The Influence of Structural Inheritance and Multiphase Extension on Rift Development, the NorthernNorth Sea

Abstract

The northern North Sea rift evolved through multiple rift phases within a highly heterogeneous crystalline basement. The geometry and evolution of syn‐rift depocentres during this multiphase evolution, and the mechanisms and extent to which they were influenced by pre‐existing structural heterogeneities remain elusive, particularly at the regional scale. \n \nUsing an extensive database of borehole‐constrained 2D seismic reflection data, we examine how the physiography of the northern North Sea rift evolved throughout late Permian‐Early Triassic (RP1) and Late Jurassic‐Early Cretaceous (RP2) rift phases, and assess the influence of basement structures related to the Caledonian orogeny and subsequent Devonian extension. During RP1, the location of major depocentres, the Stord and East Shetland basins, was controlled by favorably oriented Devonian shear zones. RP2 shows a diminished influence from structural heterogeneities, activity localises along the Viking‐Sogn graben system and the East Shetland Basin, with negligible activity in the Stord Basin and Horda Platform. The Utsira High and the Devonian Lomre Shear Zone form the eastern barrier to rift activity during RP2. Towards the end of RP2, rift activity migrated northwards as extension related to opening of the proto‐North Atlantic becomes the dominant regional stress as rift activity in the northern North Sea decreases. \n \nThrough documenting the evolving syn‐rift depocentres of the northern North Sea rift, we show how structural heterogeneities and prior rift phases influence regional rift physiography and kinematics, controlling the segmentation of depocentres, as well as the locations, styles and magnitude of fault activity and reactivation during subsequent events.