diapirien

Diapirien are geological structures formed by diapirism, the upward intrusion of a relatively buoyant and ductile layer through overlying rocks. The term is the plural form of diapir in several European languages and is used in English-language geology to refer to multiple such structures. Most commonly the rising material is salt from evaporite sequences, though gypsum and other ductile layers can also participate.

Formation occurs when a dense, brittle surrounding sedimentary sequence overlies a salt-rich or otherwise mobile layer. Under tectonic loading, differential pressure, or dissolution and withdrawal of the surrounding rock, the buoyant ductile material begins to flow slowly upward. As the diapir ascends, it pierces and displaces the overburden, creating domelike or plume-like structures that deform adjacent strata, faults, and folds. The resulting geometry can produce upright or curved diaphragms, necks, and widening collars around the rising core.

Morphology varies from classic salt domes with bulbous summits to elongated diapiric channels or necks that penetrate sedimentary layers. The interaction with surrounding rocks often forms complex fracture networks and fault systems, and the rising diapir can trap hydrocarbons by forming structural or stratigraphic traps in the overlying sediments.

Significance includes widespread occurrence in evaporite basins and their importance in petroleum geology, where diapirien can influence reservoir architecture and migration pathways. Notable regions with pronounced diapirism include the Gulf Coast of North America, parts of the North Sea region, and various evaporite basins in Europe and Asia.