Paleoenvironmental Records In Mazatagh Section And Late Cenozoic Environmental Evolution In Midwestern Tarim Basin

On a systematic geological survey,Mazatagh section,a consecutive and well-outercropping section of Cenozoic in central Tarim basin,was chose for investigation on stratigraphy,paleomagnetism and paleoclimatology.Meanwhile,the time scales of paleoclimate records were reconstructed on the systematic measurement of grainsize,magnetic susceptibility and element,combining with the magnetostratigraphy of the section.On that basis,we get some understanding about the relationship between the drought history of Tarim basin and the uplift of Qinghai-Tibet Plateau in Cenozoic. The following points mark the main conclusions of this thesis:1.Tarim basin had experienced a sedimental history of shallow lake(4.2Ma-3.4Ma), aeolian-lake(3.4Ma-3.0Ma),and alluvial plain(3.0Ma-0.8Ma).2.The mean size of aeolian component increased quickly at the age of 3.4Ma(620m) may suggest a intense aridity in Tarim basin,then the mean size of aqueous component increased quickly at 3.0Ma(460m)may suggest that sediment environment had changed from aeolian-lake to alluvial plain.3.Zr/Sr reached its peak at 3.0Ma(460m),it may suggests that there was more precipitation at 3.0Ma by contrast with aeolian accumulation in large scale in the stratum.4.The Mazatagh range uplift at 0.8Ma.5.The aridity in Tarim basin started at 3.4Ma,there had been a arid-semiarid environment in Tarim basin from 3.4Ma-1.1Ma,the rudiment of modern Taklimakan Desert appeared at 1.1Ma.