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

The Northern North Sea (NNS) Permo-Triassic rift development is studied utilizing 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 seismic characteristics and thickness variations. Rifting initiated during the latest Permian and displayed significant spatial and temporal variation. In the Oygarden, Vette, Tusse, Brage and Ninian West faults, rifting occurred over a c. 10 Ma period whilst the Sogn Graben was active throughout the Triassic (over 50 Ma). The mapped distribution of Triassic sediments together with sedimentation rates calculated from well data show that regional subsidence prevailed across the entire basin, with enhanced subsidence within active half-grabens. 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, suggests regional subsidence. In the context of Atlantic opening, changes in fault orientation from N–S to NE–SW, suggested that the NNS Permo-Triassic rift constitutes an early failed rift event, with strain being accommodated by large NE–SW oriented faults in the North Atlantic region. NNS Permo-Triassic rift development defines the structural framework for subsequent Mesozoic rifting.