Latest Quaternary rapid river incision across an inactive fold in the northern Chinese Tian Shan foreland. (1st January 2018)

• Record Type: Journal Article
• Authors: Lu, Honghua; Cheng, Lu; Wang, Zhen; Zhang, Tianqi; Lü, Yanwu; Zhao, Junxiang; Li, Youli; Zheng, Xiangmin
• Is Part Of: Quaternary science reviews. Volume 179(2018)
• Page Start: 167
• Page End: 181
• Publication Date: 2018-01-01
• Subjects: River incision -- Fluvial terrace -- Palaeoclimate -- Late Quaternary -- Tian Shan; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2017.10.017
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: This work focuses on the incision process over the Tuostai anticline, a fold of the proximal structure Belt I in the northern Chinese Tian Shan foreland, where the Sikeshu River has incised deeply into the alluvial gravels and the fold's underlying bedrock strata. Field investigation and geomorphic mapping define five terraces of the Sikeshu River (designated as T1 to T5 from oldest to youngest) preserved within the Tuostai anticline. 10 Be surface exposure dating and optically stimulated luminescence dating constrain stabilization of the highest three terrace surfaces at about 80 ka (T1 ), 16 ka (T2 ), and 15 ka (T3 ), respectively. Around 16 ka, the calculated river incision rates significantly increase from <2 mm/yr to >6 mm/yr. Undeformed longitudinal profiles of terraces T2, T3 and T4 over the Tuostai anticline suggest that this structure may have been tectonically inactive since stabilization of these three terraces. We thus think that the observed rapid river incision over the Tuostai anticline has not been largely forced by tectonic uplift. Instead, the progressively warmer and wetter palaeoclimatic condition within the Tian Shan range and its surrounding area during the period of ∼20–10 ka may have enhanced river incision across the Tuostai anticline. A reduced sediment/water ratio might have lowered the gradient of the Sikeshu River. Highlights: River terraces reveal tectonic inactivity of the Tuostai anticline during Late Quaternary. The calculated rates of river incision within the anticline increase by three times around 16 ka. The favorable palaeoclimatic condition has more likely enhanced rapid river incision.