QUATERNARY WARMING STAGES IN SOUTHERN WEST SIBERIA: ENVIRONMENT AND CLIMATE Available to Purchase

A comparison of Pleistocene soils in complete Ioess-soil sections in southern West Siberia has shown a distinct trend in the evolution of soil formation and climate during warming stages, which is consistent with the evidence of the absence of Early and Middle Pleistocene interstadial soils from loess sections in East Europe. The Late Pleistocene climate changes differed in amplitude and frequency from those in the Early and Middle Pleistocene, 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, cooler, and more arid. Although the Holocene interglacial was cooler than the previous Kazantsevo (Eemian) interglacial, it was much longer and warmer than the short warmings of Early Zyryanian and Karginian time. The trend of Late Cenozoic climate changes has turned to warming since the Holocene. During almost each Pleistocene interglacial, thermophile freshwater mollusk species migrated from Central Asia to West Siberia, which is evidence of a well-developed drainage network and a humid climate in Central Asia and Western Kazakhstan. The hypsometry of the warm Kazantsevo alluvium indicates that the river network evolved toward higher altitudes after the rise of the sea level associated with global warming and thawing of unstable ice sheets. Warming, along with greater humidity, led to higher stand of groundwaters and swamping of continental low plains. Despite some variability in their duration, the frequently alternated warm and cold stages of Holocene time show well-pronounced recurrence at intervals of about 500 years. The latest cold stage (Small Ice Age) lasted from the middle 15th to the late 19th century, until the onset of the following warming. This stage was similar to the early Middle Age in its thermal parameters; its expected duration is about 500 years.