Evolution Of Depositional Environment Since Early Pleistocene In Lop Nor, Xinjiang, China And Its Geological Significance

Lop Nur is located in the interior of Asian and the lowest part in the easternTarim Basin. It is the final destination of major river systems in Tarim Basin and theaccumulation center of salt materials.LDK01drilling is located in the middle of the Luobei depression and the depth is781.5meters.In this paper,grain size,magnetic susceptibility,carbon and oxygenisotopes,and clay minerals analysis,combined with indicators such as the lithology ofsediments, morphological characteristics and combination of saline minerals and thetectonic setting of core samples from drill hole LDK01were used to be divided into10phases to discuss the periodic changes of climate and sedimentary environmentevolution since the early Middle Pleistocene.in Lop Nor region.The results showd that fluvial, diluvium, lacustrine and aeolian facies aredeveloped in Luobei depression in Quatenary.Since the middle of early pleistocene,Lop Nor was mainly in semi-arid and subhumid climate,developed a freshwater lakeat first and has a stronger hydrodynamic.Coarse clastic rocks and glutenite depositedin the coastal area,provide evidence of a river delta environment.Since the earlymid-pleistocene,the climate started to become hot and dry,developed lakeshore andshallow lake microfacies gypseous mudstone under the environment of lake dalta,marked by gypsum-bearing mudstone began to appear. The climate get drier in latepleistocene,tectonic uplifting happened in Luobei area,causing the lake retreated andevaporated into a highly saline environment.Since the holocene Lop Nor becameextremely arid and gradually developed into playa,separated out halide such as halite.Lop Nor belongs to the typical terrigenous clastic-chemical rock salt depositmode, presented the frequent change about the alternation of lacustrine advance andretreat, the structure reflects the fresh water to salt water cycle oscillation changes.Saltlake evolution is the interaction of dry and wet climate cycles and the cyclicalrecharge of the fresh water from the mountains surrounding this lake basin.The formation and development of a series of fault and eventually formed a“High Mountain-Deep Basin” landscape in Lop Nur is the inevitable result of the Northern Tibetan plateau uplift deformation.The sedimentary record has a goodresponse relationship with the uplift process of Tibetan plateau and the Globalchange,it is an ideal area to study the uplift of Tibetan plateau and aridificationresearches.In the end of early Pleistocene(1.1~0.78Ma),this area underwent thekunlun-yellow river tectonic motion,resulted the change of directions from S-N intoNE-SW,a set of coarse clastic rocks and glutenite were deposited in this period.Sincethe early late-pleistocene, Gonghe movement generated the uplift of the main body ofTibetan Pplateau and the interior of Asian bacame more drier.The Luobei depressionformed an secondary basin affected by the neotectonic movement and a series offaults.It is a whole sedimentary cycle for the tectonic evolution process and it can bedivided into three stages: fault depression stage, depression stage, and shrink stage.