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The geodynamic reconstructions require accurate age determinations for the ancient sedimentary basins. Correlations between sedimentary deposits of different blocks of ancient oceans allow reconstructing the history of their development most accurately. This study is concerned with the investigations of Sr and C isotopic composition of Ediacaran and Cambrian carbonates of the Tuva–Mongolian and Dzabkhan (both in Mongolia now) continental blocks. These individual continental blocks evolved in the course of intensive carbonate sedimentation during the Late Neoproterozoic. At the base of these sections are deposits of glacial origin. Minimally altered carbonates (identified based on petrographic and geochemical criteria) of the Tuva–Mongolian block have Sr isotope values of 0.7073–0.7086 and δ 13 С values varying from −1.7‰ to +5.0‰. The primary 87 Sr/ 86 Sr ratios for Dzabkhan carbonate are 0.7072–0.7079 for Tsagaan Oloom Formation (δ 13 С varies from +3‰ to +14‰) and 0.7084–0.7086 for Bayan Gol Formation. We compared the 87 Sr/ 86 Sr curves of different coeval sections with the data generated by the present study and used geological data to establish that the deposits under study are accumulated asynchronously from the early Ediacaran (600 Ma) to middle of Cambrian (520 Ma).