Photic zone euxinia during the Permian-triassic superanoxic event

Area of Science:

• Paleoceanography
• Geochemistry
• Biogeochemistry

Background:

• The Permian-Triassic boundary marks a major mass extinction event.
• Understanding the environmental conditions during this period is crucial for explaining the extinction's severity and recovery.
• Previous studies suggest anoxic conditions, but the extent of euxinia is debated.

Purpose of the Study:

• To investigate the paleoceanographic conditions in the Perth Basin during the Permian-Triassic superanoxic event.
• To identify the role of euxinic conditions and sulfide toxicity in the extinction and recovery.
• To compare conditions in the Perth Basin with other contemporaneous basins.

Main Methods:

• Analysis of carbon and sulfur isotopes.
• Biomarker analysis, specifically for anoxygenic photosynthesis by Chlorobiaceae.
• Iron speciation analyses.

Main Results:

• Euxinic conditions were prevalent in the paleowater column of the Perth Basin during the Permian-Triassic superanoxic event.
• Biomarkers indicate significant anoxygenic photosynthesis by Chlorobiaceae at the boundary and into the Early Triassic.
• Similar euxinic conditions were found in contemporaneous seas off South China.

Conclusions:

• Widespread photic zone euxinic conditions suggest sulfide toxicity played a key role in driving the Permian-Triassic extinction.
• Sulfide toxicity also contributed to the protracted recovery following the extinction event.
• The findings highlight the impact of ocean anoxia and euxinia on marine ecosystems.