Pseudo-feathery dunes in the Kumtagh Desert

The Kumtagh Desert is the last explored desert in China. The unique patterns on aerial photographs and satellite images have led previous researchers to the conclusion that the Kumtagh Desert is the only place over the world where typical feathery dunes are developed, and that some unique wind regimes are at work. Recent field investigation reveals that the feathery patterns in fact reflect the albedo contrasts between the seif dunes, bright dune-like drifts and the dark inter-dune lag sediments. The wind regime in the area containing the so-called feathery dunes is typical of the regime that produces seif dunes that were considered to be shafts of the feathery dunes, and the vanes of the feathery dunes are in fact bright dune-like drifts with indistinct height from the surroundings rather than true transverse dunes. Further analysis indicates that the sediments of seif dunes, dune-like drifts and dark inter-dune flats differ in grain size distribution, mineralogy, reflectance spectrum and particle micro-morphology. Sediments that constitute seif dunes and dune-like drifts are finer and poorly rounded, contain relatively more quartz, and hence have higher albedo, while the sediments that constitute the dark inter-dune flats are coarser and better rounded, contain far less quartz but relatively more andesite and dacite, and hence have lower albedo. As a result, what was originally perceived as unique feathery dunes are in fact only pseudo-feathery dunes composed primarily of seif dunes. This discovery also demonstrates that blowing sand drifts can form dune-like patterns that remain visible for long periods of time. It is important to distinguish between the patterns of true dunes and those of dune-like drifts (pseudo-dunes) that cause albedo contrasts in interpreting remote sensing images.