Retrodeformable cross sections and Oak Ridge fault, Ventura basin, California

Conference · Tue Mar 01 04:00:00 EST 1988 · AAPG Bull.; (United States)

OSTI ID:6639590

Yeats, R S; Huftile, G F

A retrodeformable (balanced) cross section is constructed such that stratified rocks are restored to their undeformed state without loss or gain of bed length or bed thickness. Ductile strata may be area-balanced if original thickness is known. Near Ventura, folds in Pliocene-Pleistocene turbidites and Miocene-early Pliocene shales (Rincon, Monterey, Sisquoc) overlie an unfolded competent Paleogene sequence. The basal decollement of the foldbelt is in the ductile Rincon Formation (lower Miocene). The overlying Sulphur Mountain, Ventura Avenue, San Miguelito, and Rincon anticlines are fault-propagation folds developing from south-dipping, largely late Quaternary frontal ramp thrusts (Sisar-Big Canyon-Lion fault set, Barnard fault set, padre Juan fault, and C-3 fault, respectively) that rise from the decollement. Cross-section balancing shows that the overlying fold-thrust belt has shortened 2.5-6 km more than subjacent Paleogene competent strata. This excess bed length is taken up in the Paleogene sequence on the Oak Ridge fault as a ramp from the brittle-plastic transition zone through the upper crust. This implies that the basal decollement is the frontal active thrust of the Oak Ridge fault. The decollement dies out southeast of a line between Timber Canyon oil field and the west end of Oak Ridge, possibly because of decreased ductility in the Miocene decollement sequence due to appearance of sandstone interbeds. Farther southeast, late Quaternary displacement concentrated on the Oak Ridge fault itself at rates greater than 10 mm/year.

• Research Organization: Oregon State Univ., Corvallis (USA)
• OSTI ID: 6639590
• Report Number(s): CONF-8804144-
• Conference Information: Journal Name: AAPG Bull.; (United States) Journal Volume: 72:3
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
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ANTICLINES
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CENOZOIC ERA
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
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ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SHALES
STRATIGRAPHY
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USA