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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.

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.

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.