While obsidian spatial distributions are well demonstrated, it is more difficult to ascertain the temporalpatternsbecause many of the obsidian artifacts from the south-central Andes that have been sourced are from an uncertain temporal provenience. The Andean obsidian sourcing literature, organized and published primarily by Richard Burger, has provided a temporal context for obsidian samples wherever possible. Temporal control for obsidian artifacts fall into three categories

(1) excavated contexts with a temporal association.

(2) surface materials spatially associated with temporally diagnostic artifacts.

(3) direct chemical sourcing of temporally-sensitive diagnostic projectile points.

Good temporal control from excavated contexts is preferred, but a number of the samples are from the number 2group, above, because the samples have weak temporal control and are from sites that are assumed to be single component based solely on diagnostic artifacts. Finally, a fourth method, obsidian hydration dating, has been used in the Andes but with mixed results. The high diurnal and seasonal temperature variation in the Andean highlands suggests that hydration dating can only be reliably used as a relative dating method in conjunction with¹⁴C dates (Ridings 1996).

Chronologies based on stages on the one hand, and periods or horizons on the other, are used in Andean archaeology. Some pan-Andean research, such as studies of regional obsidian exchange, have used the horizons absolute chronology developed by John H. Rowe (1967) in collaboration with Dorothy Menzel and based on the Ica ceramic "master sequence". This approach allows for a maximum of compatibility between regional datasets and it has been used widely, and even extended into the Titicaca Basin (Burger, et al. 2000). However, archaeological research conducted in the Lake Titicaca Basin has largely followed a chronology based on evolutionary stages that differs from the horizon chronology primarily during the Formative Period and the Tiwanaku Period (Hastorf 1999;Kolata 2003;Stanish 2003: 85-90). As the bulk of Chivay type obsidian artifacts are found in the Lake Titicaca Basin, this dissertation will review Andean obsidian distributions using a Titicaca Basin chronology, and it will follow the Formative Period temporal divisions used by Stanish (2003). These regional data will be presented in terms of three major temporal periods in order to be consistent with the framework adopted with the new data reported for this dissertation.

Table 3-9. Temporal organization of data.

These three major temporal divisions serve to differentiate the major forces that appear to have structured obsidian procurement and distribution. Rather than focusing on the "preceramic" and "ceramic" dichotomy, which is only peripherally related to obsidian use, a decision was made to present data in terms of these three major divisions. Furthermore, socio-political changes that accompanied obsidian circulation in the Terminal Archaic are better considered in conjunction with the later developments in the Formative than together with the earlier periods of the Archaic.

The use of the term "Archaic Foragers" is not meant to suggest that no pastoralism occurred prior to 3300 BCE Many scholars place the initial domestication sometime between the Middle and the Late Archaic in the chronological terms used here (Browman 1989;Kadwell, et al. 2001;Wheeler 1983;Wing 1986). However, initial domestication and adoption of a dedicated pastoralist economy are distinct events, and the evidence from a number of sites in the south-central Andean highlands suggests that the process of shifting to a food producing economy in the Andean highlands featuring camelid pastoralism and agriculture based largely on seed-plant and tuber cultivation was complete by circa 3300 BCE in the Upper Colca region. Likewise, these divisions between "forager" and "pastoralist" are not meant to suggest that foraging activities ceased in the Terminal Archaic, merely that foraging diminished in importance in terms of caloric intake and food security.

The Early, Middle, and Late Archaic Periods have the additional benefit of being differentiated by relatively consistent changes in projectile point morphology through prehistory. A projectile point typology has recently been developed by Klink and Aldenderfer (2005) that synthesizes data from previously developed point typologies with new evidence from stratified Archaic and Formative excavations in the region. This typology has proven to be extremely useful for investigating surface distributions of projectile points, and it will was used throughout this dissertation both for assessing the age of obsidian points on a regional scale, and for assigning temporal categories to surface sites identified in the course of our 2003 survey work.

Figure 3-10. Projectile Point Typology with Titicaca Basin chronology (Klink and Aldenderfer 2005)

The temporal groups shown in Figure 3-10 visibly depict the changes in temporal control provided by projectile point evidence between the "Archaic Foragers" and the "Early Agropastoralists". With the advent of series 5 projectile point styles in the Early Agropastoralists time, the forms of projectile points became a far less effective means of differentiating time periods because projectiles do not change with as much regularity. Series 5 projectile points, except for type 5a, are diagnostic only to the time after the domestication of camelids and the dominance of food producing, pastoral economy. The following review will examine only a few of the most significant aspects of these distributions by time period, with a focus on insights from obsidian exchange on the preceramic and Early Agropastoralist stages of Andean prehistory.