Abstract
Knowledge on the age and distribution of glacial deposits is essential in order to solve issues surrounding the geological periodization of the Neoproterozoic and the large-scale changes in the environment and biosphere that took place at that time. The glacial origin of diamictites of the Precambrian Chivida Formation on the Yenisei Ridge (on the western periphery of the Siberian Platform) was proposed almost a century ago but has since been disputed. The present study confirms the glacial origin of the Chivida diamictites based on the findings of striated and faceted clasts and other characteristic features of glacial deposits. Results from U-Pb dating of zircon grains from diamictites matrix with and without volcanogenic admixture, tuffaceous sandstones and volcanic breccias interbedding the diamictites of the Chivida Formation are presented. The youngest population of zircon grains revealed in the volcanogenic and tuffogenic rocks of the Chivida Formation is assumed to characterize syn-depositional volcanic activity. Thus, its mean average age (696 ± 4 Ma) is considered to characterize the glacial sediments' time of deposition. These results prove for the first time the presence of an ice sheet on the Siberian craton during the Sturtian glaciation.
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