Timing and cycle of Late Quaternary glaciation in northeastern Tibet.

Glacial successions in the Anyemaqen and Nianbaoyeze Mountains of northeastern Tibet are reassessed and new glacial chronologies are presented for these regions. Cosmogenic radionuclide and optically stimulated luminescence dating indicates that two glacial advances occurred in marine isotope stage (MIS)-3 and MIS-2. In the Anyemaqen Mountains, a third advance occurred in the Early Holocene. We suggest that glaciation was synchronous in the Anyemaqen and Nianbaoyeze Mountains, as well as in other glaciated areas of Tibet and the Himalaya that are influenced by the Asian monsoon. The maximum extent of glaciation occurred early in the last glacial cycle (MIS-3) during a time of increased insolation when the monsoon intensified and supplied abundant precipitation, as snow at high altitude, to feed high-altitude glaciers. This suggests that precipitation, as snow, is fundamental in controlling glaciation in these regions. However, the occurrence of glacial advances during the insolation minimum of MIS-2 suggests that, despite reduced precipitation at this time, the annual temperatures were cold enough to maintain positive glacier mass balances. The numerically defined chronologies for the Anyemaqen and Nianbaoyeze Mountains presented here provide a framework for comparing glacial advances in other parts of high Asia. [ABSTRACT FROM AUTHOR]