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Disparity between Toarcian Oceanic Anoxic Event and Toarcian carbon isotope excursion

Abstract.

"The Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic) is marked by widespread marine deoxygenation and deposition of organic carbon (OC)-rich strata. The genesis of the T-OAE is thought to be associated with environmental changes caused by the emission of 12C-enriched greenhouse gasses (CO2, CH4), manifested in a negative Toarcian carbon isotope excursion (nT-CIE). The nT-CIE is commonly used to stratigraphically define the T-OAE, and despite the complex interrelationship of the different environmental phenomena, both terms (nT-CIE and T-OAE) are commonly used interchangeable. [...]".

 

Source: Springer Nature
Authors: Wolfgang Ruebsam & Lorenz Schwark 
DOI: https://doi.org/10.1007/s00531-024-02408-8

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The early Toarcian Oceanic Anoxic Event (Jenkyns Event) in the Alpine-Mediterranean Tethys, north African margin...

Full title: "The early Toarcian Oceanic Anoxic Event (Jenkyns Event) in the Alpine-Mediterranean Tethys, north African margin, and north European epicontinental seaway"

Abstract.

"The early Toarcian Oceanic Anoxic Event (Jenkyns Event) was associated with major world-wide climatic changes with profound effects on the global carbon cycle. This review revisits the available literature covering the Jenkyns Event applying an updated common stratigraphic definition, allowing illustration of the development and evolution of anoxia in the Alpine-Mediterranean Tethys [...]".

 

Source: Science Direct 
Authors: Gabriele Gambacorta et al.
DOI: https://doi.org/10.1016/j.earscirev.2023.104636

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Fossil-Bearing Concretions of the Araripe Basin Accumulated During Oceanic Anoxic Event 1b

Abstract.

"Fossils from the Araripe Basin (northeastern Brazil) are known for their remarkable preservation of vertebrates and invertebrates, even including soft tissues. They occur in carbonate concretions within organic carbon-rich strata assigned to the Romualdo Formation. Here we present integrated stable isotope, elemental and microfossil records from the Sítio Sobradinho outcrop, Araripe Basin, northeastern Brazil. Our results imply that black shales hosting fossil-bearing carbonate concretions within the lower Romualdo Formation were deposited during Oceanic Anoxic Event (OAE) 1b (Kilian sub-event). [...]".

 

Source: Wiley Online Library
Authors: Marlone H. H. Bom et al.
DOI: https://doi.org/10.1029/2023PA004736

Read the full article here.


Spatially heterogenous seawater δ34S and global cessation of Ca-sulfate burial during the Toarcian oceanic anoxic event

Abstract.

"The early Toarcian of the Early Jurassic saw a long-term positive carbon-isotope excursion (CIE) abruptly interrupted by a significant negative excursion (nCIE), associated with rapid global warming and an oceanic anoxic event (T-OAE, ∼183 Ma). However, the detailed processes and mechanisms behind widespread ocean deoxygenation are unclear. Here, we present high-resolution carbonate-associated sulfate sulfur-isotope [...]".

 

Source: Science Direct
Authors: Zhong Han et al.
DOI: https://doi.org/10.1016/j.epsl.2023.118404

Read the full article here.


Stratigraphic architecture of the Tethyan Cenomanian-Turonian succession and OAE2 in the Dokan Area, Kurdistan Region, northeast Iraq

Abstract.

"This study provides a detailed examination of a condensed Cenomanian-Turonian (C-T) succession of two sections (Dokan Dam and Khalakan) in the Kurdistan Region, Northeastern Iraq, based on biostratigraphy (calcareous nannofossils and planktic foraminifera), carbon and oxygen isotope geochemistry, and facies analysis. The C/T boundary in this region is characterized by a hiatus noticeable due to the absence of the Globigerinelloides benthonensis and Dicarinella hagni subzones and the lack of positive carbon isotope excursion (CIE) peak b during the Oceanic Anoxic Event 2 (OAE2). [...]".

 

Source: Science Direct
Authors: Fadhil A. Lawa et al.
DOI: https://doi.org/10.1016/j.jafrearsci.2023.105064

Read the full article here.


Carbonate uranium isotopes across Cretaceous OAE 2 in southern Mexico: New constraints on the global spread of marine anoxia and organic carbon burial

Abstract.

"Oceanic anoxic events (OAEs) represent discrete intervals of decreased marine oxygen concentrations often associated with volcanism, enhanced organic carbon burial coupled with positive δ13C excursions, and significant biotic turnover. Cretaceous OAE 2 (ca. 94 Mya) is especially notable for globally-distributed changes in calcareous invertebrate and plankton populations. While the presence of organic-rich facies is consistent with locally anoxic environments in many cases, determining the global extent of anoxia is more problematic. [...]".

 

Source: Science Direct
Authors: Joseph T. Kulenguski et al.
DOI: https://doi.org/10.1016/j.palaeo.2023.111756

Read the full article here.


Paleoenvironmental significance of the carbon isotope record across the Cenomanian–Turonian transition and the Oceanic Anoxic Event 2 (OAE2) ...

Full title: "Paleoenvironmental significance of the carbon isotope record across the Cenomanian–Turonian transition and the Oceanic Anoxic Event 2 (OAE2) in the southeastern Neotethys, Zagros, Iran"

Abstract.

"A high–resolution carbon isotope record of pelagic carbonates (δ13Ccarb) from the Zagros Mountains, Iran, documents a 1.8‰ positive carbon isotope excursion (CIE) in the southeastern Neotethys during the Cenomanian–Turonian transition, corresponding to Ocean Anoxic Event (OAE2). The succession is controlled by biostratigraphy that includes the Rotalipora cushmani [...]".

 

Source: Science Direct
Authors: Borhan Bagherpour et al.
DOI: https://doi.org/10.1016/j.cretres.2023.105574

Read the full article here.


Driver of eustatic change during the early Aptian Oceanic Anoxic Event 1a (∼120 Ma)

Abstract.

"Sea-level changes exert an important control on oceanic circulation and climate evolution. Researchers have proposed that sea-level rise favored accumulation of sediments enriched in organic carbon during oceanic anoxic events (OAEs), although high-frequency sea-level changes and their controlling mechanism have remained poorly constrained. Here we present a detailed sedimentological and geochemical study on Aptian (Lower Cretaceous) shallow-water carbonates of the Dariyan Formation exposed in the Zagros fold belt of southern Iran. [...]".

 

Source: Science Direct
Authors: Yiwei Xu et al.
DOI: https://doi.org/10.1016/j.gloplacha.2023.104236

Read the full article here.


The response of nitrogen and sulfur cycles to ocean deoxygenation across the Cenomanian-Turonian boundary

Abstract.

"The Cretaceous Oceanic Anoxic Event 2 (OAE2) is a greenhouse episode of severe marine anoxia at the Cenomanian-Turonian boundary. This time interval is characterized by rising sea surface temperature, enhanced marine biological productivity, and widespread occurrence of organic-rich black shales. With an export of biological production to the deep ocean, organisms consume vast amounts of oxygen and subsequently utilize nitrate and sulfate as electron acceptors in organic matter degradation, thereby affecting biogeochemical cycles of nitrogen and sulfur. [...]".

 

Source: Science Direct
Authors: Ruixiang Zhai et al.
DOI: https://doi.org/10.1016/j.gloplacha.2023.104182

Read the full article here.


Cretaceous southern high latitude benthic foraminiferal assemblages during OAE 2 at IODP Site U1516, Mentelle Basin, Indian Ocean

Abstract.

"At Site U1516 (Mentelle Basin, southeast Indian Ocean, offshore western Australia), the International Ocean Discovery Program (IODP) Expedition 369 recovered an almost complete pelagic record of the Upper Cretaceous, including the Oceanic Anoxic Event 2 (OAE 2). To better understand paleoenvironmental changes across OAE 2, 32 samples were analysed for benthic foraminiferal abundance data that represent one of the few benthic foraminiferal datasets spanning the OAE 2 in the southern high latitudes. [...]".

 

Source: Science Direct
Authors: Erik Wolfgring et al.
DOI: https://doi.org/10.1016/j.cretres.2023.105555

Read the full article here.


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