Cuenca de retroarco toarciana en Patagonia central (Chubut), Argentina: cierre, migracion del arco y ambiente tectonico durante el Jurasico Medio.

Abstract

The Chubut Basin (new name for the 'Liassic Western Chubut Basin' of other authors), developed during the Early Jurassic in the western part of central extra-Andean Patagonia in Argentina (42º30'S and 44º30'S), accumulated shallow marine and continental sedimentary beds, with pyroclastic input, of the Osta Arena Formation and equivalent units. To the west it was bounded by a coeval subduction-related magmatic arc (Subcordilleran Plutonic Belt) and a subduction complex of Late Triassic-Early Jurassic age (Chonos Metamorphic Complex). In turn, the eastern basin floor developed over the remnants of a previous Late Triassic-earliest Jurassic magmatic arc (Batholith of Central Patagonia) and over neopaleozoic sedimentary rocks of an accretionary prism. To the east, the basin was limited by a Toarcian volcanic system associated to the Karroo plume. The western magmatic arc continued to the north, where it is represented by the Icalma Member of the Nacientes del Biobío Formation, bounding this time the Neuquén Basin developed to the east. The closure of the Toarcian basin in the Middle Jurassic coincides in time with a migration to the southwest of the Toarcian magmatic arc, from a position in central extra-Andean Patagonia and a NNW orientation, to a location in the Patagonian Cordillera and a north-south orientation. Synchronously, rift-related anatectic silicic volcanism developed east of the basin. Hence, a major change in tectonic setting took place during the Middle Jurassic. It is here proposed that the migration of the arc was related to the growth of a plume under north-eastern Patagonia.

The role of slab geometry in the exhumation of cordilleran-type orogens and their forelands: Insights from northern Patagonia

“…Few discordances observed in the basin succession are correlated with minor shortening events associated with changes in plate motion and volcanic activity (Maloney et al, 2013;Figari et al, 2015;Navarrete et al, 2016Navarrete et al, , 2018. Along the Patagonian Precordillera, roughly coeval back-arc extension was triggered by a protracted slab rollback generated by low convergence rates and eastward motion of the South American Plate (Giacosa and Heredia, 2004;Suarez and Marquez, 2007;Seton et al, 2012; Maloney et al, 2013;Horton, 2018). This resulted in steepening of the slab, as evidenced by the westward migration of the magmatic arc ( Fig.…”

“…Coeval volcanism is recorded by the Middle-Upper Jurassic Lago La Plata Formation (correlated with the Ibáñez Group in Chile; Folguera and Iannizzotto, 2004;Olivero, 1982) and the Lower Cretaceous Divisadero Group (Ramos, 1981;Suárez et al, 2009). Respectively, these volcanic deposits overlie the N-NE-trending, graben/half-graben systems of the Piltriquitrón Basin (filled by the Lower-Middle Jurassic Osta Arena Formation, Piltriquitrón Formation, and equivalent units intercalated with marine successions; Gabaldón, 1982;Giacosa and Heredia, 2004;Suarez and Marquez, 2007), and the Upper Jurassic-Lower Cretaceous sedimentary successions of the Coyhaique Group hosted in the Rio Mayo Basin (Skarmeta, 1976;Olivero, 1982;Echaurren et al, 2017). As revealed by the regional unconformity observed in the upper volcanic succession of the Divisadero Group and on top of the Cañadón Asfalto Rift Basin deposits, extension was suddenly interrupted at ca.…”

Tectónica, sedimentación y volcanismo del antepaís roto durante la inversión andina en la zona central de Chubut

“…A estas unidades le siguen areniscas y pelitas silicoclásticas de edad maastrichtianodanianas asignadas a las Formaciones Paso del Sapo y Lefipán (Figura 2.3), depositadas en ambientes litorales y marinos someros asociadas a la primera ingresión atlántica (Spalletti et al 1996, Malumián 1999, Ruiz 2006, Suárez y Márquez 2007, Scasso et al 2012. Estas unidades han sido interpretadas desde un punto de vista tectónico como depósitos sinorogénicos (Ruiz et al 2005, Echaurren et al 2016.…”