pdf № 363, March

DOI: 10.19110/geov.2025.3.1

The study presents the results of hydrocarbon biomarker analysis in bitumoids extracted from Middle Devonian Eifelian rocks of the Yarega field and Permian-Carboniferous deposits of the Usinsk field in the Timan-Pechora petroleum province. It also examines bitumoids from Upper Permian Ufimian rocks of the Ashalcha and Mordovo-Karmal fields in the Volga-Ural petroleum province using a comprehensive geochemical approach. The analyzed biomarker group includes normal and isoprenoid alkanes, aromatic compounds, and cyclic isoprenoids such as steranes and triterpanes. Key geochemical parameters were determined on the basis of paraffinic, aromatic, sterane, and hopane hydrocarbons. A comparative analysis revealed similar sedimentary environments and a consistent type of original organic matter across the studied deposits. This suggests a marine origin of the original organic material, which accumulated and underwent diagenetic transformation under reducing conditions. The thermal maturity of the organic matter corresponds to the main phase of oil generation.

Keywords: bitumoid, chemofossils, biomarkers, hopanes, steranes, hydrocarbons

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DOI: 10.19110/geov.2025.3.2

Over the past two decades, significant geological exploration work, including seismic exploration, has been carried out within the junction zone of the Vilyui syneclise and the Aldan anteclise. In addition, oil and gas companies are also interested in this territory, acquiring licenses for the search and exploration for hydrocarbon deposits. The object of the study is the terrigenous deposits of the Permian system. The main oil and gas potential of this territory is associated with these Permian deposits. Within the Vilyui syneclise, there are gas fields in the Permian deposits, which provide gas to the central regions of Yakutia. Thus, it is necessary to update the oil and gas potential of the area. The study was based on seismic exploration data, deep well data, including well logging curves, core descriptions, and Permian sediment test results. Previously published literature on the geological structure of Permian rocks was also analyzed. Our seismic interpretation and analysis of well data resulted in structural surfaces. The structural surfaces characterize Permian, Triassic and Jurassic sediments. The thickness maps have been used to determine the distribution areas of Permian deposits, Triassic and Jurassic fluid-sealing rocks. Using structural maps, thickness maps, faults and well data, the most oil and gas promising zones and objects of Permian deposits were identified. The promising zones are associated with a reduction in the thickness of Permian deposits, and identified near the wedge line. The fault-limited positive structures are promising objects.

Keywords: Siberian platform, Vilyui syneclise, Aldan anteclise, Permian deposits, taragay formation, seismic surveys, oil and gas potential

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DOI: 10.19110/geov.2025.3.3

The article presents the results of the study of the distribution of rare earth and trace elements in the weathering crusts of the Southern Timan, differing in age and bedding conditions, in the Dzhezhim and Asyvvozh quarries on the Zhezhimparma Upland and in the Vadyavozh quarry on the Nem Upland. On the Zhezhimparma Upland, a similarity of the geochemical characteristics of sandstones and clayey rocks at the base of the Devonian section was obsered, confirming the tectonic origin of the clayey formations previously considered to be the weathering crust. In the Vadyavozh quarry, a geochemical analysis was conducted on Mesozoic-Cenozoic areal and linear weathering crusts developed over basement rocks. The study confirmed a genetic link between the micaceous aleurolites of the Upper Riphean Dzhezhim suite and the Riphean weathering crust formation.

Keywords: Southern Timan, Dzhezhim suite, weathering crust, rare earth and trace elements

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DOI: 10.19110/geov.202.3.4

The facies dissection of Holocene deposits in the estuary part of the Chernaya River (northwest of the Bolshezemelskaya tundra) was carried out. A geomorphological scheme of the river valley was constructed on the basis of the results of lithofacies analysis of sediments and geomorphological (morphographic and morphometric) study of the relief. The main patterns of the river valley development in the postglacial period were revealed. The degradation of the polar (Ostashkov) ice sheet at the end of the late Neopleistocene and the low position of the territory of the northern part of the Bolshezemelskaya tundra contributed to the formation of a lake-marine terrace. Simultaneously with glacioisostatic compensation and the rise of the territory, the incision of the channel system and the accumulation of sediments of the second floodplain terrace occurred. The ingression of the Pechora Sea in the late Holocene contributed to the accumulation of sediments of the first terrace and floodplain with a complex of estuarine deposits, the formation of which occurred in tidal conditions. Lake, lake-marsh and marsh sediments simultaneously accumulated on the surface of the terraces.

Keywords: Quaternary deposits, granulometric composition, mineral composition, textural analysis, lithofacies analysis, estuarine part of the Chernaya River valley

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DOI: 10.19110/geov.2025.3.5

The papar studies the stromatoporoid association of the middle part of the Upper Devonian Lymbada Formation, of the (interval of marginifera–expansa). The stromatoporoid association is represented by nine species belonging to two orders — Labechiida and Clathrodyctyida. Three species were recorded for the first time in the study area: Labechia polaris Gorsky, Rosenella miniarensis Riab., and Anostylostroma cf. variabile (Riab.). The taxonomic composition of stromatoporoids is similar to that of the Upper Famennian of the Southern, Middle and Northern Urals.

Keywords: stromatoporoids, Lymbada Formation, Famennian, North of Pai-Khoi

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