The Triassic Rift Event in the Northern North Sea, a New Tectonic Model for the Utsira High Area

ABSTRACT The North Sea rift basin is a prolific oil and gas province and is an active area of study for CO 2 sequestration. Despite the economic importance of the North Sea basin, the timing and nature of rift initiation and subsequent development are poorly constrained. To address this issue, we focus on reconstructing the spatial and temporal distribution of fault activity from the late Permian to late Triassic across the Utsira High area, a key basement high in the centre of the North Sea basin, providing a framework for understanding Northern North Sea rift development and influence on subsequent Mesozoic rift phases. Results indicate rifting initiation in the latest Permian times with continuous but spatially variable extension through the Triassic and early Jurassic. Three main phases are recognised: (i) late Permian, with widespread extension across the region and development of the Utsira High; (ii) Early Triassic, characterised by localised extension across the Horda Platform, Stord Basin and Åsta Graben; (iii) Middle to Upper Triassic phase, where extension is still localised across the eastern rift shoulder, with minor faults forming across the South Viking Graben; and (iv) Jurassic continuation of rifting, with faulting localised across the Viking Graben and a decline in activity during the Cretaceous. Combined with a new model for the tectonic evolution and palinspastic reconstruction of the region, this research builds on previously published work across the area, advancing the understanding of the Triassic tectonic history of the Utsira High region.