Rules for carbon dating
Our approach was elaborated on known-age samples from the Fifth International radiocarbon Inter-comparison (VIRI) and served as proof of concept.The method was then applied to two archaeological sites where the single bones of small mammals were AMS-dated, and the dates compared to standard-size bone samples found in the near vicinity.Here, we present the first radiocarbon dates obtained from minute amounts of bone (3–60 mg) using ECHo MICADAS, the compact AMS recently installed at Gif-sur-Yvette, France.The optimization of our bone collagen extraction protocol allowed us to decrease the sample size by two orders of magnitude, while still extracting enough material (.In effect, they provide us with windows to past societies, and contribute to our knowledge of ancient human evolution and cultural development.Hard tissues contain an organic phase (mainly the protein collagen type I) embedded in a mineral phase (made of a non-stoichiometric biogenic apatite).Recent advances in graphite sample preparation and AMS capabilities make it possible to now run very small samples (.
They can be run in triplicates in order to improve the precision, but this requires the initial sample size to be increased, thus decreasing the interest of the gas ion source for archaeological samples.
The method was then applied to two archaeological sites where reliable dates were obtained from the single bones of small mammals.
These results open the way for the routine dating of small or key bone samples. bones, teeth, antler and ivory) found in the fossil record have a tremendous informative potential relevant to the fields of archaeology, palaeoecology and the history of art and technology.
The impact of sample size on collagen extraction yield is shown in Fig. High yields (between 15 and 20%) were obtained, in accordance with results previously reported for these bones (e.g. It corresponds to the ratio of the final estimated yield over the median value of the collagen yield obtained for large samples (100 mg) samples.
We observed an inter-individual variability, but it was of the same order of magnitude for small and large samples (one sigma standard deviation 0.2).
However, this is still excessive for two classes of bone remains: (1) individual bones of small vertebrates which often weigh less than 60 mg; and (2) unique remains such as hominid bones or worked bone artefacts for which curators do not permit invasive sampling and is seldom reported in publications, even when supplementary information is available (see for example refs 16,17,18,19).