scholarly journals Extent and duration of marine anoxia during the Frasnian–Famennian (Late Devonian) mass extinction in Poland, Germany, Austria and France

2004 ◽  
Vol 141 (2) ◽  
pp. 173-193 ◽  
Author(s):  
DAVID BOND ◽  
PAUL B. WIGNALL ◽  
GRZEGORZ RACKI
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Spectrometry ◽  
Late Devonian ◽  
Oceanic Anoxic Event ◽  
Fabric Analysis ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Frasnian Stage ◽  
Early Late ◽  
Sediment Fabric

The intensity and extent of anoxia during the two Kellwasser anoxic events has been investigated in a range of European localities using a multidisciplinary approach (pyrite framboid assay, gamma-ray spectrometry and sediment fabric analysis). The results reveal that the development of the Lower Kellwasser Horizon in the early Late rhenana Zone (Frasnian Stage) in German type sections does not always coincide with anoxic events elsewhere in Europe and, in some locations, seafloor oxygenation improves during this interval. Thus, this anoxic event is not universally developed. In contrast, the Upper Kellwasser Horizon, developed in the Late linguiformis Zone (Frasnian Stage) in Germany correlates with a European-wide anoxic event that is manifest as an intensification of anoxia in basinal locations to the point that stable euxinic conditions were developed (for example, in the basins of the Holy Cross Mountains, Poland). The interval also saw the spread of dysoxic waters into very shallow water (for instance, reefal) locations, and it seems reasonable to link the contemporaneous demise of many marine taxa to this phase of intense and widespread anoxia. In basinal locations, euxinic conditions persisted into the earliest Famennian with little change of depositional conditions. Only in the continental margin location of Austria was anoxia not developed at any time in the Late Devonian. Consequently it appears that the Upper Kellwasser anoxic event was an epicontinental seaway phenomenon, caused by the upward expansion of anoxia from deep basinal locales rather than an ‘oceanic’ anoxic event that has spilled laterally into epicontinental settings.

scholarly journals Identification of early Llandovery (Silurian) anoxic palaeo-depressions at the western margin of the Murzuq Basin (southwest Libya), based on gamma-ray spectrometry in surface exposures

GeoArabia ◽  
2006 ◽  
Vol 11 (3) ◽  
pp. 101-118 ◽  
Author(s):  
Nuri Fello ◽  
Sebastian Lüning ◽  
Petr Štorch ◽  
Jonathan Redfern
Keyword(s):  
Black Shale ◽  
Gamma Ray ◽  
Regional Distribution ◽  
Uranium Content ◽  
Organic Content ◽  
Black Shales ◽  
Gamma Ray Spectrometry ◽  
Hydrocarbon Source Rock ◽  
Western Margin ◽  
Anoxic Event

ABSTRACT Following the melting of the Gondwanan icecap and the resulting postglacial sea-level rise, organic-rich shales were deposited in shelfal palaeo-depressions across North Africa and Arabia during the latest Ordovician to earliest Silurian. The unit is absent on palaeohighs that were flooded only later when the anoxic event had already ended. The regional distribution of the Silurian black shale is now well-known for the subsurface of the central parts of the Murzuq Basin, in Libya, where many exploration wells have been drilled and where the shale represents the main hydrocarbon source rock. On well logs, the Silurian black shale is easily recognisable due to increased uranium concentrations and, therefore, elevated gamma-ray values. The uranium in the shales “precipitated” under oxygen-reduced conditions and generally a linear relationship between uranium and organic content is developed. The distribution of the Silurian organic-rich shales in the outcrop belts surrounding the Murzuq Basin has been long unknown because Saharan surface weathering has commonly destroyed the organic matter and black colour of the shales, making it complicated to identify the previously organic-rich unit in the field. In an attempt to distinguish (previously) organic-rich from organically lean shales at outcrop, seven sections that straddle the Ordovician-Silurian boundary were measured by portable gamma-ray spectrometer along the outcrops of the western margin of the Murzuq Basin. It was found that the uranium content of the shales remained largely unaltered by the weathering processes and could therefore be used as a valid proxy parameter to distinguish between pre-weathering organically rich and lean shales. It is now possible to identify and map-out the thickness and approximate organic richness of the black shale using measurement of uranium radiation. Five of the newly measured sections are characterised by uranium-enriched intervals, representing areas of earliest Silurian palaeo-depressions. Major uranium peaks are absent in the spectral gamma-ray curves of two other sections, which are interpreted to mark earliest Silurian palaeo-highs. The new data on the distribution of Silurian black shales from the outcrop belt was integrated with subsurface data from the Murzuq Basin. The resulting map of the distribution of black shales may help with predictions of the occurrence of this unit in less well-explored areas of the basin. Graptolite biostratigraphic data suggests that the anoxic event centred on the middle Rhuddanian, with more oxygenated conditions and onset of deposition of organically leaner shales having commenced sometime during the late Rhuddanian. The presence of anoxic palaeo-depressions during the earliest Silurian within the Ghat outcrop belt indicates that the Tihemboka High at the western margin of the Murzuq Basin could not have been a positive structure during this time.

scholarly journals Global controls on phosphatization of fossils during the toarcian oceanic anoxic event

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sinjini Sinha ◽  
A. D. Muscente ◽  
James D. Schiffbauer ◽  
Matt Williams ◽  
Günter Schweigert ◽  
...  
Keyword(s):  
Lower Jurassic ◽  
X Ray ◽  
Oceanic Anoxic Event ◽  
Exceptional Preservation ◽  
Level Change ◽  
Environmental Controls ◽  
Anoxic Basins ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Posidonia Shale

AbstractKonservat-Lagerstätten—deposits with exceptionally preserved fossils—vary in abundance across geographic and stratigraphic space due to paleoenvironmental heterogeneity. While oceanic anoxic events (OAEs) may have promoted preservation of marine lagerstätten, the environmental controls on their taphonomy remain unclear. Here, we provide new data on the mineralization of fossils in three Lower Jurassic Lagerstätten—Strawberry Bank (UK), Ya Ha Tinda (Canada), and Posidonia Shale (Germany) —and test the hypothesis that they were preserved under similar conditions. Biostratigraphy indicates that all three Lagerstätten were deposited during the Toarcian OAE (TOAE), and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) show that each deposit contains a variety of taxa preserved as phosphatized skeletons and tissues. Thus, despite their geographic and paleoenvironmental differences, all of these Lagerstätten were deposited in settings conducive to phosphatization, indicating that the TOAE fostered exceptional preservation in marine settings around the world. Phosphatization may have been fueled by phosphate delivery from climatically-driven sea level change and continental weathering, with anoxic basins acting as phosphorus traps.

The Late Hauterivian Faraoni ‘Oceanic Anoxic Event’: an update

2014 ◽  
Vol 185 (6) ◽  
pp. 359-377 ◽  
Author(s):  
François Baudin ◽  
Laurent Riquier
Keyword(s):  
Middle Part ◽  
Time Interval ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Anoxic Events ◽  
The Mediterranean ◽  
Definition Of ◽  
Geochemical Studies ◽  
New Occurrences

AbstractMost oceanic anoxic events (OAEs) took place during the middle part of the Cretaceous and the Late Hauterivian probably recorded the first anoxic event within this peculiar time interval. The so-called Faraoni event (~131 Ma) was initially defined as a short-lived anoxic event restricted to the Mediterranean domain. Since its recognition, numerous geochemical studies were conducted on the Faraoni event and new occurrences of this event were suggested outside the Tethyan domain. This paper presents an update on the Late Hauterivian Faraoni event and examines if this event agrees with the definition of OAEs.

Cenomanian–Turonian drowning of the Arabian Carbonate Platform, the İnişdere section, Adıyaman, SE Turkey

2019 ◽  
Vol 498 (1) ◽  
pp. 189-210 ◽  
Author(s):  
O. Mulayim ◽  
O. I. Yilmaz ◽  
B. Sarı ◽  
K. Tasli ◽  
M. Wagreich
Keyword(s):  
Sea Level ◽  
Carbonate Platform ◽  
Accumulation Rates ◽  
Sea Level Changes ◽  
Carbonate Production ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Se Turkey ◽  
Arabian Platform

AbstractThe Cenomanian–Turonian carbonate ramp in the Adıyaman Region of SE Turkey (Northern Arabian Platform) records an abrupt shift from benthic carbonate deposits to pelagic deposits near the Cenomanian–Turonian boundary event (CTBE) in the İnişdere stratigraphic section and surrounding borehole sections. A positive δ13C excursion of up to 2.15% is recorded in carbonate and organic carbon deposited around the CTBE and provides evidence of a direct link between the CTBE and oceanic anoxic events and the demise of the shallow carbonate production in the Derdere Formation. The microfacies analyses, biostratigraphic dating and palaeoenvironmental interpretations suggest that the platform was drowned near the CTBE as a result of changing environmental conditions. The microfacies indicating significant deepening show a contemporaneity to equivalent surfaces globally and thus strongly support an isochronous formation of Cenomanian–Turonian facies by eustatic sea-level changes. Anoxia spreading over the platform drastically reduced the carbonate production as observed in the studied sections and, therefore, resulted in a reduction in carbonate accumulation rates. Regional/local subsidence and a coeval sea-level rise during the late Cenomanian to early Turonian interval were the cause of the drowning of the platform, including regional anoxia at the northern Arabian platform linked to the Cenomanian–Turonian oceanic anoxic event (OAE2).

scholarly journals Bio-chemostratigraphy of the Barremian–Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform

2011 ◽  
Vol 3 (2) ◽  
pp. 789-838 ◽  
Author(s):  
M. Di Lucia ◽  
M. Mutti ◽  
M. Parente
Keyword(s):  
Southern Italy ◽  
Carbonate Platform ◽  
Black Shales ◽  
Carbonate Platforms ◽  
Southern Apennines ◽  
Main Obstacle ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Isotope Stratigraphy

Abstract. Low resolution and lack of chronostratigraphic calibration of carbonate platform biostratigraphy hinder precise correlation with coeval deep-water successions. This is the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper we use carbon isotope stratigraphy to produce the first chronostratigraphic calibration of the Barremian–Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to our calibration, the "Selli level" black shales of epicontinental and oceanic basins corresponds in the southern Apenninic carbonate platform to the interval between the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana, and the second acme of Salpingoporella dinarica. The biocalcification crisis of nannoconids corresponds to the interval going from the first acme of S. dinarica to just above the top of the "Orbitolina level". Since these bioevents have been widely recognized beyond the Apenninic platform, our calibration can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys.

scholarly journals CRETACEOUS OCEANIC ANOXIC EVENTS IN WESTERN CONTINENTAL GREECE

2018 ◽  
Vol 36 (2) ◽  
pp. 846 ◽  
Author(s):  
V. Karakitsios ◽  
H. Tsikos ◽  
Y. Van Breugel ◽  
I. Bakopoulos ◽  
L. Koletti
Keyword(s):  
Black Shale ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Organic Sediments ◽  
Preliminary Study ◽  
Western Greece

Integrated chemostratigraphy and biostratigraphy in Cretaceous pelagic carbonate successions and associated organic sediments of the Ionian basin (western Greece) show the first documentation of the Cenomanian Turonian (OAE)2 and Lower Albian (OAE)1b Oceanic Anoxic Events from western Greece. Preliminary study of the Pindos basin (western Greece) has also identified a black shale horizon which may corresponds to the Lower Albian (OAE)1b Oceanic Anoxic Event.

scholarly journals New drilling of the early Aptian OAE1a: the Cau core (Prebetic Zone, south-eastern Spain)

2016 ◽  
Vol 21 ◽  
pp. 41-46 ◽  
Author(s):  
Pedro Alejandro Ruiz-Ortiz ◽  
José Manuel Castro ◽  
Ginés Alfonso de Gea ◽  
Ian Jarvis ◽  
José Miguel Molina ◽  
...  
Keyword(s):  
Carbonate Platforms ◽  
Oceanic Anoxic Event ◽  
Lower Aptian ◽  
Abrupt Changes ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Isotope Stratigraphy ◽  
Detailed Record ◽  
Global Carbon ◽  
Shed Light

Abstract. The Cretaceous was punctuated by several episodes of accelerated global change, defined as Oceanic Anoxic Events (OAEs), that reflect abrupt changes in global carbon cycling. The Aptian Oceanic Anoxic Event (OAE1a; 120 Ma) represents an excellent example, recorded in all major ocean basins, and associated with massive burial of organic matter in marine sediments. The OAE1a is concomitant with the "nannoconid crisis", which is characterized by a major biotic turnover, and a widespread demise of carbonate platforms. Many studies have been published over the last decades on OAE1a's from different sections in the world, and provide a detailed C-isotope stratigraphy for the event. Nevertheless, new high-resolution studies across the event are essential to shed light on the precise timing and rates of the multiple environmental and biotic changes that occurred during this critical period of Earth history. Here we present a new drill core recovering an Aptian section spanning the OAE1a in southern Spain. The so-called Cau section was drilled in the last quarter of 2015. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents platform deposits of the southern Iberian palaeomargin. The lower Aptian deposits of the Cau section belong to a hemipelagic unit (Almadich Formation), deposited in a highly subsident sector of the distal parts of the Prebetic Platform. Previous work on the early Aptian of the Cau succession has focused on stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry. A more recent study based on biomarkers has presented a detailed record of the pCO2 evolution across the OAE1a (Naafs et al., 2016). All these studies reveal that the Cau section represents an excellent site to further investigate the OAE1a, based on its unusually high sedimentation rate and stratigraphic continuity, the quality and preservation of fossils, and the well-expressed geochemical signatures.

scholarly journals THE USE OF CARBON AND OXYGEN STABLE ISOTOPES IN THE STUDY OF GLOBAL PALAEOCEANOGRAPHIC CHANGES: EXAMPLES FROM THE CRETACEOUS SEDIMENT ROCKS OF WESTERN GREECE

2006 ◽  
Vol 39 (1) ◽  
pp. 64 ◽  
Author(s):  
V. Karakitsios ◽  
H. Tsikos ◽  
K. Agiadi - Katsiaouni ◽  
S. Dermitzoglou ◽  
E. Chatziharalambous
Keyword(s):  
Stable Isotopes ◽  
Oceanic Anoxic Event ◽  
Palaeoenvironmental Change ◽  
Oxygen Stable Isotopes ◽  
Anoxic Event ◽  
Data Record ◽  
Anoxic Events ◽  
First Time ◽  
Western Greece ◽  
Cretaceous Sediment

In the present paper we examine the use of carbon and oxygen stable isotopes in the study of global palaeoceanographic changes, with special reference to the oceanic anoxic events (OAEs). The analysis of stable isotopes was applied to the examination of Cretaceous sediments from the Ionian and Pindos zones of Western Greece. In the Ionian zone the carbon and oxygen stable isotopes, combined with biostratigraphic data, record the palaeoenvironmental change corresponding to the anoxic events Bonarelli (Cenomanian/Turonian, OAE2) and Paquier (Lower Albian, OAE1b). In the Pindos zone, within the Cretaceous sediments, we observed two organic-carbon-rich levels. According to the biostratigraphic and isotopie analysis, the first level corresponds to an OAE of Santonian age. This local oceanic anoxic event is described for the first time. The second level, Aptian - Albian age, possibly correlates to either the Paquier event (OAE 1b) or the Selli event (OAE 1a), which in Greece were until now known only in the Ionian zone.

The Lilliput effect in crinoids at the end of the Oceanic Anoxic Event 2: a case study from Poland

2015 ◽  
Vol 89 (6) ◽  
pp. 1076-1081 ◽  
Author(s):  
Krzysztof R. Brom ◽  
Mariusz A. Salamon ◽  
Bruno Ferré ◽  
Tomasz Brachaniec ◽  
Krzysztof Szopa
Keyword(s):  
Morphological Changes ◽  
Marine Biota ◽  
Oceanic Anoxic Event ◽  
Faunal Turnover ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Greenhouse Effects ◽  
The Moment ◽  
Cretaceous Period

AbstractThe Cretaceous Period (145–66 Ma) consisted of several oceanic anoxic events (120–80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes—e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.

scholarly journals Bio-chemostratigraphy of the Barremian-Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform

Solid Earth ◽  
2012 ◽  
Vol 3 (1) ◽  
pp. 1-28 ◽  
Author(s):  
M. Di Lucia ◽  
A. Trecalli ◽  
M. Mutti ◽  
M. Parente
Keyword(s):  
Carbon Isotope ◽  
Deep Water ◽  
Carbonate Platform ◽  
Carbonate Platforms ◽  
Δ13c Values ◽  
Oceanic Anoxic Event ◽  
Strontium Isotope Stratigraphy ◽  
Anoxic Event ◽  
Anoxic Events ◽  
Isotope Stratigraphy

Abstract. Low biostratigraphic resolution and lack of chronostratigraphic calibration hinder precise correlations between platform carbonates and coeval deep-water successions. These are the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper carbon and strontium isotope stratigraphy are used to produce the first chronostratigraphic calibration of the Barremian-Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to this calibration, the segment of decreasing δ13C values, leading to the negative peak that is generally taken as the onset of the Selli event, starts a few metres above the last occurrence of Palorbitolina lenticularis and Voloshinoides murgensis. The following rise of δ13C values, corresponding to the interval of enhanced accumulation of organic matter in deep-water sections, ends just below the first acme of Salpingoporella dinarica, which roughly corresponds to the segment of peak δ13C values. The whole carbon isotope excursion associated with the oceanic anoxic event 1a is bracketed in the Apenninic carbonate platform between the last occurrence of Voloshinoides murgensis and the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana. Since these bioevents have been widely recognized beyond the Apenninic platform, the calibration presented in this paper can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys. This calibration will be particularly useful to interpret the record of the Selli event in carbonate platform sections for which a reliable carbon isotope stratigraphy is not available.

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