290 The American Geologist. November, 1903. 
by Tonto sandstone which dips into the range at an angle of 
probably 10 degrees. But on the northeast flanks is a long 
area of highly metamorphic rocks, covered in most places with 
lava. Tn this area stands Chromo (commonly called "Hay 
Stack*') butte, a large volcanic neck that towers hundreds of 
feet above the lavas of the surrounding area. 
Mr. Marvine's description of these mountains is as follows: 
"In ascending the Apache mountains, we passed directly from 
detritus composed of Tonto sandstone, without seeing granite, on to 
a portion of the [Tonto] bed itself, which here forms the summits of 
the range, its whole thickness, with -nine overlying shales in places 
still remaining. A spur to the southeast of the line of section, but 
lying much below the summit, also appeared capped with the sandstone. 
The general dip was northeast, and the mass generally lay below the 
edge of the mesa tPlateauk of which it was once a continuation, the 
displacement probably being due to a fault in the valley, the downthrow 
being on the southern side. 
The southeastern end of the range appear- to have less of (lie --and 
stone upon it, probahly being composed of underlying rock-. 
Crossing the divide, there are found upon the southwestern slope 
of the Apache mountains two or three lines of hill- composed of the 
Tonto sandstone, each preserving a gentle northeastern dip and resting 
on granite, hut faulted downward with respect to the summit mass. 
This system of faults seems to continue to the southwestern side of the 
Sierra Ancha. where c everal hills with precipitous southern sides, like 
others near the '"wheat fields" of Pinal creek, are visible." 3 
The Pina! Mountains. — Just west of Globe are the Pinal 
mountains. They run in a northwest and southeast direction 
in about the longitude of iii° to ill" 10', and continue from a 
point somewhat south of Globe to Salt river. Like the Apache 
mountains, they too were faulted portions of the Plateau, as is 
attested by the attitude of the Tonto sandstone. Their main 
mass is of granite, flanked by highly metamorphic crystalline 
schist^. But in the vicinity of Globe and to the south and 
southwest, the mountains are both flanked and occasionally cap- 
ped with a pink rhyolyte which breaks clown in rugged palis- 
ades. Mr. Marvine reported on these mountains as follows: 
"Where crossed, the main mass was of granite, hut upon their 
northeast flanks is a long series of highly metamorphic rocks, con- 
sisting mostly of crystalline schists, micaceous, chloritic. and talcose, 
"their erosion forming an intricate maze of small valleys, separated by 
sharp ridges, which present a strong contrast with the more massive 
features of the mountains. An adjacent spur of the Pinal mountains 
seems still capped with Tonto sandstone, which dips into the range at 
