Tectonic uplift of the northern Qinling Mountains (Central China) during the late Cenozoic: Evidence from DEM-based geomorphological analysis

摘要

The Qinling Mountains, which stretch from east to west in Central China, represent an important geological and geographical boundary between North China and South China. Because of the northeastward growth of the Tibetan Plateau since the late Cenozoic, the northern Qinling Mountains have been strongly reactivated and uplifted. To investigate the landscape response to the tectonic uplift, the geomorphic indices of the northern Qinling Mountains, including the hypsometry, mathematical function of the longitudinal profile, channel longitudinal profile, and steepness index were analyzed. The topographic analysis reveals that the landscape evolution of the Heihe River Basin is in a transient state. The upstream of the Heihe River Basin has undergone a long period of erosion and represents relict landscape. In contrast, the downstream represents adjusting landscape, which formed by river incision in response to the rapid uplift of the northern Qinling Mountains. This is a result of the extension of the Weihe Graben, which has formed due to the northeastward growth of the Tibetan Plateau during the late Cenozoic. The spatial distribution of the geomorphic indices reveals that the NE striking Taibai Fault has experienced strong tectonic activity since the late Cenozoic and is a secondary fault that accelerated the uplift rate of the northern Qinling Mountains. The tectonic stress due to the northeastward growth of the Tibetan Plateau has been transmitted to the northern Qinling Mountains along the Taibai Fault. Therefore, we proposed that the uplift of the northern Qinling Mountains is due to the combined effects of the Weihe Graben extension and Taibai Fault activity, forming the highest peak (Taibai Mountain) of the northern Qinling Mountains near the intersection of the Qinling Piedmont Fault and Taibai Fault.