COMPOSITION OF ORGANIC MATTER IN BOTTOM SEDIMENTS OF THE CHAUNSKAYA BAY (EAST SIBERIAN SEA) br

The relevance of the study is determined by the need to assess the regional characteristics of transport and transformation of or-ganic matter in various sedimentation and biogeochemical environments on the East Siberian Arctic Shelf, in particular in theless studied and remoted East Siberian Sea.The main aim of the study is to determine the composition and sources of organic matter of bottom sediments of the Chaunskaya Bay (East Siberian Sea).Objects: 25 surface bottom sediments sampled along the transect from the coastal zone of the Chaunskaya Bay to the inner part of the East Siberian Sea shelf during the marine expedition on the R/V 'Academician Oparin >> in September-October 2020.Methods. Rock-Eval pyrolytic analysis was used to analyze groups of hydrocarbon compounds in organic matter from bottom sedi-ments; the n-alkanes distribution was estimated based on the results of gas chromatography-mass-spectrometry. Grain size analy-sis was performed on a laser particle analyzer.Results. The composition of sedimentary material in the Chaunskaya Bay is mainly determined by the features of the underwater relief and gravity flows of the incoming terrigenous material-products of local thermal abrasion of the coastal zone (Ayon Island) and river al-luvium in the southeastern part of the bay. A certain role in the formation of the sedimentary appearance of the bay is presumably played by the processes of cryosol thawing as a result of the destruction of fast ice areas. Pyrolysis data and analysis of the distribution of n-alkanes for surface sediments indicate a mixed genesis of organic matter in surface sediments with a dominant contribution ofter-restrial organic matter of a high degree of transformation and a high content of hardly decomposable humic substances and fulvic acids. The presence of autochthonous organic matter reflects the high productivity of the Chaunskaya Bay waters