Quantifying lithic surface alterations using confocal microscopy and its relevance for exploring the Chatelperronian at La Roche-a-Pierrot (Saint-Cesaire, France)

Post-depositional modifications or alterations of the surface of lithics artefacts have been characterised at both macroscopic and microscopic scales by means of qualitative criteria. Here we introduce a new methodology for the study of surface alterations based on roughness measurements using confocal microscopy. This new approach allows for a quantified and reproducible distinction between various states of alteration among geological samples and archaeological materiar from a level attributed to the Chatelperronian at La Roche-h-Pierrot (Saint-Cesaire, France). This site, perhaps best known for discovery of Neanderthal remains in a level attributed to the Chatelperronian, plays a critical role in questions concerning the emergence of the Upper Palaeolithic and its relation to the appearance of anatomically modern humans in Western Europe. In this context, the question of the chrono-cultural integrity of the Chatelperronian at Saint-Cesaire is crucial. Our results demonstrate considerable variability in surface alterations among a sample of specific artefacts, Chatelperronian points, and those collected in the immediate vicinity of the Neanderthal remains and thus reinforces previous arguments concerning the unreliability of the Neanderthal-Chatelperronian association at Saint-Cesaire. This pilot study equally confirms the potential of roughness analysis for both taphonomic and use-wear studies of lithic industries.