Hydrocarbons-biomarkers and palynological characteristics of peat of the Mezen-Vychegda plain

The peat from the Cherny Yar section at the Vychegda river was studied by a complex of palynological and geochemical methods. We determined that among the aliphatic hydrocarbons of bitumen, the maximum concentrations were characteristic for odd n-alkanes with a predominance of C27-C31 homologues, as well as 18-norabietane. Aromatic hydrocarbons are mainly represented by structures formed during the fossilization of diterpenoids and triterpenoids of higher vegetation. Among the aromatic diterpenoids, there are 18-norabieta-8,11,13-triene, 18-norsimonellite and retene, which are markers of conifers, as well as 18-norabietane of the aliphatic fraction. Among the aromatic triterpenoids, numerous transformation products of compounds with the carbon skeleton of lupan, oleanan, and ursane, characteristic of angiosperms, have been identified. For example, dinorolean(ursa)-1,3,5(10),13(18)-tetraene, dinorolean(ursa)-1,3,5(10)-triene, pentanoroleana-1,3,5(10), 6,8,11,13,17(18)-octaene and others. The data on the composition of hydrocarbons confirm the palynological data about the presence of coniferous and hardwood pollen in the composition of peat. The change in the composition of hydrocarbons along the section confirms the change in the species composition of vegetation in the study area, diagnosed by microfossils. The comparison of the composition of peat biomarker hydrocarbons with palynological data revealed their consistency with each other and possibility of conjugated use of these methods in paleogeographic reconstructions.