Sediment characteristics and provenance of riverine dunes on the lower Tora River in Qaidam Basin, China

Abstract

A thorough understanding of the physicochemical characteristics and source materials of riverine dunes and their relationship with rivers provides deeper insights into desert evolution. Riverine dunes are widespread along the southern edge of the Qaidam Basin, China. However, accessing relevant regions poses challenges, and available data remain limited. This study analyzed the grain size, major elements, and trace elements of surface sediments in various riverbanks, dune types, and geomorphic units in the lower Tora River. The results indicated a significant correlation between the physicochemical properties of dune sediments in the study area and the surface sediments of adjacent regions, primarily comprising materials from nearby sources.

However, caution is required when interpreting weathering intensity using the Chemical Index of Alteration (CIA) at a given deposition site, particularly if the geochemical background is unknown or strongly affected by hydrological processes. The variations in surface sedimentary characteristics on either side of the river can be attributed to factors such as parent rock composition, fresh material input, vegetation, wind sorting, evaporation, and the obstruction of flowing water. Fluvial dominance, particularly during seasonal river activity within dune fields, restricted the upwind sediment transport. Furthermore, high surface salinity contributed to dune stabilization, ultimately altering the types of riverine dunes near the channel and downwind.