Temporally diagnostic projectile points can be used to look at changes in material type through time in the vicinity of the Chivay source using a time sensitive typology such as the projectile point typology developed by Klink and Aldenderfer (2005). Andeanists have observed that obsidian projectile points were more widely used with the advent of the small, triangular style recognized as belonging to later time periods (Burger, et al. 2000: 294). This style is referred to as the Series 5 point type and it is associated with the Terminal Archaic and onward. It is likely that the frequent use of obsidian for production of the smallest point styles, type 5D, was due to a change in technology, such as the adoption of bow and arrow technology (Klink 2005: 52). This interpretation is supported by the predictable knapping quality of obsidian and the ease with which pressure flaking can be used to produce small points that do not unbalance the arrow in flight, and because the precise pressure flaking also allows resharpening of arrow points with a minimum of loss of material.

Evaluating the entire Upper Colca Survey area, the diagnostic projectile points were found in the following material types. As described in chapter 5, the Series 5 points have not yet been analyzed as closely as the Series 1-4 points because the Series 5 points are not temporally sensitive to the same degree. Therefore Series 5 points are excluded from some tables below where these data are not yet available (as shown in Table 5-9).

Table 6-13. ArchID numbers for diagnostic projectile points, Series 1-4 only.

Table 6-14. Projectile point mean weights by point type and material type for Upper Colca project. Two quartzite points were excluded.

Table 6-14 shows the weights of all projectile points found on the surface of the project area. It shows that obsidian points were much smaller and much more common in the Series 5 types, and that the few type 5 that are not made from obsidian are relatively heavy. Two quartzite points that were excluded from Table 6-14 include a quartzite point of type 3b that weighted 7g, the other was a probable type 4g (Cipolla 2005) with an excurvate haft and a convex base, and it weighed 14g.

The changing use of a particular material type in association with projectile points is informative in any study region with diagnostic point styles. In the vicinity of an obsidian source these data also have the potential to inform about whether obsidian was used for projectile points out of preference or out of need.

For example, there is a type 3B projectile point, diagnostic to the Middle Archaic, made out of quartzite found in Block 2. This point was found only 16.3 km from the obsidian source, and it was found in a zone rich in obsidian, andesite, and chert, yet the coarsest material in the region was used for producing this point. Heavy materials such as fine-grained volcanics and quartzites known to have been used for projectile when mass rather than sharpness and penetrating power was being prioritized (Ellis 1997), and this is perhaps the explains the use of quartzite in this instance.

Table 6-15. All obsidian projectile points by survey block.

The evidence from all obsidian projectile points (survey and excavation) from the project area shows the prevalence of obsidian projectile points in Block 2. Proportionally, there are relatively few obsidian projectile points in Block 1 which suggests that obsidian was not undergoing advanced reduction in the quarry area. This pattern becomes even stronger in the Series 5 projectile points. While neither Series 1-4 nor Series 5 appear to be involved in advanced reduction in the proximity of the obsidian source, these data suggest that by Terminal Archaic, when Series 5 points were first produced, obsidian acquisition was perhaps more of a special purpose provisioning activity rather than an embedded activity.