Carbonate U-Pb ages constrain Paleocene initiation along the Altyn Tagh fault in response to the India-Asia collision

Abstract

The formation of the Tibetan Plateau as a result of the Cenozoic India-Asia collision had a profound impact on the Asian tectonics configuration and climate dynamics. The kinematics and deformation pattern along the Altyn Tagh fault (ATF), marking the Plateau’s northern boundary, is of great significance for resolving the dispute on the deformation mechanisms of the Tibetan Plateau. However, the timing and configuration of the initial rupture along the ATF remains debated given the limited constraints on the depositional age of associated Cenozoic syntectonic strata. Here we investigated the syntectonic Cenozoic strata in the Xorkol Basin, the pull-apart basin of the ATF. New uranium-lead analyses of the carbonate deposits yield dates of 58.9 ± 1.29 Ma. Therefore, we propose that the initiation of strike-slip motion along the ATF occurred no later than 58.9 Ma, leading to the formation of the Xorkol Basin as a composite pull-apart basin. This finding clarifies the timing and location of the initial ATF activity, indicating that the modern configuration of the ATF was established as early as the early Cenozoic. This research provides the first yet oldest radioisotopic age along the ATF and surrounding area. This age estimate is also indicative of the depositional age of the Lulehe Formation in the Qaidam Basin, suggesting that the syntectonic sedimentation in the northern Tibetan Plateau initiated during the Paleogene. This timing coincides with the ca. 60 Ma onset timing of India-Asia collision, highlighting its far-field effect. We infer stress triggered by the India-Asia collision has propagated across the entire plateau in ca. 1-2 Ma, resulting in Paleocene strike-slip faulting along the ATF and other deformation in North Tibet.