If the deformation along the Southwest margin of Gondwana began during the Devonian then Chilenia and Patagonia were part of the same allochthonous terrain that collided with Gondwana?

RENATA N. TOMEZZOLI

BOLLETTINO DI GEOFISICA TEORICA ED APPLICATA

ISTITUTO NAZIONALE DI OCEANOGRAFIA E DI GEOFISICA

Lugar: Trieste; Año: 2013 vol. 54 p. 107 - 110

0006-6729

From the proposal by Ramos (1984) to consider Patagonia as a drifting continent that collided during the Late Paleozoic to Gondwana, emerged new models that can be grouped into collisional or intracontinental deformation models (see Tomezzoli and Cristallini 2004). However, there are still doubts and controversies about the possible origin of Patagonia and especially the time that would have produced the main deformation associated with this collision., even been attributed an Antarctic provenance for Patagonia (González et al., 2011), and while for some researchers the deformation occurred in a single phase during the Late Permian - Triassic, for others started in the Late Devonian - Early Carboniferous and continued until the Permian. At least four accreted terranes have been recognized in the west of Gondwana prior to the Late Devonian - Early Carboniferous: Arequipa-Antofalla, Eastern Puna-Famatina, Cuyania-Precordillera and Chilenia. Subsequently, according to Ramos (2004) the Deseado Massif collided against the Patagonian Massif in the Early Paleozoic or according to Pankhurst et al., (2006) during the Middle Carboniferous. Martinez et al. (2011), based on evidence of high-pressure metamorphism conclude that during the Middle Devonian, Chilenia subducted beneath the North Patagonian Massif allowing them to extend the south margin of Chilenia to the current 42° South Latitude. The region analyzed in this study extends from the geological area of the Sierras Australes (Sierra de la Ventana or Ventania), Chadileuvú block until the block of San Rafael and Patagonian Massif (Figure 1) along to the ?Gondwánides belt" (Keidel 1916). Based on paleomagnetic studies (see methodology in Valencio 1980), anisotropy of magnetic susceptibility (AMS, the susceptibility anisotropy ellipsoid is coaxial with the strain ellipsoid; see methodology in Tarling and Hrouda 1993) and fieldwork in localities mentioned above, this contribution presents an alternative model of evolution for the South West margin of Gondwana that integrates the models with collision and intracontinental deformation with a strain that have been initiated in the Devonian and continued into the Permin