52 SANTA MARIA OIL DISTRICT, CALIFORNIA. 
surface vegetation. Many of the recent cases of burning are directly 
traceable to the first cause, but for those which may have taken place 
before the advent of man either the second or third cause will have 
to be invoked. 
RANGE IN TIME OF THE PHENOMENON. 
As already mentioned, the marked influence of the hardened shale 
on the topography in certain places indicates that it originated in 
those places a long time ago. The age of some of the burnt shale is 
further shown by the presence of numerous fragments of it at a 
depth of at least 10 feet below the surface in horizontal beds of Pleis¬ 
tocene age. These beds consist of sand, clay, and rough gravel, and 
form the low hills between Guadalupe Lake and the high hills to the 
west. The fragments of shale are little worn and evidently of local 
derivation, having possibly come from the cliffs already mentioned 
south of Guadalupe. The fact that the Monterey shale has under¬ 
gone this kind of baking in Pleistocene as well as in recent time indi¬ 
cates further that the accumulation of the oil and its dissemination 
in the surface rocks took place, or were taking place, before the 
latest orogenic movements in this coastal region. 
FERNANDO FORMATION (MIOCENE-PLIOCENE-PLEISTOCENE). 
GENERAL STATEMENT. 
The name Fernando was first applied by Homer Hamlin to a series 
of rocks overlying the Monterey in the San Fernando Valiev, Los 
Angeles County. The formation has since been recognized by 
Eldridge and Arnold 0 in the region of the Puente Hills, Los Angeles, 
and Santa Clara Valley oil districts, where it is a series of unaltered 
sedimentary rocks lying unconformably over the Monterey, and 
probably representing a portion of upper Miocene time, the whole of 
the Pliocene, and a part of the Pleistocene. Its lower portion is the 
equivalent of the Santa Margarita and Pismo formations, and its 
upper portion is contemporaneous with the Paso Robles formation, 
as these three are described by Fairbanks in the San Luis folio. 6 
In the region at present under discussion the name Fernando is 
applied to a similar formation that represents a large part of the 
Pliocene and probably includes the upper Miocene and part of the 
lowest Pleistocene. It consists throughout of a series of sandstone, 
conglomerate, and shale resting unconformably upon the Monterey. 
Unconformities also exist locally within the Fernando. It attains 
a thickness of at least 3,000 feet, but no one section exposes the whole 
series and it is probable that the formation includes a considerably 
greater thickness. It is widespread in the northern part of Santa 
a The Santa Clara Valley, Los Angeles, and Puente Hills oil districts, southern California: Bull. 
U. S. Geol. Survey No. 309. 1907, pp. 22-28. 
b Geologic Atlas U. S., folio 101, U. S. Geol. Survey, 1904.. 
