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Glacial history of the Pamir Mountains during the Last Glacial cycle along a semi-humid to arid transect based on 10Be surface exposure dating
Röhringer, I.; Zech, R.; Sosin, P.; Abramowski, U.; Aldahan, A.; Kubik, P.; Merchel, S.; Zöller, L.; Zech, W.
The reconstruction of past climate changes in the Pamir Mountains has high potential for identifying the dynamics of circulation systems in Asia and for understanding global environmental changes during the Late Quaternary. The Pamir Mountains are situated in a climatic transition zone between mid-latitude westerlies, the Indian summer monsoon and the Siberian High. Today main moisture to the Pamir comes with SW- cyclones along the westerly jetstream whereas the influence of the Indian monsoon typically ends south of the NW-Himalaya. Up to now the impact of the Indian monsoon on former glaciations of the Pamir Mountains has not yet been adequately examined. Even chronological information about former glaciations in the Pamir is still sparse. The objectives of our study are: To upgrade the present glacial chronology by dating glacial successions along a moisture gradient from the north-western to the southern Pamir Mountain ranges. We present preliminary 10Be ages from moraine successions of three study sites (Iskenderkul area, Muksu-Kyzlsu area, Alichur area). Our first results from the southern Pamir (Alichur area) corroborate and refine previously published findings: Extensive glaciation occurred during MIS 4 and during MIS 2. However our data indicate that glaciers in the southern Pamir also advanced during ~50 to 40 ka. Rapid deglaciation occurred after ~18 ka. So far there is no evidence for glacier advances during the Holocene. Overall, we conclude that the glacial chronology of the Pamir seems to be mainly controlled by temperature, with maxima during ~70 to 60 ka, ~50 to 40 ka and ~20 ka. Because during climatic cold phases the Indian Monsoon was weakened, we assume that glacier advances in the Pamir Mountains during the Last Glacial cycle were mainly triggered by westerly moisture supply. Analyses of further samples, from both the Muksu-Kyzlsu area and the Iskenderkul area are in progress.
Keywords: accelerator mass spectrometry; quaternary; glaciation
XXVIII INQUA (International Union for Quaternary Research) Congress, 20.-27.07.2011, Bern, Schweiz