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Marine anoxia as a trigger for the largest Phanerozoic positive carbon isotope excursion: Evidence from carbonate barium isotope record

Abstract. 

"The mid-Ludfordian Lau carbon isotope excursion (Lau CIE) represents the largest positive carbon isotope excursion in the Phanerozoic (~9‰), coincident with the biodiversity loss of many marine animal clades. Two main explanations for the Lau CIE are enhanced organic carbon burial via increased marine productivity and preservation-driven expansion of anoxia. While these two explanations are not mutually exclusive, the main driver of Lau CIE is yet to be constrained. Here, we resolve this longstanding debate using barium isotopes (δ138 Ba) of marine carbonates deposited across the Lau CIE. [...]". 

 

Source: Science Direct

Authors: Feifei Zhang et al.

DOI: https://doi.org/10.1016/j.epsl.2022.117421

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Uranium isotope evidence for extensive shallow water anoxia in the early Tonian oceans

Abstract. 

"The Earth's redox evolution has been commonly assumed to have played a key role in shaping the evolutionary history of the biosphere. However, whether and how shifts in marine redox conditions are linked to key biotic events – foremost the rise of animals and the ecological expansion of eukaryotic algae in the late Proterozoic oceans – remains heavily debated. Our current picture of global marine redox evolution during this critical interval is incomplete. This is particularly the case for the Tonian Period (∼1.0 to ∼0.717 Ga), when animals may have diverged and when eukaryotic algae began their rise in ecological importance. Here, we present new uranium isotope (U) measurements from Tonian carbonates to fill this outstanding gap. [...]".

 

Source: Science Direct 

Authors: Feifei Zhang et al.

DOI: https://doi.org/10.1016/j.epsl.2022.117437

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Placing North Pacific paleo-oxygenation records on a common scale using multivariate analysis of benthic foraminiferal assemblages

Abstract. 

"Dysoxic events are well-studied in Pleistocene and Holocene marine sediment records from the North Pacific using faunal, sedimentological, and geochemical paleo-oxygenation proxies. However, differences in proxy sensitivity and local conditions make it difficult to quantify the relative severity of dysoxia across the North Pacific. Here, we use multivariate analyses of taxonomically standardized benthic foraminiferal assemblages to quantitatively compare the severity and duration of dysoxic events at four intermediate depth sites within oxygen minimum zones in the Gulf of Alaska (GoA), Santa Barbara Basin, and Baja California Sur. Unlike previous faunal dissolved oxygen indices, the metric developed here incorporates the total faunal assemblage and is better correlated with co-registered geochemical proxies. [...]". 

 

Source: Science Direct

Authors: Sharon Sharon et al.

DOI: https://doi.org/10.1016/j.quascirev.2022.107412

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Mid-Cretaceous marine Os isotope evidence for heterogeneous cause of oceanic anoxic events

Abstract. 

"During the mid-Cretaceous, the Earth experienced several environmental perturbations, including an extremely warm climate and Oceanic Anoxic Events (OAEs). Submarine volcanic episodes associated with formation of large igneous provinces (LIPs) may have triggered these perturbations. The osmium isotopic ratio (187Os/188Os) is a suitable proxy for tracing hydrothermal activity associated with the LIPs formation, but 187Os/188Os data from the mid-Cretaceous are limited to short time intervals. Here we provide a continuous high-resolution marine 187Os/188Os record covering all mid-Cretaceous OAEs. Several OAEs (OAE1a, Wezel and Fallot events, and OAE2) correspond to unradiogenic 187Os/188Os shifts, suggesting that they were triggered by massive submarine volcanic episodes. However, minor OAEs (OAE1c and OAE1d), which do not show pronounced unradiogenic 187Os/188Os shifts, were likely caused by enhanced monsoonal activity. [...]".

 

Source: Nature Communications 

Authors: Hironao Matsumoto et al.

DOI: https://doi.org/10.1038/s41467-021-27817-0

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Chromium isotope evidence for oxygenation events in the Ediacaran ocean

Abstract. 

"Pulses of the Ediacaran ocean oxygenation were inferred from strong enrichments of redox-sensitive elements (RSEs; particularly Mo, V, U, Re) and negative pyritesulfur isotopes (δ34Spy) in black shales of the Doushantuo Formation in South China. These oceanic oxygenation events (OOEs) have been challenged by the lack of comparable RSE enrichments in correlative strata of northwestern Canada. Here we report four positive chromium isotope (δ53Cr) excursions with peak values (+0.79 ± 0.03‰ to +1.45 ± 0.06‰; 2SD) close to the average δ53Cr value of the modern ocean (+1.0 ± 0.3‰) at the intervals of OOEs, which are separated by low δ53Cr values close to that of the bulk silicate Earth (BSE, −0.124 ± 0.101‰). The positive δ53Cr excursions could be explained by episodic input of oxygenated water from the open ocean to the restricted Nanhua basin, or pulses of ocean oxygenation during the Ediacaran-early Cambrian. The two interpretations can explain the majority of the geochemical data available from the Wuhe section, but both have limitations. [...]". 

 

Source: Science Direct

Authors: Dongtao Xu et al.

DOI: https://doi.org/10.1016/j.gca.2022.02.019

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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

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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

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Calculating dissolved marine oxygen values based on an enhanced Benthic Foraminifera Oxygen Index

Abstract. 

"Marine oxygen minimum zones (OMZs) trap greenhouse gases, reduce livable habitats, a critical factor for these changes is the amount of dissolved oxygen (DO). The frequently used tool to reconstruct DO values, the Benthic Foraminifera Oxygen Index (BFOI), showed major shortcomings and lacks effectiveness. Therefore, we enhanced the BFOI and introduce enhanced BFOI (EBFOI) formulas by using all available data benthic foraminifers provide, calculating the whole livable habitat of benthic foraminifers, including bottom water oxygenation (BWO) and pore water oxygenation (PWO). Further, we introduce for the first time a transfer function to convert EBFOI vales directly into DO values, increasing efficiency by up to 38%. [...]".

 

Source: Nature Scientific Reports

Authors: Matthias Kranner et al. 

DOI: https://doi.org/10.1038/s41598-022-05295-8

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In oceanography, acoustics and hydrodynamics: An extended coupled (2+1)-dimensional Burgers system

Abstract.

"In oceanography, acoustics and hydrodynamics, people pay attention to the Burgers-type equations for different wave processes, one of which is an extended coupled (2+1)-dimensional Burgers system hereby under investigation. Based on the scaling transformation, Bell polynomials, Hirota operators and symbolic computation, we structure out two hetero-Bäcklund transformations, each of which to a solvable linear partial differential[...]"

 

Source: Science Direkt
Authors: Xin-YiGao et al.
DOI: https://doi.org/10.1016/j.cjph.2020.11.017

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Paleocene-Eocene volcanic segmentation of the Norwegian-Greenland seaway reorganized high-latitude ocean circulation

Abstract.

"The paleoenvironmental and paleogeographic development of the Norwegian–Greenland seaway remains poorly understood, despite its importance for the oceanographic and climatic conditions of the Paleocene–Eocene greenhouse world. Here we present analyses of the sedimentological and paleontological characteristics of Paleocene–Eocene deposits (between 63 and 47 million years old) in northeast Greenland, and investigate key unconformities and volcanic facies observed through seismic reflection imaging in offshore basins.[...]"

 

Source: Communications Earth & Environment
Authors: Jussi Hovikoski et al.
DOI: https://doi.org/10.1038/s43247-021-00249-w

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