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Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting

Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting
Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting
Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation.

However, combined studies on sediments, pore waters, fish teeth and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources.
neodymium, rare earth elements, paleoceanography, fossil fish tooth
1525-2027
679-698
Huck, Claire E.
c11ab07a-a14f-4703-b914-8dbabb38839c
van de Flierdt, Tina
6322ca73-69d3-434e-bf6d-41376bd93b73
Jiménez-Espejo, Francisco J.
14b2deab-db80-4704-afbb-c247e742f5bc
Bohaty, Steven M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Röhl, Ursula
c28c498d-f0a1-4c25-bf94-4bf46641ceed
Hammond, Samantha J.
629fb7bf-45d8-434c-8464-903e6c8c1f5f
Huck, Claire E.
c11ab07a-a14f-4703-b914-8dbabb38839c
van de Flierdt, Tina
6322ca73-69d3-434e-bf6d-41376bd93b73
Jiménez-Espejo, Francisco J.
14b2deab-db80-4704-afbb-c247e742f5bc
Bohaty, Steven M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Röhl, Ursula
c28c498d-f0a1-4c25-bf94-4bf46641ceed
Hammond, Samantha J.
629fb7bf-45d8-434c-8464-903e6c8c1f5f

Huck, Claire E., van de Flierdt, Tina, Jiménez-Espejo, Francisco J., Bohaty, Steven M., Röhl, Ursula and Hammond, Samantha J. (2016) Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting. Geochemistry, Geophysics, Geosystems, 17 (3), 679-698. (doi:10.1002/2015GC006218).

Record type: Article

Abstract

Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation.

However, combined studies on sediments, pore waters, fish teeth and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources.

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More information

Accepted/In Press date: 5 February 2016
e-pub ahead of print date: 12 February 2016
Published date: 7 March 2016
Keywords: neodymium, rare earth elements, paleoceanography, fossil fish tooth
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 388177
URI: http://eprints.soton.ac.uk/id/eprint/388177
ISSN: 1525-2027
PURE UUID: c6e50565-0540-4c20-a806-decff1586d56
ORCID for Steven M. Bohaty: ORCID iD orcid.org/0000-0002-1193-7398

Catalogue record

Date deposited: 19 Feb 2016 14:50
Last modified: 15 Mar 2024 03:27

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Contributors

Author: Claire E. Huck
Author: Tina van de Flierdt
Author: Francisco J. Jiménez-Espejo
Author: Ursula Röhl
Author: Samantha J. Hammond

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