SEDIMENTOLOGICAL ANALYSIS OF THE BIG BUFFALO QUARRY, BADLANDS NATIONAL PARK, SOUTH DAKOTA

The Eocene-Oligocene aged White River Group, which encompasses Badlands National Park (BADL), South Dakota, is considerably fossiliferous. Fossil localities can vary in size, ranging from smaller areas with few fossils exposed on the surface to larger and much rarer, multi-year excavations. The Big Pig Dig is a well-known example of a large fossil locality at BADL and was interpreted to represent an ancient watering hole. Recently, a new and sizable locality, the Big Buffalo Quarry, was discovered and excavation is on-going. The main goal of this research is to determine the depositional environment of the new fossil locality through detailed sedimentological analyses. We hypothesized that there would be lithological and sedimentary differences in the rocks recovered from inside the Big Buffalo Quarry compared to the surrounding sedimentary units. To investigate this hypothesis, we conducted a detailed analysis of rock samples collected from within and outside the quarry. Scanning electron microscopy and thin section analyses were used to study the mudstone zoning and types, and to analyze the sediment samples' physical and chemical characteristics. The results demonstrate that the Big Buffalo Quarry rocks have diverse characteristics that differ from the surrounding sedimentary units. The quarry sediments, which consist predominantly of blocky mudstone, are more complex than those of the surrounding areas, showing signs of bioturbation and mixing of mudstone types. Eleven mudstone types were identified in total, with the most numerous types recovered from the quarry. Additionally, the presence of green clay, likely smectite, in combination with mixed and bioturbated mudstone suggests that the quarry was an ephemeral watering hole. This research provides a better foundation of knowledge on the sedimentology of fossil quarry sites at BADL and the types of depositional processes responsible for their formation. Future work includes evaluating the taphonomy of the site, focusing on the vertebrae bones themselves. Some of the topics to be evaluated include orientation of the bones, disarticulation patterns, resolving which stratigraphic layer or layers contain bones, and evaluating the taxonomy of recovered taxa. Through this research we hope to learn more about the fossils, taphonomy, and depositional setting that created the Big Buffalo Quarry.