Earth and Planetary Science Letters 307 (2011) 201–210 Contents lists available at ScienceDirect Earth and Planetary Science Letters journal homepage: www.elsevier.com/locate/epsl Manganese enrichment in the Gowganda Formation of the Huronian Supergroup: A highly oxidizing shallow-marine environment after the last Huronian glaciation Yasuhito Sekine a,⁎, Eiichi Tajika a, Ryuji Tada b, Takemaru Hirai b,1, Kosuke T. Goto b, Tatsu Kuwatani a, Kazuhisa Goto c, Shinji Yamamoto b, Shogo Tachibana b, Yukio Isozaki d, Joseph L. Kirschvink e a Dept. of Complexity Sci. & Engr., Univ. of Tokyo, Kashiwa, Chiba 277–8561, Japan b Dept. of Earth & Planetary Sci., Univ. of Tokyo, Bunkyo, Tokyo 113-0033, Japan c Planetary Exploration Res. Center, Chiba Inst. of Tech., Tsudanuma, Chiba 275–0016, Japan d Dept. of Earth Science & Astronomy, Univ. of Tokyo, Meguro, Tokyo 153–8902, Japan e Division of Geological & Planetary Sci., California Inst. of Tech., Pasadena, California 91125, USA article info abstract Article history: Oxidative precipitation and authigenic enrichment of the redox sensitive element Mn in sedimentary rocks Received 14 February 2011 can serve as a proxy for the release of high levels of O2 during the Great Oxidization Event (GOE). Here we Received in revised form 27 April 2011 investigate Mn abundance in sedimentary rocks of the 2.45–2.22 Ga Huronian Supergroup, Canada. We found Accepted 1 May 2011 authigenic Mn enrichments with high Mn/Fe ratios following the appearance of Fe oxides in the Firstbrook Available online 23 May 2011 Member of the Gowganda Formation of the Huronian Supergroup, which was deposited immediately after the Editor: P. DeMenocal 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 Keywords: metamorphism using Mn oxides precipitated in the ocean at the time of deposition. When assuming the The Great Oxidation Event solution equilibrium between the atmosphere and shallow oceans, oxidative Mn precipitation requires that −2 Huronian Supergroup atmospheric O2 be higher than ~10 times the present atmospheric level (PAL). The cumulative Mn amount Glaciation per unit area in the Firstbrook Member is comparable in magnitude to that in the Mn deposits in the Hotazel Ocean redox state Formation of the Transvaal Supergroup, South Africa. Our results suggest an appearance of highly active Paleoproterozoic aerobic biosphere immediately after the last Huronian glaciation, supporting the hypothesis that climatic recovery from the Huronian glaciation accelerated the GOE. © 2011 Elsevier B.V. All rights reserved. 1. Introduction It has long been suggested that the abundance of redox sensitive metals, such as U, Fe, Re, Os, and Mn, preserved in sedimentary rocks Multiple lines of evidence support the idea that atmospheric O2 and paleosols can provide constraints on the evolution of atmospheric increased remarkably between 2.5 and 2.0 Ga (termed the Great O2 during the GOE (e.g., Anbar et al., 2007; Canfield, 2005; Holland, Oxidation Event (GOE)) (e.g., Anbar et al., 2007; Bekker et al., 2004; 1984; Rye and Holland, 1998). For example, the preservation of Canfield, 2005; Farquhar et al., 2000; Karhu and Holland, 1996; detrital uraninite (UO2) and pyrite (FeS2) in river deposits older than Kirschvink et al., 2000; Papineau et al., 2007; Rye and Holland, 1998). ~2.3 Ga is clear evidence for the lack of atmospheric oxygen at the Across this time interval, the O2 level appears to have increased from time of deposition (e.g., Holland, 1984; Roscoe, 1969). When the O2 less than 10− 5 of the present atmospheric level (PAL) to more than levels rose, U, Re, and Os contained in crustal minerals were dissolved 10− 2 PAL (Canfield, 2005; Farquhar et al., 2007; Pavlov and Kasting, and delivered to the oceans through oxidative weathering (e.g., 2002). However, the history of the oxygenation in the atmosphere– Canfield, 2005). Additionally, the retention of Fe in paleosols also has ocean system during the GOE remains poorly understood. Knowledge been used as an indicator of atmospheric O2 (e.g., Holland, 1984). In on the detailed history of the surface oxygenation during the GOE general, under high O2 conditions, Fe is oxidized and retained in is important for understanding the evolution of the Earth, because it paleosols. The earliest paleosol to show evidence for an oxidizing would provide an insight into the causative mechanism responsible atmosphere is the 2.2 Ga Hekpoort paleosol of the Transvaal for the rise in O2 in the atmosphere. Supergroup, South Africa, although there is considerable disagree- ment in the O2 levels proposed for its formation (Beukes et al., 2002; Yang and Holland, 2003). ⁎ Corresponding author at: Kiban bldg. 4E5, 5-1-5 Kashiwanoha, Kashiwa, Chiba To further understand the evolution of the atmospheric O levels 277–8561, Japan. Tel./fax: +81 4 7136 3954. 2 E-mail address: [email protected] (Y. Sekine). during the GOE, it is essential to obtain additional geochemical 1 Present address: Orizon Systems Co., Ltd., Tansu-machi, Tokyo 162–0833, Japan. records using other proxies for reconstructing the different levels of 0012-821X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2011.05.001 202 Y. Sekine et al. / Earth and Planetary Science Letters 307 (2011) 201–210 atmospheric O2. Because each redox sensitive metal has a different 2. Geological setting oxidation potential, the comparison of their degrees of enrichment and/or depletion in sedimentary sequences would aid in the The Huronian Supergroup crops out along the north shore of Lake reconstruction of atmospheric O2 levels by providing upper and Huron (Fig. 1A). Most of the strata are dominated by siliciclastic rocks lower bounds for their oxidization. Given the high oxidation potential that are bundled into climatically-controlled trinal cycles, each of of Mn (+490 mV at pH 7; Kopp et al., 2005) among redox sensitive which starts with glacial diamictites, followed by mudstones and metals, its authigenic enrichment would provide key information on quartzose sandstones (Fig. 1B) (Young et al., 2001). In the lower part an accumulation of high levels of O2 at the late stage of the GOE. of the Huronian Supergroup (the Matinenda and Pecors formations), In contrast to Mo, Re, and Os, Mn is less soluble under oxidizing mass independent fractionation of sulfur (MIF-S) in sulfides and conditions and precipitates as oxides in the oceans similar to Fe. occurrence of detrital uraninite and pyrite in conglomerates suggest Previous studies have noted the fact that the Mn-rich members of the low atmospheric O2 levels in the atmosphere (e.g., Papineau et al., 2.2 Ga Hotazel banded-iron Formation in the Transvaal Supergroup, 2007; Young et al., 2001)(Fig. 2B). In contrast, large fractionations in 34 33 South Africa, imply large quantities of O2 in the surface zone of the δ S values and near-zero Δ S are found in authigenic sulfides from ocean at the time of deposition (Kirschvink et al., 2000; Kopp et al., the Espanola and Gordon lake formations (Papineau et al., 2007). In 2005). The Transvaal Supergroup contains the Makganyene Forma- addition, abundant evidence for oxidative continental weathering tion glacial diamictite, which represents a low-latitude global such as red beds, have been reported in the Lorrain Formation (e.g., glaciation (i.e., the Paleoproterozoic Snowball glaciation) (Evans Young et al., 2001). These results provide evidence for an oxidizing et al., 1997; Kirschvink et al., 2000). Because the basal meter of the atmosphere at the time of deposition of the upper part of the Hotazel Formation contains dropstones just above the contact with Huronian Supergroup (Fig. 1B). the underlying units over a geographically wide area, Kirschvink et al. The upper part of the Huronian Supergroup (starting with the (2000) argued that it was the equivalent of the ‘Cap Carbonate’ for Gowganda Formation) is considered as a passive margin succession Neoproterozoic glacial units, and marked the termination of the (Young, 2004; Young et al., 2001). The lower part of the Gowganda Makganyene glaciation. They interpreted the major precipitation of Formation (the Coleman Member) consists mainly of matrix- Mn associated with Fe oxides as the result of a massive release of O2 supported diamictite, while the upper part of the Gowganda into the atmosphere and ocean as a consequence of high levels of Formation (the Firstbrook Member) consists of laminated argillite biological productivity in the aftermath of the Paleoproterozoic that grades upward into thinly bedded siltstone and fine-grained Snowball Earth (Kirschvink et al., 2000). Because the occurrence of sandstone and finally into medium- to coarse-grained sandstone of major precipitation of Mn has not been reported in other Paleopro- the Lorrain Formation. The depositional environment of the Firstbrook terozoic sedimentary sequences, it was uncertain whether such a Member is interpreted to be fluvial deltas, based on the presence of a highly oxidizing shallow-marine environment was global. prograding deltaic wedge from prodelta to delta slope (Rainbird and In this study, we measure Mn abundance in sedimentary rocks Donaldson, 1988). The quartzose sandstone in the Lorrain Formation of the Huronian Supergroup, Ontario, Canada, which is known as would have been formed as a result of intense chemical weathering one of the most continuous successions of the Paleoproterozoic under hot and humid conditions in the aftermath of the Gowganda (~2.45–2.22 Ga). This sequence includes three discrete glacial glaciation (Long et al., 1999; Sekine et al., 2010). diamictite-units (Fig. 1) (e.g., Young et al., 2001). In this study, In contrast to the Makganyene and Hotazel formations in the we focus on the uppermost glacial diamictite unit of the Gowganda Transvaal Supergroup deposited at ~2.22 Ga (Cornell et al., 1996; Formation and investigate the redox condition of the atmosphere Dorland, 2004), the depositional age of the Gowganda Formation is not and ocean at the time of its deposition.