HAwortuH. | The Upper Cretaceous. 201 
within it, which strongly imply that it was formed under ocean 
water. This formation is so largely composed of sandstone that it 
is frequently spoken of as the Dakota sandstone. It is probably 
true, however, that less than half of the thickness of the whole 
Dakota is sandstone, the remainder being different kinds of shales, 
of which clay shale is the most abundant. lLignite or brown coal is 
found in place in sufficient quantities to become an article of com- 
merce. Other changes, perhaps equally great, imply that a detailed 
study would result in the subdivision of the Dakota into a number 
of groups or formations. 
The Benton is largely composed of limestone, and is rich in 
marine fossils. Whatever may have been the character of the water 
under which the Dakota was formed it is certain that with the close 
of the Dakota ocean water covered the whole of the great inland 
area. The great abundance of shale in the Benton, constituting 
more than two thirds of the total thickness, shows how a large 
amount of earthy material was carried from the dry lands into this 
inland ocean. It is probable that the main portion of it was carried 
westward from the large continent lying to the east, although it is 
difficult to make positive statements regarding this. It is known 
that at this time portions of the Rocky mountain area existed as dry 
land covered with different forms of crystalline rock. The sedi- 
ments in the whole of the Cretaceous of Kansas from the beds of the 
Comanche to the top of the Fort Pierre seems to be entirely free 
from any fragments of crystalline rock. This strongly implies that 
the drainage was westward from the Coal Measures of the great 
interior area. 
With the close of the Benton Niobrara time was ushered in. 
During this period a less amount of sediment was carried oceanward 
from the dry lands, and a correspondingly larger amount of 
the Niobrara is composed of different forms of limestone. Why 
this decrease in the deposition of dry land sediment it is dif- 
ficult to say. -Probably it was due to the climatic change re- 
sulting in a less rainfall on the adjacent lands. However that 
may be, the conditions were such that the character of the lime- 
stone formed was very different from that found elsewhere in Kan- 
Sas, or in America outside of the Niobrara. The great mags of the 
