University of Western Ontario - Electronic Thesis and Dissertation Repository


Master of Science




Dr. Gordon Southam


A cyanobacterial mat, including associated aerobic and anaerobic heterotrophs, was grown in an airtight chamber to simulate the formation of an oxygen oasis in two different Archean-like environments. In the first experiment, methane added to the ecosystem was rapidly oxidized and then O2(g) increased to 10%. Photosynthesis resulted in a pH of 9.5 and the precipitation of magnesium-manganese carbonates within the mat. In the second experiment, daily additions of ferrous iron were rapidly oxidized, resulting in ferric hydroxide encrusted mat. The growth of cyanobacteria and iron reducing bacteria resulted in an active redox cycle between ferrous and ferric iron. Secondary precipitates, including iron-manganese nodules, dense blocky iron precipitates and iron outlined microfossils, formed at depth in the mat. This experiment suggest that a novel iron cycle may have been active in iron formations. Both experiments recreate important geochemical changes and signatures preserved in late Archean stromatolitic reefs and iron formations.

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