Unconformable relations between the Prairie du Chien and St. Peter formations have long been known in Minnesota, Wisconsin, Illinois and Missouri. The existence of this unconformity in Iowa, though long suspected, has never been demonstrated, or if it has been known to exist here, the fact has not been recorded. There is nothing in the reports of the State Geological Survey suggesting anything but conformable relations between the two formations.
Proceedings of the Iowa Academy of Science
©1917 Iowa Academy of Science, Inc.
Trowbridge, Arthur C.
"The Prairie du Chien - St. Peter Unconformity in Iowa,"
Proceedings of the Iowa Academy of Science, 24(1), 177-182.
Available at: https://scholarworks.uni.edu/pias/vol24/iss1/27