Date of Award
Master of Science (MS)
The Grassy Butte area lies in southern McKenzie County, just southwest of the deepest part of the Williston Basin, and is bordered on the north by the North Unit of the Theodore Roosevelt National Memorial Park.
the purpose of this investigation was: (1) to prepare a geological map of the area; (2) to map the geologic structure of the area; (3) to measure and describe detailed stratigraphic sections which would aid in correlating rock units in this area with previously described rock units in adjacent areas; (4) to indicate lignite beds of possible economic value.
The western three-fifths of the Grassy Butte area is thoroughly dissected into badland topography, but the eastern two-fifths is an upland plain, the Missouri Plateau.
The Tongue River formation, including the Sentinel Butte member, and the Golden Valley formation are exposed at the surface. The Tongue River formation is Paleocene in age. The Golden Valley formation, of Eocene age, was determined to be more extensive in this area than was previously supposed, and the writer used as the base of the formation an horizon approximately 25 feet lower than the “orange marker bed” which had usually been used for mapping purposes before.
A series of north plunging noses and troughs were found to be present in the western part of the Grassy Butte area. To the south, in the adjacent Elkhorn Ranch area, the plunge of the easternmost nose is reversed and anticlinal closure results. The village of Grassy Butte is located on the crest of another anticline, trending northwest-southeast. The Little Missouri River flows over the easternmost nose, which seems to exert directional control on the course of that river. The outcrop pattern also seems to be controlled to some extent by the structure of the Paleocene beds in this area.
Meldahl, Elmer G., "The geology of the Grassy Butte area, McKenzie County, North Dakota" (1956). Theses and Dissertations. 198.