Geomorphology of star dunes in the southern Kumtagh Desert,China: control factors and formation

摘要

Star dunes have received less study than other major dune types, though they are widely recognized to represent a major dune type that develops under a multidirectional wind regime. Several types that include simple, compound, and complex star dunes are identified in the south of China's Kumtagh Desert. It is suggested that the formation and development of these star dunes is controlled by wind regime, the underlying and surrounding topography, and sediment availability. A complex wind regime and rich sediment availability are generally required for the development of star dunes. Especially, wind regime appears to be the most important control factor. The wind regime under which star dunes arise is characterized by the drift potential, amount of variability in drift direction, and the direction distribution mode of the drift potential. It is strongly suggested that a rectangular bimodal wind direction distribution mode has unique significance in star dune formation. Under this mode, star dunes can develop in areas with a directional variability index typical of linear dunes or even barchan dunes. A development model is proposed for star dunes based on the following evolution: barchan dunes → transverse ridges → dune networks → simple star dunes → compound star dunes → star dunes atop complex linear dunes.