LOCATION, CHARACTER, AND FAUNA OF THE SECTIONS 257 



both vertically and laterally, so that the details of near-by sections always 

 vary. There are local thin beds of lignite, the most persistent of which 

 is near the top. The bedding is everywhere irregular, and the alternations 

 of shale and sandstone toward the top form such a gradual transition to 

 the overlying Graneros (lower Benton) shale that in most sections the 

 line between Dakota and Graneros is more or less arbitrary. Finally, 

 however, the sea prevailed and the purely marine Graneros shale was de- 

 posited over the whole region to a depth of 70 to 100 feet, followed by the 

 chalky beds of the Greenhorn limestone full of Inoceramus labmtus and 

 foraminifera, of which the most abundant form is Globigerina. A few 

 miles to the west a higher shale, the Carlile, is seen, overlain by the 

 chalky limestone and shale of the Niobrara. The section is represented 

 by number 4 of the chart (plate 4). 



The lower part of this section below the upper hundred feet of the 

 Dakota is based on well data, which indicate that rocks of Dakota type 

 have a total thickness of 350 or 400 feet, and no evidence has been found 

 that would suggest the reference of any of these rocks to an older forma- 

 tion. 



NEBRASKA SECTIONS 



On Platte Eiver 5 miles southeast of Ashland, Nebraska, and about 

 100 miles south of the typical exposures of the Dakota which have just 

 been discussed, a basal Cretaceous sandstone is exposed resting uncon- 

 formably on Penns}dvanian limestone. No fossils have been found in it, 

 but there seems to be no good reason for questioning its reference to the 

 Dakota. 



The upper part of the Dakota near Fairbury, southern Nebraska, has 

 yielded a faunule of fresh and brackish water mollusks described by C. A. 

 White 4 under the following names : 



Vnio barbouri. 

 TJnio sp. 

 Corbula hicksii. 

 Goniobasis jeffersone nsis . 

 Goniobasis sp. 

 Yiviparus hicksii. 

 Pyrgulifera meekii. 



KANSAS SECTIONS 



Farther south in northern and central Kansas the top of the Dakota 

 shows the same close relationship as in eastern Nebraska with the over- 



* U. S. Nat. Mus. Proc, vol. 17, 1894, pp. 131-138. 

 XVII— Bull. Gkol. Soc. Am., Vol. 33, 1021 



