8 GUIDEBOOK OF THE WESTERN UNITED STATES. 
At the loop which the railroad makes before it climbs the eastern 
front of the mountains there is exposed a dark shale (Benton shale 
or lower part of the Colorado group), which lies near the base of the 
Upper Cretaceous series. At Plainview the road cuts through a 
hogback? formed of the upturned edge of the underlying Dakota 
sandstone and shows some of the variegated sandstone and shale of 
the Morrison formation, which lies directly below the Dakota sand- 
Plainview, 
dash east —— the gece ae ee, the Morrison formation 
and the Carboniferous sandst 
Figure 2.—Dakota hogback and mountain front north o w, as seen from the 
“ Mord tr oad.” The 
stone, or toward the mountains. The succession of rocks in the hog- 
back and the mountain front is shown in figure 2. Beyond the 
valley formed in the soft rocks of the Morrison formation the red 
sandstone (Fountain formation) lies upturned against the mountain 
front in great triangular slabs like the teeth of a gigantic saw. 
(See Pl. III, B.) The railroad in climbing the mountain front 
pierces the projecting points of this hard layer by many short tun- 
Denver itself, but here it is so far | breaks up or “ slacks ”—the lumps fall 
h 
bed m shafts which are sunk value. Notwithstanding 
nearer the center of the basin and se defects, subbituminous coal is 
which reach the coal at different | extensively mined d a ready 
depths. market aaa the Denver region. 
The coal is what is now generally 
furious, a rank which is 
ast. I 
peels lignite,” cece of its color 
and because it has some of the proper- 
ties of a lignite, or woody coal. The 
subbituminous coal does not soil the 
hands and is a desirable domestic fuel, 
but upon exposure to the weather it 
* A name applied in the Rocky Moun- 
tain region to a sharp-crested ridge 
formed by a hard bed of rock that dips 
rather steeply downward. One of the 
best examples of this kind of surface 
feature can be seen at Canon City, 
where the Skyline Drive follows the 
sharp crest of a hogback of Dakota 
sandstone for miles, as shown in 
V (p. 78). 
<9 enagsameptanmec ace eeapriict 
