Efficient quantification procedures for data evaluation of portable X-ray fluorescence – Potential improvements for Palaeolithic cave art knowledge M. Gay a , K. Müller a , F. Plassard b , J.-J. Cleyet-Merle c , P. Arias d , R. Ontañón d , I. Reiche a,e, ⁎ a Sorbonne Universités, Université Paris 6, Laboratoire d'Archéologie Moléculaire et Structurale, UMR 8220 CNRS – Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris, France b Université de Bordeaux, UMR 5199, PACEA, Allée Geoffroy Saint-Hilaire, CS 50023-33615 Pessac Cedex, France c Musée National de Préhistoire, 24620 Les Eyzies-de-Tayac, France d Instituto Internacional de Investigaciones Prehistóricas de Cantabria, Universidad de Cantabria, av. de los Castros 52, 39005 Santander, Spain e Rathgen-Forschungslabor, Staatliche Museen zu Berlin-Stiftung Preußischer Kulturbesitz, Schloßstraße 1a, 14059 Berlin, Germany abstract article info Article history: Received 6 February 2016 Received in revised form 26 May 2016 Accepted 2 June 2016 Available online xxxx Portable x-ray fluorescence spectrometry (pXRF) has become fundamental in prehistoric research since it en- ables chemical studies that preserve the integrity of rock art or other investigated archaeological objects. This unique and fragile expression of our ancestors requires the use of non-invasive and non-destructive in situ ana- lytical techniques. This provides significant sources of physicochemical information for enhancing the compre- hension of the symbolic and ideological realm of past societies. Thus, XRF data acquired in the field allow giving more detailed insights into the pigment used by Palaeolithic artists, the rock art organisation inside the cave and the different frequentation periods of it. However, if the qualitative study is now well established and routinely used, quantitative evaluation encounters difficulties linked to the context of the study (karstic environ- ment in our case) and the heterogeneous nature of the analysed material (nature of the pigments used, presence of several layers, conservation state of the rock art, type of the rock art support). Moreover, the non-invasive na- ture of this technique is faced with a large number of data since it offers the acquisition of statistically relevant data by multiple measurements of different spots on the same figure. The present work struggles with the issue of filling the gap of well-adapted quantitative procedures devoted to caves or rock-shelters analyses, and offers efficient tools and methodologies, which take into account the specificities of the studied rock art and its context. Additionally, the evaluation procedures of the high volume of data have to be effective. The analyses of drawings, monochrome and polychrome paintings of three Palaeolithic key cave sites, namely Rouffignac and Font-de-Gaume in Dordogne, Southern-France, and La Garma in Cantabria, Northern Spain, illustrate the new approaches and procedures developed in this study. © 2016 Elsevier Ltd. All rights reserved. Keywords: Portable X-ray fluorescence analyses Prehistoric paints Cave art Iron and manganese oxides Quantification procedures Principal component analysis Monte Carlo simulations 1. Introduction The cognitive behaviour of the Prehistoric populations, which sur- rounds the artistic work in caves or rock-shelters, is still fascinating. These artistic evidences belonging to the first ones known of human mankind that reached us from this distant period belong to the longest timespan of art history. For some of this rock art, Prehistoric artists have even ventured in closed and dark spaces, sometimes over long dis- tances. On the basis on this exceptionality, the understanding of these graphic expressions is one of the key issues of prehistoric research. Many studies have been carried out since the recognition of the au- thenticity of Palaeolithic rock art in 1902. It has been described and pre- cisely surveyed to understand the symbolic and ritual significations. Physicochemical analyses, according to the instrumental developments made in the last few years in the portable XRF technique, have been in- cluded increasingly to the stylistic approach to become nearly automat- ic. These analyses focus on the determination of the chemical composition of the pigments, the methods of paint preparation and the application techniques employed. The research path is providing significant sources of information to get to the technical skills of prehis- toric artists and the “chaîne opératoire” of the painting activities (Cabrera-Garrido, 1978; Ballet et al., 1979; Vandiver, 1983; Clottes et al., 1990; Lorblanchet et al., 1990; Pepe et al., 1991; Menu and Walter, 1992; Baffier et al., 1999; Chalmin et al., 2002, 2003; Vignaud et al., 2006). However, many questions remain about the creation, dating and meaning of these artistic behaviours and research on it is still on- going. The study of rock art encounters severe restrictions, which are im- posed by the necessity of complete conservation of its integrity. The analysis has to be done on-site, non-destructively and non-invasively, to strictly preserve the artwork. Portable X-ray fluorescence (pXRF) Journal of Archaeological Science: Reports xxx (2016) xxx–xxx ⁎ Corresponding author at: Sorbonne Universités, Université Paris 6, Laboratoire d'Archéologie Moléculaire et Structurale, UMR 8220 CNRS – Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris, France. E-mail addresses: ina.reiche@upmc.fr, i.reiche@smb.spk-berlin.de (I. Reiche). JASREP-00512; No of Pages 9 http://dx.doi.org/10.1016/j.jasrep.2016.06.008 2352-409X/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Journal of Archaeological Science: Reports journal homepage: www.elsevier.com/locate/jasrep Please cite this article as: Gay, M., et al., Efficient quantification procedures for data evaluation of portable X-ray fluorescence – Potential improvements for Palaeolithic..., Journal of Archaeological Science: Reports (2016), http://dx.doi.org/10.1016/j.jasrep.2016.06.008