The geochemical and isotope (Sr, C, O) characteristics of the Vendian–Cambrian carbonate deposits of the Azyr-Tal Ridge (Kuznetsk Alatau): chemostratigraphy and sedimentogenesis environments

Results of isotope (Sr, C, and O) and geochemical studies of the carbonate deposits of the Yenisei Group of the Azyr-Tal Ridge (Kuznetsk Alatau) are presented. Using the Sr and C isotope chemostratigraphy, the age restrictions for these deposits have been made. It is shown that the sediments of the Charyshtag, Bidzha, and Martyukhina Formations and the lower part of the Sorna Formation accumulated in the Late Vendian and Early Cambrian, at 580–530 Ma, and those of the upper part of the Sorna Formation, at 525–517 Ma. Their successive accumulation in the same sedimentary basin is not confirmed by the performed geochemical studies. The deposits of the upper part (members 2 and 3) of the Sorna Formation accumulated in a sedimentary basin of other type as compared with the rest underlying deposits of the Yenisei Group. For example, at least two types of shallow-water sea basins are recognized within Kuznetsk Alatau in the Late Vendian: shelf, localized within a block with a passive tectonic regime (Charyshtag, Bidzha, and Martyukhina Formations and lower part of the Sorna Formation), and oceanic, where accumulation proceeded within oceanic islands with underwater hydrothermal activity (upper part of the Sorna Formation).