136 KANSAS ACADEMY OF SCIENCE. 
approximately at right angles. Beginning on the south these streams are: 
Smoky Hill, Saline, Solomon, Republican, Little Blue, and Big Blue. Where 
they break through the line of hills all of these streams have cut rather narrow 
valleys in the sandstones and shales. In this regard they are in marked con- 
trast to such streams of the plains as the Arkansas, Ninnescah, Platte, or Loup, 
which have broad and shallow valleys. This area constitutes the most typical 
section of the Dakota group. It is here alone that the entire thickness of strata 
from the underlying Permian to the superjacent Benton may be seen throughout 
any considerable area. The topography also differs materially from that of other 
regions. It is characterized by bold cliffs, flat-topped buttes and mesas, square 
shoulders and ledges, interspersed with steep slopes and here and there narrow 
cafons. This angularity of topography contrasts strangely with the gentle, 
rounded slopes of the Benton or Permian. The conditions indicated obtain for 
the greater part of the area. South of the Smoky Hill river the Dakota is cov- 
ered by the Benton or by the Tertiary; and the asperity of bluff and butte is 
much subdued. The same is true of the country between the Little Blue and 
Big Blue rivers, where glacial deposits have protruded. In this locality the out- 
crops are confined to bluffs near the streams where erosion has removed the later 
deposits. 
The area under consideration is about 100 hundred miles long, with an aver- 
age width of perhaps thirty miles. The greatest width is not far from sixty miles, 
extending from the high hills in western Marion county, where the base of the 
Dakota first appears, along the Smoky Hill river to a point in southern Russell 
county, where the last trace of the Dakota disappears under the Benton. This 
extreme width is due to two causes: the outlier of the Dakota, which in Marion 
county extends far east of the main body, and the long tongue of sandstone, 
which follows for a great distance up the valley of the Smoky Hill. Similar 
tongues follow the valleys of all the streams mentioned above. On the other 
hand, the shortest distance from the Permian is less than ten miles, as at Brook- 
ville, Kan., or on the state line, as mentioned above. The outcrops of the Da- 
kota in this area occupy portions of the following counties: Barton, Rice, 
McPherson, Marion, Ellsworth, Saline, Lincoln, Ottawa, Mitchell, Cloud, Clay, 
Republic, and Washington, Kansas, and Jefferson and Gage, Nebraska. 
NEBRASKA AREA, 
Salt Creek Locality.—All the exposures of this locality are in Lancaster 
county, Nebraska, except a few that are just across the Seward county line near 
Pleasantdale. In nearly every instance these exposures occur on the bluffs along 
the valleys of Salt creek and its tributaries. They are usually quite restricted 
in area, often occupying but a few hundred square yards. The greater part of 
the outcrops occur within a few miles of Lincoln, although outliers are found at 
a distance of from ten to twenty miles in every direction. Near Roca and Ben- 
nett, in the southeastern part of the county, the Dakota is found within a few 
feet of the Permian; although in no instance has actual contact been observed. 
The most eastern exposure is at Bennett, where there is a thirty-foot vertical cliff 
of the Dakota capped by ten feet of Drift boulders. (See plate V.) The Carbon- 
iferous (or Permian) limestone is exposed both north and south of the Dakota 
on a level several feet higher than the top of the sandstone. This furnishes a 
good example of the conditions so often observed throughout the Dakota area, 
where the sandstone has been deposited in eroded hollows of the old Carbonifer- 
ous floor. 
Wells in the vicinity of Lincoln reach the Carboniferous limestone at a depth 
of 270 feet. The Benton limestone near Milford is about 100 feet above the alti- 
