The sandstones under consideration lie in old gorges in Devonian limestone a short distance north of Iowa City. On account of the presence of plant remains, which, however, were too fragmentary for identification, Hall regarded the arenaceous deposits as belonging to the upper coal measures. Others visiting the places, since the announcement of the discovery in 1858, have adopted the same view as to the age of the rock without attempting to question the correctness of the assumption, or to obtain further evidence.
Proceedings of the Iowa Academy of Sciences
©1890 Iowa Academy of Science, Inc.
Keyes, Charles R.
"Age of Certain Sandstones near Iowa City,"
Proceedings of the Iowa Academy of Science, 1(Pt. 2), 26-26.
Available at: https://scholarworks.uni.edu/pias/vol1/iss2/14