Quaternary Glaciotectonics of the Ural-Siberian North1

Abstract

Abstract This is a review of previous works on glaciotectonics and recent epeirogenesis of the northern West Siberian sedimentary basin and adjacent parts of the Urals and the Siberian Craton. It is supported by the addition of detailed structural profiles of the disharmonic dislocations around Malyi Atlym settlement on the Lower Ob’ never published before. The collected data highlight sources and results of neotectonic phenomena in the north of West Siberia and their impact on distribution of hydrocarbon deposits. The rugged topography of the northern Urals and Mid-Siberian Plateau, discordant with the regional tectonic structure, is generated by compensation uplifts along the margins of thick ice sheets in the West Siberian North. Ice load vacillations were an important factor of geographical separation of hydrocarbons liquid and gaseous phases. This is evident from the west–east zonation of petroleum deposits, discordant with the south–north strike of ancient structures but concordant with thickness zonation of ice sheets. The structure of the alpine-type dislocations penetrating up to 400 m into the sedimentary basin on the Lower Ob’ reveals that the variations of their tectonic style do not fit the mechanical properties of thawed Paleogene rocks. However, they are more understandable assuming their origin from deviatoric stress in pressurized perennially frozen Paleogene rocks. Such conditions are feasible at the base of a growing thick ice sheet. Ice sheets did significant work of glaciotectonic erosion of soft Paleogene rocks of the perennially frozen substrate soldered with glacial ice. This type of erosion is evident in the Ob’ catchment area where whole blocks of intact sand and clay were transported by glaciers over hundreds of kilometers. Glaciotectonic erosion of glacier substrate is sufficient for explaining the well-known stratigraphic hiatus between Quaternary and Upper Cretaceous formations of the Siberian Arctic instead of the popular but illogical tectonic inversion of the sedimentary basin.