Patagonia: A Paleozoic Continent Adrift?

摘要

La evolución de la Patagonia como un continente independiente y exótico al resto de América del Sur ha sido una hipótesis recurrente desde el Siglo XIX, alcanzando notoriedad durante los tiempos de la discusión de la teoría de la deriva continental. Con el advenimiento de la tectónica de placas cobró nuevo impulso, dividiéndose las interpretaciones en una serie de hipótesis fijistas que la consideraron como parte autóctona del Gondwana y en otras más movilistas que postularon un origen alóctono. Después de varias décadas, si bien ha ganado consenso las hipótesis que postulan su aloctonía, no hay acuerdo en sus límites, tiempos de subducción, acreción y amalgamiento final al supercontinente de Gondwana. En esta revisión se analizan las diferentes fajas magmáticas, su metamorfismo y deformación, las cuencas sedimentarias asociadas, así como los controles geocronológicos existentes. Consciente que aún quedan notables incertidumbres se propone un modelo con dos arcos magmáticos: uno occidental que fue activo desde el Devónico hasta el Carbonífero medio, y otro que se traslapó parcialmente en el tiempo y que lleva a la colisión de la Patagonia contra el margen sudoccidental del Gondwana en el Pérmico inferior.%The evolution of Patagonia as an independent and exotic microcontinent from the rest of South America was a recurrent hypothesis since the XIX century, reaching notoriety during the discussion times of continental drift theory. The arrival of plate tectonics triggered different hypotheses, some of them with fixist interpretations that consider Patagonia as an autochthonous part of Gondwana, and others more mobi-listic that postulate an allochthonous origin. After several decades, although some consensus exists among those hypotheses that postulate its allochthony, there is no agreement in its boundaries, subduc-tion, accretion, and final amalgamation times to the Gondwana supercontinent. In this review the different magmatic belts are analyzed, their deformation and metamorphism, the associated sedimentary basins, as well as the existing geochronologic controls. Aware that important uncertainties still remain, a new model is proposed with two magmatic arcs: a western belt that was active from the Devonian to the mid Carboniferous, and a northern one partially coeval that led to the collision of Patagonia against the southwestern margin of Gondwana in the Lower Permian. It is hypothesized that the termination of the western magmatic arc activity was linked to the collision of the Antarctic Peninsula and associated terranes. The reconstruction of the plate tectonic history of Patagonia during the Paleozoic shows the existence of several episodes of fragmentation and rifting, convergence and accretion, renewed periods of rifting and reaccretion to the Gondwana margin. Those processes were intrinsic to the formation of Terra Australis orogen, controlled by the absolute motion of the Gondwana supercontinent and guided by successive global plate reorganizations.