Colour in context : pigments and other coloured residues from the Early-Middle Holocene site of Takarkori (SW Libya)

We present the multidisciplinary investigation of pigments and artefacts with traces of colour from the Early-Middle Holocene site of Takarkori, located in the Tadrart Acacus Mountains (central Sahara, SW Libya). Here, geological, archaeological, taphonomic and chemical studies (Raman, Fourier-transform infrared, X-ray powder diffraction, gas chromatography–mass spectrometry) are used to examine a vast range of artefacts (raw materials, grinding stones, painted items, as well as lithic, bone, wooden and ceramic tools) equally distributed from Late Acacus contexts related to hunter-gatherers (ca. 8900–7400 uncal years bp) to pastoral groups (ca. 7400–4500 uncal years bp). The exploited minerals (goethite, hematite, kaolinite and jarosite, among others) are locally procured and processed using quartzarenite grinding stones of different shapes and sizes. Thermal treatment of the minerals is also suggested by X-ray powder diffraction (XRD) and Raman studies. Gas chromatography–mass spectrometry (GC-MS) analyses show the addition of a lipid binder to small lumps of pigments in order to obtain a sticky product. Their fatty acid distribution differs from the residues on grinding stones, pointing to a specific use of these lumps. The grinding stones have also been used to crush and pulverize the pigments and as base for colour preparation. A sample of colour from a fallen painted slab referable to late pastoral phases shows the presence of a binder, chemically identified as casein. Taken together, the evidence collected at Takarkori conveys to suggest an articulated chaîne opératoire, not only directed towards the preparation of pigments for the parietal rock art but also to other non-utilitarian functions, such as body care and ornamentation and decoration of artefacts.