116 



KANSAS UNIVERSITY QUARTERLY. 



All of these layers exhibit the phenomena characteristic of shallow- 

 water deposits. The conglomerate is composed of small pebbles, the 

 largest noticed not exceeding an inch in diameter, and the average 

 being only about one-third that size. The pebbles are, for the most 

 part, argillaceous and silicious. Induration is more pronounced in 

 the case of the fine-grained sandstone, in which the cementing ma- 

 terial is almost wholly siliceous. 



There occur occasionally throughout the region large lenticular 

 masses of sandstone, in which the cementing material is iron oxide. 

 These masses are by far the most highly indurated of the group. The 



iron was probably depos- 

 ited under the same condi- 

 tions which prevail in 

 certain regions to-day. At 

 the present day, iron, in 

 the form of a soluble car- 

 bonate, is being brought 

 into marshes and bogs, and 

 dei^osited in the form of an 

 oxide or a carl)onate. To 

 assume that the iron of the 

 Dakota formation was de- 

 posited under similar con- 

 ditions seems to be in accord 

 with a logical interpreta- 

 tion of the facts. 



The quartz grains of the 

 Dakota sandstone are held 

 together by at least three 

 kinds of cementing mate- 

 rial, namely, iron oxide, cal- 

 cium carbonate, and silica. 

 The degree of hardness of 

 the stone depends upon 



