From dust to dust: Quaternary wind erosion of the Mu Us Desert and Loess Plateau, China
The Ordos Basin of China encompasses the Mu Us Desert in the northwest and the Chinese Loess Plateau to the south and east. The boundary between the mostly internally drained Mu Us Desert and fluvially incised Loess Plateau is an erosional escarpment, up to 400 m in relief, composed of Quaternary loess. Linear ridges, with lengths of ~102–103 m, are formed in Cretaceous–Quaternary strata throughout the basin. Ridge orientations are generally parallel to near-surface wind vectors in the Ordos Basin during modern winter and spring dust storms. Our observations suggest that the Loess Plateau previously extended farther to the north and west of its modern windward escarpment margin and has been partially reworked by eolian processes. The linear topography, Mu Us Desert internal drainage, and escarpment retreat are all attributed to wind erosion, the aerial extent of which expanded southeastward in China in response to Quaternary amplification of Northern Hemisphere glaciation.
Figure 1. A: Location map of Ordos Basin, China. Stippled pattern indicates sand deserts. B: Shaded relief map (www.geomapapp.org) of Ordos Basin. Yellow contours of mean annual precipitation (in mm) are from Porter et al. (2001). Red shading and arrows show the distribution and orientation of linear bedrock ridges in the Mu Us Desert and linear Loess Plateau topography. Black arrows show geomorphically effective wind directions, based on our interpretations of satellite images. The A-A’ and B-B’ dashed lines correspond to topographic profiles in Figure 2. Approximate distribution of Mesozoic and Cretaceous strata is shown. C: Rose diagram of linear loess topography orientations, plotted as unidirectional (wind parallel). Dark gray population is representative of windward margin of Loess Plateau. Light gray population is representative of linear topography to the south and east. Mean azimuth values and one standard deviations are indicated.
GEOLOGY, September 2015; v. 43; no. 9; p. 835–838 | Data Repository item 2015283 | doi:10.1130/G36724.1