LATE CENOZOIC LITHOLOGY AND MAGNETIC POLARITY STRATIGRAPHY IN THE JIUXI BASIN: IMPLICATIONS FOR TECTONIC EVENTS OF THE WEST QILIAN MT

The synorogenic sediments in the foreland basins preserve a potential record of varied depositional environments that respond to and are largely controlled by tectonic events of the mountain along the basin margin. In the exploration of the uplift process of the Qinghai—Tibet Plateau, research on the foreland basins around the plateau is of vital significance. Much work have been carried out on the southern margin along the Himalayas and on the eastern margin, however, seldom work was reported along the northern boundary of the plateau, this have blocked the generation of an integrative image of the evolution of the entire plateau. The Gansu Corridor, located on the northeast margin of the Qinghai—Tibet Plateau, is a Cenozoic foreland basin system formed due to the northward overthrust and overload of the plateau. Thousand of meters detrital sediments derived mainly from denudation of the Qilian orogen have deposited in the basin since Oligocene. Here we report a detailed lithologic and magnetostratigraphic work carried out on the late Cenozoic sedimentary sequences in the Jiuxi Basin, western Gansu Corridor, to investigate the neotectonism of the western Qilian Mt.