Chapter 6 began with general production indices for obsidian distributions throughout the survey blocks. Here the same indices are presented by excavation level for obsidian artifacts assemblages. These indices were described by Ericson (1984: 4) and while these measures are extremely general, the indices provide a basis for comparability between quarry studies in different regions of the world.
Briefly, the measures are calculated as follows, using counts.
Debitage Index:(Flakes) / (Flakes + Tools)
Cortex Index:(Flakes ≥20 % cortex) / (All Flakes)
Core Index:("Spent Cores" with ≥3 rotations) / (All Cores and Tools)
Biface Index:(All Flakes with BTF ≥7) / (All Flakes)
Section 6.2.2 provides a more detailed explanation and discussion of these production measures, and the Bifacial Thinning Flake Index is developed in Section 5.9.3. The production indices for excavated units are as follows.
|
Level |
No. Flakes |
Debitage Index |
Cortex Index |
|
1 |
6 |
1 |
0.667 |
|
2 |
16 |
1 |
0.438 |
|
3 |
8 |
1 |
0.5 |
|
4 |
11 |
0.917 |
0.545 |
|
5 |
12 |
0.923 |
0.334 |
|
6 |
1 |
1 |
0 |
|
7 |
2 |
1 |
0 |
|
8 |
6 |
1 |
0.334 |
|
10 |
7 |
0.875 |
0.571 |
|
11 |
10 |
1 |
0.4 |
|
Total |
79 |
0.963 |
0.443 |
Table 7-2. Q02u2 "Quarry Pit" obsidian production system indices.
Note that there was a low total number of flakes from the quarry test unit (n = 79). No Core Indexwas calculated because only three cores, and no spent cores (≥ 3 rotations) were encountered in the Quarry pit test unit. The indices from this test unit are characteristic of very early stage reduction. There is a very high Debitage Index because there were virtually no "Tools". There was only a moderately high Cortex index, perhaps because relatively little reduction occurred at this location as it appears that nodules were knapped elsewhere.
|
Level |
No. Flakes |
Debitage Index |
Cortex Index |
BTF Index |
Core Index |
|
1 |
151 |
0.944 |
0.470 |
0.007 |
0.129 |
|
2 |
151 |
0.938 |
0.675 |
0.026 |
0.127 |
|
3 |
279 |
0.952 |
0.631 |
0.014 |
0.025 |
|
4 |
204 |
0.919 |
0.794 |
0.015 |
0.130 |
|
5 |
187 |
0.940 |
0.818 |
0.016 |
0.052 |
|
6 |
55 |
0.873 |
0.564 |
0.036 |
0.286 |
|
7 |
50 |
0.943 |
0.440 |
0.000 |
0.368 |
|
Total |
1077 |
0.936 |
0.666 |
0.016 |
0.110 |
Table 7-3. Q02u3 "Maymeja Workshop" obsidian production system indices.
At the Maymeja workshop an extremely high Debitage index shows that blank production was probably the dominant pattern, as few identifiable tools were encountered in the test unit. The cortex index is higher than any other excavated context in this study, but it is still relatively moderate, perhaps because by Count the medium-stage flakes prevail. Very low BTF indices support the assertion that little advanced reduction was occurring here. Finally, the Core index values appear to be low, but these values are actually the highest in the study area. The Core Index calculation is complicated by the fact that cores and blanks were probably the principal items exported from the quarry workshop area.
|
Level |
No. Flakes |
Debitage Index |
Cortex Index |
BTF Index |
Core Index |
|
2 |
5 |
1 |
0 |
0 |
0 |
|
3 |
6 |
1 |
0 |
0 |
0 |
|
4 |
16 |
0.941 |
0.063 |
0.063 |
0 |
|
5 |
44 |
0.880 |
0.045 |
0.023 |
0.167 |
|
6 |
50 |
0.943 |
0.040 |
0.040 |
0 |
|
7 |
69 |
0.920 |
0.029 |
0.043 |
0 |
|
8 |
31 |
0.861 |
0.065 |
0.032 |
0.167 |
|
9 |
9 |
1 |
0 |
0 |
0 |
|
10 |
7 |
0.875 |
0 |
0 |
0 |
|
11 |
9 |
1 |
0.111 |
0 |
1 |
|
12 |
5 |
1 |
0 |
0 |
0 |
|
13 |
5 |
1 |
0 |
0 |
0 |
|
14 |
1 |
1 |
0 |
0 |
0 |
|
15 |
1 |
1 |
0 |
0 |
0 |
|
Total |
258 |
0.921 |
0.039 |
0.031 |
0.120 |
Table 7-4. A02-26u1 "Taukamayo" obsidian production system indices.
At Taukamayo in Block 3 a high percentage of Ob2 obsidian was in use (Table 7-4). The debitage index is relatively high, but Cortex is quite low as this site lies relatively far from the source. Very few bifacial thinning flakes (BTF) are present except in the levels 4 through 7 which date to the early part of the Middle Horizon. At Taukamayo these test units were placed in a residential portion of a raised corral area with a hearth in levels 5-7 that dated to the Late Formative. The debitage index but low cortex index shows that there were a great number of tiny flakes of advanced reduction level here. The BTF index numbers are relatively high for excavated contexts.
|
Level |
No. Flakes |
Debitage Index |
Cortex Index |
BTF Index |
|
1 |
76 |
0.894 |
0.039 |
0.053 |
|
2 |
53 |
0.946 |
0.094 |
0.019 |
|
3 |
55 |
0.887 |
0.036 |
0.018 |
|
4 |
51 |
0.927 |
0.039 |
0.039 |
|
5 |
110 |
0.932 |
0.045 |
0.036 |
|
6 |
45 |
0.865 |
0 |
0 |
|
7 |
11 |
0.917 |
0 |
0 |
|
8 |
2 |
1 |
0 |
0 |
|
Total |
403 |
0.912 |
0.042 |
0.030 |
Table 7-5. A02-39 u3 and u4 "Pausa" obsidian production system indices.
At Pausa, in Block 2, these numbers (Table 7-5) compare on a relative basis with the surface indices by survey block, shown above, because Block 2 has the highest BTF index in the survey. The high numbers of projectile points collected in the Block 2 region attest to the advanced obsidian reduction occurring in that zone. No Core index was calculated because no cores were fond in this test unit. It appears that obsidian cores were not discarded in this area; it is likely that they were used or exported.