Geodiversity Atlas—Northern Great Plains Network Index

Photo of a badlands bluff with exposed gullies and ridges.
Badlands National Park, South Dakota. View from Yellow Mounds Overlook near Dillon Pass at sedimentary exposures of the Chadron Formation and Brule Formation of the White River Group overlying the Interior and Yellow Mounds paleosols.

NPS photo by Ed Walsh

Geology and Stratigraphy of the Northern Great Plains Network Parks

The Northern Great Plains Inventory and Monitoring Network consists of 13 national park units in portions of Montana, Nebraska, North Dakota, South Dakota, and Wyoming. The park units of the Northern Great Plains Network include Agate Fossil Beds National Monument, Badlands National Park, Devils Tower National Monument, Fort Laramie National Historic Site, Fort Union Trading Post National Historic Site, Jewel Cave National Monument, Knife River Indian Villages National Historic Site, Missouri National Recreational River, Mount Rushmore National Memorial, Niobrara National Scenic River, Scotts Bluff National Monument, Theodore Roosevelt National Park, and Wind Cave National Park. Together, the parks that comprise the Northern Great Plains Network protect a combined 177,100 hectares (437,700 acres) of land and vary in size from 178 hectares (440 acres) in Fort Union Trading Post to 98,239 hectares (242,756 acres) in Badlands.

The rich geologic history of the Northern Great Plains Network dates back more than a billion years, recording the growth of ancestral North America, the rise of the Rocky Mountains, shallow continental seaways, and Pleistocene glaciations. Some of the oldest rocks underlying the park units of the Northern Great Plains Network are Paleoproterozoic crystalline rocks in Mount Rushmore and Wind Cave that form the core of the Black Hills of South Dakota and Wyoming. These metamorphic and igneous rocks include the Harney Peak Granite, used as the in situ medium for the colossal sculpted busts of U.S. Presidents Washington, Jefferson, Roosevelt, and Lincoln at Mount Rushmore. The Harney Peak Granite was emplaced as a series of sills and dikes during an ancient tectonic collisional event known as the Trans-Hudson Orogeny that occurred approximately 1.7 billion years ago (Nabelek et al. 1999; Sirbescu and Nabelek 2003).

Following the Trans-Hudson Orogeny, the geologic record in the Northern Great Plains Network only provides episodic glimpses into the past until the late Cambrian Period, approximately 495 million years ago. The diverse Paleozoic and Mesozoic bedrock underlying the park units of the Northern Great Plains Network spans from the late Cambrian through the Cretaceous, providing a richer but still incomplete view of the evolution of North America. These bedrock strata were deposited during a series of marine transgressions (sea-level rise) and regressions (sea-level fall) associated with shallow, tropical continental seaways such as the Sundance Sea and Western Interior Seaway. The Mississippian Pahasapa Limestone was deposited in this kind of marine setting and is the predominant bedrock hosting the vast cave resources of Jewel Cave and Wind Cave. During the Late Cretaceous and Paleogene, approximately 80 to 50 million years ago, the Laramide Orogeny would elevate the Northern Great Plains and uplift the Rocky Mountains and the Black Hills region (Lisenbee 1988; Lisenbee and DeWitt 1993; Sirbescu and Nabelek 2003). The Black Hills contain several Northern Great Plains Network park units (Badlands, Devils Tower, Jewel Cave, Wind Cave) and represents an exposed basement uplift or arch that displays a central core of Precambrian crystalline rocks flanked by concentric ridges and valleys underlain by much younger Paleozoic and Mesozoic sedimentary strata (Keefer 1974; Lisenbee 1988).

At the beginning of the Cenozoic Era, the last remnants of the Western Interior Seaway retreated from the Northern Great Plains as highlands to the west continued to rise. Igneous activity associated with the continuation of the Laramide Orogeny produced several igneous intrusions including what is now Devils Tower at Devils Tower National Monument. Vast amounts of sediment were shed from the young Rocky Mountains and distributed as large wedges and sheets of clastic material across the central Great Plains region; many of these sediments contain the renowned fossiliferous strata of the Eocene–Oligocene White River Group (Badlands, Scotts Bluff, Wind Cave), Arikaree Group (Agate Fossil Beds, Badlands, Fort Laramie, Niobrara National Scenic River, Scotts Bluff), and Ogallala Group (Agate Fossil Beds, Niobrara National Scenic River). Volcanism in the Western Cordilleran region (Great Basin and Rocky Mountain areas) occurred from the Oligocene through Miocene and introduced thick blankets of pyroclastic material that are associated with the White River Group and overlying Sharps Formation. Rivers draining the high plains east of the Black Hills dissected the region of Badlands, exposing the iconic layer-cake stratigraphy of the park and sculpting the namesake badlands topographic landscape (Stoffer 2003). The Quaternary history of the Northern Great Plains Network includes a period of glacial advances and retreats that are recorded by only a few park units (Fort Union Trading Post, Knife River Indian Villages, Missouri National Recreational River, and Theodore Roosevelt National Park). A diverse assemblage of Quaternary deposits mapped throughout the Northern Great Plains Network are associated with fluvial landscapes associated with the Missouri River (Fort Union Trading Post, Knife River Indian Villages, Missouri National Recreational River), Niobrara River (Agate Fossil Beds, Missouri National Recreational River, Niobrara National Scenic River), North Platte River (Fort Laramie, Scotts Bluff), Belle Fourche River (Devils Tower), Knife River (Knife River Indian Villages), and Little Missouri River (Theodore Roosevelt National Park).

A Brief Geologic History—Northern Great Plains Network

A few examples of events and Network resources in each geologic time period are highlighted below, from youngest to oldest.

The park units of the Northern Great Plains Network contain a diverse suite of Cenozoic deposits that include world-renowned fossil beds, igneous intrusions, glacial deposits, and modern fluvial sediments. Several sedimentary formations are distributed across multiple park units such as the Paleocene Sentinel Butte Formation and Bullion Creek Formation (Knife River Indian Villages, Theodore Roosevelt National Park); Eocene–Oligocene White River Group (Badlands, Wind Cave, Scotts Bluff, and possibly Niobrara); Oligocene–Miocene Arikaree Group (Agate Fossil Beds, Badlands, Fort Laramie, Niobrara, Scotts Bluff); and Miocene–Pliocene Ogallala Group (Agate Fossil Beds, Niobrara). Other formally named Cenozoic deposits include the Paleocene Fort Union Formation in Fort Union Trading Post; Miocene Anderson Ranch Formation in Agate Fossil Beds; Pleistocene Coleharbor Formation in Knife River Indian Villages and Peoria Loess in Missouri National Recreational River; and the Quaternary Oahe Formation in Knife River Indian Villages. Igneous rocks that comprise Devils Tower in Devils Tower National Monument consist of an unnamed Paleogene phonolite porphyry (Bassett 1961).

A wide variety of young, Quaternary surficial deposits has been mapped across the parks of the Northern Great Plains Network and includes glacial outwash and till (Fort Union Trading Post, Knife River Indian Villages, Missouri National
Recreational River, Theodore Roosevelt), terrace deposits (Agate Fossil Beds, Devils Tower, Missouri National Recreational River, Wind Cave), aeolian sand and loess (Badlands, Fort Laramie, Missouri National Recreational River, Scotts Bluff), alluvial deposits (Mount Rushmore, Theodore Roosevelt National Park, Wind Cave), landslide deposits (Badlands, Theodore Roosevelt National Park, Wind Cave), rockfall deposits (Devils Tower, Mount Rushmore, Scotts Bluff), alluvium (Agate Fossil Beds, Badlands, Devils Tower, Fort Laramie, Fort Union Trading Post, Jewel Cave, Missouri National Recreational River, Niobrara, Scotts Bluff, Theodore Roosevelt National Park), and colluvium (Agate Fossil Beds, Fort Union Trading Post, Missouri National Recreational River, Scotts Bluff).
Rocks of the Mesozoic Era occur in five park units of the Northern Great Plains Network, with some of the oldest units occurring in both Devils Tower and Wind Cave. Strata of the Jurassic Gypsum Spring Formation and Sundance Formation are mapped in both parks, in addition to the Morrison Formation that exclusively underlies Wind Cave. The Cretaceous Pierre Shale is widely distributed across Badlands, Missouri National Recreational River, and Niobrara. Other Cretaceous sedimentary strata include the Dakota Formation, Graneros Shale, Greenhorn Limestone, 14 Carlile Shale, and Niobrara Formation in Missouri National Recreational River, as well as the Lakota Formation and Fall River Formation in Wind Cave.
Geologic units of the Paleozoic Era are mapped in only three park units of the Northern Great Plains Network. The oldest and most diverse assemblage of Paleozoic rocks is found at Wind Cave and includes sedimentary strata spanning from the Cambrian–Ordovician through the Permian. Several units are distributed across multiple park units, such as: the Mississippian Pahasapa Limestone (Jewel Cave, Wind Cave), an important carbonate formation hosting the Jewel Cave and Wind Cave networks; Pennsylvanian–Permian Minnelusa Formation (Jewel Cave, Wind Cave); and the Permian–Triassic Spearfish Formation (Devils Tower, Wind Cave). Additional Paleozoic units are only found at Wind Cave and consist of the Cambrian–Ordovician Deadwood Formation, Devonian–Mississippian Englewood Formation, and the Permian Opeche Shale and Minnekahta Limestone.
As mentioned above, the oldest rocks underlying the park units of the Northern Great Plains Network are Paleoproterozoic igneous and metamorphic rocks in Mount Rushmore and Wind Cave that form the exposed core of the Black Hills and include the Harney Peak Granite, metagraywacke, metamorphosed black shale, quartzite, and metapelite.

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    Type Sections—Northern Great Plains Network

    small image of a report cover with a tiny color photo

    The geologic history above is excerpted from a report titled, "National Park Service geologic type section inventory: Northern Great Plains Inventory & Monitoring Network". Type sections are essential reference locations for the geoscientists who study geologic history and paleontology. A summary of the type sections in each park can be found at the links below.

    • Agate Fossil Beds National Monument, Nebraska [Site Under Development]

    • Badlands National Park, South Dakota [Site Under Development]

    • Devils Tower National Monument, Wyoming (no designated stratotypes identified)

    • Fort Laramie National Historic Site, Wyoming (no designated stratotypes identified)

    • Fort Union Trading Post National Historic Site, North Dakota and Montana (no designated stratotypes identified)

    • Jewel Cave National Monument, South Dakota (no designated stratotypes identified)

    • Knife River Indian Villages National Historic Site, North Dakota (no designated stratotypes identified)

    • Missouri National Recreational River, South Dakota and Nebraska [Site Under Development]

    • Mount Rushmore National Memorial, South Dakota (no designated stratotypes identified)

    • Niobrara National Scenic River, Nebraska [Site Under Development]

    • Scotts Bluff National Monument, Nebraska [Site Under Development]

    • Theodore Roosevelt National Park, North Dakota (no designated stratotypes identified)

    • Wind Cave National Park, South Dakota (no designated stratotypes identified)

    The full Network report is available in digital format from:

    Please cite this publication as:

    • Henderson TC, Santucci VL, Connors T, Tweet JS. 2022. National Park Service geologic type section inventory: Northern Great Plains Inventory & Monitoring Network. Natural Resource Report. NPS/NGPN/NRR—2022/2439. National Park Service. Fort Collins, Colorado.

    NPS Stratotype Inventory

    Last updated: August 25, 2023

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