154 GUIDEBOOK OF THE WESTERN UNITED STATES 
They consist largely of a thick succession of volcanic rocks of Tertiary 
age similar to those of the Peloncillo Mountains. Here, however, it 
may be seen that these rocks mantle an older mass of Paleozoic sand- 
stones and limestones, in part overlain by sandstone, limestone, and 
shale of Lower Cretaceous age (Comanche series.)'* In one area the 
intrusion of igneous rocks has changed the limestone to marble, which 
has been quarried to some extent. Blocks of this material lie along the 
railroad at Olga, a siding halfway between San Simon and Bowie. 
The deeper canyons in the mountains reveal a basement granite or 
schist of pre-Cambrian age. These mountains sustain a growth of 
pine on top and are part of the Coronado National Forest, which in- 
cludes five timbered ranges in this general neighborhood. (Turn to 
sheet 21.) 
About 15 miles southwest of San Simon is Apache Pass, a saddle of 
moderate height separating the Chiricahua Mountains from the Dos 
Cabezas Mountains and formerly the route of all emigrant travel, 
including the Butterfield stage line. This region was a favorite haunt 
of the Apache Indians because it was not far from their stronghold in 
the Dragoon Mountains. A fight near this pass in 1862 between these 
Indians and the California Column, the troops that came from Cali- 
fornia to restore Union supremacy, led to the establishment of Fort 
Bowie near the pass, which was long maintained as a military outpost. 
West-southwest of San Simon are the Dos Cabezas, the culminating 
summit of the Dos Cabezas Mountains. They consist of two rounded 
knobs of granite close together and strongly suggesting “‘two heads,” 
which the Spanish name means. This striking landmark is visible 
over a wide area in all directions.!® 
“The succession of strata in the | slopes of the Dos Cabezas Range. The 
Chiricahua Mountains is as follows: | limestone under the Martin limestone 
Sandstones and limestones (Comanche | (Devonian) has the character of the 
series) ; limestones of Carboniferous and | Abrigo beds at Bisbee, but Ordovician 
Devonian age; slabby limestone (Abri- 
go) of Upper Cambrian age; and sand- 
stone, in part quartzitic (Bolsa) of 
the arch is broken by faults. Porphy- 
ritic rocks of igneous origin cut some of 
the strata. 
** The Dos Cabezas Mountains are a | 
stone and sandstone on 150 feet of 
are separated by Apache Pass. They 
present the same Paleozoic strata as are 
exposed in the Chiricahua Mountains, 
oe oe 
the n , and the pre-Cambrian 
fossils occur in the upper beds. Most 
of this limestone here has _ slabby 
bedding, weathers to a light blue-gray . 
color, and has brown reticulating mark- 
ings of a supposed seaweed on many of 
the bedding planes. In these peculiari- 
ties it resembles the El Paso limestone 
of southwestern New Mexico. It is 
underlain by 200 feet of slabby lime- 
