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International audience; The French Central Seismological Bureau (BCSF) is celebrating its centenary this year. However, from the macroseismic studies point of view, which is the main activity of BCSF, it would be more accurate to celebrate its 92nd anniversary of activity. This is because between 1978 and 1986, macroseismic studies were assigned to the Geological and Mining Research Bureau (BRGM) owing to an obvious failure of BCSF to fulfill its mission. In this article, I aim to bring a new insight on this unfortunate, tragic episode by following two main actors of BCSF history: Edmond and Jean-Pierre Rothé, father and son. Through them I will relate the story of French macroseismic studies and, more broadly, French seismicity. In order to do so, I will focus on how they built themselves a full system of monitoring and processing earthquake data, and also on how together they owned all the macroseismic data in France for almost 60 years. I will explore how their dominance brought about the failure of BCSF after the collapse of the legitimacy of Rothé’s expertise at a time when earthquake issues were intertwined in nuclear industry stakes. This brings to light not only the history of French seismicity but also the vulnerability of seismic hazard assessment practices.

Le projet Relev s’appuie sur une approche interdisciplinaire en intégrant des compétences en risques naturels (géographie, génie civil, géologie), aménagement du territoire (urbanisme, architecture, génie urbain) et sciences humaines (psychologie, sociologie, histoire), pour permettre d’améliorer la gestion de la reconstruction des territoires et des populations à la suite de catastrophes naturelles.Le projet se concentre sur le relèvement en cours des îles de Saint-Martin et Saint-Barthélemy, à la suite des ouragans Irma et Maria en septembre 2017. L’approche s’est articulée autour de deux temporalités d’étude pour mieux comprendre l’évolution des stratégies de développement de ces territoires exposés aux catastrophes naturelles : d’une part, une analyse historique des stratégies d’aménagement ante-Irma (de 1947 à 2017), d’autre part un retour d’expérience interdisciplinaire post-Irma (2017-2022) pour suivre la reconstruction de ces territoires. Ce retour d’expérience s’est focalisé plus particulièrement sur :• La reconstruction physique des infrastructures endommagées (bâtiments, infrastructures et réseaux techniques),• Le redémarrage des activités du tourisme et des PME en incluant les conséquences de la crise sanitaire de la Covid-19,• Le relèvement humain du point de vue individuel et collectif (état de stress, solidarité, vie sociale, autonomie économique, habitat, etc.),• La réorganisation de la gouvernance locale.L’objectif est de s’appuyer sur une approche intégrée pour contribuer à l’émergence de nouveaux savoirs sur l’efficacité des stratégies de reconstruction post-catastrophe et de renforcer de manière cohérente la résilience des territoires face aux catastrophes naturelles,et par là même, l’adaptation au changement climatique. Les enseignements du projet Relev documentent la gestion de la phase de reconstruction post-catastrophe à Saint-Martin et Saint-Barthélemy, et soulignent la pertinence de planifier cette phase selon des modalités proches de celles déjà adoptées pour anticiper et préparer la gestion de crise. L’analyse interdisciplinaire a permis de mieux comprendre les liens de causalité entre la gouvernance de ces 2 îles, le relèvement psychosociologique des sinistrés, la reconstruction des infrastructures endommagées, la reprise des activités touristiques et l’histoire de l’urbanisation d’îles exposées aux risques naturels.En amont de futures catastrophes, les enseignements du projet alimenteront également l’élaboration d’outils et de méthodes pour anticiper la gestion de la phase de reconstruction post-catastrophe. L’approche interdisciplinaire initiée dans le projet Relev nous incite à poursuivre cet effort de rapprochement et d’échange entre les disciplines à l’avenir, notamment sur des sujets mêlant enjeux environnementaux et sociétaux.

Today on a global level, there is a continuous fermentation to change the established views about human. There are strong tendencies by certain groups of people on the planet that desire a more advanced human, but unknowingly perhaps, they are sketching a human with diminished potential, a human who will essentially have lost the world. A tragic human in the immense loneliness of the absence of the neighbor and the God. A human, who by mutating his nature and desiring to succeed in being omnipresent and immortal with the help of technology, ends up building a bottomless hell for himself. This study attempts a brief discussion of who human is, in the context of Christianity, as opposed to the aggressively imposed view of human that appears in today's narcissistic technological culture.

In this work, we address the difficulty of reliably identifying traces of life on Mars. Several independent lines of evidence are required to build a compelling body of proof. In particular, we underline the importance of correctly interpreting the geological and mineralogical context of the sites to be explored for the presence of biosignatures. We use as examples to illustrate this, ALH84001 (where knowledge of the geological context was very limited) and other terrestrial deposits, for which this could be properly established. We also discuss promising locations and formations to be explored by ongoing and future rover missions, including Oxia Planum, which, dated at 4.0 Ga, is the most ancient Mars location targeted for investigation yet.

Introduction: The Rosetta mission is one of the latest great scientific and technological European successes. The probe and its lander Philae, transported some very audacious and inventive instruments that for some worked beyond expectations, and gave the scientists and engineers involved an expertise and experience that we should try to build on. The COmetary Secondary Ion Mass Analyser (COSIMA) onboard Rosetta, was the first instrument applying in situ analyses of cometary grains [1]. This instrument already combined two techniques: visible microscopy that was crucial to detect routinely the collected dust and characterize its structure [2], and Time-Of-Flight Secondary Ion Mass Spectrometry that mainly allowed us to determine the elemental composition of the dust [3-4]. COSIMA covered a mass range 1–1200 u but was limited to a mass resolution m/Δm of 1400 at mass 100 u at Full Width Half Maximum (FWHM), which made the assignment of molecular signals difficult. For the next generation of extraterrestrial (especially, primitive) dust analyzers, we are proposing an instrument that combines near infrared (NIR) and visible microscopy with laser ionization mass spectrometry (LIMS). This multi-analysis instrument (named dPCA for dust Particle Composition Analyzer) was part of the Castalia+ mission proposition to the ESA M7 call, but it is potentially suited for any space mission aiming to characterize dusty materials, especially complex ones containing organic and mineral phases. In the prospect to build a new generation of mass spectrometer offering High Resolution Mass Spectrometry (HRMS) collaborative effort between consortium of French and Czech laboratories (LPC2E, LATMOS, LISA, IPAG, IJCLab, J. Heyrovsky Institute of Physical Chemistry) and University of Maryland and NASA GSFC, are on-going to settle a pulsed UV laser source with an Orbitrap™ [5] mass analyzer for planetary applications. The spaceflight and ruggedized version of the Orbitrap cell and its electronics (preamplifier, ultra-stable High Voltage), the CosmOrbitrap mass analyzer/detector, is capable of discriminating isobaric interferences with ultrahigh mass resolution m/Δm > 100,000 (FWHM), high mass accuracies and dual polarity measurements [6-10]. The NIR channel of the microscope will be based on the MicrOmega hyperspectral instrument developed at IAS (Orsay, France). Several replicas of this instrument have already flown or are currently working aboard MASCOT/Hayabusa2, on the ExoMars rover [11] and currently in the JAXA curation facility for Ryugu dust analysis [12]). In this study, we investigated the analytical value of combining these two techniques. We will show through laboratory measurements how combining infrared and mass data could be extremely useful to unambiguously characterize the targeted dust. Experimental Procedure: The main well known inputs given by the NIR spectra are: the detection and characterization of hydration signatures, especially on silicates, the detection and partial characterization of carbonates and sulfates, the detection of ammoniated compounds, the detection of the presence of organic compounds and the detection and identification of ices (H2O, CO2, etc.). In the context of main belt comets, asteroids and even the Martian moons and surface, the full characterization of hydration signatures is one of the most important information needed to complete the mass spectra characterization. For this reason, we started our set of experiments and measurements on both instruments, a laboratory MicrOmega replica at IAS, and a laboratory instrument prototype of a laser ablation / ionization Orbitrap™ mass spectrometer, the LAb-CosmOrbitrap, developed at LPC2E (Orléans, France), by focusing on hydrated and anhydrous silicates. The LAb-CosmOrbitrap integrates i) a commercial pulsed Nd-YAG laser used at 266 nm UV wavelength, ii) a set of ion focusing lenses without C-trap, and iii) a spaceflight CosmOrbitrap mass analyzer/detector. Variable output energy of laser beam can be operated thanks to a polarizing prism. Samples: To explore the capabilities of the LAb-CosmOrbitrap instrument to characterize silicate in both positive and negative ion mode, we started with analyses of a San Carlos olivine, and a natural Mg-rich serpentine dominated by antigorite and chrysotile. Both samples are obviously silicates, but the former is an anhydrous ionic solid (no covalent bond between O and Mg) and the latter is a phyllosilicate (= a hydrated silicate) where Mg is covalently bonded to O and OH. Same samples have been analyzed with MicrOmega replica instrument. Results: LAb-CosmOrbitrap measurements in positive ion modes of the serpentine sample enables detection of various oxide and hydroxide magnesium peaks at high mass accuracy (< 2.5 ppm) during a single laser shot experiment, with high mass resolution (for examples m/∆m ~ 160,000 (FWHM) for 24MgOH+ and m/∆m > 130,000 (FWHM) for 24Mg2O+). In this study, we explored the best suitable laser energy and consecutive shot sequences to find reproducible and robust measurements of oxide and hydroxide ions. These results will be presented among those on olivine and the spectra obtained with NIR microscopy. Conclusions: This study demonstrates the capabilities of a UV Laser-CosmOrbitrap instrument combined with a NIR spectrometer to detect and characterize hydrated signatures of a serpentine with an optimized protocol. Next steps that will be pursued are among others the analyses of other types of silicates and minerals, of silicate doped with organic compounds. In the prospect of a future space instrument, it is obvious that IR microscopy would be of great benefit for a fast screening of the area of the targeted dust in order to further perform LIMS analyses and increase the confidence in the identification of molecular and structural indices. Acknowledgement: We thank the Centre National des Etudes Spatiales (CNES) for their financial support. References: [1] Hilchenbach et al. (2016) ApJL 816, L32. [2] Langevin et al. (2016) Icarus 271, 76–97. [3] Fray et al. (2016) Nature 538, 72–74. [4] Bardyn, Baklouti et al. (2017) MNRAS 469, S712–S722. [5] Makarov (1999) US Patent 5, 886, 346. [6] Briois et al. (2016) PSS 131, 33–45. [7] Arevalo Jr. et al. (2018) Rapid Comm 32, 1875–1886. [8] Selliez et al. (2019) PSS 170, 42–51. [9] Selliez et al. (2020) Rapid Comm 34, e8645. [10] Cherville et al. (2021) COSPAR2021, Abstract B0.4-0018-21. [11] Pilorget and Bibring (2014) PSS 99, 7–18. [12] Pilorget et al. (2021) Nature Astronomy 6, 221–225.

Introduction With 13 years of observations, the Visual And Infrared Mapping Spectrometer (VIMS) onboard the \textit{Cassini} spacecraft has observed the surface and atmosphere of Titan through two seasons: winter and spring. In VIMS-IR spectra the surface is only seen in seven atmospheric windows due to the strong methane absorption. To retrieve the surface albedo we use radiative transfer (RT) models to compensate for the signal due to the atmosphere. Thanks to the lander Huygens, we have information about the optical properties of the aerosols above the equator that can be used in RT models. However, using the same aerosols vertical profile at high latitude doesn't work. With the help of the results of and Global Circulation Models and the Composite InfraRed Spectrometer onboard Cassini, we changed the aerosol vertical profile and optical properties in our RT model to better fit VIMS data at high latitude. While this model is not well constrained due to a lack of data, we manage to adjust the optical properties so our RT model based on Coutelier et al., (2021) retrieve surface albedo mostly between 0 and 1 instead of values crossing these boundaries like we had previously. It allow us to study with a RT model the shores and polar seas of Titan. We applied this new model on the same area of Kraken Mare in three consecutive VIMS cubes of the same flyby (subsequently named C1, C2 and C3). It allow us to validate our model on terrains with different albedo, and to notice an interesting feature in Kraken Mare that could be interpreted as sediment transport into the sea. Adaptation of the aerosols optical properties and vertical profile We decided to keep a 2 layers-based aerosol model, separated into haze and mist. We first changed the haze opacity vertical profile, using an exponential law : with the altitude of transition between mist and haze Ztr=70 km, and the scale height Hh=40 km. τh1µm is the opacity calculated by Doose et al., 2016 at 1 µm. We then changed the spectral slope of the optical depth of the mist with a simple power law as a first approximation : with Δτmnorm the normalized optical depth of the atmospheric layer of mean altitude z, τhλ0 the total optical depth at λ0 = 1 µm calculated by Doose et al 2016., λ the wavelength, and the parameter b = 2.2 +/- 0.2 The most influent parameter is the mist single scattering albedo ωm. we decided to change it depending on that of the haze ωh and a factor α = 0.4 +/- 0.1. Application and results on Kraken Mare We tuned and applyed this model on three successive VIMS cubes (full names in Fig. 1) subsequently called C1, C2 and C3. We retrieved the albedo on a zone crossing Kraken Mare, containing pixels from land, shore and methane sea. They are circled in red in Fig.1. The top part shows the VIMS cubes, and the bottom part their footprint on the geomorphologic map of Titan. That way we can have an expectation on the retrieved albedo: dark in the sea, and bright on land. Figure 1 : (top) Successive VIMS cubes from flyby 292TI (colors : R : 5.01, V : 1.28, B : 2.79 μm).(bottom) : Footprint of the VIMS pixels on the geomorphologic map from Lopez et al., 2020. The pixels in our study are circled in red. The pixels circled in blue have mixed signatures. The retrieved albedo are on Fig. 2. We still have remaining problems with negative albedo on dark pixels, mostly in the first atmospheric window. We can still differentiate very well the signatures from different terrains. Those coming from Kraken Mare are in blue, and those coming from the land are in green in Fig. 2. In C2, we have a pixel localized on the shore containing part of land and sea, circled in pink. Its signature is mixed, as we expected. However, we notice that on C1 and C3, two pixels localized in Kraken Mare (also circled in pink) also have a mixed signature. We did check that it was not a mistake in the cube geolocalization, or a difference due to a cloud. Figure 2 : Retrieved albedo of the selected pixels in Fig. 1. from the cubes C1, C2 and C3. The errors bar are calculated from the error on VIMS, and not from the error on the model. They are underestimated as a consequence. Discussion Infrared can penetrate deeply into liquid methane and ethane. The mixed signature we noticed can come from sediment transport carried by rivers flowing into Kraken Mare, issued from the erosion of the bedrock. While this aerosol model for the poles is not exact, nor well constrained, the RT model is working and gives reasonable results on different cubes from the same flyby. We can compare the different surface albedos instead of the absolute values, because the atmospheric model is the same for all of the studied pixels. The combination of the RT analysis with the geomorphologic map is a powerful tool that leads to notice unexpected signatures. With the seasons changes, we can expect that the improved polar aerosol model is not constant, so further studies should be made on other cubes through different seasons. We could that way follow through an other method the seasonal variation of the polar haze and mist layers. References Doose et al. (2016) Vertical structure and optical properties of Titan’s aerosols from radiance measurements made inside and outside the atmosphere. Icarus 270 : 355-375. Coutelier et al. (2021) Distribution and intensity of water ice signature in South Xanadu and Tui Regio. Icarus 364 : 114464. Lopes et al. (2020) A global geomorphologic map of Saturn’s moon Titan." Nature astronomy 4.3 : 228-233.

The D/H ratio is a key parameter to understand the atmospheric evolution of a planet. On Mars a D/H ~ 5 times larger than the ratio on Earth is measured. This large ratio can be explained by a preferential escape of the hydrogen compared to the deuterium due to its lower mass. However, while the thermal escape (Jeans escape) is strongly mass dependent other non-thermal processes are less mass dependent and would impact the time needed to fractionate the water from the terrestrial value to the current value. After the first detections of the deuterium Lyman-α emission from Earth (Bertaux et al. 1992, Krasnopolsky et al. 1998), the mission MAVEN performed the first systematic observations of the atomic deuterium Lyman-α emission around Mars showing a brightness of several hundreds of Rayleigh near Mars winter solstice (Clarke et al. 2017, Mayyasi et al. 2017), much larger than the Earth detections done near aphelion (~ 20 – 50 Rayleighs). This seasonal variation of the deuterium Lyman-α brightness is consistent with the variations of the hydrogen Lyman-α brightness observed from Mars Express (Chaffin et al. 2014, Chaufray et al. 2021), HST (Clarke et al. 2014), and MAVEN/IUVS (Clarke et al. 2017, Chaffin et al. 2018) and should result from the processes transporting the water vapor from the lower atmosphere to the upper atmosphere (Vals et al. 2022). In this work we will present preliminary simulations of the 3D deuterium abundance in the Martian upper atmosphere (Fig. 1) using a 3D time dependent global circulation model, including the chemical reactions between HD and HDO with the ions in the upper atmosphere, its extension in the exosphere, and a comparison of the simulated D Lyman-α brightness with the brightness measured by MAVEN/IUVS (Mayyasi et al. 2017) for the Martian year 33. Fig. 1 Simulated average dayside and nightside D density at different altitudes in the thermosphere and exosphere along one Martian year. We will also present first results of the simulated non-thermal escape of H and D produced by collisions between hot oxygen with H, D, H2 and HD as well as the escape of planetary H+ and D+ driven by the solar wind interaction. We will compare the D and H thermal escape rate with the non-thermal escape rates. References: Bertaux et al. (1992), in ESOC conference and workshop proceedings, 44, 459. Chaffin, M. et al. (2014), Geophys. Res. Lett., 41, 314-320 Chaffin, M. et al. (2018), J. Geophys. Res., 123, 2192-2210 Chaufray et al., (2021), Icarus, 353,113498 Clarke et al. (2014), Geophys. Res. Lett., 41, 8013-8020 Clarke et al. (2017), J. Geophys. Res., 122, 2336-2344 Krasnopolsky et al., (1998), Science, 280, 1576 Mayyasi et al., (2017), J. Geophys. Res., 122, 10811-10823 Vals et al. (2022), J. Geophys. Res., under revisions

Vine introduction in Burgundy (east central France) two millennia ago is responsible for land use changes and increased soil erosion to which societies have tried to adapt. In this paper we seek to figure out the relationship between land uses, agricultural practices and geomorphic dynamics in the Mercurey terroir during the Late Holocene. The method employed is based on the analysis of sedimentary deposits observed in the valley bottom and along hillslopes. It is complemented by a pedoanthracological study derived from a trench excavated into a riverbank, in order to interpret the variability of the reconstituted sedimentary signal. Our results highlight two major stages of detritism over the last 2,800 years. At least from 800 cal. BC, frost heave screes (stored since the Late Pleistocene) are transported from the upper part of hillslopes to the valley bottom by high-energy geomorphic processes (e.g., solifluction flows). This sequence of coarse colluviums is associated with the development of an agro-pastoral landscape marked by an opening forest cover. A second phase begins after 1400 cal. AD. It is characterized by a fine sedimentation and a high concentration of vine charcoal. Indeed, wine-growing spread in the medieval landscape comes with the building of agricultural infrastructures. It leads to a decrease of sediment connections from the source areas to valley bottom. The coarser sediments are retained on the hillslopes, thus bringing out soil maintenance strategy.

International audience; Cave levels at high elevations (2250-2370 m), hosting allochthonous sediments with clear provenance from the Pelvoux External Crystalline Massif were identified in the Obiou mountain, Dévoluy Massif (French Western Alps). These deposits result from burial of alluvial sediments of the paleo-Drac River in Miocene times (burial ages of ca. 10-15 Ma). The Drac River is currently situated 1600 m below the caves, indicating significant post-middle Miocene fluvial incision. The pollen analysis on clay cave infill indicates a humid and warm climate, typical for Western Europe in the mid-late Miocene. It also reveals the presence of dinoflagellate cysts from coastal and lagoon environments suggesting deposition of the clays in the caves when they were close to sea level. These findings indicate uplift of the caves of at least 2000 m since the mid-late Miocene. Furthermore, the pollen assemblage originated from different vegetation belts, in agreement with existing data for mid-late Miocene deposits in the western Alps. The pollen flora includes cool-temperate and boreal trees, suggesting high-elevated source areas for the deposits within the Pelvoux catchment. These data confirm the exceptional character of the Obiou cave deposits that provide new geomorphologic constraints for the evolution of the French Western Alps.

The project CoRob-X develops and demonstrates enabling technologies for multi-agent robotic teams to explore planetary surfaces with a focus on hard-to-reach areas where a collaborative scheme is required to efficiently explore complex environments. Exploring lava tubes is such a challenging environment and requires a team of robots able to collaborate in an autonomous way to find their way to the subsurface tube system, descend through a natural entry hole (the so-called skylight), and explore the interior with payload instruments to provide scientific data. The developed robotic exploration system that will tackle the ambitious goal is composed of three rovers with substantially different technical characteristics. The paper presents the overall approach, i.e., the control architecture, the robotic systems, and the software to be used. It also showcases the selected mission phases that will be demonstrated in a field-test campaign. In addition, a terrestrial mining use case is presented that demonstrates how the developed autonomy-enabling software can be transferred to terrestrial applications. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Highlights • First feasibility study of respiratory viral detection in Cystic Fibrosis sputum. • High concordance between sputum and nasopharyngeal samples in viral. • Multiplex-PCR performed in 30 paired samples: 83% viral congruency. • Sputum: an optimal non-invasive sample for viral diagnosis in cystic fibrosis., Viruses are important agents in lung function deterioration in Cystic Fibrosis (CF). To date, no standard operating procedures (SOPs) have been established to determine which sampling method is the most effective for an optimal virological diagnosis of respiratory viral infections in CF. Here we investigated the performances of two sampling sites, sputum samples versus nasopharyngeal (NP) swabs, for thirty participants from three CF centres presenting an acute respiratory infection. Sputum and NP samples were simultaneously collected and multiplex PCR targeting 16 to 18 viruses were performed. Viruses were detected for 18/30 patients (60%). A high concordance between the sputum and NP samples was observed in 25 (83%) paired samples of which 13 tested positive and 12 tested negative. These results highlighted the relevance of sputum sampling for diagnostic of respiratory viruses in CF, which is less invasive and better accepted by CF patients than NP, and allows accurate bacterial detection.

International audience

International audience

International audience

Cet article présente quelques illustrations d.applications de données radar polarimétriques (complètes ou partielles) pour le suivi des surfaces terrestres. La première partie est dédiée aux données radar pleinement polarimétriques. Elle est introduite par un rappel théorique présentant leur spécificité. Puis quelques exemples sont présentés, principalement concernant la cartographie de la végétation et également les processus spatio-temporels de sédimentation dans une zone semi-aride en Tunisie. La deuxième partie est consacrée aux données partiellement polarimétriques du type de celles acquises par les capteurs Radar à Synthèse d´Ouverture (RSO) à bord des satellites Sentinel-1A/1B. Celles-ci seront largement utilisés dans les années futures en raison de leur apport significatif pour les études touchant aux observations des surfaces terrestres pour les sciences de l'environnement.

(version française d'un article publié dans Journal of Archeological Sciences : Reports en 2022)

The 'disparitas conjecture' states that unicellular life may be common in the galaxy, but that multicellular life might be rare in comparison. A variation of this is that unicellular life may be common in the galaxy, but that intelligent life is rare. However, microbial life can and does indeed display characteristics of intelligence. Thus, in this work it has been investigated how life potentially could have endured through the Late Heavy Bombardment (LHB) through intelligent strategies such as decision making, association and anticipation, communication and self-awareness. At the LHB there would be for microbial life an unpredictable environmental fluctuation regarding pools of amino acids, lipids and fluids available when impacts and reimpacts launched organisms into new habitats. Thus, evolutionary strategies must have been favored that could stretch the available external and internal resources as long and as efficiently as possible. Thus, inclusive fitness or kin altruism could have emerged, where organisms adapt to acquire energy and nutrients from siblings who voluntarily autolysed in order to replenish the amino acid pool for their kin. A further strategy could also evolve where members of the same species can recognize each other and actively isolate themselves from other species, which allows them to utilize the amino acid pool better. Thus, the organisms will potentially be able to survive for a long time in these ways until new impacts launch them to new spots with amino acid pools. There has thus been an alternating increase and decrease in the number of organisms during this localized planetary reseeding and life may have endured this way until the bombardments were over. Thus, if a world inhabited only by analogous of bacteria, archaea and protists is located elsewhere in the galaxy, then this does not exclude the existence of intelligent life there.

La fouille archéologique préventive menée par l’Inrap durant l’été 2017 sur le site de la Grande Maison à Chamigny (Seine-et-Marne) a en outre révélé trois mégalithes distants de 60 m d’une sépulture collective utilisée de la fin du Néolithique à l’âge du Bronze ancien (ca. 3350-1800 av. n.è.) Le mégalithe le plus grand est une stèle décorée d’un format sub-rectangulaire de 2 m de haut pour 40 cm de large, 44 cm d’épaisseur et d’un poids estimé à deux tonnes. Son analyse technologique a permis d’appréhender des mises en forme successives et des degrés d’usure différentielle des arêtes vraisemblablement liés au déplacement du mégalithe. L’analyse iconographique a permis d’identifier plusieurs techniques de gravure pour la réalisation des décors. Par ailleurs, l’analyse géomorphologique de la stèle a permis de mettre en évidence des relations entre les méso-structures géomorphologiques et les modifications anthropiques et contribuent à une évocation anthropomorphe initiale soulignée par les aménagements gravés. Ce regard "géologique" a fait soupçonner que les éléments de la face avant, tout comme ceux de la face arrière, sont probablement intervenus dans la sélection de la dalle à destination anthropomorphique. Les particularités de cette stèle a permis d’envisager quelques facettes du quotidien de nos ancêtres néolithiques et de les confronter au présent pour permettre une réflexion sur le devenir de nos propres modes de vie, et ceci grâce à une valorisation muséale adaptée.

Stray light is an issue in any optical instrumentation. It affects the accuracy and resolution of the measurements, or their dynamics, possibly the resolution of images. Methods do exist at component leval (reflectometry, scatterometry) to measure stray light. But the measurement of stray light at system level can be difficult once integration is complete: introducing a scatterometer in the instrument is likely to be impossible.We develop a general method to measure coherent stray light at system level, to determine, in the system under test (SUT) what are the different sources of stray light, and the fraction of stray light which correponds to each of them. Time-of-flight methods inject short pulses in the system, and fast signals are measured, that indicate nominal light, as well as the "echoes" corresponding to the different sources of stray light, and the corresponding delays. This implies that the photoreceivers in the SUT are fast detectors (picoseconds) and can measure small pulses: 10^-12 if fractionnal optical amplitudes of 10^-6 are to be measured, relative to the nominal amplitude.Rather than use short pulses, we use a single mode laser source with an optical frequency scanned linearly with time, and detect all output signals (optical and electrical). For each of the signals, the presence of a fringe behaviour indicates the presence of stray light, interfering with nominal light. The stray/nominal optical path length difference is obtained from the fringe frequency, similar to conventional FMCW coherent reflectometry. The measurements require no fast detection., La lumière parasite cohérente constitue naturellement, sur une instrumentation optique, un écueil à bien des égards. Elle affecte l'exactitude ou la résolution des mesures, ou leur dynamique, ou encore la résolution des images. Des méthodes existent pour la mesure de la lumière parasite au niveau composant (réflectométrie, diffusométrie). Mais la mesure de la lumière parasite au niveau système peut poser des difficultés une fois le système assemblé (impossibilité d'introduire, par exemple, une instrumentation de mesure de la lumière diffusée). Nous développons une méthode générale de mesure de la lumière parasite cohérente au niveau système, permettant de déterminer quelles sont, à l'intérieur d'un système à tester (SAT), les différentes sources de lumière parasite, et la fraction de lumière parasite qui leur correspond. Les méthodes de type "temps de vol" injectent des impulsions courtes dans le système, et on mesure des signaux rapides traduisant, outre l'impulsion de lumière nominale, les "échos" associés aux différentes sources de lumière parasite, et les retards associés. Cela implique que les détecteurs du SAT soient suffisamment rapides (picosecondes) et par ailleurs que leur dynamique permette de détecter de très petites impulsions: 10^-12 si on souhaite détecter une amplitude optique parasite de 10^-6 comparée à l'amplitude nominale. Plutôt qu'utiliser des impulsions courtes nous utilisons une source laser monomode dont la fréquence optique est balayée, et nous détectons tous les signaux sortants (optiques comme électriques). Sur chacun des signaux, l'observation d'un comportement de type frange d'interférence indique la présence de lumière parasite, interférant avec le faisceau nominal. La différence de chemin nominal/parasite est indiquée par la fréquence de ces franges d'interférence, comme en réflectométrie cohérente FMCW. Leur mesure ne requiert aucune détection rapide.

It is a basic requirement of special relativity theory (SRT) that all relatively moving inertial observers agree on an observable (interference fringe shift, for example). It is shown that SRT leads to a disagreement on the observables (interference fringe shift) in two relatively moving inertial reference frames.

Coastal polynyas are key formation regions for Dense Shelf Water (DSW) that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. We examine how the physiographic setting, water-mass distribution and transformation, water column stratification, and sea-ice production regulate DSW formation in four East Antarctic coastal polynyas. We use a salt budget to estimate the relative contribution of sea-ice production and lateral advection to the monthly change in salinity in each polynya. DSW forms in Mackenzie polynya due to a combination of physical features (shallow water depth and a broad continental shelf) and high sea-ice production. Sea-ice formation begins early (March) in Mackenzie polynya, counteracting fresh advection and establishing a salty mixed layer in autumn that preconditions the water column for deep convection in winter. Sea-ice production is moderate in the other three polynyas, but saline DSW is not formed (a fresh variety is formed in the Barrier polynya). In the Shackleton polynya, brine rejection during winter is insufficient to overcome the very fresh autumn mixed layer. In Vincennes Bay, a strong inflow of modified Circumpolar Deep Water stratifies the water column, hindering deep convection and DSW formation. Our study highlights that DSW formation in a given polynya depends on a complex combination of factors, some of which may be strongly altered under a changing climate, with potentially important consequences for the ventilation of the deep ocean, the global meridional overturning circulation, and the transport of ocean heat to Antarctic ice shelves. Key Points We determined the physical factors enhancing (or hindering) DSW formation in four East Antarctic polynyas during a well sampled year Relatively high salinity in early winter and high sea-ice formation favor Dense Shelf Water formation in Mackenzie Polynya The properties and volume of DSW formed in a coastal polynya depend on its preconditioning as well as on sea-ice formation Plain Language Summary Coastal polynyas are regions of open water surrounded by sea ice. As sea ice forms, it is pushed offshore by strong winds blowing from the Antarctic continent, keeping the polynya ice-free. Salt is released into the water below as sea ice forms, increasing the salinity and density of the water column. In some polynyas, this water is dense enough to sink from the continental shelf to supply a network of bottom ocean currents that influences global climate. In other polynyas, the water in winter never gets dense enough to reach the ocean abyss. Using data collected by instrumented elephant seals, we investigated the main factors controlling dense water formation in four East Antarctic polynyas. We found that dense water production is related to the strength of sea-ice formation, as expected, but also depends on the salinity at the start of winter. The geographical and physical characteristics of the polynyas and regional circulation also modulate the final water density. Our findings provide insight into how dense water formation in East Antarctic polynyas might respond to future changes in climate and thereby influence the transport of ocean heat to the Antarctic continent and the melt of ice shelves.

Copernic is the name of a change of world. In the change of mathematical system that he describes, for the physics that he prepares, and in the double dimension of theoretical and affective consciousness that man takes from himself in his wake. If the scientific model ended up being widely accepted, the problem of how man can relate to a world of which he is no longer the center still poses a problem. Husserl's thought was partially written against it, already in his 1934 article "The Earth does not move", then more widely in the Krisis in 1936, accusing the scientific revolution of having covered the life-world. For Husserl, Copernicus will never be more than a change of theoretical world, but will not wait for the original dimension of the life-world. It is this idea that we would like to discuss in this article., Copernic est le nom d'un changement de monde. Dans le changement de système mathématique qu'il décrit, pour la physique qu'il prépare, et dans la double dimension de conscience théorique et affective que l'homme prend de lui-même à sa suite. Si le modèle scientifique a fini par être largement admis, le problème de la manière dont l'homme peut se rapporter à un monde dont il n'est plus le centre pose encore problème. La pensée de Husserl s'est partiellement écrite contre celle-ci, déjà dans son article de 1934 « La Terre ne se meut pas », puis plus largement dans la Krisis en 1936, accusant la révolution scientifique d'avoir « recouvert le monde de la vie ». Pour Husserl, Copernic ne sera jamais qu'un changement de monde théorique, mais n'attendra pas la dimension originaire du monde de la vie. C'est cette idée que nous voudrions discuter dans cet article.

Une carotte de glace d’une dizaine de centimètres de diamètre, extraite des profondeurs des calottes polaires lors d’expéditions internationales aussi éprouvantes pour les hommes que pour les machines : tel est l’objet au cœur de l’ice core science, une spécialité scientifique qui a joué un rôle essentiel dans la mise au jour de l’impact des activités humaines sur le climat terrestre.Comment a émergé l’idée que la glace polaire pouvait receler des indices permettant de retracer l’histoire de ce climat ? De quelle manière l’ice core science s’est-elle constituée et développée au cours des dernières décennies ? Comment est-elle organisée aujourd’hui ? Et comment ses résultats peuvent-ils être mobilisés dans les débats autour de l’« anthropocène » ?De l’installation sur les inlandsis de l’Antarctique ou du Groenland à la diffusion de spectaculaires courbes, en passant par les « manips » effectuées dans les laboratoires et la création du GIEC, cette enquête restitue une aventure scientifique décisive, en ouvrant la « boîte noire » de la production des connaissances climatiques. Parce qu’elle croise plusieurs disciplines, s’appuie sur des avancées conceptuelles et techniques, et met en jeu les rapports entre recherche, médias et pouvoirs politiques depuis les années 1960, l’ice core science permet d’interroger à nouveaux frais la place des sciences et du savoir dans nos sociétés.

Crustal Fault Zones (CFZ) are an interesting geological target for high-temperature geothermal resources in naturally frac-tured and deep basement zones. Field and laboratory studies have already shown the ability of these systems to favor fluid flow down to brittle-ductile-transition. However, several key questions about exploration still exist, in particular the role of structural dip, permeability, and the effect of mechanical stress and more broadly the fundamental role of tectonic regimes on fluid flow in naturally fractured basement domains. Considering 2D and 3D numerical modelling, with TH and THM cou-plings, two trends can be identified and integrated for the exploration of these targets (i) vertical faults concentrate the high-est temperature anomalies at the shallowest depths (ii) strike-slip systems favor the largest temperature anomalies. Geologi-cal and geophysical data suggest that, the Pontgibaud fault zone (French Massif Central) is a CFZ that host an active hydro-thermal system at a depth of a few kilometers. We conducted an integrated study to assess its high temperature geothermal potential. Field measurements are used to control the 3D geometry of the geological structures. 2D (thin-section) and 3D (X-ray microtomography) observations point to a well-defined spatial propagation of fractures and voids, exhibiting the same fracture architecture on different scales (2.5 μm to 2 mm). Moreover, measurements of porosity and permeability confirm that the highly fractured and altered samples are characterized by high permeability values, with one sample characterized by a permeability as high as 10-12 m2. Finally, a large-scale 3D numerical model of the Pontgibaud CFZ, based on THM cou-pling and the comparison with field data (temperature, heat flux, and electrical resistivity), allowed to explore the spatial ex-tent of the 150°C isotherm, which rises up to a depth of 2.3 km. Though based on simplified hypotheses, our model repro-duces field data. A multi-disciplinary integrative approach based on coupled 3D modeling proved to be an efficient way to assess the geothermal potential of CFZ and predict temperature distributions. It can be used as a predictive tool to develop high-temperature geothermal operations within basement rocks hosting large-scale fault systems., Les Zones de Failles Crustales (ZFC) constituent une cible géologique intéressante pour les ressources géothermiques à haute température dans les zones de socle naturellement fracturées. Des études de terrain et de laboratoire ont déjà montré la capacité de ces systèmes à faciliter l'écoulement des fluides jusqu'à la transition ductile-fragile. Cependant, plusieurs questions clés concernant l'exploration subsistent, en particulier le rôle du pendage, de la perméabilité, de l'effet des con-traintes mécaniques et, plus largement, le rôle fondamental des régimes tectoniques sur l'écoulement des fluides dans les domaines de socle naturellement fracturés. En considérant des modélisations numériques 2D et 3D, avec des couplages TH et THM, deux tendances peuvent être identifiées et intégrées pour l'exploration de ces cibles : (i) les failles verticales con-centrent les plus fortes anomalies de température aux plus faibles profondeurs (ii) les systèmes en décrochement favorisent les plus grandes anomalies de température. Les données géologiques et géophysiques suggèrent que la zone de faille de Pontgibaud (Massif Central français) est une ZFC qui abrite un système hydrothermal actif à une profondeur de quelques ki-lomètres. Une étude intégrée pour évaluer son potentiel géothermique de Haute Température a été effectuée. Les mesures de terrain permettent de contrôler la géométrie 3D des structures géologiques. Les observations 2D (lames-minces) et 3D (microtomographie à rayons X) mettent en évidence une propagation spatiale bien définie des fractures et des vides, pré-sentant la même architecture de fracture à différentes échelles (2,5 μm à 2 mm). En outre, les mesures de la porosité et de la perméabilité confirment que les échantillons fortement fracturés et altérés sont caractérisés par des valeurs de perméabili-té élevées, un échantillon étant caractérisé par une perméabilité aussi élevée que 10-12 m2. Enfin, un modèle numérique 3D à grande échelle de la ZFC de Pontgibaud, basé sur le couplage THM et la comparaison avec les données de terrain (tem-pérature, flux de chaleur et résistivité électrique), a permis d'explorer l'étendue spatiale de l'isotherme 150°C, qui s'élève jus-qu'à une profondeur de 2,3 km. Bien que basé sur des hypothèses simplifiées, notre modèle reproduit les données de ter-rain. Une approche intégrée multidisciplinaire basée sur une modélisation 3D couplée s'est avérée être un moyen efficace d'évaluer le potentiel géothermique de la ZFC et de prédire les distributions de température. Elle peut être utilisée comme un outil prédictif pour développer des opérations géothermiques à haute température dans des roches du socle abritant des sys-tèmes de failles à grande échelle.

Measuring vertical variations in the deuterium to hydrogen ratio with altitude is essential in understanding the processes that lead to the escape of water vapour from the Martian atmosphere. We retrieve vertical profiles of HDO and H2O from the ACS instrument, monitoring seasonal changes particularly above the water condensation level. We discuss these results in relation to previously observed seasonal variations in D/H together with the expected variations from theoretical models. Introduction The ratio of deuterium to hydrogen (D/H) is a sensitive tracer of the rate of escape of water from the Martian atmosphere over its history. Hydrogen preferentially escapes from the atmosphere over its heavier isotope (e.g. [1]), and so the greater the amount of historical escape of water vapour, the larger the average D/H ratio. On Mars, this value is measured to be around 4-6 times that of terrestrial distilled ocean water [2,3], showing that the early atmosphere of Mars contained significantly more water than it does today. In addition, a number of processes in the lower and middle atmosphere can cause relative changes in the concentrations of semi-heavy water (HDO) with respect to water vapour, notably due to differences in rates of cloud deposition (e.g. [4,5]) and photolysis (e.g. [6,7]). We therefore wish to look at spatial and temporal changes in the vertical profile of D/H, particularly above the level of water condensation, in order to better characterise the processes that influence the escape of water vapour from the lower atmosphere into space. Method The mid-infrared channel of the Atmospheric Chemistry Suite Instrument (ACS MIR, [8]) on board the ExoMars Trace Gas Orbiter obtains transmission spectra of the Martian atmosphere in solar occultation geometry, which is sensitive to trace gases at very low abundance and at high vertical resolution. We make use of observations in grating position 11, which is sensitive to a wavenumber regime in which a large number of resolvable HDO lines are present that in the best cases provide sensitivity to HDO abundance up to around 70 km. These are then inverted using the RISOTTO radiative transfer and retrieval pipeline [9,10] to give vertical profiles of HDO volume mixing ratio. Concurrent vertical profiles of H2O are obtained using the near-infrared (NIR) channel of the same instrument [11], and then the D/H ratio computed assuming that H2O and HDO are the main carriers of the two isotopes of hydrogen. Accurate quality control of the data is performed using probability-sparse Non-negative Matrix Factorisation (psNMF [12,13]). Results and Perspective We report seasonal changes in the fractionation of D/H in the middle atmosphere throughout the temporal range of the data starting from the autumn equinox in MY34 to the end of MY 35. These will be discussed in relation to the findings of seasonal changes in the vertical profiles of D/H reported by the NOMAD instrument [14], and the results interpreted in relation to predictions from Global Climate Models (GCMs) of HDO ([5,15,16]). Fig. 1: Retrieved vertical profiles of (left) water vapour from (right) D/H from the near- and mid-infrared channels respectively of the ACS instrument. References [1] Krasnopolsky, V. A., Mumma, M. J., & Randall Gladstone, G. 1998, Science, 280, 1576 [2] Owen, T., Maillard, J. P., de Bergh, C., et al. 1988, Science, 240, 1767-1770 [3] Webster, C. R.; Mahaffy, P. R.; Flesch, G. J., et al. 2013, Science, 341, 260-263 [4] Fouchet, T. & Lellouch, E. 2000, Icarus, 144, 114-123 [5] Montmessin, F., Fouchet, T. & Forget, F. 2005, J. Geophys. Res. Plan., 110 [6] Yung, Y. L., Wen, J.-S., Pinto, J. P., et al. 1988, Icarus 76, 146-159 [7] Alday, J., Trokhimovskiy, A., Irwin, P. G. J., et al. 2021, Nat. As. 5, 943-950 [8] Korablev, O., Montmessin, F., Trokhimovskiy, A., et al. 2018, Space Sci. Rev.,214,7 [9] Braude, A. S., Ferron, S., & Montmessin, F. 2021, J. Quant. Spec. Rad. Transf.,274,107848 [10] Braude, A. S., Montmessin, F., Olsen, K. S., et al. 2022, A&A,658,A86 [11] Fedorova, A. A., Montmessin, F., Korablev, O., et al. 2020, Science 367, 297-300 [12] Hinrich, J.L. & Mørup, M. 2018, Latent Variable Analysis and Signal Separation. LVA/ICA 2018. Lecture Notes in Computer Science(), 10891, 488–498 [13] Schmidt, F.; Mermy, G. C.; Erwin, J., et al. 2021, JQSRT, 259, 107361 [14] Villanueva, G. L.; Liuzzi, G.; Crismani, M. M. J., et al. 2021, Sci. Adv. 7, eabc8843 [15] Rossi, L., Vals, M., Montmessin, F., et al., J. Geophys. Res. Plan., in review. [16] Vals, M., Rossi, L., Montmessin, F., et al. 2022, J. Geophys. Res. Plan., in press.

Cet article concerne aussi le domaine de l'histoire de l'art; International audience; In this study, we focus on the composition of the Virgin and Child with Saint Anne by Leonardo da Vinci. The composition is considered first from the point of view of graphs and the genealogy of the Christ is analyzed accordingly. Then, the composition of the masterpiece is studied from the perspective of scientific knowledges in geometry. The many ellipses or part of ellipses in the composition are detailed. This study permits us to revisit the movement of the figures. Knowledges on celestial mechanics at the time of Leonardo are presented and themes like destiny and resurrection are examined consequently. Finally, the representation of instabilities and turbulences is considered in the painting and the renewal of forms is examined.

With the advent of the Gaia astrometry mission and the constantly improving geodetic VLBI program providing both optical and radio reference frames with precisions better than 0.1 mas, challenging questions arise about identifying which mechanisms are behind the optical emission as well as other emissions at higher energies, especially the γ-ray emission. We use data from Gaia EDR3, the radio ICRF3, and GeV fluxes from the Fermi-LAT 4FGL catalog for a sample of about 800 common active galactic nuclei (AGN), dominated by blazars (BL Lac and FSRQs). We investigate the general trends of such populations in terms of geometry, classification, color indices, and GeV emission.

The Bordeaux VLBI Image Database provides to the international VLBI community almost 8,000 VLBI images of radio sources at S and X band and some others at K and Q band. Such images are of interest for astrometric and astrophysical applications, such as the determination of the VLBI jet direction. We developed a fully automatic method to extract this direction from any VLBI image, which we then applied to all BVID images, resulting in the production of 9,215 jet directions for 1,221 sources. Comparing the mean jet directions over all epochs at X band to the Gaia EDR3 (optical) − ICRF3 S/X (radio) offset vector directions indicates that the offset vector is aligned within 30 • of the jet direction in roughly half of the sources, thereby confirming previous studies.

The Avignonet landslide (Isère, France) is made of Quaternary paraglacialsediments including imbricated units of till, glaciolacustrine and fluvial layers. Numerousboreholes were drilled in the mid-1980s and 2010s to detail the geological andgeotechnical framework of the inhabited part, to the south, of this slow-moving landslide.The measured parameters are very heterogeneous and make interpretation difficult. In thiswork, the aim was to combine these different parameters to produce a geological model.The results reveal a high geological complexity with the imbrication of various sedimentaryunits. Two ancient landslides, several tens of metres wide, were also identified. This workshows the interest of a multi-proxy approach in studies involving Quaternary sedimentaryunits., Analyse multi-proxy de forages dans des argiles glacio-lacustres quaternaires (glissement d'Avignonet, Trièves, France)Le glissement d'Avignonet (Isère) est constitué de sédiments paraglaciairesquaternaires parmi lesquels des couches de till, glacio-lacustres et fluviatiles imbriquées.De nombreux forages ont été réalisés au milieu des années 1980 et 2010 pour préciser lecadre géologique et géotechnique de la partie habitée, au sud, de ce glissement de terrainlent. Les paramètres mesurés sont très hétérogènes et rendent l'interprétation difficile.Dans ce travail, il a notamment été cherché à combiner ces différents paramètres pourproduire un modèle géologique. Les résultats révèlent une grande complexité géologiqueavec l'intrication de diverses unités sédimentaires. Deux anciens glissements de terrain deplusieurs dizaines de mètres de large ont été identifiés. Ce travail montre l'intérêt d'uneapproche multi-proxy dans les études impliquant des unités sédimentaires du Quaternaire.

International audience; The internal zones of the Western Alps arc are derived from an oceanic and continental subduction wedge developed beneath the Adria plate during its paleogene northward drift. Exhumation of the internal zones proceded from early Oligocene onwards due to westward extrusion of the Adria plate. The prominent fold-and-thrust structures which follow the arc shape, either forward or backward verging, postdate the initial nappe stacking and overprint differently oriented older deformations which are relevant to proper retoration of this arcuate orogen to minimise overlap problems. We document this early stacking phase through outcrop-scale structural analysis at 55 sites between the Maurienne and Ubaye valleys, along with larger-scale examples of early structures. They consistently show an initial N-to NW tectonic transport, whose kinematic indicators are overprinted by either forward (W-to SW-directed) or backward (E-to NE-directed) deformation associated with post-nappe transport along the Penninic thrust. Accordingly, restoring the Briançonnais fold/thrust system must incorporate reconstruction of the nappe stack along the initial top N-NW direction of orogenic propagation, with careful consideration of their paleogeographic origin towards the S-SE. This stack was built during the Eocene Adria-Iberia collision, and overthrust the Subbriançonnais-Valaisan trough to the NW before involving the Dauphiné-Helvetic foreland. It includes different types of Paleozoic units, either Permo-Carboniferous sediments towards its base, or polymetamorphic basement above, which can be explained by inversion of a late Variscan basin and of its southern shoulder, whereas the uppermost Prepiedmont units result from inversion of the Tethyan margin toe. Mixed breccia, locally preserved close to the tectonic contact between the latter units and the overlying "Schistes Lustrés" oceanic nappes, are interpreted as olistostromes fed by both units in a very early collision stage. 39 Ar/ 40 Ar dating suggests that these shallow tectono-sedimentary formations were involved in the subduction wedge during the early Eocene, whereas younger (late Eocene) equivalent olistostromes mark the propagation of the Briançonnais stack over the external (Dauphiné/Helvetic) foreland. The Eocene orogenic wedge was rapidly exhumed during Oligocene westward indentation and radial spreading, in a markedly different tectonic context driven by extrusion around an Adriatic upper mantle indenter, which controlled development of the Western Alps arc in relation with the Ligurian sea opening.; Les zones internes de l'arc des Alpes occidentales sont dérivées d'un prisme de subduction océanique et continental qui s'est développé sous la plaque Adria pendant son déplacement vers le nord au Paléogène. L'exhumation des zones internes a eu lieu à partir du début de l'Oligocène en lien avec l'extrusion vers l'ouest de la plaque Adria. Les principales structures de plis et de chevauchements qui suivent la forme de l'arc sont dirigées vers l'avant ou vers l'arrière, et sont postérieures à l'empilement initial des nappes car elles se superposent à des déformations plus anciennes, orientées différemment. Ces structures anciennes doivent être prises en compte pour la restauration de cet orogène arqué si l'on veut éviter les problèmes de recouvrement au coeur de l'arc. Nous documentons cette phase initiale d'empilement par une analyse structurale à l'échelle de l'affleurement sur 55 sites entre les vallées de la Maurienne et de l'Ubaye, ainsi que par des exemples à plus grande échelle de structures anciennes. Ces données montrent de manière cohérente un transport tectonique initial de N à NW, dont les indicateurs cinématiques sont affectés par une déformation plus récente soit vers l'avant (orientée W à SW), soit vers l'arrière (orientée E à NE), cette dernière étant associée au transport post-nappe le long du chevauchement pennique. En conséquence, toute restauration du système de plis et de chevauchements du Briançonnais doit d'abord prendre en compte la reconstitution de l'empilement de nappes le long de la direction initiale de propagation orogénique N-NW, ainsi donc que l'origine paléogéographique méridionale de ces nappes. Cet empilement a été édifié lors de la collision Eocène Adria-Iberia avec une vergence N-NW, et a incorporé le bassin Subbriançonnais-Valaisan subduit avant d'impliquer l'avant-pays Delphino-Helvétique. Il comprend différents types d'unités paléozoïques, dont des sédiments permo-carbonifères vers sa base et des écailles de socle polymétamorphique au-dessus, ce qui peut s'expliquer par l'inversion d'un bassin tardi-varisque et de son épaulement méridional. Les unités de marge les plus hautes, dites Prépiémontaises, résultent de l'inversion précoce du pied de marge européenne. Des brèches mixtes, localement préservées le long du contact tectonique entre ces dernières unités et les nappes océaniques inférieures des "Schistes Lustrés", sont ici interprétées comme des olistostromes alimentés par ces unités juxtaposées à un stade très précoce de la collision. Les datations 39Ar/40Ar suggèrent que ces formations tectono-sédimentaires peu profondes ont été impliquées dans le biseau de subduction au cours de l'Eocène inférieur, alors que des olistostromes équivalents plus jeunes (Eocène tardif) marquent la propagation de la pile du Briançonnais sur l'avant-pays externe (Dauphiné/Helvetique). Le prisme orogénique éocène a été rapidement exhumé pendant l'indentation vers l'ouest et la propagation radiale de l'Oligocène, dans un contexte tectonique radicalement différent dominé par l'extrusion autour d'un indenteur de manteau supérieur adriatique, qui a contrôlé le développement de l'arc des Alpes occidentales en relation avec l'ouverture de la mer Ligure.