From purpose and scope: The purpose of this report is (1) to describe the flow system within the Kootenai Formation, which is the principal aquifer, and (2) to describe the interaction between the Kootenai and overlying and underlying Mesozoic aquifers.

Introduction: In 1978 the U.S. Geological Survey began a 4-year study of aquifers in the northern Great Plains. The purpose of this map, which is a product of that study, is to show the altitude of the top of the Lakota Formation and equivalent rocks. Other maps show the total thickness (Feltis, 1982a), cumulative thickness of sandstone (Feltis, 1982b), and potentiometric surface of water (Levings, 1982) in the Lakota Formation and equivalent rocks. These maps are part of a series that describes the geology and potentiometric surface of selected rock units of Jurassic or younger age in the plains area of Montana.

From introduction: In 1978 the U.S. Geological Survey began a 4-year study of aquifers in the northern Great Plains. The purpose of this map, which is a product of that study, is to show the total thickness of the Lakota Formation and equivalent rocks.

Introduction: In 1978 the U.S. Geological Survey began a 4-year study of aquifers in the northern Great Plains. The purpose of this map, which is a product of that study, is to show the cumulative thickness of sandstone in the Lakota Formation and equivalent rocks. Other maps show the altitude of the top (Feltis, 1982a), total thickness (Feltis, 1982b), and potentiometric surface of water (Levings, 1982) of the Lakota Formation and equivalent rocks. These maps are part of a series that describes the geology and potentiomentric surface of a selected rock units of Jurassic or younger age in plains area of Montana.