In his introductory chapter to an edited volume on quarries and lithic production, Ericson (1984: 4) proposed a number of indices for the study of lithic production systems. These indices are relatively general and therefore of limited use in this study, but they are included here because they provide comparable indices between quarry areas on an inter-regional scale. The indices were calculated for artifacts collected in the course of survey in 2003, and the indices were also derived for every level of the five test excavation units that will be discussed in Ch. 7. In these indices "Flakes" (a.k.a. debitage) are taken to be unretouched, flaked obsidian, while "Tools" includes retouched flakes, bifacially-flaked items such as projectile points.
Debitage Indexis calculated from the (Flakes) / (Flakes + Tools) using count, weight, or size ratio. This calculation is of limited value because obsidian "Debitage", or simple flakes, are widely used as cutting tools, and therefore as a measure of production "by-products" an index that considers simple obsidian flakes as "waste" is questionable because these so-called waste flakes are potentially razor sharp tools.
Cortex Index(Flakes ?20 % cortex)/(All Flakes) is indicative of the importation of raw material on site. Cortical flakes were defined here as those flakes having greater than or equal to 20% cortex.
Core Index("Spent Cores" with ?3 rotations)/(All Cores and Tools) to evaluate the degree to which cores are transported or are a medium of exchange. Here, spent cores are defined as those with greater than or equal to three rotations.
Biface Index(All Flakes with BTF ?7) / (All Flakes) for measuring biface production. BTF are defined here as those with a BTF Index of greater than or equal to 7.
|
Survey Block |
No. Flakes |
Debitage Index |
Cortex Index |
BTF Index |
Core Index |
|
1 |
158 |
0.635 |
0.627 |
0.133 |
0.160 |
|
2 |
71 |
0.203 |
0.394 |
0.183 |
0.049 |
|
3 |
65 |
0.492 |
0.246 |
0.123 |
0.134 |
|
4 |
51 |
0.381 |
0.765 |
0.020 |
0.188 |
|
5 |
151 |
0.699 |
0.596 |
0.026 |
0.077 |
|
Total |
496 |
0.450 |
0.548 |
0.095 |
0.110 |
Table 6-12. Obsidian production system indices for surface survey.
Using only obsidian artifacts from surface collections, these indices show changing strategies in obsidian use with increased distance from the source. The Blocks 4 and 5 areas were inconsistently surveyed and sampled, and therefore the comparability of indices from those two blocks is limited. The Debitage Index shows that many more flakes than tools were collected in Blocks 1 and 5. Curiously, Block 4 is relatively low in the Debitage index (reflecting sampling bias), and Block 3 relatively high perhaps because Taukamayo has a relatively high number of flakes (but consisting of Ob2 obsidian) for the consumption zone. The Cortex Index in Blocks 1, 4, and 5 show that primary reduction was occurring with greater frequency near the Chivay source than it was in the residential blocks of 2 and 3. The BTF index shows that biface production was occurring at the highest rate in Block 2 (18.3%), but biface production was also occurring in Block 1 and 3 as well. The Core Index shows that cores were being reduced more frequently in Block 1 and 4, and remarkably low Core Index values resulted for Block 2 and 5. The low value in Block 5 for this variable probably reflects the lack of large residential occupations in that block.