258 T. W. STANTON DAKOTA SANDSTONE PROBLEMS 



lying marine shale of Graneros age, and the limestones tilled with 

 Inoceramus Jabiatus are less than 100 feet above the top of the Dakota. 

 The upper 100 feet or so of the Dakota here are, beyond reasonable doubt, 

 the equivalent of the typical Dakota exposures in the neighborhood of 

 Sioux City. Stratigraphy, lithology, fossil plants, and invertebrates all 

 support this correlation, and no one from the study of these rocks alone 

 would think of putting them in a different system or series from the 

 overlying marine shale. But in central Kansas, in the neighborhood of 

 Salina and southwestward, the Cretaceous rocks are well exposed from 

 the top of the Dakota, and higher, down to the contact of the Cretaceous 

 with the Permian, and in the lower hundred feet of these Cretaceous ex- 

 posures there is a marine fauna which is now known to be closely related 

 to the Comanche fauna of Texas. In the early days, when the existence 

 of the Comanche series was unknown, these beds, with their marine fauna, 

 were unhesitatingly referred to the Dakota. Later, as the stratigraphy 

 and geologic history of the general region became better known, the base 

 of the Dakota in this area and the relation which that formation holds 

 with the Comanche series became important questions. After the field 

 season of 1898, when, in company with Lester F. Ward and C. N. Gould, 

 I had studied the Cretaceous . of southern and central Kansas, I an- 

 nounced 5 that our "field-work in Kansas shows a very close stratigraphic 

 connection between the Dakota leaf -bearing sandstone and the underlying 

 marine beds of the Comanche series," a conclusion which no one has seri- 

 ously questioned since. I believed then, however, and I still believe, that 

 the fauna with a strong and definite Comanche element in central Kansas 

 is confined to the lower, or Mentor, beds, above which there are 200 to 

 300 feet of Dakota rocks. It is these rocks above the Mentor which have 

 yielded probably 90 per cent or more of the described Dakota flora. The 

 localities known as Fort Harker, Fort Ellsworth, Ellsworth County, and 

 Delphos are all in this part of the section, and it is reasonably certain 

 that nearly all of the Dakota plants credited to Kansas without more 

 definite locality were collected by Sternberg, West, and others from the 

 same horizons, ranging through, perhaps, 100 feet of strata near the 

 localities mentioned. 



Logan's description of the Dakota of central Kansas was perplexing 

 because he divided the Dakota formation into a lower, or ferruginous, 

 division containing all the Dakota flora and no mollusks, and an upper, 

 or saliferous, shale division in which the fossils are all marine inverte- 



•"• Twentieth Ann. Rept. U. S. Geol. Survey, pt. 1, p. 64. 



8 W. N. Logan : The Upper Cretaceous of Kansas. University Geological Survey of 

 Kansas, vol. 2, 1.XD7. pp. 105-234. The Dakota is described on pages 206-215. 



