BITUMINOUS STRATA-BITUMEN-FOSSILS. 
179 
bituminous and silicious rock are in tbe collection, and one of them has been submitted to 
chemical examination. It was found to contain : 
Silica. 
Alumnia and oxide of iron. 
Oxide of manganese, (trace.) 
Lime. 
Magnesia. 
Sulphuric acid. 
Phosphoric acid, (trace.) 
Potash and soda. 
Bitumen. 
Water. 
A thin splinter of the rock is translucent, and of a brown color, but when heated before the 
blowpipe becomes white, but does not fuse. The odor of bitumen is given off at the same time. 
Yields water and bitumen in a tube. It scratches glass readily. There is little doubt of the 
infusorial origin of these masses, although the organisms cannot be detected. 
The edges of the strata of the bluff are not exposed in truly horizontal lines ; they are slightly 
bent into curves of a large radius. At one point, between the landing and the mouth of the 
Los Angeles river, abrupt and sharp flexures occur, and indicate a considerable disturbance or 
lateral pressure of the beds. There is, also, the appearance of an anticlinal axis, the strata 
dipping each way from a point which extends out into the bay towards a small island. It is 
most probable that the intrusion which caused this disturbance of the strata—if it may be referred 
to intrusive rock—was in the first range inland, back of Los Angeles, where there is a thick 
dyke of trappean rock, forming the crest of the range bounding the plain of San Fernando on 
the south and east. 
No fossils were observed in these strata, but they are probably Tertiary, and a part of the 
series which forms the San Fernando range. They are, probably, continuous beneath the more 
recent deposits of the plain, and the source of the many overflows of bitumen, called Tar Springs 
by the residents of that vicinity. The quantity of bitumen which rises to the surface is very 
great, and indicates the presence of considerable deposits of vegetable remains in the strata 
below. The beds, from which it rises in such quantity, are far helow those exposed in the bluff 
at San Pedro. This is shown by the fact that the bitumen exudes from submarine springs, and 
appears in quantities upon the water many miles from the shore. These floating masses of bitu¬ 
men indicate the extension of the strata for a long distance seaward ; indeed, there is much 
reason to believe that the islands, which trend nearly parallel with the coast, are formed of 
Tertiary sandstone. 
The probability that these strata are of the age of Miocene, is increased by the fact of the 
presence of Miocene fossils in the bluffs at Santa Barbara or San Luis Obispo. They were 
collected at one of these two places by Dr. Heerman, and probably at Santa Barbara, but it is 
not certain. Mr. Conrad finds them to be, a a Mercenaria , (M. perlaminosa, Conrad,) scarcely 
differing from a species of Cumberland county. New Jersey, ( M. Ducatelii, Conrad,) a Cemoria, 
Pandora , and Cardita, of extinct species closely analogous to Miocene forms.” 1 These were 
taken from bluffs along the beach, very similar to those at San Pedro. It is, however, possible 
that these strata are older than the Miocene. 
Near the mouth of the Los Angeles river there are more modern deposits than those of the 
high bluff near the landing. They contain fossils differing but little, if any, from species now 
living on the coast, and are described under the head of Post Pliocene deposits. 
1 Mr. Conrad’s letter, Appendix, Article II. 
