Abstract: Geometry and Kinetics of the Whittier Fault in the Brea-Olinda Oil Field

BJORKLUND, THOMAS K., University of Houston, Houston, TX

At the surface the Whittier fault juxtaposes Mohnian (~11.2-7.1 Ma) rocks on the north and Delmontian (~7.1-5.1 Ma) and younger rocks on the south. The fault generally strikes N65W and dips 70 degrees to the northeast. In the Brea area a restraining left bend of the fault strikes about N72W. Geologic features associated with the bend include (1) flattened dip on the Whittier fault at shallow depths, (2) east-west fold axes, (3) steeply dipping and overturned beds and (4) north-dipping proto-Whittier faults that formed generally parallel to the Whittier fault as the Los Angeles Basin grew. The maximum vertical separation across the Whittier fault of over 4 km, also, occurs at Brea. These observations are consistent with right-lateral strike-slip movement during the Late Pliocene and Pleistocene (~3.4-0.01 Ma).

Right-lateral offset of Tonner Canyon has been attributed to strikeslip faulting on the Whittier fault ranging from 1-2 km. The south wall of Tonner Canyon at Brea is a prominent hogback that consists of conglomeratic sandstones. The presence of these beds at shallow depths may have resulted from vertical displacements on the proto-Whittier faults. A small knob on the west end of the hogback may be capped by a remnant of the hanging wall of the Whittier fault. Its elevation is consistent with the location of a flattened Whittier fault projected across Tonner Canyon. These relationships indicate to me that the right-lateral offset of Tonner Canyon is not due entirely to strike-slip faulting but may, also, reflect the presence of resistant formations.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California