Distributional analysis of the lithology, sedimentary structures, and microfauna in core samples from oil wells in Cuyama Valley allows recognition of distinctive lithofacies and biofacies in the Saltos Shale Member of the Monterey Shale. Depositional environments are determined from the interpretation of these lithofacies and biofacies. The distribution and character of the depositional environments record the basin-history for this part of the Cuyama basin during the late Saucesian through Luisian (late early to middle Miocene).

Middle bathyal, fine-grained, base-of-slope clastics predominate during the Saucesian. Intercalated, thin-bedded, turbidite sandstones are prominent in some well sections and sand/shale ratios help indicate a source to the north or northeast. Relizian depositional environments are more varied, ranging from middle bathyal shales and siltstones in the area just to the east of South Cuyama oil field, to nonmarine sandstone, conglomerate, and mudstone in eastern Cuyama Valley. The distribution of these depositional environments was controlled partly by contemporaneous tectonic activity as evidenced by depositional thinning over structural highs, abrupt thickening across at least one fault, and progradation of the shelf from the east. By Luisian time the eastern Cuyama Valley area was char cterized by shelf-to-nonmarine deposition. This is in marked contrast to upper bathyal diatomaceous mudstones and diatomites which accumulated in a low-oxygen environment immediately to the west, in the vicinity of Whiterock Bluff.

The Monterey Shale is overlain by the shallow-water Santa Margarita Formation (late Miocene), which marks the final phase of marine sedimentation in the Cuyama basin.

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