288 University of Kansas Geological Survey. 
hundred square miles. South of it, it is probably over one hundred 
square miles, exclusive of the sandhills. 
TOPOGRAPHY. 
The rough surface of the Permian to the east, the Dakota to 
the north, and the peculiar topography of the sandhills to the south- 
west, form a marked contrast to the monotonously level surface 
of the Equus beds area. There are several places where one may 
travel three or four miles without rising or descending twenty feet. 
Along the east and west section lines two miles north of McPherson 
one may travel ten miles without passing a sag of more than twenty 
feet. As a rule there is just slope enough to the surface for good 
drainage, while occasionaily the water stands in lakes and basins 
in slight swales in the surface. The largest of the lakes is Lake 
Ininan, ten miles southwest of McPherson. The largest basin is 
nearly three miles in diameter, and is situated two miles west of 
McPherson. 
The divide between the Arkansas and the Smoky Hill river passes 
through this area and averages a little more than 1500 feet above 
sea level.t The Arkansas river at the southeastern limit is 1290 
feet, a fall of 200 feet in sixty miles. The Smoky Hill river, at its 
nearest approach, is within four miles of the divide, but its bed 
is nearly 200 feet below it. The Little Arkansas river drains the 
entire area of the Equus beds except a very small portion north of 
the divide, drained by the Smoky Hill, whose small tributaries are 
rapidly cutting into the divide, and will cause it to migrate farther 
south in the course of time, as the streams on the south are already 
at their base level and are not carrying the soil away to any con- 
siderable extent. 
STRUCTURE. 
These beds consist of alternating layers of sand and clay with a 
stratum of “volcanic ash” in part of the northern area. Near the 
bottom of the deepest part of the channel there is a heavy stratum 
of gravel, as shown in sections 1, 2, and 3, figures 1, 2 and 3 of Plate 
XLVI, which pass through McPherson, Harvey county, and Hal- 
stead respectively. This bed lies at a depth of 140 to 150 feet or 
1 U. S. Topographic Sheets. 
