Abstract: The study of grain size and geochemical elements composition of sediments are very important to distinguish their sedimentary environment, dynamic conditions of transporting, migration patterns and material sources. Field survey, sampling, laboratory experiment and other methods were used in this paper. A total of 32 samples of surface sediments from different regions in the world's highest altitude desert, Kumkol Desert, on the northern Qinghai-Tibetan Plateau, were analyzed in the lab to analyze the grain size characteristics, geochemical elements composition and the elements composition of the alluvial-fan clastic. The results showed as follows:(1)Surface sediments from Kumkol Desert are mainly silver sand, its content is about 60%. There is a certain amount of very fine sand, the content of silty sand and medium sand is little and closed. A small amount of clay was contained, but excluding coarse sand component and the grain size composition is very similar. Frequency curves of grain size are the approximate symmetrical unimodal distribution, but the left side has a long tail comprised by the fine grain size which are greater than 4 φ(<0.063 mm), and are mainly the silty and clay components.(2)The M_Z range of the dunes surface sediments is 2.70-2.90 φ and mean value is 2.79 φ. The M_Z range of the field among the dunes is 2.80-2.86 φ and mean value is 2.83 φ. The range of σ₁ are 0.80-1.10φ and 0.93-1.10 φ, the mean value are 1.01 φ and 1.03 φ, sorting is middling. The range of S_K1 are 0.26-0.44 and 0.35-0.41, the mean value are 0.37, and kurtosis is positive. The range of K_G are 2.27-3.62 and 2.80-3.01, the mean value are 2.95, 2.93, and kurtosis is a single peak.(3)The geochemical elements of desert surface sediment and the alluvial clastic sediment from surrounding piedmont are similar, especially similar to the north area of Aerka Mountain in the western desert.(4)The analyzed sources of the sediment reveal that the desert surface sediment is mainly from the north area of Aerka Mountain and the south area of Qimantage Mountain, and its formation environment is mainly fluvial facies sedimentation and shallow lacustrine facies sedimentation. Since the Kumkol Desert has been formed for no long time, the sediment still shows a good inheritance to its sources. Those preliminary results have important significance for developing a comprehensive index to distinguish the sedimentary environment, dynamic conditions of transporting, migration patterns and material sources of the sediments and show the interaction between aeolian and fluvial processes in Kumkol Desert. In short, the research of Kumkol Desert, can not only reveal its cause and evolution characteristics, but also help us to understand the surrounding environment of the Kumkol Basin and the climate changes of the Qinghai-Tibetan Plateau. At the same time, the study can also extend the distribution scope of desert research area in China, to some extent, desert research of regional imbalance can be changed.

Key words: surface sediment, characteristic of grain size, provenance discrimination, sedimentary environment, Kumkol Desert