Uranium and molybdenum isotope evidence for an episode of widespread ocean oxygenation during the late Ediacaran Period

Kendall, Brian; Komiya, Tsuyoshi; Lyons, Timothy W.; Bates, Steve; Gordon, Gwyneth W.; Romaniello, Stephen J.; Jiang, Ganqing; Creaser, Robert A.; Xiao, Shuhai; McFadden, Kathleen A.; Sawaki, Yusuke; Tahata, Miyuki; Shu, Degan; Han, Jian; Li, Yong; Chu, Xuelei; Anbar, Ariel D.

doi:10.1016/j.gca.2015.02.025

Cited by 228 publications

(159 citation statements)

References 160 publications

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“…Consistent with this interpretation, U isotope data from the same samples of the Upper Velkerri Formation suggest that <25% of the seafloor was covered by anoxic waters (Yang et al, 2017). Our interpretation is also consistent with Mo concentration and isotope data for these ORM (Kendall et al, 2009(Kendall et al, , 2015b, which constrain the extent of ocean euxinia rather than general ocean anoxia (euxinic plus ferruginous conditions). The model does not preclude the possibility that a significant portion of the low-productivity regions of the deep oceans may have been covered by weakly oxygenated waters (Slack et al, 2007(Slack et al, , 2009, nor does it preclude oxygenated surface waters in highly productive regions (Sperling et al, 2014;Reinhard et al, 2016).…”

Section: Constraints On the Extent Of Mid-proterozoic Ocean Anoxiasupporting

confidence: 83%

A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

Sheen

Kendall

Reinhard

et al. 2018

Geochimica et Cosmochimica Acta

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Emerging geochemical evidence suggests that the atmosphere-ocean system underwent a significant decrease in O 2 content following the Great Oxidation Event (GOE), leading to a mid-Proterozoic ocean (ca. 2.0-0.8 Ga) with oxygenated surface waters and predominantly anoxic deep waters. The extent of mid-Proterozoic seafloor anoxia has been recently estimated using mass-balance models based on molybdenum (Mo), uranium (U), and chromium (Cr) enrichments in organic-rich mudrocks (ORM). Here, we use a temporal compilation of concentrations for the redox-sensitive trace metal rhenium (Re) in ORM to provide an independent constraint on the global extent of mid-Proterozoic ocean anoxia and as a tool for more generally exploring how the marine geochemical cycle of Re has changed through time. The compilation reveals that mid-Proterozoic ORM are dominated by low Re concentrations that overall are only mildly higher than those of Archean ORM and significantly lower than many ORM deposited during the ca. 2.22-2.06 Ga Lomagundi Event and during the Phanerozoic Eon. These temporal trends are consistent with a decrease in the oceanic Re inventory in response to an expansion of anoxia after an interval of increased oxygenation during the Lomagundi Event. Mass-balance modeling of the marine Re geochemical cycle indicates that the mid-Proterozoic ORM with low Re enrichments are consistent with extensive seafloor anoxia. Beyond this agreement, these new data bring added value because Re, like the other metals, responds generally to lowoxygen conditions but has its own distinct sensitivity to the varying environmental controls. Thus, we can broaden our capacity to infer nuanced spatiotemporal patterns in ancient redox landscapes. For example, despite the still small number of data, some mid-Proterozoic ORM units have higher Re enrichments that may reflect a larger oceanic Re inventory during transient episodes of ocean oxygenation. An improved understanding of the modern oceanic Re cycle and a higher temporal resolution for the Re compilation will enable further tests of these hypotheses regarding changes in the surficial Re geochemical cycle in response to variations in atmosphere-ocean oxygenation. Nevertheless, the existing Re compilation and model results are in agreement with previous Cr, Mo, and U evidence for pervasively anoxic and ferruginous conditions in mid-Proterozoic oceans.

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Section: Constraints On the Extent Of Mid-proterozoic Ocean Anoxiasupporting

confidence: 83%

A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

Sheen

Kendall

Reinhard

et al. 2018

Geochimica et Cosmochimica Acta

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“…2). Specifically, the molybdenum isotope (δ 98 Mo) record from shales and phosphorites show several fluctuations recorded in ~560 to 520 Myr old stratigraphic sections in China (Wille et al, 2008;Wen et al, 2011;Xu et al, 2012;Chen et al, 2015;Kendall et al, 2015;Wen et al, 2015). The last positive δ 98 Mo excursion is broadly correlated to the first appearance of trilobites in China, strong Mo enrichments and with the oxygenation event reported here (Dahl et al, 2010;Xu et al, 2012;Chen et al, 2015;Wen et al, 2015;Jin et al, 2016).…”

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confidence: 66%

“…Collectively, the Mo and U isotopes indicate a transient, rather than a persistent change in ocean oxygenation at the beginning of Stage 3. This implies that earlier positive δ 98 Mo excursions (~2 ‰) in Terreneuvian phosphorite deposits (Wen et al, 2011), and perhaps in the latest Ediacaran (Kendall et al, 2015), represent episodic events rather than persistent ocean oxygenation. Similarly, detailed studies of the bottom water redox conditions in the Nanhua Basin, South China, suggest that oxygenated waters also invaded shallower part of the basin later in the Stage 3 (Jin et al 2016).…”

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confidence: 98%

Reorganisation of Earth’s biogeochemical cycles brieﬂy oxygenated the oceans 520 Myr ago

Dahl

Connelly

Kouchinsky³

et al. 2017

Geochem. Persp. Let.

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The Phanerozoic radiation of bilaterian animals has been linked to oxygenation of Earth's oceans, due to the oxygen demand of the evolving animal ecosystems. However, how early animals may have regulated Earth's surface oxygen budget via self-stabilising feedbacks is poorly understood. Here, we report parallel positive uranium, carbon, and sulphur isotope excursions from carbonate successions in Siberia that document a brief global oxygenation episode 521-520 Myr ago, at the onset of diversification of larger arthropods known from the fossil record. Our data and model indicate that an abrupt increase in the sinking rate of marine organic matter expanded the oxygenated zone in the oceans and that reducing conditions returned 1.3 ± 0.8 Myr after the onset of this transient oxygenation episode, necessitating a strong negative feedback to the increasing levels of oxygen. We speculate that larger zooplankton could have sourced both oxygen and food to the seafloor, fueling bioturbation over wider areas and, thereby, stabilising O 2 -rich habitats in the oceans. Thus, this reorganisation exemplifies how animal ecosystems might have influenced oxygen availability in Earth's surface environment soon after their establishment. LetterIn contrast to many geochemical proxies that evaluate local ancient marine redox including iron speciation and trace metal (Mo, U, V) enrichments, the uranium isotope composition (δ 238 U, the per mille deviation of the 238 U/ 235 U ratio relative to CRM 145 standard) of seawater can be used to evaluate ocean oxygenation at 1. Natural History Museum of Denmark, University of Copenhagen, Denmark * Corresponding author (email: tais.dahl@snm.ku.dk) 2. Centre for Star and Planet Formation, University of Copenhagen, Denmark 3. Swedish Museum of Natural History, Stockholm, Sweden 4. Virginia Polytechnic Institute and State University, Blacksburg, USA a globally integrated scale. This is possible due to the long residence time and uniform δ 238 U of uranium in the modern ocean and predicted for the Cambrian ocean (Weyer et al., 2008;Dahl et al., 2014;Tissot and Dauphas, 2015). The δ 238 U proxy has been utilised to track past global ocean redox during three known oceanic anoxic events (Montoya-Pino et al., 2010;Brennecka et al., 2011;Dahl et al., 2014;Elrick et al., 2016;Lau et al., 2016), where anoxic water masses expanded over larger areas of the seafloor and caused negative δ 238 U excursions. Here, we use uranium isotopes to identify a transient global oxygenation episode during the radiation of animals in the Cambrian.Our new δ 238 U data of carbonate-associated uranium comes from limestones collected from the Siberian Platform across the provisional Cambrian Stage 2-3 boundary (~521 to 520 million years ago) (Fig. 1), when animals that shed their exoskeleton (ecdysozoa) began to diversify (Maloof et al., 2010;Kouchinsky et al., 2012). A perturbation in the marine carbon cycle is expressed at this time as a large positive carbon isotope excursion recognised globally and in all studied sections;...

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“…This interpretation implies expansion of oxygenated water masses in the Neoproterozoic. Although various paleoredox proxies indeed point to an increase in atmospheric and oceanic oxygen between ~800 and ~550 Ma (Canfield et al, 2007;Fike et al, 2006;Johnston et al, 2012;Kendall et al, 2015b;Planavsky et al, 2014b;Sahoo et al, 2012), others suggest anoxic conditions in roughly coeval strata Johnston et al, 2013;Schröder and Grotzinger, 2007;Sperling et al, 2015). Hence like the Neoarchean and Mesoproterozoic, the Neoproterozoic may have been a time of dynamic spatial and temporal redox fluctuations where NO 3 -was not abundant globally at all times.…”

Section: Neoproterozoic (10-05 Gyr)mentioning

confidence: 99%

The evolution of Earth's biogeochemical nitrogen cycle

Stüeken

Kipp

Koehler

et al. 2016

Earth-Science Reviews

290

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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Uranium and molybdenum isotope evidence for an episode of widespread ocean oxygenation during the late Ediacaran Period

Cited by 228 publications

References 160 publications

A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia

Reorganisation of Earth’s biogeochemical cycles brieﬂy oxygenated the oceans 520 Myr ago

The evolution of Earth's biogeochemical nitrogen cycle

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