Obsidian Mediterranean sources

Although we attributed artifacts to each of the four major western Mediterranean sources, our focus here is on artifacts attributed to Monti Arci, Sardinia. Figure 2 illustrates the use of elemental ratios to discriminate the major island obsidian groups by INAA. By projecting these data as logged ratios of samarium/barium on the X-axis and iron/cesium on the Y-axis, we have maximized the differences between the various Sardinian subgroups in a manner... 

NAA is commonly used in studies of obsidian. The sources of obsidian in Southwest Asia, the Mediterranean, North America, Mexico, and elsewhere have been examined using NAA. Most of the obsidian in Southwest Asia comes from sources either in the mountains of Turkey or in northern Iran, both outside the Fertile Crescent. The graph below shows the results of the NAA measurement of the elements iron (Fe) and scandium (Sc) in obsidian in Southwest Asia (Fig. 8.10). Samples were also taken from the original sources. There are clear differences among most of the sources. 

For Sardinia, the exploitation of multiple sources was noted prior to the actual identification and characterization of each outcrop. The obsidian sources in the Monte Arci region of Sardinia have now been thoroughly documented and geochemically characterized 18, 19), while the results of recent fieldwork by this author on the other islands are expected to add significantly to earlier studies on Lipari 20), Palmarola 21, 22), and Pantelleria 23, 24). The western Mediterranean sources are briefly described here ... 

In the Mediterranean Sea and Middle East area, for example, there are obsidian outflows only in Italy, in some islands in the Aegean Sea, and in Turkey. Artifacts made of obsidian, however, are widely distributed over much of this vast area. Chemical analysis of many of these artifacts has shown that most of the obsidian used to make them originated in one or another of the outflows mentioned, but also in far-distant places such as Armenia and Iran. Plotting on a graph the concentration of selected elements in samples from obsidian sources against that in samples from sites where it was used, enables the identification of the source of the samples (see Fig. 22). Moreover, this type of analysis also makes it possible to trace the routes through which obsidian (and most probably other goods) were traded in antiquity (Renfrew and Dixon 1976). 

FIGURE 22 Obsidian in the eastern Mediterranean Sea area. Studying the relative concentration of trace elements in obsidian makes it possible to identify the obsidian and to determine its provenance. Determining the relative amounts of barium and zirconium in ancient obsidian tools and in samples from different sources of the natural glass, for example, made it possible to identify the provenance of obsidian used in eastern Mediterranean Sea area sites (Renfrew and Dixon 1976). 

Gale, N. (1981), Mediterranean obsidian source characterization by strontium isotope analysis, Archaeometry 23, 41-51. 

SOURCES OF OBSIDIAN IN THE EASTERN MEDITERRANEAN AND NEIGHBOURING REGIONS... 

For the reasons outlined above, outcrops of workable obsidian are relatively few in number and are restricted to areas of geologically recent lava flows. Most sources are therefore reasonably well known, and, because of these constraints, identification of new sources in the eastern Mediterranean region becomes ever more unlikely. This makes the exercise of characterizing archaeological obsidians an attractive proposition, since, unlike potential clay sources for pottery provenance, the existence of completely unknown sources can be (cautiously) ignored. This is, of course, subject to the requirement noted above for more detailed geochemical characterization of existing sources. 

McDougall, J.M., Tarling, D.H. and Warren, S.E. (1983). The magnetic sourcing of obsidian samples from Mediterranean and Near Eastern sources. Journal of Archaeological Science 10 441-452. 

Tykot, R.H. (1998). Mediterranean islands and multiple flows the sources and exploitation of Sardinian obsidian. In Archaeological Obsidian Studies Method and Theory., ed. Shackley, M.S., Advances in Archaeology and Museum Science Series, Plenum Press, New York, pp. 67-82. 

Gratuze, B. (1999). Obsidian characterization by laser ablation ICP-MS and its application to prehistoric trade in the Mediterranean and the Near East sources and distribution of obsidian within the Aegean and Anatolia. Journal of Archaeological Science 26 869-881. 

Until recently, there was no systematic survey, documentation, and chemical and physical analyses of western Mediterranean obsidian sources. Recently, Tykot completed an extensive survey and documentation of western Mediterranean obsidian sources on the islands of Sardinia, Palmarola, Lipari, and Pantelleria (24-27) for a more detailed discussion. Samples from these sources were analyzed at MURR by INAA and/or XRF and LA-ICP-MS. As expected, INAA (and XRF and LA-ICP-MS) of geologic samples from these sources demonstrated that obsidian from each island had a unique chemical signature(s). In the case of Sardinia, six compositional groups were identified. Because of the analytical cost and semi-destructive nature of INAA, artifacts were analyzed by LA-ICP-MS rather than INAA. XRF would have provided a viable analytical alternative, but many of the artifacts were smaller than the minimum size required for this analysis on a standard laboratory-based stationary XRF instrument... 

Figure l. Comparison ofINAA elemental ratios for the four major western Mediterranean Island obsidian sources. Only geologic source samples are... 

The sources of obsidian exploited by prehistoric peoples were almost entirely restricted to more recent volcanic eruptions due to the hydration process. Few obsidian sources are greater than 10 million years old, and many are less than 100,000 years of age. In addition to the Andes Mountains of South America, obsidian is found in the Mediterranean, Turkey, Africa, central Europe, central Mexico, western United States, Alaska, Japan, and the islands of the South Pacific. 

The identity of the sources of obsidian found at early Neolithic sites provides information on both the direction and intensity of trade (Fig. 8.11). Sites along Mediterranean coast generally obtained obsidian from Anatolia, while sites in the eastern part of the region used the Armenian material. The percentage of obsidian in the total flaked stone assemblage at these sites indicates that places closest to the sources used a great deal of obsidian, while those farthest away had only a small amount available. At Jericho, for example, 700 km (400 miles) from the Turkish sources, only about 1% of the stone tools were made from obsidian. 

In chapter 11, Tykot uses electron microprobe analysis to determine the major and minor elements in obsidian collected from sources throughout the Mediterranean region. Through statistical analysis, he is able to differentiate these sources and, thereby, is able to identify the sources of archaeological obsidian artifacts found in the region. Combining these data with contextual data, the relative frequency of particular obsidians in different sites can be used to infer that complex trade patterns existed in the Early Neolithic. 

Figure L Obsidian sources in the Central Mediterranean and archaeological sites with more than 10 analyzed obsidian artifacts.

The most complete characterizations currently available for the western Mediterranean obsidian sources have been accomplished using XRF and the... 

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