The Arctic shelf is an area of national priority for Russia. Huge reserves of hydrocarbon raw materials in addition to transport and logistics communications are concentrated within its borders. The article discusses the issues of identifying the spatiotemporal patterns of the formation of a potential oil-and-gas-bearing region in the junction zone of two noncoeval continental lithospheric plates: the ancient Archean (Russian) and the young Barents Sea plates (with the Grenville basement). A description of the geodynamic evolution of the region is given, and data on the geological structure of the Neoproterozoic complexes of the Sredny and Rybachy peninsulas (Kola Peninsula) and adjacent water areas of the Barents Sea are provided. The aggregate data suggest that the relief of the western Russian Arctic was mainly formed as a result of processes involved in closure of the Proto-Atlantic and Ural paleoceans (and later the Japetus paleocean). The oil and gas potential of the described region was formed as a result of a multistage and long-duration process that led to enrichment of Neoproterozoic complexes of the northern Kola Peninsula and adjacent waters of the Barents Sea in hydrocarbon raw materials.

Contourite drift studies in six seas of Russia have been compiled and analyzed for the first time. The considered sedimentary bodies vary in size, age, and structure, are located at different depths, occur in various environments, and are attributed to several classification types. Our study combines these contourite drifts in two groups. The first includes shallow-water drifts on the shelves of Kara, Pechora, and Baltic seas; the second consists of deep-water drifts on the slopes and in the basins of the Sea of Japan, Sea of Okhotsk, and Caspian Sea. The relationship between the studied sedimentary bodies and bottom currents is considered.

Sedimentary material sampled in the southwestern Kara Sea both directly in ice scours and on background surfaces undisturbed by ice scouring has been studied. Based on studies of the physical properties and lithomineralogical features of bottom sediments in the ice scours, the boundary of ice scouring impact (exaration contact) was identified. Based on the X-ray diffraction analysis of <0.001-mm fraction, the chlorite structure is sensitive to temperature in samples taken below this contact, in contrast to the overlying samples. Together with the results of microscopic studies of thin sections, this fact indicates the neoformation of chlorite. The presence of secondary chlorite in near-surface conditions can suggest the glaciodynamic impact (pressure) of iceberg keels on bottom sediments. Microstructures of the ice scour sediments differ both in different test sites of the study area and within the same scour, depending on the location of sampling point on the transverse profile of morphosculpture.

The study is based on the results of multibeam echo-sounding and high-frequency seismic profiling during the 2018-2022 cruises of the R/V “Akademik Nikolai Strakhov” and “Akademik Boris Petrov”. Regular changes of morphometric parameters and the internal structure of pingo-like formations of the shelves of the Pechora and Kara seas were revealed. A morphometric analysis of pingo-like formations was carried out, which made it possible to draw conclusions about their relative age, as well as the role of near-bottom currents and slope processes in their modern dynamics. It was found that the density and morphological variety of pingo-like formations depend on the geological and tectonic features of the bottom area, the presence and nature of permafrost, the intensity of degassing, and the time of shelf flooding during the Holocene transgression. Pingo-like formations on the shelf, where the depth exceeds 70-80 m, emerged at the early stages of the Holocene transgression, and by now the permafrost there has largely thawed out. At the same time, pingo-like formations are still prominent in the relief and actively transformed by bottom currents, slope and, possibly, pseudovolcanic processes associated with ongoing degassing. Pingo-like formations are rare within shallow (up to 20-30 m) shelf areas close to the shore, and, apparently, continue their evolution at present. At the same time, the large thickness and continuity of permafrost prevent active fluid flow, acting as a seal. Pingo-like formations in the shallow-water zones are mainly cone-shaped mounds without intensive degassing. The density of pingo-like formations is maximum at the intermediate depths (from 20-30 to 70-80 m), in the presence of insular or discontinuous permafrost, under high fluid flow intensity within the fault zones and oil- and gas-bearing structures. Near-surface sediments in such areas are characterized by a combination of localized processes of heaving and active degassing. It predetermines a wide variety of the morphological types of pingo-like formations.Keywords: Arctic, bottom topography, degassing, pingo-like features, acoustic anomalies, multibeam echo sounding, seismoacoustic profiling

Contourite drifts were found for the first time on the SW Kara Sea shelf based on the analysis of bathymetry and seismoacoustic data obtained in the cruises 41 (2019) and 49 (2020) of R/V Akademik Nikolai Strakhov. These drifts are confined to a narrow NS depression with a depth of 240 m. They are separated from underlying sediments by the basal unconformity caused by the bottom current formed in the marine environment after melting of the Barents–Kara ice sheet during the Late Pleistocene–Holocene time. Hydrological measurements carried out in the cruise 89-1 (2022) of R/V Akademik Mstislav Keldysh made it possible to reveal the bottom current with a measured velocity of up to 10 cm/s.

Mapping of dangerous geological objects and processes by hydroacoustic methods is being intensively developed in the areas of the Arctic shelf of Russia. Considerable experience has been accumulated in identifying of these objects and in compiling of thematic maps showing their properties, spatial distribution and correlation with geological and tectonic structures. A large amount of data and the development of economic activity make it necessary to develop a methodology for compiling these maps, design of legends and an approach to updating them. The paper presents map samples of dangerous geological objects compiled according to the data of RV “Academik Nikolai Strakhov” expeditions.

The spatial distribution of subsurface seismoacoustic anomalies of the "bright spot" type in the Pechora Sea, which are indicators of free gas accumulation, is analyzed. The anomalies are associated with deep-water faults that cut the Paleozoic and, in some cases, Mesozoic sedimentary complexes, through which gas-saturated fluids migrate up to the Quaternary sediments, where the studied phenomenon is observed. Gas bursts into the water column have dangerous consequences for man-made activities in the shelf are. Gas-saturated areas in the sediments are identified in space discretely, both horizontally and vertically. Providing safe human activity on the Arctic shelves requires detailed study of the manifestations of degassing.

Sedimentary waves are represented by a series of wavelike accumulative features with various degrees of morphological expression. These morphological forms are superimposed on the underlying surface with a clear stratigraphic unconformity. The hydrophysical processes are the main relief-forming factors of such features. During expeditions 38 (2018) and 41 (2019) of the R/V Akademik Nikolay Strakhov, the seafloor was mapped between the Kanin Peninsula and inlet of Cheshskaya Bay and new data were acquired on the morphology sedimentary waves. New data obtained in summer (July–August) 2019 show rapid changes in the natural hydrodynamic environment influencing the alternation of the sedimentary waves. The occurrence of hazardous natural processes, geological and geomorphological risks, and the level of threats were identified, especially with respect to the prolonged navigation period along the Northern Sea Route.

33-й рейс НИС «Академик Николай Страхов» выполнялся в Атлантическом океане и Балтийском море, включал в себя комплекс геологических, гидрологических и гидрохимических работ. По результатам многолучевого эхолотного промера дна были построены цифровые модели донных ландшафтов. Методом драгирования получены новые геологические образцы, измерены значения геотермальных потоков в Атлантическом океане.

According to a study of the water column thermal variability in the Kvitøya trough (the northern part of the Barents Sea) substantial water temperature fluctuations in the near-bottom layer were found, both the seasonal and interannual, which affect the distribution of temperature in the upper layer of bottom sediments, and therefore the results of geothermal measurements. The contribution of temperature fluctuations on the water-sediments boundary to the values of the conductive heat flow measured during 25th cruise of the RV “Akademik Nikolaj Strakhov” was calculated. Endogenous heat flow was determined.

По результатам исследования авторами термического режима водной толщи в троге Орла (северная часть Баренцева моря) выявлена достаточно весомая изменчивость температур в придонном горизонте трога, как сезонная, так и межгодовая, что сказывается на распределении температур в верхнем слое осадков, а значит, и на результатах геотермических измерений. В статье выполнен расчет вклада колебаний температуры на границе вода-дно в величины плотности донного теплового потока, полученные по данным геотермических измерений в 25-м рейсе НИС “Академик Николай Страхов”, определен эндогенный тепловой поток.

Studies of acoustic anomalies in the water column and seismoacoustic anomalies in the Quaternary sediments of Pechora sea and their relationship with deep hydrocarbon sources were conducted by the Institute of Oceanology of the Russian Academy of Sciences and the Geological Institute of the Russian Academy of Sciences in the 38th cruise of RV “Academik Nikolaj Strakhov” in 2018. Mapping of free gas manifestations presents an additional indicator of tectonic activity and the fault network frame, which provides the flow of fluids from deep horizons. Comparison of high-resolution seismic survey data with deep seismic survey data shows that the fluid in the upper part of the section is first accumulated under the bottom of Jurassic-Cretaceous sedimentary sequences, which are fluid-resistant. Local dislocations of fluid trap lead to further rise and redistribution of free gas in Quaternary sequences. Natural or artificial break of their integrity results in the release of gas into the water column from near-surface accumulations that were found in the form of “bright spot” anomalies on seismic-acoustic records. Mapping of sound scattering objects in the water column shows the degassing areas, which are usually located above the deep faults. “Bright spots” of free gas in the Quaternary sequences have a variety of shapes – multi-tiered and inclined. Gas breaks into the water column occur near the edges of these anomalies. Systematic mapping of the considered phenomena is a necessary element in the preparation of the area for industrial operation.