Doctoral Dissertation Improvement Grant: Paleoenvironmental Context of Ancestral Puebloan Demographic and Subsistence Change in West-Central New Mexico

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Under the direction of Dr. Vance T. Holliday, Jill Onken will investigate the relationship between environmental change and shifting patterns in prehistoric human land use and in the Carrizo Wash watershed in west-central New Mexico. The initial adoption of maize agriculture (2100 B.C.), the Chaco Phenomenon (A.D. 1050-1130), and regional depopulation (A.D. 1300-1350) are among the most significant episodes in Ancestral Puebloan prehistory in the American Southwest. Current perspectives on the cultural processes and circumstances associated with these key prehistoric events, however, are limited by an incomplete understanding of past environmental conditions. Knowing the nature and degree of any environmental changes associated with these major subsistence and demographic changes is essential for refining archaeological interpretations and explanations at both local and regional scales. This geoarchaeological dissertation study will entail documentation of numerous stratigraphic sections. An extensive radiocarbon dating effort will permit the development of a detailed depositional and landscape history for this watershed that will be integrated with existing climatic and archaeological data. Analysis of sediment, soil, pollen, phytolith, carbon isotope, and tree ring records will contribute to the reconstruction of a wide range of environmental variables, including geomorphic, soil, and climatic factors that affected the viability of prehistoric maize agriculture. A geographic information system (GIS) will be used to integrate the archaeological and environmental data and to examine the relations among changing land use, environment, and agricultural potential over time and space.The Carrizo Wash watershed is well suited for this study because of its long history of archaeological research, the presence of one of the oldest known early agriculture sites in the Southwest, an abundance of alluvial exposures in modern arroyo walls with local concentrations of datable materials, and proximity to localities with long, well-studied tree-ring records. Broad similarities among Holocene alluvial records across the Southwest suggest that the Carrizo Wash environmental reconstruction will have regional relevance.The results of the proposed interdisciplinary study will be useful to archaeologists interested in the many influences of environmental change on prehistoric cultural change and human adaptation in the Southwest, as well as in semiarid regions in general. The findings will be equally significant to Quaternary geologists and geomorphologists interested in how hillslopes and streams respond to climate change in semiarid regions. Because land productivity for range, farming, and wildlife habitat is severely compromised by widespread erosion, this study will also be relevant to land managers, especially in light of modern climate change. This study will provide graduate student training, as well as learning opportunities for undergraduate students belonging to minority groups underrepresented in the geosciences through the Southern Arizona Geosciences Union for Academics, Research, and Outreach (SAGUARO) program funded by NSF. Results will be disseminated to the scientific community through publication in refereed journals and presentations at professional conferences and to the public through public interest stories, presentations in K-12 classrooms, and/or posters placed in public buildings in communities near the study area.