Middle to late holocene stream dynamics of the Santa Cruz River, Tucson, Arizona : implications for human settlement, the transition to agriculture and archaeological site preservation.

Historic records of arroyo formation have long been used as inferential tools for reconstructing paleoclimate in the American Southwest. These paleoclimatic reconstructions have attempted to demonstrate that synchronous incision of river valleys across the American Southwest was the result of large-scale (regional, global) climatic change. Projected to the past, the inferred chronological boundaries of certain climatic periods have been used by archaeologists as convenient boundaries for demarcating long-term changes in human settlement and subsistence. The rapid accumulation of new data on middle to late Holocene subsistence and settlement along the Santa Cruz River, and the application of new theoretical constructs in hunter-gatherer research require the use of higher resolution data in geoarchaeology. During the past ten years, advances have been made in our understanding of the hydroclimatological processes which cause channel changes on the Santa Cruz River and geologists are now better able to predict the circumstances under which desert streams become arroyos. Together with high-resolution geologic documentation of channel exposures, the prehistoric setting of human occupation along the Santa Cruz River can be addressed at a scale that is more relevant to the archaeological issues of today. The detail derived addresses specific geomorphic and paleoenvironmental variables that operate at the site or regional level and that have the most direct effect on human decision-making.hydrology collectio