Characterization of Sedimentation Conditions Based on the Composition of Organic Matter Dispersed in Rock of an Exploration Well on the Right Bank of the Ob River in Tomsk Oblast

The composition of biomarkers of the Upper Jurassic rocks in the Vostochno-Payduginskaya exploration well of the section of the Maryanovskaya and Naunaksk formations was investigated. The conditions of organic matter (OM) sedimentation were characterized based on data on the hydrocarbon composition, namely, the distribution of normal and isoprenoid alkanes, phenanthrenes, steranes, hopanes, and alicyclic and aromatic hydrocarbons. It was found out that OM was deposited throughout the section under study under oxidizing conditions. The sediments of the Naunaksk formation were formed in a shallow basin uncontaminated with hydrogen sulfide, while the OM of the Maryanovsk formation was formed in a lacustrine environment. The presence of low concentrations of gammacerane in the Maryanovsk formation and the lower parts of the Naunaksk formation indicated weakly saline waters of the sedimentation basin in this period. The participation of higher plants in the formation of the OM composition of the Naunaksk rocks was evidenced by high concentrations of cadalene and retene and the presence of simonellite and C₂₅ and C₂₇ n‑alkanes.