Microanalysis as a Supplement to Bulk Chemical Sourcing of Archaeological Pottery

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With National Science Foundation support Drs. Hector Neff and Michael Glascock will conduct microprobe analysis of ceramic materials collected in archaeological contexts and compare the results with those determined by instrumental neutron activation analysis. Analyses will be undertaken with wavelength-dispersive and energy-dispersive X-ray spectrometers attached to a scanning electron microscope. The instrumentation available permits quantified measurements down to ca. 100 ppm together with the generation of maps of variation in the concentrations of determined elements across the scanned image. Characteristics of elemental distributions such as uniformity; association with particular kinds of mineral grains, pores or other features; or correlation with other measured elements will permit some plausible sources of compositional patterning observed in bulk data to be understood in greater detail. The approach will be applied to at least seven pottery data sets representing several world regions, time periods and levels of sophistication of pottery technology.. This wide range and variety of example applications will afford a comprehensive test of the potential of the method for improving the precision of inferences derived from ceramic compositional analysis. Because different clay sources often differ in mineral composition, it is possible to determine the trace element composition of a ceramic recovered in an archaeological site, compare it to chemical profiles of known sources and thus determine raw material source. When sources are only poorly known, it is often still useful to determine the degree of variation exhibited in the ceramics in a single site, compare such data across sites and determine degrees and directions of interaction. By such means archaeologists can reconstruct many aspects of prehistoric social organization and therefore ceramic trace element studies play an important research role. Most often composition is determined by neutron activation analysis. A small amount of material is removed from a sherd, ground, homogenized and measured. The difficulty with this technique is that it ignores chemical variation within the sherd and assumes that the trace element pattern observed is determined solely by source composition. Although they have not been examined in detain it is unclear whether these assumptions are correct and the value of Drs. Neff and Glascock's project rests on its evaluation of these. The work will allow archaeologists to assess the results on neutron activation analysis in a more realistic fashion and assist in the development of archaeological analytic techniques.