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Vendian Taseeva Group, Southwestern Margin of the Siberian Platform: Isotope, Geochemical, and Geochronological Data, Age, and Correlation


 —A high-amplitude negative δ13C anomaly (–11‰ V-PDB) has been found in the carbonate horizons of the Chistyakovka Formation of the Taseeva Group in the type sections of the southern Yenisei Ridge. The δ18O values (–2.7 to –5.4‰ V-PDB) and the lithologic features of carbonates indicate that these are primary sedimentary rocks and their isotope parameters reflect the primary isotope composition of the paleobasin waters. The negative δ13C excursion in the Chistyakovka Formation is close in stratigraphic position and amplitude to similar isotope excursion in the Vendian strata of the southern Siberian Platform and to the global middle Ediacaran Shuram–Wonoka anomaly. According to the data on clastic zircons, the age of the Chistyakovka Formation is no older than 580 Ma, which agrees with the earlier estimated age of the Shuram–Wonoka event. As follows from the data obtained, the age of the basement of the Taseeva Group is no older than 600 Ma. This provides a more accurate correlation of the Vendian complex along the southwestern margin of the Siberian Platform. The different stratigraphic scales of the sediments indicate that the marginal trough here began to form at different times (from late Riphean to late Vendian), which explains its segmented structure.