Timing of glacier expansion during the Last Glacial in the inner Tien Shan, Kyrgyz Republic by OSL dating

Optically stimulated luminescence (OSL) dating was applied to glacial sediments and adjacent loess from moraines in the Teskey Ala-Too and At-Bashy Ranges in the inner Tien Shan, Kyrgyz Republic (Kyrgyzstan). Two large glacier expansions during the Last Glacial were observed in the two study areas; Teskey (=Terskey) Stages I and II moraines were dated to marine isotope stage (MIS) 4–early-MIS 3 and MIS 2, and At-Bashy Stage II in the At-Bashy Range dated to late-MIS 3–MIS 2. The timing of the two expansions during the Last Glacial coincided with global cold periods and with advances of the major Northern Hemisphere ice sheets. However, the fact that the greater expansion occurred in MIS 4–early-MIS 3 in the Teskey Ala-Too Range, suggests that climate during MIS 4–early-MIS 3 was more humid than during MIS 2. It is possible that the strengthened Siberian High during MIS 2 restricted the impact of the westerlies and this reduced precipitation in the study area.