Early Copán Acropolis Program 2000 Field Season

Analysis of Obsidian

A total of 2,456 pieces of obsidian have been recovered and catalogued from the ECAP excavations. A sample of 191 pieces were removed prior to 1996 for hydration dating and sourcing by the abbreviated-NAA method. Of the remaining assemblage, 1,705 pieces, or 70% of all catalogued obsidian, were analyzed by William McFarlane working in the CRIA during the summer of 2000 and supported by FAMSI Grant 99102.  There were three goals to this analysis. First, obsidian from different sources was identified to determine the nature of exchange networks and how these networks change through time. For each piece, source was determined through visual analysis (Aoyama, 1996; Braswell, Andrews, and Glascock, 1994). As there is considerable variability and overlap of diagnostic characteristics between obsidian from the El Chayal source area and the Ixtepeque source area, 19 pieces that could not be conclusively sourced by visual analysis were selected for abbreviated-NAA at the University of Missouri Research Reactor. Second, the assemblage was characterized by ancient production methods. By utilizing a behavioral (Sheets, 1975) or technological (Clark, 1988; Clark and Bryant, 1997) typology, the finished products as well as the debitage generated by the production of these tools can be considered. Further, the stage of production can be identified allowing for interpretation of the organization of production and distribution. Third, using a technological typology, direct evidence of prismatic blade production was sought. While it is thought that prismatic blade production began during the Early Classic at Copán (Aoyama, 1996:190), no direct evidence for this, such as a workshop midden, has been recovered. The nature of the ECAP assemblage does not lend itself to this form of analysis, as all sampled Sub-operations contain evidence for blade production. However, it is possible to identify prismatic blade production debitage in chronologically controlled fill contexts, thus refining an inferred starting date for blade production in the Copán Acropolis area.

Further statistical interpretation is necessary to fully realize the goals of this analysis. However, gross totals of the analyzed assemblage can be presented at this time. Four obsidian sources were identified in the sample: Ixtepeque, Chayal, San Martín Jilotepeque, and Pachuca (see Table 2). The later is from Central México and is the only non-Guatemalan source in the assemblage. Pachuca obsidian only occurs as finished blades within non-tomb contexts. Obsidian from the Pachuca source area is limited to four tunnel sub-operations (1-6, 1-7, 1-20, and 1-28).

Four broad technological categories can be used to describe the assemblage (see Table 3). As is common with Classic Period assemblages in Mesoamerica, the majority is comprised of prismatic blades and production debris. Expedient core/flake technologies, a non-specialized industry, is the second most common and bipolar percussion and bifacially thinned points make up the remainder of identifiable technologies.

Obsidian from ECAP tomb contexts were also analyzed. The Hunal tomb contains an assemblage of 24 pieces. Of these pieces, 2 have been set aside for future residue analysis. The remaining 22 pieces of the assemblage are specialized tools exhibiting use-wear suggesting all were used in the same task. However, while each of these tools are morphologically similar, 4 were produced by expedient percussion. The majority (18 of the 22) are retouched prismatic blades. Compared to the 22 formal tools, the remaining two pieces were found in a different area of the tomb, do not exhibit use-wear, and are of a completely different morphology. Further, Obs-23 is made from El Chayal obsidian and Obs-24 is of Pachuca while all other pieces are of Ixtepeque. Obs-23 is a simple expedient percussion flake. Obs-24 is a small percussion blade. It should be noted that, as a rule, Pachuca obsidian is limited to finished prismatic blades or bifacially worked points within the Copán Valley (Aoyama, 1996). Obs-24 is the exception to this rule.

The Ani Structure termination cache (Offering 90-1) contained two well-formed cores of Ixtepeque obsidian. These large cores each weigh 1.5 Kg and are in the form of a half sphere. The cores are remarkably similar in form, but do not refit to complete one large sphere. While there is evidence of retouch and lip-removal scars along the platform, whether these cores were used as formal tools or especially prepared as offerings remains unclear.

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