title: Oceanic oxygenation events in the anoxic Ediacaran ocean.
abstract: The ocean-atmosphere system is typically envisioned to have gone through a unidirectional oxygenation with significant oxygen increases in the earliest (ca. 635 Ma), middle (ca. 580 Ma), or late (ca. 560 Ma) Ediacaran Period. However, temporally discontinuous geochemical data and the patchy metazoan fossil record have been inadequate to chart the details of Ediacaran ocean oxygenation, raising fundamental debates about the timing of ocean oxygenation, its purported unidirectional rise, and its causal relationship, if any, with the evolution of early animal life. To better understand the Ediacaran ocean redox evolution, we have conducted a multi-proxy paleoredox study of a relatively continuous, deep-water section in South China that was paleogeographically connected with the open ocean. Iron speciation and pyrite morphology indicate locally euxinic (anoxic and sulfidic) environments throughout the Ediacaran in this section. In the same rocks, redox sensitive element enrichments and sulfur isotope data provide evidence for multiple oceanic oxygenation events (OOEs) in a predominantly anoxic global Ediacaran-early Cambrian ocean. This dynamic redox landscape contrasts with a recent view of a redox-static Ediacaran ocean without significant change in oxygen content. The duration of the Ediacaran OOEs may be comparable to those of the oceanic anoxic events (OAEs) in otherwise well-oxygenated Phanerozoic oceans. Anoxic events caused mass extinctions followed by fast recovery in biologically diversified Phanerozoic oceans. In contrast, oxygenation events in otherwise ecologically monotonous anoxic Ediacaran-early Cambrian oceans may have stimulated biotic innovations followed by prolonged evolutionary stasis.
authors.affiliation: Department of Geoscience, University of Nevada, Las Vegas, NV, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Sahoo
authors.affiliation: Department of Geology and Geophysics, Yale University, New Haven, CT, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Planavsky
authors.affiliation: Department of Geoscience, University of Nevada, Las Vegas, NV, USA.
authors.forename: G
authors.initials: G
authors.lastname: Jiang
authors.affiliation: Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Kendall
authors.affiliation: Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Owens
authors.affiliation: School of Earth Science and Resources, China University of Geosciences, Beijing, China.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Earth Science and Resources, China University of Geosciences, Beijing, China.
authors.forename: X
authors.initials: X
authors.lastname: Shi
authors.affiliation: Department of Chemistry and Biochemistry, School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Anbar
authors.affiliation: Department of Earth Sciences, University of California, Riverside, CA, USA.
authors.forename: T W
authors.initials: TW
authors.lastname: Lyons
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000378:metabolism*; D002681:China; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry*; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D012623:Seawater / Q000737:chemistry*