Quaternary tills at the pass of the Tanggula Mountains on the Qinghai-Tibet Plateau and their geological-environmental significance

Based on investigations and studies of modern and ancient glaciers at the Tanggula Mountain pass, coupled with the GPS data and TL, 10B-26Al-21Ne and 14C dating data, Quaternary remnants of glaciation in the study area are discussed in detail. Two glacial epochs (i.e., the late Middle Pleistocene penultimate glacial epoch and the mid-late Late Pleistocene last glacial epoch) and two Holocene glacial advances (i. e. the Neoglaciation and the Little Ice Age) have been intensively studied. The mountains had not reached the height of the snowlines in the early Pleistocene; so glaciers did not develop then. However, in the area the Tanggula pass the remnants of the early Middle Pleistocene third glaciation from the last have not been found because of the lag effects of Tibetan Plateau uplift and development of glaciers and their coupling of the Dry Pole of Asia. The authors infer that only local glaciation has developed. Further study indicates that the ancient and present snowlines have risen from the margins of the Qinghai-Tibet Plateau to the interior and the Tanggula Mountains area is ~1500 m higher than the the margins, which vividly reflects the role of the Dry Pole of Asia, as suggested by some scientists earlier. The wide distribution of lake swarms shows that the Qiangtang area is an interior drainage area into which big rivers have not yet stretched, implying that the Qinghai-Tibetan Plateau is younger. The scale of glaciers in the Tanggula Range has become smaller and smaller since the penultimate glacial epoch because of the drying process and severe shortages of moisture in the interior of the plateau due to the uplift of the plateau.