Las Capas: Early Irrigation and Sedentism in a Southwestern Floodplain

In 1998, Desert Archaeology, Inc., personnel conducted archaeological data recovery fieldwork at the request of the Arizona Department of Transportation (ADOT) for a redesigned on-ramp to the Interstate 10 (I-10) highway in the western Tucson Basin, southern Arizona. The investigated areas were within the boundaries of Las Capas, AZ AA:12:111 (ASM), a 50-hectare (123-acre) stratified site buried in the former floodplain of the Santa Cruz River. Radiocarbon dates from 46 samples of maize and other plant remains indicate these areas of the site were occupied by early agriculturalists almost continuously between 1250 B.C. and 750 B.C. According to radiocarbon dates obtained by other researchers during previous and subsequent investigations, other areas of this site were occupied by foraging groups by 2800 B.C., and by agriculturalists as early as 2100 B.C. The cultural remains documented during the work by Desert Archaeology are representative of the San Pedro phase (1200-800 B.C.) archaeological complex in the U.S.-Mexico borderlands. A total of 468 cultural features in three major strata were excavated, and 107,129 artifacts were recovered. This project also documented 12 prehistoric and historic canals, assigned the separate site number, AZ AA:12:753 (ASM), 10 of which range in age from approximately 1250 B.C. to 500 B.C. The geomorphology and stratigraphy of the site, site formation processes, chronology of occupation, excavated features, types of archaeological deposits, artifact distributions, and canals in the areas investigated by Desert Archaeology are described in this volume. Also included are: a review of 70 years of research on the San Pedro phase; a redefinition of the San Pedro complex; studies of canal geomorphologies, hydraulic characteristics, environments, estimated labor requirements, irrigated areas, and trends over time; an analysis of Early Agricultural period site patterns and landscape use in the Tucson Basin; and discussions of implications for the significant discoveries at this site. The results of comparative studies of material culture samples, subsistence remains, and environmental evidence from Las Capas; Los Pozos, AZ AA:12:91 (ASM); and several other Early Agricultural period sites in southern Arizona are summarized in other volumes.