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 4th 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.
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Little Bighorn Battlefield lies along the Little Bighorn River, which is within the western edge of the Great Plains region of the US. The ground surface is an undulating terrain created by ridges of the underlying bedrock, ravines, and coulees (small, intermittent streams). The bedrock exposed within the park is split between two formations: the Upper Cretaceous Age Judith River (~80 to 76 million years old) and younger, overlying Bearpaw Formations (~75 to 70 million years old). The Judith River Formation lies mostly in the western half of the park, which is mainly on the righthand side of the road as you drive into the park. The Judith River Formation was deposited as sandstones and shales along the shoreline of the Western Interior Seaway, which was a body of water that covered much of the middle of North America from the Gulf of Mexico up into Canada during the Cretaceous time period. The Judith River Formation is also one of the major dinosaur fossil bonebeds in the US.
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| Dolichorhynchops osborni found at Little Bighorn Battlefield, currently located in the Smithsonian National Museum of Natural History. Image courtesy of Wikimedia. |
The overlying, younger formation is the Bearpaw Formation (AKA Bearpaw Shale). This is located mainly in the eastern half of the park and covers both sides directly next to the road and to the left as you are driving into the park. The Bearpaw Formation is a shale layer deposited within the depths of the Western Interior Seaway, when that body of water covered the area. Many ammonites have been found within the Bearpaw Formation as well as a notable plesiosaur within the park. Back in 1977, a routine grave excavation was occurring in Custer National Cemetery and a NPS maintenance employee exhumed pieces of the plesiosaur Dolichorhynchops osborni. After six days of work, a nearly complete vertebral column, a complete pectoral girdle, and complete pelvic girdles were collected by after-hours volunteers and local paleontologists Russell King and Alan Tabrum.
Here is a view from Last Stand Hill that overlooks the floodplain of the Little Bighorn River. The meandering Little Bighorn River floodplain dominates the southwestern edge of the battlefield. The terrain of the battlefield was highly influential in the progression of the battle. The ridges within the landscape offered defensible high grounds for the soldiers of the 7th Cavalry, while the coulees and ravines provided shelter for the advancing Lakota Sioux and Cheyenne warriors. The markers here, and elsewhere within the park, denote the locations where people had fallen during the battle.
Besides just the markers within the battlefield itself, there are also those within Custer National Cemetery. Here many of the people who had perished during the battle had been reinterred. Both here, and within the battlefield, the white, marble stones obtained from Italy denote places where Custer's soldiers fell.
Where the Native American warriors fell are markers of red granite, although I am not entirely sure of the source of the granite. NPS sources denote it as "Radiant Red" granite from a quarry in Cold Spring, Montana. However Radiant Red granite comes from Fredericksburg, Texas, while I can't find any granites that are quarried near the town of Cold Spring, Montana. Looking at Radiant Red granite, there are a bazillion names that it can be found under, however the proper geological name is the Town Mountain Granite, that is Proterozoic (~1.1 billion years old) in age. It is coarse grained, pink to red in color, and contains abundant quartz, plagioclase feldspar, and microcline. The feldspar is what gives the rock its pinkish red hue.
South of the main section of the park is a smaller section dedicated to preserving the area known as the Reno-Benteen Battlefield. In 1926, on the 50th anniversary of the battle, Congress had authorized the placement of granite monument to memorialize the battle. Although the specific formation that the granite was from is unknown, it is known that it was obtained from the Livingston Marble and Granite Works in Livingston, Montana.
