Observed relations between facies associations, sand-body geometries and submarine fan subenvironments commonly appear anomalous when facies interpreted from cores are compared with relations described by some currently popular fan models. Such anomalous relations were observed in cores from several fields producing from the Stevens Sandstone. To explain these inconsistencies an "on-lap" model and a "confinement" model are proposed for some of the observed depositional patterns of the upper Miocene Stevens Sandstones in the San Joaquin basin.

Along the eastern margin of the basin, where deposition occurred on a relatively undeformed homoclinal surface, patterns of turbidite sedimentation and facies associations generally conform to the Mutti and Ricci Lucchi submarine fan model. However, in the central and western parts of the basin the fan model is inappropriate.

The on-lap model describes turbidite deposits which lap onto and stack vertically against rising anticline structures. Internally these sand bodies exhibit distinct sedimentation cycles and facies associations characteristic of fan progradation. Externally these sand bodies pinch out crestward, may or may not be lobe- or fan-shaped, and tend to be abnormally thick. The Paloma field is an example of the on-lap model.

In the confinement model, turbidites are confined to bathymetric lows between adjacent (en echelon) anticlines. These deposits, which accumulated in synclinal lows, tend to have an external channel-like morphology but do not necessarily exhibit facies associations commonly ascribed to channels in fan models. Deep-water sediments from Yowlumne, Tule Elk, and Elk Hills fields are best described by the confinement model.

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