This basin study includes several, elongate, in places deep, structural basins trending northwesterly to westerly, as shown on the pre-Tertiary "basement" contour map. Large faults trend similarly. Cross sections suggest that these faults and others as yet unknown or incompletely known probably have brought different basin segments into their present juxtapositions by lateral slip. True paleogeologic reconstructions of basin conditions thus would require complex palinspastic restorations. Lacking these, we can trace basin history only crudely with the aid of subcrop maps representing pre-Vaqueros, pre-Pt. Sal, pre-Monterey, and pre-Sisquoc time. Suggested depositional environments progressed from above sea-level in the Oligocene to water depths of more than 4,000 feet in ower Miocene, 1,000 feet to 1,500 feet in Middle and Upper Miocene, 1,500 feet to sea-level in Pliocene, to above sea-level in Pleistocene. Miocene cherty oil reservoirs probably are genetically related to diatomite deposited under conditions possibly similar to those now found in the Gulf of California. Tracing cherty and other reservoir facies probably requires true paleogeologic analysis. Until sufficiently sophisticated geological studies of one of California's oldest producing areas are available, the currently fashionable view that onshore California offers little for economic oil exploration is at best premature.

End_of_Article - Last_Page 1775------------