Missouri River Corridor Geologic Mapping

Science Center Objects

The priority area of mapping for this task is the reach spanned by the Missouri National Recreational River (MNRR), a unit of the National Park Service. MNRR comprises the congressionally designated reaches (2) of the Missouri River: the 59-mile reach below Gavins Point (GP) Dam, and the 39-mile reach above Lewis and Clark Lake (the reservoir held in by GP dam, which is the lowest of the 6 largest mainstem impoundments in the Dakotas up to Fort Peck in eastern Montana). The MNRR lies along the boundary between southeast South Dakota and northeast Nebraska. The lower 59-mile reach below GP dam was designated in part for its less modified condition relative to the heavily channelized condition of the remaining 750 miles of the lower river to Saint Louis.

A Task of the Greater Platte River Basins and Northern Plains Geologic Framework Studies Project.

 

The Missouri River, the longest river system in the United States, forms a major geomorphic, hydrologic, and ecologic corridor within the nation. The lower Missouri River begins at Gavins Point Dam, the lowest dam on the mainstem river. The corridor of the lower river is distinctive in its geomorphology from that of the upper river. The lower river has a much wider flood plain and bottomland (up to 30 km in width), which constrained engineering works to include channelization rather than the major dams which were built along the upper river. The abrupt transition from the upper river to the broad bottomland of the lower river coincides with the southern extent of the James River lobe of the late Wisconsin Laurentide ice sheet.

Geologic Setting

The Missouri system developed in response to both Laurentide ice sheet glaciation and to glaciation of the Rocky Mountains. About 12% of the Missouri River Basin is montane, heading on the east slope of the Continental Divide through portions of the Northern, Middle, and Southern Rocky Mountains. The course of the river through the northern and central Great Plains is near the southern limit of Pleistocene continental glaciation. Through Montana and the Dakotas, much of this glacial limit was reached by ice sheets of the latest (Wisconsinan) glaciation, but in Nebraska, Kansas, and Missouri the glacial limit was reached only during much earlier glaciations.

Project mapping area as situated in the Missouri River Basin

Segments (reaches) of Missouri National Recreational River (MNRR).

Project Objectives

The overall objective of this task is to produce integrated modern geologic mapping along the Missouri National Recreational River corridor, defined to include the river valley and adjoining uplands. The geologic mapping will provide data and interpretation in products for multiple users, including the National Park Service.

Photo of bluff exposure along Niobrara River marked with Ql, Kn, and Kc units

Bluff exposure on south side of river shows Quaternary loess (Ql) with buried soil over Niobrara Formation chalk (Kn) over Carlile shale (Kc). (Credit: Scott Lundstrom, USGS GECSC)

Photo of large gravel along Missouri River

Glacial outwash gravel forming south bank of the Missouri River near Yankton, South Dakota. (Credit: Scott Lundstrom, USGS GECSC)

River sediments

Typical pre-dam, postglacial young river sediments that form the surface of much of the modern river valley. The well-sorted point bar and channel sand (lower left) contrasts with overlying finer, heterogeneously bedded overbank and channel-fill sediments that are the parent materials of the surface soil. (Credit: Scott Lundstrom, USGS GECSC)

Yankton Area Geologic Map (Lundstrom and others, 2009; Moreno-Ward and others, 2010)

Yankton Area Geologic Map (Lundstrom and others, 2009; Moreno-Ward and others, 2010)