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Radiocarbon dating of buried Holocene soils in Siberia.

Lyubov A Orlova, Valentina S Zykina

Abstract


We have constructed a detailed chronological description of soil formation and its environments with data obtained on radiocarbon ages, palynology, and pedology of the Holocene buried soils in the forest steppe of western and central Siberia. We studied a number of Holocene sections, which were located in different geomorphic situations. Radiocarbon dating of materials from several soil horizons, including soil organic matter (SOM), wood, peat, charcoal, and carbonates, revealed three climatic periods and five stages of soil formation in the second part of the Holocene. (super 14) C ages of approximately 6355 BP, 6020 BP, and 5930 BP showed that the longest and most active stage is associated with the Holocene Climatic Optimum, when dark-grey soils were formed in the forest environment. The conditions of birch forest steppe favored formation of chernozem and associated meadow-chernozem and meadow soils. Subboreal time includes two stages of soil formation corresponding to lake regressions, which were less intense than those of the Holocene Optimum. The soils of that time are chernozem, grassland-chernozem, and saline types, interbedded with thin peat layers (super 14) C dated to around 4555 BP, 4240 BP and 3480 BP, and 3170 BP. Subatlantic time includes two poorly developed hydromorphic paleosols formed within inshore parts of lakes and chernozem-type automorphic paleosol. The older horizon was formed during approximately 2500-1770 BP, and the younger one during approximately 1640-400 BP. The buried soils of the Subatlantic time period also attest to short episodes of lake regression. The climate changes show an evident trend: in the second part of the Atlantic time period it was warmer and drier than at present, and in the Subboreal and Subatlantic time periods the climate was cool and humid.

Keywords


Paleosols;soil profiles;paleoenvironment;climate change;reconstruction;Holocene;Siberia;organic compounds;peat;sediments;Asia;Cenozoic;charcoal;Quaternary;C 14;carbon;dates;isotopes;radioactive isotopes;absolute age

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