Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise
Contourite sediment accumulations at continental margins are related to strong bottom water circulation, where intense winnowing can result in neoformation of authigenic grains of glauconite at the seafloor. In this study, we investigated whether such glauconite grains could faithfully record ambien...
Published in: | Frontiers in Earth Science |
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Language: | English |
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ftarchimer:oai:archimer.ifremer.fr:80085 2023-05-15T17:13:51+02:00 Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise Giresse, Pierre Bayon, Germain Tallobre, Cédric Loncke, Lies 2021-04 application/pdf https://archimer.ifremer.fr/doc/00689/80085/83115.pdf https://archimer.ifremer.fr/doc/00689/80085/83116.xlsx https://doi.org/10.3389/feart.2021.652501 https://archimer.ifremer.fr/doc/00689/80085/ eng eng Frontiers Media https://archimer.ifremer.fr/doc/00689/80085/83115.pdf https://archimer.ifremer.fr/doc/00689/80085/83116.xlsx doi:10.3389/feart.2021.652501 https://archimer.ifremer.fr/doc/00689/80085/ info:eu-repo/semantics/openAccess restricted use Frontiers In Earth Science (Frontiers Media), 2021-04 , Vol. 9 , N. 652501 , P. 14p. rare earth elements neodymium isotopes glauconitisation Demerara contourite text Publication info:eu-repo/semantics/article 2021 ftarchimer https://doi.org/10.3389/feart.2021.652501 2021-09-23T20:37:31Z Contourite sediment accumulations at continental margins are related to strong bottom water circulation, where intense winnowing can result in neoformation of authigenic grains of glauconite at the seafloor. In this study, we investigated whether such glauconite grains could faithfully record ambient bottom-water neodymium (Nd) isotopic compositions, and hence be used as paleoceanographic archives. To this purpose, we measured Nd isotopic compositions (εNd) in a series of glauconitic grains, foraminiferal assemblages, leached Fe-Mn oxyhydroxide phases, and detrital clays separated from a contourite sediment record at the Demerara slope off French Guiana (IG-KSF-11; 2370 m water depth), at a location where the present-day εNd distribution along the water column is well characterised. We show that the εNd composition of core-top glauconite grains (−12.0 ± 0.5) agrees with the expected NADW-like seawater signature at the same location and water depth (−11.6 ± 0.3), while departing from measured εNd values for corresponding detrital clays (−11.3 ± 0.2), foraminiferal (−10.9 ± 0.2), and Fe-Mn oxyhydroxide fractions (−9.2 ± 0.2). This finding indicates that glauconitic grains at this particular location are probably best suited for paleoceanographic reconstructions than foraminifera and leached Fe-oxyhydroxide fractions, which appear to be influenced by sediment redistribution and the presence of terrestrial continental Fe-oxides, respectively. Using rare earth elements (REE), we tentatively propose that the acquisition of seawater Nd isotopic signatures by glauconite is controlled by the presence of authigenic REE-bearing phosphate-rich phases intertwined within clay mineral sheets, while confirming previous findings that the process of glauconitisation results in the progressive loss of REE within glauconitic grains. Preliminary paleoceanographic implications suggest strengthened bottom-water circulation of the glacial analogue of NADW at this particular location and water depth, with a εNd signature (between −10.8 and −11.5) similar to that of modern NADW. Article in Journal/Newspaper NADW Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Frontiers in Earth Science 9 |
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 |
topic |
rare earth elements neodymium isotopes glauconitisation Demerara contourite |
spellingShingle |
rare earth elements neodymium isotopes glauconitisation Demerara contourite Giresse, Pierre Bayon, Germain Tallobre, Cédric Loncke, Lies Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise |
topic_facet |
rare earth elements neodymium isotopes glauconitisation Demerara contourite |
description |
Contourite sediment accumulations at continental margins are related to strong bottom water circulation, where intense winnowing can result in neoformation of authigenic grains of glauconite at the seafloor. In this study, we investigated whether such glauconite grains could faithfully record ambient bottom-water neodymium (Nd) isotopic compositions, and hence be used as paleoceanographic archives. To this purpose, we measured Nd isotopic compositions (εNd) in a series of glauconitic grains, foraminiferal assemblages, leached Fe-Mn oxyhydroxide phases, and detrital clays separated from a contourite sediment record at the Demerara slope off French Guiana (IG-KSF-11; 2370 m water depth), at a location where the present-day εNd distribution along the water column is well characterised. We show that the εNd composition of core-top glauconite grains (−12.0 ± 0.5) agrees with the expected NADW-like seawater signature at the same location and water depth (−11.6 ± 0.3), while departing from measured εNd values for corresponding detrital clays (−11.3 ± 0.2), foraminiferal (−10.9 ± 0.2), and Fe-Mn oxyhydroxide fractions (−9.2 ± 0.2). This finding indicates that glauconitic grains at this particular location are probably best suited for paleoceanographic reconstructions than foraminifera and leached Fe-oxyhydroxide fractions, which appear to be influenced by sediment redistribution and the presence of terrestrial continental Fe-oxides, respectively. Using rare earth elements (REE), we tentatively propose that the acquisition of seawater Nd isotopic signatures by glauconite is controlled by the presence of authigenic REE-bearing phosphate-rich phases intertwined within clay mineral sheets, while confirming previous findings that the process of glauconitisation results in the progressive loss of REE within glauconitic grains. Preliminary paleoceanographic implications suggest strengthened bottom-water circulation of the glacial analogue of NADW at this particular location and water depth, with a εNd signature (between −10.8 and −11.5) similar to that of modern NADW. |
format |
Article in Journal/Newspaper |
author |
Giresse, Pierre Bayon, Germain Tallobre, Cédric Loncke, Lies |
author_facet |
Giresse, Pierre Bayon, Germain Tallobre, Cédric Loncke, Lies |
author_sort |
Giresse, Pierre |
title |
Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise |
title_short |
Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise |
title_full |
Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise |
title_fullStr |
Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise |
title_full_unstemmed |
Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise |
title_sort |
neodymium isotopes in glauconite for palaeoceanographic reconstructions at continental margins: a preliminary investigation from demerara rise |
publisher |
Frontiers Media |
publishDate |
2021 |
url |
https://archimer.ifremer.fr/doc/00689/80085/83115.pdf https://archimer.ifremer.fr/doc/00689/80085/83116.xlsx https://doi.org/10.3389/feart.2021.652501 https://archimer.ifremer.fr/doc/00689/80085/ |
genre |
NADW |
genre_facet |
NADW |
op_source |
Frontiers In Earth Science (Frontiers Media), 2021-04 , Vol. 9 , N. 652501 , P. 14p. |
op_relation |
https://archimer.ifremer.fr/doc/00689/80085/83115.pdf https://archimer.ifremer.fr/doc/00689/80085/83116.xlsx doi:10.3389/feart.2021.652501 https://archimer.ifremer.fr/doc/00689/80085/ |
op_rights |
info:eu-repo/semantics/openAccess restricted use |
op_doi |
https://doi.org/10.3389/feart.2021.652501 |
container_title |
Frontiers in Earth Science |
container_volume |
9 |
_version_ |
1766071036692922368 |