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.

From introduction: This report on the geology of the Powder River Basin is one of a series of reports by the Geological Survey on sedimentary basins in the United States.

From introduction: This is a progress report on regional stratigraphic and paleontologic studies of the Upper Cretaceous Montana Group and equivalent rocks in the northern part of the western interior of the United States. It presents preliminary data on the positions of strandlines during a 14-m.y. (million year) span of the Late Cretaceous as well as our interpretations of the geologic history of this period.

From introduction: This report details the reconnaissance for uraniferous lignites in North Dakota, South Dakota, Montana, and Wyoming during 1948 and 1949.

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.

Report discussing investigations seeking uranium in deposits of black shale around the geographical areas of the Western States

From abstract: The uppermost Cretaceous Lance Formation was studied in the Powder River Basin and nearby basins of Wyoming and Montana. The Lance Formation is overlain by the continental Paleocene Fort Union Formation. This report is a petrography and stratigraphy study on these basins.

From abstract: This report is a study on the history of sedimentology and deposition of the lower Paleocene Tullock Member of the Fort Union Formation, Powder River Basin, Wyoming and Montana while looking at the geometry and sedimentary structures.

From abstract: This report describes Cambrian through Mississippian rocks in the Powder River Basin representing five depositional sequences that reflect both the biological evolution and the tectonic development of western North America.

From abstract: This report contains complete Bouguer anomaly, isostatic residual anomaly, and horizontal gradient anomaly gravity maps of the Powder River Basin and surrounding areas in southeastern Montana, northeastern Wyoming, and western South Dakota were compiled using gravity data from 21,528 stations. A total-intensity anomaly aeromagnetic map with 3 mile spaced east-west flight-lines is also presented. Also included is an analysis of these maps and data, focusing on gravity and aeromagnetic studies.

Report discussing a geological study performed to find uraniferous lignites in North Dakota, Eastern Montana, north-central Wyoming, and northwestern South Dakota. "Deposits of uraniferous lignites were discovered at Blue Buttes, eastern Montana; and at North Cave Hills, South Cave Hills, and at Slim Buttes in northwestern South Dakota."

Report describing the phosphorite deposits of the western United States with the objective of outlining features that are common to both the Kara Tau phosphorite deposits of Russia and the western United States deposits in an effort to define their origin.

Report discussing investigation of the relation of uranium and phosphate in the Phosphoria formation and its close stratigraphic equivalents.

The following report analyzes geological studies on surficial deposits in the Sheridan quadrangle of Wyoming and Montana.

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

Abstract: This report lists the machine-readable data files developed for the Madison Limestone and Northern Great Plains Regional Aquifer System Analysis (RASA) projects that are stored on magnetic tape and available from the U.S. Geological Survey. Record format, file content, and size are given for: (1) Drill-stem-test data for Paleozoic and Mesozoic formations; (2) geologic data from the Madison Limestone project; (3) data sets used in the regional simulation model; (4) hydraulic-head data for the Lower and Upper Cretaceous aquifers; and (5) geologic data for Mesozoic formations of the Northern Great Plains.

From abstract: During fiscal years 1978 through 1981, the U.S. Geological Survey contracted for the acquisition and analysis of hydrologic data from 104 surface water stations, 26 ground water stations, and 15 precipitation gages as well as for several hundred miscellaneous surface water measurements of flow and water quality. The work was performed in Montana, North Dakota, Wyoming, Utah, New Mexico, and Oklahoma, terminating at the end of the fiscal year 1981. This report is an assessment of this contracting effort from the standpoint of cost and of quality control measures employed to ensure an acceptable product.

From introduction: The overall purpose of this study were twofold: (1) To determine where greatest yielding wells at shallowest depths would produce water of suitable quality for municipal and industrial supplies; and (2) to determine regional effects of additional water development on the hydrologic system.

Abstract: A digital simulation model was used to analyze regional ground-water flow in the Madison Group aquifer in the Powder River Basin and adjacent areas. Most recharge to the aquifer originates in or near the outcrop areas of the Madison in the Bighorn Mountains and Black Hills , and most discharge occurs through springs and wells. Results from the model calculations indicate that the total flow through the aquifer in the modeled areas was approximately 200 cubic feet per second (5.7 cubic metres per second). The aquifer can probably sustain increased ground-water withdrawals probably would significantly lower the potentiometric surface in the Madison aquifer in a large part of the basin. The digital model could better predict the effects of withdrawals if more accurate estimates of the storage coefficient, transmissivity, and leakance could be obtained.

A report explaining map symbols for the geologic map of the Northern and Western Flanks of the Black Hills, Wyoming and Montana.