US Geological Survey


Date of this Version



The Journal of Geology, Vol. 21, No. 6 (Sep. - Oct., 1913), pp. 550-556


Rocks of White River (Oligocene) age have been known for many years to constitute numerous isolated buttes and mesas in the northwest corner of South Dakota, but no detailed study of their character and structural relations had been made until 1911, when, during an examination of the lignite area of that country, the writer had occasion to study the relation of the younger rocks to those containing lignite beds.

Todd, in 1895, recognized the White River formation in the Slim Buttes and called attention to the area in the following language:

3. Miocene beds, both White River and Loup Fork, with characteristic fossils, have been found overlying wide areas of the Laramie north of the Black Hills, covering quite deeply most of Harding County, with thin outliers over the north half of Butte County and south half of Ewing. In the Short Pine hills and Slim Buttes these deposits exhibit a depth of 200 to 400 feet with characteristic fossil features closely resembling those of the White River region.

4. An area of disturbance was found in the north half of Slim Buttes in northeast Harding County covering perhaps 20 to 25 square miles. This consists of sharp folds, including the Laramie and White River beds, with throws of perhaps 100 feet and dips of 25 degrees.

It is the purpose of this paper to show that the inclination of beds described above, as well as those exposed at several other localities in the Slim Buttes, is not a true dip due to a dynamic disturbance but is cross-bedding due to the peculiar manner of the accumulation of the White River formation.