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Heating of flint debitage from Upper Palaeolithic contexts at ManotCave, Israel: changes in atomic organization due to heating usinginfrared spectroscopy
Steve Weiner a, *, Vlad Brumfeld b, Ofer Marder c, Omry Barzilai d
a Department of Structural Biology and the Kimmel Center for Archaeological Sciences, Weizmann Institute of Science, Rehovot 76100, Israelb Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israelc Archaeology Division, Ben-Gurion University of the Negev, POB 653, Beer-Sheva 84105, Israeld Israel Antiquities Authority, POB 586, Jerusalem 91004, Israel
a r t i c l e i n f o
Article history:Received 3 June 2014Received in revised form6 November 2014Accepted 9 November 2014Available online 2 December 2014
The heat treatment of flint is known to change its mechanical properties and improve its fracturebehaviour during knapping. Here we examine 20 flint artifacts from Upper Paleolithic contexts fromManot Cave, Israel, using Fourier transform infrared spectroscopy and compare them to geogenic flintbeds from the walls inside the cave and from outcrops just above the cave. We show that the 512 and467 cm�1 peaks are broader in most of the flint debitage pieces as compared to the geogenic flint, andthat broadening of these peaks occurs when geogenic flint from the cave wall is heated. We also presentan empirical simple method to monitor these changes.
Flint is the preferred raw material for producing chipped stoneartifacts for various activities in prehistoric times. Flint is a sedi-mentary rock composed of very small crystallites of a-quartz(Micheelsen, 1966; Rios et al., 2001). The small size of the crystal-lites and the nature of the grain boundaries that bond themtogether, are presumably the major structural characteristics thatprovide flint with its unique fracture properties upon impact, andthus make it a material of choice for producing tools. The earliestuse of flint artifacts in the Levant is evident in the Lower Paleolithicperiod at the site of Ubeidiya, dated to ca. 1.4 Ma (Bar-Yosef andBelmaker, 2010; Bar-Yosef and Goren-Inbar, 1993). The latest sys-tematic use is the Iron Age period (ca. 1000 BC), when flint wassubstituted by metal for the purpose of tool making (Rosen, 1997).
Experienced flint knappers generally agree that controlledheating of the flint before knapping improves the mechanicalfracturing properties, thus making the material more suitable for
einer).
preparing tools (Crabtree and Butler,1964; Purdy and Brooks,1971).It is thus widely suspected that controlled heating was practiced bysome prehistoric flint knappers to improve the production processof stone tools. Laboratory studies have shown that significantchanges in various mechanical properties of flint occur after heat-ing (Domanski et al., 2009; Domanski and Webb, 1992; Domanskiet al., 1994; Schmidt et al., 2012a). In addition controlled heattreatment provides aesthetic qualities for flint implements.
At the nanometre level, the crystallites as viewed in the SEM areabout 200e300 nm inmaximum dimension (Schmidt et al., 2012a),and based on Xray diffraction line width broadening their coher-ence lengths are around 30e50 nm (Schmidt et al., 2012a). At theatomic level, flint is composed mainly of bridging SieOeSi bonds.Flint also contains a few percent by weight water, as well aschemically bound hydroxyl groups that form silanoles (SiOH).These silanole groups disrupt the bridging bonds (Schmidt et al.,2011).
Heated flint can be identified by several different methods.Measurement of thermoluminescence (TL) quantifies accumulatedtrapped charges after the heating event. The flint needs to haveinitially been heated to at least 300e400 �C (Aitken, 1990; Richteret al., 2011). Realignment of the paleomagnetic orientation after a
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e5346
heating event is determined by measurement of archae-omagnetism (Brown et al., 2009). The presence of characteristicpot-lid fractures is due to heating to relatively high temperatures(Hester and Collins, 1974). Lithic artifacts that have differences inlustrous glossy texture, are often assumed to be the product ofcontrolled heating (Crowfoot Payne, 1983; Purdy and Brooks, 1971;Schindler et al., 1982). Another method, also employed in thisresearch, is Fourier transform infrared spectroscopy (FTIR). FTIR hasbeen used to identify heated flints (Schmidt et al., 2013, 2012a) andsilcrete (Schmidt et al., 2012b), based on changes in the atomicstructures of these materials. These methods in themselves, how-ever, do not differentiate between controlled and uncontrolledheating e a key issue for understanding whether or not the heatingwas intentional.
It should however be noted that many flint types, and especiallydark coloured flints, do not show any obvious change in colourwhen heated (Domanski andWebb, 1992). Brown et al. (2009) usedTL, archaeomagnetism and maximum gloss for identifying heatedsilcretes in the MSA of South Africa, and concluded that deliberateheating of the raw materials for knapping was already in practicesome 70,000 years ago. Controlled heating of silcrete in BlombosCave, South Africa, was probably used to improve the production ofbifacial pressure-flaked points (Mourre et al., 2010). The associationbetween controlled heating and bifacial pressure-flaking was alsonoted in other regions in various time periods, for example in theUpper Palaeolithic Solutrian culture in Europe and Paleo-Indiancultures of North America (Bordes,1969; Crabtree and Butler,1964).
The earliest evidence for systematic flint heating in the Levantwas proposed for the Late Epipalaeolithic (Ramonian and Natufian)and Pre-Pottery Neolithic A periods (Edwards and Edwards, 1990;Henry et al., 2003; Nadel, 1989; Quintero, 1996) based on colourand lustre. We do note that heated flints from various caves androck shelters in the southern Levant have been dated using TL, withthe oldest being about 100,000 years (Mercier et al., 2007; Valladaset al., 1987,1988). These dated flint lithics were certainly exposed totemperatures of at least 300e400 �C in antiquity and were found inclear-cut archaeological contexts, only some of which were asso-ciated with burnt sediment assemblages. Experimental studiesexamined the possibility of controlled heating during the Natufianand Pre-Pottery Neolithic A and B, and showed that controlledheating of geological and archaeological flint samples may generatechanges in texture (to a glossy lustre) and colour (Edwards andEdwards, 1990; Nadel, 1989). The assumption that intentionallyheated flints can be identified in the southern Levant based on vi-sual criteria was recently challenged with the discoveries of severalnatural flint outcrops in Trans-Jordan that contain lustrous purple-pinkish coloured flints (Delage, 2007; Henry et al., 2003; Rollefsonet al., 2007). Thus lithics with these properties from the Natufianand Neolithic that were often assumed to have been heat treated,could have actually been obtained fromnatural geological outcrops.Accordingly the question of controlled flint heating in the prehis-toric Levant, and in other areas of the world, is not solved.
Brown et al. (2009) proposed that controlled or intentionalheating of flints should be based on at least two independentmethods for identifying past heating, should involve the analysis ofa statistically relevant sample assemblage and the samples shouldnot be from burnt contexts where unintentional heating mighthave occurred. Even these criteria are not definitive. Two inde-pendent methods for identifying past heating events are alwaysbetter than one, provided that both are really reliable. Burnt con-texts are not always apparent to the naked eye (Weiner, 2010). Astatistically relevant sample assemblage is essential, but the argu-ment is much stronger if all, or almost all the flints analysed showclear-cut evidence for having been heated. Furthermore, if it can bedemonstrated that the heating conditions were such that the flint
was unlikely to have lost its beneficial mechanical properties, thenthis could be an added criterion for controlled heating.
Here we present and apply a newmethod for identifying heatedflints based on infrared spectroscopy. This method can be applied toa statistically relevant sample and can provide some insight intopast heating conditions especially if the provenience of the flint isknown and the raw flint material can be tested. Infrared spectros-copy provides information on the short range order of the atoms,and Schmidt and his colleagues in particular have demonstratedthat certain peaks in the infrared spectrum of flint do change whenheated (Schmidt and Fr€ohlich, 2011; Schmidt et al., 2013). Theyspecifically demonstrated the heat sensitivity of peaks related tothe presence of the silanol groups, including a peak at 555 cm�1
(Schmidt and Fr€ohlich, 2011). The reduction in intensity of this peakdue to heating is thought to result in the formation of new bridgingSieOeSi bonds, and this reaction starts between 200 and 300 �C(Moxon and Reed, 2006; Schmidt et al., 2011; Schmidt and Fr€ohlich,2011). They proposed that monitoring this peak would be a goodway to determine if flint artifacts had or had not been heat treatedin antiquity (Schmidt et al., 2012a). Herewe focus on the changes inpeak properties of two other peaks, namely the 512 and 467 cm�1
peaks, which changewhen geogenic flint from insideManot Cave isheated. The 555 cm�1 peak in both the flint debitage pieces and thegeogenic flints analysed, is very weak.
2. Materials and Methods
2.1. Materials
Twenty pieces of flint debitage from archaeological layers inArea C (Units 2e4) in Manot Cave were selected randomly for theanalysis (Table 1). These layers are attributed to the Early UpperPalaeolithic on the basis of material culture and absolute chronol-ogy (Barzilai et al., 2012; Marder et al., 2013). The twenty flintschosen were divided into burnt and not burnt categories based onvisual observations and the presence (n¼ 10) or absence (n¼ 10) ofpot lids. Among the group showing an absence of pot lids, oneartifact was suspected as burnt based on colour and texture(Table 1). Among the ten artifacts that were thought to be heataffected, two of them had clear lustre differences between flakescars on the dorsal surface, which might suggest intentional heattreatment (Collins and Fenwick, 1974). For comparison, ninegeological samples were obtained from the local dolomite bed rockof the Sakhnin Formation of late Cenomanian age. Five samples ofnodules extracted from the inner cave wall were chosen, as thesecould never have previously been heated. In addition four flintnodules extracted from the bedrock above the cave, were alsoanalysed for comparison with the debitage. Although we have noproof that the debitage pieces analysed were derived from thesenodules, we assume that all the artifacts examined were derivedfrom local outcrops in the western Galilee region (Delage, 2007).One additional control was a surface collected artifact from anUpper Paleolithic site in the Western Negev (KHII).
2.2. Methods
A small (2e5 mm in longest dimension) sample was broken offthe edge of the sample using a long-nosed plier. Note that thesample size could be even smaller (comparable to a grain of sugar)if less damage to the material is desirable. Two different pieceswere sampled and analysed from each flint specimen. The sampleswere finely ground and a small representative aliquot (approxi-mately 100 mg) was mixed with a few milligrammes of infraredspectral grade KBr and pressed into a transparent pellet 7 mm indiameter using a Pike handpress. Spectra were obtained after 32
Table 1List of the 20 flint debitage pieces analysed from Area C (Units 2e4). The assessment of whether the flint was burned or not burnt is based mainly on visual inspection andpresence or absence of potlids.
Sample number Type Pot lids Texture Flake scar-gloss difference Colour Munsell code Burnt
12 Core trimming element No Mat No gloss Very pale brown tan (beige) 10YR 7/4 No13 Primary flake No Mat No gloss Light yellowish brown (beige) 10YR 6/4 No14 Flake No Mat No gloss Very pale brown tan (beige) 10YR 7/4 No15 Core trimming element No Mat No gloss Very pale brown tan (beige) 10YR 8/3 No16 Primary flake No Mat No gloss Very pale brown tan (beige) 10YR 7/4 No18 Flake Yes Glossy No differences Brown (red) 7YR 4/4 Yes19 Flake Yes Glossy No differences Reddish brown (red) 5YR 5/3 Yes20 Chunk Yes Glossy Gloss differences on dorsal side Reddish brown (red) 5YR 5/4 Yes21 Retouched blade No Natural gloss No differences Dark reddish brown (red) 25YR 3/4 No22 Core No Mat No differences Reddish brown (red) 5YR 5/4 Possibly burnt24 Flake No Mat Gloss differences on dorsal side Dark grey (black) 5Y 4/1 Yes25 Blade Yes Glossy No differences grey (black) 5YR 5/1 Yes26 Core trimming element No Mat No differences Black 5YR 2.5/1 No27 Endscraper Yes Glossy No differences Very dark grey (black) 5YR 3/1 Yes28 Chunk Yes Glossy No differences Dark grey (black) 5YR 4/1 Yes30 Core Yes Glossy No differences Grey 5YR 6/1 Yes31 Flake No Mat No differences Grey 2.5Y 5/1 No32 Flake Yes Glossy No differences Dark grey 10YR 4/1 Yes33 Core trimming element No Mat No differences Dark greyish brown (grey) 10YR 4/2 No34 Flake No Glossy No differences Grey 7.5YR 5/1 Yes
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e53 47
scans and at a resolution of 4 cm�1using a Nicolet iS5 spectrometer.The KBr pellet was reground and pressed two more times and theresults reported are only for the third grinding, in order to mini-mize the particle size effect on the peak shapes (Poduska et al.,2010; Regev et al., 2010). The dye for preparing the pellets andthe KBr itself was kept dry by mild heating under a 400 W lamp.
We used the peak deconvolution program PeakFit to charac-terize the properties of the 512 cm�1 and 467 cm�1 peaks. We firstcorrected the baseline from 600 cm�1 to the valley at around410 cm�1, and then deconvolved the spectrum using Voigt profiles,since the Voigt function describes best the FTIR band shape (see forexample (Stancik and Brauns, 2008)). The r2 values of all fits werebetter than 0.989.
We also developed a simple empirical approach to character-izing the changes in the 512 cm�1 and 467 cm�1 peaks by firstcorrecting the baseline from 600 cm�1 to the valley at around410 cm�1, and measuring the height of the 512 cm�1 peak (labelledX) and the height of the valley (Y) between the 512 cm�1 peak andthe 467 cm�1 peak (Fig. 1). The heights were measured after thespectrum had been expanded to full scale in the range from
Fig. 1. Infrared spectrum of flint showing the features analysed in this study, namely X (hei467 cm�1 peaks. The baseline is drawn from 600 cm�1 to the valley at around 410 cm�1. Weanalysed, this peak was almost absent.
950 cm�1 to 400 cm�1. We then divided X by Y and determined theso-called X/Y ratio. All samples were run in duplicate and we reportboth measurements (and not the average).
Heating was carried out in a small oven. The samples wereplaced in a ceramic container and the temperature close to thecontainer was recorded with a thermocouple. In fact the thermo-couple temperature and the overall oven temperature were withina few degrees. The oven achieved the maximum temperature setwithin 5e15 min depending on the final temperature, and at theend of the defined period, the samples were removed from the hotoven and allowed to cool to room temperature.
3. Results
We first exposed flint from a nodule that was extracted from thewall of the prehistoric cave of Manot to various elevated temper-atures (Fig. 2. See supplementary material for additional informa-tion on this flint). We chose this sample as it could not possiblyhave been subjected to heating in the past by brush fires oranthropogenic activities. Fig. 3 shows a series of infrared spectra
ght of the peak around 512 cm�1) and the height of the valley Y between the 512 andalso show the location of the 555 cm�1 peak (labelled Z). In many of the flint samples
Fig. 2. Photograph of flint nodules from the wall inside Manot Cave. Five of thesenodules were used as controls. The elongated nodule on the upper right hand side isabout 15 cm in length.
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e5348
after heating this sample for 3 h to different temperatures up to900 �C. The most conspicuous changes occur in the peak around512 cm�1 located on the shoulder of the stronger 467 cm�1 peak.The extent of reduction of the 512 cm�1 peak compared to theadjacent 467 cm�1 peak is not linear as a function of increasingtemperature, but the overall trend is towards a weaker 512 cm�1
peak. Heat treatment did not appear to significantly change otherparts of the spectrum. We therefore decided to focus on thechanges in the 512 and 467 cm�1peaks.
The first question addressed is whether or not there are differ-ences between the 512 and 467 cm�1 peaks in 20 flint debitagepieces from Area C of Manot Cave as compared to control samplesextracted from the walls inside the cave and from rock outcropsabove the cave. We used peak deconvolution to compare theproperties of the two peaks. For each flint sample two fragmentswere analysed. As flint is not necessarily homogeneous we do notaverage the results, but show the results of each fragment sepa-rately. Figs. 4 and 5 show that the full width at half height (FWHH)of both the 512 and the 467 cm�1 peaks respectively are broader inmost of the flint debitage pieces as compared to the controls, andFig. 6 shows that the areas of these peaks are the same in thecontrols and most, but not all of the debitage pieces. In fact, only 4of the debitage pieces have both duplicate analyses above the rangeof the controls.
In order to determine whether heating of the flints could ac-count for the observed differences between controls and most of
Fig. 3. Infrared spectra of cave wall sample #1 heated for 3 h to different temp
the flint pieces with respect to peak broadening, we heated a flintnodule from the wall inside the cave (that could not possibly havebeen heated in antiquity) to different temperatures. Each samplewas heated for 3 h. Figs. 7 and 8 show the effect of heating on theFWHH of the 512 and 467 cm�1 peaks respectively. Heating doescause these peaks to broaden, but the effect is clearly not linear.Some broadening occurs when the sample is heated to 200 �C, butbetween 200 and 500 �C the broadening remains fairly constant.Broadening clearly occurs in samples heated above 500 �C. Theseobservations are consistent with the flint debitage pieces (againwith a few exceptions) having been heated in antiquity.
Deconvolution of two closely associated peaks of different in-tensities does not provide unique solutions, as there are severalvariables that together can produce a statistically reasonable so-lution. In our hands, for example, the automatic “Peak Resolve”program (Omnic) did not provide the same or as consistent a set ofresults as the more manual “Peak Fit” program we used here. Wetherefore chose to develop a simple empirical quantificationmethod that provides reproducible values independent of algo-rithms, and that can be conveniently used in the field. Furthermore,the values obtained can be compared directly between differentoperators irrespective of the program used. The method isexplained in the Materials and Methods section and in Fig. 1. Fig. 9is a plot of the X/Y ratios of the same cave wall sample (#1) as afunction of temperature. For each temperature point the samplewas heated for 3 h. The X/Y ratio shows a general decrease withincreasing temperature, which is consistent with the observationsusing peak deconvolution to determine changes in peak broad-ening (Figs. 7 and 8). Here the changes occur at temperatures above400 �C.
Fig. 10 is a plot of the X/Y ratios of 20 flint debitage pieces fromArea C in the cave, as well as control flints from inside the cave andabove the cave. Almost all the control samples have higher X/Yratios than the flint debitage, with one exception (sample #21). Thisobservation is consistent with the results obtained using peakdeconvolution to monitor peak broadening (Figs. 4 and 5), wheresample #21 was also the only sample having both duplicate ana-lyses overlapping the range of the controls. These observed differ-ences in the X/Y ratio between the flint debitage and the controlflint nodules show that the decrease of the X/Y ratio at highertemperatures is an immediate consequence of the peaks broad-ening under constant area, and are consistent with the flint deb-itage having been heated and the controls not heated.
eratures. The different temperatures (�C) are shown above each spectrum.
Fig. 4. The full width at half height (FWHH) of the 512 cm�1 peak. Geogenic samples are coloured orange, and debitage samples are coloured blue. Samples 1e5 are the control flintsfrom inside the cave, samples 7e9 are control samples from above the cave, and samples 12e34 are the 20 flint debitage pieces from Area C excavated inside the cave. Note that thedebitage pieces are shown in the same order as they are listed in Table 1, where the characteristics of each piece are described. For clarity an open space was left between each groupof 5 debitage pieces. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 5. The full width at half height (FWHH) of the 467 cm�1 peak. See Fig. 4 legend for more details of the samples.
Fig. 6. The ratios of the areas of the 467 cm�1 peak divided by the area of the 512 cm�1 peak. See Fig. 4 legend for more details of the samples.
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e53 49
Fig. 7. Changes in the FWHH of the 512 cm�1 peak as a function of heating the Cave Wall #1 sample to different temperatures. Each sample was heated for 3 h.
Fig. 8. Changes in the FWHH of the 467 cm�1 peak as a function of heating the Cave Wall #1 sample to different temperatures. Each sample was heated for 3 h.
Fig. 9. The X/Y ratios of Cave Wall #1 sample heated to different temperatures. Each sample was heated for 3 h.
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e5350
Fig. 10. Plot of the X/Y ratio values for the control samples (#s 1e5 from the cave wall and #s 7e10 from nodules extracted from bedrock above the cave) and 20 flint debitage piecesfrom Area C within the cave (#s 12e34). For details on the flint debitage pieces see Table 1.
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e53 51
As we do not know whether the control flints studied herewere the source of the raw materials for producing the flintdebitage, we cannot be absolutely sure that the flint debitagepieces were heated in antiquity. An independent approach todetermining whether a particular flint sample was heated inantiquity, is to reheat the sample and determine whether the 512and 467 cm�1 peaks broaden, or the X/Y ratio decreases. Wedemonstrate this approach using one flint debitage piece thatbased on the above analyses should have been burned in antiq-uity using the X/Y ratio (Fig. 11). Heating in an oven does notsignificantly lower the X/Y ratio implying that this flint piece washeated in antiquity. For comparison we also heated a flint deb-itage piece from another site in southern Israel which had an X/Yratio which should indicate that it was not heated in antiquity(Fig. 12). Here the X/Y ratio clearly decreases as a function ofheating, which is consistent with the sample not having beenheated in antiquity.
Fig. 11. Heating of flint debitage sample #25 to differe
4. Discussion
We show using peak deconvolution that with one exception the512 and 467 cm�1 peaks of the Manot debitage flint pieces arebroader than the control flints. Furthermore heating of a controlflint extracted from the wall inside Manot Cave shows that thesepeaks also undergo broadening above 500 �C. As peak deconvolu-tion does not necessarily provide unique solutions, but depends onthe methods used, we also show that a simple empirical mea-surement of the ratio of height of the 512 cm�1 peak and the heightof the valley between this peak and the adjacent 467 cm�1, providesthe same results. The values obtained using the empirical mea-surement can be compared directly and can be conveniently ob-tained by straightforward pen and ruler measurements.
The observed differences between the Manot flint debitagepieces and the control flints are consistent with the flint debitagehaving been heated in antiquity. As we do not know that the flint
nt temperatures. Each sample was heated for 3 h.
Fig. 12. The effect of heating fragments from flint debitage KHII to different temperatures each for 3 h.
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e5352
debitage was produced from the control flint nodules, we cannotprove in this way that they were indeed heated, but can onlyconclude that the observations are consistent with the debitagepieces having been heated in antiquity. We do however demon-strate for one debitage piece that it was heated in antiquity.
Flint provenience studies in northern Israel have proved to bechallenging because of the abundance of the outcrops, and thevariability of the colours and textures, sometimes even within thesame outcrop (e.g. Druck, 2004; Delage, 2007). A study that inte-grated visual and geochemical analyses (ICP-MS and ICP-AES) hasmade advances in identifying flint outcrops from differentgeological formations and assigning lithic artifacts to them(Ekshtain et al., 2014). This still cannot resolve the issue of vari-ability within the same outcrop.
Peak broadening in infrared spectroscopy is a function of thesize of the particles analysed, as well as the extent of disorder of theatoms (Poduska et al., 2010). We tried to minimalize the particlesize effect by grinding each KBr pellet 3 times and only using thespectrum obtained from the third grind for analysis. We thereforeassume that much of the broadening is due to an increase in atomicdisorder, and that heating causes an increase in atomic disorder. Inthe cave wall flint nodule tested this increase occurs at tempera-tures above around 400e500 �C. This however could vary betweenflint types, and it is therefore not justified to use this observation todraw conclusions about the heating conditions of the flint debitagepieces, as we do not know that the geogenic nodules analysed herewere used to produce the debitage.
Schmidt et al. (2011) have elegantly shown that heat treatmentdoes reduce the number of silanol groups in the flint (which alsoabsorb at 555 cm�1ie peak Z in Fig. 1), and in the process SieOeSibonds are formed. This process generally begins at temperaturesbetween 200 and 300 �C (Schmidt et al., 2012a). In the Manotflints and controls this peak is relatively weak, and we could notobtain reproducible measurements of its properties. It may wellbe that in flint from other sources, the 555 cm�1 peak may bemore sensitive to heat than the 467 and 512 cm�1 peak broad-ening effects observed here. Both approaches should be routinelychecked.
The 512 cm�1 peak (peak X) is generally attributed to energyabsorption caused by SieO bending (Farmer, 1974). Lippincott et al.(1958) pointed out the absence of this peak in the highly disorderedform of the SiO2 polymorph silica (also known as opal) compared tothe presence of a well defined peak in quartz (Lippincott et al.,
1958). Lippincott et al. (1958) attributed this difference to theextent towhich the SiO4 tetrahedra are ordered in the lattice. This isconsistent with our interpretation that the observed broadening isdue to an increase in atomic disorder. It has been proposed thatheating also causes recrystallization in flint (Domanski and Webb,1992; Domanski et al., 2009). This can be expected to result inmore order at the atomic level, which we do not observe.
The X/Y ratio does not seem to be markedly affected by diage-netic processes following the initial heat treatment and duringburial. In fact, we did note that several cortices of some of the flintnodules from above the cave had higher X/Y ratios than the core ofthe same nodule, implying that if diagenetic processes do occur,then the tendency is for the X/Y ratio to increase, presumablyindicating an increase in atomic order.
At Manot Cave, flint lithics with X/Y ratios of 1.30 or less appearto have been heated in antiquity. Using this criterion, 19 out of the20 samples analysed were heated in antiquity. We note that neithercolour nor any other visible criteria, provided a consistent indica-tion of this heating (Table 1). The debitage fragments with pot-lidfractures cannot be distinguished from the other fragments basedon their X/Y ratios or their FWHH values.
The method used here is based on sampling a small fragmentfrom the edge of the sample, which could be as small as a grain ofsugar. Furthermore, the analysis method does not involve theproduction of thin sections or smooth surfaces, but involvescrushing and grinding a small sample and then obtaining theinfrared spectrum from a KBr pellet; a procedure that takes about10e15 min for each sample, including the time required to grindand press the sample 3 times. The method can thus be used tosurvey a relatively large number of flint samples fairly rapidly. Wedo however emphasize that flint is not a homogeneous materialand that duplicate samples from each object should be analysed.We would also advise that heating experiments be carried out onthe tools or debitage from a site being investigated, as well as onthe local raw flint materials (especially if they are known to be thesource of the rawmaterials used for knapping), to be more certainas to whether the flint was heated in antiquity. It could well bethat some flint is less susceptible to heat treatment than others,and hence might result in erroneous conclusions. Finally werecommend that both the 555 cm�1, in addition to the broadeningeffects of the 512 cm�1 and 467 cm�1 peaks be monitored, as oneor other approach may be more sensitive to heating in other flintsamples.
S. Weiner et al. / Journal of Archaeological Science 54 (2015) 45e53 53
5. Conclusions
This new FTIRmethod for identifying heated flint can be appliedto a statistically significant sample, and although it is destructive,the amount of material needed is small. Differences in the broad-ening properties of the 512 cm�1 and 467 cm�1 peaks in theinfrared spectra of flint debitage and control flints from in andabove Manot Cave, Israel, are consistent with almost all the debit-age samples analysed having been heated in antiquity.
Acknowledgements
Partial financial support was obtained from the Max Planck e
Weizmann Center for Integrative Archaeology and Anthropology, aswell as the Kimmel Center for Archaeological Science. S.W. holdsthe Dr. Walter and Dr. Trude Borchardt Professorial Chair inStructural Biology. The excavations at Manot Cave are supported bygrants from the Dan David Foundation, the Leaky Foundation, theCARE Foundation and the Israel Antiquities Authority. We thankDmitry Yegorov for his advice and help in analyzing the flintmaterial.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.jas.2014.11.023.
References
Aitken, M.J., 1990. Science-based Dating in Archaeology. Longman Group, Londonand New York.
Bar-Yosef, O., Belmaker, M., 2010. Early and Middle Pleistocene faunal and homininsdispersals through Southwestern Asia. Quat. Sci. Rev. 30, 1318e1337.
Bar-Yosef, O., Goren-Inbar, N., 1993. The Lithic Assemblages of 'Ubeidiya: a LowerPalaeolithic Site in the Jordan Valley. In: Qedem: Monographs of the Institute ofArchaeology. Hebrew University of Jerusalem, Jerusalem.
Barzilai, O., Ayalon, A., Bar-Mathews, M., Bar-Oz, G., Boaretto, E., Berna, F.,Frumkin, A., Hershkovitz, I., Khalaily, H., Marder, O.S.W., Yeshurun, R., 2012.Manot Cave: a prehistoric cave site in the western Galilee, Israel. HadashotArkheologiot 124. http://www.hadashot-esi.org.il.
Bordes, F., 1969. Traitement thermique du silex au Solutr�een. Bull. Soc. pr�ehist. fr.66, 197.
Brown, K.S., Marean, C.W., Herries, A.I.R., Jacobs, Z., Tribolo, C., Braun, D.,Roberts, D.L., Meyer, M.C., Bernatchez, J., 2009. Fire as an engineering tool ofearly modern humans. Science 325, 859e862.
Collins, M.B., Fenwick, J.M., 1974. Heat treating of chert:Methods of interpretationand their application. Plain Anthropol. 19, 134e145.
Crabtree, D.E., Butler, R., 1964. Notes on experiment in flint knapping: 1 heattreatment of silica materials. Tebiwa 1, 1e6.
Crowfoot Payne, J., 1983. The flint industries of Jericho. In: Kenyon, K.M.,Holland, T.A. (Eds.), Excavations at Jericho V. British School of Archaeology,London, pp. 622e759.
Druck, D., 2004. Raw Material Exploitation (Flint) in the Cultures of the CarmelNahal Mearot. Haifa University (in Hebrew), Haifa.
Delage, C., 2007. Chert availability and prehistoric exploitation in the Near East: anintroduction. In: Delage, C. (Ed.), Chert Availability and Prehistoric Exploitationin the Near East. BAR Int. S.1615, Oxford, pp. 1e18.
Domanski, M., Webb, J., 1992. Effect of heat treatment on siliceous rocks used inprehistoric lithic technology. J. Archaeol. Sci. 19, 601e614.
Domanski, M., Webb, J., Glaisher, R., Gurba, J., Libera, J., Zakoscielna, A., 2009. Heattreatment of Polish flints. J. Archaeol. Sci. 36, 1400e1408.
Domanski, M., Webb, J.A., Boland, J., 1994. Mechanical properties of stone artefactmaterials and the effect of heat treatment. Archaeometry 36, 177e208.
Edwards, P.C., Edwards, I.W., 1990. Heat treatment of chert in the Natufian period.Mediterr. Archaeol. 3, 1e5.
Ekshtain, R.A., Malinski-Buller, A., Ilani, S., Segal, I., Hovers, E., 2014. Raw materialexploitation around the Middle Paleolithic site of 'Ein Qashish. Quat. Int. 331,248e266.
Farmer, V.C., 1974. The Infrared Spectra of Minerals. Mineralogical Society, London.Henry, D.O., White, J.J., Beaver, J.E., Kadowaki, S., Nowell, A., Cordova, C., Dean, R.M.,
Ekstrom, H., McCorriston, J., Scott-Cumming, L., 2003. The early Neolithic site ofAyn Abu Nukhayla, southern Jordan. Bull. Am. Sch. Orient. Res. 330, 1e30.
Hester, T.R., Collins, M.B., 1974. Evidence for heat-treating of Southern Texas pro-jectile points. Bull. Tex. Archeol. Soc. 45, 219e224.
Lippincott, E.R., van Valkenburg, A., Weir, C.E., Bunting, E.N., 1958. Infrared studieson polymorphs of silicon dioxide and germanium oxide. J. Res. Natl. Bur. Stand.61, 61e70.
Marder, O., Alex, B., Ayalon, A., Bar-Matthews, M., Bar-Oz, G., Bar-Yosef Mayer, D.,Berna, F., Boaretto, E., Caracuta, V., Frumkin, A., Goder-Goldberger, M.,Hershkovitz, I., Latimer, B., Lavi, R., Matthews, A., Weiner, S., Weiss, U., Yas'ur, G.,Yeshurun, R., Barzilai, O., 2013. The Upper Palaeolithic of Manot Cave, WesternGalilee, Israel: the 2011e12 excavations. Antiquity 87. http://antiquity.ac.uk/projgall/marder337/.
Micheelsen, H., 1966. The structure of dark flint from Stevns, Denmark. Medd. Dan.Geol. Foren. 16, 285e368.
Mourre, V., Villa, P., Henshilwood, C.S., 2010. Early use of pressure flaking on lithicartifacts at Blombos Cave, South Africa. Science 330, 659e662.
Moxon, T., Reed, S.J.B., 2006. Agate and chalcedony from igneous and sedimentaryhosts aged from 13 to 3480 Ma: a cathodoluminescence study. Mineral. Mag.70, 485e498.
Nadel, D., 1989. Flint heat treatment at the beginning of the Neolithic period in theLevant. Mitekufat Haeven. J. Isr. Prehist. Soc. 22, 61e67.
Poduska, K.M., Regev, L., Boaretto, E., Addadi, L., Weiner, S., Kronik, L., Curtarolo, S.,2010. Decoupling local disorder and optical effects in infrared spectra: differ-entiating between calcites with different origins. Adv. Mat. 23, 550e554.
Purdy, B.A., Brooks, H.K., 1971. Thermal alteration of silica minerals: an archaeo-logical approach. Science 173.
Quintero, L.A., 1996. Flint mining in the Pre-Pottery Neolithic: preliminary report onthe exploitation of flint at Neolithic 'Ain Ghazal in Highland Jordan. In:Kozlowski, S.K., Gebel, H.G.K. (Eds.), Neolithic Chipped Lithic Industries of theFertile Crescent and Their Adjacent Regions, SENEPSE 3. Ex Oriente, Berlin.
Regev, L., Poduska, K.M., Addadi, L., Weiner, S., Boaretto, E., 2010. Distinguishingbetween calcites formed by different mechanisms using infrared spectrometry:archaeological applications. J. Archaeol. Sci. 37, 3022e3029.
Richter, D., Alperson-Afil, N., Goren-Inbar, N., 2011. Employing TL methods for theverification of macroscopically determined heat alteration of flint artefacts fromPaleolithic contexts. Archaeometry 53, 842e857.
Rios, S., Salje, E.K.H., Redfern, S.A.T., 2001. Nanoquartz vs. macroquartz: a study ofthe alpha-beta phase transition. Eur. Phys. J. B 75e83.
Rollefson, G.O., Quintero, L.A., Wilke, P.J., 2007. Purple-pink flint sources in Jordan.In: Delage, C. (Ed.), Chert Availability and Prehistoric Exploitation in the NearEast, BAR Int. S. 1615. John and Erica Hedges, Oxford, pp. 55e67.
Rosen, S.A., 1997. Lithics after the Stone Age: a Handbook of Stone Tools from theLevant. Altamira Press, Thousand Oaks, California.
Schindler, D.L., Hatch, J.W., Hay, C.A., Bradt, R.C., 1982. Aboriginal thermal alterationof a central Pennsylvania jasper: analytical and behavioral implications. Am.Antiq. 47, 526e544.
Schmidt, P., Badou, A., Fr€ohlich, F., 2011. Detailed FT near-infrared study of thebehaviour of water and hydroxyl in sedimentary length-fast chalcedony, SiO2,upon heat treatment. Spectrochim. Acta A 81, 552e559.
Schmidt, P., Fr€ohlich, F., 2011. Temperature dependent crystallographic trans-formations in chalcedony, SiO2, assessed in mid infrared spectroscopy. Spec-trochim. Acta A 1476e1481.
Schmidt, P., L�ea, V., Sciau, P., Fr€ohlich, F., 2013. Detecting and quantifying heattreatment of flint and other silica rocks: a new non-destructive method appliedto heat treated flint from the Neolithic Chassey culture, southern France.Archaeometry 55, 794e805.
Schmidt, P., Masse, S., Laurent, G., Slodczyk, A., Le Bourhis, E., Perrenoud, C.,Livage, J., Fr€ohlich, F., 2012a. Crystallographic and structural transformations ofsedimentary chalcedony in flint upon heat treatment. J. Archaeol. Sci. 39,135e144.
Schmidt, P., Porraz, G., Slodczyk, A., Bellot-gurlet, L., Archer, W., Miller, C.E., 2012b.Heat treatment in the South African Middle Stone Age: temperature inducedtransformations of silcrete and their technological implications. J. Archaeol. Sci.40, 3519e3531.
Stancik, A.L., Brauns, E.B., 2008. A simple asymmetric lineshape for fitting infraredabsorption spectra. Vib. Spectrosc. 47, 66e69.
Valladas, H., Joron, J.L., Valladas, G., Arensburg, B., Bar-Yosef, O., Belfer-Cohen, A.,Goldberg, P., Laville, H., Meignen, L., Rak, Y., Tchernov, E., Tillier, A.M.,Vandermeersch, B., 1987. Thermoluminescence dates for the Neanderthal burialsite at Kebara in Israel. Nature 330, 159e160.
Valladas, H., Reyss, J.L., Joron, J.L., Valladas, G., Bar-Yosef, O., Vandermeersch, B.,1988. Thermoluminescence dating of Mousterian Troto-Cro-Magnon' remainsfrom Israel and the origin of modern man. Nature 331, 614e616.
Weiner, S., 2010. Microarchaeology. Beyond the Visible Archaeological Record.Cambridge University Press, New York.
