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Global oceanic oxygenation controlled by the Southern Ocean through the last deglaciation

Abstract.

"Ocean dissolved oxygen (DO) can provide insights on how the marine carbon cycle affects global climate change. However, the net global DO change and the controlling mechanisms remain uncertain through the last deglaciation. Here, we present a globally integrated DO reconstruction using thallium isotopes, corroborating lower global DO during the Last Glacial Maximum [19 to 23 thousand years before the present (ka B.P.)] relative to the Holocene. [...]".

 

Source: Science Advances  
Authors: Yi Wang et al.
DOI: 10.1126/sciadv.adk2506

Read the full article here.


Sedimentary environment and benthic oxygenation history of the Upper Cretaceous Austin Chalk Group, south Texas...

Full title: "Sedimentary environment and benthic oxygenation history of the Upper Cretaceous Austin Chalk Group, south Texas: An integrated ichnological, sedimentological and geochemical approach"

Abstract.

"Oxygen concentration in the ocean is vital for sustaining marine ecosystems. While the potential impacts of deoxygenation on modern oceans are hard to predict, lessons can be learned from better characterizing past geological intervals formed under a greenhouse climate. The greenhouse Cretaceous containing several oceanic anoxic events [...]".

 

Source: Wiley Online Library
Authors: Charlie Y. C. Zheng et al. 
DOI: https://doi.org/10.1111/sed.13169

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Spatial pattern of marine oxygenation set by tectonic and ecological drivers over the Phanerozoic

Abstract.

"Marine redox conditions (that is, oxygen levels) impact a wide array of biogeochemical cycles, but the main controls of marine redox since the start of the Phanerozoic about 538 million years ago are not well established. Here we combine supervised machine learning with shale-hosted trace metal concentrations to reconstruct a near-continuous record of redox conditions in major marine depositional settings. We find synchronously opposite redox changes in upper ocean versus deep shelf and (semi-)restricted basin settings ('redox anticouples', nomen novum) in several multi-million-year intervals, which can be used to track the positions of oxygen-minimum zones and the primary locations of organic burial through time. [...]".

 

Source: Nature
Authors: Xiangli Wang et al. 
DOI: https://doi.org/10.1038/s41561-023-01296-y

Read the full article here.


“Hypoxic” Silurian oceans suggest early animals thrived in a low-O2 world

Abstract.

"Atmospheric oxygen (O2) concentrations likely remained below modern levels until the Silurian–Devonian, as indicated by several recent studies. Yet, the background redox state of early Paleozoic oceans remains poorly constrained, hampering our understanding of the relationship between early animal evolution and O2. Here, we present a multi-proxy analysis of redox conditions in the Caledonian foreland basin to Baltica from the early to the mid-Silurian. [...]".

 

Source: Science Direct 
Authors: Emma R. Haxen et al.
DOI: https://doi.org/10.1016/j.epsl.2023.118416

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Oxygenation of the Baltoscandian shelf linked to Ordovician biodiversification

Abstract.

"Marine biodiversity increased markedly during the Ordovician Period (~487–443 million years ago). Some intervals within the Ordovician were associated with unusually rapid and prominent rises in taxonomic richness, the reasons for which remain debated. Links between increased oxygenation and biodiversification have been proposed, although supporting marine oxygen proxy data are limited. Here we present an expansive multi-site iodine-to-calcium (I/Ca) record from Lower–Middle Ordovician marine carbonates in Baltoscandia that provides a detailed account of the spatio-temporal development of oxygen conditions across this palaeoshelf. [...]".

 

Source: Nature
Authors: Anders Lindskog et al.
DOI: https://doi.org/10.1038/s41561-023-01287-z

Read the full article here.


Sulfate triple-oxygen-isotope evidence confirming oceanic oxygenation 570 million years ago

Abstract.

"The largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we show that carbonate-associated sulfate (CAS) from three different paleocontinents all have conspicuous negative 17O anomalies (Δ′17OCAS values down to −0.53‰) during the SE. [...]".

 

Source: Nature
Authors: Haiyang Wang et al.
DOI: https://doi.org/10.1038/s41467-023-39962-9

Read the full article here.


A well-oxygenated eastern tropical Pacific during the warm Miocene

Abstract.

"The oxygen content of the oceans is susceptible to climate change and has declined in recent decades, with the largest effect in oxygen-deficient zones (ODZs), that is, mid-depth ocean regions with oxygen concentrations <5 μmol kg−1 (ref.). Earth-system-model simulations of climate warming predict that ODZs will expand until at least 2100. The response on timescales of hundreds to thousands of years, however, remains uncertain. Here we investigate changes in the response of ocean oxygenation during the warmer-than-present Miocene Climatic Optimum (MCO; 17.0–14.8 million years ago (Ma)). [...]".

 

Source: Nature
Authors: Anya V. Hess et al.
DOI: https://doi.org/10.1038/s41586-023-06104-6

Read the full article here.


Mitigation of oxygen decline in fjords by freshwater injection

Abstract. 

"The exchange of water masses between deep fjords and the open ocean is commonly constrained by a topographical barrier called the sill. While fjord water above the sill depth communicates relatively freely with the open ocean, water below the sill depth is caught inside the fjord basin. This basin water may remain stagnant in deep fjords for many successive years. During these periods, the biological consumption of dissolved oxygen is larger than the supply of new oxygen, and the fjord basin might experience hypoxia and even anoxia. [...]".

 

Source: Science Direct
Authors: Dag L. Aksnes et al.
DOI: https://doi.org/10.1016/j.ecss.2023.108286 

Read the full article here.


Reconstructing ocean oxygenation changes from U/Ca and U/Mn in foraminiferal coatings: Proxy validation and constraints on glacial oxygenation changes

Abstract. 

"Deep-sea oxygen concentrations reflect combined effects of air-sea exchange in high-latitude surface waters, ventilation through ocean circulation and the organic carbonremineralization at depth. Reconstruction of past bottom water oxygen (BWO) concentrations has been challenging due to limitations of each existing BWO proxy whose fidelity may be complicated by diagenetic or depositional factors. Therefore, evaluations on BWO changes with multi-proxy approach are always preferred. In this study, we exploit the authigenic uranium content on mixed planktonic foraminiferal coatings as a BWO proxy by presenting new foraminiferal [...]".

 

Source: Science Direct
Authors: Rong Hu et al.
DOI: https://doi.org/10.1016/j.quascirev.2023.108028

Read the full article here.


Molybdenum isotope evidence from restricted-basin mudstones for an intermediate extent of oxygenation in the late Ediacaran ocean

Abstract. 

"The Mo isotope composition of late Ediacaran global seawater and the global extent of ocean oxygenation are still debated due to the complex controls on sedimentary Mo isotope compositions and the rarity with which sediments directly capture global seawater Mo isotope compositions. Deep-water sulfidic sediments from modern severely restricted basins like the Black Sea have the best chance of capturing global seawater Mo isotope compositions. However, few studies have focused on sedimentary Mo isotope variations and their causes in late Ediacaran restricted basins. [...]". 

 

Source: Science Direct
Authors: Zhaozhao Tan et al.
DOI: https://doi.org/10.1016/j.chemgeo.2023.121410

Read the full article here.


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