16 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
its character and from the continuity of its exposure, to be identical with the granite 
of the Sierra Nevada. ‘To the south of the Mojave Desert, it is very extensively and 
boldly exposed in the San Gabriel and San Bernardino Ranges and in other portions 
of the Coast System, as far south as the Mexican boundary. It also has broad expo- 
sures in the comparatively low-lying desert floors of Southern California, as shown by 
Hershey,’ and in the Perris plain. 
To the northwest of Tejon Pass, this granite appears in a series of linearly disposed 
areas extending thru the ranges. It forms a notable feature of the Santa Lucia Range 
on the west of the Salinas Valley, and also of the Gavilan Range to the east of the same 
valley. The granite of the Santa Lucia Range runs out to sea at Point Pinos near 
Monterey, while that of the Gavilan Range extends into Santa Cruz County and appears 
on the coast at Point San Pedro, a few miles south of San Francisco. Farther north it 
is seen in the Farallon Islands, the Point Reyes Peninsula, and on Bodega Head. The 
Santa Lucia and the Gavilan thus expose two quite distinct lines of granitic outcrop, 
practically parallel, and both crossing the general trend of the Coast Ranges obliquely 
and reaching the coast. Indeed, the easterly limit of all the granite of the Coast Ranges 
crosses the entire breadth of the latter obliquely between the Tejon Pass and Bodega 
Head. This signifies, of course, that whatever manifestations of crustal deformation 
elevated these belts of granite, the lines or axes of such deformation were not coincident 
in direction with the mean trend of the Coast Ranges, or with the mean trend of either 
of the margins of the Coast Ranges. It is noteworthy, too, that all of the Coast Range 
granite as far south as the vicinity of Tejon Pass lies to the southwest of the Rift along 
which the movement occurred which generated the earthquake of April 18, 1906. 
It is further noteworthy that near the northern end of the granite belt at Tomales Bay 
and Bodega Head, the Rift actually follows the line of contact between the granite on 
the west and the sedimentary rocks which are faulted against it. These facts suggest 
that very probably the Rift is similarly situated in the more southern Coast Ranges 
with reference to a deeper-seated contact between granite and sedimentaries; in other 
words, that the eastern edge of the Coast Range batholith, whether that edge be an 
original feature of the batholith or a feature determined by faulting, is with some degree 
of probability the line which determines in part the course of the modern Rift. South- 
ward from the vicinity of Tejon Pass, however, the Rift passes into the granitic terrane. 
Folds. — The pre-Knoxville folds of the Coast Ranges are little known, owing partly 
to the burial of the Franciscan rocks by later deposits, and partly to the complexity of 
the structures where the rocks are exposed and the difficulty of discriminating the effects 
of the earlier and the later movements; but chiefly owing to the absence of adequate 
topographic maps, so necessary for such studies. The conspicuous folds of the Coast 
Ranges are those which have been imprest upon the Tertiary and older strata together. 
These are usually rather sharp and more or less symmetrical synclines and anticlines, 
involving usually many thousands of feet of strata. In some cases these are asymmetric 
and even overturned, as in the Mount Diablo region, but they are never so closely apprest 
as to induce general and important deformation of the internal structure of the rocks 
affected. The folding has been effected without flowage, except perhaps locally where 
soft clays or shales were involved, and there has been no development of slaty cleavage 
or schistosity. In general the axes of the folds have a northwest-southeast trend, but 
there are numerous deviations from this rule and the axes of the minor folds are usually 
more or less divergent, as is of course generally true. There is, however, a pronounced 
parallelism in the dominant synclines and anticlines, the axes of which extend for many 
miles. Several of these are more or less oblique to the mean trend of the Coast Range 
belt, and thus appear to be truncated on the coast line, or on the eastern margin of 


1 Bull. Dept. Geol. Univ. Cal., vol. 3, No. 1. 
