Hydrogeology of the Shell Creek area, Mountrail County, North Dakota

A field study of the geology and hydrology of the Shell Creek area in southeastern Mountrail County, North Dakota, was made during 1966 in order to determine the hydrogeology of the area. Six lithostratigraphic and lithologic units were mapped. Samples were analyzed for grain size and mineralogy. Those units are the Fort Union Group, the “Lostwood” slightly-gravelly loam, the “Lostwood” sand-gravel, the “Lostwood” silt-clay, the “Little-Knife Formation”, and the “Coteau Formation”. Mine average maximum slope and drainage integration units were used to map the morphology of the area. There are four magnitudes of flow systems observed in the Shell Creek area: (1) very small magnitude flow systems, a few hundred feet wide, characterized by seasonal variations in the flow, rapid flow of water through the system and bicarbonate-rich waters; (2) small magnitude flow systems, a few thousand feet wide, characterized by sulfate and bicarbonate waters, and a flow duration of a few years; (3) intermediate magnitude flow systems, a few miles wide, characterized by lignite and sand and gravel aquifers, which are the principal aquifers in the area, and by the high sodium sulfate content of the water; and (4) regional magnitude flow system, many tons of miles wide, characterized by sulfate and chloride-rich waters and by very long flow duration. The flow-system approach to the analysis of the hydrogeology of the Small Creek area is very informative and easy to use. It emphasizes the dynamics of the hydrogeologic system and relates it to the rest of the hydrologic cycle