New paleomagnetic constraints on syntectonic growth strata in the western Qaidam Basin, NE Tibetan Plateau

Abstract

Accompanied by crustal shortening and mountain uplift caused by the large-magnitude south-north directed shortening under the collision between India and Eurasia, syntectonic growth strata in the western Qaidam Basin document important information about intense intracontinental deformation of the NE Tibetan Plateau. To better address the development of the Qaidam basin and the propagation of the growth strata associated with multiple tectonic uplifts of the Tibetan Plateau, we conducted a detailed paleomagnetic study on the late-Neogene fluvio-lacustrine sedimentary sequence exposed at two outcrop sections and a drill core in the western Qaidam Basin, and integrated the results with previous magnetostratigraphic studies. Based on well- determined ages of the centers and limbs of the two anticlines, we found an episodic late Cenozoic crustal shortening in the center of the western Qaidam Basin, as evidenced by syntectonic offlap growth strata deposited beginning at ~3.2 Ma. Combined with data from sedimentary facies and seismic profiles, we suggest that offlap growth strata progressively became younger from southwest to northeast in the center of the western Qaidam Basin due to strong basinward propagation of the eastern Kunlun fault and quick short-lived pulses of multiple tectonic uplifts of the NE Tibetan Plateau.