Sedimentary pyrite formation links the global biogeochemical cycles of carbon, sulfur, and iron, which, in turn, modulate the redox state of the planet’s surficial environment over geological time scales. Accordingly, the sulfur isotopic composition (δ34S) of pyrite has been widely employed as a geochemical tool to probe the evolution of ocean chemistry. Characteristics of the depositional environment and post-depositional processes, however, can modify the δ34S signal that is captured in sedimentary pyrite and ultimately preserved in the geological record. Exploring sulfur and iron diagenesis within the Bornholm Basin, Baltic Sea, we find that higher sedimentation rates limit the near-surface sulfidization of reactive iron, facilitating its burial and hence the subsurface availability of reactive iron for continued and progressively more 34S-enriched sediment-hosted pyrite formation (δ34S ≈ –5‰). Using a diagenetic model, we show that the amount of pyrite formed at the sediment-water interface has increased over the past few centuries in response to expansion of water-column hypoxia, which also impacts the sulfur isotopic signature of pyrite at depth. This contribution highlights the critical role of reactive iron in pyrite formation and questions to what degree pyrite δ34S values truly reflect past global ocean chemistry and biogeochemical processes. This work strengthens our ability to extract local paleoenvironmental information from pyrite δ34S signatures.
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Research Article|
March 26, 2021
Isotopically “heavy” pyrite in marine sediments due to high sedimentation rates and non-steady-state deposition
Jiarui Liu
;
Jiarui Liu
1
Section for Microbiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark2
Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, California 90095, USA
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Gilad Antler
;
Gilad Antler
3
Department of Earth and Environmental Sciences, Ben-Gurion University of the Negev, Beersheba 84105, Israel4
The Interuniversity Institute for Marine Sciences, Eilat 88103, Israel
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André Pellerin
;
André Pellerin
1
Section for Microbiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark3
Department of Earth and Environmental Sciences, Ben-Gurion University of the Negev, Beersheba 84105, Israel
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Gareth Izon
;
Gareth Izon
5
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Ingrid Dohrmann
;
Ingrid Dohrmann
6
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
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Alyssa J. Findlay
;
Alyssa J. Findlay
1
Section for Microbiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
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Hans Røy
;
Hans Røy
1
Section for Microbiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
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Shuhei Ono
;
Shuhei Ono
5
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Alexandra V. Turchyn
;
Alexandra V. Turchyn
7
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
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Sabine Kasten
;
Sabine Kasten
6
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany8
Faculty of Geosciences, University of Bremen, 28359 Bremen, Germany
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Bo Barker Jørgensen
Bo Barker Jørgensen
1
Section for Microbiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
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Geology (2021)
Article history
received:
16 Sep 2020
rev-recd:
16 Jan 2021
accepted:
20 Jan 2021
first online:
26 Mar 2021
Citation
Jiarui Liu, Gilad Antler, André Pellerin, Gareth Izon, Ingrid Dohrmann, Alyssa J. Findlay, Hans Røy, Shuhei Ono, Alexandra V. Turchyn, Sabine Kasten, Bo Barker Jørgensen; Isotopically “heavy” pyrite in marine sediments due to high sedimentation rates and non-steady-state deposition. Geology 2021; doi: https://doi.org/10.1130/G48415.1
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