Untangling the interplay among tectonics, climate, and erosion in the Himalayas using landscape evolution modeling

The interplay between tectonic rock uplift and climatically modulated erosion governs landscape evolution and influences how mountain ranges affect climate, biogeochemical cycling, ecology, and biodiversity. The Himalayas, Earth's highest mountain range, have inspired a large body of work suggesting that Himalayan topography is primarily governed by southward-propagating tectonic deformation. Here, we use a new coupled surface process and orographic precipitation model to test this hypothesis, and to assess the extent to which orographic precipitation effects have modulated the influence of tectonics on Himalayan topography since the Neogene (circa 23 million years ago). The model is quantitatively constrained by observed topographic profiles, river profiles, precipitation profiles, erosion rates, and thermochronologic ages from eight major rivers. Results indicate that propagating rock uplift allows a maximum "no erosion" elevation of similar to 20 km, and largely governs the formation of the present-day topography of the Himalayas, with a secondary role played by orographic-rainfall-influenced fluvial processes as suggested by erosion/uplift ratios of 60-70%. Modeled sediment fluxes from the orogen are 30-40 x 10(6) m(3)/yr per 250-km width (i.e., approximately one drainage basin width). Our methods enable the integration of diverse observations to reconstruct how tectonics and climate have interacted to control the topographic evolution of mountain belts, and allow investigation into the long-term influence of important geomorphic process parameters.