The exact stratigraphic relations of, and the exact boundary line between, the latest Devonic formations and the earliest Carbonic rocks of the Mississippi valley north of the Missouri river have long remained some of the unsolved geographic problems. That the question should stand today much as it did 60 years ago is due chiefly to the circumstance that although three state geological surveys have repeatedly attacked it, all the necessary facts were not available in any one state alone. No observer seems to have had the opportunity to make critical investigations in all three of the states or to have gone over all of the ground between the mouth of the Missouri river and the Minnesota line.
Proceedings of the Iowa Academy of Science
©1912 Iowa Academy of Science, Inc.
"Nether Delimitation of Our Carbonic Rocks,"
Proceedings of the Iowa Academy of Science, 19(1), 153-156.
Available at: https://scholarworks.uni.edu/pias/vol19/iss1/25