STRATIGRAPHIC EVIDENCE 329 



Another fact of importance may be pointed out regarding this Medi- 

 cine Bow region, namely : Bowen reports that he has found dinosaurs at 

 a number of horizons that are from 300 to 500 feet above the top of the 

 'Hipper Laramie'^ as fixed by Veatch. This shows the extent of the ver- 

 tical range of the dinosaur fauna. 



In North Park, Colorado, the upper plant -bearing beds are apparently 

 the same as those in Carbon County, Wyoming, as the two areas are 

 closely connected, and from there it is but a step to the Denver basin of 

 Colorado, where Whitman Cross demonstrated the presence of the great 

 unconformity which separates the dinosaur-bearing Arapahoe and Den- 

 ver formations above from the Laramie beneath. The Laramie is here 

 reduced in thickness to about 1,600 feet, and at Colorado Springs, 75 

 miles south of Denver, which is the southernmost point at which Lara- 

 mie is known, the thickness is reduced to 425 feet. W. T. Lee has shown 

 to the satisfaction of many that the full Cretaceous section, to and in- 

 cluding the Laramie, was laid down uninterruptedly over the area where 

 the Rocky Mountains now exist. As the most complete section believed 

 to represent the Laramie— namely, near Carbon, Wyoming— has a thick- 

 ness of 5,000 feet, and as the Laramie in the Denver basin is only 425 to 

 1,600 feet thick, it is an indication that the unconformity may have re- 

 moved at least 4,000 feet of beds and probably it was very much more: 

 in fact Crosses estimates places it at 12,000 to 15,000 feet. 



Between the Denver basin and Colorado Springs is a series of arkosic 

 beds to which the name Dawson arkose has been given. The Dawson 

 rests with marked discordance on all underlying beds, and is shown by 

 its stratigraphic relations and contained flora to be the time equivalent 

 of the Denver and Arapahoe formations. The Dawson contains abun- 

 dant remains of dinosaurs, and in direct association with them Eichard- 

 son found a mammal bone which Gidley pronounces to be characteristic- 

 ally Creodont, anrl says : "From our present knowledge the type repre- 

 sented could not be older than Wasatch." This association of dinosaurs 

 and mammals is obviously of importance. 



In the Eaton Mesa region of southern Colorado and adjacent New 

 Mexico, W. T. Lee has also demonstrated the presence of the same great 

 unconformity, which by actual measurement has removed over 6,000 

 feet of beds and probably it was much more. Lee has also demonstrated 

 the presence of the unconformity of many points around the southern 

 end of the Eocky Mountains and up along the western base to soutliera 

 Colorado. In this Eaton Mesa region the beds above the unconforriiity. 

 called the Eaton formation, are not known to be dinosaur-bearing.; but 

 they do contain an ample flora, which is correlated with the Denver and 



