ELEVATED MASSES — VOLCANIC ROCKS. 67 



upraised by the granitic mass which lies between Matilihah and the Santa Lucia mountains ; 

 an upheaval through which the Peyrou river has cut its way, forming deep canons, and which 

 extends west to the head waters of the Santa Inez. It is, in fact, this immense mountain 

 district which gives origin not only to that stream, but to all the larger rivers of the south. 

 From it the Santa Clara derives its larger tributaries ; and from it, as a central point, flow the 

 San Buenaventura, Santa Cruz, Sangre de Crista, and not only the Santa Maria itself, but the 

 large tributary which flows east of the San Rafael ridge into that river, in the Cuyama plain. 

 This granitic mass is a branch of that which forms the Cordilleras and the San Jose range ; 

 uj^heaved about the same time, and having the same character of granitic rock, it drops down 

 very abruptly to the west, as it is not found in the Santa Inez, the San Rafael, or the Santa 

 Lucia mountains, which all appear to radiate from the common centre. That it has not 

 influenced either those mountains or their valleys is evident by its non-appearance in place, 

 by the axes of those several chains being found to be of a different character, and by the general 

 depression of the valleys with the rivers flowing down them. 



The rocks of the Santa Barbara chain may be treated under the heads of volcanic rocks and 

 sedimentary rocks. 



VOLCANIC KOCKS. 



The various species which enter into the composition of the axial rocks are trap, amygda- 

 loidal and scoriaceous lava, talcose and whitish magnesian rock, passing in places (as in the bed 

 of the Santa Inez river, near the Mission) into white tremolite. This latter variety forms the 

 intrusive rock in the western portions of the range, rising up and forming small hills on the 

 left bank of the river in the Santa Inez valley. At the western edge of the valley they pass 

 N.W. and enter a low range of hills, which cut off this valley from that of La Purissima, and 

 which run toward the ocean, forming the headland Punto Sal. 



Upon these amphibole rocks lie the mass of sandstones known as the Santa Inez or Santa 

 Barbara Hills. The occurrence of an elevating axis occupying a low position, or, as it were, 

 at one side of the strata upheaved, is of common occurrence in the southern valleys of the State, 

 so that the primary rock is often found occupying the plain, and the sedimentary strata form 

 the mountain mass or elevated land. 



Further to the east of this chain serpentine rock is found as the axial rock, either alone or 

 with amygdaloidal trap, sometimes accompanied by trachyte or scoriaceous lava — the former 

 occurring at Questa San Marcus, the latter at Rincon, east of Santa Barbara. Iron pyrites 

 abound in the sandstones at San Marcus, and small masses of free sulphur accompany it when 

 in contiguity with trap. Near Rincon it is also found abundantly, but in this latter place it 

 appears to have been produced by deposit from volcanic exhalations in the gaseous form, rather 

 than by decomposition of the sulphuret. 



The igneous rock of the extreme west of the range is serpentine. This rock may be seen in 

 large masses stretching into the sea at Point Arguello. In the extreme east of the range at 

 Buenaventura river the rock is amygdaloidal lava, a reddish rough aluminous rock, the cavities 

 sometimes filled with white magnesian clay, sometimes with carbonate lime, and occasionally 

 altogether empty. 



The result of these igneous rocks passing in the S.E. direction, and upheaving the strata, is 

 to present at times the back of the strata, and at times the edge to the shore, and allowing both 

 sides of the axis to be examined. There are several points along the range where the strata 



