• Chanteraud, Claire
• Monney, Julien
• Hoerlé, S.
• Salomon, Hélène
• Chalmin, Emilie

Abstract

The most common studies on colouring matter concern the question of the “chaîne opératoire” from procurement to use, dealing distinctively with archaeological remains and rock art. Only a few studies have been done on the link between excavated pieces and rock art, and even less have taken into account the correlation with geological origin. The “Grotte aux Points” presents the particularity of being decorated and archeological excavations reveal many pieces of coloured and colouring remains which are iron oxide-rich rocks brought to the site by Palaeolithic people. The red Palaeolithic paintings present a few palm-points, great signs and figurative drawings: a horse, a bison and ibexes. In 2015, coherent colouring matters, coloured limestone fragments and one µ-sample of painting were studied with complementary physico-chemical methods. To describe their morphology and composition, different instruments were used on macroscopic and microscopic scales: optical microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM), both coupled with dispersive X-ray energy probe (EDX). 10 objects were studied using proton induced X-ray emission (PIXE) in order to obtain quantitative chemical data on major and trace elements. Except for the TEM which gives information concerning the iron oxide crystal morphology and potential heat-treatment, non-invasive and non-destructive methods have been privileged to preserve the archaeological artefacts. About forty pieces of solid colouring agents were excavated in the Palaeolithic occupational levels. Most of the pieces have millimetric size (< 5 mm). At least three different raw ferruginous materials were discriminated including a ferruginous clayey rock containing green minerals dispersed in the matrix. We think that this mineral phase, which still needs to be clearly identified, is a good indicator of the geological origin of this kind of rock. In addition, three centimetric fragments of wall painting (from 3 cm to 20 cm) were discovered at the foot of the “large signs” panel. Finally, in 2012, a red palm-point with black charcoal pigment superposition was sampled from the “Niche aux Points”. The twenty-five archaeological remains (coloured limestone fragments and solid colouring agents), the 3 painted wall fragments and the micro-sample of painting were analysed in order to approach the chronology of the colouring matter used. These observations combined with chemical measurements actually permit (i) to characterize the signal of the environment on the different objects, (ii) to identify differences between macro-observations and geochemical fingerprints on the coherent matters (figures 10, 11). The raw material properties privileged by Palaeolithic people during supply were identified. First results are encouraging and enable to improve the methodology, particularly on a chemical point of view.

Topics

• impedance spectroscopy
• morphology
• mineral
• phase
• scanning electron microscopy
• laser emission spectroscopy
• transmission electron microscopy
• iron
• Energy-dispersive X-ray spectroscopy
• drawing
• trace element
• particle-induced X-ray emission spectroscopy