GEOLOGIC MAP OF THE TORTOLITA MOUNTAINS, SUIZO MOUNTAINS AND DURHAM HILLS, CATALINA METAMORPHIC CORE COMPLEX, ARIZONA

The Tortolita Mountains are part of the Catalina metamorphic core complex, which was exhumed in the mid-Tertiary by top-to-the-WSW movement of the hanging wall of the Catalina detachment fault system. Granodiorite to granite plutons, ranging from Late Cretaceous to mid-Tertiary in age, dominate the footwall domain. They intrude remnants of Paleoproterozoic Pinal Schist, Mesoproterozoic Oracle Granite, and Paleozoic sedimentary rocks. In the hanging-wall, mid-Tertiary volcanic and volcaniclastic rocks lie unconformably on Pinal Schist and Oracle Granite and are preserved in east and west tilted blocks that define a north-plunging antiform.

There are several components to the detachment fault system that were active at different times and at different crustal levels. The newly recognized Carpas Wash shear zone, at the north end of the Tortolita Mountains, is a moderately north-dipping mylonite zone with sinistral shear sense consistent with its interpretation as a lateral ramp in the top-to-the-WSW system. The brittle Guild Wash fault coincides with the immediate hanging wall of the Carpas Wash shear zone at the north end of the range. To the east, the Guild Wash fault splits into two strands, one that cuts the Carpas Wash shear zone and another that lies entirely in its hanging wall. To the southwest, the Guild Wash fault is inferred as being linked to the Lower Derrio Canyon detachment fault, which dips 5-10 degrees northwestward and has up to 200m of chloritic breccia in its footwall. Deeper in the footwall, the Tertiary Fresnal leucogranite is deformed by broad zones of mylonite and protomylonite.

The Suizo Mountains consist of Pinal Schist and leucogranite with mylonitic fabric that is well developed within tens of meters of the overlying Suizo detachment fault. The detachment projects southeastward beneath the tilt blocks at the north end of the Tortolita Mountains. The Durham Hills consist of granite with a mylonitic fabric at high structural levels, a small exposure of a detachment fault, and moderately tilted Tertiary strata.