Although wrench tectonics of the San Andreas transform fault system dominate the structure of modern central coastal California, regional sedimentary basin evolution and petroleum geology are best viewed in the context of transform tectonics superposed on an older convergent margin regime. Convergence along the central California margin continued from the Mesozoic until the mid-Tertiary, interrupted briefly in earliest Tertiary time by strike-slip faulting related perhaps to oblique subduction. Convergence finally ceased in the Oligocene with the diachronous propagation of the San Andreas marginal transform system. Apparently, the locus of shear within the transform system migrated shoreward and continentward with time to the present position of the San Andreas fault, pro ressively involving granitic basement in lateral translations.

Regional tectonics strongly control the character of central California sedimentary basins and distribution of sedimentary facies. The expansive patterns of Cretaceous and earliest Tertiary forearc basin sedimentation, less favorable in reservoir provenance, organic source-rock character, and burial history, were replaced in early Tertiary time by deposition in localized borderland basins related to strike-slip faults. However, it was the full development of the marginal transform system during the Neogene which provided the requisite elements for a productive and still prospective petroleum province: discrete, moderate-sized, structurally controlled sedimentary basins; deposition through rapid subsidence of thick piles of organic-rich marine sediments in silled, anoxic borderland bas ns; favorable reservoir provenance through deep dissection of granitic uplifts; and extensive, early wrench tectonic structuring of basin fill, often influencing syntectonic patterns of sedimentation.

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