image: Golden crystals of iron sulfide -- pyrite -- contain information about Earth's atmosphere around 2.5 billion years ago. view more
Credit: Image credit: Matthew Robert Warke
A study suggests the precise timing of the Great Oxidation Event (GOE). The GOE, a global rise in atmospheric oxygen during the Paleoproterozoic Era, occurred close in time to an early global glaciation event called Snowball Earth. Understanding links between the two events requires determining their relative timing, but the timing of the GOE is poorly constrained. Matthew Warke and colleagues uncovered data on sulfur isotope ratios from two sedimentary formations in the Kola Peninsula of northwest Russia. The GOE is recorded in Paleoproterozoic sediments as a shift from mass-independent fractionation of sulfur isotopes to mass-dependent fractionation. Sulfur isotopes in the older of the two formations exhibited patterns consistent with mass-independent fractionation. In the younger formation, the authors found signals of mass-dependent fractionation that predated glacigenic deposits within the same formation. The results suggest that the GOE occurred within the time interval spanned by the two formations, which geochronological constraints place at approximately 2,501-2,434 million years ago. This interval predates the timing of the Paleoproterozoic Snowball Earth glaciation established from geologic formations in South Africa. The results suggest that the GOE predated Snowball Earth and that global glaciation did not cause the GOE, according to the authors.
Article #20-03090: "The Great Oxidation Event preceded a Paleoproterozoic Snowball Earth," by Matthew R. Warke et al.
MEDIA CONTACT: Matthew R. Warke, University of St. Andrews, UNITED KINGDOM; tel: +44-7889791280; e-mail: mw438@st-andrews.ac.uk
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Journal
Proceedings of the National Academy of Sciences