The aim of this study is to better understand how a layered basalt sequence affects the propagation of a seismic wave, which has implications for sub-basalt seismic imaging. This is achieved by the construction of detailed, realistic models of basalt sequences, using data derived directly from outcrop analogues. Field data on the surface roughness of basaltic lava flows were captured using terrestrial laser scanning and satellite remote sensing. The fractal properties of the surface roughness were derived, and it can be shown that the lava flow surface is fractal over length scales up to approximately 2 km. The fractal properties were then used to construct synthetic lava flow surfaces using a von Karman power spectrum, and the resulting surfaces were then stacked to create a synthetic lava flow sequence. P-wave velocity data were then added, and the resulting model was used to generate synthetic seismic data. The resulting stacked section shows that the ability to resolve the internal structure of the lava flows is quickly lost due to scattering and attenuation by the basalt pile. A further result from generating wide-angle data is that the appearance of a lower-velocity layer below the basalt sequence may be caused by destructive interference within the basalt itself.

New data are presented on the offshore part of the West Greenland volcanic succession, part of the North Atlantic Igneous Province located in southern Baffin Bay. The data were obtained from the Delta-1 hydrocarbon exploration well, drilled by Cairn Energy in 2011. Wireline log data were collected over the drilled section, providing information on the physical volcanology of the volcanic succession, and 23 sidewall cores were analysed for their geochemical composition.The well encountered 65 lava flows with a well-developed core and crust signature, typical for sub-aerial eruptions. Major and trace element data showed a good correlation with parts of the succession onshore West Greenland. The XRF major and trace element data allowed careful picking of samples for 40Ar/39Ar dating, and the main part of the sequence was found to be early Eocene in age. This coincides with the second main phase of volcanism in onshore West Greenland and is likely to be linked to the change in the tectonic regime in Baffin Bay at this time. This finding substantially expands the area of West Greenland affected by volcanism during the Eocene.

We present a new method for reconstructing flood basalt lava flows from outcrop data, using terrestrial laser scanning (TLS) to generate three-dimensional (3D) models. Case studies are presented from the Faroe Islands and the Isle of Skye (UK), both part of the North Atlantic Igneous Province (NAIP). These were analyzed to pick out lava flow tops and bases, as well as dykes, lava tubes, and sedimentary layers. Three-dimensional surfaces were then generated using modeling software, and 3D geological models constructed. Finally, the models were interrogated to give data on flow thickness and crust-to-core ratio. The aim of this research is to obtain quantitative data on the internal heterogeneity of a sequence of flood basalt lava flows, and to provide high-resolution information about flow geometries and volcanic facies variations in 3D. Lava flow sequences display complex stacking patterns, and these are difficult to understand from photos or outcrop observations. Laser scanning allows us to study inaccessible outcrops, while avoiding the perspective distortion in conventional photography. The data from this study will form parts of larger models of flood basalt provinces, which will be used to improve seismic imaging in areas of basalt cover, and aid our understanding of facies architecture in flood basalts.

Flood basalt successions cover many. potentially prospective sedimentary basins world-wide, and a few instances exist of intra-basalt petroleum discoveries. However, little is known about the architecture and rock propel-ties of the lava flows, intrusions and other lithologies that make up these successions. We present a simple, effective method of obtaining information from borehole data on the different volcanic facies within a flood basalt succession. Our aims are: (1) to provide a means of determining proportions of different volcanic facies without detailed examination of borehole data or where borehole data are limited; (2) to explore the relationship between onshore and offshore observations. The facies classification scheme providing the framework for this research includes tabular-classic lava flows, compound-braided lava flows, hyaloclastites and intrusions. We show how this scheme can increase our knowledge of the offshore succession and can be useful in hydrocarbon exploration.In the Faroe Islands, three different basalt formations display a range of facies onshore. Boreholes have been drilled through these, and several kilometres' depth of log data collected. The proximity of these boreholes to onshore observations allows the identification of different facies within the wireline log data. This work demonstrates that histograms of P-wave velocities provide an efficient method of identifying the different facies, and we also explore why these distributions are so different. When applied to borehole data from published ODP wells and one commercial well, it is possible to estimate proportions of the different volcanic facies using the velocity distributions alone.

Flood basalts in associated volcanic rifled margins, such as the North Atlantic Igneous Province, have a significant component of lavas which are preserved in the present clay in an offshore setting. A close inspection of the internal facies architecture of flood basalts onshore provides a framework to interpret the offshore sequences imaged by remote techniques such as reflection seismology. A geological interpretation of the offshore lava sequences in the Faroe-Shetland Basin, using constraints from onshore analogues such as the Faroe Islands, allows for the identification of a series of lava sequences which have characteristic properties so that they can be grouped. These are tabular simple flows, compound-braided flows, and sub-aqueously deposited hyaloclastite facies. The succession of volcanic rocks calculated in this study has a maximum thickness in excess of 6800 m. Down to the top of the sub-volcanic sediments, the offshore volcanic succession has a thickness of about 2700 m where it can be clearly identified across much of the area, with a further 2700 m or more of volcanic rock estimated from the combined gravity and seismic modelling to the north and west of the region. A large palaeo-waterbody is identified oil the basis of a hyaloclastite front/apron consisting of a series of clinoforms prograding towards the eastern part of the basin. This body was > 500 m deep, must have been present at the onset of volcanism into this region, and parts of, the water body would have been present during the continued stages of volcanism as indicated by the distribution of the hyaloclastite apron.