Search

International audience; Following a thematic day on “Service and expertise through archaeological and conservation sciences” organised by the CAI-RN network (Competences Archéométriques Interdisciplinaires - Réseau National, MITI CNRS), the members of the Steering Committee of the CAI-RN network who took part in this workshop wished to bring together and clarify in this text a certain number of the points raised during the discussion. In particular, it gives a brief definition of the terms ‘service’ and ‘expertise’ and presents the different types of structures linked to the archaeometric community and carrying out these activities. This proposal for an initial analysis of the current situation also suggests a number of thought-provoking impulses.; Suite à une journée thématique « Service et expertise par les sciences archéologiques et de la conservation » organisée par le réseau CAI-RN (Compétences Archéométriques Interdisciplinaires – Réseau National, MITI CNRS) les membres du Comité de Pilotage du réseau CAI-RN ayant participé à cette journée ont souhaité rassembler et clarifier dans ce texte un certain nombre des points évoqués lors des discussions. Ceci en donnant notamment une brève définition des termes « service » et « expertise » et en présentant les différents types de structures liées à la communauté archéométrique et réalisant ces activités. Cette proposition d’une première analyse de la situation actuelle propose aussi quelques pistes de réflexion.

National audience; La multiplication des données chronologiques fournies par les différentes méthodes dedatation absolue et celles obtenues par les fouilles et l’analyse des mobiliers soulèventla question de leur traitement conjoint suivant des méthodes fiables etreproductibles. C’est pour répondre à cette question que depuis les années 90 desarchéologues, des archéomètres et des statisticiens ont développé des logiciels demodélisation chronologique utilisant des statistiques dites bayésiennes. L’éruptionplinienne dite d’Avellino, à l’âge du bronze, est un évènement majeur de l’histoirevolcanique du Vésuve. Ses dépôts ponceux sont un marqueur stratigraphique importantsur de nombreux sites archéologiques régionaux. Cet évènement est aussi synchrone dechangements culturels de l’âge du bronze en Campanie. Afin de préciser la datation del’éruption, nous avons traité l’ensemble les données chronologiques disponibles liésdirectement à l’éruption, mais aussi les informations chronologiques, stratigraphiqueset culturelles apportées par les sites archéologiques en relation avec cette éruption. Afinde contraindre au mieux cette modélisation nous avons élargi le modèle aux phasesarchéologique antérieures et postérieures. Cette modélisation a été réalisés de façonaussi proche que possible par les logiciels de statistique bayésienne Oxcal etChronoModel afin de comparer les résultats obtenus.

International audience; Absolute dating is needed to check and calibrate the relative Martian chronology presently available from meteoritic crater counting. For such purpose, a new analytical system (KArMars) has been developed to experiment the feasibility of in-situ K-Ar for future landing planetary missions. It consists in a laser ablation-based system built to vaporize a reproducible volume of rock. Potassium content is measured by laser-induced breakdown spectroscopy (LIBS) and argon by Quadrupole Mass Spectrometry (QMS). Instrument calibration, and checking of the reliability of the measurements for Martian analyses, requires terrestrial analogues. For such purpose, total chemistry, electron microprobe analyses, flame absorption spectrometry and mass spectrometry have been performed in order to qualify the stoichiometry, the mineralogy, the K concentration and the Ar isotopic composition from a collection of old terrestrial rocks. These new analyses coupled with published data allowed us to select mineral phases (e.g. feldspars, phlogopite, muscovite, amphibole) showing a large range of K content (0.3–8.5 wt%). All these mineral phases display a K-Ar age older than 300 Ma. Hence, the content of radiogenic Ar atoms per gram is within the range of Martian samples (on the order of 1 Ga for 0.4 wt% of K). We have shown that the ablated mass can be precisely estimated by measurement of Ar extracted from a similar mineral of known amount of radiogenic Ar content per gram. Then, it has been possible to derive a well-defined relationship between the ablation time and the sample mass extracted from UV-laser ablations for different minerals. Using an isochron approach from multiple ablations of several samples analyzed as unknowns, we have shown that KArMars can be successfully used for dating samples with different compositions, and with ages varying by an order of magnitude from 0.3 to 3 Ga. In-situ K-Ar ages obtained here for plagioclase and amphibole crystals display uncertainties as low as about 10%, and with accuracy, i.e. difference with the reference age, of only 10%. Such results further support in-situ K-Ar dating based on QMS and LIBS instruments as a reliable approach to be implemented onboard Martian rovers. In case a return mission is made possible, KArMars can also be a valuable tool to select the most relevant samples for return and ensure onsite which samples are representative of most of the surface at a given landing site.

National audience

The essential oil of wintergreen, which is extracted by steam distillation from Gaultheria genus leaves, is mainly used in aromatherapy. However, due to its adulteration easiness with synthetic material, it is necessary to control samples naturalness with accuracy. The purpose of this work was to develop a methodology to authenticate the essential oil of wintergreen. Wintergreen essential oil is composed of more than 99% methyl salicylate. This aromatic ester can be easily synthesized and used to adulterate wintergreen essential oil. Authentic wintergreen essential oil can be distinguished from adulterated oils by examining their compositions. The detection of methyl salicylate synthetic marker compounds (methyl 4-hydroxybenzoate, dimethyl 4-hydroxyisophthalate or dimethyl 2-hydroxyisophthalate) or the absence of several naturally occurring minor secondary metabolites (ethyl salicylate and vitispirane) contribute to the authentication. Isotopic values of bulk wintergreen essential oil have also been determined using an isotope ratio mass spectrometer (IRMS): the δ13C values of authentic samples range from −36.78 to −33.36‰, the δ2H values range from −173 to −115‰ and the δ18O values range from −1.3 to 5.7‰. However, these analytical methods cannot account for the natural variability in the essential oils. To determine the boundaries of the natural isotopic values, 14C radioactive isotope activity assessment was undertaken, which allows for the determination of the genuineness of samples that are not assessed using multistable isotope approaches. Additional studies evaluating 14C activity of a noncompliant sample using IRMS identified a 14C-labeled synthetic methyl salicylate adulteration.

The northern part of the Kedougou Kenieba Inlier (Eastern Senegal) is composed of Palaeoproterozoic volcano-plutonic and volcano-sediment areas cross-cut by differentiated plutonic bodies of gabbroic to granitic composition. They are emplaced in an arc-type environment and accreted during the Eburnean Orogeny. We present here new K–Ar ages obtained on several plutons from different mineralogical phases, each characterized by a different closure temperature for the K–Ar system. Ages from hornblende, between 2013 ± 29 and 2141 ± 30 Ma, constrain the cooling history of the magma bodies through the 550 °C isotherm. They are slightly younger than U–Pb ages previously obtained from the same units, attesting of a rapid cooling, tectonically controlled, of about 7 °C/Myr. Ages obtained on biotite minerals range from 1955 ± 28 to 1893 ± 27 Ma, suggesting that from 550 to 325 °C, cooling rate decreased to about 3 °C/Myr. Significantly younger ages ranging from 1704 ± 24 to 1615 ± 23 Ma have been obtained on plagioclase and microcline. They can be interpreted in terms of either a slow cooling with a rate of only 1 °C/Myr, from about 1.9 to 1.6 Ga, or either reflecting the occurrence of a rather limited thermal event younger than 1.7 Ga. Since no age younger than 2.0 Ga has previously been obtained for plutonic rocks from the early Birimian in the West African Craton, ages of 1.7–1.6 Ga obtained here from feldspars might be the first evidence for a regional re-heating event having occurred in the East–North Kedougou Kenieba inlier.

Soil CO2 flux measurement is a key method that can be used to monitor the hazards in an active volcanic area. In order to determine accurately the variations of the CO2 soil emission we propose an approach based on the radiocarbon (14C) deficiency recorded in the plants grown in and around the Solfatara (Naples, Italy). We twice sampled selected poaceae plants in 17 defined sites around the Solfatara volcano. 14C measurements by liquid scintillation counting (LSC) were achieved on the grass samples. The 14C deficiency determined in the sampled plants, compared to the atmosphere 14C activity, ranged from 6.6 to 51.6%. We then compared the proportion of magmatic CO2 inferred to the instantaneous measurements of CO2 fluxes from soil performed by the accumulation chamber CO2 degassing measurement at the moment of the sampling at each site. The results show a clear correlation (r=0.88) between soil CO2 fluxes and 14C activity. The determination of the plants 14C deficiency provides an estimate of the CO2 rate within a few square meters, integrating CO2 soil degassing variations and meteorological incidences over a few months. It can therefore become an efficient bio-sensor and can be used as a proxy to cartography of the soil CO2 and to determine its variations through time

We present here a digital methodology aimed at identifying the morphometry of monogenic volcanic cones including edifice height, slope angle, and volume. We recognize more than 800 monogenic volcanic cones from the Harrat Ash Shaam volcanic province (HASV, northern Arabian Plate) to the north of the Arabian plate by using Landsat7 Enhanced Thematic Mapper plus and digital elevation models (Shuttle Radar Topography Mission, SRTM data). Our results show that the volcanic cones fall into six clusters, each one having a NW-SE orientation parallel to the Red Sea rifting. The density of the cones is most likely controlled by fissure distribution and a possible rotation in the HASV lithospheric block, rather than by the age of the volcanic activity. Interaction with crustal lithologies also plays a negligible role during magma migration. However, the morphology of the monogenic volcanic cones appears to be significantly modified by erosion processes, and both the height and slope of the various cones thus can be used to estimate their relative ages. From such morphological criteria, HASV monogenetic volcanoes in Jordan and Saudi Arabia are older than those in the Golan Heights and the Jabal Al Arab Mountain in Syria, thus, supporting the hypothesis of a northward migration of the recent explosive activity. Our new data, together with the available sediment thickness data, give rise to a new volcano-tectonic interpretation. We show that variations in the cumulative volume of monogenic volcanic cones in several zones of the study area can be related with the sediment thickness (basement depth), and therefore, we propose that the sediment thickness most likely affects the properties of magma before eruption. The reactivation of a deep previous fault perhaps also explains the higher volume of monogenic volcanic cones, focused along a well-defined alignment. This study, thus, gives insight into the relations between sediment thickness, the volcanism, and tectonics. Our results based on new digital treatment of remote sensing data are in overall good agreement with the volcano-tectonic evolution of HASV. This allows us to recommend this methodology as a potential tool to study volcanic cones of other inaccessible regions, either on Earth or other terrestrial planets.

International audience

Widespread lava fields in the northern part of the Arabian platform are the subject of an open geodynamic debate on the origin of the intraplate volcanism. We present new K–Ar ages and whole-rock geochemical data for lava flows from Syria, which allow us to propose a new model of volcano-tectonic evolution highlighting how tectonics have controlled magma genesis in the region during the last 18 Ma. The Cenozoic Syrian lavas are alkaline and subalkaline rocks, typical of magma erupted in such a continental intraplate context. Basaltic samples from different Syrian volcanic provinces show significant variations in terms of incompatible trace element signatures. Crustal contamination plays a negligible role during magma migration and differentiation, and crystal fractionation is essentially restricted to olivine and clinopyroxene. Our results suggest that the Syrian lavas have been generated by variable degrees of partial melting ( c. 1–10%) from different levels of a locally heterogeneous lithospheric mantle. The light/medium rare Earth element (LREE/MREE) ratios not only illustrate how the degree of partial melting has changed spatially and temporally during the last c. 18 Ma, but also indicate that the degree and the style of extensional tectonics has changed through time. We conclude that the Cenozoic Syrian volcanism is a consequence of extensional tectonics, under periodical influence of the north- and eastwards convergence at the Arabia–Eurasia margin, which induces rotational tectonic styles. This controls the partial melting at various depths in the mantle. The volcanism of northern Arabia developed in the framework of the Red Sea rifting and initiated at the same time as the southern Red Sea volcanism. It extends up to historical time, progressively smoothed to the north in a contradictory relation with the compressional/extensional setting of the Arabia–Eurasia margin. Supplementary material: Further information on the analytical results is available at http://www.geolsoc.org.uk/SUP18681 .

La chronologie est l’un des piliers des études quaternaires, or l’expression tant écrite qu’orale des données chronologiques reste hésitante et marquée par une dispersion des systèmes de référencement. Les notations et les unités sont souvent utilisées de façon inappropriée, notamment la référence BP, ce qui conduit parfois à de véritables erreurs. Il résulte de cette situation un certain brouillage de l’information. Une prise de conscience de ce problème est nécessaire. Chronology is one of the bases of quaternary studies. However, the oral and printed expressions of chronological data are still hesitating and affected by scattering of the reference systems. Notations and units are often used erroneously, particularly for the BP reference, possibly inducing real errors. In this situation the information is somewhat jammed. It is necessary to get aware of these problems.

Recently, it was demonstrated that CD8(+) T cells are important for the response against Chlamydia pneumoniae. By use of the human monocytic cell line U937 and human monocytes taken from peripheral blood, we investigated the effect of infection on various molecules critical for CD8(+) T cell function. A strong secretion of interleukin (IL)-10 by infected cells was observed, together with an inhibited expression of major histocompatibility complex (MHC) class I antigens, but without significant alteration of tumor growth factor-beta secretion or MHC class II expression. Recombinant IL-10 added to uninfected U937 cells decreased the expression of MHC class I, whereas blocking antibodies to IL-10 and its receptor abolished the C. pneumoniae-induced inhibition of MHC class I expression. Analysis of our data provides evidence that IL-10 secretion induced by C. pneumoniae infection of monocytic cells down-regulates the expression of MHC class I molecules and thereby might reduce the presentation of bacterial epitopes by MHC. This would decrease the ability of CD8(+) T cells to eliminate infected cells.

This study deals with explosive activity of southern italian volcanoes recorded in the roman region since ca. 8,000 years. It presents chemical analyses performed on volcanic glass shards from a core (LM2 core) collected in the Maccarese lagoon, near Rome's Fiumicino Airport, in February 2010. Rome is surrounded by volcanic complexes which recent activity is regularly discussed. Alban Hills and Sabatini are the two main volcanic complexes in the South and North Rome. The last traces of Sabatini volcanic activity are dated by 40Ar/39Ar at 251 ± 8 ka. The known youngest activity of the Alban Hills is dated at 7.5 ky, according to deposits observed at the bottom of the crater lake later. However, in 2003, Funiciello et al. have described pyroclastic and lahars deposits separated by a palaeosoil dated at 5.1 ± 0.1 14C ka BP. Historical accounts also relate volcanic activity during Bronze Age, but no volcanic deposits related to this recent activity have been described. Search of tephras related to Campanian, Sicilian and Eolian volcanic activity has been extended to recent explosive events from the Roman magmatic region. Three tephra levels have been observed in the LM2 core. Their chemical analyses, as well as Radiocarbon dating performed along the core, allow the identification of (1) the Agnano-Monte-Spina eruption dated at 3.99 ± 0.03 14C ka BP, (2) probably the last eruption from the Albans Hills, dated at ca. 5 ka, and (3), for the first time in northern Italy, a tephra associated with Phlegrean Fields volcanic activity but younger than the Agnano-Monte-Spina eruption.The increase in population around the Albans Hills volcanic complex and Rome exposes a growing number of people to various volcanic hazards. Increasing the number of studied sites in this area will provide a precise chronology of the recent volcanic eruptions and a better estimate of their environmental consequences. Cette étude propose de retracer l’activité volcanique explosive du Sud de l’Italie enregistrée dans la région romaine depuis environ 8 000 ans. Cette étude est basée sur l'étude téphrochronologique d’un carottage (carotte LM2) réalisé en février 2010 dans la Lagune de Maccarese, près de l’aéroport Fiumicino de Rome. Rome est entourée de complexes volcaniques dont l’activité récente est régulièrement discutée. Les Monts Albans et Sabatini sont les deux principaux complexes volcaniques au Sud et au Nord de Rome. Les dernières traces d’activité de Sabatini sont datées à 251 ± 8 ka par 40Ar/39Ar. En revanche, les Monts Albans ont connu une activité plus tardive, et régulièrement discutée, jusqu’à 7,5 ka, d’après l'étude des plus jeunes dépôts tapissant le fond du lac de cratère le plus récent. Funiciello et al. (2003) décrivent cependant des coulées pyroclastiques et des dépôts de lahars séparés par un paléosol daté à 5,1 ± 0,1 ka 14C BP. Par ailleurs, des récits historiques relatent également des activités volcaniques pendant l’âge du Bronze. Cependant, jusqu’à maintenant, aucune étude n’a mis en évidence des dépôts volcaniques liés à cette activité récente. La recherche de téphras issus de l’activité volcanique campanienne, sicilienne et éolienne a donc été étendue à l'activité volcanique explosive récente de la région magmatique romaine. L'étude de la carotte LM2 a mis en évidence trois téphras. Leur analyse chimique, ainsi que des datations Radiocarbone, ont permis de les relier respectivement (1) à l'éruption d’Agnano-Monte-Spina (3,99 ± 0,03 ka 14C BP), (2) vraisemblablement à la dernière éruption des Monts Albans dont les dépôts ont été décrit par Funiciello et al. en 2003, et (3), pour la première fois dans le nord de l’Italie, à un niveau de téphra lié à l’activité volcanique des Champs Phlégréens et postérieur à l'éruption d'Agnano-Monte-Spina. L’augmentation de la population autour du complexe volcanique des Monts Albans et de Rome expose un nombre toujours plus grand de personnes à des risques volcaniques variés dans une région qui n’est pourtant pas assimilée au volcanisme au premier abord. La multiplication des sites d'étude permettra d'obtenir une chronologie précise de ces éruptions et d'estimer leurs conséquences environnementales.

Very recent volcanic events may be dated by using a new technology of the K/Ar dating method. Measurements on samples collected in the South of Italy gave approximate dates in agreement with historical data. Therefore such a method may be used either to characterize tephras in connection with archaeological stratigraphies or to find the geological origin of artefacts., RÉSUMÉ En utilisant une nouvelle technologie pour la méthode du Potassium-Argon il est possible de dater certains événements volcaniques récents. Ainsi des dates encore peu précises mais compatibles avec les données historiques ont été obtenues sur des volcans du Sud de l'Italie. Ces résultats montrent que la méthode peut être employée pour caractériser certains tephra repérés dans des stratigraphies archéologiques ou pour situer la provenance du matériel de certains artefacts., Lefèvre Jean-Claude, Gillot Pierre-Yves. Datation potassium-argon de roches volcaniques du Pléistocène supérieur et de l'Holocène : exemple de l'Italie du sud ; application à l'archéologie. In: Bulletin de la Société préhistorique française, tome 91, n°2, 1994. pp. 145-148.

Reunion Island is an intraplate volcano linked with the hot spot activity that is also responsible for the volcanism of Mauritius and of the Mascarene Plateau. It is composed of two main volcanic complexes, the Piton des Neiges and the still active Piton de la Fournaise. The latter exhibits a special morphostructural evolution characterized by successive nested U-shaped calderas that open seaward. We propose an analysis of this evolution which permits us to deduce a model which can be extended to the general history of the island. From the morphology of the youngest caldera on the one hand and from the K—Ar data on the cliffs corresponding to the successive rims on the other we establish the frequency of landslide collapses and estimate the volumes emitted during each successive phase. This yields evidence of an increasing disequilibrium of the southeastern flank of Piton de la Fournaise. Indeed, through time the frequency of collapses increases and collapse volume decreases. We model the phenomenon with an exponentially smoothed sinusoidal curve, with time on the abscissa and eruptive output on the ordinate. Each maximum on the curve corresponds to the successive slumps and the area of each arch represents the volume erupted during each phase. This can be extrapolated to the earlier volcanic history of Reunion, setting the first collapse at about 1.8 Ma, which affected the main part of the present island, preserving only the Massif de la Montagne at its north-northwestern end. This explains the breccias observed in the deep erosional features of the massif of the Piton des Neiges and takes into account the lack of lavas with dates between 1.8 and 1.1 Ma. Comparison between the curve of emissivity and the total volume estimated for the whole island volcano yields an age of 5 Ma for the beginning of the activity. This age coincides with the end of the main volcanic activity in Mauritius.

In pneumococcal transformation the frequency of recombinants between point mutations is generally proportional to distance. We have recently described an aberrant marker in the amiA locus that appeared to enhance recombination frequency when crossed with any other allele of this gene. The hyperrecombination that we have observed in two-point crosses could be explained by two hypotheses: the aberrant marker induces frequent crossovers in its vicinity or the mutant is converted to wild type. In this report we present evidence showing that, in suitable three-point crosses, this hyperrecombination does not modify the recombination frequency between outside markers, suggesting that a conversion occurs at the site of this mutation. To estimate the length over which this event occurs, we isolated very closely linked markers and used them in two-point crosses. It appears that the conversion system removes only a few base pairs (from three to 27) around the aberrant marker. This conversion process is quite different from the mismatch-repair system controlled by hex genes in pneumococcus, which involves several thousand base pairs. Moreover, we have constructed artificial heteroduplexes using separated DNA strands. It appears that only one of the two heteroduplexes is specifically converted. The conversion system acts upon 5′..ATTAAT..3′/3′..TAAGTA..5′. A possible role of the palindrome resulting from the mutation is discussed.

Genetic analysis of 16 deletions obtained in the amiA locus of pneumococcus is described. When present on donor DNA, all deletions increased drastically the frequency of wild-type recombinants in two-point crosses. This effect was maximal for deletions longer than 200 bases. It was reduced for heterologies shorter than 76 bases and did not exist for very short deletions. In three-point crosses in which the deletion was localized between two point mutations, we demonstrated that this excess of wild-type recombinants was the result of a genetic conversion. This conversion extended over several scores of bases outside the deletion. Conversion takes place during the heteroduplex stage of recombination. Therefore, in pneumococcal transformation, long heterologies participated in this heteroduplex configuration. As this conversion did not require an active DNA polymerase A gene it is proposed that the mechanism of conversion is not a DNA repair synthesis but involves breakage and ligation between DNA molecules. Conversion of deletions did not require the Hex system of correction of mismatched bases. It differs also from localized conversion. It appears that it is a process that evolved to correct errors of replication which lead to long heterologies and which are not eliminated by other systems.