Patterns of extensional reactivation of compressional features in rifted margins – insights from thermo-mechanical modelling

Many rifted margins form in regions that have previously undergone oceanic subduction and continent-continent collision. This implies that rifting occurs in the presence of inherited compressional features, rather than in homogeneous lithosphere, which may influence the resulting rift structures. The degree of compressional inheritance is increased in subduction systems that involve the accretion of oceanic plateaus, continental fragments, and microcontinents. In this case, a more intricate structural, rheological, and thermal inheritance is present at the onset of rifting compared to continent-continent collisions without terranes. In this study, we employ 2D thermo-mechanical numerical models to explore how such complex inherited features influence subsequent phases of continental rifting. Our models simulate orogenesis through ocean subduction, microcontinent accretion, and continental collision, followed by a quiescent phase before rifting initiates. We investigate the resulting rifted margin structures and assess the extent to which inherited compressional features are reactivated during rifting.

We find that a dynamic interplay exists between structural and thermal inheritance, which exerts a primary control on rifted margin architectures. In smaller, colder orogens, structural inheritance predominantly governs rifting, whereas in larger, warmer orogens, thermal inheritance plays a more significant role. To illustrate these contrasts, we present two end-member models and compare their resulting conjugate rifted margin architectures with natural examples from the opening of the North and South Atlantic Oceans. Our experiments demonstrate a diverse array of features, including the formation of continental fragments, allochthons, and hyper-extended segments, which arise due to the presence of inherited compressional features. These results highlight the critical role of deformation history and accreted terranes in shaping the evolution of continental rifting.