Late Devonian-early carboniferous isolated carbonate platforms of the north of the Urals and Pay-Khoy

The article considers isolated carbonate platforms known in the Sub-Polar Urals (basin of the Bolshaya Nadota River; boreholes of the Yunyakha and Levaya Grubeyu areas) and the NW Pay-Khoy (basin of the Lymbad'yakha River and coast of the Barents Sea). The three stages of formation of the platforms (Frasnian, Famennian-Tournaisian, and Visean-Serpukhovian) are distinguished, and the sedimentological models of these platforms are developed. Subsidence curves based on the back-striping demonstrate some differences in the evolution of the studied isolated carbonate platforms. Similarities and differences in the history and structure of the platforms are observed. Formation of the intra-shelf depressions (the Kozhim Depression in the Sub-Polar Urals, and the Korotaikha Depression in the Pay-Khoy) in the Frasnian - Early Famennian caused appearance of isolated carbonate platforms. The depressions probably were formed by the regional tectonics. The following development of the carbonate platforms was controlled by eustatic fluctuations. The isolated platforms differ by stratigraphic spans (Late Frasnian - Serpukhovian for the Polar Urals Platform and Famennian-Tournaisian for the Pay-Khoy Platform), relief, facies, and size. The isolated depressions differ in size as well: the Kozhim Depression is larger than the Korotaikha Depression. Additionally, it is supposed that the Polar Urals platform was of warm-water type, but the Pay-Khoy platfrom was of cool-water type.