Abstract The exploratory drilling of 200 wildcat wells along the NE Atlantic margin has yielded 30 finds with total discovered resources of c. 4.1×10 9 barrels of oil equivalent (BOE). Exploration has been highly concentrated in specific regions. Only 32 of 144 quadrants have been drilled, with only one prolific province discovered – the Faroe–Shetland Basin, where 23 finds have resources totalling c. 3.7×10 9 BOE. Along the margin, the pattern of discoveries can best be assessed in terms of petroleum systems. The Faroe–Shetland finds belong to an Upper Jurassic petroleum system. On the east flank of the Rockall Basin, the Benbecula gas and the Dooish condensate/gas discoveries have proven the existence of a petroleum system of unknown source – probably Upper Jurassic. The Corrib gas field in the Slyne Basin is evidence of a Carboniferous petroleum system. The three finds in the northern Porcupine Basin are from Upper Jurassic source rocks; in the south, the Dunquin well (44/23-1) suggests the presence of a petroleum system there, but of unknown source. This pattern of petroleum systems can be explained by considering the distribution of Jurassic source rocks related to the break-up of Pangaea and marine inundations of the resulting basins. The prolific synrift marine Upper Jurassic source rock (of the Northern North Sea) was not developed throughout the pre-Atlantic Ocean break-up basin system west of Britain and Ireland. Instead, lacustrine–fluvio-deltaic–marginal marine shales of predominantly Late Jurassic age are the main source rocks and have generated oils throughout the region. The structural position, in particular relating to the subsequent Early Cretaceous hyperextension adjacent to the continental margin, is critical in determining where this Upper Jurassic petroleum system will be most effective.

Abstract This Special Report comprehensively describes the stratigraphy and correlation of the Tertiary (Paleogene-Neogene) rocks of NW Europe and the adjacent Atlantic Ocean and is the summation of fifty years of research on Tertiary sediments by Chris King. His book is essential reading for all geologists who deal with Tertiary rocks across NW Europe, including those in the petroleum industry and geotechnical services as well as academic stratigraphers and palaeontologists. Introductory sections on chronostratigraphy, biostratigraphy and other methods of dating and correlation are followed by a regional summary of Tertiary sedimentary basins and their framework and an introduction to Tertiary igneous rocks. The third and largest segment comprises the regional stratigraphic summaries. Regions covered are the North Sea Basin, on shore areas of southern England and the eastern English Channel area, the North Atlantic margins (including non-marine basins in the Irish Sea and elsewhere) and the Paleogene igneous rocks of Scotland.

Abstract Seismic imaging beneath shallow (<5 km) Palaeogene basaltic volcanic successions on the Faroe–Shetland Margin is very challenging with conventional seismic methods. Consequently, the interpretational uncertainty that surrounds the sub-basalt structure of the region is a major source of exploration risk. This study uses gravity and magnetic data in conjunction with seismic data to map the sub-basalt structure of the Faroe–Shetland Basin and model the crustal architecture of this part of the Atlantic margin. Four crustal types are recognized using gravity data: oceanic, intruded transitional, stretched continental and normal continental crust. Map-based interpretation of the gravity and magnetic data helps redefine the basins, highs and faults in the region. The structural interpretation suggests that the boundary between normal and stretched continental crust is coincident with the long-lived left-lateral ‘West Shetland Shear Zone’, which partitioned strain during rifting of the margin. 2D/2.5D gravity and magnetic models are shown for two seismic profiles from the PGS FSB MegaSurveyPlus. The models suggest highly thinned crust, which was intruded by mafic magma beneath the Flett sub-basin, and an asymmetry to the rifting, which is consistent with a process of Wernicke simple shear.

Abstract The northern North Atlantic margins are classic examples of ‘volcanic’ rifted continental margins, where breakup was accompanied by massive volcanism. We discuss strategies used to obtain good intra- and sub-basalt seismic penetration so as to map the structure and the extruded and intruded igneous volume. We recorded deep penetration reflection data using a 12 000 m long single sensor (Q-)streamer and wide-angle seismic profiles with 85 4-component ocean bottom seismometers, along two transects across the Faroe and Hatton Bank continental margins in the NE Atlantic. Tomographic inversion of both compressional (P) and shear (S) wave crustal velocities are crucial in improving the reflection image and in constraining the nature of the sub-basalt lithology and the volume of extruded and intruded melt. Beneath the basalts, which reach 5 km thickness, is a low-velocity zone with P- and S-wave velocities characteristic of sedimentary rocks intruded by basalt sills. The underlying stretched continental basement contains abundant intrusive igneous sills on the rifted margin. Near the Faroe Islands, for every 1 km along-strike, 340–420 km 3 of basalt was extruded, while 560–780 km 3 was intruded into the continent–ocean transition (COT). Lower-crustal intrusions are focussed mainly into a narrow zone less than 50 km wide on the COT, whereas extruded basalts flow >100 km from the rift. Melt on the COT is intruded into the lower crust as sills which cross-cut the stretched and tilted continental fabric, rather than as ‘underplate’ of 100% melt, as has often been assumed previously. Our igneous thickness and velocity observations are consistent with the dominant control on the melt production being rifting above mantle with a temperature elevated above normal. The mantle temperature anomaly was up to 150°C above normal at the time of continental breakup, decreasing by c . 70–80°C over the first 10 Ma of seafloor spreading.