10Be surface exposure dating of glacier fluctuations on the eastern slope of Mount Geladandong, central Tibetan Plateau

Abstract

Moraine complexes formed by multiple glaciations are well-preserved in the Mount Geladandong area, the largest center of current glaciation in the Tanggula Mountains in western China. Studies of these glacial landforms provide insights into past glacier changes and contribute to understanding palaeoclimate and palaeoenvironment in the central Tibetan Plateau (TP). Here we report on 10Be surface exposure dating of thirteen rock samples collected from a sequence of glacial landforms associated with the Gangjiaquba Glacier. Based on the dating results, historical records (topographical maps) and morphological relationships, clear Little Ice Age (LIA) landforms are identified, and other landforms are tentatively assigned Neoglacial and global Last Glacial Maximum (LGMG) ages. Dating results for samples from modern glacial landforms demonstrate that the boulders were not affected by nuclide inheritance, and that 10Be surface exposure dating may be used to constrain glacier fluctuations during the past century in high-altitude areas that have high 10Be production rates. A comparison of the ages of a glacially polished surface and adjacent glacial deposits indicates that subglacial erosion by abrasion of the rock surface was insufficient to remove cosmogenic nuclide inventories. Thus the apparent exposure age on the polished surface includes inheritance and over-estimates the actual age for the exposure of this surface. Samples from hummocky moraine have wide age spreads, indicating long-lasting surface instability after deposition of this landform. Successive reduction in glacial extent in the Mount Geladandong area since the LGMG reflects temperature and precipitation changes over this timeframe in the central TP, with climate forcing for glacial advances correlated with cooling signals in the North Atlantic that may have been transmitted to this area by the westerlies.