T02_02

ZooMS identified chimeras – removing collagen-based cow glue contamination from Palaeolithic whale bone objects prior to radiocarbon dating

van der Sluis L^1,2,  McGrath K³, Cersoy S⁴, Thil F⁵, Pétillon J⁶, Zazzo A¹

¹Archéozoologie, Archéobotanique, Sociétés, Pratiques et Environnements (AASPE), UMR 7209, Muséum national d’Histoire naturelle, CNRS, Paris, France, ²Department of Evolutionary Anthropology, University of Vienna, Vienna, Austria, ³Department of Prehistory and Institute of Environmental Science and Technology (ICTA), Uni-versidad Autonoma de Barcelona, Barcelona, Spain, ⁴Centre de Recherche sur la Conservation (CRC), UAR 3224, Muséum national d’Histoire naturelle, CNRS, Paris, France, ⁵Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL UMR 8212, CEA-CNRS-UVSQ, Université Paris Saclay, F-91198 , Gif-sur-Yvette, France, ⁶Travaux et Recherche Archéologiques sur les Cultures, les Espaces et les Sociétés (TRACES) UMR 5608, Toulouse, France

Eliminating contamination from exogenous carbon is essential prior to radiocarbon dating. Contamination can be derived from the burial environment or post-excavation treatments involving consolidation substances, which can be synthetic as well as organic in origin. Proteomic analysis (ZooMS) of Palaeolithic bone objects from France produced markers characteristic for both whale and cow. A modified extraction resulted in diminished cow peaks and enhanced whale peaks, suggesting these were originally whale bone objects that had been consolidated with collagen-based cow glue. Before subjecting these samples to radiocarbon dating, two cleaning protocols were tested to remove this type of contamination. Bone blank samples were consolidated with one type of collagen-based glue (bone glue, hide/skin glue or old bone glue from the museum), after which samples were either cured in the laboratory or artificially aged in a climate chamber for a month. While both cleaning methods produced excellent blank radiocarbon ages, the ages obtained from the archaeological material were still much too young considering their contextual age, suggesting that the collagen-based glue contamination had most likely cross-linked to the authentic collagen molecule. While compound-specific (hydroxyproline) radiocarbon dating and XAD resin are solutions to deal with cross-linked synthetic contamination, these are unlikely to help in the case of a collagen-based contaminant. Differential scanning calorimetry showed that the denaturation temperatures of both collagens (authentic and exogenous) were very close together. More research is needed to gain a deeper understanding of the occurrence and elimination of cross-linked collagen-based glues, as well as their prevalence in museum collections.