For a long time it has been known that in Iowa and the neighboring states to the south a break in sedimentation exists at the base of the coal measures. It has been noted in various places in the reports of the Iowa geological survey and reference has been made to it in various other publications. Of its real significance no hint has ever been given.
Proceedings of the Iowa Academy of Sciences
©1900 Iowa Academy of Science, Inc.
Keyes, Charles R.
"Depositional Equivalent of Hiatus at Base of Our Coal Measures; and the Arkansan Series, a New Terrane of the Carboniferous in the Western Interior Basin,"
Proceedings of the Iowa Academy of Science, 8(1), 119-128.
Available at: https://scholarworks.uni.edu/pias/vol8/iss1/18