Scientific Goals

Our main goal is the comparative analysis of fluid and gas seepage at the West-African continental margin. This includes the study of migration pathways, gas and fluid venting, hydrate distribution and the ecosystem patterns and physical and biogeochemical processes associated with these focused gas sources. During the leg we will investigate a diversity of geological and geophysical settings for fluid and gas migration as well as hydrate deposition and intermediate gas reservoirs. We will use several geophysical and visual methods to image fluid migration structures in great detail and map the lateral and vertical extent of seeps. The following overarching objectives will be jointly addressed together with our collaborators of IFREMER in France:
- What are the mechanisms shaping different types of seep systems?
- How are geological and biological processes at seeps coupled?
- What is the environmental impact of seeps?

To tackle these questions, 5 different settings were selected for multi-scale investigations with swath bathymetric, sediment echosounder, multichannel seismic, and back-scatter systems as well as geological and biogeochemical sampling. The comparative analysis of interdisciplinary data will enhance our understanding of how gas fluxes and gas hydrate distribution in fine-grained hemipelagic sediments are influenced by the degree of deformation; what the mechanisms of gas migration and the geometries of shallow gas reservoirs are; how sediment facies control processes and structures; and whether overpressured sand-rich reservoirs favour the frequent and widespread release of gas to the sea floor and create deep water bubble streams.

Fig. 2: Working area of cruise legs M76/3a and /3b.