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Isotopic compositions of C, O, and Sr in carbonates, as well as Rb-Sr systems in the silicate mate rial from Upper Precambrian and Lower Cambrian rocks exposed by the Chapa River in the northern Yenisei Ridge, are studied. The Late Precambrian part of the section includes the following formations (from the bot tom to top): Lopatinskaya (hereafter, Lopatino), Vandadykskaya (hereafter, Vandadyk) or Kar'ernaya, Chivida, Suvorovskaya (hereafter, Suvorovo), Pod"emskaya (hereafter, Podyom), and Nemchanka. They are characterized by alternation of horizons with anomalously high and low δ 13 C values (such alternation is typ ical of the ~700-550 Ma interval). The lower, relatively thin (20 m), positive excursion (δ 13 C up to 4.3‰) was established in dolomites from the lower subformation of the Vandadyk (Kar'ernaya) Formation (hereaf ter, lower Vandadyk subformation). The upper positive excursion (δ 13 C = 2.2 ± 0.6‰) was recorded in the 3 km thick Nemchanka Formation enriched in terrigenous rocks. The lower negative excursion stands out as uniform, moderately low δ 13 C values (-2 ± 1‰) and significant thickness. It comprises the upper part of the Vandadyk Formation, as well as Chivida and Podyom formations. The upper negative excursion is related to a thin (~20 m) marker carbonate horizon of the upper Nemchanka subformation, in which δ 13 C values fall down to ⎯8.3‰. The lower part of the Lebyazhinskaya (hereafter, Lebyazhino) Formation, which overlies the Nemchanka Formation, shows a step by step increase in δ 13 C from -2.2 to 2.5‰ typical of the Vendian to Cambrian (Nemakit-Daldyn Horizon/Stage) transitional sequences. The absence of relationships between the carbon and oxygen isotope compositions and other parameters of postsedimentary alterations suggests that the excursions characterized above could form at the sedimentation stage and coincide in gen eral with δ 13 C fluctuations in seawater. The value of 87 Sr/ 86 Sr = 0.7076-0.7078 in limestones of the Podyom Formation points to their early Ediacaran age. Values of 87 Sr/ 86 Sr = 0.70841 and 0.70845 in dolomites of the lower Lebyazhino subformation correspond to the Early Cambrian. The Rb-Sr systems of the clay material from the Vandadyk and Chivida formations are approximated by a straight line, parameters of which corre spond to the age of 695 ± 20 Ma ( 87 Sr/ 86 Sr 0 = 0.7200 ± 0.0013) and probably characterize the epigenetic stage of older sedimentary rocks, which were subjected to very rapid exhumation and "polar" sulfuric acid weath ering in the course of glacioeustatic regression.