SOUTHERN PACIFIC LINES 289 
Tertiary beds also constitute the Yuha Buttes, 8 miles west of 
Dixieland. Among many fossils occurring in the sandstones on 
these mountains are numerous corals, many of them finely preserved. 
According to Vaughan, this coral fauna, which is considered to be of 
early Pliocene age, contains forms not found in the Pacific Ocean. 
Its Atlantic Ocean affinities indicate that in late Tertiary time there 
was an oceanic connection that permitted the Atlantic fauna to 
extend to the head of the Gulf of California; this connection, however, 
may have been as far south as the Isthmus of Tehuantepec. Fossils, 
especially scallop shells, occur in large numbers about Carrizo 
Mountain and near Yuha Wells, 6 miles southwest of Dixieland. 
West of Coyote Wells and extending far south and north is the 
steep east front of the Laguna Mountains, which form the extension 
of the Sierra Pedro Martir of Baja California. The range presents 
cliffs and rugged slopes of white granite, which are climbed by the 
picturesque main highway to San Diego, an ascent of more than 2,500 
feet, passing through Mountain Springs at the foot of the mountains 
and Jacumba Springs near the top. At the foot of this slope in places 
are hills of old gravel and boulder deposits rising considerably above 
the main valley slope and capped by lavas. The railroad ascends the 
valley and near Dos Cabezas siding reaches the base of the Laguna 
Mountains, in which are exposed marble and schist apparently under- 
lying the great mass of granite which rises so abruptly to the westward. 
A mile beyond Dos Cabezas foothills of granite are entered and the 
low divide into Carrizo Valley is crossed. Thence the railroad swings 
southward and ascends this valley and the deep Carrizo Gorge, at its 
head. The gorge is about 11 miles long, and there are many deep 
cuts, tunnels, and long shelves cut on the precipitous slopes, in places 
900 feet above the creek. Thescenery is remarkably impressive. The 
rock is mostly a massive light-colored granite, sculptured into many 
picturesque forms in the steep canyon walls. (See pl. 49.) The effects 
of jointing and erosion are well shown. It is believed that this valley 
is developed along a fault. Carrizo is the local name for the grass 
growing in the depths of the gorge and used by the Indians in basket 
making. Palms also grow in several places near the stream bed. 
At the head of the deep canyon the railroad comes out into a park 
which extends about 3 miles to Jacumba Springs. This park is due 
to a dropped block of lava on tuffs (Tertiary) which caps the granite 
in an area of several square miles in this region. The sketch section 
in Figure 71 shows some of the features. 
At Jacumba Springs (elevation 2,830 feet), where the granite 
appears again, there are warm springs with faint sulphureted hydro- 
gen emanation and notable mineral contents. Here a resort has been 
developed. The water was used by Indians and early aborigines, who 
have left many traces of their presence. North of Jacumba there is a 
