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Emanuela Mattioli - One of the best experts on this subject based on the ideXlab platform.
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base of the Toarcian stage of the lower jurassic defined by the global boundary stratotype section and point gssp at the peniche section portugal
Episodes, 2016Co-Authors: Rogerio Rocha, Emanuela Mattioli, J. J. Gómez, Luís V. Duarte, Bernard Pittet, Maria Cristina Cabral, Serge Elmi, Rene Mouterde, Maria Jose Comasrengifo, Stephen P HesselboAbstract:Dactylioceras (Eodactylites). The Pliensbachian/ Toarcian boundary (PLB/TOA) is contained in a continuous section forming over 450m of carbonate-rich sediments. Tectonics, syn-sedimentary disturbance, metamorphism or significant diagenesis do not significantly affect this area. At the PLB/TOA, no vertical facies changes, stratigraphical gaps or hiatuses have been recorded. The base of the Toarcian Stage is marked in the bed 15e by the first occurrence of D. (E.) simplex, co-occurring with D. (E.) pseudocommune and D. (E.) 460 Articles
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perturbation of the carbon cycle during the late pliensbachian early Toarcian new insight from high resolution carbon isotope records in morocco
Journal of African Earth Sciences, 2016Co-Authors: Stephane Bodin, Francoisnicolas Krencker, Tim Kothe, Rene Hoffmann, Emanuela Mattioli, Ulrich Heimhofer, Lahcen KabiriAbstract:Abstract Preceding the early Toarcian Oceanic Anoxic Event by ∼1 Myr, the Pliensbachian–Toarcian boundary event is in many aspects as severe and disturbing for the environment as its better-studied successor. Both events are associated with rapid and pronounced global warming, major faunal and floral turnover, increased hydrological cycling and dramatic collapses of carbonate production. To better characterize the Pliensbachian–Toarcian boundary event, a high-resolution, paired carbonate and organic matter carbon isotope survey of three sections from the Central High Atlas Basin of Morocco has been undertaken. A pronounced negative shift in the carbonate carbon-isotope record, not paralleled by a similar excursion in the organic carbon, can be linked to the collapse of the neritic carbonate factory in the earliest Toarcian. These results show that, contrary to the Toarcian Oceanic Anoxic Event, a rapid and massive injection of 13 C-depleted carbon into the atmosphere is not responsible for the environmental perturbations observed during the Pliensbachian–Toarcian boundary event. However, input of isotopically non-depleted carbon such as mantle source CO 2 into the atmosphere as a potential cause for the Pliensbachian–Toarcian boundary event cannot be excluded. This would most probably be sourced from an early pulse of the Karoo–Ferrar Large Igneous Province.
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Palaeoecological insights on Toarcian and lower Aalenian calcareous nannofossils from the Lusitanian Basin (Portugal)
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Jorge Ferreira, Emanuela Mattioli, Bernard Pittet, Mário Cachão, Jorge E SpangenbergAbstract:Abstract A comprehensive and detailed account is presented of the calcareous nannofossil evolution across the Toarcian and Early Aalenian from the strategically located Lusitanian Basin in Portugal. The basin connected NW Tethys and Mediterranean water masses during the Toarcian and thus the in situ nannoplankton community responded to this double influence. Biostratigraphic control by ammonites from two well calibrated and continuous sections was compared to an intermediate section, which rendered a complete 286 m of Toarcian and lower Aalenian succession. Quantification of calcareous nannofossils, Factor Analysis, stable carbon and oxygen isotope analysis from brachiopods shells was performed. Temperature, water masses exchanges and primary productivity were highlighted by three extracted factors. Three major ecological events were identified in this work. Throughout the Early Toarcian during the onset of a warming transgressive period with an intensified hydrological cycle where calcareous nannoplankton thrived, NW Tethys waters started flooding the Lusitanian Basin which became dominated by Mediterranean taxa such as M. jansae and Schizosphaerella . Water mixing between NW European and Mediterranean water masses occurred, as recorded by nannofossil assemblages typical of the two provinces. Across the middle and part of the Late Toarcian, as climatic conditions stabilized during the long-term regressive period that had just begun, NW European connections were still effective, waters became more stratified and primary productivity decreased as indicated by the δ 13 C data, the coeval decrease in total nannofossil abundances and increase in diversity. From part of the Late Toarcian, the connection between north and south water masses was diminutive and Mediterranean waters filled and dominated the basin, as inferred from the steady increase in Schizosphaerella and the near disappearance of Crepidolithus crassus . The calcareous nannoplankton increase in abundance and decrease in diversity show that under a humid climate, environmental conditions in such a shallow basin would tend to be more meso-eutrophic.
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calcium isotope evidence for dramatic increase of continental weathering during the Toarcian oceanic anoxic event early jurassic
Earth and Planetary Science Letters, 2015Co-Authors: Jeanmichel Brazier, Emanuela Mattioli, Guillaume Suan, Jeremy E. Martin, Theo Tacail, Laurent Simon, Vincent BalterAbstract:Abstract The early Toarcian was punctuated by pulses of massive carbon injection that are thought to have triggered, through increased greenhouse conditions, elevated continental discharge and nutrient input, marine anoxia, seawater acidification and species extinctions. Nevertheless, the mode and tempo of changes in continental weathering across this interval remains highly debated, leading to considerable uncertainty about the main causes of these perturbations. In this study we present calcium isotope measurements (δ44/40Ca) of well-preserved brachiopods and bulk rock samples from the hemipelagic strata of Pliensbachian–Toarcian age of Peniche in Portugal in order to constrain changes in the calcium cycle and hence changes in continental weathering during the early Toarcian. The data reveal a similar trend as carbon isotope data from the same section and show negative excursions of about 0.5‰ at the Pliensbachian–Toarcian transition (Pl–To) and at the base of the Toarcian Oceanic Anoxic Event (T–OAE) interval. The comparison of δ44/40Ca ratios recorded in brachiopods and bulk rock corrected for variable dolomite contribution indicates that these excursions reflect changes in the global isotopic composition of seawater rather than changes in the dominant mineralogy of calcifying organisms or in hydrological budget of the considered basin. Box modeling results suggest that the Pl–To and T–OAE δ44/40Ca excursions can be explained by a transient 90% decrease of carbonate accumulation due to seawater acidification followed by a 500% increase in continental weathering rates. The sharp increases in continental weathering inferred from the δ44/40Ca ratios seem overall consistent with lower Toarcian sedimentological and biotic records that document rapid crises in carbonate production followed by episodes of increased calcium carbonate burial. Nevertheless, the maximum of carbonate burial recorded by most NW European basinal successions occurs several hundreds of kyrs after that predicted by box modeling results. This mismatch either implies that the European records of carbonate accumulation do not reflect global trends or that the fundamental processes related to the removal of excess alkalinity caused by increased continental weathering are more complex than previously appreciated. Based on the amount of Ca input simulated by box modeling, the injection of tens of thousands of gigatons of carbon with an isotopic composition (δ13C) comprised between − 6 ‰ and − 14 ‰ appears as the most likely causes of the δ13C excursions characterizing these two events. These results indicate that environmental and biotic changes of the Pl–To and T–OAE were mainly caused a cascade of environmental changes triggered by the massive carbon emissions from the Karoo–Ferrar volcanism.
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The middle Toarcian cold snap: Trigger of mass extinction and carbonate factory demise
Global and Planetary Change, 2014Co-Authors: Francoisnicolas Krencker, Stephane Bodin, Rene Hoffmann, Emanuela Mattioli, Lahcen Kabiri, Guillaume Suan, Karl B. Föllmi, Adrian ImmenhauserAbstract:Abstract The Pliensbachian and Toarcian (Early Jurassic) ages are characterised by several, relatively short-lived carbon cycle perturbations, climate change and faunal turnover. The cause(s) of biotic and abiotic disturbances remain unclear but most probably involved increased magmatic activity in the Karoo–Ferrar large igneous province. The Toarcian oceanic anoxic event (T-OAE) might represent the most extreme of these events, and as such, is becoming increasingly well documented worldwide. So far, other critical time intervals of the Pliensbachian–Toarcian have received considerably less attention. Here, the effects of the Middle Toarcian Variabilis event on the neritic–epeiric realm are explored making use of three well-exposed and extended stratigraphic sections in the Central High Atlas, Morocco. The carbon and oxygen isotopic compositions of 112 bulk micrite samples were analysed and placed against 39 data points from carefully screened brachiopod valves in order to differentiate between palaeo-environmental and diagenetic patterns. Additionally, the phosphorus concentrations of 109 micrite samples were determined to evaluate the P-cycling. In all studied sections, an upper middle Toarcian major change from carbonate- to clastics-dominated sedimentation is recorded, pointing to a first-order carbonate production crisis. Our results reveal that these major sedimentological patterns coincide with an increase of oxygen-isotope ratios as well as a decrease of phosphorous accumulation rates. This suggests that the late middle Toarcian carbonate ramp crisis was related to a transient cooling event, potentially triggered by pulsed massive SO 4 exhalation events in the context of the Karoo large igneous province. Short-term cooling was likely amplified by the drawdown of atmospheric CO 2 levels related to the coeval decline of neritic carbonate precipitation and the warm water mass circulation disruption between the Tethys and the continental shelf. The data shown here provide the first evidence for coupled changes in carbon cycling, continental weathering and neritic systems in the aftermath of the T-OAE.
Stephen P Hesselbo - One of the best experts on this subject based on the ideXlab platform.
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magnetostratigraphy of the Toarcian stage lower jurassic of the llanbedr mochras farm borehole wales basis for a global standard and implications for volcanic forcing of palaeoenvironmental change
Journal of the Geological Society, 2018Co-Authors: Weimu Xu, James B. Riding, Conall Mac Niocaill, Micha Ruhl, Hugh C Jenkyns, Stephen P HesselboAbstract:The Lower Jurassic Toarcian Stage ( c. 183–174 Ma) is marked by one of the largest global exogenic carbon-cycle perturbations of the Phanerozoic, which is associated with the early Toarcian Oceanic Anoxic Event (T-OAE; c. 183 Ma). Climatic and environmental change at the T-OAE is reasonably well constrained in the marine realm, with marine anoxic or euxinic conditions developing locally across both hemispheres, at the same time as the T-OAE negative carbon-isotope excursion. However, high-resolution stratigraphic comparison between different palaeo-ocean basins and with the continental realm can be complicated. Palaeomagnetic reversals can provide a precise and accurate stratigraphic correlation tool between marine and continental sedimentary archives, and even between sedimentary and igneous successions. Here, we present a high-resolution magnetostratigraphic record for the Toarcian Stage in the biostratigraphically complete and expanded Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales. This study provides the first geomagnetic polarity reversal scale that is integrated with high-resolution biostratigraphy and carbon-isotope stratigraphy for the entire Toarcian Stage. This stratigraphic framework also provides a new, precise correlation with the basalt lava sequence of the Karoo–Ferrar Large Igneous Province, linking the Pliensbachian–Toarcian boundary and T-OAE climatic and environmental perturbations directly to this episode of major volcanic activity. Supplementary material: Details of the palaeomagnetic data and dip direction are available at https://doi.org/10.6084/m9.figshare.c.4052720
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carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event
Nature Geoscience, 2017Co-Authors: Weimu Xu, Stephen P Hesselbo, James B. Riding, Micha Ruhl, Hugh C Jenkyns, David Selby, David B A Naafs, Johan W H Weijers, Richard D Pancost, Erik TegelaarAbstract:The Early Jurassic Toarcian oceanic anoxic event (~183 Ma) was marked by marine anoxia–euxinia and globally significant organic-matter burial, accompanied by a major global carbon-cycle perturbation probably linked to Karoo–Ferrar volcanism. Although the Toarcian oceanic anoxic event is well studied in the marine realm, accompanying climatic and environmental change on the continents is poorly understood. Here, utilizing radioisotopic, palynological and geochemical data from lacustrine black shales, we demonstrate that a large lake system developed contemporaneously with the Toarcian oceanic anoxic event in the Sichuan Basin, China, probably due to enhanced hydrological cycling under elevated atmospheric pCO 2. We attribute increased lacustrine organic productivity to elevated fluvial nutrient supply, which resulted in the burial of ~460 Gt of organic carbon in the Sichuan Basin alone, creating an important negative feedback in the global exogenic carbon cycle. We suggest that enhanced nutrient delivery to marine and large lacustrine systems was a key component in the global carbon cycle recovery during the Toarcian oceanic anoxic event and acted to shorten the duration of the recovery of global δ13C values.
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base of the Toarcian stage of the lower jurassic defined by the global boundary stratotype section and point gssp at the peniche section portugal
Episodes, 2016Co-Authors: Rogerio Rocha, Emanuela Mattioli, J. J. Gómez, Luís V. Duarte, Bernard Pittet, Maria Cristina Cabral, Serge Elmi, Rene Mouterde, Maria Jose Comasrengifo, Stephen P HesselboAbstract:Dactylioceras (Eodactylites). The Pliensbachian/ Toarcian boundary (PLB/TOA) is contained in a continuous section forming over 450m of carbonate-rich sediments. Tectonics, syn-sedimentary disturbance, metamorphism or significant diagenesis do not significantly affect this area. At the PLB/TOA, no vertical facies changes, stratigraphical gaps or hiatuses have been recorded. The base of the Toarcian Stage is marked in the bed 15e by the first occurrence of D. (E.) simplex, co-occurring with D. (E.) pseudocommune and D. (E.) 460 Articles
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pacing of the Toarcian oceanic anoxic event early jurassic from astronomical correlation of marine sections
Gondwana Research, 2014Co-Authors: Chunju Huang, Stephen P HesselboAbstract:Abstract The Early Toarcian Oceanic Anoxic Event (OAE) in the Early Jurassic Period is associated with a major negative carbon isotope excursion (CIE), mass extinction, marine transgression and global warming. The Toarcian OAE is thought to have been caused by flood basalt magmatism, and may have been a trigger for mass extinction. However, these proposed causes of the Toarcian OAE and associated biotic crisis are not adequately resolved by a precise chronology. The duration of the Toarcian OAE has been estimated to be anywhere from ~ 0.12 to ~ 0.9 Myr, most recently 0.74 to 3.26 Myr from U–Pb dating. The CIE associated with the Toarcian OAE has a similar pattern at numerous localities, and there is evidence that the marine carbon isotope variations recorded astronomical forcing signals. Here we estimate a duration of ~ 620 kyr for the main negative CIE, ~ 860 kyr for the polymorphum zone and > 1.58 Myr for the levisoni zone based on 405-kyr astronomical eccentricity tuning of the marine section at Peniche (Portugal). This 405-kyr tuned series provides a ~ 2.5 Myr continuous high-resolution chronology through the Early Toarcian. There are 6, or possibly 7 short eccentricity cycles in the main CIE interval at Peniche. To confirm this astronomically based estimate, we analyzed three other sections at Yorkshire (UK), Dotternhausen (Germany), and Valdorbia (Italy) from marine carbon isotopic series. These four stratigraphic sections from Early Jurassic western Tethys record the Toarcian OAE with ~ 6 prominent carbon isotope cycles in the CIE that span a 600 ± 100 kyr duration. The Peniche 405-kyr tuned series indicates that the pre- and post-CIE intervals experienced strong precession–eccentricity-forced climate change, whereas the CIE interval is marked by dominant obliquity forcing. These dramatic and abrupt changes in astronomical response in the carbon isotopes point to fundamental shifting in the Early Toarcian paleoclimate system that was directly linked to the global carbon cycle.
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a carbon isotope perturbation at the pliensbachian Toarcian boundary evidence from the lias group ne england
Geological Magazine, 2010Co-Authors: Kate Littler, Stephen P Hesselbo, Hugh C JenkynsAbstract:A perturbation in the carbon-isotope record at the time of the Pliensbachian–Toarcian boundary (~ 184 Ma) in the Early Jurassic is reported, based on new data from Yorkshire, England. Two sharp δ 13 C org negative excursions, each with a magnitude of ~ −2.5 ‰ and reaching minimum values of −28.5 ‰, are recorded in the bulk organic-matter record in sediments of latest Pliensbachian to earliest Toarcian age. A similar pattern of negative carbon-isotope excursions has been observed at the stage boundary in the SW European section at Peniche, Portugal in δ 13 C carbonate , δ 13 C wood and δ 13 C brachiopod records. The isotopic excursion is of interest when considering the genesis and development of the later Toarcian Oceanic Anoxic Event (OAE), as well as the second-order global extinction event that spans the stage boundary. Furthermore, the isotope excursion potentially provides a chemostratigraphic marker for recognition of the stage boundary, which is currently achieved on the basis of different ammonite faunas in the NW European and Tethyan realms.
Rowan C Martindale - One of the best experts on this subject based on the ideXlab platform.
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stratigraphic distribution and paleoecological significance of early jurassic pliensbachian Toarcian lithiotid coral reefal deposits from the central high atlas of morocco
Palaeogeography Palaeoclimatology Palaeoecology, 2019Co-Authors: Hannahmaria R Brame, Rowan C Martindale, Lahcen Kabiri, Nicholas P Ettinger, Irena Debeljak, Raphael Vasseur, Bernard Lathuiliere, Stephane BodinAbstract:Abstract During the Early Jurassic, a group of large, aberrant bivalves called lithiotids proliferated in proximal, shallow marine environments. These lithiotids formed bioherms and extensive biostromes in the western and southern margins of the Tethys Ocean as well as eastern Panthalassa. In the Central High Atlas of Morocco, Pliensbachian and Toarcian (Lower Jurassic) lithiotid and lithiotid-coral reefal deposits occur within carbonate and mixed carbonate/siliciclastic neritic depositional settings. This study describes the stratigraphic distribution, taxonomy, and architecture of these lithiotid-rich deposits. The studied lithiotid and lithiotid-coral deposits from Morocco occur in sheltered, near-shore lagoons along tropical carbonate ramps and platforms. These facies are abundant in upper Pliensbachian strata as well as in the early Toarcian. The persistence and similarity of lithiotid-coral buildups across the stage boundary indicate that these ecosystems were not significantly affected by the Pliensbachian/Toarcian extinction in Morocco (at least, not until the Toarcian Oceanic Anoxic Event). In both the upper Pliensbachian and lower Toarcian, lithiotids (Lithioperna and Cochlearites) are frequently associated with phaceloid corals (Retiophyllia in the Pliensbachian and Phacellophyllia and Archaeosmiliopsis in the Toarcian) and solitary corals (Haimeicyclus and Archaeosmilia) as well as other corals and bivalves (Gervilleioperna, Mytiloperna, Opisoma, and rare megalodontids); however, the spatial distribution of taxa is patchy. The close association of lithiotid bivalves and corals is rarely documented in the literature, and lithiotid-coral reefal deposits are rare. Thus, these Moroccan biostromes and bioherms that record the interaction of corals and lithiotids are of particular scientific importance. Furthermore, multiple generations and successions of lithiotid-coral framestones can be observed in both Pliensbachian and Toarcian strata, which provide insight into the evolution of these communities and their resilience to ecosystem perturbations. Despite the success of lithiotid-coral communities in the Pliensbachian and Toarcian, these ecosystems were decimated by the Toarcian Oceanic Anoxic Event and never recovered.
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response of macrobenthic communities to the Toarcian oceanic anoxic event in northeastern panthalassa ya ha tinda alberta canada
Palaeogeography Palaeoclimatology Palaeoecology, 2017Co-Authors: Rowan C Martindale, Martin AberhanAbstract:Abstract In the Early Jurassic, the late Pliensbachian through early Toarcian interval exhibits significant environmental perturbations and biotic extinctions. This study documents the macrobenthic community during this interval in a region that has previously received comparatively little study: northeastern Panthalassa. The relicts of benthic communities from the Ya Ha Tinda Lagerstatte (Fernie Formation) in Alberta, Canada are primarily composed of bivalves and brachiopods, and exhibit taxonomic and ecological similarities with coeval black shale faunas from Europe. At Ya Ha Tinda, the initiation of the carbon isotope excursion that occurred during the Toarcian Oceanic Anoxic Event (T-OAE) is coincident with major faunal change. The pre-T-OAE community is composed of large epifaunal suspension-feeders (bivalves and brachiopods), lobsters, crinoids, and burrowing organisms represented as trace fossils. The onset of the isotope excursion coincided with a wholesale turnover of bivalve and brachiopod genera as well as with a significant diminution in body size of the community members as a whole. The intra-T-OAE community largely consisted of opportunistic, low-oxygen-tolerant benthic taxa that colonized the seafloor periodically along with some facultatively pseudoplanktonic taxa. Unlike the contemporary deposits in Europe, there is no sign of recovery at Ya Ha Tinda in the middle Toarcian Planulata Ammonite Zone; abundance, richness, and functional diversity of benthic taxa remained extremely low and the size of community members remained small. The primary stress on this system is interpreted to have been oxygen limitation. The minimal ecological effect on the benthic community at the Pliensbachian-Toarcian stage boundary and delayed recovery from the T-OAE of the benthos are in marked contrast to the pelagic record from northeastern Panthalassa. This suggests a decoupling of the benthic and pelagic communities in this region during the Early Jurassic.
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a new early jurassic ca 183 ma fossil lagerstatte from ya ha tinda alberta canada
Geology, 2017Co-Authors: Rowan C Martindale, Theodore R Them, Benjamin C Gill, Selva M Marroquin, Andrew H KnollAbstract:Lagerstatten —deposits of exceptionally preserved fossils—offer vital insights into evolutionary history. To date, only three Konservat-Lagerstatten are known from Early Jurassic marine rocks (Osteno, Posidonia Shale, and Strawberry Bank), all located in Europe. We report a new assemblage of exceptionally preserved fossils from Alberta, Canada, the first marine Konservat-Lagerstatte described from the Jurassic of North America. The Ya Ha Tinda assemblage includes articulated vertebrates (fish, ichthyosaurs), crinoids, crustaceans, brachiopods, abundant mollusks (coleoids with soft tissues, ammonites, gastropods, bivalves), wood, and microfossils. Paired bioand chemostratigraphies show that Lagerstatte deposition occurred during the late Pliensbachian through early Toarcian, capturing the carbon isotope excursion associated with the Toarcian Oceanic Anoxic Event. Therefore, the Panthalassan Ya Ha Tinda biota is coeval with Toarcian Lagerstatten from the Tethys Ocean (Posidonia Shale and Strawberry Bank). Comparisons among these deposits permit new insights into the diversity, ecology, and biogeography of Jurassic marine communities during a time of pronounced biological and environmental change (e.g., expanded subsurface anoxia, warming, and extinctions). They also highlight the possibility that Mesozoic Oceanic Anoxic Events are temporal foci of exceptional preservation.
Christophe Lecuyer - One of the best experts on this subject based on the ideXlab platform.
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drowning of a carbonate platform as a precursor stage of the early Toarcian global anoxic event southern provence sub basin south east france
Sedimentology, 2012Co-Authors: Bernard Pittet, Philippe Leonide, Marc Floquet, Christophe Durlet, Francois Baudin, Christophe LecuyerAbstract:The Toarcian Oceanic Anoxic Event is well-known as coinciding with a carbonate crisis, coupled with organic matter accumulation and perturbation of the carbon cycle expressed by carbon-isotope excursions. In this palaeoenvironmental setting, the present research attempts to better constrain the palaeoenvironmental conditions leading to the drowning of a carbonate platform during Late Pliensbachian to Early Toarcian times. This study is based on the integrated sedimentological, diagenetic and geochemical (stable isotopes and Rock-Eval pyrolysis) analysis of several stratigraphic successions located in the Southern Provence sub-Basin (South-east France). Eodiagenetic ferroan calcite cements below two hardground surfaces at the Pliensbachian–Toarcian transition record episodic eutrophication events. Such events were precursor stages of a global palaeoenvironmental perturbation (i.e. a global carbon cycle perturbation) that led to the demise of the carbonate platform and occurred prior to the Toarcian Oceanic Anoxic Event. Subsequently, the acme of the palaeoenvironmental deterioration that coincided with the Toarcian Oceanic Anoxic Event is recorded by a pronounced negative carbon-isotope excursion (−3‰) followed by a positive one (2·87‰), organic matter preservation and inferred high temperature of surface sea water (ca 25°C) as given by oxygen-isotope values from chondrichthyan tooth enamel. Sedimentological comparisons, as well as chemostratigraphic and biostratigraphical correlations between the Early Toarcian sedimentary series of the Southern Provence and Eastern Dauphinois sub-basins, indicate that tectonic tilting occurred earlier in the Southern Provence sub-Basin; this resulted in the preservation of organic-rich deposits in the first sub-basin and depositional hiatus in the second sub-basin. Thus, local conditions, such as contrasting structural setting, could markedly modify the sedimentary signature of a global climatic event.
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evidence for major environmental perturbation prior to and during the Toarcian early jurassic oceanic anoxic event from the lusitanian basin portugal
Paleoceanography, 2008Co-Authors: Guillaume Suan, Emanuela Mattioli, Bernard Pittet, Christophe Lecuyer, Samuel MailliotAbstract:The timing and causal relationships between the pronounced negative C isotope excursion and paleoenvironmental perturbations associated with the Toarcian oceanic anoxic event (Early Jurassic) remain unclear, particularly because biotic crises and carbonate production decrease appear to have been initiated earlier than the main C isotope anomaly. Here we present a new quantification of Late Pliensbachian–Early Toarcian calcareous nannofossils abundance and size from the Peniche reference section (Portugal) together with O and C isotope records of well-preserved brachiopod shells from the same section. The brachiopod shell δ13C curve parallels that of bulk carbonate and records two pronounced negative isotopic excursions, close to the Pliensbachian-Toarcian boundary (∼−2‰) and during the Toarcian oceanic anoxic event (∼−3.5‰). Our results indicate that both C isotope negative excursions were characteristic of benthic and shallow-water environments, suggesting that these two carbon cycle perturbations affected all epioceanic reservoirs. Coeval shifts toward lower values of brachiopod oxygen isotope compositions and closely correlated northward migrations of Mediterranean ammonite fauna suggest that both events coincided with major rises in seawater temperatures, probably as a result of increased CO2 levels and enhanced greenhouse conditions. CO2-induced changes in seawater chemistry likely affected the calcification potential of both neritic and pelagic systems, as evidenced by synchronous drops of platform-derived carbonate accumulation and drastic reductions in size (>3 μm) of the main pelagic carbonate producer Schizosphaerella. We suggest that the Early Toarcian paleoenvironmental crisis occurred in two distinct episodes that were most likely related to two successive phases of intense volcanic degassing in the Karoo-Ferrar province.
Hugh C Jenkyns - One of the best experts on this subject based on the ideXlab platform.
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magnetostratigraphy of the Toarcian stage lower jurassic of the llanbedr mochras farm borehole wales basis for a global standard and implications for volcanic forcing of palaeoenvironmental change
Journal of the Geological Society, 2018Co-Authors: Weimu Xu, James B. Riding, Conall Mac Niocaill, Micha Ruhl, Hugh C Jenkyns, Stephen P HesselboAbstract:The Lower Jurassic Toarcian Stage ( c. 183–174 Ma) is marked by one of the largest global exogenic carbon-cycle perturbations of the Phanerozoic, which is associated with the early Toarcian Oceanic Anoxic Event (T-OAE; c. 183 Ma). Climatic and environmental change at the T-OAE is reasonably well constrained in the marine realm, with marine anoxic or euxinic conditions developing locally across both hemispheres, at the same time as the T-OAE negative carbon-isotope excursion. However, high-resolution stratigraphic comparison between different palaeo-ocean basins and with the continental realm can be complicated. Palaeomagnetic reversals can provide a precise and accurate stratigraphic correlation tool between marine and continental sedimentary archives, and even between sedimentary and igneous successions. Here, we present a high-resolution magnetostratigraphic record for the Toarcian Stage in the biostratigraphically complete and expanded Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales. This study provides the first geomagnetic polarity reversal scale that is integrated with high-resolution biostratigraphy and carbon-isotope stratigraphy for the entire Toarcian Stage. This stratigraphic framework also provides a new, precise correlation with the basalt lava sequence of the Karoo–Ferrar Large Igneous Province, linking the Pliensbachian–Toarcian boundary and T-OAE climatic and environmental perturbations directly to this episode of major volcanic activity. Supplementary material: Details of the palaeomagnetic data and dip direction are available at https://doi.org/10.6084/m9.figshare.c.4052720
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evolution of the Toarcian early jurassic carbon cycle and global climatic controls on local sedimentary processes cardigan bay basin uk
Earth and Planetary Science Letters, 2018Co-Authors: Weimu Xu, James B. Riding, Micha Ruhl, Hugh C Jenkyns, Melanie J Leng, Jennifer Huggett, Daniel Minisini, Clemens V Ullmann, Johan W H WeijersAbstract:Abstract The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data ( δ 13 C ), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major- and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage, (2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin, (3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian (tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition.
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carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event
Nature Geoscience, 2017Co-Authors: Weimu Xu, Stephen P Hesselbo, James B. Riding, Micha Ruhl, Hugh C Jenkyns, David Selby, David B A Naafs, Johan W H Weijers, Richard D Pancost, Erik TegelaarAbstract:The Early Jurassic Toarcian oceanic anoxic event (~183 Ma) was marked by marine anoxia–euxinia and globally significant organic-matter burial, accompanied by a major global carbon-cycle perturbation probably linked to Karoo–Ferrar volcanism. Although the Toarcian oceanic anoxic event is well studied in the marine realm, accompanying climatic and environmental change on the continents is poorly understood. Here, utilizing radioisotopic, palynological and geochemical data from lacustrine black shales, we demonstrate that a large lake system developed contemporaneously with the Toarcian oceanic anoxic event in the Sichuan Basin, China, probably due to enhanced hydrological cycling under elevated atmospheric pCO 2. We attribute increased lacustrine organic productivity to elevated fluvial nutrient supply, which resulted in the burial of ~460 Gt of organic carbon in the Sichuan Basin alone, creating an important negative feedback in the global exogenic carbon cycle. We suggest that enhanced nutrient delivery to marine and large lacustrine systems was a key component in the global carbon cycle recovery during the Toarcian oceanic anoxic event and acted to shorten the duration of the recovery of global δ13C values.
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a carbon isotope perturbation at the pliensbachian Toarcian boundary evidence from the lias group ne england
Geological Magazine, 2010Co-Authors: Kate Littler, Stephen P Hesselbo, Hugh C JenkynsAbstract:A perturbation in the carbon-isotope record at the time of the Pliensbachian–Toarcian boundary (~ 184 Ma) in the Early Jurassic is reported, based on new data from Yorkshire, England. Two sharp δ 13 C org negative excursions, each with a magnitude of ~ −2.5 ‰ and reaching minimum values of −28.5 ‰, are recorded in the bulk organic-matter record in sediments of latest Pliensbachian to earliest Toarcian age. A similar pattern of negative carbon-isotope excursions has been observed at the stage boundary in the SW European section at Peniche, Portugal in δ 13 C carbonate , δ 13 C wood and δ 13 C brachiopod records. The isotopic excursion is of interest when considering the genesis and development of the later Toarcian Oceanic Anoxic Event (OAE), as well as the second-order global extinction event that spans the stage boundary. Furthermore, the isotope excursion potentially provides a chemostratigraphic marker for recognition of the stage boundary, which is currently achieved on the basis of different ammonite faunas in the NW European and Tethyan realms.
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A carbon-isotope perturbation at the Pliensbachian–Toarcian boundary: evidence from the Lias Group, NE England
Geological Magazine, 2009Co-Authors: Kate Littler, Stephen P Hesselbo, Hugh C JenkynsAbstract:A perturbation in the carbon-isotope record at the time of the Pliensbachian–Toarcian boundary (~ 184 Ma) in the Early Jurassic is reported, based on new data from Yorkshire, England. Two sharp δ 13 C org negative excursions, each with a magnitude of ~ −2.5 ‰ and reaching minimum values of −28.5 ‰, are recorded in the bulk organic-matter record in sediments of latest Pliensbachian to earliest Toarcian age. A similar pattern of negative carbon-isotope excursions has been observed at the stage boundary in the SW European section at Peniche, Portugal in δ 13 C carbonate , δ 13 C wood and δ 13 C brachiopod records. The isotopic excursion is of interest when considering the genesis and development of the later Toarcian Oceanic Anoxic Event (OAE), as well as the second-order global extinction event that spans the stage boundary. Furthermore, the isotope excursion potentially provides a chemostratigraphic marker for recognition of the stage boundary, which is currently achieved on the basis of different ammonite faunas in the NW European and Tethyan realms.
