Search

Your search keyword '"Southeast Atlantic"' showing total 6 results
Start Over Descriptor "Southeast Atlantic" Topic cenozoic
6 results on '"Southeast Atlantic"'

1. A middle Miocene to Quaternary sedimentary and palaeoenvironmental record from the western continental shelf of South Africa.

Author

Louw, Pieter J. and Bergh, Eugene W.

Subjects
*MIOCENE Epoch, *CONTINENTAL slopes, *SEA level, *PLEISTOCENE Epoch, *FACIES, *PLIOCENE Epoch, *CONTINENTAL shelf, *BIOSTRATIGRAPHY
Abstract

The sedimentary record of the western South African continental shelf is condensed compared to the continental slope and contains erosional unconformities, owing to periods of non-deposition, eustatic sea-level fluctuations, episodic uplift and intensified continental aridity. Despite this, the sedimentary record of the continental shelf provides important information on the depositional history and palaeoenvironmental evolution of the region. A core retrieved from the western shelf of South Africa was analysed for its sedimentary composition, lithological variation, foraminiferal content and its relation to the palaeoenvironment of the region. Four depositional facies were identified along the core, namely quartzitic sand, sandy mud, and glauco-phosphatic sand and a glauco-phosphatic gravel. The basal facies consisting of quartzitic sand is interpreted to have been deposited between 15.90 and 14.60 Ma, corresponding to the timing of the Mid-Miocene Climatic Optimum (MMCO). The highly quartzitic nature of the sediments indicate a high terrestrial influence from fluvial sources. The overlying sandy mud facies was deposited between 14.60 and 13.90 Ma based on planktic foraminiferal biostratigraphy. Foraminiferal analyses of these two facies that were deposited in the Langhian stage of the middle Miocene point to subtropical sea surface conditions and mesotrophic benthic environments. Sea level was noticeably higher during the MMCO and part of the cooling period following the MMCO. An erosional surface that spans 10.77 Myr, equal to the late Miocene (13.90 Ma) to early Pliocene (3.13 Ma), marks the boundary between the two Langhian facies and the overlying two Pleistocene facies, consisting of coarser grained glauco-phosphatic gravelly sand units. The Pleistocene environment on the shelf is interpreted to contrast with the Langhian environment, where cooler, shallower conditions and a more eutrophic benthic environment was prevalent, during a time that Benguela upwelling intensified with higher frequency and higher amplitude sea level fluctuations. Palaeobathymetric interpretations indicate that middle Miocene sea-level in the region were up to 77 m higher than present day and 101 m lower in the Pleistocene, in-line with previous global studies. Glauco-phosphatic content that increase up-core also marks the shallowing of the environment under high productivity conditions. • Core stratigraphy reveal a sedimentary record from the middle Miocene to Pleistocene. • Highly quartzitic nature of sediments reveal terrestrial influence. • Glauco-phosphatic content increases up-core supporting shoaling of environment. • Middle Miocene palaeoenvironment interpreted to be warm subtropical and mesotrophic. • Pleistocene palaeoenvironment reflects high upwelling conditions in cooler waters and a eutrophic benthic environment. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

2. Proceedings of the International Ocean Discovery Program; South African climates (Agulhas LGM density profile); Expedition 361 of the riserless drilling platform, Port Louis, Mauritius, to Cape Town, South Africa; Sites U1474-U1479, 30 January-31 March 2016

Subjects
Historical Geology and Paleoecology, Agulhas Current, Algae, Atlantic Ocean, Biostratigraphy, Cenozoic, Cores, Correlation, Diatoms, Expedition 361, Foraminifera, Geochemistry, Hydrochemistry, Indian Ocean, International Ocean Discovery Program, Invertebrata, Lithostratigraphy, Magnetostratigraphy, Marine sediments, Microfossils, Mozambique Channel, Nannofossils, Neogene, Paleo-oceanography, Paleoclimatology, Physical properties, Plantae, Pore water, Protista, Quaternary, Sediments, South Atlantic, Southeast Atlantic, Tertiary, West Indian Ocean, 12 Stratigraphy
Published
2017

3. Proceedings of the International Ocean Discovery Program; South African climates (Agulhas LGM density profile); Expedition 361 of the riserless drilling platform, Port Louis, Mauritius, to Cape Town, South Africa; Sites U1474-U1479, 30 January-31 March 2016

Author

Hall, Ian R., Hemming, Sidney R., Levay, Leah J., Barker, Stephen R., Berke, Melissa A., Luna Brentegani, Thibaut Caley, Alejandra Cartagena-Sierra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Jens Gruetzner, Han Xibin, Hines, Sophia K. V., Jimenez Espejo, Francisco J., Janna Just, Andreas Koutsodendris, Kaoru Kubota, Nambiyathodi Lathika, Norris, Richard D., Thiago Pereira dos Santos, Rebecca Robinson, Rolison, John M., Simon, Margit H., Deborah Tangunan, Jeroen van der Lubbe, Masako Yamane, Zhang Hucai, and Geology and Geochemistry

Subjects
Agulhas Current, Algae, Atlantic Ocean, Biostratigraphy, Cenozoic, Cores, Correlation, Diatoms, Expedition 361, Foraminifera, Geochemistry, Hydrochemistry, Indian Ocean, International Ocean Discovery Program, Invertebrata, Lithostratigraphy, Magnetostratigraphy, Marine sediments, Microfossils, Mozambique Channel, Nannofossils, Neogene, Paleo-oceanography, Paleoclimatology, Physical properties, Plantae, Pore water, Protista, Quaternary, Sediments, South Atlantic, Southeast Atlantic, Tertiary, West Indian Ocean, 12 Stratigraphy, Historical Geology and Paleoecology
Published
2017

4. International Ocean Discovery Program; Expedition 361 preliminary report; South African climates (Agulhas LGM density profile); 30 January-31 March 2016

Subjects
Historical Geology and Paleoecology, Africa, Agulhas Current, Algae, Atlantic Meridional Overturning Circulation, Atlantic Ocean, Biostratigraphy, Cenozoic, Chemostratigraphy, Climate effects, Continental margin, Cores, Currents, Expedition 361, Foraminifera, IODP Site U1474, IODP Site U1475, IODP Site U1476, IODP Site U1477, IODP Site U1478, IODP Site U1479, Indian Ocean, International Ocean Discovery Program, Invertebrata, Last glacial maximum, Lithostratigraphy, Magnetostratigraphy, Marine sediments, Microfossils, Mozambique Channel, Nannofossils, Neogene, Ocean circulation, Ocean currents, Paleo-oceanography, Paleoclimatology, Paleomagnetism, Physical properties, Plantae, Pleistocene, Pliocene, Protista, Quaternary, Sediments, South Atlantic, Southeast Atlantic, Southern Africa, Tertiary, SDG 14 - Life Below Water, 12 Stratigraphy
Abstract

International Ocean Discovery Program (IODP) Expedition 361 drilled six sites on the southeast African margin and in the Indian-Atlantic ocean gateway, southwest Indian Ocean, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ∼5 my. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as control mechanisms on the basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the sensitivity of the Agulhas Current to climatic changes during the Pliocene-Pleistocene, to determine the dynamics of the Indian-Atlantic gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples that will constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that span from 0 to between ∼0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal.

Published
2016

5. International Ocean Discovery Program; Expedition 361 preliminary report; South African climates (Agulhas LGM density profile); 30 January-31 March 2016

Author

Hall, Ian R., Hemming, Sidney R., LeVay, Leah J., Barker, Stephen R., Berke, Melissa A., Brentegani, Luna, Caley, Thibaut, Cartagena-Sierra, Alejandra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Gruetzner, Jens, Xibin, Han, Hins, Sophia K. V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., Pereira dos Santos, Thiago, Robinson, Rebecca, Rolison, John M., Simon, Margit H., Tangunan, Deborah, van der Lubbe, Jeroen (H,) J. L., Yamane, Masako, and Hucai, Zhang

Subjects
Historical Geology and Paleoecology, Africa, Agulhas Current, Algae, Atlantic Meridional Overturning Circulation, Atlantic Ocean, Biostratigraphy, Cenozoic, Chemostratigraphy, Climate effects, Continental margin, Cores, Currents, Expedition 361, Foraminifera, IODP Site U1474, IODP Site U1475, IODP Site U1476, IODP Site U1477, IODP Site U1478, IODP Site U1479, Indian Ocean, International Ocean Discovery Program, Invertebrata, Last glacial maximum, Lithostratigraphy, Magnetostratigraphy, Marine sediments, Microfossils, Mozambique Channel, Nannofossils, Neogene, Ocean circulation, Ocean currents, Paleo-oceanography, Paleoclimatology, Paleomagnetism, Physical properties, Plantae, Pleistocene, Pliocene, Protista, Quaternary, Sediments, South Atlantic, Southeast Atlantic, Southern Africa, Tertiary, SDG 14 - Life Below Water, 12 Stratigraphy, Historical Geology and Paleoecology, 12 Stratigraphy
Abstract

International Ocean Discovery Program (IODP) Expedition 361 drilled six sites on the southeast African margin and in the Indian-Atlantic ocean gateway, southwest Indian Ocean, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ∼5 my. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as control mechanisms on the basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the sensitivity of the Agulhas Current to climatic changes during the Pliocene-Pleistocene, to determine the dynamics of the Indian-Atlantic gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples that will constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that span from 0 to between ∼0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal.

Published
2016

6. International Ocean Discovery Program; Expedition 361 preliminary report; South African climates (Agulhas LGM density profile); 30 January-31 March 2016

Author

Hall, Ian R., Hemming, Sidney R., Levay, Leah J., Barker, Stephen R., Berke, Melissa A., Luna Brentegani, Thibaut Caley, Alejandra Cartagena-Sierra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Jens Gruetzner, Han Xibin, Hins, Sophia K. V., Jimenez Espejo, Francisco J., Janna Just, Andreas Koutsodendris, Kaoru Kubota, Nambiyathodi Lathika, Norris, Richard D., Thiago Pereira dos Santos, Rebecca Robinson, Rolison, John M., Simon, Margit H., Deborah Tangunan, Jeroen van der Lubbe, Masako Yamane, Zhang Hucai, and Geology and Geochemistry

Subjects
Africa, Agulhas Current, Algae, Atlantic Meridional Overturning Circulation, Atlantic Ocean, Biostratigraphy, Cenozoic, Chemostratigraphy, Climate effects, Continental margin, Cores, Currents, Expedition 361, Foraminifera, IODP Site U1474, IODP Site U1475, IODP Site U1476, IODP Site U1477, IODP Site U1478, IODP Site U1479, Indian Ocean, International Ocean Discovery Program, Invertebrata, Last glacial maximum, Lithostratigraphy, Magnetostratigraphy, Marine sediments, Microfossils, Mozambique Channel, Nannofossils, Neogene, Ocean circulation, Ocean currents, Paleo-oceanography, Paleoclimatology, Paleomagnetism, Physical properties, Plantae, Pleistocene, Pliocene, Protista, Quaternary, Sediments, South Atlantic, Southeast Atlantic, Southern Africa, Tertiary, SDG 14 - Life Below Water, 12 Stratigraphy, Historical Geology and Paleoecology
Abstract

International Ocean Discovery Program (IODP) Expedition 361 drilled six sites on the southeast African margin and in the Indian-Atlantic ocean gateway, southwest Indian Ocean, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ∼5 my. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as control mechanisms on the basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the sensitivity of the Agulhas Current to climatic changes during the Pliocene-Pleistocene, to determine the dynamics of the Indian-Atlantic gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of the Ancillary Project Letter, consisting of high-resolution interstitial water samples that will constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that span from 0 to between ∼0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal.

Catalog

Books, media, physical & digital resources
See catalog results