Abstract:

The 500.8 meters depth drilling hole K3 with a core recovery efficiency of 80.4% is located at the eastsouth margin of Ebinur Lake in Zhunger Basin, Xinjiang. Based on the study of OSL dating, palaeomagnetism, susceptibility, micropaleontology (ostracoda and foraminifera), palynology and lithostratigraphy in the borehole, it is determined that the drilled sequences belong to the deposits since cir. 4.2 Ma，there was a lake environment during 3.6-4.2 Ma ，and since cir. 3.6 Ma the sedimentary environment changed from hemi-deep or shallow lake to littoral lake or subaqueous delta accompanying with the Hami Movement as a result of the quickly uplifting of Qinghai-Tibet Plateau, the aridification situation was also aggravating in the study area; during Late Pliocene (cir. 2.6-3.0  Ma) there was a basin margin and fluvial fan sedimentary system; at cir. 2.6 Ma under the influence of the Xiyu Movement and Yanshuigou Movement, the meandering stream  system was developed in the study area. Since the Middle Pleistocene Revolution i.e.cir. 0.8 Ma, the aridification situation was similar to that of modern times. The uncontinuous spore-pollen diagram and ostracoda distribution show a complicated development of sedimentary dynamics and water bodies since 4.2 Ma. The environmental change in the study area had been controlled by the tecto-climatic cycles.

Key words:  Late Cenozoic, tecto-climatic cycle, environmental evolution, Ebinur Lake,Xinjiang