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Show 172 the first geological survey of the State of California. ( See Report on the Geology of tto Coast Mountain*, & c, p. 10; 1855; 8vo : Sacramento.) It mav be said in general tha; the Coast Range divides the Pacific Ocean from the valley of the San Joaquin Rivei and of the Tufares beyond San Emidio, not far from Fort Tejon, and that it comprise* all the parallel chains which reach the great bay of San Francisco. These mountains continue beyond the bays of Snisnn, San Pablo, and the Golden Gates, in a northwesterly direction. What is the principal age of this system of mountains? In a word, at what geological epoch did it make its appearance f I now think, as I did in 1854, when I saw it for the first time with my friend Whipple, that it should be referred to the end of the Eocene Tertiary deposits. Sierras of San Fernando and Santa Monica,- These mountains, which, with the Sierra Madre on the east and the Santa Susana range on the west, inclose the charming valley or plain of the ancient mission of San Fernando Rey de Espafta, run from west to east. The strata are much broken, uplifted, and inclined, and thay are all Miocene Tertiary or molassic rocks, which fixes the age of the appearance and formation of these mountains at the end of the Miocene epoch. The Santa Susana range, between the Triunfo and Simi Valleys, is but a counterfort of and an appendage to the Sierra de Santa Monica. The Sierra of San Rafael, which runs right up to the Sierra Madre, at the foot of Mount Pinos, the highest peak of this region, with the peak of San Antonio, seems to belong to this west- easterly system of the San Fernando and Santa Monica Sierras. The same is the case with the Sierra de Santa Ines, back of Santa Barbara. The Santa Clara Valley, with its prolongation almost to Soledad, forms a part of this system, as do the San Francisquito and Castac Valleys. In consequence of their directions being from west to east, this system of mountains enters the Pacific Ocean on one side and the Sierra Madre on the other, and intersect* and completely isolates Southern California from the central and northern portions of the State. The separation is even so great that the railway from San Francisco to Los Angeles is obliged to cross the Sierra Madre twice, viz, at Tehachipi Pass and at Sole-dad, through several long and costly tunnels, for the sole purpose of avoiding the barrier placed in its way by the Sierra San Rafael; and having reached the Santa Clara Valley, the railroad is still obliged to cross the San Fernando Sierra through a very long and deep tunnel, issuing at last into the San Fernando plains, whence it reaches Los Angeles by following the valley of erosion, which fortunately crosses the Santa Monica sierra, intersecting it perpendicularly almost to its eastern extremity. In reality, Southern California is more disconnected and isolated from California proper than is the latter from the States of Nevada and Oregon. Hills of Los Angelas.- The hills which surround the city of Los Angeles and separate it from the valley of Bayona or Ballona, from Monte and from Anaheim, are of the Pliocene Tertiary epoch. It is possible, and in my opinion highly probable, that their age is identical with that of the mouutains of Cajon Pass, and that they represent on the west side of the Sierra Madre the uplifts and elevations on the east side of that chain to which I have already referred. The sands and conglomerates of the summit of Cajon Pass must, then, be of the same age as the molassic rocks and sandy clays of the old Presidio de Los Angeles. In that case, the deposits of Cajon Pass, instead of being of the Post Pliocene, must be of the Pliocene epoch. At all events, these two elevations and dislocations of the hills of Los Angeles and of the summit of Cajon Pass, if they did not take place simultaneously, did so at periods by no means remote from each other. As to the various mountain- chains to the south of Los Angeles, as far as San Diego, and even farther, I can say nothing as to their relative ages, not having visited them. To sum up, we have the following systems of mountains for a portion of Southern California: I. Sierra Madre, of the Primordial epoch, or Laconic, anterior to the Silurian. II. Coast Range, of the close of the Eocene epoch.' III. Sierras of San Fernando and Santa Monica, of the close of the Miocene epoch. IV. Hi lit* of Los Angeles, of the close of the Pliocene epoch. V. Mountains of Cajon Pass, ( east side of the Sierra Madre,) of the close of the Post Pliocene or Quaternary epoch, or, perhaps, even of modern times. JULES MARCOU. CAMBRIDGE, MASS., December 30,1875. |