LOS ANGELES DISTRICT: GEOLOGIC FORMATIONS. 
145 
BLACK SCHIST. 
Black micaceous schist with a general northwesterly dip outcrops 
on the flanks of the Santa Monica Mountains about a mile north¬ 
west of Sherman and extends in a westerly direction along the south 
slope of the range for at least 15 miles. This schist is black to dark 
reddish brown in color, in some cases resembling certain hematite 
ores, and usually shows a very characteristic luster, due to the faces 
of the minute component mica flakes. Little is known concerning 
the age of these rocks except that they are older than the granite 
which bounds them on the east. It is certain, however, that they 
are pre-Cretaceous and very probable that they are Jurassic. 
GRANITE. 
A large part of the Santa Monica Mountains from the vicinity of 
Coldwater Canyon eastward to Los Angeles River is made up of 
granitic rocks similar in all respects to and probably contempora¬ 
neous with the granitic rocks which form the Verdugo hills, the 
northern part of the San Rafael hills, and the major part of the 
great San Gabriel Range to the north and east of the Santa Monica 
Mountains. In the region about Edgemont, northeast of Holly¬ 
wood, the rock appears to be a fine-grained biotite granite, showing 
considerable quartz in hand specimens, although weathering pre¬ 
cludes any exact determination of the composition. Biotite and 
hornblende granite, with some closely associated brown micaceous 
schist, appears to make up the larger portion of the crystalline area 
from Cahuenga Pass westward to Coldwater Canyon. With the pos¬ 
sible exception of the western contact, which is probably one of 
deposition, the rock of the Edgemont area appears to be separated 
from the adjacent formation by fault planes, although the exact 
nature of the shale-granite contact north of Ivanhoe was not deter¬ 
mined. The granite is younger than the black schist and is cer¬ 
tainly pre-Cretaceous and probably late Jurassic in age. 
i 
PUENTE SANDSTONE.« 
GENERAL CHARACTER. 
The oldest Tertiary rocks so far discovered in the Los Angeles 
area consist of a heavy-bedded sandstone which overlies the pre- 
Cretaceous granite and schist on the flanks of the Santa Monica 
Mountains and makes up the bulk of the Elysian Park hills and 
the hills on the northeastern side of Los Angeles River from Gaston 
southeastward to the hills east of Eastlake Park. The lower part 
of the formation is somewhat argillaceous and may correspond to 
a See note regarding divisions of Puente formation on p. 103. 
