Geology of the National Parks in Pictures - Effigy Mounds National Monument

My next post about the Geology of the National Parks Through Pictures is from our move across the country from Utah to New York. Along the way we visited 13 National Parks as well as some other sites. This was the 12th National Park along the way.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

-----------------------------------------------------------------------------

Effigy Mounds National Monument

Obligatory entrance sign

Great Bear Mound

Created by ancestral people known as the Effigy Moundbuilders, the mounds served several different purposes. Primarily they were used for human burial purposes by piling soil, sod, and clay, along with other materials, in the shapes of animals over the bodies of the deceased. These shapes include birds, bears, water spirits, deer, turtles, beaver, buffalo, canines, and other animals, however the shapes are often difficult to identify along when viewed at ground level. The Lidar image below gives an excellent example of an aerial view of the mounds, with each of these marching bear mounds reaching around 20 meters in length. 

Lidar of the Marching Bear Group in the southern portion of the park. Image courtesy of the NPS via Wikimedia.

Found throughout the region, most of the mounds within the park are conical in design. However mounds, like the Great Bear Mound, form the shape of animals (pictured from ground level above). There are also linear and compound designs found within the park, but in far fewer numbers.

Types of mounds found at Effigy Mounds NM. Image courtesy of National Park Planner. 

The construction of at least some of the mounds began by first removing the sod or leafy humus from the forest floor. A square shaped pit was then dug out and human bodies were laid to rest within the pit. One of the excavated mounds held four bodies. Soil was then piled up upon the bodies along with rocks and clam shells. Cremation ashes mixed with baked reddish clay were mixed in with the final layer of earth on top of the mound. 

The location of the mounds, especially within this region, were generally along elevated surfaces. These mounds, in the picture above, are the end of a linear series of conical mounds that end at a promontory overlooking the Mississippi River (below). By placing the mounds at an elevated location they remained isolated from the flooding common to the shores of the Mississippi River.

All of the mounds within the park are located upon an elevated plain overlooking the Mississippi River, with tributary rivers, like the Yellow River adjacent to the entrance and Visitor's Center, carving deep valleys within the plateau. The plateau is comprised primarily dolostone (a more weathering resistant variety of limestone) and sandstone. Both provide a surface that is slow to erode away.

Prairie du Chien Group seen along the hike up to the mound plateau on the northern portion of the park. 

Geologically, the mounds sit upon the Lower Ordovician age (~480 million years ago) Oneota and Shakopee Formations, which make up the Prairie du Chien Group. These beds are primarily made up of dolomite, quartz sandstone, and sandy dolomite. There is also significant amounts of chert within the beds. Below the Prairie du Chien Group, you can also see the older, Upper Cambrian in age (~490 million years old), Jordan Sandstone along the parts of the park that border the Yellow River. Both of these formations were deposited when the area was inundated by a vast sea. The sea ebbed and flowed across the land, alternating periods of deep water deposits as well as shallow coastline deposits. When the water was shallower, sand would be deposited along the coastal waters. As the water deepened, limestones and dolostones (a variety of limestone that has a high concentration of magnesium within the crystal structure), were deposited from the bodies of sea life that slowly died over time.    

Glacially, Effigy Mounds is in the Driftless Area of Iowa, meaning that it was never covered with glaciers. While these elevated plateaus did not feel the effects of glacial activity, the neighboring Mississippi River was carved out by glacial meltwaters, with glacial debris filling up the river valley up to 150 feet. 

3 Mounds

While the park is primarily an archeological site, geology plays a major role. By providing the elevated location for the mounds, to suppling the materials used that were incorporated within the mounds, such as the dolostone, clay, along with the soil and sod, geology was a major contributor to the building of the Effigy Mounds. 

References

https://www.nps.gov/efmo/learn/nature/geologicformations.htm

https://ngmdb.usgs.gov/Prodesc/proddesc_78247.htm

https://lakeshorepreserve.wisc.edu/native-americans-and-the-preserve/

https://npplan.com/parks-by-state/iowa-national-parks/effigy-mounds-national-monument-park-at-a-glance/effigy-mounds-national-monument-south-unit/effigy-mounds-national-monument-hike-to-the-marching-bear-group/

https://www.nps.gov/efmo/learn/nature/naturalfeaturesandecosystems.htm

https://commons.wikimedia.org/wiki/File:Effigy_mounds_lidar.jpg

Geology of the National Parks in Pictures - Pipestone National Monument

My next post about the Geology of the National Parks Through Pictures is from our move across the country from Utah to New York. Along the way we visited 13 National Parks as well as some other sites. This was the 11th National Park along the way.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

-----------------------------------------------------------------------------

Pipestone National Monument

Obligatory entrance sign photo

Pipestone National Monument is a sacred Native American site, known as Inyan Sa K'api to the Dakota People. It is here that they quarry the pipestone rock in order to carve pipes for ceremonial use, as well as other objects with smaller pieces of the rock. 

The geology of Pipestone National Monument has three distinct rock types. The two primary rock types are quartzite and the pipestone layer. Seen in the picture above, the floor of this outcrop quarry is the Sioux Quartzite. At the base of the wall in the picture is a thin red layer. This layer is the pipestone layer, a rock known as catlinite or Siouz Argillite. Above the Catlinite is the continuation of the Sioux Quartzite, with the third type of rock in the park, conglomerate, above the quartzite. 

The Sioux Quartzite initially formed ~1.6 billion years ago along a braided river system. This is similar to what is seen in many rocky mountains and colder climate regions today (such as Canada's Banff National Park). Within the quartzite formation, several different types of deposits can be seen including different portions of the braided river system like channel-floor lag deposits, in-channel deposits, nearly filled channel deposits, and vertical accretion deposits. The sand grains within the quartzite are primarily comprised of quartz and were eventually cemented together with silica (dissolved sand grains) forming a quartz sandstone. 

The red colors within the quartzite are caused by various minute amounts of iron oxide (AKA hematite, AKA rust). Over time, the quartz sandstone was buried and subjected to extreme heats and pressures. This essentially melted the quartz sand grains and silica cement, intermixing them to produce a solid mass of quartz. The result is a metamorphic rock known as a quartzite, a rock that is harder than ordinary steel. 

Within the Sioux Quartzite is a layer of clay, which is the pipestone layer, catlinite. The clay was deposited within the braided river system along the floodplains. When rivers flood, they break across their natural levees and deposit clay and other fine sediment along the neighboring shorelines. Within braided river systems these clay deposits are rarely preserved, though, because eventually they are eroded away as the river system meanders across the landscape. Despite the odds, this deposit of clay was preserved by a fast burial of sand on top of the clay, preventing erosion.

Named after the American Painter, George Catlin, who visited the quarries in Minnesota in 1835, catlinite is unique to this region. Catlinite is made up of a unique combination of several clay minerals including pyrophyllite, diaspore, muscovite, kaolinite, and traces of hematite (producing the red, rust, color). Most notably, there is little to no quartz found within the catlinite deposit. The resulting rock is very dense but very soft, about the same hardness as a human finger nail, making it remarkably easy to carve. The same metamorphic processes that happened to the surrounding Sioux Quartzite, were also inflicted upon the catlinite, producing this low grade metamorphic rock. 

Quarry representation. Courtesy of the NPS. 

In the words of George Catlin:

"For many miles we had the Coteau in view in the distance before us, which looked like a blue cloud settling down in the horizon . . . On the very top of this mound or ridge, we found the far-famed quarry or fountain of the Red Pipe, which is truly an anomaly in nature. The principal and most striking feature of this place, is a perpendicular wall of close-grained, compact quartz, of twenty-five and thirty feet in elevation, running nearly North and South with its face to the West, exhibiting a front of nearly two miles in length, when it disappears at both ends by running under the prairie . . . At the base of this wall there is a level prairie, of half a mile in width, running parallel to it; in any and all parts of which, the Indians procure the red stone for their pipes, by digging through the soil and several slaty layers of the red stone, to the depth of four or five feet. From the very numerous marks of ancient and modern diggings or excavations, it would appear that this place has been for many centuries resorted to for the red stone; and from the great number of graves and remains of ancient fortifications in its vicinity, it would seem, as well as from their actual traditions, that the Indian tribes have long held this place in high superstitious estimation; and also that it has been the resort of different tribes, who have made their regular pilgrimages here to renew their pipes.”

(Quote from Gurney and Heyman 2002)

While extracting the pipestone from the quarry, the overlying quartzite is slowly removed. There are several rubble piles, like pictured in the images above and below, that are produced from the overburden of the unneeded quartzite above the pipestone layer. The quarries are still mined today by Native American groups and have been for centuries. In the area surrounding the below rubble pile, Native Americans first discovered the pipestone. In this region the pipestone has had the hematite partially leached from the stone, causing speckles within the rock. These speckles are termed "spotted" pipestone. 

The overlying conglomerate, as well as other features throughout the park, including glacial erratics (known as the Three Maidens towards the entrance of the park), striations (scratches in the quartzite), and till (the overlying conglomerate and other sediment), represent the remains of glacial activity throughout the park. 

The glacial deposits within the park are thought to date between 800,000 and 500,000 years ago, some of the oldest in North America. While there are many significantly younger glacial deposits across the continental US, they did not cover the park. These glacial deposits are from the Ice Age, when vast sheets of ice covered the northern portions of the continent, dragging rocks and other debris along their bases. As they reached their limits and started to melt away, the dropped the materials they were carrying, often in a conveyor belt fashion, forming piles along their furthest extents. These piles are what are known as till, and include other artifacts like random boulders known as erratics. 

Winnewissa Falls

Through the park runs Pipestone Creek, forming Winnewissa Falls (as seen above). The water falls are produced as the creek flows over the resistant Sioux Quartzite, the to excavated lower unit of the Sioux Quartzite below the Pipestone layer. 

References

https://www.nps.gov/pipe/learn/nature/geologicformations.htm

https://siouxquartzite.com/what-is-sioux-quartzite/

https://www.mnhs.org/mnopedia/search/index/place/pipestone-quarry

https://www.nps.gov/places/the-three-maidens.htm

https://www.nps.gov/pipe/learn/nature/glaciers.htm

https://npshistory.com/publications/pipe/nrr-2017-1512.pdf

Gurney, G. and T. T. Heyman, editors. 2002. George Catlin and his Indian Gallery. Smithsonian American Art Museum, Washington, DC and W. W. Norton and Company, New York, New York.

Geology of the National Parks in Pictures - Minuteman Missile National Historic Site

My next post about the Geology of the National Parks Through Pictures is from our move across the country from Utah to New York. Along the way we visited 13 National Parks as well as some other sites. This was the 10th National Park along the way.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

-----------------------------------------------------------------------------

Minuteman Missile National Historic Site

Obligatory entrance sign photo

Minuteman Missile National Historic Site protects two locations (plus the Visitor's Center), as representatives of the once sprawling Minuteman Missile field that covered the far western portion of South Dakota. In total, there were 15 Launch Control Facilities and 150 Missile Silos the held the Minuteman Intercontinental Ballistic Missiles. The two locations preserved are one of the Launch Control Facilities, Delta-01, and the corresponding Missile Sile (Launch Facility), Delta-09. Delta-01 was only accessible via a tour, and since we were pressed for time, we only visited Delta-09 and the Visitor's Center.

The Minuteman Missile Silo Delta-09 sits within the American Great Plains, a expansive region with little topography. However, the site here does sit very close to the Badlands National Park just to the south. Per the National Park's page: 

Landforms in the Great Plains are unglaciated and retain soils formed by shallow seas that covered the region approximately seventy-five million years ago.... The seas that once covered South Dakota's Western Plains deposited limestone and sandstone overlain by soft Pierre shale.

Looking at the missile silo cap at Delta-09

The geological description of the park is a little simplistic, however there is not much that can be discerned from other online sources. They even state in their combined Historic Structures Report, Cultural Landscape Report, and Environmental Assessment report, which often contains geological information on many of the parks within the NPS, that since any proposed work would not disturb the bedrock that "further analysis of geology will be dismissed". So while they have no intention of getting into the geology of the site, if we look back into the original structure, the missile silo was obviously dug into the geological layers of the region. 

Looking down at the now defunct missile, within Missile Silo Delta-09

The missile silo itself is 12 feet in diameter and 80 feet deep. You can take a look down it, as seen above, when visiting the site. The Visitor's Center also has the nice diagram below, however, it also is lacking in geological context. 

Diagram of the Delta-09 Missile Silo

Looking at a geological map of the region does elucidate some of the geology. The map below shows a snippet of the regional geology map with a close up view of the geology of the Delta-09 site, marked by the "X". Delta-09 sits within the Qe deposit. This is wind blown sand (eolian), that dates back to the Eocene (~34 million years old). This sand is far younger than the denoted Pierre Shale at 75 million years old listed on the website. The sand here is predominantly wind blown sediment that is reworked sands from the older rocks below. 

Snippet of the Delta-09 Geology Map. Full map courtesy of the National Geologic Map Database.

On the map to the south of the Delta-09 site, you can see a different, darker shade of orange, Qoa. Qoa, the Older Alluvium, represents a different form of Eocene deposit that also formed from the reworking of even older rocks, soils, and sediments. Both of these "Q" (Quaternary), layers sit upon the thicker bedrock of the region. However, through the Qoa deposit, we can catch a glimpse of some of the true bedrock of the region. The description of the geological layers to the right of the map lists them in reverse chronological order. This means that the oldest layers are located at the bottom of the legend, with progressively younger layers stacked on top. The Pierre Shale is indeed the oldest, and thickest, bedrock layer within this region and although it only peaks out a little bit in the area of Delta-09, it is definitely a major rock unit below the surface. The Pierre Shale is Cretaceous in Age (~75 to 69 million years old) and formed when this area, and much of central North America, was covered in a vast inland sea known as the Western Interior Seaway. Within the Pierre Shale, several fossils can be found in nearby Badlands National Park, such as ammonites and mosasaurs. These lived at the same time as the dinosaurs, but since this area was covered in water during the Age of the Dinosaurs, dinosaurs were not to be found. 

The next rock unit above the Pierre Shale within this region, and likely can be found along the walls of the missile silo, is the Chadron Formation. The Chadron Formation is Eocene in age (~37 to 34.3 million years old) and was formed along an ancient river floodplain. The Chadron Formation is made up of light gray claystone beds and represent an environment similar to the Everglades today. Fossils that can be found within Badlands NP within the Chadron are alligators, early horses, and the large brontothere (AKA titanothere) mammals. Within this area though, the Chadron Formation is likely a thin layer, especially compared to the outcropping within Badlands NP. 

References

https://ngmdb.usgs.gov/Prodesc/proddesc_9826.htm

https://www.nps.gov/mimi/learn/nature/index.htm

https://npshistory.com/publications/mimi/hsr-clr-ea.pdf

https://www.nps.gov/articles/000/badl-geologic-formations.htm

Geology of the National Parks in Pictures - Badlands National Park

My next post about the Geology of the National Parks Through Pictures is from our move across the country from Utah to New York. Along the way we visited 13 National Parks as well as some other sites. This was the 9th National Park along the way.

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

-----------------------------------------------------------------------------

Badlands National Park

Obligatory entrance sign.

The Badlands are a very geological park, where the geology is the focal point of the beauty of the park. Even the term "badlands" is a geological term meaning a landscape made up of generally soft sedimentary rock that erodes easily and has a lot of streams eroding the landscape with little plant life to inhibit the erosion.  The main road, Badlands Loop Road, that travels through the park, actually does not cover the vast majority of the park, which is much more difficult to get to. However, there are still a ton of geological sites that can be viewed from the main road. Below is a picture from the visitor's center of the overview of the geological stratigraphic column featuring the main park formations. 

Geological sign from the Badlands NP Visitor's Center

The oldest formation, at the base of the park, is the Pierre Shale. The Pierre Shale is Cretaceous in Age (~75 to 69 million years old) and formed when this area was covered in a vast inland sea known as the Western Interior Seaway. The Pierre Shale covers the lower levels of the landscape towards the northwest of the park, away from the main road. There are some places along the main road that you can see the Pierre Shale, such as at the Pinnacle Overlook, near the western entrance to the park. The shale is at the base of the erosion escarpment here. Within the Pierre Shale, several fossils can be found such as ammonites and mosasaurs. These lived at the same time as the dinosaurs, but since this area was covered in water during the Age of the Dinosaurs, dinosaurs were not to be found. 

View from the Pinnacles Overlook

The yellow layer immediately above the Pierre Shale is known as the Yellow Mounds. It is a weathered extension of the Pierre Shale, that was altered when the Western Interior Seaway went away. Within this layer, which can be plainly seen at the Yellow Mounds Overlook pictured below, a rainforest grew up within the Pierre Shale and converted the upper portions of the shale into a soil, or what is now known as a paleosol (an ancient soil). 

View from Yellow Mounds Overlook

Above the Pierre Shale is the Chadron Formation. The Chadron Formation is Eocene in age (~37 to 34.3 million years old) and was formed along an ancient river floodplain. The Chadron Formation is made up of light gray claystone beds and represent an environment similar to the Everglades today. Fossils found here are alligators, early horses, and the large brontothere (AKA titanothere) mammals. In the above image, the Chadron Formation starts just above the red layer and continue upwards until they hit the layer with multiple horizontal layers within it in the left background. That is our next youngest formation, the Brule Formation. 

Conata Basin Overlook

The Brule Formation is Oligocene in age, deposited 34 to 30 million years ago, and is an interbedded siltstone and sandstone deposit with a lot of clay creating a pale-pink deposit with lots of beds. This was formed when the environment started to dry out from the floodplains of the Chadron Formation and became a savannah with rivers periodically meandering across the environment. Fossils include those of oreodonts, animals related to modern bison and camels, early dogs, and nimravids, animals that looked like saber-toothed tigers but were only distantly related. In the picture above, the Brule Formation can be seen in the upper portion of the outcrop, essentially in line with the fencing on the left side of the photo, and stretching across the view. It is also the entirety of the rock formations in the picture below (the Wild River Valley Overlook) and creates the tops of most of the erosional escarpments seen along the Badlands Loop Roads. 

Wild River Valley Overlook

The youngest rock deposit within Badlands National Park (although there are many younger sediments across the park, this is the final layer within the Badlands escarpment) is the Sharps Formation. The Sharps Formation is an Oligocene Age (30 to 28 million years old) sandstone river channel deposit. This formation can be seen in a few places in the park and is present only at the very top of some of the erosional peaks. Below it can be seen along the Fossil Exhibit Trail as the upper half of that big monolith in the middle of the image. The line about halfway up is the Rockyford Ash layer, a deposit created from a distant volcanic eruption 30 million years ago. The Sharps Formation sits directly on top of the Rockyford Ash Layer. 

Fossil Exhibit Trail outcrop view

 

This entire region then began to erode away, producing the pinnacles and peaks that we see today. This erosion started around 500,000 years ago as the Cheyenne and White Rivers eroded their way through the landscape. Because all of these rocks are very, very soft, they are eroding at a rate that is much faster than many other landscapes, especially those further west. It is estimated that 1 inch of rock is eroding away every year and that the entire badlands will be gone in the next 500,000 years. This rate is 10,000 times faster than the granitic rocks forming the center of the Black Hills where Mount Rushmore and the Crazy Horse Memorial are located.  

Geological column with the fossils displayed on the Fossil Exhibit Trail

Towards the western end of the Badlands Loop Road is the Fossil Exhibit Trail. The Fossil Exhibit Trail is a wonderful, 0.2 mile "trail", along a boardwalk with bronze exhibits of fossils with displays explaining the animals to whence they belong. As the trailhead sign states, there are seven types of animals displayed along the trail. As the climate changed in the area, each of these animals had to either move, adapt, or extinct. Since it is a loop, the fossils are laid out chronologically. We are going to go backwards through time, starting with the most recent fossils along the trail, and ending with the oldest fossils. You can see a great layout of the stratigraphic section (geology rock layers) and their associated fossils in the image above that was at one of the trailheads for the Fossil Exhibit Trail.

Oreodont fossil (Leptauchenia) display along Fossil Exhibit Trail 

The Oreodont fossil above, Leptauchenia, was found within the Rockyford Ash layer, and Leptauchenia lived from around 32 to 28 million years ago. An oreodont is what is known as an artiodactyl, which is an even-toed hoofed mammal. These include bison, big horned sheep, and camels, of which the camel is the closest living animal to the Leptauchenia.  

Dying to become a fossil exhibit

Along with the fossils, there are also these great displays which shows additional information beside just the fossil. The display attached to the Oreodont fossil is called "Dying to Become a Fossil" and illustrates some of the processes that an animal takes in order to become fossilized. 

Nimravid (Nimravus) fossil display along the Fossil Exhibit Trail

The next fossil is the Nimravid (Nimravus) fossil, which was found in the Brule Formation and lived around 32 to 30 million years ago. Nimravids are animals that resembled saber-toothed cats, of which these cats are only very distantly related. Nimravids fall under the family Nimravidae, as opposed to cats, which are Felidae, however they all fall under the order Carnivora, along with dogs and bears. Some of the differences between Nimravids and true cats is that the nimravid skulls are much shorter than cat skulls and they walked flat footed, as opposed to cats who walk on their toes.

Fight for Survival

This display, which was paired with the Nimravid skull, displays another aspect of paleontology, taphonomy. This is where paleontologists look at the various aspects of the fossil and try to discern things like how the animal died. In this instance, there is evidence by the hole punctures in the skull of one nimravid, that it was attacked by another one. 

 

Dog (Hesperocyon) fossil exhibit along the Fossil Exhibit Trail

This dog fossil (Hesperocyon) is an early ancestor to modern day dogs and was also found in the Brule Formation. This dog lived around 37 to 28 million years ago. 

It's a Dog's Life

Associated with the Hesperocyon display is the "It's a Dog's Life" display, showing the eventual evolution of the Hesperocyon into modern day dogs as we know them. 

An early horse, Mesohippus, display fossil on the Fossil Exhibit Trail

Next up on the Fossil Exhibit Trail is the Mesohippus, an early ancestor to modern day horses. Unlike modern day horses, who only have one toe, Mesohippus had three toes. Mesohippus lived from 37to 30 million years ago and this fossil was found within the Chadron Formation. 

Off to the races

Alongside the Mesohippus display is "Off to the Races", a paleontological display discussing adaptation. Mesohippus's adaptation was the reduction of digits in it's foot from 5 toes, seen in earlier ancestorial horses, to the three toes in Mesohippus, that will eventually evolve into the one toe of modern-day horses. 

Alligator fossil along the Fossil Exhibit Trail

The next fossil is that of an alligator skull, which lived in the region from 34 to 37 million years ago. This fossil was found within the Chadron Formation. 

See Yea Later, Alligator

The associated sign with the Alligator skull discusses the size disparity between ancient alligators and their modern day descendants. As can be seen with the above skull, modern day alligators are much larger, over twice as long in fact, than this ancestor.

Titanothere (Megacerops) lower jaw fossil exhibit from the Fossil Exhibit Trail

Titanotheres, also known as brontotheres, are very large hoofed mammals that evolved during the Eocene (~50 million years ago) and later went extinct in the Oligocene (~28 million years ago). They lived in Asia and North America and several well known species can be found across rocks of western North America. This Megacerops lower jaw fossil was found within the Chadron Formation, just above the Yellow Mounds layer. They lived in this area from 34 to 37 million years ago. 

Titanic Discovery

The associated sign with the titanothere fossil discusses the process of early field work, where paleontologists go out into the field and dig out the fossils, often with the aid of knowledgeable locals, who initially find the fossils eroding out of the landscape. 

Ammonite (Placenticeras) fossil exhibit along the Fossil Exhibit Trail

The final fossil on the Fossil Exhibit Trail (or the first, if you went in the opposite direction than I did), and the only fossil that isn't of a vertebrate, is the ammonite fossil Placenticeras. Ammonites are ancient relatives to octopi, squids, and nautiloids. This fossil, since it is the only marine fossil, was found in the only marine deposits, the Pierre Shale, located at the base of the rocks within the park. Ammonites lived within this area from 75 to 67 million years ago, before going extinct shortly thereafter 65.5 million years ago. 

Under the Sea

The associated sign with the ammonite fossil is "Under the Sea", that describes that throughout time the environmental conditions have changed. What is now the badlands, was once under water during the Cretaceous within the Western Interior Seaway. 

A display of several fossils found within the Badlands National Park at the Ben Reifel Visitor Center.

At the eastern end of the Badlands Loop Road is the Ben Reifel Visitor Center, and here there are several actual fossil exhibits, as opposed to the "fossils" on the Fossil Exhibit Trail which are clearly casts designed to weather the elements and visitors. The above display shows fossils from the Brule Formation. These include a Subhyracodon skull (top of picture), which was a hornless rhinoceros, a Leptomeryx, a small deer-like animal, (top right), and the Archaeotherium (large fossil on the bottom). The Archaeotherium was a "big pig", that although looked like a pig was only a distant relation to modern day pigs and was more closely related to hippos. 

A display of more fossils found within the Badlands National Park at the Ben Reifel Visitor Center.

The above shows another collection of fossils from within the park. These were found within several of the rock formations. This includes a titanothere femur and skull, an alligator skull, and a tortoise. There are also several more fossil exhibits within the visitor's center and it is a stop well worth taking your time in. 

References

https://irma.nps.gov/DataStore/Reference/Profile/2251588

https://www.nps.gov/badl/index.htm

https://www.nps.gov/articles/000/badl-geologic-formations.htm

https://ngmdb.usgs.gov/Geolex/UnitRefs/BruleRefs_7360.html

https://www.nps.gov/articles/000/oreodont.htm

https://www.nps.gov/articles/000/nimravid.htm

https://www.britannica.com/animal/titanothere

https://www.nps.gov/articles/000/big-pig-dig.htm