MINERALOGY OF HOLOCENE SEDIMENTS OF LAKE BOLSHOE YAROVOE ( <i>south of Western Siberia</i> ): THE ROLE OF THE CLIMATIC FACTOR

We report the results of lithological and mineralogical studies of Holocene bottom sediments from the hypersaline Lake Bolshoe Yarovoe (salinity 150 g/L), located on the territory of the Kulunda steppe (south of Western Siberia). Research methods: X-ray diffractometry (XRD), IR spectroscopy, laser grain-size analysis, elemental analysis, and radiocarbon dating. The thickness of the uncovered sediments is 483 cm. Terrigenous minerals throughout the section are represented by quartz, plagioclase, and layered silicates (mica, chlorite, smectite, and kaolinite). The variable amounts of omnipresent authigenic minerals include halite, gypsum, carbonates, and traces of pyrite. We identified Mg-calcites with different Mg contents and aragonite using the mathematical modeling of X-ray diffraction patterns in the assemblage of carbonate minerals. The mineralogical and crystallochemical studies of sediments supplemented by the results of other analyses have provided information about the evolution of the climate of the Kulunda steppe in the Middle to Late Holocene. The comparatively arid regional climate of the Middle Holocene became more humid in the first half of the Subatlantic, but aridization signs reappeared in the section about 600 years ago (Little Ice Age).