Late Cretaceous drainage reorganization of the Middle Yangtze River

The middle reach of the Yangtze River experienced significant drainage reorganization during the Mesozoic to Cenozoic tectonic evolution of South China. A continental-scale, westward-flowing axial river, or paleo-Middle Yangtze, formed following the Mesozoic collision between the North China and South China blocks. The river later flowed to the east as a result of the Cenozoic uplift of the Tibetan Plateau, but its reversal history remains largely unknown. Changes in detrital zircon U-Pb ages of Mesozoic to Cenozoic strata in the Three Gorges region identify a vital provenance shift in the sediments of the paleo-Middle Yangtze. Combined with paleocurrent measurements and petrography, our results indicate that the paleo-Middle Yangtze initially reversed during the late Cretaceous, followed by progressive westward capturing in the Eocene. This conclusion provides a paleogeographic explanation for the limited exposures of Upper Cretaceous to Cenozoic rocks in the Sichuan Basin and refutes the "drainage divide" hypothesis for the Three Gorges.