Both the North Tejon and Wheeler Ridge oil fields lie almost directly over the deeply buried portion of the White Wolf fault, but are found to occupy structures quite different in origin. The Wheeler Ridge anticline is one of a series of folds occurring along the southern border of the San Joaquin Valley. These folds and extensive thrust faults are easily recognized as the product of northerly directed compressive stresses. The principal North Tejon structure, located along the western side of Highway 99, has a north-south anticlinal axis striking nearly at right angles to the Wheeler Ridge axis, and does not have the related thrust faulting common to the other anticlinal folds.

Development of the North Tejon field showed the presence of numerous high-angle faults and revealed a segmentation of oil reservoirs into blocks containing oil of different gravities. The peculiar structure and distribution of Miocene basalt, capping most of the faulted reservoir rocks, and the gentle doming of formations lying above it indicate that the shape of the North Tejon structure resulted from an upwarping of the probably highly fractured basement rock with little regard to the existing faults.

A northeasterly regional tilt, accompanied by depression of gas-condensate-filled, former structural "highs" to positions below the level of present heavier oil- and water-bearing sandstones, has long been recognized in the segmented reservoirs at North Tejon field. Such a tilt may well have been caused by the large-scale sinking of the portion of the positive block of the White Wolf fault in the area just northeast of the field, which, like the negative block, was exposed to the very rapid

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accumulation of Plio-Pleistocene debris derived from adjacent uplifts.

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