Obsidian sources

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). 

Barium (p.p.m). j" G iaii Samples bom obsidian sources Sardinia... 

Bowman, H. R., F. Asaro, and I. Perlman (1973), Composition variations in obsidian sources and the archaeological implications, Archaeometry 15, 123-132. 

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

Glascock, M. D., G. E. Braswell, and R. H. Cobean (1998), A systematic approach to obsidian source characterization, in Shackley, M. S. (ed.), Archaeological Obsidian Studies Method and Theory, Plenum, New York, pp. 15-65. 

Williams-Thorpe, O., S. E. Warren, and J. G. Nandis (1997), Characterization of obsidian sources and artefacts from central and eastern Europe, using instrumental neutron activation analysis, in Korek, J. (ed.), Proc. Int. Conf. Lithic Raw Material Characterization, Budapest and Siimeg, 1996, Budapest. 

KEYWORDS Laser-induced breakdown spectroscopy, LIBS, multivariate spectral analysis, obsidian sourcing, geochemical fingerprinting... 

Geochemical studies by Hughes (1988), Ericson Glascock (2004), and Drucker (2007) employing multivariate statistical analysis have delineated major obsidian sub-sources within the CVF. This study was undertaken to ascertain the extent which LIBS could be applied to the problem of obsidian sourcing through analysis of the same suite of samples that was analyzed by Draucker (2007). 

Erickson, J.E. 1981. Exchange and production systems in Californian prehistory The results of hydration dating and chemical characterization of obsidian sources. British Archaeological Reports International Series, 110, 1-240. 

FIughes, R.E. 1988. The Coso Volcanic Field Reexamined Implications for obsidian sourcing and hydration dating research. Geoarchaeology, 3, 253-265. 

Durrani, S.A., Khan, H.A., Taj, M. and Renfrew, C. (1971). Obsidian source identification by fission track analysis. Nature 233 242-245. 

Tykot, R.H. (1997). Characterization of the Monte Arci (Sardinia) obsidian sources. Journal of Archaeological Science 24 467-479. 

Darling, J. A. and Hayashida, F. M. (1995). Compositional analysis of the Huitzila and La Lobera obsidian sources in the southern Sierra-Madre Occidental, Mexico. Journal of Radioanalytical and Nuclear Chemistry 196 245-254. 

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... 

Discriminating Obsidian Sources When Compositional Variation is Minimal Sycan Marsh and Silver Lake, Oregon... 

XRF analyses of Silver Lake and Sycan Marsh obsidian source samples suggested the possibility that the two sources could be differentiated based on small differences in strontium concentrations. However, when the standard error for strontium was taken into account, both groups overlapped at one standard deviation. Because of higher instrumental detection limits for strontium, NAA could not discriminate between the two sources. LA-ICP-MS analyses were conducted to determine if the sensitivity and precision of this analytical technique was sufficient to confirm the existence of the two compositional... 

Figure 4. Comparison ofLA-ICP-MS and XRF data for Sycan Marsh and Silver Lake obsidian source samples.

Feasibility of Field-Portable XRF to Identify Obsidian Sources in Central Peten, Guatemala... 

One of the many classes of artifacts that may have been traded through Trinidad de Nosotros was obsidian. Because there are no obsidian sources in the Maya lowlands, the material had to be transported from Mexico and highland Guatemala. The three main Guatemalan obsidian sources utilized by the lowland Maya were San Martin Jilotepeque, El Chayal, and Ixtepeque (/, 2, 7, 8) (Figure 3). In addition, obsidian from several sources in the Mexican highlands was also imported into the Maya lowlands (7). 

Figure 3. Regional map showing locations of Guatemalan (l=San Martin Jilotepeque 2=El Chayal 3=Ixtepeque) and Mexican (4=Pachuca 5=Zaragoza) obsidian sources used in the study.

San Martin Jilotepeque obsidian is more commonly excavated from archaeological sites in central Maya lowlands than from sites in Belize and northern Yucatan as well as coastal sites such as Wilde Cane Cay and Moho Cay. This presence suggests overland and riverine routes for trade of obsidian from this source (77). During the Late Classic period and with the increasing dominance of Kaminaljuyu in the Guatemala highlands (and the El Chayal obsidian source), San Martin Jilotepeque was traded west to the Pacific coast, north to the Chiapas, and the central Maya lowlands (72). 

The Ixtepeque obsidian source is located 85 km from the El Chayal source zone (ca. 300 km from Trinidad de Nosotros, as the crow flies). It is found at archaeological sites east and north of the source, along the coast of Belize, northeastern Pet6n, the Belize Valley, and northern Yucatan (7, 14). Obsidian artifacts dating to the Late Preclassic, Terminal Classic and Postclassic periods are predominately from this source and it was the main source during the Postclassic period (77, 75, 17). 

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