DEFORMATION PRODUCED BY OBLIQUE RIFTING
WITHJACK, Martha Oliver
Mobil Technology Corporation, P. O. Box 650232,
Dallas, TX 75265-0232, USA
JAMISON, William R.
Department of Earth Sciences, Memorial University, St.
Johns, Newfoundland A1B 3X5, Canada
We have used a series of analytical and experimental (clay) models to
simulate the deformation patterns associated with oblique rifting.
With oblique rifting, both extension perpendicular to the rift trend and
shear parallel to the rift trend contribute to rift development. The
relative amounts of extension and shear depend on a, the acute angle
betweeen the rift trend and the relative displacement direction
between opposite sides of the rift. In models with combined extension
and left-lateral shear, conjugate sets of steeply dipping strike-slip
faults develop if a is less than 30°. If a is 30°, strike-slip, oblique-
slip, and normal faults form. The strike-slip faults with left-lateral
and right-lateral displacement trend at small and large angles to the
rift trend, respectively. The normal faults strike about 30°
counterclockwise from the rift trend. If a exceeds 30°¡, only normal
faults form develop. They have moderate dips and generally strike
obliquely to the rift trend and to the relative displacement direction
between opposite sides of the rift. If a equals 90° , the normal faults
strike parallel to the rift trend and orthogonally to the displacement
Our modeling results apply to the gulfs of California and Aden,
two Tertiary continental rifts systems produced by combined
extension and shear. The modeling results explain the presence and
trends of oblique-slip and strike-slip faults along the margins of the
Gulf of California and the oblique trend (relative to the rift trend) of
many normal faults along the margins of both the gulfs of California
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