152 
uation of the Providence Mountains. 
GUIDEBOOK OF THE WESTERN UNITED STATES, 
To pass the south end of this 
range the railway has to be deflected far southward in its course 
beyond Goffs. 
At milepost 646 the railway passes the south end of the Iron 
Mountains! and bears slightly north of west to Cadiz. Along the 
west side of the mountains is a westward-facing cliff 
Cadiz. 
Elevation 821 feet. 
Kansas City 1,569 miles. 
of the sandstone and limestone, surmounting rugged 
ri of granite. At a point on the mountain slope 
miles northeast of Cadiz a quarry has been opened 
in dark el es limestone, which yields a material of attractive 
appearance, but it has not yet been shipped to any great extent. 
At Cadiz the main line is joined by a branch from Phoenix, Ariz., 
which crosses Colorado River at Parker, 60 miles below Needles, and 
rises with easy grade over the divide that separates the river valley 
from the long basin extending to Cadiz and beyond. One branch of 
this basin is followed by the main line of the railway from Goffs to 
Cadiz, far down its slope. 
From Cadiz westward the course of the track is somewhat north of 
west, through the center of a series of wide basins bordered on both 
sides by high mountain ranges. The bottom of this basin is reached 
1The Iron Mountains present a con- 
siderable variety of rocks, including pre- 
Cambrian granite and overlying quartz- 
ites, limestones, and shales af Cambrian 
altered most of the limestone to marble. 
In places thick deposits of voleanic ash 
and tuff lie on the older rocks and are in 
turn overlain by a thick sheet of black 
body of overlying limestone and shale, 
all dipping steeply to the east. From the 
vicinity of milepost 645, which is about 
halfway between Siam and Cadiz, the 
contact of these sedimentary rocks on the 
granite is visible about half a mile north- 
west of the track, as shown in figure 37. 
The contact and the beds all dip at a 
moderate angle to the east. The granite 
has a wave-worn surface, and the beds 
FIGURE 37.—Sketch section showing quartzite (hard san sandstone) on granite at south end of the Irom 
Mountains, southwest of Siam, Cal., looking north. 
lava (basalt), capped by a sheet of light- 
colored lava (rhyolite). The sheets of 
lava cap a succession of high eastward- 
of tin range, 6 to 8 miles north of the rail- 
a in the 
two gaps near the south end of the range. 
It is overlain in ridges north and south of 
these gaps by rocks of Cambrian age, con- 
sisting of a basal quartzite with a thick 
were deposited on this surface when it — 
was a sea bottom, a fact which establishes 
the age of the granite as pre-Cambrian. 
A small knob a short distance west of 
milepost 644 is of Brel ie like the knobs 
east of Siam and o 
the © east side of the te Mountains. 
Cambrian fossils have been found and — 
apparently the southernmost outcrop of ss 
the Paleozoic rocks in this region = 
rs farther north on 
PN 
