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This paper reports the data on the structure of the northwestern boundary of the Middle Amur sedimentary basin which were obtained after resumption of audiomagnetotelluric soundings. The geoelectric sections for two profiles across the basin strike are constructed, the sedimentary cover and basement structures are studied, and their electrical properties are determined. The compared data of the earlier and present studies show low-resistivity zones of 50-150 Ohm m beneath high-resistivity rocks of 500-1000 Ohm m in the northwestern part of the Ul’dura-Churki uplift at a 2-4 km depth, which are absent in the southwestern part of the uplift. This fact is related to strike-slip-overthrust processes due to graben formation in the area of junction with the Jiamusi-Bureya Massif in the Kur fault zone (YYilan-Yitong branch of the Tan-Lu fault zone) and also to global left-lateral strike-slip displacements and volcanic activity. [ABSTRACT FROM AUTHOR]

The structure and evolution of the passive continental margins of the Arctic Ocean are considered on the example of the South Kara Basin. Its development is associated with the evolution of the West Siberian Plate and the formation of the Arctic Ocean. Until the Late Cretaceous, the South Kara Basin was the north margin of the West Siberian Plate, whose formation is related to the Permian-Triassic processes of riftogenesis accompanied by the eruptions of traps. In the Mesozoic, due to the opening of the Arctic Ocean, the South Kara basin became a part of the continental margin, where the accumulation of marine sandy-clayey rocks continued. [ABSTRACT FROM AUTHOR]