The lower measures of the Iowa-Missouri coal field consist of a series of sandstones, shales, fire clays and coal beds, which have been found to interlock in a characteristically irregular manner. The different individual beds have, with rare exceptions, only a limited extent, and frequently grade into each other in a mariner making their stratigraphy quite complex. This variability has been recognized by many workers and has recently been elaborated so fully that only a reference is necessary in this connection.
Proceedings of the Iowa Academy of Sciences
©1893 Iowa Academy of Science, Inc.
Bain, H. Foster
"Structure of the Mystic Coal Basin,"
Proceedings of the Iowa Academy of Science, 1(Pt. 4), 33-36.
Available at: https://scholarworks.uni.edu/pias/vol1/iss4/14