DENVER & RIO GRANDE WESTERN ROUTE. 



121 



pure to be worked profitably. The lowermost of these formations 

 is the Weber shale, which lies directly above the Leadville limestone 

 but which is so soft that it makes no showing at the surface. Above 

 the Weber shale lies 200 or 300 feet of sandstone and shale that have 

 a strong reddish tint, and above this for 1,000 feet or more the rocks 

 consist mainly of light-colored sandstone separated by layers of 

 shale. On account of this alternation of rocks the hillside appears 

 to be ribbed horizontally by beds of white rock. 



As the railroad curves back toward the west the river cuts into 

 the Leadville limestone. The rock is first seen near milepost 301, 

 but it rises steeply and at the milepost is 30 feet above the track. 

 Here the direction in which the beds of rock trend or strike begins 

 to be affected by the northward plunge of the Holy Cross anticline,^^ 

 so that the Leadville limestone, instead of becoming higher and 



Figure 31. — Anticline (at left) and sjncline (at right). Perspective view.*: and vertical 

 sections showing the half-cigar-shaped mountains of hard rocks on the anticline and 

 the canoe-shaped point of the syncline. After Willis. 



higher as the train descends the valley, dips down the stream, and 

 before the train reaches Minturn the beds are below water level. 



The town of Minturn is built on a broad, flat valley bottom in 

 which no hard rocks are exposed, but a mile below the station the 

 same beds of rock which before were seen only 

 in the cliffs on the east form the mountain side 

 on the west, showing that the beds of rock are 

 swinging more toward the west than they do 

 farther up the river. The red sandstone that was 

 so conspicuous above disappears on the right about the mouth of 

 Gores Creek. This creek is a clear mountain stream that heads in 

 the high peaks of the Gore Kange on the east, some of which may 

 be seen by looking directly up its valley. The stream is noted for 



Minturn. 



Elevation 7,825 feet 

 Population 298. 

 Denver 302 miles. 



"An upward bulge or fold of the 

 rocks is termed an anticline; if it is 

 long and narrow it is frequently called 

 an arch, but if it is sliort and nearly 



circular in outline it is called a dome. 

 The corresponding downfold is called 

 a syncline. These folds are repre- 

 sented in figure 31. 



