Lithogeochemical characteristics of the pelitic and silty–pelitic bottom sediment samples, collected during Cruise 89 of the R/V Akademik Mstislav Keldysh (September 2022), from several areas in the southwestern Kara Sea (Baidaratsk Bay, Pukhuchansk Depression, West Kara Step, and Novaya Zemlya Depression) are discussied. It has been established that the muds contain a significant proportion of the lithogenic component. This conclusion agrees well with the localization of sediment data points on various discriminant diagrams near the reference points of average Paleozoic graywackes and PAAS. Such component could be sourced either from the fine-grained suspended particulates of the Ob River or from the sedimentary rocks and friable sediments of the Yamal and Yugra Peninsulas, Vaigach, and Novaya Zemlya. Although the upper layer of bottom sediments in the southwestern Kara Sea contains a noticeable amount of the mafic igneous rock fragments from Novaya Zemlya, which should make a significant contribution to their erosion products in the mud composition, parameters of the chondrite-normalized REE distribution in the sediments are inconsistent with such assumption.

Sands make up 5-7% of the surface bottom sediments in the West Kara zone and slightly more in the Ob-Yenisei zone. Analysis of the bulk chemical composition of the sands has shown that they contain greywackes, lithites, and subarkoses. This suggests that there is currently no significant clastic averaging in the Kara Sea and that sand composition is largely determined by the composition of the provenance. The concentrations of a number of trace elements, normalized to the composition of the average Phanerozoic cratonic sandstone, indicate their significant difference from this reference material. This difference is also confirmed by the localization of data points of sands from different areas of the Kara Sea on discriminant diagrams. The REE systematics of sands suggest that the contribution of erosion products of major igneous rocks is significant only for the Yenisei Bay sands. The sands from other areas have (La/Yb)(N) and Eu/Eu* values indicating the predominant role of erosion products of felsic igneous rocks in their composition.

The mineral, bulk chemical composition (main rock-forming oxides), and systematics of rare-earth elements, Sc, Cr, Zr, and Th in surface bottom sediments taken in several cruises of the R/V Akademik Mstislav Keldysh in the Nordic Seas (Mona, Knipovich, Kolbeinsey, and Aegir ridges; deep basins in the Norwegian and Greenland seas; continental slope of Spitsbergen; western continental margin of the Barents Sea, and others) are considered to determine sources of the fine-grained material of bottom sediments. The primary influence of terrigenous input is obvious for coastal sediments. Seaward sediments, however, are affected by the “relatively warmer” Atlantic waters, leading to their dilution with calcium carbonate produced mainly by planktonic foraminifers. It is concluded that the fine-grained aluminosiliciclastics for most of the studied samples were derived from both felsic and mafic igneous rocks (volcanic rocks of Iceland) in different proportions.

The paper presents data from grain size and mineralogical analyzes of surface bottom sediment samples obtained on several cruises of the R/V Akademik Mstislav Keldysh (2016–2018) from different parts of the Barents Sea. Pebble and gravel material is found in surface sediments in the form of impurities scattered throughout the sea. Such a chaotic distribution pattern is apparently associated with ice separation. Coarse material is most common in the Barents Sea off the coast of the Kola Peninsula, off the coast of Novaya Zemlya, Spitsbergen, where it accumulates due to coastal abrasion. In addition, a fraction >1 mm is widespread at depths where fine fractions are stirred and leached. The most common sediments in coastal shallow water are sands. Sands (0.1–1 mm) are widespread in the southern and southeastern regions of the sea, in the region of the Pechora polygon, the Kaninsky shallow water, the Kola Peninsula, and in the northwest, off the coast of Svalbard. With increasing depth, the sands are replaced by mixed sediments with a low admixture of pelite. Pelitic sediments are prevalent in the central part of the sea. Precipitation with a pelitic fraction (<0.01 mm) of more than 50% occupy about 70% of the Barents Sea. They are widespread in deep-sea hollows and trenches, as well as in the numerous fiords of the North Island of Novaya Zemlya and Franz Josef Land. Surface sediments have a predominantly terrigenous composition; only at the border with the Norwegian Sea the proportion of biogenic material increases. The mineral composition of sediments is dominated by quartz and feldspars, clay minerals are mainly represented by illite, smectite and kaolinite.

The paper presents data from a granulometric analysis based on the results of studying of 44 surface (0–5 cm) sediment samples obtained on cruise 67 of the R/V Akademik Mstislav Keldysh (2016) from different parts of the Barents Sea. Pebble and gravel material is found in surface sediments as an admixture scattered throughout the sea. Such a chaotic distribution pattern is apparently associated with ice rafting. Coarse material is most common in the Barents Sea off the coast of the Kola Peninsula, Novaya Zemlya, and Svalbard, where it accumulates due to coastal abrasion, glacial exaration and bottom erosion. In addition, the >1 mm fraction is widespread at depths where fine fractions are stirred and washed away. The most common sediments in coastal shallow waters are sands. Sands (0.1–1 mm) are widespread in the southern and southeastern regions of the sea, in the region of the Pechora test area, the Kanin Shoal, the Kola Peninsula shallows; and in the northwest, off the coast of Svalbard. With increasing depth, coarse sediments are replaced by mixed sediments with a low pelite admixture. Fine-grained sediments are prevalent in the central part of the sea. Sediments with a pelitic fraction (<0.01 mm) of more than 50% occupy about 70% of the Barents Sea. They are widespread in deep-sea depressions and troughs, as well as in the numerous fiords of the Northern Island of Novaya Zemlya and Franz Josef Land.

The article presents a brief lithological description of modern bottom sediments collected in the Barents Sea during Cruise 67 of the R/V Akademik Mstislav Keldysh at test sites: (1) “Pechora Sea”; (2) “Western slope of the Kanin Shoal”; (3) “Central Barents Sea (Shtokman area)”; (4) “Russkaya Gavan Fjord”; (5) “Medvezhinsky Trough”; (6) area south of Spitsbergen; (7) “Kola Meridian”; (8) “Spitsbergen–Franz Josef Land Archipelago”; (9) “Cambridge Strait.” Distribution of Cr, Ni, Cu, Zn, Cd, and Pb in samples of modern bottom sediments (pelitic, aleuritic–pelitic and sandy–aleuritic–pelitic ooze) is compared with background concentrations and contents of these elements in the Post-Archean Australian Shale (PAAS). The data obtained are consistent with the notion that the distribution of heavy metals and other elements in bottom sediments is controlled primarily by the global geochemical background. Relationship of Sc, V, Cr, Ni, Y, Zr, Nb, Mo, Hf, Th, U, and REE concentrations with contents of the fine pelite (<0.001 mm) fraction and organic carbon (Corg) is considered. It was found that most of these elements are characterized by a moderate positive correlation with the fine pelite fraction in samples. Based on the coefficient of their correlation with the Corg content, the above elements can be assigned to three groups with: (1) moderate positive correlation, (2) low positive correlation, and (3) virtual absence of correlation. Distribution of element-indicators of the source rock composition (Sc, Th, Co, Cr, La, and Sm) and REE in modern bottom sediments of the Barents Sea indicates that the majority of them are geochemically mature, and they were sourced from the Kola Peninsula and Spitsbergen (?).Bottom sediments of the Cambridge Strait are represented by geochemically less mature material, which, apparently, entered the sea as a result of erosion of rocks of the Franz Josef Land Archipelago.

The paper presents the first results of a study of seasonal variations in the grain size distribution and mineral compositions of suspended particulate matter (SPM) of the Northern Dvina River. The SPM samples were collected every month during 2016–2017 at the outlet of the Kuznetchiha arm to Dvina Bay of the White Sea. The grain size fractions were separated by Petelin’s water-mechanical method with retention of fractions for subsequent analyses using an electron microscope, energy-dispersion microanalyzer, and X-ray difractometer. The results demonstrated that the pelitic and subcolloidal fractions predominated in the grain size distribution of river SPM, with subordinate coarser fractions. Seasonal variations in the SPM concentration and the total amount of detrital and clay minerals are influenced by river water discharge and achieved a maximum in high water periods (spring flood and partly at the end of summer–autumn heavy rains). The subcolloidal fraction in the March sample stands out in the fine fraction distribution. Its share in this sample was the highest among these fractions throughout the year. The reason is probably related to the highest content of fine dispersed detrital minerals in the fraction. The question of why this is encountered only in March remains open.

A comprehensive examination of the elemental (including radionuclides and heavy metals), mineral, and grain-size composition of sediments from different areas of the Barents Sea was performed. Sediment cores were sampled in the Central Deep, Cambridge Strait (Franz Josef Land Archipelago), Russkaya Gavan’ Bay (Novaya Zemlya Archipelago), and Bear Island Trough. We aim to evaluate how the modern and more ancient environmental conditions are reflected in the elemental and mineral composition, as well as to test indicative elemental ratios. The applied methods include elemental analysis using gamma-ray spectroscopy, X-ray fluorescence (XRF), Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and X-Ray Difractometry XRD analysis of minerals. Difference in sedimentation rates, grain-size composition, and sources of material, are reflected in downcore variation of Si/Al, Mn/Fe, P/Al, Ti/K, and quartz-feldspar ratios. At boundary Early Holocene/Late Deglaciation, intensive bottom currents from the West-Southern shelf areas contributed to increase of Si/Al and Zr/Ca ratios. Distinct growth of the Si/Fe ratio within the sediments deposited over Late Pleistocene to Mid Holocene may be caused by increased contents of the coarse sand material, as well as by abundant fluxes of clay-mineral-loaded glacial meltwater during the main deglaciation phase. The Mn/Fe ratio used as redox proxy, displayed peaks at different depths related to oxygen concentration growth in bottom water.

Pelagic sediments from three cores in the northern tropical Pacific zone (the northeast basin) have been analyzed for particle size and composition, as well as for number, mass and the distribution of protosyngenetic authigenic manganese micronodules (MN) in them. The sequences are represented by Quaternary carbonate-free clayey–radiolarian, radiolarian–clayey oozes, miopelagic clays, sometimes enriched in radiolarians, pre-Pleistocene miopelagic and eupelagic clays, zeolite–clayey sediments, and zeolitites. Based on factual data (volume of wet sediment, weight of dry sediment and micronodules, their number and proportions of four fractions, the contribution of MN in sediment, and others), the values of different parameters were calculated. The obtained parameters are statistically similar, which allowed us to reveal background and anomalous horizons of sediments and to assume their sedimentation conditions. Similar values of РMN/NMN, Рfr > 0.05 mm, РMN/Рsed and the mass of micronodules suggest that precisely these parameters reflect the main variations in conditions of pelagic sedimentation.

The lithological analysis of sediments from Core SO201-2-85KL (18 m long) taken from the Shirshov Ridge in the western part of the Bering Sea (57°30.30′ N, 170°24.79′ E, water depth 968 m), which recovered the section spanning from the penultimate glaciation till Holocene, revealed their mostly terrigenous composition with several intercalations of diatomaceous ooze. The latter was accumulated mainly during relatively warm epochs (last interglacial and Holocene) with elevated bioproductivity of surface waters. Sedimentation during the penultimate glaciation was strongly influenced by bottom currents. Ice rafting of detrital material was intensified during cold marine isotope stages (MIS 6, MIS 4, MIS 2). Glaciations were accompanied by increased sedimentation rates probably due to the glacioeustatic sea level falls, desiccation of the Bering Sea shelf, and enhanced influx of sedimentary material transported by large rivers immediately to the deepwater basin.