GEODYNAMICS OF MOUNTAINS IN EASTERN YAKUTIA AND OPENING OF THE EURASIAN BASIN

Abstract

The highest and longest ridges of the East Yakutian mountainous province exist on its periphery as the Verkhoyansk system in the west and the Chersky and Moma systems in the east. Northward, the ridges give way to the Primor'ye lowlands that grade into the Laptev Sea shelf separated from the Eurasian ocean basin by the continental slope. The ridges of the Verkhoyansk system make an asymmetric arch complicated by younger normal faults. The system of the Chersky and Moma ridges is likewise an arch cut with strike-parallel rift basins (Moma, Upper Selennyakh, etc.). The Cenozoic fill of the basins adjacent to the ridges provides evidence that rapid uplifting of the latter started in the Oligocene. Doming in the Late Miocene-early Pliocene was accompanied by compression, which produced imbricated thrusts with horizontal displacements of up to several kilometers. In the Late Pliocene-Early Pleistocene, the crust of the region experienced a large-scale extension responsible for the opening of the Moma rift and normal fautling in the Verkhoyansk ridge. The growth of mountain ridges in Eastern Yakutia may be related to the interaction of the Eurasian and North American plates in the Cenozoic and the opening of the Arctic Eurasian ocean. Multiple changes in the position of the plates' rotation poles through the Cenozoic caused alternation of extension and compression regimes. The opening of the Eurasia basin and the formation of mountain ridges in Eastern Yakutia were, apparently, nearly synchronous geodynamic events.