GREAT TRANSPOSITION AND ORIGIN OF JURASSIC SEDIMENTARY IN QAIDAM BASIN

The stratigraphic distributions of Early Jurassic,Middle Jurassic and Late Jurassic in Qaidam Basin are greatly different.The deposit center had two times of great transpositions.The first transposition was from northwest to north,and the second one was from north to east.In the Early Jurassic,the paleoclimate was warm and damp,while the marshes,ravels and lakes in fault basin were distributed in the northwest.In the Middle Jurassic,the paleoclimate was warm and damp,while marshes,ravels and lakes in broad basin were distributed in the northern edge of the basin.In the Late Jurassic,the paleoclimate was dry,and mountain aprons were distributed in the east.The analyses on ages of granites in the northwestern basin and on the ancient latitudes of Qaidam plate,Tarim plate and Qiangtang plate based on paleomagnetic stratigraphy show that the origin of greatly sedimentary transpositions in Jurassic relied on the different interaction plates.