Computer-Aided Section Construction and Restoration in Extensional Terranes

Mark G. Rowan, Roy Kligfield, J. Geiser

Microcomputers are powerful tools in generating balanced cross sections in fold-and-thrust belts. The techniques have been modified and expanded for easy application to continental rifts, passive margins, salt tectonics, and inversion structures. Before section construction can begin, however, the appropriate graphical method must be chosen. Various techniques exist for graphically approximating deformation geometries in extensional terranes, e.g., the constant-heave method, the inclined-shear model, bed-length balance techniques, and variable-heave methods. These techniques are used to predict listric-fault trajectories from hanging-wall rollover shape as well as to construct, restore, and balance sections. Each model implicitly assumes a characteristic deformation style and associated strain state and can be evaluated by comparison with the observed and theoretical deformation mechanisms of normal faults. The appropriate graphical method can be chosen from knowledge of the active deformation mechanisms or computer modeling using the different techniques. Interactive construction and restoration then quickly and easily lead to a balanced interpretation compatible with the available data base (well, surface, and seismic data). Furthermore, sequential restoration to different times aids realistic modeling of thermal maturation and timing of hydrocarbon migration. These computer-aided techniques can greatly benefit the geologist trying to interpret complex extensional terranes.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.