Map restoration of an early Pliocene horizon along the Hosgri-Purisima-Lompoc fault system, central California margin

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:425646

Sorlien, C C; Kamerling, M J ^[1]; Mayerson, D ^[2]

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1. Univ. of California, Santa Barbara, CA (United States)
2. Minerals Management Service, Camarillo, CA (United States)

The Hosgri fault is the southern part of the San Gregorio-Sur-San Simeon-Hosgri fault system, an important element of the Neogene California transform system. The Hosgri fault proper (top 1-2 km) is located in the hanging-wall of a 10 to 20 km wide zone of mostly E-dipping faults, the Hosgri-Purisima-Lompoc fault system. These faults have undergone Miocene extension, and have been reactivated by post-Miocene contraction or transpression. This wider fault system is truncated against or merges with the E-striking faults in northwestern Santa Barbara Channel. From this starting point of zero displacement, right-lateral displacement on a N- S fault can not be more than the sum of N-S shortening east of it, the N-S extension west of it, and the right-lateral slip fed into it by other faults. We are using a 3-D map restoration technique to quantify the displacements along this fault system. Depth-contoured folded surfaces are flattened using the software UNFOLD, and the restored surfaces are fit back together across faults using an interactive graphic program. Displacements are calculated by comparing the restored surface to the present state with respect to a relatively-fixed block. Our mapping of the early Pliocene top Sisquoc horizon indicates that broad, gentle folds characterize the Point Arguello oil field. Folds located between Point Arguello and Point Sal, are characterized by abrupt changes in amplitude, symmetry, and vergence along strike. The folded surface is unfaulted over wide areas, despite dips up to 45{degrees}. These folds are the result of basin inversion along former rift border faults. Folds are amplified where the basin fill is transpressed against NW-striking restraining bends in a regional NNW-striking system of right-reverse-oblique faults.

• OSTI ID: 425646
• Report Number(s): CONF-960527--
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
99 GENERAL AND MISCELLANEOUS
CALIFORNIA
GEOLOGIC FAULTS
GEOMETRY
MAPPING
OIL FIELDS
PLIOCENE EPOCH
U CODES