10Be surface exposure dating of young glacial landforms on eastern slope of Mount Geladandong,central Qinghai-Xizang Plateau
The young glacial erosional and depositional landforms beyond the modern glaciers on the Qinghai-Xizang Plateau and its surroundings are direct imprints of the glacier fluctuation during the past several decades or century,and contain important palaeoclimatic and palaeoenvironmental information. Studies of these land-forms could provide insights into the spatiotemporal variations of these ancient glaciers. Improved logistics and the development and application of the terrestrial in situ cosmogenic nuclide (TCN) 10Be surface exposure dating techniques,are making it to be possible to investigate the young glacial landforms in the Mount Geladandong ar-ea,which locates in the west segment of the Tanggula Mountains,central Qinghai-Xizang Plateau. Here we re-port on 10Be surface exposure dating of six samples collected from modern glacial landforms associated with the Gangjiaquba Glacier on the eastern slope of Mount Geladandong. Dating results demonstrate that the boulders[samples from G19-02 to G19-06 and their ages are (125±15) a、(65±13) a、(86±13) a、(96±15) a、(104±15) a]were almost not affected by nuclide inheritance,and the 10Be surface exposure ages could be used to constrain glacier fluctuations during the past century in this high-altitude area. However,a comparison of the ages of a gla-cially polished surface[sample of G19-01 and its age is (11076±688) a]and boulders indicates that subglacial erosion by abrasion of the rock surface was insufficient (<2 m) to remove cosmogenic nuclide inventories. Thus,the apparent exposure age on the polished surface includes inheritance and overestimates the true age of this surface. Our study suggests that a cautious sampling and interpretation strategy should be adopted with bed-rock samples,and the 10Be surface exposure dating techniques have potential applications for dating glacier fluc-tuations on a 101-year time scale in these high-altitude areas with high 10Be production rates. Meanwhile,this study also provides a new reference for the application of 10Be exposure dating technique in dating the young land-forms in high altitude areas.
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