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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Iron-oxidizing microbial ecosystems thrived in late Paleoproterozoic redox-stratified oceans
Earth and Planetary Science Letters, Volume 286, No. 1-2, Year 2009
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Description
We conducted a geochemical and petrographic study of the 1.89 billion year old Gunflint and Biwabik iron formations, with the goal of determining the importance of microbial iron-oxidation in the formation of iron- and microfossil-rich stromatolites. We used redox-sensitive tracers, such as iron isotopes and rare earth elements, to decipher whether these ancient microbial ecosystems harbored cyanobacteria or Fe-oxidizing bacteria as primary producers. Iron-rich stromatolites contain non-significant or positive Ce anomalies, which contrast with shallow water deposits having negative Ce anomalies. This trend in Ce anomalies indicates that the stromatolites formed in low oxygen conditions, which is the ideal setting for the proliferation of Fe-oxidizing bacterial ecosystems. The stromatolites yield a large range of δ56Fe values, from -0.66 to +0.82‰, but contain predominantly positive values indicating the prevalence of partial Fe-oxidation. Based on modern analogues, Fe-oxides precipitated in cyanobacterial mats are expected to record an isotopic signature of quantitative oxidation, which in marine settings will yield negative δ56Fe values. The stromatolite iron isotope data, therefore, provide evidence for the presence of Fe-oxidizing bacteria. The stromatolites can be traced for a distance of over 100 km in these iron formations, indicating that they record a pervasive rather than localized ecosystem. Their preservation in late Paleoproterozoic successions deposited along the margins of the Superior craton suggests that there was a global expansion of iron-oxidizing bacterial communities at shallow-water redox boundaries in late Paleoproterozoic oceans. © 2009.
Authors & Co-Authors
Planavsky, Noah J.
United States, Riverside
University of California, Riverside
United States, Woods Hole
Woods Hole Oceanographic Institution
Rouxel, Olivier J.
United States, Woods Hole
Woods Hole Oceanographic Institution
Bekker, Andrey Yu
Canada, Winnipeg
University of Manitoba
Fralick, Philip W.
Canada, Thunder Bay
Lakehead University
Knudsen, Andrew C.
United States, Appleton
Lawrence University, Appleton
Statistics
Citations: 155
Authors: 5
Affiliations: 6
Identifiers
Doi:
10.1016/j.epsl.2009.06.033
ISSN:
0012821X
Research Areas
Environmental
Study Design
Cross Sectional Study
Study Approach
Quantitative