245 Archaeological Geology (Posters)

Wednesday, 3 November 2010
8:00 AM - 6:00 PM
Hall D

PORTABLE XRF ANALYSIS OF GRAVESTONES COMPOSED OF FINE-GRAINED METAMORPHIC AND SEDIMENTARY ROCKS FROM EARLY MEDIEVAL IRELAND

Paper number: 245-3
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Early Medieval communities spanned the western Irish coast from the 5th to the 12th centuries. Despite the relative geographic isolation of these groups, it is believed that they engaged in the exchange of goods and raw materials with one another. The presence of similar grave markers at different sites supports the idea of this exchange; however, there is no quantitative evidence to suggest that this reflects local production, external trade, or both. Through the Cultural Landscapes of the Irish Coast project, over the course of the 2009 and 2010 summer field seasons, we sought to establish a quantitative link between the Early Medieval gravestones and the sites at which they are found. The vast majority of the gravestones, and the bedrock of the local islands, are composed of fine-grained phyllites and schists; limestones and other sedimentary lithologies are much more restricted in their occurrence.

Portable XRF (PXRF) technology has enabled the elemental analysis of an expanded range of materials with an increased array of elements. In this study we utilize an Innov-X Omega PXRF instrument to analyze the elemental composition of Early Medieval gravestones and potential source rocks from several small islands off the west coast of Ireland. The PXRF instrument was operated in two-beam mining and soil modes. Analysis was conducted with two beams each collecting data for one minute allowing the possible detection of 31 elements for discrimination. Complementing our PXRF data, are data on the magnetic susceptibility and mineralogical properties of each gravestone. In addition, we analyzed bedrock samples from each island to establish potential sources. In total, over 120 gravestones and bedrock sources were analyzed. Preliminary assessment of the data indicates that we can identify potential gravestone production locals and the movement of materials across the Early Medieval Irish landscape.