A Late Archean Sulfidic Sea Stimulated by Early Oxidative Weathering of the Continents
Christopher T. Reinhard,1
Rob Raiswell,2
Clint Scott,1
Ariel D. Anbar,3
Timothy W. Lyons1,*
Iron speciation data for the late Archean Mount McRae Shale
provide evidence for a euxinic (anoxic and sulfidic) water column
2.5 billion years ago. Sulfur isotope data compiled from the
same stratigraphic section suggest that euxinic conditions were
stimulated by an increase in oceanic sulfate concentrations
resulting from weathering of continental sulfide minerals exposed
to an atmosphere with trace amounts of photosynthetically produced
oxygen. Variability in local organic matter flux likely confined
euxinic conditions to midportions of the water column on the
basin margin. These findings indicate that euxinic conditions
may have been common on a variety of spatial and temporal scales
both before and immediately after the Paleoproterozoic rise
in atmospheric oxygen, hinting at previously unexplored texture
and variability in deep ocean chemistry during Earth’s
early history.
2 University of Leeds, School of Earth and Environment, Leeds, UK LS2 9JT.
3 Arizona State University, School of Earth and Space Exploration and Department of Chemistry and Biochemistry, Tempe, AZ 85287, USA.
* To whom correspondence should be addressed. E-mail: timothyl{at}ucr.edu
