DENVER & RIO GRANDE WESTERN ROUTE. 175 
sight of the station of Cimarron nestling beneath the spreading 
branches of giant cottonwoods is therefore most 
Cimarron. welcome. From the station it is impossible to de- 
Perunte 05 feet. termine why the canyon has come to an end and 
i. . 
Denver 329 miles. why one can look out through the trees into open 
country beyond. This change, like many others, is 
due to the geology, and it can be better understood by the traveler 
when he is at least part way up the long grade to Cerro Summit. At 
Cimarron the automobile road on the south side of the river joins the 
railroad, and together they climb to the summit on their way to Un- 
compahere Valley. 
Immediately after leaving Cimarron the traveler will see that, so 
far as the surface features are concerned, he is in an entirely differ- 
ent world. He has just passed through a region of the hardest rocks, 
where he could see little if any soil, but here he can see no rock, at 
Ss. § N. 
Tongue Mesa 
STs 
VA) 
‘ 
‘ 
IN 
Ficurs 46.—Section across Black Canyon at Cimarron. The rocks have broken along the 
fault shown in the section, and the granite on the north has been forced up far above 
its original position. 
least nothing that resembles the rocks of the canyon, though on closer 
examination he will see that the rock is the softest kind of shale—the 
Mancos shale. He may also notice that the contact between the rocks 
of the canyon and those of the plain is extremely abrupt, and if he 
could follow that contact he would find that the same beds are not 
in contact at all places. This variability in contact indicates that 
the rocks of the plain and those of the canyon are separated by a 
fault. In other words, the hard rocks of the canyon have been 
broken away from their fellows down below and lifted until they 
now stand actually higher than the shale, as shown in figure 46. This 
fault has been traced for a long distance, and in all places the edges _ 
of the sedimentary rocks are in contact with the granite. (See rt 4 
LXXXVII, A, B, p. 216.) ; 4 
After leaving Cimarron the train begins its steep climb to the — 
divide which separates the drainage of Cimarron Creek from that — 
of Uncompahgre River. This grade, which is one of the steepest 
grades on the road, is 4 per cent, or 211 feet to the mile. In making 
