A Triassic chronostratigraphic and palaeogeographic framework for the Utsira High area, northern North Sea: Reconstructing a basin‐scale drainage divide
The Triassic succession of the northern North Sea comprises a series of interbedded sandstones, mudstones and conglomerates deposited under a fluctuating arid to semi‐humid climate regime, which are often difficult to correlate regionally due to differing lithostratigraphic schemes and poor age control. Despite existing regional studies on the Triassic of the North Sea, the corresponding fluvial stratigraphy in the Utsira High area has been largely overlooked. Utilising a recently published structural framework, we analyse data from 242 wells and use biostratigraphic data together with interpreted lithofacies associations to reconstruct the evolution of depositional environments and palaeogeography of the Utsira High and surrounding area. By developing well correlation and palaeogeographic maps, we divide the area in three provinces with separate evolution and review the chronostratigraphic framework of the Triassic across the region, emphasising the role of the Utsira High in providing sediments to adjacent basins, and its role as a drainage divide between the central and northern North Sea throughout the Triassic. Our results suggest that the Utsira High separates two provinces during the Triassic: a SE one dominated by large distributive fluvial systems (DFS) sourced from the Fennoscandia region and a NW with local sediment input sourced directly from the Utsira High, creating a drainage divide for E‐W sediment connectivity. We also suggest that the Hardangerfjord valley was the likely source area for large DFSs throughout the Triassic in the study area. We highlight stratigraphic differences in the Triassic succession between the Utsira High region and the northern and central North Sea and suggest how these can be resolved across the region. This work will help advance predictive models of rift basin development, by discussing CO 2 storage potential and hydrocarbon prospectivity across the area, and establishing a foundation for future exploration and development of Triassic units in the North Sea.