Changes in productivity and redox conditions in the Panthalassic Ocean during the latest Permian

Algeo, Thomas J.; Hinnov, Linda A.; Moser, Jessa; Maynard, J. Barry; Elswick, Erika; Kuwahara, Kiyoko; Sano, Hidehiko

doi:10.1130/g30483.1

Cited by 162 publications

(60 citation statements)

References 26 publications

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“…Commonly, models of this process invoke an extended period of sluggish ocean circulation, producing deep-ocean anoxia and accumulation of H 2 S. This interpretation was previously challenged by numerical models of the ocean-climate system suggesting that the deep ocean was most likely well ventilated throughout the Late Permian-Early Triassic interval (35). We propose that the geochemical data and numerical models can be reconciled by hypothesizing expanded and more intense oxygen-minimum zones at middepths in the late-Permian ocean (7,9,32). Suboxic deep-ocean conditions during the Late Permian prior to the EH (9, 32) would have decreased the U concentration of the ocean, lowering the residence time of U in seawater and setting the stage for the rapid shift in Th/U at the EH observed at Dawen (Fig.…”

Section: Resultsmentioning

confidence: 84%

“…Proposed kill mechanisms have included a nearby supernova, bolide impacts, periods of extreme volcanism (e.g., Siberian Traps), extensive glaciation, and widespread oceanic anoxia (2). Evidence for shallow-ocean anoxia in conjunction with the end-Permian mass extinction is widespread (3)(4)(5)(6), but the intensity and timing of oceanic redox changes remain uncertain (7)(8)(9)(10). Recent hypotheses have invoked the release of hydrogen sulfide gas (H 2 S) from seawater as a kill mechanism (11)(12)(13).…”

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confidence: 99%

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Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction

Brennecka

Herrmann

Algeo

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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309

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Periods of oceanic anoxia have had a major influence on the evolutionary history of Earth and are often contemporaneous with mass extinction events. Changes in global (as opposed to local) redox conditions can be potentially evaluated using U system proxies. The intensity and timing of oceanic redox changes associated with the end-Permian extinction horizon (EH) were assessed from variations in 238 U∕ 235 U (δ 238 U) and Th/U ratios in a carbonate section at Dawen in southern China. The EH is characterized by shifts toward lower δ 238 U values (from −0.37‰ to −0.65‰), indicative of an expansion of oceanic anoxia, and higher Th/U ratios (from 0.06 to 0.42), indicative of drawdown of U concentrations in seawater. Using a mass balance model, we estimate that this isotopic shift represents a sixfold increase in the flux of U to anoxic facies, implying a corresponding increase in the extent of oceanic anoxia. The intensification of oceanic anoxia coincided with, or slightly preceded, the EH and persisted for an interval of at least 40,000 to 50,000 y following the EH. These findings challenge previous hypotheses of an extended period of whole-ocean anoxia prior to the end-Permian extinction.carbonates | uranium isotopes | paleoredox T he end-Permian extinction represents the largest mass extinction in Earth history, with the demise of an estimated 90% of all marine species (1). While it has been extensively studied, the exact nature and cause of the end-Permian extinction remains the subject of intense scientific debate. Proposed kill mechanisms have included a nearby supernova, bolide impacts, periods of extreme volcanism (e.g., Siberian Traps), extensive glaciation, and widespread oceanic anoxia (2). Evidence for shallow-ocean anoxia in conjunction with the end-Permian mass extinction is widespread (3-6), but the intensity and timing of oceanic redox changes remain uncertain (7-10). Recent hypotheses have invoked the release of hydrogen sulfide gas (H 2 S) from seawater as a kill mechanism (11-13). Such models call upon strong expansion of oceanic anoxia below the oxygenated surface layer to allow buildup of H 2 S, followed by an upward excursion of the chemocline that releases the poisonous gas into the atmosphere (13). In this study, we examine the 238 U∕ 235 U and Th/U (thorium/ uranium) ratios in a carbonate section spanning the end-Permian extinction horizon (EH) to evaluate the timing and scale of these possibilities. Samples for this study were collected from the Dawen section of the Yangtze Block in southern China (Fig. 1), which has been correlated with the global stratotype section and point (GSSP) of the Permian-Triassic boundary at Meishan (14).Due to the geochemical properties of U, the ratio of 238 U∕ 235 U can be used as a tool to investigate the history of ocean oxygenation at a global scale, as opposed to the local redox information provided by most commonly used proxies. The long residence time (∼500 ky) of U in the oceans leads to a homogeneous U concentration in seawater (15, 16), as well as to ...

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Section: Resultsmentioning

confidence: 84%

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confidence: 99%

Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction

Brennecka

Herrmann

Algeo

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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309

204

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“…In the modern ocean, continental shelves comprise ∼7% of the seafloor area but host a disproportionate share of marine animal diversity, biomass, and the burial of biogeochemically important elements (e.g., carbon and sulfur). Our uranium data, combined with biomarker support for photic-zone euxinia (6) and petrographic, geochemical, and modeling evidence for an expanded oxygen minimum zone (OMZ) rather than deep-ocean anoxia (20,(29)(30)(31), indicate that anoxic waters may have bathed a large fraction of Early Triassic outer continental shelves and upper slopes in anoxic waters. These conditions could explain the limited diversity and ecological complexity of marine ecosystems (3), as well as the reduced maximum and mean body sizes of benthic animals (25).…”

Section: Discussionmentioning

confidence: 85%

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Lau

Maher

Altıner

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

241

193

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Delayed Earth system recovery following the end-Permian mass extinction is often attributed to severe ocean anoxia. However, the extent and duration of Early Triassic anoxia remains poorly constrained. Here we use paired records of uranium concentrations ([U]) and 238 U/ 235 U isotopic compositions (δ 238 U) of Upper Permian−Upper Triassic marine limestones from China and Turkey to quantify variations in global seafloor redox conditions. We observe abrupt decreases in [U] and δ 238 U across the end-Permian extinction horizon, from ∼3 ppm and −0.15‰ to ∼0.3 ppm and −0.77‰, followed by a gradual return to preextinction values over the subsequent 5 million years. These trends imply a factor of 100 increase in the extent of seafloor anoxia and suggest the presence of a shallow oxygen minimum zone (OMZ) that inhibited the recovery of benthic animal diversity and marine ecosystem function. We hypothesize that in the Early Triassic oceans-characterized by prolonged shallow anoxia that may have impinged onto continental shelvesglobal biogeochemical cycles and marine ecosystem structure became more sensitive to variation in the position of the OMZ. Under this hypothesis, the Middle Triassic decline in bottom water anoxia, stabilization of biogeochemical cycles, and diversification of marine animals together reflect the development of a deeper and less extensive OMZ, which regulated Earth system recovery following the end-Permian catastrophe.paleoredox | uranium isotopes | biogeochemical cycling | carbon isotopes | Early TriassicT he end-Permian mass extinction-the most severe biotic crisis in the history of animal life-was followed by 5 million years of reduced biodiversity (1, 2), limited ecosystem complexity (3), and large perturbations in global biogeochemical cycling (4, 5). Ocean anoxia has long been invoked both as a cause of the extinction (6-8) and as a barrier to rediversification (9). Numerous lines of evidence demonstrate widespread anoxic conditions around the time of the end-Permian mass extinction (e.g., refs. 6 and 10-12). In contrast, the prevalence of anoxia during the 5-to 10-millionyear recovery interval remains poorly constrained (13,14).Reconstructing paleoredox conditions is challenging because some indicators of anoxia characterize only the local conditions of the overlying water column, whereas other indicators may be influenced by confounding factors, such as weathering rates on land. Here, we use paired measurements of [U] and δ 238 U in marine carbonate rocks to differentiate changes in weathering of U from variations in global marine redox conditions. Microbially mediated reduction of U(VI) to U(IV) under anoxic conditions at the sediment−water interface results in a substantial decrease in uranium solubility and a measureable change in 238 U/ 235 U (15-18). Because 238 U is preferentially reduced and immobilized relative to 235 U, the δ 238 U value of seawater U(VI) decreases as the areal extent of bottom water anoxia increases (Fig. S1). Consequently, a global increase in the extent of anoxi...

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“…However, as suggested by Algeo et al (2010), paleoenvironmental conditions in the Permian-Triassic Panthalassa Ocean, which was *50% larger than the modern Pacific and covered an entire hemisphere of the Earth's surface (Kiessling et al 1999), have received little attention. This is chiefly due to the scarcity of reliable sections from this region.…”

Section: Introductionmentioning

confidence: 99%

Early Triassic peritidal carbonate sedimentation on a Panthalassan seamount: the Jesmond succession, Cache Creek Terrane, British Columbia, Canada

Sano

Onoue

Orchard

et al. 2011

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The Jesmond succession of the Cache Creek Terrane in southern British Columbia records late Early Triassic peritidal carbonate sedimentation on a mudflat of a buildup resting upon a Panthalassan seamount. Conodont and foraminiferal biostratigraphy dates the succession as the uppermost Smithian to mid-Spathian. The study section (ca. 91 m thick) is dominated by fine-grained carbonates and organized into at least 12 shallowing-upwards cycles, each consisting of shallow subtidal facies and overlying intertidal facies. The former includes peloidal and skeletal limestones, flat-pebble conglomerates, stromatolitic bindstones, and oolitic grainstone, whereas the latter consists mainly of dolomicrite. The scarcity of skeletal debris, prevalence of microbialite, and intermittent intercalation of flat-pebble conglomerate facies imply environmentally harsh conditions in the mudflat. The study section also records a rapid sea-level fall near the Smithian-Spathian boundary followed by a gradual sea-level rise in the early to mid-Spathian.

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Changes in productivity and redox conditions in the Panthalassic Ocean during the latest Permian

Cited by 162 publications

References 26 publications

Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction

Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction

Marine anoxia and delayed Earth system recovery after the end-Permian extinction

Early Triassic peritidal carbonate sedimentation on a Panthalassan seamount: the Jesmond succession, Cache Creek Terrane, British Columbia, Canada

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