The impact of an evolving salt front setting on active methane seepage in the Lower Congo Basin


Donnerstag, 12. Dezember 2013 - 16:15 Uhr
GEO-Gebäude, Raum 1550 (Hörsaal)
Stefan Wenau

Abstract

The investigation of gas seepage from the seafloor has been a topic of research focus for some years as it allows for better understanding of methane input into the ocean and the atmosphere. Knowledge about the geological setting of such seepage sites enables better estimates of global methane escape from the seafloor, which may affect the methane budget of the atmosphere once it passes the water column.
The thesis focuses on the structure and geological setting of methane seepage sites in the Lower Congo Basin. A variety of geophysical methods including multichannel seismics, high-frequency echosounders and swath echosounders were applied for deep geological investigation as well as seafloor mapping. The Lower Congo Basin is a favourable site to study the setting of active methane seepage in the context of different geological processes such as active salt tectonics, large scale sediment input via the Congo River as well as a prolific hydrocarbon basin. The origin of seeping methane in this area depends on migration pathways and includes biogenic as well as thermogenic sources.
On the lower slope of the basin, a connection was found between the evolution of the deformation front of the salt basin and the setting of seafloor methane seepage. Salt-induced deformation may initially facilitate seepage but may also hinder seepage in areas of advanced deformation. Furthermore, the large scale deep sea Congo Fan influences seepage through changes in sediment properties. Overall, a wide variety of seepage settings could be documented at the salt front that shows a different evolution than seafloor seepage in further upslope regions of the basin.




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