LOS ANGELES DISTRICT : FERNANDO FORMATION. 
151 
of the Miocene and the upper fossiliferous sand and conglomerate of 
the Pliocene, represented by a period of deformation and subsequent 
erosion. Just what plane in the stratigraphic sequence of beds marks 
this period, however, has not been determined. The interbedded 
conglomerate found in the fossiliferous lower Pliocene sandstone con¬ 
tains numerous waterworn and pholas-bored fragments of the charac¬ 
teristic white Miocene shale, and this evidence clearly proves the con¬ 
ditions of a break or unconformity. A marked unconformity is 
usually discernible between the Monterey shale and subsequent for¬ 
mations at most places throughout the Coast Range where the two 
formations are in contact, so that it is not at all surprising to meet this 
evidence here. Over many areas, both north and south of the Los 
Angeles district, similar evidence is corroborated by the presence of 
marked structural unconformities. Here this latter evidence appears 
to be lacking. 
It is necessary, therefore, to draw an arbitrary line separating the 
two formations. Because of the almost complete absence of the hard 
white siliceous shale from the Pliocene (Fernando) the line separating 
the Miocene (Puente) and the Pliocene (Fernando) has been drawn at 
the top of the uppermost layer of hard, white shale. This line is prob¬ 
ably somewhat lower than if it were drawn on paleontologic evidence. 
In other words, the lower part of what is here termed the Fernando 
formation (Pliocene) is possibly Miocene and may be contempora¬ 
neous with some portion of the San Pablo (upper Miocene) of central 
California. 
The basal portion of the Fernando formation consists of about 500 
feet of soft to compact, thin-bedded sandstone and sandy shale, with 
some zones in which the shale is fine grained and clayey. (See PI. 
XXIV, A.) The color of the beds ordinarily varies from gray and 
light yellow to rusty brown, except in those strata that are or have 
been impregnated with oil, many of which are chocolate, purple, or 
bright yellow. Above the purely sandy strata is a zone about 500 feet 
thick in which some of the shale is calcareous and very hard. Some of 
this hard shale, especially that which shows a tendency to concre¬ 
tionary structure, closely resembles certain of the Miocene shales. 
This zone of calcareous shale is also rich in gypsum, some of the veins 
being 2 inches wide. Most of the veins occur between the bedding 
planes of the shale, although some cut the strata transversely. 
Above the shaly portion of the Fernando are thick-bedded, soft 
gray to light-yellow sandstone and coarse conglomerate associated 
with some thin-bedded bluish-gray sandy shale or shaly sandstone. 
The thin beds of conglomerate in this portion of the formation are 
those already mentioned as being composed largely of waterworn and 
pholas-bored fragments of the siliceous Puente shale. This conglom¬ 
erate, as well as the sandstone and sandy shale, yields a characteristic 
