Interactions between rivers and actively uplifting folds
Beveled folds in the foreland of the Tian Shan.
In the foreland of the Tian Shan, folds that are uplifting several millimeters per year have at some times in the past been completely planed off by rivers. How do such wide erosion surfaces form? And why do most rivers at the modern-day incise deep canyons into the folds? We demonstrate that through changes in sediment and water fluxes, the rate at which rivers migrate laterally can change by orders of magnitude, and that such changes are probably the cause for alternating periods of planation and incision.
Ongoing work is aimed at testing the link between sediment fluxes and the formation of planation surfaces. Do rivers cut wide platforms when sediment fluxes are high, and incise narrow canyons when those fluxes are low? We use the erosion rates in the mountains upstream of the planation surfaces (measured using 10Be in Quartz) as a proxy for the sediment transport of rivers. We measure these erosion rates at the time of planation, using deposits left behind by the river on top of the planated terraces, and compare them with rates measured in the modern, incising, rivers.
Video of analog experiments performed at St Anthony Falls Laboratory.
Bufe, A., Burbank, D.W., Bookhagen, B., Liu, L., Chen, J., Li, T., Thompson, J., Yang, H. Variations of lateral bedrock erosion rates control planation of uplifting folds in the foreland of the Tian Shan, NW China. (in press at JGR-Earth Surface)
Bufe, A., Paola, C., Burbank, D.W. (2016), Fluvial bevelling of topography controlled by lateral channel mobility and uplift rate. Nature Geoscience, 9(9), 706-710.