KUHLE, NATHAN J., Texas A&M University, Dept. of Geology and Geophysics, College Station, TX
ABSTRACT: Inversion Tectonics: Effects of Burial Depth and Inversion
Magnitude
on
Fault-Fold Evolution
Inverted basins can form significant hydrocarbon traps, particularly where fracturing and faulting enhance reservoir and transport properties. Our understanding of inversion structures has been improved through geophysical imaging, and physical and theoretical modeling; however, important questions remain.
Published seismic sections display inversion structures to depths of at least 5.5 km.
Overburden pressure at these depths will significantly influence the mean ductility and
strength of strata, and thus, it will influence fault-fold growth and reactivation upon
basin inversion. This study will investigate the effects of burial depth and magnitude
of
inversion on the geometry and kinematics of inversion. Physical models, deformed under
confining pressure in a triaxial de formation apparatus, will
consist of a 1 cm-thick layer of limestone above a rigid layer containing a precut fault
dipping at 70 degrees. Models will undergo extension parallel to layering to form normal
faults, followed by different magnitudes of coaxial contraction to induce folding and
reverse-reactivation of the preexisting faults. Different burial paths will be simulated
by changes in confining pressure, utilizing extension and contraction under either the
same or different mean stress to simulate various depths and fluid pressure states. I
expect that low confining pressure (simulating shallower burial depths) will promote
reverse-reactivation of the extensional faults, and higher confining pressure (simulating
deeper burial depths) will promote formation of new faults and a wider zone of
deformation. The results of this study should further our understanding of fault
reactivation in continental shelf, intra-continental and collisional mountain belt
terrains that have undergone positive inversion.
AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid