Geomorphological hierarchies for complex mega-dunes and their implications for mega-dune evolution in the Badain Jaran Desert

The evolution of mega-dunes is sometimes attributed to factors other than the wind but evidence for this is lacking. It is assumed that the dominance of wind in maintaining the evolution of mega-dunes should be characterized by regular height–spacing relationships that have been found for simple dunes or wind ripples which are dominantly formed by the wind. In this context, we studied the height–spacing relationship for the complex reversing mega-dunes in the Badain Jaran Desert, which features the tallest mega-dunes in the world. The complex mega-dunes were divided into three hierarchical orders according to the cumulative probability plots of dune height and spacing measurements, and the coefficients of variability of dune heights and spacings were in accordance with values reported for other deserts. The relationship between dune spacing and height for all the three orders of dunes could be expressed reasonably well by a uniform linear function that was also applied to the height–wavelength relationship for wind ripples in other deserts. This relationship was found to be similar to those for several other deserts and subaqueous bedforms. This implies that there should be few unique factors in maintaining the evolution of complex mega-dunes in the Badain Jaran Desert compared with the superimposed simple dunes and dunes in other deserts, dune fields and subaqueous bedforms, and that the tallest mega-dunes on the earth can be maintained by the wind.