Formation and evolution of the Badain Jaran Desert, North China, as revealed by a drill core from the desert centre and by geological survey
Abstract The deserts in north China are regarded as direct records of the process of inland Asian aridification. Amongst these deserts, those proximal to the Chinese Loess Plateau (CLP) are especially important because of their role as sediment source areas. In order to investigate the formation history of the Badain Jaran Desert, the largest desert proximal to the CLP, a 310 m-long drill core was obtained from the desert centre, which reached the underlying basement rock. The lithology of the core consists of an upper layer of aeolian sand, with three intercalated layers of lacustrine sediments, overlying alluvial/fluvial deposits which are developed unconformably over red-coloured basement rock. A geological survey indicates that the lower red-coloured basement rock is of late Cretaceous age, and is cut by a Mesozoic erosion surface widely developed over the Badain Jaran area. On the basis of optically stimulated luminescence and electron spin resonance dating, and stratigraphic correlation, a preliminary chronological framework was established which was improved by tuning the aeolian sand proportion of the drill core to Earth orbital obliquity and precession. This final chronology suggests that: 1) the basal age of the desert strata is at least ~ 1100 ka, corresponding to the formation of the Badain Jaran Desert; and 2) that the formation of the erosion surface terminated and the surface had begun to subside by at least ~ 1200 ka. The formation of the desert can be summarized as follows: the alluvial/fluvial fan formed by the Heihe River draining the Qilian Mountains provided sufficient sedimentary material to form the desert under an arid climate, while the Asian winter monsoon and the Westerlies entrained the clastic sediments from the fan area which finally accumulated downwind. More distant sediment transport was prevented by the intervening mountainous terrain. These coupled processes were driven by Tibetan Plateau uplift and ongoing global climatic cooling. After initial formation of the desert, three humid phases occurred, in MIS 13–15, MIS 5 and the Holocene, during which extensive lakes developed. The sequential drying out of the lakes may reflect inter-relationships between global climate and the intensity of the Asian summer monsoon and the Westerlies.