Geology topics
Research about Montana, Wyoming
Source-linked reports with geographic coverage including Montana, Wyoming.
Estimates of the ultimate number of oil and gas fields expected to be found in the Minnelusa Play of the Power River basin, Wyoming
No abstract available.
Estimated resources of non-leased federal coal, Powder River Basin, Montana and Wyoming
Maps are generated by combining digital ownership data with geologic resource estimates and other spatial coal data in a geographic information system (GIS). For example, we merged the newly compiled Federal coal ownership files with resource calculations from the 1970's for the Powder River Basin (Trent, 1986). For the first time, we are able to visually display the location of Federally owned coal in each 7.5' quadrangle along with the published coal resource estimates for those areas (fig. 8).
Preliminary charts of selected structure & thickness maps and diagrams from the Powder River Basin, Wyoming & Montana
No abstract available.
Hydrogeology and simulation of water flow in strata above the Bearpaw Shale and equivalents of eastern Montana and northeastern Wyoming
The Powder River, Bull Mountains, and Williston basins of Montana and Wyoming were investigated to understand the geohydrology and subsurface water flow. Rocks were separated into: Fox Hills-lower Hell Creek aquifer (layer 1), upper Hell Creek confining layer (layer 2), Tullock aquifer (layer 3), Lebo confining layer (layer 4), and Tongue River aquifer (layer 5). Aquifer transmissivities were estimated from ratios of sand and shale and adjusted for kinematic viscosity and compaction. Vertical hydraulic conductance per unit area between layers was estimated. Potentiometric surface maps were drawn from limited data. A three-dimensional finite-difference model was used for simulation. Five stages of simulation decreased and standard error of estimate for hydraulic head from 135 to 110 feet for 739 observation nodes. The resulting mean transmissivities for layers 1-5 were 443, 191, 374, 217, and 721 sq ft/d. The corresponding mean vertical hydraulic conductances per unit area between the layers were simulated; they ranged from 0.000140 to 0.0000150. Mean annual recharge across the study area was about 0.26 percent of average annual precipitation. Large volumes of interlayer flow indicate the vertical flow may be significant.
Lithofacies map, cross section, and favorable areas for uranium deposits, Powder River basin, Wyoming and Montana
No abstract available.
Flood estimates for ungaged streams in Glacier and Yellowstone National Parks, Montana
Estimates of 100-year discharges were made at 59 sites in Glacier National Park and 21 sites in Yellowstone National Park to assist the National Park Services in quantifying stream inflow and outflow in the Parks. The estimates were made using regression equations previously developed for Montana. The resulting 100-year discharges are listed in tables; the discharges ranged from 260 to 53,200 cu ft/s in Glacier National Park and from 110 to 27,900 cu ft/s in Yellowstone National Park. (USGS)
Map showing altitude of the top of the Swift Formation, Montana
No abstract available.
Thickness, percent sand, and configuration of shallow hydrogeologic units in the Powder River basin, Montana and Wyoming
No abstract available.
Petrology and petrography for USGS test wells 1, 2, and 3 in the Madison Limestone in Montana and Wyoming
The need for large quantities of energy has created interest in the Fort Union coal region of the Northern Great Plains. Extensive development of this coal, which may include on-site steam-power generation, gasification, liquefaction, and slurry-pipeline transport of the coal out of the region, would place a heavy demand on the region's limited streamflow. Paleozoic rocks that underlie the Fort Union coal region might supply, at least on a temporary basis, a significant part of the water required for coal development. Paleozoic rocks in the Northern Great Plains are related to the geologic history of the western border of the stable interior of the continent. The central part of the continental interior (Paleozoic craton) was made up of a stable core, the Canadian shield. To the west of the Canadian shield, the broad western flank of the Paleozoic craton made up the Cordilleran shelf, which is the site of the shallow-water marine rocks described in this report. The area of study covers approximately 200,000 square miles, and includes eastern Montana, western North Dakota and South Dakota, northeastern Wyoming, and northwestern Nebraska. The Madison Limestone, or Group, where it is divided, consists of a lower argillaceous limestone (Lodgepole Limestone); a middle unit of fossiliferous carbonate rock (Mission Canyon Limestone); and an upper unit of anhydrite, halite, and interbedded carbonate rock and shale (Charles Formation). The total section is made up of numerous cyclic, marker-defined units. The Madison Limestone was subdivided into units bounded by "marker beds" that consist of thin and widespread shaly carbonate or dark shale recognizable in the subsurface on geophysical logs. The five marker beds used for regional correlation purposes are as follows: M-1 represents the base of the Madison Limestone; M-3 is near the Kinderhookian-Osagean boundary; M-7 and M-8.5 fall within the Osagean; and M-12 is near the Osagean-Meramecian boundary. The top of the Madison Limestone is the Mc marker. Petrology and petrography of the Madison Limestone and associated rocks were studied from cores taken in three test wells of the U.S. Geological Survey. Six major rock types are recognized within cored intervals of the three test wells. Dolomite forms two-thirds of the total and limestone about 20 percent. The remainder consists of anhydrite, carbonate breccia, carbonate mudstone, and chert. Crystalline dolomite is the only abundant rock type in wells 1, 2, and 3 that has high enough porosity and permeability to provide significant yields of water. Crystalline dolomites not associated with evaporites may have formed by some sort of meteoric water-sea water mixing process in the subsurface shoreline environment by recrystallization of mud-rich limestones. Porosity and permeability values of all cored intervals of the Madison Limestone were determined. Mean porosity for the Madison Limestone is 8.4 percent, and mean permeability is 15.8 millidarcies. Because the Madison Limestone is relatively heterogeneous, permeability has a wide range in value.
Kriging analysis of mean annual precipitation, Powder River Basin, Montana and Wyoming
Kriging is a statistical estimation technique for regionalized variables which exhibit an autocorrelation structure. Such structure can be described by a semi-variogram of the observed data. The kriging estimate at any point is a weighted average of the data, where the weights are determined using the semi-variogram and an assumed drift, or lack of drift, in the data. Block, or areal, estimates can also be calculated. The kriging algorithm, based on unbiased and minimum-variance estimates, involves a linear system of equations to calculate the weights. Kriging variances can then be used to give confidence intervals of the resulting estimates. Mean annual precipitation in the Powder River basin, Montana and Wyoming, is an important variable when considering restoration of coal-strip-mining lands of the region. Two kriging analyses involving data at 60 stations were made--one assuming no drift in precipitation, and one a partial quadratic drift simulating orographic effects. Contour maps of estimates of mean annual precipitation were similar for both analyses, as were the corresponding contours of kriging variances. Block estimates of mean annual precipitation were made for two subbasins. Runoff estimates were 1-2 percent of the kriged block estimates. (USGS)
Long-term highwall stability in the northwestern Powder River basin, Wyoming and Montana
Time-dependent behavior of natural and and excavated slopes in sedimentary rocks is a subject that is poorly understood at present but that is now an important consideration in the design, operation, and reclamation of energy-extraction facilities, in part because of the environmental considerations mandated by the Surface Mining Control and Reclamation Act of 1977 (Public Law 95-87.) A slide in an abandoned, unreclaimed strip mine northwest of Sheridan, Wyoming, has been analyzed as an example of a long-term slop failure in the region. This slide occurred in early 1975, some 20 years after cessation of mining. This investigation used Spencer's limiting equilibruim method and an elastic-plastic finite element method incorporating the Drucker-Prager yield criterion.
Catalog of earthquakes in the Yellowstone Park - Hebgen Lake region from November 1972 to December 1975
The U.S. Geological Survey (USGS) began operating a network of seismograph stations in Yellowstone Park in 1964. The stations were self-contained and their locations were limited by the necessity for year-round access, 110-volt power, and a light-tight recording area. The network had a maximum of 5 permanent stations and was supplemented for 60 days in 1965 with up to 5 portable, battery-powered seismograph stations. Epicenters of earthquakes located with this network were published in Eaton et al. (1975).