Photo #2

The mylonitic gneiss shows some brecciation at least tens of meters, and possibly up to a hundred meters, structurally below the detachment fault.
Broken, angular feldspar grains (white) are visible, but this rock shows no other evidence of brittle deformation, and much of the rock is still intact. The compositional banding is therefore well-preserved.
East Saguaro National Park, southern Arizona. Keys for scale.
Photo courtesy of Professor Ramón Arrowsmith

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