50 University Geological Survey of Kansas. 
topographically lower level in the direction of the dip of the 
gypsum rocks. 
The shales and gypsum in the Smoky Hill river region are 
irregularly folded and broken, as a result of settling, possibly 
by the leaching out of former salt beds and part of the gypsum. 
The salt water may have percolated downward, to rise again in 
the salt springs of that region. 
Southern Gypsum Area.—The southern Kansas gypsum, 20 
to 50 feet thick, extending into Oklahoma and Texas, is found 
in the Red Beds. Near Medicine Lodge it forms the cap of the 
hills, but further west it is covered by red sandy shales, and the 
same kind of shales are found everywhere below the gypsum. 
Strata of sandstone of varying thickness are seen in the shales 
below, and the base of the Gypsum Hills consists of a heavy 
stratum of sandstone. Some of the sandstone is ripple marked, 
giving evidence of shallow water conditions. 
The entire series of shales, sandstones, and gypsum is very uni- 
form in character through the whole region. The gypsum is 
not broken by clay seams, and is compact and remarkably pure. 
The shales below contain selenite and satin spar layers run- 
ning in all directions, forming a network. A short distance be- 
low the solid gypsum occurs a layer of sand and gypsum nodules 
cemented together by gypsum, forming a very enduring layer 
of greenish color, which projects from the hillsides and can be 
readily traced throughout the region. The dip of the strata is 
slight and somewhat irregular, but it appears to be mainly south 
or southwest and the deposit thickens in that direction. 
The caves, natural bridges, and the irregular upper surface of 
the gypsum, as well as the selenite layers in the shales below, 
give evidence of great removal through solution. A salt deposit 
occurs to the southwest in the Salt Plains district, but no trace is 
found close to the gypsum. 
Small deposits of gypsum are found between the northern and 
central areas, and a few between the central and southern areas. 
In age, the gypsum deposits are older at the north and younger 
to the south. In level above the sea, the deposits are lower at 
the north and higher toward the south. 
