In situ characterization of prehistoric rock paintings: the Côa Valley (Portugal)

Abstract

This paper draws on the study of the prehistoric art complex of the Côa Valley in north-east Portugal. Its main goal was to apply an in situ methodology for characterising prehistoric rock paintings. Thus, panels exhibiting red motifs were analysed by colour spectrophotometry and portable Raman spectroscopy. Motifs, crusts developed on the decorated surfaces and the backdrop stones have been analysed. Motifs from four sites within this archaeological complex were grouped considering their CIELAB and CIELCH parameters L*, a*, b*, C*ab and h due to their different colours. Raman spectroscopy showed that hematite is the predominant pigment in the motifs. Goethite, quartz and feldspars have also been identified in some motifs; their presence may reveal the use of ochre but may also come from the backdrop.