Abstract:

The research of tectonic deformation of northeastern Tibetan Plateau is an important way to recognize the process and mechanism of the entire plateau uplift, and the remote effects of IndoEuropean plate collision, too. The Qaidam Basin is bounded by the Kunlun fault, Altyn Tagh fault and Qilian fault to the northwest, south and northeast, respectively, developed the thick Cenozoic sediments and have recorded the tectonic deformation information of northeastern Tibet. Especially, the western Qaidam Basin has undergone strong tectonic deformation and well exposed the Late Cenozoic strata, which is the ideal area to study the Late Cenozoic tectonic deformation history and driving mechanism. Combined with the latest highprecision paleomagnetic age, the balanced crosssection restoration and paleomagnetic structure rotation were used to reconstruct the Late Cenozoic tectonic deformation history of the western Qaidam Basin. The results show that the tectonic deformation was mainly manifested as the strata shortening and the structure rotation under the compressive stress since 22 Ma. The extent of the shortening and the amount of the rotation presented a phasic growth. The deformation history can be divided into three stages: quiet period of tectonic activity (229.1 Ma); tectonic deformation relatively strengthened (9.12.65 Ma); and the tectonic movement reaching the peak (since 2.65 Ma). The Late Cenozoic strata shortening and clockwise rotation of the western Qaidam Basin resulted from the Late Cenozoic IndoEuropean plate continually extruding northward, the KunlunQimen Tagh Mountains strongly thrusting to the Qaidam Basin, and the Altyn Tagh sinistral strikeslip fault being revived on a large scale.

Key words:  tectonic deformation, Late Cenozoic, tectonic rotation, balanced crosssection, the western Qaidam Basin