Trace element geochemistry in Balchit obsidian (Upper Awash, Ethiopia)

autorisation des éditeurs de l'ouvrage par email du 01/07/05The only identified source on the left bank of the Awash River is obsidian of type A (Balchit main lava outcrop). Thus, differences observed among the analysed samples concerning obsidians of types B and C may reflect minor variations among a single source during the emplacement of the lava or refer to unidentified sources upstream or on the left bank basin of the Awash River. Obsidian of type D collected south of the Awash River in Simbiro Creek formations is a grey vitrous fluidal lava with a porphyric microstructure; quartz and feldspar crystals are oriented according to the fluidal structure. This material appears to be an ignimbrite facies which vitreous bedsole rapidly cooled in the contact with the substratum. We have identified several similar ignimbrites in this area. The Balchit obsidian lava and its reworked debris are widely distributed in the paleoenvironment and form a major raw material source for prehistoric artefacts. In the future we may expect to identify more obsidian types in primary and secondary positions and including some flaked by hominids, especially in the southern part of the Melka Kunture are

Monte Arci Obsidians: Some More Geochemical Data from EMP-WDS, SEM-EDS and PIXE

We bring new geochemical data on Monte Arci (Sardinia) obsidians from elemental analyses by electron microprobe (EMP) and proton-induced X-ray emission (PIXE). Obsidians from the geochemical groups SA, SB1, SB2 and SC can be sorted out from their major element contents by EMP and from their trace element contents by PIXE. While EMP analysis requires for analysis a few milligrams polished fragment, PIXE is strictly non-destructive. Forty samples were part of a program aimed at the geochemical characterization of Monte Arci secondary sources

Denudation of the Côte d'Ivoire-Ghana transform margin from apatite fission tracks.

Apatite fission track analysis of samples from the shoulder (marginal ridge) of the Côte d'Ivoire-Ghana transform continental margin reveal a cooling of the margin between 85 and 65 Ma for the central and eastern parts of the ridge. All samples were heated in situ during sedimentary burial with a temperature >120 °C, except for two samples located in the eastern part which were heated between 105 and 120 °C. For the first time, age/depth diagram along a transform margin shows a shape involving erosion starting at the bottom of the continental slope, then stepping backwards towards the edge of the slope. This retrogressive erosion can result from the deepening of the lithospheric plate sliding along the transform margin, from thick continental crust to thin continental crust, and finally to oceanic crust. This process could be at the origin of the shoulder uplift by flexural response to the important crustal discharge (>2 km)

PIXE analysis of the obsidian support of two paintings from<br />the Louvre by Murillo

The very unusual black backings of two paintings by the Spanish master Murillo (1617-1682) representing Passion Scenes, on display at the Louvre museum, have been analyzed by PIXE with the AGLAE facility of the C2RMF. The support proved to be obsidian, a natural volcanic glass widely employed to produce archeological artefacts, in particular in South and Meso-America. Five archeological artifacts with similar shape to the paintings called “obsidian mirrors”, originating from Mexico and belonging to the collections of the Mus´ee de l'Homme in Paris, have been analyzed and the composition of four of them showed to be very similar to Murillo's obsidians. The comparison with the results obtained on reference obsidian samples from Mexican sources and with data from the literature by instrumental neutron activation analysis (INAA) suggested that the Ucareo/Zinap´ecuaro, Michoac´an, Mexico is the source of the obsidian employed for the paintings. A field trip to this area was therefore organized to collect samples whose natural slab shape and chemical composition confirmed the Ucareo provenance hypothesis. The rectangular backing of Murillo's paintings are unlikely archaeological artefacts but rather objects specially made after the Spanish conquest by Mesoamerican craftsmen, among which some were exported to Europe where Murillo spent all his life. The observation, in the walls of the church and other Christian monuments in Ucareo, of obsidian inlays, a material of particular significance in the pre-Hispanic culture, underlines the complex intrication of native culture and European influences which are also carried by Murillo's paintings. Meanwhile, a third painting on obsidian by Murillo as been identified in the Museum of Fine Arts of Houston, Texas, U.S.A. This study also points out that even if the ranges of elements dosed by PIXE and INAA do not fully overlap, the measurements obtained by both techniques can be efficiently used for provenancing obsidians objects

Вплив різних видів анестезіологічного забезпечення на неспецифічну ланку імунітету вагітних під час кесарева розтину

Компоненты хирургической операции – операционная травма, стресс, общая анестезия, кровопотеря, антибактериальная – терапия приводят к снижению защиты иммунной системы и развитию вторичной иммунной недостаточности. В результате операционно-анестезиологического стресса в организме больного возникает состояние иммунодепрессии, которое необходимо нивелировать путем выбора анестетиков, минимально угнетающих иммунные реакции. Такой подход дает возможность разработать и внедрить в клиническую практику оптимальные методы анестезии у беременных. Проведенное исследование показало, что операционный стресс негативно влияет на неспецифический иммунитет беременных. В зависимости от вида анестезии проявления негативного влияния будет различным. Установлено, что спинальная анестезия сопровождается минимальным влиянием на фагоцитарную активность лейкоцитов, а общая анестезия имеет депрессивное влияние, которое сопровождается более пяти дней.Components surgery . surgical trauma, stress, general anesthesia, blood loss, antibiotic . therapy leads to a decrease in defense of the immune system and the development of secondary immune deficiency. As a result of operational and anesthetic stress in the patient.s body a state of immunosuppression, which is necessary to level by selecting the anesthetic minimally depressing the immune response. This approach provides an opportunity to develop and introduce into clinical practice the best methods of anesthesia in pregnant women. The study showed that operational stress affects the nonspecific immunity of pregnant women. Depending on the type of anesthesia, manifestations of the negative impact will be different. Established that spinal anesthesia with a minimum influence on the phagocytic activity of leukocytes and general anesthesia has a depressive effect which is accompanied by more than five days

Obsidian Economy in the Rio Saboccu Open-Air Early Neolithic Site (Sardinia, Italy)

Integrated provenance/typo-technologic/chaînes opératoires studies on obsidians from Early Neolithic (EN) assemblages are still quite exceptional in the western Mediterranean region. The Rio Saboccu S1-S2 EN dwelling structures (Central-western Sardinia) 14C dated to the last three centuries of the VIth millennium BC provided us with an opportunity to apply such an approach. A comprehensive provenance study of its 1.114 obsidian artefacts was realized through a combined visual/instrumental approach. Elemental compositions were determined mostly by ion beam analysis (PIXE) and by electron microprobe (SEM-EDS). The S1-S2 structures are situated inside the so-called supply zone of the Monte Arci volcanic complex. A technological analysis of the implements revealed a non-opportunistic behaviour in relation to obsidian procurement among the four (SA, SB1, SB2, SC) Monte Arci types locally available in various contexts (from primary to secondary sources). A comparison with other Sardinian EN sites suggests that the human groups settled near the Monte Arci sources might have acted as a ‘filter’ in the first stages of the diffusion of obsidians in Sardinia and possibly elsewhere in the northern Tyrrhenian area

Tendances actuelles dans la caractérisation des obsidiennes pour les études de provenance

Les recherches de provenance des obsidiennes de sites paléolithiques et néolithiques connaissent actuellement une grande expansion, notamment par leur intégration dans les études de chaînes opératoires, qui nécessitent de déterminer l’origine de la matière première de séries importantes de pièces archéologiques. Il existe par ailleurs une forte demande de mesures peu à non destructives et éventuellement à effectuer in situ. D’où un certain nombre de développements méthodologiques récents. Le but de cette contribution est d’en présenter le statut actuel.Sourcing studies involving obsidians from Palaeolithic and Neolithic sites are presently undergoing a period of change, notably in terms of the average number of samples analyzed per project, due largely to their integration into the chaînes opératoires approach of lithic technologies. This can entail working with a large number of artifacts from an archaeological context. There is also an ever-increasing demand to employ quasi non-destructive characterization methods and completely non-destructive methods that eventually could be performed in situ. As such, recent methodological advances have taken several directions. The purpose of this short note is to give an overview of these approaches

Les datations par traces de fission de l'Uranium. Principes et applications aux problèmes du Quaternaire.

International audienc

L' obsidienne dans le processus de Néolithisation du Proche-Orient (12000-6500 av. j.-C. cal.)

La Néolithisation du Proche-Orient est un vaste sujet de recherche impliquant des spécialistes issus de disciplines variées. Le présent travail y contribue à travers l étude d une matière première lithique diffusée à grande échelle : l obsidienne. L intérêt de ce matériau consiste notamment en sa prédisposition pour les études de provenance. Il est d autant plus déterminant dans ces civilisations dépourvues de céramique, l obsidienne restant alors le seul marqueur d échange univoque. D un point de vue géologique et géochimique, le corpus sur les sources de l obsidienne proche-orientale demeurait lacunaire. Nous avons proposé de l enrichir par la caractérisation d une quarantaine de gisements répartis dans toute l Anatolie et en Transcaucasie. Une centaine d aliquotes géologiques ont été analysés par ICP-MS, ME-WDS, PIXE et MEB-EDS. Leurs potentiels de discrimination respectifs ainsi que les possibilités et limites de leur application à des artefacts archéologiques parfois précieux ont été discutés. Ces considérations ont conduit à la mise en place d une stratégie analytique originale pour déterminer la provenance de 500 obsidiennes archéologiques issues d horizons spatio-temporels diversifiés. Leur étude a dispensé une meilleure connaissance de l exploitation des sources d obsidienne d une part, de la distribution de leurs produits respectifs d autre part. A la lumière de ces résultats, une synthèse renouvelée sur le phénomène obsidienne a été proposée, celui-ci en outre repensé dans une optique à la fois synchronique et diachronique à chaque étape du processus de Néolithisation. Les données ainsi réunies ont conduit à considérer l obsidienne non plus comme un simple traceur d échanges mais comme une caractéristique du Néolithique, au même titre que d autres critères (économie de subsistance, architecture, technologie). Le phénomène obsidienne s est révélé partie intégrante du phénomène social total qu est la Néolithisation.The Neolithisation of the Near East is a vast topic of research implying specialists of various fields. This work contributes to its better understanding through the study of a lithic raw material diffused on a large scale : obsidian. This material is of particular interest based on its predisposition for provenance studies. In aceramic civilisations, obsidian remains the only univocal marker of exchange.From a geological and chemical point of view, the corpus of the Near Eastern obsidian sources was still incomplete. We proposed to enrich this knowledge by the characterization of about forty sources spread through Anatolia and Transcaucasia. About 100 geological aliquotes were analyzed by ICP-MS, EMP-WDS, PIXE and SEM-EDS. Their respective potential for discrimination within the samples was weighed against the limitations in the application to sometimes precious archaeological artefacts. Those considerations led to the creation of an original analytical strategy to determine the provenance of 500 archaeological obsidian samples from various spatio-temporal horizons. Their study allowed a better understanding of both the obsidian sources exploitation, and their respective products distribution. According to these data, we proposed a renewed synthesis on the obsidian phenomenon , a summary now considered with a synchronic and diachronic perspective at each step of the process of Neolithisation . The data led us to consider obsidian, not only as a simple exchange tracer, but also as a characteristic of the Neolithic, along with other criteria such as subsistence economy, architecture and technology. The obsidian phenomenon appears to be an integral part of the total social phenomenon that constitutes Neolithisation.BORDEAUX3-BU Lettres-Pessac (335222103) / SudocSudocFranceF

Obsidian provenance studies in Colombia and Ecuador: obsidian sources revisited

International audienceThe field occurrences, elemental compositions and formation ages of Colombian and Ecuadorian obsidians are revisited. It is shown that the regional sources of this raw material are linked to two major volcanic structures: the Chacana and the Paletara calderas, localised on the eastern cordillera of Ecuador and on the central Andean cordillera of south Colombia respectively. Seventy-two samples were analysed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS) and/or particle induced X-ray emission (PIXE). The same 10 types of elemental compositions were identified independently from ICP and PIXE. Four of these types were previously unknown. The formation ages of these obsidians previously determined by fission tracks dating are in the range 0.17–1.58 Ma at Chacana and 3.46–4.27 Ma at Paletara. Most Colombian and Ecuadorian pre-Hispanic artefacts present elemental compositions compatible with a Chacana- or Paletara-derived origin of the raw material. However, some of them present fission track ages discordant with the present-day known obsidian occurrences, which implies that the regional source inventory is not yet exhaustive