CONICET | Buscador de Institutos y Recursos Humanos

The extent of amino acid racemisation (AAR) in fossil samples has been used as a dating technique since the 1960s. It has several advantages, one of which being that this method extends beyond the scope of radiocarbon dating, thus yielding chronological information on Palaeolithic archeology and Quaternary climate events. Although AAR has been attempted on many different materials, some have shown more reliable results, dependent on the inherent ability to protect their organic fraction. Shells are among the best materials for AAR, but leaching and contamination can occur in the inter-crystalline fraction of shell protein [1, 2]. However, the intra-crystalline fractions of some shell inorganic matrixes have been shown to behave as closed-system, protecting the intra-crystalline proteins during diagenesis. Isolation of these systems are vital for the application of geochronology, and for studying the kinetics of degradation reactions, such as hydrolysis and racemisation. Conventionally, AAR was based on the analysis of the entire organic fraction of the shells, but a new approach allows the isolation of the intra-crystalline fraction - through an oxidation process - and therefore more accurate and consistent results [3]. Shells provide an excellent material to date, as they are ubiquitous in archaeological sites. However, some mollusks are unreliable for dating because they do not contain intra-crystalline closed system protein. This presentation will show the study and characterization of Mytilus edulis as potential sample for AAR dating. Analyses on modern samples (opened mechanical and ethnographically) and aging tests on these modern samples were carried out on the two different inorganic fractions of this species calcite and aragonite in order to study the different behavior and preservation of the organic fractions.