Timing and significance of the initiation of present day deserts in the northeastern Hexi Corridor, China

The Tengger Desert and Badain Jaran Desert are two typical deserts in the Northwest Arid Area of China (NAAC), located near the margin of the monsoonal region. Through chronological research of the oldest loess sections formed from synchronous deposition of the desert dusts, we suggest that the initial present day Tengger and Badain Jaran deserts appeared no later than about 0.85 Ma. Because this timing of present day desert initiation in the eastern part of the NAAC is very similar to the other two deserts in the west, we suggest that the NAAC formed at approximately 0.85 Ma. The uplifting of the Tibetan Plateau accelerated at around 0.85 Ma, an event that caused the Plateau to enter the cryosphere. This resulted in remarkable enhancement of the winter monsoon as well as bifurcation of the mid-lower Westerlies. This is the most fundamental factor that affected the formation of the NAAC.