Cenozoic Environmental Changes And Uplift Of Plateau In Baqing Area, Southern Qinghai

Uplift of Qingzang (Tibet) plateau is an important event during the history of our globe. Qingzang (Tibet) plateau is the best field laboratory for continental dynamics, involves many scientific problems in the frontiers and hotspots of modem earths sciences. Up to now, because individual views and different methods were used, the conclusions were different in uplift Qingzang Plateau. According to the experience of predecessors, we concluded that the direct evidences of uplift include Planation surfaces, Molasse, River terrace, and so on, the indirect include volcanic activity, sedimentary, pollen composition, environmental evolution, etc. In the course of the study we should perfectly combine these evidence, will be able to more fully reflect the whole process of uplift.Baqing basin has been rebuilt two times during Cenozic. In Paleocene, slip faults controlled the sediment in Baqing basin, but from Neogene to now the graben or half graben system controlled the sediment. In the Miocene, the volcanic activity was very strong in Baqing basin. The magma came from the bottom of crust. This time of volcanic activity was the end of shortener of crust, and was the beginning of the second rapid uplift. In Cenozoic, environmental changes in the Qinghai-xizang plateau, and the uplift of Qinghai-xizang plateau impacted the environmental changes of the globe.The region in the northern-eastern of Qingzang (Tibet) have experienced three times of major uplift and tow times of planatation science late Cretaceous period to today, and the environment was changed several times with the uplift. From the late Cretaceous period to Oligocene, it happened the first of uplift in the Qingzang plateau in the condition of squeezing between India plate and euroasia plate. The speed of uplift was very slow. The phenomenon of uplift was measured by molasses of Tuotuohe formation. During this phase, the denudation was the role of activity resulting in formation of the old planation surface. According to the analysis of pollen's character, the average altitude of Qingzang (Tibet) plateau was about 1000m at the end of the first time of uplift. During the Miocene, Volcanic activity was very frequent, that is the representative of the second times of uplift. We couldn't infer the altitude of Qinghai-Xizang plateau, because there was not record of climate. Form Pliocene to early Pleistocene, the speed of uplift became very slow, the denudation was the role of activity resulting in formation of the new planation surface. At the same time, the altitude was about 2000m. Since early Pleistocene, Qingzang plateau has experienced a rapid course of uplift, Today this speed of uplift is very rapid. The climate became cold and dry in the impact of plateau monsoon.