Timing and distribution of tectonic rotations in the northeastern Tibetan Plateau

Abstract

We report paleomagnetic data from the northeastern margin of the Tibetan Plateau to help understand the timing and distribution of deformation (i.e., vertical-axis rotations ) during the India-Asia collision. Paleomagnetic results throughout Xining Basin strata, recently dated using magnetostratigraphy to between 52 and 17 Ma, show that some 25° of clockwise rotation with respect to the stable Eurasian continent occurred at ca. 41 Ma. In view of a regional compilation of existing paleomagnetic data from the northeastern Tibetan Plateau, these results suggest that this region experienced clockwise rotations in the regional Paleocene-Miocene basin system, including rotation in the Xining Basin, ca. 41 Ma, thus establishing the existence of widespread deformation at this time. During a mid-Miocene phase, between 17 and 11 Ma, clockwise rotations were restricted to the Miocene-Quaternary basin system, implying that the Laji Shan thrust belt, which separates the two basin systems, was active during this time interval.