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Journal of the Geological Society

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Discussion on ‘An Eocene age for the proposed Silverpit Impact Crater' Journal, Vol. 165, 781–794

Watcombe, 92 Church Road, Winscombe, N. Somerset BS25 1BP, UK

*Corresponding author (e-mail: peter.o@which.net)

The first 20% of the full text of this article appears below.

A recent paper in the JGS (Wall et al. 2008) presented a reassessment of seismic data, predicated on the assumption that the structure known as the Silverpit Crater was formed by a meteorite impact (Stewart & Allen 2002). This speculative hypothesis is merely based on a perceived similarity between the morphology of the Silverpit crater and impact craters, and has no scientific support.

Stewart & Allen (2002) dated the geological event that formed the circular faults mapped at the top Chalk level by taking the lowest seismic reflector not affected by the faulting (apart from minor accommodation) to represent the latest date before which the faulting must have occurred. The unjustified assertion made now is that all coherent seismic events below the reflector CF (Wall et al. 2008, fig. 5) and top Chalk are sea-bed multiples, in particular the package MU (Wall et al. 2008). However, the time interval between the possible sea-bed multiple (a strong peak just above the base of the sequence) and the primary from which it may have been derived (the trough picked as HA) decreases up dip. There is no indication from other published profiles of the area that the sea depth changes rapidly enough to cause such convergence; nor could it be due to a migration effect because the actual dips (about 4.5°) are too shallow. Furthermore, coherent reflectors on other profiles (Wall et al. 2008, fig. 8, to the ESE of the crater; fig. 4, to the NW of the crater; . . . [Full Text of this Article]