Pleistocene climatic history in the Minusinsk Basin, southern Siberia, Russia

Climatic evolution in Siberia during the Pleistocene is still insufficiently known. A complete, high-resolution palaeoclimatic record for the last two glacial-interglacial cycles in southern Siberia has been studied at Kurtak in the Northern Minusinsk Basin. The unique, 34 m thick Late Quaternary sequence of loess and palaeosols (Section 29) with a differential degree of pedogenic development provides evidence of a strongly fluctuating, but patterned climatic change, with an increasing deviation amplitude during the Late Pleistocene cycle (130-10 ka). Mineralogical composition and grain morphology of the undifferentiated (aeolian and colluviated) loess indicates a local provenance and a short transport of the silt derived by glacial erosion of the granitic and metamorphic bedrock in the Kuznetskiy Alatau and the Eastern Sayan Mountains, and subsequently subaerially redeposited from the alluvial plain in the Yenisey River valley.;Recorded palaeoclimatic regularities manifested by a succession of Chernozemic, Brunisolic and Gleyed Regosolic soils are consistently traced by magnetic susceptibility characterized by markedly increased values during cold intervals, and decreasing values for warm intervals. This specific pattern (with the magnetic susceptibility minima in the most weathered interglacial soils) radically differs from the Chinese loess record, where the ferromagnetic concentration in palaeosols correlates directly with the enhanced degree of pedogenesis. A process of ferromagnetic mineral depletion during soil development under periodic oxidation and reduction conditions is proposed to account for the magnetic susceptibility decline because of leaching of less stable iron hydroxides. Increased amounts of unweathered iron minerals (magnetite, titanomagnetite and ilmenite) in the Siberian loess inherited from the glacially-eroded primary geological sources, coupled with the more intense aeolian activity during cold climatic intervals, are believed to be the main controlling factors.;The loess-palaeosol record from the Kurtak area, well-correlated with the marine Oxygen Isotope Stages 1-5 provides evidence of a pronounced climatic change in the Minusinsk basin during the Late Pleistocene, with very cold and dry glacial stages, and cool and more humid mid-last glacial interstadials. The last interglacial sensu lato (130-73 ka) includes several cold and warm substages with a strongly continental trend during its first half. The palaeoclimate evolution is manifested by shifts in the major ecotones, with southern taiga established during the early interglacial and early interstadial stages under more humid and warmer conditions, succeeded by semiarid steppe and tundra-steppe, respectively. A gradual transition into glacial stages is evidenced by expansion of boreal forest and tundra-forest, eventually replaced by cold periglacial tundra-steppe with intensive loess sedimentation during glacial maxima. A cold-adapted arboreal vegetation appeared during warmer oscillations. Fossil fauna and cultural remains suggest analogous Late Pleistocene environments throughout southern Siberia.