A Macintosh application program for simulating shear-sense indicators using object-oriented programming

Abstract

Kinematic indicators play an increasingly important role in the interpretation of rocks that experienced deformation in the deep crust. Because most ductile shear zones lack clearly offset markers, small-scale structures such as asymmetric porphyroclast tails, porphyroblast inclusion trails, and composite planar (S-C) fabrics usually provide the only records of the sense of displacement. Field observations and analog models have demonstrated that these types of structures can yield reliable shear-sense information, but no single quantitative model has been able to simulate the diverse geometries exhibited by known shear-sense indicators. We have developed such program for Macintosh computers, using object-oriented programming techniques. The program, named ShearSense, demonstrates that the development of most abundant shear-sense indicators is governed by a small number of kinematic variables and that it may be possible to read shear strain magnitude from structural geometries. The program also illustrates the potential of object-oriented programming for computer simulation of geologic phenomena.