Initiation of Clockwise Rotation and Eastward Transport of Southeastern Tibet Inferred from Deflected Fault Traces and GPS Observations

Abstract

Eastward transport and clockwise rotation of crust around the southeastern margin of the Tibetan Plateau dominates active deformation east of the Eastern Himalayan Syntaxis. Current crustal movement inferred from GPS measurements indicates ongoing distortion of the traces of the active Red River fault and the Mesozoic Yalong-Yulong-Longmen Shan thrust belt. By extrapolating current rates back in time, we infer that this pattern of deformation developed since 10.1 ± 1.5 Ma. This date of initiation is approximately synchronous with a suite of tectonic phenomena, both near and far, within the wide Eurasia/Indian collision zone, including the initiation of slip on the Ganzi-Yushu-Xianshuihe fault and crustal thinning and E-W extension by normal faulting on N-S−trending rifts in the plateau interior. Accordingly, the eastward movement of eastern Tibet and the clockwise rotation of that material seem to be local manifestations of a larger geodynamic event at ca. 10−15 Ma that changed the kinematic style and reorganized deformation not only on the plateau-wide scale, but across the entire region affected by the India/Eurasia collision. Convective removal of some or all of Tibet’s mantle lithosphere seems to offer the simplest mechanism for these approximately simultaneous changes.