Ediacaran oxidation and biotic evolution.
The link between the radiation of various lineages of eukaryotes in the latest Proterozoic and massive environmental changes--oxygenation, global ice ages and bolide impact--is the focus of much research interest. Fike et al. use carbon and sulphur isotope-chemostratigraphic data from Oman to propose three stages of oxidation in the Ediacaran oceans, and link the second and third stages to eukaryote diversification. The second stage, signalled by strongly 13C-depleted sedimentary carbonates (the 'Shuram excursion'), is believed to result from oxidation of a large, deep-ocean reservoir of organic carbon. Fike et al. use our data to assert that a correlative carbon isotope excursion in Australia coincided with the initial diversification of acanthomorphic acritarchs. Peak diversity is claimed to have coincided with subsequent deposition of 13C-enriched carbonate and the third oxidation stage. However, the authors seem to have misinterpreted our data, which instead indicate that diversification significantly preceded the Shuram excursion; this weakens their argument for a link between the inferred oxidation events and eukaryote evolution.
Geological Survey of Western Australia, Department of Industry and Resources, East Perth, Western Australia 6004, Australia.
Kathleen
K
Grey
Clive R
CR
Calver
D000818:Animals; D001315:Australia; D044822:Biodiversity; D005075:Biological Evolution; D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes; D005057:Eukaryotic Cells / Q000145:classification* / Q000378:metabolism*; D005580:Fossils; D049690:History, Ancient; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D015203:Reproducibility of Results; D012107:Research Design
D002247:Carbon Isotopes; D002244:Carbon