Geochemistry of hydrocarbons-biomarkers and carbon isotopes of organic matter in the Domanik Deposits of the Timan-Pechora Basin

Abstract

It has been established that the average values of some hydrocarbons biomarker coefficients of bitumens from the Domanik deposits and oils from the Domanik–Tournaisian complex coincide. These are the proportions of C27–C29 steranes, tri-/pentacyclanes ratio, and coefficients 2 × С17/С16 + С18 and 2 × С27/С26 + С28 calculated from n-alkane composition. Such indicators as the Pr/Ph, (Pr + Ph)/(n‑C17 + n‑C18), dia-/reg-steranes, and the sterane/hopane ratios in oils are slightly lower than in the bitumen. The average values of δ13C in asphaltene, resin, aromatic hydrocarbons, and aliphatic hydrocarbons fractions from oils of the Domanik genotype and in the studied bitumens are similar. The carbon isotope composition of asphaltenes in oils is depleted in 13С compared to those of resins and aromatic hydrocarbons, and vice versa in bitumens. A heterogeneous composition of the bacterial flora in the sediments of the Domanik Sea is suggested. In some places, species with high concentrations of diplopterol or hexafunctional bacteriohopanes likely dominated over bacteriohopantetrol.