Widespread Upper Permian pre-Otoceras deposits of northeastern Russia contain rich assemblages of marine invertebrates (brachiopods, bivalves, and foraminifera), but are not characterized by ammonoids. Only single finding of the Late Permian ammonoids is known in the Southern Verkhoyanie. In the fifties of the last century, a cyclolobid shell was found here in alluvial or deluvial deposits, later described as the holotype of the type species Paramexicoceras aldanense Popow, 1970. There was no stratigraphic position for this goniatite, and for more than half a century of searching, the researchers failed to find it again. A variety of assumptions have been made about the stratigraphic position of South Verkhoyanian Paramexicoceras, and their synchronism or asynchrony with the Paramexicoceras found in the Changhsingian deposits of the East Greenland has also been discussed. Most researchers agreed that South Verkhoyanian Paramexicoceras comes from the Imtachan Formation, but the new data discussed in this article refute these assumptions. Numerous shells of Paramexicoceras aldanense were found in the lower part of the Nekuchan Formation in the Dyby River basin. This finding belongs to the Changhsingian Stage, which approximately corresponds in geological age to the distribution level of the Greenlandic Paramexicoceras. All Otoceras in the Allakh-Yun structuralfacies zone are found above the Paramexicoceras level, therefore, the deposits with Changhsingian cyclolobids are separated into Paramexicoceras aldanense Beds, which underlie the Otoceras concavum Zone. Despite the Changhsingian age, the invasion of Paramexicoceras is historically associated with the initial phase of the Early Triassic sedimentation cycle in the Verkhoyanian basin. Paramexicoceras (goniatite) and early Otoceras (ceratite) probably belonged to a single warm water ammonoid community that came to South Verkhoyanian basin at the beginning of the Nekuchanian time.

The paper presents the results of petro and geochemical studies of the kimberlite pipes within the KhompuMay field (Central Yakutia). Their trace element data were compared with the analogues from the Yakut Kimberlite Province, Russia and the Kimberly Kimberlite Province, RSA. We present the data on petrographic composition and results of postmagmatic carbonation of the Manchary, A.P. Smelov, and Daban pipes kimberlites. The generalized model of the upper parts of the pipes show three conventional horizons: the lower horizon of least altered rocks, the middle horizon of fragments of kimberlite carbonates, and the upper horizon of intensely carbonated rocks without recognizable tex tural and structural characteristics. The obtained data on chemical and trace element compositions of rocks from pipes of the KhompuMay field reflect their material specificity, suggesting similar conditions for formation of kimberlites in Central Yakutia and South Africa.

The generalization of data on the chemical composition of dolerites of the Vilyui-Markha dike swarm (Vilyui paleorift) made it possible to identify geochemically anomalous areas among them. We found that the amount of TiO₂ and a number of highly charged and rare earth elements (Th, Ta, Hf, Y, Nb, REE) practically doubled in the dolerites of dikes located near kimberlite pipes. Moreover, a similar behavior of elements was observed in the dolerites of dikes located near the kimberlites of the Kuoyk field (Molodo dike swarm, Olenek paleorift). Therefore, we conclude that there is a paragenetic relationship between the increase in the content of titanium and rare earth elements in dolerites and kimberlites. We assume that protokimberlites indirectly influenced the tholeiite melt at the time of its melting, which led to local enrichment of the tholeiite melt with refractory components. Weakly manifested processes of geochemical alignment between high-Ti and ordinary basites ensured the locality of the distribution of the former. The kimberlites that penetrated after the basites were located near the dikes of high-titanite dolerites. Thus, the high-Ti dolerites of the dike swarms can be used as one of the criteria for the kimberlites prospecting. Considering the above, two new sections have been allocated within the Vilyui-Markha dike swarm: Tenkelyakh and Kyulyanke, with prospective for the discovery of kimberlites here. We also assume that protokimberlites indirectly influenced the tholeiite melt at the time of its melting, which led to local enrichment of the tholeiite melt in refractory components. Weakly manifested processes of geochemical alignment between high-Ti and ordinary mafic rocks ensured the local distribution of the former. The kimberlites in truded after the basites were located near the dikes of high-Ti dolerites. Thus, high-Ti dolerites of dike belts can be used as one of the search criteria for kimberlites. Finaly two new sites have been identified within the Vilyui-Markhin dike belt: Tenkelyakhsky and Kyulyankinsky, both promising for the discovery of kimberlites here.

The work is devoted to geochemical studies on the organic matter of rocks along the section of the Upper Jurassic of the Ilin-Tassky anticlinorium using natural outcrops and core material from the foreland zone, where the Upper Jurassic deposits were thrust over the Cretaceous. There are no materials on organic geochemistry for the Jurassic sediments in contrast to the Cretaceous and Cenozoic, that would allow us to assess their oil source potential. The results of geochemical studies of Jurassic rocks of the allochthon (foreland) will make it possible to predict the oil source properties in the autochthonous area under the Cretaceous deposits of the inner part of the trough. New obtained data on the composition and chemical structure of bitumoids showed that the initial organic matter was of a mixed nature with a predominance of planktonic material capable generating large amount of liquid hydrocarbons. The predominantly aliphatic composition of the hydrocarbon part of the bitumoids was mainly due to the aquagenic nature of the initial material, as indicated by the chromatomass spectrometry data on the distribution of saturated hydrocarbons. At the same time, the shift of the maximum of n-alkanes to the high-molecular-weight region, the noticeable presence of polyarenes, and aromatic character of the carbon skeleton of resins and asphaltenes could be due to the admixture of carbonized residues. In general, the obtained results showed that the geochemical features of the organic matter of the Upper Jurassic deposits of the Indigiro-Zyryansky basin allow them to assess as oil source. The presence of allochthonous bitumoids indicates migration processes that took place within the Jurassic strata. This suggests that oil accumulations can be expected on the Alazeysky uplift in the area of pinch-out of the Jurassic rocks.

In this study we tested a centrifugal vibration concentrator developed by the Institute of Mining of the North SB RAS. Unlike existing analogues, the working body of the concentrator performs vibrations directed along its rotation axis. The test results showed a high degree of influence of the vibration frequency on the extraction of heavy minerals. The new centrifugal concentrator has the ability to control the parameters of vibrations, enabling an active use of the new effective mechanism for segregation (trapping) of heavy components. The best level of extraction of heavy minerals (63.9 %) was achieved with an oscillation frequency of 22 Hz and an amplitude of 2 mm when separating an artificial mixture consisting of river sand and magnetite with a grain size of –0.5 mm. The accumulative bed of heavy minerals in the working organ of the centrifugal vibration concentrator passes into an active loosened state with an oscillation amplitude of more than 1.5 mm. Experimental selection and justification of the most rational regime conditions is applicable in the case of processing natural mineral complexes.

The article presents the results of engineering and geo-cryological studies of the permafrost zone in natural conditions and during the area development. We have quantitatively estimated the influence of snow, vegetation and ground cover on the formation of thermal soil regime of the annual heat turnover layer. The influence of technogenic impacts on the thermal soil regime is described using mathematical modeling. We provide the forecast results of the thermal state of soils during the territory development of the northern taiga, the forest-tundra, and the southern tundra. We discuss the main tasks of geo-temperature monitoring in the process of organizing stations and polygons in the areas under development.

The article presents a review of publications from 1980–2022 which deal with the study of post mining soils (PMS) in the territory of the Republic of Sakha (Yakutia). Though mining in Yakutia began in the 1920s and 1930s, the study of PMS in this territory began only in 1992. Over the past decades, the number of publications on the problem has increased more than 10 times. Still, there are no exact figures on the area of PMS in this territory. The inventory of the latter as a scientific problem has not yet been posed. This study of the properties of the young soils on post mining dumps was carried out in all the climatic zones of Yakutia from tundra to the middle taiga. A classification of biotopes according to the degree of anthropogenic transformation in the permafrost zone has been proposed. We tested a hierarchical scheme of bioindication of disturbed permafrost ecosystems, including coenotic, population, ontogenetic and cytogenetic levels. Three methodological approaches (physicochemical, microbiological, phytotest) for studying the biogenic stage of primary soil formation in cryolithozone was assessed. The information content of the classical genetic soil science positions for the classification of young PMS under the conditions of different climatic zones of Yakutia is shown. We identified the informativeness of various methodological approaches for diagnosing the state of PMS in the permafrost zone.

We studied the distribution of dendro- and tamnobiont sawflies within geobotanical districts in the middle taiga subzone of Yakutia. The sawflies fauna similarity of geobotanical districts was investigated using cluster analysis, the biotopic distribution of dendro- and tamnobiont sawflies was analysed according to the main types of forest formations. Due to the large number of species and high population density, sawflies play an important role in Yakutian biocenoses and take the leading position among phytophage insects. Many of them are secondary pests of trees and shrubs including such dangerous species as Acantholyda posticalis (Matsumura, 1912) and Diprion pini (Linnaeus, 1758). The study was based on materials collected by the author during 2001–2019 in Central, Western and Southern Yakutia, as well as on entomological collection of sawflies of the Institute for Biological Problems of Cryolithozone SB RAS. The forests of the middle taiga subzone of Yakutia were stated to be a habitat for 176 species of dendro - and tamnobiont sawflies from 34 genera and 6 families. The results of Symphyta fauna analysis by geobotanical districts showed that the Lena-Amga District had the richest Symphyta species diversity, while the least number of species was identified in the Vilyuy District. The cluster analysis revealed the most similar sawflies faunas from the Lena-Amga and Middle-Lena Districts. According to the results of biotopic distribution analysis, the largest species diversity of the tamno- and dendrobiont sawflies was recorded in larch forests, while the smallest in pine forests.

A retrospective analysis of the hydrochemical conditions of the largest lakes in Yakutsk (Beloe, Khatyng-Yuryakh, Ytyk-Kuel, Sergelyakh, Saysary) was carried out in accordance with a registered database covering the period from 1985 to 2021. The studied lakes are mainly sodium bicarbonate with increased mineralization and moderately hard water. The main contribution to the total volume of cations is made by Na⁺ and Ca²⁺ , HCO₃ ^– and Cl^– anions. They also demonstrate a decrease in mineralization with a low value of approximation reliability. The variation of water hardness values directly depends on the content of Ca²⁺ and Mg²⁺ cations and hydrocarbonates. The average value of suspended materials in the lakes is significantly higher than the existing Maximum Concentration Limit (MCL). The change in their content in each lake is individual, however the highest was found in Beloe, Saysary and Khatyng-Yuryah lakes. Mineralization and hardness of water are the most significant factors in the formation of the hydrochemical conditions. The established mechanisms are characteristic of the whole sample, which reflects the nature of the formation of the hydrochemical conditions of urban lakes. The trace element composition is characterized by an increase in Zn and Cu concentrations.

The article presents a comparative study of morphometric parameters of fossil and modern grey wolves (Canis lupus L. 1758) from northeastern Yakutia. Wolf fossils were found in Abyysky and Kolymsky regions of Yakutia. The findings have been dated to the late Neopleistocene. We compared the proportions of the skull and the condition of the dental system of the wolf. Fossil wolf was on average slightly smaller than modern arctic tundra wolf, though their dental system has more powerful premolar rows responsible for cutting meat and breaking bones. The height of occipital bones of the wolves in Neopleistocene also indicates a more powerful development of their neck and chewing muscles. These features may indicate a predominantly scavenger role of the wolves in Neopleistocene ecosystems.

The entire territory of the Republic of Sakha (Yakutia) is located in the zone of extreme climate. Harsh and continental climatic factors of the North slow the processes of self-healing and self-purification of the natural landscapes. The decrease in the rates of biological and chemical transformations in the aquatic and terrestrial ecosystems leads to a significant accumulation of chemical components of anthropogenic origin in them. The adverse effects of the habitat were little studied until the end of the 20th century. The relationships between chemical heterogeneity of the biosphere and the occurrence of various changes in the human body and even diseases have been found. Biogeochemical factors (microelements of soil, water, air, products of biotic and abiotic origin, industrial and agricultural waste) have a significant impact on the normal functioning and functional reserves of the human body. Recent estimates of the WHO attributes 50 % of health outcomes of the population to behaviour, 20 % to genetics, 20 % to social and physical environment, 10 % to the quality of medical care. In this regard, the aim of the work was to study the microelement status in the biological media (hair, blood) of residents of the Republic of Sakha (Yakutia) living in the basins of the Vilyu and Markha rivers.

In this article we present the research results of a year-round accumulation dynamics of the metabolites in the needles of Scots pine (Pinus sylvestris L.) growing in Central Yakutia. Pine needles contain valuable bioactive substances effective for preventing and curing metabolic disorders in diabetes mellitus type 2 and the formation of other metabolic disorders associated with hypercholesterolemia. They also contain substances with cryoprotective properties. The highest content of antioxidants in the Pinus sylvestris L. (gallic acid, benzoic acid, aminobutyric acid) were observed in autumn. Moreover, the content of polyols, amino acids and carbohydrates increased in them during this period. Thus, we suppose it is rational to the use P. sylvestris needles gathered in autumn to produce biopreparations for normalizing carbohydrate metabolism or protecting skin from the effects of low temperatures.

Polymer composite materials (PCM) based on polytetrafluoroethylene (PTFE) are of great research interest due to their thermal stability, high chemical and corrosion resistance and excellent anti-friction properties. This paper presents the results of a study on the effect of carbon fibers (CF) along with molybdenum disulfide (MoS₂) with ultrasonic treatment on the mechanical and tribological properties, as well as on the structure of PTFE. Polymer composite materials were obtained according to the well-known technology for processing PTFE: the method of cold pressing and sintering. We found that ultrasonic treatment of MoS₂ is a more effective way to activate the filler compared to mechanical activation. Based on the results of physical and mechanical studies, we demonstrated that the tensile strength properties of PCM remained at the level of unfilled PTFE, the compressive stress increased by 75 %, and the hardness increased by 48 % compared to the original polymer. Structural studies have shown a fairly uniform distribution of fibers in the bulk of the polymer and isotropic reinforcement of the material. The degree of crystallinity of PCM increased by 9–11 % relative to the initial polymer. The developed composite materials are characterized by a low mass wear rate of composites by 1100 times and a low value of the friction coefficient. Microscopic studies of the friction surface of PCM revealed that hydrocarbons and MoS₂ are localized on the friction surface and protect the material from wear. The developed materials can be offered as parts in friction units, where the use of lubricating oils is limited or its use is unacceptable.

This paper presents the results of a study of the properties and structure of ultra-high molecular weight polyethylene (UHMWPE) depending on grades and molecular weight. We compared the grades of UHMWPE 510 and 517 synthesized in the Federal Research Center Boreskov Institute of Catalysis, and GUR grades 4022, 4130 and 4150 from Celanese (Germany and China). Powders were processed according to the technology of hot pressing in a vulcanizing press in accordance with GOST 16337-77 to obtain samples for research. The structure of the polymers was studied by X-ray diffraction analysis and scanning electron microscopy. The study of powder morphology indicates that UHMWPE powders consist of clusters of smaller subparticles interconnected by polymer fibrils. At the same time, the supramolecular structure of UHMWPE is characterized by the formation of spherulites, the size of which decreases with increasing molecular weight. X-ray patterns of UHMWPE show that with increasing molecular weight, a more defective structure is formed. This phenomenon is confirmed by the method of differential scanning calorimetry, a decrease in the values of the enthalpy of melting and the degree of crystallinity with increasing molecular weight was revealed. We established that the value of the degree of crystallinity and density of Russian-made brand 517 is comparable to foreign brands. In terms of physical, mechanical and tribological parameters, this brand is not inferior to foreign analogues, since it has a high tensile strength, which reaches up to 45 MPa, and a low mass wear rate of 0.07 mg/h.