Paper No. 169-41
Presentation Time: 9:00 AM-1:00 PM
WHOLE ROCK AND FOSSIL GEOCHEMISTRY COMPARISONS OF WESTERN US AND KYRGYZSTAN USING X-RAY POWDER DIFFRACTION PATTERNS AND MINERAL COMPOSITION FOR PALEOCLIMATIC RECONSTRUCTIONS
Whole rock geochemistry is applied in a variety of methods in an attempt to determine paleoclimatic variables for fossil sites. We are applying XRD as one method to investigate how results from carbonate nodules, siliciclastic sediments, bone, and dental enamel differ, and if a correction between sources is calculable. We examined mineral composition to discern paleoclimatic reconstructions at multiple study sites from each of the following Neogene fossiliferous areas: Northeast Nevada, Oregon, Southern California, and Kyrgyzstan. We used an XRD to analyze powdered fossil and rock samples to create X-ray powder diffraction patterns for mineral identification. Pronounced D-values from the sites include 1.8390 Å, 2.2481 Å, 2.7878 Å, 3.3375, 3.4531 Å, and 4.2162 Å. Rocks collected from US formations tend to have more aluminum and sodium than fossil bone and tooth fragments. Since the fossil bone contains more fluorapatite and actinolite, and lower proportions of quartz and albite, we suggest the bone has undergone diagenetic alteration. Fossil enamel and bone from the localities have primarily hydroxylapatite and fluorapatite observed intensities above 55%, consistent with the interpretation that organisms fractionate minerals differently than the environment around them, but do so in consistent patterns seen across a variety of depositional environments and geologic formations. Rock collected from the same units have quartz, orthoclase, and sanidine with observed intensities above 55%, indicating that siliciclastic materials with soil development are also reflecting environmental proxies similar to organic material concentrated in fossil and bone. Further, fossils from the sites contain higher levels of radiation, suggesting a consistent water source percolating through the enamel and bone. Consistent variations of rock and fossil mineralization and concentration of intensities between the same sites indicate that while permineralization pathways are different for different sources, comparisons across localities, environments, and taxa are possible. The use of XRD to collect data paves way for availability in paleoclimatic reconstructions.