Misleading residues on lithics from Star Carr: Identification with Raman microspectroscopy

Ancient trace residues left on stone artefacts by people represent a source of potentially fruitful data about diet, technology, and behaviour, but their investigation is not problem-free. Rather, correct identification of degraded residues and determination of their natural or anthropogenic origin remains at the heart of current methodological development in lithic residue analysis. It is increasingly becoming clear that reflected visible light microscopy (VLM) is insufficient to make secure identifications of ambiguous residues. Confocal Raman microspectroscopy (micro-Raman) is a non-destructive technique that can identify the specific molecular nature of microscopic residues with high spatial resolution. Here, the identification of artefact residues as anthropogenic by visual inspection alone was found to be incorrect in all cases tested. Micro-Raman provided the key source of information to unambiguously determine the chemical nature of residues and hence their origin.