The Santa Maria Province is in the California coastal belt between North Latitudes 34° 30′ and 35° 25′ and West Longitudes 119° 42′ and 120° 54′. It is roughly triangular and is bounded on the west by the Pacific Ocean, on the south by the Santa Ynez Mountains, and on the north and northeast by the Santa Lucia and related mountain ranges. The province consists of several somewhat isolated structural basins with similar sedimentary histories and related types of present and possible productive zones and traps.

The type of rocks underlying the zones of present and prospective production and the geologic age of these rocks are variable. True basement, in the sense of completely altered sediments or igneous rocks below or within which the discovery of indigenous commercial pools of oil or gas is an impossibility, is unknown. For this reason the term basement, as herein applied, refers to those rocks, older than Eocene, that consist primarily of Jurassic serpentines and schists and of Cretaceous and Jurassic sediments that have undergone various degrees of alteration. Commercial production from these rocks is considered unlikely, excepting under abnormal fault or overlap conditions.

Basement rocks, as thus defined, consist of Jurassic metamorphic rocks near the northern limit of the province, Cretaceous and probably Jurassic sediments along the eastern border, and Cretaceous sediments along the southern margin. Basement rocks crop out also, or are known at shallow depths, at various isolated localities within the interior of the area. The accompanying map and stratigraphic sections