"The top is a major palaeokarstic surface, with extensive dissolution and palaeosol formation of the ooidal grainstone at the top of the Formation. This is overlain by micritic limestones and green clay (Clydach Halt Member) forming the basal part of the overlying Llanelly Formation."@en . "Gilwern Oolite Formation"@en . . "10 m in the Clydach Gorge to 20 m on the east crop."@en . . "Gilwern Oolite [Obsolete: use GWO]"@en . "344.5"^^ . "Massive ooidal grainstone, shelly, crinoidal bed at base; becomes dolomitized on the east crop of the coalfield."@en . "Dolostone and ooid-limestone. Stratified bedrock. Occurs onshore. Deposited during the Chadian Substage (Carboniferous Period) (346.7-344.5 Ma BP)."@en . . . "GWO"@en . . . . . "Gilwern Oolite Formation"@en . "stable"@en . . "The base is placed at an erosion surface. In the type area, this is cut in micritic limestones of the underlying Coed Ffyddlwn Formation (Darren Ddu Member), which is overlain by coarse shelly, crinoidal grainstone (Craig-y-Gaer Coral Bed) at the base of the Gilwern Oolite Formation."@en . . "346.7"^^ .