Molybdenum Isotope Evidence for Widespread Anoxia in Mid-Proterozoic Oceans

Arnold, Gail Lee; Anbar, Ariel D.; Barling, Jane; Lyons, Timothy W.

doi:10.1126/science.1091785

Cited by 611 publications

(410 citation statements)

References 24 publications

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“…We hypothesize that atmospheric O 2 levels increased immediately after the second Palaeoproterozoic glaciation sufficient to mobilize continental Os into the hydrological cycle. Because a large part of the oceans was possibly still anoxic at that time 5,24 , the dissolved Os delivered via rivers would have been reduced to immobile Os over a short period, probably before mixing homogeneously in the oceans. In such case, most of the delivered Os would have accumulated within shallow-marine environments ( Fig.…”

Section: Discussionmentioning

confidence: 99%

Osmium evidence for synchronicity between a rise in atmospheric oxygen and Palaeoproterozoic deglaciation

et al. 2011

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Early Palaeoproterozoic (2.5-2.0 billion years ago) was a critical phase in Earth's history, characterized by multiple severe glaciations and a rise in atmospheric o 2 (the Great oxidation Event). Although glaciations occurred at the time of o 2 increase, the relationship between climatic and atmospheric transitions remains poorly understood. Here we report high concentrations of the redox-sensitive element os with high initial 187 os/ 188 os values in a sandstone-siltstone interval that spans the transition from glacial diamictite to overlying carbonate in the Huronian supergroup, Canada. Together with the results of Re, mo and s analyses of the sediments, we suggest that immediately after the second Palaeoproterozoic glaciation, atmospheric o 2 levels became sufficiently high to deliver radiogenic continental os to shallow-marine environments, indicating the synchronicity of an episode of increasing o 2 and deglaciation. This result supports the hypothesis that climatic recovery from the glaciations acted to accelerate the Great oxidation Event.

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Section: Discussionmentioning

confidence: 99%

Osmium evidence for synchronicity between a rise in atmospheric oxygen and Palaeoproterozoic deglaciation

et al. 2011

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“…While some organic carbon may still have been converted to CO 2 under those conditions, the organic-bound ammonium would likely have accumulated in the water column, as in the Black Sea. In other words, an ecosystem dominated by sulfate reduction, for instance along continental margins in the late Archean and midProterozoic when euxinia was more widespread (Arnold et al, 2004;Kendall et al, 2009;Kendall et al, 2011;Partin et al, 2015;Poulton et al, 2004;Reinhard et al, 2009;Scott et al, 2011;Sperling et al, 2015), may have favored high NH 4 + concentrations in deep water. Large quantities of dissolved NH 4 + may thus have been a rather localized phenomenon, restricted to euxinic environments.…”

Section: Was the Precambrian Ocean Rich In Nh 4 + ?mentioning

confidence: 99%

“…Sulfur isotopes and evaporites indicate that marine sulfate concentrations probably tracked pO 2 with a peak during the Paleoproterozoic Schröder et al, 2008), followed by a minimum between ~1.7 Ga and ~1.0 Ga (Kah et al, 2004;Luo et al, 2014b;Scott et al, 2014). The Mesoproterozoic ocean was likely ferruginous at depth, but euxinia apparently prevailed along continental margins (Arnold et al, 2004;Planavsky et al, 2011;Sperling et al, 2015). Atmospheric pO 2 probably reached near-modern levels during the "Neoproterozoic Oxygenation Event" (NOE) between 0.8 Gyr and…”

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confidence: 99%

The evolution of Earth's biogeochemical nitrogen cycle

Stüeken

Kipp

Koehler

et al. 2016

Earth-Science Reviews

329

287

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Nitrogen is an essential nutrient for all life on Earth and it acts as a major control on biological productivity in the modern ocean. Accurate reconstructions of the evolution of life over the course of the last four billion years therefore demand a better understanding of nitrogen bioavailability and speciation through time. The biogeochemical nitrogen cycle has evidently been closely tied to the redox state of the ocean and atmosphere. Multiple lines of evidence indicate that the Earth"s surface has passed in a non-linear fashion from an anoxic state in the Hadean to an oxic state in the later Phanerozoic. It is therefore likely that the nitrogen cycle has changed markedly over time, with potentially severe implications for the productivity and evolution of the biosphere. Here we compile nitrogen isotope data from the literature and review our current understanding of the evolution of the nitrogen cycle, with particular emphasis on the Precambrian. Combined with recent work on redox conditions, trace metal availability, sulfur and iron cycling on the early Earth, we then use the nitrogen isotope record as a platform to test existing and new hypotheses about biogeochemical pathways that may have controlled nitrogen availability through time. Among other things, we conclude that (a) abiotic nitrogen sources were likely insufficient to sustain a large biosphere, thus favoring an early origin of biological N 2 fixation, (b) evidence of nitrate in the Neoarchean and Paleoproterozoic confirm current views of increasing surface oxygen levels at those times, (c) abundant ferrous iron and sulfide in the midPrecambrian ocean may have affected the speciation and size of the fixed nitrogen reservoir, and (d) nitrate availability alone was not a major driver of eukaryotic evolution.

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“…a) Total sulfide: ∑S(-II) = H2S + HS -+ S Table S1: Chemical characteristics of modern euxinic basins and inferred composition for the Walcott basin [20][21][22].…”

Section: A21 Slow Mo Accumulation In Chuar Basinmentioning

confidence: 99%