CREATION AND APPLICATION OF A DATABASE OF RARE EARTH ELEMENT SIGNATURES FROM VERTEBRATE FOSSILS ON FEDERAL LANDS: A TOOL TO MANAGE FOSSIL RESOURCES AND MITIGATE FOSSIL POACHING

Unauthorized collection of scientifically important vertebrate and invertebrate fossils from Federal lands has become a serious problem due to their high commercial value on the black market. The Paleontological Resources Preservation Act of 2009 calls for management of paleontological resources on Federal lands using scientific principles and expertise. In previous studies, rare earth element (REE) signatures and trace element (TE) concentrations have been used to determine vertebrate fossil provenance, reworking and time averaging, paleoenvironment, and duration of fossilization. REE signatures in vertebrate fossils are distinctive in some stratigraphic zones and geographic areas. When coupled with other properties, such as cathodoluminescence of secondary minerals in Haversian systems, REE signatures and TE concentrations of fossils may allow the collection site of poached fossils to be determined, enabling management and protection of paleontological resources and prosecution of poachers. We have begun to create a database, including REE signatures, of vertebrate fossils from the Eocene-Oligocene White River Group in South Dakota and Nebraska for a preliminary feasibility study. Shale-normalized (N) REE signatures can be compared visually; by using scatter-plots of significant ratios (e.g., La_N/Sm_N vs. La_N/Yb_N), or ternary or quaternary diagrams (e.g. Nd_N-Gd_N-Yb_N or La_N-Nd_N-Gd_N-Yb_N). However, cross-correlation and multi-dimensional statistical tests, such as principal component, discriminant, and heirarchial analysis of signature properties, including NASC-normalized Ce and Eu anomalies, tetrad effects, La_N/Nd_N, Nd_N/Gd_N, Gd_N/Yb_N, Ho_N/Yb_N, and Y/Ho can also successfully distinguish fossils from different source areas. This method works best for beds or units with simple taphonomic histories. Beds with significant time or spatial averaging can have fossils with greatly differing signatures which may be more difficult to discriminate. In our current study, four sites near Toadstool Geologic Park in northwest Nebraska were investigated. In most cases, fossils could be associated with their original site >90% of the time using REE/TE ratios. Detailed taphonomic histories within each site can also be clarified from differences in the signatures.