lable at ScienceDirect

Journal of Archaeological Science 40 (2013) 4635e4647

Contents lists avai

Journal of Archaeological Science

journal homepage: http : / /www.elsevier .com/locate/ jas

Review

Minateda rock shelters (Albacete) and post-palaeolithic art of theMediterranean Basin in Spain: pigments, surfaces and patinasq

Martí Mas a,*, Alberto Jorge b,1, Beatriz Gavilán c,2, Mónica Solís a, Enrique Parra d,3,Pedro-Pablo Pérez e,4

aDepartamento de Prehistoria y Arqueología, UNED (Universidad Nacional de Educación a Distancia), Paseo Senda del Rey 7, 28040 Madrid, SpainbMuseo Nacional de Ciencias Naturales, CSIC (Agencia Estatal Consejo Superior de Investigaciones Científicas), Calle José Gutiérrez Abascal 2, 28006Madrid, SpaincDepartamento de Historia I, Universidad de Huelva, Avenida tres de marzo s/n, 21007 Huelva, Spaind Laboratorio de Materiales, Instituto del Patrimonio Cultural de España, Calle Pintor El Greco 4, 28040 Madrid, Spaine Larco Química y Arte SL, Calle Nebli 54, 28691 Villanueva de la Cañada, Madrid, Spain

a r t i c l e i n f o

Article history:Received 20 April 2013Received in revised form16 July 2013Accepted 17 July 2013

Keywords:Pigment analysisLevantine artSchematic artMediterranean BasinMinateda rock sheltersTaphonomy

q These studies have been conducted within the frafor I þ D þ i Modelos de actuación para el Patrimoniomance models for Historical Heritage 2009e2011) ofHAR2008-0119/HIST (Ministerio de Economía y Comp* Corresponding author. Tel.: þ34 91 398 6715.

E-mail addresses: mmas@geo.uned.es (M. Mas), ajbeatriz.gavilan@dhis1.uhu.es (B. Gavilán), msolis@enrique.parra@mecd.es (E. Parra), pedropgeol@hotma

1 Tel.: þ34 91 411 1168.2 Tel.: þ34 959 21 9086.3 Tel.: þ34 91 550 4450.4 Tel.: þ34 91 816 2636.

0305-4403/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jas.2013.07.019

a b s t r a c t

The inorganic and organic fractions of two microsamples of prehistoric paint from the same site, theMinateda rock shelters, are analysed here for the first time. The two samples correspond to two rockshelters of different styles (Levantine and schematic) e Abrigo Grande de Minateda (The Great Rock Shelterof Minateda) and Abrigo del Barranco de la Mortaja (Del Barranco de la Mortaja Rock Shelter). Since itsdiscovery, historiographical tradition has emphasised the Abrigo Grande de Minateda, with its magnifi-cence and complexity, as emblematic of the origin and evolution of rock art in the Mediterranean Basinof the Iberian Peninsula (a UNESCO World Heritage Site). Four complementary techniques eMicropho-tography, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDX), RamanSpectroscopy and Gas ChromatographyeMass Spectroscopy (GCeMS)e were combined to identify andcharacterise the physicochemical properties of the paint and of the surface. We present an interpretationof the results that leads us to define complex taphonomic alterations beyond the usual distinction oflayers that include the surface, pigments and patinas.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The rock art of the Mediterranean Basin in the Iberian Peninsulawas declared aWorld Heritage Site by UNESCO in 1998 based on the757archaeological sites present in the area. Twodifferent styles havebeen identified: the naturalistic style, traditionally called Levantineart and exclusive to the Mediterranean Basin, and the schematic-abstract style, which extends throughout the Iberian Peninsula.

mework of the National PlanHistórico 2009e2011 (Perfor-the Universidad de Huelva.etitividad).

orge@mncn.csic.es (A. Jorge),madrid.uned.es (M. Solís),il.com (P.-P. Pérez).

All rights reserved.

Levantine art was the creation of hunter-gatherer groups and sche-matic art the creation of the first food-producing communities(AcostaMartínez,1968), demonstrating a conceptual unity betweenthe Neolithic and the Chalcolithic periods. Theories regarding theorigin and evolution of Levantine art are divided into those thatrelate it to theEpipalaeolithicperiod, although itmayhave continuedto develop later, and those that consider it exclusively Neolithic(created by acculturated hunter-gatherers) (García Arranz et al.,2012). The oldest absolute dates, obtained from calcium oxalatepatinas (AMS 14C) via ante quem dating, place Levantine art before5000 or 6000 cal BC (Ruiz et al., 2006, 2012; Mas et al., 2012).

The Abrigo Grande de Minateda and the Abrigo del Barranco de laMortaja are rock shelters formed inmarine biocalcarenites from theMiocene (Breuil, 1920,1935) (Hellín, Albacete), and these structuresform part of one of the most important rock shelter groups (Min-ateda) in the Mediterranean Basin (Fig. 1). The two sites are sig-nificant in terms of the quantity and quality of the paintings thatdecorate the Abrigo Grande de Minateda and contribute to thespecificity of the Abrigo del Barranco de la Mortaja, which containsexclusively schematic art.

Fig. 1. Location of the Minateda rock shelters in the Mediterranean Basin on the Iberian Peninsula.

Fig. 2. Reproduction of the Abrigo Grande de Minateda according to Breuil (1920) [fromBeltrán Martínez (1968)].

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e46474636

The work of Breuil (1920, 1935) (Figs. 2 and 3) represented oneof the first attempts at determining the origin and evolution ofLevantine art and used a systematisation that has been followed bynumerous researchers and applied to other sites for decades,although with some chronological nuances influenced by differenthistoriographical trends developed during the twentieth century.State-of-the-art technologies are now used to enhance the preci-sion of the definition and analysis of paintings.

We can identify an initial phase (Abrigo Grande de Minateda)with characteristic representations that can be related to the styledefined by some authors as V (Epipalaeolithic) (Bueno Ramírezet al., 2007; Mas et al., 2012) as well as, to a minor extent, a finalphase that is quantitatively underrepresented, representing a stylewith schematic tendencies. This final phase has an explicit presencein the Abrigo del Barranco de la Mortaja. The intermediate sequence(Levantine art) exhibits not only important technical, stylistic, andthematic variability, with considerable overlap and infrapositions,but also considerable formal homogeneity.

Studies conducted to date (vibrational, infrared (IR) and Ramanspectroscopies and other complementary techniques such as SEM-EDX) (Hernanz et al., 2008) have revealed that the rock paintings ofthe Serranía de Cuenca (Levantine and schematic art) consist pre-dominantly of haematites and, in some cases, maghemite andamorphous oxyhydroxides such as lepidocrocite. The filler mate-rials in the pigments used in the Levantine style include quartz,muscovite, and apatite (calcium phosphate from organic sources,the mineral phase of bone), with apatite being particularly signif-icant. Quartz and anatase (major components) and some phyllosi-licates (minor components) have been found in white paint, whichis also present at the aforementioned sites although in smallerproportions (Levantine art). Other components related to the pig-ments have been reiteratively characterised. Amorphous carbon(soot or charcoal) was later detected in a schematic zoomorphpainted in black in the Abrigo de la Hoz de Vicente (Minglanilla,Cuenca) (Hernanz et al., 2010). Organic binders have not beenconclusively detected (Hernanz et al., 2008, 2010). Experimental

Fig. 3. Reproduction of the Abrigo del Barranco de la Mortaja according to Breuil (1935).

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e4647 4637

studies suggest, however, that rock paintings in shelters or open airrequire some type of binder (Mas Cornellà, 2005; Rogerio-Candelera et al., 2011). We believe that the pioneering studies(Clottes et al., 1990), which identified recipes and filler pigments,

Fig. 4. Large bovid of naturalistic tendency from the Abrig

have led certain researchers to unnecessarily force a working hy-pothesis. In fact, the composition of the paints may simply reflecttrace elements included in the raw material. Without any elabo-rative process and as indicated by other early analysesein this case,in the Mediterranean Basine the chemical compositions of theLevantine and schematic paintings were thought to be similar(Montes Bernárdez and Cabrera Garrido, 1991e1992). These con-siderations do not rule out an intricate elaboration of the pigmentaimed at achieving a high quality in the paintings (Mas Cornellà,2005; Fiore et al., 2008).

Our study focuses on the characterisation of the paint used tomake of one of the most representative paintings in the AbrigoGrande de Minateda, the large bovid of naturalistic tendency locatedin the central zone (Fig. 4) (Levantine art), as well as a comparisonof the bovid with a quadruped of schematic tendency and smallerdimensions in the Abrigo del Barranco de la Mortaja (Fig. 5) (sche-matic art). We used two non-destructive techniques, SEM-EDX andRaman microspectroscopy, to determine the similarities and dif-ferences in paint composition between these two pictorial styles,which are likely separated bymillennia and had different meaningsand uses. Thus, we contribute data regarding the pigments orsubstances in the paintings, information which is relevant to theconservation of these sites. In addition, gas chromatography wasutilised to confirm or refute the presence of organic compoundsincluding binders (or colouring substances). We believe that thedevelopment of new techniques to facilitate in situ analysis (Roldán,2009) will allow us to propose stratigraphic characterisations suchas those discussed here. As noted by other authors (HernanzGismero et al., 2012), these characterisations are not as sensitiveas those made in the laboratory. However, with new and robustworking hypotheses, we can decide whether to conduct furthersampling.

2. Materials and methods

2.1. Sampling and sample preparation

Our sampling techniques followed established protocols. Thesamples were obtained using sterile scalpels, latex gloves, andmasks to avoid any possible contamination and then stored in

o Grande de Minateda, indicating the point sampled.

Fig. 5. Quadruped of schematic tendency from the Abrigo del Barranco de la Mortaja, indicating the point sampled.

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e46474638

Eppendorf tubes. All samples were less than 1 mm2. To minimisedeterioration and facilitate the sampling process, special attentionwas focused on sites containing tiny cracks, flakes, or scales. Beforeand after the extraction, macro- and microphotographs were takento document the process (Hernanz et al., 2006).

The samples were embedded in methacrylate resin and cutcrosswise for SEM-EDX and Raman analyses. The samples werephotographed and measured using reflected-light optical micro-scopy (Olympus BX 51 microscope coupled with an ultraviolet illu-mination system or Wood’s lamp). Microfragments of the samesampleswere subjected toX-raydiffractionandgaschromatography.

2.2. Microphotography

Digital photographs were taken in situ using a Nikon SMZ ste-reomicroscope (5e25� magnification), a technique we use toobserve the morphology of the brush strokes and to suggest theinstruments that may have been used to apply the paint. Usingthese photographs, we could also observe the particle sizes of thepigments, as well as observing evidence of the processes of thealterations that had occurred.

2.3. Scanning Electron Microscopy and Energy Dispersive X-RayMicroanalysis (SEM/EDX)

The micromorphology, topography, and distribution of thesample components were determined using a Philips FEI INSPECT(Hillsboro, Oregon, USA), a scanning electron microscope (SEM).SEM analysis in a low-vacuum mode with a backscattered electrondetector (BSED) allows for hydrated samples to be studied in theiroriginal condition. To obtain comparative results, weworked undervacuum conditions of 30 Pa, a high voltage of 20 kV, the electronbeam diameter was the suitable for particular magnification andyou achieve good focus and astigmatism correction and a workingdistance of approximately 10 mm to the detector. The X-ray energymicroanalysis (EDX) of the samples and the analysis of areas formapping were conducted with an energy-dispersive X-ray

spectrometer (INCA Energy 200 energy dispersive system, OxfordInstruments).

The quantitative analysis allowed us to establish not only whichelements were present but also the concentration of each element,which required an accurate intensity measurement for each peak inthe spectrum. We used the maximum peak intensities obtained bya least-squares fitting routine that used standard peaks correlatedto a spectrum of known compounds. After these intensities weredetermined, matrix corrections were applied (Pouchou and Pichoir,1991) to determine the concentration of each element. Thiscorrection method uses approximated exponential curves and the4(rZ) model to describe the shape of the curves. Thus, improvedmeasurements of light elements in a heavy-element-rich matrixand samples that are tilted in the direction of the incident electronbeam can be obtained.

Because the correction factors are dependent on the samplecomposition (which is the object of our analysis), the actual con-centrations must be created using an iterative procedure. Apparentconcentrations are then used to calculate correction factors andmake more “accurate” estimates of the concentrations. After suc-cessive iterations, concentrations that are accurate to approxi-mately 0.01% can be achieved.

To calculate the statistical error in the concentration, the weightpercentage of the sigma value should be used to determinewhether the element is below the detection limits of the sampleanalysis. We were conservative in this study and used a strictercondition that requires an element’s weight percentage to begreater than three times the weight percentage of the sigma valueresulting from the analysis.

The mapping method was used to collect and store X-ray mapsand to acquire electronic images and data.

The Cameo þ mode allowed us to observe the chemical compo-sition and topography of the images. The detailed electronic imagesappear together with a superposition of colours denoting the varia-tion in the X-ray spectrum, which may indicate changes in compo-sition. The X-ray photonswere assigned a colour depending on theirenergy in the electromagnetic spectrum. This colour input was usedto highlight a conventional electronic image and to allow each

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e4647 4639

compound to appear clearer in the electronic images by providingthe spectrum of each compound with a characteristic colour.

2.4. Raman microspectroscopy

For the micro-Raman spectroscopic study and for all of thespectra obtained, we used a Thermo Fisher DXR Raman spectro-graph (Madison, WI, USA) coupled with an Olympus BX-RLA2 mi-croscope with a CCD detector (1024 � 256 pixels), a motorised XYplatina, and auto-focus objectives from the Olympus microscopeUIS2 series (West Palm Beach, FL, USA), which were all controlledusing OMNIC 8.1 software.

A solid laser with a wavelength of 532 nm (maximumpower ¼ 10 mW) was used as the excitation light with double Ndfrequency: YVO4 DPSS. The samples were inspected using the10� objective to select areas in which the pigment was concen-trated and to ensure that the substrate was free of fibres andother contaminants. The spectra were obtained using the 20�and 50� confocal objectives with a pinhole or slit diameter of50 mm and a grating of 900 lines/mm. These conditions andexcitation at 532 nm provide an average spectral resolution of 2e4 cm�1 in the spectral range of 100e2500 cm�1, also for theRaman spectrum of the OH region (2500e5500 cm�1). Thesample point size was w1.2 mm, which is consistent with theobjective used. An integration time of 10 s with four accumula-tions was sufficient to obtain acceptable signal-to-noise ratios (S/N) in the pigment samples. However, 20 s and two accumulationswere necessary to analyse substrates that had undergone 30 s ofbleaching. The spectrograph was calibrated and aligned usingpure polystyrene.

2.5. Gas chromatography

Gas chromatography analysis was focused on detecting fattyacids, terpenic compounds, and amino acids. Fatty acids and ter-penic compoundswere analysed viamethylation of the samplewithMeth prep II (a methanolic solution of p-tolyltrimethylammonium

Fig. 6. Microphotographs of the paint in the two analysed figures. Differences in density, inteBarranco de la Mortaja.

hydroxide in methanol, Alltech Assoc., Inc.) using 10 mL of reactantand 10 mL of toluene per 50 mg of powdered sample and allowing thesample to stand for 1 h at room temperature. Chromatography wasperformedby injecting5mL of a clear solution into the splits/splitlessinjector of a Perkin Elmer Clarus� gas chromatograph. The splitterwas set to 5/1. The ovenwas programmed as follows: 130 �C (2min),then an increase of 20 �C/min to 310 �C (15 min). The nitrogen flowwas fixed at 1 mL/min. A 30-m Sugelabor SG-5 columnwith phenylsilicone was used as the stationary phase with a 0.35-mm id and a0.17-mmphase thickness. Aflame ionisationdetector thermostatisedat 310 �C was used.

To measure the amino acids, w75 mg of the powdered samplewas subjected to acid hydrolysis in a 1-mL closed vial using 200 mLof 6 M HCl (distilled) under a nitrogen atmosphere. The resultingsolution was subjected to a vacuum until dry, and the resultingpowder was derivatised using terbutyldimethylsilyl tri-fluoroacetamide (75 mL) in pyridine (100 mL) and triethylamine(5 mL) as a catalyst. The chromatography was performed in a 30-m-long SGE-1701 column (with a poly-cyanopropylsiloxane stationaryphase) with a 0.35-mm i.d. and a 0.17-mmphase thickness. The ovenwas programmed as follows: 110 �C for 5 min with an increase of5 �C/min to 280 �C (15 min); the flame ionisation detector was setto 290 �C.

3. Results and discussion

As shown by the microphotographs of the samples from AbrigoGrande de Minateda and the Abrigo del Barranco de la Mortaja(Figs. 4 and 5), the red pigment has a lower density and intensity inthe former painting (particle sizes of 5e10 mm). This observationmay be the result of ageing (in the former, the alteration layer isalso thicker) because appreciable granulometric differences are notobserved (although the grains appear coarser in the secondpainting). These data can be corroborated by the digital photo-graphs taken in situ through a Nikon SMZ stereoscopic microscopeat 5, 10 and 20� (Fig. 6). These results (although they most likelycannot be extrapolated to other geographical areas), in which finer

nsity, and particle size can be observed in the Abrigo Grande de Minateda and Abrigo del

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e46474640

particles can be observed in the schematic painting (HernanzGismero et al., 2012), are particularly relevant. We should notforget that the formal homogeneity and technical precision ofLevantine art opposes the heterogeneity of schematic art (in termsof theme, technique, and style).

3.1. Inorganic fractions of the rock surfaces and pigments

3.1.1. SurfacesSEM-EDX of the samples taken from the rock surface of the

paintingsdetectedcalciumcarbonates. The formations are associatedwith siliciclastic minerals (quartz, feldspars and clays), evaporiticminerals (gypsum and halite), iron oxides, and dispersed titaniumand organic matter (Inline Supplementary Fig. S1(a)e(c)).

Inline Supplementary Fig. S1 can be found online at http://dx.doi.org/10.1016/j.jas.2013.07.010.

Concentrations of calcium phosphates were detected in the rocksurface (Inline Supplementary Fig. S1(a), (b), (d)), common com-ponents of some bioclasts (foraminifera, bryozoans, echinoderms,etc.) (Fort et al., 2002), which, in our case, complicates the formu-lation of hypotheses regarding the complexity of the pigment

Fig. 7. Raman spectra of the minerals composing the rock surface on which the AbrigoGrande de Minateda rock paintings were created; (a) whewellite, gypsum, calcite,feldspar, quartz and amorphous coal; (b) quartz and calcite; (c) feldspar, gypsum, andamorphous coal; (d) haematite, magnetite, calcite, and amorphous carbon;(e) haematite, quartz, calcite and whewellite; (f) dolomite and amorphous carbon; (g)whewellite, calcite, haematite, gypsum, and quartz; (h) calcite and quartz; (i) anatase,whewellite, feldspar, and amorphous carbon. Abbreviations of mineral names: q,quartz; h, haematite; g, gypsum; g(H2O), hydrated gypsum bands; w, whewellite; f,feldspar; mg, magnetite; ca, amorphous carbon; do, dolomite; c, calcite; an, anatase.

composition, which includes charred bones. The presence of char-red bones has been defended and has led to interpretations thatthese components may result from rituals in other areas of theMediterranean Basin (Hernanz et al., 2008, 2012).

Raman spectroscopy of the rock surface detected dolomite-calcite (CaMg(CO3)2eCaCO3) in both the Abrigo Grande de Mina-teda and the Abrigo del Barranco de la Mortaja (in greater quantitiesin the second painting due to a minor degree of replacement).These dolomite formations, CaMg(CO3)2, are secondary and arisefrom the transformation processes (replacement) of the consoli-dated existing limestone (Figs. 7(e), (f), (h) and 8(e), (f), (g)). Be-tween evaporitic minerals we detected gypsum (CaSO4$2H2O) inthe Abrigo Grande de Minateda (Fig. 7(a), (c), (g)) and anhydrite(CaSO4), a dehydrated calcium sulphate in the Abrigo del Barrancode la Mortaja (Fig. 8(a)), haematites, a-Fe2O3, amorphous carbon,quartz (SiO2), feldspar, whewellite and anatase as common min-erals (Figs. 7(b), (d) and 8(b), (c), (d)).

The two rock surfaces contain abundant calcium oxalates(Fig. 9(a), (b), (d), (f)). Euhedral crystals of barite (BaSO4) andcelestite (SrSO4) of approximately 20 mm in length have also beenobserved between the dolomite (Fig. 9(c), (e)). The mixture ofdiluted, alkaline sulphide-rich groundwater equilibrated withdolomite in an acidic reduced brine that is rich in metals such asbarium and also equilibrated with dolomite causes the dissolutionof the dolomitic encasement due to the intrinsic effects of thechemical mixture (the effects of ionic strength and pH-pCO2

Fig. 8. Raman spectra of the minerals composing the rock surface on which the Abrigodel Barranco de la Mortaja rock paintings were created: (a) quartz, haematite, gypsum,calcite and whewellite; (b) feldspar, haematite and calcite; (c) haematite and calcite;(d) haematite and gypsum; (e) haematite, quartz and calcite; (f) calcite, haematite, andamorphous carbon; (g) anatase, haematite, and calcite. Abbreviations of mineralnames: q, quartz; h, haematite; g, gypsum; g(H2O), hydrated gypsum bands; w,whewellite; f, feldspar; ca, amorphous carbon; c, calcite; an, anatase.

Fig. 9. (a) SEM image of calcium oxalate with iron oxides; (b) SEM image of calcium oxalate associated with sodium chloride (halite); (c) SEM image of dolomite with a bariteeuhedral crystal; (d) SEM image of calcium oxalates associated with siliciclastic minerals such as feldspars and quartz; (e) SEM image of dolomite in which the overlapping crystalsof celestite can be observed; (f) SEM image of calcium oxalate accompanied by gypsum.

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e4647 4641

[partial pressure of CO2]) and the precipitation of barite. Celestitefrequently encases the barite (Corbella et al., 2007).

3.1.2. Pigments of the Abrigo Grande de MinatedaIn our analysis of the paint, we separated the inorganic fraction

from the organic fraction.In the Raman spectra, the strong band at 465 cm�1 was accom-

panied by other weaker bands at 208 and 128 cm�1 (Fig. 10(a)),corresponding to a-quartz (SiO2) grains (Hernanz et al., 2008).

Calcium oxalate appears over the entire area of the samplebecause it has low solubility. Calcium oxalate is associated withgypsum, quartz, feldspar, and iron oxides and exhibits shadesranging from grey-blue to yellowish or whitish. Thewhewellitewaseasily identified by the Raman intense doublet 1462/1489 cm�1 andthe 895, 592, 502, 222, 205, and 162 cm�1 spectral bands (Carmonaet al., 1997; Frost and Weier, 2003) (Fig. 10(a), (b), (d)).

The origin of the hydrated calcium oxalates found in the cavitiesand shelters of the stone surface is well documented (Del Monteet al., 1987). The presence of these substances implies conserva-tion problems, as the formation of oxalate crystals can cause in-ternal stresses and promote the ageing process. Paradoxically, thesesame substances can seal and protect the paint. The literaturedealing with the formation of calcium oxalate proposes twopossible hypotheses for its origin: biological and chemical. Ac-cording to the former hypothesis, the hydrated calcium oxalatesmay be precipitated from oxalic acid secreted during the biologicalactivity of microorganisms such as fungi, lichens, or bacteria thatcan colonise the calcium-rich substrates. The second hypothesissuggests that the oxalates may result from the degradation oforganic media and constitute the end product of the alteration ofsome binders (Maravelaki-Kalaitzaki, 2005).

The oxalate encrustations observed in the painted panels of theAbrigo Grande de Minateda exhibit some black carbonaceous par-ticles in the rocky substrate and in the pigmented area. The Ramanspectrum contains the general bands D1 at w1342 cm�1 and G atw1585 cm�1 (Fig. 10(e)) for amorphous carbon (Beyssac et al.,2003), a characteristic component of carbon black, bone black,ivory black, or charcoal, as described in previous rock art studies

(Smith et al., 1999; Hernanz et al., 2006; Ospitali et al., 2006). Arecent study demonstrates that the presence of black-colouredparticles is not necessarily attributable to pigment use but couldresult from the metabolic activities of lichen, fungi, and other mi-croorganisms (Darchuk et al., 2009). Thus, we should carefullyconsider the working hypothesis that has identified charcoalsketching as a precursor to painting (Hernanz et al., 2008).

We also observed Raman spectral bands that were more char-acteristic of calcium sulphate, with a strong band at 1007 cm�1

(Fig. 10(b)). To characterize the crystalline phase of calcium sul-phate was extended the region Raman (3000e5500 cm�1) wheremolecular H2O bonds can be observed. A strong band at 3494e3405together with another phase confirms that the gypsum doublyhydrated is found (Inline Supplementary Fig. S2(d)). Other weakerbands at 1135, 618, 492, 412, and 177 cm�1 were detected(Herzberg, 1945; Edwards et al., 2000). Gypsum is frequently foundas a product of the natural deterioration of biocalcarenites, whichoccur in the rock shelter of Abrigo Grande de Minateda and consti-tute the rock surface of the decorated panels. The presence ofgypsum is an effect of haloclastism, which acts on the outer verticalsurfaces. Gypsum salts are deposited in the proximity of externalsurfaces when water on the surfaces evaporates. Therefore, thedepositions are associated with wetting and drying processes.These gypsum salts enhance the corrosion and granular degrada-tion of the biocalcarenites due to the salts’ mineralogical compo-sition and distinct physical (thermal expansion coefficients),mechanical (resistance to compression), and hydraulic properties(gypsum is hygroscopic). Thus, gypsum salts act as a wedge, me-chanically peeling away the outer surface of the biocalcarenites andresulting in blisters and taphoni (Fig. 11).

Inline Supplementary Fig. S2 can be found online at http://dx.doi.org/10.1016/j.jas.2013.07.010.

Small concentrations of calcium phosphate were detected byRaman spectroscopy in specific areas of the sample. A strong bandat 962 cm�1, which is characteristic of apatite, Ca5(PO4)3(F,Cl,OH),was found next to those most characteristic of whewellite(Fig. 10(c)). Some authors have formulated several hypothesesregarding the origin of this material (i.e., native apatites included in

Fig. 10. (a) Raman spectrum (D cm�1) of a-quartz associated with calcium oxalate, ironoxides, and hydrated calcium sulphates (gypsum); (b) spectrum of hydrated calciumsulphates (gypsum); (c) Raman spectral band of calcium phosphate that distinguishesit from the characteristic bands of calcium oxalate; (d) characteristic Raman spectra ofiron oxides, haematite, and magnetite associated with calcium oxalates and potassiumfeldspars; (e) typical spectrum of amorphous carbon. Abbreviations of mineral namesare as follows: q, quartz; h, haematite; g, gypsum; w, whewellite; ap, apatite; f, feld-spar; mg, magnetite; ca, amorphous carbon. Abrigo Grande de Minateda.

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e46474642

fragments of raw material collected by the painters, remnants oftools used to paint or grind the pigment, or charred and milledbones intentionally added to the paint). The last possibility suggeststhat these materials were filler pigments in a paint recipe related tothe practice of rituals (Hernanz et al., 2008, 2012). We havedetected concentrations of calcium phosphates in the rock surface,which, in our case, complicates the formulation of thesehypotheses.

Raman bands characteristic of haematite were identified, a-Fe2O3, at the vibrational frequencies of 222, 246, 292, 498, and612 cm�1 (De Faria et al., 1997; Hernanz et al., 2006) and areassociated with potassium feldspars (KAlSi3O8) of microcline ororthoclase type (K-feldspar) with Raman spectral bands at 180, 477,and 812 cm�1. The broad band at 1314 cm�1 was assigned to thescattering of two magnons of haematite. The spectrum of a smallblack particle located at the edge, below the encrustation, exhibits a

Raman band at 668 cm�1, the typical frequency of magnetite, Fe3O4(De Faria et al., 1997), although other, weaker magnetite bands at550 and 312 cm�1 were not detected (Fig. 10(d)).

The SEM-EDX analysis was critical to establish search protocolsfor use in the subsequent molecular characterisation of the samplestarting from the elemental analysis. The following elements weredetected: iron (Fe) in low concentrations (<1e3%) accompanied bydifferent phosphorus (P) concentrations, common components ofsome bioclasts (foraminifera, bryozoans, echinoderms, etc.), silicon(Si), oxygen (O2), aluminium (Al), calcium (Ca), potassium (K), andcommon components such as titanium (Ti) (Inline SupplementaryFig. S3). In addition, phyllosilicates that form part of these bio-calcarenites and can form a wide range of minerals including illite,smectites such as montmorillonite and nontronite, kaolinite,microcline, orthoclase, albite, anorthite, mica, glauconite, andothers were detected (Table 1).

Inline Supplementary Fig. S3 can be found online at http://dx.doi.org/10.1016/j.jas.2013.07.010.

The mapping of the Abrigo Grande de Minateda indicates con-centrations of potassium feldspars (K-feldspar) of the microcline ororthoclase type, which accompany the inorganic pigment fractions(Fig. 12).

3.1.3. Pigments of the Abrigo del Barranco de la MortajaThe Raman analyses suggest that iron oxides are found primarily

in haematites; in some cases, the presence of goethite (Fe(OH)) wasalso detected. These oxides and hydroxides of iron are associatedwith oxalates, calcium carbonates (Fig. 13(a)e(c)) and potassiumfeldspars (Fig. 13(c)).

The replacement of calcium oxalatemonohydrates, identified bythe band doublets 1462/1489 cm�1, is less apparent (Abrigo Grandede Minateda) (Fig. 13(d)) and is concentrated in the area of contactwith the calcium sulphates,1007 and 412 cm�1 (Fig. 13(e)), which isalso located in a small area because this sample has experiencedless deterioration (possibly related to a more recent date of thepainted figure) than that in the Abrigo Grande de Minateda. Char-acterized the crystalline phase in these calcium sulphate region(3000e5500 cm�1) as anhydrite, a calcium sulphate dihydratewithout the presence of water groups. In the stability of variousphases of gypsum, it is suggested that at any condition of pressure,temperature and humidity the gypsum must be dehydrated inanhydrite (Prasad et al., 2001) (Inline Supplementary Fig. S2(e)).

The Raman spectra exhibited bands characteristic of calcite andfeldspars. The orthoclase- or microcline-type K-feldspar weredetected in Raman spectral bands at 180, 201, 413, 477, and514 cm�1 (Fig. 13(c)), although it may coexist with other feldsparsin the hydrated mica group such as illite (K,H3O)(Al, Mg, Fe)2(Si,Al)4O10[(OH)2(H2O)]. Calcite has a strong Raman spectral band at1086 cm�1 and other sidebands at 713, 355, 282, and 155 cm�1

(Fig. 13(f), (g)). Raman spectroscopy was unable to detect thepresence of apatite.

With a strong band at 144 cm�1 (Fig. 13(g)), the identification ofanatase (TiO2) is interesting but not surprising, as anatase is foundin this area (biocalcarenites, marls, conglomerates, and tertiarysands) and is also present on the rock surface.

The SEM-EDX results confirmed the presence of iron (Fe) inidentical concentrations (<1e3%), phosphorus (P) as a componentof the bioclasts (Fig. 14) and silicon (Si), oxygen (O2), aluminium(Al), calcium (Ca), potassium (K), magnesium (Mg) and titanium(Ti) (Inline Supplementary Fig. S3), which are all components thatare common in terrigenous materials and can form the wide rangeof minerals found in Abrigo Grande de Minateda (Table 1).

The scanning results from the Abrigo del Barranco de la Mortajasample indicate the presence of microcline or orthoclase potassiumfeldspars (K-feldspar) along with the pigment (Fig. 15).

Table 1Characterisation and identification of the organic and inorganic fractions of twomicrosamples of paint from the Abrigo Grande de Minateda (Min) and Abrigo del Barranco de laMortaja (Mor).

Sample Area SEM-EDX Raman GCeMS

Min 1 C(25%), O(49%), Al(<1%) Si(2%), S(6%), P(<1%) K(<1%), Ca(16%), Fe(<1%) WhewelliteFeldsparHaematiteGypsumQuartz

Fatty acids: (C16:0), (C18:0)

Min 2 C(23%), O(49%), Al(<1%) Si(3%), S(7%), K(<1%) Ca(14%), Fe(3%) WhewelliteFeldsparHaematiteGypsumQuartz

Fatty acids: (C16:0), (C18:0)

Min 3 C(31%), O(46%), Al(<1%) Si(3%),P(<1%), S(4%) K(<1%), Ca(13%), Fe(2%) WhewelliteFeldsparHaematiteGypsumApatite

Fatty acids: (C16:0), (C18:0)

Mor 1 C(19%), O(63%), Na(<1%) Mg(<1%), Al(<1%), Si(6%) P(<1%), S(<1%), Cl(<1%) K(<1%), Ca(7%), Fe(3%) WhewelliteCalciteHaematiteFeldsparAnhydriteGoethiteQuartz

Mor 2 C(20%), O(61%), Na(<1%) Mg(<1%), Al(<1%), Si(<1%) S(1%), Cl(<1%), K(<1%) Ca(13%), Fe(3%) WhewelliteCalciteHaematiteAnhydriteFeldspar

Mor 3 C(17%), O(58%), Na(<1%) Mg(<1%), Al(<1%), Si(<1%) P(<1%), S(2%), Ca(22%) WhewelliteCalciteAnhydriteFeldspar

Mor 4 C(19%), O(60%), Na(<1%) Mg(<1%), Al(<1%), Si(<1%) S(1%), K(<1%), Ca(19%) Fe(<1%) WhewelliteCalciteGypsumHaematiteFeldspar

Fig. 11. (a) SEM image of the Abrigo Grande de Minateda; (b) the alteration in the form of a wedge produced by calcium sulphates; (c) the granular degradation caused by calciumsulphate in the rock surface; (d) corrosion caused by gypsum salts on the biocalcarenites.

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e4647 4643

Fig. 12. (a) SEM image of the sample from the Abrigo Grande de Minateda; (b) colour image (Cameoþ) as a function of the scattered photon energies (keV) of the compositionalchemical elements and their corresponding spatial distributions: C (carbon), O (oxygen), Si (silicon), Al (aluminium), K (potassium), Mg (magnesium), S (sulphur), Ca (calcium), andFe (iron).

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e46474644

Fig. 13. (a) Raman spectrum of iron hydroxide or goethite; (b) Raman spectral bands ofhaematite-type iron oxide; (c) Raman spectrum of haematite mixed with orthoclase ormicrocline potassium feldspars plus calcium oxalate; (d) calcium oxalate mixed withpotassium feldspars; (e) calcium oxalates associated with feldspar, anydrite, and cal-cium carbonates; (f) spectrum characteristic of calcite; (g) Raman spectral bandcharacteristic of titanium oxides mixed with other calcite bands. Abbreviations ofmineral names: go, goethite; h, haematite; ah, anhydrite; w, whewellite; f, feldspar; c,calcite; an, anatase. Abrigo del Barranco de la Mortaja.

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e4647 4645

Both in the Abrigo Grande de Minateda as in the Abrigo del Bar-ranco de la Mortaja, analyzes of the pigment samples were per-formed by X-ray diffraction (XRD). The data that were obtainedfrommineral phases are not present because we believe provide nomore relevant information we obtained by Raman and this way weavoid duplication.

Fig. 14. Backscattering images taken by SEM. Well-defined forms of bioclasts ca

3.2. Organic pigment fraction

Neither sample subjected to GC (Abrigo Grande de Minateda orAbrigo del Barranco de la Mortaja) exhibited positive results foramino acid content. Amino acids appeared in quantities so low thatthey could not be considered a positive result. Unfortunately, manyamino acids are not detected due to their chemical instability and,in this case, their considerable age.

Media rich in sulphates, as in this case, usually produce largecontamination ghost peaks in the chromatograms that can maskthe presence of some amino acids, such as leucine, isoleucine,proline, valine, and serine, which are fundamental to establishinguseful amino acid patterns to detect lowamino acid concentrations.

The sample corresponding to the Abrigo Grande de Minatedaexhibited trace quantities of fatty acids, terpene compounds of thepalmitic (C16:0) and stearic (C18:0) types at concentrations below1 ppm. These low concentrations are likely due to the age of thepainting. These substances appear repeatedly in analyses conductedin South America (Domenench Carbó, 2010). Degraded animal fats(Copley et al., 2005; Spangenberg et al., 2006) can serve as binders(Boschín et al., 2002; Fiore et al., 2008; Vázquez et al., 2008) and aresometimes mixed with the pigments while processing, applying, orstoring them. These latterworkinghypotheses (Fiore et al., 2008) areparticularly interesting. Since thefirst analyseswerepublished (Pepeet al., 1991), the literature has abounded with references to fattymaterials.However, experimentationhas shownthat thesematerialsare inadequate binders (Couraud, 1988; Mas Cornellà, 2005).

Althoughonly fatty acidsweredetected,manyessentially proteicnatural materials and adequate binders (among which are animalblood, milk, egg, acacia gum, etc.) contain traces (<1%) and some-times higher proportions of fatty acids (Mills and White, 1986:66e68, 78e79). Because the protein or polysaccharide fractions in thesematerials is themajority fraction, degradation ismuchmore rapid inan outdoor or semi-outdoor environment; consequently, only thedegradation products, including oxalates or traces of free-form,esterified, or saponified fatty acids, ultimately remain.

4. Conclusions

The elemental compositions of both paint samples are almostidentical. Thus, these paints do not follow recipes and do notinclude filler pigments, which would be unnecessary if abundanthigh-quality raw pigmenting materials were readily available.Rather, these paints may have been made from iron oxides andterrigenous sediments derived from lithogenesis in the environ-ment and used at two chronological moments separated by severalmillennia. Therefore, the similarity in the compositions of the paintsamples does not imply any cultural relationship between the

n be observed in the rocky panel of the Abrigo del Barranco de la Mortaja.

Fig. 15. (a) SEM image of the sample taken from Abrigo del Barranco de la Mortaja; (b) colour image (Cameoþ) as a function of the scattered photon energies (in keV) arising fromthe chemical elements that compose the sample and their corresponding spatial distributions: C (carbon), O (oxygen), Si (silicon), Al (aluminium), K (potassium), Mg (magnesium), S(sulphur), Ca (calcium), and Fe (iron).

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e46474646

paintings. The raw material for the paint was collected in aconvenient and random manner based on its red pigmentation.

The continual deposition of calcium oxalate, beginning at themoment that a figure is painted and leading up to the current date,can convert an image into a real alteration layer that covers thepaint, as is evident in the Abrigo Grande de Minateda. This fact,together with the low pigment density, leads us to believe that thissample is older than previously estimated.

The occurrence of calcium oxalate in the surface of the paintingand in the paint layers of both samples indicates that a complextaphonomic process has merged with the outer alteration layer.This finding calls into question the results of analyses based onstratigraphic layers because these layers appear fused and contin-uously altered. However, calcium oxalate can be integrated into theraw material and into the surface itself, inserting a random factorinto the process of dating the paintings.

This study indicates that the surface must be differentiated fromthe paint that is transformed by taphonomic processes, a processthat raises difficulty in defining the organic fraction. The presenceof specific fatty acids should be considered with caution but maylead to new and interesting interpretive perspectives, which maybe corroborated by future analyses. These circumstances supportthe hypothesis that the patina of calcium oxalate has a biologicalorigin (fungi, lichens or bacteria), also supported by the presence ofcarbonaceous particles, product of the metabolism of thesemicroorganisms.

Care must be taken when interpreting the presence of sub-stances such as calcium phosphates detected in the pigments asoriginating from rituals or other actions. These interpretations areinvalidated when the substances are found in the rocky substrateitself and are therefore likely to derive from the immediatesurroundings.

M. Mas et al. / Journal of Archaeological Science 40 (2013) 4635e4647 4647

The detection of calcium phosphate moves us to consider, as ahypothesis, the degradation of shells of invertebrates and frag-ments of foraminifera, partially replaced by phosphate.

The particle size distribution exhibits finer grinding in theLevantine art than in the schematic art. The latter case correspondsto a painting of simple and thick lines that utilises a relatively crudetechnique compared to the Levantine art, which is characterised bydenser silhouetting with flat ink. Both techniques are characteristicand representative of schematic and Levantine art, respectively.

Acknowledgements

The archaeological research project El arte rupestre en el Campode Hellín (Albacete) 2005-2008 (Rock Art at the Campo de Hellín(Albacete) 2005-2008) was authorised and funded by the DirecciónGeneral de Patrimonio y Museos of the Junta de Comunidades deCastilla-La Mancha, the UNED, and the Museum of Hellín.

We gratefully acknowledge the generous assistance from LauraTormo and Marta Furio in the production of SEM photographs, andMaria Teresa Cuartero in the cartographic production andgeographic information (Museo Nacional de Ciencias Naturales,CSIC).

Analyses related to X-ray diffraction and gas chromatographyhave been performed by Larco Química y Arte SL.

References

Acosta Martínez, P., 1968. La pintura rupestre esquemática en España. Universidadde Salamanca, Salamanca.

Beltrán Martínez, A., 1968. Arte rupestre levantino. Facultad de Filosofía y Letras,Zaragoza.

Beyssac, O., Goffé, B., Petitet, J.P., Froigneux, E., Moreau, M., Rouzaud, J.N., 2003. Onthe characterization of disordered and heterogeneous carbonaceous materialsby Raman spectroscopy. Spectrochimica Acta Part A 59, 2267e2276.

Boschín, M.T., Seldes, A.M., Maier, M., Casamiquela, R.M., Ledesma, R.E., Abad, G.E.,2002. Análisis de las fracciones inorgánica y orgánica de pinturas rupestres ypastas de sitios arqueológicos de la Patagonia septentrional argentina. Zephyrus55, 183e198.

Breuil, H., 1920. Les peintures rupestres de la Péninsule Ibérique. XI: Les rochespeintes de Minateda (Albacete). L’Antropologie XXX, 1e50.

Breuil, H., 1935. Les peintures rupestres schématiques de la Péninsule Ibérique. IV:Sud-est et Est de l’Espagne. Fondation Singer-Polignac, Lagny-sur-Marne.

Bueno Ramírez, P., Balbín Behrmann, R., Alcolea González, J.J., 2007. Style V dans lebassin du Douro. Tradition et changement dans les graphies des chasseurs duPaléolithique Supérieur européen. L’Anthropologie 111, 549e589.

Carmona, P., Bellanato, J., Escolar, E., 1997. Infrared and Raman spectroscopy ofUrinary Calculi. Biospectroscopy 3, 331.

Clottes, J.,Menu,M.,Walter, P.,1990. La préparationdespeinturesmagdaléniennes descavernes ariégeoises. Bulletin de la Société Préhistorique Française 87, 170e192.

Copley, M.S., Bland, H.A., Rose, P., Horton, M., Evershed, R.P., 2005. Gas chromato-graphic, mass spectrometric and stable carbon isotopic investigations of organicresidues of plant oils and animal fats employed as illuminants in archaeologicallamps from Egypt. Analyst 130, 860e871.

Corbella, M., Cardellach, E., Ayora, C., 2007. Disolución y precipitación de carbonatosen sistemas hidrotermales. Implicaciones en la génesis de depósitos tipo MVT.Boletín de la Sociedad Geológica Mexicana LIX, 83e99.

Couraud, C., 1988. Pigments utilisés en Préhistoire. Provenance, préparation, moded’utilisation. L’Anthropologie 92, 17e28.

Darchuk, L., Stefaniak, E.A., Vázquez, C., Palacios, O.M., Worobiec, A., Van Grieken, R.,2009. Composition of pigments on human bones found in excavations inArgentina studied with micro-Raman spectrometry and scanning electron mi-croscopy. e-Preservation Science 6, 112e117.

De Faria, D.L.A., Venâncio Silva, S., De Oliveira, M.T., 1997. Raman microspectroscopyof some iron oxides and oxyhydroxides. Journal of Raman Spectroscopy 28,873e878.

Del Monte, M., Sabbioni, C., Zappia, G., 1987. The origin of calcium oxalates onhistorical buildings, monuments and natural out-crops. Science of the TotalEnvironment 67, 17e39.

Domenench Carbó, M.T., 2010. Caracterización de aglutinantes orgánicos de laspinturas rupestres y problemas asociados a su conservación. In: Ponencias delos Seminarios de Arte Prehistórico desde 2003e2009. VeVIeVIIeVIIIeIXeX,Gandía-Tirig. Serie Arqueológica 23. Real Academia de Cultura Valenciana,Valencia, pp. 47e67.

Edwards, H.G.M., Newton, E.M., Russ, J., 2000. Raman spectroscopic analysis ofpigments and substrata in prehistoric rock art. Journal of Molecular Structure550e551, 245e256.

Fiore, D., Maier, M., Parera, S.D., Orquera, L., Piana, E., 2008. Chemical analyses of theearliest pigment residues from the uttermost part of the planet (Beagle Channelregion, Tierra de Fuego, Southern South America). Journal of ArchaeologicalScience 35, 3047e3056.

Fort, R., Bernabeu, A., García del Cura, M.A., López de Azcona, M.C., Ordoñez, S.,Mingarro, F., 2002. Novelda stone: widely used within the Spanish architecturalHeritage. Materiales de construcción 52 (266), 19e32.

Frost, R.L., Weier, M.L., 2003. Raman spectroscopy of natural oxalates at 298 and 77K. Journal of Raman Spectroscopy 34, 776e785.

García Arranz, J.J., Collado Giraldo, H., Nash, G. (Eds.), 2012. The Levantine Question.Post-palaeolithic Rock Art in the Iberian Peninsula. El problema “Levantino”.Arte rupestre postpaleolítico en la Península Ibérica. Archaeolingua Alapítvány,Budapest-Cáceres.

Hernanz, A., Mas, M., Gavilán, B., Hernández, B., 2006. Raman microscopy and IRspectroscopy of prehistoric paintings from Los Murciélagos cave (Zuheros,Córdoba, Spain). Journal of Raman Spectroscopy 37, 492e497.

Hernanz, A., Gavira-Vallejo, J.M., Ruiz López, J.F., Edwards, H.G.M., 2008.A comprehensive micro-Raman spectroscopic study of prehistoric rock paint-ings from the Sierra de las Cuerdas, Cuenca, Spain. Journal of Raman Spec-troscopy 39, 972e984.

Hernanz, A., Ruiz-López, J.F., Gavira-Vallejo, J.M., Martin, S., Gavrilenko, E., 2010.Raman microscopy of prehistoric rock paintings from the Hoz de Vicente,Minglanilla, Cuenca, Spain. Journal of Raman Spectroscopy 41, 1394e1399.

Hernanz Gismero, A., Ruiz López, J.F., Gavira Vallejo, J.M., 2012. Pigmentos, agluti-nantes y pátinas: caracterización fisicoquímica de la tecnología de las pinturasrupestres levantinas (Pigments, binders and accretions: physico-chemicalidentification of Levantine rock art paintings technology). In: GarcíaArranz, J.J., Collado Giraldo, H., Nash, G. (Eds.), The Levantine Question. Post-palaeolithic Rock Art in the Iberian Peninsula, El problema “Levantino”. Arterupestre postpaleolítico en la Península Ibérica. Archaeolingua Alapítvány,Budapest-Cáceres, pp. 345e365.

Herzberg, G., 1945. Molecular Spectra and Molecular Structure II. Infrared andRaman Spectra of Polyatomic Molecules. Van Nostrand Reinhold, New York.

Maravelaki-Kalaitzaki, P., 2005. Black crusts and patinas on Pentelic marble fromParthenon and Erechtheum (Acropolis, Athens): characterization and origin.Analytica Chimica Acta 532, 187e198.

Mas Cornellà, M., 2005. La Cueva del Tajo de las Figuras. Universidad Nacional deEducación a Distancia e Diputación de Cádiz, Madrid.

Mas, M., Maura, R., Solís, M., 2012. Cronologías absolutas y cronologías relativas. Entorno a las secuencias iniciales del arte rupestre postpaleolítico en el ArcoMediterráneo (Absolute chronologies and relative chronologies. On the initialsequences of post-Palaeolithic rock art in the Mediterranean arc). In: GarcíaArranz, J.J., Collado Giraldo, H., Nash, G. (Eds.), The Levantine Question. Post-palaeolithic Rock Art in the Iberian Peninsula, El problema “Levantino”. Arterupestre postpaleolítico en la Península Ibérica. Archaeolingua Alapítvány,Budapest-Cáceres, pp. 187e207.

Mills, J., White, R., 1986. The Organic Chemistry of Museum Objects. Butterworths,London.

Montes Bernárdez, R., Cabrera Garrido, J.M., 1991e1992. Estudio estratigráfico ycomponentes pictóricos del arte prehistórico de Murcia (Sureste de España).Anales de Prehistoria y Arqueología 7-8, 69e74.

Ospitali, F., Smith, D.C., Lorblanchet, M., 2006. Preliminary investigations by Ramanmicroscopy of prehistoric pigments in the wall-painted cave at Roucadour,Quercy, France. Journal of Raman Spectroscopy 37, 1063e1071.

Pepe, C., Clottes, J., Menu, M., Walter, P., 1991. Le liant des peintures paléolithiquesariégeoises. Comte Rendu Académie des Sciences. Série II 312, 929e934.

Pouchou, J., Pichoir, F., 1991. Electron Probe Quantitation. Plenum Press, New York.Prasad, P.S.R., Pradhan, A., Gowd, T.N., 2001. In situ micro-Raman investigation of

dehydration mechanism in natural gypsum. Current Science 80, 1203e1207.Rogerio-Candelera, M.A., Jurado, V., Laiz, L., Sainz-Jimenez, C., 2011. Laboratory and in

situ assays of digital image analysis based protocols for biodeteriorated rock andmural paintings recording. Journal of Archaeological Science 38, 2571e2578.

Roldán, C., 2009. Análisis de pigmentos en conjuntos de arte rupestre. In: LópezMira, J.A., Martínez Valle, R., Matamoros de Villa, C. (Eds.), El arte rupestre delArco Mediterráneo de la Península Ibérica. 10 años en la Lista del PatrimonioMundial de la UNESCO. Actas del IV Congreso. Valencia, 3, 4 y 5 de diciembre de2008. Generalitat Valenciana, Valencia, pp. 269e277.

Ruiz, J.F., Mas, M., Hernanz, A., Rowe, M.W., Steelman, K.L., Gavira, J.M., 2006. Pre-mières datations radiocarbone d’encroûtements d’oxalate de l’art rupestrepréhistorique espagnol (First radiocarbon dating of oxalate crusts over Spanishprehistoric rock art). International Newsletter on Rock Art 46, 1e5.

Ruiz, J.F., Hernanz, A., Armitage, R.A., Rowe, M.W., Viñas, R., Gavira-Vallejo, J.M.,Rubio, A., 2012.CalciumoxalateAMS14Cdatingandchronologyofpost-Palaeolithicrock paintings in the Iberian Peninsula. Two dates from Abrigo de los Oculados(Henarejos, Cuenca, Spain). Journal of Archaeological Science 39, 2655e2667.

Smith, D.C., Bouchard, M., Lorblanchet, M., 1999. An initial Raman microscopicinvestigation of prehistoric rock art in caves of the Quercy District, S.W. France.Journal of Raman Spectroscopy 30, 347e354.

Spangenberg, J.E., Jacomet, S., Schibler, J., 2006. Chemical analyses of organicsresidues in archaeological pottery from Arbon Bleiche 3, Switzerland-evidencefor dairying in the late Neolithic. Journal of Archaeological Science 33, 1e13.

Vázquez, C., Maier, M.S., Parera, S.D., Yacobaccio, H., Solá, P., 2008. Combining TXRF,FT-IR and GC-MS information for identification of inorganic and organic com-ponents in black pigments of rock art from Alero Hornillos 2 (Jujuy, Argentina).Analytical and Bioanalytical Chemistry 391, 1381e1387.