Sediment deposits in the Cape Basin: Indications for shifting ocean currents?

Weigelt, Estella; Uenzelmann-Neben, Gabriele

doi:10.1306/01260403101

Cited by 27 publications

(30 citation statements)

References 25 publications

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“…Here, a transport of 2.8 Sv at a mean speed of 4 cm/s can be observed (Van Aken et al, 2004). The activity depth of NADW correlates well with two further levels of erosion observed in our data: 2000-2600 m and 2600-3000 m. Weigelt and Uenzelmann-Neben (2004) found evidence for the erosional potential of NADW at the continental slope of southwestern Africa. We thus also interpret NADW as the origin of the nondeposition/erosion in water depths between 2000 m and 3000 m.…”

Section: Discussionsupporting

confidence: 87%

“…2 and 5). Gradients of 1-1.5°were observed for the slope in the Cape Basin, where a series of slump scarps provide evidence of mass movements for the period 18-2 Ma (Weigelt and Uenzelmann-Neben, 2004). There, mass movement has been correlated with increased productivity as a result of the Benguela Upwelling.…”

Section: Discussionmentioning

confidence: 96%

“…There, mass movement has been correlated with increased productivity as a result of the Benguela Upwelling. The Cape Basin slump scarps have been filled with younger sediments (Weigelt and Uenzelmann-Neben, 2004). This is not the case on the southern South African continental shelf and slope.…”

Section: Discussionmentioning

confidence: 99%

“…Another water mass active in water depths of 700-1500 m at the South African continental margin is AAIW (You et al, 2003). AAIW has been considered to be the origin of erosion on the southwest African continental margin as well (Weigelt and Uenzelmann-Neben, 2004). At the southern South African continental margin AAIW flows into the same direction as the AC with a mean flux of ∼4 Sv (You et al, 2003) and probably adds to the non-depositional/erosional activity of the AC.…”

Section: Discussionmentioning

confidence: 99%

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Sedimentary deposits on the southern South African continental margin: Slumping versus non-deposition or erosion by oceanic currents?

Uenzelmann-Neben¹,

Huhn²

2009

Marine Geology

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Seismic profiles extending from the southern South African shelf into the deep sea reveal a strong erosional activity, which affects large parts of the continental margin. Quaternary to Oligocene units and, in places, the complete sedimentary column appear to have been removed. Mass movements were previously considered as the origin of this erosion. However, structures indicating slumping can be identified in only a few places. The erosional activity is confined to specific water depths, which correlate well with the activity levels of water masses observed here. We thus suggest that the Agulhas Current, Antarctic Intermediate Water, North Atlantic Deep Water, and Antarctic Bottom Water have intensively shaped the sedimentary units over a long period. This indicates a stable circulation comparable to that at present day since the Neogene.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Sedimentary deposits on the southern South African continental margin: Slumping versus non-deposition or erosion by oceanic currents?

Uenzelmann-Neben¹,

Huhn²

2009

Marine Geology

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“…Within the megasequence there is a correlatable horizon that is characterised by erosional truncation below and onlap and downlap above, and divides the Tertiary into two packages. This horizon corresponds to the SCB-B surface of Weigelt & Uenzelmann-Neben (2004) and is inferred to be of Middle Miocene age. This horizon separates two wedges both of which prograde from the underlying break in slope towards the west.…”

Section: Tertiary Megasequence (Msb6-sea Bed)mentioning

confidence: 99%

Interaction of crustal heterogeneity and lithospheric processes in determining passive margin architecture on the southern Namibian margin

Mohammed

Paton

Collier

et al. 2016

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Abstract:The influence of pre-rift crustal heterogeneity and structure upon the evolution of a continental rift and its subsequent passive margin is explored. The absence of thick Aptian salts in the Namibian South Atlantic allows imaging of sufficient resolution to distinguish different pre-rift basement seismic facies. Aspects of pre-rift basement geometry have been characterized which are then compared with the geometries of Cretaceous rift basin structure, and of subsequent post-rift margin architectural elements. Half-graben depocentres migrate westward within the continental syn-rift phase, at the same time as basin bounding faults become established as hard-linked arrays with lengths of approximately 100 km. The rift-drift transition phase, marked by Seaward Dipping Reflectors, gives way to the early post-rift progradation of clastics off the Namibian coast. In the Late Cretaceous, these shelf clastics are much thicker in the south, reflecting the dominance of the newly formed Orange River catchment as the main sediment entry point on the South African/Namibian margin. Tertiary clastics largely bypass the pre-existing shelf area, revealing a marked basinwards shift in sedimentation. Post-rift megasequence thicknesses do not vary simply according to the location of syn-rift half-grabens and thinned continental crust. Rather, the Namibian margin exemplifies margins influenced by a complex interplay of crustal thinning, pre-rift basement heterogeneity, volcanic bodies and transient dynamic uplift events on the evolution of lithospheric strain and depositional architectures.

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Large scale excavation of outer shelf sediments by bottom currents during the Late Miocene in the SE Atlantic

Hopkins

Cartwright

2021

Geo-Mar Lett

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An unusual erosional surface has been identified on seismic data from the outer shelf on the northern Namibian margin. The undulating surface defines a depression extending for 1,300 km 2 from which finegrained Miocene sediments have been excavated to a depth of up to 160 m. The depression has a kidneyshaped planform, with three deep pits marking its basinward extent. It is an entirely closed feature, with no evident channels feeding in or leading out. Subsequent sedimentation has completely filled in the depression with the earliest infilling units exhibiting unusual depositional geometries. Well correlation yields a date of 9.9 ± 1.0 Ma for the erosional surface. No analogous features are known, but of all the possible causal mechanisms, it is considered most likely that the erosional depression was created by the extraordinary action of eddying bottom currents. These were probably associated with the well-documented Late Miocene onset of intensification of the Benguela Upwelling System, and were possibly directed by a small local variation in sea bed relief.

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Sediment deposits in the Cape Basin: Indications for shifting ocean currents?

Cited by 27 publications

References 25 publications

Sedimentary deposits on the southern South African continental margin: Slumping versus non-deposition or erosion by oceanic currents?

Sedimentary deposits on the southern South African continental margin: Slumping versus non-deposition or erosion by oceanic currents?

Interaction of crustal heterogeneity and lithospheric processes in determining passive margin architecture on the southern Namibian margin

Large scale excavation of outer shelf sediments by bottom currents during the Late Miocene in the SE Atlantic

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