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Ironstone as a proxy of Paleozoic ocean oxygenation

Abstract. 

"Marine ironstone is a Phanerozoic biochemical sedimentary rock that contains abundant primary iron. Although rare, ironstone is conspicuous in the Paleozoic sedimentary record. Its iron source remains contentious, with traditional models invoking a continentally derived source. Increasing sedimentologic evidence suggests that many Paleozoic ironstones formed along favourably oriented continental margins where coastal upwelling delivered ferruginous waters, with the postulated source of iron being deep-ocean hydrothermal fluids. [...]".

 

Source: Science Direct 
Authors: Edward J. Matheson et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117715

Read the full article here.


Continental configuration controls ocean oxygenation during the Phanerozoic

Abstract. 

"The early evolutionary and much of the extinction history of marine animals is thought to be driven by changes in dissolved oxygen concentrations ([O2]) in the ocean. In turn, [O2] is widely assumed to be dominated by the geological history of atmospheric oxygen (pO2). Here, by contrast, we show by means of a series of Earth system model experiments how continental rearrangement during the Phanerozoic Eon drives profound variations in ocean oxygenation and induces a fundamental decoupling in time between upper-ocean and benthic [O2]. [...]". 

 

Source: Nature
Authors: Alexandre Pohl et al.
DOI: https://doi.org/10.1038/s41586-022-05018-z 

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Mo isotope composition of the 0.85 Ga ocean from coupled carbonate and shale archives: Some implications for pre-Cryogenian oxygenation

Abstract.

"This study addresses marine palaeoredox conditions of the mid-Neoproterozoic by analysing the Mo isotope, trace element, and U-Th-Pb isotope compositions of shallow water microbial carbonate, deep water pelagic carbonate, and shale from the Stone Knife Formation (SKF) in NW Canada. The U-Th-Pb isotope SKF systematics of reef microbialite carbonates, and the moderately expressed negative Ce anomalies are consistent with the presence of dissolved O2 in the surface waters. [...]".

 

Source: Science Direct 
Authors: Edel Mary O'Sullivan et al.
DOI: https://doi.org/10.1016/j.precamres.2022.106760

Read the full article here.


Decoupled oxygenation of the Ediacaran ocean and atmosphere during the rise of early animals

Abstract. 

"The Ediacaran Period (∼635 to 541 Ma) witnessed the early diversification and radiation of metazoans, in the form of the Ediacaran Biota. This biological revolution, beginning at ∼575 Ma, has been widely attributed to a temporally restricted episode of deeper ocean oxygenation, potentially caused by a contemporaneous rise in atmospheric oxygen levels. However, quantitative geochemical-record-driven estimates of Ediacaran atmospheric and oceanic redox evolution are lacking, and hence possible links between oceanic and atmospheric oxygenation remain speculative. [...]". 

 

Source: Science Direct 
Authors: Wei Shi et al.
DOI: https://doi.org/10.1016/j.epsl.2022.117619

Read the full article here.


Constraints on Early Paleozoic deep-ocean oxygen concentrations from the iron geochemistry of the Bay of Islands ophiolite

Abstract. 

"The deep ocean is generally considered to have changed from anoxic in the Precambrian to oxygenated by the Late Paleozoic (∼420–400 Ma) due to changes in atmospheric oxygen concentrations. When the transition occurred, that is, in the Early Paleozoic or not until the Late Paleozoic, is less well constrained. To address this, we measured Fe3+/ΣFe of volcanic rocks, sheeted dykes, gabbros, and ultramafic rocks from the Early Paleozoic (∼485 Ma) Bay of Islands (BOI) ophiolite as a proxy for hydrothermal alteration in the presence or absence of O2 derived from deep marine fluids. [...]".

 

Source: Geochemistry, Geophysics, Geosystems 
Authors: Daniel A. Stolper et al. 
DOI: https://doi.org/10.1029/2021GC010196

Read the full article here.


Linkage of the late Cambrian microbe-metazoan transition (MMT) to shallow-marine oxygenation during the SPICE event

Abstract.

"Microbe-metazoan transitions (MMTs), representing a switch from microbe-mediated to metazoan-mediated carbonate production, have been linked to major changes in Earth-surface conditions. The ‘late Cambrian MMT’ (nomen novum), during which microbial reefs were replaced by maceriate and lithistid sponge reefs, coincided with a sharp rise in atmospheric O2 levels attributed to the Steptoean Positive Carbon Isotope Excursion (SPICE) at ~497–494 Ma. However, relationships between atmospheric oxygenation, marine redox conditions, and the MMT have not been thoroughly investigated to date. [...]". 

 

Source: Science Direct 
Authors: Lei Zhang et al.
DOI: https://doi.org/10.1016/j.gloplacha.2022.103798

Read the full article here.


Covariation of Deep Antarctic Pacific Oxygenation and Atmospheric CO2 during the Last 770 kyr

Abstract. 

"We present new geochemical evidence of changes in oxygenation of the deep Antarctic Pacific over the last 770 kyr. Our data are derived from redox-sensitive metals and export production proxies extracted from gravity core ANT34/A2-10 at 4217 m water depth. Our results show that oxygen levels in the deep Antarctic Zone (AZ) varied in line with the release of deeply sequestered remineralized carbon to the atmosphere during glacial–interglacial (G–IG) cycles, with lower oxygen concentrations and more carbon storage during glacial periods. Subsequent reductions in the amount of carbon stored at depth were closely associated with improved ventilation during glacial terminations. [...]".

 

Source: Lithosphere

Authors: Zheng Tang et al. 

DOI: https://doi.org/10.2113/2022/1835176

Read the full article here.


A transient oxygen increase in the Mesoproterozoic ocean at ∼1.44 Ga: Geochemical evidence from the Tieling Formation, North China Platform

Abstract.

"Oxygen availability is crucial for the evolution of eukaryotes in geological history, yet detailed Mesoproterozoic oceanic-atmospheric redox conditions remain enigmatic. In contrast to the generally accepted hypothesis of an anoxic mid-Proterozoic ocean and atmosphere, several transient oxygenation events may occur at the Earth’s surface during the Mesoproterozoic, especially for the period around 1.4 Ga. The North China Platform develops one of the most complete and continuous Mesoproterozoic stratigraphic successions globally, preserving key information on the redox state of the surface ocean–atmosphere system during the mid-Proterozoic. [...]".

 

Source: Science Direct

Authors: Yang Yu et al.

DOI: https://doi.org/10.1016/j.precamres.2021.106527

Read the full article here.


Major Early-Middle Devonian oceanic oxygenation linked to early land plant evolution detected using high-resolution U isotopes of marine limestones

Abstract.

"The middle Paleozoic (∼420-350 Myr) records a major increase in ocean-atmosphere oxygen levels; however, the timing and pattern of oxygenation are poorly constrained. Two well-dated North American locations in Nevada and Illinois were used to generate a high-resolution U-isotopic profile (U) spanning ∼70 Myr of the middle Paleozoic. Stratigraphic and geochemical data support the interpretation that the Nevada profile represents a near-primary record of global-ocean redox variations. First-order U trends indicate strongly reducing oceans during the late Silurian and Early Devonian, terminated by a major oxygenation event near the Emsian-Eifelian boundary (∼395 Ma). More oxic seawater conditions persisted for the next 30+ Myr, but were punctuated by multiple Myr-scale anoxic events during the Middle-Late Devonian and Early Mississippian that correlate with known global biotic crises, positive C excursions, and widespread organic-rich facies deposition. [...]".

 

Source: Science Direct

Authors: Maya Elrick et al.

DOI: https://doi.org/10.1016/j.epsl.2022.117410

Read the full article here.


Methane oxidation in the waters of a humics-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humics

Abstract.

"Small boreal lakes are known to contribute significantly to global methane emissions. Lake Lovojärvi is a eutrophic lake in Southern Finland with bottom water methane concentrations up to 2 mM. However, the surface water concentration, and thus the diffusive emission potential, was low (< 0.5 μM). We studied the biogeochemical processes involved in methane removal by chemical profiling and through incubation experiments. δ13C-CH4 profiling of the water column revealed methane-oxidation hotspots just below the oxycline and within the anoxic water column. In incubation experiments involving the addition of light and/or oxygen, methane oxidation rates in the anoxic hypolimnion were enhanced 3-fold, suggesting a major role for photosynthetically fueled aerobic methane oxidation. A distinct peak in methane concentration was observed at the chlorophyll a maximum[...]"

Source: Biogeoscience
Authors: Sigrid van Grinsven et al.
DOI: https://doi.org/10.5194/bg-2021-3

Read the full article here.


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