Cenozoic tectonics and geomorphic evolution of the lower Jinsha River on the southeastern margin of the Tibetan Plateau

Abstract

The southeastern margin of the Tibetan Plateau is distinguished by a vast transition zone with hundreds of thousands of square kilometers of low-relief surfaces, which provides an ideal window for unraveling the timing, process, and mechanisms of the tectonic propagation and surface uplift. In order to reveal the Cenozoic tectonic response and geomorphic evolution of the southeastern margin of the Tibetan Plateau, a comprehensive study in the lower Jinsha River was conducted with a tectonic investigation, tectonic-landform and low-temperature thermochronological data analysis. The results show that the southeastern margin of the Tibetan Plateau remained in NW-shortening as early as the Eocene, forming widespread folds. However, we suggest that in the Paleogene, the lower Jinsha River of the southeastern margin of the Tibetan Plateau was marked by a low hilly topography with rather limited surface uplift. In the Late Oligocene–Early Miocene, the study area was characterized by a long-term stage with low denudation rates, which promoted the formation of widespread low-relief surfaces. Since the late Neogene, the southeastern margin of the Tibetan Plateau has undergone regional shortening deformation and significant surface uplift with a simultaneous incision along large rivers, forming the present landforms characterized by high-elevation low-relief surfaces and deep gorges. The late Neogene surface uplift across the southeastern margin of the Tibetan Plateau is suggested to be closely related to the shortening deformation and associated crustal thickening. In contrast, the mid-lower crustal thickening by channel flow might not be indispensable.

Keywords

• southeastern margin of the tibetan plateau
• tectonic analysis
• thermochronology
• tectonic landform
• fission track