The movement of magma through the shallow crust and the impact of subsurface sill complexes on the hydrocarbon systems of prospective sedimentary basins has long been an area of interest and debate. Based on 3D seismic reflection and well data, we present a regional analysis of the emplacement and magmatic plumbing system of the Palaeogene Faroe-Shetland Sill Complex (FSSC), which is intruded into the Mesozoic and Cenozoic sequences of the Faroe-Shetland Basin (FSB). Identification of magma flow directions through detailed seismic interpretation of approximately 100 sills indicates that the main magma input zones into the FSB were controlled primarily by the NE-SW basin structure that compartmentalise the FSB into its constituent sub-basins. An analysis of well data shows that potentially up to 88% of sills in the FSSC are <40 m in thickness, and thus below the vertical resolution limit of seismic data at depths at which most sills occur. This resolution limitation suggests that caution needs to be exercised when interpreting magmatic systems from seismic data alone, as a large amount of intrusive material could potentially be missed. The interaction of the FSSC with the petroleum systems of the FSB is not well understood. Given the close association between the FSSC and potential petroleum migration routes into some of the oil/gas fields (e.g. Tormore), the role the intrusions may have played in compartmentalisation of basin fill needs to be taken fully into account to further unlock the future petroleum potential of the FSB.

Since the first seismic data acquired in the Parnaíba Basin during the1970s to the present day, there has been a technological advance that allowed to improve the seismic imaging of the subsurface data, as well as the geological knowledge of the basin, which has resulted in several gas discoveries. The petroleum system considered for these discoveries is defined as atypical, where the magmatism is a critical point for generation processes, as well as important to the processes of migration and preservation of hydrocarbons, becoming in this case, part of the elements of the system as trap and seal. The evolution of a magmatic event can compromise the petroleum system if the timing of the igneous intrusion is not adequate for the trap and the seal be ready before the hydrocarbon migration. This work aimed to analyze the importance of the two magmatic events in the basin previously described as Triassic-Jurassic and Cretaceous ages, to understand what their contribution to the processes of generation and preservation. For that, thousands of kilometers of seismic data were mapped, dozens of wells were studied and from them, a great set of geochemical data from intrusive rocks was collected, and a highresolution U-Pb (ICP-MS and TIMS) dating was performed on part of those samples previously analyzed Using wells drilled up to the Devonian age sequence it was possible to estimate at least 128,000Km 3 of volume of magma emplaced in this interval, which raises the largest volume estimation for the basin so far in about 20%. The geochronological analyses indicate for intrusions whitin Poti Formation, 217 ± 6My to the well 1-OGX-114-Ma and 192 ± 4My to the well 1-OGX-22-MA and for rocks intruded whitin Tiagua Formation 201.22 ± 0,11My to the well 1-OGX-22-MA, which is an event related to Penatecaua magmatism of the Triassic / Jurassic limit, with no association to the Cretaceous event. The geochemical analyses from the subsurface did not allow to separate Mosquito and Sardinha formations into geographical domains as postulated by several authors. Finally, based on the data obtained and the seismic interpretation, an events chart was proposed for the plays already proved in the basin, being defined that the critical point on the traps and seal is related to the Triassic / Jurassic magmatism according to the geochronological analyses, being the Cretaceous magmatism, possibly associated with the tectonism that occurred during the breakup of the Gondwana and possibly responsible for open traps already formed.

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The movement of magma in sedimentary basins often occurs through an extensive and interconnected complex of sills. Field-, modelling-, and seismic reflection-based studies indicate that the emplacement of shallow-level sills is commonly accommodated by the formation of forced folds, which may be expressed at the free surface and onlapped by younger strata. If the age of these onlapping strata can be constrained, important insights can be gained into the timing of magma emplacement and associated regional, tectono-magmatic events. Previous studies have focused on isolated intrusions that are overlain by an individual forced fold formed during a single tectono-magmatic event. However, the structure and evolution of 'compound' folds developed above stacked, interconnected sills, and what they may reveal about polyphase intrusive events has not been investigated. In this study, we use 3D seismic reflection data from the Irish Rockall Basin, offshore western Ireland, to constrain the structural style and emplacement history of a sill complex that contains 82 seismically resolved intrusions. Individual forced folds, <41 km 2 in plan view and with mean fold amplitudes of 111 m, are developed above single intrusions. However, where sills are stacked, broader (100-244 km 2 ), larger amplitude (mean of 296 m) compound folds occur following the coalescence of individual folds. Stratigraphic onlap and truncation observed within the folds throughout the Palaeocene-to-Middle Eocene succession, indicates that emplacement and forced folding initiated at the end Maastrichtian and lasted for ca. 15 Ma, before ceasing near the end of the Ypresian. We demonstrate (i) intrusion-induced forced folds evolve dynamically and can form broad areas of sustained local uplift, and (ii) that the formation of sill complexes within the upper crust may occur over prolonged time periods. This study also highlights the importance of seismic reflection data to understanding the structural style and age relationships between igneous systems.