2003 Strategic Environmental Assessment SEA4 Technical report - Continental shelf seabed geology and processes (north UKCS)

The report was prepared by the British Geological Survey as part of the UK Department of Energy and Climate Change's Offshore Energy Strategic Environmental Assessment programme. The information presented for this report forms a small part of the seabed data available from the BGS series of 1:250,000 scale published maps and regional reports of solid geology, Quaternary geology and seabed sediments that cover SEA4 south of 62 N. The maps were compiled from interpretations of regional single channel seismic reflection survey profiles and from seabed grab and core samples. The regional seismic reflection profiles used during compilation of the published maps were spaced some 10-15 km apart. The Quaternary and seabed sediment maps include supplementary information from interpretations of nearshore close-survey sidescan sonar and single-channel echo sounder data that has been released by the Hydrographic Office (HO) to the British Geological Survey (BGS) for publication at 1:250,000 scale. Other known systematic close surveys or swath regional surveys on the continental shelf include commercial site investigations for drilling rigs, development platforms, pipelines and cable routes. These data had been released for incorporation into the BGS maps up to the time of their publication completed in 1993. The post-1993 commercial sources of data have not been released and are not reviewed for this report. The samples sites averaged less than 10km spacing but north of 61 N may be spaced up to approximately 15-20km apart. Most of the seabed samples were processed for particle size analyses, % carbonate in various size fractions and inorganic geochemistry. Many of the superficial and shallow cores were tested for geotechnical properties in addition to particle size analyses.

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