"Clay with subsidiary limestone and trace coal and seat-earth mudstone. Stratified bedrock. Occurs onshore. Deposited during the Arundian Substage (Carboniferous Period) (344.5-343 Ma BP)."@en . "Garn Caws Sandstone Formation"@en . "The base is placed at the karstified top of the underlying Penllwyn Oolite Member, where the basal green clay of the Gilwern Clay Member drapes the irregular surface of the Penllwyn Oolite Member."@en . . "Gilwern Clay Formation [Obsolete: use GWCL]"@en . . "Gilwern Clay Member"@en . . "GWCL"@en . "5m (Cwar yr Hendre) to 7.4m (Llanelly Quarry)."@en . . . . . . . "344.5"^^ . "Gilwern Clay Member"@en . "343.0"^^ . "stable"@en . . "Green and red-brown and purple mottled clay with limestone (\"calcrete\") nodules and, locally, a grey rootlet bed (seatearth) and a thin coal at the top."@en . "The top is placed at the sharp, disconformable junction between the topmost clay (a seatearth at Llanelly Quarry) and the overlying sandy limestone forming the base of the Dowlais Limestone Formation. Where the Garn Caws Sandstone is present, the top is placed at the irregular scoured surface where the topmost clays of the member are erosively overlain by the Garn Caws Sandstone Formation [note that Wright (1981) included this sandstone in the Gilwern Clay, but it was subsequently given separate formation status by Barclay (1989)]."@en .