Architecture of an active mud-rich turbidite system: The Zaire Fan (Congo–Angola margin southeast Atlantic)

Droz, Laurence; Marsset, Tania; Ondréas, Hélène; López, Michel; Savoye, Bruno; Spy-Anderson, F.-L.

doi:10.1306/03070300013

Cited by 108 publications

(114 citation statements)

References 20 publications

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“…Sedimentation on the slope is dominated by fine terrigenous sediments and hemipelagic drape reworked by bottom currents, probably in relation with upwelling (Séranne and Nzé Abeigne, 1999). On the lower slope and deep basins, turbidites accumulated downstream of major rivers (Ogooue (Mougamba, 1999), Congo (Droz et al, 2003). Turbidites are fed to the lower slope and basin by canyons cross-cutting the shelf, within the lower Miocene stratigraphic interval (Wonham et al, 2000).…”

Section: Late Drift : Oligocene-present Deep-sea Fansmentioning

confidence: 99%

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

Séranne¹,

Anka²

2005

Journal of African Earth Sciences

132

106

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Africa displays a variety of continental margin structures, tectonic styles and sedimentary records. The comparative review of two representative segments: the equatorial western Africa and the SW Africa margins, helps in analysing the main controlling factors on the development of these margins. Early Cretaceous active rifting south of the Walvis Ridge resulted in the formation of the SW Africa volcanic margin that displays thick and wide intermediate igneous crust, adjacent to a thick unstretched continental crust. The non-volcanic mode of rifting north of the Walvis ridge, led to the formation of the equatorial western Africa margin, characterised by a wide zone of crustal stretching and thinning, and thick, extensive, synrift basins. Contrasting lithologies of the early post-rift (salt vs shale) determined the style of gravitational deformation, whilst periods of activity of the decollements were controlled by sedimentation rates. Regressive erosion across the prominent shoulder uplift of SW Africa accounts for high clastic sedimentation rate during Late Cretaceous to Eocene, while dominant carbonate production on equatorial western Africa shelf suggests very little erosion of a low hinterland. The early Oligocene long-term climate change had contrasted response in both margins. Emplacement of the voluminous terrigenous Congo deep-sea fan reflects increased erosion in equatorial Africa, under the influence of wet climate, whereas establishment of an arid climate over SW Africa induced a drastic decrease of denudation rate, and thus reduced sedimentation on the margin. Neogene emplacement of the African superswell beneath southern Africa was responsible for renewed onshore uplift on both margins, but it accelerated erosion only in the Congo catchment, due to wetter climatic conditions. Neogene high sedimentation rate reactivated gravitational tectonics that had remained quiescent since late Cretaceous.

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Section: Late Drift : Oligocene-present Deep-sea Fansmentioning

confidence: 99%

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

Séranne¹,

Anka²

2005

Journal of African Earth Sciences

132

106

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“…Bathymetry and acoustic imagery show the continuity of channel-levee systems, while seismic data were used to analyze facies, geometries and stratigraphic interrelations to reconstruct the architecture of the fan. Correlations with ODP Leg 175 indicate that the studied portion of the Congo fan started to form in the Upper Pleistocene (780 ka) and allow us to propose a tentative timing for the construction of the fan (Droz et al, 2003)..4 A brief overview of the Quaternary Congo fan . …”

mentioning

confidence: 99%

“…4). The stacking of channel-levee systems, in response to lateral shifts of the channels due to successive avulsions, defines the architecture of the fan (Droz et al, 2003). From the lower to the upper fan, the network of channels is hierarchically organized into progressively greater and more intricate sedimentary features.…”

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confidence: 99%

Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Savoye

Babonneau

Dennielou

et al. 2009

Deep Sea Research Part II: Topical Studies in Oceanography

129

155

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The Congo deep-sea fan is one of the largest fans in the world still affected by presently active turbidity currents. The present activity of deep-sea sedimentary processes is linked to the existence of a direct connection between the Congo River estuary and the Congo canyon head that allows relatively continuous sediment feeding of the deep-sea environment, in spite of a wide continental shelf (150 km). Because of this important activity in terms of sedimentary processes, the deep-sea environment of the Congo-Angola margin presents major interests concerning physical, chemical and biological studies near the sea floor. The main aim of this paper is to present the initial geological context of the BioZaire Program, showing a synthesis of the major results of the ZaïAngo Project including (1) the brief geological setting of the Congo-Angola margin, (2) the structure of the modern Congo deep-sea fan, (3) the sedimentary architecture of the recent Congo turbidite system (from the canyon to the distal lobes), and (4) the recent and present turbidite sedimentation. In order to provide useful information and advice relevant to biological and geochemical studies across the Congo sedimentary system, this article focuses on the present sedimentary processes and the present activity of turbidity current along the Congo canyon and channel.Keywords : Congo-Angola margin, Congo channel, sedimentary deposits, turbidite .1 IntroductionThe accumulation of marine sediment seaward of the Congo River estuary is probably one of the greatest in the world for a submarine system that is still active today. In the continental domain, the Congo sedimentary system is composed by a wide drainage basin, the river and its tributaries. In the nearshore and marine domain: it consists of the estuary, the canyon, which acts mainly as a by-pass zone, and finally an area of preferential sedimentation at the foot of the continental slope and in the deep basin. The Congo submarine system has been geologically studied since Buchanan in 1887 (submarine cable survey) and was the focus of the ZaïAngo project team from 1998 to 2005. Several types of evidence of Holocene and very recent activity in the canyon have been described and linked to sedimentary processes such as turbidity currents, river floods, slides, gas hydrate formation and fluid escape. The aim of this paper is to synthesize the geological knowledge of the area and in particular the results of the ZaïAngo project in order to provide useful information and advice relevant to biological and geochemical studies across the Congo sedimentary system. Marine biologists and oceanographers are usually not familiar with turbidite deposits. These sedimentary deposits were first recognised and described in outcrops of ancient sedimentary series (Bouma, 1962;Walker, 1978;Mutti, 1992). They are generated by submarine gravity processes and they build large sedimentary systems in deep-water environments, termed deep-sea fans. Deep-sea fans are well developed from the foot of the continental slope...

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“…As the system stabilizes, a channel and levee may develop over the lobe (Lopez, 2001;Maier et al, 2012). High-amplitude continuous-to-discontinuous reflection packages (Posamentier and Kolla, 2003) are preserved between or underlying channel and levee deposits, as identified in the Amazon, Indus, Zaire, and Bengal fan systems (Damuth et al, 1988;Flood et al, 1991;Normark et al, 1997;Pirmez et al, 1997Pirmez et al, , 2000Lopez, 2001;Droz et al, 2003;Kolla, 2007). However, Ortiz-Karpf et al (2015) provide a subsurface example of a deep-water avulsion cycle where there is a zone between the point of avulsion and the updip pinchout of the avulsion lobe.…”

Section: An Exhumed Example Of An Avulsion Nodementioning

confidence: 99%

Integrating outcrop and subsurface data to assess the temporal evolution of a submarine channel–levee system

et al. 2016

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The morphological evolution of submarine channel systems can be documented using high-resolution three-dimensional seismic data sets. However, these studies provide limited information on the distribution of sedimentary facies within channel fills, channelscale stacking patterns, or the detailed stratigraphic relationship with adjacent levee-overbank deposits. Seismic-scale outcrops of unit C2 in the Permian Fort Brown Formation, Karoo Basin, South Africa, on two subparallel fold limbs comprise thin-bedded successions, interpreted as external levee deposits, which are adjacent to channel complexes, with constituent channels filled with thick-bedded structureless sandstones, thinner-bedded channel margin facies, and internal levee deposits. Research boreholes intersect all these deposits, to link sedimentary facies and channel stacking patterns identified in core and on image logs and detailed outcrop correlation panels. Key characteristics, including depth of erosion, stacking patterns, and cross-cutting relationships, have been constrained, allowing paleogeographic reconstruction of six channel complexes in a 36-km 2 (14-mi 2 ) area. The system evolved from an early, deeply incised channel complex, through a series of external levee-confined and laterally stepping channel complexes culminating in an aggradational channel complex confined by both internal and external levees. Down-dip divergence of six channel complexes from the same location suggests the presence of a unique example of an exhumed deep-water avulsion node. Down-dip, external levees are supplied by flows that escaped from channel complexes of different ages and spatial positions and are partly confined and share affinities with internal levee successions. The absence of frontal lobes suggests that the channels remained in sand bypass mode immediately after avulsion.

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Architecture of an active mud-rich turbidite system: The Zaire Fan (Congo–Angola margin southeast Atlantic)

Cited by 108 publications

References 20 publications

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

Geological overview of the Angola–Congo margin, the Congo deep-sea fan and its submarine valleys

Integrating outcrop and subsurface data to assess the temporal evolution of a submarine channel–levee system

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