The source of obsidian artefacts found at East Chia Sabz, Western Iran
Introduction
The site of East Chia Sabz is a settlement in western Iran containing deposits from the Transitional Neolithic period (ca. 9500–8000 BC). The site was discovered during an archaeological survey inside the reservoir of Seimareh dam in 2007 (Brojeni, 2007) and excavated by an Iranian team under the leadership of H. Darabi in 2009. Evidence shows that East Chia Sabz was occupied from the early 9th–early 7th millennium BC (Darabi et al., 2011). The first season of salvage excavation resulted in identification of seven phases indicating cultural changes through time, mostly attested by lithic industry. Table 1 lists the proportions of chipped stone recovered from the stratigraphic levels of trench #2 (the only trench with complete information) for all seven phases. As the result of analysis of lithic artefacts, a change from flake to blade-bladelet production was observed. The change is accompanied by a transition from use of local chert to flint and then to small amount of obsidian. The latter, thus, was only used in the late (I–III) phases. Twenty obsidian samples from all excavated trenches at East Chia Sabz were submitted to the Archaeometry Lab at the University of Missouri Research Reactor (MURR) for chemical analyses. Analysis of the artefacts by X-ray fluorescence (XRF) indicated that all were chemically similar. However, because the two possible sources – Bingöl A and Nemrut Dağ – have similar chemical fingerprints that are difficult to separate by XRF [although see Orange et al., in press], it was necessary to further analyze the samples by neutron activation analysis (NAA) which gives a more definite result. This article presents the chemical results and discusses them archaeologically.
Section snippets
Background
Since the early 1960s, considerable research has been devoted to locating Anatolian obsidian sources and determining chemical fingerprints for them (Rapp and Hill, 1998: 137). Early research was undertaken by Renfrew (1969) who attributed the Anatolian sources for obsidian tools found at Ali Kosh to southeastern Turkey. Subsequently, other researchers using a variety of chemical analytical methods have identified more than 30 possible obsidian sources in Armenia, Azerbaijan, Georgia, and
Analytical procedures
The samples were analyzed initially by energy-dispersive XRF with a Bruker III–V+ portable spectrometer at MURR. The spectrometer is equipped with an air-cooled rhodium anode with 140 micron Be window and a thermoelectrically cooled Si–PIN diode detector. The detector has a resolution of 180 eV for the 5.9 keV peak from iron. Beam dimensions are approximately 2 × 3 mm. The X-ray tube was operated at 40 kV using a tube current of about 17 μA and produced a count rate of about 1200 counts per
Results
The compositional data for Fe, Rb, Sr, Y, Zr, and Nb measured in the artefacts by XRF are listed in Table 2. Table 3 presents the means and standard deviations for samples collected from the Bingöl and Nemrut Dağ subsources. Fig. 2 shows a scatterplot of Rb versus Zr with the artefacts projected against 90% confidence ellipses for the major sources in southeastern Turkey and Armenia. Fig. 2 and the results for elements in common with Frahm (2012) are consistent with the identification of Bingöl
Discussion
Obsidian is formed in lava flows and as blocks in tuff from explosive volcanic eruptions; it is globally distributed from Alaska to Himalayas (Rapp and Hill, 1998: 137). Throughout the Neolithic of the Old World, however, obsidian was traded and used as a desired raw material to produce stone tools. In the Near East, the most important sources of obsidian are located in Anatolia and the Caucasus which can be grouped into four distinct geographical clusters: central Anatolia, northeast Anatolia,
Conclusion
Based on XRF the Bingöl A and Nemrut Dağ subsources 2–6 were recognized as possible source(s) for the artefacts from East Chia Sabz. But the compositional data for Br, Cs, and Mn were also measured by NAA and determined that all of the obsidian artefacts came from the Nemrut Dağ-2 subsource. These results are clearly consistent with what has already been discussed on the sources of obsidian pieces in the neolithic sites of the region. Moreover, it has been assumed that obsidian must be firstly
Acknowledgments
We acknowledge James Blackman, Tristan Carter, Ellery Frahm, Bernard Gratuze, and Bastien Varoutsikos who shared source samples from Turkey, Armenia, Georgia, and Azerbaijan to enable a database for the ancient Near Eastern obsidian sources to be established in the Archaeometry Lab at MURR. Research at the Archaeometry Laboratory was supported in part by National Science Foundation grant BCS-1110793. We are also grateful to S. Saeedi who kindly transported the obsidian samples to the USA for
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