Décollement
![Fig. 1 Imbricate fan in a thrust system with a basal décollement. The section below the décollement is undeformed basement rock. Above the décollement deformation has occurred due to compression. A series of branching faults terminating at depth.[1][2]](/uploads/202501/08/page1-220px-Decollement_in_a_compressional_setting.pdf4006.jpg)
![Decollement formation in an extensional setting.Décollements can form from high angle normal faults. Uplift in a second stage of extension allows the exhumation of a metamorphic core complex. A half graben forms, but stress orientation is not perturbed due to high fault friction. Next, elevated pore pressure (Pp) leads to low effective friction that forces σ1 to be parallel to the fault in the footwall. A low-angle fault forms and is ready to act as a décollement. Then, the upper crust is thinned above the décollement by normal faulting. New high-angle faults control propagation of the décollement and help crustal exhumation. Finally, major and rapid horizontal extension lifts the terrain isostatically and isothermally. A décollement develops as an antiform that migrates toward shallower depths.[10][18]](/uploads/202501/08/page1-220px-Decollement_formation_in_an_extensional_setting.pdf4006.jpg)
Décollement (/dɛ.kɒll.mɔːn/; from the French décoller, 'to detach from') is a gliding plane between two rock masses, also known as a basal detachment fault. Décollements are a deformational structure, resulting in independent styles of deformation in the rocks above and below the fault. They are associated with both compressional settings (involving folding and overthrusting) and extensional settings.