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Abstract:
The Jinshan Gorge in the middle Yellow River, northern China, currently connecting the upstream Hetao Graben to the downstream Weihe Graben, is hypothesized to have recently developed, which implies changing incision rates along the gorge. However, different integration processes have been proposed, such as paleolake regression in the Weihe Graben or integration with a paleolake in the Hetao Graben. These different mechanisms imply different timings, from the Late Miocene to the Late Pleistocene. In this study, we model variations in channel profiles and incision in response to different integration processes using the stream power law. We show that variations due to paleolake regression in the Weihe Graben or integration with paleolake in the Hetao Graben are inconsistent with the incision history preserved by river terraces and reconstructed by inverse analysis of tributary profiles. Instead, a recent increase in the slip rate of the Weihe Graben's boundary faults can explain the main features. Inverse analysis of channel profiles along the Jinshan Gorge suggests that relative uplift rates were a steady ∼0.04 mm/yr before the Early Pliocene, and increased to ∼0.16 mm/yr at present, especially since the Middle-Late Pleistocene. Our analysis is supported by further data from paleoseismic, drilling and paleostress studies.
