Conditions required for oceanic anoxia/euxinia: Constraints from a one-dimensional ocean biogeochemical cycle model

Ozaki, Kazumi; Tajima, S; Tajika, Eiichi

doi:10.1016/j.epsl.2011.02.011

Cited by 62 publications

(65 citation statements)

References 72 publications

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“…Persisting high levels of MSR suggests a prevailing large OC pool, together with a long-lasting (∼800 ky) increase in continental weathering (35), a perturbed carbon cycle, and high global temperatures, the latter two returning in intervals throughout a period of almost 4 My (47,48). These Earth surface processes are regarded as an important negative feedback loop of the carbon cycle, where enhanced production and sequestration of OC is stimulated by global warming and subsequent chemical weathering rates (36). The prolonged disturbance after the EPME contradicts a fast return (<100 ky) to predisturbance climate and carbon cycle, enforced by carbon sequestration, as suggested for other events marked by greenhouse warming, such as the Cenozoic hyperthermals (49).…”

Section: Resultsmentioning

confidence: 99%

“…Increased OC degradation by MSR is a strong and robust argument for the reconstructed scenario and explains the observed δ 18 O CAS excursion. Independent numerical exercises with higher complexity models suggest that >4 times enhanced continental weathering considerably increases the primary productivity in shelf settings (12,36), followed by anoxic and sulfidic conditions as a consequence of increased (an)aerobic OC remineralization.…”

Section: Resultsmentioning

confidence: 99%

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Flourishing ocean drives the end-Permian marine mass extinction

Schobben

Stebbins

Ghaderi

et al. 2015

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

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The end-Permian mass extinction, the most severe biotic crisis in the Phanerozoic, was accompanied by climate change and expansion of oceanic anoxic zones. The partitioning of sulfur among different exogenic reservoirs by biological and physical processes was of importance for this biodiversity crisis, but the exact role of bioessential sulfur in the mass extinction is still unclear. Here we show that globally increased production of organic matter affected the seawater sulfate sulfur and oxygen isotope signature that has been recorded in carbonate rock spanning the Permian−Triassic boundary. A bifurcating temporal trend is observed for the strata spanning the marine mass extinction with carbonate-associated sulfate sulfur and oxygen isotope excursions toward decreased and increased values, respectively. By coupling these results to a box model, we show that increased marine productivity and successive enhanced microbial sulfate reduction is the most likely scenario to explain these temporal trends. The new data demonstrate that worldwide expansion of euxinic and anoxic zones are symptoms of increased biological carbon recycling in the marine realm initiated by global warming. The spatial distribution of sulfidic water column conditions in shallow seafloor environments is dictated by the severity and geographic patterns of nutrient fluxes and serves as an adequate model to explain the scale of the marine biodiversity crisis. Our results provide evidence that the major biodiversity crises in Earth's history do not necessarily implicate an ocean stripped of (most) life but rather the demise of certain eukaryotic organisms, leading to a decline in species richness.sulfur cycle | end-Permian mass extinction | primary productivity

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Flourishing ocean drives the end-Permian marine mass extinction

Schobben

Stebbins

Ghaderi

et al. 2015

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

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show abstract

“…However, neodymium isotope ratios in fish teeth from the western equatorial Atlantic (Demerara Rise) and the north European Chalk Sea may reflect hydrothermal input from the Caribbean and/or Arctic Large Igneous provinces (23,28). Alternatively, geochemical box modeling suggests that enhanced P from continental weathering was important for the initiation of OAE 2, followed, as a positive feedback, by its sustained availability due to the widespread reduction of P-bearing iron oxides (29) and more generally enhanced P recycling under anoxic conditions (26).…”

Section: Significancementioning

confidence: 99%

Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2

Owens

Gill

Jenkyns

et al. 2013

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

134

136

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The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon-and sulfurisotope data from four European OAE 2 sections spanning the Cenomanian-Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ∼5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ∼30× greater than the small euxinic fraction present today (∼0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining wholeocean euxinia.carbonate-associated sulfur | geochemical modeling

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“…(8,9). This is perhaps reinforced by ocean acidification, which reduces biomineral formation and thus causes organic matter to sink slower (10), and ocean warming, which increases stratification (11).…”

Section: Looking Back To See the Futurementioning

confidence: 99%

Terrestrial influences on carbon burial at sea

Keil

2011

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

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Conditions required for oceanic anoxia/euxinia: Constraints from a one-dimensional ocean biogeochemical cycle model

Cited by 62 publications

References 72 publications

Flourishing ocean drives the end-Permian marine mass extinction

Flourishing ocean drives the end-Permian marine mass extinction

Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2

Terrestrial influences on carbon burial at sea

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