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