Controls on variations in rift structure, fault development and strain distributions within the South Viking Graben, northern North Sea

Continental rifting generates complex normal fault systems that record basin deformation and controls syn-rift depocentre geometry and stratigraphy. We investigate the structural evolution of a Middle to Late Jurassic fault array along the South Viking Graben and the western flank of the Utsira High, northern North Sea, using high-resolution 3D and 2D seismic reflection datasets, calibrated with borehole data. We constrain the spatio-temporal development of normal faults and associated depocentres through quantitative kinematic analysis and time-thickness (isochron) mapping. We identify three rift stages: (1) an early syn-rift phase (Toarcian/Aalenian–Bathonian) with deformation focused on the southern Vana Fault with minimal activity further north; (2) a phase of distributed deformation (Bathonian–Middle Callovian) characterized by the activity and then death of numerous intra-basinal faults; and (3) a phase of localised deformation (Callovian–Berriasian), where strain was focused on NE–SW-striking, E-dipping border faults. Along-strike structural variability defines three provinces: i) a W-tilted, N–S- to NE-SW-trending, half-graben with salt-detached intrabasinal faulting in the south; ii) a central transfer zone defined by a moderately symmetrical, N-S-trending graben that accommodates a ∼25 km westward step of the basin-bounding master fault; and iii) a northern province characterized by N-S-striking, E-dipping, domino-style faults. This variability is governed by pre-existing, basement-involved shear zones, pre-rift distribution of Zechstein Supergroup salt and mechanical influence of the adjacent Permo-Triassic Stord Basin. Overall, south-to-north migration of peak fault activity occurred, linking local fault kinematics with the regional development of the North Sea and North Atlantic rift margin.