Raman microscopy of prehistoric rock paintings from the Hoz de Vicente, Minglanilla, Cuenca, Spain

Abstract

The third painted panel of the Hoz de Vicente rock shelter (Minglanilla, Cuenca, Spain) contains a series of prehistoric pictographs which were studied by Raman microscopy. Scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX) and petrographic polarised light microscopy were used as auxiliary techniques. The results obtained indicate that well-crystallised haematite (α-Fe2O3) of grain size less than 1 μm was used as red pigment. However, amorphous carbon, probably vegetable charcoal or soot, was used as the black pigment. A patina of whewellite and weddellite covers the areas of the painting panel with pictographs. The microstratigraphic study of a schematic figure revealed that the layer of pigment is sandwiched between layers of these hydrated forms of calcium oxalate produced by the activity of fungi and lichens. These products have also been detected in the layer of pigment. These findings will enable obtaining limiting radiocarbon 14C accelerator mass spectrometry (AMS) dates for the corresponding pictorial events. On the other hand, crystallisation of gypsum in the external layers of the panel is related to the deterioration observed in the flaking areas. Gypsum and clayish minerals appear as the main components of an ochre-coloured accretion covering several parts of the panel. Copyright © 2010 John Wiley & Sons, Ltd.