The Northeast Rockall Basin and its significance in the evolution of the Rockall-Faeroes/East Greenland rift system

Abstract

The newly mapped Northeast Rockall Basin lies between the Wyvile–Thomson Ridge and an ESE lineament extending from the onshore Ness Shear Zone. It contains a window in the early Tertiary flood-basalts through which a syn-rift sedimentary succession is imaged on seismic data. This succession was mapped in detail, calibrated to wells and boreholes drilled on the basin margins, and integrated with results from gravity, magnetic and backstrip modelling. Modelling and seismic stratigraphic analysis show that the Wyville–Thomson Ridge is a late Eocene to Oligo–Miocene fault-propagation fold, comprising basalt at the seabed and folded low density sediments within its core. Together with the co-linear Munkegrunnur and Ymir Ridges, this fold developed from positive inversion above a composite, crustal-scale ramp-flat detachment during N–S compression. Prior to mid-Tertiary inversion of the Wyville–Thomson Ridge, the basin may have formed a link between the main part of the Rockall Trough to the south and the Faeroe–Shetland and East Greenland rift systems to the north. Triassic, Jurassic and Early Cretaceous syn-rift sediments have been penetrated in the adjoining West Lewis Basin, and the Northeast Rockall Basin may contain sediments with a similar age range beneath the Tertiary flood basalts. Estimates from modelling allude to a resurgence of rifting from mid- to latest Cretaceous times, perhaps coeval with voluminous axial volcanism in the adjacent Rockall Trough. This episode of syn-rift volcanism, underlying the Paleocene volcanics, prohibits deeper seismic resolution to the south of the lineament in the main part of the Rockall Trough. The present-day bathymetry has resulted from a complex interaction between the loci of Mesozoic stretching, renewed post-basalt subsidence and major late Eocene to Oligo–Miocene inversion.