GRIMSLEY. | Geology and Geography. 49 
tity of the gypsum has been carried away by stream erosion, a 
destructive erosion which has revealed the store of mineral 
wealth in these hills in the sections along their banks. No 
traces of salt were found near the gypsum rock. 
The geological sections show that the gypsum occurs about 
20 feet above the Cottonwood limestone, which is taken by 
Prosser as the base of the Permian, so that the gypsum comes 
at the base of the Neosho division outlined in his paper. 
The gypsum is 8 to 9 feet thick and rests upon limestone un- 
derlaid by sandy shales. It is covered by non-fossiliferous 
sandy shales, with limestones containing Permian fossils and 
flint nodules, 50 and 100 feet above the gypsum. The cover of 
compact shales has served to protect the underlying gypsum 
from solution by circulating water to a considerable extent, thus 
explaining the absence of the marked erosion and solution effects 
noted in the areas farther south. 
Central Gypsum Area.—In the central area the gypsum rock 
rests upon shales, and dips toward the west. Its thickness is 
somewhat greater than in the northern area, reaching 14 feet, 
and it is covered by sandy shales. In the central part of this 
area the gypsum is compact, and in the lower portion contains 
the small selenite oval crystals which give the rock a spotted ap- 
pearance. In the upper portion it is often filled with more or 
less irregular dark streaks which give a banded appearance. 
At the Solomon mine the gypsum layers are intercalated with 
beds of shale, giving a distinctly stratified appearance to the 
whole series. Abundant traces of salt occur in springs and 
wells near the Solomon river, but no salt is associated directly 
with the gypsum. Just to the southwest of the gypsum area, 
in the Hutchinson-Kingman-Lyons region, occur the large salt 
deposits, which have placed Kansas in the first rank of salt- 
producing states of the Union. 
The Dakota red sandstone forms the top of the hills south of 
Gypsum City and nearly 300 feet above the lower gypsum hori- 
zon, so the gypsum of Saline and Dickinson counties belongs 
to the Marion formation of the Permian. The salt beds men- 
tioned above come higher in the Permian, though found at a 
