Late Mesozoic-Cenozoic multistage exhumation of the central Bangong-Nujiang Suture, Central Tibet

Abstract

The Cenozoic rise of the Tibetan Plateau has significantly altered global climate change and the biological redistribution of Asia. However, there remain great controversies about its detailed topographical evolution, especially in the hinterland of the Plateau, such as around the Bangong-Nujiang Suture (BNS). Here, we choose the Gaize Basin, which is located in the central BNS, as our target research area. New low-temperature thermochronology data have been used to quantify the cooling history of the intrusive rocks and sedimentary strata from the N-S edges of the Gaize Basin. Our thermochronology results show that 1) zircon (UTh)/He ages range from 54 ± 3.7 to 113 ± 8.4 Ma, 2) apatite fission track ages mostly cluster around ~55 Ma, and 3) apatite (UTh)/He ages are between 34 ± 3.3 and 63 ± 4.4 Ma. Combined with the results from thermochronology modelling, we suggest that there were three cooling stages recorded around the Gaize Basin: 1) the late Mesozoic (120–100 Ma), which was probably due to the BNS closure and subsequent Qiangtang-Lhasa collision, 2) the Late Cretaceous-early Paleogene (85–55 Ma), which was perhaps related to the far-field effects of the Neo-Tethyan oceanic subduction, and 3) 47–30 Ma, in response to the continuous India-Asian collision. Similar to today, low relief topography has finalized in the central Tibetan Plateau after the last cooling stage and is mainly aided by river incision and erosion on both sides of the BNS.