Late Quaternary aeolian sedimentation in central and south-eastern Tibet

The geomorphology and the cover sediments in the central and south-eastern part of the Tibetan Plateau provide information about climatic change. Lumi nescence 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 cov er of aeolian mantles in Tibet, only a few payers have focussed on them up to now. Samples from silt layers on top of Pleistocene moraines or solifluc tion 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 th e "Bomi-moraine" in southeastern Tibet situated at an elevation of about 30 00 m asl, provides an age of 25 ka. According to geomorphological investiga tions 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 sedimen tary and geomorphological situation. In the Tibetan Plateau Pleistocene loe ss mainly occurs below 4000 m asl. the Holocene material, a more sandy silt , lying above 4000 m asl. However, aeolian material capping the moraines pr ovides only minimum ages for the terminal moraines: the time interval betwe en glacier retreat and the accumulation of aeolian sediments may be several thousand years. The most important fact is the trapping of dust. In genera l, lakes and a denser vegetation cover are or were the main traps for the t ypical loess found in the mountain areas of the Tibetan Plateau. (C) 2000 E lsevier Science Ltd and INQUA. All rights reserved.