The geophysical expression of Tertiary dykes in the southern North Sea

Brown, G. A.; Platt, Nigel H.; McGrandle, A.

doi:10.3997/1365-2397.1994011

Cited by 23 publications

(18 citation statements)

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“…Exploration well 43/25-1 passed close to the limit of the feature, but no lithologies other than typical Tertiary siliciclastics are recorded on the composite and mud logs. Paleogene igneous dykes have in fact previously been interpreted from geophysical data in the southern North Sea (Brown et al, 1994; see also northwest-southeast-trending lineations in the top right part of Fig. 1B).…”

Section: Discussionsupporting

confidence: 53%

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3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea

Stewart

Allen²

2005

Geol Soc America Bull

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The fi rst comprehensive mapping of the Silverpit multi-ringed crater is presented, based on fi ve adjoining 3D seismic surveys that together provide 78% (216 km 2 ) areal coverage of the structure with spatial and depth sampling of ~10 m. The top Cretaceous surface shows an excavated crater 3 km in diameter surrounded by 10-15 concentric ring structures out to a radius of 9.4 km. Seismic sequence stratigraphy and drilled wells indicate the lower age bound is a disconformity spanning 74-54 Ma. The upper bound is Eocene termination of concentric ring fault growth (ca. 45 Ma). The inner rings are extensional faults defi ning rotated fault blocks that would be considered part of the crater in an impact structure interpretation, giving a fi nal impact crater diameter of 8 km. The outer rings show a surprising variation in style, from graben in the west to compressional structures in the east. This may be explained by postcratering gravity spreading on easterly dipping intra-Cretaceous detachments. Within the crater, the top Cretaceous seismic refl ector is disrupted and blocky, but defi nes a central uplift with a slight crestal depression. Below this uplift, the prominent base Cretaceous seismic refl ector shows Jurassic strata rising into a cone 300 m high and 1 km wide, characterized by radial faults. This central uplift within the crater may structurally balance the inner ring fault blocks via a slumping model, but we also identify low seismic velocity in the uplifted Jurassic, so fracturing may have contributed to growth of the central peak. At a radius of 2.5 km, base Cretaceous shows a dish-shaped depression that we interpret as marking either the extent of slumping toward the crater at this structural level or the limit of shockwave-induced porosity collapse. Seismic refl ectors above the top Cretaceous excavated crater show differential com-paction during the Eocene, accommodated by drape structure plus two conical faults that defi ne narrow ring graben and represent the fi nal phase of crater-related tectonics.

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Section: Discussionsupporting

confidence: 53%

“…The concentric ringed feature is a unique structural style in the basin. Northwest-southeast-trending lineations in the northeast part of the map may be Tertiary igneous dykes(Brown et al, 1994).…”

mentioning

confidence: 99%

3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea

Stewart

Allen²

2005

Geol Soc America Bull

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“…Hence apparent exhumation in the SNS (Fig. 4b) is probably influenced by salt growth structures (Brown et al 1994). However, salt growth structures would only be witnessed by relatively localized noise superimposed on the more widespread trends of exhumation of the Cleveland Hills/Sole Pit inversion axes and regional, SNS-wide exhumation being considered here.…”

Section: Apparent Exhumationmentioning

confidence: 95%

Regional Tertiary Exhumation in and around the United Kingdom

Hillis¹

1995

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Sonic velocities in the Upper and Middle Chalk, the Bunter Sandstone and the Bunter Shale were used independently to quantify apparent exhumation (amount of missing section) in the UK Southern North Sea (SNS). Apparent exhumation results derived from these units are statistically similar. The consistency of results from chalks, shales, and sandstones in the UK SNS, and in other areas (Inner Moray Firth and Celtic Sea/South-Western Approaches), suggests that, at a formation and regional scale, burial-depth is the primary control on velocity (and porosity) in these units, and validates the use of lithologies other than shale in maximum burial-depth determination. The consistency of apparent exhumation results from units of Early Triassic to Late Cretaceous age suggests that Tertiary exhumation was of sufficiently great magnitude to mask any earlier Mesozoic periods of exhumation, and that maximum Mesozoic-Cenozoic burial-depth was attained prior to Tertiary exhumation.The analysis of sonic velocities, apatite fission tracks, vitrinite reflectance, normalized drilling rate and clay mineral diagenesis all suggest that there was a regional component of approximately I km of exhumation during Tertiary times, which affected structurally uninverted areas in and around the UK. The widely-recognized inversion-related exhumation is superimposed on regional Tertiary exhumation. Regional Tertiary exhumation need not have been contemporaneous with structural inversion. Further refinement beyond Tertiary age is not possible from the sonic velocity data. Regional exhumation, however, is most likely to be associated with regional Palaeocene or Oligocene/Miocene unconformities.The evidence for regional exhumation implies that there was a pre-exhumational phase of burial (during which the eroded sedimentary rocks were deposited). Exhumation and prior burial associated with the regional Tertiary event need to be incorporated in aspects of basin analysis such as sediment decompaction and diagenetic and maturation modelling, and can, for example, account for the maturity of the Carboniferous of the onshore East Midlands Shelf, and the Lias exposed on the north coast of Somerset. The regional, Tertiary tectonic uplift associated with exhumation must have had a thick-skinned origin, and, in areas where there is no evidence for significant Tertiary igneous activity, a decoupled, two-layer model of lithospheric compression is invoked to account for the subsidence/uplift patterns of both inverted and uninverted areas.

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“…Dykes have rarely been interpreted using 3D seismic reflection data due to problems in imaging vertical bodies in the subsurface. In the southern North Sea dykes have only previously been interpreted using 2D seismic reflection data and magnetic modelling (Kirton & Donato, 1985; Brown et al , 1994). In this paper we use 3D seismic reflection data to investigate dykes in the southern North Sea.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2010

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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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The geophysical expression of Tertiary dykes in the southern North Sea

Cited by 23 publications

References 0 publications

3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea

3D seismic reflection mapping of the Silverpit multi-ringed crater, North Sea

Regional Tertiary Exhumation in and around the United Kingdom

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

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