Ethnohistoric and ethnographic accounts attest to the prominence of the Colca in regional trade networks both in terms of the size and capability of pastoralists in the upper Colca area to launch long-distance caravans, and for the draw created by the Colca valley agricultural sector on regional caravans. While archaeological evidence of passing camelid caravans is often subtle, in the course of survey work in 2003 a number of features were encountered that are potentially linked to caravan mobility.
The most extensive pastoral features in the Upper Colca survey area lie in the dense Block 2 occupation along the eastern toe of the Huarancante lava flow. The area has been occupied fairly consistently since the Early Archaic and a distinctive land use pattern was documented in 2003 related to pastoral occupations, including corrals and associated residential structures, along the margins of the lava flow. As is characteristic of pastoral occupations, the structure of these sites is blurred by multiple non-contemporaneous occupations, refuse disposal is shallow, and stone corral walls and rock shelters serve as the few permanent feature types that persist through time from previous pastoral occupations (Nielsen 2000: 480-483). The Block 2 survey revealed that many of the larger estancias contain multicomponent sites, indeed most of these choice locations are occupied to this day in some capacity. However, the small and mid-sized pastoral bases in the area show more variability, as ceramic distributions suggest that some sectors were settled while others were abandoned at times in prehistory. The number of active corrals and the herd size potential in a given time period is difficult to estimate due to this pattern of shifting locations for small and mid-sized pastoral bases.
Based on systematic survey work in 2003 it appears that a number of the animal control features in Block 2 exceed the local capacity for seasonal grazing and were perhaps linked to short-term stays by passing caravans. These large animal control structures primarily take the form of vestiges of corrals that appear as bases of stone enclosures on top of low mounds rising from surrounding pampa. While it is difficult to estimate animal numbers due to shifting pastoral occupation, seasonal changes in land use, and the brevity of the 2003 observational period, the conditions in Block 2 appear to be the "Caravan rest areas" that were first discussed in Section 3.2.5.
Larger sites that are the result of repeated occupation as rest areas are well documented in ethnoarchaeological accounts of camelid caravans (Lecoq 1988: 185-186;Nielsen 2000: 461-462, 500-504;West 1981: 70). According to these accounts, in the course of a multi-week caravan journey the team will rest periodically, usually for two or three nights, in order to allow for recovery by the animals and for conducting routine maintenance tasks by the caravan drivers such as repairing cargo panniers and stitching up the shoes made for the llamas' feet. Typically, these rest areas are situated adjacent to a rich grazing area with plentiful water and little competition for pasture access. The rest stops commonly are located immediately before or after a strenuous section of trail.
The Block 2 area is something of a natural bottleneck at the transition zone between the Colca valley and the puna, and it also contains the largest bofedal in the study area. The Block 2 puna is situated just outside of the rugged volcanic terrain that rings the Colca valley. It is the first extensive area of prime grazing encountered after caravans have crested the ascent out of the Colca, and the ascending animals would have presumably been loaded with agricultural cargo. It is therefore unsurprising that large corral facilities were encountered in this location.
The lithic and ceramic artifacts associated with these abandoned corral features are also telling. While local LIP and LH sherds are common in Block 2, the unslipped Chiquero-style pottery of Formative production, are also widespread in Block 2. Obsidian flakes are extremely common in the vicinity of these mounds. As demonstrated in the testing work at A03-39, small hearths and obsidian knapping at medium and advanced reduction stages occurred on the margins of these corral structures.
One plausible scenario for the quantity of obsidian in the Block 2 area would have caravan drivers resting for several days after the arduous climb from the Colca valley and knapping obsidian in the Block 2 area while their herds recover from the climb. Perhaps caravans would periodically venture into the Maymeja area of the Chivay source and recover larger nodules. Local herders also use the Block 2 puna and perhaps they were involved in obsidian procurement. Local herders, arguably more familiar with the obsidian source itself, could have brought obsidian to this area and passing caravans resting in the area may have traded for nodules and this would have contributed more obsidian to the Block 2 area.
The evidence from Block 2, however, is overwhelmingly of advanced stage obsidian reduction, and therefore if whole nodules were being exported from the Chivay source in whole form then they were not being knapped at Block 2. This evidence suggests that nodules were being reduced at the Maymeja workshop over in Block 1, or being exported from the region in whole form. Primary reduction and the use of large obsidian artifacts was not occurring in Block 2. As mentioned above, 10% of the flakes in Block 2 were over 4cm in length and neither cortical, nor non-cortical, flakes approach this size potential in Block 2. The absence of large flakes in this area, a zone rich in small obsidian flakes, is curious and it suggests that non-local caravans were responsible for the quarrying activity in Block 1. The larger (15-20 cm long), Ob1 nodules would have had to have been quarried, and some fraction of them knapped, in the Maymeja zone and then transported from the region without further processing in areas such as Block 2.
A principal question concerning the Chivay obsidian source area, when it was finally located in the 1990s, was whether cultural materials showing Titicaca Basin stylistic affiliation would be found at the source area. The lack of known Pukara or Tiwanaku materials in the vicinity of the source, as confirmed by the Upper Colca research project, suggests that access to the source was not physically restricted, and that perhaps neighboring groups were granted access as needed. Other plausible explanations are that, even in the Middle Horizon, material moved through down-the-line trade and no diagnostic, non-perishable materials were reciprocated back to the source area. Alternately, a freelance trading entity was responsible for transporting the material towards Titicaca, but this group traded exclusively with Titicaca Basin polities and curiously none of the material found its way into the Wari sphere despite the proximity of Wari-influenced sites in the lower valley. Given Tiwanaku's demonstrated strategy of placing colonies, sometimes integrated multiethnic, directly adjacent to resources of interest (Goldstein 1989), it seemed possible that a site with a Tiwanaku component would be found adjacent to the Chivay source.
The obsidian data do not appear to conform to the expected pattern of postulated multiethnic "artisan islands" within the vertical archipelago model proposed by John Murra (1972, pp. 442-443) in which rare or restricted resources such as metal ores, or here different obsidian types, are shared by different groups; in this case, each group (Huari and Tiahuanaco) would have had colonies to acquire the resource for the distant homeland (Burger, et al. 2000: 342).
A central goal of the 2003 research at the Chivay source was to examine the source area for evidence of such "artisan island" sites, but no such sites were encountered.
The circuit mobility model of Nuñez and Dillehay (Dillehay and Nuñez 1988;1995 [1979]) depicts the regional integration between "axis settlements" as articulated by circuits of caravan traffic (Section 3.2.6). Some of these circuits grew to become the dominant exchange routes in a region. Despite the historical and adaptational focus of the circuit mobility model, the model's emphasis on the integrating role of camelid caravan networks linking dispersed communities in the altiplano highlights the importance of regional context in the emergence of political power in the transegalitarian milieu of the Titicaca Basin Formative.
The dynamic and decentralized Nunez and Dillehay model is compelling for understanding regional obsidian distributions in two ways. First, this model emphasizes the regular interaction that linked dispersed communities, often second-tier communities, across broad spaces. Obsidian appears to have had some social and symbolic significance, but it was only moderately rare and therefore it appears to have circulated relatively widely and continually between regional centers and also within second-tier and smaller communities. Thus the significance of obsidian is not principally as a "wealth item" like precious metals that served to differentiate elites in a type of network strategy (Blanton, et al. 1996). Rather, obsidian circulation, and the parties responsible for procuring and circulating it, depicts the subsistence level economic and cultural links upon which early aggrandizers likely constructed their political strategy.
During earlier time periods, such as during the Terminal Archaic when obsidian was first being intensified, it could be argued that obsidian was a rare "prestige technology" (Hayden 1998) that would confer advantages on the owner and would otherwise serve to differentiate people. Helms (1992: 159) describes how those conveying exotic materials were "long-distance travelers or contact agents as politico-religious specialists" in contact with the mysterious and distant (see discussion in Section 2.2.5). Such associations would arguably have been more likely during the earlier, emergent stages of regular caravan networks (e.g., the Terminal Archaic) under the assumption that sustained contact and diminished scarcity of a non-local material like obsidian would have probably reduced the social or symbolic power of such goods. Nevertheless, obsidian appears to have retained symbolically exotic associations that persisted in some form given the Late Prehispanic contexts: concentrations of obsidian in ritual mounds at Tiwanaku, and unmodified Chivay nodules at the gates of Machu Picchu (Section 3.5.3). However, given its abundance in the Early and Middle Formative sites, and the occurrence of obsidian in both commoner and elite contexts in the Late Formative, it would be difficult to argue that obsidian was status-conferring due simply to its non-local origin in that time period.