PALEONTOLOGY, SEDIMENTOLOGY AND STRATIGRAPHY OF THE POLESLIDE MEMBER, BRULE FORMATION, BADLANDS NATIONAL PARK

Badlands National Park has one of the best preserved records of Chadronian through Arikareean (North American Land Mammal Age) vertebrate faunas. Through the National Park Service Natural Resources Preservation Program, staff at Badlands National Park are working in partnership with cooperating museums and universities to further document the paleontology, stratigraphy, and sedimentology of the Poleslide Member of the Brule Formation. Data from this project will provide the basis for a paleontological inventory and monitoring program to further document this valuable resource. The Poleslide Member in the Cedar Pass Area is 50 meters thick and can be divided into three informal stratigraphic divisions. Individual beds in the Poleslide Member can be recognized throughout the Cedar Pass Area, which allows for high resolution stratigraphic positioning of vertebrate sites (to within the nearest 0.5 m). To date, over 1000 individual fossil sites have been located with high resolution GPS. A fossil site is defined as a cluster of fossils, ranging from isolated, identifiable vertebrate bone elements, to an entire skeleton, and includes clusters of snail shells or trace fossils. About 25% of the fossils are in situ specimens, and the rest occur as float. All sites are described in order to understand the areal distribution of the fossils. At the current time, 1.5 m sq. km of outcrop have been searched, and over 1000 fossil sites have been documented. Based on studies of paleosol profiles associated with vertebrate accumulations, environments within the Poleslide Member appear to have varied between long term stable land surfaces marked by dense zones of fossil roots, dung balls and burrows, and periods of rapid aeolian aggradation marked by massive volcaniclastic siltstones with sparse paleosol features.