. Bulletin of the United States Geological Survey--The Santa Clara Valley, Puente Hills and Los Angeles Oil Districts. ld decreases in a corresponding manner. The productive LOS ANGELES DISTRICT : CENTRAL FIELD. 171 area is locally interrupted in the region immediately west of Coronadostreet, by the fractures attending the change in the direction of thestrike of the beds. A line of minor faults, some normal, others reverse or thrust, isdeveloped on the south flank of the major flexure. A normal faultoccurs on Welcome street 150 feet south of Council, and an excellentexample of the thrust fault
. Bulletin of the United States Geological Survey--The Santa Clara Valley, Puente Hills and Los Angeles Oil Districts. ld decreases in a corresponding manner. The productive LOS ANGELES DISTRICT : CENTRAL FIELD. 171 area is locally interrupted in the region immediately west of Coronadostreet, by the fractures attending the change in the direction of thestrike of the beds. A line of minor faults, some normal, others reverse or thrust, isdeveloped on the south flank of the major flexure. A normal faultoccurs on Welcome street 150 feet south of Council, and an excellentexample of the thrust faults is shown about 25 feet north of Coltonstreet on the west side of Lake Shore avenue. This secondary lineof disturbance seems to mark practically the northern limit of theproductive territory over a considerable portion of the field, but it isproblematical whether this is merely a coincidence of position—theproductiveness of the sands depending on their distance from the axisof the anticline or their depth below the surface, or both—or whetherthe minor faults really seal the upper ends of the oil-bearing beds. 1818 lEft c layeysha e S andy sha e ^^ |B~g Hard siliceousshale orshell Oil sand andterbedded shale Fig. 13.—North-south section across the central field on the line C-F, Pis. XVIII, XIX, along thewestern side of Lake Shore avenue, Los Angeles. and thus limit the field. The fact that a few productive wells arefound north of the line of faulting offers evidence refuting the absoluteI effectiveness of the barrier even though it is operative over a portionof the territory, unless the explanation is that these wells pass throughthe tilted fault plane and derive their oil from the productive bedsbelow 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 relattion to the major structural features or to each other. The generalanticlinal structure of the major flexure described
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