The Siberian loess record and its significance for reconstruction of Pleistocene climate change in north-central Asia

Abstract

The Siberian loess represents the most significant terrestrial proxy record of Quaternary climatic history in northern Asia. Loess is extensive in southern Siberia, between the Irtysh Basin in the west and the Angara Basin in the east. Palaeoenvironmental multi-proxy data (magnetic susceptibility (MS), grain size, % CaCO3, % TOC, pollen, etc.) from high-resolution loess-palaeosol sections provide evidence for a strongly fluctuating climatic sequence in north-central Asia during the Late Quaternary, displaying the globally diagnostic sequences found in the deep-sea oxygen isotope records. MS provides the most continuous and detailed record (encompassing the last two interglacial-glacial cycles) in loess sections in the Minusinsk Basin (Yenisei area) and on the northern Altai Plains. Evidence for periodic atmospheric shifts is provided by gradual changes in the main vegetation zones, with parkland-steppe and mixed taiga during warm interglacial/interstadial stages being replaced by boreal tundra-forest and arid periglacial tundra-steppe during stadials. Climatic pulses from warm intervals to cold are recorded by incipient (forest/steppe)-tundra gleysols. The occurrence of the highest sediment accumulation rates in glacial stages (OIS 4 and OIS 2) in the southern plains and depressions indicates that the most intensive aeolian dust deposition followed the glacial maxima, with the most recent interval dated to ca. 19-15 ka BP. Because of its zonal distribution and pronounced climatic continentality, the Siberian loess region represents an important data source for reconstructing past climates in the Northern Hemisphere. It provides a key to the correlation of other loess regions within the West-East Eurasian continental zone. (C) 2003 Elsevier Ltd. All rights reserved.