192 



GUIDEBOOK OF THE WESTERN UNITED STATES. 



The structure or attitude of the beds in this part of the canyon is 

 simple. The rocks rise abruptly at an angle of 30° from the shale 

 valley on the north, but they soon flatten and for some distance lie 

 flat or dip slightly toward the southwest. The railroad follows the 

 A'alley of Salt Creek, but the bends of the creek are so short that 

 they do not everywhere accommodate the railroad, and about a mile 



from Mack it cuts 

 through one of the 

 small bends by a 

 short tunnel in the 

 sandstone member of 

 the McElmo. 



About a quarter of 

 a mile beyond mile- 

 post 472 the railroad 

 reaches the rirer, and 

 from this point to 

 AVestwater it follows 

 the right bank. The camon, because of its red color, is generally 

 called Ruby Canyon, but the most strongly marked red rocks do not 

 appear until the traveler is about half a mile below 

 ^* the siding named Rubv. Here the massive sandstone 



Elevation 4,407 feet. ^^ , it t ■» r 't-it it i 



Denver 473 miles. that Underlies the McJLlnio comes up suddenly m a 

 great fold,^^ which may be seen on the opposite side 

 of the river. (See fig. 50.) The uppermost bed in this fold is not red 

 but nearly white, although generally it is stained pink from the 

 overlvinar McElmo 



shale. The white 

 sandstone (La Plata) 

 has a thickness of 

 nearly 100 feet, but 

 below it is a bed of 

 somewhat softer sand- 



FiGDBE 50. — Short fold in massive sandstone (on the left 

 of the westbound train) opposite Ruby siding, below 

 Mack. 



Figure 51. 



Different types of anticlines. 



stone, which is deep red. The fold is very short but steep, the beds 

 having a dip of about 45°. The angle of dip decreases, however, and 

 in a very short distance the beds lie practically flat. 



^ The rock folds in the plateau dis- 

 trict of Colorado and Utah are differ- 

 ent from those which the traveler has 

 seen in the Rocky Mountain region. 

 Generally anticlines are great upward 

 bulges in the rocks, in which the beds 

 are nearly equally curved in all parts, 

 as shown in A, figure 51. In the pla- 

 teau region the general effect of an 



anticline may be the same, but the 

 location and form of the fold may be 

 very different," as sho\vn in B. The 

 beds are very strongly folded on the 

 flanks of the anticUue, but the area 

 affected by the fold is very narrow. 

 The traveler may see many such folds 

 as that shown in B before he reaches 

 Salt Lake City. 



