Structural evolution of the Whipple and South mountains shear zones, southwestern United States.

The Whipple and South mountains of the SW US have undergone a strikingly similar sequence of deformations. We suggest that detachment faults and associated zones of brecciation, cataclasis, and seismic slip were originally continuous downdip along the low-angle shear zones into mylonitic gneisses formed below or near the ductile-brittle transition. As the mylonites were drawn out from beneath the brittley extending upper plate, they were progressively uplifted above the ductile-brittle transition and were overprinted by successively more brittle structures.-from Authors