Vol 55, No 2 (2024)

The article discusses the current state of chronostratigraphy and paleogeography of the loess-soil sequence of the Pleistocene of Western Siberia, which is one of the most complete in Northern Eurasia. It is shown that genetically loess is closely related to eolian formations formed as a result of activation of eolian processes in earlier arid epochs of the Late Cenozoic in North Asia. A deflationary and accumulative eolian relief, paragenetically associated with the formation of the subaerial formation, is described, showing a slight transfer of material that forms the loess stratum. It has been established that the eolian relief and the activation of eolian processes occurred during the cold periods of the Pleistocene with the predominance of southwestern winds. The basis of the stratigraphic subdivision and correlation of sections of the loess strata are fossil soils formed under strictly defined climatic conditions. Consistent tracking of the loess and soil horizons of the loess sequence of the Pleistocene of Western Siberia, taking into account radiocarbon and luminescent dating and the use of climatostratigraphic correlations, showed that its structure and composition clearly reflect the uniqueness of each paleogeographic epoch, associated with changes in the intensity of atmospheric circulation in the cold and warm epochs of the Pleistocene. The features of each specific epoch are recorded in a combination of unique individual features of certain horizons of the loess-soil sequence. In the alternating horizons of loesses and soils, a record of global and regional changes in landscapes and climate has been preserved, reflecting the originality and uniqueness of the paleogeography of each time epoch. The structure and composition of the loess strata reflect the different intensity of atmospheric circulation during the cold and warm epochs of the Pleistocene. It is shown that the chronological sequence of the loess-soil sequence of Western Siberia, based only on OSL dates, does not always coincide with the loess-soil sequence of Western Siberia, built on the integration of various approaches, with the predominant use of the paleopedological method, and therefore needs to be corrected. The best correlation results are achieved by combining all available dating methods with the involvement of biostratigraphic, sedimentological and geological data, based on the climatostratigraphic principle.

The Kuldara site, situated near the Khovaling loess plateau in Southern Tajikistan, stands as the most ancient stratified site of the Early Paleolithic in Central Asia. Here, at the end of the 20th century, stone tools were discovered in pedocomplexes 11 and 12, with an estimated age of ~0.9 million years according to geological data. This discovery marked the archaeological materials from Kuldara as evidence of the earliest penetration of ancient people into the southeastern regions of Central Asia. However, despite the significant importance of the site in understanding the conditions and chronology of the initial settlement in the region, a chronostratigraphic study of the complete section of loess-paleosol series at the site had never been conducted before. Consequently, the regional correlation of this monument was critically challenging.

We present the results of a comprehensive study of the stratigraphic sequence of the Kuldara section from modern soil to pedocomplex 11 on the cliff of the eastern bank of the same-named stream. We conducted soil description and detailed paleomagnetic research, measured magnetic susceptibility and its frequency dependence, and carried out archaeological work. Based on the obtained data, we performed, for the first time, a correlation with the oxygen isotope scale of the World Ocean, allowing us to estimate the age of the exposed pedocomplexes and identify significant erosion events in the upper part of the section. As a result of the archaeological work conducted, a collection of stone tools was obtained from pedocomplexes 4, 5, 6, and 10. These artifacts indicate the regular presence of ancient people at the site after the initial episode of settlement around ~0.9 million years ago, and the conducted chronostratigraphic correlation enables a more precise estimation of the timing of individual stages of this presence.

The paper presents a study conducted at a monitoring site near the village of Galyovo on the right bank of the Votkinsk reservoir. The research focuses on the processes of mass movement of fine and clastic material, including the destruction of rockfall slopes and the displacement of debris. The following methods and results were employed. Observations were conducted on the destruction of rockfall slopes, primarily composed of siltstones undercut by abrasion. The peculiarities of debris displacement were also noted. High-precision tacheometric surveying in non-reflective mode was used to determine the rates of slope failure. This method allowed for accurate measurements of slope movement. The rates of debris displacement were calculated by analyzing images obtained from drones and conducting topographic surveying. Mass measurements of the debris position were used to quantify the displacement rates. For the first time, the rates of slow mass movement of material delivered to the shoal due to bank destruction were determined and quantified. The main contribution to the volume of loose material entering the reservoir at the monitoring site was caused by weathering of high slopes. The rate of slope retreat was determined to be 14—15 cm/year, resulting in an input of colluvium of 6.6—7 m³ per linear meter per year. In the seasonally submerged areas of the shallow coastal zone, sediment transport was found to be related to various processes, including wave activity and mass movement of material in underwater conditions. The study recorded the displacement of sediments lining the shallow coastal zone before the formation of seasonal ice cover, with sliding distances of 15—20 meters by the beginning of spring water discharge. The movement of boulders was also observed, mainly in the range of 10—20 cm/year. It was noted that mass displacement of fine sediments in the summer was compensated by the input of products of crumbling, collapse, and bank abrasion. The data obtained from this study can be used to assess the role of various processes in the shallow water of the reservoir and calculate the rate of siltation of the reservoir. This information is valuable for understanding and managing the geomorphological dynamics of the coastal area and the reservoir.

The investigation of the Pleistocene small mammal faunas from the south-western regions of the Russian Plain permits to reconstruct their principal evolutional stages during last ~1 400 000 yr. These materials took the possibilities to date the Pleistocene alluvial, liman and marine deposits and also the horizons of the fossil soils.

The unique small mammal and brackish-water mollusk localities in marine and liman-deltaic deposits of the Black Sea permits to demonstrate a direct correlation between the events in the Black Sea basin and on the continent. The direct correlations of the events (transgressions) in the Black Sea and on the continent were made based on the joint finds of the brackish-water mollusks and the small mammal remains. Thus, the Tiraspolian faunas synchronous to the Chaudian transgression of the Black Sea; the faunas of the Gunkovian small mammal assemblage (MIS 11, Likhvin interglacial) are correlated to the Early Euxinian transgression. The faunas existing in the last warming (Interglacial?) of the Middle Pleistocene (MIS 7) are synchronous to the Uzunlar transgression, and the faunas of the Mikulino (=Eemian) Interglacial are correlated with Karangat transgression (MIS 5e). The species of the open (steppe and forest-steppe) landscapes prevailed in the all of the faunas.

The article presents new data on cryogenic structures of different periods found in sections in the south of the Lower Volga Region. Based on a comprehensive cryolithological analysis, cryogenic origin of these structures was confirmed. Absolute dating by the method of optically stimulated luminescence was used to determine the age of enclosing, overlying deposits and filler of the structures. Four stages of cryogenesis were established in in firth-marine deposits of the Lower Volga region: I stage ~115—105 ka (КОС-4 and КОС-3 horizons), II stage ~90—83 ka (КОС-2), III stage ~47—45 ka (CY-1), IV stage ~23—22 (КОС-1). In the south of the Caspian Lowland, with generally arid conditions existed throughout the Late Pleistocene, the humidity of sediments (determined by the geomorphological position of the sections) played a decisive role in the development of cryogenesis of cold stages. This study makes it possible to move the boundary of the maximum distribution of the Late Pleistocene permafrost area for this territory by 250 km to the south than previously assumed. The new data significantly refine our understanding of the stages and scales of the development of cryogenesis in the southeast of the East European Plain, and allow us to improve paleogeographic reconstructions for the Late Pleistocene of the Caspian Lowland.