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Research about Montana, Wyoming

Source-linked reports with geographic coverage including Montana, Wyoming.

At least 91 records · Page 5Linked to original sources
USGS1990

Isopach map of the interval from surface elevation to the top of the Pennsylvanian and Permian Minnelusa Formation and equivalents, Powder River basin, Wyoming and Montana

This map is one in a series of U.S. Geological Survey Miscellaneous Field Studies (MF) maps showing computer-generated structure contours, isopachs, and cross sections of selected formations in the Powder River basin, Wyoming and Montana. The map and cross sections were constructed from information stored in a U.S. Geological Survey Evolution of Sedimentary Basins data base. This data base contains picks of geologic formation and (or) unit tops and bases determined from electric resistivity and gamma-ray logs of 8,592 wells penetrating Tertiary and older rocks in the Powder River basin. Well completion cards (scout tickets) were reviewed and compared with copies of all logs, and formation or unit contacts determined by N. M. Denson, D.L. Macke, R. R. Schumann and others. This isopach map is based on information from 1,480 of these wells that penetrate the Minnelusa Formation and equivalents.

Montana, Wyoming↗
USGS1990

Map showing contours on the top of the Pennsylvanian and Permian Minnelusa Formation and equivalents, Powder River basin, Wyoming and Montana

This map is one in a series of U.S. Geological Survey Miscellaneous Field Studies (MF) maps showing computer-generated structure contours, isopachs, and cross sections of selected formations in the Powder River basin, Wyoming and Montana. The map and cross sections were constructed from information stored in a U.S. Geological Survey Evolution of Sedimentary Basins data base. This data base contains picks of geologic formation and (or) unit tops and bases determined from electric resistivity and gamma-ray logs of 8,592 wells penetrating Tertiary and older rocks in the Powder River basin. Well completion cards (scout tickets) were reviewed and compared with copies of all logs, and formation or unit contacts determined by N. M. Denson, D.L. Macke, R. R. Schumann and others. This isopach map is based on information from 1,480 of these wells that penetrate the Minnelusa Formation and equivalents.

Montana, Wyoming↗
USGS1989

Depositional aspects and a guide to Paleocene coal-bearing sequences, Powder River Basin

The Paleocene coal-bearing sequences in the northern Powder River Basin are contained in the Tongue River Member of the Fort Union Formation and include anomalously thick (54 m) subbituminous coals. These thick coals have been the target of exploration and development for the past few decades. For the past decade, these coals have also been the object of depositional modeling studies [Law, 1976; Galloway, 1979; Flores, 1981, 1983, 1986; Ethridge and others, 1981; Ayers and Kaiser, 1984; Warwick, 1985; Ayers, 1986; Moore, 1986; Warwick and Stanton, 1988]. Intensive modeling of these coals has resulted in two major schools of thought. Firstly, Galloway [1979], Flores [1981, 1983, 1986], Ethridge and others [1981], Warwick [1985], Moore [1986], and Warwick and Stanton [1988] believe that the coals formed from peat that accumulated in swamps of fluvial systems. The fluvial systems are interpreted as a basin axis trunktributary complex that drained to the north-northeast into the Williston Basin. Secondly, Ayers and Kaiser [1984] and Ayers [1986] believe that the coals formed from peat swamps of deltaic systems. These deltas are envisioned to have prograded east to west from the Black Hills and infilled Lebo lake that was centrally located along the basin axis. In order to explain the low ash content of the thick coals, Flores [1981] proposed that they are formed as domed peats, similar in geomorphology to swamps associated with the modern fluvial systems in Borneo as described by Anderson [1964]. Ethridge and others [1981] suggested that these fluvial-related swamps are platforms well above drainage systems and are fed by ground water that is recharged from surrounding highlands. Warwick [1985], Warwick and Stanton [1988], Satchell [1984], and Pocknall and Flores [1987] confirmed the domed peat hypothesis by investigating the petrology and palynology of the thick coals. The purpose of this paper is to provide a guide to the depositional aspects of the thick coals in the Tongue River Member of the Fort Union Formation and, because of the biases of the field trip leaders, it elaborates on the fluvial origin of the swamps in which the thick coals formed. Case histories of these thick coals and associated sediments in the Gillette, Powder River, and Kaycee-Linch areas of Wyoming and in the Decker-Tongue River area of Montana (fig. 1) are highlighted on this field trip.

Montana, Wyoming↗
USGS1989

Comparative facies formation in selected coal beds of the Powder River Basin

Petrologic studies of thick coal beds [Warwick, 1985; Moore, 1986; Moore and others, 1986; Moore and others, 1987; Warwick and Stanton, in press], which build on sedimentological interpretations [Flores, this volume] of associated units, provide data to interpret and contrast the varieties of peat formation in the Powder River Basin. Detailed analyses of the composition of coal beds lead to more complete interpretations regarding the depositional environment on a regional and local scale. Our efforts in the Powder River Basin [areas A-D in fig. 1 of Flores, this volume] have resulted in a series of site-specific studies that interpret the types of peat formation from the arrangement of different facies which comprise the coal beds and from the spatial form of the coal beds. Our approach was to use a combination of megascopic criteria for facies sampling, and where only core was available, to analyze many interval samples to discriminate facies by their maceral composition. Coal beds in the Powder River Basin are composed of laterally continuous, compositional subunits of the bed (facies) that can be discerned most easily in weathered highwall exposures, less readily in fresh highwalls, and very poorly in fresh-cut core surfaces. In general, very low ash (

Montana, Wyoming↗
USGS1988

A seismic-stratigraphic investigation of the Madison and associated aquifers; application to ground-water exploration, Powder River basin, Montana-Wyoming

This seismic-stratigraphic investigation is part of a larger 5-year project the "Madison Project" undertaken by the Water Resources Division of the U.S. Geological Survey to study the hydrology of the Madison and associated aquifers. The objectives and methods of investigation of the Madison Project are described by the U.S. Geological Survey (1975).

Montana, Wyoming↗