Because organic material for radiocarbon dating is uncommon in the high Himalaya and the Tibetan Plateau, the timing of past glaciations has been difficult to constrain. As a result, it is unknown whether Quaternary glaciation was synchronous throughout the Himalayan orogen and whether changes in glacier ice volume were contemporaneous with global climate fluctuations. Recent application of numerical dating techniques such as surface exposure dating has allowed significant progress in determining the driving forces behind Quaternary glaciations in the Himalaya and Tibet. Glacial chronologies defined by numerical dating have suggested that the south Asian summer monsoon is important in delivering moisture to Himalayan-Tibetan glaciers in monsoon-influenced regions, allowing them to advance most effectively in times of low latitude insolation maxima when the monsoon is most intense. This work suggests that glaciation was generally synchronous in monsoon-dominated regions of the Himalaya and Tibet. However, the importance of the mid-latitude westerlies in delivering moisture to Himalayan-Tibetan glaciers has not been determined, and may be particularly significant in semi-arid areas that are distal to the monsoon influence, such as southwestern Tibet. To examine the nature of glaciation in a semi-arid region of Tibet and to test the possible dominance of the mid-latitude westerlies in forcing glaciation, we have examined the glacial geology of Gurla Mandhata (Naimona'nyi), a 7,728 m-high massif in southernmost SW Tibet. In this region, glacial landforms record a progression from expanded ice cap glaciation, to piedmont, and, ultimately, to entrenched valley glaciation. Using the cosmogenic 10Be surface exposure age of moraine boulders and scoured bedrock surfaces, we are developing a glacial chronology for the massif. This allows us to compare the glacial chronology and style of glaciation with other proxies, including ice core and deep sea sediment records, to test for regional and global glacial synchroneity.
See more of Poster Session II
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)