Abstract: The NE Atlantic region evolved through several rift episodes, leading to break-up in the Eocene that was associated with voluminous magmatism along the conjugate margins of East Greenland and NW Europe. Existing seismic refraction data provide good constraints on the overall tectonic development of the margins, despite data gaps at the NE Greenland shear margin and the southern Jan Mayen microcontinent. The maximum thickness of the initial oceanic crust is 40 km at the Greenland–Iceland–Faroe Ridge, but decreases with increasing distance to the Iceland plume. High-velocity lower crust interpreted as magmatic underplating or sill intrusions is observed along most margins but disappears north of the East Greenland Ridge and the Lofoten margin, with the exception of the Vestbakken Volcanic Province at the SW Barents Sea margin. South of the narrow Lofoten margin, the European side is characterized by wide margins. The opposite trend is seen in Greenland, with a wide margin in the NE and narrow margins elsewhere. The thin crust beneath the basins is generally underlain by rocks with velocities of >7 km s −1 interpreted as serpentinized mantle in the Porcupine and southern Rockall basins; while off Norway, alternative interpretations such as eclogite bodies and underplating are also discussed.

Abstract: Seismic refraction data and results from receiver functions were used to compile the depth to the basement and Moho in the NE Atlantic Ocean. For interpolation between the unevenly spaced data points, the kriging technique was used. Free-air gravity data were used as constraints in the kriging process for the basement. That way, structures with little or no seismic coverage are still presented on the basement map, in particular the basins off East Greenland. The rift basins off NW Europe are mapped as a continuous zone with basement depths of between 5 and 15 km. Maximum basement depths off NE Greenland are 8 km, but these are probably underestimated. Plate reconstructions for Chron C24 ( c. 54 Ma) suggest that the poorly known Ammassalik Basin off SE Greenland may correlate with the northern termination of the Hatton Basin at the conjugate margin. The most prominent feature on the Moho map is the Greenland–Iceland–Faroe Ridge, with Moho depths >28 km. Crustal thickness is compiled from the Moho and basement depths. The oceanic crust displays an increased thickness close to the volcanic margins affected by the Iceland plume.

Abstract: Over the last few decades, a number of wide-angle seismic experiments have been conducted in the Faroe–Shetland Channel area with the objective of mapping the crustal structure. However, the volcanic rocks covering most of the area present a challenge for the imaging of sub-basalt structures. The results of the seismic studies are consistent in describing the Faroe–Shetland Channel as thinned continental crust and in establishing the presence of sub-basalt sediments. However, the various datasets often show differences in depth to crystalline basement and to the Moho. This paper presents a review of the velocity models in the Faroe–Shetland Channel and analyses the differences at line intersections. Down to top basalt the models are fairly consistent, while there are deviations of up to 1 km s −1 in basalt velocities and sub-basalt sediment velocities, 2 km in basalt thickness, 3.2 km in depth to crystalline basement, and 11.7 km in depth to the Moho.

Abstract The development of methods of seismic imaging beneath basalts is still hindered by a lack of knowledge about the elastic properties of basaltic sequences and the degree of three-dimensional heterogeneity. The SeiFaBa project (2002–2005) is funded by the Sindri Group as part of the programmes for licensees within the Faroese area and will attempt to address these issues. The Glyvursnes-1 well was drilled by SeiFaBa through the Upper Basalt Formation outside Tórshavn in 2002. A full core and numerous wireline logs were acquired from the 700 m deep well. During the same operations, the existing 660 m deep Vestmanna-1 well drilled mainly into the Middle Basalt Formation was reamed and logged. The two wells are central to a number of closely co-ordinated experiments, which are all targeted at creating models for seismic wave propagation through a succession of basalt by combining detailed analysis at core, log and seismic scales. Data from these two wells, in combination with the data for the Lopra-1 well drilled into the Lower Basalt Formation, will give new stratigraphic and petrophysical control of the Lower, Middle and Upper Basalt formations on the Faroes. The seismic programme was initiated in 2002 and the main acquisition was carried out during 2003. The well site at Glyvursnes gives optimal conditions for combining VSP, offset-VSP and surface seismic experiments both onshore and offshore and the seismic effects of a nearby near-vertical shear zone can be studied in detail. Preliminary analysis of log data from the Lopra-1 well suggests that the acoustic properties of these basalt flows are mainly controlled by porosity of a stiff matrix filled with clay minerals and water. Further studies will allow for explanations of the sonic response of basalt in terms of physical and compositional properties and a better understanding of the seismic signatures of flood basalt successions.

ABSTRACT A novel quantitative inverse procedure for modeling the self-consistent evolution of salt and sediments is applied to investigate and compare the dynamical evolution of two salt structures from the North Sea and Gulf of Mexico, respectively. Control information in the form of the present day salt shape, salt volume, and the sedimentary bed locations around the salt, is used to constrain both the paleo-structure and stratigraphy of the salt and sediments. Control criteria can be any combination of 1) required geometries of the depositional surfaces through time, 2) required compaction history of the sediments, and 3) required salt volume variations through time. The self-consistent combined evolution of salt and sediments then permits an evaluation of the inter-relationship between salt movement, including “mushroom” cap and rim syncline developments, and sedimentary bed distortions. The present-day observed sedimentary bed geometries suggest that the evolutions of the structures investigated follow different paths through time; the significant differences found might not otherwise have been uncovered so readily without quantitative investigation. Armed with the dynamically self-consistent behavior, the high contrast in thermal conductivity between salt and sediments is then used to evaluate the thermal focusing of heat by the evolving salt/sediment system−of interest in evaluating hydrocarbon potential. The structural and thermal evolutionary histories are important for lowering risk in the search for oil and gas plays associated with salt structures. Furthermore, the different evolution histories provide insights into the influences of the depositional and tectonic regimes upon salt structure growth in the two basins.

ABSTRACT Quantitative basin analysis techniques were used to study the structural history of Jurassic, Cretaceous, and Tertiary sediments in northern Louisiana, based on geological and geophysical data from 140 petroleum wells and 8 seismic lines. The uniformly distributed wells provide good control, on the regional scale, of the present day geometries of Cretaceous and Tertiary sediments. Seismic lines were used to identify deep Jurassic sediments, especially the Louann salt. The structural history in northern Louisiana can be separated into five major stages: (1) Jurassic rifting and extension; (2) Late Jurassic and Early Cretaceous subsidence; (3) mid-Cretaceous upwarping and westward tilting; (4) Late Cretaceous and Early Tertiary subsidence; and (5) Tertiary flexural downwarping. The regional tectonics and structures impact both the regional sediment deposition and lithology distribution. The hydrocarbon generation, migration and accumulation can be tied to the structural and depositional features. The dynamic salt movement associated with structural evolution could enhance the likelihood of hydrocarbon accumulations in sediments around salt diapirs.