TIMING AND STYLE OF GLACIATION ON THE GURLA MANDHATA MASSIF: A TEST FOR SYNCHRONEITY OF SEMI-ARID TIBETAN GLACIERS WITH GLOBAL CLIMATE CHANGE

The driving forces behind Quaternary glaciations in the Himalaya and Tibet have not been resolved despite the climatic importance of the region. In particular, it has not been determined if Quaternary glaciation was synchronous throughout the orogen and whether changes in glacier ice volume were contemporaneous with global climate fluctuations. Recently, 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 cosmogenic surface exposure dating we are developing a glacial chronology for the massif. This allows us to compare the glacial chronologies and style of glaciation with other proxies, including ice core and deep sea sediment records, to test for regional and global glacial synchroneity.