122 GUIDEBOOK OF THE WESTERN UNITED STATES. 
miles north. Between mileposts 13 and 15 the Kaibab limestone, 
which underlies the lava, appears at the surface in several localities, 
but the irregular margin of the lava extends to milepost 18. From 
several points there are excellent views of Mount Sitgreaves to the 
east and Kendrick Peak to the northeast. 
Beyond milepost 18 the entire surface is Kaibab limestone, which 
constitutes most of the great Arizona Plateau. This limestone rises 
gradually northward to the rim of the Grand Canyon and is trenched 
at intervals by small valleys opening westward and draining into 
Cataract Creek, a stream which flows inito the Grand Canyon 60 miles 
to the northwest. In this region the plateau does not bear the pine 
forest which is so characteristic of it farther east, and even the 
junipers and pifions are widely scattered, much of the surface being 
covered by small brush. This change is due to diminished rainfall, 
for the other conditions are identical with those found farther east. 
Lava 125 feet 
Plateau —_——— SESS 
Ee] Saari 
SS SO —eO———eee 
FIGURE 27.—Section th h Red Butte, near Grand Canyon, Ariz. 
From points near milepost 40 (see sheet 19a, p. 130) Red Butte is a 
conspicuous feature, rising about 850 feet above the plateau a few 
miles east of the railway. As shown in figure 27, this butte is an 
isolated pile of gray and red shales, red sandstone, and conglomerate, 
protected by a 125-foot cap of black lava (basalt), The preservation 
of these beds in this butte is of great interest, for it shows that 
younger rocks formerly covered the Kaibab limestone of the plateau 
to a thickness of at least 800 feet. These rocks have been removed 
