Vol 511, No 2 (2023)

Elements of the structure of the Svecokarelian pericratonic zone of the Karelian Massif (SE Fennoscandia), formed after the main events of the Svekofennian tectogenesis, have been identified and characterized. Dated age intervals of the orogenic stage and post-orogenic extensional collapse manifestation, determined the depth levels of the corresponding structures and visualized the scheme of differentiated exhumation of the deep complexes of the post-Proterozoic Savo-Ladoga movable zone. Approximate estimations of exhumation rates of deep material at certain stages of the Precambrian evolution of this zone are given.

New data of U-Th-Pb age (SIMS) of magmatic (T = 730–744°C) zircon from intermediate and acid metavolcanics (1923–1926 Ma) of the supracrustal complex in the Kaskama block of the Inari terrane (north-west of the Kola-Norwegian region of the Fennoscandian shield) were obtained, which makes it possible to attribute them to the Kalevian suprahorizon. The source of primary melts of metariodacites and metabasaltes in the Kaskama block was the paleoproterozoic continental lithosphere not younger than 2390–2384 Ma. It is shown that the age of the tonalites of the Kuroaivi massif (1936 ± 7 Ma, εNd(T) = +0.1) as well as the granitoid massifs of the Southern Pechenga zone (1950–1940 Ma), are older, within the errors of U-Th-Pb age determinations, than the volcano-sedimentary rocks of the Kaskama unit and the Vepsian of the Southern Pechenga zone. This period of granite formation separates the early geodynamic stages of the continental rifting at the Yatulian-Ludikovian time from regimes, similar to the suprasubductional formation of the continental lithosphere, of the Inari terrane (1926–1850 Ma).

One year after the emergency diesel fuel spill in Norilsk, hydrocarbon concentrations in bottom sediments of the Norilo-Pyasinsky water system decreased. But on average in the areas they decreased in the same sequence (µg/g) as in 2020: the mouth of the Ambarnaya R. (835, σ = 1788) > Bezymyanny Cr. – the Daldykan R. – the Ambarnaya R. (306, σ = 273) > Pyasina R. (23, σ = 20) > Lake Pyasino (12, σ = 8). Concentrations decreased due to degradation of low molecular weight hydrocarbons. The content of polycyclic aromatic hydrocarbons in 2021 also changed in a smaller range (0–1027 ng/g) than in 2020 (0–3865 ng/g). Petroleum origin of hydrocarbons in the sediments of the Ambarnaya R. (including the mouth), Bezymyanny Cr. and Daldykan R. confirms the dominance of alkylated naphthalene homologues in their composition. Hydrocarbons accumulation in some horizons of the sedimentary strata is caused not only by seepage of diesel fuel, but also to the introduction of organic matter from the surrounding swamps from wetlands and floodplain lakes, as well as the burial of the surface layer by the 2021 flood.

For the first time, a granulometric analysis of lateritic soils was carried out and the sources of the substance involved in the formation of the degradation zone in the bauxite-bearing laterite profile of the bauxite-bearing province of Futa Jallon-Mandingo were identified. Throughout the province, on the stony rocks of the lateritic covers, the soil horizon occurs everywhere - the uppermost element of the vertical profile of the weathering crust. In the soil horizon, most of the components become mobile, leaching processes predominate, and laterites are mobilized and redistributed. The study of these continental formations made it possible to establish the genetic relationship between the soil horizon of the weathering crust and the underlying bauxite ores, and to determine the degree of influence of soil composition on the processes of bauxite formation.

In this paper we compare metamorphic transformations in acid and mafic rocks in a zone of intense tectonic movements. The object of study is the exhumed part of damage zone of Primorsky fault – main collision suture, which connects the Siberian Craton and the Olkhon Terrane. The studied area is located near the Khorga River. Collected metamorphic rock samples are represented by both acid (plagiogranitegneiss) and mafic (amphibole-biotite plagiogneisses) rocks. The samples present two different parent rocks contacting each other but differ in chemical composition. The formation of identical metamorphic minerals belonging to the groups of garnet and epidote is noted in both types of rocks. Mineral formation was associated with high-pressure regional metamorphism and possibly with later collision. Studying chemical composition of rock-forming minerals has allowed to determine the P-T condition of metamorphism in these rocks via the method of multimineral thermobarometry. It was established that conditions of early metamorphism retain in amphibole-biotite plagiogneiss. Early metamorphism is characterized by high-pressure amphibolite facies of medium temperature next to eclogite facies. In plagiogranitegneisses were found conditions of later metamorphism that formed rocks at the same pressure but at a lower temperature in the paragonite-kyanite-zoisite subfacies of the eclogite facies next to the greenschist facies. Minerals formed in the early metamorphism are poorly preserved.

A 3D model of the Earth’s crust for the Laptev Sea continental margin and the adjacent part of the Eurasian Basin was built using the latest seismic and gravity data. The thickness of the Earth’s crust in the research area equals 7–11 km, which corresponds to a highly extended continental or oceanic crust. Basement formation and sedimentation in this area most likely began in the Late Jurassic. The south-eastern part of the Eurasian Basin is separated from the rest of the basin by a dextral shear zone, the displacement along which during the Paleogene was more than 100 km.

This paper elaborates on specific aspects of P- and S-receiver functions. The functions that are researched in this paper were calculated using waveforms obtained by three adjacent broadband seismic stations within the Avacha bay area in proximity to the subduction zone of the Pacific plate. The subduction zone in seismological context manifests as a layer of high seismic velocities, which are known to introduce a level of distortion to the receiver functions. To specify the level of this effect we parsed through two sets of P and S receiver functions in this research. The first set contains events that pass through and theoretically are affected by the subduction zone of the Pacific plate and the second set contains events that do not. The paper demonstrates that converted waves and their multiples formed at the boundaries of the high-velocity layer significantly affect P-receiver functions starting with 30-th second after the primary phase. However, no notable effects on S-receiver functions were revealed. Thus, we empirically confirm that [at least in the investigated area] local single-dimensional models are valid to be used for the inversion of the receiver functions to the depth of up to 200 km after which point the seismic noise produced by the subducting plate effectively limits the applicability of such models.

Contourite drifts were for the first time detected on the SW Kara Sea shelf basing on аnalysis of bathymetry and seismoacoustic data obtained in RV “Akademik Nikolay Strakhov” cruises 41 (2019) and 49 (2020). The drifts are confined to narrow nearly NS-striking depression with depth reaching 240 m. They are separated from underlying sediments by basal unconformity, conditioned by origination of bottom current in marine environment after Barents-Kara shield melting during Late Plestocene – Holocene. Hydrological measurements performed during Cruise 89–1 of RV “Akademik Mstislav Keldysh” (2022) shows existence of bottom current with measured velocity up to 10 cm/s.

According to the data of weather stations for the period 1991–2020, as well as radiometric measurements of the surface temperature T_S of Moscow region by Terra and Aqua satellites for the period 2000–2020, the daily course and long-term changes of the urban ‘heat island’ (UHI) of Moscow in the field of both the air temperature T at a height of 2 m and the T_S were studied. For the analysis of T_S 1379 satellite images were selected for 21 years in clear and slightly cloudy sky, when the UHI analysis is possible. The average annual values of T_S were obtained using their normalization for separate seasons. The daily course of Moscow UHI in the air is weakly expressed, especially when compared with the countryside not only of the city center, but also of its entire area: only the weakening of this phenomenon in autumn and in the pre-winter season (from October to December) is reliable. According to satellite data, the ‘surface UHI’ is marked by a maximum in June-July with the strongest vegetation development, a minimum in autumn when leaves fall, and intermediate values in winter and spring. The rapid growth of T took place in 1991–2020 both in Moscow and in rural areas with approximately the same speed. As a result, there have been no statistically significant directional changes in the UHI intensity both in the air and on the surface as a whole over the past 20–30 years. The probable reasons for the general stabilization of the UHI in Moscow are both natural and socio-economic factors: the approximate constancy of the probability of clear weather (which promotes the strengthening of this phenomenon) and the vegetative activity in the region (which determines heat losses due to transpiration by plants), slowing down and stopping the growth of the population and energy consumption of the city, as well as its deindustrialization. Additional reasons are the gradual relocation of residents to the new outskirts of Moscow, as well as quarantine restrictions due to the COVID-19 pandemic in 2020.

A methodology has been proposed to assess the hydrophysical and chemical-biological characteristics of unexplored small and medium lakes (with an area of up to 100 km²) in the Arctic territories of Russia using remote sensing and mathematical modeling methods. The methodology is based on the use of a one-dimensional model of hydrothermodynamic and chemical-biological processes in water bodies FLake. The technique makes it possible to obtain an estimate of heat transfer between the atmosphere, ice, water, and bottom sediments, the date of ice cover formation, its thickness, and duration of existence of freeze-up, calculate profiles of water and bottom sediment temperature and dissolved oxygen by depth based on information on geographical coordinates and lake’s surface area. Contact measurements are not required, which is extremely important for hard-to-reach and poorly explored northern territories of our country.

The process of quasi-one-dimensional spreading of oil product spots on the water surface has been experimentally and theoretically investigated. The theoretical model is based on an approximate equation obtained using the laws of conservation of the mass of the decomposed product and the total energy of the system. Approximate solutions of this equation and the results of experimental studies on the spreading of machine oil and crude oil in a narrow extended container are presented, and their good compliance with the theory is shown. A comparison is made with the process of two-dimensional axisymmetric spreading of a spot of the same petroleum products.

In the bottom sediments of lakes Shira and Uchum, located in the south of Siberia in the steppe zone of the North Minusinsk depression (Republic of Khakassia and Krasnoyarsk Territory), distributions of charcoal particles >100 µm. The age of the studied sediments of the two lakes was up to 1400 and 500 years ago, respectively. Charcoal particles of three types were found in the sediments of both lakes. The first group has an elongated shape and is interpreted as the remains of herbaceous plants and/or needles. The second group looks like thin flat blades and is interpreted as the remains of leaves. The third group consists of bulk particles of various irregular shapes, which are presumably the remains of the combustion of wood and coal. Particles of the first type are mainly indicators of natural fires, and their flux does not show a noticeable increase in the modern period. The flow of coal particles of the second and, to the greatest extent, the third groups has increased sharply in the last about a hundred years, which reflects an increase in the amount of wood and coal burned by people in the vicinity of the studied lakes in the modern industrial period. The data obtained reflect an increase in the amount of wood and coal burned by people in the modern industrial period, as well as a possible increase in the number of wildfires, which may also be due to human activities in the form of accidental or deliberate arson. Thus, for the first time for this region, an increase in the influx of charcoal particles into the bottom sediments of lakes over the past about a hundred years has been revealed, which is unprecedented over the period covered by our study. Thus, evidence of the anthropogenic impact on the dynamics of charcoal particles in bottom sediments has been obtained. The information obtained can be useful for reconstructing the dynamics of natural fires and paleo-climate in this region of southern Siberia in the Late Holocene.