SANTA CLARA VALLEY: STRUCTURE. 
29 
leading feature is the contained bowlders of sandstone, differing but 
slightly in composition from the matrix or body of the rock itself. 
It appears only in the limited area between the Sespe and Modelo 
formations. A somewhat similar occurrence is found at the east end 
of the Upper Ojai Valley, where Sisar Creek leads out from it. The 
stratigraphic relations of this rock are uncertain, but its composition 
suggests that it may be the remnant of a Recent formation of bowlder 
sand which here and there skirts the Upper Ojai Valley, forming 
along its northern side, locally, extensive benches. In the region of 
the Lion Canyon wells the rock is impregnated with bitumen, and 
seepages spring from it. It is penetrated by the wells, but it is 
believed that they derive their oil from the underlying formation. 
GENERAL STRUCTURE OF DISTRICT. 
INTRODUCTORY STATEMENT. 
It has been deemed expedient to divide the discussion of the struc¬ 
ture of the region bordering the Santa Clara Valley into two sections. 
The first, -embracing a brief exposition of the more important fea¬ 
tures, is included in the pages immediately following. The second, 
dealing with those details so essential for purposes of practical appli¬ 
cation, is subdivided, each portion being included in the description 
of the territory to which it refers. It may be well to call the reader’s 
attention to the general sections on Pis. Ill and IV. These sec¬ 
tions, together with the structural features depicted on the map (PI. I, 
pocket), will doubtless more vividly portray the writer’s interpre¬ 
tation of the structure than many chapters of descriptive text. 
SANTA CLARA VALLEY. 
The structure of the rocks underlying the Santa Clara Valley is per¬ 
plexing. For several miles below Saugus the great body of younger 
conglomerate, sandstone, and clay of the Fernando formation passes 
diagonally across the bottom lands into the hills on either side, main¬ 
taining a strike of N. 50°-60° W. and a dip of 25°-50° NE. Within 
this area there is no apparent break in the regularity of the strati¬ 
graphic succession. From the mouth of Salt Creek westward, how¬ 
ever, the hill formations become more and more folded, or even 
faulted, while the continuity of structure between the two sides of the 
valley is interrupted by a broad belt of river gravel. Lithologic simi¬ 
larity of both Miocene and Pliocene sediments at the several horizons 
adds still further to the difficulties attending a correct interpretation 
of the geologic conditions. The great mass of evidence suggests an 
enormous fault along the valley in the region north of South Mountain, 
the displacement dying out as it passes up the river. Final interpre¬ 
tation of the valley structure has, however, been reserved for a time 
