Copper Canyon turtleback. There are three turtlebacks in the Black Mountains, named because their broadly convex-upwards geometries resemble turtle shells (Curry, 1938). Each turtleback exposes a core of metamorphosed sedimentary and basement rock separated from an upper plate of sedimentary or volcanic rock by a fault zone. This photograph shows green-colored metamorphic rock faulted against red- and tan-colored sedimentary rock just south of Copper Canyon.