scholarly journals Termination of Organic-Rich Accumulation of the Oceanic Anoxic Event 2 in the Deep-Water Carpathian Basins Based on Carbon Stable Isotope Data

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 420
Author(s):  
Marta Bąk ◽  
Krzysztof Bąk
Keyword(s):  
Stable Isotope ◽  
Deep Water ◽  
Black Shales ◽  
Carbon Stable Isotope ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Isotope Data ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Stable Isotope Data

Organic-rich black shales intercalated with green radiolarian shales and bentonites, 2.2 m thick, represent an equivalent of the Bonarelli Level in the Outer Carpathian deep-water succession. Carbon stable isotope data from four sections in the Outer Carpathians show that termination of organic-rich accumulation, related to the oceanic anoxic event 2 (OAE2), occurred at the same time in this part of the Western Tethys. The excellent marker of this event is a first horizon of Fe–Mn layer (nodules), a few centimeters thick, directly covering the youngest black shale layer of the Bonarelli-equivalent Level, which is regarded as the regional chronohorizon. The youngest succession of the organic-rich shales, ca. 30 cm thick, corresponds to the latest Cenomanian interval of δ13Corg values displaying a negative trend, which represents a terminal part within the OAE2 carbon isotope excursion. A deep negative shift which ends this falling trend, close to the Cenomanian–Turonian boundary in δ13C curves from many sections around the world, is not visible in the Outer Carpathian successions. The reason for this was the long period of stratigraphic condensation, which is reflected in the ferromanganese sediments of this area.

The oceanic anoxic event 2 at Es Souabaa (Tebessa, NE Algeria): bio-events and stable isotope study

2018 ◽  
Vol 11 (8) ◽  
Author(s):  
Sihem Salmi-Laouar ◽  
Bruno Ferré ◽  
Khoudair Chaabane ◽  
Rabah Laouar ◽  
Adrian J. Boyce ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Isotope Study ◽  
Stable Isotope Study

Evaluation of combined radiocarbon and carbon stable isotope data of PM2.5 carbonaceous aerosol in Debrecen, Hungary

2020 ◽  
Author(s):  
István Major ◽  
Enikő Furu ◽  
Tamás Varga ◽  
Anikó Horváth ◽  
István Futó ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Total Carbon ◽  
Carbonaceous Aerosol ◽  
Supplementary Information ◽  
Aerosol Sample ◽  
Carbon Stable Isotope ◽  
Carbonaceous Particle ◽  
Development Fund ◽  
Isotope Data ◽  
Stable Isotope Data

<p>Comprehensive atmospheric studies have demonstrated that carbonaceous aerosol is one of the main components of atmospheric particulate matter over Europe. Despite its significant role in atmospheric processes, the characteristic of carbonaceous particle sources and the contributions from modern and fossil sources in the Pannonian Basin are still less known. Using radiocarbon as a tracer, the ratio of modern (biological aerosol, wood burning etc.) and fossil (coal or oil burning, transportation) sources for an aerosol sample can unambiguously be determined but identification of exact sources is not possible. Considering other isotopic techniques, carbon stable isotope results can provide us such supplementary information that can be used in separating different large source clusters (e.g. burning of C3 type wood, coal burning or transportation). Different aerosol sources have well defined carbon stable isotope ranges, which can be used in source apportionment models. Nevertheless, these ranges often overlap each other, making the accurate source identification rather difficult. Combined radiocarbon and carbon stable isotope measurements can however help us to differentiate more precisely numerous modern or fossil sources.</p><p>In our study, the isotopic composition of carbon in the PM<sub>2.5 </sub>atmospheric aerosol collected on weekly basis in Debrecen, Hungary was investigated. In doing so, the organic and elemental carbon content, the specific <sup>14</sup>C content and the δ<sup>13</sup>C values of total carbon were measured using a Sunset OC/EC analyser, an accelerator mass spectrometer (AMS) and an EA/IRMS instrument, respectively. Based on our three-year long carbon stable isotope data of carbonaceous aerosol, relatively enriched δ<sup>13</sup>C results can be observed in each wintertime period, which are supposed by other authors to be related to the effect of coal combustion (mainly in heavily industrialised areas). Contrarily, radiocarbon measurements imply the dominance of modern sources for the same wintertime periods when the biological activity of vegetation is moderate. Consequently, according to our assumption, these values are caused by modern sources having more positive δ<sup>13</sup>C value such as biomass burning of residences. In contrast to single stable isotope or radiocarbon measurements our study sheds light on the importance of combined carbon isotopic investigations. The research was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016-00009 ‘ICER’</p>

Oceanic Anoxic Event 1d (late Albian) in deep-water sediments of the Outer Carpathians, Poland; Carbon isotope and agglutinated foraminiferal records

2021 ◽  
Author(s):  
Krzysztof Bąk ◽  
Górny Zbigniew ◽  
Marta Bąk
Keyword(s):  
Carbon Isotope ◽  
Deep Water ◽  
Environmental Parameters ◽  
Taxonomic Composition ◽  
Black Shales ◽  
Feeding Strategies ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Lithostratigraphic Units ◽  
Outer Carpathians

<p>The Albian–Cenomanian transition is stratigraphically still poorly constrained in deep-water environments below the CCD. For this reason, the recognition of the OAE1d in such sedimentary records is extremely rare. Our high-resolution carbon-isotope (δ<sup>13</sup>C<sub>org</sub>) stratigraphy of the Upper Albian and Lower Cenomanian turbidite/hemipelagic succession, accumulated in the marginal Silesian Basin of the Western Tethys, made it possible to identify the interval corresponding to the OAE1d. It has been recognized within two lithostratigraphic units of the Silesian Nappe of the Outer Carpathians (the Lower and Middle Lgota Beds), which are composed mostly of turbidite sediments containing a large amount of bioclastic material occurring in the silty and sandy fraction (locally over 70%). Bioclasts were redeposited from marginal shelf of the European Platform. The hemipelagic non-calcareous claystones which separate the turbidite sequences contain deep-water agglutinated foraminiferal (DWAF) assemblages, and are devoid of calcareous benthic foraminifers.</p><p>Using the analysis of the DWAF morphogroups, as well as changes in the benthos abundance and its taxonomic composition in relation to the characteristics (colour and TOC content) of hemipelagic sediments, we indicated changes in the environmental conditions that took place during the OAE1d at the bottom of the Silesian Basin. The most abundant horizons of organic-rich shales are characteristic of the lower part of the OAE1d succession corresponding to the Pialli Level from the Umbria-Marche Basin, although thin intercalations of black shales are also present along the upper part of this succession, where the hemipelagic sediments are dominated by green-coloured shales. The variability of organic matter in the studied sediments only slightly correlates with the abundance of the DWAFs and with their taxonomic composition. The more visible features in the latest Albian agglutinated benthos concern relative proportions of foraminiferal morphogroups which correspond to life-style and feeding strategies, and in this way reflect changes in selected environmental parameters. It seems that fluctuations in the morphogroup distribution along the OAE1d succession reflects the influence of two groups of factors: (i) oxygen concentration in bottom waters (low in the older part of the OAE1d, with fluctuations in the younger part of this isotope event), and (ii) the organic carbon flux that was linked to the onset of a massive redeposition of biogenic material from the European shelf. The last factor is related to the sea level fall during the 3-rd order regressive cycle.</p>

The rhythmic expression of mid-Cretaceous Oceanic Anoxic Event 2 at IODP Sites U1513 and U1516 (southwest of Australia) 

2021 ◽  
Author(s):  
Sietske Batenburg ◽  
Kara Bogus ◽  
Matthew Jones ◽  
Kenneth Macleod ◽  
Mathieu Martinez ◽  
...  
Keyword(s):  
Organic Matter ◽  
Indian Ocean ◽  
Water Column ◽  
North Atlantic ◽  
Black Shales ◽  
Carbonate Content ◽  
Intergovernmental Panel ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event

<p>The widespread deposition of organic-rich black shales during the mid-Cretaceous hothouse at ~94 Ma marked a climatic extreme that is particularly well studied in the Northern Hemisphere. The expression of Oceanic Anoxic Event 2 (OAE 2) in the NH was characterised by low oceanic oxygen concentrations, likely caused by the input of nutrients through volcanism and/or weathering in combination with a peculiar geography in which the proto-North Atlantic was semi-restricted (Jenkyns, 2010; Trabucho Alexandre et al., 2010). The extent of water column anoxia outside the North Atlantic and Tethyan domains remains poorly resolved, as few Southern Hemisphere records have been recovered that span OAE 2, and only a portion of those Indian and Pacific Ocean localities experienced anoxia and organic matter deposition (Dickson et al., 2017; Hasegawa et al., 2013).</p><p> </p><p>Here we present new results from IODP Expedition 369 offshore southwestern Australia. Sedimentary records across the Cenomanian-Turonian transition from Sites U1513 and U1516 in the Mentelle Basin (Indian Ocean) display rhythmic lithologic banding patterns. The OAE 2 interval is marked by a dramatic drop in carbonate content and the occurrence of several thin organic-rich black bands. The spacing of dark bands within a rhythmic sequence suggests a potential orbital control on organic matter deposition at our study sites. Time series analyses of high-resolution (cm-scale) elemental data from XRF-core scanning reveal the imprint of periodicities that can be confidently linked to Earth’s orbital parameters. The new OAE 2 records from Sites U1516 and U1513 allow us to i) evaluate existing time scales over the Cenomanian-Turonian transition, and ii) investigate the mechanisms leading to a recurrent lack of oxygen in the Indian Ocean.</p><p> </p><p>Climatic mechanisms translating changes in insolation to variations in organic matter deposition may have included variations in nutrient input from nearby continents and shifts in water column structure affecting local to regional stratification versus deep water formation and advection. Investigating ventilation of the deep sea during the OAE2 interval is of heightened relevance as current global warming is leading to a worldwide expansion of oxygen minimum zones (Pörtner et al., 2019).</p><p> </p><p>References:</p><p>Dickson, A.J., et al., 2017. Sedimentology 64, 186–203.</p><p>Hasegawa, et al., 2013. Cretaceous Research 40, 61–80.</p><p>Jenkyns, H.C., 2010. Geochemistry, Geophysics, Geosystems 11, Q03004.</p><p>Pörtner, H.O., et al., 2019. IPCC Intergovernmental Panel on Climate Change: Geneva, Switzerland.</p><p>Trabucho Alexandre, J., et al., 2010. Paleoceanography 25, PA</p>

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