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Published July 1, 2011 | public
Journal Article

Manganese enrichment in the Gowganda Formation of the Huronian Supergroup: A highly oxidizing shallow-marine environment after the last Huronian glaciation


Oxidative precipitation and authigenic enrichment of the redox sensitive element Mn in sedimentary rocks can serve as a proxy for the release of high levels of O_2 during the Great Oxidization Event (GOE). Here we investigate Mn abundance in sedimentary rocks of the 2.45–2.22 Ga Huronian Supergroup, Canada. We found authigenic Mn enrichments with high Mn/Fe ratios following the appearance of Fe oxides in the Firstbrook Member of the Gowganda Formation of the Huronian Supergroup, which was deposited immediately after the last Huronian glaciation. The Mn-bearing minerals in the Firstbrook Member are spessartine-rich almandine and Mn-bearing chlorite, which are likely to have been formed through post-depositional diagenesis and/or metamorphism using Mn oxides precipitated in the ocean at the time of deposition. When assuming the solution equilibrium between the atmosphere and shallow oceans, oxidative Mn precipitation requires that atmospheric O_2 be higher than ~ 10^(−2) times the present atmospheric level (PAL). The cumulative Mn amount per unit area in the Firstbrook Member is comparable in magnitude to that in the Mn deposits in the Hotazel Formation of the Transvaal Supergroup, South Africa. Our results suggest an appearance of highly active aerobic biosphere immediately after the last Huronian glaciation, supporting the hypothesis that climatic recovery from the Huronian glaciation accelerated the GOE.

Additional Information

© 2011 Elsevier B.V. Received 14 February 2011; revised 27 April 2011; accepted 1 May 2011. Editor: P. DeMenocal. Available online 23 May 2011. The authors thank M. Hailstone and A. Pace at the Ontario Geological Survey, Canada, for advice and access to their core library, without which this project could not have been done. This study is partly supported by Grant in Aid from the Japan Society for the Promotion of Science (No. 14403004 and No. 18340128), the 21 century COE Program at Dept. of Earth and Planetary Science, Univ. of Tokyo, the Mitsubishi foundation, the NASA Exobiology program, and the Agouron Institute.

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October 23, 2023