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Modeling multiple crack propagation in the material point method by J-integral methods accounting for other cracks intersecting the J contour
No full textInternational audienceNumerical crack propagation modeling of multiple, explicit cracks requires methods that can resolve interacting, and potentially intersecting, cracks as well as methods to calculate crack-tip parameters with sufficient accuracy for predicting when and where cracks propagate. These problems were solved using the material point method (MPM). First, the MPM method for modeling a single explicit crack known as CRAMP method was extended to account for two interacting explicit cracks by tracking four instead of original two crack velocity fields needed to resolve one explicit crack. Second, crack propagation and propagation direction were found using crack-tip integral with partitioning into mode I and mode II stress intensity factors. calculations, however, must be augmented whenever other cracks intersect the contour for a propagating crack. If the intersecting crack’s tip is inside the contour, the contour must be adapted to avoid that tip. A robust calculation algorithm with intersecting-crack corrections is provided. Several examples show the new corrections are accurate. Selected crack propagation examples show the new methods have sufficient accuracy for interacting crack propagation calculations without any need to remesh or highly refine crack-tip regions
World Flora Online: a global resource for botanical information
No full textInternational audienceWorld Flora Online (worldfloronline.org, WFO) is a freely available, authoritative global overview of the diversity of plant species. This international initiative, established in 2012 under the Global Strategy for Plant Conservation, is backed by 55 partner institutions, and a growing community of hundreds of taxonomists working in Taxonomic Expert Networks curating the global consensus classification. A key product is the WFO Plant List – the only community-supported global list of plant names - which is published as 6-monthly, citable versions (wfoplantlist.org; doi.org/10.5281/zenodo.14538251). Digital tools, such as APIs enabling machine access to the static/live data, and name matching tools to link data, facilitate use of the WFO Plant List by third parties in their data management system
A preliminary non-Destructive Multi-Method Approach to the Archaeometric Study of Serpentinite Vases in Bronze Age Crete, 2650-1450 BCE
No full textInternational audienceMinoan material culture (Bronze Age Crete, 3100-1150 BCE) is characterized by an important production of stone vases showcasing advanced craftsmanship and regional variation in production techniques and stylistic preferences. A particularly wide variety of raw materials was used, with serpentinite, chloritite, and limestone being among the predominant types of stone employed in vase production. The geological characterisation of Minoan stone vases thus provides unique insights into the strategies of material selection and use in Aegean Bronze Age societies. The project involves the non-destructive archaeometric analysis of different Minoan objects produced in serpentinite. Geochemical data were obtained using portable X-ray fluorescence (pXRF), while crystallography was examined through handheld portable Raman spectroscopy (HH-Raman). Since serpentinisation is typically associated with the formation of ferromagnetic minerals, a portable magnetic susceptibility meter (pMS) has also been used to measure the magnetic response level. The analysis of archaeological material has then been compared to a field sampling of the different known Cretan serpentinite outcrops, which have been characterized by solution-ICP-MS for whole-rock geochemistry and pXRF calibration, XRD for semi-quantitative mineralogy, and µ-Raman of polished samples for in situ mineralogical characterization.To date, the project has completed its pilot phase with the study of a protopalatial artisans’s Quarter at Malia (Quartier Mu, 1800-1700 BCE). While precise provenance determination remains challenging at this stage, the results offer new perspectives on the factors influencing material selection, including local availability and physical properties. Preliminary results from the analysis of Quartier Mu at Malia have suggested the use of a more talc-rich serpentinite rock than that previously defined by the researchers, and our initial conclusions suggest that these talc-rich rocks were selected for their greater tenderness. Furthermore, our study highlighted specific artisanal production techniques depending on lithology.This presentation finally seeks to foster discussions on the non-destructive characterization of serpentinite, which is known to be poor in distinctive characteristics between outcrops, and on the complexities of establishing artifact provenance in the absence of documented quarries
Systematic and Biogeography, Ontology and Vicariance
No full textInternational audienceIn this chapter, our aim is to emphasize that evolutionary theory should be considered an integrative science and elucidate its ontology through a semantic approach. This exploration aligns with Nelson & Platnick’s perspective on Comparative Biology, as presented in their book. Evolutionary theory stands out as the unifying theory in biology through precise formalization and modelling. We will anchor our discourse in a particular branch of Philosophy of Sciences i.e., the semantics conception of scientific theories and we will illustrate how the graphic representation of a rooted tree i.e., a hierarchy, plays a pivotal role in this formalization. This mathematical depiction is essential in enabling the characterization of various facets of the theory and fostering interdisciplinary connections. Notably, it integrates methods, resources, and technologies within a unified model, providing a holistic perspective of evolutionary theory, including systematics and biogeography
Multiple Mantle Melting and Metasomatism during the Initial Stages of Subduction: Multi-Geochemical and Os-Isotope Evidence from Well-Preserved Kızıldağ Ophiolite, southern Türkiye
No full textInternational audienceThe processes governing ophiolite formation and evolution remain incompletely understood. The Kızıldağ ophiolite, a well-preserved remnant of the Neo-Tethyan oceanic lithosphere in the Anatolian region, southern Türkiye, offers critical insights into subduction-related processes and geodynamics. This study presents new element data for mineral and whole-rock samples, combined with Re-Os isotopic compositions of mantle peridotites and associated crustal rocks and extrusives. Petrographic observations identify two distinct groups of peridotites: (1) those with very low modal clinopyroxene, interpreted as highly depleted harzburgites and preserving primary mineral assemblages, and (2) depleted harzburgites containing secondary clinopyroxene with elevated trace element contents, inferred to have crystallized from percolating melts and thus reflecting metasomatic modification. Spinel and orthopyroxene compositions indicate 17–25% degrees of partial melting, with evidence for melting in both garnet and spinel stability fields. However, mineral and whole-rock compositions also record subsequent cryptic and modal metasomatism. Crustal rocks and extrusives exhibit geochemical signatures transitional between fore-arc basalts and boninites, consistent with subduction initiation settings. Variations in Os isotope ratios (187Os/188Os) in crustal rocks further reveal melt–rock interactions and the incorporation of radiogenic Os from subducted oceanic crust. The integration of petrographic, geochemical, and isotopic data supports a four-stage tectonic model for subduction initiation and mantle wedge evolution, consistent with global models proposed for supra-subduction zone (SSZ) ophiolites, particularly those of the Tethyan domain. These findings provide new constraints on mantle melting, metasomatism, and subduction initiation processes and contribute to a broader understanding of SSZ mantle evolution in both regional and global contexts
Surveying slave quarters within Martinique’s colonialplantations: ongoing research into the historicalmemory of a postcolonial territory
No full textInternational audienceHistorical maps and archaeological surveys are combined to study colonial slavery, Cartography informs on slave quarter architectureand spatial segregation, Aerial imagery demonstrates the legacy of these quarters in the present-day landscape, Slave quarters’ detailed locationon the map facilitates its archaeological survey
Rapport de campagne DIADEM
No full textEn Janvier-Février 2023, la campagne DIADEM (Deep Investigations At DEMerara, ou DIve At DEMerara) s’est déroulée à bord du Navire Océanographique Pourquoi Pas ?, au Nord-Est du plateau sous-marin de Demerara, au large de la Guyane française et du Suriname. Cette campagne océanographique a utilisé une panoplie d’outils de mesures, de prélèvement et d’observation en fond de mer : le Nautile, sous-marin d’observation et de prélèvements, l’AUV (Autonomous Underwater Vehicle) IdeFx opérant des mesures géophysiques près du fond (cartographie bathymétrique, sondeur de sédiment, courants et paramètres physiques des eaux de fond), un mouillage pour mesurer les variations temporelles des courants et des paramètres physiques des eaux de fond, des carottiers pour prélever des sédiments meubles (Calypso pour une carotte d’une trentaine de mètres de long, Fantacore pour des carottes métriques préservant l’interface entre l’eau de fond et le sédiment), et une drague pour prélever des roches indurées.Cette campagne était multidisciplinaire et multisites. Les deux principaux objectifs étaient de:-Comprendre l’interaction entre les courants de fond, la morphologie du fond de la mer, et la sédimentation récente. La partie du plateau de Demerara étudiée pour cette thématique est balayée par la North Atlantic Deep Water (NADW), qui s’y écoule vers le Sud-Est. Cet écoulement est marqué dans la morphologie par des dépressions allongées (nommées queues de comètes), initiées sur des reliefs (nommés têtes de comètes). Le champ de comètes « Tangara » a été étudié en détail grâce à 6 plongées AUV, 4 plongées Nautile, (incluant des carottages d’interface au moyen de push-cores) et un mouillage. Sept autres sites ont été carottés autour de Tangara, afin d’obtenir une archive sédimentaire la plus complète possible dans les zones contouritiques présentant les taux de sédimentation maxima.Les observations faites pendant la campagne montrent que les têtes de comètes sont constituées de carbonates lités, souvent fortement basculés, et ont confirmé le rôle des courants de fond dans la sédimentation et morphologie sous-marine du secteur.-Cartographier et échantillonner les roches pre- et syn-rift affleurant sur la bordure du plateau. Cela concernait deux horsts ou blocs basculés (Plateau Bastille et Ride Buteur) sur la bordure Est du plateau (marge divergente), et différents sites (Ride des 60°, Canyon Poubelle) sur la bordure Nord du plateau (marge transformante), avec un socle formé de coulées basaltiques héritées du rifting Jurassique, recouvert par des séries sédimentaires associées au rift Crétacé. Au total, 6 plongées Nautile et 6 dragues ont permis d’observer et/ou d’échantillonner autant de coupes, et ont confirmé la nature presque exclusivement basaltique du socle du plateau.-Enfin, deux plongées Nautile ont été dédiées à des objets pouvant être associés à la sortie en fond de mer de fluides profonds. Une plongée a eu lieu sur une structure en forme de dôme, initialement supposée être un volcan de boue, mais qui s’est révélée être composée d’un empilement de carbonates lités. Une autre plongée a eu lieu dans la cicatrice sommitale des glissements gravitaires affectant le Nord Est du plateau de Demerara.-L’ensemble des plongées a observé une densité d’organismes importante en fond de mer. Des champs de nodules polymétalliques ont également été observés, associés aux affleurements de basaltes
Homogeneous fish communities use intertidal salt marshes at high tide, despite environmental diversity: insights from a large-scale monitoring program on French coasts
No full textInternational audienceSalt marshes have dramatically declined in area throughout history and are still subject to numerous anthropogenic pressures. These habitats appear essential for certain fish species, which use them in high abundances. Some studies suggested that fish habitat use of salt marshes could greatly depend on the condition of the vegetation and notably its management. However, most of these studies were restricted to limited numbers of sites or samples, making it difficult to confirm these assumptions. To meet this challenge, a large-scale, standardized and temporally coordinated monitoring program has been set up on a network of 18 salt marshes distributed over the French coasts of the English Channel and the Atlantic, with the aim of describing fish communities and identifying potential driving environmental factors of fish diversity and abundances. Creeks were environmentally characterized and sampled for fish in three seasons in 2015, 2017, 2019 and 2021. Fish captures were greatly variable in abundances among space and time, poorly diversified (<= 10 species per sample), and largely dominated by mullets, gobies and seabasses. The abundances of the main fish taxa in the captures were poorly explained by the environmental variables considered. Overall, only seafront and salinity might have conditioned the occurrence and abundance of some species across the network. Our results emphasize the crucial importance of long-term, large-scale monitoring initiatives to deal with the inherent variability of fish community composition in salt marshes, and the need for further research to better understand the utilization of this habitat by fish