Characterization of Archaeological Metal Remains in Micromorphological Thin Sections Using mu XRF Elemental Mapping

The soil micromorphological examination of thin sections obtained from archaeological profiles is a well-established approach in geoarchaeology. However, it provides only limited information about the nature of metal inclusions (shape and taphonomy but not elemental composition). Laboratory micro-X-ray fluorescence (μXRF) elemental mapping is a non-destructive technique that can be applied directly to the resin-impregnated sediment blocks from which thin sections are made. However, resin blocks may not always compare to the final thin sections, since some material is lost during the fabrication process, affecting the investigation of millimeter-sized features, such as metal fragments or hammerscale, features essential for determining the type of metal working taking place at a particular site. In this study, we investigate the potential of μXRF elemental maps acquired directly from covered thin sections. Our experiment demonstrates that a wide array of elements useful for metal fragment identification (Fe, Cu, Zn, As, Ag, Sn, Au, Pb) are detectable even in coverslipped sections. This conclusion extends the potential of μXRF beyond the resin blocks from which thin sections were made, to metal fragments in the thin sections themselves, enriching the archaeological interpretation and providing information missed by traditional techniques, such as optical microscopy.