Developing FTIR microscopy for lithic residue analysis

Archaeology provides one of the best means of studying the ability of human societies to respond to climatic and environmental change. Throughout the course of human evolution, stone tools have been the primary medium by which humans have interacted with the environment through the modification of natural resources for food, shelter, clothing, and other material needs. Therefore, stone tools in archaeological sites represent one of the most important data sets for reconstructing prehistoric human adaptations. Yet one of archaeologists' greatest challenges remains the rigorous interpretation of stone tool functions. Currently, one of the ways this is done is through the identification of microscopic remains of materials worked by stone tools (e.g., plant and animal tissue), which are sometimes preserved on tool surfaces. Existing methods of microscopic residue analysis, however, are either destructive or produce ambiguous results. Newer, non-destructive, replicable methods based upon analytical chemistry are available, but need to be developed. This project will develop Fourier-Transform Infrared (FTIR) microscopy as a new method of residue analysis. It will have three major impacts. First, application of this method will provide a more direct means of inferring past human activities than the current ambiguous approaches. Second, the development of FTIR microscopy for residue analysis will provide a non-destructive means of identifying not only residues, but the composition of most archaeological materials, such as paints, pigments, textiles, food residues, ceramics, and the like. This has crucial implications for the conservation of the non-renewable archaeological record of the United States, the cultural patrimony of the United States. It also has important implications for heritage studies at home and abroad, as indigenous groups are increasingly wary about the destruction of cultural artifacts. The development of non-destructive, non-invasive methods such as this one will be a boon to researchers working with ethnographic and prehistoric materials of all kinds. Third, this project will train graduate and undergraduate students (many of whom are women, including ethnic minorities) in cutting-edge scientific methods, providing skills applicable to a wide range of jobs.

The aim of this project is to create a library of experimental reference samples of FTIR reflectance spectra that will be standards against which archaeological spectra can be compared. The standards will include some of the most common residues on stone tools, such as animal muscle, fat, skin, bone, and hair; bird feathers; fish scales; plant fibers, wood, resin, ochre, and manganese. These residues will be generated experimentally on a variety of stone surfaces, from which reflectance spectra will then be obtained using FTIR microscopy. In addition, experimental pieces will be placed in a simulated burial environment for one year, to generate standards on residues altered by burial. In addition to publishing the results in peer-reviewed journals, all of the standards will be made available to the research community, in perpetuity, on open-source websites.