173 research outputs found
A Lithocodium and Bacinella signature of a late Hauterivian, local microbial event: the Urgonian limestone in South-East France
Sediment binding crusts of Lithocodium aggregatum and associated Bacinella irregularis abound in a shallow water limestone layer, in SouthâEast France. The sudden appearance of these crusts denotes a local, conspicuous change in an otherwise balanced, open marine depositional environment. Based on regional correlation, the layer belongs to the Lower Hauterivian, Ligatus Zone, directly dated by an assemblage of orbitolinid foraminifera, and indirectly by a specimen of ammonite. It is older than the Faraoni oceanic anoxic event (OAE), (latest Hauterivian, Angulicostata auct. Zone), and presumably not linked with a global climate change. Two facies are recognized: (1) Lithocodium bindstone, with Bacinella, other microencrusters, and fluorescent automicrite of microbial origin; (2) fl oatstones containing numerous fragments of Lithocodium and accompanying biota. Coarse rhombohedral dolomite is locally present. Two modern analogues of microbial mediation are put forward to explain the Lithocodium event: (a) Lagoa Vermelha, in Brazil, along with anoxic, marginal marine conditions; (b) Highborne Cay, in the Bahamas, along with oxic, open marine conditions. A stack of four Upper Hauterivian parasequences is described: Parasequence 1 ends with oolitic deposits; the somewhat deeper water Parasequence 2 occurs only in the south-eastern part of the study area, towards the Subalpine depocenter; Parasequence 3 matches the layer with Lithocodium and Bacinella, of variable thickness (0.8 m â 11 m), resulting from syn-sedimentary tectonic activity in the area of the Vuache fault system which is a major feature; Parasequence 4 corresponds with the resumption of the normal, Urgonian carbonate factory
Commentaires sur "Estimating the impact of early diagenesis on isotope records in shallow-marine carbonates: A case study from the Urgonian platform in western Swiss Jura" par A. Godet et al. [Palaeogeography Palaeoclimatology Palaeoecology 454 (2016) 125-138]
A recent paper by Godet et al. on Urgonian carbonates from the Swiss Jura concluded that diagenesis may hinder chemostratigraphic correlations of deep- to shallow-water facies. Although we agree with this conclusion we question their arguments and interpretations. These authors correctly identified diagenesis as the key factor, but we question the timing of events in their paragenetic sequence. In particular, they reported the leaching of originally calcitic oolitic cortices but failed to discuss this puzzling feature properly. In addition, the backbone of their argument is the stratigraphic correlation of a specific sequence from three dominantly shallow-water sections together with a basinal reference section. However, a reliable alternative biostratigraphic framework shows that this attempt of long-distance correlation might be erroneous.Une publication récente de Godet et al. sur les carbonates urgoniens du Jura suisse concluait que la diagenÚse pouvait compromettre les corrélations chimiostratigraphiques des faciÚs distaux vers les proximaux. Bien que nous soyons d'accord avec cette conclusion, nous nous interrogeons sur les arguments des auteurs et leurs interprétations. Ils ont bien identifié la diagénÚse comme étant le facteur déterminant, mais nous mettons en doute la chronologie des événements de leur séquence paragénétique. Ils ont notamment signalé la dissolution de cortex d'ooïdes originellement calcitiques mais n'ont pas abordé sous un bon angle cet élément étonnant. De plus, leur argumentaire s'appuie sur la corrélation stratigraphique d'une séquence spécifique identifiée dans trois coupes aux faciÚs essentiellement peu profonds avec une coupe de bassin utilisée comme référence. Toutefois, un autre cadre biostratigraphique plus robuste que celui utilisé par Godet et al. suggÚre que leur tentative de corrélations sur de longues distances est erronée
The Cretaceous of the Swiss Jura Mountains: an improved lithostratigraphic scheme
In the course of the HARMOS project of the Swiss Geological Survey, the lithostratigraphic subdivisions of the Cretaceous sedimentary rocks outcropping in the Swiss Jura Mountains were revisited. New formation names are proposed where only inadequate facies terms existed so far. As in some cases outcrop conditions in the Swiss Jura do not allow for logging complete sections to characterise the formations, type localities in neighbouring France have been chosen. The following formations (Fm.) are defined to describe the Cretaceous lithological units (from bottom to top): Goldberg Fm., Pierre-ChĂątel Fm., Vions Fm., Chambotte Fm., Vuache Fm., Grand Essert Fm., Gorges de lâOrbe Fm., Vallorbe Fm., Perte du RhĂŽne Fm., Narlay Fm. Dating of the formations is based on biostratigraphy (ammonites, echinids, dasycladalean algae, foraminifera, calpionellids, dinocysts, nannofossils). The fossils indicate Berriasian through to Coniacian ages. The lithostratigraphic units describe the general evolution from a shallow, peritidal platform to deeper-water shelf environments, then the installation of a carbonate platform, and finally the drowning of this platform followed by the predominance of pelagic conditions. The common lateral and vertical changes in facies and sedimentation rates as well as numerous hiatuses within the formations testify to a complex interplay of tectonics, climate, and sea level that controlled the Swiss Jura realm during the Cretaceous
Successful Treatment of Anterior Tracheal Necrosis after Total Thyroidectomy Using Vacuum-Assisted Closure Therapy
Total thyroidectomy involving the adjacent structures of the trachea can cause tracheal damage such as early tracheal necrosis. The authors describe the first case of anterior tracheal necrosis following total thyroidectomy treated using vacuum-assisted closure device. After two weeks of VACââtherapy, there was no evidence of ongoing infection and the trachea was partially closed around a tracheotomy cannula, removed after 3 months. The use of a VACââtherapy to reduce and close the tracheal rent and to create a rapid granulation tissue over tracheal structure appeared as a good opportunity after anterior tracheal necrosis
Barremian ammonite fauna from L'Estellon section (Baronnies, SE France): preli-minary biostratigraphic results
The study of the ammonite fauna in the L'Estellon section (DrÎme department, SE France) allows us to date episodes with gravitational deposition in this area of the "Vo-contian Trough". They span most of the Barremian Stage, from the Nicklesi Zone up to the Giraudi Zone. We did not identify any Bedoulian redeposits, the "Bedoulian ridge" auct. being latest Barremian in age.L'étude de l'ammonitofaune de la coupe de L'Estellon (département de la DrÎme, France) permet de dater les épisodes de la sédimentation gravitaire dans ce secteur de la "Fosse vocontienne". Ils couvrent pratiquement l'ensemble du Barrémien, depuis la Zone à Nicklesi jusqu'à celle à Giraudi. Nous n'y avons pas caractérisé de resédimentation bédoulienne, la "barre bédoulienne" auct. Cor-respondant au Barrémien terminal
3e journée d\u27étude du Comité français Unimarc
La 3e Journée d\u27étude du Comité français Unimarc présente les nouveautés des formats pour les notices bibliographiques et d\u27autorité, publiés en 2008 et 2009 respectivement, et aborde les mutations de l\u27environnement normatif dans lequel s\u27inscrit Unimarc.
La journée se divise en quatre temps : L\u27activité du CfU, les évolutions d\u27Unimarc, Unimarc dans le contexte normatif international, le catalogage du livre ancien dans Unimarc.
Les notices des interventions, en français, proposent à la fois l\u27enregistrement audio et le diaporama accompagnant la communication
The Extraordinary Mid-infrared Spectrum of the Blue Compact Dwarf Galaxy SBS0335-052
SBS0335-052 is a blue compact dwarf galaxy (BCD) with one of the lowest known
metallicities, ZZ_{\sun}/41, making it a local example of how
primordial starburst galaxies and their precursors might appear. A spectrum
obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope
clearly shows silicate absorption features, emission lines of [SIV] and
[NeIII], and puts strong upper limits on the PAH emission features. The
observed low resolution spectrum (R~90) extends from 5.3 to 35microns and peaks
at ~28microns. The spectrum is compared to IRS observations of the prototypical
starburst nucleus NGC7714. SBS0335-052 is quite unlike normal starburst
galaxies, which show strong PAH bands, low ionization emission lines, and a
continuum peak near 80microns. The continuum difference for m
implies a substantial reduction in the mass of cold dust. If the spectrum of
this very low metallicity galaxy is representative of star forming galaxies at
higher redshifts, it may be difficult to distinguish them from AGNs which also
show relatively featureless flat spectra in the mid-IR.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 4 pages, 2 figure
La Formation du Grand Essert (Jura franco-suisse; Valanginien supérieur p.p. à Hauterivien supérieur basal)
Le terme de Formation du Grand Essert a Ă©tĂ© proposĂ© en 2016 pour remplacer ceux de « Marnes dâHauterive » auct. et « Pierre jaune de NeuchĂątel » auct. attribuĂ©s Ă lâ« Hauterivien » auct. dans le Jura franco-suisse. Lâobjet de cette note est, dans un premier temps, de dĂ©crire et dâinterprĂ©ter la lithologie de la coupe-type reprĂ©sentative de cette nouvelle formation, dâune Ă©paisseur de 112,5 m, relevĂ©e dans la localitĂ©-type du Grand Essert le long de la route D991, entre Confort et ChĂ©sery, sur la rive gauche de la vallĂ©e de la Valserine (Jura mĂ©ridional, Ain, France). La Formation du Grand Essert comprend, Ă la base, le Membre dâHauterive composĂ© de 52 m de marnes dans lesquelles apparaissent des bancs et des nodules calcaires contenant souvent des grains de quartz et de glauconie. Les faciĂšs indiquent un milieu calme en dessous de la limite de lâaction des vagues de beau temps, avec lâapport pĂ©riodique de matĂ©riel bioclastique allochtone. Au-dessus, le Membre de NeuchĂątel dâune Ă©paisseur de 60,5 m se compose de calcaires bioclastiques localement quartzo-glauconieux. Au sein de ce membre sâintercale un horizon marneux dâorigine marine, les Marnes des Uttins. Les bancs calcaires montrent des structures sĂ©dimentaires entrecroisĂ©es qui suggĂšrent la prĂ©sence de courants tidaux. Dans un deuxiĂšme temps, les auteurs proposent des corrĂ©lations basĂ©es sur la biostratigraphie (ammonites et dinokystes) et lâanalyse sĂ©quentielle, entre la coupe-type et dâautres coupes et forages publiĂ©s dans le Jura franco-suisse. La corrĂ©lation avec une coupe du Bassin vocontien (Haut Vergons) permet de discuter jusquâĂ quel point lâenregistrement sĂ©dimentaire de la Formation du Grand Essert Ă©tait contrĂŽlĂ© par des fluctuations du niveau marin. Finalement, les ammonites et dinokystes permettent de bien dater la Formation du Grand Essert qui sâĂ©tend du Valanginien supĂ©rieur pro parte jusquâĂ la base de lâHauterivien supĂ©rieur. Le Membre dâHauterive commence dans la zone Ă Peregrinus. Lâintervalle Peregrinus-Furcillata est partout fortement condensĂ© (comme la partie sommitale de la Formation du Vuache sous-jacente dans le Jura neuchĂątelois) tandis que les sĂ©diments de la zone Ă Radiatus sont bien reprĂ©sentĂ©s. La limite entre le Membre dâHauterive et le Membre de NeuchĂątel se situe dans la zone Ă Loryi. Le Membre de NeuchĂątel occupe la partie supĂ©rieure de la zone Ă Loryi et toute la zone Ă Nodosoplicatum. La limite Nodosoplicatum / Sayni se trouve au sein de la partie sommitale du Membre de NeuchĂątel. La base de la Formation des Gorges de lâOrbe sus-jacente est datĂ©e de la zone Ă Sayni
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