Nature and timing of Quaternary glaciation in the Himalayan–Tibetan orogen

• Evidence for Himalayan–Tibetan Quaternary glaciation is reviewed and evaluated.
• Numerical dating methods used to define timing of glaciation are evaluated.
• Strong regional contrasts in timing and extent of glaciation occur across the orogen.
• Glaciation influenced by Asian monsoon, mid-latitude westerlies and topography.
• Recommendations made to help advance future Himalayan–Tibetan glacial research.

Much effort has been made in recent years to define the timing and extent of Quaternary glaciation throughout the Himalayan–Tibetan orogen. These studies are challenging because of the logistical and political inaccessibility of the region, and the inherent problems associated with the application of numerical dating techniques. Nevertheless, the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions. Studies are showing that Himalayan–Tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global Last Glacial Maximum glacier advances were significantly less extensive. However, along the more monsoonal-influenced Greater Himalaya, there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle, but this has yet to be fully assessed. In addition, the new studies are showing that throughout most Himalayan–Tibetan regions, significant glacier advances occurred during the Lateglacial and early Holocene, with minor advances in some regions during the mid-Holocene. The still relatively poor chronological control in the Himalayan–Tibetan orogen, however, makes it difficult to construct correlations across the region, and with regions elsewhere in the world. This in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the Himalayan–Tibetan orogen, and to quantify paleoclimate change in this high altitude subtropical region. The Lateglacial and Holocene glacial records, however, are particularly well preserved in several Himalayan–Tibetan regions. Glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating, and geomorphic and sedimentologic methods to derive high-resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions.