Spatial Variation in Grain Size of Riparian Dunes in Typical Cold and Arid Deserts of China and Its Implications for Identifying Sediment Sources

Riparian dunes in deserts exhibit unique geographic features due to aeolian-fluvial interactions. In this study, we collected 510 surface sediment samples from eight drainage basins and conducted a systematic analysis to examine the grain size characteristics of major riparian dunes in the typical cold and arid deserts of China. The results indicate that major riparian dunes of deserts in study area can be classified into three types based on their grain size characteristics. The Bartlett test of sphericity and the Kaiser-Meyer-Olkin (KMO) test were also performed, and their significance values were found to be 0.000 and 0.584, respectively. The results of the principal component analysis revealed that the cumulative contribution rate of the total variance reached 85.9% for the two principal components with characteristic roots greater than 1.0. The primary principal component included medium sand, whereas the secondary principal component included fine sand. We conducted a cluster analysis and classified the samples into three major types. Type I rivers include the Keriya River, Langqu River, Tora River and Heihe River, which are characterized by by fine particle size, and well-sorted. Type II includes Mu Bulag River, Kuye River, and the Xar Moron River, Compared with type I, it has a relatively coarser mean grain size and relatively poor sorting for this type. Type III includes the Maquan River, which is characterized mainly by fine sand and medium sand, accounting for more than 90%, and the sorting coefficient (0.52) suggests relatively well sorting in this pattern. Moreover, principal component analysis was applied to determine the particle sizes of samples from different watersheds. Moreover, these sediments exhibit both hydromorphic and aeolian features. At the drainage basin scale, the mode and intensity of aeolian-fluvial interactions depend on climatic conditions. In arid and semi-arid climate regions, wind is the dominant force, and the grain size exhibits significant aeolian features. Conversely, in the semi-humid region, flowing water is the dominant force, and riparian dunes in this region are formed by aeolian-fluvial interaction. The angle between the wind direction and flow direction in different reaches influences both the supply of sediment sources and the development of riparian dunes. This study will provide a new perspective for evaluating aeolian-fluvial interactions on riparian dunes in the deserts of China’s cold and arid regions.