Pleistocene warming stages in Southern West Siberia: soils, environment, and climate evolution

A comparison of Neopleistocene soils in complete loess-soil sequences in southern West Siberia has shown a distinct trend in the evolution of soil formation and climate during warming stages. The Late Neopleistocene climate changes differed in amplitude and frequency from those in the Early and Middle Neopleistocene, when the territory of southern Siberia was dominated by a temperate warm and humid climate. The amplitude and frequency of climatic fluctuations changed significantly after the Kazantsevo interglacial. Warming stages at that time were much shorter, colder, and more arid. Early Neopleistocene soils are represented by Meadow and Meadow-Chernozem soils, formed upon heavy clay sediments in semi-hydromorphic conditions under wet meadow vegetation. They show intense humus accumulation, gleying features, R2O3 enrichment and lessivage. In the Middle Neopleistocene, Chernozem soils with double humic profiles and Grey Forest-Chernozem poligenetic soils formed on porous loess-like sediments. In the Late Neopleistocene, Chernozems and Grey Forest soils have reduced weakly differentiated profiles and humus horizons, which are half as thick relative to the soils of the previous stages. Correlation of the Neopleistocene loess-soil sequences in West Siberia with the oxygen isotope record from deep oceanic sediments shows that climate change in mid-latitude regions is in line with the global change controlled by Earth's orbital parameters. Climate change occurs in 100 kyr cycles that correspond to major glacial-interglacial alternation. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved.