While the test unit did not expose diagnostic artifacts or datable material, such as carbon, that would have facilitated identifying the culture group associated with the quarrying, it revealed changes in stratigraphy and material that contribute to understanding the prehistory of the Chivay source. Provisional estimates, based on comparisons with dates from the adjacent workshop test unit Q02-2u3, suggest that the bulk of quarrying at Q02-2u2 occurred in the Early Formative. It should be stressed here that because the test excavation is into a debris pile in Q02-2u2, levels are invertedso higher levels in the test unit came from lower in the Q02-2 quarry pit.

Figure 7-9. Q02-2u2 quarry pit south and west profile diagrams showing excavation levels.

Figure 7-10. South profile of Q02-2u2 at quarry pit at the top of levels 11/12.

The test unit Q02-2u2 stratigraphy indicates that episodic filling events occurred in this location. In the profile figure, excavation levels are represented approximately as indicated by strata lines. The profile photo (Figure 7-10) shows the south profile wall, therefore the quarry pit is located off of the left side of the photo frame. As expected, the stratigraphy generally slopes downwards towards the right. However, in level 2 and to a lesser extent in level 3 the stratigraphy levels out and even rises slightly, indicating there was major deposition on the quarry debris pile. These profiles suggest that the quarrying took place in two major episodes with what appears to have been some minor quarrying activity before and after each larger episode. The soil characteristics and artifact evidence provides more insights in to the circumstances surrounding the quarrying.

Table 7-7. Q02-2u2 Excavation levels from test unit at quarry pit. Excavation photos available online.

Table 7-8. Q02-2u2 lithic technical class by test unit excavation level.

The vast majority of obsidian fragments at Q02-2 were non-cultural in origin. The artifact data show that culturally derived flakes were found as low as level 11, and cores and retouched items were found in level 10. These data suggest that the quarry pit area was being exploited for obsidian production with in-situ production before it was being excavated on the scale of the later pit. The distributed nature of the cores, flakes, and retouched artifacts in a stratigraphic profile that is predominantly made up of excavation debris, points to a general focus on procuring whole nodules from this location.

Table 7-9. Q02-2u2 quarry pit obsidian artifact material type and color by level.

A principal question concerning the ancient excavation of the quarry pit is: why excavate for obsidian when it is available on the surface? What desirable characteristics of subsurface obsidian justify the effort expended in digging this quarry pit? Here, the consistency and visual qualities of the obsidian artifacts excavated from Q02-2u2 are examined in order to determine if there were patterns in those characteristics of the material. As shown in Table 7-9, Ob2 obsidian accounted for 7.2% of the artifacts analyzed from the test unit at Q02-2u2, which is comparable to the ratio of projectile point use in the project overall where just 7.8% of the obsidian projectile points observed in the course of 2003 fieldwork were produced on Ob2 obsidian.

Table 7-10. Q02-2u2 Color in quarry pit artifacts compared with all obsidian projectile points from fieldwork.

These data indicate that obsidian from the quarry pit had variability in color of material that was comparable to obsidian use over the entire region. In other words, quarrying individuals at the Q02-2 quarry in the past could expect a relatively low percentage of Ob2 material and color distributions that are consistent with the percentages used for tool production. However, as obsidian was acquired from a number of surface sources, the material quality and color of obsidian from the Q02-2 quarry pit does not appear to have been a principal motivation for excavating in that location. It appears that the quarry pit was relatively typical of the tool characteristics in the region.

However, a difference in cortical flake size from the quarry pit was noted.

Table 7-11. Q02-2u2 quarry pit: Lengths of flakes and cores with >20% cortex.

Because production appears to have been largely conducted elsewhere, the counts for cortical flakes are relatively low. The pattern here suggests that larger nodules were available in deeper in the quarry. Again, levels are invertedin the test unit because the excavation is into a secondary debris pile (Figure 7-7), so higher levels in the 1x1m test unit came from lower levels in the original Q02-2 quarry. It appears that there was an abundance of large nodules and limited flaking was occurring later in the use of the quarry, and therefore larger flakes were being discarded. In a later discussion below, these data are compared with data presented in Table 7-26, from test unit Q02-2u3 at the A03-126 quarry workshop, in order to explore the connection between the quarry pit and the workshop.

A natural slope has been estimated from the surface map created using a total station in 2004 (Figure 7-7). Subtracting the surface map elevation from the calculated natural slope elevation at the location of the Q02-2u2 test unit allows for an estimate of depth at which one would encounter the sterile natural slope in the excavation unit.

Table 7-12. Calculated depth of strata in Q02-2u2.

This independent calculation is confirmed by the Q02-2u2 excavation because sterile soil was encountered at approximately 85 cm depth. Based on the thin strata in the test unit profile, it appears that quarrying in this location was initially low-intensity, but that two episodes of large scale quarrying appear to have occurred in level 3, and especially level 2, of the strata profile which correspond to later episodesin the history of the quarry pit.