A paleosol record of the evolution of Cr redox cycling and evidence for an increase in atmospheric oxygen during the Neoproterozoic.

Autor: Colwyn DA; Department of Geology and Geophysics, Yale University, New Haven, CT, USA., Sheldon ND; Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA., Maynard JB; Department of Geology, University of Cincinnati, Cincinnati, OH, USA., Gaines R; Geology Department, Pomona College, Claremont, CA, USA., Hofmann A; Department of Geology, University of Johannesburg, Johannesburg, South Africa., Wang X; Department of Geology and Geophysics, Yale University, New Haven, CT, USA.; Department of Marine Sciences, University of South Alabama, Mobile, AL, USA.; Dauphin Island Sea Lab, Dauphin Island, AL, USA., Gueguen B; Department of Geology and Geophysics, Yale University, New Haven, CT, USA.; Institut Universitaire Européen de la Mer, CNRS UMS 3113, Université de Brest, Plouzané, France., Asael D; Department of Geology and Geophysics, Yale University, New Haven, CT, USA., Reinhard CT; School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA., Planavsky NJ; Department of Geology and Geophysics, Yale University, New Haven, CT, USA.
Jazyk: angličtina
Zdroj: Geobiology [Geobiology] 2019 Nov; Vol. 17 (6), pp. 579-593. Date of Electronic Publication: 2019 Aug 22.
DOI: 10.1111/gbi.12360
Abstrakt: Atmospheric oxygen levels control the oxidative side of key biogeochemical cycles and place limits on the development of high-energy metabolisms. Understanding Earth's oxygenation is thus critical to developing a clearer picture of Earth's long-term evolution. However, there is currently vigorous debate about even basic aspects of the timing and pattern of the rise of oxygen. Chemical weathering in the terrestrial environment occurs in contact with the atmosphere, making paleosols potentially ideal archives to track the history of atmospheric O 2 levels. Here we present stable chromium isotope data from multiple paleosols that offer snapshots of Earth surface conditions over the last three billion years. The results indicate a secular shift in the oxidative capacity of Earth's surface in the Neoproterozoic and suggest low atmospheric oxygen levels (<1% PAL pO 2 ) through the majority of Earth's history. The paleosol record also shows that localized Cr oxidation may have begun as early as the Archean, but efficient, modern-like transport of hexavalent Cr under an O 2 -rich atmosphere did not become common until the Neoproterozoic.
(© 2019 John Wiley & Sons Ltd.)
Databáze: MEDLINE
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