Long-term topographic evolution of the Central Tianshan (NW China) constrained by low-temperature thermochronology

Abstract

The Tianshan belt forms the southwestern part of the Central Asian Orogenic Belt, and its current topography is a product of punctuated Meso-Cenozoic intra-continental deformation that is still active today. This study provides new apatite fission track data on the Paleozoic rocks in and adjacent to the Chinese Central Tianshan, including two age-elevation profiles in the Alagou and Gangou areas. Inverse thermal history modelling reveals that the Central Tianshan experienced regional slow to moderate cooling during most of the Mesozoic, and that the present-day topography was mainly built by Cenozoic uplift and erosion. Geomorphological observation reveals several fragments of flat, low-relief surfaces within the Central Tianshan, which were likely to have formed in the Mesozoic as evidenced by thermal history modelling of the Alagou age-elevation profile. Furthermore, our data suggest that the Chinese Central Tianshan and its adjacent terranes did not undergo intensive relief building during its long-term Mesozoic evolution, as several pre-Mesozoic deep-rooted regional faults did not record evidence for a strong Mesozoic reactivation. Finally, differential exhumation in the Western Chinese Tianshan and Junggar is discussed, and we propose that the development of regional brittle faults could significantly influence the processes of intra-continental deformation.