INTRODUCTION. 
11 
in the early fifties. a In the report on this work the larger topo¬ 
graphic features were well described, the presence of asphaltic rocks 
was briefly noted, and the Tertiary age of most of the sedimentary 
rocks was recognized, but the structural features and the relations of 
the rocks were in the main misinterpreted. 
During the course of the geological survey of California by J. D. 
Whitney a hasty reconnaissance was made of a part of this region . 6 
He says in his report: 
The region to the west of the San Rafael Range, between the Santa Ynez and Cuya- 
mas rivers, was cursorily examined by our party. * * * The region is occupied 
by hills of moderate height. No metamorphic rock was seen; but pebbles of serpen¬ 
tine and metamorphic sandstone were noticed, especially for 3 or 4 miles north 
of Alamo Pintado. * * * These hills were covered with gravel derived from the 
bituminous slates. At times, especially near the Santa Maria River, the hills were 
capped by a modern horizontal deposit (post-Pliocene?). The underlying rock, 
when seen, was the bituminous slate, sometimes dipping to the north and sometimes 
to the south. 
Near Foxen’s, on the south side of the valley, there were hills of nearly horizontal 
strata from 200 to 300 feet high, the north slopes of which were very steep, usually 
about 35°. Beneath the soft sandstone, which made up the principal part of these 
hills, was a stratum of infusorial rock resembling chalk in appearance, exceedingly 
light, its specific gravity not being more than 0.6 or 0.7; the thickness of this stratum 
was over 20 feet. The age of this formation is not yet definitely ascertained. 
North of the valley, at Foxen’s, the bituminous slate occurs with a high dip to the 
north, and asphaltum is found in several localities near. In places the slates are 
altered and silicified, sometimes resembling semiopal in appearance, the finest lami- 
nse of the original structure being preserved. 
So far as the writers are aware no further investigation of the geol¬ 
ogy of the region was made until H. W. Fairbanks made examina¬ 
tions of portions of the Coast Ranges and reported on them for the 
State mining bureau in 1894. In his paper on the “ Geology of 
northern Ventura, Santa Barbara, San Luis Obispo, Monterey, and 
San Benito counties” reference is made c to the region under discus¬ 
sion, especially to the Santa Ynez Mountains. Regarding the Santa 
Ynez Range he says: “It is formed, so far as is known, of Miocene 
rocks exclusively.” And again: 
There can be no doubt that the main portion of the Santa Ynez Range is Miocene 
with a general anticlinal structure, well shown in the San Marcos Pass. The center 
of the anticlinal is not generally the highest portion of the range, but lies on the east¬ 
ern slope. The normal type of anticlinal structure is also marked by an east and west 
compression, producing features, however, of secondary importance. 
As viewed from the south at various points the range consists of heavy-bedded sand¬ 
stone, dipping at a high angle to the south. * * * At the western end, in the vicin¬ 
ity of Point Arguello, no anticlinal structure is apparent, but steeply inclined and 
broken strata. Asphaltum is found in many places near the sea from Point Arguello 
to Ventura County. 
a Pacific R. R. Repts., vol. 7, 1857, Chaps. VIII, IX, and X. 
b Geological Survey of California, Geology, vol. 1, 1865, pp. 135-138. 
c Twelfth Ann. Rept. California State Mining Bureau, 1894, pp. 498-506. 
