River network flow direction from River capture in the middle reaches of the palaeo-Yarlung Zangbo River

There are 51 tributaries in the middle reaches of the Yarlung Zangbo River (YZR), and the confluences of 87% of the tributaries west of Jiacha Gorge are high-angle or perpendicular, reflecting the anomalous development of these tributaries. In this paper, field investigation and digital elevation model (DEM) methods were used to analyse the causes of this anomalous phenomenon, and it was found that there was a watershed in the area of the Jiacha Gorge. The palaeo-YZR west of the Jiacha Gorge flowed westward before the early Pleistocene into the Zada, Zhongba, Jilong and Gamba–Dingri palaeolakes, which featured a large amount of total accommodation space in the western Qinghai–Tibet Plateau; thus, this river was a continental river. With the intensification of the collision between the Indian plate and the Eurasian plate, the Qinghai–Tibet Plateau experienced rapid uplift and formed a landscape with high elevations in the west and lower elevations in the east, promoting the headward erosion of the eastward-flowing river. During the early Pleistocene, the river east of the Jiacha Gorge crossed the watershed and captured the palaeo-YZR, causing a reversal in the flow direction of the palaeo-YZR.

雅鲁藏布江中游共有51条支流，其中加查峡谷以西的支流中，87%的支流与干流的汇流角度为高角度或近垂直，反映出此类支流的发育存在异常特征。本文采用野外调查与数字高程模型（DEM）方法，对该异常现象的成因展开分析，发现加查峡谷区域存在一处分水岭。早更新世之前，加查峡谷以西的古雅鲁藏布江向西径流，注入札达、仲巴、吉隆以及岗巴—定日古湖；该区域在青藏高原西部拥有充足的沉积可容空间，因此当时该河流属于内陆河。随着印度板块与欧亚板块碰撞作用加剧，青藏高原快速隆升，形成了西高东低的地貌格局，助推了东流河流的溯源侵蚀。早更新世时期，加查峡谷以东的河流越过该分水岭，袭夺了古雅鲁藏布江，导致古雅鲁藏布江的流向发生反转。