Modern exploration offshore from southern California dates from the late 1950s in California state waters and from the 1960s on the federal outer continental shelf (OCS). Following the 1968 OCS lease sale in the Santa Barbara Channel and a subsequent blowout and oil spill in 1969, exploration activity languished until 1973 when OCS Sale 35 was announced for the areas between the Channel Islands near Santa Barbara and the vicinity of the Mexican border. Geophysical exploration intensified from then until Sale 35 was held in December 1975. Exploration drilling is now in progress. OCS Sale 48, scheduled for mid-1979, includes 217 tracts in the area of Sale 35 and in the Santa Barbara Channel.

Four local Tertiary basins comprise the regional Pacific basin south of Point Conception: the San Diego trough and the offshore Los Angeles, Outher Banks, and Ventura-Santa Barbara Channel basins. The San Diego trough has not been tested by deep wells. The offshore Los Angeles basin produces oil and gas from Neogene sandstones in giant oil fields which extend onshore. The Outer Banks basin is primarily a Late Cretaceous and Eocene-Oligocene basin which does not extend onshore; six test wells have been drilled since the 1975 sale, but no discoveries have been announced. The offshore Ventura-Santa Barbara Channel basin produces oil and gas from Pliocene, Miocene, Oligocene, and Eocene sandstones and from fractured Monterey chert and siliceous shale of Miocene age; major future reserves re expected to be found in these reservoirs.