Abstract:

on the basis of the analysis of structure and sedimentary evolution of the seismic section in Western Qaidam Basin and combining the  basement lithology, faults distribution and history of tectonic movement, we reconstructed the dynamical evolution framework of structure and sedimentation of Western Qaidam Basin during the Cenozoic. Our results suggested that Western Qaidam Basin was under the compression tectonic background of the Tibetan Plateau uplift caused by the collision of India and Eurasia in the Cenozoic and underwent two violent periods of tectonic deformation. The Western Qaidam Basin had undergone two periods of tectonic deformation. The first ocurred in the Paleocene, and reached the peak at the E23; the second was in the NeoceneQuaternary, and the deformation intensified rapidly. The forces transmitted from the south to the north, while the tectonic deformation spread from the west to the east, which indicated that the thrust of the Kunlun fault and the slip of the Altyn Tagh fault were controlled by the collision of the IndiaAsia Plate and the northward uplift of the Tibetan Plateau. Changes of the sedimentary facies indicatd that Western Qaidam Basin has undergone a process: Inflowsedimentationrecession  and the evolution of sedimentary facies were the result of tectonics. Separated by Youbei fault, in northern region of Western Qaidam Basin there existed thrust folders with the interphase upwarping and depression, generally with closed anticlines and relatively broad synclines, whose axial direction was consistent with the trend of Kunlun Mountains. Between Youbei fault and Ⅺ fault was the palingenetic Yingxiongling orogenic which made obvious elevation difference (about 800m) between the Yingxiongling region and the northern and southern Western Qaidam Basin. The characteristics of structuresedimentation evolution in Western Qaidam Basin was in response to Tibetan Plateau uplift, and was a good record of intermittent spread of the Tibetan Plateau northward as well.

Key words: Western Qaidam Basin, structuresedimentation evolution, sedimentary facies, Tibetan Plateau uplift