Styles of extensional reactivation in rifted margins – comparing numerical modeling results to nature

Many rifted margins develop in regions that previously experienced oceanic subduction and continent–continent collision. This implies that continental rifting commonly occurs in a lithosphere that contains significant inherited features, rather than in a homogeneous medium. Such inheritance can be broadly classified into three categories – structural, rheological, and thermal – which typically coexist. Inherited features may strongly influence rift evolution and resulting margin architecture.

In this study, we use 2D thermo-mechanical numerical models to investigate how complex inheritance, featuring structural, rheological and thermal components, affects subsequent phases of continental rifting. Our models simulate rifting following orogenesis that occurs through oceanic subduction, microcontinent accretion, and continental collision. By varying the size and complexity of the pre-rift orogen, we evaluate the relative importance of different types of inheritance in the development of rifted margins. We compare the resulting margin architectures with natural examples.

We find that a dynamic interplay exists between structural, rheological, and thermal inheritance, strongly influencing the resulting rifted margin architectures. In small, cold orogens, structural inheritance is predominant, whereas in large, warm orogens, thermal and rheological inheritance play more significant roles. The relative importance of thermal and rheological inheritance is particularly challenging to assess, but we propose that the former plays the more prominent role. To illustrate these contrasts, we compare conjugate rifted margin architectures of two end-member models with natural examples from the opening of the North and South Atlantic Oceans. Our experiments reproduce a diverse array of features observed in the natural examples, including the formation of continental fragments and allochthons. They illustrate the complex deformation pathways through which rifted margin structures may have been achieved. Our results thus highlight the critical role of deformation history in shaping the evolution of continental rifting.