title: Ocean oxygenation in the wake of the Marinoan glaciation.
abstract: Metazoans are likely to have their roots in the Cryogenian period, but there is a marked increase in the appearance of novel animal and algae fossils shortly after the termination of the late Cryogenian (Marinoan) glaciation about 635 million years ago. It has been suggested that an oxygenation event in the wake of the severe Marinoan glaciation was the driving factor behind this early diversification of metazoans and the shift in ecosystem complexity. But there is little evidence for an increase in oceanic or atmospheric oxygen following the Marinoan glaciation, or for a direct link between early animal evolution and redox conditions in general. Models linking trends in early biological evolution to shifts in Earth system processes thus remain controversial. Here we report geochemical data from early Ediacaran organic-rich black shales (∼635-630 million years old) of the basal Doushantuo Formation in South China. High enrichments of molybdenum and vanadium and low pyrite sulphur isotope values (Δ(34)S values ≥65 per mil) in these shales record expansion of the oceanic inventory of redox-sensitive metals and the growth of the marine sulphate reservoir in response to a widely oxygenated ocean. The data provide evidence for an early Ediacaran oxygenation event, which pre-dates the previous estimates for post-Marinoan oxygenation by more than 50 million years. Our findings seem to support a link between the most severe glaciations in Earth's history, the oxygenation of the Earth's surface environments, and the earliest diversification of animals.
authors.affiliation: Department of Geoscience, University of Nevada, Las Vegas, Nevada 89154, USA.
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Sahoo
authors.forename: Noah J
authors.initials: NJ
authors.lastname: Planavsky
authors.forename: Brian
authors.initials: B
authors.lastname: Kendall
authors.forename: Xinqiang
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Shi
authors.forename: Clint
authors.initials: C
authors.lastname: Scott
authors.forename: Ariel D
authors.initials: AD
authors.lastname: Anbar
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Lyons
authors.forename: Ganqing
authors.initials: G
authors.lastname: Jiang
mesh_terms: D000818:Animals; D001272:Atmosphere / Q000737:chemistry; D044822:Biodiversity; D005075:Biological Evolution; D002681:China; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry; D049690:History, Ancient; D046448:Ice Cover; D007501:Iron / Q000032:analysis / Q000737:chemistry; D008982:Molybdenum / Q000032:analysis; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis* / Q000378:metabolism; D012623:Seawater / Q000737:chemistry*; D013440:Sulfides / Q000032:analysis / Q000737:chemistry; D013460:Sulfur Isotopes; D014131:Trace Elements / Q000032:analysis / Q000737:chemistry; D014639:Vanadium / Q000032:analysis
chemical_list: D013440:Sulfides; D013460:Sulfur Isotopes; D014131:Trace Elements; D014639:Vanadium; C011342:pyrite; D008982:Molybdenum; D007501:Iron; D010100:Oxygen