Obsidian artifacts

Also in the Mediterranean Sea region, obsidian artifacts are frequently found at prehistoric sites in northern Italy and southern France. Most of the... 

Giauque, R. D., F. Asaro, F. H. Stross, and T. R. Hester (1993), High-precision nondestructive X-ray fluorescence method applicable to establishing the provenance of obsidian artifacts, X-Ray Spectrom. 22, 44—53. 

Miller, D. S. and G. A. Wagner (1981), Fission track ages applied to obsidian artifacts from South America, Nucl. Tracks 5, 147-155. 

Yegingil, Z. and T. Lunel (1990), Provenance studies of obsidian artifacts determined by using fission track ages and trace element analysis, Nucl. Tracks Rad. Meas. 17(3), 433. 

Negash, A., Shackley, M.S., Aleve, M. 2006. Source provenance of obsidian artifacts from Early Stone Age (ESA) site of Melka Konture, Ethiopia, Journal Archaeological Science, 33, 1647-1650. 

Bigazzi, G., Ercan, T., Oddone, M., Ozdogan, M. and Yegingil, Z. (1993). Application of fission track dating to archaeometry provenance studies of prehistoric obsidian artifacts. Nuclear Tracks and Radiation Measurements 22 757-762. 

Bigazzi, G., Meloni, S., Oddone, M., and Radi, G. (1986). Provenance studies of obsidian artifacts trace elements analysis and data reduction. Journal of Radioanalytical and Nuclear Chemistry 98 353-363. 

Traditionally, archaeological chemistry has been restricted almost en-tirely to the study of problems for which the only remaining evidence was the material to be analyzed. For example, earlier studies in our laboratory which provided results that allowed identification of the geological sources of Hopewell obsidian artifacts (I) are what could be called classical archaeological chemistry. Must we, however, restrict archaeological chemistry to periods and areas where artifacts are the chief sources of information and avoid problems of importance in more recent times simply because written records exist Clearly, the significance of the problem to be studied should be the criterion, and two of the three studies reported here indicate a close and productive interaction between... 

Shackley, S. M. Eklund, E. Ogasawara, C. Report Source Provenance of Obsidian Artifacts Jiskairumoko (189), Peru University of California Berkeley Archaeological XRF Laboratory Department of Anthropology, Berkeley, CA May 2004 p 10. 

Speakman, R. J. Popelka, R. S. Glascock, M. D. Robertson, J. D. Report. Analysis of Obsidian Artifacts from Southern Peru Using a Field-Portable X-Ray Fluorescence Spectrometer, University of Missouri Research Reactor Center Columbia, MO, 2005. 

To test the feasibility of the portable XRF and to create a robust obsidian data set from an inland trade port/trans-shipment locale, we analyzed a number of Postclassic obsidian artifacts from Trinidad de Nosotros in the central Pet6n lakes region (Figure 1). Obsidian is ubiquitous in the archaeological record, and can be easily traced to its source area because each volcanic eruption that produces volcanic glass has a unique chemical composition. In Mesoamerica, most obsidian artifacts originate from about 40 known sources of which only about ten were heavily used by the Maya (/). 

Obsidian artifacts sourced to El Chayal have been excavated from archaeological sites around the Usumacinta River basin, in northeastern Pet6n, in the Belize Valley, and the Toledo District of southern Belize (72). Hammond (75) suggests that highland Maya transported and traded obsidian to the lowland communities by inland routes through the Usumacinta and Sarstoon River basins or it could have been transported down the Rio Pasidn to Seibal and then north to Tikal (77, 7<5). 

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). 

All obsidian samples were analyzed as unmodified samples they were washed in the field. Each sample was placed in the sample chamber with the flattest part of the surface facing the x-ray beam. All samples were at least 3 cm in length with varying widths and thicknesses. The width of the sample did not produce errors when comparing obsidian artifact to potential obsidian source. Accuracy errors result from inaccuracies of the regression model, statistical error of the calibration spectra, inaccuracy of the intensity of the calibration curve and the energy calibration. When the error is taken into account, the relative analytical uncertainty for this project is less than seven percent with this portable XRF unit (26) ... 

Table I. Frequency of Postclassic Period Guatemalan and Mexican Obsidian Artifacts from Selected Archaeological Sites3...

The obsidian excavated from Trinidad de Nosotros demonstrates that obsidian trade during the Postclassic period was as complex as other periods. And, inland trade, as seen, through evidence of a trans-shipment port, was different than coastal trade. In addition to the cultural aspect of this study, we have demonstrated that it is possible to successfully use a field-portable XRF to correlate obsidian artifacts to their sources. Not only were sources identified, but the process was rapid (4-6 minutes per sample), cost-effective, and as accurate and precise as more traditional methods of analysis. Above all, and perhaps most importantly, when working with artifacts from museum collections and foreign countries, the process was non-destructive to the artifacts. 

Use of obsidian in South America has been documented from about 13,000 years B.P. through the beginning of the Spanish Conquest. Several of the most archaeologically important sources of obsidian in South America are located in the Andes. mountain region of southern Peru. Due to the difficult terrain and volatile political environment, the locations for many of these sources were unknown to archaeologists until quite recently. Neutron activation analysis and X-ray fluorescence have been used to measure the compositional patterns for individual sources. The comprehensive source database established by this work enables definitive and cost-effective assignments of provenance to obsidian artifacts from archaeological sites in Peru and northern Bolivia. 

Obsidian artifacts retain most of their physical properties from fabrication... 

Obsidian artifacts are nearly indestructible in most archaeological environments... 

Studies of obsidian artifacts and sources can be used to examine resource procurement patterns, to identify long-distance exchange networks, to study manufacturing processes, and to establish site chronologies. In addition, obsidian artifacts may be used to extract dating information through hydration dating. 

Undeniably, one of the most widely recognized roles for obsidian involves provenance research (i.e., sourcing). Provenance research connects artifacts to their sources such that interpretations about the movement of obsidian can be made with a high degree of confidence. The process of obsidian artifact sourcing relies on making comparisons of one or more characteristics of obsidian artifacts with those same characteristics for all possible sources. In order to have a successful outcome, one must demonstrate that the characteristics of the artifact and the source are the same to the exclusion of all other possible sources. Usually, the greater the number of characteristics used in the comparison, the more reliable the result. 

Most obsidian sources are chemically homogeneous, with variations in composition on the order of a few percent or less. However, the individual sources have different trace-element compositions as a reflection of the compositions of parent rocks and changes taking place in the magma chamber prior to eruption. The major elements are restricted to a relatively narrow range of composition but the abundances of trace elements can differ by orders of magnitude between obsidian sources. If the variations within sources are smaller than the differences between sources, then the provenance of obsidian artifacts can be successfully established. 

In 2006, a table-top energy-dispersive XRF (ED-XRF) spectrometer was acquired by the Archaeometry Lab to facilitate non-destructive analysis of obsidian and other types of artifacts. One of the first projects performed on the new XRF spectrometer was the re-analysis of the geological samples from sources in Peru. As a result, it is now possible for the Archaeometry Lab to use either XRF or NAA to successfully determine the provenance of obsidian artifacts from Peru. Due to its light weight, the spectrometer also has the potential to be transported from the laboratory to museums and to archaeological sites for in situ analysis. 

The chemical profile known as Quispisisa obsidian was observed in 45% of the artifacts analyzed by LBNL and in more than 90% of the artifacts from archaeological sites located in central and northern Peru (41-42). The northernmost extent of Quispisisa obsidian artifacts was in the Department of Junin. Based on incorrect information, the source of this obsidian was originally presumed to be near San Genaro in the Province of Castrovirreyna, Department of Huancavelica (50). The assumption that the Quisipisia mine was located near San Genaro was widely accepted for a number of years, before the error was discovered during the course of this work. 

Table V. Summary of provenance assignments for obsidian artifacts from analyzed by MURR and LBNL.

Burger, R. L. Asaro, F. Trace Element Analysis of Obsidian Artifacts from the Andes New Perspectives on Pre-Hispanic Economic Interaction, Lawrence Berkeley Laboratory Report 6343 Berkeley, CA 1977 pp 1-88. 

---