Provenance and transport process for interdune sands in the Kumtagh Sand Sea, Northwest China

摘要

Interdune areas are an important part of dune systems, as they affect dune evolution and sand sea development. However, there has been little work on the provenance of interdune sediments. Our lack of knowledge of these sediments prevents a more complete understanding of sand sea formation and evolution. In the present study, we focused on the provenance of interdune sediments in the Kumtagh Sand Sea based on their granular, mineral and geochemical characteristics, then further identified the spatial scope of the contribution of these sources to the interdune sediments and the associated transport mechanisms. Although sediment supply analysis suggested that the interdune sand may derive from the Altyn Tagh Mountains, Beishan Mountains, and Sanlongsha dune field, the provenance signature based on the K/Rb and K/Ba ratios revealed that the ultimate sources were the Altyn Tagh Mountains (in the south) and the Beishan Mountains (in the north). By plotting the identified provenance results on a map of the sand sea, we found that the spatial scopes of contributions from these sources were separated at around 40 degrees N. However, the existence of a fluvial load (EM1) and of reworked coarse particles (EM3) in the northern sand sea demonstrated that the interdune sands in this region were partly derived from the Altyn Tagh Mountains in the south. Consequently, by combining our results with the transport agents condition, we concluded that the Altyn Tagh Mountains supplied sediments to interdune areas by fluvial transport throughout the sand sea, but that sediment in the northern sand sea was subsequently reworked and mixed with windblown sand originated from the Beishan Mountains. (c) 2020 Elsevier B.V. All rights reserved.