Tim Cowman is the state geologist and director of the South Dakota Geological Survey. “To understand what the Niobrara Formation is and how it was formed, we have to go back in geological time to the Cretaceous Period, which ended around 66 million years ago,” Cowman explains. “During this time, a large sea covered most of the Great Plains, and at the bottom of the seabed, rock layers were settling and forming. In a time when the sea was very deep, all these little microscopic animals that lived in the sea. sea, like plankton and so on, whose calcareous shells have died and are deposited on the bottom of the sea. “
“Their calcareous shells then cemented together and formed a layer of chalk and limestone, and that’s what the Niobrara formation is all about. Even though it was a lot of these little animals, microscopic animals, we often find in the Niobrara formation larger fossils. So, for example, you can also often find fossils of clam shells in the Niobrara formation. And sometimes we find a plesiosaur or a mosasaur, which were large marine reptiles that swam in this sea and died and also incorporated into the formation. “
There are shallow exposures of Niobrara chalk in various places around the Great Plains.
“The Niobrara Formation exists under most of South Dakota,” Cowman explains, “but in most cases it is buried deep within other sediment. However, there is what we call outcrops or variation. surface of the Niobrara Formation along the Missouri River Valley, particularly between Pickstown and Vermillion. One of the best places to see them is probably along the south shore of Lewis and Clark Lakes. The majestic yellowish-brown cliffs that you see there are made up of the Niobrara training. “
European immigrants would hew stone from these same cliffs to build their homes, churches and barns. Niobrara’s chalk was also used for making cement for some time at the former Western Portland cement plant in Yankton.
The Bon Homme Colony, the oldest and largest Hutterite settlement in the area, once had several large structures built of limestone, including a waterwheel flourmill, community center, and barn. Today, a small welding workshop and a residence remain.
Most of the historic limestone structures in Bon Homme County are in a state of disrepair.
St. John the Baptist Church in Lakeport, Yankton County, built in 1884, is possibly the best-maintained limestone structure in the area.
While limestone had to be harvested from specific locations, field stone was readily available everywhere.
“If we move quickly through geologic time until about two million years ago, the Pleistocene epoch began and it lasted until about ten thousand years ago – essentially the last Ice Age. During this time, large glaciers originating in Canada moved south and covered roughly the northern third of the United States. But as these large ice caps moved south, they scraped the rock on which they rested. And so there was a lot of igneous and metamorphic rocks, such as granites and quartzite in Canada and northern Minnesota – they were scraped and incorporated into these glaciers. And then, as the glaciers melted and fell. were pulling out, they left these rocks in the native geological formations of South Dakota. “
The last ice age also deposited “boulders” in northern and central Europe. Some cultural groups, including the Czechs, brought with them to eastern South Dakota an established history of fieldstone building.
The John Frdyrych Farm Barn near Tyndall is possibly the largest fieldstone building in the region, built with stone masonry and timber framing. But the barn is showing its age and could become a ruin without some reconstruction efforts.
“What my dad told me about his dad,” says Mike Slama, who rents the land where the Frydrych barn is located, “it was the Frydrych brothers, in the 1880s, I think it was – pretty much About the same time the railroad came through here – they started building this barn. They brought all the stones around here. It took them over seven years to build. I think it It’s over two hundred feet long and 30, 40 feet wide. And every stone that was put in that building was one at a time. “
“When you stop and think about it,” Slama says, “starting a barn of this size was a major undertaking. “
“They and my grandfather were working together at the time,” Slama recalls. “All the Czechs, the Bohemians, settled here west of Tabor. And if you’ve ever been to the Czech Republic, everything is done there with stones. So this barn would fit perfectly into Czech culture. “
Susan Paul’s family have owned a property near Tyndall since 1900. A small fieldstone house on the property remained in a dilapidated condition for many years, until Paul hired a team of seasoned stonemasons to rebuild the house stone by stone.
“I would say that judging from the buildings that I have seen in the south of France that have been restored, this restoration job should be rated from good to very good,” says Paul.
Sometimes stone masonry structures are hidden under a layer of stucco. Sometimes when additions have been added, stone masonry walls exist only indoors and can then be obscured by layers of plaster or other materials.
The Sedlacek family spent considerable time discovering a combined chalk stone and fieldstone interior wall (over three feet thick) in their home outside of Tabor.
“Often times you will find in these old buildings that it is not easy to get the money to continue building or maintaining a house like this,” says Erin Sedlacek. “The banks don’t want to give you money to maintain a structure that they don’t understand or to ensure a structure that they are not sure is solid. But it has been around for a hundred and seventy years. I would say that it’s solid, it’s not going anywhere. ”