MEDORA Well exposed rock formations and the scenic awesome beauty of the North Dakota Badlands in Theodore Roosevelt National Park have long attacted scientific explorers and countless other visitors to this area.
John Hoganson, Bismarck, state paleontologist with the North Dakota Geological Survey, is quite familiar with the park's South Unit near Medora and North Unit near Watford City. In the 1990s, Hoganson, assisted by Johnathan Campbell, spent 50 days mapping fossils in the park. Few paleontological investigations had been previously done in the park which covers a total of 70,228 acres.
"The rocks that are exposed in Theodore Roosevelt Park were deposited during the Paleocene Age, which was about 55 to 60 million years ago," said Hoganson.
Eloise Ogden/MDN --
The unusual rock formations seen here in the South Unit of Theodore Roosevelt National Park Aug. 21, are caused by weathering – rain and wind producing unusual and beautiful shapes.
He said there are two rock formations exposed in the park the Bullion Creek Formation and the overlying Sentinel Butte Formation. He said the two formations are distinguished mainly by color. Bullion Creek is lighter and beige and the overlying Sentinel Butte is more gray colors.
The Bullion Creek Formation is exposed only in the park's South Unit.
"In both rock formations there are some sandstone deposits that often form big blocks that will break away and roll down the slope," he said. "Rain water gets in the cracks, freezes and creates larger fractures, and the blocks break away and roll down the slope."
The red rock seen in the park is often referred to as scoria but clinker is the proper geologic term for this rock, Hoganson said. "It forms when lignite is ignited, often by lightning. The lignite burns underground at times for many years. The overlying rock is "baked" as if it were in a kiln. This alters the rock and often turns it red, although it can also be other colors. Clinker is quarried, crushed and put on the roads as gravel in western North Dakota."
Minot and glacial drift
Hogan explained why this part of the state is so different than the Minot area.
"The rocks beneath Minot are the same as those exposed in the park Badlands. Those rocks were not subject to erosion like those in the Badlands because they are overlain by glacial drift. So the rocks beneath the glacial drift beneath Minot are not eroded to form Badlands they would be in relatively flat layers," he said.
"The glacial material that Minot is built on is sediment (mud, silt, sand, boulders, etc.) that was carried in the glacial ice from Canada the first Canadian imports. In some places in the Minot area, near Velva, for example, rivers have eroded through the glacial deposits to expose some of the older bedrocks," he said.
The Badlands were mainly formed through the erosion of the Little Missouri River.
"All the rivers before this glacial age flowed north into the Hudson (Bay)," Hoganson said. He said the Little Missouri River flowed north into the Hudson Bay drainage and was diverted by glacial ice during the last Ice Age. The Red River on the North Dakota/Minnesota border still flows north.
The climate of what is now North Dakota was totally different millions of years ago than it is now, Hoganson said. At that time, it was a subtropical climate. "We know this because we find fossils of crocodiles and palm trees in these rocks in the park," he said.
He said the dark layers in the rocks in the park are lignite. "Those dark layers represent the time when swamps existed there. North Dakota really was forested swampland at this time," he said.
Modern-day animals of the park, like the buffalo, wild horses and prairie dogs, were preceded by ancestral animals.
"Ancestral horses lived in western North Dakota 30 million years ago," Hoganson said. He said remains of those ancestral horses called the Mesohippus, are found in western North Dakota.
"The big difference between those and the modern-day horse, is the Mesohippus was much smaller 18 inches to 2 feet tall (adults)," he said. He said fossils of these early-day horses have been found in the South Heart area, about 22 miles east of the park. He said he is not aware of any found in the park.
A Messohippus exhibit was installed in the North Dakota Cowboy Hall of Fame in Medora about two years ago, Hoganson said. "We updated that exhibit this spring and included fossils from badlands rocks exposed in the Medora area including remains of crocodiles and turtles. We also included in this new exhibit remains of dinosaurs including the brow horn of a triceratops."
The ancestral bison called the Bison latifrons was huge and had horns spanning about 7 feet compared to about 2 feet for the modern-day bison. It lived during the Ice Age or about 50,000 years ago when the woolly mammoth also lived in the area, Hoganson said. He said the Bison latifron is the oldest bison found in North Dakota.
A skull of that ancient bison was found near New Town by Kent Pelton of Watford City. It the only Bison latifrons skull found in N.D. The North Dakota Heritage Center in Bismarck has the original skull. Casts of the skull were provided for the Three Tribes Museum west of New Town, Long X Visitor Center in Watford City, National Buffalo Museum in Jamestown and the U.S. Army Corps of Engineers Headquarters in Riverdale.
Prairie dogs are rodents and remains of rodent-like animals have been found in the rocks outside the park at a Medora dig site, Hoganson said.
For more about the geology and paleontology in North Dakota visit the North Dakota Department of Mineral Resources Web site at (www.dmr.nd.gov) and go to the link for the N.D. Geological Survey.