Inclined-shear restoration of growth folds

WP present a technique of progressively restoring seismic, well, and outcro p data, as well as structural interpretations of contractional growth folds . Data restorations allow viewing of seismic, well, and outcrop information in the restored state, providing a basis to evaluate whether structural in terpretations are balanced and geologically reasonable. Validating structur al interpretations helps to reduce the exploration risks associated with tr ap definition; moreover, sequential restorations reveal folding kinematics and define the geometry of structures at various stages in geologic history . These sequential restorations may be used to define the timing of trap de velopment relative to hydrocarbon migration and to determine how traps may have been modified by subsequent deformation. To restore fold growth, we use the approximation of inclined-shear restorat ion vectors parallel to the axial surfaces of the folds and propagate them homogeneously downward in the section. This choice of restoration vectors i s commonly based on direct observation of axial surface orientations in dat a and generally satisfies appropriate balancing constraints. Inclined-shear restoration works well for simple kink-band migration folds and gives good approximations of restored geometries for folds developed by limb rotation and some more complex folding mechanisms. We present examples from souther n California, the Spanish Pyrenees, and Angola.