Detachment fold

Topographic map showing detachment folds in the eastern Sichuan Basin, China.

A detachment fold, in geology, occurs as layer parallel thrusting along a decollement (or detachment) develops without upward propagation of a fault; the accommodation of the strain produced by continued displacement along the underlying thrust results in the folding of the overlying rock units. As a visual aid, picture a rug on the floor. By placing your left foot on one end and pushing (with your left foot) towards the other end of the rug, the rug slides across the floor (decollement) and folds upward (detachment fold). Figure 1, is a generalized representation of the geometry assumed by a detachment fault.

Figure 1. The general geometry of a detachment fold illustrating the shortening above a layer parallel decollement and the resulting geometry of a detachment fold in a compressional environment.