Impact of Paleoclimate Variation on the Settlement History of the Columbia Plateau

Abstract:

The settlement history of the Columbia Plateau has been compiled through the record of riverine villages along the Columbia River and its many major and minor tributaries. The chronologies that were established based on the radiocarbon dates obtained from these villages are the result of large river and dam surveys and data recoveries that occurred throughout the 20^th Century. These chronologies have seldom been revisited and reanalyzed in the years since their publications in major syntheses of the 1980s-1990s. Analysis of these records using modern analytical techniques, such as summed probability distributions and GIS, will allow for a fuller picture of past settlement activities. Summed probability distributions have become the de facto technique for analyzing aggregate radiocarbon dates. This technique provides an analysis that can be robustly analyzed for determining high and low points in the distribution that are “real” and not artifacts of sampling strategies. Additional analysis of the radiocarbon dates using GIS documents the change in spatial distribution of dated villages over time, indicating the abandonment of old villages, establishment of new villages, and the possible return to old village locations. Comparing the peaks and valleys of the radiocarbon distributions with paleoclimate records indicates a correlation between cool periods and the greater intensity of house occupation. Gaps or valleys that occur in the summed probability distributions may be indicative of portions of the settlement record that are not encapsulated in an archaeological database biased toward riverine settings. These missing components of the settlement history are thought to be the habitation of upland villages appears to coincide with warmer periods of time. Notable low points in the radiocarbon distribution are between 4100-3700 cal BP and 2100-1500 cal BP, these may be periods in which people were not inhabiting riverine villages and instead moved into the uplands. Revisiting these chronologies with modern analytical strategies paired with ever-more-detailed paleoclimate models allows for a better understanding of the settlement history of the Columbia Plateau.