LATE QUATERNARY GLACIATION IN THE HIMALAYA AND TIBET

Tibet and the bordering mountains are the most extensively glaciated tract outside the polar regions, exerting an important influence on regional and global environmental change. Glaciation in this region is controlled by two major climatic systems: the mid-latitude westerlies and the South Asian monsoon. In addition, significant interannual climatic variability in the region is associated with El Nino-Southern Oscillation. Furthermore, glaciation is strongly influenced by topographic constraints. Yet despite the regional and global importance of glaciation in High Asia, the dynamics, extent and timing of glaciation in this region are poorly understood and defined. To test the relative importance of the different climatic systems and topographic constraints on glaciation, as well as the associated hydrological changes, we have been systematically examining the glacial and associated geology throughout the region, and dating landforms and sediments using cosmogenic radionuclide (CRN) surface exposure and optically stimulated luminescence (OSL) techniques. To date, we have undertaken detailed studies in the following mountain regions: Chitral, Swat, Nanga Parbat, Hunza Valley, Lahul, Ladakh, Zanskar, Garhwal, Nanda Devi, Langtang, Khumbu, Gonga Shan, Gangdise, Nyainqentangulha, Tangula, Kunlun, Nianbaoyeze, Anyemaqen, La Ji and Qilian Shan. This work has included detailed mapping, together with ~1000 numerical dates on moraines and associated landforms that define the extent and timing of glaciation. These data indicate a strong monsoonal influence on glaciation, synchroneity of glaciation and topographic constraints on extent of glaciation throughout Tibet and the bordering mountains. Glacial oscillations are shown to correlate with changes in the hydrological system and sediment flux that, in turn, largely control landscape changes.