Hydrocarbons in the Holocene Sediments of the Southwestern Part of the Kara Sea

Data on the content and composition of hydrocarbons, like aliphatic and polycyclic aromatic hydrocarbons, in Holocene sediments (undisturbed cores 0–30 cm) are presented. The samples were collected in the southwestern region of the Kara Sea during the first part of cruise 89 of the R/V Akademik Mstislav Keldysh in September 2022. It has been established that the distribution of hydrocarbons, unlike organic carbon, does not depend on the lithotype of bottom sediments, because, along with methane, high molecular weight hydrocarbons are formed in the gas-saturated zone. This leads to an increase in the proportions of aliphatic (>1%) and polycyclic aromatic hydrocarbons (>1 × 10–3%) in the organic carbon composition, as well as to the change in their distribution and composition within the sedimentary sequence. In the lower horizons of columns, the HC composition becomes more autochthonous due to the growth of low molecular weight alkanes and naphthalenes. Changes in the redox potential in the sedimentary sequence also affect the concentrations and composition of hydrocarbons.