Portable X-ray Fluorescence Analysis of Pottery at the Bayshore Homes Site in Pinellas County, Florida

The Bayshore Homes site was occupied intermittently over a period of approximately twelve hundred years, with the two main occupation periods being CE 150-550 and CE 900-1350. During those lengthy occupations a substantial amount of plain and decorated pottery was discarded at the site. A portable X-ray fluorescence (pXRF) spectrometer was utilized to analyze the elemental composition of 133 sherds, both decorated and plain. The resulting elemental composition data were then analyzed using multivariate statistics in an attempt to discern discrete clay sources that may have been exploited by inhabitants of the Bayshore Homes site. Principal component analysis (PCA) and discriminant function analysis (DA) were employed to identify three discrete clay sources exploited in the production of pottery. The results of the statistical analyses were then used to answer two basic, yet pertinent, questions about the Bayshore pottery: 1) Were the same clay sources exploited during both occupation periods? 2) Were the same clay sources exploited for both decorated and plain pottery? The results of the statistical analyses indicate that the same clay sources were exploited for both occupation periods, though evidence suggests that the dominant clay source in use did change over time. The results also imply that the same clay sources were utilized in the production of plain and decorated pottery, which suggests that at least some portion of the decorated pottery excavated from the Bayshore site was produced locally, and not obtained through trade. Finally, the results of this research demonstrate that pXRF is a useful tool for preliminary differentiation of clay sources in Florida