Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A detailed rock-magnetic and archeointensity study was carried out on materials baked by a western Mexican artisan following traditional techniques to produce faithful reproductions of archeological pieces of the Michoacan region (Western Mesoamerica). The field strength at the site (41.0 +/- 0.51 mu T) was measured with a fluxgate magnetometer and the temperature of the furnace during the baking process was monitored continually by means of a thermocouple placed in the middle of the baking cavity.;Rock-magnetic experiments performed on the raw material (clay and paste) and on in situ prepared baked ceramics and bricks included measurement of thermomagnetic curves (susceptibility and strong-field magnetization versus temperature), first-order reversal curves (FORC), anisotropy of magnetic susceptibility (AMS) and anisotropy of thermoremanent magnetization (A-TRM). Magnetite and probably hematite are present in the samples as carriers of the remanence. Hysteresis ratios suggest that the samples fall in the pseudo-single-domain grain size region, which may indicate a mixture of multidomain and a significant amount of single-domain grains.;Ceramic pieces and brick fragments were subjected to the Thellier-Coe archeointensity method and to an alternative paleointensity experiment, with a TRIAXE magnetometer, in order to check whether they are faithful recorders of the local geomagnetic field strength.;Mean raw-intensity of sample M1 (pottery) overestimates a 7% the expected site intensity, while those corresponding to the brick samples (LQ1 and LQ2) underestimate it 15%. Brick sample LNQ shows a slightly lower intensity (7%), but agrees with the expected site intensity within the experimental uncertainty. The intensity retrieved from the volcanic fragment also included closely reproduces the expected intensity. After A-TRM and cooling-rate corrections, all mean raw values move closer to the expected intensity.;Measurement of temperatures at different parts inside the kiln (bottom and upper parts of both central and peripheral parts) revealed the existence of significant thermal gradients, similar to those observed in ovens from other localities. Different cooling rates are then expected in a single oven.;The scatter in the intensity determinations observed in this study, retrieved from pieces elaborated together in the same oven, could arise from this differentiated cooling rate within the oven and thus, to an inappropriate cooling rate correction in the archeointensity protocol. As this situation was probably reproduced in the baking of ancient ceramic artifacts, a better knowledge of the temperature distribution inside these types of kiln would be desirable in order to choose the appropriate cooling rate correction.
ISSN: 0031-9201

hal-00644559
https://hal.archives-ouvertes.fr/hal-00644559
DOI : 10.1016/j.pepi.2011.06.007

Éditeur(s) : HAL CCSD Société des américanistes
Résumé : International audience
Experimental approach of the pre-Columbian navigation in the Antilles. Understanding the navigation capacities of the Eastern Caribbean pre-Columbian population is crucial for the community working in the Antilles. We have chosen to focus our work on an experimental approach of these techniques. Our ambition was to set up an experimental program including all the aspects associated with the building and the utilization of the kanawa. Thus, we have conducted an ethno-archaeological study of the kanawa building process followed by the Kali'ña from French Guyana. Then, the « Akayouman » kanawa was made into a 3D model to support a hydrostatic analyse. Finally, the heart of the project was composed of gathering and studying the data collected during our expeditions in the kanawa.
La comprensión de las capacidades de navegación de las poblaciones precolombinas del Caribe Oriental es actualmente fundamental para la comunidad que trabaja en las Antillas. Hemos optado por centrar nuestro trabajo en una practica experimental de estas técnicas. Nuestra ambición era crear un programa de experimentación que incluye todos los aspectos asociados a la construcción y la utilización de las kanawa. Por lo tanto, hemos realizado un estudio etnoarqueológica del proceso de construcción de las kanawa seguido por los Kali'na de Guyana Francesa. Entonces, la kanawa « Akayouman » ha sido modelizado en 3D para apoyar un estudio hidrostático. Por fin, el corazón del proyecto está constituido por la recopilación y el estudio de los datos recogidos durante nuestras expediciones .
Devenue plus centrale au cours des dernières années, la question des capacités de navigation des populations amérindiennes n'est pas nouvelle dans l'archéologie antillaise. Nous avons choisi de principalement concentrer nos efforts sur une approche expérimentale de ces techniques. Notre ambition était de mettre en place un programme d'expérimentation prenant en compte les différents aspects liés à la construction et à l'utilisation des kanawa. Nous avons donc mené une étude ethnoarchéologique de la chaîne opératoire de construction des kanawa mise en place par les artisans kali'ña en Guyane française. Puis, une fois produite, la kanawa « Akayouman » a fait l'objet d'une modélisation numérique 3D qui a servi de support à une analyse hydrostatique. Enfin, le coeur du projet a été constitué par la collecte et le traitement des données issues de notre programme de navigation.
ISSN: 0037-9174

hal-01671143
https://hal.univ-antilles.fr/hal-01671143
https://hal.univ-antilles.fr/hal-01671143/document
https://hal.univ-antilles.fr/hal-01671143/file/JSA102_2_20_art_berard2.pdf
DOI : 10.4000/jsa.14843

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Numerous archeomagnetic studies have provided high quality data for both the direction and the intensity of the geomagnetic field, essentially in Europe for the last 10 millennia. In particular, Greece supplies a lot of archeological materials due to its impressive cultural heritage and volcanic activity, so that numerous data have been obtained from burnt clays or historical lava flows. The most recent Greek secular variation curves are available for the last 8 millennia for the intensity and the last 6 millennia for the direction. Nevertheless, the coverage still presents several gaps for periods older than 2500 BC. In an effort to complete the Greek curve and extend it to older times, we present the archeointensity results from three Neolithic settlements in Northern Greece. The samples are of two different natures: burnt structures from Avgi (5250 ± 150 BC) and Vasili (4800 ± 200 BC), as well as ceramics from Dikili Tash (4830 ± 80 BC) and Vasili (4750 ± 250 BC). The samples have been subjected to standard rock magnetic analyses in order to estimate the thermal stability and the domain state of the magnetic carriers before archeointensity measurements. Surprisingly, very few ceramic samples provided reliable archeointensities whereas samples from burnt structures presented a very good success rate. Complementary studies showed that a detailed examination of the matrix color, following archeological information and classification standards can be a decisive test for pre-selection of sherds. In spite of these unsuccessful measurements from ceramics, we obtained an intensity value of 73.5 ± 1.1 μT for Dikili Tash, a higher value than the other data obtained in the same area, during the same period. However we do not have evidences for a technical artefact during the experiment. The burnt structures yielded two reliable archeointensities of 36.1 ± 1.8 μT and 46.6 ± 3.4 μT for Avgi and Vasili, respectively. Finally, we achieved a new archeomagnetic dating for these sites by comparing these new archeointensity values, combined to the directional measurements already published, with the Bulgarian secular variation curve. These new results contribute to extend the Greek secular variation reference curve towards older periods.
ISSN: 0031-9201

hal-00805575
https://hal.archives-ouvertes.fr/hal-00805575
DOI : 10.1016/j.pepi.2012.10.011