We use three‐dimensional (3D) seismic reflection and magnetic data to interpret and describe the 3D geometry of igneous dykes in the southern North Sea. The dykes were emplaced into Paleozoic and Mesozoic sediments and have a common upper termination in Early Tertiary sediments. We interpret the dykes to be part of the British Tertiary volcanic province and estimate the age of the dykes to be 58 Ma. The dykes are characterized by a narrow 0.5–2 km wide vertical disturbance of seismic reflections that have linear plan view geometry. Negative magnetic anomalies directly align with the vertical seismic disturbance zones and indicate the presence of igneous material. Linear coalesced collapse craters are found above the dykes. The collapse craters have been defined and visualized in 3D. Collapse craters have formed above the dyke due to the release of volatiles at the dyke tip and resulting volume loss. Larger craters have potentially formed due to explosive phreatomagmatic interaction between magma and pore water. The collapse craters are a new Earth analogue to Martian pit chain craters.

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This paper integrates interpretations of modern long-offset seismic datasets with potential field anomalies derived from dense grids of 2D gravity and magnetic data to present a regional-scale synthesis of Devonian, Carboniferous and Early Permian basin development beneath the UK Central North Sea. The 95 000 km2 study area has had little modern exploration for petroleum systems beneath the Upper Permian. Seismic interpretation and potential field modelling confirm that along the southern fringe of the Central North Sea, as in northern England, Lower Carboniferous basin development was strongly influenced by the disposition of granite-cored Lower Palaeozoic basement blocks – Farne Block, Dogger Block and Devil's Hole High. This study adds a previously unidentified WNW–ESE trending pre-Devonian basement block, the Auk–Flora Ridge, that exerted a profound control on Late Devonian to Mesozoic structural evolution of the south-Central North Sea. From the Flora Field, where it is overlain by relatively thick mid-Devonian to earliest Permian strata, the sub-Permian relief of this block becomes progressively shallower towards the NW. On its southern flank lies a parallel half-graben, akin to the Stainmore Trough in northern England, and interpreted as also containing several thousand feet of Lower Carboniferous strata. As indicated by the coal measures section in well 39/7-1, these strata are likely to include prolific source rocks, which have been modelled as being fully mature for oil generation in Quadrant 29. Potential field modelling extends this interpretation beyond the current seismic coverage, and suggests that Carboniferous to earliest Permian basin development in the Central North Sea was strongly influenced by an underlying Scottish–Norwegian SW–NE trending Caledonoid structural fabric. An earliest Permian, Lower Rotliegend unit thickens southwards towards the Auk–Flora Ridge, and rests unconformably on one or more undrilled NE–SW trending Carboniferous basins. Red-bed fluvial facies akin to those at Flora are likely to dominate the substantial post-Dinantian fill of these basins, but significant thicknesses of Westphalian coal-measure source rocks may also be present locally. As in central Scotland, the Dinantian strata underlying a widespread mid-Carboniferous unconformity in these basins are likely to contain further coal-measure intervals and local developments of oil-shale source rocks. These Westphalian and Dinantian source rocks are key elements of a Carboniferous petroleum system that remains largely untested across large areas of the Central North Sea.

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<p>The Earth’s oldest oceanic lithosphere preserved in-situ is in the eastern Mediterranean Sea. It can offer essential information on the oceanic plate evolution. Yet, its thickness and other properties have been difficult to determine by means of seismic imaging due to the high heterogeneity of the region. Here, we combine a large, new surface wave dataset with published wide-angle data in order to map the properties and lateral variability of the oceanic lithosphere, as well as the ocean-continent transition in the easternmost Mediterranean beneath the Levant Basin. We use stochastic joint inversion of broad band, phase-velocity dispersion measurements and seismic refraction P-wave velocity models to obtain 1-D, shear wave velocity models down to 300 km depth and compare the structure beneath the Ionian Sea and the Levant Basin. The thickness of the crust is about 16.4 ± 3 km and 22.3 ± 2 km beneath the chosen locations within the Ionian Sea and the Levant Basin, respectively. The Poisson’s ratio of about 0.32 and Vp/Vs of about 1.93 in the crystalline crust, yielded by the inversion, confirm the presence of oceanic crust beneath the Ionian Sea. The thickness of the Ionian oceanic lithosphere is around 180 km, whereas the continental lithosphere beneath the eastern Levant Basin is ~70 km thick, with low crustal Vp/Vs (~1.7) and Poisson’s (~0.24) ratios. According to 3-D shear wave velocity tomography using the surface wave data, the thickness of the oceanic lithosphere increases from the Triassic Ionian Sea towards the Permian-Carboniferous Libyan Sea and Herodotus Basin. Thicknesses of the Permo-Triassic oceanic lithosphere considerably larger than 100 km indicate that oceanic lithosphere can thicken by cooling substantially beyond the limits suggested by the plate cooling model. The transition from oceanic to continental lithosphere occurs at about 31°E in the crust, as indicated by magnetic and gravity measurements. The continental mantle lithosphere further to the east of this boundary is ~150 km thick beneath the westernmost Levant Basin, as indicated by shear wave velocity tomography and long wavelength gravity anomalies, and strongly thins eastward towards the area of the Levantine Coast and the Dead Sea Fault. The localization of the lithospheric deformation and crustal seismicity along the Dead Sea Fault correlates spatially with the thinning of the underlying continental lithosphere.</p><p><strong>Key words:</strong> surface wave tomography, wide angle seismic imaging, joint inversion, Vp/Vs and Poisson’s ratios, eastern Mediterranean, Oceanic Lithosphere, Continental Lithosphere, Dead Sea Fault.</p>