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Paleo-environmental changes and glacial fluctuations of the last millennium in the sediments of Lake Ala Kol (Tien Shan, Kyrgyzstan)

A series of limnological markers have been measured in the clastic sediments of Lake Ala Kol (northeastern Kyrgyzstan). Fed by a glacier, this one documents paleo-environmental changes and glacial fluctuations over the past millennium in the Central Tian Shan. Magnetic and geochemical data from rocks provide evidence for three episodes of glacier expansion occurring in 1200–1400 AD, 1500–1850 AD, and 1900–1950 AD, and a period of retreat during 1000–1200 AD. The maximum extent of the glacier is recorded between 1500 and 1850 AD, and corresponds to the cold and wet conditions present during the Little Ice Age in this region. This is deduced from a high magnetic susceptibility (strong detrital inputs), elementary ratios Si / inc + coh, Ca / inc + coh and a low magnetic ratio ARM30 / ARM (size of the larger magnetite grains) . The periods of glacier growth and decline recorded in the sediments of Lake Ala Kol show a close correspondence with the rate of ice accumulation observed in the northern Tibetan Plateau. These results suggest that changes in precipitation over the past millennium are the main driver of glacial fluctuations in the Tian Shan. However, temperature may also have exerted a more complex influence on centuries-old time scales.

Rousseau M., Demory F., Miramont C., Brisset E., Guiter F., Sabatier P., Sorrel P., Palaeoenvironmental change and glacier fluctuations in the high Tian Shan Mountains during the last millennium based on sediments from Lake Ala Kol, Kyrgyzstan, Palaeogeography, Palaeoclimatology, Palaeoecology,
1/09/2020

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