P-XRF compositional analysis of obsidian from the Middle Moquegua Valley, Peru: Interaction on the Tiwanaku and Wari frontier

Abstract

Provenance studies of exotic materials along the frontiers of expansionary states provide invaluable evidence of cultural interactions and systems of exchange. Here we present portable X-ray fluorescence (pXRF) data on obsidian artifacts from the Middle Moquegua Valley of southern Peru. This region is the only known shared border where colonists of both the Tiwanaku and Wari states settled during the Andean Middle Horizon (AD 600–1000). A total of 50 obsidian artifacts housed in the Museo Contisuyu in Moquegua, Peru was analyzed from ten archaeological sites affiliated with Tiwanaku, Wari, and indigenous Huaracane groups across Formative Period and Middle Horizon contexts. The paucity of obsidian recovered from Tiwanaku sites in Moquegua highlights different lithic traditions, material preferences, and access to obsidian sources compared to their Wari counterparts in the valley. Although Tiwanaku settler groups maintained strong social identities tied to their homeland region, pXRF results show that obsidian was one of the few materials that crossed cultural boundaries in Moquegua. We assess how obsidian provenance can be used as a proxy for cross-cultural interaction in borderland regions and to reconstruct economic systems related to state provisioning versus bottom-up processes of regional exchange.