Le guerrier de Saint-Maur (Oise). À la redécouverte d’une œuvre majeure de l’art gaulois

La figure de guerrier en tôle chaudronnée de Saint-Maur est l’un des rares exemples de sculpture anthropomorphe attribuable à la fin de l’époque gauloise ou au début de l’époque gallo-romaine. À l’occasion de sa restauration en 2016, de nouvelles observations et analyses (spectrométrie de fluorescence X, microscopie numérique 3D, scanner 3D) ont été menées par une équipe pluridisciplinaire. Elles ont apporté des résultats inédits sur les matériaux et les techniques mises en œuvre pour la réalisation et l’assemblage des différentes pièces composant la figure du guerrier, ainsi que pour la caractérisation de ses attributs. Elles ont également permis de restituer les traitements rituels subis par l’œuvre avant son enfouissement et d’affiner sa datation.The statue of a warrior in Saint-Maur is one of the rare examples of anthropomorphic sculpture in sheet metal dating from the end of the Gallic period or the Early Roman Empire. During its restoration, undertaken by a multidisciplinary team, new observations were made. These analyses (X-ray fluorescence, 3D digital microscopy, 3D scans) provided unprecedented data concerning our knowledge of the materials, the techniques employed to make and assemble the different parts of the statue, as well as the type of attributes with which the warrior is equipped. They also enabled us to reconstitute the ritual treatments applied to the statue before it was buried

Reconstitution de l historique des apports en radionucléides et contaminants métalliques à l estuaire fluvial de la Seine par l analyse de leur enregistrement sédimentaire

L estuaire de la Seine est l exutoire d un bassin versant très anthropisé. Certaines zones marginales du fleuve ont piégé les particules fines auxquelles sont associés de nombreux contaminants ; elles donnent accès aux enregistrements sédimentaires des dernières décennies. Des carottages ont été effectués en trois sites : la Seine fluviale, l estuaire fluvial de la Seine, et son embouchure. Après datation, ces carottes ont permis de reconstituer l historique des apports particulaires en contaminants en chacun de ces sites. La comparaison entre les séries temporelles des concentrations de certains éléments dans les matières en suspension et dans les sédiments des carottes datées montre que ces derniers constituent un enregistrement conforme aux particules transportées aux mêmes sites. Les flux particulaires de 55 éléments stables et 18 radionucléides ont ainsi pu être été calculés de 1960 à 2002. La comparaison des données acquises dans la partie fluviale de la Seine et dans l estuaire fluvial a permis de distinguer et de quantifier les sources intra-estuariennes de contaminants, dominées par les rejets de phosphogypses effectués dans les années 70 dans la région de Rouen (estuaire fluvial). L intensité du pompage tidal dans l estuaire fluvial a pu être quantifiée en utilisant les rapports d activité de certains transuraniens. Enfin, à partir de l historique des activités atmosphériques et des données acquises sur les carottes, un modèle de transfert du 137Cs de l atmosphère vers le fleuve, fondé sur une loi de lessivage par ruissellement et érosion, est alors proposé.The Seine estuary is the outlet of a highly anthropogenized catchment area. Marginal areas of the river have trapped fine-grained sediment particles which a number of contaminants are bound to; they give access to the sedimentary records of the past decades. Corings were carried out in three areas: the Seine River, the upper Seine estuary, and at the river mouth. After dating, these cores have led to reconstruct the history of the inputs particulate elements in each of these areas. The comparison of the time series of elemental concentrations between (i) suspended matter during the last decades and (ii) dated sediments along the cores shows that the latter are representative of the former. Particulate fluxes of 55 stable elements and 18 radionuclides were estimated, from 1960 to 2002. Comparison of data acquired in the Seine River and in the upper estuary led to distinguish and quantify the intra-estuarine sources of contaminants that are dominated by phosphogypsum discharges during the 1970s in the Rouen harbour area (upper estuary). The intensity of tidal pumping up to the upper estuary was quantified using transuranics activity ratios. Based on the atmospheric 137Cs activities over the last decades and core derived 137Cs activities, a transfer model from the watershed to the river, based on a solid wash-off transfer function by runoff and erosion, is then proposed.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Rapport I.3 Sédiments et dynamique sédimentaire en baie de Seine

Sediments and sedimentary dynamics in the bay of Seine. A large multidisciplinary study of the bay of Seine has begun since 1981. Sedimentological and hydrological investigations permit to describe the superficial sediments and their seasonal variations, to explain the mechanisms of erosion and transport, and to identify the sources of material. The sediment dynamics is mainly controlled by storm waves which are responsible for the resuspension of fine-grained deposits. At the same time, high river flows cause the extension of mud zones in the river mouths. Seawards, measurement of heavy metal concentrations in deposited sediments of the bay has permitted to take fluvial contribution into consideration. Nevertheless, the establishment of a sedimentary mass balance has not been made oût because of the diversity of the sources of material and the complexity of dynamics processes.Un vaste programme de recherche pluridisciplinaire sur la baie de Seine est en cours depuis 1981. Dans le domaine sédimentologique, l'effort porte sur l'étude de la nature des fonds et de leurs fluctuations saisonnières, la compréhension des mécanismes d'érosion et de transport des sédiments, l'identification des sources de matériel. Ces travaux montrent que la dynamique sédimentaire est principalement contrôlée par les houles de tempête qui remettent en suspension une partie du matériel fin. Parallèlement, lors des crues, les apports fluviatiles provoquent des envasements dans les embouchures, et leur influence sur la sédimentation en baie de Seine a pu être appréciée par l'examen des métaux-traces d'origine anthropique dans les dépôts. L'établissement d'un bilan global reste cependant difficile compte-tenu de la diversité des sources de matériel et de la complexité des processus dynamiques.Avoine Jacques, Crevel Laurent, Dubrulle Laetitia, Boust Dominique, Guéguéniat Pierre. Rapport I.3 Sédiments et dynamique sédimentaire en baie de Seine. In: L'hydraulique et la maitrise du littoral. Problèmes côtiers posés par le mouvement des sédiments et la pollution. Dix-huitièmes journées de l'hydraulique. Marseille, 11-13 septembre 1984. Tome 1, 1984

Semiautomatic Toolmark Classification in Chased Metals Using Surface Microtopography

Chasing is one of the main decorative techniques found in metal work. The imprints left by different chasing tools are unique not only to the tool, but also to the chaser. The analysis and characterisation of toolmarks provide vast information that is valuable for the understanding of an object. Microtopography is a non-contact imaging technique that allows a metrical analysis of a surface on a microscopic scale. In this paper, metal mock-ups made using different chasing tools were scanned using microtopography, and their morphological features were used to classify the tools used for their fabrication. The mock-ups were artificially aged to replicate conditions of real archaeological metal objects. The overall classification accuracy obtained for the non-aged mock-ups was 91% for brass and 84% for copper mock-ups. After ageing, the classification accuracy was 65% for brass and 68% for copper. The change in classification accuracy before and after ageing was caused by the corrosion on the aged mock-ups. These results show that this is a promising methodology that could be applied on real chased metal objects

Distinct diversity of the czcA gene in two sedimentary horizons from a contaminated estuarine core

International audienceIn estuarine ecosystems, trace metals are mainly associated with fine grain sediments which settle on mudflats. Over time, the layers of sediments accumulate and are then transformed by diagenetic processes, recording the history of the estuary’s chemical contamination. In such a specific environment, we investigated to what extent a chronic exposure to contaminants could affect metal-resistant sedimentary bacteria in subsurface sediments. The occurrence and diversity of cadmium resistance genes (cadA, czcA) was investigated in 5- and 33-year-old sediments from a highly contaminated estuary (Seine France). Primers were designed to detect a 252-bp fragment of the czcA gene, specifically targeting a transmembrane helice domain (TMH IV) involved in the proton substrate antiport of this efflux pump. Although the cadA gene was not detected, the highest diversity of the sequence of the czcA gene was observed in the 5-year-old sediment. According to the percentage of identity at the amino acid level, the closest CzcA relatives were identified among Proteobacteria (α, β, γ, and δ), Verrucomicrobia, Nitrospirae, and Bacteroidetes. The most abundant sequences were affiliated with Stenotrophomonas. In contrast, in the 33-year-old sediment, CzcA sequences were mainly related to Rhodanobacter thiooxydans and Stenotrophomonas, suggesting a shaping of the metal-resistant microbial communities over time by both diagenetic processes and trace metal contamination. © 2014, Springer-Verlag Berlin Heidelberg

Les metaux-traces dans l'estuaire de la Seine et ses abords

Available from CEN Saclay, Service de Documentation, 91191 Gif-sur-Yvette Cedex (France) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Hydrodynamics of Suspended Particulate Matter in the Tidal Freshwater Zone of a Macrotidal Estuary (The Seine Estuary, France)

International audienc

Diversity of active microbial communities subjected to long-term exposure to chemical contaminants along a 40-year-old sediment core

International audienceIn estuarine ecosystems, metallic and organic contaminants are mainly associated with fine grain sediments which settle on mudflats. Over time, the layers of sediment accumulate and are then transformed by diagenetic processes mainly controlled by microbial activity, recording the history of the estuary's chemical contamination. In an environment of this specific type, we investigated the evolution of the chemical contamination and the structure of both total and active microbial communities, based on PhyloChip analysis of a 4.6-m core corresponding to a 40-year sedimentary record. While the archaeal abundance remained constant along the core, a decrease by one order of magnitude in the bacterial abundance was observed with depth. Both total and active microbial communities were dominated by Proteobacteria, Actinobacteria, and Firmicutes in all sediment samples. Among Proteobacteria, alpha-Proteobacteria dominated both total (from 37 to 60 %) and metabolically active (from 19.7 to 34.6 %) communities, including the Rhizobiales, Rhodobacter, Caulobacterales, and Sphingomonadales orders. Co-inertia analysis revealed a relationship between polycyclic aromatic hydrocarbons, zinc and some polychlorobiphenyls concentrations, and the structure of total and active microbial communities in the oldest and most contaminated sediments (from 1970 to 1975), suggesting that long-term exposure to chemicals shaped the structure of the microbial community

Temporal record of Pu isotopes in inter-tidal sediments from the northeastern Irish Sea

International audienceA depth profile of 239Pu and 240Pu specific activities and isotope ratios was determined in an inter-tidal sediment core from the Esk Estuary in the northeastern Irish Sea. The study site has been impacted with plutonium through routine radionuclide discharges from the Sellafield nuclear reprocessing plant in Cumbria, NW England. A pronounced sub-surface maximum of ~ 10 kBq kg-1 was observed for 239 + 240Pu, corresponding to the peak in Pu discharge from Sellafield in 1973, with a decreasing trend with depth down to ~ 0.04 kBq kg-1 in the deeper layers. The depth profile of 239 + 240Pu specific activities together with results from gamma-ray spectrometry for 137Cs and 241Am was compared with reported releases from the Sellafield plant in order to estimate a reliable sediment chronology. The upper layers (1992 onwards) showed higher 239 + 240Pu specific activities than would be expected from the direct input of annual Sellafield discharges, indicating that the main input of Pu is from the time-integrated contaminated mud patch of the northeastern Irish Sea. The 240Pu/239Pu atom ratios ranged from ~ 0.03 in the deepest layers to > 0.20 in the sub-surface layers with an activity-weighted average of 0.181. The decreasing 240Pu/239Pu atom ratio with depth reflects the changing nature of operations at the Sellafield plant from weapons-grade Pu production to reprocessing spent nuclear fuel with higher burn-up times in the late 1950s. In addition, recent annual 240Pu/239Pu atom ratios in winkles collected during 2003–2008 from three stations along the Cumbrian coastline showed no significant spatial or temporal differences with an overall average of 0.204, which supports the hypothesis of diluted Pu input from the contaminated mud patch