Stable carbon isotope variations in primarily offshore Proterozoic carbonates of the Eselekh, Neleger, and Sietachan Formations in the Kharaulakh Range of northern East Siberia provide important information on the depositional history of the Riphean complexes and allow an age estimate to be made for potentially petroliferous Precambrian strata in the northeast of the Siberian Platform. The results of petrographic, geochemical, and isotopic studies of the measured samples demonstrate that the carbonates are recrystallized without substantial postdepositional alteration of the carbon isotope system and that the acquired δ13C values are accurate and can be used for the purposes of chemostratigraphy. The Riphean strata of the Kharaulakh Range are characterized by mostly high (5.5–8.6‰c) δ13C values. Based on carbon isotope data, the studied section could not be correlated with Mesoproterozoic strata of the Anabar and Olenek Uplifts but occupies a rather higher stratigraphic position. It can be correlated with the Baikal Group of the West Pre-Baikal Area and the Dal’nyaya Taiga Group of the Patom Upland; specifically, the negative shift in the uppermost Sietachan Formation possibly corresponds to the Zhuya negative excursion. Comparison with the model curve of carbon isotope evolution in the Precambrian ocean suggests that the age of the studied section does not exceed 820 Ma. Most likely, the studied strata are younger than 635 Ma (i.e., postdate the Marino glaciation) but older than the Gaskiers glaciation (580 Ma).