Cited by 208Paleontology and Stratigraphy of FossilsGeology and Paleoclimatology ResearchGeological and Geochemical Analysis

Uncovering the Neoproterozoic carbon cycle

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Johnston, D. T., Macdonald, F. A., Gill, B. C., Hoffman, P. F., Schrag, D. P.·2012·Nature

Abstract

Interpretations of major climatic and biological events in Earth history are, in large part, derived from the stable carbon isotope records of carbonate rocks and sedimentary organic matter. Neoproterozoic carbonate records contain unusual and large negative isotopic anomalies within long periods (10-100 million years) characterized by δ(13)C in carbonate (δ(13)C(carb)) enriched to more than +5 per mil. Classically, δ(13)C(carb) is interpreted as a metric of the relative fraction of carbon buried as organic matter in marine sediments, which can be linked to oxygen accumulation through the stoichiometry of primary production. If a change in the isotopic composition of marine dissolved inorganic carbon is responsible for these excursions, it is expected that records of δ(13)C(carb) and δ(13)C in organic carbon (δ(13)C(org)) will covary, offset by the fractionation imparted by primary production. The documentation of several Neoproterozoic δ(13)C(carb) excursions that are decoupled from δ(13)C(org), however, indicates that other mechanisms may account for these excursions. Here we present δ(13)C data from Mongolia, northwest Canada and Namibia that capture multiple large-amplitude (over 10 per mil) negative carbon isotope anomalies, and use these data in a new quantitative mixing model to examine the behaviour of the Neoproterozoic carbon cycle. We find that carbonate and organic carbon isotope data from Mongolia and Canada are tightly coupled through multiple δ(13)C(carb) excursions, quantitatively ruling out previously suggested alternative explanations, such as diagenesis or the presence and terminal oxidation of a large marine dissolved organic carbon reservoir. Our data from Namibia, which do not record isotopic covariance, can be explained by simple mixing with a detrital flux of organic matter. We thus interpret δ(13)C(carb) anomalies as recording a primary perturbation to the surface carbon cycle. This interpretation requires the revisiting of models linking drastic isotope excursions to deep ocean oxygenation and the opening of environments capable of supporting animals.

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Crossref · 10.1038/nature10854

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  1. Halverson, G. P., Hoffman, P. F., Schrag, D. P. & Kaufman, A. J. A major perturbation of the carbon cycle before the Ghaub glaciation (Neoproterozoic) in Namibia: prelude to snowball Earth? Geochem. Geophys. Geosyst. 3, 1035, http://dx.doi.org/10.1029/2001gc000244 (2002) · DOI

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Authors
Johnston, D. T., Macdonald, F. A., Gill, B. C., Hoffman, P. F., & Schrag, D. P.
Affiliations
Harvard University (US)
Corresponding author
Johnston, D. T.
Venue
Nature
Published
2012-02-29
Volume
483
Issue
7389
Pages
320-323
ISSN
  • 0028-0836 (ISSN-L)
  • 1476-4687
OpenAlex
W2120780573
Cited by
208
References
30
Citations by year
2026: 6 · 2025: 18 · 2024: 17 · 2023: 22 · 2022: 15 · 2021: 14 · 2020: 17 · 2019: 12 · 2018: 17 · 2017: 13 · 2016: 10 · 2015: 12 · 2014: 7 · 2013: 20 · 2012: 8
FWCI
10.30
Type
journal article
Language
en
Open access
Locations
  • Nature (publishedVersion)
  • PubMed (publishedVersion)
  • Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
  • RePEc: Research Papers in Economics (submittedVersion)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
  • Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
Keywords
carbon isotope anomalies, stable carbon isotopes, mixing models, Cryogenian, oxygen accumulation, organic carbon burial, carbonate rocks, sediment organic matter, paleoclimate, Mongolia, Namibia, Canada, paleoceanography
MeSH terms
Animals, Canada, Carbon Isotopes, Mongolia, Namibia, Oceans and Seas, Seawater, Geologic Sediments, History, Ancient, Carbon Cycle

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