THE IAEA C-14 INTERCOMPARISON EXERCISE 1990

As a follow-up to the meeting of experts convened at the International Atomic. Energy Agency (IAEA) in February 1989, and the International C-14 Workshop held in Glasgow in September 1989, the C-14 Quality Assurance Program was formulated. In a joint effort of several radiocarbon teams and IAEA staff, we have prepared a set of five new intercomparison materials. These are natural materials frequently used by radiocarbon laboratories. The materials were distributed to 137 laboratories in May 1990. In February 1991, a meeting of experts was convened in Vienna to evaluate the results, to determine the radiocarbon activity of the five samples expressed in % Modem (pMC) terms and to define the C-13/C-12 ratio, and to make recommendations on further use of these materials. We present here the results of the exercise and the agreed consensus values for each of the five materials and discuss the different analyses that were undertaken

Out of the Cave and into the Light: Perspectives and Challenges of Radiocarbon Dating an Open-Air Aurignacian Site (Régismont-le-Haut, Mediterranean France)

International audienceThis article presents the methods and results regarding the radiocarbon (AMS) dating of the site of Régismont-le-Haut. This site is one of the very few well-preserved Aurignacian open-air sites in southern France. It is also one of the only Aurignacian sites in France and Europe, more generally, to have conserved evident features, including many in situ fire-related structures. We selected charcoal and bone from all the major occupation sectors excavated so far, as well as from others which were important for understanding site formation. Considering difficulties faced when comparing the lithic industry of a site located in a poorly documented area with those belonging to the Aquitaine basin, where the "classical" definition of the Aurignacian was outlined, dating was conducted to accurately place the site within this technocomplex's internal chronology. In total, 19 charcoals (identified to Pinus sp. or gymnosperm) and 3 bones were submitted for AMS radiocarbon dating, each to one of three laboratories. We implemented a strict charcoal screening protocol for radiometric dating that required genus-identified individual charcoals that were well-associated with the fire-related structures. Despite this careful selection , most of the charcoals and all of the bones contained insufficient carbon for dating. Of the 19 charcoal dates attempted, 5 produced dates, from two loci. All fall in the span between the Middle Aurignacian and the Recent Aurignacian (between around 32,500 and 28,000 uncalibrated 14 C BP). An older subset of the dates (32.5-32 ka BP, ca. 37.5-35.5 ka cal BP) appears to be the most reliable. These results represent the first AMS dates ever performed on an Aurignacian open-air site in the Mediterranean area. The dates are compared to other recently dated southwestern France sites to establish which ones might be useful for future detailed archaeological comparisons. They are also instructive from a methodological point of view, in order to better appreciate the resolution of radiocarbon in this context. The focus of this article is on presenting the dating work, especially the protocol used in the selection of samples, the laboratory methods used for obtaining the dates and the challenges faced at this site. Among these, the divergence of dates between loci contrasted with geomorphological and archaeological evidence, with the latter two strongly pointing to one living floor, and either a single occupation or a few very close in time. This forced a reassessment of the chronological dating evidence. This article serves to show the importance of multi-prong approaches to archaeological dating, comparing and contrasting both contextual evidence and actual dates