Geologic Map of the Canyon Ferry Dam
30’ x 60’ Quadrangle, West-Central Montana

The geologic map of the Canyon Ferry Dam 30’ x 60’ Quadrangle, West-Central Montana, portrays the geology within an area of approximately 4,200 square kilometers, extending from near the capital city of Helena east approximately 74 kilometers and 55 kilometers from south to north. The area encompasses the scenic canyons of the Missouri River, the Gates of the Rocky Mountains, and the Smith River through the west end of the Little Belt Mountains. It includes some of the most complicated geologic structures in the Rocky Mountain thrust belt as well as geologically young basins resulting from faults that are still active.

Three map sheets and an extended pamphlet, which comprise U.S. Geological Survey Scientific Investigations Map 2860, describe details of the geology and the many rock units. Earth scientists, government agencies, ranchers and farmers, and visitors to this scenic area can use the publication for mineral, fossil fuel, and water resource exploration; land-use planning; and understanding views during scenic tours. Sheet 1, shown in part here, features the geologic map, tectonic map, and associated geologic cross sections.