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2018 AAPG International Conference and Exhibition

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Rifting History and Magmatism West of Britain

Abstract

Volcanic rifted margins are characterised by voluminous intrusive and extrusive magmatism, typically emplaced over short timescales preceding and during continental breakup. Although traditionally such margins have been considered largely unprospective, interest has increased in recent years since the volcanic accumulations are often situated over pre-existing sedimentary basins, which may have proven petroleum systems in areas outwith and under the volcanic cover. Current views of such volcanic systems are commonly based on broad regional studies and often therefore limited by the availability of data. However, and increasing amount of high quality seismic data in the West of Britain region, combined with recent wells (e.g. Brugdan, Lagavulin) penetrating several kilometres of Palaeogene basaltic lava, allow us to study the link between magmatic stratigraphy and basin evolution. The North Atlantic Igneous Province (NAIP) has been extensively studied where it outcrops onshore, in Northern Ireland, western Scotland, Faroe Islands, Iceland, and east and west Greenland; however, the offshore succession, which represents the bulk of the NAIP, is less well constrained. Detailed understanding on a localised basin scale is available where wells have penetrated the volcanic succession, but with only 43 such wells across the NE Atlantic Margin, the margin-wide volcanic stratigraphy is only broadly understood. Hydrocarbon discoveries in association with the lava field (e.g. Rosebank and Cambo in the Faroe-Shetland Basin, Benbecula in the Rockall Basin) indicate the existence of petroleum systems, resulting in renewed interest in the prospectivity of the basins to the west of Britain. However, without a detailed volcanic stratigraphic framework and an understanding of how this relates to rifting, a major challenge in the regional correlation of strata still exists. Recent work (Hole et al. (2015) and Millet et al. (2015)) indicate that there is cyclicity in the style and composition of magmatic activity, suggesting a possible underlying genetic control, which should be manifested in the lava field stratigraphy. This study integrates regional high quality seismic data, detailed well control through basalt subcrop west of Britain, and biostratigraphic and geochemical control, to interpret key volcanic horizons across the region, in order to improve detailed understanding of the volcanic stratigraphy and its relationship to the rift-to-drift tectonics of the NE Atlantic.