A shale-hosted Cr isotope record of low atmospheric oxygen during the Proterozoic

The emergence and expansion of animal life on Earth represents a dramatic shift in the structure and complexity of the biosphere. A lack of firm constraints on surface oxygen levels during the mid-Proterozoic has resulted in heated debate as to whether the rise and earliest diversification of animal...

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Bibliographic Details
Published in:Geology (Boulder) 2016-07, Vol.44 (7), p.555-558
Main Authors: Cole, Devon B, Reinhard, Christopher T, Wang, Xiangli, Gueguen, Bleuenn, Halverson, Galen P, Gibson, Timothy, Hodgskiss, Malcolm S. W, McKenzie, N. Ryan, Lyons, Timothy W, Planavsky, Noah J
Format: Article
Language:English
Subjects:
atmosphere
Biosphere
black shale
chemostratigraphy
Chromium
clastic rocks
Cr-53/Cr-52
Eukaryotes
geochemistry
isotope fractionation
isotope ratios
isotopes
metals
Oxidation
Oxygen
paleoenvironment
Precambrian
Proterozoic
sedimentary rocks
stable isotopes
Stratigraphy
upper Precambrian
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Summary:The emergence and expansion of animal life on Earth represents a dramatic shift in the structure and complexity of the biosphere. A lack of firm constraints on surface oxygen levels during the mid-Proterozoic has resulted in heated debate as to whether the rise and earliest diversification of animals was directly linked to a change in environmental oxygen levels or, instead, simply reflects the timing of innovations in gene expression and developmental regulation and was independent of a direct environmental trigger. Here, we present chromium (Cr) isotope data from marine black shales that provide evidence for minimal Cr oxidation throughout the mid-Proterozoic leading up to the diversification of eukaryotes and the rise of animals during the late Neoproterozoic. This observation requires very low background oxygen levels (
ISSN:0091-7613
1943-2682
DOI:10.1130/G37787.1