Abstract

The San Miguelito and Rincon oil fields are located along the northern edge of the western Ventura basin. Both fields produce from the approximately 3350 m (11,000 ft) thick sequence of turbiditic Plio-Pleistocene strata contained in the Ventura Avenue anticlinal trend. The anticlinal trend formed against the basin-bounding north-dipping reverse faults of the Red Mountain fault system. Red Mountain faulting, which may have begun as early as late Miocene in the area of the ancient Red Mountain seaknoll, resulted in the formation of an unyielding barrier against which later basinal deformation to the south occurred.

The formation of the anticlinal trend has been rapid and complex. The Ventura Avenue and Rincon anticlines are separated at the surface by the San Miguelito anticline. The San Miguelito anticline is a fault-propagation fold restricted to the hanging wall of the south-dipping Padre Juan reverse fault. The Ventura Avenue and Rincon anticlines, in contrast, are flexural-slip folds which are continuous beneath the Padre Juan fault. Geologic evidence from the Ventura area indicates that the anticlinal trend did not begin to form before 600,000 years ago, and possibly not before 200,000 years ago. For the Rincon anticline and San Miguelito anticline-Padre Juan fault pair alone, this results in shortening rates of 4.2 to 12.5 mm/yr (0.16 to 0.49 in/yr) or greater.