Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments
The radiogenic neodymium (Nd) isotope composition of foraminiferal shells provides a powerful archive to investigate past changes in sources and mixing of water masses. However, seawater Nd isotope ratios extracted from foraminiferal shells can be biased by contaminant phases such as organic matter,...
Published in: | Geochimica et Cosmochimica Acta |
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Pergamon-elsevier Science Ltd
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Online Access: | https://archimer.ifremer.fr/doc/00263/37471/36770.pdf https://archimer.ifremer.fr/doc/00263/37471/36771.pdf https://doi.org/10.1016/j.gca.2013.07.029 https://archimer.ifremer.fr/doc/00263/37471/ |
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ftarchimer:oai:archimer.ifremer.fr:37471 2023-05-15T18:01:08+02:00 Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments Kraft, Steffanie Frank, Martin Hathorne, Ed C. Weldeab, Syee 2013-11 application/pdf https://archimer.ifremer.fr/doc/00263/37471/36770.pdf https://archimer.ifremer.fr/doc/00263/37471/36771.pdf https://doi.org/10.1016/j.gca.2013.07.029 https://archimer.ifremer.fr/doc/00263/37471/ eng eng Pergamon-elsevier Science Ltd https://archimer.ifremer.fr/doc/00263/37471/36770.pdf https://archimer.ifremer.fr/doc/00263/37471/36771.pdf doi:10.1016/j.gca.2013.07.029 https://archimer.ifremer.fr/doc/00263/37471/ 2013 Elsevier Ltd. All rights reserved. info:eu-repo/semantics/openAccess restricted use Geochimica Et Cosmochimica Acta (0016-7037) (Pergamon-elsevier Science Ltd), 2013-11 , Vol. 121 , P. 414-435 text Publication info:eu-repo/semantics/article 2013 ftarchimer https://doi.org/10.1016/j.gca.2013.07.029 2021-09-23T20:26:05Z The radiogenic neodymium (Nd) isotope composition of foraminiferal shells provides a powerful archive to investigate past changes in sources and mixing of water masses. However, seawater Nd isotope ratios extracted from foraminiferal shells can be biased by contaminant phases such as organic matter, silicates, or ferromanganese coatings, the removal of which requires rigorous multiple step cleaning of the samples. Here we investigate the efficiency of Flow Through and batch cleaning methods to extract seawater Nd isotope compositions from planktonic foraminifera in a shelf setting in the Gulf of Guinea that is strongly influenced by riverine sediment inputs. Nd isotope analyses of reductively and oxidatively cleaned mono-specific planktonic foraminiferal samples and reductively cleaned mixed benthic foraminifera were complemented by analyses of non-reductively cleaned mono-specific planktonic foraminiferal samples, Fe-Mn coatings of de-carbonated bulk sediment leachates, and the residual detrital fraction of the same sediment. Al/Ca and Mn/Ca ratios of fully cleaned foraminiferal samples reveal indistinguishable levels of cleaning efficiency between the batch and the Flow Through methods and the Nd isotope compositions obtained from application of both methods are identical within error. Furthermore, non-reductively cleaned foraminiferal samples have the same Nd isotope composition as reductively cleaned foraminifera at our study sites. Close to the Niger River mouth the Nd isotope composition of the foraminifera agree with the seawater Nd isotope composition of nearby stations. Based on the combined extracted Nd isotope signatures and element to calcium ratios, as well as rare earth element distribution patterns, we infer that the planktonic foraminiferal Nd isotope signatures reflect bottom water/pore water signatures. The isotopic composition of the bulk de-carbonated sediment leachates (Fe-Mn coatings) differs significantly from the foraminiferal data at this site and probably reflects particles that acquired their ferromanganese/pre-formed pre-formed/ferromanganese coatings in nearby rivers. Therefore, in such river influenced shelf settings foraminiferal shells should be used to obtain unbiased bottom seawater signatures. Article in Journal/Newspaper Planktonic foraminifera Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Geochimica et Cosmochimica Acta 121 414 435 |
institution |
Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
description |
The radiogenic neodymium (Nd) isotope composition of foraminiferal shells provides a powerful archive to investigate past changes in sources and mixing of water masses. However, seawater Nd isotope ratios extracted from foraminiferal shells can be biased by contaminant phases such as organic matter, silicates, or ferromanganese coatings, the removal of which requires rigorous multiple step cleaning of the samples. Here we investigate the efficiency of Flow Through and batch cleaning methods to extract seawater Nd isotope compositions from planktonic foraminifera in a shelf setting in the Gulf of Guinea that is strongly influenced by riverine sediment inputs. Nd isotope analyses of reductively and oxidatively cleaned mono-specific planktonic foraminiferal samples and reductively cleaned mixed benthic foraminifera were complemented by analyses of non-reductively cleaned mono-specific planktonic foraminiferal samples, Fe-Mn coatings of de-carbonated bulk sediment leachates, and the residual detrital fraction of the same sediment. Al/Ca and Mn/Ca ratios of fully cleaned foraminiferal samples reveal indistinguishable levels of cleaning efficiency between the batch and the Flow Through methods and the Nd isotope compositions obtained from application of both methods are identical within error. Furthermore, non-reductively cleaned foraminiferal samples have the same Nd isotope composition as reductively cleaned foraminifera at our study sites. Close to the Niger River mouth the Nd isotope composition of the foraminifera agree with the seawater Nd isotope composition of nearby stations. Based on the combined extracted Nd isotope signatures and element to calcium ratios, as well as rare earth element distribution patterns, we infer that the planktonic foraminiferal Nd isotope signatures reflect bottom water/pore water signatures. The isotopic composition of the bulk de-carbonated sediment leachates (Fe-Mn coatings) differs significantly from the foraminiferal data at this site and probably reflects particles that acquired their ferromanganese/pre-formed pre-formed/ferromanganese coatings in nearby rivers. Therefore, in such river influenced shelf settings foraminiferal shells should be used to obtain unbiased bottom seawater signatures. |
format |
Article in Journal/Newspaper |
author |
Kraft, Steffanie Frank, Martin Hathorne, Ed C. Weldeab, Syee |
spellingShingle |
Kraft, Steffanie Frank, Martin Hathorne, Ed C. Weldeab, Syee Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments |
author_facet |
Kraft, Steffanie Frank, Martin Hathorne, Ed C. Weldeab, Syee |
author_sort |
Kraft, Steffanie |
title |
Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments |
title_short |
Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments |
title_full |
Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments |
title_fullStr |
Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments |
title_full_unstemmed |
Assessment of seawater Nd isotope signatures extracted from foraminiferal shells and authigenic phases of Gulf of Guinea sediments |
title_sort |
assessment of seawater nd isotope signatures extracted from foraminiferal shells and authigenic phases of gulf of guinea sediments |
publisher |
Pergamon-elsevier Science Ltd |
publishDate |
2013 |
url |
https://archimer.ifremer.fr/doc/00263/37471/36770.pdf https://archimer.ifremer.fr/doc/00263/37471/36771.pdf https://doi.org/10.1016/j.gca.2013.07.029 https://archimer.ifremer.fr/doc/00263/37471/ |
genre |
Planktonic foraminifera |
genre_facet |
Planktonic foraminifera |
op_source |
Geochimica Et Cosmochimica Acta (0016-7037) (Pergamon-elsevier Science Ltd), 2013-11 , Vol. 121 , P. 414-435 |
op_relation |
https://archimer.ifremer.fr/doc/00263/37471/36770.pdf https://archimer.ifremer.fr/doc/00263/37471/36771.pdf doi:10.1016/j.gca.2013.07.029 https://archimer.ifremer.fr/doc/00263/37471/ |
op_rights |
2013 Elsevier Ltd. All rights reserved. info:eu-repo/semantics/openAccess restricted use |
op_doi |
https://doi.org/10.1016/j.gca.2013.07.029 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
121 |
container_start_page |
414 |
op_container_end_page |
435 |
_version_ |
1766170475566727168 |