This transverse section extends from the Tertiary outcrop section west of the San Antonio River (R. 25 S., R. 10 E.), Monterey County, in a general north-northeast direction across the San Antonio Hills, the Salinas River, the San Ardo oil field, and the Gabilan Mesa to the San Andreas fault (T. 21 S., R. 12 E.).

Several interesting features are shown including the relationship of the deep Miocene shale basin underlying the San Antonio Hills to the thin veneer of sediments in the San Ardo field and the Gabilan Mesa, the "King City" thrust fault, and two interpretations of the stratigraphy in the controversial San Ardo group.

The name Aurignac sand is proposed for the lower producing zone in the San Ardo field. The Aurignac sand is separated from the upper producing sand, the Lombardi, by a thin siltstone bed and is underlain by basement within the limits of the field. The term "Orradre sand" was formerly applied to the Aurignac sand in the Campbell pool, but subsequent drilling has proved the two sands to be one. It is suggested that the name "Orradre sand" be dropped. The name Lombardi silt is proposed for the siltstone member underlying the Santa Margarita sand and overlying the Lombardi sand. The name Aurignac silt is proposed for the siltstone separating the Lombardi and Aurignac sands.

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