Marine geology between Cape San Martin and Pt. Sal, south-central California offshore

Wagner, Holly Clyde

doi:10.3133/ofr74252

Cited by 12 publications

(18 citation statements)

References 2 publications

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“…From south to north locations are by Helmberger et al (1992), Byerly (1930), Hanks (1979), Smith (1978), and Gawthrop (1978). Offshore faults are from D. S. McCulloch (1980), Wagner (1974), and Jennings (1975): onshore faults are from Gawthrop (1978). Outlined region offshore indicates section of the study area mapped in detail in Figure 2.…”

Section: Overviewmentioning

confidence: 99%

Hosgri fault zone, offshore Santa Maria Basin, California

Steritz¹,

Luyendyk²

1994

Geological Society of America Special Papers

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The Hosgri fault zone (HFZ) Is the name given to the southern section of the major coastal fault in central California. The Hosgri separates Transverse Range structure from offshore Santa Maria Basin structure and is a key element for any tectonic model that includes this economically significant region. Previous published maps have not adequately defined the southern termination of the HFZ, the style of faulting on the HFZ, and the relation of the HFZ to surrounding structures. Using more than 1,500 mi of processed seismic reflection data, we have mapped upper Miocene and Pliocene structure in the region of the HFZ offshore from Point Sal in the north, to Point Conception in the south where the HFZ ends against east-west structures in the westernmost Santa Barbara Channel. In the same area, eastwest-trending structures in the western Transverse Ranges north of the channel abut against the HFZ.The HFZ is an oblique right-slip fault along most of its length, but significant changes in the style of faulting are associated with variations in fault trend. North of Point Arguello, the HFZ appears to dip at a high angle in the upper 2,000 m of section and is distinguishable from thrust and reverse faults developed to its west. Between Point Arguello and Point Conception it may be a northeast-dipping thrust. Along its mapped length, east-side-up vertical separation is typical and may be more than 400 m on a Pliocene unconformity. Older horizons show more separation; the lower Miocene is up on the east by almost 1 km off Purisima Point. However, individual en echelon segments of the fault show west-side-up vertical separation where expected in an oblique right-slip fault system. No piercing points were found to define strike separation. Pliocene drag folds indicate dextral slip in Pliocene and later time.

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Section: Overviewmentioning

confidence: 99%

Hosgri fault zone, offshore Santa Maria Basin, California

Steritz¹,

Luyendyk²

1994

Geological Society of America Special Papers

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“…2). Profiles across the 3-5 km wide Hosgri Fault zone (Wagner/ 1974) on the east show considerable east-side-up vertical separation on steep easterly dipping faults along which presumed Franciscan basement rocks have been elevated to near the surface (Fig. 4).…”

Section: Appraisal Of the Ocs Potentialmentioning

confidence: 99%

Geology, environmental hazards, and petroleum resources for 1982 OCS lease sale 73, offshore central and northern California

McCulloch¹,

Clarke²,

Dolton³

et al. 1982

Open-File Report

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“…The Hosgri fault zone, named by Wagner (1974), is the 120-km southward extension of the onshore San Simeon fault (Hall, 1975). The fault zone forms a 2-6 km wide zone along the east and northeast margin of the sale area (pis.…”

Section: Faultsmentioning

confidence: 99%

“…There has apparently been at least 80-95 km of right slip along the Hosgri fault zone since Pliocene time (Hall, 1978). According to Wagner (1974), the apparent vertical separation in the fault zone, based on the offset of an unconformity on top of the pre-Tertiary unit, ranges from 458 to 1,830 m. In the sale area, apparent vertical separation was nearly impos-sible to measure owing to the difficulty of correlating reflectors across a fault and to the complex structure in the fault zone. Maximum displacement of Quaternary sediment is 45 m downthrown to the west along the major fault trace (pi.…”

Section: Faultsmentioning

confidence: 99%