scholarly journals Biostratigraphic constraints of the Early Toarcian Oceanic Anoxic Event: new data from calcareous nannofossil investigations of Boreal and Tethyan sections

2019 ◽  
Author(s):  
Stefano Visentin ◽  
Elisabetta Erba ◽  
Joerg Mutterlose
Keyword(s):  
Calcareous Nannofossil ◽  
Northern Germany ◽  
Lower Saxony ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
First Occurrence ◽  
Calcareous Nannofossil Biostratigraphy ◽  
Posidonia Shale ◽  
Boreal Realm ◽  
Interval Expression

Calcareous nannofossil biostratigraphy was carried out in Upper Pliensbachian – Lower Toarcian sediments, which cover the Toarcian Oceanic Anoxic Event (T-OAE) interval. In particular, semiquantitative analyses were performed on a total of 156 samples in the composite Sogno Core (Lombardy Basin, Southern Alps) representing a pelagic Tethyan section. Quantitative investigations were applied to additional 168 samples across the Amaltheenton Fm. and Posidonienschiefer Fm., from two cores of the Boreal Realm (Lower Saxony Basin, northern Germany). Primary and secondary events of the Tethyan and Boreal zonations were recognized, allowing the identifications of the NJT5, NJT6 nannofossil Zones for the Sogno Core and the NJ5, NJ6, NJ7 Zones for the German sections, respectively. The sequence of nannofossil biohorizons is generally consistent with data available for various areas at lower and higher latitudes, confirming their reproducibility and reliability for intra and inter-regional correlations. Geochemistry evidences the presence of the negative C isotopic excursion across the “Fish Level” black shale interval expression of the T-OAE in the Sogno Core. The same anomaly is recorded in the German successions at the base of the Posidonia Shale witnessing the passage from well oxygenated to predominantly anoxic conditions. Our results show that the T-OAE C isotopic excursion recorded in the Sogno Core is excellently constrained by the first occurrence (FO) of Carinolithus superbus at the onset and the last occurrence (LO) of Mitrolithus jansae at the end. A significant decrease in abundance and size of Schizosphaerella punctulata (the “S. punctulata crisis”) and an abundance drop of M. jansae further characterise the T-OAE perturbation. Only S. punctulata shows a recovery at the end of the T-OAE, while M. jansae barely survived the palaeoenviromental stress and disappeared soon after its termination. The extreme rareness of S. punctulata and the absence of M. jansae in the Boreal Realm prevent the recognition of the “S. punctulata crisis” and the M. jansae decline. Our study reveals the LO of Biscutum finchii together with the FO of C. superbus as an additional event approximating the onset of the C isotopic excursion exclusively in the German successions. Further events, such as the LOs of Biscutum grandis, Crepidolithus granulatus and Parhabdolithus liasicus are detected within the C isotopic anomaly exclusively in the German sections. Nannofossil biostratigraphy permits the effective dating and correlating of Early Jurassic major palaeoceanographic events and particularly of the T-OAE which are of a great importance to derive a definitive model for the Posidonia Shale deposition.

scholarly journals Biostratigraphic constraints of the Early Toarcian Oceanic Anoxic Event: new data from calcareous nannofossil investigations of Boreal and Tethyan sections

2019 ◽  
Author(s):  
Stefano Visentin ◽  
Elisabetta Erba ◽  
Joerg Mutterlose
Keyword(s):  
Calcareous Nannofossil ◽  
Northern Germany ◽  
Lower Saxony ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
First Occurrence ◽  
Calcareous Nannofossil Biostratigraphy ◽  
Posidonia Shale ◽  
Boreal Realm ◽  
Interval Expression

Calcareous nannofossil biostratigraphy was carried out in Upper Pliensbachian – Lower Toarcian sediments, which cover the Toarcian Oceanic Anoxic Event (T-OAE) interval. In particular, semiquantitative analyses were performed on a total of 156 samples in the composite Sogno Core (Lombardy Basin, Southern Alps) representing a pelagic Tethyan section. Quantitative investigations were applied to additional 168 samples across the Amaltheenton Fm. and Posidonienschiefer Fm., from two cores of the Boreal Realm (Lower Saxony Basin, northern Germany). Primary and secondary events of the Tethyan and Boreal zonations were recognized, allowing the identifications of the NJT5, NJT6 nannofossil Zones for the Sogno Core and the NJ5, NJ6, NJ7 Zones for the German sections, respectively. The sequence of nannofossil biohorizons is generally consistent with data available for various areas at lower and higher latitudes, confirming their reproducibility and reliability for intra and inter-regional correlations. Geochemistry evidences the presence of the negative C isotopic excursion across the “Fish Level” black shale interval expression of the T-OAE in the Sogno Core. The same anomaly is recorded in the German successions at the base of the Posidonia Shale witnessing the passage from well oxygenated to predominantly anoxic conditions. Our results show that the T-OAE C isotopic excursion recorded in the Sogno Core is excellently constrained by the first occurrence (FO) of Carinolithus superbus at the onset and the last occurrence (LO) of Mitrolithus jansae at the end. A significant decrease in abundance and size of Schizosphaerella punctulata (the “S. punctulata crisis”) and an abundance drop of M. jansae further characterise the T-OAE perturbation. Only S. punctulata shows a recovery at the end of the T-OAE, while M. jansae barely survived the palaeoenviromental stress and disappeared soon after its termination. The extreme rareness of S. punctulata and the absence of M. jansae in the Boreal Realm prevent the recognition of the “S. punctulata crisis” and the M. jansae decline. Our study reveals the LO of Biscutum finchii together with the FO of C. superbus as an additional event approximating the onset of the C isotopic excursion exclusively in the German successions. Further events, such as the LOs of Biscutum grandis, Crepidolithus granulatus and Parhabdolithus liasicus are detected within the C isotopic anomaly exclusively in the German sections. Nannofossil biostratigraphy permits the effective dating and correlating of Early Jurassic major palaeoceanographic events and particularly of the T-OAE which are of a great importance to derive a definitive model for the Posidonia Shale deposition.

Early Aptian bay deposits at the southern margin of the Lower Saxony Basin: Integrated Stratigraphy, palaeoenvironment and Oae 1a

2012 ◽  
Vol 62 (1) ◽  
pp. 35-62 ◽  
Author(s):  
Jens Lehmann ◽  
Oliver Friedrich ◽  
Dieter Von Bargen ◽  
Thomas Hemker
Keyword(s):  
Stable Carbon Isotopes ◽  
Glacial Till ◽  
Northern Germany ◽  
Lower Saxony ◽  
Oceanic Anoxic Event ◽  
Lower Saxony Basin ◽  
Southern Margin ◽  
Anoxic Event ◽  
Integrated Stratigraphy

ABSTRACT Lehmann, J., Friedrich, O., von Bargen, D. and Hemker, T. 2012. Early Aptian bay deposits at the southern margin of the lower Saxony Basin: Integrated stratigraphy, palaeoenvironment and OAE 1a. Acta Geologica Polonica, 62 (1), 35-62. Warszawa. The present study establishes a lithostratigraphic subdivision, a bio- and chemostratigraphy and describes the sedimentology of the Alstatte Bay at the southern margin of the Lower Saxony Basin in northern Germany. The socalled Fischschiefer is developed in the lower part of the section, a 2.1 m thick laminated interval that shows TOC values of up to 2 % and is interpreted as local expression of the global Oceanic Anoxic Event 1a (OAE 1a). The basal part of the Fischschiefer is fairly continuously laminated, whereas its upper part is characterized by an alternation of laminated and non-laminated beds. Stable carbon isotopes (δ13 C carb ) show a characteristic pattern for the Fischschiefer interval that can be correlated with sections from the Tethyan Realm. Immediately above the Fischschiefer, however, the studied section might reveal a diagenetic overprint as indicated by very negative carbon stable isotope values. The remaining part of the section is characterized by a rather monotonous claystone succession, terminated by a greenish layer rich in glauconite overlain by glacial till of Pleistocene age. The fauna is typically Boreal in the lower part of the section, but changes around 2 m above the Fischschiefer towards an assemblage indicating a distinct Tethyan influx. The faunal shift is considered to be due to the maximum flooding of the continuous, long-term sea level rise of the Early Aptian which led also to a supposed shift from a restricted to open bay environment.

Onset of Oceanic Anoxic Event 2 in the Lower Saxony Basin – Insights fromhigh-resolution stable isotope stratigraphy and geochemical modelling

2021 ◽  
Author(s):  
Pia Müller ◽  
Ulrich Heimhofer ◽  
Christian Ostertag-Henning
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Stable Isotope ◽  
Carbon Cycle ◽  
Geochemical Modelling ◽  
Positive Anomaly ◽  
Lower Saxony ◽  
Data Set ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

<p>The Oceanic Anoxic Event (OAE) 2 spanning the Cenomanian-Turonian boundary (93.5 Ma)<br>represents a major perturbation of the global carbon cycle and is marked by organic-rich<br>sediments deposited under oxygen-depleted conditions. In many studies the eruption of the<br>Caribbean LIP is considered to be the cause for rapidly increasing CO2 concentrations and<br>resulting global warming accompanied by widespread oceanic anoxia. In the Lower Saxony<br>Basin of northern Germany, the deposits of the OAE 2 are exposed in several industry drill<br>cores. In this study, the lower part of the OAE 2 has been studied in the HOLCIM 2011-3 drill<br>core. Sedimentary rocks are composed of limestones, marly limestones, marls and black<br>shales and have been analysed with a high-resolution stable isotope approach<br>(approximately one sample every 2 cm) combined with geochemical modelling. Using stable<br>carbon isotopes, bulk rock parameters and petrographic analysis, the onset of OAE 2 has<br>been investigated in detail. The high-resolution δ<sup>13</sup>C curve exhibits overall stable values<br>around 3 ‰ before the onset of the Plenus event. This background level is interrupted by<br>three short-lived and small but significant negative carbon isotope excursions (CIEs) down to<br>δ<sup>13</sup>C values of 2.5 ‰, 2.7 ‰ and 1.9 ‰. Immediately before the main rise in the Plenus bed,<br>a longer-lasting negative CIE down to 2.8 ‰ is observed, preceding the large positive CIE of<br>the OAE 2 to values of 5.2 ‰ over 33 ka. Thereafter, the δ<sup>13</sup>C values decrease to 3.5 ‰ over<br>a period of approximately 130 ka. The results can be correlated with the lower-resolution<br>data set of Voigt et al. (2008) but enable a more accurate characterization of the subtle<br>features of the CIE and hence events before and during this time interval. Carbon cycle<br>modelling with the modelling software SIMILE using a model based on Kump & Arthur (1999)<br>reveals that the negative excursion before the Plenus bed can be explained by a massive<br>volcanic pulse releasing of 0.95*10<sup>18</sup> mol CO2 within 14 ka. This amount corresponds to only<br>81 % of the calculated volume of CO<sub>2</sub> release during emplacement of the Caribbean LIP by<br>Joo et al. (2020). In the model the volcanic exhalation increases atmospheric CO<sub>2</sub><br>concentrations. This will increase global temperatures, intensify the hydrological cycle and<br>thus increase nutrient input into the ocean, resulting in an expansion of the oxygen minimum<br>zone, the development of anoxic conditions and an increase in the preservation potential for<br>organic material. In the model enhanced primary productivity and organic matter preservation<br>can be controlled by the implemented riverine phosphate input and the preservation factor for<br>organic matter. For the positive anomaly, the riverine phosphate input must be nearly<br>doubled (from 0.01 μmol/kg PO<sub>4 </sub>to 0.019 μmol/kg) for the period of the increasing δ<sup>13</sup>C<br>values (app. 33 ka), with a concomitant rise of the preservation factor from 1 % to 2 %. This<br>model scenario accurately reproduces the major features of the new high-resolution δ<sup>13</sup>C<br>record over the onset of the OAE 2 CIE.</p>

scholarly journals Pleistocene Calcareous Nannofossil Biostratigraphy and Gephyrocapsid Occurrence in Site U1431D, IODP 349, South China Sea

Geosciences ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 388
Author(s):  
Jose Dominick S. Guballa ◽  
Alyssa M. Peleo-Alampay
Keyword(s):  
South China Sea ◽  
South China ◽  
Emiliania Huxleyi ◽  
Calcareous Nannofossil ◽  
Local Climate ◽  
China Sea ◽  
Climate Anomalies ◽  
First Occurrence ◽  
Calcareous Nannofossil Biostratigraphy ◽  
Morphologic Changes

We reinvestigated the Pleistocene calcareous nannofossil biostratigraphy of Site U1431D (International Ocean Discovery Program (IODP) Expedition 349) in the South China Sea (SCS). Twelve calcareous nannofossil Pleistocene datums are identified in the site. The analysis confirms that the last occurrence (LO) of Calcidiscus macintyrei is below the first occurrence (FO) of large Gephyrocapsa spp. (>5.5 μm). The FO of medium Gephyrocapsa spp. (4–5.5 μm) is also identified in the samples through morphometric measurements, which was unreported in shipboard results. Magnetobiochronologic calibrations of the numerical ages of LO of Pseudoemiliania lacunosa and FO of Emiliania huxleyi are underestimated and need reassessment. Other potential markers such as a morphological turnover of circular to elliptical variants of Pseudoemiliania lacunosa and a small Gephyrocapsa acme almost synchronous with the FO of Emiliania huxleyi may offer biostratigraphic significance in the SCS. The morphologic changes in Gephyrocapsa coccoliths are also examined for the first time in Site U1431D. Placolith length and bridge angle changes are comparable with other ocean basins, suggesting that morphologic changes are most likely evolutionary novelties rather than being caused by local climate anomalies.

Climate changes across Oceanic Anoxic Event 1a: new data from the Boreal realm

2021 ◽  
Author(s):  
Stephane Bodin ◽  
Carlette Blok ◽  
Jon Ineson ◽  
Kresten Anderskouv ◽  
Alicia Fantasia ◽  
...  
Keyword(s):  
Global Scale ◽  
Feedback Mechanism ◽  
Precipitation Pattern ◽  
Humid Climate ◽  
Linear Change ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Climatic Evolution ◽  
The One ◽  
Boreal Realm

<div><span>Our understanding of the climatic evolution during the early Cretaceous in general, and the Oceanic Anoxic Event 1a (OAE-1a) in peculiar, is widely derived from the investigation of Tethyan localities, leaving large uncertainties about their significance on a global scale. In this study, we have performed high-resolution clay-mineral assemblage analyses in the upper Hauterivian to lower Aptian of the </span><span>North Jens-1 core, located in the Danish central graben that was part of the Boreal realm. High amount of detrital Kaolinite is observed throughout the core, indicating the presence of a local, kaolinite-rich source. A long-term decline in Kaolinite content is occurring from the lower Hauterivian to the lowermost, pre-OAE-1a Aptian, followed by a sharp rise within the OAE-1a. This trend is similar to the one observed in the Tethyan realm, indicating a supra-regional climatic evolution from humid conditions in the late Hauterivian toward drier conditions in the latest Barremian – earliest Aptian, followed by renewed humid conditions during the unfolding of OAE-1a. Precise timing of climate change during the OAE-1a differs however in between the Tethyan and Boreal realm. Shift toward humid conditions coincides hence with the onset of OAE-1a (segment C3) in the Tethyan realm, followed by a return to drier conditions in the second half of OAE-1a. In the Boreal realm, the onset of OAE-1a is characterized by a relatively dry climate, followed by the installation of humid climate during the mid-OAE-1a (segments C4-C5) that persists through the remainder of the early Aptian. Across latitudinal belts, there is thus a non-linear change in precipitation pattern during the unfolding of OAE-1a. Similar observations have been made for other OAEs, suggesting more complex weathering feedback mechanism during hyperthermal events than generally assumed.</span></div>

scholarly journals Calcareous nannofossil, ostracode and foraminifera biostratigraphy of Plio-Pleistocene deposits, Rhodes (Greece), with a correlation to the Vrica section (Italy)

2001 ◽  
Vol 20 (2) ◽  
pp. 143-154 ◽  
Author(s):  
Erik Thomsen ◽  
Tine L. Rasmussen ◽  
Annette Hastrup
Keyword(s):  
Deep Water ◽  
Brackish Water ◽  
Southern Italy ◽  
Early Pleistocene ◽  
Calcareous Nannofossil ◽  
Marine Deposits ◽  
First Occurrence ◽  
Degree Of Certainty ◽  
Relative Delay ◽  
Calcareous Nannofossil Biostratigraphy

Abstract. The Kalithea Bay section is situated on the southeastern coast of the island of Rhodes. The section comprises a sedimentary sequence ranging from brackish water gravel and nearshore sand to deep-water clay. The brackish water and nearshore deposits are assigned to the Kritika Formation, while the deep-water deposits are assigned to the Lindos Bay clay. Calcareous nannofossil biostratigraphy shows that the age of the marine sequence is Early Pleistocene. The brackish water sediments cannot be dated with any degree of certainty. The marine deposits are rich in ostracodes and foraminifera and several species have been recognized, which previously have been used as biostratigraphic markers in the Plio-Pleistocene deposits of Rhodes. Biostratigraphic correlation between the Kalithea Bay section and the Plio-Pleistocene boundary stratotype at Vrica, southern Italy, shows that the ostracodes and foraminifera events generally are diachronous relative to the calcareous nannofossil events. The only exception is the first occurrence of the benthic foraminifera Hyalinea balthica. As calcareous nannofossil events are thought to be virtually synchronous within the Mediterranean region, it is concluded that the diachroneity is due to a relative delay in the appearance of ostracodes and foraminifera at Kalithea, caused by differences in the palaeobathymetric settings between the two sites.

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