Chukchi Arctic continental margins: Tectonic evolution, link to the opening of the Amerasia Basinстатья

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[1] Chukchi arctic continental margins: Tectonic evolution, link to the opening of the amerasia basin / S. D. Sokolov, G. V. Ledneva, M. I. Tuchkova et al. // ICAM VI: Proceedings of the International Conference on Arctic Margins VI. Stone D.B., Grikurov G.E., Clough J.G., Oakey G.N. — Petersburg: VSEGEI, 2014. — P. 97–114. The Arctic margin of Chukotka (Chukotka fold belt) comprises two tectonic units, namely the Anyui-Chukotka fold system (the ACh) and the South Anyui suture (the SAS). In terms of the paleotectonic reconstructions, the ACh represents the Chukotka microcontinent whereas the SAS is the suture, which is the result of collision of the Chukotka microcontinent with the Siberian active margin (the Verkhoyansk-Kolyma fold system). Tectono-stratigraphic units of the South Anyui suture were thrust northward over the passive margin of the microcontinent during the collision. The tectonic evolution of the continental margin of Chukotka can be divided into four main tectonic stages corresponding to the Late Precambrian-Early Paleozoic, the Late Paleozoic- Early Mesozoic, the Middle Jurassic- Early Cretaceous and the Aptian-Albian. The metamorphic basement has the Neoproterozoic age and is assumed to represent a relict of the ancient Arctida continent. In the Early Paleozoic, Arctida was separated from Siberia and Laurentia by oceanic basins. The Chukotka microcontinent was situated next to Siberia until the Devonian and was accreted to Laurentia during the Ellesmerian orogeny. The wide ProtoArctic Ocean connected with the PaleoUral Ocean can be reconstructed for Late Paleozoic time. The Siberian margin was active whereas the North American margin was passive. After the closure of the Paleo Ural Ocean, the ProtoArctic Ocean became a gulf of the PaleoPacific Ocean. However, it separated structures of the North American and Siberian continents. In the latest Permian-earliest Triassic, the continental crust of the Chukotka microcontinent was destroyed as Pangea broke up. The Lower Triassic turbidites contains dikes and sills of diabases. Starting in Early Jurassic time, tectonic events taking place at the continental margin of Chukotka are well correlated with the main phases of the Amerasia Basin opening. The Late Jurassic was characterized by termination of spreading in the ProtoArctic Ocean and transformation of the latter into the closing South Anyui turbidite basin. The Chukotka microcontinent was subducted beneath the Siberian active margin (the Oloy volcanic belt) until the Valanginian. In the Hauterivian-Barremian, an oblique collision was initiated simultaneously with spreading in the Canada Basin. This collision resulted in formation of the South Anyui suture. As both subduction and collision was terminated, formation of an oceanic crust within the Amerasia Basin ceased.

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