A late Quaternary loess – paleosol record at Kurtak, southern Siberia

Abstract

A high-resolution paleoclimatic record for the last two glacial – interglacial cycles has been documented at Kurtak in southern Siberia. A unique, 34 m high late Quaternary loess section (section 29) with a series of 32 variably developed paleosol horizons provides evidence of a strongly fluctuating, but patterned, climatic change. Mineralogical composition and grain morphology of the undifferentiated (aeolian and colluviated) loess indicate 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 eastern Sayan mountains, and subsequently subaerially redeposited from the alluvial plain in the Yenisey River valley. The succession of Chernozemic, Brunisolic, and Gleyed Regosolic soils, alternating with nonweathered or weakly weathered loess events, matched by parallel changes in magnetic susceptibility, can be correlated with marine isotope stages 1 – 7. The magnetic susceptibility pattern is completely opposite to that of the Chinese loess record, where magnetic susceptibility is highest in paleosols, as opposed to lowest in Kurtak paleosols. The reason for this is not completely understood. Nevertheless, the magnetic susceptibility profile correlates well with the last two glacial – interglacial cycles. Furthermore, isotope stage 5 includes several short-duration, relatively small amplitude susceptibility signals corresponding to equivalent signals in the δ18O record. These include the colder intervals (stadials?) 5b and 5d, warmer intervals (interstadials?) 5a and 5c, and the "optimum" warm interval 5e.