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Successful seafloor sampling in Skjálfandi Bay

15.10.2013

Orkustofnun recently collected cores from the seafloor of Skjálfandi Bay in order to seek thermogenic gas in the sediments.

The sampling took place in two attempts, first 9 through 11 September, after which unfavourable wind and wave conditions lead to a postponement of the sampling. The sampling was finished on 30 September through 2 October when the weather conditions were suitable for the coring to take place. Djuptaekni ehf was the drilling contractor for the project; they own and run a vibrocorer which is necessary in order to be able to drill into the firm sediments involved. Attempts were made in 2003 to core in the area using a gravity corer, but the cores collected were too short for geochemical analyses due to the firmness of sediments.

Core locations in Skjalfandi Bay September-October 2013 (red stars). Yellow circles mark locations of holes on the seafloor that may be due to outflow of gas from the sediments. Map from Sigridur Magnusdottir of the University of Iceland.

Bryndis Brandsdottir and Sigridur Magnusdottir of the University of Iceland picked the positions of the cores based on data available for the Skjálfandi Bay, including Sigridur's MS-thesis that she defended this year. Cores were collected in several different area, e.g. where holes are visible on the seafloor which may indicate gas outflow, on or near the Husavik-Flatey fracture zone and near Husavik where signs of sedimentary gas are visible in the data. Djuptaekni's ROV was used to video the seafloor at certain core locations as a part of preparation for the coring i.a. to study the holes on the seafloor.

The goal of collecting 20 cores in the sampling campaign was successfully reached and the lowest part of the cores was placed in metal cans that were kept frozen and then sent to Norway for geochemical analyses such as of short-chain organic gases. The longest core was nearly 4 m but the shortest one was 50 cm, which was too short to be useable for geochemical analyses. The other cores were all of sufficient length.

The objective of the coring was to confirm the presence of thermogenic gases in the sediments of Skjálfandi Bay, as there are multiple indications for the presence of gas in the area. It is not clear, however, whether the gas involved is of biogenic or thermogenic origin. Further information on the preparation for the sampling and the available data can be found in a report by Bjarni Richter and Karl Gunnarsson of Iceland GeoSurvey from 2010. The results on the analyses of the samples may be expected within the next 3 months.