Quaternary glacial chronology of the Kanas River valley, Altai Mountains, China

The Kanas River originates on the southern slope of Youyi Peak, the largest center of modern glaciation in the Altai Mountains in Central Asia. Glaciers advanced and retreated repeatedly during Quaternary glacial-interglacial cycles in the Kanas River valley, and four moraine complexes and associated glaciofluvial deposits are preserved in the valley. Optically stimulated luminescence (OSL) dating has been used to determine ages of glaciofluvial deposits (sand lenses sandwiched between tills in moraines) using a single aliquot regenerative-dose (SAR) protocol. Based on dating results from this and previous studies (including 14C, electron spin resonance (ESR) and OSL dates) and geomorphic relationships, the innermost moraine complex was concluded to deposit during the Little Ice Age (LIA), the second (Akekule) moraine complex was deposited during the Neoglacial, the third (Kanas) moraine complex was deposited during the last glacial cycle (marine oxygen isotope stage (MIS) 2-4) and the outermost set of moraines is MIS 6 in ages (penultimate glaciation). The Kanas moraine complex could be divided into three subsets (III1, III2 and III3), with inferred ages of MIS 2, mid-MIS 3 and MIS 4, respectively, which is consistent with moraine records from other areas in Central Asia and climate reconstructions from the Guliya ice core. The glaciers in the Kanas valley at their maximum extents during the LIA, Neoglacial, last glaciation and penultimate glaciation were 13.8 km, 32 km, ∼100 km, and ∼120 km long, respectively.