Climate and sediment mobility modulate topography-tectonic link in the Andes

The strong gradients in climate and tectonics along the Chilean-Argentine Andes offer the perfect opportunity to study wider landscape controls on mountain topography.

Between 33 and 37^oS we observe the largest variability in mountain elevation and erosion rates. For this region, we isolate the tectonic contribution to topography by modelling the mechanical dislocation of the crustal scale faults in response to plate convergence. We then use this spatially variable uplift field to determine to what extent the existing topography records this tectonic signal. While local relief and channel steepness do record responses to faulting on the Chilean side of the cordillera, the broader areas of highest uplift in Argentina have the lowest local relief and channel steepness. We therefore explore how this relationship between tectonics and topography may have been modified by the spatial variability in bedrock lithology, sediment cover and mean annual precipitation. We find that channel steepness does not vary significantly with bedrock lithology but does map onto trends in precipitation and sediment cover. The lowest local relief and channel steepness regions have low precipitation rates and widespread sediment cover, suggesting sediment mobility, modulated by climate, maybe an important control on bedrock incision rates in this high uplift zone. We therefore highlight the importance of climate in the recovery of post-glacial landscapes and the modulatory effect sediment cover can have in the evolution of large scale topography.