Notwithstanding the facts that it was in Iowa rocks of Cretaceous age were first recognized in this country, and that the Meek and Hayden now famous, or type, section of the rocks of this age for the continental interior was constructed along the Missouri River, the stratal succession of this region is not genetic expression of the actual sedimentation. The Iowa section is really far from being a characteristic development of the provincial series. The Cretaceous depositions have to be viewed as the product of a great mediterranean sea, of which the black-mud body now variously called the Benton, Pierre, or Mancos shales, or whatnot, constitute the median mass into which from the east interdigitate the various sandstones, limestones, chalks, etc., of the Iowa section. From the west, in Utah and Colorado, there is similar interdigitation eastward. Meek's dictum of Prionocyclas as the characteristic fossil of the Benton basal shales carries the so-called Benton up to and high into the Pierre. This Nautiloid shell is rather a fossil of the entire great median black shale-body.
Proceedings of the Iowa Academy of Science
©1934 Iowa Academy of Science, Inc.
"Reconstruction of Iowa's Cretaceous Stratigraphy,"
Proceedings of the Iowa Academy of Science, 41(1), 239-240.
Available at: https://scholarworks.uni.edu/pias/vol41/iss1/69