Santa Monica Bay embraces an area extending more than 45 km. between Point Dume on the north and Palos Verdes Point on the south, and from the shoreline out into Santa Monica basin. Principal features are the mainland shelf (0 to 80 meters), the basin slope (80 to about 900 meters), and the basin floor which extends down to about 938 meters. The mainland shelf is a truncated positive feature separating the Santa Monica basin on the west from the filled Los Angeles basin on the east. Exposed Miocene-Pleistocene rocks on the shelf suggest this feature was formed during the Quaternary. Relict upper Pleistocene-Holocene sediments and faunas provide evidence of an episodic transgression of sea-level across the shelf.

Analysis of 85 bottom samples indicates that Recent sediments become finer offshore with the exception of relict grains, and nitrogen values generally are higher in the deeper, fine-grained sediments. Echinoderms and mollusks dominate the megafauna near the edge of the shelf.

General foraminiferal trends are: foraminiferal abundance increases offshore; live specimens are most abundant in the central shelf area; living species are most abundant in the central shelf area and in the bathyal zone; higher live/dead ratios occur on the central and outer shelf in areas of slow deposition; arenaceous types dominate dead populations on the central shelf; and live hyaline types are more than 8 times as abundant as live arenaceous forms in most areas.

Inshore foraminiferal groups are characterized by species of Rotorbinella, Discorbis, and Elphidium. Open shelf biofacies are characterized by Buliminella elegantissima, Eggerella advena, Bulimina marginata denudata, and Trochammina pacifica. Species of Nonionella, normally abundant, are relatively rare, possibly because of ocean pollution. A Bolivina acuminata group of species is characteristic of the shelf edge and the upper basin slope. A deeper water Bolivina argentea basin facies appears at about 400 meters and is dominant on the floor of Santa Monica basin.

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