Pleistocene glaciations in southern and eastern Tibet

Abstract

Summary This paper focuses on four case studies on Pleistocene glaciation in the eastern and southern Tibetan Plateau. The extent of glaciers during the local last glacial maximum is identified from their sediments and erosion features, e.g. cirques and U-shaped valleys. Pleistocene moraines resulting from valley glaciers, plateau glaciers, cirque glaciers and ice streams can be found frequently in the surroundings of the mountain systems. The shape and composition of the Pleistocene moraines on the Tibetan Plateau is strongly controlled by bedrock geology and tectonics. The best currently-available reconstruction of the extent of the Pleistocene mountain glaciation on the Tibetan Plateau is, in the authors' opinion, the map presented by Li et al. (1991). It shows limited Late Pleistocene glaciation in the interior and expanded ice caps and valley glaciers on the margin of the Tibetan Plateau during the Last Glaciation. In spite of the small scale of this map, the glaciated areas in the mountains are well represented. In the drier parts of the Tibetan Plateau, a Pleistocene snowline-depression of 300 to 500 m occurred. In the wetter parts at the margin of the plateau the Pleistocene snowline-depression increased to values from 600 m to more than 1000 m. Based upon the results of fieldwork in several mountain systems on the eastern and southern part of the Tibetan Plateau, two major Pleistocene glaciations can be differentiated based on the degree of weathering of sediments and the connection with different gravel floors and terraces. In contrast to the deeply weathered Middle Pleistocene moraines, which are often only preserved as eroded remnants, the Late-Pleistocene moraines represent two main glacial stages. A third, less extensive stage is more rarely represented.