An analysis of sedimentary characteristics of Shangyoushashan and Xiayoushashan Formations and the features of seismic reflection in western Qaidam Basin su ggest that the Altyn Mountains were uplifted during the Mid_Late Miocene, which resulted in an eastward migration of the basin depocenter. Uplifting chron ological data from the surrounding mountains also indicate that the uplifting of the northern margin of the Qinghai-Tibet Plateau was coincident with the regional tectonic events of southern Qinghai-Tibet Plateau during the Mid_Late Miocene . It is also demonstrated that the Mid-Late Miocene is an important period for the northward growth of Qinghai-Tibet Plateau. The uplift event of the Altyn Moun tains was directly related to the wedging of the Tarim Plate underneath the Qaid am Plate. The plateau uplifting dynamic source was derived from the continuous northward subduction of the India Plate after its collision with the Eurasia continent