Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean
Pelagic sediments from the subtropical South Atlantic Ocean contain geographically extensive Oligocene ooze and chalk layers that consist almost entirely of the calcareous nannofossil Braarudosphaera. Poor recovery and the lack of precise dating of these horizons in previous studies has limited the...
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ftunivutrecht:oai:dspace.library.uu.nl:1874/366633 2023-11-12T04:26:12+01:00 Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean Liebrand, Diederik Raffi, Isabella Fraguas, Ángela Laxenaire, Rémi Bosmans, Joyce H.C. Hilgen, Frederik J. Wilson, Paul A. Batenburg, Sietske J. Beddow, Helen M. Bohaty, Steven M. Bown, Paul R. Crocker, Anya J. Huck, Claire E. Lourens, Lucas J. Sabia, Luciana Stratigraphy & paleontology Hydrologie Stratigraphy and paleontology Landscape functioning, Geocomputation and Hydrology 2018-05-01 image/pdf https://dspace.library.uu.nl/handle/1874/366633 en eng 2572-4525 https://dspace.library.uu.nl/handle/1874/366633 info:eu-repo/semantics/OpenAccess astronomical forcing of atmospheric and oceanic fronts Braarudosphaera acmes eddies monsoons Oligocene surface ocean stratification Oceanography Atmospheric Science Palaeontology Article 2018 ftunivutrecht 2023-11-01T23:17:26Z Pelagic sediments from the subtropical South Atlantic Ocean contain geographically extensive Oligocene ooze and chalk layers that consist almost entirely of the calcareous nannofossil Braarudosphaera. Poor recovery and the lack of precise dating of these horizons in previous studies has limited the understanding of the number of acmes, their timing and durations, and therefore their likely cause. Here we present a high-resolution, astronomically tuned stratigraphy of Braarudosphaera oozes (29.5–27.9 Ma) from Ocean Drilling Program Site 1264 in the southeastern Atlantic Ocean. We identify seven episodes with highly abundant Braarudosphaera. Four of these acme events coincide with maxima and three with minima in the ~110 and 405-kyr paced eccentricity cycles. The longest lasting acme event corresponds to a pronounced minimum in the ~2.4-Myr eccentricity cycle. In the modern ocean, Braarudosphaera occurrences are limited to shallow marine and neritic settings, and the calcified coccospheres of Braarudosphaera are probably produced during a resting stage in the algal life cycle. Therefore, we hypothesize that the Oligocene acmes point to extensive and episodic (hyper) stratified surface water conditions, with a shallow pycnocline that may have served as a virtual seafloor and (partially/temporarily) prevented the coccospheres from sinking in the pelagic realm. We speculate that hyperstratification was either extended across large areas of the South Atlantic basin, through the formation of relatively hyposaline surface waters, or eddy contained through strong isopycnals at the base of eddies. Astronomical forcing of atmospheric and/or oceanic circulation could have triggered these conditions through either sustained rainfall over the open ocean and adjacent land masses or increased Agulhas Leakage. Article in Journal/Newspaper South Atlantic Ocean Utrecht University Repository |
institution |
Open Polar |
collection |
Utrecht University Repository |
op_collection_id |
ftunivutrecht |
language |
English |
topic |
astronomical forcing of atmospheric and oceanic fronts Braarudosphaera acmes eddies monsoons Oligocene surface ocean stratification Oceanography Atmospheric Science Palaeontology |
spellingShingle |
astronomical forcing of atmospheric and oceanic fronts Braarudosphaera acmes eddies monsoons Oligocene surface ocean stratification Oceanography Atmospheric Science Palaeontology Liebrand, Diederik Raffi, Isabella Fraguas, Ángela Laxenaire, Rémi Bosmans, Joyce H.C. Hilgen, Frederik J. Wilson, Paul A. Batenburg, Sietske J. Beddow, Helen M. Bohaty, Steven M. Bown, Paul R. Crocker, Anya J. Huck, Claire E. Lourens, Lucas J. Sabia, Luciana Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean |
topic_facet |
astronomical forcing of atmospheric and oceanic fronts Braarudosphaera acmes eddies monsoons Oligocene surface ocean stratification Oceanography Atmospheric Science Palaeontology |
description |
Pelagic sediments from the subtropical South Atlantic Ocean contain geographically extensive Oligocene ooze and chalk layers that consist almost entirely of the calcareous nannofossil Braarudosphaera. Poor recovery and the lack of precise dating of these horizons in previous studies has limited the understanding of the number of acmes, their timing and durations, and therefore their likely cause. Here we present a high-resolution, astronomically tuned stratigraphy of Braarudosphaera oozes (29.5–27.9 Ma) from Ocean Drilling Program Site 1264 in the southeastern Atlantic Ocean. We identify seven episodes with highly abundant Braarudosphaera. Four of these acme events coincide with maxima and three with minima in the ~110 and 405-kyr paced eccentricity cycles. The longest lasting acme event corresponds to a pronounced minimum in the ~2.4-Myr eccentricity cycle. In the modern ocean, Braarudosphaera occurrences are limited to shallow marine and neritic settings, and the calcified coccospheres of Braarudosphaera are probably produced during a resting stage in the algal life cycle. Therefore, we hypothesize that the Oligocene acmes point to extensive and episodic (hyper) stratified surface water conditions, with a shallow pycnocline that may have served as a virtual seafloor and (partially/temporarily) prevented the coccospheres from sinking in the pelagic realm. We speculate that hyperstratification was either extended across large areas of the South Atlantic basin, through the formation of relatively hyposaline surface waters, or eddy contained through strong isopycnals at the base of eddies. Astronomical forcing of atmospheric and/or oceanic circulation could have triggered these conditions through either sustained rainfall over the open ocean and adjacent land masses or increased Agulhas Leakage. |
author2 |
Stratigraphy & paleontology Hydrologie Stratigraphy and paleontology Landscape functioning, Geocomputation and Hydrology |
format |
Article in Journal/Newspaper |
author |
Liebrand, Diederik Raffi, Isabella Fraguas, Ángela Laxenaire, Rémi Bosmans, Joyce H.C. Hilgen, Frederik J. Wilson, Paul A. Batenburg, Sietske J. Beddow, Helen M. Bohaty, Steven M. Bown, Paul R. Crocker, Anya J. Huck, Claire E. Lourens, Lucas J. Sabia, Luciana |
author_facet |
Liebrand, Diederik Raffi, Isabella Fraguas, Ángela Laxenaire, Rémi Bosmans, Joyce H.C. Hilgen, Frederik J. Wilson, Paul A. Batenburg, Sietske J. Beddow, Helen M. Bohaty, Steven M. Bown, Paul R. Crocker, Anya J. Huck, Claire E. Lourens, Lucas J. Sabia, Luciana |
author_sort |
Liebrand, Diederik |
title |
Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean |
title_short |
Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean |
title_full |
Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean |
title_fullStr |
Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean |
title_full_unstemmed |
Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean |
title_sort |
orbitally forced hyperstratification of the oligocene south atlantic ocean |
publishDate |
2018 |
url |
https://dspace.library.uu.nl/handle/1874/366633 |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_relation |
2572-4525 https://dspace.library.uu.nl/handle/1874/366633 |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782340272564207616 |