346 The American Geologist. June, 1895 
another in the same dike. In its general characters the gran- 
ite of Mon1|ara is identical with that of the Farallones and of 
Toraales point to the north of the Golden Gate. It is also 
identical petrographically with the granite of the Santa Cruz 
mountains to the south, and is undoubtedly continuous with 
it beneath the mantle of Tertiary strata which covers portions 
of the range. Montara mountain thus appears to lie about 
midway in a range of granite which may be traced in a series 
of very extensive exposures from Bodega Head to the town of 
Santa Cruz, a distance of over 100 miles. This granite is 
known at various places to be intrusive in a pre-existing sedi- 
mentary terrane. The granite mass is clearly of the nature 
of a great batholito, which has invaded the crust from below 
and from its extensive exposures at Montara mountain, where 
it has been first studied, it may be designated the Montara 
bathoUte. 
The Franciscan Skkies. 
The Franciscan series reposes upon the worn surface of the 
Montara granite, and the basal strata of the series have origi- 
nated from its waste, being conglomerates with granite boul- 
ders and coarse grits composed of the granitic debris. What 
extent of geological time is represented by the interval be- 
tween the invasion of the region by the Montara batholite and 
the deposition of the basal Franciscan rocks upon its eroded 
surface is not yet determined. The simplest and most natural 
hypothesis that suggests itself is, that the granite corresponds 
in age with that of the Sierra Nevada, and this hypothesis 
has not yet been exhausted of its strong probability of truth. 
The granites of the Sierra in so far as their age is known are 
clearly postx-Jurassic. Granites of about this age are exten- 
sively developed all along the west coast of North America 
from Alaska southward. The granites of the southern and 
northern Coast ranges seem to be geologically continuous 
with those of the Sierra Nevada. The fact that the Sierra 
are separated from the Coast ranges by the valley of Califor- 
nia is immaterial to the discussion, since the latter is clearly 
a delta-filled geo-syncline of late Tertiary or post-Tertiary 
origin. There is therefore a strong presumption in favor of 
the view that the granites of the Coast ranges and those of 
the Sierra Nevada are of common origin and common history 
