The discovery in August, 1957, of a small commercial oil field in the Ventura Basin east of the San Gabriel-Palomas Canyon fault trend has led the industry to increased interest and a flurry of exploratory activity in this area. The sedimentary rocks of the region, also a topographic basin, are bounded on the north, east, and south by mountainous masses of pre-Tertiary igneous and metamorphic rocks. On the west the area is delineated by the San Gabriel-Palomas Canyon fault trend beyond which, to the west, lies the main part of the Ventura Basin.

The oldest rocks of the sedimentary sequence are Paleocene marine clastics exposed against the northern basement mass. Unconformably overlying the Paleocene strata is the fluviatile Oligocene Vasquez formation. Above the Vasquez with unconformable relation the Mint Canyon group of fluviatile and lacustrine origin was deposited during early to late Miocene time. A subsequent invasion of the sea from the west led to the deposition of the Modelo(?) (Castaic formation). In outcrop the Modelo(?) unconformably overlies the Mint Canyon, while along the southwest edge of the area subsurface evidence suggests interfingering with the Mint Canyon. To the north, the Modelo(?) section grades to the overlying basal part of the Ridge Basin group. Following a period of erosion, the southwest part of he area was encroached upon by Pliocene seas to deposit the Pico formation. At the edges of this Pico sea there were contemporaneously deposited the fluviatile sediments of the Saugus formation. Later in Pliocene time the sea retreated westward and the non-marine Saugus rocks blanketed the area. Prominent post-Saugus Pleistocene to recent terrace deposits are found along the main drainages and the intervening ridges.

The part of the area occupied by sediments is a broad westerly plunging syncline which has several smaller folds superimposed upon its flanks. Nearly all the anticlines plunge west or northwest with areas of critical east closure rare and insignificant. Faulting is most prominent in the pre-Miocene formations and is developed in a northeast-southwest system between the San Andreas and San Gabriel major faults. The San Gabriel-Palomas Canyon fault trend involves beds as young as Pliocene and, during a part of the Miocene, it appears to have acted as a barrier or sill to deposition.

Approximately 125 wildcat wells have been drilled in the 132 square miles of area covered by the Mint Canyon-Modelo(?)-Saugus outcrops. Of the above, 50 wells tested only the Mint Canyon formation; 50 wells tested primarily the Modelo(?) strata; and 25 wells were tests of the Pico-Saugus section. To date, one small field (Tapia) has established commercial production in the area. This field is a stratigraphic trap in as and of that part of the Saugus beds equivalent to the downdip Pico formation. Sub-commercial production has been obtained from the Modelo(?) in the Elizabeth Lake Canyon area and on the eastern edge of the Honor Rancho field. A small amount of oil has recently been obtained from Mint Canyon beds in the Bouquet Canyon area, and this formation has also demonstrated low-vo ume gas in several locales.

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