DENVER & RIO GRANDE WESTERN" ROUTE. 



125 



animals in the upper part of this formation north of Canon City 

 is described briefly on page 70. 



Above the Gunnison formation lies the Dakota sandstone, wliich 

 crosses the track near milepost 317. This sandstone marks the base 

 of the Upper Cretaceous and is one of the most persistent and wide- 

 spread formations of the Rocky Mountain region. It extends from 

 northern Wyoming to central New Mexico and from Omaha to cen- 

 tral Utah. In the valley of Eagle River it consists of a single layer 

 of brownish-yellow sandstone 30 to 40 feet thick. It slopes up the 

 hillside on the right and forms the crest of a ridge that runs nearly 

 parallel with the railroad for a mile or more. Across the river it 

 fomis the northeastern slope of the hill in what geologists call a 

 " dip slope." 2^ 



The formations so far described are fairly hard, and consequently 

 they form the walls of a rather narrow canyon, but immediately over 

 the Dakota sandstone lies the Mancos shale, which is one of the 

 softest rocks in this region. It is so soft that it readily wears away 

 under the action of the weather and the streams, and consequently it 

 seldom or never forms high or large hills. Where Eagle River 

 crosses the outcrop of the Dakota sandstone and cuts into the shale 

 the valley immediately expands to a width of nearly a mile and con- 

 tains several ranches. In fact, nearly all the shale on the left side of 

 the river has been removed and the valley takes the form of a rock- 

 rimmed basin. The. beds of rock on the east side of the basin are 

 steeply upturned, but those on the west side dip toward the middle 

 of the basin at a very low angle, which can hardly be detected but 

 which may be seen in the cliffs of shale almost directly ahead. This 

 little basin or downfold of Cretaceous rocks forms the extreme south- 

 ern tip of the great s\Ticline or basin of Cretaceous rocks which car- 

 ries the valuable coal beds of Routt and Moffat counties, in the 

 northwestern part of the State, and which underlies most of south- 

 western Wyoming. 



As the train passes milepost 317 the traveler, by looking back the 

 way he came, may obtain another glimpse of the high peaks of the 

 Holy Cross Range, which, if they are covered with snow, are still 

 consfjicuous objects above the horizon. After the traveler passes the 

 axis of the syncline, between mileposts 317 and 318, he can see the 

 gentle rise of the rocks on the west (left) of the railroad in a great 

 cliff of shale, which is nearly ahead but which may be seen on the 

 left from milepost 318. Some bands of white, impure limestone can 



"•a dip slope is formed by a bed of 

 hard rock from wLich overlying soft 

 material has been removed by rains 

 and streams, and as the slope of the 



surface is the same as the dip of the 

 bed tliat controls the surface it is 

 linown as a dip slope. 



