"Coal. Stratified bedrock. Occurs onshore. Deposited during the Asturian Substage (Carboniferous Period) (310-307.5 Ma BP)."@en . . "Coal."@en . . . "Hughes Coal (South Wales)"@en . . . "310.0"^^ . "307.5"^^ . "Wenallt Coal (South Wales)"@en . . "stable"@en . . . "Hughes Coal (South Wales)"@en . . "Pwll Big Coal [South Wales Coalfield]"@en . . "HUGC"@en .