Pleistocene glaciations of Central Asia:: results from 10Be surface exposure ages of erratic boulders from the Pamir (Tajikistan), and the Alay-Turkestan range (Kyrgyzstan)

We have determined the timing of glaciations in the Pamir (Tajikistan) and the Alay-Turkestan Range (Kyrgyzstan) using Be-10 surface exposure dating. Glacial advances in the area have occurred > 93-136, similar to 60-80, (40-55), similar to 27-25, similar to 22-20, similar to 19-17, similar to 16-15, similar to 15-13, and 11-9 cal ka BP. All Late Pleistocene glaciers in the Pamir, and the Alay-Turkestan Ranges have been valley glaciers except for the most extended glaciers on the Pamir plateau, which have formed local piedmont glaciations. In the eastern Pamir, these are characterized by ELA depressions of similar to 370-380 in (THAR 0.5). In the Turkestan Range and Alay Range, ELA depressions at the same time were > 750 and 600 in, respectively. Late Pleistocene glacier advances all over western High Asia were contemporaneous with climatic cold phases rather than monsoonal maxima. Their maximum extent and that of the western hemisphere ice sheets were asynchronous, due to increasing aridity in the region over the course of the Last Glacial. Late Pleistocene climate in Central Asia seems to have been influenced by the interplay of the westerly circulation and the Siberian anticyclone. Some indirect monsoonal influence in the eastern Pamir may be responsible for the existence of some of the Lateglacial moraine stages in this area. High altitude glaciers seem to have reached their maximum extent earlier (MIS 5-4) than low altitude glaciers (first half of MIS 3), possibly due to prolonged glacial aridity imparting with moisture advection onto high altitude sites, inducing glacial retreat, but prolonged cold during the same time imparting with glacier ablation at lower attitude sites, inducing glacial advance. (c) 2005 Elsevier Ltd. All rights reserved.