Residue analysis

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esidue analysis refers to the study of materials (i.e., residues) that are transferred and adhere to implements (stone tools, grinding stones, bone tools) during use or preparation for use (production, hafting or maintenance). The great variety of residues that can potentially be encountered on used tools requires the application of a wide range of analytical techniques, the selection of which depends on the visual, elemental, and molecular characteristics of the residues.

At TraceoLab, morphological characteristics of residues are initially studied with stereomicroscopes and metallurgical microscopes, which can yield accurate identifications of morphologically distinct residues such as plant tissue, phytoliths and starch grains. In some cases, these remains need further analysis with transmitted light microscopy, which requires the extraction and transfer of the residue to a glass slide. Deposits with distinct elemental compositions, such as iron oxide residues, can be accurately identified with scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The identification of residue types that lack characteristic morphologies and elemental compositions, e.g. tar and resins, requires biomolecular methods such as gas chromatography–mass spectrometry (GC-MS).

Within the field of functional analysis, residue analysis of stone tools has been employed to obtain precise information on materials that have been in contact with the stone tool during its active lifecycle (production, hafting, use and maintenance). One of the most crucial preconditions for obtaining reliable functional information from residues is the analyst’s ability to distinguish between anthropogenic and post-depositional particle remains. Criteria for making this distinction include patterning, visual characteristics (e.g., smearing, directionality), and the association with corresponding wear features related to tool lifecycle. Successful residue analysis further requires a profound understanding of the burial context and the effect of postdepositional processes on residues.

Further reading

• Cnuts D. & Rots V., 2018 – Extracting residues from stone tools for optical analysis: towards an experiment-based protocol. Archaeological and Anthropological Sciences 10: 1717-1736
• Fullagar R. & Matheson C., 2014 – Stone tool usewear and residue analysis. In: Smith C. (ed.), Encyclopedia of Global Archaeology. Springer: 7062-7065
• Hayes E. & Rots V., 2019 – Documenting scarce and fragmented residues on stone tools: an experimental approach using optical microscopy and SEM-EDS. Archaeological and Anthropological Sciences 11: 3065-3099
• Perrault K.A., Stefanuto P.H., Dubois L., Cnuts D., Rots V. & Focant J.-F., 2016 – A new approach for the characterization of organic residues from stone tools using GC×GC-TOFMS. Separations 3: 16
• Rots V., Hayes E., Cnuts D., Lepers C. & Fullagar R., 2016 – Making sense of residues on flaked stone artefacts: learning from blind tests. PLoS ONE 11: e0150437
• Rots V., Lentfer C., Schmid V.C., Porraz G. & Conard, N.J., 2017 – Pressure flaking to serrate bifacial points for the hunt during the MIS5 at Sibudu Cave (South Africa). PLoS ONE 12: 0175151