Grain-size Characteristics and Paleoclimate Response of Terrace Sediments in Sandaohe River of Yili Basin

Fluvial sediments carry some key information on paleoclimate and paleoenvironment changes. In this paper, the sedimentary environment of the Sandaohe section is discussed according to the grain size, magnetic susceptibility and OSL age. The results show that the frequency curve of the grain size includes single peak and double peak, and the accumulation frequency curve is mainly three-section type. The characteristics of grain size reflect that the deposition of the first terrace has experienced the evolution process from low-energy lake facies, high-energy river facies to medium-high energy river facies. The results of magnetic susceptibility show that a minimum value appears in H1, a rapid increase in B-A warm period and a decrease-increase-decrease in YD period. The first terrace of Sandaohe formed in late Pleistocene to early Holocene, being the evidence of three major climate change events (YD, B-A and H1) since the last deglaciation.