Quaternary drainage evolution of the Datong River, Qilian Mountains, northeastern Tibetan Plateau, China

Abstract

Drainage basins are useful recorders of tectonics and climate. The Datong River, which drains the Qilian Mountains, China, is one of the most elongated river basins of the world. How this unusual basin configuration was established remains unknown, despite this area being ideal for assessing the controlling effects of tectonics and climate on the drainage evolution. In this study, we reconstruct the history of the drainage evolution of the Datong River, using integrated provenance methods (UPb dating, heavy mineral and gravel compositions) and river terrace dating. The drainage system of the modern Datong River began to form at ~1100 ka, and the drainage basin was limited to the area of the lower modern Datong River. Since then, it has gradually extended through headward erosion. The river channelized into the Menyuan Basin between ~620 ka and ~420 ka, and it captured the upper Datong River between ~130 ka and ~60 ka. We suggest that the rapid uplift of the Qilian Mountains disrupted and longitudinally deflected the transverse rivers over the past 1100 ka. Additionally, intensified precipitation and glacial meltwater enhanced the river incision and captured the middle and upper Datong River during 620–420 ka and 130–60 ka, respectively. This model shows that the direction of drainage pattern evolution is controlled by tectonics and that the timing of drainage reorganization is controlled by climate change in the active fold-thrust belt.