The Southern Gondwana Margin In Patagonia and the Mesozoic Opening Basins

Radiometric and geophysical data precise the activity and developing of the Gondwana margin during the Upper Carboniferous – Lower Permian times and their correlation with geological processes occurred from Mendoza to Chubut Provinces in Argentina. Southern granitoids reveals the magmatic arc activity with ages ranging between 299 +/- 7 Ma to 261 +/- 6 Ma, coincidental with granites bodies cropping out to the north in southern Mendoza to San Juan Provinces. This continuous activity in the Gondwana magmatic arc, changed abruptly to an extensional process that slowed down the subduction and allowed the intrusion of epizonal granites during Upper Permian times. During the Early Mesozoic and as a consequence of a transpressional - transtensional faulting process due to the Gondwana breaking, the active margin was fractured and moved adapting to the stress fields occurring in that sector, the southern part of the inactive Gondwana magmatic arc was moved to the West and the northern one the East. The Neuquen basin begun to developed at the Northeast of this main structure feature as the result of the strong extensional process that occurred from the Upper Permian onwards. By that time a new volcanic arc started to develop towards to the West, while in the continental crust an extensional magmatism process started during the Upper Permian to Triassic and continue until the Jurassic in several areas. To the South of the southern Gondwana magmatic arc section, the Pampa de Agnia Basin begun to develop during the Upper Triassic to Early Jurassic times and was maintained active until the Toarcian times.