The First 5700-Year History of Vegetation and Climate of the North-Minusinsk Basin According to a Decadal-Resolution Palynological Record from the Sediments of Lake Shira

First results of reconstruction of the natural environment of the North-Minusinsk Basin based on the study of a continuous, 280-cm long sedimentary core from meromictic Lake Shira are presented. The age model is based on ten AMS 14C dates. The main part of the section is represented by annually laminated series, or varves, which became the basis for the reconstruction with an average temporal resolution of 20 years. It is established that limnogenesis at the lake’s geometric center began ca. 5700 calibrated years ago. Vegetation changes in the northern Minusinsk Basin and around Lake Shira suggest a semiarid climate with decadal-centennial fluctuations in plant-available moisture over the study time interval. The local vegetation around Lake Shira was predominantly steppe and forest-steppe during the last 5700 years. The maximum expansion of steppe vegetation and the lowest lake level during the study period are reconstructed at ca. 5700–4600 cal BP and 880–510 cal BP. The latter correlates with the Little Ice Age, the main glacial stage of the Holocene in the Russian Altai Mountains. Botryococcus algae abundance minima correlate well with the formation of whitish carbonate silts in Lake Shira sediments and can indicate not only a lake level decline but also disruption of its water column stratification.