关键词: 巴丹吉林沙漠, 高大沙山, 形成发育, 更新世, 古风系

Abstract: High megadunes in the Badain Jaran desert, with a height ranging from 200 to 300 m in general and maximum height of 500 m or more are seldom seen in the other sand seas of the world. Up to present no much work associated with the formation and growth of high megadunes have been done. On the spot investigations of the Badain Jaran desert and a series of research work, including sand dune types and their spatial features, megadunes strata and TL dating, palaeowind direction measurement and modern wind data analysis, indicate that the formation and growth of high megadunes in the Badain Jaran desert are controlled by sand source, prevailing wind patterns, underlying relief of megadunes and vegetation on sand dunes. Ruoshui system developed in the western and northwestern Badain Jaran area was a main sand source for the formation and growth of high megadunes. Dips from fossil sand dunes cross bedding and steep face orientations in three locaties distributed in the Badain Jaran desert demonstrate that the prevailing palaeowind patterns over the Badain Jaran desert are at variance throughout the Quaternary period. Before last glaciations westerly winds originating from westerly circulation predominated but that there were also important northwestly winds from East Asian monsoon circulation at the time of high megadune growth. Since last glaciations, northwestly winds have dominated the area but accompanied also with the relatively important westerly winds in the processes of megadune growth. Simultaneously, the initial stages of the magedunes are related to the wave like airflow motion caused by the intimidation from underlying hilly relief which become an obstacle against moving wind blown sand. The shrub and grass on sand dunes, fed by rainfall during stronger summer monsoon, encourages the growth and development of megadunes by trapping and accumulating upwind windblown sand and combating wind erosion as well as promoting roughness over dune surface. Intergrated aeolian bedforms in the area went through a temporal development process from barchans, barchanic ridges, compound barchans, megabarchans to high megadunes since the Quaternary.

Key words: Badain Jaran desert, high megadunes, formation and growth, paleowind pattern