Geology of the Fort Peck area, Garfield, McCone, and Valley Counties, Montana

Abstract

The Fort Peck area, in the central part of northeast Montana, includes a little more than three 15-minute quadrangles and covers an area of about 600 square miles. The area is in the northern part of the Great Plains physiographic province and is predominantly an undulating grassy treeless prairie upland which rises gradually to the north. The Milk and Missouri Rivers have carved their channels into this prairie upland, so that steep scarps as much as 200 feet high border the wide bottom lands. South and southwest of the rivers, the surface rises abruptly and irregularly through a belt of "breaks" to a rolling dissected prairie with badland areas along many of the drainage courses.