Middle and late quaternary oceanography and climatology of the Zaire-Congo fan and the adjacent Eastern Angola basin

Jansen, J H Fred; Weering, Tj.C.E. van; Gieles, R.; Iperen, Jolanda Van

doi:10.1016/0077-7579(84)90048-6

Cited by 147 publications

(65 citation statements)

References 50 publications

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“…(See the section dealing with the stratigraphy.) This core has rather constant MARS of ca 0.60 g cm-* ka-' for the interval 3-7 m below the core top and 0.21 g cm-* ka-' for the upper 3 m [15,47]. In the lower interval, short-term increases of terrigenous input are indicated by the presence of quartz and mica grains and of a few turbiditic laminae.…”

Section: Dating With 'Obementioning

confidence: 92%

“…Therefore, all samples were collected from hemipelagic and pelagic cores whereas turbidites were evaded. The sampled sediments are siliceous oozes with an inorganic component consisting mainly of terrigenous clay minerals smaller than 2 pm [15,16].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…Previously, because of the low carbonate concentrations of the sediments, sometimes large samples of 20 cm or more had to be collected or organic carbon had to be dated, which gives results not accurate enough for the purpose of this study [15]. Mass accumulation rates (MAR) for the measured core tops were calculated from the new 14C measurements (table 2) and the ages mentioned above (table 1).…”

Section: Dating With 14cmentioning

confidence: 99%

“…g-' [46], an order of magnitude lower. This may be explained by the fact that the greater portion of the terrigenous component in the Zaire fan has grain sizes smaller than 2 pm [15,16]; it forms a selection of the clay mineral fraction which is capable to adsorb Be.…”

Section: Jh F Jansen Et Al / Terrigenow Supply Of "Bementioning

confidence: 99%

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Terrigenous supply of 10Be and dating with 14C and 10Be in sediments of the Angola basin (SE Antlantic)

Jansen

Alderliesten

Bennekom

et al. 1987

Nuclear Instruments and Methods in Physics Research Section B:

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"Be concentrations were measured in 20 (hemi)pelagic core top samples with an age control partly based on AMS 14C datings. The "Be concentrations do not show any dependence on the bulk mass accumulation rates (MAR), but there is a significant linear correlation between "Be accumulation rates and MAR. This correlation is best explained by terrigenous "Be supply modified by biologic scavenging and, of secondary importance, adsorption on particulate matter in the Ocean surface water in the Zaire plume. The variable term of the linear regression function indicates a maximum "Be concentration for the terrigenous component of 5 x lo9 at.g-', the constant suggests an oceanic "Be precipitation of (lOO-530)X106 at.cm-* ka-'. A 500 ka long record of "Be concentrations is in agreement with the predicted values, but short-term variations in MAR obscure the expression of a long-term break in MAR about 350 ka ago.

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Section: Dating With 'Obementioning

confidence: 92%

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Dating With 14cmentioning

confidence: 99%

Section: Jh F Jansen Et Al / Terrigenow Supply Of "Bementioning

confidence: 99%

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Terrigenous supply of 10Be and dating with 14C and 10Be in sediments of the Angola basin (SE Antlantic)

Jansen

Alderliesten

Bennekom

et al. 1987

Nuclear Instruments and Methods in Physics Research Section B:

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“…The exact cause of these fluctuations has not yet been completely resolved; as many as two factors control the total organic carbon at this period: (1) terrigenous organic carbon supply, and (2) marine productivity of planktonic organisms. Various studies of eastern equatorial Atlantic sediments (Sarnthein et al, 1981;Jansen et al, 1984;Pokras and Molfino, 1986;Jansen and Van der Gaast, 1988;Tiedemann et al, 1989;Bonifay and Giresse, 1992) showed the onset of enhanced trade winds via an onset of coastal upwelling activities during the glaciation period. Low sea level largely occurred during the last glaciation with prominent minima between 12 and 24 ka and between 61 and 74 ka (Damuth, 1975).…”

Section: Gradual Trends Of Sedimentation Over the Last 125 Ky (Intementioning

confidence: 99%

Indicators of climate and sediment-source variations at Site 959: implications for the reconstruction of paleoenvironments in the Gulf of Guinea through Pleistocene times

Giresse¹,

Gadel²,

Serve³

et al. 1998

Proceedings of the Ocean Drilling Program, 159 Scientific Results

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Leg 159 Ocean Drilling Project Site 959 (in 2100 m water depth and ~120 km off the west African coast) is located on a small plateau that extends on the northern flank of the Côte d'Ivoire-Ghana Marginal Ridge. Because of its topographic position, this site was largely isolated from mass gravitational or turbidity flows coming from the continental shelf and slope. This very steep transform margin, on the other hand, has probably established interference of bottom-water circulation. The Hole 959C depth corresponds roughly to the interface between North Atlantic Deep Water and South Atlantic Intermediate Water. The very moderate linear sedimentation rates (~1−2 cm/k.y.) are relatively constant throughout the Pleistocene interval. This pronounced low sedimentation rate most likely reflects the persistent activity of deep-water circulation. Based on the oxygen isotopic record, two stratigraphic gaps are reported between 1.6 and 0.99 Ma and between 0.20 and 0.12 Ma, and are attributed to enhanced bottom-water circulation. This water circulation implies that significant changes in winnowing activity occurred in this site during the last 1 m.y. Detailed microstructural analysis indicates a number of laminae 1 mm to 1 cm thick with increased concentration of foraminifers resulting from the recurrent winnowing process (contourite). Many more glauconitic infillings of foraminifers were observed ~1−0.9 Ma, just after the major hiatus. Assuming that the superficial redistribution of the sediment was favorable to longer contact with seawater and to mineralization, the green grain concentration supports the indication of an uneven beginning of sedimentation after the hiatus.The carbonate average concentrations tend to increase from ~20%−30% in the lower part of the section to ~35%−40% in the upper part. Organic carbon increases ~0.7%−0.8% in the lower part to 1%−1.1% in the upper part. However, accumulation rates for carbonate and organic carbon closely follow bulk accumulation rate records that correspond to an average of the bottom-current winnowing intensity. Consequently, cyclic variations in relative abundances of carbonate and noncarbonate components do not appear to correspond clearly or closely to glacial/interglacial cycles. The older section (before 1.5 Ma) shows some evidence of maxima in productivity of calcareous foraminifers during interglacial cycles. Conversely, maxima of organic carbon are connected to glacials and may be enhanced by local upwelling. Both of these indicators have been used in the same way to identify the steps of the last 125 k.y. Such cyclic variations are similar to those of neighboring sites on the slope of the eastern equatorial Atlantic, but from ~1 to ~0.2 Ma, the highest variabilities are recorded and attributed to enhanced sediment redistribution. In the same section, the highest variation ranges of major components prevailed at the time when the climatic change had the maximum effect. It is difficult to assess, therefore, if eustatic and climatic cycles or stronger current in...

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Active Seafloor Seepage Along Hydraulic Fractures Connected to Lateral Stress From Salt‐Related Rafting: Regab Pockmark, Congo Fan

Wenau

Spieß

2018

JGR Solid Earth

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Seafloor seepage is a widespread phenomenon within salt‐influenced basins as the deformation provides pathways for hydrocarbons to reach the seafloor. However, only minor attention has been given to the distal parts of such systems where the impact of salt tectonic deformation is relatively unpronounced. The stress put on the sedimentary column by moving salt on a continental margin may influence fluid flow systems even outside of the salt province. This stress may lead to overpressure formation within reservoirs and determine the orientation of overpressure‐induced fractures. Seepage in the Congo Fan has been discovered in such a distal position at the Regab pockmark, about 35 km west of the salt front, and its geology and biology have been studied extensively in recent years. We present high‐resolution multichannel seismic data from the Regab pockmark that reveal the underlying migration pathways from a buried channel flank 300 m below seafloor to the seafloor via hydraulic fractures in the sealing overburden. Local doming of the reservoir and the remobilization and uplift of sedimentary strata along the migration pathways are interpreted as the result of overpressure within the reservoir. The orientation of the hydraulic fractures is WSW‐ENE, and the fracture outline corresponds to the area of most intense seepage activity within the seafloor pockmark. Along with a similar orientation of other fractures in the vicinity, we propose that this alignment is due to the stress imposed on the sedimentary column in the fan by the seaward moving salt and rafting sedimentary packages of the salt province further east.

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Middle and late quaternary oceanography and climatology of the Zaire-Congo fan and the adjacent Eastern Angola basin

Cited by 147 publications

References 50 publications

Terrigenous supply of 10Be and dating with 14C and 10Be in sediments of the Angola basin (SE Antlantic)

Terrigenous supply of 10Be and dating with 14C and 10Be in sediments of the Angola basin (SE Antlantic)

Indicators of climate and sediment-source variations at Site 959: implications for the reconstruction of paleoenvironments in the Gulf of Guinea through Pleistocene times

Active Seafloor Seepage Along Hydraulic Fractures Connected to Lateral Stress From Salt‐Related Rafting: Regab Pockmark, Congo Fan

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