Geology of the northern sector of the Cura Mallín Basin in the Lagunas de Epulaufquen, Neuquén

Abstract

The exposed sequences in the eastern Andes around the Argentinian-Chilean boundary between 36º40´-50´S, 71º-71º10´O are associated with two contrasting genesis. On one hand, the lowest sequences have been accumulated in an extensional intra-arc basin, where synrift units from the Lumabia Member of the Cura Mallín Basin are overlied by sequences associated with thermal cooling of the Arroyo Pincheira Member. On the other hand, the upper sequences of the Cajón Negro Formation represent a volcanic arc that were superimposed to a previously inverted intraarc basin. There are three compressive phases in the area. The two first are associated to thin-skinned deformation (Early and Middle Miocene), while the last one to thick-skinned deformation related to the tectonic inversion of the Cura Mallín intraarc basin (Late Miocene). Geochemical studies suggest that a major change in crustal thickening was reached between Arroyo Pincheira Member and Cajón Negro Formation. This last phase of contraction produced most of the Andean structures at the eastern slope of the high Andes around 36º40´-50´S.