"Gwastaden Group"@en . "432.9"^^ . . . . "Coarse silicate-sandstone, mudstone and sandstone. Stratified bedrock. Occurs onshore. Deposited during the Llandovery Epoch (Silurian Period) (443.1-432.9 Ma BP)."@en . . "Mudstones, shales, flags and grits."@en . "stable"@en . . . . . "Gwastaden Group"@en . "GG"@en . "Drawn at the base of the Gwastaden Group where mudstones rest conformably upon shales of the Blue Black Shales Formation."@en . "443.1"^^ . . "552 metres approximately."@en . "Drawn at the conformable upward passage of grits of the Gwastaden Group where it is unconformably overlain by the Caban Group."@en .