Timing and extent of glaciation since the Last Glacial Maximum in the upper Kalguty basin, Russian Altai Mountains

The mountains systems of Central Asia are primary targets to study late Pleistocene climate evolution given their location at the crossroads of several atmospheric circulation systems. The timing of glacier extent during this period remains understudied, especially in the Altai Mountains. Here, we have reconstructed glacier extent during three main Late Pleistocene stadials in the upper Kalguty basin (south-eastern Russian Altai) based on field-based geomorphic analysis. Additionally, surface exposure dating with Be-10 and Al-26 at a key site was used to infer a minimum-limiting age for the outermost well-preserved Pleistocene frontal moraine system and to date the inception of glacier withdrawal. According to our data, around 20.6 +/- 1.8 ka Kalguty Glacier was still 200 m thick at the key site, 10 km upstream of the outermost moraine, and the site was totally deglaciated shortly after 20.4 +/- 0.4 ka. These results point to a rapid retreat of this low-gradient valley glacier after its probably MIS 2 maximum which was prior to 21 ka and probably prior to 22.5 ka. Two other glacier stages have been identified upvalley, characterized by a depression of the equilibrium-line altitude of 420 and 314 m with respect to the Little Ice Age, thus corresponding to Lateglacial advances. Our glacier reconstruction further provides a geomorphological and geochronological background to put into context archaeological findings in this area.