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, IJ to 5 miles wide. 

 Serpentine. 



Talcose and chloritic slates. 



Green conglomerates, 60 feet exposed. 



Brown and red sandstones, with Dosinm, 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. Kunuing 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 



