Abstract
New materials on the microfauna and lithology of the Kuznetsovskaya and Sedelnikovskaya Formations of the same horizons are presented. These data have allowed us to clarify the age of the boundary Turonian–Coniacian deposits of the Middle and Upper series of the Cretaceous system. Based on a comparison with geological units of marginal regions, where finds of secretion-calcareous foraminiferal shells are known, the Сoniaсian age of the Sedelnikovskaya Formation was established. The time interval of the regional break between the Turonian and Coniacian stages was determined, apparently, corresponding to the Early Сoniacian. The studied sections of the northern region are characterized by the absence of foraminiferal assemblage known in the sections of Kamyshlovskiye wells of the Omsk depression and in some places of the Trans-Urals.
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