3D seismic imaging of a Tertiary Dyke Swarm in the Southern North Sea, UK

Abstract

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.

Lateral Magma Flow in Mafic Sill‐complexes

“…The lack of dike imaging, which is attributed to the low amount of acoustic energy that reflects back to the surface off the subvertical wall of a dike, therefore biases seismic-based interpretations of plumbing systems. The role of dikes within sill complexes can, however, be investigated from (1) field analyses (e.g., Muirhead et al, 2014); (2) the interpretation of subvertical chaotic zones of reflection in seismic data as dikes (Thomson, 2007;Wall et al, 2010); and (3) the mapping of magma flow patterns in sills to identify potential dike feeders (see following). Through the careful application of these techniques and by comparison to field observations, seismic data can be used to delimit magma plumbing systems in more detail than field or other geophysical techniques.…”

An integrated geophysical study of the Beattie Magnetic Anomaly, South Africa

“…These regions are made up of a complex array of elongate geological units and zones of intense shear that can change over less than a kilometre and are not easily delimited. We therefore assume that the entire zone would be characterised by complex reflectivity patterns (Wall et al, 2009;Welford and Clowes, 2006), and that only larger shear zones would be resolvable as high conductivity anomalies on the MT data. For the Williston anomaly it appears that the zones of complex reflectivity do correlate with conductive zones, which we assume to be shear zones within the amphibolite facies Mzumbe terrane.…”

An integrated subsurface analysis of clastic remobilization and injection; a case study from the Oligocene succession of the eastern North Sea

“…Sand injectites are very well-known from the Paleogene North Sea succession, while Tertiary dyke swarms only recently have been reported from the Southern North Sea (Wall et al, 2010). Lower Permian igneous intrusions, however, occur across much of the Norwegian-Danish Basin (e.g.…”