CHAPTER I. 
GEOLOGY OF THE COAST OF SOUTHERN CALIFORNIA. 
CoMPARISON OF STRUCTURE OF COAST MCUNTAINS NORTH AND SOUTH OF SAN FRANCISCO —EVIDENCES OF IDENTITY.—INFUSORIAL BEDS 
D 
THE COAST MOUNTAINS.— VI0CENE STRATA OF COAST MOUNTAINS WANTING IN SIERRA NEVADA,—SIERRA NEVADA OLDEST.—Mnr. 
MARCOU'S DESCRIPTION OF THE “COAST RANGE SYSTEM.”—RAISgD SEA BOTTOMS AND SHELL BEDS AT SAN LUIS OBISPO, SAN PEDRO 
AND SAN DIEGO. 
That portion of California lying south of San Francisco has been so fully explored by the 
geologists of the Pacific Railroad Surveys, Dr. Antisell and Mr. Blake, that, in the hasty exami- 
nation I was able to make of parts of it, I could hardly hope to furnish any considerable addi- 
tions to the knowledge of its geology already possessed by the public. It was, however, a 
matter of extreme interest to me to continue the line of observation which I had carried from 
the mouth of the Columbia to San Francisco, from that point to the southern line of the State, 
with particular reference to the structure of the Coast mountains, and to determine the coinci- 
dences or differences which might be presented by their northern-and southern extensions. 
In my report to Lieutenant Williamson on the geology of Northern California and Oregon, 
(Pacific Railroad Surveys, Vol. VI,) I ventured to assert the identity of the Tertiary sandstones 
and shales of Astoria, Coose bay, and Port Orford, with those of the San Francisco group, and 
suggested the unity of structure of the Coast mountains throughout the interval between these 
points; confirming, so far as my observation extended, the opinion which had already been 
advanced, that the superficial sedimentary rocks of the Coast mountains, from the mouth of the 
Columbia to the bay of San Francisco, were of Miocene age. It is known, however, to those 
who are familiar with the subject, that paleontological evidence of this identity was for the 
most part wanting; the strata in most localities being destitute of fossils, and where those had 
been found, absolute identity of any species had not been proven. 
The indications of geological parallelism in the different parts of the Coast mountains, from 
San Francisco northward, consisted, first, in the general resemblance of their molluscous fossils— 
more careful study of which would, it was to be presumed, furnish positive proofs of identity; 
second, in the lithological characters of the sandstones and shales to which I have referred, as 
exhibited at their various points of exposure; third, in the beds of lignite which they include; 
and fourth, in the continuity of the strata. 
Going south from San Francisco, we stopped at Monterey, San Luis Obispo, Santa Barbara, 
San Pedro, and San Diego. The geology of all these points has been quite fully illustrated in 
the luminous reports of the gentlemen before mentioned, as well as in those of Dr. Trask, the 
geologist of the State of California. It is, therefore, quite unnecessary that I should give in 
detail even the observations which my limited time permitted me to make. It was, however, 
& source of no little satisfaction to trace in the geological exposures of such points on this 
coast as I examined a striking parallelism with those of the coast line north of San Francisco. 
Some local features are presented in the infusorial beds of Monterey, the asphaltic effusions of 
Santa Barbara, San Luis Obispo, and San Pedro, which, at first sight, would seem to militate 
against the general harmony which I have suggested; but these discrepancies are rather apparent 
than real. r io 
Ihave mentioned in my former report, speaking of tle section presented on the southern 
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