"Gamlan Shale Group [Obsolete: use GN]"@en . "150 to 240m"@en . "Conformable and transitional with overlying black mudstones of the Clogau Formation (Mawddach Group)."@en . "499.0"^^ . . . "GN"@en . . "508.0"^^ . . . "Mudstone with subsidiary sandstone and trace volcaniclastic-mudstone. Stratified bedrock. Occurs onshore. Deposited during the St David's Series (Cambrian Period) (508-499 Ma BP)."@en . . "Gamlan Formation"@en . "stable"@en . . "Grey, green and purple colour-banded, locally pyritic mudstones and thin, coarse-grained turbiditic sandstones. Upper part of Formation manganiferous, with thin mudstone beds near the top."@en . "Conformable, sharply overlain by turbiditic siltstones of the Barmouth Formation."@en . . . "Gamlan Formation"@en . "Gamlan Black Shales [Obsolete: use GMSH, GN]"@en . . .