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Keywords:

  • Raman microscopy;
  • SEM/EDX;
  • rock art;
  • pigment;
  • prehistoric paintings

Abstract

An extensive micro-Raman spectroscopic study of prehistoric paintings found in open air rock shelters at the Sierra de las Cuerdas (Cuenca, Spain) was carried out. In situ optical microscopy, petrological polarized light microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX) were used as auxiliary techniques. Haematite (α-Fe2O3) of three granular types was the pigment that was most frequently encountered alone and in admixture with non-stoichiometric iron oxyhydroxides. A white pigment, but rarely used, results from a combination of white earths (α-quartz, anatase, muscovite and illite) and calcined bones (apatite); the presence of calcined bones also appears frequently in the red pigmented pictographs. The presence of significant amounts of charcoal underlying the white paint is suggestive of previous sketching on the shelter walls. Accretions of whewellite and weddellite resulting from the activity of fungi or lichens (e.g. Verrucaria nigrescens) are present in the painting panels, and carotenoids from this biological colonization were detected on several pictographs. The crystallization of gypsum and barytes in spallating areas of the painted surfaces is associated with sandstone weathering processes. An unusual deterioration of the art work caused by electric welding splashes resulting from the erection of protective ironwork grilles around the rock art panels was also detected. Copyright © 2008 John Wiley & Sons, Ltd.