The existing geological maps of Iowa show a continuous blanket of Cretaceous rocks underlying the glacial drift of northwest Iowa. Previous workers have recognized that the Cretaceous was not continuous under the drift and might have a very irregular distribution along the borders as mapped. As a result of over two years of extensive sub-surface studies, assisted during the last nine months by H. G. Hershey, considerable revision of the boundaries of the Cretaceous has been made.
Proceedings of the Iowa Academy of Science
©1937 Iowa Academy of Science, Inc.
Tester, A. C.
"New Mapping of Geological Boundaries of Northwest Iowa,"
Proceedings of the Iowa Academy of Science, 44(1), 133-134.
Available at: https://scholarworks.uni.edu/pias/vol44/iss1/35