For several reasons the section of Cretacic strata in northwestern Iowa is of especial interest. It was in this section, near the mouth of the Big Sioux River, that for the first time in the New World the stratigraphic equivalents of the English Cretacic formations were clearly recognized. In this section true chalk, made up of countless myriads of microscopic organic remains, was first discovered in this country. This section is also a part of the classic locality for the Mid-Cretacic formations of America.
Proceedings of the Iowa Academy of Science
©1913 Iowa Academy of Science, Inc.
"Complete Succession of Iowan Cretacic Terranes,"
Proceedings of the Iowa Academy of Science, 20(1), 199-201.
Available at: https://scholarworks.uni.edu/pias/vol20/iss1/18