The Origin of the "Silverpit Crater" - the Case for Salt Withdrawal

Conway, Zana K.¹, John R. Underhill² (1) The University of Edinburgh, Edinburgh, United Kingdom (2) School of Geosciences, The University of Edinburgh, Edinburgh, United Kingdom

Controversy has surrounded the genesis of the spectacularly imaged “Silverpit Crater” in the UK Southern North Sea. The prevailing view has been that the feature, which is best seen at the top of the Upper Cretaceous Chalk Group, was formed by meteor impact. However, detailed analysis of the deeper section suggested that the mobility and withdrawal of Upper Permian Zechstein Group evaporites at depth was a plausible alternative. Results of an interpretation of a large, regional 3-D seismic volume (equivalent in area to the State of Delaware) has provided the means by which to evaluate the role of halokinesis in controlling the structural and stratigraphic evolution of the greater Silverpit area and to test the competing theories for the genesis of the “Crater”. It can be demonstrated that major salt mobility affected the Silverpit area during the Early Cenozoic with the formation of major salt walls, diapirs and pillows and intervening thinning and local grounding of Late Permian and Triassic sediments on Lower Permian sediments belonging to the Rotliegend Group. As well as highlighting the importance of halokinesis in general, the results have also provided important new insights into how evaporite mobility has affected prospectivity in both the highly-prospective sub-salt (Carboniferous) play and in controlling gas charge to supra-salt (Triassic) anticlinal traps.