The role of the heterogeneous rheological architecture of rifted margins in the building of mountain belts has challenged our view of how a collisional orogen formed. We show, using two-dimensional numerical experiments of collision built by the inversion of rifted margins, that a weak pre-extensional evaporitic layer delays the growth of topography and the onset of syn-orogenic sedimentary record in foreland basins. In tectonic models lacking a weak décollement layer, the orogen grows by progressive accretion of basement thrusts. With a 2-km-thick salt layer, the orogen develops an antiformal stack in the deep crust that is kinematically connected to a shallow thin-skin thrust belt in the foreland as observed in many orogens. A 5-km-thick weak layer leads to the quasi-absence of topography and widespread salt tectonics and obliterates thrusts propagation while promoting crust and mantle underthrusting. During convergence, the preservation of a marine seaway emphasizes that collision may involve a significant period of submarine continental accretion, which duration is controlled by the thickness of the weak décollement layer. From these experiments we infer that the thicker the salt layer, the longer the delay between the onset of far-field shortening and the formation of the orogen. Our study explains first-order features recognized in many orogens controlled by variable salt thickness and extension.

Western Makran is one of the few subduction zones left with a largely unconstrained seismogenic potential. According to the sparse GPS stations, the subduction is accumulating some strain to be released during future earthquakes. To enhance the seismic hazard assessment, we here propose to study the finite deformation of the western Makran accretionary wedge. Mechanical modelling is used to retrieve the spatial variations of the frictional properties of the megathrust, and discuss its seismogenic potential. To do so, we first build a structural map along the Iranian part of the Oman Sea and investigate three N-S seismic profiles. The profiles are characterized by a long imbricated thrust zone that takes place at the front of the wedge. A diapiric zone of shallow origin lies in between the imbricated zone and the shore. Along the eastern and western shores, active listric normal faults seem to root down to the megathrust. Eastern and western domains have developed similar deformation, with three zones of active faulting: the normal faults on shore, thrusts ahead of the mud diapirs, and the frontal thrusts. On the contrary, no normal faults are identified along the central domain, where a seamount is entering into subduction. Two mechanical analyses are performed to retrieve the frictional prop-

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