Deformation studies of folding and faulting: Cross-section kinematics, strain analysis, and three-dimensional geometry

Field and theoretical studies of the geometry, kinematics, and strain produced by folding and faulting are examined. In two-dimensional cross sections, the assumptions of flexural slip deformation for contractional structures and vertical or oblique slip for extensional structures allow the application of kinematic models to predict subsurface fault trajectories, incremental and finite strain variation, and the physical viability ("balance") of a geologic interpretation. The practical application of these methods and their implications are illustrated with several examples. In the Arkoma basin (Oklahoma), a series of incremental restorations suggest the presence of a reactivated normal fault, a new explanation for hydrocarbon production from the Wilburton deep gas field. Balanced cross section analysis is used to eliminate potential subsurface geological interpretations for the Yucca Mountain (Nevada) repository area, and a balanced model is presented which allows incremental restoration and forward modeling of future configurations and deformation. A complex fault-bend/fault-propagation kinematic model of fold evolution is used to track the incorporation and continuing deformation of syntectonic sediments during Tertiary growth of the subsurface Selva anticline in the Po Plain (Italy).; The validity of assuming flexural slip deformation in many contractional structures is corroborated by combining detailed strain analyses and deformation mechanism partitioning with a kinematic model of folding for structures in the central Helvetic nappes of Switzerland. In addition, the assumptions and limitations of the {dollar}Rsb{lcub}f{rcub}{dollar}-{dollar}phi{dollar} method of strain analysis are considered, particularly how pre-deformational sedimentary fabrics can influence the estimation of tectonic strain. Techniques for isolating the sedimentary fabric are presented, as well as a statistical bootstrapping method for constraining the precision of strain estimates.; Finally, two-dimensional kinematic faulting and folding models are extended to three dimensions. Two-dimensional fault-propagation fold models are combined with theoretical and empirical models of fault-displacement variation to create periclinal fold geometries which mimic natural structures. Analysis of natural fold geometries corroborates theoretical models of fault growth and provides a means of extrapolating fold and fault geometries along strike with limited data control. Incremental and finite deformation characteristics of the theoretical fold models are used to explain the commonly observed phenomenon of axial extension.