Geometry of rollover: Origin of complex arrays of antithetic and synthetic crestal faults

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6762281

Bischke, R E; Suppe, J ^[1]

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1. Princeton Univ., Princeton, NJ (USA)

Rollovers form by the collapse or bending of a hanging wall as it slides over bends in a normal fault. Once the authors know the particle motion of the collapse, commonly antithetic Coulomb shear, they can develop a simple relationship between fault shape and rollover geometry that is a function of the relative rates of fault slip and sedimentation. The dip of the rollover is a function of the angle fault bend, which is verified in some structures. A fanning of dips in the rollover is predicted for continuously flattening faults. In contrast, numerous rollovers from the US Gulf Coast, Brunei, and elsewhere do not show significant fanning of dips but show a nearly constant dip that is less than the magnitude predicted from Coulomb shear. These structures show complex arrays of small synthetic and antithetic normal faults on the crest of the rollover, including keystone grabens. High-quality seismic images show that many of these crestal faults suddenly disappear downdip, apparently to run along bedding. These observations indicate that part of the rollover collapse is by bedding slip after a critical rollover angle is reached; the bedding slip extends from the master normal fault up to the crest of the rollover where it breaks upward to be the imaged synthetic and antithetic crestal faults. Modeling of this process shows that variation in the relative rates of fault slip and sedimentation predict the different observed styles of complex crestal faulting in offshore Texas, Brunei, and elsewhere.

• OSTI ID: 6762281
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580000 -- Geosciences
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GEOLOGY
GULF COAST
MATHEMATICAL MODELS
NORTH AMERICA
PETROLEUM GEOLOGY
USA