Geomorphic indices and longitudinal profile of the Daba Shan, northeastern Sichuan Basin: Evidence for the late Cenozoic eastward growth of the Tibetan Plateau

The Daba Shan Orocline is located in the northeastern Sichuan Basin, and has undergone foreland propagation and distinct surface uplift owing to the eastward expansion of the Tibetan Plateau since the late Cenozoic. In order to describe and quantify the earth surface processes respond to deep geological mechanisms, and to detect the kind of tectonic deformation in the Daba Shan area during the late Cenozoic, various geomorphic indices were analyzed for study area. The obtained results are: (1) The northeast of the Hanzhong Basin, the Hannan-Micang Massifs, along the Chengkou-Fangxian fault, and the Shennongjia Massif exhibit intense tectonic activity. (2) The spatial patterns of the channel steepness indices indicate that the western segment of the northern Daba Shan (Fenghuang Shan and Paotaizi region) have higher uplift rates than the eastern. (3) The longitudinal profile analysis revealed that the landscape evolution of the Shennongjia Massif is in a transient state, with an uplift amplitude of 1700–1900 m since the end of the Paleogene (25 Ma), and an average uplift rate of 0.072 ± 0.004 mm/a. The paleochannel reconstruction indicate an incision of ~900–1000 m since the late Neogene (3.0–3.4 Ma), with the average uplift rate being 0.3 ± 0.03 mm/a. (4) Three tectonic deformation zones can be distinguished in the Daba Shan (from west to east), the shortening deformation, strike-slip deformation, and vertical uplift zones. These observations suggest that the eastward growth of the Tibetan Plateau has affected the Daba Shan area and shaped the modern landscape.