期刊
MARINE AND PETROLEUM GEOLOGY
卷 83, 期 -, 页码 140-157出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.marpetgeo.2017.02.030
关键词
Lower Congo Basin; Pockmark formation; Pliocene Congo Fan; Salt tectonics; Multichannel seismics; Gas seepage
资金
- DFG-Research Center/Cluster of Excellence The Ocean in the Earth System MARUM - Center for marine Environmental Sciences [DFG-EXC 309]
- Bremen International Graduate School for Marine Sciences (GLOMAR) - German Research Foundation (DFG) [DFG-GSC 119]
- DFG [Sp296/23-1]
- German Ministry of Science and Education (BMBF) [03G0567CA]
- German federal and state governments to promote science and research at German universities
Effective seal breaching is a major contributor to methane seepage from deep sea sediments as it ensures the migration of gas and liquid hydrocarbons from buried reservoirs to the seafloor. This study shows two giant pockmarks on the lower slope of the Lower Congo Basin associated with salt-tectonic faulting and the buried Pliocene Congo deep sea fan. The progressive burial of Pliocene fan deposits results in mobilization of methane from gas hydrates at the Base of the Gas Hydrate Stability Zone which migrates through the hemipelagic seal towards the seafloor along salt-induced faults. Seal-breaching in this part of the Lower Congo Basin relies solely on salt-tectonic faulting contrasting with upslope seafloor seepage settings where polygonal faulting within the hemipelagic seal occurs. Dedicated 2D and 3D seismic and acoustic surveying allows the detailed reconstruction of the evolution of pockmarks which appear to have been active for the last 640 kyr. We also show indications that the modern seafloor depression formed due to reduced sedimentation in the vicinity of active seepage. The presented seafloor seepage features illustrate the mode of gas release from the Pliocene fan in the Lower Congo Basin, which contrasts with previously investigated seepage environments further upslope. (C) 2017 Elsevier Ltd. All rights reserved.
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