Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Map of shallow gas in marine sediments of the Skagerrak - Western Baltic Sea Region

Description of the result
A contour map indicating the depth of shallow gas below seafloor was constructed based on a dense grid of acoustic lines. The map is stored digitally as an ESRI shape file, allowing shallow gas occurrences to be compared with other relevant data rather easily. In most areas of the region the depth intervals shown are: (1) 2-4 m; (2) > 4 m; (3) gas plumes. Better resolution was, however, obtained for the Aarhus Bay area: (1) < 0.5 m; (2) 0.5-2 m; (3) 2-4 m; (4) >4 m.

The contour map is available on CD-ROM including GIS software allowing the user to see map details at any given scale. Data on: 1) sediment type; 2) gas seeps; 3) authigenic carbonates and 4) tracks of acoustic profiles, are also stored on the CD-ROM. Selected acoustic profiles (sparker and chirp) are included to allow the user to look up details using the internet browser. The shallow gas maps including gas seep occurrences are being used to test the presumptions made earlier on methane escape to the atmosphere from the area.

Key innovations:
Seismic mapping of shallow gas in sediments is a new tool, that can be used in connection with environmental monitoring. Until now few cores have been taken and methane contents have been measured directly in the sample, but the seismic studies will make it possible to give qualified estimates of methane volumes and distribution.

Current status and use:
Attempts are being made to combine shallow gas information with pore water chemistry to test applicability of acoustic surveys for monitoring the state of condition in coastal areas vulnerable to oxygen deficit. The Western Bornholm Basin area will be studied by GEUS under the umbrella of Geocenter Copenhagen, which includes the Univ. of Copenhagen’s Dept for Geology and Geography within the follow-up project Bathy-Sed esearch-themes/bathy-sed-dk.htm. The project is running from August 2005 until July 2006 and plans to obtain detailed bathymetry and sedimentology data, using multi-beam technology. A cruise with MS Line was done already in 2005 in the same areas covered by a METROL cruise, but for the first time taking Rumohr lot samples. Now, further lab work is planned until August 2006.

Users interested in the result
Marine geologists, microbiologists may benefit from the overview of gas occurrences in the area.

Environmental agencies in charge of monitoring the condition in coastal areas, e.g. NERI for Denmark.

Expected benefits:
Acoustic surveys may become useful for monitoring the state of condition in coastal areas vulnerable to oxygen deficit.

Verwandte Informationen

Reported by

GEUS - Geological Survey of Denmark and Greenland
Øster Voldgade 10
1350 Copenhagen K
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