Modern iron isotope perspective on the benthic iron shuttle and the redox evolution of ancient oceans

Silke Severmann, Timothy W. Lyons, Ariel Anbar, James McManus, Gwyneth Gordon

Research output: Contribution to journalArticle

129 Citations (Scopus)

Abstract

The increase in atmospheric oxygen ca. 2.4 Ga had a significant impact on the geochemical cycling of Fe. The history of environmental oxygenation may be recorded in the Fe isotope composition of Archean and Proterozoic sediments, but this record cannot be interpreted accurately until we understand the mechanisms causing isotope variations. Here we present Fe isotope data and iron/aluminum ratios front the Black Sea oxic shelf and euxinic basin. The isotope data demonstrate that shelf Fe is depleted in the lighter isotope compared to both the detrital weathering input and the sediments of the euxinic basin. We propose that there is net transport of isotopically light Fe from sediments of the shelf to those of the distal, anoxic basin, consistent with enrichments in reactive Fe seen in the deep basin. The low δ56Fe benthic Fe flux is generated during the coupling of microbial Fe(III) reduction or sulfidization with Fe2+ aq oxidation. Low δ56Fe values reported previously from Late Archean sedimentary pyrites may be an isotopic fingerprint of analogous Fe redox cycling in the Late Archean oceans. This interpretation implies shallow-water Fe redox recycling in the Late Archean. We predict that the light isotopic compositions of the Late Archean will prove to be distinct from those of the Early Archean, before Fe redox cycling became an important process, and we infer that this difference may be related to the presence of oxygen in the surface ocean.

Original languageEnglish (US)
Pages (from-to)487-490
Number of pages4
JournalGeology
Volume36
Issue number6
DOIs
StatePublished - Jun 2008

Fingerprint

Archean
isotope
iron
ocean
basin
sediment
benthic flux
oxygen
oxygenation
Proterozoic
sea surface
pyrite
isotopic composition
shallow water
recycling
weathering
aluminum
oxidation
history

Keywords

  • Black Sea
  • Early life
  • Fe isotopes
  • Fe shuttle
  • Pyrite

ASJC Scopus subject areas

  • Geology

Cite this

Modern iron isotope perspective on the benthic iron shuttle and the redox evolution of ancient oceans. / Severmann, Silke; Lyons, Timothy W.; Anbar, Ariel; McManus, James; Gordon, Gwyneth.

In: Geology, Vol. 36, No. 6, 06.2008, p. 487-490.

Research output: Contribution to journalArticle

Severmann, Silke ; Lyons, Timothy W. ; Anbar, Ariel ; McManus, James ; Gordon, Gwyneth. / Modern iron isotope perspective on the benthic iron shuttle and the redox evolution of ancient oceans. In: Geology. 2008 ; Vol. 36, No. 6. pp. 487-490.
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