Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction

Gregory A. Brennecka, Achim D. Herrmann, Thomas J. Algeo, Ariel Anbar

Research output: Contribution to journalArticle

191 Scopus citations

Abstract

Periods of oceanic anoxia have had a major influence on the evolutionary history of Earth and are often contemporaneous with mass extinction events. Changes in global (as opposed to local) redox conditions can be potentially evaluated using U system proxies. The intensity and timing of oceanic redox changes associated with the end-Permian extinction horizon (EH) were assessed from variations in 238U/ 235U δ 238U) and Th/U ratios in a carbonate section at Dawen in southern China. The EH is characterized by shifts toward lower δ 238U values (from -0.37‰ to -0.65‰), indicative of an expansion of oceanic anoxia, and higher Th/U ratios (from 0.06 to 0.42), indicative of drawdown of U concentrations in seawater. Using a mass balance model, we estimate that this isotopic shift represents a sixfold increase in the flux of U to anoxic facies, implying a corresponding increase in the extent of oceanic anoxia. The intensification of oceanic anoxia coincided with, or slightly preceded, the EH and persisted for an interval of at least 40,000 to 50,000 y following the EH. These findings challenge previous hypotheses of an extended period of whole-ocean anoxia prior to the end-Permian extinction.

Original languageEnglish (US)
Pages (from-to)17631-17634
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number43
DOIs
StatePublished - Oct 25 2011

Keywords

  • Carbonates
  • Paleoredox
  • Uranium isotopes

ASJC Scopus subject areas

  • General

Fingerprint Dive into the research topics of 'Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction'. Together they form a unique fingerprint.

  • Cite this