From abstract: The northern Black Hills bentonite mining district includes parts of Crook County, Wyo., Carter County, Mont., and Butte County, S. Dak. Within this district, many beds of bentonite occur interspersed with sedimentary strata of Cretaceous age that have an average total thickness of about 3,000 feet and consist chiefly of marine shale, marl, and argillaceous sandstone. The bentonite beds occur in formations ranging upward from the Newcastle sandstone to the lower part of the Mitten black shale member of the Pierre shale. Tertiary (?) and Quaternary deposits of gravel, sand, and silt are present on extensive terraces, and deposits of such materials also extend along stream courses in all parts of the district.

From introduction: This report is intended as a descriptive summary. The fieldwork on which it is based was completed in the central Western States in 1952-56, and additional studies were made in the Central and Eastern States before and after the western studies. Research and compilation were completed in 1956-59. Other reports will describe in detail the geology and origin of the oxidized zinc deposits in Colorado, Utah, Nevada, and California. (See also Heyl and Bozion, 1960.)

Introduction: "A program of geological mapping and exploratory core drilling was carried out from 1951 to 1953 by the U.S. Geological Survey on behalf of the U.S. Atomic Energy Commission to determine the areal distribution, thickness, and uranium content of coal in the eastern part of the Red Desert area, Sweetwater County, Wyo. Results of the field an laboratory studies of the distribution of uranium and other trace metals and hypotheses concerning the origin and mode of emplacement of the trace elements in the coal are presented in this report."