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Marine redox fluctuation as a potential trigger for the Cambrian explosion

Abstract.

The diversification of metazoans during the latest Neoproterozoic and early Cambrian has been attributed to, among other factors, a progressive rise in surface oxygen levels. However, recent results have also questioned the idea of a prominent rise in atmospheric oxygen levels or a major or unidirectional shift in the marine redox landscape across this interval. Here, we present new carbonate-associated uranium isotope data from upper Ediacaran to lower Cambrian marine carbonate successions. [...]"

Source: Geology
Authors: Guang-Yi Wei et al.
DOI: 10.1130/G40150.1

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Climate and marine biogeochemistry during the Holocene from transient model simulations

Abstract.

"Climate and marine biogeochemistry changes over the Holocene are investigated based on transient global climate and biogeochemistry model simulations over the last 9500 years. The simulations are forced by accelerated and non-accelerated orbital parameters, respectively, and atmospheric pCO2, CH4, and N2O. The analysis focusses on key climatic parameters of relevance to the marine biogeochemistry, and on the physical and biogeochemical processes that drive atmosphere–ocean carbon fluxes and changes in the oxygen minimum zones (OMZs). [...]"

Source: Biogeosciences
Authors: Joachim Segschneider, Birgit Schneider, and Vyacheslav Khon
DOI: 10.5194/bg-15-3243-2018

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UNM scientists find widespread ocean anoxia as cause for past mass extinction

"New research sheds light on first of five major mass extinctions

For decades, scientists have conducted research centered around the five major mass extinctions that have shaped the world we live in. The extinctions date back more than 450 million years with the Late Ordovician Mass Extinction to the deadliest extinction, the Late Permian extinction 250 million years ago that wiped out over 90 percent of species. [...]"

Source: EurekAlert!

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Stepwise oxygenation of early Cambrian ocean controls early metazoan diversification

Abstract.

"The Ediacaran–Cambrian transition is a critical period in Earth history, during which both marine environment and life experienced drastic changes. It was suggested that pervasive oxygenation and associated chemical changes in the ocean have potentially triggered the rapid diversification of early Cambrian metazoans. The timing and process of ocean oxygenation, however, have not been well constrained. [...]"

Source: Palaeogeography, Palaeoclimatology, Palaeoecology
Authors: Xiangkuan Zhao et al.
DOI: 10.1016/j.palaeo.2018.05.009

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Coupling of oceanic carbon and nitrogen facilitates spatially resolved quantitative reconstruction of nitrate inventories

Abstract.

"Anthropogenic impacts are perturbing the global nitrogen cycle via warming effects and pollutant sources such as chemical fertilizers and burning of fossil fuels. Understanding controls on past nitrogen inventories might improve predictions for future global biogeochemical cycling. Here we show the quantitative reconstruction of deglacial bottom water nitrate concentrations from intermediate depths of the Peruvian upwelling region, using foraminiferal pore density. [...]"

Source: Nature Communications
Authors: Nicolaas Glock et al.
DOI: 10.1038/s41467-018-03647-5

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New insights into Cenomanian paleoceanography and climate evolution from the Tarfaya Basin, southern Morocco

Abstract.

"A 325 m long continuous succession of uppermost Albian to lower Turonian pelagic (outer shelf) deposits was recovered from a new drill site in the central part of the Tarfaya Basin (southern Morocco). Natural gamma ray wireline logging, carbonate and organic carboncontent, bulk carbonate and organic carbon stable isotopes and X-ray fluorescence (XRF)-scanner derived elemental distribution data in combination with planktonic foraminiferal biostratigraphy indicate complete recovery of the Cenomanian Stage. [...]"

Source: Cretaceous Research
Authors: Sebastian Beil et al.
DOI: 10.1016/j.cretres.2017.11.006

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Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean

Abstract.

"The interplay between ocean circulation and biological productivity affects atmospheric CO2 levels and marine oxygen concentrations. During the warming of the last deglaciation, the North Pacific experienced a peak in productivity and widespread hypoxia, with changes in circulation, iron supply and light limitation all proposed as potential drivers. [...]"

Source: Nature Geoscience
Authors: William R. Gray et al.
DOI: 10.1038/s41561-018-0108-6

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Oxygenation of the Mesoproterozoic ocean and the evolution of complex eukaryotes

Abstract.

"The Mesoproterozoic era (1,600–1,000 million years ago (Ma)) has long been considered a period of relative environmental stasis, with persistently low levels of atmospheric oxygen. There remains much uncertainty, however, over the evolution of ocean chemistry during this period, which may have been of profound significance for the early evolution of eukaryotic life. [...]"

Source: Nature Geoscience
Authors: Kan Zhang
DOI: 10.1038/s41561-018-0111-y

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Multiple episodes of extensive marine anoxia linked to global warming and continental weathering following the latest Permian mass extinction

Abstract.

"Explaining the ~5-million-year delay in marine biotic recovery following the latest Permian mass extinction, the largest biotic crisis of the Phanerozoic, is a fundamental challenge for both geological and biological sciences. Ocean redox perturbations may have played a critical role in this delayed recovery. However, the lack of quantitative constraints on the details of Early Triassic oceanic anoxia (for example, time, duration, and extent) leaves the links between oceanic conditions and the delayed biotic recovery ambiguous. [...]"

Source: Science Advances
Authors: Feifei Zhan et al.
DOI:10.1126/sciadv.1602921

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Ocean euxinia and climate change "double whammy" drove the Late Ordovician mass extinction

Abstract.

"The Late Ordovician mass extinction (LOME, ca. 445 Ma) was the first of the "Big Five" Phanerozoic extinction events and comprised two extinction pulses. Proposed kill mechanisms include glacially induced global cooling and the expansion of water-column anoxia and/or euxinia (sulfidic conditions), but no general consensus has been reached with regard to the precise role of these mechanisms. [...]"

Source: Geology
Authors: Caineng Zou et al.
DOI: 10.1130/G40121.1

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