The Paleo-environment Variation In Tarim Basin Recorded By Loess On The North Slope Of Kunlun Mountains Since The Last Deglaciation

The loess of Kunlun Mountains, which is the thickest loess deposition that have ever been found in arid china, is close to the south margin of Taklimakan desert. Kunlun loess has been regard as the synchronous sediment with Taklimakan desert, which recorded the evolution of atmospheric circulation and the varying of environment change in Tarim basin. In order to have better understanding of the atmospheric circulation and arid drive mechanism in arid central Asia, it is necessary to rebuild the paleo-evironment in Tarim basin where locates in the center of arid central Asia. In addition to that, oases in arid central Asia are facing continually increased environmental issues and mainly triggered by global warming, the researches on paleo-climate change in arid central Asia can also provide suggestions for oasis’s development in the future. This study tries to interpret the climate information of Kunlun loess by analyzing environmental magnetism, grain size and geochemical parameters of Pulu loess profile on North Slope of Kunlun Mountains.The characteristics of magnetic minerals and their morphology showed that magnetic minerals of Pulu loess were mainly original, which indicated that loess here were less pedogenic and reflected the features of source dust. The results of grain size showed that Pulu loess was coarse compared with loess of other areas, like Yili basin and China Loess Plateau, as a result of short distance from Taklimakan Desert. Geochemical analysis of Pulu loess demonstrated that elements featured as good solubility were weak leached in the whole profile, which indicated element immigration in loess was weak after deposition and elemental characteristics were mainly influenced by source dust. Kinds of climate parameters consistently revealed that Pulu loess was very weakly reformed after deposition; characteristics of magnetic minerals and geochemical element were controlled by source substance in Tarim Basin. Therefore, it is possible to rebuild the paleo-environment in Tarim Basin by researching on loess on North Slope of Kunlun Mountains. The age frame of Pulu profile was constructed by using optically stimulated luminescence (OSL) results and age-grain size model, the bottom of Pulu profile can be dated as 17500a BP. Based on grain size and CaCO3%, the paleo-environment since 17500a BP in Tarim Basin was discussed preliminarily in this paper.According to grainsize-age model and climate parameters, such as CaCO3% and grain size, the paleo-environment in Tarim Basin was discussed in different phases. Before 17000a BP, the low content of fine grain size and CaCO3 demonstrated that Tarim Basin was in arid; During 17000-14000a BP, the environment of Tarim Basin turned to be warm and wet; During 14000-9600a BP, which is the end of last Deglaciation and early phase of Holocene, Pulu loess became coarse and CaCO3% value dropped dramatically, which indicated arid environment in Tarim Basin; From 9600a BP to 650a BP, content of fine grain size and CaCO3 continually increased except some small drops in 5700 a BP,3900 a BP,2700 a BP, which demonstrated that Tarim Basin was increasingly wet during this period and reached the wettest in the late of Holocene; After 650a BP, the grain size of Pulu loess significantly turned to be coarse and CaCO3% dropped sharply, which indicated the quick turn to arid in this phase, apart from climate change in the last hundreds years, the influence of human activities in this area is also need take into consideration.