Rapid fluvial incision along the Yellow River during headward basin integration

Abstract

The onset of fluvial erosion in an area of tectonic uplift is thought to reflect the timing of the uplift. Geomorphological data from the Yellow River in Tibet, indicate that the rapid incision of this river channel occurred as a result of climate change, at least six million years after the onset of plateau uplift. The onset of rapid exhumation along the high relief margins of orogenic plateaux is often used as a proxy for the timing of surface uplift1,2,3. However, processes that inhibit incision by rivers, such as spatially variable rock uplift4, orographic changes in rainfall5 and channel damming by glaciers or landslides6,7 may lead to exhumation that significantly lags surface uplift8. Here we reconstruct the timing, rate and pattern of fluvial incision along the Yellow River in northeastern Tibet using stratigraphic, geochronologic and geomorphic data from sedimentary basins along the present-day river course. We find that the onset of fluvial incision occurred substantially later than the onset of mountain building, 14–8 million years (Myr) ago9. Fluvial incision initiated at the plateau margin 1.8 Myr ago10 and progressed upstream11 at a rate of approximately 350 km Myr−1. We conclude that the fluvial incision was a result of a climatically driven expansion of lake systems in the region12,13 that led to lake spillover and consequently the integration of the modern Yellow River.