Electron microprobe analysis of elemental distribution in excavated human femurs

Elemental distributions have been determined for femur cross sections of eight individuals from the Gibson and Ledders Woodland sites. The analyses were obtained by x-ray fluorescence with a scanning electron microscope. Movement of an element from soil to bone should give rise to inhomogeneous distributions within the bone. We found that the distributions of zinc, strontium, and lead are homogeneous throughout the femur. In contrast, iron, aluminum, potassium, and manganese show clear buildup along the outer surface of the femur and sometimes along the inner (endosteal) surface, as the result of postmortem enrichment. The buildup penetrates 10-400 micron into the femur. The major elements calcium and sodium show homogeneous distributions, but considerable material could be lost by leaching (10-15%) without causing a palpable effect on the electron maps. Magnesium shows buildup on the outer edge of some samples. These results suggest that diagenetic contamination may exclude Fe, Al, K, Mn, and probably Mg from use as indicators of ancient data. The homogeneous distributions of Zn, Sr, and Pb suggest that these elements are not altered appreciably and may serve as useful dietary indicators.