Archeometrical Characterization of Rock-Art Pigments from Puerto Roque Open-Air Rock Art Shelter (Valencia De Alcantara, Extremadura, Spain)

Abstract

The study seeks to unravel the intricate operational sequence involved in preparing prehistoric pigments for rock art within the Puerto Roque rock art shelter. Sixteen pigment samples, identified as Lab Code Puerto_1 to Puerto_16, were meticulously collected from specific figurative representations. Additionally, three ochre samples (Puerto_17, Puerto_18, and Puerto_19) were sourced from the shelter's soil. Employing a comprehensive multi-analytical approach, including Raman microspectroscopy, X-ray microfluorescence (EDxrf), Fourier-transform Infrared spectroscopy (ATR-FTIR), and Scanning Electron Microscopy (SEM), all nineteen samples underwent thorough analysis. The research unveiled a spectrum of distinct red pigments within the rock art depictions. The sampling strategy for the 16 panels in the Puerto region was meticulously designed to capture the diverse array of rock art manifestations, each presenting unique characteristics that warranted detailed scientific investigation. The selection of these panels was guided by the recognition of various artistic techniques employed in the creation of the paintings, the nuanced hues exhibited, prevalent erosion issues, potential effects of sunlight exposure, and the intriguing hypothesis of distinct chronological periods due to several superimpositions detected. Notably, darker pigments in samples Puerto_02, Puerto_10, and Puerto_19 revealed a composition of hematite with the added presence of carbon. Meanwhile, Puerto_08 exhibited an orange hue primarily composed of goethite. Bright red pigments in samples Puerto_01, Puerto_03, Puerto_05, Puerto_07, Puerto_09, and Puerto_11 were predominantly characterised by hematite, as confirmed by Raman analysis. EDxrf analysis demonstrated an elemental composition akin to the three ochre pieces examined. Furthermore, ATR-FTIR spectroscopy suggested the potential influence of a heating process in enhancing red coloration, corroborated by spectral results from specific samples. This finding aligns with prior research, underscoring the technological sophistication embedded in early artistic endeavours. The detailed understanding of pigment types and their preparation methods provides insights into the artistic choices and technological adeptness of prehistoric communities. Beyond the archaeological implications, these findings contribute significantly to the ongoing conservation efforts of rock art sites. The amalgamation of diverse analytical techniques showcased their efficacy in elucidating the intricate world of pigment preparation. Recognizing the unique microclimates at each rock art site that influence pigment preservation, this localised approach aids informed decisions in safeguarding these invaluable cultural resources. In essence, this study not only unravels the artistic past but also advocates for the sustainable conservation of our shared cultural heritage.