136 GUIDEBOOK OF THE WESTERN UNITED STATES. 
spanning gulches, and finally scaling the south wall of the canyon. 
The line takes a short cut for the valley of Roaring Fork, up which 
it is carried to and across the Continental Divide at Hagerman Pass. ° 
So far the geologic structure of the great upfold (anticline) is 
comparatively simple, having been broken at one point only. The 
highest point in the fold, the axis, is passed near milepost 354, and 
beyond that point the quartzite rapidly approaches railroad level, 
but it is broken by so many faults that few travelers can trace the 
formations and understand the manner in which they appear and 
disappear. By the aid of the map, however, those who are interested 
in geologic structure may obtain a fairly good idea of what has 
happened here and of the shape in which the rocks were left. 
All the formations are regular as far as milepost 355, near Grizzly 
siding, where the quartzite has been abruptly dropped from a height 
of at least 350 feet above the railroad to water level. This change 
in the position of the rocks is the result of a fault,4? which trends 
slightly west of north, probably cutting the high bluff on the west 
side of Grizzly Creek, which here enters the river from the north. 
Beyond this fault the beds rise gradually until the white quartzite, 
which is at water level at Grizzly, is above the railroad and the 
canyon is rough and rugged, as shown in Plate LIX. Half a 
mile beyond milepost 356 about 50 feet of the pink quartzite has 
made its appearance. At this point the granite on the opposite side 
of the river rises to a height of at least 300 feet. This discrepancy 
marks another fault, which does not cross the railroad but trends 
nearly east and west directly along the stream. The rocks on the 
south side of this fault have dropped about 300 feet, or those on the 
north have been lifted a similar distance. 
Beyond the point where the railroad approaches the fault most 
closely the rocks descend, and within a short distance most of the 
quartzite has disappeared; but the road here enters Noname Park, 
and it is almost impossible from the moving train to determine the 
structure. However, a little farther along the Leadville lime- 
stone also dips steeply toward the south and is broken by a fault 
that runs nearly parallel with the one just described. This fault 
lies near the south wall of the park. The Leadville limestone is 
dropped on the north side of the fault and may be seen topping the the 
“As the term “fault” means a | faults seen from the Denver & *G 
break in the rocky strata of the earth 
and as the breaking is always accom- 
panied by slipping and erushing, one 
might expect to find the surface of the 
ground disturbed along a fault. It 
undoubtedly is disturbed when the 
movement takes place, but all the 
Grande Western trains : 
long ago that any break or msearhe 
ance of the surface they caused has 
been obliterated by the streams and — a 
the weather. Examples of the lack of 
evidence of faults on the surface are 
shown in Plate LXXXVI, 4 and B. 
