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2005 Strategic Environmental Assessment SEA6 Technical Report - The Distribution and extent of methane-derived authigenic carbonate (Irish Sea)

This report is a contribution to the Strategic Environmental Assessment (SEA6) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). Methane-derived authigenic carbonate (MDAC) is formed as a consequence of the anaerobic oxidation of methane by consortia of bacteria. MDAC develops as a rock-like concretion when a carbonate precipitate cements normal seabed sediment; the carbon of this carbonate is derived from methane. It occurs as crusts or slabs at the seabed, or as exposed lumps. The occurrence of MDAC is evidence of methane seepage, although the seepage is not necessarily going on at the present time. Large quantities of MDAC indicate that methane seepage has occurred over a prolonged period of time. 'Submarine structures formed by leaking gas' have been identified by the European Commission's Habitats Directive as habitats worthy of protection.

The distribution of MDAC in UK waters is poorly known. This report summarises the available information relevant to MDAC in the SEA6 area, including data acquired by surveys specifically conducted in support of this SEA in 2004. Carbon isotope data for samples recovered in 2004 have confirmed that the cemented hard grounds from two of the areas studied, Texel 11 and Holden's Reef, are composed of MDAC.

Simple

Date (Publication)
2005-03-01
Identifier
British Geological Survey / BGS_SEA_92
Custodian
  British Geological Survey (BGS) - Paul Henni
Murchison House, West Mains Road , Edinburgh , EH9 3LA , UK
+44 (0)131 667 1000
Originator
  Department for Energy and Climate Change (DECC)
Admiralty Way , London , SW1A 2HD , UK
+44 0300 060 4000
+44 (0) 1823 284077
Maintenance and update frequency
notPlanned Not planned
Name
Documents
Keywords
  • NDGO0001
SeaDataNet Parameter Discovery Vocabulary
  • Bathymetry and Elevation
  • Concentration of alkanes in sediment samples
  • Sediment acoustics
  • Seismic reflection
  • Side-scan sonar
GEMET - INSPIRE themes, version 1.0
  • Geology
SeaVoX Vertical Co-ordinate Coverages
  • crust
  • sediment
Use limitation
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.
Access constraints
intellectualPropertyRights Intellectual property rights
Distance
5  http://standards.iso.org/ittf/PubliclyAvailableStandards/ISO_19139_Schemas/resources/uom/gmxUom.xml#m
Metadata language
EnglishEnglish
Topic category
  • Environment
  • Geoscientific information
  • Oceans
Date (Revision)
2006-01-01
Unique resource identifier
Irish Sea
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Begin date
2005-01-01
End date
2005-01-01
Supplemental Information
http://www.offshore-sea.org.uk/site/index.php
Reference system identifier
OGP / urn:ogc:def:crs:EPSG::4326
Distribution format
OnLine resource
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.

Hierarchy level
dataset Dataset
Statement

The report was prepared by Dr A. G. Judd as part of the UK Department of Energy and Climate Change's Offshore Energy Strategic Environmental Assessment programme. There are no published reports of methane-derived authigenic carbonate (MDAC) in the SEA6 area, but carbon isotope data have confirmed that the cemented hard grounds of two areas studied for the SEA6 project, Texel 11, and Holden's Reef, are composed of MDAC. Geophysical surveys, sampling and photographic surveys of other parts of the SEA6 area have confirmed that indicators of gas seepage (seep plumes, and pockmarks) are present in several other areas, and that acoustic turbidity (shallow gas) is widespread.

A specific objective of the SEA6 surveys was to investigate possible occurrences of MDAC in examples of a range of the geological contexts present in the SEA6 area. To that end 12 study areas were identified. Two surveys were undertaken during the period 24th August to 31st October 2004 geophysical surveys (S/V Meridian): single-beam echo sounder (SBES), multi-beam echo sounder (MBES), side-scan sonar (SSS), and chirp sub-bottom profiler (SBP); photography, seabed sediment sampling, and water sampling (S/V Kommandor Jack).

File identifier
aba64100-c150-4de3-e044-0003ba6f30bd XML
Metadata language
EnglishEnglish
Hierarchy level
dataset Dataset
Date stamp
2011-08-30
Metadata standard name
MEDIN Discovery Metadata Standard
Metadata standard version
Version 2.3.5
Point of contact
  British Geological Survey (BGS) - Mary Mowat
+44 (0)131 667 1000
+44 (0)131 668 4140
 
 

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