Evolution of the proto-Weihe River system during the Eocene–Oligocene: Evidence from sediment provenance of the Weihe Basin

The Weihe River, originating from the northeastern Tibetan Plateau, is one of the most important tributaries of the Yellow River. The Cenozoic evolution of the Weihe River provides critical insights into the geomorphologic uplift of the northeastern Tibetan Plateau, and the drainage evolution of the Yellow River. However, the Paleogene evolution of the Weihe River remains poorly understood. The Weihe Basin, located adjacent to the northeast of the Tibetan Plateau and at the lower reaches of the Weihe River, preserved continuous sediments record spanning from the middle Eocene to the Oligocene. Source to sink analysis offers valuable evidence for deciphering regional drainage evolution. This study investigates the sediment provenance of the Eocene-Oligocene sedimentary strata in the Weihe Basin and its temporal variations, employing detrital zircon UPb dating on 19 new samples alongside sedimentary analyses. We find that the regional river drainage underwent two evolutionary of stages during this period. During the Eocene (ca. 46–34 Ma), the Weihe Basin was characterized by a shallow lacustrine environment, receiving clastic materials primarily from the surrounding areas. By the early Oligocene (ca. 34–31.7 Ma), contributions from the modern upper reaches of the Weihe River increased. This suggested that the proto-Weihe River system began to form during the Oligocene, exhibiting a pattern that closely resembles its modern configuration. This drainage evolution was mainly controlled by tectonic deformation of the northeastern Tibetan Plateau, and enhancement in headwards erosion due to increased precipitation.