The modern Santa Barbara basin displays the east-west structural grain of the Transverse Ranges. Plate-tectonic theory suggests this grain evolved late in Tertiary time. However, Paleogene and early Neogene paleostructural and paleogeographic reconstructions suggest an Early-Middle Tertiary inception of the western Transverse Range province. Episodic diastrophism indicates that this evolution was also irregular.

Generally northwest-trending Paleocene shorelines in the eastern Santa Monica Mountains have been mapped by Campbell and Yerkes. This earliest Tertiary record is largely missing in the western Transverse Ranges, However, by middle to late Eocene time, a more westerly alignment is evidenced by the southward "flowing" proximal submarine fans of the Matilija

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and Sacate Formations. That this westerly shift continued is documented by Oligocene (Sespe) isopach trends and paleocurrent-slope indicators. In late Paleogene-early Neogene time, Vaqueros sands, unconformably overlying the nonmarine Sespe, were winnowed over time-persistent, east-west structural highs.

The culmination of the development of the western Transverse Ranges is marked by middle Miocene rifting, foundering, and volcanism. Deep-basin sedimentation essentially began with this event. The synclinal distribution of late Miocene turbidite sands is evidence for the continued growth of the early formed structural highs.

Late Neogene sediments within the Santa Clara graben offer a classical example of structurally controlled sedimentation. Pleistocene and Holocene submarine-fan deposits reflect the impingement of the westward-plunging Montalvo anticlinorium. Contrasting northern and southern shelf deposits of similar age also are controlled by early formed structural trends. Many of these structures are the oil and gas fields of the modern Santa Barbara basin.

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