Hematitic microbreccia derived from granite, cut by discrete fault surface, Pinaleno Mountains, Arizona


I collected this in ~1980 in the immediate footwall (lower plate) of the Eagle Pass detachment in the Pinaleno Mountains in southeastern Arizona. The fault is essentially horizontal, and historically had been interpreted as a thrust fault, and not an extensional detachment fault.  Miocene fanglomerate and volcanic rocks reside in the immediate hanging wall (upper plate).  I like the combination of the cataclastic fabrics and the discrete fault surface, and in a rock that is quite cohesive.

Age & Formation
I believe the granite is late Paleoproterozic, ~1.6 Ga.