TJie Missourian Series of the Carbo)iiferous. — Keyes. 313 
Distribution of Mtssourian Rocks. 
The approximate limits of the Missourian formations are 
shown on the Missouri and Kansas maps. There are, how- 
ever, several points in the dififerent districts to which attention 
should be called. 
Nebraska Area. Certain peculiarities in the relations of the 
geological formations of Nebraska give the Missourian rocks 
much less areal extent than the}' ordinarily would be expected 
to have. The Missourian rocks occupy only the extreme 
southeastern portion of the state. They extend over all of the 
county of Richardson, and parts of Pawnee, Nemaha, Otoe, 
Cass, Sarpy and Douglass counties. 
To the northwest the Missourian and the Oklahoman as 
well, are limited by the overlapping of the Cretaceous. Pre- 
vious to the deposition of the latter the underlying strata were 
subjected to profound erosion, and were bevelled off at a con- 
siderable angle. In consequence the Cretaceous rocks repose 
in marked unconformity upon the Carboniferous. The eastern 
border of the former extends directly southwestward from 
Omaha. 
The formations of the Missourian that are represented in 
Nebraska are: Cottonwood limestone, Atchison shales, 
Forbes limestone, Platte shales, Plattsmouth limestone, and a 
few feet of the Lawrence shales. 
Southwestern lozva District. The relations of the Carbonif- 
erous and Cretaceous are essentially the same in Iowa as they 
are in Nebraska. The younger deposits come in from the 
northwest and overlap the Missourian, Des Moines and Miss- 
issippian series. While normally the Missourian would occu- 
py, as the surface rock, about one-fifth of the total area of the 
state, it in reality, owing to the Cretaceous covering, forms 
considerably less than one-half of this extent. The Cretaceous 
extends southward in a long tongue nearly to the southern 
boundary of the state. The unconformity of the younger and 
older rocks is even more marked than in Nebraska. 
In Iowa the Missourian formations occupy all of Union, 
Ringgold, Taylor, Fremont and Mills counties; and parts of 
Guthrie, Adair, Madison, Clark, Decatur, Adams, Page, Mont- 
gomerv, Cass, Pottawattamie, Flarrison and Monona. 
