Climate change and Late Pliocene acceleration of erosion in the Himalaya

Studies of active mountain ranges suggest that atmospheric and geodynamic processes may be strongly coupled through erosion - a hypothesis that has led to a debate over the relative importance of climate and far-field tectonic forcing in influencing erosion. We addressed this debate by developing the detailed long-term erosional history of a transect in the central Annapurna Range of Nepal for comparison with the climate and tectonic forcing histories of the region. Patterns of apatite fission-track and muscovite 40Ar/39Ar apparent ages with elevation indicate a five-fold increase in apparent erosion rate between 2.5 and 0.9 Ma ago. The time frame for this change corresponds to that of global climate destabilization associated with the onset of Northern Hemisphere glaciation and an intensification of the Asian monsoon. There is no evidence for important changes in the far-field tectonics of the Himalayan-Tibetan orogenic system over that interval, suggesting a largely climatic driver for enhanced erosion at the Himalayan range front.