Geohydrology of the Madison and associated aquifers in parts of Montana, North Dakota, South Dakota, and Wyoming

Abstract

Precambrian rocks _______________________________________ Cambrian and Lower Ordovician rocks ___________________________ Ordovician rocks ___.________________.________________.___ Silurian and Devonian rocks ____________________________._____ Mississippian rocks _______________________________________ Pennsylvanian and Permian rocks _______________________________ Triassic rocks ___________________________________________ 14 Jurassic rocks ___________________________________________ 14 Geologic structure _______________________________________ Hydrologic setting__.________________________________.______ Description of digial-simulation model _______________________________ Theory ..

Aquifer systems in the Great Basin region of Nevada, Utah, and adjacent states; summary report

“…Thus the ages could be overestimated if more vein calcite, which has lighter carbon-13 composition than the primary calcite, is exchanging carbon with the water than the 50 percent assumed for determining ages for flow-velocity estimates. However, age-calculated flow velocities, 9.6 to 144 ft/yr, are in the range of velocities simulated for the Madison aquifer in Montana, Wyoming, and South Dakota (Downey 1984). The Madison aquifer is a carbonate-rock aquifer similar to the carbonate-rock aquifers of southern Nevada.…”

Geologic framework for the national assessment of carbon dioxide storage resources: Williston Basin, Central Montana Basins, and Montana Thrust Belt study areas

“…Average porosity in the porous intervals of the Kibbey Formation and Madison Group SAU is 7 to 16 percent, with a most likely value of 10 percent (Nehring Associates, Inc., 2010). Net-togross was interpreted from geophysical logs and porous interval contour maps (Downey, 1984(Downey, , 1986, and resulted in an average net porous interval thickness that ranges from 150 to 450 ft, with a most likely value of 300 ft for the Kibbey Formation and Madison Group SAU. Average permeability in the SAU is 0.01 to 1,800 mD, with a most likely value of 4 mD (Nehring Associates, Inc., 2010).…”

Major geochemical processes related to the hydrology of the Madison aquifer system and associated rocks in parts of Montana, South Dakota, and Wyoming

“…The following discussion of geohydrology is based largely on the results of the geohydrologic study conducted for the Madison project by Downey (1982).…”