Seismic-stratigraphic analysis of 3, 1, and 0.25 sec reflection records has permitted an interpretation of the depositional history in Santa Monica basin at several dimensions and time scales. The present form of the basin was established during orogenic episodes in late Miocene and late Pliocene time. Subsequent deformation of the onlapping Quaternary basin fill has been relatively minor. Beneath the basin plain the fill is 640 m thick and is divisible into two units. The lower unit (400 m) represents a pre-Pasadenan accumulation of sediment delivered to the basin through Hueneme, Mugu, Dume, and Redondo submarine canyons. Transport through Santa Monica canyon was inhibited by a structural barrier at the mouth of the canyon. Post-Pasadenan strata (240 m) represent overfl w from the Los Angeles and Ventura basins. This latter stage of basin filling is characterized by a significant increase in the rate of sedimentation and extensive growth of the Hueneme and Mugu canyon-fans. During this time, sediment delivery to the basin through Dume and Redondo canyons was diminished, occurring only intermittently. The secular pattern of canyon activity and sedimentation appears to be tectonically controlled.

Glacio-eustatic effects have been secondary. Examination of high-resolution echo characteristics indicates a general southward decrease in the amount of surficial coarse-bedded sediment and that the major transport path since Wisconsinan time has been through Hueneme canyon. Large-scale mass movement, which is an important depositional process in several adjacent basins, is relatively unimportant in Santa Monica basin and is restricted to the canyons.

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