Sedimentological and geochemical characteristics of sediments and their potential correlations to the processes of desertification along the Keriya River in the Taklamakan Desert, western China

Abstract

Desertification is a key environmental concern in arid and semi-arid regions. The sedimentological and geochemical characteristics of sediments are closely related to desertification processes, but the relationship between them is still unclear. This study aimed to identify the sedimentological and geochemical characteristics of different sediments in the Taklamakan Desert and to monitor changes in sediment composition as the intensity of desertification varied in the last decades. We examined the grain size, major, trace and rare earth elements of surface sediments collected from loess, sandy loess, fluvial sands, vegetated dunes and mobile dunes along the Keriya River in the Taklamakan Desert. Major element analysis found that loess had the highest degree of chemical weathering, while weathering of surface sediments on dunes (both mobile and vegetated ones) was relatively weak. Trace and rare earth element analysis found sediments were mainly derived from the West Kunlun and West Tianshan Mountains. This study also analyzed vegetation and wind data from 2000 to 2018 and found that the intensity of desertification processes weakened. The near-surface mean wind speed also decreased from 2000 to 2018, resulting in an increase in both the grain size of aeolian sediments on the surface of mobile dunes and the degree of chemical weathering. Additionally, this study confirmed that clay-sized components can be carried by high-altitude westerlies or formed by pedogenesis. With the strengthening of westerlies and the increase of chemical weathering, it is likely that more clay components will be added to the loess located on the northern slope of the Kunlun Mountains. This study demonstrates that the landscape evolution of the Keriya River in the Taklamakan Desert is primarily driven by fluvial processes, vegetation and wind dynamics, and that these processes may be affected by the intensity of desertification.