This article examines the structure, composition, and textural features of the Griva Sequence in the Volchya Griva section and the paragenetically associated relief. Additional data supporting the aeolian origin of the Griva Sequence and the Griva relief are presented. Optically stimulated luminescence and infrared stimulated luminescence dating of the Volchya Griva section indicate that the Griva Sequence formed during the last glaciation and fully corresponds to Marine Isotope Stage (MIS) 2. The findings confirm that aeolian relief formation and the intensification of aeolian processes occurred during cold glacial periods of the Late Pleistocene, when southwesterly winds prevailed. The textural and structural characteristics of the Griva Sequence are similar to those of Upper Pleistocene niveo-aeolian sands that formed in cold, periglacial, arid regions of the world and are distributed along the southern margin of the last glacial ice sheets from Northwestern Europe to Western Siberia and Alaska. The formation of a deflationary truncation and a system of mega-yardangs in the northern part of the Lake Chany basin indicates a significant intensification of aeolian processes at the transition between the deposition of the lower and upper members of the Griva Sequence. The orientation of the Griva relief, which coincides with the prevailing direction of modern winds, suggests that wind directions during the cold and warm epochs of the Quaternary in southern Western Siberia were similar. The complete stratigraphy of the Volchya Griva section, its correspondence to the last glaciation and MIS 2, the presence of the largest Eurasian mammoth faunal locality, its distinct lithological characteristics, and the relatively high degree of its study allow this section to be considered one of the reference sections for the Upper Pleistocene of Siberia. It should be regarded as the stratotype of the widely distributed Griva Sequence in this area, which is proposed as a separate Baraba horizon (formation) for the south of Western Siberia, comprising the Eltsovka and Bagan loesses and the Suma soil that separates them.
This special issue of the journal Russian Geology and Geophysics comprises studies presented in the wake of the scientific conference "Processes of mineral formation at high pressures: the origin of diamond and mantle magmas", dedicated to the 90th anniversary of the birth of the outstanding researcher of diamond formation processes, Academician Nikolai Vladimirovich Sobolev. The conference was held on June 17-19, 2025, at the V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, in Novosibirsk Akademgorodok. The range of topics addressed, from detailed studies of crystal lattice defects in individual diamond crystals and their inclusions to the regimes and timing of the plate tectonics on the early Earth, fully reflects N.V. Sobolev's contribution to the formation of our modern understanding of the evolution of the Earth's mantle composition and the formation settings of kimberlites and diamonds.
This study extends the classical skin-factor concept originally proposed by M.F. Hawkins. A fundamental limitation of the Hawkins model is identified: the permeability of the drilling-fluid filtrate invasion zone is assumed to remain constant (kskin = const). Based on an analysis of recent experimental evidence, an integrated skin-factor model is developed in which the permeability (k) of the near-wellbore region is represented as a function of both the radial distance (r) from the wellbore wall and pressure (p): k=k(r,p). The proposed model comprises three characteristic invasion zones, each governed by a distinct mechanism of permeability variation. Comparative simulations reveal substantial differences between the classical Hawkins model and the proposed three-zone model, k = k(r), as well as the integrated model, k=k(r,p). Assuming a linear radial variation in permeability, comparative relationships are obtained between the normalized production rate and the skin factor, as well as between the skin factor, the production rate, and pressure drawdown. The classical Hawkins model is shown to overestimate the production rate by an average of 15–25%, with deviations increasing to 40–50% in the zone of maximum invasion. The results are of fundamental importance for the theory of flow through porous media and have practical significance for oilfield development planning by providing a basis for selecting well stimulation methods according to the characteristics of individual invasion zones.
This paper presents a synthesis of published and new geological, geochronological, biogeographic, paleomagnetic, and petrological-geochemical data. The goal is to substantiate the tectonic zoning of the Central Asian Fold Belt and its Vendian–Paleozoic geodynamic evolution as a complex folded structure composed of deformed fragments of collisional and accretionary orogens. It is shown that the belt formed at the junction of the collisional and accretionary margins of the Siberian Craton. This setting is analogous to the modern tectonic interactions between the Indo-Atlantic and Pacific global tectonic segments of the Earth and their respective interactions with Eurasia. During the Vendian and Early Ordovician, two active margins existed along the periphery of the Siberian Craton: the collisional Tuva-Mongolian margin and the accretionary Kuznetsk-Altai margin. These margins separate the craton from the tectonic plates of the Paleo-Asian Ocean (Indo-Atlantic segment) and the Paleo-Pacific Ocean (Pacific segment), respectively. A distinctive feature of the Paleo-Asian Ocean plate is its complex structure, which includes fragments of oceanic crust and Precambrian Gondwanan continental blocks that contain fragments of the Grenvillian orogeny. Grenvillian detrital zircons (1.3–0.9 Ga) are widely found in Vendian–Paleozoic sedimentary deposits from various geodynamic settings of the collisional orogen. In contrast, a distinctive feature of the accretionary orogen is the widespread presence of oceanic crust fragments and the absence of Precambrian Gondwanan blocks. Consequently, there are no Grenvillian detrital zircons in the Vendian–Paleozoic sedimentary rocks of various geodynamic settings that represent the accretionary orogen. The early to middle Paleozoic Charysh–Terekta–Ulagan–Sayan–Olkhon suture–strike-slip zone separates the collisional orogen from the shelf of a back-arc basin. This basin is located in the northern part of the Altai-Sayan Folded Area, which frames the Siberian Craton. The suture–strike-slip zone consists of fragments of Vendian–early Paleozoic oceanic crust from a back-arc basin, Ordovician blueschist, and Ordovician–Silurian turbidite, as well as late Silurian–Devonian collisional metamorphic rock and granite. Based on the structural position of the suture–strike-slip zone, petrology, and geochronology, this zone is interpreted as a subduction-collision complex. It formed in the back-arc basin of the Vendian–Cambrian Tuva-Mongolian island arc. Late Paleozoic strike-slip faults and thrusts manifested in the Central Asian Fold Belt during the Late Devonian and early Carboniferous. These structures resulted from the collision of the Kazakhstan-Baikal orogen (a composite continent) with the Siberian Craton, which led to the formation of the North Asian continent. Subsequently, during the late Carboniferous and Triassic, the collision of the East European and North Asian continents led to the formation of Eurasia. As a result of these collisional events, the originally linear structures of the collisional and accretionary orogens were deformed into large oroclinal folds. These structures were further fragmented by strike-slip faults and thrusts into numerous blocks. Within these blocks, the Vendian–Paleozoic structures are complicated by thrust-fold deformations.
This paper presents the results of developing a pulse height analyzer for a downhole geophysical instrument intended for spectrometric gamma-ray logging. The module is implemented using a field-programmable gate array and enables real-time signal processing. An algorithm for converting biexponential responses of a scintillation detector into trapezoidal pulses is proposed. The efficiency of the implemented algorithm has been demonstrated in resolving pile-up pulses with a time delay of 300 ns. Using calibrated gamma-ray sources – Am241, Eu152, Cs137, Co60, and Th228 – the system’s energy coverage in the range of 50 to 3000 keV is confirmed. The pulse height analyzer features universal architecture and is compatible with various types of gamma-ray detectors.
