Comparison of depositional sequences and tectonic styles among the West African deepwater frontiers of western Ivory Coast, southern Equatorial Guinea, and northern Namibia

Coterill, Katrina; Tari, Gábor; Molnar, Jim; Ashton, Paul R.

doi:10.1190/1.1523747

Cited by 9 publications

(5 citation statements)

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“…This inference is reinforced by the presence of a large submarine fan downslope of the Ceiba canyon that includes a sinuous, leveed submarine channel ( Fig. 1; Coterill et al, 2002).…”

Section: Contrasting Canyon Morphologies On the Modern Seafloormentioning

confidence: 97%

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Jobe

Lowe

Uchytil

2011

Marine and Petroleum Geology

165

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Most submarine canyons are erosive conduits cut deeply into the world's continental shelves through which sediment is transported from areas of high coastal sediment supply onto large submarine fans. However, many submarine canyons in areas of low sediment supply do not have associated submarine fans and show significantly different morphologies and depositional processes from those of 'classic' canyons. Using three-dimensional seismic reflection and core data, this study contrasts these two types of submarine canyons and proposes a bipartite classification scheme.The continental margin of Equatorial Guinea, West Africa during the late Cretaceous was dominated by a classic, erosional, sand-rich, submarine canyon system. This system was abandoned during the Paleogene, but the relict topography was reactivated in the Miocene during tectonic uplift. A subsequent decrease in sediment supply resulted in a drastic transformation in canyon morphology and activity, initiating the 'Benito' canyon system. This non-typical canyon system is aggradational rather than erosional, does not indent the shelf edge and has no downslope sediment apron. Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the canyons. Intra-canyon lateral accretion 2 deposits indicate that canyon concavity is maintained by thick (> 150 m), dilute, turbidity currents. There is little evidence for erosion, mass wasting, or sand-rich deposition in the Benito canyon system. When a canyon loses flow access, usually due to piracy, it is abandoned and eventually filled. During canyon abandonment, fluid escape causes the successive formation of 'cross-canyon ridges' and pockmark trains along buried canyon axes.Based on comparison of canyons in the study area, we recognize two main types of submarine canyons: 'Type I' canyons indent the shelf edge and are linked to areas of high coarse-grained sediment supply, generating erosive canyon morphologies, sandrich fill, and large downslope submarine fans/aprons. 'Type II' canyons do not indent the shelf edge and exhibit smooth, aggradational morphologies, mud-rich fill, and a lack of downslope fans/aprons. Type I canyons are dominated by erosive, sandy turbidity currents and mass wasting, whereas hemipelagic deposition and dilute, sluggish turbidity currents are the main depositional processes sculpting Type II canyons. This morphology-based classification scheme can be used to help predict depositional processes, grain size distributions, and petroleum prospectivity of any submarine canyon.

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“…This inference is reinforced by the presence of a large submarine fan downslope of the Ceiba canyon that includes a sinuous, leveed submarine channel ( Fig. 1; Coterill et al, 2002).…”

Section: Contrasting Canyon Morphologies On the Modern Seafloormentioning

confidence: 97%

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Jobe

Lowe

Uchytil

2011

Marine and Petroleum Geology

165

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“…The chart is based on the sections and chart published in (1) Marton et al (2000) that identified three steps in the Kwanza Basin (a pre-riftthe Lucula Fm of the same age as the Lukunga Fm, see Fig. 4 a rift and a sag phase -Cuvo Fm) and ( 2) Coterill et al (2002) for the Namibe Basin.…”

Section: Deformation Charts (Fig 6)mentioning

confidence: 99%

“…the Lower Congo. The knowledge of the Namibe Basin is more critical, 367 because only one publication (Coterill et al, 2002) (Carvalho, 1961). Because the age attribution 378 and the stratigraphic sequence pattern of the Santos Basin (Moreira et al, 2007) are similar to those of the Campos Basin (Winter et al, 2007), the age of the different formations of the Santos Basin is deduced from the Campos Basin, where biostratigraphic data are available.…”

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confidence: 99%

Paleogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: Paleotopographic and geodynamic implications

et al. 2013

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International audienceThe geodynamic processes that control the opening of the central segment of the South Atlantic Ocean (between the Walvis Ridge and the Ascension FZ) are debated. In this paper, we discuss the timing of the sedimentary and tectonic evolution of the Early Cretaceous rift by drawing eight paleogeographic and geodynamic maps from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollen) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains, with a two phases evolution of the pre-drift ("rifting") times: a rift phase characterized by tilted blocks and growth strata, followed by a sag basin. The southern domain includes the Namibe, Santos and Campos Basins. The northern domain extends from the Espirito Santo and North Kwanza Basins, in the south, to the Sergipe-Alagoas and North Gabon Basins to the north. Extension started in the northern domain during the Late Berriasian (Congo-Camamu Basin to the Sergipe- Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain (emplacement of the Parana-Etendeka Trapp). Extension started in this southern domain during the Early Barremian. The rift phase is shorter in the south (5-6 Ma, Barremian to base Aptian) than in the north (19 to 20 Myr, Upper Berriasian to base Aptian). The sag phase is of Middle to Late Aptian age. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age. From the Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower organic-rich one with no more highs. The lake migrates southward in two steps, until the Valanginian at the border between the northern and southern domains, until the Early Barremian, north of Walvis Ridge

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“…Prior to the present study, anhydrite, gypsum and dolomitic carbonate layers exposed landward in Namibe Basin were only briefly mentioned (De Carvalho, ; Pautot et al ., ) and no salt has yet been reported seaward. It is assumed, however, that the area north of the Walvis Ridge, where Aptian mounded platform carbonates have been identified, constitutes the southern flank of the African Salt Basin (Coterill et al ., ). The northern flank of the salt basin is located at the Ascension fracture zone, north of the Gabon Basin (Davison, ).…”

Section: Geological Settingmentioning

confidence: 97%

Diagenetic evolution of Aptian evaporites in the Namibe Basin (south‐west Angola)

et al. 2014

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The widespread and dissected nature of the Angolan gypsiferous salt residuals offers a uniquely detailed view of the lateral and vertical relations inherent to secondary evaporite textures, which typify exhumed salt masses worldwide. Such secondary textures are sometimes misinterpreted as primary evaporite textures. Thin, metre-scale and patchy, dome-like gypsum accumulations are well-exposed within strongly incised present-day river valleys along the eastern margin of the Namibe and Benguela basins (southwest Angola). These sections are time equivalent to the main basinward subsurface evaporites (Aptian Loeme Formation) which mostly consist of halite. The gypsum (here called the Bambata Formation) is interpreted to represent the final residual product of fractional dissolution and recrystallization of the halite mass that occurred during Late Cretaceous margin uplift and continues today. This halite underwent multiple episodes of diagenetic alteration between its deposition and its final exhumation, leading to the formation of various secondary gypsum fabrics and solution-related karst and breccia textures that typify the current evaporite outcrop. Four different diagenetic gypsum fabrics are defined: thinly bedded alabastrine, nodular alabastrine, displacive selenite rosettes and fibrous satin-spar gypsum. Current arid conditions are responsible for a thin weathered crust developed at the top of the outcropping gypsum, but the fabrics in the main core of the current at-surface evaporite unit mostly formed during the telogenetic stage of uplift prior to complete subaerial exposure. Alteration occurred as various dissolving and rehydrating saline minerals encountered shallow aquifers in the active phreatic and vadose zones. Geomorphological and petrographic analyses, mostly based on the cross-cutting relations and crystallographic patterns in the outcrop, are used to propose a sequence of formation of these different fabrics.

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Comparison of depositional sequences and tectonic styles among the West African deepwater frontiers of western Ivory Coast, southern Equatorial Guinea, and northern Namibia

Cited by 9 publications

References 0 publications

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea

Paleogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: Paleotopographic and geodynamic implications

Diagenetic evolution of Aptian evaporites in the Namibe Basin (south‐west Angola)

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