A report about the Duck Creek Pass quadrangle which forms a large part of the bedrock of western Montana and adjoins other areas in which geologic studies are already completed or in progress.

A report which includes 200,000 square miles in the southern part of the Williston basin of North Dakota, South Dakota, and Montana. The Devonian rocks consist mostly of marine carbonate, evaporite, and shale beds.

A report which compares 20,000 feet of Belt rocks in the Mission Mountains Primitive Area in Montana with 40,000 feet of Belt rocks in the Pend Oreille area in Idaho and Montana.

A report about phosphates found in the Permian Phosphoria formation of the Rocky Mountains. This area constitutes one of the worlds largest reserves of phosphate.

A report about the Clark Fork quadrangle which is underlain by more than 38,000 feet of low-grade metasedimentary rocks of the Precambrian Belt series. The quadrangle has both metallic and nonmetallic mineral deposits of considerable value.

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: The St. Regis-Superior area was studied during the summers of 1953 and 1954 as a part of geologic investigations by the U.S. Geologic Survey in and near the Coeur d'Alene district. The object of the present work was primarily threefold: to ascertain the main structural features in the area, with particular attention to the Osburn fault zone; to investigate the mineral deposits; and to determine the stratigraphic relations of the rocks.

From abstract: The chromite deposits of the central part of the Stillwater complex lie in a belt 9 miles long between the valleys of Boulder River and the West Fork of the Stillwater River in Sweet Grass County, Mont. The chromite occurs as layers near the middle part of the ultramafic zone in the lower part of the complex. The layers, originally horizontal, have been tilted so that they dip northeastwards at angles ranging from nearly horizontal to nearly vertical, and are cut by many cross faults, the largest with a horizontal offset of 3,000 feet. Investigations by the United States Geological Survey and the United States Bureau of Mines have shown that in this belt there are 5 sections ranging in length from 850 to 3,800 feet along the strike where the continuity and grade of the chromite can be reasonably inferred.

From introduction: The Stanford-Hobson area project was undertaken by the United States Geological Survey, in cooperation with the United States Bureau of Reclamation, as part of a program for the geologic mapping and investigation of mineral resources in the Missouri River basin. The field work that is the basis of the ensuing report consisted of mapping the geology and determining stratigraphic relationships in sufficient detail to evaluate the mineral resources, especially the oil and gas possibilities in the area.

From introduction: This reconnaissance study was undertaken to determine the major geologic features of the western part of Mineral County, Mont., principally in the drainage basin of the St. Regis River.

From abstract: The Rosebud coal field, named from Rosebud Creek and the village of Rosebud, includes an area of about 1,050 square miles and forms a very small part of the subbituminous and lignite coal fields of eastern Montana and Wyoming and the western part of the Dakotas. It is an irregularly bounded tract lying south of the Yellowstone River in eastern Rosebud County and western Custer County and measures 50 miles from east to west and 28 miles from north to south. It adjoins the Forsyth coal field, on the west, the Ashland coal field, on the south, and the Miles City coal field, in part, on the north.

From abstract: The Richey-Lambert coal field is an area of about 900 square miles in Richland and Dawson Counties, eastern Montana, along the divide between the Missouri and Yellowstone Rivers. In this region only flat-lying continental rocks occur near the surface. About 300 feet of the Lebo shale member and about 930 feet of the coal-bearing Tongue River member of the Fort Union formation, of Eocene age, are exposed in the area. Deposits of terrace gravel at two levels in the field are tentatively correlated with the gravel on the Cypress Hills, Saskatchewan, which has been assigned to the Oligocene by the Canada Geological Survey, and with the Flaxville gravel, of upper Miocene or Pliocene age.

From abstract: This paper gives the results of a resurvey of certain areas in Montana to which renewed interest has been directed by the development recently of a market for crude phosphate rock in British Columbia, nearby.

From abstract: This report describes a rectangular area of about 2,600 square miles in Chouteau, Hill, and Liberty Counties, Mont., adjacent to the international boundary. The area is a portion of the Missouri Plateau, a section of the Great Plains province, and lies between the Highwood Mountains, Bearpaw Mountains, and Sweetgrass Hills, of north-central Montana. The southern part of the area is drained by the Missouri River and its tributary Marias River, but the northern part is drained by the Milk River. These streams are trenched in narrow valleys several hundred feet deep. The land surface between them is a rolling plain interrupted by very broad, shallow valleys that probably were eroded during the Pleistocene epoch by large streams whose courses were doubtless diverted from time to time by the continental glaciers. These valleys are now occupied only by very small creeks.

This report follows geological studies of the Duck Creek Pass quadrangle, Montana during the summers of 1956 and 1957.

This report gives a brief geological description of the Clark Fork quadrangle on the Idaho-Montana border.

This report studies Devonian rocks in an approximately 200,000-square-mile area between Williston Basin, central Montana, and north-central Wyoming.

This report studies the several aspects of the basalts in the Columbia River Basalt Group in the Spokane quadrangle, Washington, Idaho, and Montana.

This report investigates the physical stratigraphy of the Permian Phosphoria formation of the central and northern Rocky Mountains.

The following report presents the geology and mineral resources of part of the Anaconda quadrangle near Butte, Montana.

The following report presents an evaluation of the mineral potential of the Spanish Peaks primitive area, Montana.