Analysis and State of Conservation of Prehistoric Pigments in Juanita Rock Art-Shelter, (Oliva De Mérida, Badajoz, Spain)

This paper investigates Prehistoric rock art painted figures attributed to the post-palaeolithic schematic style. Through SEM-EDS, Raman spectroscopy and X-microfluorescence analysis, a chemical-mineralogical characterisation is made, and natural alteration products (biological, by lichen and chemical, through the formation of patina) are investigated to assess the impact of lichen colonization on the open-air rock-art sites. The aim is to develop a control strategy for the Juanita rock-shelter in Extremadura, Spain. The main mineral component in the red pigment (hematite) was identified using micro-Raman spectroscopy. Energy-Dispersive X-ray microfluorescence (ED-µXRF) registered iron, aluminium, and potassium as main elements in the pigments, indicating red ochre or earth ochre were used to produce them. The presence of calcium and phosphorus is linked to alteration, as both elements can be attributed to the substrate or to mineral accretion over the pigment itself. SEM observations have revealed the presence of early lichen colonization on the painted surface. Furthermore, amorphous carbon particles were identified on this surface. From these observations it is hypothesized that the state of conservation of the rock art is related to external factors (organic materials, patina, fire) more than to alteration of the substrate.