Current Activities

 

In addition to the basic research of the laboratory involving the elemental characterization of materials such as bone, pottery, stone, pigments, soil, shell, and mortar, we have several  areas of specific research:

    Collaborative projects have included compositional studies of bone assemblages from many sites and contexts throughout the world. The composite data base resulting from these studies, which now includes more than three thousand analyses, is producing new methods of inquiry about paleodiet.
    Our interest in the alkaline-earth elements in bone has led to research in the isotopic patterns of strontium and lead in bones and teeth. Through comparisons of strontium isotopes in bone and tooth enamel we were also able to successfully identify immigrants among various residential groups at the archaeological site of Grasshopper in central Arizona. We are currently further developing this technique to access individual life histories as well as continuing the study of migration patterns in Central and South America and Europe.
    We also have been exploring the development of an efficient, inexpensive, and easily accessible means of chemically characterizing archaeological ceramics. This method was recently used to obtain many thousands of compositional analyses of pottery from the southwestern U.S. to understand the evolution of the Salado Polychroime tradition.  We are enhancing our existing methods to include the laser microprobe to provide direct analysis of the solid matrix of potsherds and to extend our studies to obsidian and other lithic materials. We are also using X-ray diffraction analyses to examine pigments and other fine-grained materials.
    A further pursuit is the chemical analysis of soils from modern, ethnographic contexts and from archaeological sites to discern chemical patterns representing functional behaviours. This has been applied to soils from archaeological contexts in the United States, Guatemala, and Oaxaca, and is currently being used to study living-floor sediments from Catalhöyük.
    Other projects include the chemical "fingerprinting" of a wide variety of archaeological materials, recent sucesses include being able to distinguish archaeological shells from different sources and map prehistoric trade routes.


 
 

Assessment of factors affecting barium and strontium levels in bone

Recent investigations of barium and strontium reveal that there are quantitative relationships between environmental levels of barium and strontium and levels of these elements in bone. Bone-chemistry projects have included bone assemblages from historic cemeteries in Ireland, Neandertal specimens from Yugoslavia, bone from Nelson Bay Cave in South Africa, from the American Southwest and the coasts of South America, and many other sites and contexts. The composite data base resulting from these studies, which now includes more than five thousand analyses, is producing new methods of inquiry about paleodiet, paleoclimate, and even provenience. One significant example of such is the recognition that barium is an indicator of marine versus terrestrial resources in the diet. Other significant results have included procedures for evaluating and minimizing the post-depositional chemical contamination of archaeological bone, which to-date has been the most serious obstacle of trace element studies.  Current research focuses upon environmental factos influencing the distributions of elements in bone, extending our research to elements beyond the alkaline-earth elements, and the study of isotopic patterns in skeletal materials.
 

Strontium isotopes in human teeth and bones as a monitor of mobility

Direct evidence of human residential mobility has been difficult to obtain in prehistory. Archaeologists have generally used artifact styles as a proxy for people to investigate population movement. We approach this problem by comparing strontium isotope ratios in human bones and in teeth . Dental enamel forms during early childhood and retains Sr isotopes from the local geology at that time, while bone, which is chemically remodeled, assimilates Sr isotopes reflecting residence during the last years of one's life. Thus differences in strontium isotope ratios between bone and tooth enamel reveal movement during the life of the individual. Strontium isotope ratios in teeth that do not match those of the local geology should indicate immigrants to a site. Results of such analyses allow us to document the structure of population movement at both intraregional and interregional levels, and how these patterns contribute to an understanding of intrasite variability. Comparisons of strontium isotope ratios in human bone among sites, along with analysis of local bedrock and faunal remains, further define the strontium isotope compositions for the region and constrain the areas from which mobile individuals were leaving. A strontium isotope study of bone and teeth from the site of Grasshopper in the American Southwest has demonstrated that there are measurable and meaningful differences between bones and teeth from the same individuals, among individuals from the same site, and between communities in the study area.
 

An efficient method for chemically characterizing potsherds

     We recently developed an efficient chemical methodthat reliably correlates genetically related ceramics with one another. The method uses an ionic-extraction of the ceramic paste that is highly sensitive to the composition of the clay paste and to production parameters such as firing temperature. In all test cases, the method was able to correctly correlate fired, tempered clays regardless of temper, and to match potsherds with one another and with the archaeological clay from which they were made. In tests using modern ethnographic ceramics of known provenience, the method not only correctly differentiated the vessels by village, but also by individual potters. In an archaeological example, the method was used to chemically differentiate intrusive ceramics appearing at archaeological sites on the Oaxaca coast and to match them chemically with stylistically similar wares from Monte Alban. It is currently being used to analyze many thousands of sherds from the southwestern U.S. to trace the evolution of various ceramic traditions. It is also being explored as a method for assessing firing temperatures.
    Although we are using ICP spectroscopy, a highly-sensitive multi-element technique, it was possible in test cases to reliably correlate ceramics with only three or four elements, detectable at levels which could be measured by widely available instrumentation (e.g. flame atomic absorption) and at extraordinarily low costs. While our ceramic analyses are addressing archaeological problems, the primary objective is to develop a reliable method of ceramic compositional analysis that can be used by those without access to sophisticated instrumentation or large research budgets.

The chemical characteristics of anthropogenic soils

Human activities can impact soil formation to the extent that natural soil formation is altered and a new, human influenced (anthropogenic or anthropic) soil formed. can be substantially different from adjacent, contemporary, natural soils. These differences can be interpreted, and the behavior that led to their creation reconstructed. This has long been recognized with respect to phosphorus, but only recently with respect to a wider range of elements and compounds also found in anthropogenic soils. Multielement analysis by ICP/AES of an acid extract of soil provides a rapid and inexpensive means of characterizing the properties of anthropogenic soils. Samples (as little as .5g) can be collected on a uniform grid from a house floor, or from selected features. Comparison between archaeological soils and soils from a contemporary paleo-land surface or sterile context allow the identification of activity areas, hearths, floor areas, and external surfaces. These data can aid in the interpretation of the spatial organization within a structure and in the identification of specific features. The laboratory has analyzed soils from a wide range of modern and archaeological contexts including Mexico, the United States, Canada, Sweden, Denmark, and the Middle East. This database provides a powerful aid in the interpretation of archaeological chemical residues in soils.
This page maintained by J. Burton <jhburton@facstaff.wisc.edu>, last updated February 1999.