Seismic reflection data. Submarine fan growth, the dominant mode of basin filling. Mass movement processes important locally. Suprafan is the primary locus of coarse sediment deposition. Long-distance coarse sediment transport during Late Wisconsinan lowstand of sea level. Because Santa Monica and San Pedro basins are small, enclosed, tectonically active basins that receive sediment from relatively large drainage areas, proximal-to-distal changes in sand layer thickness, abundance, and frequency are less pronounced than those observed in deep-sea environments.--Modified journal abstract.