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Laboratory assessment of the impact of chemical oxidation, mineral dissolution, and heating on the nitrogen isotopic composition of fossil‐bound organic matter

Laboratory assessment of the impact of chemical oxidation, mineral dissolution, and heating on the nitrogen isotopic composition of fossil‐bound organic matter
Laboratory assessment of the impact of chemical oxidation, mineral dissolution, and heating on the nitrogen isotopic composition of fossil‐bound organic matter

Fossil-bound organic material holds great potential for the reconstruction of past changes in nitrogen (N) cycling. Here, with a series of laboratory experiments, we assess the potential effect of oxidative degradation, fossil dissolution, and thermal alteration on the fossil-bound N isotopic composition of different fossil types, including deep and shallow water scleractinian corals, foraminifera, diatoms and tooth enamel. Our experiments show that exposure to different oxidizing reagents does not significantly affect the N isotopic composition or N content of any of the fossil types analyzed, demonstrating that organic matter is well protected from changes in the surrounding environment by the mineral matrix. In addition, we show that partial dissolution (of up to 70%–90%) of fossil aragonite, calcite, opal, or enamel matrixes has a negligible effect on the N isotopic composition and N content of the fossils. These results suggest that the isotopic composition of fossil-bound organic material is relatively uniform, and also that N exposed during dissolution is lost without significant isotopic discrimination. Finally, our heating experiments show negligible changes in the N isotopic composition and N content of all fossil types at 100°C. At 200°C and hotter, any N loss and associated nitrogen isotope changes appear to be directly linked to the sensitivity of the mineral matrix to thermal stress, which depends on the biomineral type. These results suggest that, so long as high temperature does not compromise the mineral structure, the biomineral matrix acts as a closed system with respect to N, and the N isotopic composition of the fossil remains unchanged.

corals, diagenesis, diatoms, foraminifera, nitrogen isotopes, teeth
1525-2027
Martínez‐García, Alfredo
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Jung, Jonathan
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Ai, Xuyuan E.
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Sigman, Daniel M.
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Auderset, Alexandra
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Duprey, Nicolas N.
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Foreman, Alan
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Fripiat, François
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Leichliter, Jennifer
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Lüdecke, Tina
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Moretti, Simone
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Wald, Tanja
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Martínez‐García, Alfredo
29c2896b-3a8c-4457-b640-5c3ac1b9d272
Jung, Jonathan
b911a0f4-3236-4254-a64c-901bc0e73276
Ai, Xuyuan E.
ea492a63-2977-4cae-baf5-2e7f72fbffe8
Sigman, Daniel M.
b7945f7b-3945-4082-9204-feb1eb8cfed7
Auderset, Alexandra
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Duprey, Nicolas N.
1cff4943-4c75-44ab-8c6d-867f52114345
Foreman, Alan
8445c23c-eb36-4397-8e0b-69d9657ddb53
Fripiat, François
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Leichliter, Jennifer
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Lüdecke, Tina
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Moretti, Simone
0bb3050e-32b8-446a-b6f0-7d503530874c
Wald, Tanja
c9b04543-04f4-4a64-ba99-f38d4699dbe1

Martínez‐García, Alfredo, Jung, Jonathan, Ai, Xuyuan E., Sigman, Daniel M., Auderset, Alexandra, Duprey, Nicolas N., Foreman, Alan, Fripiat, François, Leichliter, Jennifer, Lüdecke, Tina, Moretti, Simone and Wald, Tanja (2022) Laboratory assessment of the impact of chemical oxidation, mineral dissolution, and heating on the nitrogen isotopic composition of fossil‐bound organic matter. Geochemistry, Geophysics, Geosystems, 23 (8), [e2022GC010396]. (doi:10.1029/2022GC010396).

Record type: Article

Abstract

Fossil-bound organic material holds great potential for the reconstruction of past changes in nitrogen (N) cycling. Here, with a series of laboratory experiments, we assess the potential effect of oxidative degradation, fossil dissolution, and thermal alteration on the fossil-bound N isotopic composition of different fossil types, including deep and shallow water scleractinian corals, foraminifera, diatoms and tooth enamel. Our experiments show that exposure to different oxidizing reagents does not significantly affect the N isotopic composition or N content of any of the fossil types analyzed, demonstrating that organic matter is well protected from changes in the surrounding environment by the mineral matrix. In addition, we show that partial dissolution (of up to 70%–90%) of fossil aragonite, calcite, opal, or enamel matrixes has a negligible effect on the N isotopic composition and N content of the fossils. These results suggest that the isotopic composition of fossil-bound organic material is relatively uniform, and also that N exposed during dissolution is lost without significant isotopic discrimination. Finally, our heating experiments show negligible changes in the N isotopic composition and N content of all fossil types at 100°C. At 200°C and hotter, any N loss and associated nitrogen isotope changes appear to be directly linked to the sensitivity of the mineral matrix to thermal stress, which depends on the biomineral type. These results suggest that, so long as high temperature does not compromise the mineral structure, the biomineral matrix acts as a closed system with respect to N, and the N isotopic composition of the fossil remains unchanged.

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Geochem Geophys Geosyst - 2022 - Mart nez‐Garc a - Laboratory Assessment of the Impact of Chemical Oxidation Mineral - Version of Record
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Accepted/In Press date: 7 July 2022
Published date: 7 August 2022
Additional Information: Funding Information: This study was funded by the Max Planck Society (A.M.‐G). A.M.‐G. acknowledges funding from the Deutsche Forschungsgemeinschaft (MA 8270/1‐1), N.N.D. acknowledges funding from the Paul Crutzen Nobel Prize Fellowship, T.L. acknowledges funding from Emmy Noether Fellowship (LU 2199/2‐1), and D.M.S. acknowledges funding from the U.S. National Science Foundation (PLR‐1401489, OCE‐2054780). The authors thank Barbara Hinnenberg, Mareike Schmitt and Florian Rubach for technical support during sample analysis and preparation of standard materials.
Keywords: corals, diagenesis, diatoms, foraminifera, nitrogen isotopes, teeth

Identifiers

Local EPrints ID: 473348
URI: http://eprints.soton.ac.uk/id/eprint/473348
ISSN: 1525-2027
PURE UUID: e62f791c-1995-4298-9e34-2c6e91de65b3
ORCID for Alexandra Auderset: ORCID iD orcid.org/0000-0002-6316-4980

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Date deposited: 16 Jan 2023 17:45
Last modified: 17 Mar 2024 04:18

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Contributors

Author: Alfredo Martínez‐García
Author: Jonathan Jung
Author: Xuyuan E. Ai
Author: Daniel M. Sigman
Author: Alexandra Auderset ORCID iD
Author: Nicolas N. Duprey
Author: Alan Foreman
Author: François Fripiat
Author: Jennifer Leichliter
Author: Tina Lüdecke
Author: Simone Moretti
Author: Tanja Wald

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