Geology and ground water resources of Wells County, North Dakota

Wells County is in east-central North Dakota on the eastern flank of the Williston Basin. It is underlain by 4000 to 6000 feet of Paleozoic and Mesozoic rocks that dip gently to the west. The uppermost Cretaceous rocks, the Hell Creek, Fox Hills and Pierre Formations, lie directly beneath the glacial drift; isolated exposures of the Fox Hills and Pierre rocks occur in the Sheyenne River valley. Glacial drift covers the entire area averaging about 100 feet thick. In certain buried valleys it is more than 400 feet thick.