Crust erosion characteristics in the middle reach of the Purlung Tsangpo River

Abstract

To reveal the tectonic evolution process of the eastern Himalayan syntaxis and provide basic geological data for probable significant engineering construction, this study reports 9 biotite 40Ar/39Ar ages in the middle reach of the Purlung Tsangpo River and semiquantitatively calculates the rock erosion rates represented by these ages using the modeling code "Pecube". The measured biotite 40Ar/39Ar ages range from 103-12.5 Ma, corresponding to erosion rates ranging from 0.068-0.5 km/Ma. The rock erosion rates of the Purlung Tsangpo River have obvious differences between the western and eastern sections, which are characterized by the downstream section (western section) being significantly higher than that of the middle section (eastern section). Ages and simulation results show that in contrast to the eastern Himalayan syntaxis, the crust erosion rate in the middle reach of the Purlung Tsangpo River is lower and stable. The Purlung Tsangpo River was captured by the Yarlung Tsangpo River, which allowed the Purlung Tsangpo River downstream (western section) to change into a youth stage of fluvial geomorphological evolution again.The rapid river incised likely resulted in the erosion rate differences between the western and eastern sections.

Keywords

• the eastern himalayan syntaxis
• purlung tsangpo river
• biotite 40ar/39ar
• crust erosion
• river evolution