45 Marine Anoxia over Geologic Time—Where, When, Why, and Cause and Effect Relationships to the Evolving Biosphere III
Thursday, 11 August 2005
9:00 AM - 12:00 PM
EUXINIA AS THE CAUSE OF THE END-PERMIAN MASS EXTINCTION: EVIDENCE FROM SULFUR ISOTOPE CHEMOSTRATIGRAPHY
Paper number: 45-3
Program: THEME SESSIONS
Time: 9:40 AM – 10:00 AM
Authors
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Pedro J. MarencoUniversity of Southern California, Los Angeles, CA
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Aymon BaudGeol Museum, Lausanne
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David BottjerUniversity of Southern California, Los Angeles, CA
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Alan J. KaufmanUniv of Maryland, College Park, MD
Abstract
High-resolution δ34S data from carbonate associated sulfate reveal extreme and rapid sulfur isotopic fluctuations (up to 10‰) in association with the end Permian mass extinction in Turkey, followed by smaller but significant rhythmic fluctuations in the Early Triassic. During the latest Permian, a large reservoir of anoxic and sulfidic deep water and a much smaller oxygenated surface ocean, susceptible to rapid isotopic adjustment because of its small volume, likely existed. The euxinic deep water expanded into the photic zone (as demonstrated by recent biomarker studies) where the flux of 34S-depleted sulfide drove the rapid isotopic changes within the surface water mass. The rhythmic isotopic fluctuations (~5‰) following the Permo-Triassic boundary may represent the shrinking influence of the euxinic water mass and argue against some extrinsic catastrophic mechanism for the extinctions (e.g., bolide impact). The release of toxic H2S into the surface ocean and perhaps the atmosphere had drastic consequences for marine and terrestrial life and likely led to the largest mass extinction in Earth's history.