Detall
Effects of surface processes on fold development. SEMINARIS DE LA FACULTAT DE GEOLOGIA I L'INSTITUT DE CIÈNCIES DE LA TERRA 'JAUME ALMERA'
Marine Collignon (Geological Institute, ETH Zurich, Suïssa)
Over the past decades, the interaction between surface processes and development of mountain belts has been extensively studied. While syntectonic sedimentation appears to control the external development of the fold-and-thrust belts, erosion strongly influences the evolution of internal regions within mountain belts. To numerically investigate the effects of surface processes and multilayer folding in three dimensions, we have developed a finite-element based landscape evolution model (both erosion and sedimentation) using PETSc, and coupled it to the 3D mechanical code LaMEM. The landscape evolution model uses a non-linear diffusion formulation (Simpson and Schlunegger, 2003), taking into account both hillslope and channel processes.
Model results show that surface processes do not have a strong control on the fold pattern across the fold and thrust belt. Nevertheless, erosion reduces the amount of shortening required to initiate folding and increases the exhumation rates. Increased sedimentation in the synclines contributes to this effect by amplifying the fold growth rate by gravity. The main contribution of surface processes is rather due to their ability to strongly modify the initial topography and hence the initial random noise, prior to deformation. Moreover model results have shown that at the scale of the structures, surface processes can modify linkage mode, the location of the saddle point, as well as its distance to the crest of the anticline, and thus the characteristic of hydrocarbon traps. Finally, the model results can be applied to the Zagros Folded Belt. The model also reproduces most of the geomorphic criteria used in the recognition of lateral fold growth and described in previous studies.
