Continental rifts often develop from linkage of distinct rift segments under varying degrees of extension obliquity. These rift segments arise from rift initiation at non-aligned crustal heterogeneities and need to interact to develop a full-scale rift system. Here, we test the effects of 1) oblique extension and 2) initial heterogeneity (seed) offset on continental rift interaction with the use of an improved analogue model setup. X-Ray computer tomography (CT) techniques are used to analyse the 3D models through time and the results are compared with additional numerical models and natural examples. The experimental results reveal that increasing extension obliquity strongly changes rift segment structures from wide rifts in orthogonal settings to narrower rifts with oblique internal structures under oblique extension conditions to narrow strike-slip dominated systems towards the strike-slip domain. We also find that both decreasing seed offset and increasing extension obliquity promote hard linkage of rift segments through the formation of continuous rift boundary faults at the surface. (Initial) soft linkage through the formation of relay ramps is more likely when seed offset increases or extension is more orthogonal. Rather than linking at depth, the rift boundary faults curve around each other at depth and merge towards the surface to form a continuous trough. Orthogonal extension promotes the formation of intra-rift horsts, which may provide hydrocarbon traps in nature.

Rifted margins mark a transition from continents to oceans and contain in their architecture a record of their rift history. Recent investigations of rift architecture have suggested that multiphase deformation of the crust and mantle lithosphere leads to the formation of distinct margin domains. The processes that control transitions between these domains, however, are not fully understood. Here we use high-resolution numerical simulations to show how structural inheritance and variations in extension velocity control the architecture of rifted margins and their temporal evolution. Distinct domains form as extension velocities increase over time and deformation focuses along lithosphere-scale detachment faults, which migrate oceanwards through re-activation and complex linkages of prior fault networks. Our models demonstrate, in unprecedented detail, how faults formed in the earliest phases of continental extension control the subsequent structural evolution and complex architecture of rifted margins through fault interaction processes, hereby creating the widely observed distinct margin domains.

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S U M M A R YLithospheric density and thickness variations are important contributors to the state of stress of the plates. The relationship between the lithosphere's isostatic state, subcrustal structure and stress field, however, remains unresolved due to the uncertainties on its thickness, composition and rheology. To study the influence of lithospheric structure on intraplate stresses, we use a new model of global lithospheric structure (TDL) that accounts for the presence of depleted mantle to explore the effects of isostatic compensation, mantle density structure, lithospheric thickness (base depth) and mechanical coupling within the lithosphere on wavelengths >200 km. We compute the mean lithostatic stress ( ) of 2 • × 2 • lithospheric columns and then solve for the resulting global 'tectonic' stress field for a homogeneous elastic lithosphere with the finite element package ABAQUS. For a 100 km base depth, a historically common value for lithospheric thickness, tectonic stress patterns are largely insensitive to mantle density structure and match patterns in the world stress map, for both isostatically compensanted and non-compensated lithospheric structure. Increasing the base depth up to 250 km to account for thick continental roots, however, leads to sharp variations in the stress field between isostatic lithospheric structure models and TDL as the mantle portion of the lithosphere dominates . Decreasing the model base depths up to 25 km as a proxy for vertical strength variations due to low viscosity channels within the crust or lithosphere as a whole, strongly alters stresses in magnitude, azimuth and regime, as the influence of topography and shallow crustal structure increases. We find that restricting spatial changes in to a specified region to mimic lateral variations in strength also has a large effect on the resulting stresses, which leads us to conclude that regional models may not always be adequate for modelling the stress field. Strong deviations from long-wavelength patterns on the world stress map in models with a shallow (<<100 km) or deep (>>150 km) uncompensated model base depth likely reflect that the globally averaged lithospheric thickness is close to 100 km and large deviations from this depth generate unrealistic stress patterns related to uncompensated buoyancy forces. Because the stresses are so sensitive to base depth, we conclude that using to represent spatial and vertical variations in lithospheric structure is not an adequate approximation. Our results suggest that future studies must incorporate the full 3-D variations in density and rheology of the lithosphere to elucidate the source and nature of the lithospheric stress field. These studies have become possible with the advent of modern computational tools and advances in our knowledge of lithospheric structure and rheology.