Report 570
Geological investigation of pockmarks in the Scanner Pockmark SCI area
(2015)
Gafeira, J. & Long, D.
This report is the product of a desk study by the British Geological Survey (BGS) for the Joint Nature Conservation Committee (JNCC). The scope of the desk study included a comparison of the JNCC 2012 multibeam/sidescan dataset from the Scanner and Braemar pockmarks areas in the northern North Sea with similar historic datasets noting morphological change. Also within scope were a record of gas seepage and Methane-Derived Authigenic Carbonate (MDAC) observations and an examination of sedimentation rates and evidence of anthropogenic causes of sedimentation.
 

Introduction


 

The focus in this study is on the pockmarks found in Scanner Pockmark SCI area, and looks at evidence of gas seepage and specific factors that influence the formation and exposure of methane-derived authigenic carbonate (MDAC) structures within the pockmarks.

The new data collected by Centre for Environment, Fisheries & Aquaculture Science (CEFAS) at the end of 2012, cruise CEND19x/12 commissioned by JNCC, provided the main dataset for this study. The multibeam dataset collected was used to semi-automatically map and characterise the morphology of the pockmarks. The information extracted from the mapped pockmarks was then compared to the information extracted from previous surveys. Backscatter data and side scan sonar data was used to characterise the nature of the seafloor, in particular the presence of methane-derived authigenic carbonate (MDAC). The study confirmed changes in the volume of sediment infill of the pockmark but no clear sediment source was identified.

 
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ISSN 0963 8091
 
Please cite as: Gafeira, J. & Long, D., (2015), Geological investigation of pockmarks in the Scanner Pockmark SCI area, JNCC Report 570, ISSN 0963 8091