. "Brackenslack Limestone"@en . . "Brackenslack Limestone"@en . "BKNL"@en . "Bedrock. Occurs onshore. Formed during the Brigantian Substage (Carboniferous Period) (330.9-330.3 Ma BP)."@en . . "330.9"^^ . . . "stable"@en . . "330.3"^^ .