204 University of Kansas Geological Survey. 
outcrops of Niobrara are found south of the Arkansas, but a few 
isolated outcrops occur in the great Tertiary area north of that 
river. Two such instances are found in the southeastern portion of 
Scott county, which are probably the ones referred to by Hay as 
belonging to the Fort Pierre! A larger Niobrara area is found in 
the western part of Greeley county, which is Fort Hays limestone 
and extends across into Colorado. Another small exposure of 
Hort Hays limestone is found along the tributaries of the Arkansas 
a few miles north of Coolidge on both sides of the state line. 
TOPOGRAPHY. 
There is a marked similarity in general topographic features of 
the Cretaceous and the Carboniferous formations in Kansas. Be- 
cween the Cottonwood Falls limestone of the Permian and the 
Lower Coal Measures we find four great limestone groups which 
serve to produce marked changes in topographic features. In the 
Cretaceous and the Tertiary areas above the Cottonwood Falls 
limestone we also find four rock formations which serve a similar 
purpose. The four members of the first group are, beginning with 
the lowest, the Hrie limestone, the Iola limestone, the Garnett 
limestone, and the Oread limestone. The members of the upper 
group are, the Dakota sandstone, the Benton limestone, the Fort 
Hays limestone, and the “Mortar beds.” Throughout the state 
wherever there is an exposure of any one of these groups, similar 
irregularities of surface have been produced. Along the eastern 
border of each exposure mounds of shale protected by the more dur- 
able rock are found. Above the point where the limestone or sand- 
stone disappears under the surface, a comparatively ievel but grad- 
ually ascending plain extends westward until the next limestone 
or sandstone group is reached, where nearly the same topographic 
features are repeated. Therefore in passing from the eastern 
part of the state to the west north of the Arkansas river, we ascend 
a number of terraces, each one having a very irregular border. Of 
these upper terraces, the Dakota presents the greatest diversity in 
iopographic features, a condition due largely to the varying texture 
of the sandstone. The sandstone hills of the Dakota group are 
1 See Doctor Williston’s report on the Niobrara, in this volume. 
