Late Glacial and Holocene in the south of Western Siberia: geochemical indices and pollen data in Kyrtyma Lake sediments

This paper presents some conclusions of a study of a long-term lake sequence in the southwestern part of the Western Siberian Plain. Environment changes in the Holocene were identified according to geochemical indices, accumulation rate, plant macrofossils, and pollen data of sediment in Lake Kyrtyma. As a result, we firstly obtained the data on climatically conditioned changes of the sedimentation in the flat part of Western Siberia over at least the last 15 thousand years. Geochemical changes in the sediment properties clearly revealed climate change over the Late Glacial and the Holocene. Changes in the composition of macrophytes gave little independent information, while the pollen data are perfectly combined with the sedimentation features and serve as a reliable source for the reconstruction of vegetation changes and landscape. The transition to the Holocene was marked at about similar to 12-11.2 ka BP, subsequent ongoing warming led to the aridest Holocene phase at similar to 7.1-5.5 ka BP. Cooling and the resulting decrease in vaporation began at similar to 5.5-4.9 ka BP, but a cardinal shift in sedimentation due to a gradual increase in precipitation was at similar to 4.9-2.8 ka BP. The most significant increase in humidification and a cooling began at 2.8 ka BP.