Geochemical Typing of Organic Matter in the Bottom Sediments Based on the Molecular Composition of Saturated Aliphatic Hydrocarbons

The paper presents approaches to typing organic matter (OM) from bottom sediments based on molecular indicators and statistical analysis. The results of analyzing the molecular composition and concentration of saturated hydrocarbons (n-alkanes) in thawed and permafrost deposits from Buor-Khaya Bay (Laptev Sea) made it possible to identify specific types of n-alkane composition. Principal component analysis allowed the identification of five types of molecular spectra of differing origin, degree of bacterial transformation, and concentration of n-alkanes. It was found that at a relatively small distance (10 km) from the continent, the composition and concentration of n-alkanes change drastically, which is explained by the spatial dynamics of OM fluxes in the Late Quaternary epicontinental morpholithogenesis conditions of the Laptev Sea. The contribution of coastal vegetation and aquatic components with distance from the continent increases markedly along with an overall increase in n-alkane concentration, while deposits from coastal shallow waters differ by the dominance of terrigenous homologues and a general decrease in n-alkane concentration. No influence of cryogenesis on the molecular composition of hydrocarbons in the deposits was revealed.