GEOLOGICAL STRUCTURE OF THE CHAIN. 
49 
character of the fossils, from dislocations of the rock; the fossils are, however, noticed in full 
when describing Santa Margarita valley. 
From the outline it would appear that the structure of the chain is simple, and may be stated 
as follows, commencing west with the axis, and travelling east: 
West. 
Granite, to 5 miles wide. 
Serpentine. 
Talcose and chloritic slates. 
Green conglomerates, 60 feet exposed. 
Brown and red sandstones, with Dosinia, 200 feet. 
Soft white calcareous. 
Conglomerate, Ostrea, 50 feet. East. 
Upon the latter two series the terraces are placed south of the Mission San Miguel, and east 
of the valley Santa Margarita the San Jose mountains proper commence. Those hitherto 
treated of are the geological extension northward. 
At Santa Margarita, the Salinas river flows on the east side of the valley ; there is a col¬ 
lection of granitic hills from 600 to 1,000 feet in height, set close together, with deep cut gorges 
between. This granite occupies a breadth of six miles from the Salinas, eastward, when it 
disappears under the elevated sandstones of the Estrella. On the slopes of this granite occur 
tertiary sandstones, similar to the fossiliferous beds of Santa Margarita. Eunuing in a direction 
south 48° east, it attains a high elevation, and twenty miles southeast of Santa Margarita is 
almost 3,000 feet, its greatest probable height; it preserves its height for nearly fifty miles 
further south, where it forms the eastern edge of the Cuyamas plain, separating the latter from 
the shallow basin of the Estero and from Tulare valley. As a mountain range it is there lost. 
It may be traced, geologically, in the porphyritic hills separating the upper waters of the Santa 
Maria from those of Tulare, or from the Great Basin, and becomes confounded with the 
mountain mass of San Emilio. 
In this portion of its course the chain has an axis purely granitic, either felspathic granite or 
gneissose rock. South of San Miguel there is no longer any parallel ridge of serpentine, any 
talcose or chloritic slates. The magnesian rocks are wholly wanting, and are only represented 
by the addition of hornblende to the granitic rock, which gradually creeps in the further south 
the range extends, entering largely into the gneissoze portion, and rendering the whole rock 
more compact. Mica is still a mineral little abundant, the felspar predominating, which is 
sometimes bluish from adularia and sometimes cemented by a paste of epidote. The felspar in 
the northern range is flesh-colored, and contrasts strongly with the clear green of the epidote, 
giving a porphyritic appearance to the rock. The granites of this range are wholly of the first 
system, containing the highest amount of oxygen in them, and are mostly of the formula of 
orthose, which is found of a whitish color, and in rhomboidal prisms in the northern portions 
of the range. In San Luis and Santa Barbara counties the orthose crystals are usually in 
hexagonal prisms, with dihedral summits of a flesh-color, approaching a brick-red; the quartz 
in amorphous pasty masses, very few crystals of brown mica interspersed, and a large amount 
of the paste is of serpentine, which gives a greenish tint to the whole rock, contrasting strongly 
with the colored felspar. In the interspaces between the lines of fissure of the blocks a coating 
of amorphous carbonate of magnesia covers the surface of the granite. In Santa Barbara county 
hornblende enters into the granite very largely, giving it more the appearance of hornblende 
porphyry than a true granite. The amphibole mineral appears to replace the serpentine. 
7 U 
