CSI BIG HORN BASIN: A FORENSIC MINERALOGICAL EXPERIMENT USING EOCENE MAMMAL BONE FRAGMENTS FROM THE WILLWOOD FORMATION, NORTHWESTERN WYOMING

Eocene mammal bone fragments (Set A) came into the possession of United States Department of the Interior, Bureau of Land Management (BLM) Law Enforcement in the summer of 2011, as a result of an investigation. Locality information for these unidentifiable fragments was not available, but a locality on federally managed lands was suspected. Reconnaissance was made by BLM to the suspect locality where a second set (Set B) of Eocene mammal fragments was collected from a Willwood Formation outcrop. It was hypothesized that the geochemistry of the bones might be identical if they came from the same outcrop. The BLM National Minerals Testing Laboratory conducted an X-ray analysis of the fragments to test that hypothesis. Two bone fragments were randomly selected from both Set A and Set B. These four specimens were analyzed for mineralogical composition using a Rigaku Mini-Flex X-Ray Diffractometer. Bone fragments were prepared for X-ray diffraction using standard laboratory methods. Bones were hand pulverized in a piston assembly and further pulverized using a diamonite mortar and pestle. The resulting powder was then mounted for X-ray diffraction. Results of the X-ray diffraction patterns were analyzed using JADE-9 software, and the X-ray diffraction patterns were overlain for comparison. The four resulting X-ray patterns were 99% identical and it was concluded that there was a strong indication that the bone fragments came from the same locality. When the evidence was presented to the parties of interest in the investigation, it was disclosed to Law Enforcement that Set A had been taken from the same locality as Set B on federally managed lands. As a result of this experiment, it is concluded that X-ray diffraction may be a useful tool in identifying a fossil locality given only fossil fragments, if the results of X-ray diffraction maintain consistency. This preliminary study suggests that additional mineralogical testing using X-ray diffraction should be conducted on fossil fragments from other known localities to determine if the results from this preliminary study are consistently repeatable. If so, then this method will be helpful in determining the site location of fossils with limited provenience information, as well as enhance the BLM’s ability to manage paleontological resources on public lands for future generations.