Plio-Pleistocene drainage reorganization in the middle Yellow River of China, revealed by provenance and paleocurrent analysis of fluvial sediments

Abstract

Continental-scale drainage reorganization is generally understood to result from landform evolution forced by the coupling between tectonic activity and climate change, attracting worldwide attention. Planation surfaces and river terraces constitute the most direct geomorphological archives for integrating the history of river systems and for reconstructing processes of drainage reorganization based on provenance analysis of the fluvial sediments. The Middle Yellow River has incised into the Ordos Block, which was previously levelled by a planation surface, creating the Jinshaan Gorge and linking the Hetao Basin to the north and the Fenwei Basin to the south. Multiple lines of evidence, from terraces correlation, sedimentary characteristics, and fluvial provenance, suggest that the Middle Yellow River catchment was occupied by fluvio-lacustrine systems before drainage integration, accumulating a sedimentary sequence derived from surrounding Red Clay and bedrocks during the period between 8.3 and 3.7 Ma. The planation surface was uplifted subsequently, forcing reorganization of the fluvio-lacustrine systems. Their integration resulted in the formation of the Jinshaan Gorge prior to 1.2 Ma. Numerous terraces were created during incision by the Middle Yellow River from north to south along the gorge. Our data, obtained from zircon UPb dating and lithological composition of fluvial gravels, further points to a remarkable discrepancy in provenance between the fluvio-lacustrine systems overlying the planation surface and the terraces sequence formed by the integrated Middle Yellow River, confirming the drainage reorganization process constrained by the geomorphic records.