File:Slickenlined fault surface (Roberts Mountain Thrust Fault; near Cortez Gold Mine, Nevada, USA).jpg

English: Fault slickenlined rock from Nevada, USA. (public display, Geology Department, Wittenberg University, Springfield, Ohio, USA)

The linear features seen on this rock formed in a fault zone. Faults are fractures in rocks along which differential displacement has occurred. Dip-slip faults are those involving movement of rocks in non-horizontal directions. Strike-slip faults involve movement of rocks in horizontal directions. The two common types of dip-slip faults are normal faults and reverse faults.

Fault movement results in polishing and striating of the immediately adjacent wall rocks. Fault zones can have breccias, fault gouges, slickenlined mineral crusts, or striated to polished surfaces.

This rock consists of an actual fault surface from the famous Roberts Mountain Thrust Fault in western America. Thrust faults are low-angle reverse faults and are formed by compressional stress. The Roberts Mountain Thrust was active during the Antler Orogeny, a Middle Devonian to Early Mississippian mountain building event centered in Nevada. This tectonic event involved emplacement of a large, internally-deformed thrust sheet onto the Cordilleran margin of the Laurentian craton. The thrust sheet is called the Roberts Mountain Allochthon - it was thrust from west to east. It is a complex package of imbricated thrust sheets containing rocks of Cambrian to Devonian age. The rocks are typical of a deepwater assemblage - radiolarian cherts, graptolitic shales, turbidites, and pillow basalts. They were deposited in a deep, narrow basin close to the former western edge of the continent, which used to be a passive margin. Thrusting during the Antler Orogeny was accompanied by crustal flexure and the development of a foreland basin. The Antler Foreland Basin is filled with Upper Devonian to Mississippian siliciclastic sedimentary rocks.

The Antler Orogeny itself was caused by tectonic collision between a volcanic island arc, the Klamath Arc, and the Cordilleran margin of Laurentia. The Klamath Arc had been offshore - it was a series of volcanic islands formed by subduction, similar to modern-day Japan or Indonesia.

Locality: Roberts Mountain Thrust Fault, unrecorded/undisclosed site near the Cortez Gold Mine, north-central Nevada, USA