An Eocene age for the proposed Silverpit Impact Crater

Abstract

Three-dimensional seismic analysis is used to describe the detailed morphology of the Silverpit crater, a proposed marine impact crater located in the southern North Sea, UK. We examine and constrain for the first time the geometry, extent and age of the post-crater sediment units that define the crater fill. A circular bowl-shaped depression has been mapped and interpreted to represent the upper limit of impact deformation and the geometry of the crater at the end of cratering processes. Reflections exhibit a parallel onlap fill onto the bowl-shaped crater floor, indicating that accommodation space was created instantaneously without any contemporaneous sedimentation. Using regional lithostratigraphic markers constrained by microfossil and calcareous nannofossil analysis, we have dated the first onlapping sediments onto the crater. The age of the onlapping sediments allows us to constrain the crater formation to be Middle Eocene in age. This date is c. 10-15 Ma younger than the previous ascribed age for the crater formation and rules out the Silverpit crater as a K-T boundary impact. The age of crater formation considerably predates regional folding and accompanying salt flowage, effectively ruling out a salt withdrawal origin for the Silverpit crater.

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

“…Owing to the lack of detailed well control we cannot date these onlapping sediments with accuracy. We can observe that the date is probably Late Palaeocene–Early Eocene (58–54 Ma) due to the fact that the onlapping sediments lie close to the Cretaceous Tertiary boundary where early Eocene age tuffs have been found in regional (within 20 km) hydrocarbon exploration wells and that similar Late Palaeocene igneous activity has been well documented in the Vøring and Møre basins (Lott & Knox, 1994; Svensen et al , 2003; Jamtveit et al , 2004; Planke et al , 2005 and Wall et al , 2008) (Fig. 6).…”

Geophysical Studies of Impact Craters

“…The structure is located approximately 130 km off the east coast of England in the North Sea, is about 20 km in diameter and buried approximately 600 m below surface. Silverpit is probably an impact crater, as other explanations for the structure, such as salt withdrawal (Thomson, 2004;Underhill, 2004), are inconsistent with the observation of structural uplift at the centre of the feature, the age of the structure and the circular deformation pattern (Stewart and Allen, 2004;Wall et al, 2008). Industry-quality 3D seismic reflection data have exceptional spatial resolution, and this means that 3D geometries and structures can be mapped across the crater and placed in a structural and stratigraphic context.…”

“…Valhalla, Callisto) are closely spaced ridges and grabens, with inward-and outward-facing asymmetric scarps (see Chapter 1). Silverpit has since been interpreted as mid-Eocene in age (Wall et al, 2008), which, if correct, may mean that rings were never a topographic feature of this crater. Grabens are absent or less topographically pronounced in the suite of reflections between the top Cretaceous reflector and the midEocene reflection that is interpreted as the post-impact surface by Wall et al (2008) (Fig.…”

“…Offsets in the horizon are observed as continuous rings that are shown to be extensional fault-bounded grabens in (b). (b) A 2D vertical time slice through the 3D seismic reflection volume that crosses through the centre of the Silverpit structure (fromWall et al (2008)). The horizontal bar is 1 km and the vertical bar is 0.5 s two-way travel-time (∼1 km).…”

Development and post-depositional deformation of a Middle Eocene deep-water sandy depositional system in the Sørvestsnaget Basin, SW Barents Sea

“…Thus, the possibility of a bolide impact trigger for the Middle Eocene phase of sand intrusions in the study area is weak, although it cannot be ruled out completely. Contemporaneous seismicscale sandstone intrusions are recognized in the Norwegian North Sea (Huuse and Mickelson, 2004), and suggested to have been triggered by bolide impact (Cartwright, 2010) judged from the presence of the Middle Eocene Silverpit Crater in the southern North Sea (Wall et al, 2008). It is a possibility that the Silverpit impact has played a role in triggering intrusions in both areas.…”