Late Quaternary glaciation in the Kyrgyz Tien Shan

摘要

The Tien Shan of Kyrgyzstan contains multiple moraines and drift from late Quaternary glaciations. The spatial/temporal distribution of the glaciers inferred from the moraines suggests that the main factor controlling glacier advance here was the availability of moisture. The dominant modern climatic signatures in northern Central Asia include orographic thunderstorms in summer, cold and dry Siberian high-pressure cells in winter, and westerly cyclonic storms from the North Atlantic and eastern Mediterranean in spring and fall. Changes in any of these systems during the late Quaternary would have varied precipitation delivery to, and glacier growth in the Kyrgyz Tien Shan. Geomorphic mapping and reconnaissance-level Be-10 cosmic-ray exposure dating of moraine sequences in six drainages indicate that there were multiple "maximum" advances of similar extents and equilibrium-line depressions across the range. Glaciers in the north and east of the Kyrgyz Tien Shan last advanced to their maximum positions during marine oxygen isotope stage (MIS) 5 and again during MIS 4, while in the south and west of the range advance occurred during MIS 3. In contrast to maritime Europe and North America, there is no evidence of a major glacial advance during MIS 2. Glacier advances during MIS 2 and since were restricted to the vicinity of modern glaciers, allowing the older glacial record to be preserved well