No abstract

Heat treatment of lithic raw material is used for the first time in Europe in the Solutrean of the upper Paleolithic. The study of which heating technique was used by these groups requires analytical methods to understand and recognize the chemical and physical processes involved. Roughness measurements were tested as a tool for recognizing heat treatment and to compare them to infrared spectroscopy. We measure the surface topography of geological samples to observe its evolution as a function of heating and then compare the results with those obtained on Solutrean artefacts. We also measured ear infrared analyses was carried out for comparing the effectiveness of surface roughness measurements. This work complements our knowledge about the heating environment used by Solutrean groups by confirming the use of controlled heating. In addition, our roughness measurements provide promising results for the recognition of heat treatment through the quantification of the surface luster.

The Solutrean technocomplex is characterized by the use of innovative techniques for stone tool knapping during the Upper Palaeolithic. These processes include the development of pressure retouch and heat treatment of silica rocks. These innovations remain unprecedented at the scale of the recent European Paleolithic. The aim of our analysis is to acquire new information on the application of heat treatment, by investigating the heating technique and the lithic chaîne opératoire in which this treatment occurs. Macroscopic observations of the material combined with an infrared spectroscopic analysis of 69 archaeological samples provide new data on heat treatment in the Solutrean lithic series of Le Piage (Fajoles, Lot). Raw materials were heated in controlled conditions and to temperatures of 250-300°C. We also found that only leaf-shaped pieces were heat-treated at Le Piage. Part of the results obtained by infrared spectroscopy reveal discrepancies with macroscopic observations. These data raise questions concerning the validity of common macroscopic criteria used for recognising heat treatment and shed light on some of the choices made by Solutrean groups.