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>

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.

Major palaeoenvironmental upheavals in both marine and terrestrial realms during the Toarcian oceanic anoxic event: a multi-proxy approach

2020 ◽  
Author(s):  
Francesca Galasso ◽  
Susanne Feist­Burkhardt ◽  
Annette Schmid- Röhl ◽  
Stefano Benasconi ◽  
Elke Schneebeli-Hermann
Keyword(s):  
Carbon Isotope ◽  
Seawater Temperature ◽  
Black Shales ◽  
Land Plants ◽  
Open Pit ◽  
Large Igneous Province ◽  
Isotopic Study ◽  
Data Set ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

<p>The Toarcian oceanic anoxic event (TOAE) ~183 Ma is not only associated with oceanic anoxia and rapid seawater temperature increase but also with a marine mass extinction event. These biotic and environmental upheavals are linked to the emplacement of the Karoo-Ferrar large igneous province. Negative carbon excursions and widespread deposition of black shales are typical for Toarcian sedimentary successions.</p><p>The occurrence and growth of dinoflagellates is influenced by environmental factors like oxygen content, salinity, temperature and nutrient availability. For land plants, changes in dominance structure of ecosystems reflected in spore pollen assemblages can be indicative of ecological disturbance. Thus species composition (and morphology) of dinoflagellates and land plants can be used to understand major environmental perturbations.</p><p>An extensively studied TOAE section is the former Rohrbach Zement quarry at Dotternhausen (today Larfarge-Holcim) with comprehensive data of carbon isotope analyses, total organic and inorganic carbon content and rock eval analysis.<br>The Dotternhausen quarry is not accessible anymore but a new open pit in Dormettingen ~2 km NW of Dotternhausen offers excellent outcrop conditions. Litho- and biostratigraphy of the new section is well documented and calibrated to the old Dotternhausen section on subzone levels. Comparison of the two sites showed that sedimentology, geochemistry and faunal data are laterally constant. <br>Palynological analysis of 59 outcrop samples from the Dormettingen section yielded an excellent quantitative data set of the Early Toarcian Posidonienschiefer sediments. Here we provide a high-resolution, multi-proxy study of this section including chemostratigraphy, particulate organic matter and palynology in order to understand the environmental conditions during the TOAE.</p><p>Carbon isotopic study reveals a negative excursion during the TOAE, varying between -33.49‰ and -26.5‰, with a negative shift in the Falciferum Zone (Elengatum, Exeratum and Elegans Subzone) concurrent with the dinoflagellate "blackout".  The vegetation shows significant changes from a mixed assemblage of pollen and spores in the lower part of the section, to exclusively spore-bearing during the negative carbon isotope excursion. The isotopic signal, the marine dinoflagellate “blackout” and the changes in terrestrial vegetation indicate/document major palaeoenvironmental upheavals in both the marine and terrestrial realms.</p>

scholarly journals Small-sized <i>Trochammina</i> assemblages in deep-water Eocene flysch deposits (Outer Carpathians, Poland) and their palaeoecological implications

2015 ◽  
Vol 34 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Anna Waśkowska
Keyword(s):  
Deep Water ◽  
Global Climate ◽  
Early Eocene ◽  
Northern Margin ◽  
Western Tethys ◽  
Thermal Maximum ◽  
Energy Environment ◽  
Outer Carpathians ◽  
Tethys Ocean ◽  
C 50

Abstract. The global climate change in the early Eocene contributed significantly to the turnover of benthic foraminifera. A major extinction within agglutinated and calcareous forms and the occurrence of opportunistic assemblages resulted. The Trochammina material described here belongs to these post-crisis assemblages. Foraminiferal assemblages with numerous Trochammina species are identified within deep-water Eocene deposits of the Polish part of the Outer Carpathians. Trochammina reach up to 80% of the assemblages, the remainder consists of cosmopolitan agglutinated foraminifera, mainly Bathysiphon, Recurvoides, Paratrochamminoides and Trochamminoides. The low biodiversity (average number of species 24, of genera 15) and the presence of dwarf forms are the main characteristics of the assemblages. These assemblages occur predominantly in shales with numerous organic traces (lower Hieroglyphic beds), deposited in the Silesian Basin (Outer Carpathians) which was on the northern margin of the western Tethys Ocean during the early Eocene (Ypresian, c. 50 Ma). The Trochammina biofacies developed in the Silesian Basin after the Paleocene–Eocene Thermal Maximum crisis, and is dominated by opportunistic forms, mainly represented by mobile epifauna and shallow-water infauna, interpreted as a recolonizing assemblage in a low energy environment.

scholarly journals Mid-Cretaceous paleoenvironmental changes in the western Tethys

2018 ◽  
Vol 14 (8) ◽  
pp. 1147-1163 ◽  
Author(s):  
Cinzia Bottini ◽  
Elisabetta Erba
Keyword(s):  
Surface Water ◽  
Cold Water ◽  
Global Scale ◽  
Climatic Conditions ◽  
Black Shales ◽  
Temperature Index ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Cooling Trend

Abstract. We present a continuous record of surface water temperature and fertility variations through the latest Barremian–Cenomanian interval (ca. 27 Myr) based on calcareous nannofossil abundances from the western Tethys. The nannofossil temperature index, calibrated with TEX86 sea surface temperatures, suggests that warmest (34–36 ∘C) conditions were reached during oceanic anoxic event (OAE) 1a onset, the Aptian–Albian boundary interval hyperthermals (113, Kilian level and Urbino level OAE 1b) and during a ca. 4 Myr long phase in the middle Albian. Coolest temperatures (29 ∘C) correspond instead to the late Aptian. Generally warm conditions characterized the Albian followed by a progressive cooling trend that started in the latest Albian (at the Marne a Fucoidi–Scaglia Bianca Formation transition). Temperate conditions occurred in the Cenomanian with frequent short-term variations highlighted by abundance peaks of the cold-water nannofossil species E. floralis and R. parvidentatum. Mid-Cretaceous surface water fertility was rather fluctuating and mostly independent from climatic conditions as well as from black shales intervals. Intense warming and fertility spikes were systematically associated only with black shales of OAE 1a and of the Aptian–Albian boundary hyperthermals. The Albian–Cenomanian rhythmic black shales are, in fact, associated with varying long-term climatic and fertility conditions. The similarity of western Tethys climatic and fertility fluctuations during OAE 1a, OAE 1b, the middle Albian and OAE 1d with nannofossil-based records from other basins indicated that these paleoenvironmental conditions were affecting the oceans at supra-regional to global scale.

scholarly journals Record of Early Toarcian carbon cycle perturbations in a nearshore environment: the Bascharage section (easternmost Paris Basin)

2014 ◽  
Vol 6 (1) ◽  
pp. 1073-1100 ◽  
Author(s):  
M. Hermoso ◽  
D. Delsate ◽  
F. Baudin ◽  
L. Le Callonnec ◽  
F. Minoletti ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotope ◽  
Isotopic Signature ◽  
Oxygen Isotopic Composition ◽  
Black Shales ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Carbon Isotope Excursion ◽  
Oxygen Isotopic ◽  
Global Nature

Abstract. In order to understand the significance of worldwide deposition of black shale facies in the Early Toarcian (~ 183 Ma), considerable attention has been drawn to this Early Jurassic sub-Stage over the last three decades. The discovery of a pronounced negative carbon isotope excursion (CIE) within the black shales disrupting the generally positive trend in carbon isotopes has stimulated many studies, particularly with a view to establish the local vs. global nature of this major geochemical phenomenon. Here we document the sedimentological and chemostratigraphic evolution of a proximal environment in the Luxembourgian sedimentary area, the so-called Gutland. At Bascharage, Lower Toarcian sediments record the isotopic signature of the Early Toarcian Oceanic Anoxic Event (OAE) by a pronounced positive trend that testifies for widespread anoxia. The expression of the carbon isotope perturbation in this section however, is unusual compared to adjacent NW European sections. A first −7 ‰ negative CIE, whose onset is recorded at the top of the tenuicostatum zone, can be assigned to the well-documented and potentially global T-CIE with confidence using the well-constrained ammonite biostratigraphic framework for this section. In this interval, facies contain only a limited amount of carbonate as a result of intense detrital supply in such a proximal and shallow environment. Stratigraphically higher in the section, the serpentinum zone records a subsequent CIE (−6 ‰) that is expressed by four negative steps, each being accompanied by positive shifts in the oxygen isotopic composition of carbonate. The preservation state of coccoliths and calcareous dinoflagellates in the second CIE is excellent and comparable to that observed in under- and overlying strata, so this cannot be an artefact of diagenesis. Considering the nature of this record, and the lack of such a pronounced event in the serpentinum zone in coeval sections in Europe, we hypothesise that this second CIE was caused by local factors. The geochemical record of carbonate with a relatively light carbon and relatively heavy oxygen isotopic composition is compatible with the so-called Küspert model, by which a CIE can be explained by an influx of 12C-rich and cold waters due to upwelling bottom water masses. With the ongoing effort of high-resolution studies of the Meso-Cenozoic eras, further CIEs are likely to be found, but it has to be remembered that their (global) significance can only be determined via an integrated sedimentological, mineralogical, micropalaeontological and geochemical approach.

Surface- and deep-water response to the Early Aptian OAE 1a in the western Tethys

2021 ◽  
Author(s):  
Cinzia Bottini ◽  
Victor M. Giraldo-Gómez ◽  
Maria Rose Petrizzo ◽  
Elisabetta Erba
Keyword(s):  
Deep Water ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Black Shales ◽  
Ontong Java Plateau ◽  
Western Tethys ◽  
Organic Carbon Flux ◽  
Water Response ◽  
Matter Flux

&lt;p&gt;The Cretaceous was punctuated by interludes of widespread deposition of organic-rich sediments (black shales) in the oceans and epicontinental seas, named Oceanic Anoxic Events (OAE)s, representing major alterations in the global carbon budget. The early Aptian OAE 1a (ca. 120 Ma) coincided with a global paleoclimatic and paleoenvironmental perturbation which lasted for ca. 1.1 Myrs probably triggered by volcanogenic CO&lt;sub&gt;2&amp;#160;&lt;/sub&gt;emissions associated with the emplacement of the Ontong Java Plateau. To date, there is a comprehensive characterization of OAE 1a paleoceanographic conditions and paleoecology of surface-waters while less information is available for bottom-water evolution. In this regard, benthic foraminifera are ideal to characterize deep-water oxygen levels and the organic carbon flux. We present a high-resolution study of benthic foraminiferal assemblages across OAE 1a in the Cismon Core (western Tethys, Lombardy Basin, Northern Italy). Contrarily to many sites, the Cismon Core yields benthic foraminifera also in the Selli Level thus providing information about deep-water conditions during OAE 1a. Our data are indicative of fluctuations in bottom-water oxygenation and organic-matter flux to the sea-floor prior to, during and after OAE 1a. The integration of the new benthic foraminiferal data with calcareous nannofossil and planktonic foraminiferal datasets is here used to produce a model of surface- to bottom-water paleowater evolution through the latest Barremian-early late Aptian. In particular, the new data show coeval changes in bottom- and surface-waters conditions prior to and at the onset of OAE 1a. Anoxia was reached during the core of the negative carbon isotope anomaly, under maximum warming and higher surface-water fertility. Conversely, the repopulation of benthic foraminifera postponed the plankton recovery. Benthic foraminifera data at Cismon show, for the first time, evidence of a repopulation event during the OAE 1a suggestive for a slight increase in the supply of oxygen to the seafloor during the Selli Level deposition.&lt;/p&gt;

scholarly journals An open marine record of the Toarcian oceanic anoxic event

2011 ◽  
Vol 3 (1) ◽  
pp. 385-410 ◽  
Author(s):  
D. R. Gröcke ◽  
R. S. Hori ◽  
J. Trabucho-Alexandre ◽  
D. B. Kemp ◽  
L. Schwark
Keyword(s):  
Organic Matter ◽  
Carbon Cycle ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Global Carbon Cycle ◽  
Open Ocean ◽  
Black Shales ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Global Carbon

Abstract. Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic-rich sediments (black shales) and significant perturbations in the global carbon cycle. The expression of these perturbations is globally recorded in sediments as excursions in the carbon isotope record irrespective of lithology or depositional environment. During the Early Toarcian, black shales were deposited on the epi- and peri-continental shelves of Pangaea and these sedimentary rocks are associated with a pronounced (ca. 7‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the Early Toarcian is thought to represent an oceanic anoxic event (the T-OAE). Associated with this event, there were pronounced perturbations in global weathering rates and seawater temperatures. Although it is commonly asserted that the T-OAE is a global event and that the distribution of black shales is likewise global, an isotopic and/or organic-rich expression of this event has as yet only been recognized on epi- and peri-continental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg) of Early Toarcian cherts from Japan that were deposited in the open Panthalassa Ocean was analysed. The results show the presence of a major (>6‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the Early Toarcian negative CIE known from European epicontinental strata. Furthermore, a secondary ca. −2‰ excursion in δ13Corg is also recognized lower in the studied succession that, within the current biostratigraphical resolution, is likely to represent the excursion that occurs close to the Pliensbachian/Toarcian boundary and which is also recorded in European epicontinental successions. These results from the open ocean realm suggest that, in conjunction with other previously published datasets, these major Early Jurassic carbon cycle perturbations affected all active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric). An extremely negative δ13Corg value (−57‰) during the peak of the T-OAE is also reported, which suggests that the inferred open ocean mid-water oxygen minimum layer within which these sediments are thought to have been deposited was highly enriched in methanotrophic bacteria, since these organisms are the only plausible producers of such 12C-enriched organic matter.

Tectonic-sedimentary evolution of the frontal part of the Ukrainian Carpathian nappe structure

2021 ◽  
Vol 1-2 (183-184) ◽  
pp. 45-59
Author(s):  
Oleh Hnylko ◽  
Svitlana Hnylko ◽  
Maria Kulyanda ◽  
Romana Marchenko
Keyword(s):  
Deep Water ◽  
Taxonomic Composition ◽  
Black Shales ◽  
Carpathian Basin ◽  
Foraminiferal Assemblage ◽  
The North ◽  
Sedimentary Evolution ◽  
North Eastern ◽  
Compensation Depth ◽  
Latest Eocene

For the first time in the Ukrainian Carpathians, the depths and tectono-sedimentation processes in the north-eastern part of the Outer Carpathian Basin (Skyba and Boryslav-Pokuttya units) have been restored on the base of sedimentological and microfaunistic studies. It was established that in the Cretaceous-Eocene time, the deep-water (near Calcite Compensation Depth) turbidite and similar sedimentation (turbidites with Bouma textures, grainites, debris-flow deposits), which periodically alternated with (hemi)pelagic sedimentation (red, green and black shales) was dominant here. Sedimentation took place on the continental margin of the the Carpathian branch of the Tethys, where deep-water fans were formed. Cretaceous-Eocene background red and green shales are enriched in buried in situ benthic foraminifera which are similar in taxonomic composition and morphological features to the microfauna of the Carpathian-Alpine and Atlantic regions (deep-water agglutinated foraminifera), which indicate lower bathyal – abyssal depths of flysch sedimentation. Latest Eocene Globigerina Marl horizon contains the foraminiferal assemblage with plankton dominance, which indicates a general shallowing of the Outer Carpathian Basin (middle-upper bathyal conditions above a calcite compensation depth). Oligocene – lowermost Miocene Menilite-Krosno and Polyanytsia formations were accumulated in the Skyba and Boryslav-Pokuttya sub-basins. In the Miocene, shallow-water molasses were accumulated here. Probably, the tectonic uproot of flysch deposits from its substrate and their synsedymentary thrusting towards the platform caused a significant shallowing of the Skyba and Boryslav-Pokuttya sub-basins starting from the latest Eocene. These processes reflected the growth of the Carpathian frontal nappes at the final orogen formation stage.

scholarly journals Record of Early Toarcian carbon cycle perturbations in a nearshore environment: the Bascharage section (easternmost Paris Basin)

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 793-804 ◽  
Author(s):  
M. Hermoso ◽  
D. Delsate ◽  
F. Baudin ◽  
L. Le Callonnec ◽  
F. Minoletti ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotope ◽  
Isotopic Signature ◽  
Oxygen Isotopic Composition ◽  
Black Shales ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Carbon Isotope Excursion ◽  
Oxygen Isotopic ◽  
Global Nature

Abstract. In order to understand the significance of the worldwide deposition of black shale facies in the Early Toarcian (~ 183 Ma), considerable attention has been drawn to this Early Jurassic sub-stage over the last 3 decades. The discovery of a pronounced negative carbon isotope excursion (CIE) within the black shales disrupting the generally positive trend in carbon isotopes has stimulated many studies, particularly with a view to establish the local versus global nature of this major geochemical phenomenon. Here we document the sedimentological and chemostratigraphic evolution of a proximal environment in the Luxembourgian sedimentary area. At Bascharage, Lower Toarcian sediments record the isotopic signature of the Early Toarcian oceanic anoxic event (OAE) by a pronounced positive trend that testifies for widespread anoxia. The expression of the carbon isotope perturbation in this section, however, is unusual compared to adjacent NW European sections. A first −7‰ negative CIE, whose onset is recorded at the top of the tenuicostatum zone, can be assigned to the well-documented and potentially global Toarcian carbon isotope excursion (T-CIE) with confidence using the well-constrained ammonite biostratigraphic framework for this section. In this interval, facies contain only a limited amount of carbonate as a result of intense detrital supply in such a proximal and shallow environment. Stratigraphically higher in the section, the serpentinum zone records a subsequent CIE (−6‰) expressed as four negative steps, each being accompanied by positive shifts in the oxygen isotopic composition of carbonate. The preservation state of coccoliths and calcareous dinoflagellates in the second CIE is excellent and comparable to that observed in under- and overlying strata, so this cannot be an artefact of diagenesis. Considering the nature of this record, and the lack of such a pronounced event in the serpentinum zone in coeval sections in Europe, we hypothesise that this second CIE was caused by local factors. The geochemical record of carbonate with a relatively light carbon and relatively heavy oxygen isotopic composition is compatible with the so-called Küspert model, by which a CIE can be explained by an influx of 12C-rich and cold waters due to upwelling bottom water masses.

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