Los efectos producidos por la aproximación, colisión y subducción de dorsales pacíficas en los Andes Patagónicos

The Northern Patagonian Andes are an orogenic belt, which were formed by the subduction of the Phoenix-Farallón plates first and the Nazca plate latter and they present a series of deformational phases since the Late Jurassic to the Neogene. The main objective is to group this complex sequence of deformational events in two cycles, which are related to the age distribution of the subducted oceanic plates.

South of 38°S, the origin of the Northern Patagonian Andes is linked to the effects produced by oceanic ridge collision. The present picture shows how strain is distributed in the upper plate, in a low strain partitioned setting, during oblique subduction. The continental crust stacks in the retroarc area, as in the present Central Andes to the north, under a certain critical length between the Chilean trench and the oceanic ridge. When this distance reaches that threshold length the thrust systems stop, as in the Northern Patagonian Andes, where very young oceanic crust is being subducted. As the oceanic configuration changed in time along the trench because of ridge subduction, the described strain crustal types also shifted depicting two contrasting styles such as the present Central Andes vs. Patagonian Andes.

For the last 120 million years, at least two cycles of crustal thrusting and retroarc orogenic quiescence have been documented, recording the different tectonic settings in the geological record, associated with the approaching, collision and subduction of seismic oceanic ridges, obliquely oriented with respect to the South American border.
Keywords: Patagonian Andes. Oceanic Ridges. Strain Partitioning. Andean mountain building. Argentina. Chile.