Badlands National Park is host to perhaps the most scenic geology and landscape features in the Western Interior region of the United States. Ongoing erosion that forms the "badlands" exposes ancient sedimentary strata of Late Cretaceous through Oligocene age. Quaternary erosional and depositional processes are responsible for most of the modern landscape features in the park and surrounding region. This report provides a basic overview of the park geology The discussions presented within include both well-established concepts and theories and new, preliminary data and interpretations. Much emphasis is placed on presenting information about the oldest and least studied rocks in the park (particularly the Late Cretaceous and earliest Tertiary deposits that underlie the White River beds throughout the park region). Rock formations and selected fossils they contain are described. Faults, folds, unconformities, and other geologic structures in the North Unit of the park are illustrated, including features associated with the Sage Creek anticline and fault system.
