| Summary: | International audience The polyphased propagation of the deformation, generally suspected in rift systems, remains often poorly defined in terms of timing and fault reactivation and the role of transversal discontinuities in the crust is often poorly understood during the overall extensional history of a basin. Herein, we present some new concepts about the evolution of two well-separated rift propagators, the marginal basin of the Coral Sea (offshore Papua New Guinea), and the Porcupine Basin (offshore Ireland). Both basins are parts of long-lived rift systems that formed across former orogenic sutures in respect of local plate tectonics frameworks. On one side, the Coral Sea opened through the Australian Craton and the Tasmanides Orogen and its propagation ahead of the Tasman Sea was broadly controlled by the subduction of the Pacific Ocean. On the other side, the Porcupine Basin cut through the Variscides and Caledonides fold and thrust belts as a response of the North Atlantic Rift system. Despite these two different settings, our observation shows two common extensional modes for both systems. The first highlights the role of the generalised orogenic collapse in the initiation of the extension, by reactivating orogenic faults over several tens of millions of years. The second, called "real rifting", articulates within overprinted 10-to-20-Myrs-long extensional megacycles, each geographically and temporarily well defined and composed of diffused and then localised faulting events. Such a scenario implies to consider a multiphased extension, which provides variously-tilted and -oriented fault-blocks filled-in by several sedimentary sequences showing a vertical stack of syn- and post-rift unconformities. This geological architecture directly undersigns the dynamics of the continental crust in which transverse orogenic features have a dominant role onto the basin propagation by either activating or turning off the faults independently of the general plate tectonic forces
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