Portable X-ray fluorescence analysis of levantine and schematic art pigments from the river Vero shelters (Huesca, NE Spain)

Abstract

The River Vero canyon (Huesca, Spain) contains an exceptional archaeological legacy with more than sixty rock shelters with cave paintings and forms part of the World Heritage ‘Rock Art of the Mediterranean Basin on the Iberian Peninsula’. This study presents the results of the in situ and non-destructive multi-elemental composition analysis of the pigments used in eight of the main shelters through portable X-ray fluorescence spectroscopy (pXRF). Specifically, the cave paintings of the rock shelters of Chimiachas, Muriecho, and Arpán (Levantine Art); and Mallata, Barfaluy, Quizans, Lecina Superior, and Forau del Cocho (Schematic Art) were investigated. The red pigments, based on iron minerals, were the most abundant in all the River Vero rock shelters, with Fe contents in the 0.51–3.06% range. The iron contents of the paintings of Mallata B1 and I, Muriecho, and Forau del Cocho were higher than those of Arpán, Barfaluy, Lecina, and Chimiachas rock-shelters; and, in turn, these were higher than those of Quizans, pointing to noticeable differences in the degree of conservation. Black pigments, in the absence of manganese, were associated with bone char or carbon black. Through the phosphorus content, evidence is provided of the use of bone phosphates as a component of the paints, either as a filler or as a binder. Geological studies indicate that the detected gypsum is of external origin, probably associated with gypsum-rich atmospheric dust. The reported pXRF analysis of this large set of paintings may serve as a basis for future characterization studies involving other portable chemical analysis techniques.