Homéomorphies et canalisations évolutives: Le rôle de l'ontogenèse.Quelques exemples pris chez les Ammonites du Jurassique

Resume La signification paleobiologique des homeomorphies et des processus evolutifs homologues qui les ont induits, sont analyses a partir de 7 exemples choisis parmi les ammonites du Jurassique. Les formes etudiees sont soit largement repandues soit endemiques dans les mers de plates-formes de l'Europe moyenne ou regnaient au cours du Jurassique des conditions ecologiques bien differentes de celles des regions mediterraneennes-plus oceaniques-ou vecurent la plupart des ancetres de ces formes. Il est montre que les tendances evolutives repetitives observees peuvent souvent etre comprises comme les resultats de strategies evolutives impliquant, au sein de chaque groupe analyse, l'adoption p…

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…

Settlement down again patterns of a carbonated platform following up a sedimentary crisis : example of the middle-late Jurassic boundary in the southeastern part of the Paris Basin

Abstract Following a sedimentary crisis which begins in the late Lower Callovian and spans all the early Oxfordian, the settlement down patterns of a platform with carbonated sedimentation are analysed in a southeastern area of the Paris Basin (fig. 1). Ten lithostratigraphic units (reefal formations, associated bioclastic facies and marly distal lateral facies ; fig. 2) are defined (fig. 3). New ammonite and brachiopod faunas, collected in situ, allow to date accurately the sedimentary units with a precision matching an ammonite subzone of the standard bio-chronostratigraphic scale (fig. 4) of the middle-late Oxfordian (from the Parandieri Subzone, at the base of the Transversarium Zone, t…

Variabilité architecturale du test chez le genre Collyrites (Echinoidea, Disasteroidea) au Jurassique moyen.

Resume L’evolution de l’architecture du test et en particulier celle du « complexe systeme apical–periprocte » chez le genre Collyrites (Echinoidea, Disasteroidea) est analysee pour les especes des etages Bathonien et Callovien (Jurassique moyen) provenant de plusieurs localites du bassin de Paris. Le systeme apical du genre Collyrites est subdivise en deux parties : (i) une partie anterieure, denommee trivium, composee de quatre plaques genitales (1, 2, 3, 4) et de trois plaques ocellaires (II ; III ; IV) ; (ii) une partie posterieure, denommee bivium, composee de deux plaques ocellaires (I, V) et d’une plaque genitale (5), sans gonopore et non fonctionnelle, entourant le periprocte. Le pa…

The origin and timing of multiphase cementation in carbonates: Impact of regional scale geodynamic events on the Middle Jurassic Limestones diagenesis (Paris Basin, France)

The Middle Jurassic carbonates of the eastern part of the Paris Basin display surprisingly low values of porosity and permeability (Φ < 15‰ and K < 0.5 mD). The main objective of this study is to determine the causes and timing of the cementation that altered the petrophysical properties of these carbonates thereby destroying their potential as oil reservoirs; a fate that did not befall their equivalents in deeper, central parts of the Paris Basin. Using petrographic and geochemical analyses (stable O and C isotopes, Sr isotopes, major elements), we identify six calcitic spar stages, two dolomite stages, and several episodes of fracturing and stylolitization ordered in paragenetic sequence.…

Variations in Jurassic echinoid biodiversity at ammonite zone levels: Stratigraphical and palaeoecological significance

After a relatively low but stable phase of taxonomic diversity during the Lias (Lower Jurassic), echinoids diversity strongly increases from Aalenian (Dogger-Middle Jurassic) to Kimmeridgian (Malm-Late Jurassic) and a conspicuous crisis takes place in Tithonian times, before the end of the Jurassic. During these major phases, minor decreases in diversity correspond with regressions (sea-level falls), mainly in the Middle Bathonian (Middle Jurassic). From the Aalenian to Callovian, the average duration of irregular echinoid species is about 3.8 m.y. whereas it is about 5.5 m.y. for the regular ones; the later value corresponding to the average duration of a Jurassic. From Callovian to Tithon…

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…

Pierre Rat (1921-2010).

Henri Tintant à la recherche du temps de la Terre : un demi-siècle de réflexions stratigraphiques appliquées au système Jurassique.

8 pages; National audience

Le genre Nucleolites (Echinoidea, Cassiduloidea) du Bajocien à l'Oxfordien dans le Bassin de Paris : apport des données architecturales à la systématique et à la phylogénie

International audience; La classification des espèces du genre Nucleolites de l'intervalle Bajocien­Oxfordien du bassin de Paris est révisée. Une vision classique, jusqu'alors utilisée par les auteurs et fondée principalement sur la morphologie générale du test, est tout d'abord présentée. Elle est ensuite modifiée à partir de nouvelles données architecturales se référant au modèle extraxial­axial concernant la structure de l'appareil apical ainsi que la présence de plaques supplémentaires et de plaques caténales. Ces données architecturales sont considérées comme prioritaire vis-à-vis de la morphologie générale du test. Cette approche conduit à une nouvelle vision de la classification des …

La notion d'espace morphologique,outil d'analyse de la morphodiversité des organismes

Resume L'analyse de la morphologie des organismes est une base essentielle dans la mise en evidence des changementsevolutifs. La morphologie est maintenant frequemment abordee par des procedures quantitatives, dont certaines permettent de construire de veritables cartes morphologiques ou les dissemblances et ressemblances de formes entre les organismes sont directement lisibles et quantifiees. La notion d'espace morphologique, illustree ici par differents exemples, se revele particulierement feconde pour comprendre comment la diversite morphologique d'un ensemble d'organismes (stades ontogenetiques, populations, clades) se structure, et par consequent pour interpreter en termes evolutifs ou…

Les Mollusques Céphalopodes dans les Annales de Paléontologie

Resume Un peu plus de 40 articles traitent de cephalopodes dans les 91 volumes des «  Annales  » parus en un siecle. La plupart sont des monographies contribuant a une avancee significative de nos connaissances sur la biodiversite de ces mollusques qui tiennent une place importante dans le registre fossile. Les ammonites jurassiques et cretacees sont bien illustrees ; celles du Paleozoique et du Trias, les Orthoceratoidea, Nautiloidea et Dibranchiaux le sont plus rarement. Tout au long des volumes, des hypotheses concernant les applications paleontologiques et geologiques sont avancees par les auteurs : systematique, phylogenie, biostratigraphie, paleoecologie, paleobiogeographie. Toutefois…

Biogéographie des ammonites jurassiques et reconstitution palinspastique de la Téthys

Resume— La distribution geographique des ammonites jurassiques est regie par deux causes fondamentales : l’ecologie et l’histoire evolutive (evenements vicariants). L’analyse conjointe de ces deux facteurs permet de reconnaitre : d’une part des taxons dont la distribution est essentiellement controlee par des contraintes ecologiques (Phylloce-ratinae et Lytoceratinae, lies a des environnements oceaniques profonds; Clydoniceratidae et Proplanulitinae lies a des plates-formes assez superficielles); d’autre part des taxons dont l’histoire evolutive est associee a des evenements vicariants (Ammonitina liasiques euro-boreales et Cardioceratidae-Kosmoceratidae boreaux du Jurassique moyen).Les exe…

Variations morphologiques de l'oursin irrégulier disasteroidea Collyrites (Pygomalus) Analis (Agassiz): Implications taxonomiques, paléoécologiques et évolutives

Resume Les variations morphologiques de la forme generale et de l'anatomie du test de Collyrites (Pygomalus) analis ( Agassiz ) sont abordees pour 17 populations du Bathonien superieur du Bassin de Paris (Nievre, Saone-et-Loire et Sarthe), parfaitement calees dans l'echelle chronostratigraphique standard des ammonites jurassiques (zones a Retrocostatum et Discus). La description de la morphologie s'appuie sur l'analyse biometrique de 8 variablest et 8 indices traites par des methodes statistiques. Les effectifs eleves et l'amplitude de taille des individus permettent un suivi des modifications morphologiques au cours de l'ontogenese. Dans chaque population, la forme du test presente une var…

Les ammonites du Bathonien-Callovien du Boulonnais : biodiversité, biostratigraphie et biogéographie

Resume La faune d'ammonites des series affleurantes du Bathonien-Callovien du Boulonnais (Nord de la France) est decrite en detail pour la premiere fois. Au Bathonien moyen et superieur les specimens sont rares, reduits a quelques Perisphinctidae ( Procerites ) et Clydoniceratidae ( Clydoniceras , Delecticeras ). L'abondance et la diversite des associations augmentent au Callovien ou elles ont un net cachet subboreal marque par la presence des Gowericeratinae ( Kepplerites , Sigaloceras ), Kosmoceratinae ( Kosmoceras ) et Proplanulitinae ( Proplanulites ), associes a des taxons boreaux, Cadoceratinae ( Cadoceras ) et Cardioceratidae ( Quenstedtoceras ) et submediterraneens, Pseudoperisphinc…

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…

Caractérisation et interprétation de cycles géochimiques sur la plate-forme bourguignonne (France) au Bajocien-Bathonien

Resume Un forage (Ravieres, Yonne; Sud-Est du Bassin de Paris, France), dans les sediments de plate-forme carbonatee du Bajocien-Bathonien, permet une analyse sedimentologique et sequentielle couplee a des analyses geochimiques (Sr, Mg, Fe, Mn et δ18O). Grâce au signal du strontium, des cycles geochimiques correlables aux cycles sedimentaires de transgression-regression de facies sont mis en evidence. Cependant, l'interpretation des cycles geochimiques necessite un changement de referentiel par rapport aux travaux jusqu'ici realises en domaine de bassin.

Marqueurs d'une structuration extensive jurassique en arrière de la marge nord-téthysienne (monts du Mâconnais, Bourgogne, France)

Structural analysis of extensional faults in the Mâconnais Hills shows that low-intensity extensional phenomena occurred back from the passive margin of the Ligurian Tethys, the axis of which lay some 400 km southeast of the study area in Mid-Jurassic times. Storm-induced rip current directions and coral lens positions suggest that the palaeotopography was maintained by early faulting.

Séries condensées et indice de préservation d'unité biostratigraphique: exemple de l'ennoiement de la plate-forme nord-bourguignonne (France) au Callovo-Oxfordien

Abstract Several depositional environments associated with Callovian-Oxfordian condensed series of the southeast of the Paris Basin are defined. As sedimentation rates were very low, variations in palaeodepth, which were synchronous at regional scale, were taken to directly reflect fluctuations in accommodation potential. Within a major trend toward increased accommodation potential, five sharp upturns and one sharp downturn are detected. A biostratigraphic unit preservation index is denned to quantify and discuss the low preservation of sediments in these condensed series. This index is seen to vary with accommodation potential.

Tornquistes helveticus (Jeannet, 1951) (Ammonitina, Pachyceratidae) de l'Oxfordien inférieur du Jura Suisse; nom. nov. pro. “Herznachites” helveticusJeannet, 1951

Resume Le genre Herznachites Jeannet , 1951 est soumis a une revision. Il ne fait pas partie de la famille des Oppeliidae comme le pensait Jeannet. L'analyse morphologique montre que le seul echantillon du genre, a la disposition de Jeannet, doit etre rattache au genre Tornquistes de la famille des Pachyceratidae. L'holotype de Tornquistes helveticus ( Jeannet ) est un macroconque; un nouveau specimen, trouve depuis la description originale, est une forme microconque de la meme espece. Ce dernier collecte in situ , permet de fixer l'âge de l'espece de la sous-zone a Cordatum, de la zone a Cordatum, de l'Oxfordien inferieur.

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.

Phanerozoic geological evolution of Northern and Central Africa: An overview.

61 pages; International audience; The principal paleogeographic characteristics of North and Central Africa during the Paleozoic were the permanency of large exposed lands over central Africa, surrounded by northerly and northwesterly dipping pediplanes episodically flooded by epicontinental seas related to the Paleotethys Ocean. The intra-continental Congo–Zaire Basin was also a long-lived feature, as well as the Somali Basin from Late Carboniferous times, in conjunction with the development of the Karoo basins of southern Africa. This configuration, in combination with eustatic sea-level fluctuations, had a strong influence on facies distributions. Significant transgressions occurred duri…

World distribution of middle Jurassic ammonites (Upper Aalenian to Middle Bathonian): relationships between biodiversity and palaeogeography

Abstract The break up of the Pangea takes place in the Jurassic; the palaeoceanographic consequences are the opening of seaways, particularly at the place of the future Atlantic and Indian oceanic areas. During the Toarcian, and from the late Aalenian to the middle Bathonian, the so-called “Hispanic corridor” (or “Atlantic seaway”) exists between the “western Tethys” and the “American Pacific border”, through the “Caribbean Tethys”. Two additional seaways which play as by-passes of the Pangea are proposed, one along the northern border of Laurasia (Boreal sea), and a second along the southern border of Gondwana (South Pacific Sea); however, if these two last could be effectively used for fa…

Chronostratigraphy and geochronology: A proposed realignment.

We propose a realignment of the terms geochronology and chronostratigraphy that brings them broadly into line with current use, while simultaneously resolving the debate over whether the Geological Time Scale should have a “single” or “dual” hierarchy of units: Both parallel sets of units are retained, although there remains the option to adopt either a single (i.e., geochronological) or a dual hierarchy in particular studies, as considered appropriate. Thus, geochronology expresses the timing or age of events (depositional, diagenetic, biotic, climatic, tectonic, magmatic) in Earth’s history (e.g., Hirnantian glaciation, Famennian-Frasnian mass extinction). Geochronology can also qualify r…

Tithonia oxfordiana, a new irregular echinoid associated with Jurassic seep deposits in south-east France

The infaunal irregular echinoid, Tithonia oxfordiana, is described and compared to congeneric species previously described from Upper Jurassic and lowermost Cretaceous strata. This new species characterizes a monospecific echinoid assemblage, which occurs only in some places where deep-marine middle Oxfordian deposits are exposed in south-east France. Specimens are closely packed and clearly concentrated at the top of small carbonate chemoherms; a close connection of the echinoids with the emission of reduced chemicals, which were oxidized by chemoautotrophic bacteria, is highly probable. Based on general test shape and plate architecture, T. oxfordiana probably was a deposit feeder on chem…

Le Dogger supérieur calcaire de la Côte dijonnaise et nuitonne et des plateaux du Chatillonnais - Stratigraphie, sédimentologie, paléoenvironnements, pierres de construction et d'ornement d'hier et d'aujourd'hui.

22 pages; National audience

Stage boundaries, global stratigraphy, and the time scale: towards a simplification

International audience; This paper examines four facets of stratigraphic terminology and usage considered faulty and proposes corrective measures. The four perfectible areas are: (1) The system of dual nomenclature requiring discrete terminologies for the superpositional and temporal aspects of rock units. (2) The premise that a GSSP establishes the base of a stage as being coincident with the top of the preceding stage rather than simply defining it as the boundary between stages. (3) The rejection of supplementary (auxiliary) sections that would broaden the knowledge of a GSSP and enlarge the area in which it is easily usable. (4) The current dual system of nomenclature for Precambrian an…

Sous-espèces géographiques et/ou contrôle environnemental de la variabilité morphologique chez “Thomasites” gongilensis (Woods, 1911), (Ammonitina, Acanthocerataceae, Vascoceratinae) du Turonien inférieur de la Haute Bénoué (Nigéria)

Resume L'ammonite “Thomasites” gongilensis ( Woods , 1911) est une espece classique des calcaires du Turonien inferieur de la Haute-Benoue (Nigeria). Dans tous les gisements, elle caracterise un banc isochrone a l'echelle de cette partie du bassin; au sein de la faune ammonitique, “Thomasites” constitue toujours l'element dominant avec une representativite de 80 a 98%. L'amplitude de la variabilite morphologique de la coquille de cette ammonite est tres importante et bien connue dans le celebre gisement d'Ashaka ou elle a ete decrite comme une espece representee par plusieurs “formes”, dont les extremes sont gongilense et compressum, avec des intermediaires telles que tectiforme, crassicost…

Echelles biostratigraphiques du Meso-Cenozoique, ouest-europeen; synthese, applications et perspectives--The Meso-Cenozoic biostratigraphic framework of Western Europe; synthesis, applications and outstanding problems

Modalites sequentielles de la transgression aaleno-bajocienne sur le sud-est du Bassin parisien

Abstract Sedimentologic, biostratigraphic and diagenetic studies made on Middle Aalenian to Lowermost Bathonian deposits in 25 outcrops of the Burgundy High (southeastern Paris basin) lead to a sequence stratigraphy subdivision of the early Dogger record into 7 third order depositional sequences. These sequences make up a second-order transgressive phase whose lower limit is a tectonically enhanced unconformity (the Mid-Cimmerian unconformity), associated with a large scale uplift during the Upper Toarcian and the Lower Aalenian. In the largest outcrops, where the geometry of sedimentary bodies is observable at the hectometre to kilometre scale, the combination of diagenetic, biostratigraph…

Notice explicative de la carte géologique de la France (1/50000) - feuille Saint-André-de-Valborgne (911).

Orléans : BRGM Editions, 138 pages ISBN : 978-2-7159-1911-2; Notice explicative de la carte géologique par Brouder P., Alabouvette B. & Faure M., 2009.

Modalités évolutives du genre bullatimorphites (Ammonitina) au Bathonien-Callovien (Jurassique moyen) en Europe occidentale

Abstract The genus Bullatimorphites, (macroconchs Bullatimorphites, Kheraiceras; microconchs Bomburites, Schwandorfia, Spbaeroptycbius, Treptoceras), is characterized by an ontogenesis with three morphologic phases: serpenticone, sphaerocone and ellipticone. Within the successive populations, the relative development of these morphologies allows the defined species to be placed in an evolutive and stratigraphic lineage. The history of the genus comprises five steps: 1) emergence (Early Middle Bathonian), 2) first gradual evolution (Middle-Upper Bathonian), 3) first morphological diversification (Uppermost Bathonian), 4) second gradual evolution, 5) second morphological diversification and e…

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.

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…