The long period intervening between the deposit of the Cretaceous rocks of Iowa and the advent of the glaciers has left in this state no record in deposits. Its history must be gathered entirely from the land forms then created, and from inferences drawn from orographic changes known to have taken place in other regions.
Proceedings of the Iowa Academy of Sciences
©1894 Iowa Academy of Science, Inc.
Bain, H. Foster
"Preglacial Elevation of Iowa,"
Proceedings of the Iowa Academy of Science, 2(1), 23-26.
Available at: https://scholarworks.uni.edu/pias/vol2/iss1/8