436 research outputs found
Systematics and biostratigraphy of the Perisphinctoidea(Ammonoidea) across the Tithonian/Berriasian boundary in South East France
The present thesis documents and revises the systematics and biostratigraphy of the Perisphinctoidea (Ammonoidea) faunas across the Tithonian/Berriasian boundary from three basinal sections (i.e. Charens, Le Chouet and Les Combes) of eastern DrĂŽme (South East France). Emphasis is laid on the specific diagnosis, ontogeny and dimorphism of new and little-studied Himalayitidae Micracanthoceras, Protacanthodiscus, Boughdiriella, Pratumidiscus, Ardesciella, Chapericeras and Praedalmasiceras, Neocomitidae Pseudargentiniceras, Busnardoiceras, Berriasella, Elenaella, Delphinella, Pseudoneocomites and Strambergella as well as the Olcostephanidae Proniceras. New data is provided on the systematic and age of the Neocomitidae Pseudosubplanites, Hegaratella and Retowskiceras. The distribution of these key biochronological genera is plotted next to accurate litho-logs and compared to the calpionellid zonation documented in the three sections. This provides the sound basis for a refined zonal scheme. The base of the upper Tithonian is fixed at the First Appearance Datum (FAD) of M. microcanthum that falls within the upper part of the tintinnid Chitinoidella Zone. The revision of the âMediterranean Durangitesâ supports the rejection of a Durangites spp. Zone as part of the standard zonation for the upper Tithonian, and its replacement by the P. andreaei Zone. The lower boundary of the zone is fixed at the FAD of Protacanthodiscus andreaei that falls within the lower part of the calpionellid C. intermedia Subzone of the Crassicollaria Zone. Both zones are workable at the scale of the Mediterran-Caucasian Subrealm. The Elenaella cularense biohorizon that typifies the base of the Berriasella jacobi Zone auctorum is documented for the first time in South East France and occurs in the uppermost part of the calpionellid C. intermedia Subzone of the Crassicollaria Zone. This occurrence confirms the diachronism between the base of the B. jacobi Zone auctorum and those of the Calpionella Zone previously documented in southern Spain. This diachronism strongly alters the current definition of the Tithonian/Berriasian boundary. Re-examination of the type specimens of Berriasella jacobi supplemented by newly collected material show that this taxon should be transferred to the genus Strambergella. Preliminary integrated data on the stratigraphic distribution of Strambergella jacobi questions its value as an index species for the base of the Berriasian. No major faunal turnover is documented across the Tithonian/Berriasian boundary and the provincialism of Mediterran-Caucasian Perisphinctoidea is much higher than it was previously assumed in the literature. As a result, no ammonite species can be considered as consistent candidate for a primary boundary marker for the base of the Berriasian
A revised ammonoid biostratigraphy for the Aptian of NW Africa:Essaouira-Agadir Basin, Morocco
International audienceA revised ammonoid biostratigraphy is presented for the Aptian of NW Africa, Essaouira-Agadir Basin (EAB), Morocco, based on detailed analysis of 5 key sections. A number of bio-events are documented and 26 genus and 43 species fully documented, forming the largest published Aptian ammonite collection made from NW Africa. The section at Tiskatine is documented as the type section, and 8 zones and subzones are defined, of which 5 are new. This work allows correlation of the Aptian of the EAB to the Standard Mediterranean Ammonite Scale (SMAS). Two main hiatuses are identified at the scale of the basin scale: a major one that includes most of the lower Aptian and the base of the upper Aptian and a second one encompass the top of the upper Aptian and the base of the lower Albian. The ammonite fauna displays a clear Tethyan palaeobiogeographic character affected by a fairly high degree of endemism at the genus and species level. The new genus and species Elsaisabellia tiskatinensis is introduced.(C) 2017 Elsevier Ltd. All rights reserved
Integrated multi-proxy source-to-sink analysis of Late Barremian (Lower Cretaceous) clastic systems in the Essaouira-Agadir Basin
This study investigates the provenance of the continental and marine Late Barremian clastics of the Bouzergoun Formation, exposed in the Essaouira-Agadir Basin (EAB). Thin section petrography, Scanning Electron Microg- raphy, heavy minerals analysis, and detrital zircon dating were conducted and integrated with a large dataset of published Low-Temperature Thermochronology (LTT) studies to reconstruct the associated source-to-sink system (s). The results constrain the source and size of the system, and composition of deposited clastics, and investigate the mechanism for delivery of coarse clastics into the offshore domain, a key target for hydrocarbon exploration.The homogeneity of rock composition fingerprints throughout the basin indicates a common provenance for both the northern and southern studied transects. Hinterland analysis based on LTT data identifies the Western Meseta and Massif Ancien de Marrakech (MAM) regions as the only possible source candidates exhuming during the Late Barremian, confirmed by detrital zircon geochronology. Heavy mineral populations reveal partly recycled sediment including a probable igneous source. Rock fragment populations comprise limestones, sand- stones, and volcanic composition, which correlate with lithologies of the MAM.The integration of all data suggests a best-fit model for the Late Barremian of a source-to-sink system of moderate size (200â300 km long), dominantly sourced from the MAM (western High Atlas). This provided a sand-rich mix of sediment resulting from the erosion of exhuming Triassic continental basins, with associated clays from the weathering of basalts and Triassic/Jurassic mudstones.Late Barremian eustatic sea level fall, together with regional uplift in the hinterland, is interpreted to have resulted in a forced regression that allowed the system to prograde towards the slope margin, offering enhanced potential for sand delivery into the deep offshore domain. Seismic imaging offshore provides tentative inter- pretation of synchronous high reflectivity deepwater channels located in structural lows controlled by diapiric salt movement.The Mesetian domain was likely undergoing denudation at the same time and shedding clastic-rich sediments to the northern part of the EAB, beyond the studied region. Sediment supply from the MAM may be mixed with the Mesetian sands to the northern part of the EAB and tentatively in the offshore Essaouira
La stratigraphie isotopique du Strontium est-elle une méthode fiable pour dater les plates-formes carbonatées à la transition du Barrémien à l'Aptien ? Révision de cas d'études en Téthys occidentale.
Strontium-isotope measurements on Lower Cretaceous marine rocks derive from belemnite material sampled in ammonite-constrained basinal successions. A group of values with a narrow range across the Barremian/Aptian boundary does not allow the separation of the uppermost Barremian (Martelites sarasini ammonite zone) from the lower Aptian pro parte (Deshayesites oglanlensis-D. forbesi ammonite zones). Growing numbers of studies applied Sr-Isotope Stratigraphy (SIS) on Barremian-Aptian shallow-marine sequences (Urgonian facies) in order to solve controversial results obtained by using different shallow-water biological time markers. Based on re-examination of case studies, we conclude that Sr-isotope values can neither be used to prove nor to disprove the location of the putative Barremian/Aptian boundary based on biostratigraphy. Pending more data available, SIS should be used with caution for dating ammonite-free carbonate sediments in the corresponding time interval.Les mesures de l'isotope du Strontium dans des roches carbonatĂ©es marines du CrĂ©tacĂ© infĂ©rieur proviennent de restes de bĂ©lemnites rĂ©coltĂ©s dans des sĂ©ries de bassins datĂ©es directement par ammonites. Autour de la limite BarrĂ©mien/Aptien, une gamme Ă©troite de valeurs du Strontium ne permet pas de distinguer le BarrĂ©mien supĂ©rieur (Zone d'ammonite Ă Martelites sarasini) de l'Aptien infĂ©rieur pro parte (zones d'ammonite Ă Deshayesites oglanlensis et D. forbesi). Pourtant, lâapplication de la Stratigraphie Isotopique du Strontium (SIS) sur des sĂ©quences marines carbonatĂ©es barrĂ©moâaptiennes (Ă faciĂšs urgonien) apparaĂźt dans un nombre croissant dâĂ©tudes, essentiellement afin de rĂ©soudre les datations souvent controversĂ©es des marqueurs biologiques dâenvironnements peu profonds. La rĂ©vision de ces cas d'Ă©tude montre que lâutilisation des valeurs de l'isotope du Strontium nâest pas un outil fiable pour prouver ou rĂ©futer la localisation de la limite BarrĂ©mien/Aptien telle que dĂ©duite par la biostratigraphie. Dans l'attente de donnĂ©es complĂ©mentaires, la SIS doit ĂȘtre utilisĂ©e avec prĂ©caution pour dater des sĂ©ries carbonatĂ©es non datĂ©es directement par ammonites dans l'intervalle de temps concernĂ©
Integrated multi-proxy source-to-sink analysis of Late Barremian (Lower Cretaceous) clastic systems in the Essaouira-Agadir Basin
This study investigates the provenance of the continental and marine Late Barremian clastics of the Bouzergoun Formation, exposed in the Essaouira-Agadir Basin (EAB). Thin section petrography, Scanning Electron Micrography, heavy minerals analysis, and detrital zircon dating were conducted and integrated with a large dataset of published Low-Temperature Thermochronology (LTT) studies to reconstruct the associated source-to-sink system(s). The results constrain the source and size of the system, and composition of deposited clastics, and investigate the mechanism for delivery of coarse clastics into the offshore domain, a key target for hydrocarbon exploration.
The homogeneity of rock composition fingerprints throughout the basin indicates a common provenance for both the northern and southern studied transects. Hinterland analysis based on LTT data identifies the Western Meseta and Massif Ancien de Marrakech (MAM) regions as the only possible source candidates exhuming during the Late Barremian, confirmed by detrital zircon geochronology. Heavy mineral populations reveal partly recycled sediment including a probable igneous source. Rock fragment populations comprise limestones, sandstones, and volcanic composition, which correlate with lithologies of the MAM.
The integration of all data suggests a best-fit model for the Late Barremian of a source-to-sink system of moderate size (200â300 km long), dominantly sourced from the MAM (western High Atlas). This provided a sand-rich mix of sediment resulting from the erosion of exhuming Triassic continental basins, with associated clays from the weathering of basalts and Triassic/Jurassic mudstones.
Late Barremian eustatic sea level fall, together with regional uplift in the hinterland, is interpreted to have resulted in a forced regression that allowed the system to prograde towards the slope margin, offering enhanced potential for sand delivery into the deep offshore domain. Seismic imaging offshore provides tentative interpretation of synchronous high reflectivity deepwater channels located in structural lows controlled by diapiric salt movement.
The Mesetian domain was likely undergoing denudation at the same time and shedding clastic-rich sediments to the northern part of the EAB, beyond the studied region. Sediment supply from the MAM may be mixed with the Mesetian sands to the northern part of the EAB and tentatively in the offshore Essaouira
DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France
We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39â3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18â0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
The systematic affinities between the Lower Cretaceous Ammonoidea Protacanthoplites abichi (Anthula, 1900) and Acanthohoplites aschiltaensis (Anthula, 1900)
This work provides the first revision and illustration of the type material of the ammonite species Parahoplites abichi Anthula [Type species of Protacanthoplites Tovbina] and Parahoplites aschiltaensis Anthula [Type species of Acanthohoplites Sinzow] from the upper Aptian (Lower Cretaceous) of Dagestan, Russia. The close affinities and synonymy between these two species are confirmed, and Acanthohoplites aschiltaensis is here retained as the senior valid name by its long quoting history and its historical use as a zonal index of the upper Aptian. The genus Protacanthoplites should be thus synonymised with Acanthohoplites by priority in the date of publication. Comparison with, and distinction from, closely allied Acanthohoplitidae is provided
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