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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 37 (1953)

Issue: 12. (December)

First Page: 2776

Last Page: 2776

Title: The Sespe Formation of the Santa Barbara Embayment.: ABSTRACT

Author(s): Robert H. Paschall

Article Type: Meeting abstract


The Sespe formation, composed of red, buff, and gray sandstone and conglomerate, and red and green siltstone, has a landward extent of about 1,250 square miles, and a volume of about 950 cubic miles. Its seaward extent may be greater or much less than that on land, since its presence in the Channel Islands chain is confined to Santa Rosa Island. Its maximum thickness of about 7,000 feet is found in the Simi Valley, near the formation's present east margin. In general the formation thins westward, due in part to gradation into beds of definite marine character.

The Sespe has an age range possibly as great as from upper middle Eocene to middle Miocene. The formation's vivid colors and scarcity of organic matter, especially in its eastern portion, combined with its lateral gradation into beds of undisputed marine character, are suggestive of a non-marine origin for the bulk of the formation. The Sespe does not appear to be a unique unit from the standpoint of time-lithology association. Many other sedimentary basins in Southern California possess similarly appearing rocks occupying about the same place in the geologic column. It would seem that widespread climatic and orogenic factors contrived to produce these formational cousins at about the same time.

Sespe oil production has been established over an east-west belt 90 miles long. Current production from the Sespe is about 17,000 barrels daily, 95% of which comes from fields on the 17-mile-long Oak Ridge uplift. Different zones in the Sespe formation produce from field to field, even along Oak Ridge, in a manner suggestive of varying or multiple sources for the Sespe's oil.

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