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Controversies persist regarding the formation of terraces under the control of tectonic factors or climatic changes. This work focuses on the Yushanguxi River in the southern piedmont of Tian Shan, which is an intense tectonic uplift area where the terraces are very developed and the river has deeply downcut. Nine main terraces are distinguished (labelled T 1 to T h , from youngest to oldest) based on the interpretation of a high-resolution remote sensing image, field investigations and detailed surveying with differential GPS. The results of the determination of 10 Be exposure and 14 C show abandoned ages of ~2.1 ka for T 1 , ~4.1 ka for T 2 , ~4.2 ka for T 3 , ~8.2 ka for T 4 , ~18.1 ka for T 5 , ~18.8 ka for T 6 , ~102.1 ka for T 7 , ~100.6 ka for T 8 1 , ~113.9 ka for T 8 2 , ~144.6 ka for T h 1 , ~210.7 ka for T h 2 , and ~284.3 ka for T h 3 . Since ~18 ka, the incision rate began to increase from ~0.6 mm a −1 to ~12 mm a −1 , which is obviously higher than the fault slip rate of ~0.7 mm a −1 . We suggest that the rapid downcutting along the Yushanguxi River during the Holocene has mainly been caused by frequent climate fluctuations. [ABSTRACT FROM AUTHOR]

The Yulin River in the northern Tibetan Plateau, consists of multiple geomorphological features, including alluvial fans, fluvial terraces, and river profile knickpoints. Collectively, these provide a natural laboratory for exploring the late Quaternary fluvial landform evolution in response to both climatic change and tectonic activities in the region of the Altyn Tagh Fault. In this study, we investigated the distribution, sequences and sediment characteristics of the fluvial landforms along the Yulin River based on high-precision (0.5 m-resolution) Worldview satellite images and field observations. Mid-Pleistocene alluvial fans formed the highest fluvial landform surface into which ten major inset fluvial terraces were developed, distributed along three stream segments. Real-time kinematic global positioning system (RTK-GPS) measurement of terrace surfaces and the modern river longitudinal profiles was conducted across the Dongbatu Shan to show fluvial landform geometry and tectonic deformation. Fluvial terrace surfaces were deformed due to fault uplift as illustrated by spatially variable surface geometries. The chronological sequences of terraces along the Yulin River since 160 ka were reconstructed based on 10Be terrestrial cosmogenic nuclides (TCNs) dating. Results indicated that river incision occurred mainly during periods of climate transition, suggesting that terrace evolution was partly controlled by climate changes. Moreover, terrace exposure ages showed an upstream younging trend along the river, demonstrating a probable response to knickpoint retreat. Combined with terrace deformation and ages, fault uplift rates were constrained, which were lower than the river incision rates during the Late Quaternary, indicating that crustal shortening was mainly absorbed by the growth of the regional anticline. Collectively, our results suggest that the evolution of fluvial landforms along the Yulin River is a function of interplay between regional tectonic activities and climatic changes, which is significant to understand the NW-outward splay of the Altyn Tagh Fault. • Yulin River fluvial landform sequences since 160 ka were established via 10Be dating. • Knickpoint recession plays a significant role in terrace evolution along Yulin River. • Fault uplift rates were lower than the river incision rates in the Late Pleistocene. • Tectonic deformation was absorbed mainly by the uplift of the entire anticline. • Climate and tectonic uplift control river incision and fluvial landform evolution. [ABSTRACT FROM AUTHOR]