The results of studying the quantitative, material, and morphometric composition of rock debris in sediments sampled by a box-corer on Lomonosov Ridge (83° N), Arctic Ocean, during the Severnyi Polyus 41 expedition of the Arctic and Antarctic Research Institute are presented. Clasts ≥ 1 cm in size were sampled from each distinguished layer according to the lithological description. The age model was created by the lithostratigraphic correlation with previously dated cores. The content of clasts on the eastern slope and summit is significantly higher than on the western slope, which is explained by the higher sedimentation rate on the western slope after the deglaciation peak. The change in the rock composition from carbonate to igneous and the increase in roundness with time indicate a higher input of Eurasian material in MIS 1.

Outcrops of the coal-bearing Tankhoi Formation (Oligocene–Pliocene), traced along the southern shore of Lake Baikal, submerge under its Southern Basin, where several hydrate-bearing zones of the focused hydrocarbon fluid discharge have been found. To test the hypothesis that coals of the Tankhoi Formation can be the sources of hydrocarbon gases in these zones, we collected coal samples from the Shakhterskaya Gorka outcrop. Experiment on gas generation from the selected samples was carried out in a special autoclave at a temperature of 90°C for eight months. This paper presents the obtained results, which confirm an important role of the process of gas generation from coals in the formation of fluids in the Kedr mud volcano. The further migration of gases was accompanied by the biodegradation and formation of secondary microbial methane due to CO2 reduction. This was one of the reasons for the carbon isotopic pattern observed in methane (heavier than –50‰ VPDB) and carbon dioxide (positive values) taken from the near-surface sediments and hydrates of the Kedr mud volcano, as well as for the significant enrichment of authigenic siderites in the heavy 13C isotope.

The paper presents the characteristics of the coarse clasts (psephites, larger than 1 cm) sampled in the northern part of the Franz Victoria Trough (Barents Sea) during the “Transarktika-2019” expedition. The studied sedimentary section was formed during the transition from the last deglaciation environments to the marine Holocene settings. The amount of psephites in deglacial sediments is much higher than the one in Holocene sediments. The petrographic composition of the psephites, their roundness (according to Waddell and Khabakov classifications) and shape (according to Zingg classification) were studied in detail. It is shown that the majority of psephites is represented by non-rounded or poorly rounded varieties. Isometric and disc-type shapes are predominating among coarse clasts. Isometric psephites prevail in “deglacial sediments”, while disc-shaped, bladed, and rodlike, as a rule, are current in marine Holocene sediments. The petrographic composition of psephites is mostly represented with carbonate (limestone and dolomite) and sandstones. The amount of carbonates increases from the Holocene to the deglacial part of the sediment section. Other rocks found in smaller quantities are represented by quartzites, cherts, shales, basalts, crystalline schists, gneisses, granites, pyrite. During the last deglaciation at the Late Pleistocene the iceberg rafting was the main mechanism of psephites delivery to the sampling points. The major sources of the icebergs were Franz Josef Land and the Belyi — Victoria Islands region. Rocks of Franz Josef Land are represented mainly by Cretaceous gabbro-basalt complex and Triassic sandstones and siltstones. Upper Paleozoic terrigenous and carbonate rocks, as well as Proterozoic metamorphites, occur in the west of the studied area (the area of the Belyi — Victoria Islands). The results of studying the petrographic composition of psephites allow us to conclude that during the last deglaciation icebergs from both sources were heading north towards the Nansen Basin through the Franz Victoria Trough. Both streams of icebergs failed to reach the opposite sides of the Franz Victoria Trough, mixing with each other approximately in the axial part of the trough and leaving it in northern directions.

Preliminary results of the Transarktika-2019 winter expedition in the Arctic Ocean on the R/V “Akademik Tryoshnikov” are presented. The expedition program included studies on meteorology, hydrology, hydrochemistry, hydrobiology, geology, geophysics and an extensive complex of ice measurements in the Northern Barents Sea from the drifting ice and from the ship. During the expedition, it was possible to complete a wide range of tasks. The data obtained comprise a unique material for a comprehensive study of the current state of the environmental conditions in the Barents Sea. This paper highlights the most significant preliminary results of multidisciplinary observations in various environments, which will be further comprehensively analyzed and published in separate thematic articles.

1 — State Scientifi c Center of the Russian Federation Arctic and Antarctic Research Institute, St. Petersburg, Russia 2 — Lomonosov Moscow State University, Moscow, Russia 3 — St. Petersburg State University, St. Petersburg, Russia 4 — Southern Scientifi c Center of the Russian Academy of Sciences, Rostov-on-Don, Russia 5 — Murmansk Marine Biological Institute, Kola Sciencetifi c Center, Russian Academy of Sciences, Murmansk, Russia 6 — VNIIOkeangeologiya, St. Petersburg, Russia 7 — Polar Geophysical Institute, Apatity, Russia

Summary The main idea of this study was to identify the background and anomaly distribution of hydrocarbon molecular markers in sediments of the lake Baikal and to define organic matter sources and specificity of its formation under the diagenetic and fluid discharge conditions. The study has shown that processes of hydrocarbon biodegradation are widespread in sediments of the oil discharge zone of the lake Baikal, but are not characteristic for the areas of mud volcanism and hydrothermal venting. The composition of hydrocarbon molecular markers in sediments near the mud volcano and hydrothermal vent area testify to the active growth of microbial biomass that uses methane and low molecular weight hydrocarbons coming from the deep as a main carbon source.