Carbon and sulfur isotopic data, together with biomarker and iron speciation analyses of the Hovea-3 core that was drilled in the Perth Basin, Western Australia, indicate that euxinic conditions prevailed in the paleowater column during the Permian-Triassic superanoxic event. Biomarkers diagnostic for anoxygenic photosynthesis by Chlorobiaceae are particularly abundant at the boundary and into the Early Triassic. Similar conditions prevailed in the contemporaneous seas off South China. Our evidence for widespread photiczone euxinic conditions suggests that sulfide toxicity was a driver of the extinction and a factor in the protracted recovery.

Data on rocks from Spitsbergen and the equatorial sections of Italy and Slovenia indicate that the world's oceans became anoxic at both low and high paleolatitudes in the Late Permian. Such conditions may have been responsible for the mass extinction at this time. This event affected a wide range of shelf depths and extended into shallow water well above the storm wave base.

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A newly studied Permian-Triassic (P-Tr) boundary section in Jameson Land, East Greenland, contains an abundant and well-preserved marine fauna as well as terrestrial palynomorphs. For the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section. The sediments record a negative excursion in δ 13 C carb values of 8‰-9‰, and in δ 13 C org values of 10‰-11‰. The presence of the conodont Hindeodus parvus, combined with the δ 13 C carb record, enables correlation with the proposed global stratotype section at Meishan. This shows that the Greenland section is the most expanded P-Tr section known. Collapse of the marine and terrestrial ecosystems took between 10 and 60 k.y. It took a further few hundred thousand years for the final disappearance of Permian floral elements. Collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the δ 13 C record.

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The widespread development of anoxic and dysoxic deposition in marine settings occurred during the Permian-Triassic (P-Tr) transition interval. Facies varied according to paleobathymetry and paleolatitude. Thus, dark gray, uranium-enriched shales characterize deeper shelf locations over wide areas of northern Boreal seas, whereas the oceanic record consists of condensed, organic-rich, black shales. Finely laminated, pyrite-rich, micritic mudstones occur in equatorial Tethyan sections. Contemporaneous dolomitization in many shallow-marine settings provides further indirect evidence for widespread P-Tr anoxia. Similarly, common reports of unusual stromatolites in the earliest Triassic Griesbachian Stage could reflect the widespread occurrence of direct calcite precipitation from carbonate-saturated anoxic bottom waters. Oxygen-poor conditions are first recorded from the Late Permian, deep-water, accreted oceanic terranes of Japan. Such conditions vastly increased in extent in the interval between the latest Permian and the late Griesbachian, when dysaerobic facies developed in all but the shallowest of marine settings. The Panthalassa ocean was probably truly euxinic in this interval. Anoxia was never so extensive or so intense after this interval, and the superanoxic event ceased abruptly in equatorial Tethyan latitudes in the latest Griesbachian. Elsewhere, anoxia persisted at least into the Dienerian Stage in the Perigondwanan shelf sections of the Neo-Tethys, and deep-water anoxia may have persisted in Panthalassa until the middle Triassic.

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