DEVELOPMENT OF A STANDARDS-BASED QUANTITATIVE XRF METHOD FOR FOSSILIZED BONE

Accurate major and trace element analysis of fossilized vertebrate material is of increasing importance in order to understand complex relationships between the chemistry of such material and the environments in which the animals were fossilized. Major and trace element concentrations in fossilized bone are commonly determined by semi-quantitative methods, such as scanning electron microscope-energy dispersive microanalysis. Standards-based quantitative analysis using x-ray fluorescence (XRF) are not commonly used, in part because of the lack of geochemical reference standards for fossilized bone. The objective of this research is to develop a replicable quantitative XRF method for major and trace element analysis of fossilized bone using readily available geochemical reference standards. Eight taxonomic indeterminate fragments of marine and non-marine (provenance unknown) fossil bone were first analyzed by inductively coupled-plasma mass spectrometry (ICP-MS) in order to obtain concentration profiles for major and trace elements. A quantitative XRF analytical method was then developed using a combination of USGS and NIST geochemical reference standards, each characterized by element concentrations similar to those measured by ICP-MS in the fossil bone (i.e., 'target element concentrations'). Each standard was analyzed 30 times, observing that the means of the target element concentrations fell within the concentration ranges specified by the standards' Certified Reference Material Reports. The eight fossil fragments were then analyzed for all elements. Comparison of the XRF and ICP-MS fossil fragment data via Student T-test for unequal variances shows no statistically significant difference between the data sets. These results suggest that standards-based quantitative XRF analysis should be further explored as an analytical tool for paleontologists to unravel the taphonomy of vertebrate fossil material.