Huincul Fault or Huincul Fault Zone (Spanish: Falla de Huincul, Zona de falla Huincul) is an east-west oriented continental-scale fault that extends from the Neuquén Basin eastwards into the Argentine Shelf. To the west it has been proposed that fault extends across the Andes into the Chilean Coast Range.
In Neuquén Basin the fault is slightly curved path, being convex to the north. Being a major geological discontinuity, it truncates the north-south oriented Pampean orogen among other structures. Because of this, it has been proposed to represent the northern geological limit of Patagonia.
The fault develops on the suture zone between the Patagonian terranes and western Gondwana. In a broader sense the Huincul Fault Zone is a belt of deformation and is thus the suture zone itself. The first and main deformation phase along the fault zone begun in the Toarcian age continued through the Valanginian age before vanishing in Albian times.Strike-slip movement along the fault began in the Toarcian. The main stress vector (i.e. direction of compression) was originally NW-oriented but shifted over time to the NWW. In the Late Miocene the last phase of deformation began with east-west compression followed by tectonic extension in Pliocene times.
The different stages of deformation were a concequence of the successive subduction of Aluk, Farallon and Nazca plates of beneath the plates of Gondwana and then South America.