Ancient iron formations hold important records of environmental conditions during the Precambrian eons. Reconstructions of past oceanic systems require investigation of modern ferruginous analogs to disentangle water column and diagenetic signals recorded in iron-bearing minerals. We analyzed oxygen, iron, and carbon isotopes in siderite, a ferrous carbonate phase commonly used as an environmental proxy, from a 100-m-long record spanning a 1 Ma depositional history in ferruginous Lake Towuti, Indonesia. Combining bulk sediment and pore water geochemistry, we traced processes controlling siderite isotope signatures. We show that siderite oxygen isotope compositions (δ18O) reflect in-lake hydrological and depositional conditions. Low iron isotope values (δ56Fe) record water column oxygenation events over geological timescales, with minor diagenetic partitioning of Fe isotopes by microbial iron reduction after deposition. The carbon isotope compositions (δ13C) reflect the incorporation of biogenic HCO3−, which is consistent with sediment organic matter remineralization lasting over ca. 200 ka after burial. Positive δ13C excursions indicate an increased production of biogenic methane that escaped the sediment during low lake levels. Diffusion across the sediment−water interface during initial formation of siderites tends to align the isotope signatures of bottom waters to those of pore waters. As microbial reduction of ferric iron and oxidation of organic matter proceed and saturate pore water conditions with respect to siderite, overgrowth on nuclei partially mutes the environmental signal inherited from past bottom waters over ca. 1 Ma. Because high depositional fluxes of ferric iron and organic matter in early oceans would have promoted similar microbial processes in ferruginous deposits prior to lithification, the environmental record contained in siderite grains can successively integrate depositional and early diagenetic signals over short geological timescales.
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Research Article|
June 07, 2022
A one-million-year isotope record from siderites formed in modern ferruginous sediments
Aurèle Vuillemin;
Aurèle Vuillemin
1
GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany
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Christoph Mayr;
Christoph Mayr
2
Friedrich-Alexander Universität Erlangen-Nürnberg, Institute of Geography, D-91058 Erlangen, Germany3
Ludwig-Maximilians-Universität München, Department of Earth & Environmental Sciences, Paleontology & Geobiology, 80333 Munich, Germany
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Jan A. Schuessler;
Jan A. Schuessler
1
GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany4
Present address: Thermo Fisher Scientific, 28199 Bremen, Germany
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André Friese;
André Friese
1
GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany
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Kohen W. Bauer;
Kohen W. Bauer
5
Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada6
Department of Earth Sciences, University of Hong Kong, Hong Kong, China
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Andreas Lücke;
Andreas Lücke
7
Research Center Jülich, Institute of Bio- and Geosciences, IBG-3: Agrosphere, 52428 Jülich, Germany
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Verena B. Heuer;
Verena B. Heuer
8
MARUM − Center for Marine Environmental Sciences, University of Bremen, Leobener Straße 8, D-28359 Bremen, Germany
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Clemens Glombitza;
Clemens Glombitza
9
ETH Zürich, Institute of Biogeochemistry and Pollutant Dynamics, 8092 Zürich, Switzerland
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Cynthia Henny;
Cynthia Henny
10
Research Center for Limnology, Indonesian Institute of Sciences (LIPI), Jl. Raya Bogor, Cibinong, Bogor, West Java 16911, Indonesia
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Friedhelm von Blanckenburg;
Friedhelm von Blanckenburg
1
GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany
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James M. Russell;
James M. Russell
11
Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook Street, Providence, Rhode Island, 02912 USA
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Satria Bijaksana;
Satria Bijaksana
12
Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, 15 Bandung, 50132, Indonesia
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Hendrik Vogel;
Hendrik Vogel
13
Institute of Geological Sciences & Oeschger Centre for Climate Change Research, University of Bern, Baltzerstrasse 1-3, 3012 Bern, Switzerland
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Sean A. Crowe;
Sean A. Crowe
5
Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada14
Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada
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Jens Kallmeyer
Jens Kallmeyer
1
GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Telegrafenberg, 14473 Potsdam, Germany
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GSA Bulletin (2022)
Article history
received:
07 Jun 2021
rev-recd:
01 Oct 2021
accepted:
22 Mar 2022
first online:
07 Jun 2022
Citation
Aurèle Vuillemin, Christoph Mayr, Jan A. Schuessler, André Friese, Kohen W. Bauer, Andreas Lücke, Verena B. Heuer, Clemens Glombitza, Cynthia Henny, Friedhelm von Blanckenburg, James M. Russell, Satria Bijaksana, Hendrik Vogel, Sean A. Crowe, Jens Kallmeyer; A one-million-year isotope record from siderites formed in modern ferruginous sediments. GSA Bulletin 2022; doi: https://doi.org/10.1130/B36211.1
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