DETERMINING THE STRATIGRAPHIC PROVENANCE OF EX-SITU FOSSILS USING PORTABLE X-RAY FLUORESCENCE TECHNOLOGY: A CASE STUDY FROM THE MIDDLE CAMBRIAN OF WESTERN UTAH, USA

The stratigraphic and geographic provenance of a fossil is critical context for any paleontological study, but not every specimen in museum collections has these precise and accurate data. Recently, the Natural History Museum of Utah curated over 2,250 middle Cambrian (Miaolingian) fossils from the Wheeler, Marjum, and Weeks formations of the House Range in western Utah, U.S.A. These fossils were originally illegally collected and part of a Bureau of Land Management law enforcement case prior to coming to the museum, and thus have limited and/or dubious locality information. The formation of origin is specified for some specimens, but other observations sometimes contradict this information, and the specific locality is unknown for all specimens. This collection is of particular scientific significance, as it includes hundreds of soft-bodied fossils, multiple new taxa, and complete specimens of previously poorly-known species, from three Konservat-Lagerstätten.

To estimate the locality and formation of origin for these specimens, we collected 64 matrix samples from 12 well-known localities in the House Range across all three formations. We then used portable X-Ray Fluorescence (pXRF) technology to non-destructively analyze the elemental composition and abundances of these rock matrix samples, as well as those from fossil specimens in the new collection with limited provenance information. The multivariate statistical method linear discriminant analysis (LDA) was implemented using the software package PAST to explore how elemental abundance varied across different localities and formations in the known samples, ask whether these data could be used to separate these sites and units, and to infer the provenance of fossils with limited stratigraphic data. The LDA was able to easily discriminate between the three different formations and classify unknown samples. Clear discrimination was more difficult at the locality level, although a number of sites from each formation, such as Weeks Quarry 1, Weeks Quarry 4, Kell’s Knoll Quarry and the U-Dig Quarry, were distinct. These results show that this method is largely successful for formation-level inference, but robust locality-level provenance reconstruction might require additional data.