Geochemical composition and grain size of surface sediments from reticulate dunes in the Tengger Desert, China

Abstract

Reticulate dunes are the prevalent type of dunes found in deserts worldwide. However, compared to other dune types, systematic research on reticulate dunes remains limited, and aspects such as their formation mechanisms, grain size characteristics, and elemental composition characteristics remain inadequately understood. This study integrated regional wind regime data to analyse the grain size characteristics of reticulate dunes (specifically, the primary and secondary ridges) in the Tengger Desert, Considering both primary and sub-wind seasons. Additionally, we examined the elemental composition characteristics and degree of weathering of these dunes. The results indicate that the primary and secondary ridges of the reticulate dunes in the Tengger Desert are predominantly composed of fine sand and very fine sand with a mean grain size of 2.52Φ. Compared with other deserts in China and abroad, the sediments exhibit relatively finer grain sizes and better sorting. Furthermore, the grain size characteristics of surface sediments in the primary and secondary ridges exhibited two distinct distribution patterns during different wind seasons, indicating differences in the formation mechanisms of the primary and secondary ridges. The major elements in the surface sediments of the reticulate dunes in the Tengger Desert are SiO₂ and Al₂O₃, while the predominant trace elements are primarily Ba, Sr, Zr, and Cr. This indicates that the geochemical composition of the sediments is influenced not only by the intrinsic characteristics of the elements but also by the regional climate and the supply of fresh materials, which are significant factors affecting their chemical behavior and content differences. The chemical weathering indices (CIA, residual coefficient, and ICV), along with the A-CN-K and A-CNK-FM triangular diagrams, suggest that the sedimentary environment of the reticulate dune sediments in the Tengger Desert is characterised by a cold, dry climate with a low degree of weathering. The weathering process occurs during the initial stages of plagioclase chemical weathering. These findings lay the foundation for further research on the formation mechanisms, evolutionary processes, and sedimentary environments of reticulate dunes, contributing to a deeper understanding of these complex geomorphological features.