Abstract
Mass extinction of life at the end of the Permian ca. 250 million years ago was characterized by (1) abrupt and coincident extinctions in the ocean and on land during a period of only 10,000 years and (2) delay of ecosystem recovery during the following 10 million years encompassing the largest known turnover of marine and land biota. Previously suggested direct causes of this major event include gradual extreme warming, oceanic anoxia, a decrease in ozone by mass release of H2S and CH4, and gradual atmospheric hypoxia. A positive anomaly in the 34S/32S ratio of carbonate-associated sulfate (CAS) in uppermost Permian marine sediments implies that H2S accumulated in the ocean during a period of 〜1 million years. The accumulation period was followed by massive release of H2S (evidenced by a decrease in the 34S/32S ratio of CAS) coinciding with the mass extinction. Oxidation of the H2S would have caused a significant decrease in atmospheric O2. The hypoxia event occurred over a much shorter time period (104 years) than previously suggested (107 years) and can explain the rapidity of the major end-Permian mass extinction which triggered development of the Earth's modern biota.
