Strategies For Combining Elemental Distribution Data Derived From Multiple Images and Samples

Data from digital electron probe x-ray microanalysis (EPXMA) images can be used to generate high resolution profiles of Ca binding within sarcomeres of vertebrate striated muscle. While ratios of elemental peak to bremstrahlung at each point (Hall method) have been used in many studies to allow comparison of data taken from different samples, this procedure has limitations for our application. A different normalization procedure is described here which provides a means of assessing variation among elemental and bremstrahlung profiles obtained from different images and samples.Freeze dried cryosections of chemically skinned frog or rabbit skeletal muscle were prepared as previously described. Digital EPXMA images were collected for 24 to 36 hours using a Zeiss EM910 STEM and an Oxford ExL2 microanalysis system. Calcium and bremstrahlung counts were summed within one pixel wide masks placed at successive positions along each half sarcomere, as previously described, using an automated routine in IPLAB on a Power Mac 7100.

Provenance of Kanjera Fossils by X-Ray Fluorescence and Ion Microprobe Analyses

XRF and Ion mfcroprobe analyses of fossils of known and uncertain provenance from the Lower-Middle Pleistocene locality of Kanjera. Kenya, are reported. The goal of this study was to develop a nondestructive technique of provenancixig fossils, which could be applied to the Kanjera sample. The fossils of known provenance were collected in the excavations of the 1987 Smithsonian Expedition. Three fossils of uncertain provenance, two specimens of Theropithecus oswaldi and a hominid fossil, were analyzed as test cases.Both qualitative and quantitative XRF analyses of Kanjera fossils were carried out. In the qualitative analysis, the elemental peak areas from each fossil's XRF spectrum were calculated and normalized to the peak area of the incoherently scattered radiation. Results of the analysis showed that fossils from the Lower-Middle Pleistocene Kanjera Beds, for the most part, had higher levels of yttrium (Y) and zirconium (Zr) than those of the younger Apoko (Ap) Bed. black cotton soil (BCS) and modem bones (MD). The relative concentrations of uranium (U) v strontium (Sri and thorium (Th) were diagnostic of the Kanjera Bed of origin. These findings were confirmed by quantitative XRF and ion microprobe analyses of a subsample of Kanjera fossils. The T. oswaldi and hominid fossils had trace element concentrations suggestive of K2 and BCS provenances, respectively. These findings provide a framework for the qualitative XRF provenancing of other surface collected fossils from the locality.