OSL and ESR dating of glacial deposits and its implications for glacial landform evolution in the Bogeda Peak area, Tianshan range, China

摘要

The Bogeda Peak area is the largest center of modern glaciation in the eastern Tianshan range in China. Four moraine complexes and associated fluvioglacial deposits are well preserved in the valleys, indicating multiple Quaternary glaciations in this region. Optically stimulated luminescence (OSL) and electron spin resonance (ESR) dating were used to determine the ages of the glacial tills and associated sediments in the Gubanbogeda and Heigou valleys. A total of eighteen samples were collected from moraines and fluvioglacial deposits. Fourteen samples were dated using OSL with a single-aliquot regenerative-dose (SAR) protocol, and the other four samples were analyzed by ESR dating of germanium (Ge) centers in quartz grains, which are sensitive to both sunlight and grinding. The results indicate that the fluvioglacial deposits are more suitable for OSL dating than the tills. Most ages show good agreement with the geological setting and field investigations, and the OSL and ESR ages are consistent with each other for the samples collected from the fourth set of moraines. Based on the ages as well as geomorphic and stratigraphic, the first and second moraine complexes of the Bogeda Peak area were deposited during the Little Ice Age (LIA) and Neoglaciation respectively. The low and high glacial terraces of the third set of moraines in the Gubanbogeda and Heigou valleys were deposited during marine oxygen isotope stages (MIS) 2 and 4. The fourth set of moraines has MIS 6 ages associated with the penultimate glaciation.