TEMPERATURE REGIME RECONSTRUCTION OF TWO CAUCASIAN MOUNTAIN LAKES BASED ON DIATOM ANALYSIS
The authors present the analysis of data on diatom assemblages from the bottom sediments in Lake Karakyol (Karachayevo-Circassian Republic) and Lake Donguzorun (Kabardino-Balkarian Republic). Both lakes are of glacial origin. The sediments samples were drilled in the deepest parts of lakes. The temperature regime of lakes was reconstructed according to taxonomic composition of diatom assemblages. The calculations of temperature variations were based on the unification principle of bioindication methods. The prospects of application of this new method for paleoclimatic reconstructions are discussed. The results of the isotopic dating and the geochemical analysis of lacustrine sediments were used. On the basis of diatom assemblages the long-term trends of temperature variations for study lakes were revealed. Moreover, the authors determined short-term periods of increasing and decreasing of water temperature in Lake Donguzorun which were probably connected with seasonal changes. Previously, the periods of sediment redeposition resulted from mud flow activity have been determined for both lakes. According to the results of diatom analysis it was found that these processes always coincided with periods of the relative temperature increasing in the lake.