Journal
MARINE AND PETROLEUM GEOLOGY
Volume 59, Issue -, Pages 359-370Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.marpetgeo.2014.09.013
Keywords
Gas hydrate; Pockmark; Chloride profile; Infrared thermal imaging; Fluid flow; Nigerian continental margin; MeBo drill rig
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Funding
- DFG-Research Center/Excellence Cluster The Ocean in the Earth System MARUM - Center for Marine Environmental Sciences
- BMBF [03G0824A]
- China Scholarship Council (CSC)
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A joint research expedition between the French IFREMER and the German MARUM was conducted in 2011 using the RN 'Pourquoi pas?' to study gas hydrate distributions in a pockmark field (1141-1199 m below sea surface) at the continental margin of Nigeria. The seafloor drill rig MeBo of MARUM was used to recover sediments as deep as 56.74 m below seafloor. The presence of gas hydrates in specific core sections was deduced from temperature anomalies recorded during continuous records of infrared thermal scanning and anomalies in pore water chloride concentrations. In situ sediment temperature measurements showed elevated geothermal gradients of up to 258 degrees C/km in the center of the so-called pockmark A which is up to 4.6 times higher than that in the background sediment (72 degrees C/km). The gas hydrate distribution and thermal regime in the pockmark are largely controlled by the intensity, periodicity and direction of fluid flow. The joint interaction between fluid flow, gas hydrate formation and dissolution, and the thermal regime governs pockmark formation and evolution on the Nigerian continental margin. (C) 2014 Elsevier Ltd. All rights reserved.
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