Single-Grain Optically Stimulated Luminescence Ages of Brownware Pottery in the Middle Rocky Mountains and the Spread of Numic Ceramic Technology

Abstract

This study presents the results of a single-grain optically stimulated luminescence (SG-OSL) analysis of brownware pottery from four Late Prehistoric-period sites in the Middle Rocky Mountains, Wyoming, USA. SG-OSL of quartz ceramic temper provides improved age control for sites where radiocarbon dating has proven problematic due to old wood, recent wildfires, and calibration uncertainties. SG-OSL results are compared to fine-grain infrared stimulated luminescence (FG-IRSL) results from the same sherds and associated radiocarbon ages. We find that the single-grain technique applied to quartz sand temper provides improved accuracy and precision over both FG-IRSL and radiocarbon. We compare our results to directly dated brownwares from the southern and eastern Great Basin based largely on thermoluminescence analysis. While brownware ceramics appear earliest in the southwestern Great Basin, our data show that the technology spread quickly to the northeastern margin of the Numic homelands. We suggest that knowledge of ceramic technology in Formative (i.e., Ancestral Pueblo and Fremont) societies was important in the adoption of pottery by Numic hunter-gatherers and that, like in the southwestern Great Basin, this technological adaptation in the Middle Rocky Mountains may have occurred within a context of resource intensification during the last 800 years.