METAMORPHIC ROCKS-TERTIARY-SAN PEDRO-BITUMEN. 
55 
forty-five degrees, and appears, to be from the granitic rocks forming the high ridges on the 
west side of the pass. The materials forming these strata appear to have been derived from 
the abrasion of granitic and metamorphic rocks, many large fragments of them being found in 
some of the beds. All the strata have a light pink or flesh-red color, which appears to he 
caused by the pink feldspar. The weather has fashioned these outcrops into sharply-pointed 
pinnacles, and in other places worn holes and openings through the beds, so that a little soil or 
earth has found a lodgment, and serves to support shrubbery and vines. No fossils were found 
in these strata ; they were evidently deposited in water much affected by currents. Their 
aspect is very modern, and they are probably Tertiary. 1 
Granitic and metamorphic rocks. —Although the granitic rocks do not appear at the summit, 
they rise in high ridges on each side of the valley of the pass. In the higher ridges they are 
generally very compact, and yet give evidences of being to a great extent metamorphic. Large 
blocks of a white crystalline limestone were found in the bed of the creek, but no outcrops 
were seen. These fragments exhibit bands and lines of deposition, and show the metamorphic 
character of the parent mass. 
In the lower parts of the pass the rocks approach nearer on each side, and the sandstone 
strata disappear. The stream flows down over the outcrops of granite, gneiss and similar 
rocks, in a narrow rugged channel. At the base of the mountains, talcose and micaceous slates 
occur, similar to those in the pass of San Francisquito, further west. 
Slope to the Pacific. —From the base of the mountains the survey follows a long and gentle 
descent to tbe Pacific over formations of comparatively modern origin. The surface is formed of 
post-tertiary accumulations overlying tertiary strata. These strata appear in hills not far from 
Los Angeles, and are mainly composed of white clay or marls and sand. Several outcrops 
along the road to the mission of San Fernando are white and chalk-like, and appear to have 
been quarried into under the supposition that they were limestone. The rock is compact and 
very light, but is not calcareous, being chiefly white clay and silex. In the San Fernando 
hills I obtained tertiary fossils of the genera Ostrea, Peden and Turritella. 
San Pedro. —I had an opportunity of examining a section of some of the strata of the slope, 
at the vertical bluff facing the bay of San Pedro. At that place the beds are formed of ferru¬ 
ginous sandstone and argillaceous sandstone, and thick layers of bluish and grey, and some¬ 
times greenish clay. No fossils were found in these strata. They differ lithologically from 
those exposed in the pass of San Fernando, but they are probably Tertiary. At another point 
along the bay south of the landing, more modern accumulations are exposed in bluffs about 30 
feet high, they being the margins of a plain or terrace. Near the summit of the bluffs there 
is a layer of fossil-shells in a fine state of preservation, and very abundant. The following- 
species were obtained there by the writer in 1853 : Saxicava abrupta , Petricola Pedroana , 
Schizothcerus Nutalli, Tapes diversum, Penitella spelceum, Fissurella crenidata, Sowerby, Ncissa 
interstriaia, N. Pedroana , Strephona Pedroana , Littorina Pedroana , and Buccinum inter striatum. 
With the exception of one, these were all described and named by Mr. T. A. Conrad. 2 These 
fossils show that the formation is littoral ; and this is also shown by the position in which they 
are found, they being mingled together and surrounded by fragments of broken shells. Below 
the fossils the bank is chiefly beach-sand. The lower molar of an extinct elephant was also 
found in the bank, not far from this locality of fossils. It appears to differ from the teeth of 
Elephas primigenius, in the greater distance between the plates, and in their smaller number. 
Bitumen and “ Tar springs.” —The broad slope on which Los Angeles is built is dotted in 
several places by black lakes or pools of semi-fluid bitumen, which rises up from the strata below. 
These are known as tar sjsrings, and the inhabitants make use of the bitumen for covering 
1 These strata are more particularly described in the author’s report on the geology of the route surveyed in California, 
by Lieutenant R. S. Williamson, U. S. Topographical Engineers. 
2 See Description of the Fossils and Shells collected in California by W. P. Blake, Appendix to Preliminary Geological 
Report : Washington, 1855. See also the report in 4to 
