Exploring Controls on Post-Orogenic Topographic Stasis of the Pyrenees Mountains With Inverse Landscape Evolution Modeling

Abstract

How high topography can be sustained over long timescales in post-orogenic mountain belts is a longstanding research question in tectonic geomorphology and geodynamics. Here we utilize the well-documented orogenic paleo-topography and spatial-temporal exhumation patterns of the Pyrenee Mountains in a numerical modeling study investigating controls on post-orogenic topographic stasis. Orogenic activity in the Pyrenees Mountains ceased at ca. 25-20 Ma, but topographic decay has only been on the scale of hundreds of meters since that time. We use the landscape-evolution model FastScape coupled with the neighborhood-algorithm inversion method to explore the influence of precipitation, lithology, and stream power parameters on post-orogenic topographic stability. The inversions are constrained using topography (elevation, slope) and low-temperature thermochronology data. We find that incorporation of an erodibility threshold is required for moderating post-orogenic topographic decay, without which post-orogenic topography declines significantly on Myr timescales. While other evaluated parameters such as lithology and precipitation also contribute to topographic stability, they are secondary to the erodibility threshold in maintaining long-term post-orogenic topography. Our results provide valuable insights into the mechanisms governing post-orogenic landscape evolution and emphasize the importance of thresholds in landscape evolution modeling of mountain belts.