Oceanic Euxinia Component1 #393979 Oceanic anoxic events refer to intervals in the Earth's past where portions of oceans become depleted in oxygen (O2) at depths over a large geographic area. During some of these events, euxinia develops - anoxic waters that contain high concentrations of hydrogen sulfide (H2S). Although anoxic events have not happened for millions of years, the geological record shows that they happened many times in the past, and coincide with, and may have contributed to, several mass extinctions. [1] |
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+Citations (3)
- CitationsAdd new citationList by: CiterankMapLink[2] Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia
Author: Lee R. Kump, Alexander Pavlov, Michael A. Arthur Publication info: 2004, Geology, v. 33 no. 5 p. 397-400 doi: 10.1130/G21295.1 Cited by: David Price 8:19 PM 28 May 2015 GMT URL: |
Excerpt / Summary Simple calculations show that if deep-water H2S concentrations increased beyond a critical threshold during oceanic anoxic intervals of Earth history, the chemocline separating sulfidic deep waters from oxygenated surface waters could have risen abruptly to the ocean surface (a chemocline upward excursion). Atmospheric photochemical modeling indicates that resulting fluxes of H2S to the atmosphere (>2000 times the small modern flux from volcanoes) would likely have led to toxic levels of H2S in the atmosphere. Moreover, the ozone shield would have been destroyed, and methane levels would have risen to >100 ppm. We thus propose (1) chemocline upward excursion as a kill mechanism during the end-Permian, Late Devonian, and Cenomanian–Turonian extinctions, and (2) persistently high atmospheric H2S levels as a factor that impeded evolution of eukaryotic life on land during the Proterozoic. |