PREHISTORIC IRRIGATED SOILS IN THE HIGH ATACAMA OF CHILE: PRELIMINARY RESULTS FROM A TERRACED AGRICULTURAL COMPLEX

As part of an interdisciplinary investigation of pre-Hispanic settlements and sociopolitical change on the margins of the hyperarid Atacama Desert, a geomorphological and pedological study of natural and agricultural terrace soils was conducted at the archaeological sites of Topaín and Paniri, located ~70 km northeast of Calama, Chile. Springs fed by snowmelt provided water to canals that irrigated a complex system of high elevation (~3200 m) agricultural terraces constructed on bedrock and Pleistocene alluvial fan hillslopes. Initial terrace construction and irrigation date to ~A.D. 1000. Natural and terraced soils (n=16) were excavated, described, and sampled for physical and chemical analyses. Natural soils display greater pedogenic development (e.g., secondary clay and probable secondary silica) than have been documented at lower elevations in the Atacama. Preliminary data demonstrate that natural soils were modified intentionally (terracing, removal of gravel, probable fertilization) and unintentionally (CaCO₃ enrichment due to spring irrigation water). Topaín and Paniri are examples of sustainable food production in an agriculturally marginal environment and provide additional insights into pre-Hispanic soil management.