Iowa geologists have long experienced great difficulty in isolating good key beds in the younger Pennsylvanian strata. This difficulty is due to the cyclothemic nature of the sediments. The marked success of the Missouri Geological Survey in distinguishing southward extensions of these strata in Missouri on the basis of their insoluble residues has led to a similar attempt in Iowa.
Proceedings of the Iowa Academy of Science
©1942 Iowa Academy of Science, Inc.
Wenberg, E. H.
"Some Insoluble Residue Correlations of Missouri and Virgil Strata in Iowa,"
Proceedings of the Iowa Academy of Science, 49(1), 335-338.
Available at: https://scholarworks.uni.edu/pias/vol49/iss1/58