GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 218-9
Presentation Time: 3:50 PM


HAVIG, Jeff, Department of Geology, University of Cincinnati, 500 Geology-Physics Building, Cincinnati, OH 45221, HAMILTON, Trinity, Biological Sciences, University of Cincinnati, 731F Rieveschl Hal, Cincinnati, OH 45221-0037 and GRETTENBERGER, Christen, Earth and Planetary Sciences, University of California, Davis, One Shields Building, Davis, CA 95616,

Streams impacted by acid mine drainage (AMD) represent local environmental and ecological disasters; however they may also present an opportunity to study microbial communities in environments analogous to past conditions. Following the emergence of oxygenic photosynthesis, atmospheric O2 generated by Cyanobacteria came into contact with streams and rivers on continental surfaces replete with detrital pyrite, producing ideal conditions for pyrite oxidation similar to that found at modern AMD-impacted sites. We sampled sites that exhibited a range of AMD-impact (e.g., pH from 2.1 to 7.9, Fe2+ from 5.2 mmol/L to below detection limits, SO42- from 0.3 to 52.4 mmol/L) and found i) nearly all analytes correlated to sulfate concentration, ii) all sites exhibited the presence (and even predominance) of a single microbial taxon most closely related to Ferrovum myxofaciens which is capable of nitrogen fixation and chemoautotrophy via Fe2+ oxidation, iii) signs of potential inorganic carbon limitation and nitrogen cycling. From these findings, we present a conceptual model of continental surfaces during the Paleoproterozoic. Our model suggests a connection between O2 production in the ocean to AMD-type pyrite oxidation on continental surfaces through a negative feedback loop. Sulfate production through oxidative weathering of terrestrial surfaces would be delivered to near-shore environments which in turn drove euxinia through the action of sulfate reducing organisms. Thus, the result of the model is a potential negative feedback loop/throttle for O2 production during the Paleoproterozoic.