Lupker M., Blard P. H., Lave J., France-Lanord C., Leanni Laetitia, Puchol N., Charreau J., Bourlès D. (2012). Be-10-derived Himalayan denudation rates and sediment budgets in the Ganga basin. Earth and Planetary Science Letters, 333, p. 146-156. ISSN 0012-821X.
Titre du document
Be-10-derived Himalayan denudation rates and sediment budgets in the Ganga basin
Lupker M., Blard P. H., Lave J., France-Lanord C., Leanni Laetitia, Puchol N., Charreau J., Bourlès D.
Source
Earth and Planetary Science Letters, 2012,
333, p. 146-156 ISSN 0012-821X
The Himalayas represent the archetype of mountain building due to active continental collision and are considered in many studies as the locus of intense interactions between climate, denudation and tectonics. Estimates of modern denudation rates across the entire range remain, however, relatively sparse. In this study, in situ-produced cosmogenic Be-10 concentrations were measured in detritic quartz in order to determine basin-scale denudation rates for the central part of the Himalayan range. River sand was sampled over several years in the main trans-Himalayan rivers, from the Himalayan front to the Ganga outlet in Bangladesh. The calculated Be-10 denudation rates of the trans-Himalayan river basins range from 0.5 to 2.4 mm yr(-1) (average 1.3 mm yr(-1)) and vary by up to a factor of 3 between sampling years. These denudation rates strongly contrast with the 0.007 mm yr(-1) denudation rate of southern tributary basins draining the Indian craton. This work also shows that in the Ganga basin, no systematic evolution of average Be-10 concentrations is observed during floodplain transfer, implying that distal samples can be used to estimate the integrated denudation rate of the whole central Himalayan range. Samples from the Ganga in Bangladesh display remarkably low variability in Be-10 concentration, implying an average Himalayan denudation rate of 1.0-1.1 mm yr(-1). However, within the floodplain, several samples suggest a recent perturbation of sediment transport dynamics with a recent increase in the relative sediment contribution from southern tributaries. The Himalayan sediment flux, deduced from the Be-10 denudation rate of the range, is 610 +/- 230 Mt yr(-1). This flux is consistent, within uncertainty, with sediment fluxes derived from sediment gauging. The similarity of the two flux estimates suggests that Himalayan erosion fluxes have remained stable over the last centuries, even if the large uncertainties associated with each method hamper more precise assessments.
Plan de classement
Hydrologie [062]
;
Géologie et formations superficielles [064]
