|Madison Group, Williston Basin
The Big Snowy Group top seal has a restricted extent and is present only in part of Montana and the east part of North Dakota. Fracture systems and lineaments affect the fluid flow by performing either as barriers or as conduits. A facies map for the Big Snowy Group, a Paleozoic structural fault map, and the lineament pattern map were added to the GIS data base for this area.
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.