Rutile and zircon U-Pb dating as a constraint on sedimentary provenance of the Jianchuan Basin: Implications for paleo-drainage evolution

The Yangtze River is the largest river in Asia, and its evolution has been a subject of debate for more than a century. The formation of the First Bend is widely recognized as a key drainage reorganization event that led to the birth of the modern Yangtze River. In this study, we use new detrital rutile U[sbnd]Pb ages to constrain the sedimentary provenance of the Cenozoic deposits in the Jianchuan Basin. Our results show that detrital rutile U[sbnd]Pb ages of the Eocene sandstones from the Jianchuan Basin are similar to those of the Yalong River and Jinsha River, indicating that the upper Yangtze is likely to have flowed through the Jianchuan Basin in the late Eocene. Moreover, the characteristic zircon age signature of the Yalong and Jinsha Rivers also appear in the Jianchuan Basin, which is consistent with the rutile data. Our new rutile data and previous detrital zircon data suggest that the upper Yangtze River is likely to connect the Red River via the Jianchuan Basin since the late Eocene.