Alluvial stratigraphy and geoarchaeology in the American Southwest

Many of the activities of prehistoric people who lived in the American Southwest were concentrated around alluvial environments. In this arid to semiarid environment, alluvial settings provided freshwater for drinking, a biologically rich environment for hunting and gathering, and water for agriculture. When investigating the prehistory of cultures centered around an alluvial environment, an understanding of the geologic history of that environment is important. The geologic history of deposition, erosion, and stability of any stream is recorded in its stratigraphy of sediments, erosional unconformities, and soils. Stratigraphy provides the framework to chronologically order and date archaeological sites. Further, the stratigraphic record allows archaeologists to ascertain the effects of geological processes on the preservation of the archaeological record, determining which parts of the archaeological record are absent, which have potentially been preserved, and how fragmentary are the preserved portions of the record. The limitations that geologic processes impose on the archaeological record must be recognized and understood before meaningful interpretations of prehistory can be made. Geoarchaeological studies of alluvial environments also provide the information needed to reconstruct changes that occurred to the environment during the late Quaternary. These landscape reconstructions provide the environmental context that may help to explain changes that occurred to human cultures over time. These concepts are illustrated with examples from the American Southwest where alluvial environments were crucial for survival and cultural development. © 2000 John Wiley & Sons, Inc.