LATE QUATERNARY EVOLUTIONS OF DESERTS IN NORTHWESTERN CHINA

The desert landscapes in northwestern China include sand seas, gravel deserts, desert steppe, steppe and scrub-woodlands environments distributed in a wide range of the geomorphological and tectonic settings, from 155 m below the sea level in the Tulufan Basin to more than 5,000 m asl in the Kulun Mountains. Under the support from the National Natural Science Foundation of China we have been studying the evolutions of deserts in this extensive region during the Late Quaternary and their dynamic relationship with global changes. Detailed field investigations have been carried out in the Badain Jaran Desert of the western Inner Mongolia and in the Taklamakan Desert of southern Xinjiang. Great attention has been given to geomorphological and sedimentological evidence. The stratigraphy of the dunes in the Badain Jaran Desert, high lake levels in the areas near and within the large deserts indicate a much more humid climate in the western China during the marine isotope stage three. However, the period after 24 ka to the end of the Pleistocene was mostly characterised by increased temperature and reduced precipitation in the Tarim Basins. During the Holocene, higher lake levels, stratigraphy of dunes and results of palynological, isotopical and sedimentological analyses of lacustrine sediments in the western China suggest a few wetter periods, especially in the earlier part of the Holocene. We think, however, broad regional differences needed to be considered for the understanding of palaeoclimates in Central and East Asia.