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The PhD work aims at studying the role of volcanism in influencing winter climate variability (especially, NAO) over the North Atlantic-Mediterranean sector at inter-annual scale. The first part is devoted to characterizing the simulated NAO signal in winters following stratospheric volcanic eruptions using three long transient simulations of the past millennium (500-1849 CE) by IPSL-CM6A-LR in the frame of PMIP4. The robustness and sensitivity of the response related to the latitude, season and strength of the eruptions are also explored. The second part extends further to decrypt the physical mechanism regarding different components of volcanic radiative forcing (the surface cooling and stratospheric warming). The work focuses on three 25-members ensemble simulations by IPSL-CM6A-LR following the VolMIP protocol for the well observed Mt. Pinatubo tropical eruption (Philippines, June 1991). Sensitivity experiments indicate that the surface positive NAO signature in our model experiments is primarily attributable to heating in the lower tropical stratosphere which generates stronger subtropical zonal winds through the thermal wind balance and accelerates the polar vortex. Stationary planetary wave propagations are also playing indispensable modulations effects., La thèse vise à étudier le rôle du volcanisme ainsi ses impacts sur la variabilité climatique hivernale (spécialement l'ONA) dans le secteur Atlantique Nord-Méditerranée à l'échelle interannuelle. La première partie est consacrée à la caractérisation du signal d'ONA en hiver à la suite d'éruptions volcaniques stratosphériques grâce à trois simulations transitoires du dernier millénaire (500-1849 CE) par IPSL-CM6A-LR dans le cadre de PMIP4. La robustesse et la sensibilité de réponse liée à la latitude, la saison et la magnitude des éruptions sont ainsi explorées. La deuxième partie étend plus loin pour décrypter le mécanisme concernant différentes composantes radiatives du forçage volcanique (le refroidissement de la surface et le réchauffement du stratosphère). Le travail est axé sur trois 25-membres ensembles de simulation par IPSL-CM6A-LR suivant le protocole VolMIP sur l'éruption tropicale Mt. Pinatubo (Philippines, juin 1991), la meilleure observée. Les expériences de sensibilité indiquent que la signature d’ONA positive de surface dans nos expériences de modèle est principalement attribuée au réchauffement dans la basse stratosphère tropicale qui génère des vents zonaux subtropicaux plus forts à travers le bilan de vent thermique et accélère le vortex polaire. Les propagations d'ondes planétaires stationnaires jouent également des effets de modulations indispensables.

Basaltic caldera-rift systems provide unique opportunities to study a range of volcanic processes, including lateral magma transport, caldera collapse, and magma replenishment. Some of the largest basaltic calderas in the world, however, are located in dangerous or difficult- to-access regions. In such regions, remote sensing measurements of ground deformation, degassing, and thermal anomalies offer alternative means to assess volcanic activity. Ambrym, an exceptionally active, basaltic volcanic island in Vanuatu has undergone numerous episodes of ground deformation over the past 20 years. Since 2015, two eruptions have occurred within its 12 km wide caldera. The first event, a moderate-sized eruption in February 2015, occurred after more than 15 years of persistent degassing and lava lake activity, punctuated by intervals of quiescence. It activated a portion of the caldera-ring fault and drained a reservoir located ∼4.1 km depth b.s.l. The most recent event, which occurred in December 2018, was significantly larger. This event drained the main craters’ lava lakes and intruded >0.4 km3 of magma into the SE rift zone. The dike travelled more than 20 km away from the main craters, and had an opening of >4 m at depth. Magma drainage from a central storage region caused widespread caldera subsidence and ring-fault activation, and resulted in the eruption of basaltic pumice offshore. These two events confirm that Ambrym’s caldera ring-faults are active structures. Ring- fault reactivation may contribute to continued deepening of Ambrym’s large caldera, whose formation mechanism is contested. Some authors [Robin et al., 1993] propose that caldera ring-faults were formed by an initial Plinian eruption and subsequent phreatomagmatic eruptions. Ring-fault activation detected with Interferometric Synthetic Aperture Radar (InSAR) allows us to hypothesize that hundreds of moderate- to- large sized dike intrusions may contribute to further deepening of the caldera by draining magma from one of Ambrym’s numerous magma lenses. Separate from these main eruptive events, we document two inter-eruptive episodes of fast subsidence measured with InSAR (2004 – 2007 and 2015 – 2017, ∼10 cm year-1). Neither of these time periods are associated with recorded eruptions. Inter-eruptive subsidence is challenging to interpret without additional constraints. Using the understanding gleaned from the 2015 and 2018 eruptions, we investigate possible physical mechanisms explaining these deformation signals. We conclude that the 2004 – 2007 episode is most likely due to a dike intrusion accompanied by depressurization of the shallow sill hydraulically connected to the lava lakes. This interpretation is drawn from the joint analysis of ground deformation, SO2 gas emissions, and thermal anomalies. We then hypothesize that the 2015 – 2017 subsidence episode may be due to degassing-induced depressurization of a large (>10 km3) magmatic reservoir, using a theoretical model developed by Girona et al. [2014] to couple degassing and reservoir depressurization.To investigate the role played by replenishment of the system, two periods of uplift have been identified. Variations in thermal anomalies and SO2 degassing complement displacement measurements, allowing for more robust interpretations of the volcanic deformation episodes. At Ambrym, uplift during replenishment may be limited to time periods when the system is closed, such as after lava lake drainage in 2019 – 2020 and perhaps in 2007 – 2010, following the previously unreported diking event in 2005. Remote sensing data has allowed us to analyse the activity of Ambrym volcano over the past two decades. By comparing Ambrym’s unrest with that of other calderas (Kīlauea, Bárðarbunga, Sierra Negra, etc.), the results obtained in this dissertation can further our understanding of basaltic caldera-rift systems and their underlying magmatic plumbing systems., Les systèmes volcaniques rift-caldera basaltiques fournissent les conditions propices à l’étude de plusieurs processus volcaniques, comme le transport de magma, les effondrements de caldera et le remplissage magmatique. Certaines des plus grandes calderas dans le monde, cependant, sont situées dans des régions isolées dont l’accès peut être dangereux ou logistiquement complexe. La télédétection des déformations du sol, du dégazage et des anomalies thermiques, offre une alternative pour y suivre l’activité volcanique. Ambrym, une île volcanique du Vanuatu isolée mais très active, a subi de nombreux épisodes de déformation du sol au cours des 20 dernières années. Depuis 2015, deux éruptions ont eu lieu à l’intérieur de sa caldera de 12 km de diamètre. La première éruption a eu lieu après 15 ans de dégazage passif et d’activité des lacs de lave. L’éruption la plus récente, en décembre 2018, a vidangé les lacs de lave des cratères sommitaux, provoquant l’intrusion d’un volume >0.4 km3 dans la zone de rift sud-est. Le dike engendré a parcouru une distance de plus de 20 km, et s’est ouvert de plus de 4 mètres en profondeur. La vidange du magma a produit une subsidence de la caldera à grande échelle, associée à une activation des failles bordant la caldera, et a alimenté une éruption sous-marine de ponces basaltiques. Une éruption plus modeste a eu lieu en février 2015, activant également une portion de la caldera, et extrayant du magma depuis une chambre située à une profondeur de ∼4.1 km. Ces deux événements confirment que les failles bordières de la caldera d’Ambrym sont des structures actives. L’activité de ces failles contribue à la topographie de la caldera d’Ambrym, dont le mécanisme de formation est discuté (éruption Plinienne initiale à 2ka, suivie d’éruptions phréatomagmatiques). La détection d’une activation des failles de caldera par la géodésie spatiale nous permet de formuler l’hypothèse que des centaines d’intrusions de tailles modérées à grandes peuvent contribuer à un approfondissement de la caldera, en drainant le magma stocké temporairement sous la caldera d’Ambrym. Outre ces deux événements éruptifs majeurs, nous mettons en évidence deux épisodes (2004–2007, 2015–2017) de subsidence rapide (∼10 cm an-1), mesurés par InSAR. Aucune de ces deux périodes n’est associée à une éruption répertoriée. A partir des informations glanées au cours des éruptions de 2015 et 2018 (e.g., la profondeur des zones de stockage, le volume des intrusions, la relation entre l’activité éruptive et les lacs de lave), nous explorons les mécanismes physiques pouvant expliquer cette subsidence inter-éruptive. L’épisode de 2004–2007 est probablement associé à une intrusion de dike (en l’absence d’éruption), engendrant la dépressurisation d’un sill superficiel, hydrauliquement connecté aux lacs de lave. A partir d’un modèle théorique proposé par Girona et al, 2014, en couplant le dégazage passif (mesuré par spectroscopie satellitaire) et la dépressurisation du réservoir magmatique (déduite de la géodésie spatiale), nous proposons que l’épisode de 2015–2017 ait pour origine la dépressurisation d’un réservoir magmatique de grande taille (>10 km3). Par contraste, de courtes périodes de soulèvement pourraient être limité aux périodes de temps pendant lesquelles le système est fermé, par exemple en 2019–2020 après l’épisode de vidange des lacs de lave en 2018, et potentiellement en 2007–2010 à la suite d’un événement d’intrusion non répertorié en 2005. En comparant les phases de regain d’activité d’Ambrym avec celles observées dans les autres systèmes rift-caldera basaltiques (Kīlauea, Bárðarbunga, Sierra Negra, etc.), les résultats obtenus dans cette dissertation permettent de mieux comprendre l’activité des lacs de lave, le développement de la caldera, les processus de déformation induits par le dégazage, le remplissage magmatique, et la géométrie et le fonctionnement des systèmes rift-caldera basaltiques.

International audience; The Tambora eruption (1815 AD) was one of the major eruptions of the last two millennia and has noequivalents over the last two centuries. Here, we collected an extensive network of earlymeteorological time series, climate simulation data and numerous, well-replicated proxy records from Eastern Canada to analyze the strength and the persistence of the Tambora impact on the regional climate and forest processes. Our results show that the Tambora impacts on the terrestrial biosphere were stronger than previously thought, and not only affected tree growth and carbon uptake for a longer period than registered in the regional climate, but also determined forest demography and structure. Increased tree mortality, four times higher than the background level, indicates that the Tambora climatic impact propagated to influence the structure of the North American taiga for several decades.We also show that the Tambora signal is more persistent in observed data (temperature, river ice dynamics, forest growth, tree mortality) than in simulated ones (climate and forest-growth simulations), indicating that our understanding of the mechanisms amplifying volcanic perturbations on climates and ecosystems is still limited, notably in the North American taiga.

Mt. Vulture volcano is located on the thrust front of the southern Apennines. Its mid-Pleistocene products are spread southeastward in the adjacent Bradano foredeep basin. The stratigraphic record of the volcano within the Quaternary sedimentary successions helps to better understand the paleo-environmental setting of the foredeep. Volcaniclastic deposits cropping out close to the edifice, tephra levels and associated paleosols recovered from the southernmost sector of the foredeep are of key importance in reconstructing the Pleistocene morpho-climatic conditions in which they formed, using a multiproxy approach. Geomorphological observations and stratigraphic sampling come from the Venosa lacustrine-alluvial basin and from the areas of Irsina and Pomarico villages, where pumice fall levels and related paleosols are present at the top of the lower-middle Pleistocene sedimentary succession. Geochemical and mineralogical analyses of paleosols and pyroclastic rocks have indicated that the Pomarico pumices, reworked and deposited in an alluvial environment, could be likely correlated to the Fara d'Olivo ignimbrites (39Ar/40Ar age

International audience; The first Vanuatu archaeological site discovery dates back to the 1960s, then the scientific and archaeological knowledge of this archipelago have increased. Nevertheless, the human activities–palaeoenvironmental changes relation in Vanuatu is still a matter of debate. In order to better determine this relation, reviewing the literature on past and actual environment is needed. This paper presents here a state of knowledge on Vanuatu geology, climate, biodiversity and archaeology, from the mid-Holocene to our present-day. The young archipelago results from strong volcanic and tectonic activity, due to the active subduction zone between Australian and Pacific plates. The atmosphere–ocean interactions determine the wet and dry seasons. Fauna and flora are principally derived from Southeast Asia. The occurrence of several species and subspecies endemic to the archipelago, if not to some islands, is probably due to the Vanuatu isolated location, the size of the islands and the climatic gradient between north and south. The first human populations reached the archipelago around 3200 yr BP. The Lapita culture, characterized by decorated potteries, is shared across the whole Vanuatu between 3200 and 2900 yr BP. After 2900 yr BP, cultures differ from one island to another. After 600 yr BP, the Polynesian culture dominates in Vanuatu.; La découverte des premiers sites archéologiques du Vanuatu remonte aux années 1960. Depuis, les connaissances scientifiques et archéologiques sur cet archipel ont grandement augmenté. Cependant, les relations entre l’Homme et les différents changements paléoenvironnementaux du Vanuatu restent un sujet débattu. Afin de mieux décrire ces relations, il est important de faire un point sur ce que nous savons des environnements passés et présents. Cet article présente donc un état des lieux des connaissances sur la géologie, le climat, la biodiversité et l’archéologie du Vanuatu, de l’Holocène moyen jusqu’à nos jours. L’archipel du Vanuatu est relativement jeune et issu d’une forte activité volcanique et tectonique de la zone de subduction entre la plaque Pacifique et la plaque Australie. Le climat est majoritairement influencé par les relations atmosphère–océan Pacifique, déterminant les saisons humides et sèches. La faune et la flore sont principalement originaires d’Asie du Sud-Est mais l’isolement de l’archipel, la taille des îles et le gradient climatique entre le nord et le sud sont à l’origine de la présence de certaines espèces et sous-espèces endémiques à l’archipel, voire à quelques îles. Les premières populations humaines n’ont atteint l’archipel qu’autour de 3200 ans BP. Entre 3200 et 2900 ans BP, la culture Lapita, caractérisée par des poteries très décorées, est commune à tout le Vanuatu. Après 2900 ans BP, les cultures divergent et diffèrent d’une île à une autre. À partir de 600 ans BP, la culture polynésienne domine au Vanuatu dans les îles du centre et du sud.

Miocene arc volcanism is manifested widely in the Valle del Cura-El Indio belt region (29°30´–30° South latitude), in the southern Central Andes of Argentina and Chile. The magmas that fed this volcanism are well represented by the Cerro de las Tórtolas Formation, which is divided into two volcanic episodes based on petrographic, chemical and age differences: an older basaltic-andesitic event (16–14Ma) and a younger andesitic to dacitic (13–10Ma) one. Representative plagioclase, orthopyroxene, clinopyroxene and amphibole phenocrysts from rock samples already characterized from geochemical and isotopic viewpoints were selected for electron microprobe determination of mineral chemistry. Results indicate an overall homogeneous composition for each of the mineral phases. Equilibrium temperatures were estimated through two-pyroxenes, amphibole-plagioclase and amphibole geothermometers, which show a consistent temperature range between 970 to 850°C. Equilibrium pressure calculated using amphibole composition for volcanic suites produced the most comprehensive results for pressure equilibrium conditions, with results close to 4kb. Changes in the residual mineral assemblages and variations in isotopic signatures indicate that primary magmas were equilibrated at the lower crust with a gradual increase of crustal thickness. These melts evolved towards intermediate magma chambers, where crystallization of phenocrysts occurred at the same temperature and pressure conditions, hence, no increase in depth of intermediate magma chambers is registered although the increase of crustal thickness registered from Lower to Middle Miocene times.

This chapter summarizes the principal experimental and theoretical approaches used to investigate the physics of pyroclastic density currents (PDCs), which are gravity driven hot gas–particle mixtures commonly generated during explosive volcanic eruptions. PDC behavior ranges from pyroclastic surges, which are dilute turbulent suspensions, to pyroclastic flows, which are dense (fluidized) granular avalanches. Most PDCs consist of a coupled basal flow and an overriding surge, which renders their physics particularly complex. Experiments and phenomenological theory have been used to characterize the propagation and deposition mechanisms of PDCs. Most work has used turbulent gravity currents as an analogue to dilute PDCs and has provided fundamental insight into propagation and deposition dynamics and mixing with their surroundings. Dense PDCs have been investigated as granular and fluidized flows, and these studies have provided insight into deposit levée-channel morphology typical of coarse-grained flows, shown that fines-rich flows may behave as inertial fluid currents, and suggested that deposits of PDCs may form by aggradation. Numerical formulations ranging from continuum depth-averaged to discrete element models have been used to simulate PDC emplacement on real topographies and are fundamental in the context of volcanic hazard assessment and mitigation.

International audience; Gravimetric and geologic data show that the reactivation of the Neogene Interandean depression and/or the ~75 - 65 Ma ophiolite suture into the modern dynamic of the Andes controlled the Gulf of Guayaquil Tumbes basin (GGTB) location and evolution during the past 1.8 - 1.6 Myr at least. Depending on whether the remobilization occurred along the in- terandean depression or the ophiolite suture, the GGTB evolved trough pure or simple shear mechanisms, respectively. Because the GGTB exhibits an along strike tectonic asymmetry associated with a pervasive seismic gap, the simple shear solution is more likely. Tectonic inversion occurred along a mid-crust detachment (the Mid-Crust detachment hereafter) matching the ophiolite suture that accommodates the North Andean Block (NAB) northward drift. The so-called Decoupling Strip located at the shelf slope break accommodated the tensional stress rotation from N-S along the shelf area i.e. NAB-drift induced to E-W along the continental margin i.e. subduction-erosion-induced. The land- ward dipping Woollard detachment system located at the Upper-Lower slope boundary connects the subduction channel at depth, allowing the Upper slope to evolve independently from the Lower slope wedge. The long-term recurrence in- terval between earthquakes, the strong interplate coupling, and the aseismic creeping deformation acting along the main low-angle detachments i.e. the Woollard and the Mid-Crust detachments may account for the pervasive seismic gap at the GGTB area. Because the subduction channel exhibits no record of significant seismic activity, no evidence exists to establish a link between the GGTB sustained subsidence and a basin-centered asperity. Because the GGTB is a promis- ing site of hydrocarbon resources, to understand processes at the origin of this escape-induced forearc basin has a major economic interest.

Resume L’ouvrage de Faujas de Saint-Fond (1778) , Recherches sur les volcans eteints du Vivarais et du Velay , comporte six Lettres d’un enigmatique abbe de Mortesagne. L’examen d’archives a permis de l’identifier comme etant Gui de Mortessagnes et de determiner les circonstances qui ont conduit ce jesuite a d’originales observations sur le volcanisme du haut Vivarais et Velay. Comme l’atteste un acte portant leurs deux signatures, la rencontre initiale entre Faujas et Mortessagnes eut lieu en 1767, a Montelimar. Ancien professeur de physique au College de Montpellier, Mortessagnes fut initie a la geologie dans le bas Vivarais, par Faujas dont il completera le travail en explorant le haut Vivarais et le Velay. Faisant preuve d’un grand sens de l’observation des produits volcaniques et de leurs contextes, il agita des idees sur la nature des basaltes, leurs interactions avec les sediments et eut meme recours a l’experience pour demontrer la fusibilite des basaltes.

The comparison of two shallow ice cores recovered in 1999 and 2000 from the same place on Chimborazo summit glacier revealed the influence of the coincident Tungurahua volcanic eruption on their stable isotope and chemical records. The surface snow melting and water percolation induced from the ash deposition caused a preferential elution and re-localization of certain ionic species, while the stable isotope records were not very affected. Additionally, the comparison of the ionic amount and some selected ratios preserved along the ice core column reports under which processes the chemical species are introduced in the snow pack, as snow flake condensation nuclei, by atmospheric scavenging or by dry deposition. This preliminary study is essential for the interpretation of the deep Chimborazo ice core, or for other sites where surrounding volcanic activity may disturb the glaciochemical records.

We investigated past climate variability and the zonal short and long-range transport of air masses in tropical South America using chemical, isotopic and palynological signals from a 42 m-long ice core recovered in 2003 from the saddle of the Nevado Coropuna, southern Peru (72°39´ W; 15°32´ S; 6080 m a.s.l.). We found that precipitation at this site depends mainly on the easterly circulation of air masses originated from the tropical Atlantic Ocean. Nevertheless, sporadic Pacific air masses arrivals, and strong cold waves coming from southern South America reach this altitude site. In spite of post-depositional effects, we were able to identify two strong ENSO (El Niño-Southern Oscillation) event signatures (1982–1983 and 1992) and the eruptive activity of the nearby Sabancaya volcano (1994).

The ambiguity in the genetic interpretations in the formation of the Mo&U deposits of the Streltsovsky ore field led us to perform additional studies which have established that closely associated U and F were progressively gained in the Late Mesozoic volcanic rocks from the older basic (170 Ma) to the younger silicic ones (140 Ma). The Early Cretaceous postmagmatic hydrothermal epoch (140-125 Ma) is subdivided into preore, U ore, and first and second postore stages. The primary brannerite-pitchblende ore was formed associated with fluorite. During the first postore stage, it was replaced by a U-Si metagel, previously identified as coffinite. The preore metasomatic alteration and related veined mineralization were formed under the effect of Na (bicarbonate) chloride solution at temperatures of 250-200°C. Uranium ore formation began with albitization and hematization of rocks affected by a supercritical fluid at 530-500°C; brannerite and pitchblende precipitated at 350?300°C. The chondrite-normalized REE patterns of pitchblende hosted in trachybasalt, trachydacite, and granite demonstrate a pronounced Sm-Nd discontinuity and a statistically significant tetrad effect of W type. These attributes were not established in REE patterns of rhyolites derived from the upper crustal magma chamber. These data and the gap of 5 Ma between silicic volcanism and ore formation do not allow us to suggest that U was derived from this magma chamber. According to the new proposed model, an evolved silicic Li-F magma was a source of U. U4+, together with REE were fractionated into the fluids as complex fluoride compounds. The U mineralization was deposited at a temperature barrier., Les nouveaux travaux que nous avons réalisé nous ont permis d'établir que U et F on été progressivement enrichis depuis les volcanites basiques (170 Ma), jusqu'aux volcanites acides (140 Ma). L'épisode hydrothermal post-magmatique Crétacé (140-125 Ma) a été subdivisé en stades: préminéralisation, synminéralisation et les premier et deuxième stades post-minéralisation. La minéralisation primaire à brannérite-pechblende est associée avec la fluorite. Lors du premier stade postminéralisation les minéraux d'U ont été remplacés par des méta-gels U-Si antérieurement identifiés comme de la coffinite. L'altération anté-minéralisation et la minéralisation U ont été formées par des fluides chlorurés et bicarbonatés sodiques entre 250 et 300°C. La minéralisation U a commencé avec une albitisation et une hématisation de l'encaissant lors de la percolation d'un fluide supercritique à 530-500°C. Brannérite et pechblende ont précipité vers 350-300°C. Les spectres des éléments des terres rares (ETR) de la pechblende localisée dans les trachybasaltes, trachydacites et granites ont une forte anomalie positive en Sm et Nd et un effet tétrade W marqué, caractéristiques différentes de celles des rhyolites dérivées d'une chambre magmatique localisée dans la croûte supérieure. Ces données et l'intervalle de 5 Ma séparant le magmatisme siliceux de la formation de la minéralisation U ne permet pas de proposer que l'U dérive de cette chambre. Nous proposons qu'un magma acide riche en Li et F est la source de l'U. U(IV) ainsi que les ETR ont été fractionnés dans les fluides comme complexes fluorés. La minéralisation U a été déposée au niveau d'une barrière thermique

Bermudan and Bahamian Quaternary deposits are characterized by the alternation of carbonates and paleosols. Up to now, atmospheric material, especially Saharan dust, was considered as the main component of the pedological formations. XRD analyses revealed that the mineralogical assemblage of the Bermuda paleosols predominantly includes carbonates, clay minerals (kaolinite, chlorite and chlorite/vermiculite), phosphates, aluminium and iron oxides/hydroxides. It is strikingly close to the mineralogy of the altered Bermuda volcanic seamount, but noticeably different from the mineralogy of Saharan dust. Moreover, volcanic lithoclasts are found in numerous paleosol profiles all over the archipelago, in all the recorded time intervals. We thus consider the volcanic seamount as the main source of non-carbonate minerals detected in the paleosols. The atmospheric dust reaching Bermuda all along the Quaternary period is probably diluted by the local flux of insoluble residues and remains undetectable by the XRD method. Carbonates dominate Bahamian paleosols mineralogical assemblage. Recent formations contain kutnahorite, older hydrotalcite. We carried out a comparative study on the evolution of the San Salvador and Eleuthera paleosols mineralogy. It is supported by the speciation model CHESS. It demonstrates that soil evolution is driven by the local platform physiography and by the substratum mineralogy. The clay assemblage from Bahamian paleosols and marine sediments is inherited from North African and probably from North American sources (Mississippi Valley Loess)., Les îles des archipels des Bermudes et des Bahamas sont caractérisées par l'alternance de dépôts carbonatés et de paléosols. L'origine de ces formations a été rapportée à l'accumulation puis à l'altération des poussières sahariennes. La minéralogie des paléosols des Bermudes est composée de carbonates, de minéraux argileux, de minéraux phosphatés et d'oxydes et hydroxydes de fer et d'aluminium. Le cortège argileux est composé de kaolinite, de chlorite et d'interstratifiés chlorite/vermiculite. Son analyse montre que le matériel à l'origine des paléosols provient de l'édifice volcanique sous jacent. L'apport volcanique est renforcé lors des périodes de bas niveau marin. Le matériel est soufflé sur l'île où il subit alors l'altération pédologique. Le taux d'accumulation du matériel volcanique était probablement supérieur au taux d'altération par pédogenèse. Le flux de particules atmosphériques d'origine saharienne demeure invisible. La minéralogie des paléosols d'Eleuthera (Bahamas) est dominée par les carbonates. Les formations récentes contiennent de la kutnahorite ; les formations anciennes contiennent de l'hydrotalcite. L'étude comparative des paléosols de San Salvador et d'Eleuthera montre que l'évolution des unités pédologiques est liée à leur capacité à lessiver leur contenu carbonaté. Ce facteur est contrôlé par la structure de la plate-forme sous-jacente ou par la nature du substratum. Le cortège argileux des paléosols et des forages marins des Bahamas présente une forte teneur en illite qui traduit l'importante des apports nord sahariens alors que sa teneur élevée en chlorite illustre l'existence d'une composante nord-américaine.

International Conference : Fire Between Air and Water, Volcanic islands in science and myth, Preservation and Valorisation. Lipari, september 2002. Résumé.; If recent huge projects in Auvergne, as Vulcania near Clermont-Ferrand for example, try to use vulcanism as a matter of sustainable local development, attracting either seasonal touristic flow or all-year academic activities, the remote highlands of Velay begin to discover that archaeology and vulcanism make an original combination to increase interest of populations and can be a key for sustainable rural development.