Cénac-et-Saint-Julien – Grotte Vaufrey

Date de l'opération : 2009 (EX) Datation par luminescence des dépôts sédimentaires L’objectif de l’étude initiée en 2008 est d’obtenir de l’information chronologique sur la mise en place du remplissage sédimentaire de la Grotte Vaufrey. Dans ce but, et pour compléter les données radiométriques déjà obtenues par application de la méthode Uranium-Thorium à des vestiges carbonatés et par thermoluminescence sur des fragments de calcite et des silex brûlés, no..

How reliable are our beta-source calibrations?

International audienceThe calibration of any artificial-source attached to a luminescence reader is fundamental for the accuracy of luminescence dating results. Here, we present calibration results obtained for a-source attached to a single grain Risø reader in Bordeaux using a series of quartz of different origins. The quartz was irradiated with three different-irradiators. An unexpected variability of the apparent dose rates was observed and our results suggest that the-irradiation is the main reason for this variability. Further work is needed to clarify the underlying reasons

Datation des sédiments quaternaires par luminescence stimulée optiquement : un état de la question

Au cours des vingt dernières années, la datation des sédiments par luminescence stimulée optiquement (OSL pour Optically Stimulated Luminescence) s’est grandement développée: de nombreuses applications ont été réalisées sur des dépôts d’origines variées, en parallèle d’efforts méthodologiques soutenus. Ces études ont conduit à définir pour les différents types de minéraux, plusieurs approches et protocoles de détermination de l’âge dont la fiabilité a été évaluée au fil du temps. Dans cet article, nous proposons de faire un historique de ces différentes approches et de les expliciter succinctement, en insistant sur leurs avantages respectifs, leurs limitations ainsi qu’en exposant les hypothèses qui les soutendent. Les développements les plus récents qui sont en cours d’évaluation et les espoirs qu’ils suscitent, seront aussi exposés.During the last twenty years, the dating of sediments by the Optically Stimulated Luminescence (OSL) method largely developed: numerous applications were realized on deposits of various origins, in parallel of constant methodological efforts. These studies led to define for the different types of minerals, several approaches and protocols for the determination of the age whose reliability was progressively estimated. In this article, we propose to make a review of these various approaches and to clarify them briefly, by insisting on their respective advantages, their limitations as well as by explaining the underlying hypotheses. The most recent developments which are in the course of evaluation and the hopes that they arouse, will also be explained

Le site du Lac Bleu et la question de l'extension du pergélisol en France au Pléistocène supérieur

La revue des données issues de l'archéologie préventive et programmée, des descriptions de coupes naturelles ou des photos aériennes conduit à recenser plusieurs centaines de structures périglaciaires dans le Sud-Ouest de la France. Plusieurs catégories sont distinguées : 1) réseaux de polygones supradécamétriques correspondant à des coins à remplissage sableux primaire ou mixte, 2) coin à remplissage sableux primaire et, 3) réseau de petits polygones correspondant à des fentes de gel à maille semi-métriques à métriques. La datation OSL du remplissage de plusieurs coins sableux et l'information stratigraphique issue de sites préhistoriques montre que ces différentes structures traduisent plusieurs d'extension méridionale du pergélisol pléistocène. L'interprétation de la signification paléoclimatiques des structures, sans être univoque, conduit à distinguer des épisodes de pergélisol continu/discontinu et/ou sporadique. L'hypothèse d'une récurrence de phases d'extension du Pergélisol européen pléistocène en réponse aux événements de Heinrich entre 32ka et 17ka est avancée

Luminescence age calculation through Bayesian convolution of equivalent dose and dose-rate distributions:The De_Dr model

In nature, each mineral grain (quartz or feldspar) receives a dose rate (Dr) specific to its environment. The dose-rate distribution, therefore, reflects the micro-dosimetric context of grains of similar size. If all the grains were well bleached at deposition, this distribution is assumed to correspond, within uncertainties, with the distribution of equivalent doses (De). The combination of the De and Dr distributions in the De_Dr model proposed here would then al- low calculation of the true depositional age. If grains whose De values are not representative of this age (hereafter called “outliers”) are present in the De distribution, this model al- lows them to be identified before the age is calculated, en- abling their exclusion. As the De_Dr approach relies only on the Dr distribution to describe the De distribution, the model avoids any assumption about the shape of the De distribu- tion, which can be difficult to justify. Herein, we outline the mathematical concepts of the De_Dr approach (more details are given in Galharret et al., 2021) and the exploitation of this Bayesian modelling based on an R code available in the R package “Luminescence”. We also present a series of tests using simulated Dr and De distributions with and without outliers and show that the De_Dr approach can be an alter- native to available models for interpreting De distributions.Using the world in ancient societies : processes and forms of appropriation of space in Long TimeCREDit - Chronological REference Datasets and Sites (CREDit) towards improved accuracy and precision in luminescence-based chronologie

First dating results for the Middle Pleistocene industries (Acheulean – Early Middle Palaeolithic) in the Pyrenees – Garonne region: a multi methods geochronological approach (TL, OSL and TT-OSL) of the Duclos and Romentères sites

The recent development work of the A65 highway has given the opportunity to broaden the corpus of Lower and Middle Palaeolithic open-air sites known in the southern Aquitaine basin. The sites of Duclos (Auriac, Pyrénées-Orientales) and Romentères (Le Vignau, Landes), discovered in this context, have yielded an abundant lithic record which has been attributed to the Acheulean of Iberian type for the earlier and, essentially, to the Early Middle Palaeolithic for the latter. The archaeological levels are intercalated in sequences that comprise aeolian silts and colluvial units separated by interglacial luvisols. The pedostratigraphic context of the two sites has provided a rare opportunity to propose a reliable chronostratigraphic framework in this area. To achieve this objective, a study combining several methods of luminescence dating was conducted to complete the geomorphological data. Optically Stimulated Luminescence (OSL) and Thermically Transferred OSL (TT-OSL) dating methods were applied in order to determine the ages of sedimentary quartz grains and thus, of the sampled deposits. In parallel, heated flint and quartzite samples were dated by thermoluminescence (TL). The Pyrenees-Garonne Acheulean industry of Duclos has been attributed to the boundary between Marine Isotopic Stages (MIS) 7 and 6 while the human occupations of Romentères date from MIS 6 for the most recent series (Early Middle Palaeolithic) and from MIS 9 and 8 for the older

Infrared Radiofluorescence (IR-RF) of K-Feldspar:An Interlaboratory Comparison

Infrared Radiofluorescence (IR-RF) is a relatively new method for dosimetric dating of the depositional timing of sediments. This contribution presents an interlaboratory comparison of IR-RF measurements of sedimentary feldspar from eight laboratories. A comparison of the variability of instrumental background, bleaching, saturation, and initial rise behaviour of the IR-RF signal was carried out. Two endmember samples, a naturally bleached modern dune sand sample with a zero dose and a naturally saturated sample from a Triassic sandstone (~250 Ma), were used for this interlaboratory comparison. The major findings of this study are that (1) the observed IR-RF signal keeps decreasing beyond 4000 Gy, (2) the saturated sample gives an apparent palaeodose of 1265 ± 329 Gy and (3) in most cases, the natural IR-RF signal of the modern analogue sample (resulting from natural bleaching) is higher than the signal from laboratory-induced bleaching of 6 h, using a solar simulator (SLS). In other words, the laboratory sample bleaching was unable to achieve the level of natural bleaching. The results of the investigations are discussed in detail, along with possible explanations

Infrared radiofluorescence (IR-RF) dating:A review

International audienceLuminescence dating methods on natural minerals such as quartz and feldspars are indispensable for establishing chronologies in Quaternary Science. Commonly applied sediment dating methods are optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). In 1999, Trautmann et al. (1999a, b) proposed a new related technique called infrared radiofluorescence (IR-RF). IR-RF denotes the infrared luminescence signal of feldspar resulting from exposure to ionizing radiation and potentially offers a significant methodological advance compared to OSL and IRSL regarding luminescence signal stability, dating range and required measurement time. The method has rarely been applied due to a lack of commercially available measurement equipment but experienced a revival during the last years. The present article provides a state-of-the-art overview of the physical background of IR-RF, its challenges, applications and the potential as a dating method. The paper particularly addresses practical considerations for applying IR-RF dating, including signal bleachability and saturation behaviour, and summarizes proposed solutions