postorogenic

Postorogenic refers to the geological phase and processes that occur after an orogenic event, the mountain-building episode that thickens the crust through compressional tectonics. The term is used to describe the evolution of a region once peak orogenic deformation has ended, including tectonic, magmatic, and surface processes that follow the main phase of crustal strengthening.

In a postorogenic regime, the crust commonly relaxes and thickened portions experience gravitational collapse and extensional deformation. Normal faults and graben systems may develop as the thickened crust thins and stretches. Sedimentary basins form or widen as the crust subsides and accommodation space increases, and magmatic activity can occur as decompression and crystallization alter the thermal regime. Erosion and differential uplift shape the landscape, gradually reducing relief created by the earlier orogeny.

The concept is applied in studies of continental margins and inland belts where an initial phase of compression is followed by extension and basin development. A classical example is the extensional tectonics and basin formation that followed the late Cretaceous–Paleogene Sevier-Laramide orogenies in western North America, often described as postorogenic. Elsewhere, postorogenic processes can accompany post-collisional settings and contribute to late-stage crustal evolution long after peak orogenic activity.

Notes: postorogenic is sometimes used interchangeably with related terms such as postorogenic extension or post-orogenic tectonics, reflecting the shift from compressional to extensional regimes in the wake of mountain-building.