Print this pageAbstract: Structure of Aliso Canyon Field, Eastern Ventura Basin, California
The Aliso Canyon oil field underlies the southern foothills of the Santa Susana Mountains west of the San Fernando Valley in Los Angeles County, California. The dominant structural element of the area is the north-dipping Santa Susana fault consisting of a lower, nearly horizontal strand which is truncated by a younger, higher strand. Subsurface mapping shows that the younger strand displaced the older strand so that the offset continuation of the older strand in the subsurface is structurally higher and folded, with its west-trending fold axis roughly coincident with that of the Oat Mountain anticline. The younger strand of the Santa Susana fault maintains a fairly constant 60° north dip at depth, is simple in geometry, and may be active.
Below the fault are the oil-producing and gas-storage formations of the Aliso Canyon field, including the Pico Formation (Aliso, Porter, and Del Aliso zones), Modelo Formation (Sesnon zone), and undifferentiated Eocene (Frew zone), which occur in the east-southeast plunging Aliso anticline unrelated to the Oat Mountain anticline above the Santa Susana. Reservoir closure is provided by the Santa Susana, Roosa, Ward, sub-Frew, and Frew faults, and by the plunge of the Aliso anticline.
Structural history of the Aliso Canyon field following deposition of the Pico Formation and formation of the Aliso anticline includes: (1) late Pliocene reverse separation along the Ward fault, south side up; (2) late Pliocene-early Pleistocene reverse separation along sub-Frew and Frew faults, southwest side up; (3) early Pleistocene (pre-Saugus) reverse separation of Roosa fault, north side up; (4) early Pleistocene (post-Saugus) reverse separation on older Santa Susana, north side up, and associated uplift of the Santa Susana Mountains; (5) late Pleistocene folding, together with the Oat Mountain anticline and breakthrough to the surface of the younger trace of the Santa Susana.
AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma