian Substage (Carboniferous Period) (319-318 Ma BP)."@en . "stable"@en . . "FDC"@en . . "Coal."@en . "318.0"^^ .