HR: 0830h
AN: T21C-0468    [PDF]
TI: Numerical Modeling of the Evolution of the Himalayas of Central Nepal due to Active Tectonics and Fluvial Incision
AU: * Godard, V
EM: godard@geologie.ens.fr
AF: Laboratoire de G\'{e}ologie, Ecole Normale Sup\'{e}rieure, 24, rue Lhomond, Paris, 75005 France
AU: Cattin, R
EM: cattin@geologie.ens.fr
AF: Laboratoire de G\'{e}ologie, Ecole Normale Sup\'{e}rieure, 24, rue Lhomond, Paris, 75005 France
AU: Lav\'{e}, J
EM: Jerome.Lave@ujf-grenoble.fr
AF: LGCA, Universit\'{e} Joseph Fourier, 1381, rue de la Piscine, St Martin d'Heres, 38400 France
AB: The recent developments on coupling between tectonics and erosion have emphasized the key role of the fluvial network in active mountainous areas, in particular in leading landscape denudation. However, few of the numerical modeling studies that permitted to investigate this coupling have tried to consider realistic erosion laws, in particular the fluvial erosion processes. We have developed a simplified 2D analytic formalism to introduce landscape denudation by fluvial incision (a detachment limited model) and hillslopes landsliding into a mechanical finite element code (ADELI). We thus investigate the coupling between tectonics and erosion at timescales of 100 ky, and try to evaluate the sensitivity of our model to the chosen erosion formalism and the different responses of the system to external forcing. For this particular study, the model geometry reproduces roughly the structure of the Himalayas of Central Nepal. This area is both one of the most active compressional orogen on Earth, and one of the best documented regarding internal and external processes, in particular for the calibration of a fluvial incision law. First, the introduction of an erosion law derived from dominant fluvial incision leads to much more realistic topographic profiles than a simple diffusion law. The free parameters of the fluvial incision law, like pluviometry or structure of the hydrographic network have a moderate influence on the near-equilibrium topographic profiles, but a significant incidence on uplift, incision and denudation rates across the range. In contrast it appears that variations in bedrock erodability strongly modulate the mean elevation profiles for rivers and topography. Finally, the influence of crustal rheology and its links with the modality of surface denudation are also investigated. We underline the importance of a stratified crustal rheology, i.e. a basic lower crust and a quartz-like upper crust, in association with fluvial incision processes, in order to reproduce Himalayas main features: topographic profiles, denudation rates profiles and subsidence rate in the foreland basin.
DE: 1815 Erosion and sedimentation
DE: 3210 Modeling
DE: 8102 Continental contractional orogenic belts
DE: 8159 Rheology--crust and lithosphere
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2003 Fall Meeting