Keywords:
Environmental degradation
Degradation
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The Little Bear Creek area of the Moorhead Coal Field, 27 miles south of Ashland, Montana, contains large reserves of Federally owned coal that have been identified for potential lease sale. A hydrologic study was conducted in the area to describe existing hydrologic system and to assess potential effects of surface mining on local water resources. Hydrologic data collected from private wells, observation wells, test holes and springs indicate that the aquifers are coal and sandstone beds in the upper part of the Tongue River Member, Fort Union Formation (Paleocene age), and sand and gravel layers of valley alluvium (Pleistocene and Holocene age). Surface water is available from ephemeral flow along stretches of the main streams, and from stock ponds throughout the area. Mining the Anderson and Dietz coal beds would destroy one stock well and several stock ponds, would possibly interfere with the flow of one spring, and would lower the potentiometric surface within the coal and sandstone aquifers. The alluvial aquifer beneath Little Bear Creek and Davidson Draw would be removed at the mine site, as would sandstone and coal aquifers above the mine floor. Although mining would alter existing hydrologic systems, alternative water supplies are available. Planned structuring of the spoils and reconstruction of the alluvial aquifers could minimize downstream water-quality degradation. (USGS)
Alluvial fan
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The Deep Creek and Reservoir-North Roadless Areas in northwest Montana contain highly thrust faulted and folded sedimentary rocks that range from Cambrian to Early Cretaceous in age.The areas have a high potential for hydrocarbons and a low potential for metallic mineral resources.The areas contain high purity dolomite and high calcium limestone.The roadless areas contain hydrocarbon source rocks, reservoir rocks, and structural traps.The thermal history of the area suggests that the potential for gas accumulation is greater than the potential for oil.
Mineral resource classification
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Quadrangle
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potential 3 Introduction 3 Appraisal of identified resources 5 History of mining 5 Identified resources 5 Assessment of potential for undiscovered resources 5 Geology 5 Geochemistry 6 Geophysics 8 Gravity and magnetic studies 8 Gravity-anomaly data 8 Magnetic-anomaly data 9 Conclusions 9 Electrical studies 9 Mineral and energy resources 12 References cited 12 Appendix 15 PLATE [Plate is in pocket] 1. Maps showing mineral resource potential, geology, geochemical sample localities, and geophysical data for the Farlin Creek Wilderness Study Area FIGURES 1. Index map showing location of the Farlin Creek Wilderness Study Area and mining districts 2 2
Mineral resource classification
Wilderness area
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Bedrock
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Mercury
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