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

Abstract.

"Emerging geochemical evidence suggests that the atmosphere-ocean system underwent a significant decrease in O2 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).  [...]"

Source: Geochimica et Cosmochimica Acta
Authors: Alex I.Sheen et al.
DOI: 10.1016/j.gca.2018.01.036

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Oxygenation as a driver of the Great Ordovician Biodiversification Event

Abstract.

"The largest radiation of Phanerozoic marine animal life quadrupled genus-level diversity towards the end of the Ordovician Period about 450 million years ago. A leading hypothesis for this Great Ordovician Biodiversification Event is that cooling of the Ordovician climate lowered sea surface temperatures into the thermal tolerance window of many animal groups, such as corals. [...]"

Source: Nature Geoscience
Authors: Cole T. Edwards
DOI: 10.1038/s41561-017-0006-3

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The influence of oxygen exposure time on the composition of macromolecular organic matter as revealed by surface sediments on the Murray Ridge

Abstract.

"The Arabian Sea represents a prime example of an open ocean extended oxygen minimum zone (OMZ) with low oxygen concentrations (down to less than 2 mM) between 200 and 1000 m water depth. The OMZ impinges on the ocean floor, affect ingorganic matter (OM) mineralization. We investigated impact of oxygen depletion on the composition of macromolecularOM (MOM) along a transect through the OMZ on the slopes of the Murray Ridge. This sub-marine high in the northern Arabian Sea, with the top at approximately 500 m below sea surface (mbss), intersects the OMZ. We analyzed sediments deposited in the core of OMZ (suboxic conditions) [...]"

Source: Geochimica et Cosmochimica Acta 206
Authors: Nierop, K.G.J.; Reichart, G.-J.; Veld, H.; Sinninghe Damsté, J.S
DOI: dx.doi.org/10.1016/j.gca.2017.02.032

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