Abstract: The coexistence of barchan dune and linear dune under unidirectional wind had been thought to be coursed by the difference of cohesive sediment content around the Chalhan Salt Lake in the Qaidam Basin. In order to investigate the characteristics of the cohesive sediment, field investigations had been carried out to explore the particle size characteristics of the sediment, salt content of the dune samples and the moisture content. This study will provide further information for the study of the influence of cohesive sediment on the formation and evolution of dune landforms. The results show that the average particle size of the interdune sediment is the thickest which is approximately 2.39 Φ. Particle size of the barchan dune sediment is a little thicker than the linear dune sediment, but there is no significant difference. In the study area, the main part of the sediment particle size distribution is the fine sand (about 84%), there are fewer content of middle sand and very fine sand, and the content of middle sand in the interdune sediment is slightly higher. All of the sediments show excellent grain sorting, and the linear dune sediment is slightly better than the barchan dune. The salt content of interdune sediment is the highest (about 6.88%). The salt content in the linear dunes is higher than that in the barchan dunes. The moisture content of the interdune sediments is the highest, which is about 1.93% in the deep vertical range of 30 cm. Moisture content in the barchan dune (about 0.12%) is significantly lower than that of the linear dunes (0.55%) in the depth of 1 meters. The spatial difference of sediment water content is also an important environmental factor of dune shape changes besides the cohesive sediment (salt, silt and clay).

Key words: cohesive sediment, Chalhan Salt Lake, linear dune, barchan dune