The Huincul Fault or Huincul Fault Zone ( es, Falla de Huincul, Zona de falla Huincul) is an east-to-west-oriented, continental-scale fault that extends from the Neuquén Basin eastwards into the

Argentine Shelf The Argentine (sometimes referred to as Patagonian) Shelf is part of the South American continental shelf belonging to the Argentine Sea on the Atlantic seaboard, south of about 35°S. It adjoins the coasts of Uruguay, Argentina and the Fa ...

. To the west, it has been proposed to extend across the Andes to the

Chilean Coast Range The Chilean Coastal Range ( es, Cordillera de la Costa) is a mountain range that runs from north to south along the Pacific coast of South America parallel to the Andean Mountains, extending from Morro de Arica in the north to Taitao Peninsula ...

. In the Neuquén Basin, the fault exhibits a slightly curved path, being convex to the north. It is a major geological discontinuity and it truncates the north-to-south-oriented Pampean orogen, among other structures. Because of this, it has been proposed to represent the northern geological limit of Patagonia.

Origin and development

The fault develops on the suture zone between the Patagonian terranes and western

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...

. In a broader sense, the Huincul Fault Zone is a belt of deformation, thus it is the suture zone itself. The first and main deformation phase along the fault zone began 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 northwest-oriented but shifted over time to the north-northwest. In the Late Miocene, the last phase of deformation began with east–west compression followed by tectonic extension in

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

of the Aluk, Farallon, and

Nazca Nazca (; sometimes spelled Nasca; qu, Naska) is a city and system of valleys on the southern coast of Peru. It is also the name of the largest existing town in the Nazca Province. The name is derived from the Nazca culture, which flourished in ...

plates beneath the plates of Gondwana and then

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

Geological structures

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such a ...

associated with the fault, the Huincul basement high or Huincul Ridge ( es, Dorsal de Huincul) divides the Neuquén Basin in two parts. The

basement high In geology, a basement high is a portion of the basement in a sedimentary basin that is higher than its surroundings. Commonly, structures referred to as basement highs are hidden by the sedimentary fill of the basin. Usually basement highs are e ...

is one of the most studied features of the Neuquén Basin, given its importance for

hydrocarbon exploration Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas, in the Earth using petroleum geology. Exploration methods Visi ...

and production. The basement high has an approximate length of . Various ideas have been expressed concerning the nature of this structure. In the 1970s and 1980s, it was proposed to be a transpressive fault zone. Later, Pángaro ''et al''. described it as being made up of inverted half-grabens. East of city of Neuquén, the fault roughly follows the path of the upper course of Río Negro. In this region, a series of

s and small pull-apart basins has formed along the fault, reflecting a clockwise movement.

References

{{Major South American geological formations Seismic faults of Chile Seismic faults of Argentina Strike-slip faults Suture zones Geology of Araucanía Region Geology of Buenos Aires Province Geology of La Pampa Province Geology of Neuquén Province Geology of Río Negro Province Faults