aba64100-c0fe-4de3-e044-0003ba6f30bd English dataset Mary Mowat British Geological Survey (BGS) +44 (0)131 667 1000 +44 (0)131 668 4140 offshoredata@bgs.ac.uk pointOfContact 2011-08-30 MEDIN Discovery Metadata Standard Version 2.3.5 urn:ogc:def:crs:EPSG::4326 OGP 2001 Strategic Environmental Assessment SEA2 Technical report - Pockmarks in the UK sector of the North Sea 2001-08-01 publication BGS_SEA_7 British Geological Survey This report is a contribution to Strategic Environmental Assessment SEA2 conducted by the Department of Trade and Industry (now Department of Energy and Climate Change) and it reviews the distribution and character of pockmarks - shallow seabed depressions - which are common in the area of the North Sea to the north-east of Scotland known as the Fladen Ground. Pockmarks are believed to be produced by the escape of fluids (gas or water, but generally gas in the North Sea) from the seafloor and are found in areas where the seabed sediments are soft, silty clays. Processes of pockmark formation, their geometry, age and distribution, and the sources of gas in the underlying geological strata are discussed. While the great majority of pockmarks are inactive at the present time, a few are observed to be actively seeping gas. In order to provide a stronger basis upon which the significance of pockmarks within mature oil and gas provinces of the North Sea might be assessed, the Department of Trade and Industry commissioned the acquisition of new data directed towards increasing the scientific understanding of sandbanks and pockmarks as part of the SEA2 process. The survey vessel Kommandor Jack was chartered in April 2001 and, among other operations, conducted high-resolution geophysical surveys of pockmarks in the Fladen Ground. Preliminary results from that operation are included in this report. Paul Henni British Geological Survey (BGS) +44 (0)131 667 1000 Murchison House, West Mains Road Edinburgh EH9 3LA UK offshoredata@bgs.ac.uk custodian Department for Energy and Climate Change (DECC) +44 0300 060 4000 +44 (0) 1823 284077 Admiralty Way London SW1A 2HD UK enquiries@decc.gsi.gov.uk originator notPlanned Documents NDGO0001 Bathymetry and Elevation Sediment acoustics Seismic reflection Side-scan sonar SeaDataNet Parameter Discovery Vocabulary 2011-03-25 revision Geology GEMET - INSPIRE themes, version 1.0 2008-06-01 publication crust sediment SeaVoX Vertical Co-ordinate Coverages 2008-06-01 publication The SEAs data were produced as part of the UK Department of Energy and Climate Change's Offshore Energy Strategic Environmental Assessment programme; Crown Copyright, all rights reserved. The DECC SEA must be acknowledged in any maps or publications that make use of the data. All the data files are freely available to the public. The Strategic Environmental Assessment (SEA) data portal provides free access to available data and reports which have been produced through the SEA process. The site is run and managed by BGS on behalf of the Department of Energy and Climate Change (DECC). Many files can be downloaded directly from this website. Those that are too large to download can be ordered via the website for postal delivery from BGS. BGS (NERC) has been contracted by DECC to publish SEA datasets on its behalf. All intellectual property rights (including , without limitation, copyrights, database rights and all other rights which subsist or may at any time in the future subsist in the Dataset(s)) in the Dataset(s) ('Intellectual Property Rights') are owned by DECC (formerly the Department of Trade and Industry, and the Department for Business, Enterprise and Regulatory Reform). BGS has been authorised by DECC to use SEA datasets for all purposes but on a 'not-for-profit basis'. BGS has been authorised by DECC to pass on SEA datasets to third parties so that they can use them for all purposes but on a 'not-for-profit' basis. intellectualPropertyRights 5 English environment geoscientificInformation oceans SeaVoX salt and fresh water body gazetteer 2006-01-01 revision North Sea -1.9 3.3 52.8 61.8 2001-04-20 2001-05-05 http://www.offshore-sea.org.uk/site/index.php http://www.bgs.ac.uk/data/sea/home.html Strategic Environmental Assessment (SEA) data portal The Strategic Environmental Assessment (SEA) data portal provides free access to available data and reports which have been produced through the UK Department of Energy and Climate Change SEA process. The site is run and managed by BGS on behalf of the Department of Energy and Climate Change (DECC). Many files can be downloaded directly from this website. Those that are too large to download can be ordered via the website for postal delivery from BGS. download dataset In April 2001 the survey vessel Kommandor Jack among other operations, conducted high-resolution geophysical surveys of pockmarks in the Fladen Ground as part of the UK Department of Energy and Climate Change's Offshore Energy Strategic Environmental Assessment programme. Geophysical surveying was undertaken using the following equipment: Swath Bathymetry: Simrad EM1002; Side scan sonar: Geoacoustics 159; Sub-bottom profiling: Datasonics Chirp profiler; Positioning: DGPS. This report was prepared by Dr Alan Judd (University of Sunderland) in 2001. Data from offshore site survey reports (made available by the British Geological Survey with permission of the relevant oil companies), as well as published and publicly available material were also used to compile the report.