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We present new data from the debris-rich basal ice layers of the NEEM ice core (NW Greenland). Using mineralogical observations, SEM imagery, geochemical data from silicates (meteoric 10Be, εNd, 87Sr/86Sr) and organic material (C/N, δ13C), we characterize the source material, succession of previous glaciations and deglaciations and the paleoecological conditions during ice-free episodes. Meteoric 10Be data and grain features indicate that the ice sheet interacted with paleosols and eroded fresh bedrock, leading to mixing in these debris-rich ice layers. Our analysis also identifies four successive stages in NW Greenland: (1) initial preglacial conditions, (2) glacial advance 1, (3) glacial retreat and interglacial conditions and (4) glacial advance 2 (current ice-sheet development). C/N and δ13C data suggest that deglacial environments favored the development of tundra and taiga ecosystems. These two successive glacial fluctuations observed at NEEM are consistent with those identified from the Camp Century core basal sediments over the last 3 Ma. Further inland, GRIP and GISP2 summit sites have remained glaciated more continuously than the western margin, with less intense ice-substratum interactions than those observed at NEEM.

International audience; Hydrogen occurs at the near percent level in the most hydrated chondrites (CI and CM) attesting to the presence of water in the asteroid-forming regions. Their H abundances and isotopic signatures are powerful proxies for deciphering the distribution of H in the protoplanetary disk and the origin of Earth's water. Here, we report H contents and isotopic compositions for a set of carbonaceous and ordinary chondrites, including previously analyzed and new samples analyzed after the powdered samples were degassed under vacuum at 120 °C for 48 hours to remove adsorbed atmospheric water. By comparing our results to literature data, we reveal that the H budgets of both H-poor and H-rich carbonaceous chondrites are largely affected by atmospheric moisture, and that their precise quantification requires a specific pre-degassing procedure to correct for terrestrial contamination. Our results show that indigenous H contents of CI carbonaceous chondrites usually considered the most hydrated meteorites might be almost a factor of two lower than those previously reported, with uncontaminated D/H ratios differing significantly from that of Earth's oceans. Without pre-degassing, the H concentrations of H-poor samples (e.g., CVs chondrites) are also affected by terrestrial contamination. After correction for contamination, it appears that the amount of water in chondrites is not controlled by the matrix modal abundance, suggesting that the different chondritic parent bodies accreted variable amounts of water-ice grains. Our results also imply that (i) thermal metamorphism play an important role in determining the H content of both CV and ordinary chondrites but without affecting drastically their H isotopic composition since no clear D enrichment is observed with the increase of petrographic type and (ii) the D enrichment of ordinary chondrite organics does not result from the loss of isotopically light H2 induced by metal oxidation but is rather linked to the persistence of a thermally resistant D-rich component

International audience; The Indian monsoon and tectonic both control the Himalayan erosion. Tectonic generates uplift and maintain high elevation of the range and earthquakes weaken the mountain front. Monsoon seasonal intensity controls the glacier cover, landslide activity, river incision, vegetation cover, and export of sediments towards the floodplain. The monsoon also exerts a primary control on the chemical erosion as weathering rates are clearly dependent upon river discharge. In the floodplain, sediment export is also tightly controlled by climate. The seasonality and intensity of the monsoon generate discharge high enough to ensure the efficiency of river transport of sand-rich sediments to the delta and shelf (Lupker et al. JGR, 2011). IODP Expedition 354 allowed to drill a series of seven sites along an E-W transect at 8 • N in the Bengal fan. This generated a comprehensive record of Himalayan erosion since 20 Ma. Bengal fan sediments are dominated by turbidites characterised by high accumulation rate and variable grain size raging from clayey silt to sand. Plio-Pleistocene turbidites reveal frequent channel levee deposition with massive sand deposition in inter-levee intervals. Overall, sand represents at least a third of the fan deposition. Turbidites are intercalated with hemipelagic sediments characterised by low accumulation rates, 20 to 50% of biogenic carbonates, fine grains and bioturbation. Turbidites have petrographic and geochemical signatures characteristic of sediments derived from the Himalaya such as the Ganga and Brahmaputra rivers that supply the fan (see A. Galy et al. this session). Major and trace element geochemistry show relatively stable compositions throughout the Neogene and Quaternary. They reveal a very weak regime of chemical weathering with no significant variation through time. Concentrations in mobile elements such as Na and K relative to Al are significantly higher than in modern river and northern fan sediments. This suggests that weathering and/or soil erosion are amplified in the modern time. Detrital carbonate concentration vary significantly with higher concentrations during the Miocene then falling during the Plio-Pleistocene. This suggests either a change in the exposition of Tethyan series in Himalaya or significantly lower chemical weathering during Miocene. Finally, clay composition is dominated by illite which also differs with the present Ganga which is rich in smectite. The record at 8 • N contrasts with the ODP Leg 116 record at 1 • S in the distal fan, which from 7 to 1 Ma shows a high degree of weathering associated to lower accumulation rates. The record at 8 • N indicates that these variations do not reflect changes in the continental source basin but rather reflect a change in the turbiditic export. The Bengal Fan record at 8 • N suggests that an erosion regime dominated by physical erosion able to drive large amount of sand and silt with low weathering was established at least 20 Ma ago and remained relatively stable in spite of the global climate variations. These observations suggest that erosion sustained by a highly seasonal climate able to ensure rapid transport of sediments such as the monsoon was already active 20 Ma ago.

International audience; En Himalaya, la mousson et la tectonique de convergence Inde-Asie contrôlent directement l'érosion. La tectonique engendre la haute élévation de la chaîne et les tremblements de terre qui fragilisent l'ensemble. L'intensité de la mousson contrôle la couverture glaciaire, les glissements de terrain, l'incision, la couverture végétale et l'export des sédiments vers la plaine. La mousson contrôle également l'intensité de l'érosion chimique. Dans la plaine, la saisonnalité et l'intensité de la mousson permettent d'atteindre des débits suffisamment élevés pour assurer l'efficacité du transport sédimentaire vers le delta. Ce transport rapide est également un facteur limitant de l'altération en réduisant le temps de séjour dans la plaine. Ces sédiments sont ensuite exportés vers la baie du Bengale ou ils alimentent le plus important système turbiditique de la planète. L'Expédition IODP 354 a foré le Cône du Bengale en 2015 et a restitué un enregistrement quasi continu de l'érosion de l'Himalaya au cours du Néogène et du Quaternaire (France-Lanord et al. 2016). Les sédiments sont principalement composés de turbidites issues du bassin du Gange-Brahmapoutre. L'Expedition 354 a foré un transect E-W de sept Sites sur 320 km à 8° N afin de couvrir autant que possible les déplacements de dépocentre. Le site le plus profond U1451, atteint la base du cône datant un début de sédimentation turbiditique vers 20 Ma sur le flanc de la ride Ninetyeast. Les sédiments présentent des analogies minéralogiques, géochimiques et isotopiques avec les sédiments modernes du Gange-Brahmapoutre. La variabilité interne révèle que les turbidites ne sont pas en permanence un mélange des deux fleuves. Au Quaternaire, il est évident que le Brahmapoutre était parfois la seule source de turbidites. La géochimie des éléments majeurs et des éléments traces montre des compositions relativement stables tout au long du Néogène et du Quaternaire. Ils révèlent un très faible régime d'altération sans variation significative dans le temps. Ces données comparées à celles des sédiments modernes du Gange et du Brahmapoutre impliquent que l'altération ou l'érosion des sols est amplifiée par la pression anthropique. Au plan paléoenvironnemental, les compositions isotopiques d'hydrogène et de carbone des cires foliaires datent l'expansion connue des plantes de type savane (C4) dans le bassin vers 6 Ma et montrent que depuis le Miocène les paléoprécipitations sont fortement appauvries en deutérium. Ce point implique que dès le Miocène, le régime de mousson indienne est établi, le Pléistocène étant marqué par une augmentation de la variabilité. Les paléoconcentrations en 10 Be du quartz ont pu être appliqués pour la première fois sur des sédiments marins détritiques pour déduire les vitesses d'érosion. Elles démontrent une stabilité depuis le Miocène supérieur qui implique que la mise en place de l'alternance glaciaire interglaciaire a eu un impact limité sur l'intensité de l'érosion en Himalaya.

International audience; Stable isotopic studies (H and O) have been continuously performing from the major large rivers like Kosi and Narayani as well as their small tributaries to understand the water cycle from yearly isotopic record in relation with direct precipitation. Here we present a set of data, mostly from the southern Himalayan flank, including daily sampling of rivers in Narayanghat, Khudi, Marshyandi, Trisuli and Kosi as well as precipitation water data since the pre-Gorkha Earthquake (Mw 7.8) of 25 April 2015. For the precipitation at a given location, data are marked by strong seasonal contrast (e.g. Zhang et al. 2001, Gajurel et al. 2006) probably related to source of moisture and amount effect.Strong seasonality in oxygen isotopic composition of river water (4-5‰) in the catchment of Narayani River in the Himalaya in 2010 is recorded. In contrast, the composition evolves much more stable with a slight tendency to increase during the monsoon in 2015. The Kosi data set of 2015 shows a variation in δ18Osmow from -12‰ to -8‰, and for the δDSMOW from -80‰ to -50‰ (Fig. 1). The data set situated on line δD = 7.7 × δ18O + 7.7‰) is close to the GMWL. The seasonal trend in δ18O generates an offset particularly between June-July and August that influence on river isotopic composition. The river isotopic compositions are progressively depleted in heavy isotopes during the monsoon reflecting the seasonal evolution of precipitation, however, it is buffered by the ground water reservoir. At the beginning and end of the monsoon, the contrast between precipitation and ground water is large and precipitation events generate scattered river variations depending on direct runoff to ground water supply, however, such trend is not always observed particularly after 2015 Gorkha earthquake.

International audience; Since the Oligocene, the Himalayan erosion drives one of the most important detrital flux to the oceans. More than 500 Mt of sediments are transferred annually from the Bangladesh delta to the shelf and submarine canyon, the Swatch of No Ground. From the canyon, turbidity current drive sediments along channel levees and disperse sediment over 3000 km south of the delta. On land, the Ganga river and its main tributaries export particulate carbonate resulting from the physical erosion of limestone, marls and marble present mainly in the Tethys Himalaya and lesser Himalaya. In spite of high runoff, these rivers reach carbonate saturation and export particulate carbonate to the ocean. The modern river system exports ≈ 3 wt% of calcite and dolomite, and comparable concentrations are observed in Holocene sediments from the Northern Bay of Bengal. Detrital carbonates are easily sorted from marine carbonates thanks to their low  18 O and high 87 Sr/ 86 Sr acquired during metamorphic stage. Their proportion increase in LGM sediments, likely reflecting weaker conditions of weathering during this period [1-2]. Recent IODP Exp. 354 on the Bengal Fan documented Himalayan derived turbiditic sedimentation at 8°N/≈3600 mbsl over the whole Neogene. There, large variations of detrital carbonate proportion are observed with maxima around 10 wt% reached during the upper Miocene. Analyses of the carbonate load also reveal the minor presence of biogenic carbonates, and the significant presence of diagenetic carbonates. They are characterized by high  18 O around-2‰ PDB, low  13 C ≈-8‰ and 87 Sr/ 86 Sr near seawater composition. Their occurrence and proportion are closely associated with the fine clay fraction of the sediments. The average concentration of this diagenetic component is 1.2 wt% and it can reach 4 wt% in clay-rich samples. Pore-water compositions suggest that they were not produced in situ. Rather they may be produced up-fan and incorporated in the tubiditic mixing. 1 Lupker, M. et al. 2013

One of the major challenges in Earth Sciences during the last decades has been to improve our knowledge of the interaction between the different components of the Earth System. Key aspects to improve the understanding of these processes are the acquisition of new data and the development of models to explain both mass and energy transfer between the deep and superficial components of the Earth system. The goal of this thesis is to study these transfers through the geochemical cycle of volatile elements trapped in fluid inclusions of various materials of the Earth crust. The first part of my work presents experimental study of halite. The study of oxygen isotope fractionation and equilibrium kinetics between H2O and CO2 during the evaporation of brines shows that corrections have to be made on the oxygen isotope measurements for high salinity solutions. The elaboration of an experimental protocol to form halite in controlled environment reveals the potential of fluid inclusions for palaeo climatic reconstructions. Combination of microthermometric data plus hydrogen and oxygen isotopic compositions of aqueous inclusions allows to estimate the sources and the temperature of the parental water of halite as well as the wind speed at the water-air interface during the crystal growth. This method was then applied to the Messinian halite deposits of Sicily. The second part of my work is dedicated to the identification of both the chemical compositions and the sources of fluids circulating in the crust and at the interface crustmantle through the analysis of isotopic compositions of fluid inclusions in granites and granulites., Un des enjeux majeurs en Science de la Terre ces dernières décennies est de comprendre les interactions entre les différentes enveloppes terrestres. Le but poursuivi par ce travail est d’aborder quelques aspects de ces interactions du point de vue des cycles géochimiques des éléments volatils H2O et CO2 en se basant sur l’étude des inclusions fluides piégées dans des roches variées de la croûte terrestre, depuis sa surface jusqu’à l’interface croûte–manteau. La première partie de mon travail présente des travaux expérimentaux effectués sur de la halite. L’étude du fractionnement isotopique de l’oxygène et des cinétiques d’équilibration entre H2O et CO2 lors de l’évaporation de saumures a montré l’importance des corrections à effectuer sur les mesures isotopiques de l’oxygène pour des solutions de haute salinité. L’élaboration d’un protocole expérimental de précipitation de halite en milieu contrôlé a permis de mettre en évidence le potentiel des inclusions fluides pour les reconstitutions paléoclimatiques. La combinaison des données microthermométriques et des compositions isotopiques de l’hydrogène et de l’oxygène des inclusions aqueuses permet d’estimer les sources et la température de l’eau de formation de la halite ainsi que la vitesse du vent à l’interface eau-air pendant la croissance du cristal. Cette méthode a été ensuite appliquée aux dépôts de halite de Sicile datés du Messinien. La deuxième partie de mon travail est consacrée à l’identification des compositions chimiques et des sources des fluides circulant dans la croûte et à l’interface croûte-manteau à travers l’analyse des compositions isotopiques des inclusions fluides des granites et granulites.