200 University of Kansas Geological Survey. 
portion of this formation. It would seem that in some way ocean 
water remained over these areas longer than it did farther to the 
south, as they have younger rocks than can be found in some of the 
southern parts. Plate XX VI is a section drawn north and south 
near the west side of Kansas to represent the relative positions and 
arrangements of the various Cretaceous rocks which were formed 
during the time now under discussion. It will be noted that at the 
extreme southwestern part of the state the Dakota sandstone occurs 
at the surface. As one passes northward one finds the relatively 
thin edges of succeeding formations in the order of their deposition, 
first the Dakota, then the Benton, next the Niobrara, and later the 
Fort Pierre. Could this section. be continued farther northwest it 
would show succeeding formations, the Fox Hill and the Laramie, 
belonging to the Cretaceous. So far as the indications in Kansas are 
concerned, therefore, it would seem that this great inland sea was 
drained to the north by the elevation of the continent being greatest 
on the south. 
The study of the Cretaceous formations in the great inland area 
progressed slowly from the first excursions of Meek and Hayden in 
the ’50’s until quite recent times. Slightly different systems of 
nomenclature have been suggested by different ones, each of which 
has had its advocates. They have more or less been abandoned, how- 
ever, or combined, until at the present time it is customary to classify 
the upper Cretaceous rocks in the following manner: 
INCH Hy J0Cae ISHN seOWI Oss o's olaiciaoo100 6655004 
INO, 2h [bomE IPLewES GiROWD. o406o000c0b sco ce \ 
mie & Niobrara, Cramp ' Colorado Formation. 
ING, 2 IBELUOIN, | GAROWIDS ib bb oo 6 6'5 o'b0b 4 6.0.0 od « \ 
No Dalkkotail Group epsnicn tcueuene ois cau tieeaan nererainan Dakota Formation. 
Of these all but No. 5 are found in Kansas and are included in 
the following description. 
l Montana Formation. 
50010 00 000050 0:0 0.0 O'0)0 0 
The Dakota formation is interesting and peculiar in some re- 
spects on account of the strong indications in different parts of 
America that it is of fresh water origin. By descriptions given of it 
for both north and south of Kansas, it would seem to represent 
fresh water deposits, but here in Kansas it furnishes marine inverte- 
brate fossils, and has other properties, such as salt and gypsum 
