Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China. (15th April 2016)

• Record Type: Journal Article
• Authors: Li, Yanan; Li, Yingkui; Harbor, Jon; Liu, Gengnian; Yi, Chaolu; Caffee, Marc W.
• Is Part Of: Quaternary science reviews. Volume 138(2016)
• Page Start: 105
• Page End: 118
• Publication Date: 2016-04-15
• Subjects: Cosmogenic nuclides -- Little Ice Age glacial advances -- Nuclide inheritance -- Eastern Tian Shan; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2016.02.023
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10 Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430 ± 100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270 ± 55 yr. However, 10 Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10 Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790 ± 300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430 ± 100 yr likely reworked or covered deposits from this earlier event. Highlights: We present 10 Be age constraints on LIA glacial advances in the Chinese Tian Shan. Available 10 Be ages suggest three LIA glacial events (∼790 yr, ∼430 yr, and ∼270 yr). LIA maximum occurred asynchronously in different sections of the Tian Shan. Nuclide inheritance affects dating of LIA moraines from small, thin glaciers.