Late Quaternary aeolian sedimentation in central and south-eastern Tibet

Abstract

Abstract The geomorphology and the cover sediments in the central and south-eastern part of the Tibetan Plateau provide information about climatic change. Luminescence dating of aeolian and colluvial silts on top of different moraine sequences provides the first indications for the timing of these sediments during the Late Quaternary and Holocene. Although there is a widespread cover of aeolian mantles in Tibet, only a few papers have focussed on them up to now. Samples from silt layers on top of Pleistocene moraines or solifluction debris from central and southern Tibet at elevations above 4000 m asl provide early Holocene ages in most sections. The aeolian silt on top of the “Bomi-moraine” in southeastern Tibet situated at an elevation of about 3000 m asl, provides an age of 25 ka. According to geomorphological investigations the Bomi moraine dates from the last ice age, which can be confirmed by the luminescence data. Moreover, one sample from a silt layer in-between gravel layers (Xainxa) is also Pleistocene in age according to its sedimentary and geomorphological situation. In the Tibetan Plateau Pleistocene loess mainly occurs below 4000 m asl, the Holocene material, a more sandy silt, lying above 4000 m asl. However, aeolian material capping the moraines provides only minimum ages for the terminal moraines: the time interval between glacier retreat and the accumulation of aeolian sediments may be several thousand years. The most important fact is the trapping of dust. In general, lakes and a denser vegetation cover are or were the main traps for the typical loess found in the mountain areas of the Tibetan Plateau.