HIGUERA-DIAZ, IVAN C., Northern Illinois University, Department of Geology and Environmental Geosciences, DeKalb, IL

ABSTRACT: 3-D Geometry and Kinematics of the Nuncios Detachment Fold Complex in the Sierra Madre Oriental, Monterrey Salient, Mexico

Fault-related folds are significant hydrocarbon traps in many geologic settings throughout the world. Because of this and an increasing use of fault-related folds in seismic risk assessment, the past twenty years has witnessed an explosion of research into the fault-related folding process. Though commonly limited to 2-D plane strain environments, these studies have dramatically improved our understanding of such things as folding rates, fault geometry, fault-slip rates, fold-related strain, and the competition between hinge migration and limb rotation.

However, significant gaps remain in our understanding of the 3-D fault-related folding process. In folds with curvilinear axes or plunges exceeding ~ 20 degrees, substantial out-of-plane material transport can occur. Existing models cannot account for this type of deformation and a precise field characterization of these 3-D motions has never been published. This study aims to produce such a characterization by studying mesostructures and thickness variations throughout the plunging nose of a map-scale detachment fold in the Sierra Madre Oriental of northeast Mexico. The hypothesis is that in a fold exposed over a large geographic area with high topographic relief, preserved mesostructures and stratigraphic thickness variations will constrain the true 3-D fold kinematics.

The development of this 3-D model of deformation will permit the restoration to the real position of data that have been taken in folded structures.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid