Obsidian Assemblages from Test Pit Excavations

In total, 725 obsidian artifacts were analyzed from excavated contexts at eight sites. Materials from six more sites where test pit excavations were conducted still need to be analyzed. The array of materials from test pits analyzed to date, though, represents varied locations and settlement types throughout the survey region. Somewhat consistent with the survey material, the mean weight of artifacts (Table) is greater at some of the sites that are closer to the Aliso-Pumayacu obsidian source, like Bermejo and Oritoyacu, and lesser at sites further away, like Sardinas Chico and Vega. Borja, however, in the northeast arm of the survey area, does not fit this pattern. This may be due to its proximity to the confluence of the Quijos and Cosanga Rivers, which could have resulted in the availability of larger cobbles there. It could also indicate that access to obsidian was not solely dictated by availability in the immediate locality. The cases of La Palma, Pituro and Santa Lucía del Bermejo do not fit the pattern either. Thus again, availability alone may not have dictated obsidian use. Alternatively, it is possible that the pattern detectable from these excavated materials is less straightforward than that evident through survey materials due to the narrower spectrum of collections from test pits at each site, compared to the wider and full coverage spectrum of survey collections.

The obsidian from three of the above sites was re-analyzed in 2007 to determine artifact types. This analysis revealed that expedient flake and bipolar informal artifacts comprised the chipped stone assemblage at these sites. The proportion of expedient flake artifacts (Table) from Oritoyacu and Bermejo is very similar, while Vega yielded a relatively high proportion of bipolar artifacts. In total, 25% of Vega artifacts were produced by bipolar reduction, likely reflecting its location farthest from the Aliso-Pumayacu obsidian source. As noted above, mean artifact measurements indicate that artifacts from Vega were, on average, smaller than artifacts recovered from Oritoyacu and Bermejo; which corresponds to the correlation between distance from source and artifacts size identified in the survey assemblage.

Based on excavation stratigraphy, no changes in artifact or material type over time were observed at any of the three sites re-analyzed. Expedient flake production, primarily of clear obsidian (Table), dominated the assemblages through time. The predominance of clear obsidian at Bermejo was surprising considering its location in the southern subregion of the survey area. However, shatter also comprised a large proportion of this site’s assemblage and may reflect access to a particularly poor quality of black obsidian, which may have encouraged the use of the rarer, but higher quality clear obsidian. Overall, the intra-site patterns of obsidian use paralleled those observed throughout the survey area. Expedient flake artifacts were the most common artifact found at all sites. Flakes and bipolar reduction were the most common clear obsidian artifacts, while flakes, bipolar reduction, and shatter were most common of the black artifacts.

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