The Geology of Theodore Roosevelt National Park, North Dakota

Theodore Roosevelt National Park is made up of three separate units — the North Unit, the South Unit and the Elkhorn Ranch Unit — along the Little Missouri River in Billings and McKenzie counties, western North Dakota. It was established as Theodore Roosevelt National Memorial Park on April 25, 1947, and became a national park on November 10, 1978. Covering about 28,508 hectares (70,447 acres), it protects scenic badlands and part of Roosevelt's Elkhorn Ranch.

The park honors Roosevelt's work to conserve the nation's natural resources, which included founding the U.S. Forest Service and establishing five national parks, 18 national monuments, 150 national forests and many wildlife preserves. The rugged, colorful North Dakota badlands helped inspire his conservation ethic, and they still inspire visitors.

The National Park Service's Geodiversity Atlas summarizes the park's geology, drawing on the Geologic Resources Inventory.

Setting

The park lies in the Great Plains physiographic province, on the line between the glaciated and unglaciated parts of the Missouri Plateau, and shares its geologic history with a region reaching far beyond its boundaries.

The rocks of the badlands

The bedrock beneath the park is Paleocene in age, and two formations are well exposed in the badlands:

• Bullion Creek Formation: yellowish-brown sandstone, siltstone and mudstone, found in the Elkhorn Ranch and South units.
• Sentinel Butte Formation: lying above the Bullion Creek, widespread in the North and South units, made of grayish-brown sediments with tuffs and beds of bentonite.

Younger Quaternary deposits are mapped across the park: upland gravels, mantled pediment deposits, landslide debris, alluvial sediments and alluvium.

Concretions and badlands. Image from the National Park Service's page.

Fossils and old mines

Fossils in the park, as in all national parks, are protected by the Paleontological Resources Preservation Act of 2009. More on them is on the park's fossils page. Abandoned mine sites in national parks can be valuable cultural sites and habitat, but many are hazardous to people and wildlife and harm water, landscapes and other resources: stay out and stay alive.

Maps and reports

The park's digital geologic map. Image from the National Park Service's page.

The Geologic Resources Inventory's scoping summary, digital geologic maps, report and poster for the park are on the NPS DataStore, along with its completed soil resources inventory. The park's own geology page has more.

Sources

• National Park Service: "NPS Geodiversity Atlas—Theodore Roosevelt National Park, North Dakota," citing Biek and Gonzalez (2001), Brinkley (2009) and National Park Service publications (2014, 2016). Its image of the inventory report's cover is not reproduced.