Search

The article presents the AMS (accelerator mass spectrometry) radiocarbon dating results of the Giant of Bevoay, which is a very large Grandidier baobab (Adansonia grandidieri Baill.) of Madagascar. The investigation of this baobab shows that it has a cluster structure, which consists of 3 perfectly fused stems. The calculated wood volume of the tree is 520 m3, which makes it the third largest Grandidier baobab and also the third largest individual of all Adansonia species. Two samples were collected from the outer part of the stems. The oldest dated sample segment had a radiocarbon date of 525 ± 23 BP, which corresponds to a calibrated age of 585 ± 10 years. According to this value, the Giant of Bevoay is 825 ± 50 years old.

International audience; La fouille de près de 5000 m² réalisée en 2014 sur la commune de Marigny-le-Châtel (Aube), lieu-dit « L’Epine Gérard », s’inscrit dans le cadre d’un vaste projet d’aménagement du territoire, l’implantation du gazoduc « Arc de Dierrey » sous la maîtrise d’ouvrage de GRT gaz. Celui-ci parcours plus de 300 kilomètres depuis le nord vers le centre de la France, dont près de 88 kilomètres (266 hectares) en Champagne-Ardenne (département de l’Aube et de la Haute-Marne). L’emprise de ce tracé a fait l’objet d’une attention archéologique particulière de la part du service régional de l’archéologie, d’abord par la prescription d’un diagnostic archéologique exhaustif sur toute la largeur de la bande concernée, parfois même d’un décapage intégral immédiat des zones soupçonnées être les plus prometteuses. L’ouvrage traverse en effet la Seine à deux reprises dans des secteurs déjà richement documentés, en particuliers les terrains alluviaux convoités par l’exploitation de granulats, le Nogentais et dans une moindre mesure le Vaudois. Il rencontre aussi des territoires peu soumis à la recherche archéologique, le sud de la Brie, le Pays d’Othe, le Barrois, et plus généralement le plateau crayeux champenois. Au total près de 45 occupations archéologiques ont été révélées, qui se sont traduites par près de 20 ha de prescriptions.

Around 50 graves were revealed in part of the Villenauxe-la-Grande necropolis (10, Aube), in 2014. These tombs belong to two distinct chronological phases: Late Roman Empire and the Carolingian Dynasty. This work aims to combine the different dating results obtained for each burial. These dates come from the typology of artefacts, coins, radiocarbon analyses and stra- tigraphic relationship. Bayesian statistics and ChronoModel software were used to synthesise all these dating methods. The dating range obtained provides a very detailed chronology and thus informs on the occupation dynamics of the necropolis. This method facilitates dialogue between the various specialists working on the different dating techniques., Une partie de la nécropole de Villenauxe-la-Grande (10, Aube) a révélé, en 2014, une cinquantaine de sépultures. Ces tombes appartiennent à deux phases chronologiques distinctes : l’Antiquité tardive et le haut Moyen Âge. L’enjeu de ce travail est de synthétiser les résultats des différentes datations obtenues pour chaque inhumé. Ces dates proviennent de la typologie du mobilier, des analyses radiocarbone, des monnaies et des relations stratigraphiques. La synthèse de toutes ces méthodes de datations a pu être menée via l’utilisation des statistiques bayésiennes et du logiciel ChronoModel. Les intervalles restitués permettent d’obtenir une grande finesse dans les datations et ainsi d’aborder la dynamique d’occupation de la nécropole. La méthode rend possible le dialogue entre les différents intervenants qui travaillent sur les datations.

The article discloses the accelerator mass spectrometry (AMS) radiocarbon dating results of the Big Reniala of Isosa, which is a massive Grandidier baobab (Adansonia grandidieri Baill.) of Madagascar. The investigation of this baobab shows that it consists of 5 perfectly fused stems and exhibits a cluster structure. The calculated wood volume of the tree is 540 m 3 , which makes the Big Reniala of Isosa the largest individual of all Adansonia species and also the biggest known angiosperm in terms of volume. Several samples were collected from the outer part of the stems. The oldest dated sample had a radiocarbon date of 934 ± 24 BP, which corresponds to a calibrated age of 845 ± 25 years. This value indicates an age of 1000 ± 100 years for the big Reniala of Isosa.

The article reports the growth stop phenomenon, which was documented only for baobabs, i.e. for trees belonging to the Adansonia genus. The identification of growth stop was enabled by radiocarbon dating, which allows a complex investigation of samples collected from the trunk/stems of baobabs. In several cases, the outermost rings of baobabs, which were close to the bark, were found to be old, with ages of several hundreds of years, instead of being very young. Dating results of samples collected from six baobabs are presented. For multistemmed baobabs, the growth stop may occur only for one or several stems. We identified four factors that may induce the growth stop: (i) stress determined by severe climate conditions, (ii) old age, (iii) the need to keep a stable internal architecture, and (iv) the collapse of stems that survive this trauma. Baobabs and their stems affected by growth stop may survive for several centuries, by continuing to produce leaves, flowers, and fruits. This phenomenon was associated with the capacity of baobabs to store large amounts of water in their trunks/stems in the rainy season. This reservoir of water is used during the dry season and allows the trees to survive prolonged drought periods.

Evidence from DNA phylogeny, Plio-Pleistocene ocean currents, giant tortoise dispersal, evolution of plant defences, radiocarbon dates and archaeology indicates that the endemic giant tortoises on the Mascarenes and Seychelles colonized naturally and were not translocated there by humans. Giant tortoises have fascinated Indian Ocean travellers since their first discovery on Mauritius by the Dutch in 1598 (Cheke & Bour, 2014), and a Reunion tortoise was among the earliest biological specimens to reach Europe from the Malagasy region (in 1671: Bour, 2004), but Wilme et al. (2016a) are the first to suggest that humans introduced them, their main arguments being that: Sea drift is too rare, uncertain and contrary to currents to account for the presence of tortoises on so many western Indian Ocean islands. The existing phylogeny, with dating considered uncertain, does not rule out rapid evolution in recent millenia as some tortoise mtDNA is known to mutate very rapidly. Hence, they imply that it is more likely that humans populated the Mascarene and Seychelles islands with tortoises. Specifically, they propose that Austronesian transoceanic colonists, with implied identity to settlers on Madagascar c. 4000 yr bp, distributed tortoises from Madagascar or Africa to Aldabra and the Mascarenes (Mauritius, Reunion, Rodrigues) as a food resource; the granitic Seychelles, oddly, are unmentioned. There are numerous reasons to reject this hypothesis. While Austronesians may have taken chickens and various crops from the Sunda Islands to East Africa and Madagascar (e.g. Boivin et al., 2013; but see Anderson et al., in press), there is no archaeological evidence that they discovered or visited the Mascarenes, granitic Seychelles or the Aldabra group atolls (Blench, 2010; Anderson et al., in press). In addition, the phylogeographical, ecological, evolutionary, palaeontological and archaeological evidence all strongly indicates the contrary. (Resume d'auteur)

The article reports the radiocarbon investigation of Anzapalivoro, the largest za baobab (Adansonia za) specimen of Madagascar and of another za, namely the Big cistern baobab. Several wood samples collected from the large inner cavity and from the outer part/exterior of the tree were investigated by AMS (accelerator mass spectrometry) radiocarbon dating. For samples collected from the cavity walls, the age values increase with the distance into the wood up to a point of maximum age, after which the values decrease toward the outer part. This anomaly of age sequences indicates that the inner cavity of Anzapalivoro is a false cavity, practically an empty space between several fused stems disposed in a ring-shaped structure. The radiocarbon date of the oldest sample was 780 ± 30 bp, which corresponds to a calibrated age of around 735 yr. Dating results indicate that Anzapalivoro has a closed ring-shaped structure, which consists of 5 fused stems that close a false cavity. The oldest part of the biggest za baobab has a calculated age of 900 years. We also disclose results of the investigation of a second za baobab, the Big cistern baobab, which was hollowed out for water storage. This specimen, which consists of 4 fused stems, was found to be around 260 years old.

The article reports the AMS radiocarbon investigation of the two largest known Adansonia grandidieri specimens. The two baobabs, which are named Tsitakakoike and Pregnant baobab, are located in Southwestern Madagascar, near Andombiro. A third specimen from this area, the House baobab, was also investigated. According to measurements, Tsitakakoike is the biggest individual above ground level of all Adansonia species. The House baobab was selected for its exposed structure, which is identical to the closed ring-shaped structure with false cavities identified by us in large and old Adansonia digitata specimens. According to our research, Tsitakakoike and the Pregnant baobab have multi-stemmed cylindrical trunks which are mainly hollow; the two very large baobabs also possess a ring-shaped structure. The radiocarbon dates of the oldest wood samples collected from the large trunks were 1274 ± 20 bp for Tsitakakoike and 930 ± 20 bp for the Pregnant baobab. According to their original positions and to the architectures of the two A. grandidieri , the ages of Tsitakakoike and Pregnant baobab would be between 1300 and 1500 years. Therefore, A. grandidieri becomes the third Adansonia species with individuals that can live over 1000 years, according to accurate dating results.

We present an overview on different environmental zones within coastal areas and summarise the physical basis behind the three most important methods that are available to date Holocene coastal sediments. Besides radiocarbon and uranium series dating, Optically Stimulated Luminescence (Osl) has increasingly been applied for dating in coastal settings over the past decade. This is illustrated by a number of case studies showing that Osl can be applied to sediments from almost any kind of coastal environment, covering a potential dating range from some years up to several hundred thousand years. Osl dating may hence be the method of choice for deciphering natural environmental change along coasts as well as the presence and the impact of human occupation in such areas. In addition, we briefly show how and where these dating methods could be applied to constrain the palaeo-environmental context of an archaeological site at Vohemar in north-eastern Madagascar. Nous présentons un aperçu sur les différentes zones environnementales dans les secteurs côtiers et proposons de résumer les bases physiques des trois méthodes les plus importantes disponibles à ce jour pour dater les sédiments côtiers de l’holocène. Outre le radiocarbone et la datation série de l’uranium, la luminescence stimulée optiquement (Osl) a été la plus appliquée pour la datation en milieu côtier durant la dernière décennie. Ceci est illustré par un certain nombre d’études de cas montrant que l’Osl peut être appliquée à des sédiments à partir de presque n’importe quel type de milieu côtier, couvrant une datation potentielle de quelques années jusqu’à plusieurs centaines de milliers d’années. La datation par Osl peut donc être une méthode de choix pour décrypter les changements environnementaux naturels le long des côtes ainsi que la présence et l’impact de l’occupation humaine dans ces zones. De plus, nous avons brièvement montré comment et où ces méthodes de datation pourraient être appliquées pour circonscrire le contexte paléo-environnemental d’un site archéologique comme Vohémar, dans le nord-est de Madagascar.

Le site de Saint-Pierre-les-Églises - dans la commune actuelle de Chauvigny - est un lieu d'une grande beauté, qui ne laisse aucun visiteur indifférent. Ses qualités environnementales ont été très tôt repérées et exploitées, comme en témoigne son occupation dès l'Antiquité. Les peintures murales qui ornent l'abside de cette petite église font l'objet d'une polémique. en effet, leur chronologie est très discutées, entre certains historiens de l'art qui les placent à l'époque romane, et d'autres spécialistes qui défendent une datation carolingienne ou plus largement antérieure à l'an mil. Basée sur des arguments iconographiques, stylistiques et partiellement architecturaux, aucune de ce deux hypothèses ne disposait jusqu'à ce jour d'indices chronologiques décisifs et discutables L'objet de cet article est donc d'apporter des élément de datation déterminants, afin de mettre fin à la polémique qui agite les historiens de l'art depuis un demi-siècle, et de replacer solidement ces peintures dans le contexte historique. Après une brève présentation du site et en se référant aux publications antérieures, l'auteur présente deux aspects de récentes investigations réalisées sur cet édifice et plus particulièrement sur ses peintures : les nouvelles données dont on dispose aujourd'hui sur la datation des enduits peints par le radiocarbone et le projet d'étude interdisciplinaire que l'auteur propose afin d'assumer la conservation de ce patrimoine.

18 pages; In India, soils have, for a long time, been classified according to their colour. Nilgiri soils have not escaped this rule and Francis (1908), in the district gazetteer dealing with this region, noticed that ‘four varieties are usually recognised. These are the black, which is a rich loam and the best of all... the brown... the yellow... and the red soil...'. This study focuses exclusively on the ‘black soils' of the Nilgiri Hills. Detailed results regarding their properties, genesis, and classification in modern taxonomies are provided and demonstrate that these soils, which occur on hillslopes and hilltops, are very different from the other ‘black' soils occurring in South India: namely peat soils, which are also found in the Nilgiri Hills but are restricted to valley floors; and Vertisols, which occur on colluvio-alluvial parent material in the Deccan traps as well as portions of the Precambrian basement. Isotopic results bring to light the influence of palaeoecological conditions, particularly the impact of a colder period, characterised by grassland vegetation at the end of the Pleistocene, on the in-situ accumulation of organic matter.

Un exemple, pris en Inde du Sud, montre les potentialités offertes par l'étude d'andosols non allophaniques d'altitude pour reconstituer l'histoire paléoenvironnementale locale. Dans ce type de sol, la matière organique est stabilisée sous forme de complexes organométalliques qui ne migrent que très lentement. Comparé au signal général enregistré par les tourbières, le signal retenu par la matière organique paraît beaucoup plus ponctuel ; ceci permet des études paléoenvironnementales plus précises. Cette application vient à un moment où des reconstitutions paléoclimatiques précises sont nécessaires pour bâtir des modèles climatiques fiables.