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 ~. 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 ~. 80-75. ka. Circumstantial evidence points to glacial advances at ~. 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 ~. 28 and 24. ka and reflect the aridization trend during the course of the last glacial cycle. Deglaciation started ~. 21. ka, interrupted by minor stillstands or readvances at ~. 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.