Stratigraphy, structure and geodynamic evolution of the Paleozoic rocks in the Cordillera del Viento (37º S latitude, Andes of Neuquén, Argentina)

Abstract

The Pre-Andean Paleozoic substrate from the Cordillera del Viento anticline is a polyorogenic basement composed of two groups of preorogenic rocks with different stratigraphy and deformation. The oldest set consists of pre-Late Devonian metasedimentary rocks belonging to the Guaraco Norte Formation. The upper set is formed by the thick volcano-sedimentary sequence of the Carboniferous Andacollo Group. This group is composed from bottom to top of the silicic volcanic rocks of the Arroyo del Torreón Formation (early Carboniferous) and the marine sedimentary rocks of the Huaraco Formation (late Carboniferous) developed in an extensional basin. Both formations are locally separated by minor syn-extensional unconformities.The relationship between the metamorphic rocks of the Guaraco Norte Formation and the volcano-sedimentary sequence of the Andacollo Group is not observed, but we inferred a major angular unconformity associated with the Late Devonian-early Carboniferous Chanic orogeny. The main Chanic structures are tight vertical and subvertical folds with slight W-WSW vergence, formed under low-grade metamorphic conditions, with the development of a pervasive axial-plane cleavage (S1), affected by a disjunctive crenulation cleavage (S2).In the early Permian, during the San Rafael orogeny of the Gondwanan orogenic cycle, deformation occurred under very low-grade to non-metamorphic conditions. The main structures are thrusts and associated folds that are re-folded by the Cordillera del Viento anticline, related to the Andean orogeny. The WNW-oriented and SSW-vergent folds are associated with an incipient axial-plane cleavage in the pyroclastic rocks and pencil lineation in shales.The pre-Andean Paleozoic basement rocks are intruded and unconformably covered by early Permian to Early Triassic? granitoids and silicic volcanic rocks from the Huingancó volcanic-plutonic Complex (equivalent to the Choiyoi Group), establishing the beginning of the Andean orogenic cycle in this region.Keywords: Andes, Paleozoic, Tectonics, Chanic Orogeny, Cordillera del Viento Resumen El sustrato paleozoico pre-andino que aflora en el anticlinal de la Cordillera del Viento, es un basamento poliorogénico que está compuesto por dos conjuntos de rocas preorogénicas con estratigrafía y condiciones de deformación diferentes. El más antiguo tiene una edad devónica superior y está formado por las rocas metasedimentarias de la Formación Guaraco Norte, en tanto que el conjunto superior son las espesas acumulaciones volcano-sedimentarias carboníferas del Grupo Andacollo. Este grupo, integrado en su parte inferior por rocas volcánicas silíceas de la Formación Arroyo del Torreón (Carbonífero inferior) y hacia techo, por las sedimentitas clásticas marinas de la Formación Huaraco (Carbonífero superior) fue desarrollado en el marco de una cuenca extensional y pueden estar separadas localmente por discordancias menores de carácter sin-extensional.Las relaciones entre las rocas metamórficas y la secuencia volcano-sedimentaria del Carbonífero no se ...

Evolución Geodinámica de los Andes argentino-chilenos y la Península Antártica durante el Neoproterozoico tardío y el Paleozoico Late Neoproterozoic-Paleozoic geodynamic evolution of the Argentine-Chilean Andes and the Antarctic Peninsula

“…En el margen de Chilenia, con el área fuente situada al oeste, la edad de la sucesión preorogénica abarca desde el Ediacárico (López de Azarevich et al, 2009;Varela et al, 2011) al Devónico Superior (Giacosa et al, 2014a), esta última obtenida a partir de circones detríticos (ca. 374 Ma) en rocas metamórficas por Zappettini et al (2012).…”

“…9). En las zonas internas de la parte sur del Orógeno Chánico afloran también rocas plutónicas, desde sin-a postorogénicas (Heredia et al, 2012;Giacosa et al, 2014a), entre las que destaca la apenas deformada Tonalita del Carrizalito (ca. 334 Ma, Caminos et al, 1979).…”

“…El área fuente de estos sedimentos se encontraba en los relieves de la cordillera que se estaba formando, que junto con la deformación y el depocentro de la cuenca migraron hacia el oeste en la rama occidental y hacia el este en la oriental (Heredia et al, 2012). El Orógeno Chánico se encuentra postdatado en algunos lugares por rocas del Carbonífero inferior (Viseense superior) (Azcuy et al, 1981;Astini et al, 2011;Giacosa et al, 2014a) y de forma generalizada por sedimentos del Carbonífero superior-Pérmico inferior (Furque, 1979;Heredia et al, 2002;Álvarez-Marrón et al, 2006;Heredia et al, 2012;García-Sansegundo et al, 2014b;Colombo et al, 2014) (Fig. 10B).…”

Geometry of Middle to Late Triassic extensional deformation pattern in the Cordillera del Viento (Southern Central Andes): A combined field and geophysical study

“…U-Pb SHRIMP dating confirms partly an Upper Devonian age, yielding a maximum depositional age of 374 Ma and 389 Ma (Zappettini et al, 2012). The Guaraco Norte Formation was deformed and metamorphosed in Late Devonian -early Carboniferous times by the Chanic orogeny (Giacosa et al, 2014).…”

Preface: Palaeozoic geodynamics of the southwestern margin of Gondwana: controls on the present architecture of the Argentine-Chilean Andes

“…These authors conclude that Chanic structures were generated in the inner part of the western branch of the Chanic orogen (Middle Devonian-early Carboniferous) along the eastern margin of Chilenia terrane. Giacosa et al (2014) (8 in Fig 1A) describe three different sequences of rocks in the Palaeozoic basement of the Cordillera del Viento (Neuquén province, Argentina) and separate the Chanic, Gondwanan, and Andean deformations. These authors propose a new geodynamic evolution for the Palaeozoic in the study area and also for the Central Andes between 28º and 39º SL, including the eastern areas affected by the Famatinian orogeny.…”