Stable carbon and nitrogen isotope analysis of 571 archaeobotanical samples was performed to assess agricultural practices at Cerro de Oro in the Cañete Valley, Peru, during the transition between the Early Intermediate Period and the Middle Horizon. This thesis presents a comprehensive range of δ13C and δ15N values for the major C3 and C4 plant resources at the site. No differences were found in the δ15N values of charred and desiccated maize cobs, suggesting that both types of plant remains can provide reliable δ15N measurements. Generally, the δ15N values of plants at the site were relatively high, with the exception of most of the legumes, suggesting that organic fertilizers were extensively used. Camelid dung and fish offal are the most likely fertilizers used at Cerro de Oro, but some very high δ15N values suggest that seabird guano may also have been used. Peanuts, a legume, had higher δ15N values than would be expected for legumes, suggesting that this plant may have been companion-planted alongside maize or other more heavily fertilizer crops. Cotton had the highest δ13C value among all of the C3 plants sampled from the site, suggesting that this crop grew in the driest conditions, possibly reflecting a deficit irrigation system. This study reveals how intensive and extensive agriculture supported the emergence and growth of Cerro de Oro, a monumental site of great regional importance.
Author Keywords: Andean Archaeology, Carbon and Nitrogen Stable Isotope Analysis, Cerro de Oro, Early Intermediate Period and Middle Horizon, Intensive and Extensive Agriculture, Plants