Multi-stage Cenozoic exhumation history of southern Central Tian Shan: implications for geodynamic and sedimentary evolution

Abstract

Despite important implications for tectonic, sedimentary, geodynamic and climatic evolution in central Asia, Cenozoic exhumation history of the Tian Shan remains highly debated. Here, we report unexpectedly young zircon fission-track and zircon (U-Th)/He dates from the Tomor Peak region in southern Central Tian Shan. Together with new and published biotite 40Ar/39Ar and apatite (U-Th)/He data, the exhumation history since latest Jurassic is reconstructed. An initial increase in exhumation rate from ≤0.01 to ~0.1-0.2 km/Myr occurred at ~25-20 Ma, which is thought to be a response to changed regional stress field due to growth of the Tibetan-Pamir Plateau driven by deep geodynamic processes relating to India-Asia convergence. The second stage of exhumational acceleration took place at ~12-6 Ma, with an apparent rate of ~1.0 km/Myr, which probably relate to the “hard collision” between the Indian lithospheric mantle and the Tarim-Tajik lithospheric mantle beneath the Pamir and western Tibet. After ~5 Ma, the mean exhumation rate of sampled rocks dropped to be ~0.5 km/Myr due to drier climate condition and redistributed strain accompanying the formation of Kuqa foreland thrust system. Finally, based on the presented bedrock exhumation history and available sedimentary records from foreland basins, we propose a coupled tectono-sedimentary evolution model to reconcile the conflicting tectonic interpretations between low temperature thermochronological and sedimentological studies.