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Le projet se concentre principalement sur les oliviers du Liban, où deux anciennes oliveraies sont sélectionnés. Plusieurs méthodes sont utilisées : les isotopes stables du carbone, de l'azote, de l'oxygène et de l'hydrogène pour évaluer les changements climatiques et environnementaux passés enregistrés par l'arbre ; les teneurs en mercure et les isotopes pour retracer la pollution dans les arbres ; la tomographie à rayons X pour évaluer la largeur et la structure périodique des cernes de l'arbre ; la datation au radiocarbone pour aider à faire correspondre les âges aux différentes méthodes utilisées. Ce projet aborde les questions environnementales à différents niveaux, à la fois dans l'espace et dans le temps, et utilise des approches interdisciplinaires pour établir des liens entre l'hydrologie, l'écologie et la biogéochimie des oliviers monumentaux dans la région de la Méditerranée orientale. En intégrant les enregistrements passés, cette étude vise à examiner les conditions actuelles des oliviers monumentaux, à étudier leur persistance et leur adaptation à travers les variations environnementales et climatiques de l'histoire, et à présenter un modèle qui pourrait nous aider, ainsi que les recherches futures, à anticiper et à prévoir les écarts climatiques.; The project mainly focuses on olive trees of Lebanon, where two ancient olive groves areselected. Multiple proxies are used: stable isotopes of carbon, nitrogen, oxygen and hydrogen to assess the past climatic and environmental changes recorded by the tree; mercury contents and isotopes to trace the pollution in the trees; X-Ray CT scan tomography to assess the width and periodic structure of tree rings; radiocarbon dating to help match the ages to the different used proxies. This project tackles environmental issues at different levels, both spatially and temporally, and uses interdisciplinary approaches to relate between the hydrology, ecology and biogeochemistry of monumental olive trees in the eastern Mediterranean region. Through integrating past recordings, this study aims to examine the present conditions of monumental olive trees, to study their persistence and adaptation throughout history’s environmental and climatic variances, and to present a model that may assist us and future researches to anticipate and predict climatic discrepancies.

International audience

Partie B; International audience; Incidental zinc sulfide nanoparticles (nano-ZnS) are spread on soils through organic waste (OW) recycling. Here we performed soil incubations with synthetic nano-ZnS (3 nm crystallite size), representative of the form found in OW. We used an original set of techniques to reveal the fate of nano-ZnS in two soils with different properties. 68 Zn tracing and nano-DGT were combined during soil incubation to discriminate the available natural Zn from the soil, and the available Zn from the dissolved nano-68 ZnS. This combination was crucial to highlight the dissolution of nano-68 ZnS as of the third day of incubation. Based on the extended X-ray absorption fine structure, we revealed faster dissolution of nano-ZnS in clayey soil (82% within 1 month) than in sandy soil (2% within 1 month). However, the nano-DGT results showed limited availability of Zn released by nano-ZnS dissolution after 1 month in the clayey soil compared with the sandy soil. These results highlighted: (i) the key role of soil properties for nano-ZnS fate, and (ii) fast dissolution of nano-ZnS in clayey soil. Finally, the higher availability of Zn in the sandy soil despite the lower nano-ZnS dissolution rate is counterintuitive. This study demonstrated that, in addition to nanoparticle dissolution, it is also essential to take the availability of released ions into account when studying the fate of nanoparticles in soil.

Located on the edge of the Seine River, the site of les Herbages in Les Mureaux (Yvelines) was the object of two preventive archaeology operations, in 2013 and 2014, in advance of the extension of industrial infrastructures used by Airbus and its subsidiary, Astrium Space Transportation. The first operation included the partial exploration of a mortuary group that yielded a Butterwick-type copper alloy dagger (Van den Bossche and Blin, 2014), from the initial stage of the Early Bronze Age. The second operation focused on an occupation from the beginning of the Chassean culture. On the edge of this occupation, a new mortuary group was discovered and dated to the Early Bronze Age as well. Both sectors were strongly impacted by earthworks carried out in the 1960s to protect the military installations of the former Étienne Mantoux air base from potential flooding from the Seine. This work naturally affected the highest formations and sometimes reached the Protohistoric levels. It is probably responsible for the generalized leveling of the burial pits and the alterations of the exhumed osseous remains. The two groups each contain three and four individual inhumations. Only one of the tombs contained artifacts. Most of the chronological information is therefore based on AMS radiocarbon dates realized by the University of Groningen (Netherlands) and the Beta Analytic laboratory in Miami, Florida. The dates of the mortuary group excavated in 2014 cover a relatively limited period from the middle of the 22nd century to the end of the 20th century BC. They suggest a short-term use of the mortuary space during the transition from the end of the Bronze A1 and the beginning of the Bronze A2 in Île-de-France and concur with the dates established for the mortuary group studied in 2013 (Van den Bossche and Blin, 2014). Due to the exceptional presence of an artifact type whose production centers are located on the British Isles, isotopic analyses of the three best-preserved burials from the 2014 excavation were also realized, as well as of two inhumations exhumed in 2013. The aim was to confront the 87Sr/ 86Sr signal recorded in the bioapatite of the dental enamel of the individuals in question to obtain information on their geographic origin(s). The interindividual results argue in favor of a homogeneous population for the groups identified in 2013 and 2014. The signature obtained for the neighboring sediments, on the other hand, show much higher values. These significant variations between the human and local sedimentary signals probably indicate residential mobility, though it is not possible to identify the provenance of the inhumed subjects or to determine the period in their life during which this hypothetical migratory episode would have occurred. At the local scale, clear parallels can be observed between the two mortuary groups at les Herbages. These consist of small areas covering a few dozen square meters containing a handful of slightly dispersed tombs. The mortuary practices identified have many points in common. All the burials studied correspond to primary individual inhumations contained in simple, most often large, pits. The bodies, most often in the supine position, are oriented in the east-west axis, with the head most often at east. A significant difference is seen in the artifact, which is found in only one of the burials. Replacing these data within their broader context enables us to review our state of knowledge of the mortuary practices of the Early Bronze Age in Île-de-France. Paradoxically, the few analogies observed at Les Mureaux do not indicate any normalization of the regional mortuary traditions. Even if the available corpus is still small (38 burials distributed among 23 sites), it appears that there was no dominant rule, whether in the treatment of the deceased, the position and orientation of the bodies, the grave goods, the burial method, or the arrangements of the graves. Despite this diversity, there appears to have been a fundamental evolution of behaviors concerning death tending toward a greater focus on the individual and leading to a multiplication of small mortuary units, which is very different from the typical models from the end of the Neolithic Almost all the known trifaces come from southwestern France, but according to the literature, some also exist or may exist in other areas in the South (Chalosse area, Deux-Sèvres, Ardèche and maybe in Alpes-de-Haute-Provence). They also occur in Dordogne in sites attributed to the Southern Acheulean, but they are marginal compared to the other components of lithic assemblages. Indeed, in most of sites, there are only few trifaces. Thus, a definition of the Southern Acheulean based solely on this lithic concept does not seem relevant. Moreover, the absence of the trifacial system in assemblages with similar composition may result from taphonomic processes, site functions or activities. A more in-depth study of several former collections may enhance our understanding of the variability of this concept and links between the techno-complexes of Southern Europe during the final Middle Pleistocene., Localisé en bord de Seine, le site des Herbages aux Mureaux (Yvelines) a fait l’objet de deux opérations archéologiques, en 2013 et 2014. La première a permis l’exploration partielle d’un ensemble funéraire du début du Bronze ancien, d’où provient un poignard en alliage cuivreux de type Butterwick. La seconde a porté sur une occupation du Chasséen septentrional, en marge de laquelle a été mis au jour un nouvel ensemble funéraire, également daté du Bronze ancien. Ces deux groupes comprennent respectivement trois et quatre inhumations individuelles, principalement datées par des mesures radiocarbone. Celles-ci suggèrent une utilisation assez courte des espaces funéraires considérés, située entre la fin du Bronze A1 et le début du Bronze A2. Considérant la présence d’un artefact, dont les centres de production sont situés dans les îles britanniques, des analyses isotopiques ont été menées (87Sr/ 86Sr) visant à obtenir des précisions sur l’origine géographique des différents sujets étudiés. Les résultats interindividuels plaident en faveur de l’homogénéité populationnelle. Le rapport obtenu sur les sédiments environnants affiche des valeurs nettement supérieures, signes d’une probable mobilité résidentielle sans qu’il soit possible de préciser la provenance des sujets inhumés. À l’échelle locale, des parallèles évidents peuvent être établis entre les deux ensembles funéraires des Herbages. La mise en perspective de ces données fournit l’occasion d’établir un état des connaissances des pratiques funéraires propres à l’âge du Bronze ancien francilien. Les analogies relevées aux Mureaux ne vont pas dans le sens d’une quelconque normalisation des traditions funéraires régionales. Aucune règle ne semble prévaloir, que ce soit dans le traitement des défunts, la position et l’orientation des corps, la dotation funéraire, le mode d’ensevelissement ou encore dans les agencements sépulcraux. Au-delà de cette diversité, transparaît pourtant une évolution fondamentale des comportements face à la mort., Corona Aloïs, Bossche Benjamin Van Den. Un nouveau groupe funéraire du Bronze ancien aux Mureaux (Yvelines) : retour sur les pratiques funéraires franciliennes entre 2200 et 1600 av. J.‑C.. In: Bulletin de la Société préhistorique française, tome 116, n°3, 2019. pp. 515-537.

International audience; Carbon (delta C-13) and nitrogen (delta N-15) stable isotope analyses are used in marine ecology to study trophic relationships and migrations of species since they reflect dietary sources consumed which may vary geographically. However, better estimations of isotope incorporation rates and trophic discrimination factors (TDF) under controlled conditions are required. Moreover, variability of isotope incorporation rates and TDF among and within populations has been poorly described, especially in fish scales, whereas the use of non-lethal method is becoming a standard. This study aimed to experimentally assess whether carbon and nitrogen isotope incorporation rates (lambda C and lambda N, respectively) and TDF of scales vary in the European sea bass (Dicentrarchus labrax) among (1) Atlantic, West Mediterranean and East Mediterranean populations, (2) sexes and (3) individuals. Fish were reared under controlled conditions and switched from a diet 1 to a diet 2 with different delta C-13 and delta N-15 values. Scales were sampled repeatedly on 16 fish within the three populations, from the day of diet change (day 0) to the end of the experiment (day 217). Isotope incorporation rates of scales and TDF were determined using a time-dependent model. Isotopic carbon and nitrogen half-lives (t(50)C and t(50)N) were similar among the three populations but males had significantly lower t(50)C and t(50)N than females (29 +/- 2 and 35 +/- 2 days vs. 53 +/- 7 and 80 +/- 11 days, respectively). Females had higher growth rates but lower catabolic rates than males. Variability of lambda C . and lambda N was large within sexes: t(50)C ranged from 17 to 159 days and t(50)N ranged from 18 to 342 days among individuals. Thus, variability between sexes and among individuals must be considered to avoid misinterpretation in field-based studies. For the 48 fish, TDF were 4.91 +/- 0.03 and 2.46 +/- 0.06 parts per thousand for carbon and nitrogen, respectively, and similar between sexes and among populations. Besides, TDF varied among individuals from 2.95 to 5.59 parts per thousand and from 0.93 to 3.55 parts per thousand for carbon and nitrogen, respectively. Empirical mixing models were run to estimate how different TDF influenced estimation of the contributions of food sources to diet of their consumer. The output differed considerably when using TDF from fish literature or those estimated herein, which confirms that a tissue-specific TDF must be used to avoid misinterpretation in field-based studies. Individual variation in TDF did not, however, influence estimation of the contributions of food sources, confirming that scales are a valid tissue for non-lethal sampling.

For more than two decades, research groups in hydrology, ecology, soil science, and biogeochemistry have performed cryogenic water extractions (CWEs) for the analysis of δ2H and δ18O of soil water. Recent studies have shown that extraction conditions (time, temperature, and vacuum) along with physicochemical soil properties may affect extracted soil water isotope composition. Here we present results from the first worldwide round robin laboratory intercomparison. We test the null hypothesis that, with identical soils, standards, extraction protocols, and isotope analyses, cryogenic extractions across all laboratories are identical. Two standard soils with different physicochemical characteristics along with deionized (DI) reference water of known isotopic composition were shipped to 16 participating laboratories. Participants oven-dried and rewetted the soils to 8 and 20 % gravimetric water content (WC), using the deionized reference water. One batch of soil samples was extracted via predefined extraction conditions (time, temperature, and vacuum) identical to all laboratories; the second batch was extracted via conditions considered routine in the respective laboratory. All extracted water samples were analyzed for δ18O and δ2H by the lead laboratory (Global Institute for Water Security, GIWS, Saskatoon, Canada) using both a laser and an isotope ratio mass spectrometer (OA-ICOS and IRMS, respectively). We rejected the null hypothesis. Our results showed large differences in retrieved isotopic signatures among participating laboratories linked to soil type and soil water content with mean differences compared to the reference water ranging from +18.1 to −108.4 ‰ for δ2H and +11.8 to −14.9 ‰ for δ18O across all laboratories. In addition, differences were observed between OA-ICOS and IRMS isotope data. These were related to spectral interferences during OA-ICOS analysis that are especially problematic for the clayey loam soils used. While the types of cryogenic extraction lab construction varied from manifold systems to single chambers, no clear trends between system construction, applied extraction conditions, and extraction results were found. Rather, observed differences in the isotope data were influenced by interactions between multiple factors (soil type and properties, soil water content, system setup, extraction efficiency, extraction system leaks, and each lab's internal accuracy). Our results question the usefulness of cryogenic extraction as a standard for water extraction since results are not comparable across laboratories. This suggests that defining any sort of standard extraction procedure applicable across laboratories is challenging. Laboratories might have to establish calibration functions for their specific extraction system for each natural soil type, individually.

Polyaromatic hydrocarbons (PAHs) are a group of toxic and carcinogenic organic compounds formed by petrogenic and incomplete pyrolytic processes. Although emission reductions were observed over the past 20 years, PAH contamination is still an environmental concern as these compounds are the main contaminants in the Seine watershed. Many tools were developed to identify their origins and fate. However, these methods do not always allow accurate identification of emission sources. A method integrating the variations of the isotopic ratios of δ13C and δ2H among 16 compounds was developed and compared to those of the molecular diagnostic ratio techniques. The development of the protocol consisted of the preparation and the validation of a selective extraction method by matrix type (water / sediment) and a purification step to obtain for each molecule, a resolution adapted to its isotopic analysis. That method applied to various combustion products in the Ile-de-France region, such as samples of atmospheric deposition, water and river sediments. The measurement of δ13C and δ2H signatures confirmed the presence of local sources and helped to characterize the seasonal variations of the ratios. The originality of this research work is the use of δ2H on individual PAH instead of bulk compounds. The results allow considering new perspectives for the use of isotopic measurements., Les hydrocarbures aromatiques polycycliques (HAP), sont des molécules toxiques, voire cancérigènes principalement issues de la combustion incomplète de matière carbonée. De nombreux outils ont été développés afin d’identifier leurs origines et leur devenir. Cependant, ces derniers ne permettent pas toujours de parvenir à une identification précise des sources d’émissions. Une méthode prenant en compte les variations des rapports isotopiques δ 13C et δ 2H dans 16 composés a été développée et comparée à celle des ratios moléculaires. Le développement du protocole a consisté en la préparation puis la validation d’une méthode d’extraction sélective par type de matrice (eau/sédiment) et d’une méthode de purification permettant d’obtenir pour chaque molécule une résolution adaptée à leur analyse isotopique. Cette méthode a été appliquée sur divers produits de combustion franciliens ainsi que sur des échantillons de dépôts atmosphériques, d’eau et de sédiments de rivière. La mesure du δ13C et du δ2H a permis de confirmer la présence de sources locales et de caractériser les variations saisonnières de ratios. L’originalité de ce travail de recherche réside dans l’utilisation du δ2H spécifique à chaque molécule et non sur un mélange de composés. Les résultats permettent d’envisager de nouvelles perspectives sur l’utilisation des mesures isotopiques. Cette thèse représente un premier élément de réponse sur la problématique de l’emploi d’outils de traçage de molécules dans des environnements complexes.

The rise of high throughput (HT) strain engineering tools accompanying the area of synthetic biology is supporting the generation of a large number of microbial cell factories. A current bottleneck in process development is our limited capacity to rapidly analyze the metabolic state of the engineered strains, and in particular their intracellular fluxes. HT (13)C-fluxomics workflows have not yet become commonplace, despite the existence of several HT tools at each of the required stages. This includes cultivation and sampling systems, analytics for isotopic analysis, and software for data processing and flux calculation. Here, we review recent advances in the field and highlight bottlenecks that must be overcome to allow the emergence of true HT (13)C-fluxomics workflows.

In terrestrial ecosystems, plant-available pools of magnesium and calcium are assumed to be stored in the soil as exchangeable cations adsorbed on the surface of mineral and/or organic particles. The pools of exchangeable magnesium and calcium are measured by ion-exchange soil extractions. These pools are sustained in the long term by the weathering of primary minerals in the soil and atmospheric inputs. This conceptual model is the base of input-output budgets from which soil acidification and the sustainability of soil chemical fertility is inferred. However, this model has been questioned by data from long-term forest ecosystem monitoring sites, particularly for calcium. Quantifying the contribution of atmospheric inputs, ion exchange and weathering of both primary, secondary and non-crystalline phases to tree nutrition in the short term is challenging. In this study, we developed and applied a novel isotopic dilution technique using the stable isotopes of magnesium and calcium to study the contribution of the different soil phases to soil solution chemistry in a very acidic soil. The labile pools of Mg and Ca in the soil (pools in equilibrium with the soil solution) were isotopically labeled by spraying a solution enriched in 26Mg and 44Ca on the soil. Labeled soil columns were then percolated with a dilute acid solution during a 3-month period and the isotopic dilution of the tracers was monitored in the leaching solution, in the exchangeable (2 sequential 1 mol L−1 ammonium acetate extractions) and non-crystalline (2 sequential soil digestions: oxalic acid followed by nitric acid) phases. Significant amounts of Mg and Ca isotope tracer were recovered in the non-crystalline soil phases. These phases represented from 5% to 25% and from 24% to 50%, respectively, of the Mg and Ca labile pools during the experiment. Our results show that non-crystalline phases act as both a source and a sink of calcium and magnesium in the soil, and contribute directly to soil solution chemistry on very short-term time scales. These phases are very abundant in acid soils and, in the present study, represent a substantial calcium pool (equivalent in size to the Ca exchangeable pool). The gradual isotopic dilution of Mg and Ca isotope ratios in the leaching solution during the experiment evidenced an input flux of Mg and Ca originating from a pool other than the labile pool. While the Mg input flux originated primarily from the weathering of primary minerals and secondarily from the non-crystalline phases, the Ca input flux originated primarily from the non-crystalline phases. Our results also show that the net calcium release flux from these phases may represent a significant source of calcium in forest ecosystems and actively contribute to compensating the depletion of Ca exchangeable pools in the soil. Non-crystalline phases therefore should be taken into account when computing input-output nutrient budgets and soil acid neutralizing capacity. (Resume d'auteur)

article i nfo There is a critical need to document the long-term variability of the West African Monsoon (WAM) in the Sahel region. We present here a multidecadal proxy record of the past hydrology from AD 460 to 1090 in the Saloum Delta, Senegal. The Saloum Delta is a hypersaline estuary where the salinity and the water isoto- pic composition are highly sensitive to rainfall variations. The past hydrology was studied using the oxygen isotopic ratio of Anadara senilis fossil shells, since mollusk shell isotopic composition (δ 18

Soil represents an important carbon sink, which inputs and outputs are governed by numerous biotic and abiotic factors. We focused on two essential biotic factors: litter inputs, the main source of SOM; and earthworms, key soil engineers in temperate regions. We investigated the fate of 13C-labelled Ryegrass root and shoot litter, in soil and epi-anecic earthworm casts (Lumbricus terrestris), based on a one year mesocosm experiment. Soil samples were collected at two depths, as well as surface casts, regularly during the 54 weeks of experiment. SOM complexity and heterogeneous composition was considered, using a multidisciplinary approach at different spatio-temporal scales to quantify, localize and characterize the organic carbon incorporated in soil and earthworm casts. The chemical composition of roots and shoots had a significant impact on the fate of carbon in soil, with an increased contribution from root-derived carbon in soil and casts after one year. The chemical composition tended to influence the litter palatability for earthworms. As organo-mineral associations tended to increase during drying and ageing of casts, physical interactions might have also played an important role in cast formation and evolution. Earthworms tended to minimize the diverging fate of root and shoot residues on both soil and cast carbon, after the year of experiment. Thus, while studying soil carbon incorporation, decomposition and stabilization, the role of soil invertebrates should be particularly considered. We also observed the crucial role of microorganisms in decomposing litter and their potentially high participation to stable carbon pool in soil and particularly in casts., Le sol représente un puits de carbone important, dont les entrées et les sorties sont gouvernées par de nombreux facteurs biotiques et abiotiques. Nous nous intéressons à deux facteurs biotiques essentiels : la qualité de la litière, principale source des MOS; et les vers de terre, ingénieurs clés des sols tempérés. Nous étudions le devenir de parties racinaires et aériennes, marquées au carbone 13, dans le sol et des turricules de Lumbricus terrestris, au cours d'une expérimentation en mésocosmes d'une année. Nous utilisons une approche pluridisciplinaire à différentes échelles spatio-temporelles pour quantifier, localiser et caractériser le carbone organique incorporé dans le sol et les turricules, pendant les 54 semaines d'expérimentation. La composition chimique des parties racinaires et aériennes a un impact significatif sur le devenir du carbone dans le sol et semble influencer la palatabilité de la litière pour les vers de terre. Après une année d'expérience, la contribution des racines, par rapport aux parties aériennes est plus importante dans le sol et les turricules. Les interactions physiques semblent également jouer un rôle important dans la formation et l'évolution des turricules. Les vers de terre minimisent l'effet contrasté des parties racinaires et aériennes sur le carbone du sol et des turricules. Les invertébrés du sol doivent être pris en compte lors de l'étude des processus d'incorporation, de décomposition et de stabilisation du carbone dans le sol. Les microorganismes jouent un rôle essentiel dans la décomposition de la litière et semblent contribuer au carbone stable du sol, et ce particulièrement dans les turricules.

Researches on the most primitives meteorites, the chondrites, bring information on solar system formation. Among its distincts steps of formation, accretion of the first planetesimals which would have formed the solar system is yet not well understood.Analyses of Ti and Mg isotopes might be essential to understand various phenomena. Indeed, isotopic analyses of Ti might be useful to better understand the chondrules/matrix complementarity observed in carbonaceous chondrites. On the other hand, analyses of one of Mg isotopes (26Mg ) might be used for new dating method which employed short lived radionuclides.This report presents several methods for isotopic analysis of Ti and Mg, and discuss about the innovation that it could bring for meteorites studies., L’étude des météorites primitives, les chondrites, apporte des informations sur le mode de formation du système solaire. Parmi les différentes étapes de sa formation, l’étape d’accrétion des planétésimaux, qui auraient formé les différentes planètes, reste encore peu comprise, difficile à dater et à modéliser.L’analyse des isotopes du Ti et du Mg pourrait s’avérer cruciale pour la compréhension de certains phénomènes. En effet, l’analyse des isotopes du Ti pourrait permettre de mieux comprendre la complémentarité chondres/matrice observée chez les chondrites carbonées. D’autre part, l’analyse d’un des isotopes du Mg (le 26Mg) pourrait permettre la mise en place de nouvelles méthodes de datation qui font intervenir des éléments radioactifs avec une courte demi-vie (26Al).Ce rapport présente les différentes méthodes mises en place pour ces analyses et discute de leur caractère innovant pour l’étude des météorites.

International audience; We aim to improve our knowledge of the dynamic of the vegetation in Central Africa during the last 5 kyrsand to discuss the main hypothesis described in the literature - humans versus climatic impacts- both suggestedas responsible of the Congo basin rainforest decline observed between 3 and 2.5 kyrs. We use the carbon isotopiccomposition of well-dated Central African soils to reconstruct the dynamic of the vegetation cover.We will discussthe carbon isotopic composition of the soil organic carbon methodology for reconstructing palaeovegetation in thelight of Rayleigh distillation model. We showed that numerous sites exhibit a carbon isotopic ratios reflectingthe Rayleigh distillation but few sites recorded real vegetation changes. Our study suggests that the vegetationof the Guineo-Congolian Region was disturbed between 3000 and 2000 BP (Before Present) without an extremesavannah expansion. We discussed the two hypotheses human versus climate impacts that may conduct to suchnew physiography of the vegetation. We suggest that the climate hypothesis is more likely than the human impactto explain the reduction of the Guineo-Congolian rainforest 3000 years ago.

Varios cuerpos ígneos alcalino-basálticos han sido identificados en la sección sedimentaria cretácica de la cuenca ecuatoriana oriente (≅ 110-80 ma). Los mismos están caracterizados por valores bajos en los radios LILE/HFSE y en los radios isotópicos de Sr y Nd, todos dentro del rango observado en las signaturas composicionales de basaltos de isla oceánica o punto caliente (“hot-spot”), consistentes con una fuente astenosférica. Sísmica de reflexión muestra que la ubicación de los distintos centros eruptivos es controlada por las estructuras pre-existentes del rift triásico-Jurásico invertido en un régimen transpresivo a partir del cretácico superior. edades radiométricas y el registro biostratigráfico de los sedimentos cretácicos sugieren una variación diacrónica de la posición geográfica de este volcanismo alcalino, ocurrido al menos a partir del albiano (40Ar/39K, 106±5Ma) en la parte septentrional de la Cuenca Oriente, y hasta el Campaniano (40Ar/39Ar, 84±2 Ma y 82±0,5 Ma) en la parte occidental-central (zona subandina).Se propone un mecanismo de “slab roll-back”, originado a partir de la cesación de los procesos de subducción en el Cretácico Inferior (≅130-120 Ma), como el modelo geodinámico más probable para explicar la generación de este magmatismo. El mismo está asociado con la migración lateral y vertical de material astenosférico hacia zonas previamente adelgazadas de la corteza o “thin-spots” litosféricos. Por lo tanto, el paleo-rift triásico-Jurásico ejerció un control fundamental en la generación de estos magmas alcalinos, facilitando la fusión parcial de una fuente astenosférica no afectada por procesos de subducción. Finalmente, la inversión tectónica del Cretácico Superior da lugar a la reactivación de las estructuras extensivas pre-existentes en un régimen transpresivo, lo que originó la migración del magmatismo hacia el sur-suroeste principalmente a lo largo del Corredor Sacha-Sushufindi de la Cuenca Oriente.

Marine microbiologists commonly assay lipase activities by using a synthetic fluorescent analog, 4-methylumbelliferyl (MUF)-oleate. The technique is convenient, but it is considered to be unspecific because of the structure of this analog. This study reports the design of a new specific and sensitive lipase assay based on the use of a radiolabeled triglyceride, [ 3 H]triolein. Free fatty acids (FFA) resulting from its hydrolysis are isolated as a function of time in a one-step liquid-liquid extraction and then radioassayed. MUF-oleate and [ 3 H]triolein techniques were compared by measuring lipase activities at similar substrate concentrations along a trophic gradient in the Southwest Lagoon of New Caledonia, near Nouméa. Hydrolysis rates decreased from the nearshore station to the offshore station and showed similar trends regardless of the technique used. Rates decreased from 5.83 to 0.88 nmol of FFA · liter −1 · h −1 and from 0.76 to 0.23 nmol of 3 H-FFA · liter −1 · h −1 , respectively. These results appeared to be consistent with bacterial production results, which also decreased similarly (from 0.59 to 0.26μ g of C · liter −1 · h −1 ). However, the ratio of MUF-oleate activities to [ 3 H]triolein activities, which was constant at the offshore stations (3.8 ± 0.1), gradually increased at the nearshore stations (from 4.1 to 7.6). This result shows that the two assays respond in different ways to changes in environmental conditions and validates the need to set up more specific enzymatic assays.

A new ice core record from the Nevado Illimani (16°S), Bolivia, covers approximately the last 18 000 years BP. A comparison with two published ice records, from Sajama (18°S), Bolivia [Thompson et al., Science 282 (1998) 1858-1864] and Huascarán (9°S), Peru [Thompson et al., Science 269 (1996) 46-50], documents a regionally coherent transition from glacial to modern climate conditions in South America north of 20°S. The strong resemblance between the Illimani and Huascarán water isotope records and their differences from the Sajama record, in particular during the period from 9000 years BP to 14 000 years BP, suggest that local water recycling or local circulation changes played a major role for Sajama. We interpret the common Illimani/Huascarán water isotope history in terms of a common change from wetter/cooler conditions during glacial times to drier/warmer conditions in the Early Holocene. A 2003 Elsevier Science B.V. All rights reserved. (résumé d'auteur)

Diploastrea heliopora forms dense, robust, dome-shaped coral colonies throughout the reef ecosystems of the tropical Pacific and Indian Oceans. This slow-growing (2 to 6 mm/yr) coral has the potential to yield continuous paleoclimate records spanning up to 1000 yr for the warmest waters on Earth, the Indo-Pacific Warm Pool, and has a long fossil history as a single recognizable species. Despite the potential of Diploastrea to be an important new paleoclimate archive, little is known about the systematics of geochemical tracers incorporated into its skeleton. To fill this knowledge gap, we compared skeletal δ18O signatures in live Diploastrea and Porites colonies from Southwest Lagoon, near Amédée Lighthouse, New Caledonia (at the southern latitudinal limit for Diploastrea) and Alor, Indonesia (in the core area of the Indo-Pacific Warm Pool). We designed a new microsampling technique to minimize smoothing and distortion of the isotopic records due to the complex calyx architecture and slow growth of Diploastrea. High-resolution isotope profiles from the septal portion of the Diploastrea corallite are attenuated, whereas those restricted to the central columella are similar in quality to those extracted from the well-established Porites coral archive. The δ18O-temperature relationship for the columellar portion of Diploastrea (−0.18‰/°C) is in good agreement with that derived for a nearby Porites (−0.19‰/°C; Quinn et al., 1996), on the basis of comparison with an in situ sea surface temperature record from Amédée Lighthouse. There is a measurable difference of 0.3 ± 0.1‰ between the kinetic/biological disequilibrium offsets from seawater δ18O composition for Diploastrea and Porites. Despite this offset in mean δ18O, Diploastrea accurately records the regional differences in mean temperature and salinity between New Caledonia and the Indo-Pacific Warm Pool. Additional tests show that Diploastrea records El Niño–Southern Oscillation (ENSO) interannual variability in sea surface temperature and salinity across the southwestern Pacific, indicating that it should yield dependable paleo-ENSO records. Based on these results, we propose that D. heliopora has the potential to provide an important new coral archive of tropical paleoclimate.

In Peruvian Amazonia, cropping techniques manipulating the biological processes of soil fertility have been tested to increase productivity and sustainability of crops. Special attention was paid to earthworms since theircommunities are dominant in natural ecosystems and severely depleted in cultivated soils, and also because their populations can be manipulated. The objective of this work was to evaluate the impact of the endogeic earthworm Pontoscolex corethrurus on soil organic matter dynamics, by comparing treatments with and without earthworms. Carbon dynamics is described using particle-size fractionation and in situ natural isotopic labelling (carbon 13) obtained by shift of C3 to C4 vegetation. After 6 years of maize cultivation, the organic carbon stock of the 0-10 cm layer decreased respectively by 4 and 27 % in the control and the earthworm inoculated treatments. For the inoculated treatment this decrease mainly occurred in the large particle size (plant residues) Seventy % of the carbon derived from forest was lost during 6 years in the 2000-200 pm fractions in the inoculated treatment and 19 % in the control. However, the incorporation of carbon derived from maize in soil, especially in the large particle fractions (> 50 μm), was lower in the earthworm inoculated treatment. Accordingly, the proportions of carbon derived from forest and from maize were the same in the two treatments. Thus, the main effect of earthworm inoculation was a more important mineralisation of the carbon derived from forest and maize, especially in the large particle size fractions (> 50 μm).

The Raspas Metamorphic Complex of southwestern Ecuador is regarded as the southernmost remnant of oceanic and continental terranes accreted in the latest Jurassic–Early Cretaceous. It consists of variably metamorphosed rock types. (1) Mafic and ultramafic rocks metamorphosed under high-pressure (HP) conditions (eclogite facies) show oceanic plateau affinities with flat REE chondrite-normalized patterns, eNd150 Ma ranging from +4.6 to 9.8 and initial Pb isotopic ratios intermediate between MORB and OIB. (2) Sedimentary rocks metamorphosed under eclogitic conditions exhibit LREE enriched patterns, strong negative Eu anomalies, Rb, Nb, U, Th, Pb enrichments, low eNd150 Ma values (from � 6.4 to � 9.5), and high initial 87 Sr/ 86 Sr and 206,207,208 Pb/ 204 Pb isotopic ratios suggesting they were originally sediments derived from the erosion of an old continental crust. (3) Epidote-bearing amphibolites show N-MORB affinities with LREE depleted patterns, LILE, Zr, Hf and Th depletion, high eNd150 Ma (>+10) and low initial Pb isotopic ratios. The present-day well defined internal structure of the Raspas Metamorphic Complex seems to be inconsistent with the formerly proposed

The isotopic content of rainfall was measured in Niamey (Niger) over a period of eight years (1992–1999). Seasonal distribution of rainy events depends on the monsoon movement over the region. At the beginning and at the end of the rainy season, low rainfall, high temperatures and low relative humidity favour isotopic enrichment. In the middle of the rainy season, heavy rainfall, low temperatures and relative humidity close to saturation lead to isotopically depleted contents because of the mass effect; moreover, in the case of low rainfall, marked vertical convective development favours high altitude condensation. How far the Intertropical Front moves north, determines the quality of the rainy season and influences the isotopic contents. Thus the isotopic contents of rainfall are good climatic indicators. To cite this article: J.-D. Taupin et al., C. R. Geoscience 334 (2002) 43–50

International audience

11 pages, 3 figures, 4 tables, Knowing the trophic ecology of marine predators is essential to develop an understanding of their ecological role in ecosystems. Research conducted on deep-sea and threatened shark species is limited. Here, by combining analyses of individual stomach contents and stable isotope values, we examined the trophic ecology (dietary composition and trophic position) of the kitefin shark Dalatias licha, a deep-sea shark considered as near threatened globally and as data deficient in the Mediterranean Sea. Results revealed the importance of small sharks in the diet of the kitefin shark at short- and long-term scales, although finfish, crustaceans and cephalopods were also found. Predation on sharks reveals the high trophic position of the kitefin shark within the food web of the western Mediterranean Sea. Stable isotope values from liver and muscle tissues confirmed our results from stomach content analysis and the high trophic position, JN and MC were supported by a research contract of the Marie Curie Career Integration Grant Fellowships to the BIOWEB project. MC was also funded by a postdoctoral contract of the Ramon y Cajal Program (Spanish Ministry of Economy and Competiveness). CB was supported by a doctoral fellowship CONICYT-Becas Chile. This study forms a contribution to the project ECOTRANS (CTM2011-26333, Ministerio de Economía y Competitividad, Spain)

International audience; Lateritic surface processes have shaped large platform and cratons of the tropical belt. Constraining the timing of such processes is crucial to decipher their role in cratonic morphogenesis and their response to long-term climatic change and lithospheric deformation. Weathering histories have been documented for South America, Africa and Australia, but precise time constraints of the lateritic weathering processes in South India are still lacking. We present 40Ar/39Ar ages of supergene cryptomelane (K-Mn oxide) formed in the Sandur Mn ore deposits exposed on the highest lateritic paleolandsurface that once covered the Mysore plateau and the adjacent Deccan Traps. Significant 40Ar/39Ar ages are estimated between ~ 36 and ~ 26 Ma from well-defined plateaus in step heating 39Ar release spectra and from best-fitted inverse isochrones. These ages constitute firm time constraints that document intense late Eocene-Oligocene lateritic weathering over Peninsular India under the influence of warm and wet climate comparable to that prevailing in tropical humid forests. These results imply that Southern India was weathered between ~ 36 and 26 Ma and may have been dissected mostly in the Neogene.

The Lapita colonization,which occurred in the late Holocene, is one of the most remarkable prehistorical human colonizations. To explore the possible influence of El Niño–Southern Oscillation (ENSO) on this event, bulk oxygen (δ18Oshell) and carbon (δ13Cshell) stable isotope records were obtained from eight fossil Tridacna sp. and Hippopus hippopus giant clams, unearthed from Lapita archeological sites of New Caledonia and Vanuatu. These giant clamswere dated ca. 3.8–2.3 ka BP. These δ18Oshell and δ13Cshell records were used as proxies for combined sea surface temperature and salinity and precipitation. In addition, geochemical records were obtained from modern conspecifics from New Caledonia to create a baseline against which fossil giant clam records could be compared. The isotopic records revealed the occurrence of two distinct climate states in New Caledonia ca. 3.2–2.3 ka BP: one climate state was characterized by climatic conditions similar to those observed today and the second was comparable to warmer and wetter conditions similar to Vanuatu's modern climate. Considering that previous paleo-climate reconstructions in the West Pacific did not show a shift of the mean climatic state and that they revealed aweak centennial climate variability, our results suggest that the climatic mean state has been alternating between these two states at a decadal or an inter-annual frequency. This strong climate variability recorded in the giant clam shells may reflect an increase in the ENSO variability, supporting the hypothesis of an ENSO-forced Lapita colonization as suggested by Anderson et al. (2006).

Estimation of groundwater recharge in arid and semi-arid areas is difficult due to the low amount and variability of recharge. A combination of radiotracers investigation based on simple mixing models allows direct investigation of relatively long-term renewal rates of an aquifer. The recharge process of the shallow Continental Terminal aquifer in the Iullemeden basin (Niger) was investigated using a geochemical and isotopic approach. This study investigates the area in the one degree square of Nianey (13–14°N, 2–3°E). In this area, recharge is highly heterogeneous and mainly occurs through a drainage system of temporary streams and pools during the rainy season. Heterogeneity of the recharge is reflected through the wide variation in electrical conductivity and oxygen-18 content of the groundwater. The carbon-14 activity range for most of the groundwater falls between 69 and 126 pmc showing pre and post-aerial thermonuclear test recharge. Two renewal rate models have been investigated: the first one models a well-mixed reservoir and the second one is derived from a piston flow model, in which mixing is in equal proportions. Major ions in tritium data analyses allow exclusion of non-representative samples and confirm the carbon-14 renewal rate estimations. Both models give similar results for the relatively low renewal rate investigated in the area. Using carbon-14, the mean annual rates of groundwater renewal range from 3 to 0.03% of the aquifer volume with a median of 0.1%. Assuming the median is representative of the overall renewal rate of the area, the recharge rate is in the order of 5 mm a −1 . The shallow aquifer recharge extends from the last small humid period (around 4000 a) up to now. High recharge rates are found in depressions whereas low recharge occurs below the plateaux.

Le volcanisme récent de l'arc insulaire des Nouvelles Hébrides (Vanuatu) est influencé par sa collision avec la ride d'Entrecasteaux. La géochimie des éléments en trace et l'étude des compositions isotopiques des laves de cet arc permettent de nuancer les interprétations antérieures faisant état d'un gradient de composition, au nord et au sud de la zone de collision. Les données géochimiques montrent une variation nette, évoluant de compositions calco-alcalines à l'aplomb de la zone de collision à tholéiitiques de part et d'autre. Par contre, les signatures isotopiques varient de façon progressive, définissant des sources de moins en moins enrichies à des distances croissantes de la zone de collision, évoluant vers des sourcse "normales" de type MORB. Ce gradient isotopique suggère l'existence de deux contaminations, l'une magmatique, par une lithosphère ancienne au front de la zone de collision (variation du 206Pb/204Pb), et l'autre mantellique, par un manteau de type "enrichi" (type Dupal) débordant largement cette dernière. (Résumé d'auteur)

The lake Barombi Mbo pollen record goes back to about 28,000 yr B.P. The pollen diagram based on 82 samples is subdivided into four main pollen zones. Zone I (ca. 28,000 to 20,000 yr B.P.) is characterized by relatively high frequencies of Caesalpiniaceae and also by a montane element with Olea capensis. The climate was cool and relatively wet. Zone II (ca. 20,000 to 10,000 yr B.P.). A sharp increase in Gramineae, the main non-arboreal land pollen taxon, began around 20,000 yr B.P. and lasted until 10,000 yr B.P. During this period the forest receded, giving way to a more open vegetation, but significant patches of forest (refuges) persisted in the area. This is confirmed by isotopic analyses (δ13C of sedimentary detritic organic matter from the catchment. Until ca. 13,000 yr B.P. Olea capensis was well represented indicating a relatively cool climate. Between 13,000 and 12,000 yr B.P. a warming trend associated with a strong increase in precipitation occurred. After this an abrupt reduction in precipitation linked to an increase in seasonality, but without temperature lowering, intervened between ca. 11,500 and 10,400 yr B.P. This last phase corresponds partly to the Younger Dryas time period. Zone III (ca. 10,000 to 2800 yr B.P.). After ca. 10,400 yr B.P. the climate became very wet until ca. 3000 yr B.P. A sharp decrease in the Gramineae intervened at ca. 10,000 yr B.P.; from ca. 9500 to 3000 yr B.P. they remained very low, between 0 and 3%, and the forest trees reached their maximum extension. Most of the trees exhibited large variations with quasi-periods of around 1000 to mainly 2000 yr (ca. 2200 calendar years), which could be related to large sylvigenetic or successional cycles. In this zone the Caesalpiniaceae were relatively well represented, with a maximum extension between 4500 and 3000 yr B.P. Podocarpus, a typical tree of the montane stratiform cloud forests, exhibited very low frequencies before 10,000 yr B.P. but their relative increase during the early and middle Holocene can only be explained by its growth on distant mountains. Its maximum extension phase was roughly synchronous with that of Caesalpiniaceae. The climate was warm and wet, but cooler on the mountains. Zone IV (ca. 2800 yr B.P. to present time). Around 2800 yr B.P. a sharp increase in the Gramineae, peaking at 30 to 40% of total pollen between ca. 2500 and 2000 yr B.P., indicates a sudden phase of vegetation opening and forest retreat, accompanied by severe erosion. Alchornea, a typical pioneer taxon, increased rapidly at the same time to large frequencies because it develops abundantly in all the openings. Elaeis guineensis, originally a pioneer palm tree, follows the same pattern. The climate was warm, relatively dry, and linked to an increase of seasonality. After 2000 yr B.P. the Gramineae returned to low frequencies, around 10%, associated with a strong increase in trees, indicating that the forest expanded again but not to the same extent as in the early and middle Holocene. The climate was warm and relatively wet, rather similar to the present-day climate.

International audience; The mid-Holocene climate is characterized by an insolation seasonality decrease in the Southern Hemisphere but measurements of its actual impact on monthly resolved sea surface temperature (SST) in the southwest Pacific region are still insufficient. A New Caledonian 5.5 ka cal BP coral provides a 20-year-long seasonally-resolved record of ocean surface conditions as inferred from coral Sr/Ca and Ba/Ca. Results were compared to monthly series of Paleoclimate Modeling Intercomparison Project phase 2 (PMIP2) model simulations. Anomalous stable isotope and U/Ca values are observed in a restricted area of the skeleton related to dissolution features. The mid-Holocene SST seasonal amplitude mean and variability are higher than presently in New Caledonia, the increased seasonal amplitude in the mid-Holocene being most probably due to the occurrence of colder winters. Other southwest Pacific mid-Holocene coral data showed also such an increased seasonal amplitude. This could mean that the South Pacific Convergence Zone (SPCZ) was weaker or reached locations more northerly than at present, which could fit with northward shifts of the inter-tropical convergence zone (ITCZ) during South Hemisphere winter. Inversely, strong rainfalls during the summer, deduced from the Ba/Ca signal and reconstructed sea surface salinity (SSS), were interpreted as reflecting pronounced southwestward shifts of the SPCZ in summer, as those occurring today during La Niña events. None of the six PMIP2 models used reproduce the proxy-based mid-Holocene increase of SST seasonal amplitude. Model maps show a less intense SPCZ in winter that would be consistent with higher SST seasonal amplitude. Finally, we stress the need for more seasonally-resolved data to validate this enhanced mid-Holocene SST seasonal amplitude in the southwest Pacific region and to better understand the underlying mechanisms.

Bélékoni watershed (120km2 ) is located in the upper basin of Niger River in Mali. The climate context (Sudanian zone) justify cotton production program. Analysis of last decades agricultural evolution impacts is the objective of the present study. Research methods include in situ observations and measurements and laboratory analysis. According French soil classification of 1967, three main soil types are distinguished in the watershed: Lithosol (soil1), Ferruginous Tropical Soil (soil2) and Mineral Hydromorphic Soil (soil3). Sol1 is marginal for cropping and wood development and the two others soils are indicated for actual agricultural intensification. Concerning land use, there are mainly cropland and land under natural vegetation, subjected to vainly grazing. The general trend is the soil degradation whereas land use. Carbon stock is low (20.2 t.ha-1 in the first 30 cm of soil profile). Soil 1 and 2 are affected by erosion, respectively 2.7 and 5.7 t.ha- 1 .yr-1 or 0.4 and 0.2 cm.yr-1 ; Soil3, located in the depression along river system is a sedimentation site: 10.1t.ha-1 .yr-1 or 0.7 cm.yr-1 . Major process currently affecting Bélékoni watershed are land use change, soil degradation and sedimentation in the river.

EnglishSince Athanase Peltier, in 1840, physicists, meteorologists, and climatologists have shown an interest for tornadoes in France, especially in the second half of the 19th century and since the end of the 20th century. The association Climat-Energie-Environnement has established a database, presently containing 525 cases collected in France since 1680, enabling scientists to propose a climatology of the phenomenon. The present study focuses on the spectacular manifestations of tornadoes, including the noise surrounding the incoming meteor, the removal of water, persons, animals, and objects upon its passage, the projection of various materials, and, finally, the damages due to the effects of the excess of pressure.This study reveals the evolution of observations, along that of physics and meteorology, and it will be useful for the classification of the intensity of tornadoes on the improved Fujita scale, as well as for the knowledge of risks incurred on the metropolitan territory. francaisLa composition isotopique des precipitations est utilisee depuis longtemps pour reconstruire la variabilite climatique passee a partir de sa conservation dans des archives comme les glaciers, les speleothemes, etc. Elle permet aussi d'aborder et de decortiquer des mecanismes qui regissent le climat present. La mise sur le marche d'une nouvelle technique a permis d'etendre les mesures isotopiques sur la phase vapeur et d'acceder a une information continue dans le temps. A travers divers exemples choisis sur des terrains varies, des regions polaires aux tropiques, cet article illustre le potentiel de la composition isotopique de la vapeur d'eau en surface, en regard de donnees meteorologiques plus classiques, pour etudier des processus aussi divers que le melange de masses d'air, l'origine de la vapeur d'eau, la structure, l'intensite et l'organisation de la convection, la formation et la dissipation des nappes de brouillard et la circulation atmospherique a differentes echelles de temps.

In arid and semi-arid regions water scarcity is one of the main limiting factors for economic growth. In the context, an experimental setup was conceived to monitor seasonal water consumption of citrus plant irrigated by drip irrigation system in Agafay station, middle of Morocco. For that, an Eddy-Covariance system, meteorological station, fluxmeter, as well as measurements of soil moisture and temperature were continuously operated during experimentation. The stable isotope was used to partition Evapotranspiration (ET) components. By using the water balance equation, the results showed that about 37% of total irrigation and rainfall is lost by infiltration and runoff. Additionally, the partitioning of evapotranspiration using the stable isotope showed that soil evaporation is very small compared to the transpiration at least during tow sampling days. This result confirms that the irrigation method applied by the farmer was very appropriate for the orchard but it is necessary to re-examine amount of water applied and timing of irrigation in order to minimise the loss by infiltration

International audience; Origin of groundwater salinity (current seawater vs. saline deep water) in a coastal karst aquifer based on Sr and Cl isotopes. Case study of the La Clape massif (southern France) a b s t r a c t In this study a typical coastal karst aquifer, developed in lower Cretaceous limestones, on the western Med-iterranean seashore (La Clape massif, southern France) was investigated. A combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer. Water samples were collected between 2009 and 2011. Three groundwater groups (A, B and C) were identified based on the hydrogeological setting and on the Cl À concentrations. Average and maximum Cl À concentrations in the recharge waters were calculated (Cl Ref. and Cl Ref.Max) to be 0.51 and 2.85 mmol/L, respectively). Group A includes spring waters with Cl À concentrations that are within the same order of magnitude as the Cl Ref concentration. Group B includes groundwater with Cl À concentrations that range between the Cl Ref and Cl Ref.Max concentrations. Group C includes brackish groundwater with Cl À concentrations that are significantly greater than the Cl Ref.Max concentration. Overall, the chemistry of the La Clape groundwater evolves from dominantly Ca–HCO 3 to NaCl type. On binary diagrams of the major ions vs. Cl, most of the La Clape waters plot along mixing lines. The mixing end-members include spring waters and a saline component (current seawater or fossil saline water). Based on the Br/Cl molar ratio, the hypothesis of halite dissolution from Triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater. Groundwaters display 87 Sr/ 86 Sr ratios intermediate between those of the limestone aquifer matrix and current Mediterranean seawater. On a Sr mixing diagram, most of the La Clape waters plot on a mixing line. The end-members include the La Clape spring waters and saline waters, which are similar to the deep geo-thermal waters that were identified at the nearby Balaruc site. The 36 Cl/Cl ratios of a few groundwater samples from group C are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix. Finally, PHREEQC modelling was run based on cal-cite dissolution in an open system prior to mixing with the Balaruc type saline waters. Modelled data are consistent with the observed data that were obtained from the group C groundwater. Based on several trac-ers (i.e. concentrations and isotopic compositions of Cl and Sr), calculated ratios of deep saline water in the mixture are coherent and range from 3% to 16% and 0% to 3% for groundwater of groups C and B, respectively. With regard to the La Clape karst aquifer, the extension of a lithospheric fault in the study area may favour the rise of deep saline water. Such rises occur at the nearby geothermal Balaruc site along another lithospheric fault. At the regional scale, several coastal karst aquifers are located along the Gulf of Lion and occur in Mezosoic limestones of similar ages. The 87 Sr/ 86 Sr ratios of these aquifers tend toward values of 0.708557, which suggests a general mixing process of shallow karst waters with deep saline fossil waters. The occurrence of these fossil saline waters may be related to the introduction of seawater during and after the Flandrian transgression, when the highly karstified massifs invaded by seawater, formed islands and peninsulas along the Mediterranean coast.

Quantifying the magnitude of soil organic carbon loss linked to the conversion of forest to arable land in tropical environments requires long-term estimates of soil redistribution trends within the catchment. In order to assess the cumulative soil carbon loss that occurred since deforestation and cropping started in 1967, a multidisciplinary study was carried out in a small catchment (67 ha) with a swamp area in its middle part, characterized by steep slopes under shifting cultivation of upland rice, typical for northern Laos's landscapes. Using 137Cs and total organic carbon (TOC) inventories, it was possible to estimate a soil TOC depletion rate of 0.039 kgC m−2 yr−1 in 42 years (1963–2005), corresponding to ca. 21% of its initial content in the top 10 cm. Because farmers preferred clearing more fertile soils located downhill and leave forest on poorer soils on the crests, the redistribution of 137Cs and TOC along slopes of the catchment was mainly controlled by the topographic position of soils and the cultivation frequency. Estimates of soil TOC accumulation in wetlands with δ13C measurements and sediment volumes by electrical resistivity tomography showed that TOC accumulation rates were linked to land use change since the 1960s with three successive periods corresponding to undisturbed forest, deforestation-first rice crop and rice-fallow rotations. Forest clearing triggered a higher soil TOC delivery to the swamp (19.6 ± 5.5 kgC ha−1 yr−1) over 8 years (1967–1975) than the former undisturbed forest (8.5 ± 1.8 kgC ha−1 yr−1) and crop-fallow rotations over 30 years (1975–2005, 6.4 ± 4.8 kgC ha−1 yr−1). Due to the small size of the area covered by the swamp, only a limited fraction of eroded soil organic carbon (ca. 7 wt.%) was stored in wetlands of the catchment. Mineralization apparently played a key role for soil TOC depletion since first forest clearing.

Année de publication: 2012-2013; International audience; The Ligury, known for its particular abundanceof archaeological findings dated tothe Pre and Proto-historic period, is a regionwell-suited for scientific studies on paleodiet.In this paper, a summary of the resultson carbon and nitrogen stable isotopesanalyses, performed on human and animalremains selected from sites placed in thewestern part of Ligury, is presented. A moredetailed description focuses on unpublishedresults obtained from two sites of theBronze Age and early Iron Age: Grotta delPertuso and Buco del Diavolo (Triora, Imperia).The diachronic analyses of the wholedata set shows how, during the later Prehistorystage, two important ruptures occurredin terms of food habits. The first oneis related to the phenomenon of the settling;indeed terrestrial resources effectively replacedthe aquatic resources in the diet. Thesecond relevant change was detected duringthe Iron Age: terrestrial resources representthe main intake. But it is interesting to notethat an appreciable amount of C4 plantswere consumed in addition to the traditionalintroduction of C3 plants, evidenced by asignificant shift in stable isotope levels. Severalhypotheses are proposed in order to explainthe isotopic variations and the highlighteddietary diversity; La Ligurie, de par sa richesse en découvertesarchéologiques datant de la période Pré- etProto-historique, est un terrain favorablepour développer des études spécifiques surla paléoalimentation. Dans ce travail, unesynthèse des résultats sur les analyses desisotopes stables du carbone et de l’azote estprésentée. Ces résultats ont été obtenus àpartir de restes humains et animaux de différentssites de la partie ouest de la Ligurie.Une description plus détaillée est consacréeaux résultats inédits de deux communautésde l’âge du Bronze-début âge du Fer: Grottadel Pertuso e Buco del Diavolo (Triora, Imperia).L’analyse diachronique de l’ensembledes données montre comment, au cours de laPréhistoire récente, se manifestent deuxgrandes ruptures en termes d’habitudes alimentaires.La première se produit avec lanéolithisation, lorsque les ressources terrestresdominent très largement les ressourcesaquatiques dans le régime alimentaire. Ladeuxième est détectée à l’âge du Fer: les ressourcesterrestres sont à la base de l’alimentationmais il est intéressant de noter l’introductiondes plantes de type C4 (tel que lesmillets) dans l’alimentation. Différentes hypothèsessont proposées dans le but d’expliquerles variations isotopiques et la diversitéalimentaire mise en évidence; La Liguria, per la particolare ricchezza diritrovamenti archeologici di epoca Pre eProtostorica, ha permesso di sviluppareun’approfondita analisi di tipo paleonutrizionale.In questo lavoro viene presentatauna sintesi di quanto emerso dall’analisidegli isotopi stabili di carbonio ed azoto diresti umani e animali di alcune comunitàdel Ponente ligure. Una descrizione maggiormentedettagliata è dedicata ai risultatiinediti ottenuti da due siti dell’età delBronzo-inizio età del Ferro: Grotta del Pertusoe Buco del Diavolo (Triora, Imperia).Nel complesso, l’analisi diacronica mettein evidenza come, nel corso della Preistoriarecente, si siano verificati due grandi momentidi rottura a livello di abitudini alimentari.La prima si manifesta con il fenomenodella sedentarizzazione, dove lerisorse terrestri vengono a sostituire le risorseacquatiche nella dieta e un secondoconsiderevole cambiamento si rileva incorrispondenza dell’età del Ferro: purmantenendosi le risorse terrestri alla basedell’alimentazione, si nota come a piantedi tipo C3 si integri un consumo apprezzabiledi piante di tipo C4 con un notevoleshift a livello isotopico. Vengono illustratedifferenti ipotesi per spiegare le origini diquesti variazioni

In north-central Chile, a wide shore platform is morphologically connected with a high fluvial terrace and a pediment. The eastward extension of Quaternary coastal uplift in the Southern Central Andes is poorly constrained since no age correlation between marine and continental landforms has been reported. We use Al-26 and Be-10 concentrations to constrain the geomorphic evolution of these marine and continental landforms near the Choapa valley (31.6 degrees S). Be-10 ages for the shore platform indicate that this surface was repeatedly reoccupied during sea-level highstands between similar to 800 and 500 ka and uplifted after 500 ka. While 'zero erosion' ages for the pediment between similar to 600 and 300 ka only partly overlap the shore platform age range, more realistic exposure ages calculated for an erosion rate of 1 m/Ma are between similar to 945 and 475 ka, fitting the age range of the correlated shore platform. Be-10 concentrations of the high fluvial terrace are highly scattered evidencing vertical mixing of clasts probably due to slow lowering of the surface. Although it is not possible to determine an age for this landform, the scattering among its Be-10 concentrations implies that this marker is several hundreds of thousands of years old and that the high fluvial terrace began to form at similar to 1200 ka or after. Finally, Be-10 concentrations of the high fluvial terrace, the pediment and the shore platform are of the same order of magnitude, which is consistent with the clear morphologic correlation between these three types of landforms. These data suggest that the marine and continental landforms studied formed synchronously, with some local differences, during a long period of relative tectonic stability between similar to(1200?) 800 and 500 ka and uplifted after 500 ka. Our results confirm recent studies showing a post-400 +/- 100 ka renewal of uplift along the Pacific coast after a Lower to Middle Pleistocene period of slow uplift. Moreover, the extension of the surfaces suggests that a broad region of similar to 40 km has been uplifted ca. 150 m during the Quaternary.

Cet article présente de nouveaux résultats isotopiques (δ13C and δ15N) obtenus sur un groupe humain du Néolithique moyen issu de l'ensemble funéraire du site de Pontcharaud 2 (Puy-de-Dôme, Auvergne, France). L'intérêt s'est initialement porté sur cette région notamment en raison de l'intéressante diversité écologique qu'offre cet espace géographique pour l'exploitation des ressources naturelles. L'acquisition de nouvelles données sur les comportements alimentaires au Néolithique dans une zone géographique, distincte de celles étudiées précédemment dans d'autres programmes de recherche, permet de développer une approche comparative relative aux choix alimentaires opérés par les Néolithiques en intégrant des aspects sociaux et environnementaux. Notre étude porte, d'une part, sur une analyse paléoalimentaire de la série ostéologique de Pontcharaud 2, par une approche isotopique intra-populationnelle intégrant les données biologiques et archéologiques et, d'autre part, sur une analyse inter-régionale entre trois zones géographiques: l'Auvergne, la Garonne et le Languedoc. L'objectif de cette comparaison est multiple et s'attache à savoir s'il existe des différences alimentaires entre les groupes méridionaux et plus septentrionaux de la deuxième moitié du Ve millénaire, et si ces différences peuvent être mises en relation avec l'environnement propre de chacune de ces aires géographiques ou avec des choix culturels. Le site de Pontcharaud 2 à Clermont-Ferrand en Auvergne a livré un vaste ensemble funéraire dont les premières datations radiométriques réalisées sur os proposent une fourchette chronologique de 4460-4030 BC cal. (LY7916: 5640 ± 70 BP ; LY7918: 5330 ± 55 BP ; LY 7917: 5430 ± 50 BP) correspondant au Néolithique moyen 1 de la Limagne. Dans notre étude, deux nouvelles datations ont été réalisées sur des individus de l'inhumation multiple. Les résultats (5350 ± 40 BP Poz-41914: 4324-4051 BC cal. ; 5380 ± 40 BP Poz-41915: 4335-4059 BC cal.) montrent que cet ensemble particulier a fonctionné dans le même intervalle chronologique que les sépultures. Une étude anthropologique a été réalisée préalablement aux analyses isotopiques. Selon le stade de croissance, différentes méthodes ont été appliquées pour estimer l'âge au décès des individus. Dans le traitement statistique, les individus immatures ont été répartis en 3 catégories: [0-4], [5-14] et [15-19] ans. Ce classement est défini par des critères biologiques. Le sexe des individus adultes a été déterminé dans un premier temps par une diagnose sur l'os coxal. La méthode de diagnose sexuelle probabiliste (DSP), élaborée à partir de données métriques, a été privilégiée. Les critères archéologiques retenus pour cette étude concernent, d'une part, la présence d'architecture pérenne ou non et, d'autre part, la distinction des sépultures individuelles des inhumations. Les isotopes stables (δ13C and δ15N) du collagène osseux humain et animal ont été dosés afin d'appréhender l'origine environnementale des protéines consommées et le niveau trophique des individus. Au total, 37 adultes, 21 immatures et 7 animaux associés ont été échantillonnés et analysés par EA-IRMS. Les résultats isotopiques indiquent pour l'ensemble du groupe une importante consommation de protéines animales. La variabilité isotopique intra-groupe souligne des différences dans la proportion de protéines consommées entre les sujets ainsi que la possible consommation de ressources d'eau douce pour certains.

Bien que la minéralisation du phosphore organique puisse jouer un rôle important dans la nutrition des plantes, sa mesure a toujours été limitée du fait de problèmes méthodologiques. Notre objectif est de montrer si la détermination des cinétiques d'échange isotopiques peuvent donner des informations sur la minéralisation nette de composés organo-phosphatés dans les sols. En utilisant cette technique, la minéralisation de deux phosphates organiques (adénosine triphosphate, ATP, et nicotinamide adénine dinucléotide, NAD) est étudiée dans un alfisol mis en incubation. Les paramètres qui décrivent l'échange isotopique, r(1)/R, n et cp, ont été utilisés pour calculer la quantité d'ions phosphate (P) présents dans le compartiment d'ions libres et dans le compartiment de P isotopiquement échangeable entre 1 minute et 1 jour. De plus, le P extrait par les résines a été mesuré dans les mêmes échantillons. Après ajout d'ATP et NAD, le P est rapidement libéré dans la solution du sol, ce qui accroit le contenu de P dans le compartiment d'ions libres, compartiment qui ensuite diminue au cours de l'incubation. Le P minéralisé dans les sols avec ATP ou NAD, et restant extractible à l'eau ou dans le compartiment d'ions libres est corrélé positivement à la quantité de P minéralisé restant extractible par les résines. La méthode isotopique mesure la quantité de P minéralisé qui reste immédiatement biodisponible. Les changements dans le contenu de P du compartiment de P échangeable entre 1 minute et 24 h n'ont pas pu être corrélés à la minéralisation du P organique. Ce manque de relation est à relier aux variations de la valeur n qui ont pour origine la minéralisation du P organique pendant l'échange isotopique lui-même, ou à cause de l'hétérogénéité de l'échantillon. Ainsi, l'étude de la minéralisation du P organique nécessite une attention particulière lors de l'extrapolation des quantités isotopiquement échangeable du phosphate. (Résumé d'auteur)

National audience

In the Indian Ocean, the blue shark Prionace glauca and the silky shark Carcha rhinus falciformis represent the 2 main shark bycatch species in pelagic longline and purse seine fisheries, respectively. With the increasing market demand for fins, catches may increase in the future, with potential effects on ecosystem trophic functioning through top-down cascading effects. Knowledge of the species' trophic ecology is therefore crucial but is limited by the lack of data from the Indian Ocean. Stable isotope analysis was therefore performed on muscle tissues (δ 15 N and δ 13 C) of these 2 shark species from the western Indian Ocean. Our study showed that body length, season, and zone effects were relatively small for the 2 species. However, significant δ 13 C differences between the 2 species suggest niche partitioning, with silky sharks having a more inshore foraging habitat than blue sharks. Finally, lower muscle δ 15 N values were observed in juvenile silky sharks caught by purse seiners around fish aggregating devices (FADs) compared to juveniles caught by longliners. One hypothesis is that FADs could act as an ecological trap for juvenile silky sharks, leading to a po- sition at lowest trophic level for these individuals. However, different foraging habitats could also explain the observed patterns between juveniles. Although preliminary, our results provide a basis for the implementation of species-specific protection and management strategies.

This study investigates eddy induced transport processes that affect the sources and sinks of organic matter in the Mozambique Channel (MC). Eddies generated in the MC interact with the continental shelf and have been hypothesized to act as conveyor belts that entrain coastal production offshore. A combination of natural isotope tracers, elemental composition and physico-chemical variables allowed distinguishing two sources of organic matter within the eddy dipole. Near the surface, coastal POM was entrained at the anti-cyclonic boundary and further transferred into the eddy. Anti-cyclonic surface POM containing coastal POM was downwelled into deeper layers where decomposition greatly affected its composition. In contrast, cyclonic water promoted new production, by upwelling nutrient-rich deep waters into the euphotic zone. This production circulated through the mixed layer of the cyclone and was possibly advected into the boundary. Boundary F(max) and surface waters shared characteristics with the cyclone and anti-cyclone respectively as the result of both import of primary production of cyclonic origin occurring at F-(max) and entrainment of coastal biological material at the surface. In the overall low productivity environment of the MC, it is likely that the continuous migration of mesoscale eddies along the shelf plays an important ecological role both in enhancing pelagic production and transporting coastal production offshore.

We report results of a regional survey of helium isotopes measured in water and gas samples in volcanic sulfataras and geothermal springs from the Central Andes of northern Chile and Bolivia between the latitudes 15°S and 23°S. The highest 3He4He ratios (reported as RRA ratios: R = sample 3He4He, RA = air 3He4He) are associated with the active volcanic arc of the Western Cordillera (0.92 < RRA < 5.52) and approach ratios found at other convergent margins in the circum-Pacific region. A significant 3He component is also present in fluid and gas samples from the high Altiplano plateau (0.48 < RRA < 3.56) and the Eastern Cordillera (0.03 < RRA < 1.2), up to 300 km east of the active arc and more than 300 km above the subducting slab. This wide zone of 3He anomalies is delineated both to the east and the west by regions with low 3He4He ratios ( ⩽ 0.2RA), typical of radiogenic helium production in the crust. Studies of the regional groundwater regime suggest that the wide zone of elevated 3He4He values away from the active volcanic arc is unlikely to be caused by lateral and shallow transport of magmatic helium and there is no evidence for significant crustal sources of 3He. The high 3He4He ratios are interpreted as reflecting degassing of volatiles from mantle-derived magmas emplaced over an area 400 km wide beneath and into crust up to 75 km thick. The subducting slab is at depths of 100–350 km in this region. In the west, underneath the active volcanic arc, mantle melting is probably largely controlled by mantle hydration and dehydration and the helium isotope data can be used to delineate the extent of the asthenospheric mantle wedge at depth. In contrast, mantle melting behind the arc, beneath the Altiplano and Eastern Cordillera, may be a result of convective removal of the base of the lithosphere. The sharp cut-off in the mantle helium signal in the east is interpreted as marking the western edge of thick and relatively cold lithosphere, devoid of mantle melts, which could transport mantle volatiles towards the surface. This may coincide with the limit of underthrusting of the Brazilian shield beneath the eastern margin of the Central Andes.

International audience; West African tropical estuaries play an important role in the growth and survival of many commercially exploited fish species and enable the sustainability of considerable artisanal fishery yields. However, their trophic functioning remains poorly understood. In the Sine Saloum estuary (Senegal), a marine protected area (MPAs) was designated in 2003 to manage fisheries resources. The present study aimed to determine the structure, trophic functioning and seasonal patterns of the fish assemblages in this MPA. Throughout the study, 28 fish species were collected, with higher values of biomass (3826 kg km-2) recorded during the wet season and lower values during the dry season (1228 kg km-2). Fish assemblages in both seasons were dominated by species with marine affinity, which accounted for 87% of the total biomass in the wet season and 70% in the dry season, with their abundance varying from 83% to 57%, respectively. Based on stable isotopic composition ([delta]13C and [delta]15N), species were combined into trophic groups. Primary consumers were partitioned into suspensivores (pelagic copepods, oysters and mussels), which fed mainly on particulate organic matter, and intermediate consumers, feeding on freshly deposited organic matter and benthic microalgae (Sarotherodon melanotheron and Arca senilis). Secondary consumers were divided into three groups. The first group included mullet, which fed by grazing on benthic microalgae (benthic affinity feeders). The second group, pelagic affinity feeders, was the most heterogeneous and fed mainly on pelagic components. The last secondary consumer group termed the intermediate group, included piscivores and benthic and pelagic invertebrate feeders, which dominated the top of the food web. The food chain in October was lengthened due to the occurrence of tertiary consumers. Food webs were dominated by secondary consumers, which constituted 89% of total biomass in the dry season and 71% in the wet season. The fish food web varied largely with season in faunal composition and food chain length. This study highlighted the need to take into account the seasonal dynamic of the food web both in terms of composition and structure to assess carbon fluxes in tropical estuaries

International audience; A proximité de La Paz, les indicateurs marquants de la tendance climatique sont a) une augmentation de la température de ré-analyse à 500 hPa de 0,017°C.an-1 entre 1973 et 2004, b) à la station météorologique Laïca Cota, entre 1995 et 2004, une élévation de la température de 0,03°C.an-1 , une diminution de l'humidité relative de 0,6 %.an-1 , c) une augmentation du δ 18 O des précipitations de 0,26 ‰.an-1 et de leur excès en deutérium de 0,1‰.an-1. Une des principales conséquences de cette tendance est un recul du front du glacier Zongo de 12 m.an-1 entre 1991 et 2004 (réduction de 2% par an des surfaces glaciaires de 1997 à 2004 :1,84 km 2 en 2004). L'analyse temporelle concomitante des données montre que la variabilité des conditions ENSO a des conséquences en phase à l'échelle infra-annuelle pour la température, l'humidité relative, la précipitation, le bilan glaciaire, et des conséquences en déphasage, sur des périodes dépassant l'année, pour le rapport isotopique des précipitations andines.

Uncertainties in sea-level projections for the 21st century have focused ice sheet modelling efforts to include the processes that are thought to be contributing to the recently observed rapid changes at ice sheet margins. This effort is still in its infancy, however, leaving us unable to make reliable predictions of ice sheet responses to a warming climate if such glacier accelerations were to increase in size and frequency. The geological record, however, has long identified examples of nonlinear ice sheet response to climate forcing (Shackleton NJ, Opdyke ND. 1973. Oxygen isotope and paleomagnetic stratigraphy of equatorial Pacific core V28–239, late Pliocene to latest Pleistocene. Geological Society of America Memoirs145: 449–464; Fairbanks RG. 1989. A 17,000 year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep ocean circulation. Nature342: 637–642; Bard E, Hamelin B, Arnold M, Montaggioni L, Cabioch G, Faure G, Rougerie F. 1996. Sea level record from Tahiti corals and the timing of deglacial meltwater discharge. Nature382: 241–244), thus suggesting an alternative strategy for constraining the rate and magnitude of sea-level change that we might expect by the end of this century. Copyright © 2009 John Wiley & Sons, Ltd.