Archéologie et Archéométrie

We have measured radiocarbon in prebomb known-age shells and coral from the Indian Ocean and southeast Asia to determine marine reservoir age corrections. Western Indian Ocean results show a strong 14 C depletion due to upwelling in the Arabian Sea, and indicate that this signal is advected over a wide area to the east and south. In contrast, the surface waters of the South China Sea contain relatively high levels of 14 C, due in part to the input of well-equilibrated water masses from the western Pacific. The easternmost regions of the Indian Ocean are also strongly influenced by the flowthrough of Pacific waters north of Australia.

A program of individual precipitation events and river water sampling and of water isotopic measurements (δD, δ 18 O) was carried out during summer 1996 along a northeast/southwest transect of the Tibetan Plateau. The spatial distribution of both δ 18 O and deuterium excess (d = δD‐8*δ 18 O) of the precipitation reveals three distinct regions. Simulations with a simple isotopic model and seasonal isotopic variations measured at two extreme south and north locations support our interpretation in terms of different summer moisture origins: (1) South of the Himalayan mountains, the moisture provided by the Indian monsoon has been recycled over the Indian peninsula. (2) Between the Himalayas and the Tanggula mountains the oceanic moisture is directly transported from the Bay of Bengal along the Brahmaptra River valley. (3) North of the Tanggula mountains, the moisture is not provided by the monsoon anymore but by continental water recycling.

Isotope studies show that the Vostok ice core consists of ice refrozen from Lake Vostok water, from 3539 meters below the surface of the Antarctic ice sheet to its bottom at about 3750 meters. Additional evidence comes from the total gas content, crystal size, and electrical conductivity of the ice. The Vostok site is a likely place for water freezing at the lake-ice interface, because this interface occurs at a higher level here than anywhere else above the lake. Isotopic data suggest that subglacial Lake Vostok is an open system with an efficient circulation of water that was formed during periods that were slightly warmer than those of the past 420,000 years. Lake ice recovered by deep drilling is of interest for preliminary investigations of lake chemistry and bedrock properties and for the search for indigenous lake microorganisms. This latter aspect is of potential importance for the exploration of icy planets and moons.

W e studied 54 patients operated on for combined supraspinatus and infraspinatus rotator-cuff tears. The presence or absence of the dropping and hornblower's clinical signs of impaired external rotation were correlated with Goutallier stage-3 or stage-4 fatty degeneration of infraspinatus and teres minor. These grades of fatty degeneration have previously been correlated with a poorer outcome from reconstructive surgery.

High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind 14 C dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are obtained. We also highlight the procedures, problems, and uncertainties involved in determining atmospheric and surface ocean 14 C/ 12 C in these archives, including a discussion of the various methods used to derive an independent absolute timescale and uncertainty. The types of data required for the current IntCal database and calibration curve model are tabulated with examples.

Abstract The grey wolf ( Canis lupus ) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage ( Canis familiaris ) lived 1–8 . Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT88 40,000–30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.

= 98) (7000-3000 BCE). Using the genetic substructure observed in European hunter-gatherers, we characterize diverse patterns of admixture in different regions, consistent with both routes of expansion. Early western European farmers show a higher proportion of distinctly western hunter-gatherer ancestry compared to central/southeastern farmers. Our data highlight the complexity of the biological interactions during the Neolithic expansion by revealing major regional variations.

L’extraction des sables et graviers en rivière a augmenté dans les pays développés depuis au moins le milieu du XXe siècle, en particulier pour la construction (béton) et les remblais (voies ferrées et routières, conquête de terrains en zone inondable, plates-formes en mer). Dans les 30 dernières années, ce phénomène a connu une grande expansion dans les pays en développement tels que la Chine, l’Inde et dans d’autres pays asiatiques à croissance rapide. Les impacts négatifs de l’extraction des ressources fluviales sont bien documentés en Europe et aux États-Unis depuis le début des années 1980 et des études sont maintenant disponibles sur les extractions en Asie du Sud-est et notamment en Chine.Le Bas Mékong et ses bassins tributaires sont des hauts lieux de la biodiversité mais ils ont connu un essor considérable de la construction des barrages, en particulier sur le cours chinois du Mékong, le Lancang. L’enjeu actuel le plus important dans le bassin du Mékong est sans aucun doute la menace qui pèse sur les côtes du delta car l’importance de ce dernier est remarquable en termes de sécurité alimentaire pour les populations en forte croissance du Vietnam et du Cambodge. Les raisons les plus souvent citées pour expliquer le recul du delta sont le piégeage des sédiments qui se fait dans les retenues du haut bassin et le changement climatique. Les extractions de sable et gravier dans le chenal du Mékong et sur ses affluents n’ont pas encore été prises en considération.Cet article fournit la première évaluation de l’extraction des ressources en granulat sur les 2 400 km du cours principal du Bas Mékong, de la frontière chinoise au delta. Le Fonds Mondial pour la Nature (WWF) a réalisé un relevé en 2011-2012. Des entretiens systématiques ont été réalisés dans les quatre pays du bas Mékong pour évaluer les types de matériaux extraits, les techniques utilisées, les volumes extraits, les tendances enregistrées ces dernières années et les changements attendus dans la géographie des extractions. Les résultats révèlent que le volume annuel de sable et de gravier extrait, en dépit d’une sous-évaluation évidente, excède le volume de sable et de gravier transporté par le fleuve. Les résultats soulignent aussi l’importance considérable de ce facteur dans les changements géomorphologiques et écologiques enregistrés dans les différents tronçons du Mékong et dans son delta.

Two cruises (April and June 1997) were carried out in the Bay of Seine, a nitrate-and ammonium-enriched ecosystem of Western Europe, to identify the major mechanisms that control 15 N and 13 C in spring particulate organic matter (POM). Particulate organic nitrogen (PON) 15 N ranged between 0.8 and 5.2 in April and between 2.2 and 6.2 in June, while particulate organic carbon (POC) 13 C ranged between -24.3 and -19.7 , and between -20.0 and -16.2 during the same periods. During spring 1997, POM was highly dominated by autochthonous phytoplankton. It is shown that the variation of PON 15 N is due to both nitrate mixing between river and marine waters and fractionation of N stable isotopes during nitrate utilization by phytoplankton. Therefore, similarly to what was previously shown for open ocean, 15 N can be used as a proxy of spring fractional nitrate utilization in coastal ecosystems. It is also shown that POC 13 C in spring is controlled by POC concentration and C:N ratio (in addition to 'temperature effects'), which are considered here as indicators of primary production and phytoplankton degradation, respectively. The co-variation of 13 C and 15 N describes the spring phytoplankton dynamics: at the start of phytoplankton development, nitrate concentration is high (low 15 N) and phytoplankton production is low (low 13 C); then primary production increases ( 13 C becomes higher) and the nitrate pool diminishes ( 15 N becomes higher); at a later stage, the nitrate pool is depleted (high 15 N), part of the phytoplankton becomes degraded and production is still high (high 13 C).

In this study, the purification by cross-flow filtration (CFF) and freeze drying of poly(D,L-lactic acid) (PLA) nanoparticles prepared by an emulsion-diffusion technique using poly(vinyl alcohol) (PVAL) or poloxamer 188 (P-188) were investigated. The stability of the suspensions was correlated to the affinity of the stabilizers for the nanoparticle surface, the resistance of the coating layer to continuous filtration and to freeze-thawing procedures. The results indicated a clear difference between the two stabilizers, suggesting that the nature of the coating layer has a very important role during CFF and freeze-drying. Nanoparticles prepared with PVAL were filtered and freeze-dried without nanoparticle fusion. This behaviour was attributed to the formation of a stable thick layer (similar to that found for polystyrene latex). In contrast, aggregation of nanoparticles was observed during CFF for the batches prepared with P-188, indicating that the polypropylene oxide blocks present in the copolymer have little affinity for the PLA surface. However, these suspensions were successfully recovered when using stabilizer solutions as diafiltration media, suggesting a dynamic exchange between the P-188-adsorbed chains and those of the identical polymer remaining in the bulk solution. The presence of P-188 did not prevent nanoparticle aggregation after freeze-drying. Therefore, the use of cryoprotectants was necessary. Aggregation may have been due to an increase in the solubility of P-188 in the bulk solution, which provokes a destabilization of the suspension by desorption and partial coverage of the surface. The best cryoprotectants were found to be sugars containing glucose units. The cryoprotective effect was related to the hydrogen bonding capability of these sugars, which prevented aggregation by dehydration of P-188 forcing it to the PLA surface.

We analyze the surface δ 18 O‐salinity relationships of the Bay of Bengal and the Arabian Sea, in the northern Indian Ocean, known for their contrasting hydrological conditions. New measurements of these tracers show a very low δ 18 O‐salinity slope associated with the strong dilution in the Bay of Bengal, but a slope more typical of this latitude in the Arabian Sea. Although this region is marked by a complex monsoonal regime, numerical modeling using a box model and a general circulation model is able to capture the δ 18 O‐salinity slope and its geographical variation. Both models clearly show that the low δ 18 O‐salinity slope is due to the evaporation‐minus‐precipitation balance, with an important contribution of the continental runoff in the Bay of Bengal. Although the low value of these slopes (∼0.25) makes past salinity reconstructions uncertain, insight into the Last Glacial Maximum conditions shows a probable stability of these slopes and limited error on paleosalinity.

Abstract Wood plays an important role in stream ecology and geomorphology. Previous studies of wood in rivers have quantified spatial distributions but temporal dynamics remain poorly documented. The lack of such data is related to limitations of existing methods, especially when applied to large rivers. Five techniques are field‐tested to assess their utility for quantifying the temporal dynamics in rivers: repeated high‐resolution aerial surveys, the measurement of wood physical characteristics as proxies for 14 C dating, passive and active radio frequency identification (RFID) tags, radio transmitters, and video. The spatial distribution of wood is surveyed using aerial imagery with a resolution finer than 0·10 m. The estimation of temporal trends by repeated aerial‐based surveys needs to consider vegetation growth and hiding. Wood residence times can be calculated using 14 C analysis, but the assessment of wood physical characteristics including decay status and wood density offers a cheaper, if less accurate, alternative. Wood resistance to penetration is tested but results are not significant. Radio transmitters are reliable for multi‐year (∼5 year) surveys and can be detected at 800 m. Passive RFID tags are limited by a read range of 0·30 m but are reliable for longer term (>5 year) studies. Active RFID tags combine a moderate read range (10–300 m) and low cost with in‐flood detection but require more testing. Video monitoring of wood passing on the surface of a river is successfully implemented. For a single flood on the Ain River (France), wood transport rates are an order of magnitude higher on the rising limb of the hydrograph than on the falling limb. Overall, the techniques improve the ability to gather the data needed to understand wood transfer processes and calibrate budgets of wood in rivers. Copyright © 2009 John Wiley & Sons, Ltd.

Foraminiferal assemblages were studied in northern Barents Sea core ASV 880 along with oxygen and carbon isotope measurements in planktonic ( N. pachyderma sin. ) and benthic ( E clavatum ) species. AMS C‐14 measurements performed on molluscs Yoldiella spp. show that this core provides a detailed and undisturbed record of Holocene climatic changes over the last 10000 calendar years. Surface and deep waters were very cold (<0°C) at the beginning of the Holocene. C. reniforme dominated the highly diverse benthic foraminiferal assemblage. From 10 to 7.8 cal. ka BP, a warming trend culminated in a temperature optimum, which developed between 7.8 and 6.8 cal. ka BP. During this optimum, the input of Atlantic water to the Barents Sea reached its maximum. The Atlantic water mass invaded the whole Franz Victoria Trough and was present from subsurface to the bottom. No bottom water, which would form through rejection of brine during winter, was present at the core depth (388 m). The water stratification was therefore greatly reduced as compared to the present. An increase in percentage of I. helenae/norcrossi points to long seasonal ice‐free conditions. The temperature optimum ended rather abruptly, with the return of cold polar waters into the trough within a few centuries. This was accompanied by a dramatic reduction of the abundance of C. reniforme. During the upper Holocene, the more opportunistic species E. clavatum became progressively dominant and the water column was more stratified. Deep water in Franz Victoria Trough contained a significant amount of cold Barents Sea bottom water as it does today, while subsurface water warmed progressively until about 3.7 cal. ka BP and reached temperatures similar to those of today. These long‐term climatic changes were cut by several cold events of short duration, in particular one in the middle of the temperature optimum and another, which coincides most probably with the 8.2 ka BP cold event. Both long‐ and short‐term climatic changes in the Barents Sea are associated with changes in the flow of Atlantic waters and the oceanic conveyor belt.

Abstract Paleoprecipitation reconstructions on the basis of pollen are well known, but they do not provide high temporal resolution for glacial periods. High-resolution paleoprecipitation reconstructions for the last glaciation based on the isotopic record organic matter in loess from Nussloch (Rhine Valley, Germany) are consistent with paleoprecipitation inferred from peat in the same area using an independant method. Thus, δ 13 C of loess organic matter can be used as a proxy for paleoprecipitation.

Here we present and analyze the complete Vostok ice cores deuterium excess record which spans the last four climatic cycles, back to ∼420,000 years B.P. To extract paleoclimate information from this record, we use isotopic modeling showing that changes in deuterium excess ( d = δD‐8δ 18 O) of Vostok precipitation reflect changes in the average temperature of oceanic moisture sources. Over the last 250,000 years the deuterium excess is strongly anticorrelated with changes in Earth's obliquity. This reflects changes in the relative contribution of low and high latitudes to the Vostok precipitation, resulting from changes in the latitudinal annual mean insolation gradient governed by the obliquity. However, this modulation by obliquity is not observed prior to 250,000 years B.P. We attribute this difference to the ice flow, the deeper ice under Vostok station having accumulated in a location upstream Vostok, receiving precipitation from different oceanic origins. Despite this difference between the earlier and the later portions of the record, the deuterium excess changes during all the glacial inceptions are similar in amplitude and timing relative to the deuterium decrease. The glacial inceptions are characterized by high deuterium excess, indicating the significant role of the tropics in supplying moisture to the already cold poles.

After a brief presentation of the experimental protocols, this article discusses the results of the 14C dates obtained from charcoal specimens collected on the walls (drawings and torch-wipes) and on the ground of the Chauvet Cave. The dates, which are coherent, can be divided into two periods a few millennia apart: between 33000 and 29000 14C years BP (33 samples including the five parietal representations) and between 27000 and 24500 14 C years BP (13 samples including the four torch-wipes).

The carbon and oxygen stable isotope composition of wood cellulose (delta(13)C(cellulose) and delta(18)O(cellulose), respectively) reveal well-defined seasonal variations that contain valuable records of past climate, leaf gas exchange and carbon allocation dynamics within the trees. Here, we present a single-substrate model for wood growth to interpret seasonal isotopic signals collected in an even-aged maritime pine plantation growing in South-west France, where climate, soil and flux variables were also monitored. Observed seasonal patterns in delta(13)C(cellulose) and delta(18)O(cellulose) were different between years and individuals, and mostly captured by the model, suggesting that the single-substrate hypothesis is a good approximation for tree ring studies on Pinus pinaster, at least for the environmental conditions covered by this study. A sensitivity analysis revealed that the model was mostly affected by five isotopic discrimination factors and two leaf gas-exchange parameters. Modelled early wood signals were also very sensitive to the date when cell wall thickening begins (t(wt)). Our model could therefore be used to reconstruct t(wt) time series and improve our understanding of how climate influences this key parameter of xylogenesis.

Abstract Soil carbon dynamics is strongly controlled by depth globally, with increasingly slow dynamics found at depth. The mechanistic basis remains however controversial, limiting our ability to predict carbon cycle-climate feedbacks. Here we combine radiocarbon and thermal analyses with long-term incubations in absence/presence of continuously 13 C/ 14 C-labelled plants to show that bioenergetic constraints of decomposers consistently drive the depth-dependency of soil carbon dynamics over a range of mineral reactivity contexts. The slow dynamics of subsoil carbon is tightly related to both its low energy density and high activation energy of decomposition, leading to an unfavourable ‘return-on-energy-investment’ for decomposers. We also observe strong acceleration of millennia-old subsoil carbon decomposition induced by roots (‘rhizosphere priming’), showing that sufficient supply of energy by roots is able to alleviate the strong energy limitation of decomposition. These findings demonstrate that subsoil carbon persistence results from its poor energy quality together with the lack of energy supply by roots due to their low density at depth.

The loess series at St. Pierre‐les‐Elbeuf and St. Sauflieu are key successions for the western European Quaternary stratigraphy. The present study proposes a detailed record of the last interglacial‐glacial climatic cycle at St. Pierre and its integration into the synthetic pedosedimentary record of north‐western France using detailed correlations with the type sections of St. Sauflieu and Achenheim. Finally, comparisons with the marine isotope, Greenland GRIP chronologies and dust records are proposed. At St. Pierre, the pedostratigraphic and sedimentological analyses (total iron, organic matter, carbonate, grain size), in association with low field magnetic susceptibility measurements, demonstrate that this loess succession records the major climatic events of the Upper Pleistocene. The basal soil complex at St. Pierre is similar to those from the main successions of North (St. Sauflieu) or Northeast France (Achenheim). It shows a Bt horizon of brown leached soil, a deeply reworked grey forest soil and two isohumic steppe soils separated by a non‐calcareous loess layer. This loess level corresponds to the first aeolian event clearly observed in the succession and can be correlated with Marker II of the Central European stratigraphy located around the marine isotope stage (MIS) 5/4 boundary. The main aeolian sedimentation starts after the soil complex and ends with the top soil (brown leached soil). Finally, a good parallel is observed between the strongest peaks of the dust records of the ice cores and the main period of loess deposition in St Pierre‐lès‐Elbeuf occurring during MIS 2.

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