This investigation utilizes as a natural sedimentological laboratory a group of modern continental-margin submarine basins with known sediment-source areas. Measurement of sedimentary fill of these basins and its internal structure by continuous-seismic-reflection profiling for comparison to source, distance from shore, and other variables in an analysis of marine processes has been the primary objective. The region selected for these studies is the California Continental Borderland off southern California and northern Baja California. It is near the center of a region of topographic and geologic diversity, being bounded on the north by the Transverse Range Province, on the east by the Peninsular Ranges Province, which forms the backbone of Baja California, and on the west and southwest by the submarine Baja California Seamount Province. Rocks of Miocene age form the most common sedimentary strata of the Borderland and adjacent areas of the northern margin, and Cretaceous marine and nonmarine sediments are most common in the southern terrestrial margin. The Continental Borderland may be divided into five integrated structural zones: (1) the part north of, and including, the Channel Islands Transverse Range structure, (2) the southern Borderland area of predominant northwest-trending faults bounded on the north by the Santo Tomás fault, (3) in the central Borderland between (1) and (2) the outer fault zone primarily associated with the continental slope fault (the Patton Escarpment), (4) the inner fault zone, an extension of northern Peninsular Range structure, and (5) the oval-shaped central region of probable en echelon-oriented major folds. A map of litho-orogenic units (Pl. 14) amplifies the data of the structural map (Pl. 13) in showing a large central region of preorogenic sedimentary rock, largely Miocene in age, flanked on either side by topographic and structural highs of volcanic and basement rocks. The extensive areal continuity and relative simplicity of internal structure within these rocks suggest that their origin was by deposition on an open continental terrace or in a simple broad basin rather than in isolated block-faulted basins. The major northwest-trending fault zones of the region are believed to have formed in middle Miocene with compression as a result of wedging of the contained block causing folding in the central region. Regional stress causing the tectonics is suggested to be the result of spreading of the sea floor, and accompanying drag of marginal continental crust, originating from spreading centers within the Gulf of California. Reactivation of spreading in Pliocene and Pleistocene time has formed new basin and feeder-canyon systems in the inner borderland associated with the inner fault zone. Sequences of folded and faulted preorogenic rocks which form the present topographic basins are differentiated from the postorogenic fills of the basins. The thickness of sediments accepted as postorogenic are plotted areally to define volumetric distribution and its relation to such potential controlling factors as coastal sediment sources, currents, and bathymetry. The time and rate of deposition of the basin fill are estimated on the basis of calculated uncompacted thicknesses of the deposits and total weight of terrigenous detritus, as compared to independent estimates of these factors. If it is assumed that 1 m.y. can be allowed for total deposition, the resulting rates of 5 to 212 cm/1000 yr are compatible with those based upon radiocarbon dates, and the total weight of sediment is comparable to that which should be introduced to the area from the coastal drainage-basin system in the assumed period. It is concluded, on the basis of volumetric distribution, internal structure and time and rate of deposition, that deposition by turbidity currents has been of paramount importance, virtually masking any hemipelagic deposition in the basins. Presented as a working hypothesis is a system of processes designed to bring sediments to the basins and to satisfy the structural and distributional requirements brought out by this study without violating earlier topographic and lithologic data. The proposed transportation-deposition system involves broad geologic implications concerning processes of sediment transport, deposition, and erosion of the continental margins in general. It (1) reaffirms glacial periods of the Pleistocene as being times of submarine-canyon formation and deposition of much of the known deep-sea turbidites; (2) reaffirms the corollary that pre-Pleistocene continental terraces were, in general, in the process of progradation of shoreline and continental slope during that period; (3) downgrades hemipelagic deposition to a position of little importance with respect to its volumetric contribution to slope progradation and basin fill, and substitutes shelf-generated, low-density, low-velocity turbidity currents flowing diagonally away from the shoreline as the primary constructional process; (4) suggests that regional stream discharge during Pleistocene time rather than wave erosion of shelf sediments was the major contributor of sediments; (5) postulates that stratigraphically thick sections of coarse-grained turbidites are strong evidence favoring the existence during deposition of one or more feeder submarine canyons or gullies with heads in either the nearshore sand-transport zone, the delta front of a major river, or an active estuary; and (6) proposes that the system of distributaries supplying these coarse turbidites will act also to intercept and funnel to turbidite basins large volumes of bottom turbid layers carrying silt- and clay-sized particles.