Bedload‐Bedrock Contrasts Form Enigmatic Low‐Relief Surfaces of the Pyrenees

Abstract

AbstractLow‐relief, high‐elevation surfaces in mountain belts highlight the dynamic nature of landscapes and have provided evidence for changes in tectonics and/or climate. Yet quantifying when changes occurred from topographic data is challenging and relationships between erosion rate, lithology and precipitation are complex. In the Pyrenees, low‐relief, high elevation surfaces are found across both plutonic massifs and the surrounding softer rocks and channel steepness values are relatively uniform between these lithologies. This suggests a weak relationship between erosion rate and lithology despite a clear relationship between the drainage network configuration and the location of the plutonic rocks. We explore this conflicting evidence for strength of the relationship between lithology and erosion rate using a landscape evolution model which accounts for the contrast between bedrock and bedload erodibility. This contrast produces dispersed channel steepness values and predicts the in situ development of low‐relief surfaces, under steady forcing conditions.