Large sulfur isotope fractionations associated with Neoarchean microbial sulfate reduction
Zhelezinskaia, I.; Kaufman, A.; Farquhar, J.; Cliff, J. (2014). Large sulfur isotope fractionations associated with Neoarchean microbial sulfate reduction. Science (Wash.) 346(6210): 742-744. http://dx.doi.org/10.1126/science.1256211
In: Science (Washington). American Association for the Advancement of Science: New York, N.Y. ISSN 0036-8075; e-ISSN 1095-9203, more
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| Authors | | Top |
- Zhelezinskaia, I.
- Kaufman, A.
- Farquhar, J.
- Cliff, J.
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| Abstract |
The minor extent of sulfur isotope fractionation preserved in many Neoarchean sedimentary successions suggests that sulfate-reducing microorganisms played an insignificant role in ancient marine environments, despite evidence that these organisms evolved much earlier. We present bulk, microdrilled, and ion probe sulfur isotope data from carbonate-associated pyrite in the ~2.5-billion-year-old Batatal Formation of Brazil, revealing large mass-dependent fractionations (approaching 50 per mil) associated with microbial sulfate reduction, as well as consistently negative ?33S values (~ –2 per mil) indicative of atmospheric photochemical reactions. Persistent 33S depletion through ~60 meters of shallow marine carbonate implies long-term stability of seawater sulfate abundance and isotope composition. In contrast, a negative ?33S excursion in lower Batatal strata indicates a response time of ~40,000 to 150,000 years, suggesting Neoarchean sulfate concentrations between ~1 and 10 µM. |
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