Marine Oxygen Isotope Stage (MIS)‐6 Glacial Advances on the Tibetan Plateau More Extensive than during MIS‐2 due to More Abundant Precipitation
Marie‐Luce Chevalier, Shiguang WANG, Anne Replumaz, Haibing LI
Abstract
Abstract Numerous studies dated glacial deposits within the Himalayan‐Tibetan orogen. While most focus on young deposits, i.e., younger than the Last Glacial Maximum (LGM or Marine oxygen Isotope Stage (MIS)‐2, ∼20 ka), older moraines such as those from MIS‐6 (∼130–191 ka) are much harder to date and interpret due to the less well‐preserved nature of their surfaces and boulders, as well as their scattered and continuous age distribution due to long‐lived erosion since deposition. Here, we dated with 10 Be, two imbricated moraines near Yadong in southern Tibet, as MIS‐2 and 6, showing that the most extensive, smooth surfaces were abandoned during MIS‐6. Compiling published data from 54 MIS‐6 moraines on the Tibetan Plateau reveals that they exist in most regions, dry or humid. They are particularly well‐preserved (sharp crests) in eastern and northern Tibet, while in southern and central Tibet, their crests are rounded to sub‐rounded. Because both MIS‐2 and 6 were equally cold, and because MIS‐6 moraines are much more extensive than those from the LGM, we conclude that MIS‐6 glacial advances were controlled by more abundant precipitation than during MIS‐2. This would be consistent with the peak in Asian monsoon during MIS‐6, revealed by sediments from the South China Sea.