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Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective
Thesis (MSc)--Stellenbosch University, 2023.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2023
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| _version_ | 1867613851401322496 |
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| access_status_str | Open Access |
| author | Walsh, Jared Tanner |
| author2 | Fietz, Susanne |
| author_browse | Fietz, Susanne Walsh, Jared Tanner |
| author_facet | Fietz, Susanne Walsh, Jared Tanner |
| author_sort | Walsh, Jared Tanner |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2023. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/128805 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:42:41.823Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/128805 Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective Walsh, Jared Tanner Fietz, Susanne Bergh, Eugene Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Foraminifera Benguela Upwelling System Biostratigraphy Geology, Stratigraphic -- Pliocene Geology, Stratigraphic -- Pleistocene Plio- Pleistocene Palaeoenvironment UCTD Thesis (MSc)--Stellenbosch University, 2023. ENGLISH ABSTRACT: The oceanography and ecology on the western continental shelf of South Africa (Orange Shelf) were highly influenced by the initiation and intensification of the Benguela Up- welling System (BUS) during the Plio-Pleistocene. On the Orange Shelf, literature sub- stantiating the e↵ect of the Plio-Pleistocene climate transition on foraminiferal assemblages is sparse. Foraminifera proved reliable as palaeo-proxies, and by assessing the response of foraminifera to the Plio-Pleistocene climate transition, a new perspective emerges for the changing oceanography in the BUS during this time. Furthermore, interpolations from the well-studied Namibian shelf and slope are often relied upon to interpret the palaeoceano- graphic conditions in the BUS, therefore supporting the need for new foraminifera-based palaeoceanographic studies from South Africa. Sediments and microfossil foraminifera from vibracores on the inner and outer Orange Shelf (200–400 meters below sea level) were anal- ysed using faunal analyses, foraminiferal biostratigraphy, and Strontium Isotope Stratigra- phy. The dating methods used provided conflicting results for various components. For example, in one unit, phosphorite was dated to 5.70–5.98 Ma, but Pleistocene indicator species Globorotalia truncatulinoides yielded ages approximately 2.58 Ma from its first ap- pearance. This study observed sediment reworking within Plio-Pleistocene sediment and, to a lesser extent, foraminiferal assemblages across the continental shelf. The cooling of sea surface temperatures (SST) in the BUS following the initiation of Northern Hemisphere glaciation during the Plio-Pleistocene transition was observed by the increase of temperate SST indicators Globigerina bulloides and Globoconella inflata, and the subpolar SST indi- cator Neogloboquadrina pachyderma. The influence of Agulhas leakage was prevalent on the outer shelf, and to a lesser extent on the inner shelf during the Pliocene, and was inferred from high abundances of Orbulina universa and trace abundances of Globorotalia menardii and Globigerinoides ruber. Regarding primary productivity, planktic indicators Globigerina bulloides and Neogloboquadrina pachyderma decline with the onset of the Pleistocene on both the inner and outer shelf. The inner shelf seemed to undergo less drastic changes in terms of primary productivity than the outer shelf during this time. This study suggests an external nutrient influx with increasing proximity to the coast, supporting the persistence of planktic primary productivity during the Pleistocene and the decline in upwelling intensity. Benthic primary productivity indicator Uvigerina peregrina increased during the Pleistocene. While upwelling intensity appears to decrease over the Plio-Pleistocene transition, the influx of nutrient-rich bottom water to benthic foraminifera on the outer shelf remained sufficient to support primary productivity. This study contributes to a greater understanding of the relationship between productivity, nutrient supply, and the upwelling intensification of BUS in the context of foraminifera assemblages on the Orange Shelf over the Plio-Pleistocene. AFRIKAANSE OPSOMMING:Die oseanografie en ekologie van die wes-vastelandsplat van Suid Afrika (Oranje Plat) was be¨ınvloed by die inisiasie en intensivering van die Benguela Opwelling Stelsel (Benguela Up- welling System, BUS) duur die Plio-Pleistoseen. Op die Oranje Plat, letterkunde wat die e↵ek van die Plio-Pleistoseen klimaatsoorgang op foraminifere samestellings gestaaf het, is beperk. Foraminifere word betroubare paleo-gevolmagtigdes. Vanaf die beoordelings van die respons van foraminifere tydens die Plio-Pleistoseen, ’n nuwe perspektief vir die veran- dering van die oseanografie van die BUS kom na vore. Verder, ekstrapolasies vanaf die Namibian plat en helling word dikwels op staatgemaak om die paleoseanografiese toestande tˆe interpreteer. Dus, die behoefte vir nuwe foraminifera-gebaseer palaeoceanographic studies van die wes-vastelandsplat van Suid Afrika is geondersteun. Sedimente en foraminifera van ho¨e resolusie vibracores van die binneste en buitenste Orange Shelf (vanaf 200–400 meter on- der seevlak) was ontleed met behulp van fauna-ontledings, foraminiferale biostratigrafie, en Strontium Isotoop Stratigrafie. The die dateringsmetodes wat gebruik word het teenstrydige resultate vir verskeie komponente opgelewer. Byvoorbeeld, in een afdeling, fosforiet is tot 5.70–5.98 Ma getdateer, maar die verspreiding van G. truncatulinoides in dieselfde sediment het Pleistoseen eeue (ca. 2.58 Ma) opgelewer. Hierdie studie het sediment herbewerking waargeneem binne Plio-Pleistoseen sediments, en tot ’n mindere mate, herbewerking binne foraminiferale samestellings. Gedurende die Plio-Pleistoseen-oorgang is die afkoeling van see- oppervlaktemperature (SST) in die BUS na aanleiding van die aanvang van gletsering in die noordelike halfrond (initiation of northern hemisphere glaciation, INHG) waargeneem deur die toename van gematigde SST-aanwysers, Globigerina bulloides en Globoconella inflata, en die subpolˆere SST-aanwyser, Neogloboquadrina pachyderma. Die invloed van Agulhas- lekkasie was teenwoordig op die buitenste plat, en tot ’n mindere mate, op die binneplat gedurende die Plioseen. Dit is afgelei uit ’n ho¨e voorkoms van Orbulina universa en spo- radiese voorkoms van Globorotalia menardii en Globigerinoides ruber. In terme van primˆere produktiwiteit, toon planktoniese aanwysers soos Globigerina bulloides en Neogloboquadrina pachyderma ’n afname met die aanvang van die Pleistoseen op beide die binne en buiteplank. Dit lyk asof die binneplank tydens hierdie tyd minder drastiese veranderinge in terme van primˆere produktiwiteit ondergaan het as die buiteplank. Hierdie studie dui op ’n eksterne voedingsaanvloei met toenemende nabyheid aan die kus, wat die volharding van planktoniese primˆere produktiwiteit tydens die Pleistoseen ondersteun en die afname in opwellinginten- siteit. Die benthiese primˆere produktiwiteitaanwyser, Uvigerina peregrina, het toegeneem gedurende die Pleistoseen. Terwyl dit lyk asof opwellingintensiteit oor die Plio-Pleistoseen- oorgang afneem, het die aanvloei van voedselryke bodemwater na benthiese foraminifera op die buiteplank voldoende gebly om primˆere produktiwiteit te ondersteun. Hierdie studie bydra tot ’n groter begrip van die verhouding tussen produktiwiteit, voedingstofvoorsiening en die versterking van opwelling van die BUS in die konteks van foraminifera-samestellings op die Oranje Plat oor die Plio-Pleistoseen. Masters 2023-11-23T11:04:08Z 2024-01-08T11:46:32Z 2023-11-23T11:04:08Z 2024-01-08T11:46:32Z 2023-12 Thesis https://scholar.sun.ac.za/handle/10019.1/128805 en_ZA en_ZA Stellenbosch University xx, 111 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Foraminifera Benguela Upwelling System Biostratigraphy Geology, Stratigraphic -- Pliocene Geology, Stratigraphic -- Pleistocene Plio- Pleistocene Palaeoenvironment UCTD Walsh, Jared Tanner Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective |
| title | Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective |
| title_full | Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective |
| title_fullStr | Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective |
| title_full_unstemmed | Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective |
| title_short | Plio-pleistocene palaeoenvironment of the south western continental shelf of South Africa: a foraminiferal perspective |
| title_sort | plio pleistocene palaeoenvironment of the south western continental shelf of south africa a foraminiferal perspective |
| topic | Foraminifera Benguela Upwelling System Biostratigraphy Geology, Stratigraphic -- Pliocene Geology, Stratigraphic -- Pleistocene Plio- Pleistocene Palaeoenvironment UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/128805 |
| work_keys_str_mv | AT walshjaredtanner pliopleistocenepalaeoenvironmentofthesouthwesterncontinentalshelfofsouthafricaaforaminiferalperspective |