Hardground, gap and thin black shale: spatial heterogeneity of arrested carbonate sedimentation during the Jenkyns Event (T-OAE) in a Tethyan pelagic basin (Gerecse Mts, Hungary)

2021 ◽  
pp. SP514-2020-266
Author(s):  
Tamás Müller ◽  
Gregory D. Price ◽  
Emanuela Mattioli ◽  
Máté Zs. Leskó ◽  
Ferenc Kristály ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Black Shale ◽  
Carbonate Production ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Carbonate Sedimentation ◽  
Environmental Perturbations ◽  
Carbon Isotope Excursion ◽  
Supplementary Material ◽  
Tethys Ocean

AbstractThe Jenkyns Event or Toarcian Oceanic Anoxic Event (T-OAE) was an episode of severe environmental perturbations reflected in carbon isotope and other geochemical anomalies. Although well studied in the epicontinental basins in NW Europe, its effects are less understood in open marine environments. Here we present new geochemical (carbon isotope, CaCO3, [Mn]) and nannofossil biostratigraphic data from the Tölgyhát and Kisgerecse sections in the Gerecse Hills (Hungary). These sections record pelagic carbonate sedimentation near the margin of the Tethys Ocean. A negative carbon isotope excursion of ∼6‰ is observed in the Tölgyhát section, in a condensed clay and black shale layer where the CaCO3 content drops in association with the Jenkyns Event. At Kisgerecse, bio- and chemostratigraphic data suggest a gap in the lower Toarcian. The presence of an uppermost Pliensbachian hardground, absence of the lowermost Toarcian Tenuicostatum ammonite zone, and the condensed record of the Jenkyns Event at Tölgyhát, together with a condensed Tenuicostatum Zone and the missing negative carbon isotope anomaly at Kisgerecse implies arrested carbonate sedimentation. A calcification crisis and sea-level rise together led to a decrease in carbonate production and terrigenous input, suggesting that volcanogenic CO2-driven global warming may have been their common cause.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5355342

Primary versus carbonate production in the Toarcian, a case study from the Llanbedr borehole (Mochras Farm, Wales)

2021 ◽  
pp. SP514-2021-19
Author(s):  
Alessandro Menini ◽  
Emanuela Mattioli ◽  
Stephen P. Hesselbo ◽  
Micha Ruhl ◽  
Guillaume Suan
Keyword(s):  
Sea Water ◽  
Initial Perturbation ◽  
Carbonate Production ◽  
Nutrient Delivery ◽  
Content Type ◽  
High Productivity ◽  
Oceanic Anoxic Event ◽  
The Core ◽  
C Isotopes ◽  
Supplementary Material

AbstractThe leading hypothesis for the Toarcian oceanic anoxic event (T-OAE; ∼183Ma) and the associated negative C-isotope excursion is the massive release of 12C favouring greenhouse and continental weathering. The nutrient delivery to shallow-basins supported productivity and, because of O2-consumption by organic-matter respiration, anoxia development. However, several works showed that calcareous nannoplankton experienced a decrease during the T-OAE. Nannofossil fluxes measured in the Llanbedr borehole (Mochras Farm; Wales, UK) were the highest prior to the negative C-isotope excursion, along with high amounts of taxa indicative of nutrient-rich environments (Biscutaceae). Such conditions attest to high productivity. Fluxes show the lowest values in the core of the event, along with a size decrease of Schizosphaerella and a peak in Calyculaceae. The recovery of nannofossil fluxes and Schizosphaerella size occurred concomitant with the return of C-isotopes to more positive values. Concomitantly, deep-dwellers (Crepidolithus crassus) dominated, indicating a recovery of the photic-zone productivity. These observations demonstrate that the cascade of environmental responses to the initial perturbation was more complex than previously considered. In spite of elevated nutrient delivery to epicontinental basins in the early Toarcian, carbonate and primary productions of nannoplankton were depressed in the core the T-OAE likely because of prolonged thermohaline sea-water stratification.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5541440

scholarly journals Stenopterygiids from the lower Toarcian of Beaujolais and a chemostratigraphic context for ichthyosaur preservation during the Toarcian Oceanic Anoxic Event

2021 ◽  
pp. SP514-2020-232
Author(s):  
Jeremy E. Martin ◽  
Guillaume Suan ◽  
Baptiste Suchéras-Marx ◽  
Louis Rulleau ◽  
Jan Schlögl ◽  
...  
Keyword(s):  
Content Type ◽  
Oceanic Anoxic Event ◽  
Sulfate Reducing ◽  
Exceptional Preservation ◽  
Environmental Perturbations ◽  
Anoxic Event ◽  
European Distribution ◽  
Supplementary Material ◽  
Carbonate Concretion ◽  
Early Carbonate

AbstractWe report new ichthyosaur material excavated in lower Toarcian levels of the LafargeHolcim Val d'Azergues quarry in Beaujolais, SE France. A partially articulated skull and a smaller, unprepared but likely subcomplete skeleton preserved in a carbonate concretion are identified as stenopterygiids, a family of wide European distribution during the Early Jurassic. These specimens are among the finest preserved Toarcian exemplars known from Europe and in one of them, soft tissue preservation is suspected. Their state of preservation is attributed to the combination of prolonged anoxic conditions near the water-sediment interface and early carbonate cementation resulting from the activity of sulfate-reducing bacteria. We also present carbon and strontium isotope values obtained from the study site that allow detailed temporal comparisons with other Toarcian vertebrate-yielding sites and environmental perturbations associated with the Toarcian Oceanic Anoxic Event (T-OAE). These comparisons suggest that the relatively high abundance and good preservation state of Toarcian vertebrates was favoured by a prolonged period of low bottom water oxygenation and accumulation rates. The environmental conditions that prevailed during the T-OAE were probably responsible for the extensive nature of Lagerstätte-type deposits with exceptional preservation of marine organisms. Whether the T-OAE had a biological impact on marine vertebrates requires a precise chemostratigraphic context of the fossil record spanning the Pliensbachian-Toarcian interval.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5315223

scholarly journals Biotic and stable-isotope characterization of the Toarcian Ocean Anoxic Event through a carbonate-clastic sequence from Somerset, UK

2021 ◽  
pp. SP514-2020-263
Author(s):  
Ian Boomer ◽  
Philip Copestake ◽  
Kevin Page ◽  
John Huxtable ◽  
Tony Loy ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Laminated Sediments ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
The United Kingdom ◽  
Clastic Sediments ◽  
Carbon Isotope Excursion ◽  
Anoxic Event ◽  
Supplementary Material

AbstractThis study focuses on a condensed sequence of alternating carbonate-clastic sediments of the Barrington Member, Beacon Limestone Formation (latest Pliensbachian to early Toarcian) from Somerset (south west England). Abundant ammonites confirm (apart from the absence of the Clevelandicum and Tenuicostatum ammonite subchronozones) the presence of Hawskerense Subchronozone to Fallaciosum-Bingmanni subchronozones. Well-preserved, sometimes diverse assemblages of ostracods, foraminifera, nannofossils and low diversity dinoflagellate assemblages support the chronostratigraphic framework. Stable-isotope analyses demonstrate the presence of a carbon isotope excursion (CIE), relating to the Toarcian Oceanic Anoxic Event (T-OAE), within the early Toarcian. Faunal, geochemical and sedimentological evidence suggest that deposition largely took place in a relatively deep-water (sub-wave base), mid-outer shelf environment under a well-mixed water column. However, reduced benthic diversity, the presence of weakly-laminated sediments and changes in microplankton assemblage composition within the T-OAE indicates dysoxic, but probably never anoxic, bottom-water conditions during this event. The onset of the CIE coincides with extinction in the nannofossils and benthos, including the disappearance of the ostracod suborder Metacopina. Faunal evidence indicates connectivity with the Mediterranean region, not previously recorded for the United Kingdom during the early Toarcian.Supplementary material at https://doi.org/10.25500/edata.bham.00000574

Pacing of late Pliensbachian and early Toarcian carbon cycle perturbations and environmental change in the westernmost Tethys (La Cerradura section, Subbetic Zone of the Betic Cordillera, Spain)

2021 ◽  
pp. SP514-2021-27
Author(s):  
R. L. Silva ◽  
M. Ruhl ◽  
C. Barry ◽  
M. Reolid ◽  
W. Ruebsam
Keyword(s):  
Regional Climate ◽  
Geographical Area ◽  
Betic Cordillera ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Carbon Isotopic ◽  
Detailed Assessment ◽  
Isotope Stratigraphy ◽  
Supplementary Material ◽  
Tethys Ocean

AbstractThe detailed assessment of high-resolution elemental and isotopic geochemical datasets collected from the marl-limestone alternations cropping out at La Cerradura (Subbetic domain of the Betic Cordillera, Spain) and chrono- and chemostratigraphic correlation with the reference Mochras borehole (Cardigan Bay Basin, UK) unveiled valuable new insights to the understanding of late Pliensbachian-early Toarcian palaeoenvironmental dynamics at a key geographical area between the northern European seaway and the Tethys Ocean.This study shows that deposition in the study area took place under dominantly oxic water column conditions, indicated, for example, by the generalised lack of enrichment in organic matter and redox metals typically associated with anoxia and euxinia. Carbon isotope stratigraphy (δ13CTOC) allowed to recognise the spinatum (=emaciatum in the Submediterranean Province), Pliensbachian-Toarcian, and early Toarcian Oceanic Anoxic Event negative carbon isotopic excursions and the late Pliensbachian positive carbon isotopic excursion. It is here suggested that the observed periodic changes in lithology and sedimentary geochemistry occur at orbital frequencies (i.e., long and short eccentricity and, tentatively, precession), hinting at an astronomical control of the local-regional climate and environment during the Pliensbachian and Toarcian in the mid-low latitude South Iberian palaeomargin area.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5473754

scholarly journals The palaeoenvironmental context of Toarcian vertebrate-yielding shales of southern France (Hérault)

2021 ◽  
pp. SP514-2021-16
Author(s):  
Brahimsamba Bomou ◽  
Guillaume Suan ◽  
Jan Schlögl ◽  
Anne-Sabine Grosjean ◽  
Baptiste Suchéras-Marx ◽  
...  
Keyword(s):  
Oxygen Deficiency ◽  
Causal Link ◽  
Large Igneous Province ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Carbon Burial ◽  
Carbon Isotope Excursion ◽  
Supplementary Material ◽  
Marine Vertebrates ◽  
Rock Eval

AbstractThe Early Jurassic was marked by several episodes of rapid climate changes and environmental perturbation. These changes culminated during the Toarcian Oceanic Anoxic Event (T-OAE), an episode of global warming that led to the widespread deposition of organic-rich shales. The Toarcian shales of NW Europe have also yielded exceptionally preserved fossils of marine vertebrates and invertebrates, but the potential links between the occurrences of these exceptionally preserved fossils and the T-OAE remain poorly investigated. Palaeontological excavations realised in Toarcian strata near Lodève (Hérault, S France) have yielded several specimens of marine vertebrates and abundant invertebrate fauna. We have developed a multi-proxy approach (ammonite biostratigraphy, XRD-bulk mineralogy, Rock-Eval pyrolysis, stable isotopes, trace element, phosphorus and mercury contents) to place these findings in a well-defined temporal and palaeoenvironmental context, and hence constrain the factors that led to their remarkable preservation. The Jenkyns Event interval, unambiguously identified at the base of the Toarcian organic-rich shales by a 5 ‰ negative carbon isotope excursion (CIE), records higher mercury fluxes, which suggest a causal link with intense volcanic activity of the Karoo-Ferrar large igneous province. This interval is very condensed and unfossiliferous, and might have been deposited under abnormally low salinity conditions. Our data show that the deposition of the vertebrate-yielding horizons post-dated the T-OAE by several hundreds of kyr, and took place during a prolonged period of widespread oxygen-deficiency and elevated carbon burial. Our results indicate that the unusual richness in vertebrates of the studied site can be explained by a combination of regional factors such as warming-induced, prolonged seafloor anoxia, and more local factors, such as extreme condensation due to reduced dilution by carbonate and detrital input.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5509789

Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event

2021 ◽  
pp. SP514-2021-2
Author(s):  
Weimu Xu ◽  
Johan W. H. Weijers ◽  
Micha Ruhl ◽  
Erdem F. Idiz ◽  
Hugh C. Jenkyns ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sichuan Basin ◽  
Large Scale ◽  
Algal Growth ◽  
Black Shales ◽  
Content Type ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Supplementary Material ◽  
The Sichuan Basin

AbstractThe organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is the first stratigraphically well-constrained lacustrine succession associated with the Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The formation and/or expansion of the Sichuan mega-lake, likely one of the most extensive fresh-water systems to have existed on the planet, is marked by large-scale lacustrine organic productivity and carbon burial during the T-OAE, possibly due to intensified hydrological cycling and nutrient supply. New molecular biomarker and organic petrographical analyses, combined with bulk organic and inorganic geochemical and palynological data, are presented here, providing insight into aquatic productivity, land-plant biodiversity, and terrestrial ecosystem evolution in continental interiors during the T-OAE. We show that lacustrine algal growth during the T-OAE accounted for a significant organic-matter flux to the lakebed in the palaeo-Sichuan mega-lake. Lacustrine water-column stratification during the T-OAE facilitated the formation of dysoxic-anoxic conditions at the lake bottom, favouring organic-matter preservation and carbon sequestration into organic-rich black shales in the Sichuan Basin. We attribute the palaeo-Sichuan mega-lake expansion to enhanced hydrological cycling in a more vigorous monsoonal climate in the hinterland during the T-OAE greenhouse.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5433544

Palaeolatitudinal distribution of the Ediacaran macrobiota

2021 ◽  
pp. jgs2021-030
Author(s):  
Catherine E. Boddy ◽  
Emily G. Mitchell ◽  
Andrew Merdith ◽  
Alexander G. Liu
Keyword(s):  
Taxonomic Composition ◽  
Supplementary Information ◽  
Cambrian Explosion ◽  
Content Type ◽  
Link Type ◽  
Environmental Perturbations ◽  
Significant Difference ◽  
Evolutionary Trajectories ◽  
Cambrian Radiation ◽  
Supplementary Material

Macrofossils of the late Ediacaran Period (c. 579–539 Ma) document diverse, complex multicellular eukaryotes, including early animals, prior to the Cambrian radiation of metazoan phyla. To investigate the relationships between environmental perturbations, biotic responses and early metazoan evolutionary trajectories, it is vital to distinguish between evolutionary and ecological controls on the global distribution of Ediacaran macrofossils. The contributions of temporal, palaeoenvironmental and lithological factors in shaping the observed variations in assemblage taxonomic composition between Ediacaran macrofossil sites are widely discussed, but the role of palaeogeography remains ambiguous. Here we investigate the influence of palaeolatitude on the spatial distribution of Ediacaran macrobiota through the late Ediacaran Period using two leading palaeogeographical reconstructions. We find that overall generic diversity was distributed across all palaeolatitudes. Among specific groups, the distributions of candidate ‘Bilateral’ and Frondomorph taxa exhibit weakly statistically significant and statistically significant differences between low and high palaeolatitudes within our favoured palaeogeographical reconstruction, respectively, whereas Algal, Tubular, Soft-bodied and Biomineralizing taxa show no significant difference. The recognition of statistically significant palaeolatitudinal differences in the distribution of certain morphogroups highlights the importance of considering palaeolatitudinal influences when interrogating trends in Ediacaran taxon distributions.Supplementary material: Supplementary information, data and code are available at https://doi.org/10.6084/m9.figshare.c.5488945Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion

scholarly journals A global event with a regional character: the Early Toarcian Oceanic Anoxic Event in the Pindos Ocean (northern Peloponnese, Greece)

2011 ◽  
Vol 148 (4) ◽  
pp. 619-631 ◽  
Author(s):  
N. KAFOUSIA ◽  
V. KARAKITSIOS ◽  
H. C. JENKYNS ◽  
E. MATTIOLI
Keyword(s):  
Carbon Isotope ◽  
Passive Margin ◽  
Oceanic Anoxic Event ◽  
Northern European ◽  
Carbon Isotope Excursion ◽  
Anoxic Event ◽  
Considerable Controversy ◽  
Regional Character ◽  
Globally Distributed ◽  
Ammonite Zones

AbstractThe Early Toarcian (Early Jurassic, c. 183 Ma) was characterized by an Oceanic Anoxic Event (T-OAE), primarily identified by the presence of globally distributed approximately coeval black organic-rich shales. This event corresponded with relatively high marine temperatures, mass extinction, and both positive and negative carbon-isotope excursions. Because most studies of the T-OAE have taken place in northern European and Tethyan palaeogeographic domains, there is considerable controversy as to the regional or global character of this event. Here, we present the first high-resolution integrated chemostratigraphic (carbonate, organic carbon, δ13Ccarb, δ13Corg) and biostratigraphic (calcareous nannofossil) records from the Kastelli Pelites cropping out in the Pindos Zone, western Greece. During the Mesozoic, the Pindos Zone was a deep-sea ocean-margin basin, which formed in mid-Triassic times along the northeast passive margin of Apulia. In two sections through the Kastelli Pelites, the chemostratigraphic and biostratigraphic (nannofossil) signatures of the most organic-rich facies are identified as correlative with the Lower Toarcian, tenuicostatum/polymorphum–falciferum/serpentinum/levisoni ammonite zones, indicating that these sediments record the T-OAE. Both sections also display the characteristic negative carbon-isotope excursion in organic matter and carbonate. This occurrence reinforces the global significance of the Early Toarcian Oceanic Anoxic Event.

scholarly journals Coring the sedimentary expression of the early Toarcian Oceanic Anoxic Event: new stratigraphic records from the Tethys Ocean

2019 ◽  
Vol 26 ◽  
pp. 17-27
Author(s):  
Elisabetta Erba ◽  
Gabriele Gambacorta ◽  
Stefano Visentin ◽  
Liyenne Cavalheiro ◽  
Dario Reolon ◽  
...  
Keyword(s):  
Black Shale ◽  
Northern Italy ◽  
Global Changes ◽  
Future Scenarios ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Reference Sections ◽  
Anoxic Event ◽  
Tethys Ocean ◽  
Integrated Stratigraphy

Abstract. The Toarcian Oceanic Anoxic Event (T-OAE) interval was cored at Colle di Sogno and Gajum in the Lombardy Basin (Southern Alps, northern Italy). The Sogno and Gajum cores recovered 26.83 and 31.18 stratigraphic metres, respectively, of pelagic sediments consisting of marly limestones, marlstone, marly claystone, and black shale. Drilling at both sites resulted in 100 % recovery of unweathered material. The pelagic succession comprises a relatively expanded black shale interval of 4.98 m in the Sogno core and 15.35 m in the Gajum core, with lower and upper boundaries without evidence of hiatuses. The Sogno and Gajum cores can be considered reference sections for the pelagic lower Toarcian interval of the western Tethys and will provide high-resolution micropaleontological, inorganic and organic geochemical, isotopic multiproxy data. Integrated stratigraphy and cyclostratigraphy are predicted to result in estimates of durations and rates to model the ecosystem resilience to the extreme perturbations of the T-OAE and gain a better understanding of current global changes and help provide better projections of future scenarios.

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