A series of offshore intra-basinal igneous centres have been documented across the North Atlantic Igneous Province including the United Kingdom, Ireland and Greenland. However, inconsistent cross-border terminology implies that similar features are not present in the Norwegian offshore which, in turns, leads to misperceptions of cross-border geological differences. This manuscript presents evidence for a series of Norwegian igneous centres and suggests a consistent non-genetic cross-border terminology. In the Møre Basin, several igneous centres sit close to the continent ocean boundary (COB) which have previously been identified as seamounts and/or ‘outer highs’. To provide cross-border consistency these features are consolidated under umbrella terms; igneous centres or volcanic fissures. Further centres are likely present within the Møre Basin (east of the COB) where 3D seismic data were not available. In the Vøring Basin two new igneous centres, one intrusive and one extrusive, are identified within the continental domain. Additionally, a possible deep magmatic upwelling associated with the regionally significant T-Reflector is identified. These igneous centre end-members represent the complexity of the magmatic plumbing across the Norwegian margin. With further data it is likely that further igneous centres will be identified offshore mid Norway.

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Sills are important components of magmatic plumbing systems due to their role as storage features of magma. Previous studies have indirectly investigated sill propagation and architecture by using laboratory experiments, remote sensing, modelling and theory. These studies, however, often struggle to include the complexity of natural systems, which often includes strong interplay between host and intruder. To elevate the importance of host rock and magma interaction, we present the results from a study of combined UAV- and outcrop datasets from world-class 1.3 km long, 30 m high 3D exposure of a 12 m thick alkaline trachybasalt sill in Mussentuchit Wash, San Rafael Swell, Utah. The sill intruded into Jurassic, dominantly sandy, sedimentary rocks. Results of this study shows that the propagation of the Mussentuchit Wash Sill features both fracture-driven- and complex non-brittle fluid interaction emplacement, which are strongly influenced by local sedimentology and presence of porewater. Segregated melt emplaced progressively within the sill during emplacement is used to document the evolution of sill inflation. The fracture-driven propagation is initiated along sedimentary discontinuities through hydrofracturing, while the non-brittle fluid interaction is caused by the presence of local porewater within the sedimentary host rocks. This suggests that local lithology may exert strong control on the architecture and morphology of sills in sedimentary basins. Supplementary material: The 3D model of the Mussentuchit Wash Sill (e.g. Figure 4) will be published on V3Geo.com (currently open-access database for 3D models) when the manuscript is published. Uninterpreted images of the sill will be published on figshare and are included as DR1.

The sub-basalt domain of the Norwegian continental shelf (NCS) is one of the last remaining hydrocarbon exploration frontiers in Europe. While there is an established geological and tectonic framework, little has been published that addresses the remaining hydrocarbon exploration risks/uncertainties. Unlike the Faroe Shetland Basin and Rockall Trough, at the time of writing, there are currently no industry-drilled sub-basalt well penetrations on the Norwegian continental shelf. Numerous potential Mesozoic sub-basalt hydrocarbon plays exist on the NCS but, due to the lack of industry-drilled sub-basalt penetrations, there is a perceived large exploration risk. By using cross-border analogues, basin modelling workflows and integration of available seismic data the main uncertainties across the NCS are outlined including charge timing, structural definition, and details of reservoir presence. Generically the Late Cretaceous and Middle Jurassic intervals are potential plays which may be present on the Norwegian Margin. However, there is considerable uncertainty on their depth and preservation. Although significant challenges and uncertainties remain, the authors believe that the integration of well results, consideration of basin modelling driven heat flow estimates and new 3D seismic data may open sub-basalt opportunities for a new exploration frontier on the NCS. Thematic collection: This article is part of the New learning from exploration and development in the UKCS Atlantic Margin collection available at: https://www.lyellcollection.org/topic/collections/new-learning-from-exploration-and-development-in-the-ukcs-atlantic-margin