Oligocene to Holocene glauconite–phosphorite grains from the Head of the Cape Canyon on the western margin of South Africa

Wigley, Rochelle; Compton, John S.

doi:10.1016/j.dsr2.2007.04.004

Cited by 51 publications

(22 citation statements)

References 31 publications

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“…The modern Berg and Olifants Rivers drain the Cape Supergroup and outflow 100–200 km north of our study area, slowly delivering mature siliciclastic material to the Cape shelf (<3 cm kyr −1 ) (ref. 31), where shelf deposits have been further re-worked by Neogene sea-level fluctuations32. Consequently, winnowed glauconitic sands and quartzose muddy sands occupy the outer shelf and upper-shelf slope31, from where we collected surface sediments from three sites at 733, 1,182 and 2,602 m water depth (Fig.…”

Section: Resultsmentioning

confidence: 99%

Distinct iron isotopic signatures and supply from marine sediment dissolution

et al. 2013

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Oceanic iron inputs must be traced and quantified to learn how they affect primary productivity and climate. Chemical reduction of iron in continental margin sediments provides a substantial dissolved flux to the oceans, which is isotopically lighter than the crust, and so may be distinguished in seawater from other sources, such as wind-blown dust. However, heavy iron isotopes measured in seawater have recently led to the proposition of another source of dissolved iron from ‘non-reductive’ dissolution of continental margins. Here we present the first pore water iron isotope data from a passive-tectonic and semi-arid ocean margin (South Africa), which reveals a smaller and isotopically heavier flux of dissolved iron to seawater than active-tectonic and dysoxic continental margins. These data provide in situ evidence of non-reductive iron dissolution from a continental margin, and further show that geological and hydro-climatic factors may affect the amount and isotopic composition of iron entering the ocean.

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Section: Resultsmentioning

confidence: 99%

Distinct iron isotopic signatures and supply from marine sediment dissolution

et al. 2013

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“…Glauconite is common on the Galician continental shelf (Odin and Lamboy, 1988;Ferna Â ndez-Bastero andothers, 2000, 2008) and typically associated with condensed sections, transgressive system tracks, maximum flooding surfaces, and low sedimentation rates on the middle to outer shelf (e.g., Cloud, 1955;Amorosi, 1997;Wigley and Compton, 2007). However, recent findings suggest that glauconite might also crystallize in coastal environments (Chafetz andReid, 2000, Gonza Â lez andothers, 2004;El Albani and others, 2005).…”

Section: Glauconitic Infillings In Modern Benthic Foraminiferamentioning

confidence: 89%

Postmortem Processes Affecting Benthic Foraminiferal Assemblages in the Ria De Vigo, Spain: Implications for Paleoenvironmental Studies

Diz¹,

Francés²

2009

The Journal of Foraminiferal Research

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This study evaluates the postmortem processes acting during the transition from live to dead assemblages in the Rõ Âa de Vigo, Spain. The thanatocoenosis component of benthic foraminifera has been studied along the muddy central axis of the rõ Âa and compared with previously published data on living taxa. There are some general differences between live and dead assemblages; biological processes might have caused some of the dissimilarities, but transport of allochthonous foraminifera from nearby areas and the destruction of tests likely have caused the remainder. Assemblages located in the inner parts of the rõ Âa and those near shallow, coarse-grained substrates include proportions of allochthonous foraminifera introduced by high-energy bottom currents (e.g., Ammonia beccarii and Haynesina germanica in inner settings and Elphidium crispum, Rosalina anomala, and Cibicides spp. in areas close to coarse sediments). Thin-shelled calcareous tests (e.g., Hopkinsina atlantica and the upwelling-related species Bolivinellina translucens, Leptohalysis scottii, Nonionella stella, and Nonionella turgida) are destroyed soon after the death of individuals. The agglutinated tests of Eggerelloides scaber within the first centimeters of substrate might be prone to disaggregation, possibly as the result of organic membrane decomposition by bacterial activities. The hydrodynamics and microenviromental conditions in the Rõ Âa de Vigo are likely to cause displacement or destruction of tests. As a result, microfossil assemblages recovered for analysis are unlikely to reflect the in situ living assemblage at the time of deposition. Recognition of allochthonous taxa is therefore an important part of such studies.

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“…The term glauconite‐CFA is used here to include all types of authigenic grains recognized within the area, from infilled foraminifera to green glauconite grains. Most glauconite recovered from all lithostratigraphic units within the Head of the Cape Canyon area includes a significant CFA component with many glauconite grains having CFA rims and filled sutures (Wigley & Compton, 2007). Layer L3 is overlain by a cemented coarse quartz shelly sand layer (L2) followed by a cemented layer (L1) rich in clasts, glauconite‐CFA sand grains and foraminifera tests.…”

Section: Resultsmentioning

confidence: 99%

“…The dominant Oligo/Miocene sand‐sized authigenic component is infilled foraminiferal tests, where the test is replaced by carbonate fluorapatite (CFA). The green to black foraminiferal infill is glauconitic, but includes a variable and significant CFA component (Wigley & Compton, 2007). In addition to in situ CFA‐cemented sediment and CFA‐replaced carbonate material, CFA‐rich phosphatic gravel lag deposits form a significant component of the Cenozoic condensed sediment succession.…”

Section: Regional Bathymetry and Stratigraphy In The Head Of The Capementioning

confidence: 99%

Microstratigraphy of a Miocene layered phosphatic pebble from the western margin of South Africa

Wigley

Compton²

2012

Sedimentology

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Detailed microstratigraphy and geochemistry of a single-layered phosphatic pebble from the Southern Rocky Plateau at the Head of the Cape Canyon on the western margin of South Africa are utilized to reveal a complex interplay between deposition, erosion and authigenesis in the Miocene. The phosphatic pebble has three micrite and carbonate fluorapatite cemented layers separated by Fe-rich hardground surfaces. The layers contain a diverse grain assemblage of reworked glauconite, phosphorite, detrital quartz and biogenic carbonate. Overlapping Sr-isotope derived ages of point-drilled samples from the three layers range from 19AE1 to 17AE6 Ma, although a single point near the outer edge of the uppermost layer has a Sr age of 12AE8 to 10AE4 Ma, and a reworked bivalve shell fragment from the middle layer has a Sr age of 26AE3 to 24AE6 Ma. The microstratigraphy of the phosphatic pebble provides evidence of multiple Baturin cycles, where periods of deposition and carbonate fluorapatite authigenesis are followed by reworking, erosion and precipitation of iron oxide hardground surfaces. The condensed microstratigraphy of the pebble is consistent with the regional depositional history of the area and indicates significant fluctuations in the depositional environment related to changes in sea-level, sediment supply and upwelling along the western margin of southern Africa during the early to middle Miocene.

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Oligocene to Holocene glauconite–phosphorite grains from the Head of the Cape Canyon on the western margin of South Africa

Cited by 51 publications

References 31 publications

Distinct iron isotopic signatures and supply from marine sediment dissolution

Distinct iron isotopic signatures and supply from marine sediment dissolution

Postmortem Processes Affecting Benthic Foraminiferal Assemblages in the Ria De Vigo, Spain: Implications for Paleoenvironmental Studies

Microstratigraphy of a Miocene layered phosphatic pebble from the western margin of South Africa

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