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Research about Powder River County, Montana

Source-linked reports with geographic coverage including Powder River County, Montana.

16 recordsLinked to original sources
USGS2013

Erosional and depositional changes wrought by the flood of May 1978 in the channels of Powder River, southeastern Montana

Powder River’s second largest flood of record (1919–2012) moved through northeastern Wyoming and southeastern Montana during May 1978. Within a ninety-kilometer reach of the channel in southeastern Montana, the most prominent planform effects of the flood were the growth of meander bends by bank erosion (this was most intense just downriver of bend apexes, causing 1–2 channel widths of lateral displacement) and the erosion of new cutoff channels through the necks of two large and two small meanders. Surveys of cross sections, made before and after the flood, show the responses of the channel to the flood waters, which ranged from minimal (bedrock control) to large (maximum channel curvature in unconsolidated bank and terrace deposits). Geomorphic work done during two weeks of extreme flooding in May 1978, as measured by cross-channel erosion and new sediment deposition, was approximately equal in magnitude to the work done during the two decades (1978–1998) that followed the flood.

Montana↗
USGS1979

Coal resource and coal quality of Pumpkin Creek EMRIA site, Powder River County, Montana: With a section on chemical analysis

The Pumpkin Creek EMRIA site, an area of about 94 square miles, is located mainly in the southwestern part of the Coalwood coal field on the slightly westward dipping beds of the Tongue River Member of the Paleocene Fort Union Formation in Powder River County, Montana. Three coal beds, A, Sawyer, and Mackin-Walker, were evaluated by 32 drill holes. Coal resources--measured, indicated, and inferred--within the site and in beds more than 5 feet thick are 191,660,000 short tons, 1,356,950,000 short tons, and 34,400,000 short tons, respectively. The coal has an apparent rank of lignite A as shown by the analyses of 17 core samples. The average Btu value of 15 core samples of the Sawyer from the site on the as-received basis is 6,970, average ash content is 6.8 percent, and average sulfur content is 0.4 percent. A comparison of the analyses of samples from the Sawyer coal bed with other analyses of Powder River region coal samples shows that moisture, hydrogen, and oxygen contents are significantly higher, and volatile matter, fixed carbon, carbon, nitrogen, and total sulfur contents and heat of combustion are significantly lower in the Sawyer bed samples. A statistical comparison of the elemental compositions of the two sample groups shows that the Sawyer bed has significantly higher contents of B, Ba, Mn, Nb, U, Y, and Yb and significantly lower contents of Be, Co, Cr, Cu, Ni, Pb, Sc, Se, and Th. The sample of the lower split of the Sawyer bed (bed A) in drill hole PWW8 has a relatively high sulfur content of 1.7 percent, and presumably would not be mined with the rest of the Sawyer. The Mackin-Walker has a Btu value of 7,220, an ash content of 6.9 percent, and a sulfur content of 1.0 percent.

Montana↗