Cuyama, California’s newest oil province, discovered January 1, 1948, has produced to June 1, 1958, 156,949,760 barrels of premium-grade crude oil valued at $471,000,000. Current production is about 42,000 barrels per day under controlled withdrawal.

Accumulations discovered so far have been confined to structural traps located on one structural trend. With one exception, they lie easterly of a prominent northwest-southeast-trending right-lateral fault zone of late Pliocene age. With one exception they are either partly or entirely concealed by major thrust faults of Quaternary age.

The productive trend roughly parallels a hinge position between a shelf area on the west and a depositional sag on the east. The depositional sag, elongate northwest-southeast, occupied a position in lower Miocene time somewhat similar to the existing Carriso Plains. It received in addition to other sediments, up to 13,000 feet of principally marine sediments of Oligocene and lower Miocene age as compared with none on parts of the shelf. Thick non-marine counterparts developed near the San Andreas rift and fanned out over a large part of the southeastern part of the province. The thick sedimentary section of the depositional sag was thrust westerly onto the shelf and hinge positions during the Pleistocene orogeny. Contemporaneously, a thick Cretaceous and Tertiary section on the southwest was thrust northeasterly over the shelf area. None of the anticlines on the hanging walls of the overthrusts is commercially productive to date. None of the known stratigraphic traps contains oil or gas.

It may be inferred from the evidence that the highly organic, marine shales of Mohnian, Luisian, and Relizian age may have yielded little if any hydrocarbons despite the appearance of satisfying the presumed requirements of source beds of oil and gas. The Soda Lake shale, Saucesian-Zemorrian age, may be the major source of hydrocarbon substances in this province. Its areal distribution with respect to structural traps may account for the prolific accumulation of oil in some traps and the absence of it in others. With one possible exception, accumulations of oil and gas in strata younger than upper Saucesian appear to be the result of leakage along fault planes from a common reservoir in the lower Miocene.

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