|Madison Group, Williston Basin
The Madison carbonate-evaporite system was deposited in carbonate-platform environments that graded laterally and vertically to deep-water facies. The Madison Group is formed by the Lodgepole Limestone (cyclic carbonate sequence), Mission Canyon Limestone (coarse limestone to finer limestone and evaporates at the top), and the Charles Formation (evaporite sequence, anhydrite, and halite). Vertical leakage is restricted by shale, halite beds, and stratigraphic traps or low-permeability zones.
Downey, J. S., 1986, Geohydrology of bedrock aquifers in the northern Great Plains in parts of Montana, North Dakota, South Dakota and Wyoming: U.S. Geological Survey Professional Paper 1402-E, 87 p.
Downey, J. S., 1984, Geohydrology of the Madison and associated aquifers in parts of Montana, North Dakota, South Dakota and Wyoming: U.S. Geological Survey Professional Paper 1273-G, 47 p.