"BRV"@en . "448.75"^^ . . . "Broad Vein Mudstone Formation"@en . "Pale-medium blue, silty-mudstone, intensely bioturbated in parts."@en . "400 to 560m"@en . . "No lower boundary is exposed but the pale-medium blue mudstones of the Formation rest with sharp contrast upon the black mudstones of the Nod Glas Formation."@en . "Broad Vein Mudstone Formation"@en . . . . . "stable"@en . "Broad Vein Formation [Obsolete: use BRV]"@en . . "Red Vein [Obsolete: use BRV]"@en . "The upper boundary can be examined at Aberllefenni Quarry, where the contact is transitional, over 0.5m, from the pale-blue of the Broad Vein Mudstone Formation to a medium-blue, laminated silty mudstone of the Narrow Vein Mudstone Formation, accompanied by the development of lamination."@en . "445.2"^^ . "Silty mudstone. Stratified bedrock. Occurs onshore. Deposited during the Rawtheyan Stage (Ordovician Period) (448.75-445.2 Ma BP)."@en . "Broad Vein [Obsolete: use BRV]"@en . . . .