Modeling of lithospheric deformation: Application to the evolution of rifting and passive margins

The tectonic evolution of rifts and passive margins is affected by a variety of geological and physical processes that interact in a complex way. The work presented in this thesis is an attempt to isolate the phenomena that affect their evolution using both forward and inverse modeling. To achieve this goal, I used constraints on the mechanical behavior of the lithosphere derived from experimental work, geological and geophysical observations.; Forward models of the lithosphere are used to isolate the physical processes that determine the overall elastic strength of the lithosphere and control finite offset on normal faults. Using parametrizations of elastic strength obtained from the analysis of viscous-elastic-plastic rheological models, I demonstrate that the sedimentary cover can significantly affect the strength of the continental lithosphere at foreland basins and passive margins. I am also able to show that the lower crust should have a strong plagioclase rheology.; Using a newly developed numerical method used to model the spontaneous formation of faults in an elastic-plastic layer, I am able to determine the geological conditions that should lead to the formation of either very large offset or small offset normal faults. The key result of this study is that the inactive part of the very large offset faults are flexurally rotated to a low-angle configuration similar to that observed at core complexes.; Finally, I develop a methodology to reconstruct the tectonic and stratigraphic evolution of west African margin along two seismic profiles. It integrates estimates of continental flexural strength to obtain better estimates of its isostatic response of the lithosphere. Palinspastic reconstruction and two dimensional flexural backstripping are combined to perform the reconstruction of the faulting that disrupts the stratigraphy of the margin. This method enables me to obtain an estimate of the evolution of the geometry and paleowater depth through time. I show that the margin geometry and sedimentation is affected by the drastic changes following Cenozoic climatic transitions. The reconstructions also allow me to distinguish between climatic and tectonic control on the evolution of margin by highlighting the local effect of the Miocene tectonic uplift of the margin.