7m Se ” 
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, which 
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 
forms the northeastern slope of the hill in what geologists call a 
“dip slope.” %° 
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 syncline 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 
Conspicuous 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 | surface is the same as the dip of the 
hard rock from which overlying soft | bed that controls the surface it is 
material has been removed by rains | known as a dip slope, 
and streams, and as the slope of the 
