Influence of Surface Processes on Postrift Faulting During Divergent Margins Evolution

We used thermomechanical numerical models to simulate the formation and evolution of divergent continental margins since continental rifting, taking into account surface processes of erosion of the continental escarpment. We found that the degree of crust–mantle coupling, the magnitude and extent of erosion of the coastal landscape, and the preexistence of weakness zones in the continental crust are important elements that control the reactivation of faults along divergent margins during the postrift phase. The numerical experiments indicated that the presence of a lower crust with a relatively low viscosity, facilitating the decoupling of the upper crust and the development of hyperextended margins, could also contribute to the development and/or reactivation of normal faults in the interior of the continent when the margin is continually subjected to differential denudation and consequent flexural response of the lithosphere. This effect is suppressed in scenarios where the lower crust presents a relatively high viscosity, consequently inducing the coupling of the upper crust with the lithospheric mantle. In this case, the long wavelength of the flexural response of a coupled lithosphere to erosional unloading has a minor impact on the reactivation of faults in the upper crust. As an application of our model, we propose that the combination of a decoupled continental lithosphere, escarpment retreat due to erosion, and the preexistence of shear zones parallel to the coast contributed to the development of postrift Cenozoic tectonism in southeastern Brazil.