Late Quaternary palaeoenvironment change and landscape evolution along the Keriya River, Xinjiang, China: the relationship between high mountain glaciation and landscape evolution in foreland desert regions

The sedimentology and geomorphology of landforms along Keriya River, that traverse the Kunlun Mountains and Taklamakan Desert, were studied to examine the relationship between environmental change and landscape evolution in mountains and desert margins of the Taklamakan Desert. The region is divided into four geomorphic provinces: desert with active dunes and sand seas; desert pediment with fans; and foothills with deep gorges and glaciated mountains. A succession of three fans with dunes is differentiated on the basis of morphostratigraphy and relative weathering. The oldest fan and dunes are radiocarbon dated to similar to29 ka. This fan probably formed as a response to increased meltwater and sediment loads as glaciers retreated at the end of the local last glacial maximum in the Kunlun Mountains. Periglacial and glacial features throughout the region show that, during the last glacial, the snowline was lowered to similar to4000 m a.s.l., permafrost existed down to an altitude of similar to1800 m a.s.l., and that the likely temperature depression was similar to10degreesC. Radiocarbon dates on sand dunes and tamarisk hills help define the age of the lower two terraces to >1.5 ka and a few hundred years BP. This suggests that these terraces may have formed in response to increased precipitation during more humid times at similar to2 ka and during the Little Ice Age, respectively. The landforms and sediments in this region are polygenetic in origin, being transported, eroded and deposited by glacial, fluvial, aeolian and lacustrine processes. Particle size characteristics show that the fluvial sediments were substantially modified down basin. In contrast, the aeolian sediments were modified as they were transported toward the mountains from the desert by the dominant northerly winds. This complex interaction between environmental change and earth surface processes provides an important framework for examining the environmental consequences of the recently growing population and intensified agricultural activities along the mountain and desert margins of the Taklamakan Desert. (C) 2002 Elsevier Science Ltd and INQUA. All rights reserved.