Russian Journal of Earth Sciences

In the context of high anthropogenic pressure and eutrophication of the waters in the southeastern Baltic Sea, it is important to monitor the plume of highly productive waters from the Kaliningrad Lagoon through the Baltic Strait. Seasonal and interannual variability in plume propagation was estimated using satellite data from January 2020 to October 2024, and was then compared with expeditionary salinity measurements. The plume area was largest during the flood period (February–March) and the summer period (June–July), when strong winds contributing to plume dissipation were absent. Analysis of wind conditions and plume movement direction showed that, in most cases, the plume propagates along the coast to the northeast towards Cape Taran, predominantly in response to southwest and southeast winds. In autumn, dominant westerly winds press the plume to the coast. The hydrophysical structure of the plume corroborates the findings derived from satellite data.

The Verkhnekamsk potassium-magnesium salt deposit (VKSD) is one of the largest in the world. The primary challenge in underground salt mining is maintaining the integrity of the groundwater protective layer, which separates the mined seams from aquifers. In this context, the Verkhnekamsk deposit is mined using a chamber system room-and-pillar method, ensuring the stability of the protective layer through inter-chamber pillars. This paper presents the results of a preliminary analysis of the geological and mining conditions in one of the mines of the Verkhnekamsk deposit. The procedure for forming the initial data set is discussed. Test calculations based on a limited data set were performed, demonstrating the potential of combining artificial neural network algorithms and discrete mathematical analysis. The results achieved on the formed dataset successfully identified hazard classes. Thus, it can be concluded that this technology is fundamentally effective for assessing the risk of groundwater protective layer failure. The proposed approach establishes links between phenomena, their associated risks, and the deformations of underground workings and the Earth's surface, enabling proactive measures to protect mines from flooding.

The purpose of this work is to draw the reader's attention to a paradoxical fact – the existence of two different dispersion relations for linear Rossby waves: with Doppler and nonDoppler shifts. This paper highlights aspects arising from studying the interaction of Rossby waves and large-scale stationary flows within the framework of the linear wave approximation. The methods used in the work consist of the analysis of dispersion relations obtained by different authors. They are subordinated to the main task of the study – to establish where and when a non-Doppler shift appears in the system of two-dimensional linear equations of Rossby waves. Assuming that the flow is homogeneous, additional terms appear in the dispersion relation of Rossby waves for the solution in a plane wave, which can have both Doppler and non-Doppler effects. The paper shows that the non-Doppler character of the dispersion relation of Rossby waves on the current appears due to an additional assumption about the slope of the free surface, or the slope of the interface in a two-layer model (pycnocline for the ocean, and tropopause for the atmosphere). It is established that to derive some of these relations, excessive requirements for boundary conditions or separate terms in the equation for potential vorticity were previously applied. It is shown that to deduce the dispersion relation of Rossby waves with a non-Doppler shift, it is not necessary to throw out the topographic term in the boundary condition or abandon the hydrostatic approximation.

In this study, we focus on the crustal structure in the vicinity of the source area of the May 20, 2011 Khastakh earthquake with Mw = 4.7. An interest in this seismic event is connected with a fact that it occurred within the Lena-Anabar trough at the margin of the Siberian platform, which is characterized by very low level of seismic activity. Spatial characteristics of the gravity and magnetic fields were studied and 3D models of the crustal density and magnetization contrasts were constructed using data on gravity and magnetic surveys and GIS INTEGRO software. A network of buried faults, to one of which the Khastakh earthquake is related, has been revealed. The presence of a magmatic intrusion, probably, playing a role in the redistribution of the crustal stress-strain state in the vicinity of the considered seismic event, is suggested based on the constructed crustal 3D models. The obtained results regarding structural frames of the Khastakh earthquake source were verified by previous magnetotelluric and seismic studies.

The article presents the results of a comprehensive analysis of fault tectonics in the north-western part of the Verkhoyan-Kolyma orogenic region. The studies were performed on a regional scale. Based on a digital relief model, lineaments were identified manually and automatically. The results obtained in combination with literature data allowed us to perform tectonophysical recon-structions using the model of P. L. Hancock (1985). Based on the reconstructions, we determined the expected areas of tectonic structures that had the highest hydraulic activity during collision processes, which are presumably associated with gold deposits and ore occurrences in Eastern Yakutia. Areas promising for the discovery of new ore objects were identified.

The results of facies analyses of Jurassic-Lower Cretaceous sections of Western Siberia, the Upper Palaeozoic of the Taimyr, Tunguska and Pechora basins, and the Vendian deposits of the Baltic Syneclise are summarised. Has been developed the conceptual sedimentological model describing the migration of depositional conditions during sea level changes in epicontinental paleobasins of humid climate. General regularities of the structure of transgressive-regressive layer sequences were established. The results obtained represent an effective tool for paleogeographic reconstructions and sequential analysis of terrigenous grey facies in geologic history regrades of their geotectonic position and paleogeography location.

This article provides a thorough analysis of the potential for petroleum within the Pre-Jurassic Volcanic-Sedimentary Complex (PJVC) of the West Siberian Sedimentary Basin. Based on existing petrogenetic classifications of the complex's volcanic rocks, the article develops a model of major eruptive cycles, delineating the distribution of reservoir and non-reservoir rocks. To minimise uncertainty in inter-well correlation, the article proposes a methodology for rock discrimination using standard wireline logging suites. This incorporates fracture analysis to evaluate the likelihood of petrogenetic types belonging to the reservoir or non-reservoir categories. The integrated interpretation of seismic data, well logs, core petrography and lithology enabled cycle elements to be identified within the seismic field and surfaces to be constructed representing conditional geological bodies associated with natural reservoirs. Applying this workflow to a field in Western Siberia involving over 300 wells revealed that the PJVC comprises a series of ten lenticular packages exhibiting an imbricate lateral overlap pattern, ranging from a single package in the east to three superimposed packages in the northwest. Further investigation into the hydrodynamic connectivity between these units is required, however, as this is complicated by the high levels of lateral and vertical heterogeneity and faulting. This investigation is necessary in order to build a complete PJVC model that is suitable for field development planning and appraisal drilling. Nevertheless, this study establishes a foundational framework for the efficient investigation of similar rock complexes in the future.

The article presents results of studies of the stromatolites from Middle Ordovician deposits of the Moyero River section (Siberian platform). It demonstrates that despite the growing dominance of skeletal metazoans against the backdrop of Great Ordovician Biodiversification Event (GOBE) in Siberian Platform reef systems, microbial communities remained integral components of reef formation from the Middle Ordovician onward. These communities functioned both as crucial auxiliary elements and as sole framework builders. Stromatolites are associated with bioherms dominated by skeletal metazoan reef-builders (Angarella sp., Moyeronia sp., tabulate coral, Cryptolichenaria miranda, and stromatoporoid, Priscastroma gemina). This indicates that in some parts of the platform, due to regional peculiarities, microbial communities not only retained their role in Middle Ordovician reef systems, but also formed bioherms without symbiosis with other reef builders. Microbial communities form two distinct stromatolite types: less numerous spheroidal forms (SS and SS-I) and more prevalent stromatolite bioherms (SS → LH). The persistence of microbial influence in this region is attributed to specific depositional environment conditions. Due to their morphology and diagenetic alterations, these stromatolites have a potential for hydrocarbon reservoir formation. The study highlights that while contemporary reef zones in the Ordovician of West Taimyr are prospective yet poorly understood reservoirs, the Moyero River organogenic build-ups serve as valuable geological models. Further research into their structure, texture, and genesis is essential to refine predictions for Ordovician reservoir distribution. These findings emphasize the need to consider stromatolites as significant targets in reservoir exploration.