The Russian sector of the Eastern Arctic is characterized by large basins with thick sedimentary filling, primarily on the shelf and continental slope of the seas of the Arctic Ocean. A number of geological, geophysical, and geochemical features point to a hydrocarbon potential. At the same time, the age and composition of the sedimentary infill of the shelf basins have been controversial until now due to the lack of wells drilled in the shelf area. Six stratigraphic wells were drilled with core sampling in the eastern Laptev Sea (Anisin-Novosibirsk block owned by Rosneft) with a depth of 100 to 199.5 m during the Rosneft Stratigraphic Drilling in Arctic (RoSDAr) project in 2021. The results of complex biostratigraphic studies of the core show that the oldest strata in the well sections are Upper Barremian - Lower Aptian deformed silty mudstones (folded basement assemblage) overlain with angular unconformity by sands, silts, and clays of the Paleocene. The wells also penetrate the Eocene, Oligocene, and Miocene-Quaternary clastic rocks. A comprehensive analysis of stratigraphic drilling and seismic data refines the geological models of the region and provides better understanding of its hydrocarbon potential. The data show that Cenozoic strata play a more significant role in the sedimentary cover of the Laptev Sea than was previously assumed.

The results of a comparative analysis of the structure and history of the Neogene–Quaternary development of 18 intermontane basins in Northern Armenia and Eastern Turkey are presented. The research is based on expeditionary works carried out by the authors in 2012–2023 and supplemented by published materials from other researchers. Paleontological, magnetostratigraphic, and radioisotope data on the stratigraphy of the basins are analyzed. The comparison made it possible to identify four stages of basin development, expressed by the type of sedimentation: (i) marine sedimentation; (ii) predominantly lacustrine accumulation of fine-grained clastic material transported from low uplifts; (iii) lacustrine–alluvial sedimentation with a significant proportion of coarse material carried down from neighboring uplifts: (iv) involvement of the basins in the total uplift of the region, which in most basins is expressed by increased incision of watercourses into previously emerged landforms and in the Sevan depression is combined with ongoing lacustrine–alluvial sedimentation. Consistent rejuvenation of stages (i)–(iii) of basin development in the northern direction is revealed, caused by the growth and northward expansion of uplift of the Taurus Ridge in the process of its thrusting onto the Arabian Plate. At the same time, development of the basins revealed the impact of tectonic events in the Middle and South Caspian. It was expressed in the Early Pliocene by an unconformity and the appearance of coarse-clastic rocks, reflecting the increasing contrast of vertical movements between the Caucasian and Caspian regions, and at the end of the Late Pliocene by penetration of waters of the Akchagylian transgression of the Caspian Sea into some basins. These features of the development of the basins did not depend on differences in their origin, which was governed by the influence of several factors. Among them, the main ones were movements on faults as a result of the interaction of lithospheric blocks, and subsidence, caused by movements of sublithospheric masses, expressed by volcanism. Secondary roles were played by the behavior of the ophiolitic substrate and the tectonovolcanic damming of river valleys.

ABSTRACT The Severnaya Dvina River valley crosses the former south‐eastern margin of the last Scandinavian Ice Sheet. Despite a long research history, there remains considerable controversy about the maximum ice‐sheet extent and the expansion of proglacial lakes within the Severnaya Dvina fluvial system. The goal of this study was to address these issues using new material from the valleys of the Severnaya Dvina and the lower Vychegda, thereby contributing to an understanding of the history of the south‐eastern sector of the last Scandinavian Ice Sheet and its periglacial areas. We studied a number of geological sections using radiocarbon and optically stimulated luminescence (OSL) dating, pollen and carpological analyses, and found that the Last Glacial Maximum (LGM) proglacial lake occupied the Severnaya Dvina valley between 20–19 ka and about 15.5 ka. The lake was localized within the proglacial isostatic depression and occupied only the Severnaya Dvina valley extending no further than the confluence of the Vychegda River, no more than 110 km from the edge of the ice sheet. The lake formation did not cause any drainage reorganization within and outside the Vychegda fluvial system. Given the small size of the lake and presence of the oldest OSL ages along the entire length of the former lake, we suggest that the onset of the proglacial lake marks the maximum extent of the ice sheet in the area. Consequently, the onset of the local LGM may be dated to 20–19 ka, somewhat earlier than assumed by most previous researchers. The LGM ice sheet boundary was located in the Severnaya Dvina valley downstream from the Vychegda confluence and did not extend into the Vychegda valley, despite previous suggestions. During deglaciation, the lake disappearance together with crustal rebound caused an incision episode in the Vychegda – Severnaya Dvina system and the formation of the Lateglacial alluvial terrace with relative height rising downstream due to the uneven rates of the postglacial uplift.

We discuss geological and biotic aspects of the extensive Akchagylian transgression that occurred in the Caspian region of Eurasia near the Plio-Pleistocene transition, in Piacenzian and Gelasian. It is shown that the onset of the Akchagylian marine sedimentation in Western Turkmenistan (ca. 3.2 Ma) preceded that in the Kura Basin (ca. 3.0 Ma). The position of the upper boundary of the Akchagylian remains uncertain (ca. 2.1 or 1.8 Ma). The analyzed biotic content of the Akchagylian includes molluscs, microfossils (pollen, dinocysts, foraminifers), and mammals. It is noted that specific forms of the Akchagylian aquatic biota co-occur with microfossils that clearly indicate a connection with the World Ocean or related seas. The palynology of the Akchagylian time signals a directed cooling in the Pliocene and Early Pleistocene with several warm and humid epochs. The Akchagylian transgression was preceded by a change of a structural-sedimentary pattern of the region. In the latest Miocene and Early Pliocene, a pre-existed longitudinal tectonic zonation of the Caucasian-Caspian segment of the Paratethys gradually changed into clearly transverse tectonic zonation. The latter was manifested in the tectonic uplift of the Greater Caucasus, its northern piedmonts and the Lesser Caucasus, and in the subsidence of the western parts of the South and Middle Caspian basins. The interplay of longitudinal and transverse tectonic features shaped the configuration of the Akchagylian brackish-water basin and controlled thickness of its deposits. It was the transverse zonation that dominated in the thickness pattern. The increasing role of the transverse zonation in the post-Akchagylian time is manifested in the magnitudes and rates of the Quaternary tectonic uplift. These parameters were calculated based on current heights of the top of the Akchagylian marine deposits in different parts of the basin. The highest magnitudes of uplift are found in the Eastern Caucasus (up to 1980 m on the NE slope and about 2500 m in the axial part) and in the west of the Lesser Caucasus in eastern Turkey (up to 1750 m). The maximum level of the Akchagylian transgression is estimated at 40-50 m above the present level of the World Ocean. We show a low probability of connection of the Akchagylian basin with the Mediterranean Sea or the Persian Gulf, and a high probability of its connection with the Arctic Ocean through the northern tributaries of the Kama River and the Pechora Basin in the NE of East European Plain.

The Great Lakes Depression in northwestern Mongolia contains widespread Late Neogene continental deposits, reaching thicknesses of several hundred metres. The Late Neogene Khyargas Nuur formation (also known as the Khirgis-Nur formation) has a significant biostratigraphic value for Central Asia, as it encompasses a unique palaeontological record and has a wide geographical distribution in the region. The stratotype of this formation was described in the Khyargas Nuur 2 (=Khirgis-Nur-2) section on the northern shore of Khyargas Lake. Bio- and magnetostratigraphic studies conducted in the 1970s and 1980s identified the Miocene-Pliocene boundary (corresponding to the Turolian and Ruscinian biochrons) within Unit A, or the Lower Khyargas Nuur subformation. This study aims to refine the age and stratigraphic subdivisions of the Khyargas Nuur formation in light of new data. Examination of the geology of the Lower Khyargas Nuur Subformation stratotype, along with a revision of the associated mammalian assemblage (carnivores, ungulates, and rodents), supports the conclusion that this faunal complex corresponds to the Late Turolian (MN13) of the continental biochronological scale, thus assigning this section to the terminal Miocene. These findings provide new insights into the geological history of the Great Lakes Depression and the faunal history of Central Asia.

The Stratigraphic Drilling Project of the Russian Arctic Shelf conducted by the PJSC Rosneft is aimed at discover the stratigraphic age and rock composition of sedimentary succession of its subsurface. In 2021, six shallow wells for the first time have been drilled with core sampling in the east of the Laptev Sea. Drilling revealed folded sedimentary succession dated back to the Late Barremian – Early Aptian. The synrift complex overlying unconformably dates to the Paleocene. The upper strata dates from Eocene to Pleistocene and contains significant hiatuses. The data discovered together with the results of seismic interpretation clarified the regional geological model and dated the stages of its tectonic evolution.

An Erratum to this paper has been published: https://doi.org/10.1134/S0016852123140017

The Stratigraphic Drilling Project of the Russian Arctic Shelf, conducted by the Rosneft Oil Company, focuses their attention on the stratigraphic age and composition of rock complexes of the sedimentary basins. In 2021, six shallow boreholes for the first time were drilled with core sampling in the eastern part of the Laptev Sea. Drilling recovered sedimentary rocks of the folded basement that have been dated to the Late Barremian–Early Aptian. The synrift complex lying with angular unconformity has been dated to the Paleocene. The section of the overlying Eocene–Pleistocene sediments contains significant hiatuses. The data obtained by drilling together with the results of seismic interpretation allowed us to clarify the regional geological model and to date the stages of its tectonic evolution.

Molasses of foredeeps are important indicators of the newest orogenic uplifts, as well as the data source on climate and landscape changes. One of the fullest sections of Neogene–Quaternary deposits is studied in valleys of the Belaya, Pshekha, and Psekups Rivers at the junction of the Western and Northwestern Caucasus with Eastern Kuban and Western Kuban foredeeps. The formation of the deposits corresponds to the main evolution stages of the Great Caucasus orogen, as well as the foredeeps. Summary of extensive published and original tectonostratigraphic materials has shown that the lowland and then hilly relief in an axial zone of Western Caucasus existed since, at least, from the Middle Miocene. At the same time, the northern flank of the present-day orogen and the foredeeps were located at the sea level and were repeatedly flooded by the seas up to the Kuyalnikian (Piacenzian–Gelasian) time, and the Western Kuban Foredeep – even later. The main data on stratigraphy of the upper molasses and Pliocene–Quaternary tectonic movements of the region are based on facies analysis and bio- and magnetostratigraphic studies of the Upper Pliocene–Lower Pleistocene Belorechensk Formation. Its sedimentation started at the beginning of the Kuyalnikian as a result of an increase of the energy of mountain rivers due to the uplift of riverheads. It is stated that the minimum averaged rate of uplift of the Western Caucasus in the basin of the Belaya River is 0.8 mm/year over last 4 Ma with acceleration up to 1.7 mm/year from the beginning of the Calabrian. The Belorechensk Formation includes three subformations, which successively become coarser-clastic and correspond to the main stages of the accumulation of upper molasses in the Late Pliocene and Early Pleistocene during the intensification of uplifts and landscape-climate changes of Western Caucasus and Ciscaucasia.

The Late Pliocene Gilbert-type delta is described in the western Erzurum Basin (NE Turkiye) and its position in the Late Cenozoic development of the basin is defined. The Erzurum Basin originated no later than Late Miocene between two Mesozoic ophiolite zones, continuing the Izmir–Ankara–Erzincan suture. In the Late Miocene–Pliocene, the basin was filled with fine-grained clastic and carbonate sediments of lacustrine-lagoon type. The Gilbert-type delta formed at the top of these deposits in the western part of the basin. The delta consists of 11 wedge-shaped bodies of clay, silt, sand, and gravel that were deposited as foresets of different phases of the delta development. The foreset bodies are dipping at 5° to 35° E. Some bodies underwent soft sediment deformation. The delta deposits are dated to Late Pliocene based on remains of small mammals and molluscs, palynological, and magneto-stratigraphic analysis. The delta eroded surface is overlain by alluvial pebbles dated to Early Pleistocene by archaeological finds. The Erzurum Basin is the westernmost member in a row of intermontane basins that continues to the east with the Pasinler, Horasan, and Agri basins that are drained by the Araxes River and its tributaries. It is likely that the paleo-Araxes River spread to the west in Late Pliocene and the studied delta was formed by its upper reaches that flowed into the water body of the Erzurum Basin. The delta deposits were covered by coarse alluvium in Early Pleistocene when the Erzurum Basin was tectonically isolated from the Araxes drainage system. In the latest Early Pleistocene or early Middle Pleistocene, the paleo-Araxes upper reaches were captured by the Euphrates River upper reaches that drain the Erzurum Basin now. The Upper Miocene and Pliocene deposits of the Erzurum, Pasinler, and Horasan Basins are similar and were accumulated in a single basin of sedimentation. Therefore, it can be assumed that the deposits of the upper Pliocene, containing the Akchagylian marine biota in the Horasan Basin, extended into the Erzurum Basin. However, the assumption that the upper reaches of the Euphrates River and the Erzurum Basin were the channel, through which the open sea biota entered the Akchagylian basin, is very unlikely for two reasons. Firstly, the Erzurum basin was limited by the described delta of the river, which flowed into it from the west. Secondly, the upper reaches of the Euphrates penetrated into the Erzurum Basin after the completion of the Akchagylian stage of sedimentation.

A study of landscape and climate changes over the last 14000 cal year BP in Northern Mongolia is presented in the paper, based on a comprehensive analysis of friable sediments and seventeen AMS 14C dates from two sections in the Orkhon River basin. The Orkhon and Darkhan sections are located in similar geomorphological conditions on the first above-floodplain river terrace but have some differences. The Orkhon section is located directly at the riverbed, not far from the mountain range, while the Darkhan section is located in a ravine that cuts the terrace surface, at a distance from the river and mountains. This geomorphological difference causes the completeness and complexity of the paleoarchives in the studied sections. Both sections have a thick soil-sediment sequence with several heterochronous paleosols separated by sediments of varying genesis (mainly aeolian and fluvial). The paleosols were formed during periods of slow relief transformation, reflecting the most optimal bioclimatic conditions. The interlaying sediments (sandy-silty layers) display the phases of soil degradation due to frequent droughts and increased aeolian processes, with sporadic and catastrophic rainfalls (horizontally and lenticularly layered strata with a large amount of detritus and gravel). According to our data, the soil profile that was formed in the Late glacial period is characterized by a humid type of soil formation, and according to palynological data, meadow vegetation was widespread. In the Early Holocene, there was one stage of optimal conditions (increased heat and moisture) proper for soil development in Northern Mongolia. In the Middle Holocene, there are at least three stages. Finally, there were two stages with increased climate humidity in the Late Holocene. In the Early Holocene, Northern Mongolia had more humid forest-steppe conditions, which were replaced by steppe conditions in the Middle Holocene, when the climate changed more significantly. An expansion of forest vegetation (pine forests), probably on the northern slopes, is noted in the pollen spectra of Middle Holocene soils. Steppe and semi-desert landscapes predominated. Several stages of enhanced aridization were reconstructed: about 3800-4000, between 8400-8000 years BP. In the Darkhan section, the period of 8394-2775 years was a significant hiatus in soil formation. About 50 cm of sand accumulated over 5600 years, and there are no soils in this layer. Plausibly, the surface was essentially denudated before the second paleosol formation. At the same time, the Orkhon section accumulated aeolian sediment more than 70 cm thick. It suggests the existence of a period of severe droughts at the end of the Middle Holocene (after 3000 years BP). In the Late Holocene, climate humidification was reconstructed, when meadow steppes predominated again. The uppermost paleosol in the Darkhan section was formed in the second half of the Late Holocene.

The paper considers geological structure of the coastal region of the South Caspian, including paleontological and magnetostratigraphic dating of the Neogene–Quaternary deposits. Western and eastern segments of the region between the South Caspian Basin and the Alborz Ridge developed differently in the Late Cenozoic. In the west, marine sediments did not penetrate beyond the coastal plain into the neighboring lowered part of the Alborz Ridge during the Pliocene–Quaternary. This indicates the stability of the marine basin boundary or its expansion due to the abrasion of the Alborz slopes. In the east, a piedmont step emerged, bounded by thrust faults. The marine deposition at the piedmont step occurred in the Miocene. At the end of the Miocene, the marine sediments were folded and eroded. The Akchagylian (Piacenzian–Gelasian) marine sediments accumulated at the northern edge of the piedmont step. The Khazar fault raised these sediments up to 120–150 m and isolated the piedmont step. Thus, the expansion of the Alborz mountain building and the reduction of the South Caspian Basin occurred in the eastern part of the coastal area from the Late Miocene. The differences between the western and eastern segments of the coastal area are related to the development of the South Caspian Basin. Until the Late Miocene, it remained a residual trough of the Paratethys. During the Pliocene–Quaternary, the eastern part was filled with sediments up to 6 km thick and retained the features of a thinned continental crust 30–37 km thick with sedimentary cover up to 16 km thick. The western part of the basin was filled with sediments about 10 km thick and acquired the features of suboceanic crust with the Mohorovichich surface at a depth of 28–30 km with a thickness of the sedimentary cover exceeding 20 km.

The highest Shahdag-Qusar segment of the South-Eastern Caucasus, located on the border of Azerbaijan and Russia, is considered. Ridges of Greater Caucasus axial zone are the closest to the Caspian Sea coast here, and the latest marine deposits cover the high-mountainous watershed surfaces. Research results of the Plio-Quaternary tectonic movements and stratigraphy are presented. Morphostructural and facies analysis of the northern macro-slope of the mountain system was performed to reconstruct the history of Plio-Quaternary orogenesis of this territory. Findings of shells of molluscs, an indicator of the Akchagylian basin, in the sediments of the homoclinal Qusar plateau at altitudes up to 2020 m asl made it possible to estimate the rate of the Quaternary uplift in the South-Eastern Caucasus and compare these data with the results of previous studies in Transcaucasia. The reconstruction of the mountain system development in the Pliocene with acceleration of the average Pliocene uplift is presented, and the probable reasons for this acceleration are discussed.

The paper presents new data on brackish-water Upper Pliocene and Lower Pleistocene deposits that were studied in the Demirkent (Kars) and Pekecik (Erzurum) sections, NE Turkey. The Demirkent section is situated in the southwestern slope of the Shirak Late Cenozoic intermontane basin near the Turkish-Armenian border. The Pekecik section is situated to the SW of the Demirkent in the southwestern slope of the Horasan intermontane basin. Both sections are composed of clays, silts, and poorly cemented fine-grained sandstones and contain the brackish-water dinocysts of the Akchagylian type. The age of the deposits is determined by combined analysis of associations of molluscs and small mammals, palynological spectra, including dinocysts and algae, and magnetostratigraphic data. The Demirkent and Pekecik sections are dated to the Late Pliocene (Piacenzian). The maximum spread of the Akchagylian transgression influenced the inland areas of NE Turkey prior to the early Gelasian. The pollen spectra demonstrate progressive aridisation during sedimentation of the lower part of the Demirkent section and the wetter and cooler climate during sedimentation of the lower part of the Pekecik section. The analysis of brackish-water dinocysts and fresh-water algae in different beds of the Demirkent section indicates gradual freshening of the basin probably due to the sea level fall. In the Pekecik section, the brackishwater dinocysts are found in the lower part that is covered by the lignite-bearing layers without signs of marine influence. Recent altitudes of the Akchagylian brackish-water deposits give a possibility to estimate magnitudes and average rates of the Quaternary uplift of the western Lesser Caucasus. The elevation of the Upper Pliocene deposits of Demirkent and Pekecik sections shows the uplift rate of ca. 0.6-0.7 mm per year during 2.6 Ma.

The Vychegda – Severnaya Dvina fluvial system crosses the eastern margin of the Last Scandinavian ice sheet boundary located both in the former glacial and extraglacial zones of the northeastern Europe. Thus this area has raised a considerable interest as one of the key places for studying the palaeoenvironmental history of MIS 2 and LGM. Long study history of the region created a number of contradictions between different concepts of the LGM ice sheet boundaries and expansion of glacially dammed lakes that supposedly existed within the Vychegda – Severnaya Dvina fluvial system. The goal of this study was to collect new data concerning the history of the extraglacial part of this Scandinavian Ice Sheet sector and try to resolve these contradictions. We have studied a number of sections and landforms in the valleys of Vychegda and Severnaya Dvina using radiocarbon and OSL dating as our main dating methods, as well as pollen and carpological analyzes, and were able to reconstruct the MIS 2 history of the Vychegda – Severnaya Dvina fluvial system. During MIS 2, within the valleys the 1st river terraces were formed. The LGM-lake formed between 19 and 17 ka, had a limited expansion only within the Severnaya Dvina valley and was seemingly largely influenced by glacioisostatic subsidence; subsequent deglaciation and lake degradation caused an incision in Vychegda – Severnaya Dvina system with the formation of Late Glacial terrace. Lastly, it was found that aeolian activity in the region was previously underestimated, with its peak corresponding to 17-11 ka, being partly contemporaneous with that in other parts of Europe at the periphery of Last Scandinavian Glaciation.

Время заселения человеком Русской равнины и культурные особенности ее первых поселенцев остаются предметом дискуссий. В статье анализируются материалы древнейшей на юго-востоке Русской равнины стратифицированной ашельской стоянки Хрящи на Нижнем Дону. Суммируются сведения о стоянке, приводятся предварительные результаты новых исследований. Анализ остатков мелких млекопитающих, малакофауны и палинологические данные показывают, что стоянка существовала во время лихвинского климатического ритма («большой лихвин», MIS 11-9, ~ 420–270 тыс. л. н.). Культуросодержащий слой стоянки, залегающий стратиграфически ниже слоя с теплолюбивой лихвинской малакофауной, сформировался в отно­сительно засушливую фазу этого интервала. Это тонкий (10–30 см) слой базального галечника III надпойменной террасы р. Северский Донец (IV надпойменной террасы р. Дон?), залегающий под почти 30-метровой толщей отложений различного генези­са, включающей не менее трех ископаемых почв. Культурные остатки представлены главным образом каменными изделиями. Кости крупных млекопитающих малочисленны, это остатки копытных, обычных для среднего и позднего плейстоцена Европы (бизон, благородный олень). Окатанность некоторых изделий позволяет предполагать, что деятельность людей происходила на пляже реки, место стоянки посещалось ими неоднократно. О кратковременном характере стоянки свидетельствует отсутствие нуклеусов и использование в ряде случаев приносного сырья. Каменная индустрия стоянки, по-видимому, не леваллуазская. В ней хорошо выражены оформленные орудия: крупные режущие орудия и более мелкие орудия из отщепов и обломков сырья. Наличие бифасов и широкий спектр крупных режущих орудий указывают на принадлежность ее к индустриям с ашельской технологией (ашелю). Индустрия стоянки своеобразна. Прямые аналогии каменной индустрии Хрящей пока не выявлены, но некоторые признаки ее технологии и типологии орудий прослеживаются в ашельских индустриях Центральной Европы и Западного Кавказа. The period when humans settled in the Russian plain and cultural traits of its first settlers remain a matter of debate. This paper analyzes materials from a stratified site known as Kryashchi located in the Lower Don region which is the earliest Acheulean site in the southeastern part of the Russian plain. The paper summarizes data on the site, and provides preliminary results of recent excavations. The analysis of remains of small mammals, malakofauna and palinological data demonstrate that the site was occupied during the Likhvin Interglacial (‘Big Likhvin’, MIS 11-9, ~ 420–270,000 years ago). The occupation layer located stratigraphically beneath the layer with thermophilic Likhvin malakofauna was formed during a relatively dry phase of this interval. It is a thin (10–30 cm) layer of basalt pebble stone of the 3rd terrace above the flood-plain of the Severskiy Donets (the 4th terrace of the Don River?) underlying rock masses almost 30 m thick, these masses have different genesis of accumulation and include at least three buried soils. Remains from the occupation layer are represented mainly by stone items. Bones of large mammals are few and include remnants of the ungulates typical for the Middle and the Late Pleistocene of Europe (bison and red deer). Roundness of the items from the occupation layer suggests that humans were engaged in various activities on the river beach and that they visited the site repeatedly. A lack of cores and the use of materials brought from other places imply that the site was occupied for a short period of time. Its lithic industry does not appear to be Levallois and is well represented by trimmed tools such as large cutting tools and implements and smaller tools made on flakes and stone fragments. Presence of bifaces and a wide range of large cutting tools suggest that this industry belongs to those with Acheulean technologies. The industry of the site has some distinguishing traits. Direct analogies to the Khryashchi lithic industry have not yet been found; however, some technological characteristics and tool typology can be identified in Acheulean industries of Central Europe and the Western Caucasus.

Integrated paleogeographic studies have been performed on the loess and soil sequence in the lower reaches of the Orkhon R., northern Mongolia. The samples were taken continuously through the sequence and studied using a broad assortment of field and laboratory analyses. There are five paleosols exposed in the section under study crowned with the present-day soil and separated from each other by loess horizons or proluvial-deluvial deposits. The dating by radiocarbon proved the soil development beginning from the early Holocene. The two lower soils (PS4 and PS5) formed at that interval are noted for the minimum salinity and a considerable content of carbonates. The soils dated to the middle Holocene (PS3 and PS2) contain the least proportion of organic matter and increased salinity, which may be attributed to a dryer climate (even at optimum intervals) than in the early and late Holocene. In common with the present-day soil, the PS1 buried soil is characterized by negligible (or absent) salinity, and a noticeable accumulation of organic matter and carbonates indicative of favorable warm and relatively wet conditions. All the pollen assemblages indicate the dominance of grass vegetation; it may be safely suggested that open meadow and steppe landscapes, occasionally replaced by semi-deserts, prevailed in the considered region during the Holocene.

The paper is devoted to the Middle and Upper Pleistocene stratigraphy of the Vychegda River basin, located in the far northeast of Europe, in the Timan-Pechora-Vychegda subzone of the Middle-Late Pleistocene glaciations. The available litho-/chrono-/biostratigraphy data were have been obtained from more than 20 natural outcrops along the valley of Vychegda and its tributaries, which were studied lithostratigraphically. Also radiocarbon, OSL, IR-OSL and 230Th/U dating was performed, together with pollen and palaeocarpological analyses. The oldest glacial deposits are related to the Pechora horizon (MIS 8), and the oldest numerically dated relate to the Rodionovo horizon (Schoningen, MIS 7), embracing the chronostratigraphic archive of the last similar to 250 ka. The Vychegda horizon (Drenthe + Warthe, MIS 6) includes surficial tills, glaciofluvial and glaciolacustrine sedi-ments dated back to 186-111 ka. This ice sheet produced the ice-dammed lake which overflowed into the Kama -Volga and Caspian basin. The Last Interglacial-Glacial cycle is associated with the Sula horizon (Eemian + Lower Weichselian, MIS 5), and the Nenetsky superhorizon with the Laya (Middle Weichselian, MIS 4), Byzovaya (Middle Weichselian, MIS 3) and Polar (Upper Weichselian, MIS 2) horizons, reflecting alluvial and aeolian sedimentary environments. The chronostratigraphic record of the Byzovaya (67-27 ka) and Polar (27-1 1.7 ka) horizons is well supported with C-14, OSL, IR-OSL and Th-230/U-dates and biostratigraphic data. Unlike the predecessors' descriptions no glaciolacustrine deposits had been identified for these horizons. The Holocene floodplain, aeolian and peat bog deposits dated from 11.7 ka are widespread over the Vychegda catchment area.