Large spatial and temporal variations in Himalayan denudation

• First systematic orogenwide quantification of erosion and denudation rates in the Himalaya.
• Large spatio-temporal along-strike and orogen-perpendicular variations in denudation found.
• First systematic variation in denudation between GHS-N and GHS-S discovered.
• Punctuated periods of GHS-N denudation over spatio-temporal scales of ~300–1700 km and 2–4 Myr.
• Over the last 10 Ma >1000 km stretch of GHS-S where sustained and high denudation rates were present.

In the last decade growing interest has emerged in quantifying the spatial and temporal variations in mountain building. Until recently, insufficient data have been available to attempt such a task at the scale of large orogens such as the Himalaya. The Himalaya accommodates ongoing convergence between India and Eurasia and is a focal point for studying orogen evolution and hypothesized interactions between tectonics and climate. Here we integrate 1126 published bedrock mineral cooling ages with a transient 1D Monte-Carlo thermal–kinematic erosion model to quantify the denudation histories along ~2700 km of the Himalaya. The model free parameter is a temporally variable denudation rate from 50 Ma to present. Thermophysical material properties and boundary conditions were tuned to individual study areas. Monte-Carlo simulations were conducted to identify the range of denudation histories that can reproduce the observed cooling ages. Results indicate large temporal and spatial variations in denudation and these are resolvable across different tectonic units of the Himalaya. More specifically, across >1000 km of the southern Greater Himalaya denudation rates were highest (~1.5–3 mm/yr) between ~10 and 2 Ma and lower (0.5–2.6 mm/yr) over the last 2 My. These differences are best determined in the NW-Himalaya. In contrast to this, across the ~2500 km length of the northern Greater Himalaya denudation rates vary over length scales of ~300–1700 km. Slower denudation (<1 mm/yr) occurred between 10 and 4 Ma followed by a large increase (1.2–2.6 mm/yr) in the last ~4 Ma. We find that only the southern Greater Himalayan Sequence clearly supports a continuous co-evolution of tectonics, climate and denudation. Results from the higher elevation northern Greater Himalaya suggest either tectonic driven variations in denudation due to a ramp-flat geometry in the main décollement and/or recent glacially enhanced denudation.