"The formation is a heterolithic succession dominated by fissile mudstones and monospecific oyster beds, with subordinate limestone, algal limestone and calcareous sandstone beds. The oysters are Praeexogyra hebridica (Forbes), indicating strong marine influence. They are preserved in limestone or mudstone matrices and the shell beds vary from a single shell plaster to oyster beds 2m thick. Within the Great Estuarine Group, Praeexogyra hebridica is confined to the Duntulm Formation."@en . . "165.3"^^ . "stable"@en . . "Duntulm Formation"@en . "DTM"@en . "The base of the formation is defined by the first upsection occurrence of the oyster Praeexogyra hebridica (Forbes). Lithologically, this boundary is gradational with the fissile mudstones with marine fossils of the lowermost Duntulm Formation overlying the fissile mudstones with freshwater faunas of the uppermost Valtos Sandstone Formation (Harris and Hudson, 1980, fig.8; Cox, Page and Morton, 2002, fig.6.29)."@en . "168.2"^^ . . . . "Mudstone and shelly mudstone with subsidiary carbonaceous mudstone, sandstone and siltstone and trace limestone. Stratified bedrock. Occurs both onshore and offshore. Deposited during the Bathonian Age (Jurassic Period) (168.2-165.3 Ma BP)."@en . "Ostrea Hebridica Beds [Obsolete: use DTM]"@en . . . "Lower \"Ostrea\" Beds [Obsolete: use DTM]"@en . . "Duntulm Formation"@en . "Thicknesses are from Harris and Hudson (1980) unless otherwise indicated. They also claim Anderson and Dunham's (1966) 60 ft (18m) estimate for Trotternish is incorrect, probably repeated elsewhere (e.g. British Geological Survey, 2006a). The greatest thickness cited is at the type section in Trotternish: Harris and Hudson (1980) estimate 55m thick, Andrews and Walton (1990) give about 33m. The unit thins southwards: Raasay 0-10m (British Geological Survey, 2006b) Strathaird at least 17m (Andrews and Walton, 1990), although Harris and Hudson (1980) give 8m, Eigg at least 9m and Muck at least 11m (Andrews and Walton, 1990)."@en . . "The top of the formation is marked by the range top of Praeexogyra hebridica, and the first upsection occurrence of the ostracod-bearing limestones interbedded with shales, of the Kilmaluag Formation. This boundary is not observed at the type section at Trotternish. The formation is unconformably overlain by extrusive rocks of the Paleocene Skye Lava Group in places."@en . .