The river system shapes the landscape of the mainland and controls the transport of erosive material to the ocean. Fluvial geomorphology is extremely sensitive to tectonic movement and climate change, and records rich information on regional and global tectonic activities, climate change and environmental evolution events by topography, sedimentology and geochronology. As the largest tributary of the Yarlung Zangbo river system, Parlung Zangbo occupies an important position in the southeastern Tibet. Due to the unique tectonic setting and climatic conditions, the surface processes in the Parlung Zangbo Basin are active and the fluvial geomorphology is rapidly evolving, but it has not received enough attention of scholars. In this paper, by field investigation and sampling, morphological and sedimentological analysis of fluvial geomorphology; using OSL and 14C dating, combined with relevant research results, the fluvial geomorphology evolution of the Parlung Zangbo Basin, especially the terraces formation and evolution of the main stream and the Dongjiu River tributary research has been carried out systematically. We found, firstly, the shape of the Parlung Zangbo is relatively straight and linear. The main stream is approximately linear, the tributaries are pinnately distributed, and the intersection of the main stream and the tributary is at right angles, indicating that the river form is affected by the Jiali fault zone. Secondly, the climate change since the last glacial period has divided the fluvial geomorphology of the Parlung Zangbo into three segments. 1）The valleys below 2 600 m above sea level are “V” shaped canyons. The deposit ages of the terraces are between 9.0 kaBP and 2.0 kaBP. The sedimentary properties are dominated by river facies and slopes, which proves to be the climate warming conditions since the Holocene. 2）The middle reaches of the valley with an altitude of 2 600～3 300 m are ice-eroded valley basins and U-shaped troughs. The ice ridges on both sides of the main valley are developed, and the remains of ancient ice margins are preserved. The deposits are mainly composed of paleo-lake phase, ice-water phase and river facies. The dating results are between 29.8～10.9 kaBP and 50.9～39.8 kaBP, indicating that it was once the ice-edge lake system, and it dredged by the current Parlung Zangbo. 3）The elevation of the river above 3 300 m is a typical glacier U-shaped trough, with a flat bottom and a modern icy lake. It only develops the I terrace and is covered with glacial deposits. It has the remains of the last glacial ice margin; but it mainly shaped by the warm glaciers. Showing the characteristics of modern ice margins. On the whole, the upper and lower reaches of the Parlung Zangbo River formation are late, which is the landform formed since the Holocene; the middle reaches of the river are relatively old, retaining the ice margin geomorphology of the last glacial periods, and retaining a wide range of paleolake deposits. The lacustrine deposits show that the current fluvial topography of Parlung Zangbo has been formed since the last glacial period, especially since the Holocene.
Yungchen Lhamo Ji Jianqing Xu Qinqin Wang Changsheng Su Jun Tu Jiyao Peng Yuheng Shao Yuanyan Zhong Dalai Memar Tsering. Fluvial geomorphological characteristics and its evolution of the Parlung Zangbo in Southeast Tibet[J]. Chinese Journal of Geology, 2019, 54(4): 1062-1084.