SOUTHERN PACIFIC LINES 169 
Between Animas and Pratt sidings the railroad crosses a sheet of 
black scoriaceous basalt, a local lava flow of relatively recent age. 
Pratt Several low cinder cones mark vents through which 
tion 4,425 feet, the lava reached the surface. About 2 miles west of 
New ¢ Orleans 1,34 Pratt sandstone of Comanche (Lower Cretaceous) 
age constitutes a ridge extending for a mile or more 
along the east slope of the mountain just north of the railroad, and a 
short distance northeast of this ridge, or about 1 mile siopthioresh of 
Pratt, is a conical butte of limestone of the Magdalena group. 
West of these features the railroad passes through Antelope Pass, a 
deep gap in the Peloncillo Mountains, and descends about 450 feet into 
the San Simon Valley, which drains into the Gila River. This moun- 
tain range extends for about 100 miles along the southwestern margin 
of New Mexico and consists mainly of Tertiary lava flows similar to 
those constituting the Animas Mountains and many other ranges, ina 
thick succession which is considerably flexed and faulted. Heavy 
beds of massive lava * and tuff lying nearly horizontal are well 
exposed on the north side of the gap. There are also necks and 
craters which were sources of outflow, but the region has been so 
deeply eroded since the time of eruption that the volcanic history is 
difficult to decipher. 
About 12 miles north of Antelope Gap is Granite Gap, through which 
highway 80 crosses the Peloncillo Mountains in a low pass. Here the 
rocks underlying the Tertiary sige are revealed rising in a 
large mound in the center of the range.” 
Beyond Antelope Gap the railroad bends southward and ascends 
the broad alluvial valley of San Simon Creek in order to pass around 
the south end of the Chiricahua Mountains. This high rugged 
range, rising grandly to the west of the railroad, presents an intricate 
mass of high peaks and a steep mountain front deeply 
notched by canyons. The higher part of the range 
is made up of a thick succession of lava flows which 
lie on an irregular floor of Paleozoic and Mesozoic 
, sandstones, and shales. There are many 
faults, flexures, overlaps, pad other fe 
= 
%® Rhyolite with phénoerysts of 
quartz and orthoclase, as oa 
by C. 8. Ross, of the U. S. Geologi 
ey. 
27 The El Paso limestone, here ex- 
posed, presents the same features as 
the Franklin Mountains, near El Pass 
but is much thinner. A massive dark 
limestone 30 feet thick strongly suggests 
the Fusselman. It is overlain by 100 
152109°—33——12 
feet of dark shale, jecbaniy Percha 
(Devonian), which is capped by lime- 
stones similar to the Escabrosa (Missis- 
sippian) of southeastern Arizona. The 
Magdalena group is well r 
by 
overlying limestone, the outerop of 
e 
which extends far to the north. 
granite is exposed in an area of about 
1 square mile, 
a 
