During the Late Formative, significant social ranking developed and dominated the socio-political landscape in the Lake Titicaca Basin. The complex polities that emerged on either end of Lake Titicaca were distinguished by architecture, stoneworking, and ceramic traditions. A three-tiered site size hierarchy is evident in the Late Formative, and the construction of prominent terraced mounds with sunken courts occurred in a few major sites at this time. The elite ceramics and stoneworking, and the construction of elaborate mounds as a venue for large-scale feasts and human sacrifice at sites like Pukara and early Tiwanaku, can be interpreted as a means of demonstrating the large-scale organization of labor by elites (Stanish 2003: 143).
The patterns of obsidian circulation that emerged at the end of the Middle Formative became very well established in the Late Formative. Excavations at centers in the North Basin have found a reduction in the presence of Alca obsidian in the Titicaca Basin, but the Alca material is still present although it is found in minor quantities at the larger sites as compared with Chivay obsidian. The diversity of obsidian types in the Titicaca Basin samples reported by Burger et al. (2000: 306-308) for this time span is low, as compared with the diversity of types used in the Cusco area, because in the Titicaca Basin it is virtually all Chivay obsidian.
In recent excavation work at Pukara on the central pampa at the base of the Qalasaya, Elizabeth Klarich (2005: 255-256) found that obsidian was generally available and obsidian use was not associated with any intrasite status differences. Probable representations of obsidian points and knives appear in Pukara iconography, and small discs have been found at Pukara and Taraco that were possible ceramic inlays (Burger, et al. 2000: 320-321). The Late Formative Period on the southern end of the Titicaca Basin has small amounts of Chivay obsidian at Chiripa and Kallamarka. InGiesso's (2000: 167-168)review of lithic evidence from several Formative Period sites he found no obsidian use in these collections except for samples from Khonkho Wankane which recent research directed by John Janusek has revealed to be principally a Late Formative center. The furthest confirmed examples of transport of Chivay obsidian are these examples encountered in southern Titicaca Basin sites. The two furthest confirmed contexts for Chivay obsidian transport are represented bytwo samples from a Late Formative context at Kallamarka (Burger, et al. 2000: 308, 319, 323) and six samples found at Khonkho Wankane (Giesso 2000: 346), both about 325 km from the Chivay source, or 72 hours by the walking model.
At Qillqatani, the obsidian returns to being primarily Chivay type during the Late Formative although 1 out of the 9 obsidian artifacts analyzed from Late Formative levels was of the Tumuku type (SectionX3.4.2X). During the Late Formative there is a steady decline in the percentage of debitage made from obsidian at Qillqatani, a trend that continues in the Tiwanaku period.
In the Colca Valley, there are few traces of the Late Formative consumers of Chivay obsidian. As will be further explored in this research project, there is very little Qaluyu or Pukara material diagnostic to the Middle or Late Formative in the Chivay obsidian source region. Steven Wernke found a diagnostic classic Pukara sherd with a post-fire incised zoomorphic motif that resembles a camelid-foot from a Formative site above the town of Yanque in the Colca (Wernke 2003: 137-138).
Pukara materials are known to have circulated, probably through trade links, throughout the south-central Andes. Pukara sherds have been found in the valley of Arequipa in association with the local Formative Socabaya ceramics (Cardona Rosas 2002: 55). In the Moquegua valley, both Chiripa-related and Pukara pottery have been found (Feldman 1989), and a Pukara textile was found in a possible elite grave context in the Ica Valley (Conklin 1983).
The decline in forest cover in the Lake Titicaca Basin beginning during the Early Formative intensified throughout the Formative Period. Between 2500 - 800 cal. BCE a decline in fine particulate charcoal was detected in a lakecore drawn from the southern end of Lake Titicaca's Lago Grande(Paduano, et al. 2003: 274). The pollen and charcoal record indicates thatforest cover finally disappeared around AD0, coincident with population increases and resource pressure associated with Late Formative Period socio-economic intensification.
The obsidian circulation during the Late Formative shows distinct patterns in the Titicaca Basin and in Cusco. In the Titicaca Basin, the diversity of sources is reduced, with virtually all the material coming from Chivay and Alca, and the Alca samples are primarily affiliated with a single period at Taraco. Even at the site of Qillqatani, the diversity is reduced as compared with the previous Middle Formative level (Qillqatani Formative C). Current evidence suggests that the economic circulation was more integrated and that it was probably under some form of control by the dominant regional centers of this time. The furthest confirmed evidence of Chivay obsidian transport is from among Late Formative contexts at Kallamarka and Khonkho Wankane.Yet, diagnostic evidence from Titicaca Basin Late Formative polities in the Colca valley area is scarce. Part of the difficulty in understanding the Formative at the Chivay obsidian source area is that the Formative ceramic sequence in the Arequipa highlands is still being refined.