Late Quaternary aggradation and incision in the headwaters of the Yangtze River, eastern Tibetan Plateau, China

Abstract

River aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change, and surface processes which all adjust the ratio of sediment load to transport capacity of a channel. But how the river responds to differential tectonic and extreme climate events in a catchment is still poorly understood. Here, we address this issue by reconstructing the distribution, ages, and sedimentary process of fluvial terraces in a tectonically active area and monsoonal environment in the headwaters of the Yangtze River in the eastern Tibetan Plateau, China. Field observations, topographic analyses, and optically stimulated luminescence dating reveal a remarkable fluvial aggradation, followed by terrace formations at elevations of 55−62 m (T7), 42−46 m (T6), 38 m (T5), 22−36 m (T4), 18 m (T3), 12−16 m (T2), and 2−6 m (T1) above the present floodplain. Gravelly fluvial accumulation more than 62 m thick has been dated prior to 24−19 ka. It is regarded as a response to cold climate during the last glacial maximum. Subsequently, the strong monsoon precipitation contributed to cycles of rapid incision and lateral erosion, expressed as cut-in-fill terraces. The correlation of terraces suggests that specific tectonic activity controls the spatial scale and geomorphic characteristics of the terraces, while climate fluctuations determine the valley filling, river incision and terrace formation. Debris and colluvial sediments are frequently interbedded in fluvial sediment sequences, illustrating the episodic, short-timescale blocking of the channel ca. 20 ka. This indicates the potential impact of extreme events on geomorphic evolution in rugged terrain.

Using music and music‐based analysis to model and to classify terrain in geomorphology

“…In this research, particular emphasis is placed on the application of the terrain music modelling method driven by DBP. While differing from DBP, the gully shoulder line (Zhou et al, 2010) and river longitudinal profile (Yu et al, 2022) are intimately linked to surface erosion processes and the evolution of negative terrain. By incorporating these diverse section lines into the terrain music modelling framework, researchers can gain a more comprehensive understanding of landform characteristics.…”

“…In this research, particular emphasis is placed on the application of the terrain music modelling method driven by DBP. While differing from DBP, the gully shoulder line (Zhou et al, 2010) and river longitudinal profile (Yu et al, 2022) are intimately linked to surface erosion This study shows a promising path to enhance the capacity of expressing terrain information through music and utilizing music as a method for data observation to facilitate data interpretation. As terrain information is translated into musical expressions, the proper utilization of intervals becomes essential in capturing the desired characteristics and nuances of the terrain.…”

Analysis of Flood Water Level Variation in the Yichang–Chenglingji Reach of the Yangtze River after Three Gorges Project Operation

“…Research on the impacts of climate change and human activities in the Yangtze River and Dongting Lake has been widely conducted, indicating that river dynamics and flood characteristics, such as river incision, streamflow, flood occurrence, river water surface, and water storage, can be affected by climate change [20][21][22][23]. To discuss their impacts on flood water levels in the YCR in a more straightforward way, river morphological processes and backwater for Dongting Lake should be analyzed.…”

Prolonged Response of River Terrace Flooding to Climate Change

“…Next, a detailed examination of the significance of the changing lithology, ultimately with silty deposits replacing gravel deposition towards the end of terrace formation, is needed. Secondly, external factors, such as climate possibly interrelated with tectonic and/or intrinsic control, are usually held responsible for triggering river incision (e.g., [5,[9][10][11][12][13][14][15][16][17]). But it remains a pertinent question how a relatively abrupt (climate) trigger is expressed in the responding fluvial morphology and sedimentology [5,6,15,18,19].…”