Morphological and isotopic study of pedogenic carbonate coatings from steppe and forest-steppe areas of Baikal region, South-Eastern Siberia

Golubtsov, V.; Bronnikova, M.; Khokhlova, O.; Cherkashina, A.; Turchinskaia, S.

Авторы: Golubtsov Viktor, Bronnikova Maria, Khokhlova Olga, Cherkashina Anna, Turchinskaia Sofiia
Журнал: Catena
Том: 196
Год издания: 2021
Издательство: CATENA Verlag
Местоположение издательства: Germany
Первая страница: 1
Последняя страница: 20
Номер статьи: 104817
DOI: 10.1016/j.catena.2020.104817
Аннотация: In this study we investigated different age carbonate coatings in the surface steppe and forest-steppe soils andpaleosols of the Baikal region and its relationship with environmentalfluctuations of the Late Pleistocene andHolocene. The14C age of thin pedogenic carbonate laminae indicate four periods of coating formation: thesecond half of MIS-3 (24.1–23.3 and ~34.0–35.0 kyr BP), from the warm phases of the Late Glacial to the MiddleHolocene (12.9–4.6 kyr BP) and thefinal of the Middle Holocene (3.6–3.3 kyr BP). Thus, studied carbonatecoatings are mainly relict feature of the previous epochs of pedogenesis and Middle Holocene stage of surfacesoil formation. Paleoecological conditions reconstructed for the identified stages of formation of carbonatecoatings correlate well with the trend of climatic changes in the Baikal region and adjacent areas. They reflectthe effect of temperature and moisturefluctuations on the dynamics of soil-forming processes. Distinctδ18O andδ13C values suggest that the coatings of Transbaikalian steppes and forest-steppes of Fore-Baikal region havebeen formed under contrast environmental conditions. It is assumed that the formation of pedogenic carbonatesin Transbaikalia is mainly confined to the summer season, when the soil is most warmed up, and the plantsactively consume water and emit a large amount of CO2. This agrees well with the slightly higher temperaturesof the warm season and the greater aridity of this region. In turn, carbonate precipitation in Fore-Baikal regionoccurred during the degassing of soil solutions in the course of periodic freezing and thawing, alternation ofphases of snowmelt and rainwater infiltration into the soil and its subsequent freezing, which can be observed inthe region in spring and autumn. A significant CaCO3content in the studied soils contributed to the high growthrates of pendants. Holocene coatings are characterized by maximum growth intensity, which correlates with thehighest carbonate content in the slope sediments where they are found. At the same time, MIS-3 coatings formedmainly on significantly less carbonate-rich alluvial deposits, which apparently affected their lower growth in-tensity. Based on an analysis of the growth rates of coatings, comparison of the isotopic composition of differentage groups of pendants and soil micromorphology the more humid climatic conditions of the MIS-3 is assumed incomparison with the Middle Holocene. The temperature conditions of pedogenesis may be similar. Both for theMiddle Holocene and for the MIS-3 relatively low temperatures of pedogenesis and long-term seasonal soilfreezing are supposed.
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