. . "stable"@en . . "Bottom Holers Coal (Birmingham)"@en . . . "BTHL"@en . "Coal. Stratified bedrock. Occurs onshore. Deposited during the Westphalian Stage (Carboniferous Period) (319-307.5 Ma BP)."@en . "Bottom Holers Coal (Birmingham)"@en . . "307.5"^^ . "Coal."@en . . "319.0"^^ .