Geoarchaeology, Paleoecology, and Holocene Subsistence Change on the Upper Snake River Plain, Idaho

This dissertation presents new data on geochronology, site formation processes, projectile-point typology, and lithic technological organization in the Intermountain West’s Snake River Plain and Bonneville Basin, relating diachronic change in lithic artifacts to paleoenvironmental changes. This research is divided into three related articles, first focusing on site formation processes at the Pioneer site of southeastern Idaho. This study provides an example of the archaeological and paleoclimatic value of studying alluvial stratigraphic sequences in arid environments. Stratigraphic analyses were used to date mid-late Holocene archaeological horizons, as well as contribute to the late Quaternary geomorphic history of the Big Lost River drainage. There is also evidence of a high-energy erosional event at ~3800 years ago indicating a large middle Holocene flood. Next, this dissertation updates the geochronology of strata from Veratic Rockshelter, southeastern Idaho, to contribute to the diagnostic projectile point typology of the upper Snake River Plain. Results indicate that Western Stemmed Tradition points at Veratic are younger and more morphologically diverse than previously thought. In addition, Elko point forms coeval with Northern Side Notched points are found to pre-date the classic age range of Elko. Finally, an analysis of dart point variability shows a distinct drop in diversity during the late Holocene. This research concludes with a comparison of lithic assemblages from Veratic and Bonneville Estates (eastern Nevada) rockshelters, focusing on how paleoecological “crises” affected subsistence, lithic technological organization and raw material procurement. Results show that changes in aridity during the Holocene correspond with relative changes in raw material preference, ground stone use, bifacial stage of reduction, and formal vs. informal tools use at both sites. However, increased variability in raw material preference at Bonneville Estates potentially relates to the harsher, more variable and patchy ecological conditions of the Bonneville Basin compared to the more homogenous sagebrush steppe of the Snake River Plain. Ultimately, this dissertation provides geoarchaeological and geochronogical contexts for important Snake River Plain archaeological sites, providing a better understanding of prehistoric subsistence and mobility for the Snake River Plain and neighboring regions and the relation of these adaptations to climatic change