Armenia, Georgia) and Eastern Turkey, Part 1: Source Characterization*
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bs_bs_banner Archaeometry 56, 1 (2014) 25–47 doi: 10.1111/arcm.12006 NEW DATA ON THE EXPLOITATION OF OBSIDIAN IN THE SOUTHERN CAUCASUS (ARMENIA, GEORGIA) AND EASTERN TURKEY, PART 1: SOURCE CHARACTERIZATION* C. CHATAIGNER Archéorient, UMR 5133, CNRS/Université Lyon 2, 7 rue Raulin, 69007 Lyon, France and B. GRATUZE† IRAMAT CEB, UMR 5060, CNRS/Université d’Orléans, 3 D rue de la Férollerie, 45071 Orléans Cedex 2, France A large analytical programme involving both obsidian source characterization and obsidian artefact sourcing was initiated recently within the framework of the French archaeological mission ‘Caucasus’. The results will be presented in two parts: the first part, this paper, deals with the presentation and characterization of obsidian outcrops in the southern Caucasus, while the second presents some results obtained from a selection of artefacts originating from different Armenian sites dated to between the Upper Palaeolithic and the Late Bronze Age. The same analytical method, LA–ICP–MS (laser ablation inductively coupled plasma mass spec- trometry), has been used to characterize all the studied samples (both geological and archaeo- logical). This method is more and more widely used to determine the elemental composition of obsidian artefacts, as it causes minimal damage to the studied objects. We present in this first part new geochemical analyses on geological obsidians originating from the southern Cau- casus (Armenia, Georgia) and eastern Turkey. These data enhance our knowledge of the obsidian sources in these regions. A simple methodology, based on the use of three diagrams, is proposed to easily differentiate the deposits and to study the early exploitation of this material in the southern Caucasus. KEYWORDS: OBSIDIAN GEOCHEMISTRY, LESSER CAUCASUS, ARMENIA, GEORGIA, EASTERN TURKEY, OBSIDIAN OUTCROPS, LA–ICP–MS ANALYSES INTRODUCTION The southern Caucasus is a region in which obsidian represents practically the only material used by prehistoric populations for their tools and weapons. Indeed, obsidian deposits are plentiful in Armenia as well as beyond the periphery of its territory, in southern Georgia, western Azerbaijan and eastern Turkey (Fig. 1). Analysis of the chemical composition of these sources (Keller et al. 1996; Blackman et al. 1998; Poidevin 1998) and of artefacts coming from approximately 70 Transcaucasian archaeo- logical sites dating from the sixth to the first millennia bc (Badalyan et al. 2004) have enabled the establishment of an initial cartography of the movements of obsidian between the Neolithic and the Iron Age, and confirmation of the great variability in their distribution in the region. The villagers obtained their supplies either from a single source or from several sources, and the nearest deposits were not necessarily the most favoured; the factor of direct linear distance, *Received 28 May 2012; accepted 12 July 2012 †Corresponding author: email [email protected] © 2013 University of Oxford 26 C. Chataigner and B. Gratuze Figure 1 The distribution of the obsidian sources in the southern Caucasus and eastern Turkey. often considered as a determinant in the choice of outcrops (Renfrew 1984), was thus not so important. The areas of diffusion of the obsidian sources also appear to have been highly contrasting. In certain cases (Chikiani), the material travelled in large quantities over great distances and in various directions. In other cases (Hatis), the area of diffusion is limited in quantity, distance and direction. Elsewhere (Geghasar), the obsidian was diffused in a limited quantity, but over very long distances or, on the contrary (Arteni), in high quantities over a limited territory. SOURCES OF OBSIDIAN AND ANALYTICAL METHOD The studied corpus Many sources of obsidian exist across the southern Caucasus. An exhaustive survey has enabled the collection of samples from all these sources, except for those in western Azerbaijan, and the study of the conditions of accessibility to the different primary (flows, domes) and the secondary © 2013 University of Oxford, Archaeometry 56, 1 (2014) 25–47 Obsidian in the Caucasus (Armenia, Georgia) and eastern Turkey, part 1 27 (blocks transported by the rivers) deposits. Fifty-five geological samples, from different sources in Georgia and Armenia, as well as 25 samples from sources in eastern Turkey, have been analysed by LA–ICP–MS (IRAMAT, CNRS/Université d’Orléans) (Table 1). LA–ICP–MS analysis Analyses of obsidian objects conducted at the Centre Ernest-Babelon of the IRAMAT (Orléans) are carried out using an Element XR mass spectrometer from Ther- mofisher Instrument and a VG UV microprobe ablation device. Routinely, concentrations of 38 elements are determined in obsidian objects. Among them, we find: • the main major and minor constituents (silicon, sodium, potassium, aluminium and iron), which enable classification of the obsidians according to their different types (calc-alkaline, peralkaline, hyperalkaline, hyperaluminous and metaluminous); • the main hydromagmaphile elements (Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Hf, Ta Th, U and rare earths), which characterize the magma and the volcanic rocks that derive from it (Cauvin et al. 1991; Gourgaud 1998). LA–ICP–MS analysis of obsidian objects operates as follows. The objects are placed in the ablation cell together with the reference standard materials and are alternatively sampled by a laser beam, which is generated by an Nd–YAG pulsed laser (maximum energy of 3–4 mJ and at a maximum pulse frequency of 15 Hz) operating at 266 nm (quadrupled frequency). The diameter of the ablation crater ranges from 60 mmto100mm, and its depth is around 250 mm. Classic parameters are 70 s of ablation (20 s for pre-ablation and 50 s for analysis) and a 6–8 Hz laser shoot rate. The pre-ablation time of 20 s is set to eliminate the transient part of the signal and ensure that surface contamination or corrosion does not affect the results of the analysis. An argon gas flow carries the ablated aerosol to the injector inlet of the plasma torch, where the matter is dissociated, atomized and ionized (typical flow rate values range from 1.15 l min–1 to 1.35 l min–1, depending on the cell size). The ions are then injected into the vacuum chamber of a high-resolution system, which filters the ions depending upon their mass-to-charge ratio, and they are then collected by the channel electron multiplier or the Faraday cup. The measurements are carried out in peak jump acquisition mode, taking four points per peak for counting and analogue detection modes, and 10 points per peak for Faraday detection. Automatic detection mode is used for most of the elements; only sodium, silicon, aluminium and potassium are systematically detected with the Faraday detector. Silicon is measured on the 28 isotope and is used as an internal standard. With our analytical parameters, the scanning time necessary to measure the 38 selected isotopes is about 2 s. As most of the encountered isobaric interferences could be resolved by working on uninterfered isotopes, all the measurements are carried out in low-resolution mode. Two different standard reference materials are used to calculate the response coefficient factor Ky as defined by Gratuze (1999) and thus to convert data into fully quantitative analyses: • The glass standard reference material (SRM) manufactured by NIST: SRM610. It is a soda– lime–silica glass doped with trace elements in the range of 500 ppm. Certified values are available for a very limited number of elements. Concentrations from Pearce, Norman and Hollocher (Hollocher and Ruiz 1995; Norman et al. 1996; Pearce et al. 1997) are used for the other elements. SRM610 is used to calculate all the Ky response coefficient factors except for magnesium, potassium and iron, which are present at levels that are too low, and aluminium, the value of which is not certain enough. © 2013 University of Oxford, Archaeometry 56, 1 (2014) 25–47 28 C. Chataigner and B. Gratuze Table 1 Volcanic complexes Number Subgroups Location Number Samples and obsidian of of provided by outcrops samples samples Geochemical groups Georgia Chikiani (Paravani, 7 Southern flank 2 Authors Kojun Dag) Northern flank 2 North-east flow 3 Armenia Ashotsk (Eni-Ël, 3 Aghvorik (= Eni-Ël) village 3 Authors Kechut) Tsaghkunyats 8 Tsaghkunyats 1 Damlik 3 Authors Ttvakar 2 Tsaghkunyats 2 Kamakar 2 Authors Aïkasar 1 Akhurian River 3 Akhurian 1 Near Shirakavan 1 Authors (= Sarikamis (Sarikamis NW) North) Akhurian 2 Near Shirakavan 2 Authors (Sarikamis NE) Arteni 7 Arteni 1 Satani Dar 1 Authors Mets Arteni 1 Arteni 2 Pokr Arteni 2 Authors Aragats flow 1 Arteni 3 Pokr Arteni 1 Authors Aragats flow 1 Gutansar 7 Dzhraber 3 Authors Fontan 1 Alapars 1 Gjumush 1 Aivazan 1 Hatis (Atis) 4 Hatis 1 Akunk (south-west) 2 Authors Kaputan (north-west) 1 Hatis 2 Zerborian (south-east) 1 Authors Gegham 7 Spitaksar, 3 Authors Geghasar 4 Vardenis 1 Khorapor 1 Authors Syunik 8 Syunik 1 Bazenk 2 Authors Syunik 2 Mets Satanakar 1 Authors Syunik 3 Mets Sevkar 3 Authors Pokr Sevkar 2 Eastern Turkey Tendürek 9 From a flat area on the mountain 9 M. D. Glascock Meydan Dag 4 On the outcrops, south-east of the 3 C. Kuzucuoglu summit caldera and C. Marro Concentration of blocks, on the 1 south-east flank of the volcano Süphan Dag 9 2 km east of Harmantepe 2 M. D. Glascock 5 km east of Harmantepe 4 3 km north of Mum village 3 Sarikamis 3 Sarikamis 1 Along the road from Karakurt to Sarikamis 1 M.-C. Cauvin South Sarikamis region 1 Sarikamis 2 Along the road from Karakurt to Sarikamis 1 M.-C. Cauvin © 2013 University of Oxford, Archaeometry 56, 1 (2014) 25–47 Obsidian in the Caucasus (Armenia, Georgia) and eastern Turkey, part 1 29 • Corning glass B. This glass was designed to match the compositions of ancient plant ash glass (Verità et al.