LOS ANGELES DISTRICT : CENTRAL FIELD. 
171 
area is locally interrupted in the region immediately west of Coronado 
street, by the fractures attending the change in the direction of the 
strike of the beds. 
A line of minor faults, some normal, others reverse or thrust, is 
developed on the south flank of the major flexure. A normal fault 
occurs on Welcome street 150 feet south of Council, and an excellent 
example of the thrust faults is shown about 25 feet north of Colton 
street on the west side of Lake Shore avenue. This secondary line 
of disturbance seems to mark practically the northern limit of the 
productive territory over a considerable portion of the field, but it is 
problematical whether this is merely a coincidence of position—the 
productiveness of the sands depending on their distance from the axis 
of the anticline or their depth below the surface, or both—or whether 
the minor faults really seal the upper ends of the oil-bearing beds 
Fig. 13.—North-south section across the central field on the line C-F, Pis. XVIII, XIX, along the 
western side of Lake Shore avenue, Los Angeles. 
and thus limit the field. The fact that a few productive wells are 
found north of the line of faulting offers evidence refuting the absolute 
effectiveness of the barrier even though it is operative over a portion 
of the territory, unless the explanation is that these wells pass through 
the tilted fault plane and derive their oil from the productive beds 
below and to the south of it. 
North of the main line of disturbance the beds for the most par- 
show local flexures with low dip; these apparently bear little relat 
tion to the major structural features or to each other. The general 
anticlinal structure of the major flexure described in the preceding 
paragraphs is evidenced, however, by the recurrence in two knolls, 
cut through by Sunset boulevard northwest of Echo Lake, of the 
coarse sandstone (oil sands) found south of the axis in immediate 
proximity to the northern boundary of the central field. 
