"Cold case files" takes on new meaning for geochemists like Oak Ridge National Laboratory's Steven Turgeon, co-author of a Science paper that might explain a 248-million-year-old event that killed 90 percent of all marine species and 70 percent of terrestrial vertebrae species. This "extinction event" occurred at the Permian-Triassic boundary and is noteworthy because it had a global effect. After examining biomarkers and isotopic data from rocks from western Australia and southern China, Turgeon and colleagues theorize that many areas of the world's oceans became oxygen-depleted and sulfidic. This made the oceans and atmosphere toxic to living organisms. The researchers' conclusion was supported by the finding of remains of molecules derived from blue-green bacteria that thrive in regions where there is light but no oxygen. Also supporting this conclusion were carbon and sulfur isotope ratios that indicate a major global-scale disruption of geochemical cycles. This research, published on the Science Express website Jan. 20, was performed while Turgeon was with the University of Oldenburg in Germany.
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