Tracing drainage capture between the two large tributaries of the Yangtze River in the southeastern Tibetan plateau: Insights from detrital apatite fission-track thermochronology

The evolution of drainage patterns in the southeastern Tibetan Plateau remains a highly controversial topic. In this study, we provide solid evidence that the Dadu and Anning Rivers, located in the southeastern Tibetan Plateau, have undergone reorganization after the plateau uplift. Through detrital apatite fission-track dating on modern sediments from both rivers, as well as the upper Pliocene - lower Pleistocene Xigeda Formation of the Anning, we reveal that the modern sediments of the Dadu River are dominated by young AFT ages (<5 Ma), consistent with the bedrock ages in its drainage basin. Similarly, the Anning modern sediments and the Xigeda Formation exhibit a significant portion of young ages (peaking at 4.2 and 4.4 Ma, respectively), contrasting with the older ages observed in the bedrocks of the Anning drainage basin but comparable to those of the Dadu drainage basin. We conclude that the Anning and Dadu Rivers were connected during the deposition of the Xigeda Formation, and the modern Anning River receives significant recycled sediments from this formation.