Cyclostratigraphic Estimate of the Duration of the Negative δ 13 C Anomaly of the Zhuya Group (Shuram–Wonoka Event) in the Vendian Reference Section in the Southern Part of the Siberian Platform

A cyclostratigraphic study of the Late Precambrian Zhuya Group (Nikolskoye and Chencha Formations), and Torgo formation in the southern part of the Siberian Platform was carried out to determine the duration of the C-isotope anomaly imprinted in them. The similarity of the ratios of the period lengths of the cyclic components of the magnetic susceptibility in the coeval deposits of the remote sections of the Nikol’skoye and Torgo Formations indicates the connection between the revealed cyclicity and the basin-scale environment changes. According to the astrochronological model, the duration of the formation of the studied intervals of the Nikol’skoye (57 m) and Chencha (147 m) formations was 850 and 2500 ky, respectively. Extrapolation of the data obtained shows that the duration of the C-isotope anomaly of the Zhuya Group in the Vendian reference section on the Ura uplift was about 10 My, which is consistent with most estimates of the Shuram anomaly’s duration and its stratigraphic analogues.