SOME FEATURES OF THE FORT DODGE GYPSUM.^ 



JAMES H. LEES. 



A New Basal Conglomerate. — During the proseeiition of field 

 study of the gypsum for the Iowa Geological Survey the writer 

 found immediately beneath the gypsum in several places a basal 

 conglomerate which has not heretofore been described in reports 

 on the region. The locality where this conglomerate is best de- 

 veloped is in a ravine on the west side of Des Moines river op- 



Fig. 194. — ^Cong'lomerate beneath gypsum in the ravine opposite Two Mile 

 creek, Webster county. The dark sliadow across the middle of the picture 

 divides the gypsum from the conglomerate. 



posite Two ]\Iile creek about three miles south of Fort Dodge. 

 The Fort Dodge, Des Moines and Southern railway extends 

 along this ravine and has exposed the conglomerate in some of 

 its cuttings. In the lower part of the ravine the gypsum is seen 

 to lie on the black or dark colored Coal Measures shales. In 

 places the contact is direct while in other places about six inches 

 of clay, evidently residual, intervenes. Perhaps one-half mile 

 up the ravine there is exposed beneath the gypsum a reddish or 



^Published with permission of the Director of the Iowa Geological Survey. 



