The Late Devonian-early carboniferous isolated carbonate platform in the Subpolar Urals (Bol'shaya Nadota river)

A number of outcrops located in the basin of the Bol'shaya Nadota River (Subpolar Urals) supply a unique possibility to study the Middle Palaeozoic isolated carbonate platform and to reconstruct its composition and development. The Middle Devonian - Lower Carboniferous sequence of the region is represented by the Middle Devonian Nadotamylk Formation composed of argillites and siltstones overlaid by clayey carbonates, the Frasnian Matyashor Formation composed of detritic and organogenous limestones, the Famennian-Tournaisian (?) Bolshaya Nadota Formation comprising oolitic limestones, Izvestnyakovo-Dolomitovaya and Izvestnyakovo-Brtekchevaya formations of the Late Visean - Serpukhovian age composed of detritic, clastic, and oolitic limestones, and the Olysya Reef of the Late Visean - Serpukhovian age. Three facies belts possessing different evolution of the sedimentation are detected in the area under consideration. The Eastern and Central facial belts are dominated by organogenous buildups, and the detritic and oolitic limestones are characteristic for the Western facial belt. These facies compose the Bol'shaya Nadota shoal (isolated carbonate platform) similar to Great Bahamas Bank. Elaborated models of evolution of sedimentation reflect development of buildups and surrounding areas in the Early Frasnian - Serpukhovian time. Composition of the Bol'shaya Nadota shoal and distribution of biota suggest a warm-water environment for the isolated carbonate platform.