FAUNAL ANALYSIS OF A FOSSIL MICROSITE FROM THE LATE CRETACEOUS HELL CREEK FORMATION, NORTH DAKOTA

The Hell Creek Formation of the western United States is a series of 66-million-year-old mudstones and sandstones that is well-known for its fossils from the latest Cretaceous period. It represents a low-lying coastal plain environment cut by numerous river channels. In contrast to the large-dinosaur fossil excavations the Hell Creek Formation is famous for, fossil microsites (collections of small invertebrate and vertebrate fossils, often concentrated by stream currents) can offer more nuanced insights into local ecosystems due to their faunal abundance and diversity. This project documented the presence and abundance of taxa at a fossil microsite within the Hell Creek Formation near Marmarth, North Dakota. Microfossils and bulk sediment samples were collected from a newly-identified microsite yards away from and at the same stratigraphic level as several dinosaur fossils. The site was divided into five regions and each region was searched by closely examining the ground surface and collecting all fossil material. The site was first sampled during the summer of 2016 and revisited in 2017 and 2018. Fossils were identified to the most specific taxonomic level possible and tallied to determine their abundance. Identifiable taxa at this site include theropod dinosaurs, turtles, crocodilians, fish and bivalves. These results will be used to provide greater environmental context and depositional information for nearby dinosaur excavation sites and future research in the area.