A NEW FOSSIL VERTEBRATE MICROSITE FROM THE HELL CREEK FORMATION, SOUTH DAKOTA

In the summer of 2014, a field team from Westminster College collected vertebrate microfossils from the Dakota Prairie Grasslands of South Dakota. Microfossil material was recovered from a new late Cretaceous locality (DP-31) within the Hell Creek Formation. This study focuses on two components of the microsite: 1) identification of fossil teeth, and 2) determining mudstone clay mineralogy. The microsite yielded fossil teeth that included fish, crocodile, champsosaur, and dinosaur. Fossil teeth were identified by morphological comparisons, and used to reconstruct a preliminary late Cretaceous vertebrate faunal assemblage. Fossil teeth from previously known Hell Creek microsites in North America were compared to those in the current study. All identified taxa from DP-31 are represented at the other Hell Creek microsite locations. Based on the taxa present and their relative abundances, DP-31 exhibits a smaller percentage of strictly aquatic taxa, and a larger percentage of crocodile and dinosaur. Mudstone samples were collected for X-ray diffraction (XRD) to determine composition and relative abundances of clay minerals. XRD analyses indicate the presence of quartz and illite which are typical of continental deposition. These data will assist in the interpretation of sedimentary and paleoenvironmental conditions. Thus, the combined knowledge of fossil vertebrate representatives and mudstone composition from the new microsite will contribute additional information about the late Cretaceous.