Age and extent of a giant glacial-dammed lake at Yarlung Tsangpo gorge in the Tibetan Plateau

摘要

Many glacier dams on major rivers at the southeastern edge of the Tibetan Plateau had been previously determined through remote sensing and glacier terminal position calculation. It was hypothesized that such damming substantially impeded river incision into the plateau interior. Investigation on the large glacial-dammed lake at the entrance of Tsangpo gorge is critical for understanding this hypothesis. So far, the issues, such as age, lake surface elevation, and stages of this dammed lake, are still in debate. Our field survey of lacustrine deposits and loess distribution along the middle Yarlung Tsangpo River and its tributary, Nyang River, suggested that the lake surface elevation was at about 3180 m asl. The 23 quartz optically stimulated luminescence (OSL) and 4 organic AMS C-14 ages all fall into the Last Glacial period (similar to 41-13 ka). The OSL and C-14 ages are in general agreement with each other where applicable. There might be only one long damming event because the ages of lacustrine deposits from 2970 to 3100 m asl are similar, and every lacustrine section is sustained for a long time. The estimated lake surface area was 1089 km(2), and the volume was similar to 170 km(3), which differ from previous estimations which suggested two-stage (about early Holocene and 1.5 ka) lakes, and the largest lake surface elevation reached 3500 m. (C) 2015 Elsevier B.V. All rights reserved.