Tectonic evolution of the North Patagonian Andes (41°-44° S) through recognition of syntectonic strata

• Autores: Echaurren Gonzalez, Andres; Folguera Telichevsky, Andrés; Gianni, Guido M.; Orts, Darío Leandro; Tassara, A.; Encinas, Alfonso; Gimenez, Mario E.; Valencia, V.
• Año de publicación: 2016
• Idioma: español castellano
• Tipo de recurso: artículo
• Materia: Ciencias Ambientales y de la Tierra; North Patagonia; Fold-thrust Belt; Syntectonic Strata; Andean Orogenesis; Ciencias Ambientales y de la Tierra
• Institución: Universidad Nacional de Río Negro

Fil: Echaurren Gonzalez, Andres. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina.
Fil: Echaurren Gonzalez, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Folguera Telichevsky, Andrés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina.
Fil: Folguera Telichevsky, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Gianni, Guido M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina.
Fil: Gianni, Guido M. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Orts, Darío L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina.
Fil: Orts, Darío L. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: il: Tassara, A. Universidad de Concepción; Chile
Fil: Encinas, Alfonso. Universidad de Concepción; Chile
Fil: Gimenez, Mario E. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina.
Fil: Gimenez, Mario E. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Valencia, V. Washington State University; Estados Unidos
The North Patagonian fold-thrust belt (41° 44° S) is characterized by a low topography, reduced crustal thickness and a broad lateral development determined by a broken foreland system in the retroarc zone. This particular structural system has not been fully addressed in terms of the age and mechanisms that built this orogenic segment. Here, new field and seismic evidence of syntectonic strata constrain the timing of the main deformational stages, evaluating the prevailing crustal regime for the different mountain domains through time. Growth strata and progressive unconformities, controlled by extensional or compressive structures, were recognized in volcanic and sedimentary rocks from the cordilleran to the extra Andean domain. These data were used to construct a balanced cross section, whose deep structure was investigated through a thermomechanical model that characterizes the upper plate rheology. Our results indicate two main compressive stages, interrupted by an extensional relaxation period. The first contractional stage in the mid Cretaceous inverted Jurassic Lower Cretaceous half graben systems, reactivating the western Cañadón Asfalto rift border 500 km away from the trench, at a time of arc foreland expansion. For this stage, available thermochronological data reveal forearc cooling episodes, and global tectonic reconstructions indicate mid ocean ridge collisions against the western edge of an upper plate with rapid trenchward displacement. Widespread synextensional volcanism is recognized throughout the Paleogene during plate reorganization; retroarc Paleocene/Eocene flare up activity is interpreted as product of a slab rollback, and fore to retroarc Oligocene slab/asthenospheric derived products as an expression of enhanced extension. The second stage of mountain growth occurred in Miocene time associated with Nazca Plate subduction, reaching nearly the same amplitude than the first compressive stage. Extensional weakening of the upper plate predating the described contractional stages appears as a necessary condition for abnormal lateral propagation of deformation.