The heavy metals (Cu, Ni, Zn, As, Pb, and Cd) in 93 bottom sediment samples collected from shelf northwestern Bering Sea were studied due to this area is very important for the fishing and is strategically vital sections of the Northern Sea Route. For the first time in this region the sediment quality indices, ecological and human health risk assessments of metals were determined. The mean Cu, Ni, Zn, Pb, and As contents were 11.32, 13.4, 49.7, 14.54, and 11.4 ppm, respectively. The maximal Cd, Pb and As concentrations were observed on several stations from the Kresta Bay and the Mechigmenskiy Gulf where demonstrated higher values of environmental indicators that could be deal with industrial exploitation of ore deposits or lithogenic factors. Nevertheless, the results of hazard index and carcinogenic risks for all HM from ingestion and dermal pathways indicated a no potential health risk.

Studies were carried out in three key areas in the eastern Gulf of Finland during joint cruises of the A.P. Karpinsky Russian Geological Research Institute and the Shirshov Institute of Oceanology of the Russian Academy of Sciences in 2023. Multibeam echosounding, sub-bottom profiling, and various sediment sampling techniques were performed, and a significant amount of new geological and geophysical data was collected. Analyses of seismic sections, supported by sediment sampling data and a digital elevation model (DEM) of the sea floor, allowed for the revelation of six acoustic unions (AU) which are divided by reflecting interfaces and have unique acoustic waveforms. The sediments of the AUs were developed in different stages of deglaciation and in the postglacial period of the Late Pleistocene - Holocene. A complex analysis of collected and archived data allowed for the construction of DEMs of buried paleo-relief surfaces. Both the sea floor and paleo-relief DEMs allowed for the mapping and discovery of geomorphological features of landforms specific to the study area, such as submerged end moraine, drumlins, eskers, De Geer, etc. The studies provide new data on the Gulf of Finland basin deglaciation and establish sedimentological processes, features, and the impact of exogenous processes on the geological environment.

New data on the lithology of surface sediments in the coastal areas of the East-Siberian Sea (between Wrangel and Novaya Sibir islands), obtained within the framework of the state geological mapping at the scale of 1:1M, was used to clarify the distribution of granulometric types, mineral composition, and geochemistry of surface seabed sediments in this area. The main sources of sedimentary material and sedimentation patterns of the coastal part of the Western and Eastern sectors of the East-Siberian Sea were considered. An important factor determining sediment redistribution along the seabed, violating the regularities of mechanical differentiation of matter, consists in the plowing of the seabed surface by drifting ice to depths of 50 m.

The article addresses issues related to the study of lithodynamic processes on the shelf as dangerous phenomena. On the example of the coastal zones of South Sakhalin where hazardous exogenous processes on the shelf are state-monitored, it is shown that an annual redistribution of bottom sediment accumulation and erosion zones occurs within the identified key areas. Other examples from the practice of similar works in the Gulf of Finland of the Baltic Sea indicate that lithodynamic processes in the coastal zone lead to a significant disturbance of the coast, which poses a specific danger to the population. It is concluded that lithodynamic processes should be studied via standard lithological and geophysical methods used in marine geological work.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23060168

Based on two years of monitoring of modern bottom sediments of two sections of the Kaliningrad shelf of the Baltic Sea - "Curonian Spit" and "Northern Sambian" - an assessment of the sources of pollution with organotin compounds (OTs) and heavy metals was carried out. The content of individual organotin compounds and OTCs spectra obtained by gas chromatography with mass spectrometry of relatively coarse-grained bottom sediments indicate the presence of organotins in significant quantities - the total OTs content (& sum;OTs) is from 0.6 to 8.3 ng/g. However, the content of tributyltin (TBT), the main component of anti-fouling systems for marine vessels and the most dangerous endocrine-disrupting compound among the hazardous substances for marine ecosystems, is at a low level (0-2.3 ng/g) in all studied samples and has not increased over the two-year observation period (biodegradation index 1.7-12.4). At the same time, the presence of abnormally high concentrations of mono-, triphenyl- and tricyclohexyltin in the sediments of the "Northern Sambian" site (up to 30, 7 and 6.4 ng/g, respectively) indicates an additional source of pollution of coastal waters and shelf sediments (for example, plastic litter and agricultural runoff). The absence of significant shipping in the study areas ensures a consistently low level of pollution with tributyltin and its derivatives (less than 0.3 and 2.3 ng/g of TBT in 2017 and less than 0.1 and 1.3 ng/g in 2018 for the sites "Curonian Spit" and "Northern Sambian", respectively), which indicates the activity of the processes of TBT transformation and selfcleaning of sandy sediments. However, the identified trends and their predictive accuracy require long-term observation and monitoring of the sediment environment using data on the deep-water part of the shelf, enriched in clay and humus components.

The near-shore zone of the East Siberian Sea is one of the least studied marine areas of the Russian Arctic. One of the important unsolved problems is the existence of a glacier sheet in the area of the New Siberian Islands, and the related debatable issue of the age and genesis of underwater ridges (bars) around the archipelago. Based on comprehensive analysis of the geological and geophysical data obtained by the Karpinsky Russian Geological Research Institute, St. Petersburg, Russia (VSEGEI) in 2018 and 2020 and subsequent laboratory studies, two types of submarine ridges, principally different in morphology, sediment composition, age, and genesis, were distinguished. The ridges of the first type located on the outer periphery of the underwater valley of the pra-Kolyma River and around New Siberia Island are asymmetric. They have a relative height of 1–2 m to 4–6 m, an average width of 2–4 km (up to a few tens of km), and an average length of 25–30 km (up to 100 km). According to the sampling data, the ridges of this type are composed of very dense clayey silts without an admixture of coarse clastic material. The age of the deposits forming the ridges is Late Pleistocene (18–13 ka BP). The Middle–Upper Pleistocene formations are exposed in the inter-ridge hollows. The composition, morphology, and age of the ridge deposits suggest that their genesis is associated with denudation processes, but the mechanism of their formation is not obvious. The ridges of the second type include a system of coastal bars located at a distance of up to 30 km from the coast of New Siberia Island and are composed of fine-grained, well-sorted sands. The width of the ridges varies from 1 to 2 km; the height, from 4 to 8 m; and the length is 10–15 km. They are slightly asymmetric in shape, with a gentler slope from the side of the island. This system of ridges was formed as a result of accumulative processes in the Holocene. The ridges of terminal moraines were not established within the seabed segments studied. The obtained data do not support the hypothesis of the extension of the Late Pleistocene ice sheet to the shelf.

Problems of the paleogeographical evolution and changes in sedimentation environment within the Indigirka River paleovalley (the East Siberian Sea) are discussed. Based on the results of geophysical and geological research and a high-resolution study of sediment cores (grain size analysis, geochemistry, macro- and micropaleontology, pollen analysis, radiocarbon dating) the development of the Holocene marine transgression has been reconstructed, sedimentation rates have been calculated, and the basic principles of changes in sedimentation processes have been established.

The bottom sediments of the Russian Arctic seas have been studied to varying degrees. The least attention has been paid to the East Siberian Sea, the Quaternary geology of which remains largely overlooked. This article summarizes the results of a comprehensive research on the East Siberian Sea, including the first paleomagnetic analysis of nine sediment cores collected during three cruise expeditions as part of the program “State Geological Mapping of the Territory and Continental Shelf of the Russian Federation at the Scale of 1:1 000 000”. The results obtained show that the processes and conditions of sedimentation vary in different parts of the East Siberian Sea.

New data are presented on the geological sequence, composition, and genesis of Late Pleistocene–Holocene deposits in the southern part of the East Siberian Sea (Long Strait to Chaun Bay). Basic materials were collected during a marine geological expedition by the A.P. Karpinsky Russian Geological Research Institute (VSEGEI) carried out in 2018 for geological mapping of sheets R-56–R-60. Research included sub-bottom profiling, side-scan sonar survey and multibeam echo sounder, sediment sampling (box corer and gravity corer). Processing and interpretation of geophysical data and study of sediment cores, including layer-by-layer grain-size, geochemical, diatom, and palynological analysis, as well as radiocarbon dating, were used to update the knowledge on reconstruction of the geological development of the region and refine the palaeoclimatic and palaeogeographic characteristics of the natural environment in the Late Pleistocene–Holocene. During the Sartan Cooling within the off-shore study area, continental conditions prevailed, but no seafloor landforms or any sediments formed by glacial activity were found, since erosional processes dominated at that time. Sediments accumulated within shallow freshwater lakes (possibly thermokarst in origin), river valleys, and semienclosed lagoons. Since the end of Pleistocene, the sea level rose irregularly, as evidenced by characteristic seafloor landforms (longshore bars, underwater terraces, foredeltas, etc.). Holocene sedimentation is characterized by high facial diversity, low sedimentation rates, and weak sorting of sedimentary material.

The seafloor of the eastern Gulf of Finland (the Baltic Sea), especially its easternmost part – Neva Bay – has experienced anthropogenic impacts since the beginning of the XVIII century. The aim of this paper is: i) to analyze results of different stages of anthropogenic impact on the geological environment and ecosystem, ii) to assess the influence of dredging, dumping, and aggregates (sand, gravel) and ferromanganese concretions extraction on bottom relief and sedimentation processes, and iii) to establish the major spatial and temporal trends of heavy metal accumulation in the soft bottom sediments. Since the establishment of St. Petersburg, and into the 1960s, there was a physical impact on the seabed through the construction of artificial islands, dredging, and dumping. From 1960s to the 1990s, these types of activity became even more intense, as nearshore submarine terraces were used for sand and gravel extraction, and sediment pollution (e.g., heavy metals) has become one of the main environmental problems of the region. Based on extensive geochemical data collected for the first time in the study area, we examined a vertical distribution of heavy metals in cores obtained from different sedimentary basins. Results demonstrate a trend of increasing concentration values from the 1940s to the 1990s. Background concentrations of heavy metals are based on the geochemistry of catchment areas, decreasing in concentrations from the northwest to the southeast, while the maximum concentrations of hazardous substances deposited from the 1970s to the 1990s were observed in the easternmost part of the gulf. Since the 1990s the heavy metal input to the Gulf of Finland has significantly decreased, so the concentration of these hazardous substances in the surface sediments dropped as well, demonstrating a spatial distribution corresponding more to background (natural, pre-industrial) values. On the other hand, big hydrotechnical projects, realized during the last 20 years – artificial territories and new harbors construction, accompanying with dredging and dumping, ferromanganese concretion extraction, etc. – led to resuspension and secondary pollution of water. The other problem is the expansion of anoxic areas, caused both by climate change and human-stimulated eutrophication. Near-bottom anoxic conditions stimulate heavy metal migration from bottom sediments into the water column. All these processes impacted benthic communities as our review of previously published studies reveals. Geological and geophysical research revealed that within some areas anthropogenic impact caused a complete change of the sedimentation processes such as direction and rates of transport, which led to the total transformation of bottom relief, surface sediment distribution, and the benthic communities.

Coastal reclamation is a major feature of contemporary land planning. As a multicomponent natural system, the coastal zone is impacted by various external processes (inundation, erosion, etc.) and land habitat demands an increased focus on anthropogenic activity. For the first time, a coastal vulnerability index (CVI) has been determined for the easternmost area of the Gulf of Finland (the Baltic Sea) (EGoF) in order to assess vulnerability of the coastal zone to erosion. The parameters for the CVI assessment were identified on the basis of existing field observations and analysis of environmental factors expressed in the EGoF. This research is focused on coastal segments prone to the rapid development of erosion, a subject highly relevant for coastal management. The CVI assessment, based on a method proposed by Gornitz (1991), uses seven physical parameters grouped according to geological, geomorphological, lithodynamic and hydrodynamic characteristics. Storminess, or susceptibility to destructive storm events, was applied for the study area not only because of the global increase in storm activity but also because this area undergoes a “bay-effect”. An experts’ assessment distinguished the most crucial parameters that triggered the coastal erosion process, namely that coastal geology and the number of destructive storms affected coastal processes.

Results of organotin and heavy metals pollution study of bottom sediment within three key areas in the Eastern Gulf of Finland (Baltic Sea) in the vicinity of Gogland and Moschny Islands and Vyborg Bay sampled during two seasons of 2017 and 2018 are presented.The studied bottom sediments contain organotin compounds in amounts ( n-ary sumation OTs from 5.7 to 123 ng/g) exceeding the permissible international standards, which can have a toxic effect and lead to pathological changes of aquatic organisms. The tributyltin was the prevail component of organotin compounds in bottom sediments in 2017, which high content (average 6.3 and 30 ng/g for Moschny and Gogland islands respectively) and low degradation coefficient (BDI: 0.1-0.8) indicate a permanent source of pollution. But the 2018 samples show an increase in BDI up to 1.7-3.3 that reveals the degradation of tributyltin over the annual period. But further monitoring of environmental pollution in the study areas is obviously necessary in view of the potential impact of these components on the irreversible change in the environmental situation for the entire Baltic region.

The paleoclimatic events of the Late Pleistocene and Holocene have been clarified based on the results of detailed lithological, geochemical, pollen, and paleomagnetic studies of sediment cores collected in the eastern Gulf of Finland. The time frame of the change from lacustrine to marine sedimentation conditions has been refined based on the radiocarbon dating. For deposits of the marine phase of the Baltic Sea in the eastern Gulf of Finland, hypoxia cycles associated with periods of warming during the Holocene have been revealed.

This paper presents an age–depth model based on an ultra‐high‐resolution, 80‐m‐thick sedimentary succession from a marine continental shelf basin, the Kattegat. This is an area of dynamic deglaciation of the Fennoscandian Ice Sheet during the Late Pleistocene. The Kattegat is also a transitional area between the saline North Sea and the brackish Baltic Sea. As such, it records general development of currents and exchange between these two systems. Data for the succession were provided through the Integrated Ocean Drilling Program Site M0060. The site indicates onset of deglaciation atc. 18 kaBPand relatively continuous sedimentation until 13 kaBP. At this point, sediments record a hiatus untilc. 9–7 kaBP. The uppermost sedimentary unit contains redeposited material, but it is estimated to represent only the lastc. 9–7 kaBP. The age–depth model is based on 17 select, radiocarbon‐dated samples and is integrated with a set of physical and chemical proxies. The integrated records provide novel constraints on the timing of major palaeoenvironmental changes, such as the transition from glaciomarine proximal to glaciomarine distal and marine conditions, and their connections to known major events and processes in the region and the North Atlantic. Depositional evidence specifically documents connections between the Fennoscandian Ice Sheet behaviour and atmospheric and oceanic warming. Glacial retreat may have also depended on topographic factors such as changes in basin width and depth, linked to relative sea level changes and land uplift. The results indicate an early response of the Fennoscandian Ice Sheet to changing climate, and the ice sheet's possible influence on oceanic circulation during the Late Pleistocene deglaciation.

The results of both onshore and offshore monitoring of the coastal zone in the Russian Baltic reveal the high intensity and recent acceleration of coastal dynamics caused by an increasing frequency of extreme hydrodynamic events and anthropogenic impacts on the diverse geology. Stable coasts dominate in the eastern Gulf of Finland, but the local rate of shoreline recession is up to 2.0 m a −1 , reaching 5 m in one extreme storm event. The coastal zone of the Kaliningrad area is diverse. The western coast of the Sambia Peninsula is controlled by anthropogenic influences linked to the exploitation of geological resources. The beaches advance when the supply of artificial sediments from opencast amber mines increases, whereas the shoreline retreat reaches 10–20 m a −1 when the input is interrupted. Active landslides and beach degradation dominate along the northern coast of the Sambia Peninsula. Large areas of pre-Quaternary deposits, outcrops and boulders in the nearshore provide evidence of sediment deficiency offshore. The coastal geological hazards are dependent on climate. A comprehensive understanding of the main trends in climate change is important for predicting and mitigating future damage to the coastal infrastructure and for selecting adaptation strategies. Thematic collection: This article is part of the Mapping the Geology and Topography of the European Seas (EMODnet) collection available at: https://www.lyellcollection.org/cc/EMODnet

Forecasting the coastal zone development under possible climatic changes and technogenic impact is an extremely important task. This forecasting is based on our understanding of the mechanism of the hydrodynamic processes impact on the coastal zone. The goal of this work is to describe the hydrodynamic conditions (currents, sea level, surface waves) of coastal waters and to assess the influence of hydrodynamic parameters on the general dynamics of the beach. The object of this study is a part of the southern coastal zone of the Gulf of Finland (Baltic Sea). The method of research is a full-scale experiment and mathematical modeling. The initial data for the analysis are climatic characteristics of the hydrodynamic regime of the sea (velocity and direction of currents, sea level, integral parameters of wind seas and swell), as well as interannual variations in the position of the coastline in the region of the Izhora village in the eastern part of the Gulf of Finland. Interannual variations in hydrodynamic parameters and volumes of bottom material transported under the influence of wind seas and swell were estimated. Main conclusion: swell waves determine the general background in the patterns of the bottom material transport, and the contribution of wind seas is in the formation of beach properties, namely, the accumulation or decrease of beach material.

A brief analysis of the history of environmental geological study of the Barents Sea is given. It shows that at the beginning of industrial development the geological environment was characterized by a low level of disturbance and pollution. On example of the Kola Bay, an assessment of the current environmental geological conditions of the fjords in the eastern part of the Barents Sea is given. Seismic-acoustic studies confirm the predominantly tectonic origin of the bay and the hazardous spread of gravitational rocks movement within the coastal slopes. The background geochemical characteristics of recent bottom sediments are quantified. It is shown that geochemical zoning of the bottom of the bay is a consequence of both natural and anthropogenic processes. According to the content of Cu, Zn, As, Cd, Pb, Hg and hexane-soluble petroleum products (PP) in the bottom sediments, the characteristics of various areas were obtained. It is shown that the distribution of PP and several other pollutants in the main components of aquatic and coastal geosystems is a leading element of the environmental monitoring system, quantitative assessment of anthropogenic impact and accumulated environmental damage. Active economic activity within the southern leg of the Kola Bay, as well as the naval bases, significantly affects the distribution of chemical elements. The data concerning distribution of chemical elements forms in bottom sediments are given that suggest a high probability of secondary pollution of the bottom water when the physicochemical conditions of sedimentation processes change. A comparative analysis showed that bottom sediments of the Kola Bay are characterized by the highest concentration of chemical elements in the North-West Region of the Russian Federation.