Permo-Triassic rift development in the Northern North Sea: an age-constrained tectonostratigraphic framework for the Triassic succession of the Tampen Spur area and adjacent regions

We studied Permo-Triassic rift development in the Northern North Sea using 2D and 3D seismic reflection datasets, gravity data, wireline logs and palynological data. Tectonostratigraphic analysis of four key sub-basins identified six age-constrained packages, differentiated by their seismic characteristics and variations in thickness. Rifting initiated during the latest Permian and displayed significant spatial and temporal variations. Rifting occurred over a c .10 Ma period in the Øygarden, Vette, Tusse, Brage and Ninian West faults, whereas the Sogn Graben was active throughout the Triassic (over a period of 50 Ma). The mapped distribution of Triassic sediments, together with the sedimentation rates calculated from well data, show that regional subsidence prevailed across the entire basin, with enhanced subsidence within the active half-graben. In the Tampen Spur area, the lack of tectonic activity throughout the Triassic period, coupled with an average sediment accumulation rate of 35 m Ma −1 , suggests regional subsidence. In the context of the opening of the Atlantic Ocean, changes in fault orientation from north–south to NE–SW suggest that the Northern North Sea Permo-Triassic rift constitutes an early failed rift event, with strain being accommodated by large NE–SW-oriented faults in the North Atlantic region. Permo-Triassic rift development in the Northern North Sea defined the structural framework for subsequent Mesozoic rifting.