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Abstract The paper presents the results of the study of Karginsky and Sartansky deposits of the Kolyma Lowland, synchronous with marine isotope stages (MIS) 3 and 2, and microphytofossils from them. During the accumulation of Karginsky deposits, various landscapes existed in this territory: communities of humid and dryish tundras, larch sparse forests, and tundra swamps, including habitats occupied by pioneer and steppe vegetation. The Sartansky deposits were formed under more uniform, cold and dry conditions. The results of the microbiomorphic study indicate the predominance of tundra herbaceous, mainly cereal associations in combination with the moss cover. Satisfactory preservation of microphytofossils from these strata is due to the specificity of the cryolithozone with a predominance of low temperatures throughout the year and low microbiological activity. The presence of spores and pollen with physical damage (ruptures and cracks) and corroded forms of phytoliths can be associated with their presence in the seasonally thawed layer during alternating freezing and thawing cycles.

The results of the study of the structure of buried soils of Marine Isotope Stage (MIS) 3 on the Kolyma Lowland and of the analysis of microphytofossils from these soils are given. The data of the spore-pollen and phytolith analyses confirm the similarity of the natural conditions for the formation of buried soils and the tundra aspect of reconstructed landscapes under a progressive decrease in heat and moisture supply during MIS 3.

The results of interdisciplinary research conducted at the Eneolithic archeological site Oroshaemoe (5–7 ka BC) in Saratov oblast are presented. The studied soils are calcareous light chestnut soils (Eutric Cambisols (Loamic, Protocalcic, Ochric)); in the archeological excavation, they are human-modified and contain various artifacts. A set of pedological, paleopedological, paleoclimatic, and paleobotanical methods and radiocarbon dating have been applied. Information on alternation of the periods of humidization and aridization of the territory, stages of soil formation and sedimentation, and on the vegetation cover in the Holocene at the archeological site has been obtained and refined. According to our data, periodic alternation of more humid and more arid conditions has taken place since 7245 ± 60 BP. The stages of aridization were accompanied by the short-term sedimentation related to the activation of eolian processes. Loesslike sediments deposited during these stages are archeologically sterile (do not contain artifacts) and are relatively thin in comparison with the cultural layers separating them. The stages of humidization were marked by more active sedimentation accompanied by soil formation. The obtained data suggest that the past 5000 years have been the period of some humidization of climatic conditions. Preliminary estimates of sedimentation and soil formation rates in the Holocene in the study area attest to their considerable fluctuations. Thus, the rate of soil formation varied from 35 to 0.8 cm per century. The results of this study allow us to refine paleoclimatic reconstructions for the considered area. Periodic changes in the environmental conditions during the Holocene affected the life of the tribes, patterns of human settling, and regional and, possibly, global migration processes. The reconstruction of natural and climatic features of the archeological site and its comparison with published data attest to the uneven paleogeographic situation in the Lower Volga region. It is argued that the chronology of landscape and climatic changes during the Holocene as presented in the publications for the southern arid regions of the East European Plain needs to be revised and made more detailed.

An Erratum to this paper has been published: https://doi.org/10.1134/S0869593822960012

Spore–pollen spectra of surface samples characterizing different plant associations in the Lower Kolyma River basin are studied. The formation features of the studied spore–pollen spectra are determined, as well as their potential for past vegetation reconstruction, paleogeographic constructions, and stratigraphic correlation of Quaternary deposits in Northeastern Russia.

The distribution of carbon in an agrochernozem’s profile was studied by the natural 13C abun dance method during the C3–C4 vegetation transition and the analysis of the soil phytolith complex under a continuous corn monoculture. A young pool of soil organic matter (SOM) formed during 43 years of monoc ulture growing was detected by the isotope analysis in the 0 to 60cm layer, while the analysis of the phytolith complex identified this pool deeper: corn phytoliths were detected in the 0 to 80cm layer. The maximum size of the young pool was found in the upper soil horizon; it reached 6.4% of the SOM in the 0 to 20cm layer. The apparent time of the SOM turnover was 635 and 2225 years in the 0 to 20 and 40 to 60cm layers, respectively. The high values of the mean residence time were related to the low input of plant residues to the soil at the growing of corn for silage and the high initial content of organic carbon in the chernozem. The changes in the isotope composition after the decalcification of the soil to remove carbonates and the variation of the δ13C in the corn biomass during the vegetation period significantly affected the calculated value of the mean residence time.

The results of the investigation into the history of soilscapes in the Kislovodsk Depression are discussed. It is shown that up to 60–70% of the area of slopes and interfluvial plateaus at the heights of 900–1500 m a.s.l. was terraced in the Late Bronze-Early Iron ages, during the Kobansk cultural stage (1200–600 BC). Under these conditions, a sharp change in the climate with a considerable increase in the annual precipitation in the middle of the first millennium BC resulted in the activation of erosion and the formation of a layer of colluvial sediments overlying the buried soil on the terraces. Thus, the middle of the first millennium BC can be considered the zero moment for the modern stage of soil formation in the region. Problems of the current state of the terrace complexes and the development of erosion on them are also discussed.

A detailed study of the Duvanny Yar section in the Kolyma Lowland (Yakutia) provides the most extensive knowledge to date about late-Pleistocene soil formation processes and environments in the North–East Siberian Arctic. Late-Quaternary palaeoenvironmental changes were reconstructed using paleopedological data and a range of palaeoecological bio-indicators (palynomorphs, plant macrofossils and insects). The frozen sediments representing marine isotope stage 3 (MIS-3), which encompasses the Karginsky interstadial, include profiles of four palaeosols of different ages. The oldest palaeosol is early Karginskian, and three overlying soil horizons represent a late-Karginskian pedocomplex. Palaeopedological data indicate a change of from synlithogenic soil formation processes to epigenic ones during these intervals. The intervening periods of synlithogenic pedogenesis were accompanied by active accumulation of eolian deposits. The Earlier Karginskian period of pedogenesis occurred in the absence of eolian sedimentation and when summer conditions were warm. The wide spectrum of peaty and peaty-gley soils observed in the late-Karginskian deposits developed under conditions of progressive cooling. The structure and content of fossil rodent burrows dated to approximately 30 000 yr BP from frozen late-Pleistocene deposits at Duvanny Yar indicate an arid and severe climate, a depth of active layer of 60–80 cm, and a wide distribution of disturbed habitats with pioneer and steppe vegetation.

The comparative analysis of palynomorphs and plant megafossils (fruits, seeds, twigs, leaves) in the Upper Pleistocene host sediments and materials filling in fossil burrows of gophers, their coprolites included, at the Duvannyi Yar, Stanchikovskii Yar and Zelenyi Mys sites of the Kolyma Lowland is carried out. Genera Salix, Lychnis, Silene, Draba, Potentilla, Larix, and families Poaceae, Polygonaceae, Cyperaceae, Compositae, and Leguminosae are determined among palynological remains and megafossils. Factors responsible for qualitative and quantitative differences in taxonomic compositions of palynological and megafossil assemblages are biological peculiarities of plants, different character of fossilization of palynomorphs and large plant remains, geographic conditions, different genesis of assemblages (allochthonous for microfossils and autochthonous for megafossils), and inadequately known morphology of certain spore and pollen taxa. The comprehensive paleobotanical analysis leads to the conclusion that the study region was occupied in the Late Pleistocene by plant communities of humid to somewhat dryer tundra with separate areas of pioneering and steppe vegetation.