The Quaternary Congo Deep-Sea Fan: Preliminary Results on Reservoir Complexity in Turbiditic Systems Using 2D High Resolution Seismic and Multibeam Data
Published:December 01, 2000
Jacques Vittori, Alain Morash, Bruno Savoye, Tania Marsset, Michel Lopez, Laurence Droz, Michel Cremer, 2000. "The Quaternary Congo Deep-Sea Fan: Preliminary Results on Reservoir Complexity in Turbiditic Systems Using 2D High Resolution Seismic and Multibeam Data", Deep-Water Reservoirs of the World, Paul Weimer
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The Congo deep-sea fan was surveyed recently by a unique set of data that includes as of today more than 30 piston cores and 25,000 km of 2D high resolution seismic acquisition. During the different cruises, the following tools were used simultaneously: an EM12 dual Simrad swath bathymetric and sonar system, a 3.5 kHz mud penetrator, an oceanographic seismic system (6 traces), and a multichannel seismic streamer (96 traces) with G.I. air gun source. The data set covers an area in excess of 200,000 km2 from the canyon head to the most recent depositional lobes 700 km downslope. In this four year project cosponsored by ELF and IFREMER, the prime objective was to gain comprehension of the construction and the lateral evolution of the recent fan. As a result, we were able to build a chronostratigraphic and architectural model at the fan scale.
The Congo Canyon geometry has been enhanced and has confirmed the lack of any tributaries downdip from the continental shelf. Furthermore, no real large scale slumped blocks have observed at the base of the steep submarine canyon slopes. Therefore, widening of the canyon seems to have occurred through progressive sliding and creeping of the bordering Congolese and Angola platform into the canyon valley.
The recent Congo fan growth results from the stacking and overlapping of at least 3 main stratigraphic units. Each unit is composed of numerous channel-levee complexes laterally switching path through time by avulsion. Previous interpretation of “distributaries” at the toe of the Congo submarine canyon is invalidated as this surveys shows that they are in fact abandoned channel-levee complexes. It has also been confirmed that in this particular mud-rich submarine fan setting, only one channel is active at a time. The present day “active” fan channel as well as the canyon are eroding into previously deposited sediments.
In the levees, individual sub-kilometer scale morphological features have been mapped, and sedimentary and/ or structural processes responsible for such geometries have been reviewed.
The present day depositional lobe is more than 700 km away from the Congo River mouth. It occupies an area of around 300 km2 and shows clustered lobes, 20 km long, prograding down slope.
It is now clear that multibeam coverage of the lower part of the canyon, over complex lobe, and channel avulsion zones shows strong similarities with seismic attribute maps of West Africa’s structurally controlled turbiditic channel complexes.