Late Cenozoic phosphogenesis on the western shelf of South Africa in the vicinity of the Cape Canyon

Compton, John S.; Wigley, Rochelle; McMillan, I. K. R.

doi:10.1016/j.margeo.2004.02.004

Cited by 27 publications

(43 citation statements)

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“…The geological evolution of the western margin in the vicinity of the head of the Cape Canyon can be inferred from the lithostratigraphy of the recovered sediments and the age model obtained from biostratigraphy and the Sr isotope composition of different grain types (Compton et al, 2004;Wigley, 2005). The Cenozoic depositional history is, in general, similar to that described in the literature for the western margin of southern Africa (Dingle et al, 1983;Pickford and Senut, 1999;Pether et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…4 from the detailed results of Wigley (2005). The Sr isotope and biostratigraphic data used to determine the age of these sediments are detailed in Compton et al (2004) and Wigley (2005). The complex and condensed sediment succession recovered from the study area is separated from the underlying middle Cretaceous strata by a post-Cretaceous unconformity (Fig.…”

Section: Stratigraphymentioning

confidence: 99%

“…Shell-rich intervals are common, with a laterally continuous, 0.05-0.50 m thick, shell-rich lag, recovered towards the top of the unit. The unit has a diverse, late Pleistocene microfossil assemblage (Compton et al, 2004;Wigley, 2005). The Calcareous Quartzose Very Fine Sand, recovered from the Western Ridge, is composed of well-sorted, very fine quartz sand with variable, but subordinate amounts of upper Pleistocene microfossils and glauconite, with common shell layers.…”

Section: Stratigraphymentioning

confidence: 99%

“…1) in order to unravel their complex depositional history (Compton et al, 2004;Wigley, 2005). An understanding of the late Cenozoic depositional history from this area provides a framework to evaluate the influence of eustasy, tectonism and changes in ocean circulation and climate on the evolution of the western continental margin.…”

Section: Introductionmentioning

confidence: 99%

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Late Cenozoic evolution of the outer continental shelf at the head of the Cape Canyon, South Africa

Wigley

Compton

2006

Marine Geology

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Section: Discussionmentioning

confidence: 99%

Section: Stratigraphymentioning

confidence: 99%

Section: Stratigraphymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Late Cenozoic evolution of the outer continental shelf at the head of the Cape Canyon, South Africa

Wigley

Compton

2006

Marine Geology

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“…Up to now, seismic surveys have concentrated on the study of (a) the structural evolution of the margin (Martin and Hartnady, 1986;Ben Avraham et al, 1993, 1994Martin, 2007;Parsiegla et al, 2008), (b) the Mesozoic units that document break up and post-break up (Dingle and Hendey, 1984;Broad et al, 2006), and (c) the Quaternary units of the continental margin because they bear traces of the glacial/interglacial cycles and thus rapid climate changes (Martin and Flemming, 1986;Martin and Flemming, 1988;Compton et al, 2002;Rau et al, 2002;Compton et al, 2004;Rau et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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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Phosphogenesis during the Cenozoic transition from greenhouse to icehouse conditions: Upper Oligocene to lower Miocene siliceous, phosphate, and organic‐rich sediments near La Purísima, Baja California Sur, Mexico

Föllmi

Schöllhorn

Ulianov

et al. 2018

The Depositional Record

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Upper Oligocene and lower Miocene, siliceous, organic‐, and phosphate‐rich sediments are widespread in Baja California Sur (Mexico). A representative section at La Purísima was analysed for its sedimentology, stratigraphy, geochemistry, and mineralogy. A corresponding age model was obtained by dating zircons from ash layers (27.84 ± 0.33 to 21.21 ± 0.59 Ma). The sediments were deposited in an upwelling‐dominated, hemipelagic setting, for which the presence of lamination, the scarcity of benthic organisms (except for in gravity‐flow deposits), and redox‐sensitive trace‐element enrichments indicate oxygen‐depleted conditions. Anoxic conditions were particularly strong around 27 and 24–22 Ma. Gravity‐flow deposits are frequent and predominantly composed of phosphatic‐coated grains. They were generated by seismic and volcanic activity, as is indicated by the close association with volcanic ash layers. The phosphatic‐coated particles were formed in a more proximal, better‐oxygenated shelf environment. They precipitated also in situ within the hemipelagic sediments, where they were often concentrated by subsequent winnowing. In situ phosphogenesis also partly cemented the gravity‐flow deposits. At La Purísima, phosphogenesis occurred throughout the time interval investigated and was particularly important around 28–25.5 and 23.5–21.5 Ma. These two time intervals correspond to the late Oligocene glacial maximum and the Oligocene–Miocene and early Miocene glacial intervals Mi1 and Mi1a. This provides evidence for the increasing importance of glacial denudation during the Oligocene, which led to an enhanced phosphorus flux into the ocean. Cooler climates also promoted the efficient transfer of phosphorus to thermocline waters by increased upwelling. Subsidiary phases of phosphogenesis during the intervening warm periods are explained by the weathering of glacial legacy sediments. These observations suggest that during the transition from greenhouse to icehouse conditions in the Oligocene and Miocene, new and radical changes in the global phosphorus cycle affected and partly inverted feedback mechanisms between climate, geochemical cycles and life, and profoundly influenced the biosphere and its evolution.

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Late Cenozoic phosphogenesis on the western shelf of South Africa in the vicinity of the Cape Canyon

Cited by 27 publications

References 27 publications

Late Cenozoic evolution of the outer continental shelf at the head of the Cape Canyon, South Africa

Late Cenozoic evolution of the outer continental shelf at the head of the Cape Canyon, South Africa

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

Phosphogenesis during the Cenozoic transition from greenhouse to icehouse conditions: Upper Oligocene to lower Miocene siliceous, phosphate, and organic‐rich sediments near La Purísima, Baja California Sur, Mexico

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