The geology of the Wiley Canyon area, Oak Ridge anticline, T 3-4 N, R 18-19 W, Ventura County, California

Abstract

The accompanying map and thesis comprise a report on the geology of an area lying on the Oak Ridge anticline about six miles southeast of the town of Fillmore, California. The Oligocene Sespe is the oldest formation exposed. The other formations found are Vaqueros, Modelo, Pico, Saugus, and finally, Recent terrace gravels and alluvium. The Sespe-Vaqueros and the Vaqueros-Modelo contacts appear to be conformable and are differentiated by a transition in lithology. A marked unconformity exists between the Modelo shale and Pico sandstone; this is not as pronounced on the west end as on the east end. The Saugus appears to overlap the Pico progressively from west to east. The main structural features are the Oak Ridge fault, the Oak Ridge anticline, and the Eureka anticline and the Baker fault. Other subsidiary folds are present. The trend of the large structures is, on the whole, east and west; that of the lesser ones is mostly southeast and northwest. The Oak Ridge fault is down-thrown on the north side; its plane is vertical at Torrey Canyon but is overturned at Wiley Canyon. The Oak Ridge anticline consists of a series of small, connected domes. Oil production has been established on several of these domes. A new wildcat is now drilling on a small surface closure in Wiley Canyon. The Eureka anticline plunges westward towards the Baker fault. The evidence found in the field indicates that this is an unusual structure. It forms a part of a large, recumbent fold which has been further folded into an asymmetrical anticline. It is terminated on the west end by what is here called the Baker fault (after the Baker Ranch). Competent beds are conglomerates and sandstones; fossil evidence indicates their age to be late Pico (probably San Diego. Model sandstones and shales make up the remainder of the exposed rocks. The Baker fault runs southwest from the Santa Clare River through the first canyon west of Torrey Canyon. Two interpretations can be placed on the relationship of the rocks: the Baker fault may have originated with, and therefore can be terminated against, the Oak Ridge fault; or it may possible represent a different period of faulting, cutting the Oak Ridge fault and eventually joining up with the western end of the Santa Susana fault. Because of lack of sufficient evidence to the contrary, the first possibility is used.