Geomorphological analysis and tectonic significance of the Pumqu Basin, southern Xizang

Since the Cenozoic, the geological processes of the Qingzang (Tibet) Plateau have controlled the crustal near-west-east extensional tectonics with a series of near-south-north oriented normal faults, which have significantly influenced the evolution of the plateau's geomorphology. The Pumqu Basin, located in the front edge of the plateau within the India-Eurasia collision zone, and its main stream cut through the Himalayan ridge belt and flows into the Ganges River, becoming part of the Indian Ocean water system, recording the tectonic impact on the plateau landforms and the water system. Based on ASTER GDEM V3 data, this paper uses GIS spatial analysis techniques to extract river Hack profiles and river geomorphological parameters such as the stream length-gradient index (SL), hypsometric integral (HI), and hypsometric curve (HC), to quantitatively analyze the geomorphological tectonic characteristics of the basin and to explore the impact of tectonic activities on its geomorphology. The results show that in the upper reaches, HI values range between 0.05 and 0.36, with concave hypsometric curves, indicating the mature–old basin landform evolution stage, and minor erosion and tectonic activity. In contrast, in the lower reaches, HI values range from 0.37 to 0.67, and the hypsometric curves are mostly convex, indicating strong tectonism, serious surface erosion, intense downcutting, and the basin landform evolution has entered the youthful–mature stage. This suggests that the lower reaches are more tectonically active than the middle and upper reaches, possibly related to the present-day intensive tectonic activity of the Kharta fault and the Dinggye fault. In general, the Pumqu Basin is tectonically active and in the mature stage of geomorphic evolution. Based on a comprehensive discussion of factors such as the regional geological background, precipitation, and lithology, it is believed that strong tectonic activity controls the development of water system landforms in the study area.