DTI Strategic Environmental Assessment Area 2 (SEA2) geological processes (interpretation of multibeam, sidescan sonar, chirp and grain size data acquired in 2001 from the seafloor of the Norfolk Banks and Dogger Bank, southern North Sea)

• Main Authors: Holmes, R., Wild, J.B.L.
• Format: Report
• Language: English
• Published: British Geological Survey 2003
• Subjects: Dogger Bank; Ice Sheet
• Online Access: http://nora.nerc.ac.uk/id/eprint/527395/; https://nora.nerc.ac.uk/id/eprint/527395/1/CR03188N.pdf

The focus of this study is on the offshore sandbanks occurring in the mature southern North Sea gas producing fields on the UK continental shelf. New geological interpretations have been made from bathymetric, sidescan sonar and seabed photographic and sample surveys carried out for the Department of Trade and Industry in 2001 over the Norfolk Banks and the Dogger Bank. The survey data were acquired in water depths varying from approximately 10m to 40m or more. The new survey data were collected to fill information gaps on the seabed processes influencing the seabed sand transport directions, composition of the seabed habitat and sandbank function. Interpretative data have been collected for bedforms ranging in size from sand banks more than 20km long and spaced more than 5km apart to sand ripples less than 2m long and spaced less than 60cm apart. Existing geological information has been integrated with the new survey information to present the interpretations of the variety of the modern seabed habitats in their wider historical and regional contexts. The research findings from the seabed study are interpreted from data collected during relatively calm spring/summer wave conditions and without surge-driven tides. • Under the range of seasonal hydrodynamic conditions the sandbanks interact with the flood and ebb tidal currents, wind and wave and storm surge currents so that the seabed on the sandbanks is characterised by superimposed mobile small to very large mobile bedforms. The exceptions found were on and adjacent to the crest of the Dogger Bank and on the crests of the Norfolk Banks all in less than approximately 18m water depth. In these areas the larger transverse bedforms appear to have been destroyed at the bank crests by waves. • The Dogger Bank is a glacial outwash feature that was deposited under conditions of prolific sediment supply when the southern North Sea basin was partly covered by a terrestrial ice sheet more than 14,000 years ago. Although it is now covered by mobile sand at seabed, the ...