Cumulative production of the Santa Maria district to January 1, 1947, was 250,637,000 barrels of which an estimated 77% originated in fractured rocks and 23% in oil sands. 74.5% of the oil was produced from fractured rocks in the Monterey formation and 2% from fractured "Knoxville" sandstone. Monterey fractured rocks in order of importance include (1) Mohnian cherts, (2) Luisian calcareous shale, and (3) Mohnian platy siliceous and porcellaneous shale. The distribution, age, and character of fractured zones are illustrated by stratigraphic sections. The distribution of maximum chert development suggests chert originated as a sedimentary facies. General characteristics of potentially productive fractured rocks of the district are analyzed and their permeabilities and poros ties as indicated by production data are discussed.

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