Of late years the Carboniferous terranes, or formations of the Mississippi basin west of the great river have been widely studied. They are now capable of being classified in detail. For a long time much confusion existed in regard to the relations that the schemes of various investigators, and especially those of the pioneers, bore to one another, and to the more modern widely correlated arrangement. The adjustment of the results of all workers, extending over a period of fifty years, in a field embracing the greater part of six states, was fraught with many difficulties.
Proceedings of the Iowa Academy of Sciences
©1899 Iowa Academy of Science, Inc.
Keyes, Charles R.
"Formational Synonomy of the Coal Measures of the Western Interior Basin,"
Proceedings of the Iowa Academy of Science, 7(1), 82-105.
Available at: https://scholarworks.uni.edu/pias/vol7/iss1/13