High-resolution clay mineralogy as a proxy for orbital tuning: example of the Hauterivian-Barremian transition in the Betic Cordillera (SE Spain).

11 pages; International audience; The response of clay mineral assemblages to potential orbital forcing is tested in Mesozoic hemipelagic marl- limestone rhythmites of the Río Argos section (Betic Cordillera, Southeastern Spain). Along the section, marls are pervasively enriched in kaolinite and illite, whereas limestones are enriched in smectite-rich illite/smectite mixed-layers, suggesting that marl-limestone alternations are produced by cyclic high-frequency fluctuations of continental runoff. Spectral analyses show that clay mineral assemblages evolve accordingly to precession, obliquity and eccentricity cycles. Durations of ammonite zones are assessed at 535 kyr for the Late Hauterivia…

Carbon cycle and sea-water palaeotemperature evolution at the Middle-Late Jurassic transition, eastern Paris Basin (France).

14 pages; International audience; A very high-resolution carbon and oxygen stable isotope analysis (bulk-carbonate) of a biostratigraphically well-constrained Callovian-Oxfordian series is provided here for the first time. The homogeneity of the clayey series and the weak diagenetic alteration allow the isotopic signal variations to be considered as primary in origin. A prominent and brief negative excursion in the δ13C curve (−2‰), occurring at the start of the Middle Callovian (Jason Zone - Obductum Subzone) and correlated regionally, suggests a possible methane release. The increasing δ13C values thereafter up to the Early Oxfordian, concomitant with a warming episode, highlight the buri…

Étude paléoenvironnementale et paléoclimatique multiproxiesdes bassins fini-carbonifères à permiens du N-E duMassif central.

National audience; Les bassins intracontinentaux fini-carbonifères à permiens d'Autun et de Decize-LaMachine (NE du Massif central) ont fait l'objet d'un travail de thèse s'appuyant sur denombreuses méthodes d'analyse appliquées à haute résolution sur des données deforages et quelques coupes.Les interprétations des résultats sédimentologiques (faciès, diagraphies, sismique), destratigraphie séquentielle, de géochimie et isotopie organique (carbone et azote) et deminéralogie ont permis de reconstituer de la manière la plus précise possible l'évolutiondes environnements sédimentaires de ces bassins dans l'espace et au cours du temps.Il en ressort que les deux bassins étudiés dominés par des d…

Signatures terrigène et volcanique des bassins sédimentaires : implications stratigraphiques et paléoclimatiques

Evidence of aerial volcanic activity during the Valanginian along the northern Tethys margin.

7 pages; International audience; Stratigraphic measurement and sampling on three sections (Vergol, La Charce, and Montclus) through Valanginian deposits from the Vocontian Basin (southeastern France) reveals the occurrence of centimetre thick ochre-coloured layers, which can be correlated from one section to another. At least twelve of these are identified in sediments dated from the Pertransiens to Furcillata ammonite Zones. These horizons appear similar to previously described Oxfordian and Aptian bentonites, also from the Vocontian Basin. Clay-mineralogical and geochemical data are similar in the Valanginian ochre horizons and their enclosing marls except in one of these that shows a cla…

Formation of microbial organic carbonates during the Middle Oxfordian (North East Amu Darya Basin, Uzbekistan): palaeoenvironmental significance and implications for Jurassic anoxic events

International audience; The Late Jurassic was a period of major global carbon cycle perturbations with episodes of anoxia leading to regional accumulation of organic matter in sediments worldwide. The Tubegatan section (SW Gissar Mountains, Uzbekistan) located in the Northern Tethys, shows atypical organic-rich limestone and marl deposits (up to 6% of total organic carbon) marked by pronounced excursions of δ13Ccarb (amplitude of ca. 12‰) and δ13Corg (amplitude of ca. 4‰) recorded during the Middle Oxfordian (Transversarium Zone). A transdisciplinary approach including sedimentology, palynofacies study, mineralogy, organic and inorganic geochemistry was carried out to elucidate the origin o…

Étude paléoenvironnementale et paléoclimatique multi-proxies des bassins fini-carbonifères à permiens du N-E du Massif central.

International audience

Étude de niveaux de cendres volcaniques de la formation d'Igornay du stratotype Autunien du bassin d'Autun (France).

12 pages; National audience

Detailed record of the mid-Oxfordian (Late Jurassic) positive carbon-isotope excursion in two hemipelagic sections (France and Switzerland): A plate tectonic trigger?

14 pages; International audience; The Oxfordian (Late Jurassic) was a time of widespread change in Jurassic marine (carbonate) sedimentation patterns. A marked positive excursion in δ13C is dated as Middle Oxfordian in age. In this study we investigate if changes in carbonate sedimentation coincided with altered carbon cycling and climate. We use C-isotope records as a proxy for the evolution of the carbon cycle and compare δ13C-trends with the evolution of sedimentation in a segment of the opening Tethys seaway. One of the studied sections is located in the Subalpine basin of France (Trescléoux and Oze), the other in the Swiss Jura mountains (Liesberg). Carbon-isotope stratigraphy of carbo…

High-resolution dynamics of Early Jurassic marine extinctions: the case of Pliensbachian–Toarcian ammonites (Cephalopoda).

Abstract: The Pliensbachian–Toarcian interval was marked by major environmental disturbances and by a second-order mass extinction. Here, we reappraise the taxonomic, spatiotemporal and selective dynamics of extinctions over the whole interval, by analysing a high-resolution dataset of 772 ammonite species from NW Tethyan and Arctic domains. On average, 40–65% of ammonite species disappeared during each subchronozone, but higher extinction pulses (reaching 70–90%) prevailed from the Margaritatus to the Dispansum Chronozone. The main extinctions, corresponding to the Gibbosus, Pliensbachian–Toarcian boundary, Semicelatum, Bifrons–Variabilis, and Dispansum events, differed in their dynamics, …

Enregistrement du cycle du carbone au Pliensbachien (Jurassique inférieur) sur la marge sud téthysienne (Amellago, Haut-Atlas Central, Maroc)

International audience; Le Pliensbachien s’inscrit dans un contexte climatique greenhouse au Jurassique, en période de dislocation de la Pangée. De récentes études dans le domaine nord-ouest téthysien ont démontré une certaine variabilité climatique soutenue notamment par des variations isotopiques remarquables dans le cycle du carbone, comparables en amplitude et en durée à d’autres événements du Toarcien (e.g. T-OAE). Malgré la multiplication des travaux le long de la marge nord téthysienne avec la mise en évidence de changements géodynamiques importants, la marge sud n’a jamais été étudiée à haute résolution. Nous proposons, dans un cadre biostratigraphique extrêmement précis (ammonites …

Characterization and correlation of Upper Jurassic (Oxfordian) bentonite deposits in the Paris Basin and the Subalpine Basin, France

Explosive volcanic activity is recorded in the Upper Jurassic of the Paris Basin and the Subalpine Basin of France by the identification of five bentonite horizons. These layers occur in Lower Oxfordian (cordatum ammonite zone) to Middle Oxfordian (plicatilis zone) clays and silty clays deposited in outer platform environments. In the Paris Basin, a thick bentonite (10–15 cm), identified in boreholes and in outcrop, is dominated by dioctahedral smectite (95%) with trace amounts of kaolinite, illite and chlorite. In contrast, five bentonites identified in the Subalpine Basin, where burial diagenesis and fluid circulation were more important, are composed of a mixture of kaolinite and regular…

Evolution climatique au Jurassique inférieur (Sinémurien supérieur) de la zone Nord-Ouest européenne, déduit de la minéralogie des argiles et des isotopes du carbone

International audience

Mineralogical variability of Callovo-Oxfordian clays from the Paris Basin and the Subalpine Basin.

High-resolution clay mineralogical data at the Middle/Upper Jurassic boundary from the French Subalpine Basin, the Jura Mountains and the Paris Basin (ANDRA boreholes) from Callovo-Oxfordian clayey deposits allow spatial and temporal terrigenous flux evolution to be considered over a period of 6 to 7 Myr. Recorded diachronisms of major mineralogical changes and complex clays distribution at the Paris Basin scale result to combined palaeogeographic/eustatic variations and climate input. In the French Subalpine Basin, mineralogical homogeneity confirms the burial diagenesis influence, but other terrigenous supplies must be involved in contrast to the Paris Basin domains. Volcanogenic clays (b…

Le bassin intracontinental fini-carbonifère - permien de Lucenay-lès-Aix (nord-est du Massif Central) : réévaluation sédimentologique et implicationspaléoenvironnementales

International audience; Les bassins sédimentaires intracontinentaux fini-carbonifères à permiens du nord-est du Massif Central (Autun, Aumance, Decize-La Machine et Blanzy-Le Creusot) se mettent en place dans un contexte de transition géodynamique, entre la fin de l'accrétion de la Pangée et le début de sa dislocation, et durant un passage d'un climat de type icehouse (Late Paleozoic Ice Age)à greenhouse. Leur étude est donc cruciale pour mieux comprendre si, et comment, ces grands changements géologiques s'enregistrent au sein de leurs séries sédimentaires. Le bassin houiller de Lucenay-lès-Aix, prolongement sud du bassin de Decize-La Machine, se situe en sub-surface sous la couverture séd…

Diagenesis of clay minerals and K-bentonites in Late Permian/Early Triassic sediments of the Sichuan Basin (Chaotian section, Central China).

10 pages; International audience; Detailed clay mineralogical analyses were carried out on Late Permian/Early Triassic carbonate sediments exposed on the Chaotian section (Sichuan Basin, Central China). The clay assemblages are dominantly composed of illite in platform carbonates and clay seams, and illite-smectite mixed-layers (I/S) in tuff layers (K-bentonites) intercalated in the carbonate succession. Detrital and authigenic volcanogenic clay minerals have been partially replaced through illitisation processes during burial, raising questions about diagenetic effects. The precise determination of I/S occurring in K-bentonites shows that the sediments reached a temperature of about 180 °C…

Caractérisation pétro-géochimique et datation U/Pb du volcanisme contemporain des bassins d’âge fini-Carbonifère à Permien du Nord du Massif Central

International audience; La formation de la chaîne hercynienne, dont l’apogée a lieu au Carbonifère, participe à l’assemblage de la Pangée, qui se démantèlera par la suite à partir du Trias. La limite Carbonifère- Permien correspond donc à une période clé dans l’évolution géodynamique globale, à la transition entre une période orogénique et une période de rifting. Cependant, les reconstitutions paléogéographiques et paléoclimatiques pour cette époque sont assez peu contraintes, notamment du fait du manque de datations radiométriques et de corrélations stratigraphiques fiables entre les différents domaines sédimentaires. Plusieurs bassins sédimentaires fini-carbonifères à permiens sont préser…

Environmental and climatic controls of the clay mineralogy of Albian deposits in the Paris and Vocontian basins (France)

18 pages; International audience; High-resolution clay mineral analyses were performed on lower and middle Albian deposits from the Paris and Vocontian basins in order to specify the weathering conditions that prevailed at that time. The clay mineral assemblages are composed of small proportions of chlorite and vermiculitic clays associated with abundant illite, R0 type illite-smectite mixed-layers (smectite) and kaolinite. Clay minerals originated from the physical alteration and chemical weathering of rocks and soils outcropping on the Variscan massifs bordering the studied areas. In the Paris Basin, the covariation of illite and kaolinite suggests the reworking of these latter minerals f…

U-Pb age constraints on Carboniferous-Permian French continental basins - implications for their depositional history and correlations with European basins

International audience; Late Carboniferous to Permian basins of western Europe (~Gzhelian to Artinskian), developed during thelate stages of the Variscan orogeny in equatorial paleolatitudes. The stratigraphic context of most of thesebasins remains poorly constrained, because mainly based on “continental stages” (e.g., Stephanian, Autunian,Saxonian and Thuringian) that are diachronous. Therefore, correlating these basins together and withinternationally recognized stratigraphic marine stages requires precise radiochronologic ages.To the south of the Paris Basin (France), volcanic ash-fall layers (i.e., tonsteins) are interbedded in theCarboniferous-Permian sedimentary successions of the Aum…

Reconstitution des environnements de dépôtdu Carbonifère supérieur/ Permien inférieurau Sud du bassin de Paris : implicationgéodynamique

National audience; La période Carbonifère-Permien marque un changement drastiquede régime tectonique (fin de l’Orogenèse hercynienne -début d’une phase de rifting). Cette transition s’enregistre dansles bassins sédimentaires contemporains. En Europe de l’Ouest,ces bassins, principalement constitués de sédiments continentauxet de séries volcano-sédimentaires (largement sous-estimées),sont mal contraints sur beaucoup d’aspects (sédimentaire, tectonique,volcanique et corrélations spatio-temporelles). Le cadrechronologique de ces bassins est également mal connu dans lamesure où les principaux âges ont été estimés par palynologie àpartir de faciès floristiques ayant pu coexister dans le temps.Un…

Structure and evolution of the Gissar carbonate platform (Uzbekistan): a record of palaeoenvironmental changes in the Northern Tethys margin during the Middle and Late Jurassic

International audience; The SW-Gissar range (westernmost part of the Tien Shan) consists of a succession of anticlines andsynclines forming a relief between the Amu Darya and Afghan-Tajik basins. Recent fieldwork has beenperformed to study the development and the architecture of a vast Middle-Upper Jurassic carbonate platform. The studied carbonate series crops out along cliffs overlying Lower to Middle Jurassic continental then marine deposits. Carbonate thickness reaches 500 m in the central and southern Gissar and thins up northwards, near the paleo-border of the Amu Darya Basin. The goal of this study was to build a highresolution stratigraphic framework for these deposits, based on che…

Contrôle géodynamique de la sédimentation argileuse du Callovien-Oxfordien moyen dans l'Est du bassin de Paris: influence eustatique et volcanique

The Middle Callovian to Middle Oxfordian clay deposits drilled in the eastern Paris Basin (borehole HTM 102, ANDRA) show a strong mineralogical change occurring in the lowermost Oxfordian (Scarburgense subzone, Mariae zone). Such a change probably results from the initial development of connections between the young Atlantic Ocean and the Paris Basin. A bentonitic layer identified close to the boundary between Lower and Middle Oxfordian and also recognized in the subalpine Basin (South-East of France) at the same age, reflects a volcanic activity probably resulting from an extensional regime located in the North Sea.

Integrated stratigraphy of the Oxfordian global stratotype section and point (GSSP) candidate in the Subalpine Basin (SE France).

44 pages; International audience; An integrated biostratigraphic approach, based on ammonites, calcareous nannofossils, dinoflagellates, combined with sedimentology, carbon-isotope and physical stratigraphy, is proposed for the Subalpine Basin (Thuoux and Saint-Pierre d'Argençon sections). Within the expanded marl deposits of the Terres Noires Fm., the Callovian-Oxfordian boundary is particularly well defined by ammonite taxa from different families (i.e. Cardioceratidae, Oppeliidae, Aspidoceratidae and Perisphinctidae), calcareous nannoplankton (first occurrence of large-sized Stephanolithion bigotii) and dinoflagellate cysts (first occurrence of Wanaea fimbriata). This precise biostratigr…

Minéralogie (fraction argileuse) de la région stratotypique.

5 pages; National audience

Reconstitutions paléoenvironnementales et enregistrement paléoclimatique fini-carbonifère à permien du bassin d’Autun (Nord-Est du Massif Central)

International audience; Les bassins sédimentaires tardi-orogéniques fini-carbonifères à permiens du Nord-Est du Massif Central (bassins d’Autun, de l’Aumance, de Decize-La Machine et de Blanzy-Le Creusot) ont été principalement étudiés pour leur potentiel en ressources carbonées jusque dans les années 1980. Le regain d’intérêt qu’ils suscitent aujourd’hui s’appuie sur des aspects plus fondamentaux afin de mieux comprendre la période charnière qu’est la fin du Paléozoïque. Les séries sédimentaires préservées dans ces bassins continentaux enregistrent en effet le démantèlement des reliefs hercyniens ainsi que l’évolution climatique (transition icehouse-greenhouse) se produisant entre la fin d…

Jacques Thierry (1941-2014).

10 pages; International audience

Orbital chronology of the lower-middle Aptian: palaeoenvironmental implications (Serre Chaitieu section, Vocontian Basin).

4 pages; International audience; A detailed cyclostratigraphic study conducted on several proxies including spectral gamma ray, magnetic susceptibility, clay minerals, and carbonate content suggests that the return to equilibrium in the carbon cycle after the major disturbance linked with Oceanic Anoxic Event 1a occurred in about 2 Myr. The minimum duration of the D. furcata zone is estimated at 0.46 Myr and that of the E. subnodosocostatum zone at 1.45 Myr. Strengthening of the obliquity record in the furcata zone confirms the cooling that characterizes this period.

An orbital floating time scale of the Hauterivian/Barremian GSSP from a magnetic susceptibility signal (Río Argos, Spain).

10 pages; International audience; An orbital floating time scale of the HauterivianeBarremian transition (Early Cretaceous) is proposed using high-resolution magnetic susceptibility measurements. Orbital tuning was performed on the Río Argos section (southeast Spain), the candidate for a Global boundary Stratotype Section and Point (GSSP) for the HauterivianeBarremian transition. Spectral analyses of MS variations, coupled with the frequency ratio method, allow the recognition of precession, obliquity and eccentricity frequency bands. Orbitallytuned magnetic susceptibility provides minimum durations for ammonite biozones. The durations of well-constrained ammonite zones are assessed at 0.78…

Volcanisme explosif aérien au passageCarbonifère-Permien dans les bassinsstéphano-autuniens d’Europe de l’Ouest

National audience; Les bassins stéphano-autuniens d’Europe de l’Ouest, associésà un régime d’extension post-orogénique, ont enregistrésde fréquentes manifestations volcaniques. Ces évènements sonttoutefois encore relativement peu étudiés et datés en particulierdans les bassins sédimentaires bordant le Massif Central. Uninventaire des épisodes volcaniques associés aux retombées decendres est établi, dans l’optique de préciser la nature du volcanisme,la localisation des sources et fournir des âges radiométriquesU-Pb. Ces âges numériques sont fondamentaux pour calibrer lesséries sédimentaires continentales européennes et les corréler auxéquivalents temporels des séries marines d’Asie ou des Et…

Synthesis of recent stratigraphic data on bathonian to oxfordian deposits of the eastern Paris basin

International audience

Carbon and Oxygen Isotope Signals from the Callovian–Oxfordian in French Sedimentary Basins

3 pages; International audience; High-resolution carbon and oxygen isotope data from the Paris Basin and the Subalpine Basin (France) are available in a precise biostratigraphic framework for the Callovian-Oxfordian stages. A biostratigraphically well-constrained δ13C curve, derived from bulk carbonates in the Paris Basin and the Subalpine Basin, is provided in order to document carbon-cycle evolution and to serve as a chemostratigraphic reference for the Callovian-Oxfordian in the Tethyan domain. Sea-temperature reconstructions, using diagenetically screened belemnite and oyster data, reveal major climate perturbations at the Middle-Late Jurassic transition.

Characterization of Upper Jurassic organic-matter-rich carbonates in the Gissar Mountains (Tubiegatan section, Uzbekistan)

International audience; New investigations are currently underway on the Middle-Upper Jurassic carbonates of the Gissar Mountains in the Amu-Darya Basin. Located in the southwest of the Gissar Mountains (SE Uzbekistan), the Tubiegatan section corresponds to 30-meter-thick limestone, overlain by 10-meter-thick dark limestone and marl interval. These dark, “black shale-type deposits” were also recognized in cores from the subsurface of the Amu-Darya Basin. The organic-rich deposits interval is precisely dated to the Luciaeformis and Schilli Subzones (Transversarium Zone, Middle Oxfordian) by ammonites. A transdisciplinary approach including sedimentology, organic matter characterization (Rock…

Astrochronology of the Valanginian-Hauterivian stages (Early Cretaceous): chronological relationships between the Paraná-Etendeka large igneous province and the Weissert and the Faraoni events.

16 pages; International audience; The Geological Time Scale shows large uncertainties on durations and ages of Berriasian to Albian stages (Early Cretaceous), which impact climate and paleoceanographic reconstructions. Here, we provide a new astrochronology of the Hauterivian Stage anchored on (1) recent biostratigraphically well-constrained published radio-isotopic dates, and (2) a previously published astrochronology of the Valanginian Stage. A new duration of the Hauterivian Stage is assessed here at 5.93 ± 0.41 myr. The retained age model, anchored on a latest CA-ID-TIMS U–Pb age from a tuff level in the Hauterivian of the Neuquén Basin (Argentina), dates the base of the Valanginian Sta…

Analyse lithostratigraphique de deux coupes géologiques de puits de mines foncés dans la concession de Chambois (Autunien inférieur du bassin d'Autun, France) .

16 pages; National audience

The stratigraphic record of the Middle-Late Jurassic Transition events on the Peri-Tethyan carbonate platforms

The Middle and Upper Jurassic peri-Tethyan carbonate platforms host some of the largest hydrocarbon reserves in the world. Over the past decades, extensive research has led to the construction of high-resolution stratigraphic frameworks on the northwestern (e.g., Paris Basin) and southern (e.g., Arabian Platform) Tethyan margins. These studies and others show that although being a period of elevated carbonate production, the Callovian-Oxfordian interval is marked by major changes in carbonate production and platform architecture, stratigraphic gaps and condensed series. These changes have commonly been linked to regional to global climatic and tectonic events associated with the so-called M…

The first 40Ar-39Ar date from Oxfordian ammonite-calibrated volcanic layers (bentonites) as a tie-point for the Late Jurassic.

AbstractEight volcanic ash layers, linked to large explosive events caused by subduction-related volcanism from the Vardar Ocean back-arc, interbedded with marine limestones and cherts, have been identified in the Rosso Ammonitico Veronese Formation (northeastern Italy). The thickest ash layer, attributed to the Gregoryceras transversarium ammonite Biozone (Oxfordian Stage), yields a precise and reliable 40Ar–39Ar date of 156.1 ± 0.89 Ma, which is in better agreement with GTS2004 boundaries than with the current GTS2012. This first biostratigraphically well-constrained Oxfordian date is proposed as a new radiometric tie-point to improve the Geologic Time Scale for the Late Jurassic, where a…

Astrochronology of the Valanginian stage from GSSP candidates and hypostratotype.

Valanginian; Astrochronology; Gamma-ray spectrometry; Weissert event; Paraná-Etendeka; International audience; The Valanginian Stage currently displays no radiometric age, which severely hampers palaeoceanographic reconstructions for this time interval. An astrochronology of the Valanginian Stage using the stable 405-kyr eccentricity cycle was performed on biostratigraphically well-calibrated standard sections from the Vocontian Basin (southeastern France). High-resolution gamma-ray spectrometry signals were obtained from orbitally driven marl-limestone alternations from five sections in the basin, and they display the same long-term trends. The spectral analyses present the pervasive recor…

Typologie du zircon des bentonites du Frasnien (carrière du Lion, Belgique) : utilité avant la datation U-Pb.

5 pages; National audience

In situ Laser Induced Breakdown Spectroscopy as a tool to discriminate volcanic rocks and magmatic series, Iceland.

7 pages; International audience; This study evaluates the potentialities of a lab-made pLIBS (portable Laser-Induced Breakdown Spectroscopy) to sort volcanic rocks belonging to various magmatic series. An in-situ chemical analysis of 19 atomic lines, including Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Na, Si, Sr and Ti, from 21 sampled rocks was performed during a field exploration in Iceland. Iceland was chosen both for the various typologies of volcanic rocks and the rugged conditions in the field in order to test the sturdiness of the pLIPS. Elemental compositions were also measured using laboratory ICP-AES measurements on the same samples. Based on these latter results, which can be used to ident…

Un nouveau modèle d'âge pour l'Autunien du bassin d'Autun à partir de datations U-Pb sur des tonsteins

National audience; Le bassin d’Autun, bassin historique français stéphano-permien connu pour ses huiles de schistes et ses fossiles de plantes et vertébrés terrestres, a permis de définir le stratotype Autunien au 19ème siècle, référence pour les « étages » continentaux du Permien d’Europe. Pendant très longtemps, les âges du bassin et du stratotype Autunien ont reposé sur les biozonations établies par les microflores et macroflores, plus récemment à partir des faunes d’insectes, de crustacés et d’amphibiens (Schneider et al., 2020). L’équivalence d’âge en étages marins reposait sur des corrélations complexes à partir d’environnements mixtes marins et continentaux permettant d’utiliser, ent…

Water mass exchange and variations in seawater temperature in the NW Tethys during the Early Jurassic: evidence from neodymium and oxygen isotopes of fish teeth and belemnites.

10 pages; International audience; Oxygen and neodymium isotope analyses performed on biostratigraphically well-dated fish remains recovered from the Hettangian to Toarcian of the Paris Basin were used to reconstruct variations of Early Jurassic seawater temperature and to track oceanographic changes in the NW Tethys. Our results indicate a strong correlation between δ18O trends recorded by fish remains and belemnites, confirming the paleoenvironmental origin of oxygen isotope variations. Interestingly, temperatures recorded by pelagic fishes and nektobenthic belemnites and bottom dwelling fishes are comparable during the Late Pliensbachian sea-level lowstand but gradually differ during the …

Reconstitutions paléoenvironnementales des bassins finicarbonifères à permiens en contexte tardi-orogénique (N-E du Massif central) : implications paléogéographiques et géodynamiques

International audience

Deep basin record evolution of chemical weathering and physical erosion as response to the tectonic uplift of the South African Plateau during the upper Cretaceous

<p>During the upper Cretaceous the South African Plateau underwent an uneven uplift period that coincided with the onset of a long-term climate cooling. This uplift recorded two pulses, an early pulse during the Turonian that affected the eastern margin and a later pulse occurred during the Campanian affecting the western margin (van der Beek et al., 2002; Braun et al., 2014; Baby et al., 2020). We aim here to determine the response of physical erosion and chemical weathering to this tectonic event, that may have played a role in the long-term climate cooling by promoting silicate weathering and associated atmospheric CO<sub>2</sub> drawdown. In thi…

Différentes approches pour la datation U/Pb des tonsteins intercalés dans les séries continentales d’âge fini-carbonifère à permien de Lucenay-lès-Aix (Sud du Bassin de Paris, France)

International audience; D’une manière générale, la présence de niveaux volcaniques (cendres ou laves) intercalés dans les séries sédimentaires présente un avantage non négligeable pour dater la sédimentation de ces séries. Des datations précises peuvent même permettre d’estimer des taux de sédimentation, ou encore de proposer des corrélations à l’échelle de différents bassins.Les séries sédimentaires du Carbonifère-Permien de Lucenay-lès-Aix, étudiées par forage, sont géographiquement situées entre des séries de même âge connues à l’affleurement : Decize-La Machine (au nord), Aumance (à l’ouest) et Autun (à l’est). Ce (ou ces) bassin(s) sont consti- tués de dépôts continentaux dans lesquels…

Pétrographie et environnements sédimentaires.

345 pages; National audience; Cet ouvrage présente les processus sédimentaires, de l’érosion jusqu’à la transformation en roche, en passant par le transport et le dépôt. Il associe les aspects descriptifs des sédiments et roches sédimentaires et leurs processus de formations à travers quelques exemples choisis. Les méthodes d’observations des roches sédimentaires et les techniques avancées de la pétrographie sédimentaire sont décrites (coloration, cathodoluminescence, diffraction X, Microscopie électronique...). De nombreuses photographies de terrain, d’échantillons macroscopiques et de lames minces permettent d’appréhender la discipline à différentes échelles. L'utilisation des différentes…

Astrochronology of the Valanginian Stage from reference sections (Vocontian Basin, France) and palaeoenvironmental implications for the Weissert Event.

12 pages; International audience; High-resolution gamma-ray measurements performed on five biostratigraphically well-dated reference sections from the Vocontian Basin (south-eastern France) are used to develop a new astrochronology of the Valanginian Stage and its subdivisions (i.e. ammonite and calcareous nannofossil zones and subzones). Spectral analyses show a pervasive dominance of 405-kyr eccentricity cycles with the expression of 100-kyr eccentricity, obliquity and precession. Previous rough estimates of Valanginian Stage duration ranged from 3.9 to 6.5 myr but were generally based on less reliable or indirect methods. This study provides a precise duration of 5.08 myr, tuning the ser…

Continental weathering and climatic changes inferred from clay mineralogy and paired carbon isotopes across the early to middle Toarcian in the Paris Basin.

Abstract Lower Toarcian strata (Lower Jurassic) have been extensively studied with a view to understanding the oceanographic, climatic and biological processes that drove the Earth's system into an Oceanic Anoxic Event (OAE). For this time period, the evolution of the European marine seaways is now relatively well constrained owing to multiple geochemical studies, but investigations regarding climatic trends in the continental realm remain sparse. In the present study, we test the clay mineralogy as a continental climate-sensitive proxy in the well-documented Sancerre core (southern Paris Basin). We compare variations in the kaolinite content with p CO 2 fluctuations (derived from paired ca…

Discovery of an Autunian macroflora and lithostratigraphic re-investigation on the western border of the Lodève Permian basin (Mont Sénégra, Hérault, France). Paleoenvironmental implications.

11 pages; International audience; Re-investigation of the western edge of the Lodève basin allows reassignment of one sandstone-conglomerate formation previously identified as "terminal Stephanian" to Early Autunian. The existence of two unconformable (Stephanian and Autunian) megasequences, separated by a sedimentary gap, which had been rejected, is thus re-affirmed. The authors also found, less than 20 m above the basal Autunian conglomerate, a macroflora with taxa characteristic of the famous Tuilières flora from a site, located in the eastern part of the basin near Lodève, in the Grey Autunian group. This confirms that the new Mont Sénégra fossiliferous beds belong to the Lower Autunian…

Hafnium-neodymium isotope evidence for enhanced weathering and tectonic-climate interactions during the Late Cretaceous

<p>Over million-year timescale the carbon cycle evolution is driven by mantle CO<sub>2</sub> degassing (source) and by continental weathering that drawdowns atmospheric CO<sub>2</sub> through silicate weathering reactions (sink). Based on a novel geochemical proxy of chemical weathering intensity (i.e. using measurements of Hf and Nd isotope ratios in clay-size fractions of sediments) and clay mineralogy, we discuss the links between tectonic, continental weathering and climate evolution during the late Cretaceous. That period records the very first step of the last greenhouse to icehouse transition and is concomitant to …

Formation of microbial organic carbonates during the Late Jurassic from the Northern Tethys (Amu Darya Basin, Uzbekistan): implications for Jurassic anoxic events.

23 pages; International audience; The Late Jurassic was a period of major global carbon cycle perturbations with episodes of anoxia leading to regional accumulation of organic matter in sediments worldwide. The Tubiegatan section (SW Gissar Mountains, Uzbekistan) located in the Northern Tethys, shows atypical organic-rich limestone and marl deposits (up to 6% of total organic carbon) marked by pronounced negative excursions of δ13Ccarb (amplitude of ca. 12‰) and δ13Corg (amplitude of ca. 4‰) recorded during the Middle Oxfordian (Transversarium Zone). A transdisciplinary approach including sedimentology, palynofacies characterization, mineralogy, organic and inorganic geochemistry was carrie…

Le stratotype Autunien du bassin d'Autun (Bourgogne-France) : évolution de la stratigraphie et des âges.

18 pages; National audience

Late Cretaceous palaeoenvironments expressed by the clay mineralogy of Cenomanian–Campanian chalks from the east of the Paris Basin

Abstract The clay fraction of Cenomanian–Campanian chalks cored at Poigny and Sainte-Colombe, close to Provins (east-south-east of Paris), includes variable proportions of smectitic minerals, illite and kaolinite. The smectitic sediments (which constitute the background of low-terrigenous supply throughout the stratigraphic interval) resulted mainly from the warm, humid climate and high sea level that prevailed during Late Cretaceous in this area. During the Late Turonian, the smectitic sedimentation was interrupted by significant detrital inputs of illite and kaolinite. This reflected tectonic rejuvenation of landmasses coeval with an explosive volcanism expressed by the occurrence of bent…

Distribution of clay minerals in Early Jurassic Peritethyan seas: palaeoclimatic significance inferred from multiproxy comparisons.

13 pages; International audience; A set of published, unpublished, and new clay mineral data from 60 European and Mediterranean localities allows us to test the reliability of clay minerals as palaeoclimatic proxies for the Pliensbachian–Toarcian period (Early Jurassic) by reconstructing spatial and temporal variations of detrital fluxes at the ammonite biochronozone resolution. In order to discuss their palaeoclimatic meaning, a compilation of low-latitude belemnite δ18O, δ13C, Mg/Ca, and 87Sr/86Sr values is presented for the first time for the whole Pliensbachian– Toarcian period. Once diagenetic and authigenic biases have been identified and ruled out, kaolinite content variation is cons…

Fabric control on strain and rupture of heterogeneous shale samples by using a non-conventional mechanical test

Abstract This work was a part of the preliminary stage of the ANDRA project on a deep-seated research laboratory for the feasibility study of long-term radioactive waste storage in the Callovo–Oxfordian argillites of the Eastern part of the Paris Basin. These rocks are bedded, their density is about 2.4, and they contain an average of 30% carbonates and 25% quartz. Thick (5 mm) sections from cores were put through a non-conventional device called CGI testcell (CGI: Centre de Geologie de l'Ingenieur, i.e. Engineering Geology Centre). The aim of this versatile device is to achieve plane deformation tests under compressive uniaxial loading together with controlled temperature and humidity cond…

Conditions d'hydrolyse au cours du Lutétien-Bartonien dans le Bassin parisien : apport des forages d'Ussy-sur-Marne et du Tillet

L’évolution des conditions climatiques du Paléogène a donné lieu à plusieurs synthèses régionales et globales. Le Bassin parisien, qui est l’un des bassins historiques pour la connaissance des dépôts cénozoïques, a été paradoxalement peu étudié du point de vue des paléoclimats. Cela s’explique par des affleurements dispersés, combinés à une grande variation des environnements de dépôts alternant entre continental et marin ouvert, et un calage stratigraphique complexe. Si les reconstitutions de températures sont accessibles par les données floro-faunistiques et isotopiques (δ18O), l’évolution des conditions hydriques et leurs conséquences sur la production et le transport des sédiments terri…

Evolution climatique au Jurassique inférieur (Sinémuriensupérieur) de la zone Nord-Ouest européenne, déduit de laminéralogie des argiles et des isotopes du carbone

National audience; L’étude des minéraux argileux et des isotopes stables (carbone) du Sinémuriensupérieur du bassin de Cardigan Bay (forage de Mochras, Pays de Galles) et du bassinde Paris (forage de Montcornet, France) permet de mettre en évidence les conditionsenvironnementales et climatiques dominantes à cette période. Dans les deux bassins,situés à des paléolatitudes proches (30 à 35°N), les assemblages de minéraux argileuxcomprennent des chlorites, des illites, des interstratifiés illite-smectite (IS R1), dessmectites et des kaolinites dans des proportions variables. L'influence de la diagenèsed’enfouissement et de l'authigénèse étant négligeable dans les deux forages, lesminéraux argi…

Climatic ups and downs in a disturbed Jurassic world.

4 pages; International audience; The tropical, warm, and equable climate of the Jurassic world is regularly challenged by geoscientists, especially since oxygen isotopes ( 18O) of fossil hardparts have been used to reconstruct the paleotemperature history of seawater. By applying the innovative “SiZer” (significant zero crossings of the derivatives) statistical approach to a newly compiled 18O database for the Jurassic, we demonstrate the occurrence of major and multiscale 18O changes mainly related to climate disturbances. For the first time, two long-term anomalies in 18O are identified during the Toarcian and the Late Jurassic, in conjunction with intensive volcanism in large igneous pro…

Reconstitutions paléoenvironnementales des bassins finicarbonifèresà permiens en contexte tardi-orogénique (N-E duMassif central) : implications paléogéographiques etgéodynamiques

National audience; Les bassins intracontinentaux fini-carbonifères à permiens du nord-est du Massifcentral s'inscrivent dans la dynamique fini-paléozoïque, dans le cadre de l'extensiontardi- orogénique de la chaîne varisque.Les bassins d'Autun et de Decize-La Machine (région de Lucenay-lès-Aix, ensubsurface) ont fait l'objet d'une étude visant à mieux caractériser les environnementsde dépôt sédimentaires, basée principalement sur des données de forages carottés. Lescarottes ont été décrites en termes d'associations de faciès, permettant de déterminerles environnements de dépôt et leur évolution au cours du temps.Dans le bassin d'Autun, les dépôts silicoclastiques grossiers témoignent de dép…

Enregistrement du cycle du carbone à la transition Oxfordien inférieur-moyen dans l'est du Bassin de Paris

Origine des carbonates organiques de la Formation Khodjaipak (Oxfordien moyen) dans le Nord-Est du Bassin d’Amu-Darya : signature paléoenvironnementale et impacts sur le cycle du carbone

Long-term lacustrine paleo-productivity and/or paleo-anoxia trends controlled by eccentricity cycles in the continental Autun Basin (France) at the Carboniferous/Permian boundary

<p>The organic-rich lacustrine beds of the Autun Basin (France) were deposited from the late Gzhelian (late Carboniferous) to the Sakmarian (early Permian), encompassing the Carboniferous-Permian boundary (∼299 Ma). Those deposits reach up to 1500 m thick, and correspond to a tropical, intra-mountainous late-orogenic basin infilling associated with the Variscan orogeny (Marteau, 1983; Schneider et al., 2006). Organic-rich and laminated facies are attributed to distal lacustrine environments which sometimes alternate with silty to sandy rich deltaic depositional environments (Mercuzot et al., 2019). The four successive formations (respectively the Igornay, Muse, …

El Ciclo Ándico de Groeber en la cuenca Neuquina, una revisión y actualización.

A state of the knowledge of the Andean cycle is presented, mainly based on our recent works, butalso on highlights of recent research of many colleagues. This synthesis allowed us to update thegeochronology of its different units. New absolute ages through U-Pb analysis in zircons by differentmethods complement those previously carried out and made possible to accurately limit the ageof these units. We have been able to define the boundary between the Tordillo and Vaca MuertaFormations very precisely between 147 and 146 Ma; the age of the Agrio Formation between 132 and126 Ma, and to present the first absolute ages of the Huitrín Formation. All these data are screenedthrough precise biostra…

Evolution stratigraphique de la plate-forme carbonatée du sud-ouest Gissar (Ouzbékistan) durant le Jurassique moyen et supérieur

Reconstitutions environnementales et climatiques multiproxis des paléo-systèmes lacustres des bassins fini-paléozoïques du NE du Massif central

National audience; Les bassins intracontinentaux fini-carbonifères à permiens du nord-est du Massif central (notamment Autun, Decize-La Machine et Aumance) s'inscrivent dans le cadre de l'extension tardi-orogénique de la chaîne varisque, et de l'acmé de la glaciation fini-paléozoïque. La récente réévaluation de leurs successions sédimentaires à dominance silicoclastique en termes de processus et architectures sédimentaires, stratigraphie séquentielle, géochimie élémentaire et isotopique, permet de préciser l'évolution spatio-temporelle des environnements de dépôt: les sédiments détritiques, incluant une large composante volcanoclastique, se sont déposés majoritairement dans des systèmes lac…

Integrated stratigraphy of the potential candidate Oxfordian GSSP at Thuoux and Saint-Pierre d'Argençon (France).

5 pages; International audience; The Thuoux and Saint-Pierre d'Argençon sections (Subalpine Basin, southeastern France) are proposed as a potential GSSP candidate for the Callovian-Oxfordian boundary. Several aspects of stratigraphy that have recently been applied in the two selected sections are discussed, including ammonite and nannofossil biostratigraphy, palynology, physical stratigraphy, and cyclostratigraphy.

Black shale deposition during Toarcian super-greenhouse driven by sea level

Abstract. One of the most elusive aspects of the Toarcian oceanic anoxic event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the end of the overarching positive trend in the carbon isotopes that characterises the T-OAE. In the present study, we have attempted to establish a sequence stratigraphic framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a…

Climatic fluctuations and seasonality during the Late Jurassic (Oxfordian–Early Kimmeridgian) inferred from delta18O of Paris Basin oyster shells.

10 pages; International audience; Oxygen isotope data from biostratigraphically well-dated oyster shells from the Late Jurassic of the eastern Paris Basin are used to reconstruct the thermal evolution of western Tethyan surface waters during the Early Oxfordian–Early Kimmeridgian interval. Seventy eight oyster shells were carefully screened for potential diagenetic alteration using cathodoluminescence microscopy. Isotope analyses were performed on nonluminescent parts of shells (n=264). Intra-shell δ18O variability was estimated by microsampling along a transect perpendicular to the growth lines of the largest oyster shell. The sinusoidal distribution of the δ18O values along this transect …

Thuoux and Saint-Pierre d’Argençon Sections (Subalpine Basin, Southeastern France): Case Studies of Ammonite Biostratigraphy for the Potential Candidate Callovian–Oxfordian GSSP

The Thuoux and Saint-Pierre d’Argencon sections (Subalpine Basin, southeastern France) display a thick silty–clayey sedimentation with abundant and diversified ammonite faunas, free of detectable hiatuses. The Callovian–Oxfordian boundary is biostratigraphically located between the Lamberti and the Mariae zones or, more precisely, between the Lamberti Subzone (paucicostatum horizon) and the Scarburgense Subzone (thuouxensis horizon). The mixing of Boreal–Sub-Boreal Cardioceratinae and Sub-Mediterranean–Tethyan Hecticoceratinae, Peltoceratinae, and Perisphinctinae in this basin allows reliable worldwide correlations that enhance the choice of the Thuoux and Saint-Pierre d’Argencon sections a…

High-resolution dynamics of Early Jurassic marine extinctions: the case of Pliensbachian–Toarcian ammonites (Cephalopoda)

The Pliensbachian–Toarcian interval was marked by major environmental disturbances and by a second-order mass extinction. Here, we reappraise the taxonomic, spatiotemporal and selective dynamics of extinctions over the whole interval, by analysing a high-resolution dataset of 772 ammonite species from NW Tethyan and Arctic domains. On average, 40–65% of ammonite species disappeared during each subchronozone, but higher extinction pulses (reaching 70–90%) prevailed from the Margaritatus to the Dispansum Chronozone. The main extinctions, corresponding to the Gibbosus, Pliensbachian–Toarcian boundary, Semicelatum, Bifrons–Variabilis, and Dispansum events, differed in their dynamics, suggesting…

Isotopic, carbon and minor element composition of the Sancerre sediments (Jurassic, Paris Basin)

One of the most elusive aspects of the Toarcian oceanic anoxic event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the end of the overarching positive trend in the carbon isotopes that characterises the T-OAE. In the present study, we have attempted to establish a sequence stratigraphic framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a combinati…