RARE EARTH ELEMENTS (REE) IN DINOSAUR BONE SITES RECORD LOCAL FRACTIONATION OF REE IN PALEO-PORE WATER: A GLIMPSE OF THE VARIOUS LOCAL DEPOSITIONAL ENVIRONMENTS IN THE LATE EARLY CRETACEOUS CEDAR MOUNTAIN FORMATION, UTAH

Rare earth element geochemistry of dinosaur bones from multiple locations in the Yellow Cat Member was determined for the purposes of taphonomic analysis and depositional environment. These sites include the Crystal Geyser Dinosaur Quarry (CGDQ), Dalton Wells Dinosaur Quarry, Suarez Site, Don's Ridge South and Don's Ridge North. The CGDQ, Suarez Site, Don's Ridge sites are all within 1.5 km of each other, while the Dalton Wells Quarry is about 40 km to the southeast. The REE patterns from site to site and lithology reveal lines of geochemical fractionation, geochemical mixing and paleo-redox trends during the time of deposition of the Yellow Cat Member (YCM). REE in bones from the sites suggest dynamic fractionation of the REE along groundwater flow paths. REE distribution can differentiate among sites as well as elucidate associations between sites. For example, the CGDQ is distinguished by its Ce anomaly, its unique spider diagram pattern, and its location on REE ternary and tetrahedral diagrams. Strong geochemical similarity is seen between bones from Don's Ridge South and bones from the lower bone unit of the Suarez Site that suggests that organisms preserved in both locations died and were fossilized at approximately the same time and in the same depositional environment. Dalton Wells Dinosaur Quarry, which is about 40 km away, has its own characteristic REE geochemistry and plots as a separate cluster from the bones in the CGDQ-Suarez Site-Don's Ridge area on ternary and tetrahedral diagrams. Positive Ce anomalies suggest fossil bones from the CGDQ were fossilized in more reducing conditions, and bones found further from the site are fossilized in more and more oxidizing conditions. Continued sampling and analysis of REE in bones in the YCM will allow for the reconstruction of paleo-conditions during the time of fossilization of the YCM fauna. Future sampling and REE analysis of bones from overlying members such as the Ruby Ranch, Poison Strip, and Mussentuchit members may bring to light varying conditions during the climate change of the early-Late Cretaceous.