36 GEOLOGY OF THE DENVEB BASIN. 



representatives of tin- Ceratops fauna have been described, the true posi- 

 tion of the particular beds in which their remains occur lias in no case, 

 outside of the present field, been so definitely determined stratigraphically 

 as to permit of their exact correlation with other known horizons. From 

 information furnished by Professor Marsh and others it appears that repre- 

 sentatives of the Ceratops fauna have been recognized at other localities 

 along the east front of the Rocky Mountain uplift from New Mexico to 

 ( !anada, and in the great bay that once extended across the uplift westward 

 to the base of the Wasatch Mountains. Wherever these remains have been 

 systematically studied by the vertebrate paleontologist, his attention has 

 been principally directed to the biological problems involved, it having been 

 assumed that the horizon occupied by them was sufficiently defined as 

 Laramie, since it was higher than the Fox Hills Cretaceous, and the affini- 

 ties of the fauna itself were regarded as Cretaceous rather than Tertiary. 



After a careful weighing of all the available evidence furnished by 

 invertebrate and plant remains, as well as l>v vertebrates found in these 

 localities, and of the somewhat meager data as to their relative stratigraphic 

 position, Mr. Cross concludes that the Ceratops fauna has not as vet been 

 described from any locality belonging beyond dispute to the true Laramie, 

 as defined by King in the Fortieth Parallel Reports, while several of the 

 known occurrences may be correlated more or less definitely with the 

 Arapahoe or Denver formations. 



POST-DENVER MOVEMENT. 



After the deposition of the Denver beds the region was subjected to 

 another orographic movement, whose dynamic effects are particularly 

 noticeable in the steeper upturning of the Mesozoic strata along the foot- 

 hills. At this time the Denver Lake was drained and the Denver beds were 

 thereafter exposed to erosion. In the absence of any recognized represen- 

 tatives of the beds that in other parts of the Rocky Mountain region, nota- 

 bly along its western flanks in the Colorado and Green River basins, were 

 mosl abundantly deposited during the latter half of the Eocene period, it 

 is impossible to fix with any definiteness the time of this movement. It 

 may have occurred at the close of the Eocene, and hence been contempo- 



