IAG 2000 Thematic Conference Abstract

IAG 2000 Thematic Conference MONSOON CLIMATE, GEOMORPHOLOGIC PROCESSES AND HUMAN ACTIVITIES
International Conference Hotel of Nanjing, China, August 25-29, 2000
Abstracts - Ying WANG and Xiaodong ZHU (Eds.)

LANDSCAPE EVOLUTION AND PALAEOCLIMATE IN THE DESERTS OF WESTERN CHINA: WITH A SPECIAL REFERENCE TO BADAIN JARAN AND TAKLAMAKAN

Xiaoping YANG

Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O.Box 9825, Peking 100029, China, xpyang@public2.east.cn.net

The deserts in western China are significant repositories of information needed for global circulation modeling. In the framework of past global change studies, these deserts service as one of the key regions for the reconstructing late Quaternary Asian monsoon fluctuations. Recent investigation reveals that the influences of the westerlies, similar as Asian monsoons, have undergone considerable variation during the late Quaternary as well. Field observations, air photos and satellite imageries show that the aerodynamic relief and desert plains are the predominant types of the geomorphological landscapes both in the Badain Jaran Desert and in the Takalamakan Desert. The aerodynamic relief, characterized by the wind-caved surface forms, is represented mainly by the dune fields. On the edge of the dune fields there are sand and gravel desert plains which extend for approximately one thousand square kilometers. In the low section of both desert areas there are ancient lakebeds which are now undergoing strong deflation. Two types of such lakebeds can be distinguished through the vegetation and surface materials:
a) historical lake surface shrinkage;
b) prehistoric lake surface shrinkage.
Due to strong deflation Yardangs have been formed in the old lake basins. On megadunes of the Badain Jaran Desert, four cemented surfaces of palaeo-dunes were observed, which are representatives of relatively moister environment. The chronological data show that four periods of more humid environment occurred in the past 30 000 years. The stabilization of dunes in a large region and the existence of many palaeo-lakes and lacustrine terraces confirm the periodic fluctuations of climate even in the extremely arid region. It implies that the influence intensity of westerlies and Asian monsoons changed in the Chinese deserts, and the periods of higher precipitation took place even in the times close to the last glacial maximum. The studies indicate that the Badain Jaran Desert reacts more sensitively to the monsoon fluctuation than the Takalamakan.