The late Pleistocene glaciation in the Bogchigir Valleys (Pamir, Tajikistan) based on 10Be surface exposure dating

Glacial chronologies from the Pamir may not only provide insights into past changes in temperature, but also into past changes in precipitation related to the northern-hemispheric westerlies and the monsoonal circulation. We present 18 new exposure ages from the Bogchigir Valleys that complement and refine our previous studies in these valleys. The most extensive dated glaciation in the area occurred similar to 100 ka, during Marine Oxygen Isotope Stage (MIS) 5, and indicates increased precipitation likely from both the westerlies and the monsoonal circulation. A subsequent glacier advance, which deposited characteristic 'chukur' moraine lobes, occurred at similar to 80-75 ka. Circumstantial evidence points to glacial advances at similar to 65 and 40 ka, the latter likely also documenting increased monsoonal moisture supply during MIS 3. Less extensive glacial advances occurred during MIS 2 at similar to 28 and 24 ka and reflect the aridization trend during the course of the last glacial cycle. Deglaciation started similar to 21 ka, interrupted by minor stillstands or readvances at similar to 16 and 12 ka. Local calibration sites and glacier-climate modeling would be very helpful to reduce the systematic methodological uncertainties (still at least 10%) and to draw more detailed paleoclimatic conclusions. (c) 2012 University of Washington. Published by Elsevier Inc. All rights reserved.