Detachment fault systems typically record displacements in the order of 10s of kilometers. The principles that control the growth of smaller magnitude normal faults are not fully applicable to the evolution of detachment fault systems. We use interpretation of 2D and 3D seismic reflection data from the mid‐Norwegian rifted margin to investigate how the structural evolution of a detachment fault interacted with the effects of isostatic footwall rollback to produce complex 3D geometries and control the configuration of associated supradetachment basins. We further investigate the effects of lateral interaction and linkage of extensional detachment faults on the necking domain configuration. In our study area, the domain‐bounding Klakk Fault Complex demonstrates how successive incision may induce a complex structural relief in response to faulting and fault plane folding. We interpret the previously proposed metamorphic core complex within its footwall as an extension‐parallel turtleback‐structure. The now eroded turtleback is flanked by a major supradetachment basin, connecting two main basin segments. We attribute footwall‐ and turtleback exhumation to Middle Jurassic‐Early Cretaceous rifting. The study area further demonstrates how detachment fault geometries can change during rifting and lead to the formation of younger, successively incising fault splays. Lateral linkage between the original detachment fault plane and these fault splays enables displacement along a detachment fault system consisting of fault segments generated at different stages in time. Implicitly, detachment faults are complex 3D systems that change configuration during their evolution, perpetually controlling associated basin formation, footwall configuration, subsidence and uplift patterns.

Late to post-Caledonian, Devonian extension remains unresolved in the SW Barents Sea, despite considerable knowledge from onshore Norway, East Greenland and Svalbard. We analyse intrabasement seismic facies in highresolution 3D and reprocessed 2D data to investigate evidence for Caledonian deformation and post-Caledonian detachment faulting in the central SW Barents Sea. These results are compared to published potential field models and analogue field studies from onshore Svalbard and Bjørnøya, substantiating that structures inherited from post-orogenic extension influenced the Late Paleozoic and Mesozoic basin evolution. The Late Paleozoic Fingerdjupet Subbasin is underlain by a NNE-striking, ESE-dipping extensional detachment fault that records a minimum eastwards displacement of 22 km. The detachment fault and associated shear zone(s) separate post-orogenic metamorphic core complexes from the syn-tectonic deposits of a presumed Devonian supradetachment basin. Spatial variability in isostatically induced doming likely governed Devonian basin configurations. Pronounced footwall corrugations and faults splaying from the detachment indicate eastward extensional transport. This ultimately led to two interacting but subsequent, east-stepping detachments. Local reactivation of the detachment systems controlled the extent of Carboniferous carbonate and evaporite basins in the Bjarmeland Platform area. Further, the Mesozoic Terningen Fault Complex and Randi Fault Set testify to how the inherited Devonian structural template continued to control spatial localisation and extent of rift structures during subsequent periods of extensional faulting in the

<p>Within rifted margins, the necking domain corresponds to the area where drastic reduction in basement thickness leads the crust to attain a wedge-shape. The crustal thinning occurs along detachment fault systems typically recording displacements in the order of 10s of kilometers. These systems commonly shape the crustal taper and eventually the taper break, where crustal thickness is thinned to 10 km or less. In recent years, it has become clear that evolutionary models for detachment fault systems remain unsatisfactory as the well-known principles for smaller magnitude fault systems are not fully applicable to these large-magnitude systems. Consequently, the detailed responses in the foot- and hanging walls and associated basin sedimentation within detachment fault systems and necking domains remain poorly understood compared to those observed in extensional half-graben basins.</p><p>We use interpretation of 3D- and 2D seismic reflection data from the Mid-Norwegian rifted margin to discuss the effects of lateral interaction and linkage of extensional detachment faults on the necking domain configuration. We investigate how the structural evolution of these detachment faults interact with the effects of isostatic rollback to produce complex 3D geometries and control the configuration of the associated supradetachment basins. The study area demonstrates how successive incision may induce a complex structural relief in response to faulting and folding. In the proximal parts of the south Vøring and northeastern Møre basins, the Klakk and Main Møre Fault Complexes form the outer necking breakaway complex and the western boundary of the Frøya High. We interpret the previously identified metamorphic core complex within the central Frøya High as an extension-parallel turtleback-structure. The now eroded turtleback is flanked by a supradetachment basin with two synclinal depocenters resting at the foot of the necking domain above the taper break. We attribute footwall and turtleback exhumation to Jurassic-Early Cretaceous detachment faulting along the Klakk and Main Møre Fault Complexes. The study area further demonstrates how detachment fault evolution may lead to the formation of younger, successively incising fault splays locally. Consequently, displacement may occur along laterally linked fault segments generated at different stages in time. Implicitly, the detachment fault system may continue to change configuration and therefore re-iterate itself and its geometry during its evolution.</p>

<p>Extensional detachment faults, core complexes and supradetachment basins play major roles in the evolution of 3D rifted margin architecture. The successive incision of basement from early to late stages in the margin evolution is rarely explained in 3D. One reason for this is likely the lack of a unifying model for how very large faults grow and link laterally, and how this, in turn, links to the temporal evolution of the margin. As fault shape exerts a fundamental control on syn-rift basin architecture, the 3D evolution of detachment faults is critical to understand sedimentation in associated basins.</p><p>In the proximal margin offshore Norway, one control on lateral variation appears to be the differential exploitation of `extraction´ structures that evolved above the ductile crust. This controlled flips in fault polarity under the proximal margin, and lateral transitions from supradetachment- to half-graben style, Late Paleozoic-Triassic basins. Extensional culminations and core complexes were associated with this deformation pattern at depth.</p><p>The growth of an extensional fault past a displacement of a few kilometers will involve a change in 3D fault shape related to the isostatic rollback of parts of the fault plane. As displacement magnitude varies along the fault plane, so will the amount of extensional unloading and associated isostatic compensation. With increasing extension this will enforce a particular shape on the fault plane, with an extensional culmination developing in the area of maximum displacement, and synclinal recesses evolving on the flanks. With continued extension, the culmination evolves into a core complex. Necking domains, where faults propagate into the ductile middle crust appear to be prime locations for this type of faulting. As large-magnitude faults combine into domain-bounding breakaway complexes, this results in intermittent occurrences of core complexes along the main breakaways and lateral transitions into steeper megafaults and fault arrays. At the Mid-Norwegian margin, we interpret the Jurassic-Cretaceous North Møre and south Vøring basins to illustrate this type of evolution. Components of strike-slip may modify this type of pattern, as illustrated by  continental core complexes exposed in areas such as Death Valley and western Norway.</p><p> </p>

Observations and modelling results from highly extended regions indicate that detachment fault systems recording displacements of 10 km or more become associated with footwall uplift and back‐rotation. This is commonly explained by the rolling hinge model, which predicts detachment fault back‐rotation and severe dip reduction (<20°) controlled by the amount of extension. Although detachment faults within necking domains at rifted margins often record displacements in orders consistent with those for the rolling hinge model, it is rarely invoked to explain the associated footwall configurations. Our study area encircles the necking domain of the mid‐Norwegian rifted margin, where the Middle Jurassic–Early Cretaceous Klakk Fault Complex (KFC) directly separates the Frøya High from the Rås Basin. The Frøya High represents the eroded footwall of the KFC detachment fault system which records displacements of 20–40 km. Seismic mapping and well correlation across the Frøya High reveal how three erosional unconformities correspond to three laterally extensive top basement segments which follow the strike of the sinuous KFC. The segments differ in terms of dip, basement geomorphology and the composition and age of the sediments that rest unconformably on the top of basement. We attribute the associated cross‐cutting basement unconformities across the Frøya High to footwall uplift and back‐rotation during fluctuating relative sea‐level and repeated subaerial exposure during Middle Jurassic–Early Cretaceous times. We herein introduce a revised tectono‐sedimentary model for the evolution of the Frøya High, with significant implications for sediment (re‐)routing across the high during rifting. The model indicates that spatio‐temporal sediment distribution was ultimately controlled by the process of necking and evolution of the KFC. Our findings indicate a rolling hinge‐type evolution for the KFC and further suggest that the associated mechanisms may be more common in the necking domains of rifted margins than previously assumed.