Thrust fault

A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger. Thrust faults are the result of compressional forces.

Thrust geometry and nomenclature

Reverse faults

Thrust faults are a special class of "reverse faulting" that typically have low dip angles. It is often hard to recognize thrusts because their deformation and dislocation can be difficult to detect when they occur within the same rocks without appreciable offset of lithological contacts.

If the angle of the fault plane is low (generally less than 20 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an overthrust. Erosion can remove part of the overlying block, creating a fenster (or window) when the underlying block is only exposed in a relatively small area. When erosion removes most of the overlying block, leaving only island-like remnants resting on the lower block, the remnants are called klippen (singular klippe).